Regressive alterationAre the group of retrogressive changes in the

teeth, which occur duo to non-bacterial causes & results in wear and tear of the tooth structures with impairment of function.

Some result from generalized aging processOthers duo to chronic persistent tissue injury

Tooth wearCauses of tooth wear:1. Attrition2. Abrasion3. Erosion4. Abfraction

Attrition It is the loss of tooth structure caused by tooth-to-tooth contact during occlusion & mastication.

Types :• Physiological A.• Pathological A.

Etiological factors for pathological attrition:Developmental Acquired Abnormal chewing habits Occupation Structural defect

Clinical features:

http://www.google.com.eg/imgres?imgurl=http://www.healthysmiles.org.nz/assets/resized/img/sm/56/23/Attrition-1-0-400-0-400.jpg&imgrefurl=http://www.healthysmiles.org.nz/default,54,image-gallery.sm&usg=__kK-yYmGclWxGrOv2yE9ucOE6n2E=&h=263&w=400&sz=28&hl=ar&start=12&zoom=1&itbs=1&tbnid=Mnzf55ogR9QxbM:&tbnh=82&tbnw=124&prev=/images%3Fq%3Dattrition%26hl%3Dar%26gbv%3D2%26tbs%3Disch:1

Abrasion It is the pathological loss of tooth structure

or restoration secondary to the action of an external agent (abnormal mechanical process).

The most common cause of abrasion is tooth brushing that combines an abrasive toothpaste with heavy pressure and a horizontal brushing stroke.

Other items: pencils, toothpicks, pipe stems and bobby pins (hair grips).

Chewing tobacco, biting thread, inappropriate use of dental floss.

Clinical features:

Erosion It is the loss of tooth structure caused by

chemical process beyond that associated with bacterial interaction with the tooth.

Types ( depending on etiology):IntrinsicExtrinsic

Etiology :Medications Acidic foods and beveragesChronic involuntary regurgitationVoluntary regurgitation (Anorexia Nervosa)Industrial environmental exposure

Clinical features:

Abfraction

Schematic view of abfraction – enamel prism fracturing due to stress effect of occlusal load which is focused on the area along the marginal edges of the crowns.

Loss of tooth structure that results from repeated tooth flexure caused by occlusal stresses.

Clinical features:

Dentinal sclerosis(Transparent dentin)

Sclerosis of 1ry dentin is a regressive alternation in tooth substance that is characterized by calcification of dentinal tubules.

Etiology: injury to dentin by caries or abrasion, normal aging process, abrasion or erosion.

Mechanism : Not well understood.

Dead tracts

http://210.44.214.13/lab/oral%20histology%20slides/images/03_17bb.jpg

Secondary dentinIt is dentin that is formed and deposited

in response to a normal or slightly abnormal stimulus, after the complete formation of the tooth.

Types :Physiological 2ry dentinReparative 2ry dentin

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http://210.44.214.13/lab/Oral%20Histology%20slides/images/03_16bb.jpg

James K. Oral development and histology. 3rd e,2002

Reticular atrophy of the pulpClinically symptomless & responds normally

to vitality tests.Histologically, presence of large vacuolated

spaces in pulp, with reduction of cellular elements. Degeneration and disappearance of odontoblasts.

Presently, this condition is purely an artifact brought about by autolysis of the pulp tissue and doesn’t occur in vivo.

Pulp calcificationTwo morphological forms of pulp calcifications

are discrete pulp stones (denticles, pulp nodules) and diffuse calcification.

Types: True denticles: made up of localized masses of

calcified tissue that resemble dentin because of their tubular structure.

1. Free D. 2. Attached D. False denticles: composed of localized masses

of calcified material & don’t exhibit dentinal tubules.

1. Free D. 2. Attached D.

True denticle False denticle

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Diffuse calcification “Calcific degeneration”Its usual pattern is in amorphous, unorganized

linear strands or columns paralleling the B.Vs and nerves of the pulp.

Etiology of pulp calcifications: unknownPathogenesis:Local metabolic dysfunction Trauma

hyalinization of injured cells Vascular damage (Thrombosis) Fibrosis Mineralization (Nidus formation) Growth with time

PULP STONE

Resorption of teeth It is chronic progressive damage or loss of

tooth structure due to the action of cells called odontoclasts.

Pathological resorption may be external or internal.

