In humans eating unrefined diets, the dentition eventually becomes severely worn [1]. Since the Industrial Revolution, the diet in the West has become softer and easier to masticate and this has resulted in a marked reduction in tooth wear: while postcanine teeth in modern humans wear at 15– 20 m/year [2], incisors wore at 280– 360 m/year in prehistoric humans [3]. Because tooth wear in modern Western populations is ordinarily low, pronounced wear tends to have pathological causes. The main forms of abnormal wear are cervical wear associated mainly with excessive toothbrushing, heavy occlusal wear associated with bruxism, and erosive wear at many surfaces due to ingestion of acidic substances or regurgitation of acid. This paper is concerned with the wear processes that operate in these conditions, and with their interactions to produce the clinically observable result. The term tooth wear denotes the gradual loss of dental hard tissues through three processes: abrasion (wear produced by interaction between teeth and other

materials), attrition (wear through tooth– tooth contact) and erosion (dissolution of hard tissue by acidic substances). It has been postulated that in a fourth wearrelated process (abfraction) abnormal occlusal loading predisposes cervical enamel to mechanical and chemical wear [4]. All four processes are distinguished from loss of dental tissues through dental caries on the one hand and acute trauma on the other. The terms abrasion, attrition and erosion have been adapted from everyday usage and their meanings in the dental context can diverge from those in other fields, in particular from that of tribology, the science of wear, friction and lubrication. Tribology recognises a variety of mechanisms by which wear can occur, of which the most relevant to the present paper are twoand three-body abrasion and tribochemical wear [5]. In two-body wear, two moving surfaces contact each other directly and wear is produced by breaking away of asperities. In three-body wear, two moving surfaces are separated by an intervening slurry of abrasive particles, which remove material from both surfaces. In tribochemical wear, attack by a chemical agent weakens the superficial region of the material and enhances its susceptibility to mechanical forces. Clearly, in tribological terms, attrition would be subsumed under abrasion, erosion would be described as a form of tribochemical wear and abfraction as a form of fatigue [5]. It has been suggested that the time has come to align tooth wear terminology with tribology [6] but it seems likely that the terms outlined above, most of which have had their current meaning for decades, will persist despite their limitations. Each tooth wear process can, under some circumstances, operate alone. For example, nocturnal grinding of teeth will cause wear by attrition alone, drinking an acidic drink through a straw directed at the labial surface of the central incisors will cause wear by erosion alone, and brushing the teeth immediately on awakening will produce wear by abrasion alone. Yet, as many authors have suggested, the tooth wear observed in an individual will have resulted from a combination of all three main processes even though one may predominate [5, 7, 8]. If tooth wear were due to purely mechanical causes (abrasion and attrition), the total tissue loss at surfaces would fit a simple additive arithmetic model but wear is less simple. For example, tooth loading could create cracks which could cause particles of hard tissue to break off and act as an abrasive, thus converting a two-body attrition process into three-body abrasion [5], or the cracks would make the tissues more susceptible to abrasion, as suggested for abfraction [4]. If there is significant erosion, then the possibility of using simple arithmetic models to predict total tooth wear over time becomes remote, because erosion both removes hard tissue directly and renders tooth surfaces more susceptible to mechanical wear. As with any oral condition which is complex even when modelled in vitro, it is always tempting to discuss the aetiology of wear without reference to the

	MyDentalWebsite.com
	Enter your ZIP code to view plan details, savings information and participating dentists for all available discount dental plans in your area.
	The most dentists in combined networks ANYWHERE! Join a plan online instantly No claim forms or deductibles
				With the rising costs of dental care, finding ways to save money becomes more and more important. A great way to save money on these procedures is with the use of a discount dental plan. It's fast and easy, and you can save on all of your dental care needs! You have the freedom to choose from many quality discount dental plans. There is sure to be a plan to fit your needs and the needs of your family. There are no sign up fees, no claim forms and no deductibles. Join online instantly and start saving today!

This entry was posted on Friday, July 10th, 2009 at 2:13 pm and is filed under Dental Plans Coupon Update. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.