dentistry - odontology pdf

1st Year 1st Semester Final Exam Odontology Topic Notes AMIT DATTANI 2012

University of Debrecen Medical and Health Science Centre – Faculty of Dentistry 1

Odontology

Final Exam Topic Notes 2012

(Edited)

Amit Dattani

"Education is our passport to the future, for tomorrow belongs to the people who prepare for it today."

-Malcolm X



Odontology Final Examination Topics 2012

Contents

1. Description of human dentition ............................................................................ 4

2. Definition and main parts of the tooth ................................................................. 8

3. Zsigmondy’s and the two-digit notations ............................................................11

4. Physical properties of the tooth surface .............................................................15

5. Attrition, abrasion and erosion of teeth. Degrees of degradation ..........................19

6. Tooth identifiers on the crown ................................................................................22

7. Tooth identifiers on the dental neck and root ....................................................25

8. The morphology of the maxilla............................................................................27

9. The morphology of the mandbile ........................................................................27

10. Development of the crown ....................................................................................32

11. Development of the root and formation of the periodontium .............................38

12. Phases of the tooth eruption .................................................................................41

13. Developmental dates of the teeth ........................................................................43

Tooth Morphology .......................................................................................................44

14. Description of permanent maxillary incisors .........................................................46

15. Description of permanent mandibular incisors .....................................................49

17. Description of permanent maxillary canine ..........................................................52

18. Description of permanent mandibular canine ......................................................53

19. Description of maxillary premolars .......................................................................55

20. Description of mandibular premolars ...................................................................57

21. Differentiation of premolars ..................................................................................59

22. Description of permanent maxillary molars ..........................................................60



23. Description of permanent mandibular molars ......................................................66

24. Differentiation of molars .......................................................................................71

25. Morphology of maxillary deciduous teeth ............................................................73

26. Morphology of mandibular deciduous teeth ........................................................77

27. Physical and chemical properties of enamel .........................................................84

28. Enamel structure and formations..........................................................................84

29. Physical and chemical properties of dentine ........................................................87

30. Dentine structure and formations .........................................................................89

31. Structure of the pulp .............................................................................................92

32. Functions of the pulp .............................................................................................92

33. Description of soft tissues of the periodontium ....................................................95

34. Description of hard tissues of the periodontium ..................................................98

These notes have been constructed from:

B.G Jansen Van Rendsburg – Oral Biology

Wheeler’s Dental Anatomy, Physiology and Occlusion 8th ed

The official lectures of the University of Debrecen Dental Department

Shimon Dantsis (Alumini) Notes

Netter’s Atlas of Human Anatomy 4th ed

(I am not responsible for the reproduction of any material in any way or form in this study pack.)

Please note, as I am also human there could be some mistakes. If you find any please message me on facebook so I can rectify these. I would also appreciate your feedback.

I dedicate this to the students at the University of Debrecen.

--

Amit Dattani (4th Year Dental Student)



1. Description of human dentition

The Human Dentition is:

Diphyodont: Having two different sets of teeth through a life time, the deciduous

(Primary) teeth and the Permanent (Secondary) teeth.

Heterodont: Contains different teeth (Incisors, Canines, Premolars and Molars) which

differ in shape and properties in the same arch.

Primary Dentition

Consists of 20 teeth (5 in each quadrant)

o 1 Central Incisor

o 1 Lateral Incisor

o 1 Canine

o 2 Molars

(NO Premolars!)

Dental Formula:

= I2 + C1 + M2

(2 Incisors, 1 Canine, 2 Molars)



Permanent Dentition

Consists of 32 teeth (8 in each quadrant) o 1 Central Incisor o 1 Lateral Incisor o 1 Canine o 2 Premolars o 3 Molars

The Incisors & Canine form the Anterior teeth

The Premolars & Molars form the Posterior teeth

Permanent teeth begin to erupt at 6 years of age and continue to erupt till 17-21 years of age.

Dental Formula:

= I2 + C1 + P2 + M3

(2 Incisors, 1 Canine, 2 Premolars, 3 Molars)

A mixed dentition refers to one that is composed of primary and permanent teeth (when the

permanent teeth are erupting, after the deciduous).

Arrangement of teeth:

Upper Arch- Maxillary (stays stationary)

Lower Arch- Mandibular (moveable)



Each arch is separated into the Upper, Lower, Left and Right quadrants, separated by a

midline (an imaginary line dividing the central incisors).

Occlusion is when the maxillary and mandibular arches are in contact.

The upper teeth usually surround (on the front and both sides) the lower teeth in a normal

occlusion (contact between teeth).

The upper arch is larger than the lower arch.

Shape of the Dental Arches:

Primary:

Upper and Lower – Semicircular



Permanent:

Upper – Semieliptical

Lower- Parabolic

Note: Canine is also called “cuspid” and a premolar is also called “bicuspid”

Role of teeth:

Primary role is Mastication

Play a role in Speech

Have an Aesthetic function

Definitions:

“Succedaneous”: The teeth of the permanent dentition that replace the primary teeth.

“Non-succedaneous”: Teeth that are not replaced by another type of teeth (Permanent Molars).



2. Definition and main parts of the tooth

“Tooth” – Independent organ belonging to the masticatory mechanism, found in oral cavity.

They have 3 main roles being mastication, speech (phonetics) and aesthetics.

A tooth has 2 main parts:

-Crown

-Root

Separated by a Cervical line/dental neck

(Cervical Line: the Cemento-Enamel Junction (CEJ) between

the crown and the root)

Basic Anatomy of the tooth:

(learn by heart now and you will understand it later…trust me on this one)

IMPORTANT: Learn detailed anatomy of tooth on Page 243 in “Oral Biology Jansen Van

Rensburg” book.

Parts of the tooth explained:

Enamel: hard tissue covering the crown of the tooth (made by ameloblasts)

Dentine: hard tissue under the enamel crown (softer than enamel). Made from odontoblasts.



Cementum: layer of calcified tissue covering the root (sofer than dentine)

Pulp Chamber: cavity where the pulp itself is located

Pulp: The central hollow chamber of a tooth, containing delicate connective tissues, nerves

and both blood and lymph vessels. It is lined peripherally by odontoblasts.

Root Canal: contains part of the pulp chamber

Gingiva: the gum surrounding the tooth

Periodontium: the surrounding tissues of the tooth which provide support for the tooth

Made of up hard and soft tissues

Hard:

Alveolar bone

Cementum

Soft:

Gingiva

Periodontal Ligaments (PDL)

The crown and root have different definitions anatomically and clinically:

Anatomical Crown: part of the tooth that is covered with enamel

Clinical Crown: part of the tooth that is exposed and visible in the oral cavity (above the gum

line)

Anatomical Root: part of the root that is covered with cementum

Clinical Root: part of the root that is located in the jaw

Surfaces of teeth: (Wheelers dental anatomy book page 10)



Facial: the surface that faces the front (face)

Labial: facial surface of anterior teeth (Incisors and canine)

Buccal: facial surface of the posterior teeth (premolars and molars)

Lingual: surface that is closest to the tongue (only for lower jaw)

Palatal: surface that is closest to the tongue side (only for upper jaw)

Mesial: surface of the tooth that is closest to the midline (also called proximal surfaces)

Distal: surface of the tooth that is furthest away from the midline (also called proximal

surfaces)

EVERY tooth has these surfaces, and they have ONE of the following:

Incisial surface: biting surface for anterior teeth



Occlusal surface: biting surface for posterior teeth

Interproximal surface: The spaces between the proximal surfaces

3. Zsigmondy’s and the two-digit notations

In total there are 3 different notification systems.

1. Zsigmondy / Palmer Notification - (Used in the UK)

2. Universal System (2 digit numbering) - (1-32 /A-T)

3. FDI (Federation Denature International) System (2 digit numbering) – quadrant and tooth

number.

These systems are used so dental offices, staff; insurance companies can better communicate

between each other regarding exact details of certain teeth.

Adolf Zsigmondy (Hungarian Dentist) developed the idea in 1861. (Also known as the Palmer

Notification System)

He divided the teeth into 4 quadrants and each tooth was given a sign according to its location

in the mouth.

Maxillary Right Maxillary Left

Mandibular Right Mandibular Left

The teeth in each quadrant are numbered from 1-8 for an adult (permanent dentition) and

roman numerals (I-V) for the deciduous dentition (milk teeth). Roman Numbers were changed

to letters A-E for the deciduous dentition. (Roman numerals were not computer friendly so

not used today, Roman numerals used in Zsigmondy system and letters in Palmer system).

