age change in dental hard tissue

1. AGE CHANGES IN DENTAL HARD TISSUES PR ESENTED BY JigyashaTimsina BDS 2 nd year

2. AGING Definition : Refers to irreversible and inevitable change that occurs with time It is also defined as sum of all morphological and functional alteration in an organism that leads to functional impairement

3. Biological aging process is : Universal : detectable in all members of the species Progressive : develop gradually and irreversibly Deleterious : harmful to the survival of individual

4. Aging and The Hard Tissues

5. Enamel changes Attrition Change in permeability Discoloration Chemical and surface changes

6. ATTRITION Physiological wear of occlusal or incisal and proximal surfaces of teeth resulting in a decrease in vertical dimension In severe attrition dentin may be exposed

7. Change in permeability Young enamel acts as a semi-permeable membrane and permits slow passage of water and molecular substances through the pores between the crystals. With age the enamel crystals grow in size and the pores between them is obliterated resulting in reduced permeability of the enamel.

8. Discoloration Normal: white to yellowish white. With age darkening seen. Thought to be because of: Loss of enamel rods- this loss alters the light reflection of enamel and results tooth color change. Deepening of dentin color seen through progressively thinning layer of enamel.

9. Chemical and surface changes Increase in fluoride and nitrogen content. Water and organic content decrease with age. Reduction in organic content reduces chance of caries in teeth with age. Loss of Perikymata

10. DENTIN The main changes in dentin associated with aging are Increase in sclerotic dentin. Increase in the number of dead tracts. Increase in formation of reparative and reactive dentin. Vitality of dentin

11. Dead Tracts In normal dentin the odontoblastic processes may disintegrate and the empty tubules get filled with air. These are called dead tracts. They appear black in transmitted light and white in reflected light. In narrow pulpal horns degeneration of odontoblast seen due to crowding of odontoblasts . thought to be the initial step in the formation of sclerotic dentin. Dead tract

12. Sclerotic Dentin\Transparent dentin Refers to the dentinal tubules that have become occluded with calcified materials. It may be result of the aging process and called physiologic dentin sclerosis or may occur due to some irritation like caries , attrition, abrasion and called reactive dentin sclerosis When this occurs in several tubules in the same area , the dentin assumes a glassy appearance and become transparent

13. Most common in apical 3 rd of the root. It appears transparent or light in transmitted light and dark in reflected light. Sclerotic dentin

14. Reparative –Reactive Dentin If the provoking stimulus cause destruction of the original odontoblasts , the new, less tubular dentin formed by newly differentiated odontoblast like cells is called Reparative dentin. However if the odontoblast survive the provoking stimuli the dentin produced by them is called Reactionary dentin

15. Reparative dentin Reactive dentin

16. Vitality of dentin Since the odontoblasts do not degenerate normally, dentin is laid down throughout life. Although after the teeth have erupted and become functional dentinogenesis slows and further dentin formation is at much slower rate

17. Cementum Hypercementosis . Cementicles. Change in permeability. Cementum re-absorption and repair

18. Hypercementosis It is an abnormal thickening of the cementum . may be generalized or localized ,diffused or limited. Hypercementosis is termed  cementum hypertrophy   if the overgrowth improves the functional qualities of the cementum and is termed cementum  hyperplasia   if it is not correlated with increased function.

19. FIG : A FIG : B

20. Cementicles They are ovoid or round calcified structure that are formed as a result of calcification of the degenerated periodontal tissue or the epithelial rests of Malssez . Cementicles may be: 1. Free in the periodontal ligament. 2. Attached the cementum 3. Embedded in the cementum FC-free cementicle SC -sessile cementicle

21. Permeability : The permeability of cementum decreases gradually by age. The permeability from the periodontal side is lost except in the most recently formed layer of cementum , while that from the dentine side remains only in the apical region. Cementum Resorption and Repair : Cementum resorption can occur after trauma or excessive occlusal forces . After resorption ceases, the damage is usually repaired. If the repair establishes the former outline of the root surface it is called   anatomic repair.  However if only a thin layer of cementum is deposited and the root outline is not constructed it is called   functional repair.

22. Alveolar bone Bone resorption is the major age change in alveolar bone. Common site of resorption- labial aspect of alveolar crest.

23. Other changes The marrow space have fatty infiltration. Loss of maxillary bone is accompanied by increase in size of maxillary sinus. Internal trabecular arrangement is more open which indicate bone loss.

24. References Orban’s oral histology and embryology Ten Cate’s oral histology Oral anatomy ,histology and embryology Berkovitz , Holland , Moxham

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