Wear of human teeth: a tribological perspective

The four main types of wear in teeth are attrition (enamel-on-enamel contact), abrasion (wear due to abrasive particles in food or toothpaste), abfraction (cracking in enamel and subsequent material loss), and erosion (chemical decomposition of the tooth). They occur as a result of a number of mechanisms including thegosis (sliding of teeth into their lateral position), bruxism (tooth grinding), mastication (chewing), toothbrushing, tooth flexure, and chemical effects. In this paper the current understanding of wear of enamel and dentine in teeth is reviewed in terms of these mechanisms and the major influencing factors are examined. In vitro tooth wear simulation and in vivo wear measurement and ranking are also discussed

Clinical measurement of tooth wear: tooth Wear Indices

Attrition, erosion, and abrasion result in alterations to the tooth and manifest as tooth wear. Each classification corresponds to a different process with specific clinical features. Classifications made so far have no accurate prevalence data because the indexes do not necessarily measure a specific etiology, or because the study populations can be diverse in age and characteristics. Tooth wears (attrition, erosion and abrasion) is perceived internationally as a growing problem. However, the interpretation and comparison of clinical and epidemiological studies, it is increasingly difficult because of differences in terminology and the large number of indicators/indices that have been developed for the diagnosis, classification and monitoring of the loss of dental hard tissue. These indices have been designed to identify increasing severity and are usually numerical, none have universal acceptance, complicating the evaluation of the true increase in prevalence reported. This article considers the ideal requirements for an erosion index. A literature review is conducted with the aim of analyzing the evolution of the indices used today and discuss whether they meet the clinical needs and research in dentistr

Prevalence, clinical features and factors associated with tooth wear in the Ukrainian young adult population

Tooth wear in young individuals has increased significantly in recent years. Thus, the purpose of the present study is to estimate the prevalence and to learn clinical features and factors associated with tooth wear in the Ukrainian adult population age to 40 years. Methodology. Data on clinical investigation were collected in a survey of 2053 employees of ore mining enterprise aged 18-40 years. It has been studied the prevalence and clinics of tooth wear depending on age and sex, and also taking into account influencing of the working-environment harmful and other etiological factors. The investigation involved the analysis of tooth contacts on working and balancing sides and the definition of type of intercuspidation which is described by occlusal concepts. Results. According to the obtained data, the prevalence of tooth wear was 27.6 ± 1.0 %. The process was the most severe in spreading and depth of loss in the presence of working-environment harmful factors (32.1 ± 1.5 % vs. 23.4 ± 1.3 %, p < 0.05). The absence of any strong correlation between progressive tooth wear and such etiological factors as age (r = 0.48; p < 0.05), work experience in harmful production (r = 0.61; p < 0.05), the dust content in air of the working zone (r = 0.63; p < 0.05), the presence of background pathology of the gastrointestinal tract (r = 0.42; p 0.05), the presence of local factors (r = 0.38; p <0.05), excessive oral hygiene (r = 0.12; p <0.05), use of carbonated drinks (r = 0.32; p <0.05) suggested the impossibility of providing a leading trigger mechanism for the development of the tooth wear. As a result of the clinical study of dental contacts in lateral occlusion, it was found that 30.0 ± 3.7 % persons had canines’ contacts and 70.0 ± 3.7 % had group contacts of canines, premolars and molars under physiological tooth wear. Otherwise, in the group of pathological (increased) tooth wear, canines’ contact on the working side was established in 23.5 ± 4.2 % of cases, group contacts – 76.5 ± 4.2 %. Thus, significant differences between the prevalence of occlusal concepts in the research group had not been found (p > 0.05). Intercuspidation on balancing side was found in 36.0 ± 3.9% of persons who have physiological tooth wear, and 63.3 ± 4.8% – pathological one (p < 0.05). Significant difference between the prevalence of bilateral balancing occlusion in research groups demonstrated that these occlusal contacts promoted increased wear of occlusal surfaces, especially chewing segments of dentition. Thus, dispensary observation of patients with tooth wear should take into account the clinical and pathogenetic features of the disease, comply with the principles of complexity of medical and diagnostic measures, fulltime care, stage and preventive direction. Conclusion. Tooth wear is a prevalent condition in this population. Significantly higher prevalence and severity of tooth wear was associated with the exposure of harmful factors of dust-gas mixture from the production. In addition, other etiological factors contribute to the development of the pathological process in enamel and dentine, among which peculiarities of occlusal contacts, described as “occlusal concepts”. To reduce the prevalence and intensity of tooth wear, in particular in the adult population age to 40 years, there is a need for dispensary, which involves early diagnosis, regular examinations, prophylaxis and treatment, aimed at preventing complications