Permanent Dentition:

Maxillary Right Maxillary Left

Mandibular Right Mandibular Left

Midline (between both Central Incisors)



E.g.

8 = Upper Right 8 (3rd

Molar)

4 = Upper Left 4 (1st Premolar)

2 = Upper Left 2 (Lateral Incisor)

Deciduous Dentition:

E.g.

C = Upper Right Deciduous Canine

A = Lower Right Deciduous Central Incisor

Universal System

Secondary Dentition (permanent):

Uses numbers from 1-32

Maxillary 1-16

Mandibular 17-32



Primary Dentition:

Users Letters from A-T

Maxillary A-J

Mandibular K-T

E.g.

16 = Upper Left 3rd

Molar

24 = Lower left Permanent Central Incisor

N= Lower Left Deciduous Lateral Incisor

T= Lower Right Deciduous 2nd

Molar

FDI System

This system uses 2 digit numbering. (This system is used in the University clinics)

The first digit represents the quadrant number



The second digit represents the tooth number (starting from the midline)

Permanent Quadrant (mouth) Deciduous

1 Upper Right (of patient) 5

2 Upper Left 6

3 Lower Left 7

4 Lower Right 8

Quadrants:

Permanent:

Deciduous:

REMEMBER THE QUADRANTS AS A CLOCK FACE (GOING CLOCKWISE!)

E.g.

11 = Upper Right Permanent Central Incisor

18 = Upper Right 3rd

Molar

35 = Lower Left 2nd

Premolar

46 = Lower Right Permanent 1st Molar

54 = Upper Right Deciduous 1st Molar

75 = Lower Left Deciduous 2nd

Molar

REMEMBER THE QUADRANTS AS A CLOCK FACE (GOING CLOCKWISE!)



4. Physical properties of the tooth surface

Strictly speaking this topic is asking about the physical properties of the tooth surfaces, but

the examiners always like to around the topic and will ask you about other properties too.

The tooth is covered by enamel, which is the outer most layer. (The tooth surface is covered

by enamel, dentine and cementum.)

The enamel surface is the hardest tissue in our body

Covers the outer surfaces of the tooth

It is of ectodermal origin

Density

~ 2.84-3.00 grams/ml

Density decreases from the surface to the amelodentinal junction (where the enamel

and dentine meet)

During tooth development the density of enamel increases progressively

Physical Properties:

Hardest tissue in the body

96-98% Inorganic Substances (mainly hydroyapetite crystals)

o Ca10 (PO4)6(OH)2

3-4% water

1% Organic material

Outer regions are harder than the inner (deeper) regions

Composed of tightly packed rods (prisms)

o Approx 2.0-2.5mm thick in cusp tips

o Enamel prisms are the elementary components of enamel

Colour

Enamel is semi-translucent

o Thick enamel is greyish / blue-white colour

o Thin enamel is yellow-white

Discolouration by:

Oral hygiene, food deposits, ageing of patient

Calcification disorders – cause white/ brown spots

Excessive fluoride intake – through incorrect water fluoridation or medication

Tetracycline staining (pictured below) – (General Antibiotic) such as

Chlorotetracylcine

Smoking – causes yellow staining by nicotine and tar. Also causes brown deposits

found between teeth.



Strength:

Very brittle

Cushioning effect of dentin makes enamel hard to withstand

Solubility

When exposed to acid medium it is subjected to DISSOLUTION (chemical basis of

cavities).

Fluoride can incorporate into hydroxyapatite crystals and REDUCE THE

SOLUBILITY of enamel and thus increases the defence against acidogenic bacteria.

The organic matrix of enamel protects the enamel from acid action

Permeability

Selectively permeable – lets some elements pass through but not everything. E.g.

Fluoride can permeate

o Cannot permeate enamel: Calcium, Zink, Silver elements

o Can permeate enamel: Fluoride, Sodium Iodide, Iodine, Urea, Nicotinamide,

Thiourea

Other:

Lines of Retzius - might be formed as a result of disturbed mineralisation

It will cause brown, dark lines on the enamel

Shallow grooves can be seen where the lines meet the enamel surface



Perikymata are incremental growth lines that appear on the surface of enamel as a series of

grooves.

Neonatal Line- accentuated (more visible) lines of retzius seen in histologic sections, these

lines can only form at birth and are used in forensic dentistry to identify the age of a person.

Enamel tufts (hypomineralised projections) arise at the dentino-enamel junction and extend

for a short distance into the enamel layer.

Enamel Spindles- short linear defects that extend into the enamel

Pictured: Enamel tufts (large fire-like structures) and spindles (short lines):

Dentin

Physical Properties

Living tissue with tubular structure

Main protion of the tooth

70-75% Inorganic material (hydroxyapatite)

18% Organic (Collagen), Citric acid, lipids and proteins

12% water

Dentine is harder than bone but softer than enamel

The inner part is softer than the peripheral (outer) layer, with age it becomes

HARDER

Dentine has a high degree of elasticity than enamel.

The presence of numerous tubules (dentine) makes dentine highly permeable.

(Permeability decreases with age).



Colour

Yellowish-white

Darker in deciduous teeth

Cementum

Covers the anatomical root surfaces of the teeth

Similar to bone, but cementum is avascular (No blood supply)

o 65% mineral, (inorganic) - hydroxyapatite

o 23% Organic

o 12% water

(See topic 29 for more about Dentine)

Summary:

Enamel Dentin Cementum

Inorganic mineral (%) 96-98 70-75 65

Organic (%) 1 18 23

Water (%) 3-4 12 12

Note: percentages are based on weight



5. Attrition, abrasion and erosion of teeth. Degrees of

degradation

There are three types of processes that aid loss of tooth substance:

1. Attrition

2. Abrasion

3. Erosion

Attrition

Is the wearing away of tooth structure as a physiological result of tooth-tooth contact and by

the friction of food.

Affects: occlusal surfaces (primarily) and proximal surfaces of teeth

Also bruxism (tooth grinding during stress or sleep) causes attrition

5 grades of attrition:

1. Loss of tooth material localised in the enamel

2. Dentin is exposed on tip of cusps and incisial edges

3. Dentin exposed to whole occlusal surface, enamel surrounds it

4. The process reaches the pulp chamber and the pulp may become inflamed

5. Tooth worn down to the gingival margin

Characteristics

The loss of tooth material (attrition) most commonly seen on the palatal surface (of upper

teeth) and the vestibular surface (also known as the facial surface) (of lower teeth)



Abrasion

Is the wearing away of a tooth by a mechanical process, other than mastication and tooth-

tooth contact.

Causes: excessive or improper tooth brushing, flossing or use of tooth-picks, can also be

caused by working in a polluted area.

It can produce sensitivity in teeth due to exposed dentine or thinning of enamel.

It produces deep “U” or “V” shaped depressions towards the cervical surface of the tooth

crown. It exposes the underlying dentine and thus causing increased sensitivity. (Pictured).

Most commonly canines and premolars are affected, or the buccal surface of 1st upper molars

Erosion

Is the wearing away of the non-occluding surfaces of teeth by chemical dissolution (mainly

through acid), reduction in saliva increases erosion (because saliva has antibacterial properties

and a natural buffer.)

Intrinsic origin of acid:

Regurgitation of gastric acid (habitual vomiting)

o Affects palatal and occlusal surfaces mainly.

Extrinsic origin of acid:

Diet (fruit juices – affects mainly incisors on their incisial surface)

Air pollution in working environment due to acid

Causes:

Dietary- (Fruits, juices)

Medical – (HCL replacement, Vitamin C, Aspirin), occlusal and palatal surfaces affected.

Gastric reflux – mineral loss of occlusal surfaces of the molars and palatal surface



6. Tooth identifiers on the crown

There are certain characteristics that can be seen on the crowns of teeth…

1. Angular characteristics – upper central incisor (permanent)

The distoincisial line angles are more rounded than the mesioincisial angle

2. Cervical line curvature

The cervical line that separates the crown from

the root curves differently on the Mesial &

Distal surfaces of the tooth to the Buccal &

Lingual surfaces

The curvature of the line is (pointed) more on

the Mesial aspect than the distal aspect

(pictured).

