DENTAL HARD TISSUE DESTRUCTION 93 



TABLE l—Covtiivicd 

 Tooth destruction — Continued 



II. Dental resorption — Continued 



B. External pe:iodontal — Continued 



17. (e) Traumatic occlusion 



18. (/) Radiation injury 



III. Dental caries 



19. (a) Enamel 



20. (6) Dentin 



21. (c) Cementum 



IV. Erosion-abrasion 



A. In vivo destruction 



22. (a) Known exogenous chemical agents (acidic juices, etc.) 



23. (fe) Known endogenous chemical agents (gastric acid, etc.) 



24. (c) Chemical and abrasive combinations 



25. (d) Therapeutic agents 



26. (e) Experimental agents 



27. (/) Idiopathic erosions 



(i) Wedge- and disc-shaped 

 (ii) Irregular and figured 

 (iii) Circumscribed 



B. In vitro destruction 



28. (a) Experimental physical 



29. (6) Experimental chemical 



C. Postmortem destruction 



30. (a) Irregular boring canals 



31. {h) Discrete surface "lacunae" 



Dental Attrition 



Normal masticatory function and aging are accompanied by oc- 

 clusal and interproximal wear of the teeth. There ensues a shorten- 

 ing of the anatomical crowns of the teeth as well as of the dental 

 arch so as to reduce the relative force of stress and strain on the 

 root socket attachment to the alveolar bone. 



Excessive wear can occur on individual teeth that are out of 

 normal position or exposed to local trauma due to habits of chewing 

 (pipestem wear, etc.) or on the whole dentition if exposed to ab- 

 normal general wear due either to unusual food habits or to diurnal 

 or nocturnal bruxism. Even with regular function and food habits, 

 rapid wear of the teeth can take place in the absence of the lubricat- 



