A Proposed Methodology to Assess the Accuracy of 3D Scanners and Casts and Monitor Tooth Wear Progression in Patients

PURPOSE

The aim of this study was to detail and assess the capability of a novel methodology to 3D-quantify tooth wear progression in a patient over a period of 12 months.

MATERIALS AND METHODS

A calibrated stainless steel model was used to identify the accuracy of the scanning system by assessing the accuracy and precision of the contact scanner and the dimensional accuracy and stability of casts fabricated from three different types of impression materials. Thereafter, the overall accuracy of the 3D scanning system (scanner and casts) was ascertained. Clinically, polyether impressions were made of the patient's dentition at the initial examination and at the 12-month review, then poured in type IV dental stone to assess the tooth wear. The anterior teeth on the resultant casts were scanned, and images were analyzed using 3D matching software to detect dimensional variations between the patient's impressions.

RESULTS

The accuracy of the 3D scanning system was established to be 33 μm. 3D clinical analysis demonstrated localized wear on the incisal and palatal surfaces of the patient's maxillary central incisors. The identified wear extended to a depth of 500 μm with a distribution of 4% to 7% of affected tooth surfaces.

CONCLUSION

The newly developed 3D scanning methodology was found to be capable of assessing and accounting for the various factors affecting tooth wear scanning. Initial clinical evaluation of the methodology demonstrates successful monitoring of tooth wear progression. However, further clinical assessment is needed.

Transitional bonding for segmented treatment: a two-phase restorative approach

When extensive dental therapy is needed, as in cases of severe attrition, interim restorations are useful in determining whether or not the proposed treatment will be successful. Transitional resin bonding is one type of interim method. In this case report, a 60-year-old patient presented with severely worn maxillary and mandibular anterior teeth; he desired treatment to be done in a timely fashion so as to be ready to attend an important wedding. Due to the urgency in timing and the complexity of the case, the treatment plan was a two-phase approach that included an initial esthetic and occlusal design to create a diagnostic wax-up followed by placement of transitional composite resin bonding, and then placement of indirect porcelain restorations. This transitional bonding approach allowed comprehensive treatment to be completed at a pace suitable to the patient's needs.

Full-mouth composite rehabilitation of a mixed erosion and attrition patient: a case report with v-shaped veneers and ultra-thin CAD/CAM composite overlays

Loss of tooth substance has become a common pathology in modern society. It is of multifactorial origin, may be induced by a chemical process or by excessive attrition, and frequently has a combined etiology. Particular care should be taken when diagnosing the cause of dental tissue loss, in order to minimize its impact. Several publications have proposed the use of minimally invasive procedures to treat such patients in preference to traditional full-crown rehabilitation. The use of composite resins, in combination with improvements in dental adhesion, allows a more conservative approach. In this paper, we describe the step-by-step procedure of full-mouth composite rehabilitation with v-shaped veneers and ultra-thin computer-aided design/computer-assisted manufacture (CAD/CAM)- generated composite overlays in a young patient with a combination of erosion and attrition disorder.

Managing dental erosion

The clinical signs of dental erosion are initially subtle, yet often progress because the patient remains asymptomatic, unaware and uninformed. Erosion typically works synergistically with abrasion and attrition to cause loss of tooth structure, making diagnosis and management complex. The purpose of this article is to outline clinical examples of patients with dental erosion that highlight the strategy of early identification, patient education and conservative restorative management. Dental erosion is defined as the pathologic chronic loss of dental hard tissues as a result of the chemical influence of exogenous or endogenous acids without bacterial involvement. Like caries or periodontal disease, erosion has a multifactorial etiology and requires a thorough history and examination for diagnosis. It also requires patient understanding and compliance for improved outcomes. Erosion can affect the loss of tooth structure in isolation of other cofactors, but most often works in synergy with abrasion and attrition in the loss of tooth structure (Table 1). Although erosion is thought to be an underlying etiology of dentin sensitivity, erosion and loss of tooth structure often occurs with few symptoms. The purpose of this article is threefold: first, to outline existing barriers that may limit early management of dental erosion. Second, to review the clinical assessment required to establish a diagnosis of erosion. And third, to outline clinical examples that review options to restore lost tooth structure. The authors have included illustrations they hope will be used to improve patient understanding and motivation in the early management of dental erosion.