Incisial edge

Distal Surface

Mesial Surface

More rounded (greater than 90 degrees- obtuse angle

)

Less rounded (Right angled)



Curved more than the mesial side

3. Arch characteristics

Occlusal view (cross section)

Vestibular

Mesial Distal

The curvature of the mesio-vestibular crown surface is more sharply

curved than the distovestibular

4. Cervical Contour Characteristics

Occlusal view (cross section)

Mesial Distal

At the level of the cervical line the contour of the mesial part of the tooth is FLAT, but

the distal is curved

5. Cusp inclination characteristic

(Letter “D” shape formed)



The longitudinal axis of the lower posterior teeth incline lingually, but the axis of the

upper teeth is almost vertically orientated.

Right side - buccal view

Longitudinal axis – is along the length of the tooth

Vertical axis – is in direction of the length of the tooth

------------------------------------------------------------------------------------------

Note:

Attrition characteristics:

The loss of tooth material can be usually be seen on the palatal surface of

the upper teeth and the vestibular surface of the mandibular teeth

Straight vertical axis of maxillary posterior teeth

Inclined longitudinal axis of mandibular posterior teeth



7. Tooth identifiers on the dental neck and root

1. Root inclination in the frontal plane (facial aspect)

Mesial Distal

From the facial aspect the axis of the root and the axis of the

crown intersect each other at the level of the cervical line

The angle formed by the two lines opens distally

2. Root inclination in the saggital plane

Lingual Buccal

There is an angle between the crown and the root. The root bends lingually and is in a

different direction to the crown edge.

3. Curvature of the apical root

The apical third (the last third) of the root tends to curve towards the

distal direction (pictured).

The tooth is from the lower right quadrant

(The pictured tooth makes it very obvious but normally it is not curved as

much as the pictured tooth- just slightly)



4. Difference between the mesial and distal root grooves:

The distal surface of a tooth has a groove (pictured in cross-section at the

cervical line) deeper than the mesial groove .



8. The morphology of the maxilla

9. The morphology of the mandbile

Maxilla – Purple in image above

Mandible – white/grey in image above

The part of the face between the orbit (place of eyes) and the upper teeth and each upper jaw

is formed by the paired maxillae, together known as the maxilla.

Superiorly (on top), each maxillae contribute to the inferior (lower) and medial (towards the

midline) rims of the orbit.

Laterally (towards the left and right sides), the zygomatic process of each maxillae articulates

(joins) with the zygomatic bone and medially, the frontal process of each maxillae articulates

with the frontal bone.

Laterally to the opening of the nasal cavity is the body of the maxilla

.



On the anterior (front) surface of the body of maxilla, just below the inferior rim of the orbit,

is the infra-orbital foramen.

Inferiorly, each maxilla ends as the alveolar process, which contains the teeth and forms the

upper jaw.

You mainly need to know the labelling of the maxilla and mandible for now (for

Odontology).



Mandible

The mandible has 3 main parts:

Ramus

Body

Angle



The lower jaw (mandible) is the most inferior structure in the anterior view of the skull. It

consists of the body of mandible anteriorly and the ramus of mandible posteriorly. These meet

posteriorly at the angle of mandible. All these parts of the mandible are visible, to some

extent, in the anterior view.

The body of mandible is arbitrarily divided into two parts:

the lower part is the base of mandible;

the upper part is the alveolar part of mandible.

The alveolar part of mandible contains the teeth. The base of the mandible has a midline

swelling (the mental protuberance) on its anterior surface where the two sides of

the mandible come together. Just lateral to the mental protuberance, on either side, are slightly

more pronounced bumps (mental tubercles).

Laterally, a mental foramen is visible halfway between the upper border of the alveolar part

of mandible and the lower border of the base of mandible. Continuing past this foramen is a

ridge (the oblique line) passing from the front of the ramus onto the body of the mandible.

Tooth Anatomy



10. Development of the crown

Overview

Note: “Tooth bud” – (also known as a “Tooth germ”) is an aggregation of cells that

eventually forms the tooth. The tooth bud is composed of 3 parts:

1. Enamel organ

2. Dental papilla

3. Dental follicle

1. The enamel organ is composed of the following:

Outer enamel epithelium

Inner enamel epithelium

Stellate reticulum

Stratum intermedium

These cells give rise to the ameloblasts, which produce

enamel and reduce the enamel epithelium.

The growth of the cervical loop (the location where the

outer enamel epithelium and inner enamel epithelium

join) – cells into the deeper tissues forms “Hertwig’s

epithelial rooth sheath”, which determines the shape of

the root.

(The diagram won’t make sense at the moment- its just there so you can visualise the different

parts of the enamel organ as reference after you have completed this topic.)

2. The dental papilla contains cells that develop into odontoblasts – which are ‘dentine

forming cells’. Mesenchymal cells within the dental papilla are responsible for formation

of the pulp.

3. The dental follicle gives rise to cementoblasts, osteoblasts and fibroblasts.

4.

Cementoblasts- form the cementum of the tooth

Osteoblasts- form the alveolar bone around the roots

Fibroblasts – develop the PDL (periodontal ligaments) that connect teeth to the

alveolar bone through cementum

The developing tooth bud:

The earliest steps in tooth formation (take place at the 7th week in-utero) make the

distinction between the vestibular lamina and the dental lamina. (The dental lamina

connects the developing tooth bud to the epithelial layer of the mouth).



Tooth development has 4 main stages:

1. Bud stage

2. Cap stage

3. Bell stage

4. Crown stage

1. Bud Stage

Characterised by the appearance of a tooth bud without a clear arrangement of cells

Stage begins when the epithelial cells proliferate (rapid growth) into the mesenchyme

of the jaw. (The tooth bud itself is the group of cells at the end of the dental lamina).

The epithelial lining of the oral cavity before development commences

Primary epithelial cells thicken into a ‘V’ shaped bud

The primary epithelial thickening

The epithelial thickening divides into vestibular and dental lamina



Vestibular and dental laminae

2. Cap Stage

First sign of arrangement of cells in the tooth bud

Increase in mitotic activity

Mesenchyme cells aggregate to produce the dental papilla

Tooth bud grows around mesenchymal aggregation (looks like a cap) and becomes the

enamel organ

Condensation of mesenchymal cells called the dental follicle surrounds the enamel

organ and limits the dental papilla

Eventually….

Enamel organ produces ENAMEL

Dental Papilla produces DENTINE AND PULP

Dental Follicle produces SUPPORTING STRUCTURES (cementoblasts, osteoblasts and

fibroblasts)

Cells aggregate to form the tooth bud from the dental lamina

Tooth Bud



Cap stage of development

The enamel organ looks like a cap (above).

3. Bell Stage (histo-differentiation)

The enamel organ has a Bell shape in this stage

The dental lamina disintegrates leaving the tooth separated from the epithelium

(joins later during eruption)

Cells of enamel organ separate into 4 layers:

1. Inner enamel epithelium (columnar layer) – forms ameloblasts

2. Outer enamel epithelium (cuboidal layer)

3. Stellate cells (contains alkaline phosphate, some RNA and glycogen)

4. Intermediate cells

Inner and outer epithelium grow and form the cervical loop

Inner dental enamel differentiates to form ameloblasts

Fibers, blood vessels and nerves appear in the dental papilla (forms pulp)

The enamel organ develops from oral ectoderm



The tooth germ consists of the enamel organ, the follicle and the dental papilla

4. Crown Stage (hard tissue develops)

Hard tissues form – enamel and dentine

Mitosis of inner enamel epithelium cells, it stops where the cusps form

The inner enamel epithelium cells change in shape from cuboidal to columnar

Nuclei of inner enamel epithelium cells move closer to the stratum intermedium and

away from the dental papilla

The adjacent layer of cells in the dental papilla increase in size and differentiate into

odontoblasts – cells that form dentine

After dentin formation begins, the cells of the inner enamel epithelium secrete an

organic matrix in the dentin

The matrix immediately mineralises and forms enamel

Ameloblasts- continue the process of enamel formation; adding enamel to the outer

surface of the tooth.



Formation of dentine and enamel

Root sheath of Hertwig

Root sheath of Hertwig

Determines root form

Retains a tubular form, where it divides into roots

Advanced development



Changes in the dental papilla:

During bell stage blood capillaries

appear and are indicative of metabolic

activity. This will eventually result in

dentine formation.

Nerves appear priot to the

differentiation of odontoblasts but the

nerve supply of the pulp and dentine is

poorly developed before birth.