New Bathonian (Middle Jurassic) sauropod remains from the Valtos Formation, Isle of Skye, Scotland

The discovery of a sauropod tooth and a single sauropod footprint from the Valtos Formation supplements our knowledge of these dinosaurs from the Middle Jurassic of the Isle of Skye. Although the family cannot be determined from this single tooth, it is thought that it represents a primitive eusauropod and may belong to a similar sauropod to that previously described from limited isolated osteological evidence (caudal vertebra, damaged humerus and a rib). The characteristics that suggest this affinity include evidence of denticles on one edge of the tooth, wrinkling and granulation of the enamel, wear suggesting crown-to-crown occlusion, and the spatulate tooth shape. The single sauropod footprint is the oldest record of a sauropod footprint from the Middle Jurassic of Skye

A model for the prediction of tooth wear in individuals

The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.Background: Easily applied, age-specific standards are useful in assisting clinicians to decide whether the extent of tooth wear observed in a given patient at a specific age is acceptable or whether intervention is indicated. Method: A simple method of scoring tooth wear and previously established mathematical relationships between tooth wear scores and age, provide the basis of a method for predicting tooth wear scores. In its most specific form, the method can be used to predict tooth wear scores for individual patients at subsequent ages. Alternatively, tables or graphs can be consulted to provide a less precise prediction of tooth wear that can assist clinicians to decide whether the amount of wear reflects high, moderate or low rates of wear at the specified age. Conclusion: In cases where there is no reason to believe that aetiological factors have changed significantly over time, data obtained from the methods described can assist clinicians to plan appropriate management for patients presenting with unacceptable levels of tooth wear.LC Richards, JA Kaidonis, GC Townsen

The rise of dentine hypersensitivity and tooth wear in an ageing population

Our understanding of the aetiology of dentine hypersensitivity (DH) has changed dramatically over the past few decades. It is no longer an enigma, but other problems exist. The prevalence of DH in the world and in particular in the UK is increasing, predominately due to increases in tooth wear and the erosive dietary intake in the younger population. DH is increasingly reported in all age groups and is shown to provide clinical indication of an active erosive tooth wear. As the population ages and possibly retain teeth for longer, the likelihood of tooth wear and DH could increase. This paper describes the prevalence, aetiology, diagnosis and management of DH in relation to tooth wear, which work together through a surface phenomenon. The aim is to raise awareness of the conditions and to help inform a prevention strategy in an ageing population, which starts from younger age groups to reduce disease into older age

Consequences of Tooth Loss on Oral Function and need for Replacement of Missing Teeth Among Patients Attending Muhimbili Dental Clinic