External resorption• It is lytic process occurring in the cemetum or

cementum and dentin of the roots of teeth.• Factors associated with external resorption:1. Cyst & tumors.2. Dental trauma. 3. Excessive mechanical forces.4. Excessive occlusal forces.5. Grafting of alveolar clefts.6. Hormonal imbalances.7. Intracoronal bleaching of pulpless teeth.8. Local involvement by herpes zoster.9. Paget’s disease of bone.10.P.D treatment.11.P.A inflammation.12.Pressure from impacted teeth.13.Reimplantation of teeth.14. Idiopathic.

Radiographically, appears as a “moth-eaten” loss of tooth structure in which the radiolucency is less well defined and demonstrates variation in density.

Invasive cervical resorption

Multiple idiopathic root resorption: several teeth may be involved, and underlying cause for the accelerated destruction may not be obvious.

Histopathologically, numerous multinucleated dentinoclasts located in the areas of structure loss. Areas of resorption often are repaired through deposition of osteodentin. In large defects, external inflammatory R. results in deposition of inflamed granulation tissue, and areas of replacement with woven bone may also be seen. http://www.google.com.eg/imgres?imgurl=http://

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Histologic appearance of a tooth exhibitingexternal inflammatory root resorption, showing multinucleated clast cells adjacent to resorbed dentin and bone. A chronic inflammatory cellular infiltrate is also evident in the area.

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Histologic appearance of an extensive invasive cervical resorption with radicular extensions. Masses of ectopic calcific tissue are evident both within the fibrovascular tissue occupying the resorption cavity and on resorbed dentin surfaces. In addition, communicating channels can be seen connecting with the periodontal ligament (large arrows). Other channels can be seen within the inferior aspect of the radicular dentine (small arrows). (Hematoxylin–eosin stain)

Internal resorptionTwo main patterns:1.Inflammatory R.: It occurs duo to intense inflammatory reaction within the pulp tissue. The resorbed dentin is replaced by inflamed granulation tissue.

Radiographically, a uniform, well-circumscribed symmetric radiolucent enlargement of the pulp chamber or canal.

Internal resorption ( pink tooth of Mummery)

Internal resorption. Balloon like enlargement of the root canal

Histopathology :• The pulp tissue in the area of destruction is

vascular and exhibits increased cellularity and collageniztion.

• Immediately adjacent to the dentinal wall are numerous multinucleated dentinoclasts, which are histologically and functionally identical to osteoclasts.

• An inflammatory infiltrate characterized by lymphocytes, histiocytes, and PMN leukocytes is not uncommon.

2. Replacement or metaplastic resorption:It occurs duo to absence of any

inflammatory reaction within the pulp.

Portions of the pulpal dentinal walls are resorbed and replaced with bone or cementum-like bone.

Radiographically, appears as an enlargement of the canal that is filled with a material that is less radiodense than the surrounding dentin. The outline of destruction is less defined.

J. O. Andreasen. Textbook and color atlas of traumatic injuries to the teeth

Histopathologically, the normal pulp tissue is replaced by woven bone that fuses with the adjacent dentin.

Hypercementosis( Cementum hyperplasia)

It is a non- neoplastic condition in which excessive

cementum is deposited in continuation with the normal radicular cementum.

It may be regarded as a regressive change of teeth characterized by excessive amounts of secondary cementum on root surfaces.

Types:• Localized & Generalized Etiology: Accelerated elongation of a tooth. Inflammation about a tooth. Tooth repair. Osteitis deformans, or Paget’s disease of bone. Others: hyperpituitarism, cleidocranial dysostosis.

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Excessive amount of secondary or cellular cementum deposited directly, over typically thin primary acellular cementum. Secondary cementum is called osteocementum duo to its cellular nature and its resemblance to bone. Cementum typically arranges in concentric layers around the root and frequently shows numerous resting lines parallel to root surface.

http://www.dental.pitt.edu/informatics/periohistology/en/cementum/histo123a2.htm

Cementicles• Small foci of calcified tissue, not necessarily

true cementum, which lie free in P.D.L of the lateral and apical root areas.

• The exact cause is unknown, but they represent areas of dystrophic calcification and thus are an example of a regressive or degenerative change.

• Formation :

• Types:1. Free Cementicles2. Attached or sessile Cementicles3. Embedded Cementicles

http://www.dental.pitt.edu/informatics/periohistology/en/cementum/histo125Aa2.htm