11. Development of the root and formation of the

periodontium



Starts after determination of the crown

The inner and outer epithelial cells elongate and form the cervical loop (or root sheath

of Hertwig). There is a double layer membrane with no other membrane between

them.

The root sheath determines root form, i.e. subdivides for multiple roots.

The dental follicle differentiates to form:

1. Fibroblasts - PDL (periodontal ligaments)

2. Osteoblasts - Alveolar bone

3. Cementoblasts – Cementum

Peripheral cells of the dental papilla differentiate to from odontoblasts

These 3 cells (see above) will only secrete after the sheath of Hertwig breaks down

Cementum and PDL will start to establish

Most root development continues during eruption of teeth

When the cusp appears in the oral cavity – approximately HALF the root is formed

at this point (…be prepared to answer questions on tooth eruption times!)

The PDL will change until the bone reaches its final size and the tooth will find its

place in the jaw

Important information (generally regarding tooth development)

The function of the outer dental papilla is to provide nutrition and oxygen

Enamel is ectoderm origin (and gingiva)

Dentine, PDL, cementum, alveolar bone, pulp are mesoderm origin

Number of tooth buds in the oral cavity is 52 (20 in primary teeth and 32 in

permanent)

Definitions:

“Vestibule” – space between the teeth and the cheek/lip

“Cervical loop”- the area of the enamel organ where the inner and outer dental

epithelium cells join to each other

“Ectoderm”- the outermost layer of the three primary germ layers of an embryo

“Mesoderm”- the middle layer of the three primary germ layers, from which

connective tissue, muscle, bone, and circulatory systems develop.

“Epithelial root sheath” – continuous sheet of tissue sandwiched between the

undifferentiated mesenchyme of dental papilla and the follicle.

Periodontium

The periodontium consists of 4 parts:

1. Cementum

2. Gingiva

3. PDL

4. Alveolar bone

They are classified into hard and soft tissues:



Hard Soft

Alveolar bone PDL

Cementum Gingiva

Extra points to note:

‘Sharpeys fibers’- parts of the PDL fibers embedded in cementum and those parts of the

fibers embedded into the alveolar bone.

In simple terms – Sharpeys fibers are the end-parts of the PDL. (DO NOT say this line in

the exam! - it’s for your understanding!)…IF you do say this line in the exam be prepared

for interrogation!

‘Bone fibers’- matrix of connective tissue consisting of bundles of collagenous fibers, they

connect the PDL into the cementum.

Lamina Dura:

It is an internal layer of alveolar bone

It is cellular (osteocytes)

Periodontal fibers insert into it as Sharpey’s fibers

Sharpeys fibers



12. Phases of the tooth eruption

‘Eruption’ is the movement of teeth within and through the (alveolar) bone of the upper or

lower jaw and the overlying mucosa to reach the oral cavity.

There are 3 phases of tooth eruption:

1. Pre-eruptive phase

2. Pre-functional phase (or emergence phase)

3. Functional eruptive phase (or post-eruptive phase)

Teeth erupt at a maximal rate to reach occlusal contact, and then they continue to erupt at

a slower rate to compensate for growth and occlusal wear.

Eruption of the tooth is after completion of the crown.

Tooth development starts with mineralisation of enamel and ends with formation of the

apical foramen.

1. Pre-eruptive phase

o Movements of the developing and growing tooth germs within the alveolar process

before tooth formation

o The growing teeth move in various directions to maintain their position in the

expanding jaw, accomplished by the bodily movement and eccentric growth.

‘Bodily movement’ – shift of the entire tooth germ

‘Eccentric growth’ – part of the tooth continues to grow while the rest of the tooth

remains constant

Primary teeth move in an occlusal and facial direction with distal and mesial movement

Permanent teeth develop lingual to the levels of the incisial or occlusal levels of the

primary predecessors

All movements within this phase take place within the crypts of the developing and

growing crowns before root formation



2. Pre-functional phase

o Starts with initiation of root formation

o Ends when the teeth reach occlusal contact

5 major events take place in this phase:

1. The secretory phase of amelogenesis is completed just before the onset of root formation

2. The intraosseous stage – root formation begins due to proliferation of epithelial root

sheath and mesenchymal tissue of the dental papilla and dental follicle.

3. The supraosseous stage – begins when the eruptive tooth moves occlusally through the

bone of the crypts and connective tissue of the oral mucosa

4. Clinical eruption- the tip of the crown enters the oral cavity by breaking through the

double layer of epithelial cells. (Half to three-quarters of the root has already been formed

by now.)

5. Active eruption - the erupting tooth continues to move occlusally at a maximum rate

(the clinical crown is exposed through the separation of the epithelium cells from the

crown)

Remember:

Clinical crown- part of the tooth exposed in the oral cavity

Anatomical crown- part of tooth covered by enamel

3. Functional eruptive phase

o Begins when teeth reach occlusion

o Continues for as long as the teeth remain in the oral cavity

o Alveolar process (alveolar bone) increases in height and density

o Teeth continue to move occlusally

o Roots continue to grown

Once occlusion is established….

Principle fibers of the PDL are established into separate groups

Nerves (for sensation- heat, cold, pain) develop from the apex to the gingival

Later in life… attrition may wear down the occlusal surface, so the teeth further erupt slightly

to compensate for the loss of tooth structure.

Mesial drift may occur- this is when the teeth move slightly medially (towards the midline).

This will cause bone slight bone resorption mesially and bone apposition distally.

Factors that affect tooth eruption:

Vasodilation – causes an increased eruption as blood vessels become bigger

Hyperemia- excess of blood in an area

o Summary: increased blood to the tooth causes faster tooth eruption

Stages in dentition (age):

Primary: 6-24 months



Permanent 6-18 years

Mixed (both primary and permanent): 6-12 years

13. Developmental dates of the teeth

Eruption dates:

Primary

Tooth Maxilla (months) Mandible (months)

Central Incisor 7.5 6.5

Lateral Incisor 8 7

Canine 16-20 16-20

1st Molar 12-16 12-16

2nd

Molar 20-30 20-30

Usually teeth erupt in pairs, one on right, one of left side

Permanent teeth erupt slightly earlier in girls than in boys

Mandibular teeth usually erupt earlier than maxillary teeth

Permanent

Tooth Maxilla (years) Mandible (years)

Central Incisor 7-8 6-7

Lateral Incisor 8-9 7-8

Canine 11-12 9-10

1st Premolar 10-11 10-12

2nd

Premolar 10-12 11-12

1st Molar 6-7 6-7

2nd

Molar 12-13 11-13

3rd

Molar 17-21 17-21

Mandibular teeth usually erupt earlier than maxillary

In the maxilla, first premolar erupts before the canine

Both in maxilla and mandible, first molar is before the canine

The first molar is usually the first permanent tooth to erupt

---------

The above information seems to be enough for this topic. But since the topic is titled as

“Developmental dates of teeth”, he could ask you about the dates of first calcification,

crown completion, root completion etc… so I have inserted a table from Wheeler’s Dental



Anatomy, Physiology and Occlusion (7th

ed) on the following page which will give you an

idea of the actual “Developmental” dates the examiners could ask .

Dental eruption terms

Exfoliation - the process by which the roots of a baby tooth are resorbed and dissolved until

the deciduous tooth falls out

Resorption – Osteoclasts (bone destroying cells) destroy the roots of the deciduous teeth

Congenitally missing – a tooth that has never formed because a tooth bud was never produced

Edentulous – No teeth present

Tooth Morphology

You have to understand these terms before you can discuss the morphology of a tooth:

Cusp: is a point or a peak on the occlusal surface

Cusp Slope or Cusp Ridge: inclined surface that forms an angle from the tip of a cusp



Cingulum: an enlargement or bump located on the crown lingually along the gingival or CEJ

(Cemento-enamel junction) on the anterior teeth

Ridge: longitudinal convexities of enamel (raised border)

Labial ridge: alinear elevation located on the labial side of the incisors/canines

Buccal ridge: alinea elevation located on the buccal side of the premolars/molars

Cusp ridge: an elevation that extends in the mesial and distal direction from the cusp

tip

Marginal ridge: elevated crests of enamel of the tooth where the sides meet the top –

the borders around the crown

Oblique ridge: elevated prominences on the occlusal surface of maxillary molars from

the tip of the mesiolingual to distobuccal cusp (only on maxillary molars is the

Distobuccal cusp and the Mesiolingual cusp).

