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TIKRIT UNIVERSITY COLLEGE OF

DENTISTRY

" The shape and size of maxilla to mandible in the class II malocclusion"

Submitted by

Shams Bayan Yassin

Doha Salah Omer

SUPERVISOR :

Assist.Dr.Maha Essam

AC 2020 AH1440ـ

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نكليــــــة طـب الأسنــــــــا –جامعـــــة تكــــريت

شكل وحجم الفك العلوي بالنسبه الى الفك السفلي في التصنيف “

"الثاني من سوء الأطباق

بحث مقدم من قبل:

شمس بيان أسماعيل

ضحى صلاح عمر

: المشرفون

.مها عصام عبد العزيزم.د

م0220 هـ 4014

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بسم الله الرحمن الرحيم

لْمٍ ي عِّ )وَفوَْقَ كُل ِّ ذِّ

عَلِّيمٌ(

صدق الله العظيم

(76)يوسف من الآية

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CHAPTER ONE

Abstract

The changes in the dental arch dimensions that occur as a result of growth and

treatment are of interest to the orthodontist and require careful consideration

during treatment planning. A greater understanding of these changes could

influence the patient's expectations from treatment as well as the formulation of

the treatment and retention plans by the clinician. Several researchers recognize

that there is variability in the size and shape of arch form in relation to Angle’s

classes of malocclusion . In addition, the width, length and depth of dental arches

have had considerable implications in orthodontic diagnosis and treatment

planning in a modern dentistry based on prevention and early diagnosis of oral

disease.

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CHAPTER TWO

Introduction

Malocclusion _nowadays is one of the most frequent oral cavity anomalies. It is

defined as an abnormal occlusion in which teeth are not in a normal position in

relation to adjacent teeth in the same jaw or to the opposing teeth when the jaws

are closed.(1)

Malocclusion is not a disease but a morphological variation which may or may

not be associated with pathological conditions.(1)

Class II malocclusion is the condition in which the mandibular first molars occlude

distal to the normal relationship with the maxillary first molar. The etiology of

class II malocclusion varied between skeletal, soft tissues, dental factors and

habits. Skeletal class II could be because of protrusion of maxilla, retrusion of

mandible and combination of both. The treatment modalities of any skeletal

problem include Growth modification, Dental camouflage and Orthognathic

surgery.(2)

Natural dentition represents a balanced position between the surrounding

muscles and the tongue, with the dental arch balanced with craniofacial

structures(3).

The position of the anterior tooth and rearmost molar, ridge width, length, and

height can be important standard criteria in prosthodontic treatment for the

production of a natural profile and functional restoration for edentulous and

dentate patients. Understanding the natural dental arch form is important, as the

average values of the anatomical shape and the size of the arch are useful for

prosthetic restoration.(4) For this reason, many studies have addressed the shape

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and size of the dental arch.Race and ethnicity influence the form of the human

craniofacial complex, and the dental arch form is correlated with the craniofacial

skeletal pattern In addition, the morphological characteristics of the size and

shape of the dental arch, and the arrangement of dentition differ between race,

culture, and region.(5)

Analysis of the study model is one of the undeniable procedures in orthodontic to

interpret diagnosis and treatment planning for patients with different

malocclusion. The analysis of study model has been used for three-dimensional

evaluation in the upper and lower arch forms with the relationship of occlusal

which can be calculated by mean of analysis using arch length, arch form

dimension, and mesiodistal tooth size .(6),(7) Malocclusion can be diagnosed if

there is a discrepancy or surplus of tooth material either in maxillary arch form or

mandibular arch form.(8),(9).

The dental arch form is defined as the curving shape formed by the configuration

of the bony ridge (10) Different methods have been developed to describe the

dental arch morphology ranging from simple classification of arch shape (6)

through combinations of linear dimensions(11,12) to complex mathematical

equations (9,13).

In 1932, Chuck classified the arch forms as tapered, ovoid and square for the first

time. These arch forms can also be expressed as narrow, normal and wide (6).

Especially in determining the arch wire forms utilized at the initial phase of the

treatment, he advocates that making a choice between these three forms would

be better than using a single arch form(11).The arch form should be determined in

relation with each patients’ pre-treatment dental model and especially in relation

with each patients’ ethnic group in order to achieve an esthetic, functional and

stable arch form out-come(11).