Attrition and erosion: assessment and diagnosis

The management of patients with extensively worn and badly broken down dentitions presents a difficult challenge in dental practice and restorative treatments are often complex, time consuming and costly to implement, so careful case selection and treatment planning is essential. Ultimately the success of any restorative intervention is very dependent on the stability of the oral environment and the status of the remaining tooth structure. Prior to the commencement of any restorative treatment an understanding of the importance of the disease process, the risk factors in the mouth, and the intrinsic and extrinsic factors which affect the oral balance is critical. While there is a growing range of materials and techniques available for cost effective and conservative management of these cases, failure to take a systematic approach to assessment and stabilization may result in early restorative failure, rapid recurrence of the problems and a repeat restoration cycle. Therefore successful management of these patients must include an appropriate mix of preventive and restorative strategies.

[Assessment of tooth wear depending on Smith and Knight index]

For the clinical diagnosis of tooth wear Smith and Knight have been suggested the index with the same name, the criteria for the quantification of the hard tissue loss being the size of the area affected and the depth of the defect. The aim of this study was to assess tooth wear depending on Smith and Knight index, on a group of 614 patients.

MATERIAL AND METHOD

The criteria for the selection of the patients were the age more than 18 years old and the Smith and Knight index >0.

RESULTS

The biggest proportion of tooth wear (47.3%) presented the value 2 of the Smith and Knight index. Most of the tooth wear with Smith and Knight index 3 (54.4%) are abrasions, 71.4% of the tooth wear with Smith and Knight index 1 are attritions, and 20.3% of the tooth wear with Smith and Knight index 3 are erosions. High alcohol consumption is associated with deep tooth wear, exposing dentine (value 2 and 3 of the Smith and Knight index). Currently, various indices are used, making the comparison of the results of prevalence studies difficult.

Diagnosis and management of the worn dentition: conservative restorative options

A technique is presented for the use of a transparent polyvinyl siloxane template constructed from a diagnostic wax-up to rapidly reproduce the anatomical structure with direct restorative materials in the mouth. This technique is beneficial for a number of geriatric patients who would be unable to undertake long and complex dental treatment sessions and provides an alternative for those unable to meet the immediate costs of multiple indirect restorations. Consideration of increases in vertical dimension to create space for the new restorations and reconstruction utilizing a combination of direct and indirect procedures provides control and predictability over the final restorative result. In the short to medium term, the use of minimally invasive adhesive techniques enables tooth surface loss to be replaced with minimal destruction of the remaining sound tooth material, yet still enables the option for a more definitive restorative option at a later date.

Diagnosis and management of the worn dentition: risk management and pre-restorative strategies for the oral and dental environment

The incidence of tooth wear or non-carious tooth surface loss (NCTSL) is increasing and oral rehabilitation of patients with tooth tissue loss requires strategies that address all the factors relevant to the aetiology and pathogenesis of the disease. The multifactorial nature of the disease and the variability in its clinical presentation provides treatment challenges for the clinician. Management of tooth wear must be more than just restoration. Risk assessment, compliance and a commitment from both professional and patient underpin overall success of the treatment. Understanding that long term success is affected by the patient's oral environment and how diet, lifestyle and medical factors modify this environment. Improvements in the quantity and quality of saliva and remineralization strategies to enhance the remaining tooth structure are essential pre-restorative requirements. Successful management requires recognition of the problem, stabilization of the oral environment, remineralization of the tooth structure and when appropriate restoration.

Concepts and considerations of tooth wear: Part II--The mechanical component

Identification of etiological factors is essential for successful management of tooth wear. In many cases, the diagnosis may be complicated because of the multiple etiologic factors which may confound the clinical appearance of tooth wear. Comprehensively addressing all of these factors is paramount to the long-term success of patient management.