Triangular ridge: prominent elevations, triangle in cross-section, extend from the tip

of a cusp towards the central portion of the occlusal surface. On ALL posterior teeth

Transverse ridge: made up of triangular ridges of a buccal and lingual cusp which join

to form a continuous elevation (one cusp to another)

Mamelon: a rounded prominence on the incisial ridge of a newly erupted incisor, usually

disappears as the result of mechanical wear (attrition).

Sulcus: broad depression / valley on the occlusal surface of a posterior teeth

formed by inclines of adjacent cusps or ridges which meet at an angle

Groove: A small linear depression on the surface of a tooth (It is not the kind

of groove you get on at a party!)

Developmental groove: a groove formed by the union of two lobes. It is a sharply

defined narrow linear depression

Supplemental groove: an indistinct linear depression, irregular in extent and direction

Lobe: a development segment of the tooth. As lobes develop they join to form a single unit

Fossa: a rounded / angular depression of varying size on the surface of the tooth – on ALL

posterior occlusal surfaces



Pits: when two fissures cross, they form a pit

Fissure: a fault occurring along a developmental groove caused by incomplete or imperfect

joining of lobes

Convex: curving outward or away from the focus

Concave: curving inwards or towards the focus

14. Description of permanent maxillary incisors

Maxillary Central Incisor

Root 1

Root canal 1

Pulp horns 3

Cusps 0

Eruption 7-8 years



Cervical line curves more on mesial side than distal

Crown is equal length as root

Root inclines distally

3 mamelons – worn away by attrition

Mesioincisal angle is acute, as distoincisial angle is more rounded

Labial surface is smooth

Labial surface is convex

Palatal surface is concave except cingulum is convex

Largest incisor

Maxillary Lateral Incisors

Root 1

Root canal 1

Pulp horns 1-3

Cusps 0

Eruption 8-9 years

Crown is shorter than the root




Mesioincisal angle is acute, as distoincisal edge is more rounded

Labial surface more convex than Central incisor

Palatal surface more concave than Central

Less curvature on cervical line than Central

Smaller and narrower than central

Cingulum not as well developed in Lateral

Differences between Maxillary Central and Maxillary Lateral Incisor (topic 16)

Lateral crown is smaller (generally) and narrower

Root is same length

Lateral Distoincisal angle is more curved than Central distoincisal

The pulp is relatively Large in Lateral

Labial surface more convex in Lateral than of Central

Palatal surface is more concave in Lateral than Central

Less curvature of cervical line on Mesial surface of Lateral than Central

More prominent marginal ridges in Lateral than Central



Cingulum not as well developed in Lateral

15. Description of permanent mandibular incisors

Mandibular Central Incisor

Root 1

Root canal 1 or 2

Pulp horns 3

Cusps 0

Eruption 6-7 years




Root is oval shaped in cross-section

Mesioincisal and Distoincisal angles nearly identical

3 mamelons – worn away by attrition

Lingual surface is smooth

Distal groove is more marked

Smallest permanent tooth

Straight incisal edge

Small cingulum

Mandibular Lateral Incisor

Root 1

Root canal 1

Pulp horns 3

Cusps 0

Eruption 7-8 years



Mesial side longer than distal, producing a slope

Mesioincisal angle acute, distoincisal angle rounded

3 mamelons

Groove on mesial and distal surface

Differences between Mandibular Central and Mandibular Lateral Incisor (topic 16)

Lateral is slightly larger than the Central

Incisive edge is longer mesiodistally

Distal side of Lateral is rotating lingually

Crown of lateral slopes down towards distal side

Difference between Maxillary and Mandibular Incisors (topic 16)

Maxillary have more pronounced lingual fossae

Maxillary have roots that are more rounded in cross-section

Mandibular have smoother lingual anatomy without grooves and pits

Mandibular crowns are smaller and narrower relative to length

Mandibular crowns are flatter mesially and distally than Maxillary



17. Description of permanent maxillary canine

Maxillary Canine

Root 1

Root canal 1

Pulp horns 1

Cusps 1

Eruption 11-12 years



Largest and strongest tooth in mouth

All surfaces are convex

Large pointed cusp, tips placed approximately centrally

Distal slope longer than mesial

Great bulk of dentine

Bulky cingulum

Root is almost triangular in cross-section


18. Description of permanent mandibular canine

Mandibular Canine

Root 1

Root canal 1 or 2

Pulp horns 1

Cusps 1

Eruption 9-10 years



Single cusp not as pointed as in maxillary

Marginal ridge and cingulum less well developed

Crown tilts distally since mesial surface is a straight line

Well marked cingulum on lingual surface

Root possibly flattened Mesially and Distally

Vertical Mesial and Distal grooves may be present on root

Only canine that is capable of bifurcated root

Crown and root tends to lean distally

Differences between Maxillary and Mandibular Canines

Maxillary has larger pulp cavity than Mandibular

Mandibular crown is narrower mesiodistally

Mandibular cusp on incisive edge is less pointed

Cingula on Maxillary are larger and centred mesiodistally, mandibular are slightly to the distal



19. Description of maxillary premolars

Maxillary 1st Premolar

Root 2 (Buccal & Palatal- curve distally)

Root canal 2 (one in each root)

Pulp horns 2

Cusps 2 sharply defined (buccal larger than Lingual)




Concave canine fossa on mesial surface of crown extending to pronounced longitudinal groove on mesial surface of root

Mesial surface of buccal cusp longer than distal Pulp tilts slightly mesially Occlusal outline more angular than maxillary 2nd Premolar Grooves form letter ‘H’ on the occlusal surface

Maxillary 2nd Premolar

Root 1 (flattened mesiodistally, curves distally)

Root canal 1

Pulp horns 2

Cusps 2 (nearly equal in size, buccal larger)




No canine fossa Oval Occlusal outline Mesial slope of buccal cusp shorter than distal slope Grooves form letter ‘H’ on the occlusal surface

20. Description of mandibular premolars

Mandibular 1st Premolar

Root 1 (curves distally)

Root canal 1

Pulp horns 2

Cusps 2 (sharply defined -buccal larger than lingual)




2 Occlusal fossae distal larger than mesial Buccal cusp located centrally to apex Lingual inclination of crown to root Buccal surface convex, lingual almost straight Circular Occlusal outline, flattened + grooved on mesiolingual surface Mesial longitudinal groove more marked than distal

Mandibular 2nd Premolar

Root 1 (curves distally with blunt apex)

Root canal 1 or 2

Pulp horns 2 or 3

Cusps 2 or 3 (Buccal larger)




Occlusal outline like square-ish Mesial marginal ridge higher than distal No longitudinal grooves present

21. Differentiation of premolars

Difference between Maxillary and Mandibular Premolars

Mandibular crowns tilts lingually, so lingual cusp tips may be lingual to root Outline of Mandibular is rhomboidal shape as Maxillary is trapezoidal Mandibular lingual cusps are relatively MUCH shorter than mandibular buccal cusps



Difference between Maxillary 1st Premolars and Maxillary 2nd Premolars

Maxillary 1st premolars usually have a divided root as Maxillary 2nd premolars usually have only 1 root

Maxillary 1st premolar buccal cusp larger than Lingual cusp Maxillary 2nd premolar has NEARLY equal sized cusps (buccal and lingual) Maxillary 1st premolars buccal cusp is more pointed than Maxillary 2nd premolars buccal cusp Maxillary 1st premolars occlusal surface is asymmetrical with mesial marginal ridge as

Maxillary 2nd premolars being more symmetrical with no mesial marginal ridge. Distance between the two cusps maybe greater in difference in the 1st premolar

Difference between Mandibular 1st Premolars and Mandibular 2nd Premolars

Mandibular 1st premolar buccal cusp is more pointed than Mandibular 2nd premolar buccal cusp

Mandibular 1st premolar lingual cusp is small and non-functional as Mandibular 2nd premolar cusp is functional and relatively longer

Mandibular 1st premolars have a mesiolingual groove separating the mesial marginal ridge from the lingual cusp, not found on Mandibular 2nd premolars

22. Description of permanent maxillary molars

Maxillary 1st Molar

Root 3 (1 lingual and 2 buccal)

Root canal 3 or 4

Pulp horns 4

Cusps 5 (5th is tubercle of Carabelli-non functioning)