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CHAPTER THREE

Literature Review

Occlusion:- is the manner in which the lower and upper teeth intercuspate

between each other in all mandibular positions or movements. Ash & Ramfjord

(1982)(14) state that it is a result of neuromuscular control of the components of

the mastication systems viz., teeth, maxilla & mandibular, periodontal structures,

temporomandibular joints and their related muscles and ligaments.Furthermore,

occlusion is a phenomenon that has been generally classified by experts into

three types, namely, normal occlusion, ideal occlusion and malocclusion . A–D,

Schemata of Class I normal occlusion and Class I crowded, end-to-end, and Class II

division 1 malocclusions Ideal occlusion is a hypothetical state, an ideal situation.

McDonald & Ireland (1998)(15) defined ideal occlusions as a condition when

maxilla and mandible have their skeletal bases of correct size relative to one

another, and the teeth are in correct relationship in the three spatial planes at

rest. Normal occlusion was first clearly defined by Angle (1899)(16) which was the

occlusion when upper and lower molars were in relationship such that the

mesiobuccal cusp of upper molar occluded in buccal cavity of lower molar and

teeth were all arranged in a smoothly curving line. Houston et al, (1992)

(17)defined normal occlusion as an occlusion within accepted definition of the

ideal and which caused no functional or aesthetic problems. Andrews (1972)(18)

had previously also mentioned of six distinct characteristicsobserved

consistentlyin orthodontic patients having normalocclusion,viz.,molarrelationship,

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correct crown angulation & inclination, absence of undesirable teeth rotations,

tightness of proximal points, and flat occlusal plane (the curve of Spee having no

more than a slight arch and deepest curve being (1.5 mm).

Malocclusion:-

is a misalignment or incorrect relation between the teeth of the two dental

arches when they approach each other as the jaws close and

usually caused by problems with the shape or size of the jaw or teeth. A

common cause is having too much or too little room in the jaw. If a child's

jaw is small, the teeth may grow in crowded or crooked. If there's too much

space in the jaw, the teeth may drift out of place.(13),(19)

Causes :-

Malocclusion is most often hereditary. This means it is passed down through

families. It may be caused by a difference between the size of the upper and

lower jaws or between the jaw and tooth size. It causes tooth overcrowding or

abnormal bite patterns. The shape of the jaws or birth defects such as cleft lip

and palate may also be reasons for malocclusion.Other causes include(13),(19):

Childhood habits such as thumb sucking, tongue thrusting, pacifier use

beyond age 3, and prolonged use of a bottle

Extra teeth, lost teeth, impacted teeth, or abnormally shaped teeth

Ill-fitting dental fillings, crowns, dental appliances, retainers, or braces

Misalignment of jaw fractures after a severe injury

Tumors of the mouth and jaw

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abnormally shaped or impacted teeth

poor dental care that results in improperly fitting dental fillings, crowns, or

braces

airway obstruction (mouth breathing), potentially caused by allergies or by

enlarged adenoids or tonsils .

There are different categories of malocclusion (13),(19):-

Class 1 malocclusion is the most common. The bite is normal, but the upper

teeth slightly overlap the lower teeth.

Class 2 malocclusion(20), called retrognathism or overbite, occurs when the

upper jaw and teeth severely overlap the bottom jaw and teeth.

Distal relationships mandible to maxilla

mesiobuccal cusp of maxillary first permanent molar articulates mesial to

buccal groove of mandibular permanent first molar .

Division 1:- the maxillary incisors labioversion

Division 2:- the maxillary central incisors are near normal or slightly

linguoversion

maxillary lateral incisors have tipped labially

Subdivision :- when the dislocation occurs on one side.