Basic Erosive Wear Examination (BEWE): a new scoring system for scientific and clinical needs

A new scoring system, the Basic Erosive Wear Examination (BEWE), has been designed to provide a simple tool for use in general practice and to allow comparison to other more discriminative indices. The most severely affected surface in each sextant is recorded with a four level score and the cumulative score classified and matched to risk levels which guide the management of the condition. The BEWE allows re-analysis and integration of results from existing studies and, in time, should initiate a consensus within the scientific community and so avoid continued proliferation of indices. Finally, this process should lead to the development of an internationally accepted, standardised and validated index. The BEWE further aims to increase the awareness of tooth erosion amongst clinicians and general dental practitioners and to provide a guide as to its management.

Methodological considerations concerning the development of oral dental erosion indexes: literature survey, validity and reliability

Within the context of preventing non-communicable diseases, the World Health Report (2002) and the WHO Global Oral Health Program (2003) put forward a new strategy of disease prevention and health promotion. Greater emphasis is placed on developing global policies in oral health promotion and oral disease prevention. The Decayed, Missing, Filled Teeth (DMFT) index does not meet new challenges in the field of oral health. Dental erosion seems to be a growing problem, and in some countries, an increase in erosion of teeth is associated with an increase in the consumption of beverages containing acids. Therefore, within a revision of the WHO Oral Health Surveys Basic Methods, new oral disease patterns, e.g. dental erosion, have to be taken into account. Within the last 20 years, many studies on dental erosion have been carried out and published. There has been a rapid growth in the number of indexes quantifying dental erosion process in different age groups. However, these indexes are not comparable. This article discusses quality criteria which an index intended for assessing tooth erosion should possess.

Pathological or physiological erosion--is there a relationship to age?

This conventional literature review discusses whether pathological tooth wear is age dependant. It briefly reviews the components of tooth wear and the prevalence of tooth wear in children, adolescents and adults. The emphasis on terminology relating to tooth wear varies. In some countries, the role of erosion is considered the most important, whereas others consider the process to be a combination of erosion, attrition and abrasion often with one being more dominant. The importance of tooth wear or erosion indices in the assessment and the evidence for progression within subject and within lesions is described. The data from the few studies reporting pathological levels of wear reported in children and adults are discussed, in particular its relationship with age. There is little evidence to support the concept that pathological levels of erosion or wear are age dependant. There is, however, some evidence to suggest that normal levels of erosion or wear are age dependant.

How valid are current diagnostic criteria for dental erosion?

In principle, there is agreement about the clinical diagnostic criteria for dental erosion, basically defined as cupping and grooving of the occlusal/incisal surfaces, shallow defects on smooth surfaces located coronal from the enamel–cementum junction with an intact cervical enamel rim and restorations rising above the adjacent tooth surface. This lesion characteristic was established from clinical experience and from observations in a small group of subjects with known exposure to acids rather than from systematic research. Their prevalence is higher in risk groups for dental erosion compared to subjects not particularly exposed to acids, but analytical epidemiological studies on random or cluster samples often fail to find a relation between occurrence or severity of lesions and any aetiological factor. Besides other aspects, this finding might be due to lack of validity with respect to diagnostic criteria. In particular, cupping and grooving might be an effect of abrasion as well as of erosion and their value for the specific diagnosis of erosion must be doubted. Knowledge about the validity of current diagnostic criteria of different forms of tooth wear is incomplete, therefore further research is needed.