Eruption 6-7 years



Three well developed separate roots Palatal root longest and thickest, it develops away from 2 buccal roots Buccal roots tend to curve distally Rhomboidal occlusal outline Largest maxillary tooth Mesiopalatal cusp largest Distopalatal cusp smallest Buccal cusps more pointed than palatal Crown wider buccolingually than mesiodistally 5th cusp located on the lingual side of the mesiolingual cusp Mesiolingual cusp is the largest of the four functioning cusps Mesiobuccal root has 1 or 2 root canals

Maxillary 2nd Molar

Root 3 (slight distal inclination)

Root canal 3

Pulp horns 3 or 4

Cusps 4




Occlusal Palatal Buccal

Distal Mesial

Rhomboidal occlusal outline Distal cusps greatly reduced in size 3 roots less divergent Buccal roots same length, closer together Coalescence of roots more common than Maxillary 1st molar All roots same length as Maxillary 1st molar Roots more slender and lie closer together than Maxillary 1st Molar Prominent palatal and buccal developmental grooves

Maxillary 3rd Molar



Root 3 (short, often fused and curve distally)

Root canal 1

Pulp horns 3

Cusps 3 -5 (1 lingual and 2 buccal)


Occlusal Palatal Buccal

Distal Mesial

Triangular occlusal outline Largest cusp is Mesiopalatal Crown appears too big for (short and fused) roots



23. Description of permanent mandibular molars

Mandibular 1st Molar

Root 2 (1 mesial and 1 distal- curved distally)

Root canal 3

Pulp horns 5

Cusps 5 (3 buccal, 2 lingual)

Eruption 6-7 years



Largest mandibular tooth Buccal aspect 3 cusps visible Lingual aspect 2 cusps visible Mesiobuccal cusp is largest Mesial root is the largest of the two Larger crown mesiodistally than buccolingually Oblong occlusal outline Crown is shorter distally than mesially



Crown seems asymmetrical as buccal side longer than lingual side ‘S’ shape on occlusal surface

Mandibular 2nd Molar

Root 2 (close together, partially fused, curved distally)

Root canal 3

Pulp horns 4

Cusps 4


Occlusal Lingual Buccal

Distal Mesial

Rounded-square occlusal outline Lingual cusp higher than buccal Mesial cusp larger than distal Mesial root larger than distal Crown usually smaller than Mandibular 1st Molar



Roots not as robust but maybe longer than Mandibular 1st Molar Distobuccal cusp is larger than that of the Mandibular 1st Molar Two buccal cusps of equal height Roots not as broad than of the Mandibular 1st molar ‘+’ shape on occlusal surface

Mandibular 3rd Molar

Root 2 (close together, sometimes fused, curved distally)

Root canal 3

Pulp horns 4

Cusps 4-6


Mandibular 3rd Molar patterns (in the Right molar)

They can have between 4-6 cusps and the patterns are shown. (Left)

The 3rd molar can vary in shape and position – usually malformed All cusps are short and round Square occlusal outline



Marked convex buccal surface inclined lingually Roots often underdeveloped, short and thick Roots acutely incline distally

24. Differentiation of molars

There can be a lot you can say about this topic due to the different characteristics shown by

each molar.



You can start comparing the upper and lower molars and by mentioning the:

Number of roots in the upper and lower molars

The direction of the roots (mesio-distal or bucco-lingual)

The number of root canals in each moalr

You can then compare each molar individually e.g. 1st upper and 1

st lower molar, etc…

(Tip: if you learn the bullet point list on each tooth then this will be very easy!)

The tables below should be learnt extremely well.

Permanent Maxillary

Permanent Mandibular



25. Morphology of maxillary deciduous teeth



Maxillary Central Incisor (51,61)

Buccal:

Crown is longer mesiodistally than cervico-incisially

Slightly convex labial surface is smooth

Incisive edge is straight

Vertical development grooves are rarely seen

Root is long in comparison to the crown

Lingual:

Well developed marginal ridges

Cingulum is prominent

Root narrows lingually from a slightly flat labial surface

Cross section from cervical part of root is triangular shaped

Mesial and distal:

Both surfaces are similar

Mesial and distal outlines are wedge shaped

The length bucco-lingually and cervico-incisially are almost similar, only 1mm difference between them

Curvature of the cervical margin is prominently convex incisially (not as prominent in the secondary tooth).

Maxillary Lateral Incisor (52,62)

Outline of this tooth is similar to the central incisor (maxillary)

It has a SMALLER crown than the central incisor

Mesiodistal length is shorter than the cervico-incisial height

Distal incisive angle of the crown is more rounded

Root has similar outline to the central incisor

Maxillary Canine (53,63)

Buccal:

Cannot be compared to the incisor crowns, but root shape is similar

Crown is narrowed at the neck

Mesiodistal surfaces are prominently convex

Incisive edge is long and has a well developed cusp

Mesial slope of cusp is longer than the distal ridge

Root is long



Lingual:

Prominent vertical enamel ridge

Central cingulum is seen with mesial and distal marginal ridges

Lingual tubercle on the cusp tip is an elongation of the lingual ridge connecting cingulum and cusp

Lingual fossa divides the mesiolingual and distolingual halves

Mesial and distal:

Outlines are similar to the incisor’s mesial and distal aspects, but the crown is more robust in its cervical third.

Maxillary 1st Molar (54, 64)



Greatest length of the crown is between mesial and distal contact areas where the crown narrows cervically

Roots are thin, long and divergent (3 roots)

Three roots (2 buccal ,1 palatal)

Distal root is shorter than the mesial root

Division of roots is close to the cervical margin

Lingual root is the thickest

From occlusal view: the buccal surface of crown is longer than the lingual surface

2 main cusps: o Buccal o Lingual

Buccal cusp is an elongated ridge that may be partially divided into 2 or 3 smaller cusps by developmental grooves

Usually one prominent buccal developmental groove

Shallow central developmental groove present, but broad

Lingual cusp is usually divided into a large mesiolingual and smaller distolingual cusp by a distal developmental groove

The distal marginal ridge is small compared to the mesial marginal ridge.

Buccal surface of the crown shows a prominent bulge close to the cervical margin and opposite a mesiobuccal root

Cervical margin slopes in a gingival direction mesially on the buccal side, relatively straight lingually and shows a slight mesial and distal occlusal convexity.

Maxillary 2nd Molar (55,65)

Marked divergence of roots

Bulbous shape of crown

Narrowed cervical area

Short root stem

Primary second molar resembles the permanent second molar

Cusps and roots have a similar arrangement

Mesiolingual cusp is the largest and is connected to the distobuccal cusp by a low oblique ridge.

Large mesial fossa and smaller distal fossa

Tubercle of Carabelli is often present on the lingual surface of the mesiolingual cusp

Buccal cusps are almost equal size, separated by a buccal developmental groove

Occlusal surface has a central fossa with a central pit

Well developed triangualar mesial fossa with a mesial pit

Oblique ridge present in the distal triangualar fossa

Cervical line resembles the 1st molar (primary).



26. Morphology of mandibular deciduous teeth



Mandibular Central Incisor (71,81)

Buccal:

Relatively flat without developmental grooves

Mesial and distal sides become narrower cervically from the contact area

Crown is wide in comparison to cervico-incisially

Root is long and thin, narrows to a sharp apex

Incisive edge is straight

Lingual:

Cingulum and marginal ridges present

In middle and incisial third the lingual surface is flat or may have a lingual fossa

Crown and root narrow lingually

Mesial:

Typical outline of an incisor

Generally smaller tooth than upper incisor

Labio-lingually its 1 mm shorter than the upper incisor labio-lingually

Nearly flat root

Root narrows gradually apically

Cervical outline is similar to other incisors

Distal:

Outline is similar to mesial aspect of tooth

Cervical margin is less prominent in convexity incisially

Mandibular Lateral Incisor (72,82)

Similar to central incisor but slightly larger in all dimensions except labio-lingually

Cingulum maybe somewhat larger

Lingual surface is more concave than the maxillary lateral incisor

Incisive edge shows greater tendency to descent distal

Mandibular Canine (73,83)

Few differences between maxillary and mandibular canine, except for dimensions

Tooth is smaller, especially labio-lingually than the maxillary

Cervical convexities are less prominent (labially and lingually)

Striking difference is: longer distal cusp ridge compared to mesial cusp ridge (in contrast to the ridges of the maxillary canine)



Mandibular 1st Molar (74,84)

Occlusal surface is elongated mesiodistally

4 cusps, relatively indistinct

This tooth does not resemble any other molar

Mesial surface descends nearly vertically from the contact area

Distal surface convexity is similar to other deciduous molars

Cervical margin opposite the mesial root descends apically

Cervical margin is straight on lingual surface, slight convexity towards occlusal direction on the mesial and distal surfaces

Buccal surface of crown shows prominent bulge near cervical line

2 roots, mesial and distal

Roots are long, thin and divergent

Occlusally, the mesiolingual cusp is the largest and is separated by a small distolingual cusp by a lingual developmental groove

Buccal developmental groove separates the two buccal cusps

Large distal fossa, central development groove (CDG) starts here

CDG passes between mesiolingual and mesiobuccal cusps and ends in a mesial pit, in the smaller triangualar fossa.