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Etiology of Cl II (20):-

1-Heredity 2-Developmental defects 3-Truma 》 a)prenatal truma and birth

injuries

b) postnatal truma

4-physical agents 》 a) premature extraction of primary teeth b) Nature of food

5-Habits 》 a) thumb sucking b)Tongue thrusting c)lip sucking and lip biting

d)Nail biting

6- Disease 》 a)systemic diseases b)Endocrine disorders c) local diseases

7-Malnutrition

Clinical features of Cl II DIV 1(21)

Extaoral features

• Profile :- convex

• Deep mento-labial sulcus

• Upper lip short hypotonic

• Lips- competent/incompetent

• Lip trap

Intraoral features

• Class II molar relation

• Proclined maxillary anteriors ,increased overjet

• Flaring and spaced dentition

• V shaped arch and deep palate

• Deep curve of space

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Abnormal muscle activities

• Abnormal buccinator activity

• Lower postioning of tongue

• Which predisposed of posterior cross bite

• Hyperactive mentalis muscle (retrognathic mandible)

Clinical features of Cl II DIV 2 (21)

Extraoral features

• Profile:- stright/convex

• Reduced lower facial height

• Mento-labial sulcus : normal/ deep

• Path of closure :- backward

Intraoral features

• Class II molar relationship

• Retroclined upper central proclined maxillary lateral incisors

• Overjet:- decreased,deep bites

• U shaped/square arches • Deep curves of spee

Treatment modalities(20)

Cl II malocclusion

Growing patient non_growing patient

Skeletal Dental Dental skeletal

Orthopaedic/ Function appliances Fixed orthodontic treatment

Surgical treatment

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Class 3 malocclusion(22)

definition:

according to British standards incisor classification,in class 3 malocclusion the

lower incisor edges lie anterior to the cingulum plateau of the upper incisor the

overjet is reduced or reversed according to Angle's classofication,in class 3 the

mesiobuccal cusp of the lower first molar occludes mesial to the class 1 position.

Aetiology of Cl III

1. long mandible

2.forward placement of glenoid fossa positioning the mandible more anteriorly

3.short and/or retrognathic maxilla

4.short anterior cranial base

Normal growth and development of the arch form and width(23),(10)

1. Arch dimensions change with growth.

2. It is therefore necessary to distinguish changes induced by appliance therapy

from those that occur from natural growth.

3. The average changes achieved in a sample reported by Moyers et al 1976

The changes in width vary between males and females. The male have

more growth.

More growth in the upper than the lower arch. This growth occurs mainly

between the ages of 7 and 12 years of age and is approximately 2 mm in

the lower arch and 3 mm in the upper.

After the age of 12, growth in arch width is seen only in males while the

female show constriction.

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Changes in arch width may not be accompanied by changes in arch length;

there is a tendency toward a decrease in arch depth in the third and fourth

decades.

Arch size and form in untreated adults:-

-Adulthood _ the lengthy phase following attainment of biologic maturity_ often

is perceived as a period of "no change", or one of slow deterioration. Teeth

consolidate during the adolescent age interval, apparently by mesial drift, and the

arch length decreases. Arch widths also change with age, but the magnitude of

the change is smaller

-Some variables- particularly those between arches(incisor overbite snd overjet,

molar relationship) and mandibular intercanine measures of arch width and

length changed significantly. Arch widths increased over time especially in distal

segments, whereas arch lengths decreased. These Changes significantly altered

arch shape towards shorter-broader arches. The data suggests that changes

during adulthood occur most rapidly during the second and third decades of life,

but do not stop thereafter.(23)

Studies on relapse in archform (Felton , Little and others)(24)

1. Arch form changes: 65% of cases had a change in archform, and 65%

returned to their pre-treatment shape (Total relapse).

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2. Arch width changes:-

1- Growth: There is no evidence that appliances can stimulate "growth" beyond

that which would normally occur.

-2 Age: It seems logical to consider increasing arch size at a young age so that

skeletal, dental-alveolar, and muscular adaptations can occur before the eruption

of the permanent dentition.

3- Amount: Approximately 3 mm stable upper molar expansion can be achieved

and stable. Approximately 1 mm stable lower molar expansion can be achieved

and stable .

4. Exceptional Local factors

Buccally or lingually displaced canine can be repositioned to their normal

position without risking the stability of arch width changes.

Deep-bite cases (such as Class 11/2 cases) in which lower canines have

inclined lingually in response to the palatal contour of the upper canines

(1974, Shapiro).

Cases where rapid maxillary expansion is indicated in the upper arch and

this expansion is maintained post-treatment (Haas 1972, Sanstorm, 1998)

but to very limited extents.

Implication of the size and shape of dental arch (25) :-

1-The size and shape of the dental arches have considerable implications for

orthodontic diagnosis and treatment planning. These have an effect on the space

availability, stability of dentition.