Evaluation of a profilometrical method for monitoring erosive tooth wear

The in vivo monitoring of erosive wear is difficult because lesions mostly progress relatively slowly and reliable reference points are difficult to obtain. To date, only a few methods for clinical monitoring of erosive loss have been described, which either require extensive equipment or do not provide sufficient sensitivity. The aim of the present study was to evaluate, using study models (epoxy resin material), a procedure that permits the reliable and accurate monitoring of erosive substance loss within acceptable observation periods. The method is the profilometric measurement of erosive tissue loss using acid-resistant markers, which represent both a reference area and a structure for the defined retracing of a given erosive lesion surface. The study model magnified values slightly (2.8%; not significant), the precision was < 4 microm, and the repeatability was good (95% limits of repeatability ranging from -4.7 to 5.2 microm). The estimated detection threshold for erosive loss is 15 microm, which appears to be adequate for monitoring. The method is indicated for special dental care in cases of severe dental erosion (e.g. eating disorders) and for clinical studies.

Referrals of patients with tooth substance loss

Tooth substance loss (TSL) and related problems appears to be increasing in incidence. Patients may request treatment for a variety or reasons, such as poor aesthetics of chipped and worn teeth, sensitivity and reduced masticatory function. The patient's dentist may suggest treatment because (s)he feels that the TSL is progressing and the dentition requires protection by the placement of restorations. This paper discusses the role of the general dental practitioner in the referral of patients with TSL, the importance of an examination and history taking for these patients, and a classification of TSL related to possible treatment.

CLINICAL RELEVANCE

The experience of clinicians varies, so referral to another dentist may be appropriate if the patient's dental practitioner considers that (s)he may not be in a position to treat a patient's TSL.

The coexistence of temporomandibular disorders and styloid process fracture: A clinical report

This clinical report describes the diagnosis and treatment of a patient with both temporomandibular disorders (TMD) and styloid process fracture. The presence of tender muscles of mastication, facial pain, especially upon awakening, frequent grinding sounds, and tooth attrition indicated a diagnosis of TMD with bruxism as a possible etiological factor. However, the preliminary diagnosis of styloid process fracture based on the patient's sensation of a foreign body in the throat and some discomfort when turning the head was confirmed using radiography. The styloid process fracture was treated using conservative nonsurgical therapy, and an occlusal splint was used to treat the TMD. The patient's symptoms were significantly reduced at the 12-month follow-up visit.

The worn dentition — pathognomonic patterns of abrasion and erosion

Historically, the dental literature has revealed various causes of tooth wear, yet it has failed to provide a conclusive method of differentiation and diagnosis of the condition. The categories of tooth wear encountered most commonly in dental practice are abrasion and erosion. The major causes of wear from abrasion are bruxism and toothpaste abuse, and the major causes of wear from erosion are regurgitation, coke-swishing and fruit-mulling. Through in-depth clinical study of these causes, this paper provides a diagnostic system that will enable dental professionals to determine and differentiate the exact aetiology of the worn dentition simply by the recognition of the pathognomonic wear patterns on diagnostic casts, which are based upon the position and quantity of the non-carious loss of tooth structure.

Accuracy and precision of a system for assessing severity of tooth wear

PURPOSE

The purpose of this study was to introduce a computer-assisted quantitative tooth wear-analyzing system and test its accuracy and precision.

MATERIALS AND METHODS

An image of a horizontally projected dental arch was captured, and the facet area of each tooth was calculated using a digital image analyzer. For normalization, the facet area of the individual tooth was divided by the total area of the corresponding tooth; this result was the tooth wear score. The accuracy and precision of this method were determined through the intraclass correlation coefficient using 10 dental casts. Tooth wear on the dental casts of 50 subjects was actually measured.

RESULTS

The accuracy of the tooth wear score determined by a newly trained examiner was greater than 0.85 of the intraclass correlation coefficient; this was tested against the score determined by consensus of three experienced examiners. The reproducibility within a 1-week interval was also greater than 0.85. With regard to the tooth wear score from 50 sets of dental casts, the distribution of tooth wear was generally consistent with data reported in the literature.

CONCLUSION

The results suggest that the newly trained examiner can exhibit adequate accuracy and precision after appropriate training in identifying tooth wear facets. Recorded data from 50 subjects added face validity to this new system.