Mandibular 2nd Molar (75,85)

Apart from general differences, this tooth resembles the permanent lower 1st molar- same number and arrangement of cusps and roots

Crown in comparison to the 1st primary molar, shows a more bulbous shape by a mesio-cervical constriction (not descending in a straight line)

Much larger than the 1st primary molar

Mesial and distal roots are long, thin and divergent. Bifurcate close to cervical margin

Occlusal surface has 5 cusps, (3 buccal + 2 lingual)

3 buccal cusps are more or less same size as are the lingual cusps

Total mesiodistal buccal surface is longer than the length of the lingual surface

Irregular central developmental groove runs from a mesial pit in the mesial triangular fossa to the distal pit in the distal triangular fossa

Transverse developmental grooves separate the 3 buccal cusps and 2 lingual cusps

The mesial and distal grooves continue as the buccal developmental groove and the lingual separates the two lingual cusps

Cental pit is where the lingual and mesiobuccal grooves meet the central groove



Articulation (occlusion) of the deciduous dentition

1. Mesial surfaces of upper and lower central incisors meet at midline of dental arch

2. Upper central incisors articulate with the lower central incisor and the mesial third of the lateral incisor. The incisive edges of the lower anterior teeth make contact with the lingual surface of the upper incisors.

3. Upper lateral incisor articulates with the lower lateral incisor and part of the lower canine mesially

4. Upper canine articulates with the remaining distal part of the lower canine crown and the mesial part of the 1st lower molar

5. The upper 1st molar articulates with the distal two-thirds of lower 1st molar and the mesial part of the 2nd lower molar

6. The upper 2nd moalr articulates with the remaining part of the lower 2nd molar and extends distally, beyond the distal surface of the lower 2nd molar

Mineralisation and eruption

Mineralisation begins at about 4 months of intra-uterine life

By 6 months all teeth are actively mineralised

Usually no teeth present in mouth at birth

Statistics only show an AVERAGE time of mineralisation, eruption etc… but cannot be used EXACTLY because no two individuals develop the same way.

Differences between the Deciduous and Permanent Teeth

1. Deciduous teeth are smaller overall than the permanent

2. Enamel of deciduous is whiter and more opaque, therefore, crown is a

lighter colour than permanent tooth



3. Enamel of deciduous is more permeable and more easily worn down but

permeability is lessened when tooth resorption starts

4. Depth of enamel is thinner and more consistent in deciduous (0.5-1mm

thick) and is 2.5mm thick in permanent

5. Deciduous have a pronounced cervical margin, the enamel bulges at the CEJ

6. Deciduous anterior crowns are bulbous with a pronounced cingulum

7. Newly erupted deciduous crowns are more pointed than permanent

8. Deciduous roots are shorter, less strong and lighter in colour than

permanent

9. Deciduous:

Anterior roots are longer in proportion to crown

Posterior are more divergent to allow for developing permanent

successor, they flare out more from each other wider than crown

10. Permanent pulp chambers are larger and follow exterior morphological

shape of tooth, tendency of less dentine

11. Deciduous root canals are very fine

12. Deciduous teeth have a more constant morphology, with less variations

than permanent

13. Deciduous CEJ is less sinuous than permanent

14. Deciduous dentition has 20 teeth, permanent has 32 teeth



27. Physical and chemical properties of enamel

(see topic 4 – enamel part)

28. Enamel structure and formations

Basic structural components are the enamel rods / prisms.

The enamel rods have a round head and a narrow tail. The heads are commonly directed

towards the incisal edge /towards cusps and the tail towards the necks.

The rods are composed of hexagonal hydroxyapatite crystals. Crystals have different

orientation (heads and tails) with respect to the Tomes Process.

Lines of Retzius:

Brown lines begin at the amelodentinal junction and reach the surface of the enamel. Each

line indicates amelogenesis. The first line surrounds the dentin tip. Lines of retzius form as a

result of disturbed mineralisation. The place where the lines meet the surface of enamel,

shallow grooves are seen, called perikymata.

Bands of Hunter-Schreger: Longitudinal cross-sections of enamel viewed by reflected light, appears as light and dark

bands, found in the inner part of enamel. It is caused by successive changes in direction,

followed by groups of enamel rods in the horizontal plane, which cause change in the angle of

light.



Enamel Tufts: Small branching defects found only at the DEJ, projecting into the enamel, have no clinical significance.

Enamel Spindles: Dentinal tubules found within the enamel – more abundant in cusp tips. Arise when a single odontoblasts process invades the pre-ameloblast layer during dentin development.



Enamel Lamellae: (Thin unmineralised structures) Primary: in unerupted teeth, due to shrinkage of enamel during final stages of amelogenesis Secondary: in post-eruptive phase, has the same appearance but as a result of occlusal trauma

Tomes process: Secretory surface of amelogenesis



Amelogenesis occurs in the crown stage of tooth development, always AFTER dentin formation

2 main stages of Amelogenesis

1. Secretory stage- in which proteins and organic matrix form a partially mineralised enamel 2. Maturation stage – mineralisation is completed

Secretory:

Cells of inner enamel epithelium differentiate to form ameloblasts, release enamel proteins

Enamel matrix mineralised by enzyme, alkaline phosphate

Enamel formation continues outward, away from the dentin

After first layer, the tomes process is produced

Maturation:

Ameloblast stops producing enamel

Starts to transport proteins used to complete mineralisation

29. Physical and chemical properties of dentine



Dentine forms the main bulk of the tooth, it is composed of: o 70% inorganic material (mainly hydroxyapatite) o 20% organic (mainly collage and lipids etc…) o 10% water

Softer than enamel but harder than cementum

Inner dentine is softer than outer dentine

Dentine has a tubular structure – therefore dentine has a higher permeability than enamel

Dentine has nerves and so is sensitive

Types of Dentine

Mantle dentine o First formed dentine – a the DEJ i.e. closest to enamel o Less mineralised than primary dentine

Primary dentine o Forms bulk of the tooth o Very regular tubular structure o When the root apex is closed (during formation) the primary dentine is finished

and secondary dentine starts formation

Secondary dentine o Formed after root formation o Formed slower than root formation o Less regular tubular structure than primary dentine o Its deposition reduces the pulp chamber

Tertiary dentine / reparative dentine o Deposited in reaction to noxious / traumatic stimuli e.g. caries, dental

procedures – it protects the pulp o Deposited in a localised area o Has a very few and irregular tubules

Predentine o Not completely mineralised layer 10-20um wide o Remains between odontoblasts and mineralised dentine o Contains a lot of organic matrix o After inorganic materials deposited (hydroxyapatite crystals) it becomes

mineralised to primary dentin o Predentine is mineralised in spherical forms,then the spherical forms fuse

together and predentine forms primary dentine

Physical properties

Main bulk of tooth

Living tissue with a tubular structure

Yellowish-white in permanent teeth

It is sensitive tissue, it contains very small nerve branches

It is elastic and permeable

Age affects permeability and hardness. o With age it becomes less permeable o With age hardness increases

Softer than enamel but is harder than cementum

Softer inner part of dentine

Dentine is a tooth germ in the bell stage



Inner cell of dental papilla will differentiate into odontoblasts (dentine forming cells later)

Functions of dentine

Acts as a main (bulk) portion of a tooth

Protects the pulp

Supports enamel

30. Dentine structure and formations

The three main types of dentine are primary, secondary and tertiary (topic 29)



Odontoblasts are dentine forming cells

A single cell layer covers the pulpal surface and can have different forms

They are functioning as living cells as long as the tooth is vital and when needed they react to stimulus in order to form tertiary dentine

Odontoblast processes are cytoplasmic extensions that enter the dental tubules. Each process has branches and it has a secretory function.