2-Dental aesthetics.

3-Heath status of the periodontal ligament

4-Treatment planning (space available)

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5-Treatment mechanics

6-bracket prescription

7-selection of orthodontic wires

8-Stability and prognosis.

Factors determine the arch forms(25),(26):-

1. Ethnicity with underlying genetic basis that determines the basal bone which

accommodate teeth. In Caucasian population, 45% have ovoid, 45% tapered

and 10% square.

2. Type of malocclusion, like in cl3 the majority are square form,

3. Musculature which adapt the above position to the new one

4. Environmental factors like in standing teeth, habits and crowding

5. Orthodontic treatment.

Basic Arch Forms(26)

Chuck in 1932 classified arch forms as tapered, square and ovoid, which

constitute the basic arch forms:-

1-Square Arch Forms:-

For patients with broad arches, this is used. The square form is useful in

maintaining expansion in upper-arch after rapid expansion.When superimposed,

the three shapes vary mainly in intercanine and inter-first-premolar width, giving

a range of approximately 6 mm in this area.

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Indication

Cases with broad arch forms.

In cases that require buccal uprighting and expansion of the arch.

If over expansion has been achieved.

2-Ovoid Arch Forms:-

Being the most preferred arch form, it results in minimal post-treatment relapse.

It shows a greater intercuspal distance than tapered form.

Indication

This arch form has been used in the majority of treated cases.

During initial archwire stages like when using multistrand wires, .014 and

.016 stainless steel round wires, and all Nitinol Heat-Activated nickel

titanium wires.

When using .018, .020 round stainless steel wires and rectangular stainless

steel wires (wires that significantly influence arch form) one of the above

three arch forms is selected.

3-Tapered Arch Forms:-

It has the narrowest intercanine width and is useful early in treatment for

patients with narrow, tapered arch forms, especially in cases with gingival

recession in the canine and premolar regions (27)

Indication

Patients with narrow tapered arch forms.

Gingival recession in the cuspid and bicuspid regions. This situation occurs

most frequently in adult orthodontic cases.

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Also, cases with tapered arch forms undergoing partial treatment in one

arch only benefit from this arch form, so that no expansion occurs in the

treated arch.

Note:-When comparing the arch form (square, tapered and ovoid) according to

different classes, the commonest arch form in class I was the ovoid followed by

tapered, however, in class II and class III subjects, the commonest arches were

tapered. These findings strongly suggested that ovoid form should be considered

when dealing with Class I cases and tapered form when Class II and III. (28,29,24).

Dental and Alveolar Arch Widths in Normal Occlusion, Class II Division

1 and Class II Division 2:-

findings indicate that the maxillary interpremolar width, maxillary canine,

premolar and molar alveolar widths, and mandibular premolar and molar alveolar

widths were significantly narrower in subjects with Class II division 1 malocclusion

than in the normal occlusion sample. The maxillary interpremolar width, canine

and premolar alveolar widths, and all mandibular alveolar widths were

significantly narrower in the Class II division 2 group than in the normal occlusion

sample. The mandibular intercanine and interpremolar widths were narrower and

the maxillary intermolar width measurement was larger in the Class II division 2

subjects when compared with the Class II division 1 subjects. Maxillary molar

teeth in subjects with Class II division 1 malocclusions tend to incline to the buccal

to compensate the insufficient alveolar base. For that reason, rapid maxillary

expansion rather than slow expansion may be considered before or during the

treatment of Class II division 1 patients.(30)

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CONCLUSION

Dental arch dimensions, including dental arch width, length, and form, are

important values for the diagnosis, treatment, planning, and treatment outcomes

concerning patients who are seeking orthodontic treatment in all age groups.

Different ethnic groups and populations display variable dental arch

measurements and characteristics. It is well-known that dental arch dimensions

continue changing throughout growth and development, but during adulthood,

the changes decrease.This explains why many researchers were interested in

investigating the changes in dental arch dimensions during each stage of growth

and development.

The basic principle of arch form in orthodontics is that within reason, the patient’s

original arch form should be preserved. There is no generalised, universal arch

form as each arch form is a unique expression of individual development. Thus, a

study on arch forms is an important aspect of diagnosis and treatment planning.

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CHAPTER FOUR

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