Dental topography and molar wear inAlouatta palliata from Costa Rica

Paleoprimatologists depend on relationships between form and function of teeth to reconstruct the diets of fossil species. Most of this work has been limited to studies of unworn teeth. A new approach, dental topographic analysis, allows the characterization and comparison of worn primate teeth. Variably worn museum specimens have been used to construct species-specific wear sequences so that measurements can be compared by wear stage among taxa with known differences in diet. This assumes that individuals in a species tend to wear their molar teeth in similar ways, a supposition that has yet to be tested. Here we evaluate this assumption with a longitudinal study of changes in tooth form over time in primates. Fourteen individual mantled howling monkeys (Alouatta palliata) were captured and then recaptured after 2, 4, and 7 years when possible at Hacienda La Pacifica in Costa Rica between 1989-1999. Dental impressions were taken each time, and molar casts were produced and analyzed using dental topographic analysis. Results showed consistent decreases in crown slope and occlusal relief. In contrast, crown angularity, a measure of surface jaggedness, remained fairly constant except with extreme wear. There were no evident differences between specimens collected in different microhabitats. These results suggest that different individual mantled howling monkeys wear their teeth down in similar ways, evidently following a species-specific wear sequence. Dental topographic analysis may therefore be used to compare morphology among similarly worn individuals from different species.

An assessment of stress analyses in the theory of abfraction

Wedged-shaped lesions at the cemento-enamel junction of teeth have been attributed primarily to biomechanical loading forces that cause flexure and failure of enamel and dentin. This theory, termed abfraction, remains controversial. This review examined studies on mechanical properties of enamel and dentin and studies on bite forces and mastication as background information. Abfraction is based principally on a few early finite element analysis and photoelastic models showing stress concentration at the dental cervical area without actually showing enamel and dentin fracture. However, a review of more recent dental stress analyses has been contradictory. Particularly, analyses of the periodontal ligament and alveolar bone, not modeled in previous studies, have shown that those structures may dissipate occlusal loading forces from the cervical areas. In addition, some models may not fully represent intricate dental anatomy and complex occlusal function. Therefore, the key basis of the abfraction theory may be flawed.

[Dentition of the older animal]

Ageing is accompanied by the natural loss and wear of hard and soft dental tissues. While ageing can influence pathological processes affecting the dentition, it is not the cause of these processes. The development, growth, attrition, abrasion, and loss of teeth is determined in part by ageing. Periodontal disease is the result of the accumulation of dental plaque and can occur in young animals. Unfortunately, gingivitis or periodontitis is often not diagnosed or diagnosed too late by pet owners and veterinarians.

Restorative management of the worn dentition: I. Aetiology and diagnosis

In this, the first of a four-part series on the restorative management of the worn dentition, the aetiological factors, diagnosis of toothwear and preventive measures are summarized. Later papers will deal with the management of localized anterior and posterior toothwear, the use of 'Dahl type' appliances as an effective means for the restorations and the various treatment options for the management of the dentition showing generalized wear. The series will discuss the relative merits of the treatment strategies, clinical techniques and dental materials for the restoration of health, function and aesthetics for the dentition.

Analyzing the etiology of an extremely worn dentition

Patients requiring extensive restorative care frequently exhibit significant loss of tooth structure. Specific clinical findings in an extremely worn dentition may vary widely and are often confusing. Severe wear can result from a mechanical cause, a chemical cause, or a combination of causes. The location of the wear, the accompanying symptoms and signs, and information gained from the patient interview are essential components in determining the etiology. A diagnostic decision tree facilitates a systematic analysis and diagnosis of dental wear.

A reliability study of clinical tooth wear measurements

STATEMENT OF PROBLEM

Most studies examining tooth wear severity have been performed on dental casts. This indirect approach has limited applicability to dental practice because during the assessment of the casts, the identification of dentin exposure is difficult or even impossible.

PURPOSE OF STUDY

The purpose of this study was to assess occlusal and incisal tooth wear clinically to determine the reliability of the assessment procedure and to establish the influence of selected relevant clinical variables (dental quadrant, tooth type, and severity of wear) on the reliability.

