Wear of Human Enamel: A Quantitative in vitro Assessment

Abstract

Many factors influence the extent and rate at which enamel wears. Clinical studies in humans are limited by difficulties in the accurate quantification of intra-oral wear and by a lack of control over the oral environment. The purpose of this study was to determine the wear characteristics of human dental enamel under controlled experimental conditions. An electro-mechanical tooth wear machine, in which opposing enamel surfaces of sectioned, extracted teeth were worn under various conditions, was used to simulate tooth grinding or bruxism. Enamel surface wear was quantified by weight to an accuracy of 0.1 mg, with water uptake and loss controlled. The variables considered included the structure and hardness of enamel, facet area, duration of tooth contact, relative speed of opposing surfaces, temperature, load, pH, and the nature of the lubricant. Enamel wear under non-lubricated conditions increased with increasing load over the range of 1.7 to 16.2 kg. The addition of a liquid lubricant (pH = 7) reduced enamel wear up to 6.7 kg, but when the load increased above this threshold, the rate of wear increased dramatically. With the viscosity of the lubricant constant and pH = 3, the rate of wear was further reduced to less than 10% of the non-lubricated rate at 9.95 kg, after which the rate again increased substantially. Under more extreme conditions (pH = 1.2, simulating gastric acids), the wear was excessive under all experimental loads. When saliva was used as a lubricant, the amount of wear was relatively low at 9.95 kg, but rapid wear occurred at 14.2 kg and above. These results indicate that under non-lubricated conditions, enamel wear remains low at high loads due to the dry-lubricating capabilities of fine enamel powder. Under lubricated conditions, low loads with an acidic lubricant lead to little enamel wear, whereas very low pH results in a high rate of wear under all loads.

In vivo Measurements of Tooth Wear over 12 Months

“…This may be partially due to attrition of teeth subject to relatively greater forces during parafunction and partially due to an increased rate of erosion and tongue abrasion [Vieira et al, 2006] or a combination of attrition and erosion [Kaidonis et al, 1998;Austin et al, 2010]. These findings support the belief that tooth wear is a complicated multifactorial process [Bartlett et al, 1998] rarely attributed to a single cause.…”

Yuendumu legacy of a longitudinal growth study in Central Australia

“…Wear facets, produced by tooth-to-tooth contact during extreme mandibular movements, were evident in nearly all of the dental models of Yuendumu Aboriginal people, supporting the concept that tooth grinding (or bruxism) is a very common activity in all human populations. Following on from his studies of the Aboriginal dentition, Kaidonis extended his investigations of tooth wear to include experimental approaches based on the use of tooth wear machines that allowed dental specimens to be worn at constant loads for a defined number of cycles in the presence of various lubricants (Kaidonis et al, 1992a(Kaidonis et al, , b, c, 1993Kaidonis et al, 1998). It is a matter of some interest that anthropologist Steve Molnar from the Washington University, St Louis, used his earlier experience as an engineer to develop a motor-driven machine that simulated human masticatory movements.…”

The effect of casein phosphopeptide‐amorphous calcium phosphate on erosive dentine wear

“…18 Given that micro-hardness of mantle dentine (dentine within 1 mm from the dentino-enamel junction) is significantly less than that of underlying dentine, 19 dentine specimens were worn in two phases. A primary wear phase of 7200 cycles under a load of 32 N with deionized water as lubricant ensured that wear facets of similar surface areas were prepared well into dentine before its wear characteristics were assessed.…”