Tanzanian oral health services constitute mainly of tooth extractions. Consequently, individuals susceptible to dental caries and periodontal diseases will have a substantial number of missing teeth, which can affect oral function. The main objective of this study was to determine the consequences of tooth loss on the oral function and need for replacement of lost teeth among patients seeking treatment at the School of Dentistry MUHAS. During a period of three months, patients seeking dental treatment at the School of Dentistry were recruited for the study. Criteria included age of 20 years and above with one or more missing teeth except for third molars. Participants were interviewed for demographic information, chewing ability, symptoms of temporomandibular disorder and perceived need for replacement of missing teeth. Afterwards the subjects were examined to asses: caries status, tooth mobility, occlusal tooth wear, over eruption of unopposed teeth, and signs of temporomandibular disorders. Data was analyzed using Statistical Package for Social Sciences SPSS 16. For comparison of proportions, chi-square analysis and t test were used. A linear regression analysis was performed, with the chewing ability score as the dependent variable and number of POP as the independent variable A total of 361 subjects with mean age of 40.2 years (s.d. = 14.2, range = 20-93 years) were recruited into the study. About half 175 (48.5%) of the subjects reported some difficulty with chewing. Generally the fewer the occluding pairs present the greater the difficulty in chewing observed. Subjects with more than 6 posterior occlusal pairs appeared to have little problem in chewing across the whole range of foods. The frequency of signs and symptoms of TMD and excessive tooth wear increased with decreasing number of posterior occluding pairs, being more evident in subjects with less than 3 posterior occlusal pairs remaining. Over a third of the participants had one or more teeth with severe overeruption but none reported impairment of oral function. More than half of the subjects needed replacement for missing teeth. From this study, it is concluded that tooth loss leading to a dentition of 5 to 6 occlusal pairs impairs chewing of hard foods but not soft foods. Extensive loss of teeth leading to less than 3 POP is associated with increased symptoms of TMD and excessive vii tooth wear of occluding teeth. Need for replacement of missing teeth is high for both anterior and posterior regions with the cost of dentures being the main barrier to replacement of missing teeth. Dental personnel should make an effort to identify individuals with risk of tooth loss in order to retain at least 6 well-distributed posterior occlusal pairs. Dental laboratory services need improvement in order to be able to provide quality replacement of missing teeth at affordable costs. Further long-term multicenter studies to evaluate the consequence of tooth loss and assist in giving a more accurate projection needs for dentures nationwide are required

Helical gear wear monitoring: Modelling and experimental validation

Gear tooth surface wear is a common failure mode. It occurs over relatively long periods of service nonetheless, it degrades operating efficiency and leads to other major failures such as excessive tooth removal and catastrophic breakage. To develop accurate wear detection and diagnosis approaches at the early phase of the wear, this paper examines the gear dynamic responses from both experimental and numerical studies with increasing extents of wear on tooth contact surfaces. An experimental test facility comprising of a back-to-back two-stage helical gearbox arrangement was used in a run-to-failure test, in which variable sinusoidal and step increment loads along with variable speeds were applied and gear wear was allowed to progress naturally. A comprehensive dynamic model was also developed to study the influence of surface wear on gear dynamic response, with the inclusion of time-varying stiffness and tooth friction based on elasto-hydrodynamic lubrication (EHL) principles. The model consists of an 18 degree of freedom (DOF) vibration system, which includes the effects of the supporting bearings, driving motor and loading system. It also couples the transverse and torsional motions resulting from time-varying friction forces, time varying mesh stiffness and the excitation of different wear severities. Vibration signatures due to tooth wear severity and frictional excitations were acquired for the parameter determination and the validation of the model with the experimental results. The experimental test and numerical model results show clearly correlated behaviour, over different gear sizes and geometries. The spectral peaks at the meshing frequency components along with their sidebands were used to examine the response patterns due to wear. The paper concludes that the mesh vibration amplitudes of the second and third harmonics as well as the sideband components increase considerably with the extent of wear and hence these can be used as effective features for fault detection and diagnosis

Assessment of oral hygiene habits, oral hygiene practices and tooth wear among fertilizer factory workers of Northern India: a Cross sectional study

Background: The association between oral hygiene habits & practices and severity of tooth wear lesion varies from community to community and also from occupation to occupation. The present study was conducted with to assess oral hygiene habits & practices and tooth wear among fertilizer factory workers of Punjab, India. Material and Methods: A descriptive cross sectional survey was conducted among 965 male workers who were aged between 19–58 years, who were the workers of fertilizers factory of Bathinda, India. An interview on the demographic profile, oral hygiene practices, and adverse habits followed a clinical examination for recording the Tooth Wear (Smith and Knight Index 1984) using Type III examination. The Chi–square test and a Stepwise multiple linear regression analysis were used for the statistical analysis. Confidence interval and p-value set at 95% and ≤ 0.05 respectively. Results: In the present study majority (47.2%) of the study population used chew sticks for cleaning their teeth. Overall prevalence of adverse habits was reported (92.4%). Study population showed higher prevalence of tooth wear (77.1%). Best predictors identified for Tooth Wear were oral hygiene practices, adverse habits, years of work experience and age respectively. Conclusions: Considerable percentages of fertilizer factory workers have demonstrated a higher prevalence of tooth surface loss. This may be useful in designing the investigations that aim to further explore the causes for these findings and more importantly to plan oral health promotion program implementing both preventive and curative strategies