MATERIAL AND METHODS

Forty-five volunteers (17 men, 28 women; mean age 33.7 +/- 10.7 years), 32 with temporomandibular disorders and 13 free from signs and symptoms of such disorders, were evaluated on 4 occasions. Two trained observers graded tooth wear at 2 different points in time with a 5-point ordinal scale developed for use in this study. The inter-rater and intra-rater reliability of the scale was expressed as Cohen's kappa. The influence of 2 clinical variables, dental quadrant and tooth type, on the values of kappa was tested with 1-way analysis of variance and post hoc Bonferroni tests. Probability levels of P< .05 were considered statistically significant. The influence of the final clinical variable, severity of wear, was assessed qualitatively.

RESULTS

The overall values of the inter-rater and intra-rater reliability were substantial (kappa = 0.632 to 0.678). The clinical variable dental quadrant did not influence the kappa values, whereas the inter-rater reliability during the first session was better for incisors and canines than for premolars (1-way analysis of variance: F(3,23)=4.577, P=.012; post hoc Bonferroni tests: P=.030 and.036). Qualitative assessment of severity of wear indicated that the more advanced the tooth wear, the more reliably it could be graded.

CONCLUSION

By means of the developed 5-point ordinal scale and within the limitations of this study, it was concluded that tooth wear can be assessed reliably in the clinical dental setting.

Presentation, diagnosis and initial management of patients referred to a hospital tooth wear clinic

Information on presenting complaints, diagnosis and initial management strategy was recorded on a proforma for 114 consecutive patients referred to a hospital tooth wear clinic over a two-year period. Over twice as many male patients were referred as females. Twenty percent of patients had no presenting complaint and the others shared the common complaints concerning appearance, sensitivity and their deteriorating dentitions. The assessment of aetiology identified attrition as the most common cause of tooth wear in the subject group studied. About half the group were prescribed preventative treatment only and the other half were deemed to require restorative dental treatment.

Investigation of an index to measure tooth wear in primary teeth

Tooth wear, in particular erosion, has been reported to be widespread in children in the UK. Wear may affect either dentition, but epidemiological measurement has proved difficult.

OBJECTIVES

The objectives of this study were: (a) to investigate use of a simple index of wear in primary teeth; and (b) to compare findings from visual examination and from photographs with those at histological examination of the same teeth.

SAMPLE AND METHODS

Forty-one exfoliated or extracted primary anterior teeth were assessed visually and using photographs. Ground sections of the teeth were prepared and examined using polarised light microscopy.

RESULTS

On visual examination, 31 of the 41 teeth had evidence of wear. In 14 teeth, tissue loss was confined to enamel and in 17 it extended into dentine. Findings on photographs were very similar to those on visual examination. Of the 10 teeth without erosion visually, two had evidence of loss on histological examination. Of the 14 with visual evidence of erosion confined to enamel, dentine was exposed in 11 cases. Diffuse demineralisation was evident histologically in 11 of the 31 teeth with evidence of erosion.

CONCLUSIONS

It was concluded that clinical assessment of erosion may underestimate the extent of the condition. Under the conditions of the study, photographs gave results similar to those on visual examination.

A literature review of the techniques to measure tooth wear and erosion

This paper reviews methods to measure tooth wear especially those more recently introduced as a result of improvements in technology. The review searched methods to measure tooth wear and dental erosion from large epidemiological investigations, in vitro and in vivo studies. There seems to be wide variation in techniques used to measure tooth wear and erosion. In vitro techniques may have little direct clinical relevance but can lead to new and more accurate clinical methods. In vivo studies have problems with reference points and accurate validation of the techniques. There is a need for a simple, reliable technique to quantify tooth wear due to erosion.