Dental tubules: are narrow parallel channels that do not follow a straight course. They have two curvatures, a primary and a secondary. “S” shaped curvature – primary, are layered. A secondary curvature can be seen under higher magnification. Some tubules can penetrate through the enamel (enamel spindles).

o Inside the tubules we can find odontoblasts processes and fluid o Around the tubules we can find two kinds of dentine:

1. Peritubular dentine:

o Which circles the tubules like a ring o Very hard o Highly mineralised o Absent in the pre-dentin and interglobular dentine o Its thickness increases with age

2. Intertubular dentine: o Found between tubules o Softer than peritubular dentine o It is built from a well organised collagen fiber network

Sometimes we can find small areas in the dentine, which are not fully mineralised. We can divide these into two groups:

Interglobular dentine: irregularly shaped structures near the ADJ (amelodentinal junction)

Granular layer of Tomes: near cementum, seen as dark areas, resulting from irregular loops of the dentinal tubules. (see image)



We can see different lines on dentine:

Incremental lines due to daily formation of dentine, appears as light and dark bands



1. Contour lines of Owen: different events of major changes in body metabolism, might cause hypomineralisation of the dentine

2. Neonatal lines (lines of Von Ebner): hypomineralisation line, can be seen only in milk teeth or permanent first molars

Dentine formation: dentinogenesis is the first identifiable stage in the crown stage and root development.

It must occur before enamel formation

The different stages result in different kinds of dentine formation

Odontoblasts differentiate from the dental papilla

31. Structure of the pulp

32. Functions of the pulp

The dental pulp consists of a delicate vascular connective tissue with specialised cells

The pulp is concerned with reactions of the tooth to stimuli

It has 5 main functions:

1. Inductive and formative function o Interacts with the inner enamel epithelium and leads to differentiation of

odontoblasts into dentine o …this leads on to the differentiation of ameloblasts to form enamel.

2. Reparative function o Acts as a method of protection to isolate the pulp from any kind of stimuli e.g. low

grade attrition 3. Defensive, or protective function

o Causes an inflammatory response in the pulp in reaction to acute irritation e.g. bacteria, deep cavity preparation or irritating filling.

4. Nutritive function o The blood nourishes dentine and enamel through odontoblasts

5. Sensory function o Stimuli causes pain which acts as a protective function



General appearance and structure

The dental cavity within each tooth is occupied by the dental pulp, which is surrounded by dentine except for the apical foramen, which is surrounded by cementum.

The pulp chamber can be theoretically split into two parts, the coronal pulp and the radicular pulp (root pulp)

The pulp communicates with the periapical tissues (tissues around the root) through its foramen. The foramen consists of nerves, blood vessels and lymph vessels passing through.

It is normal to see more than one small accessory foramen that connects the root canal to the periapical tissues.

The shape of the dental pulp is somewhat similar to the shape of the tooth.

The pulp horns are located as small “pointed” parts of the pulp that are located beneath cusps

Pulp is composed of:

o Cells

Odontoblasts- found close to predentin

Cell free zone- layer of Weil, beneath the odontoblasts cant be seen in developing tooth

Cell rich zone- rich in capillary and nerve network



Fibroblasts- are the most numerous cells of the pulp. Provides elasticity to the blood vessels.

o Blood vessels o Lymph vessels o Nerves o Thin collagenous fibers o …in a gelatinous ground substance

The pulp has a very rich blood supply; vessels enter and leave through the apical foramen.

Nerve supply

Both myelinated and unmyelinated nerve fibres are found in the dental pulp

Myelinated- are terminal branches of the trigeminal nerve. They can only register pain; they enter the root canals and branch out forming the plexus of Raschkow. They become unmyelinated as they reach the odontoblasts layer.

Unmyelinated - they are located in the walls of blood vessels and innervate the smooth muscle cells to regulate vasoconstriction.



33. Description of soft tissues of the periodontium

As mentioned previously, the periodontium consists of:

1. Alveolar bone 2. Cementum 3. Gingiva 4. PDL

These tissues surround and support the tooth; all components except from the gingival arise in the dental follicle.

The soft tissues of these is the Gingiva and the PDL

Gingiva

Surrounds the teeth and is bound to the buccal and lingual plates of the alveolar process

It is pale pink in colour and can be coloured by natural pigmentation



The part of the gingival closest to the cervical region is not directly attached to the tooth and is known as the free gingiva. In other cases it is known as attached gingiva.

Gingival fibers are collagen fibers that are found in the lamina propria and have an important role in maintaining and supporting the tooth. The fibers work as a functional unit, but they are arranged in 5 subgroups:

1. Dentogingiva – between the cementum and the lamina propria (beneath the junctional epithelium and marginal gingiva).

2. Dentoperiosteal – from the cementum into the periosteum (muscle) 3. Trans-septal – from the cementum and connect adjacent teeth in the arch 4. Alveologingival – from the bony alveolar crest to the lamina propria 5. Circular – run around the neck of the tooth and maintain a tight gingival collar



The interdental gingiva contains all the fiver groups illustrated above and the trans-septal fibers

The gingiva is supplied by branches of the infraorbital, nasopalatine, buccal, mental, lingual and palatine arteries.

Periodontal Ligament

It is a connective tissue that binds the tooth to the alveolar bone. It communicates with the bone marrow of the alveolar process through vascular channels (volkmann’s canals). They have nerve fibers that respond to occlusal pressure. (Note: fibroblasts synthesise fibres that become the PDL)

It’s situated within a ‘ground substance’ mainly composed of glycosaminoglycans, glycoproteins, and glycolipids. Cells making up the PDL are fibroblasts, epithelial cell rests of Malassez, osteoblasts, Osteoclasts, cementoblasts, macrophages and undifferentiated mesenchymal cells. The collagen fibers pass from the cementum and pass through the periodontal space and are embedded into the alveolar bone as Sharpey’s fibers.

The ligament has a sensory, supportive and protective function to withstand the forces of mastication and other forces alike. They also resist light occlusal impacts and have slight mobility as a cushion.

The width of the periodontal space varies from 0.1mm - 0.4mm

The periodontal fibers

Collagen is the most important structural component of the periodontal ligament. There are 5 principle fibers of the periodontium:

1. Alveolar crest group – similar to tran-septal fibers 2. Horizontal group - run horizontally below the alveolar crest 3. Oblique group- most numerous fibers and are found just beneath the coronal level 4. Apical group – surrounding the root apex 5. Inter-radicular group – at the division of roots



The periodontal fibers

The PDL are supplied by branches of the superior and inferior alveolar arteries, the apical region is supplied by branches of pulpal arteries of individual teeth.

34. Description of hard tissues of the periodontium

The hard tissues of the periodontium are cementum and alveolar bone

Cementum

Covers the root surface

Its colour is yellow

Softest between the dental mineralised tissues

Softer than enamel and dentine because it is less mineralised

Its chemical composition is similar to that of bone o 65% inorganic o 23% organic o 12% water

The main role of cementum is to serve as a medium in which the PDL can attach and stabilise the teeth

o 2 main types of cementum Acellular – lack of cellular components and covers the root surface Cellular – in the apical third of the tooth (last third)



Cells of the cementum:

1. Cementocytes- are cementum cells, they are cementoblasts and are embedded in cementum during cementogenesis

2.

3. Cementoblasts – located on the surface of cementum and produce the matrix and fibers of cementum

4. Cementoclasts – break down cementum

In the cementum we can find intrinsic and extrinsic fibers, sharpey’s fibers (collagen fibers which are embedded into cementum and alveolar bone, they are extensions of the PDL).

Alveolar bone



The alveolar process is that part of the jaw in which the teeth are found (tooth bearing). It is therefore composed of alveolar bone and supporting bone. The remaining jaw-bone is supporting the alveolar process as basal bone.

After eruption the bone is covered by a thick cortical bone and within it is spongy bone (also known as ‘Cancellous bone’).

Lamina dura – is a thin plate of alveolar bone, in the alveolar sockets that allows the passage of blood vessels to the periodontal ligament.

I hope my notes help you in passing and understanding Odontology.

Wishing you the very best in your career.



Amit Dattani

"Education is our passport to the future, for tomorrow belongs to the people who prepare for it today."

-Malcolm X

dentistry - odontology pdf

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