Investigation and treatment of patients with teeth affected by tooth substance loss: a review

Tooth substance loss, an increasing problem, may result from erosion, abrasion and attrition, often with more than one of these acting together. Investigation requires a detailed history and examination. The aim of treatment may be prevention of further damage in less affected cases. The treatment of severe tooth substance loss may be complex, especially in view of the reduced amounts of tooth substance which may be available and the need to find space because of the compensatory over-eruption of worn teeth.

Etiology and diagnosis of tooth wear: a literature review and presentation of selected cases

PURPOSE

This article presents an overview of etiologies associated with tooth wear.

MATERIALS AND METHODS

Specific types of wear based on clinical findings and patient history are described.

RESULTS

The occurrence and pattern of tooth wear are related to cultural, dietary, occupational, and geographic factors. Examples of tooth wear related to these factors with regional specificity are presented.

CONCLUSION

The dental practitioner should recognize the characteristic signs of tooth wear, as they may be the first to discuss the problem with the patient. Management should be based on accurate diagnosis.

Dental erosion: diagnostic-based noninvasive treatment

Lesions that result from dental erosion can be difficult to recognize--particularly when abrasion and attrition are also present. Consequently, dental erosion is often misdiagnosed and mistreated by radical restorative modalities that compromise the vitality of the pulp. This article provides clinicians with knowledge concerning the diagnosis of the complex lesions of dental wear and demonstrates the conservative treatment of this condition. Two cases that exhibit marked tooth wear in anterior teeth and their subsequent restoration utilizing occlusal principles and composite resin are presented.

Using partial recording to assess tooth wear in older adults

OBJECTIVES

To establish whether partial recording can be used for the measurement and reporting of tooth wear data in samples of adult populations, whilst maintaining the usefulness of the index.

METHODS

Using whole mouth coronal tooth wear data from a large random population sample of 1200 dentate older adults in England, several different partial recording systems were investigated to establish which teeth would maintain a high level of sensitivity for the most economic use of codes and index teeth. Tooth wear data were recorded on a surface-by-surface basis on all teeth in the sample using the tooth wear index.

RESULTS

Five different partial mouth recording systems were assessed, including half-mouth scoring, assessment of just upper or just lower anterior teeth, assessment of all anterior teeth and use of six index teeth. The 12 anterior teeth were the ones most often affected by moderate or severe wear, and when all 12 teeth were used as the index teeth few wear cases were missed, and all the most extensive and severe cases of coronal wear were classified as having some wear. A limited index of only six anterior teeth (three uppers and three lowers) was almost as sensitive, but allowed less flexibility when reporting the extent of coronal wear. Other systems for partial recording were less sensitive.

CONCLUSIONS

Partial recording using six or 12 anterior teeth is appropriate for measuring and reporting tooth wear data in large population surveys.

Analysis of occlusal variables, dental attrition, and age for distinguishing healthy controls from female patients with intracapsular temporomandibular disorders

STATEMENT OF PROBLEM

Confusion about the relationship of occlusion to temporomandibular disorders (TMD) persists.

PURPOSE

This study attempted to identify occlusal and attrition factors plus age that would characterize asymptomatic normal female subjects.

METHODS AND MATERIAL

A total of 124 female patients with intracapsular TMD were compared with 47 asymptomatic female controls for associations to 9 occlusal factors, 3 attrition severity measures, and age using classification tree, multiple stepwise logistic regression, and univariate analyses. Models were tested for accuracy (sensitivity and specificity) and total contribution to the variance.

RESULTS

The classification tree model had 4 terminal nodes that used only anterior attrition and age. "Normals" were mainly characterized by low attrition levels, whereas patients had higher attrition and tended to be younger. The tree model was only moderately useful (sensitivity 63%, specificity 94%) in predicting normals. The logistic regression model incorporated unilateral posterior crossbite and mediotrusive attrition severity in addition to the 2 factors in the tree, but was slightly less accurate than the tree (sensitivity 51%, specificity 90%). When only occlusal factors were considered in the analysis, normals were additionally characterized by a lack of anterior open bite, smaller overjet, and smaller RCP-ICP slides. The log likelihood accounted for was similar for both the tree (pseudo R(2) = 29.38%; mean deviance = 0.95) and the multiple logistic regression (Cox Snell R(2) = 30.3%, mean deviance = 0.84) models.

CONCLUSION

The occlusal and attrition factors studied were only moderately useful in differentiating normals from TMD patients.

Dental cervical lesions associated with occlusal erosion and attrition

Acid demineralization of teeth causes occlusal erosion and attrition, and shallow and wedge-shaped cervical lesions putatively involving abfraction. From 250 patients with tooth wear, 122 with cervical lesions were identified. From epoxy resin replicas of their dentitions, associations of occlusal attrition or erosion or no wear with cervical lesions were recorded at 24 tooth sites (total 2928 sites). Criteria used to discriminate occlusal attrition from erosion, and shallow from grooved, wedge-shaped or restored cervical lesions were delineated by scanning electron microscopy. A 96 per cent association was found between occlusal and cervical pathology. Shallow cervical lesions were more commonly found in association with occlusal erosion. Wedge-shaped lesions were found equally commonly in association with occlusal erosion, as with attrition. Grooved and restored cervical lesions were uncommon. Differences were appreciated in the associations within incisor, canine, premolar and molar tooth sites which related more to the site-specificity of dental erosion than to attrition from occlusal forces. Non-carious lesions on teeth then have multifactorial aetiology and pathogenesis in which erosion and salivary protection play central roles. Dentists should primarily consider erosion in the diagnosis, prevention and treatment of tooth wear.

Removable prostheses

Reconstruction of the dentition extensively damaged through tooth surface loss may require the use of removable prostheses. This can be the most appropriate type of treatment when either the teeth are very severely worn or the patient wishes a simpler and more economical approach than a fixed reconstruction.

Mathematical shape matching as a tool in tooth wear assessment--development and conduct

The quantitative assessment of restoration and tooth wear usually requires fixed reference points from which measurements are made. In longitudinal patient follow-up the loss or erosion of such points may preclude measurement and an alternative approach is to seek regions of coincidence and conflict in digital models of before and after wear surfaces, with a continuous refinement of the parameters of the coordinate transformations, until the closest correspondence between them is found. A computer program has been written to implement the algorithm and assess the technique's capacity to find the match between surfaces both artificially generated and from tooth replicas recorded from patients at different epochs. The program was able to achieve the desired ends, demonstrating the utility of the technique in tooth wear assessment but identifying the need to refine the program further to enhance both its difference detection capabilities and level of automation. Examination of the theory and practical experience highlighted certain situations when user understanding is invaluable to ensure a satisfactory solution. This strengthened the investigators' resolve against reliance upon commercially based surface fitting programs whose basis may not be fully understood. Notwithstanding this surface matching is a powerful tool in the investigation of dental wear.

Effects of dopaminergic drugs, occlusal disharmonies, and chronic stress on non-functional masticatory activity in the rat, assessed by incisal attrition

Observational methods and the recording of nonspecific jaw movements or masticatory muscle activity have been used to evaluate oral parafunctional movements in animal models of bruxism. In this study, we have used a new approach in which the non-functional masticatory activity in the rat was assessed by the measurement of incisal attrition, with the aim of investigating the role of diverse factors involved in the etiology of bruxism. We quantified the attrition rate weekly by making superficial notches in the lower incisors and measuring the distances to the incisor edges. Repeated stimulation of the dopaminergic system with apomorphine led to an enhancement of the non-functional masticatory activity (p < 0.0001). The severity of the apomorphine-induced oral behavior was positively correlated (r(s) = 0.69, p < 0.01) with an increase in the incisal attrition rate (20.9%, p < 0.0001). Apomorphine-induced non-functional masticatory activity was strongly enhanced by the placement of an acrylic cap on both lower incisors (306%, p < 0.0001), but not by the cutting of a lower incisor. Repeated cocaine administration also increased the attrition rate (22.5%, p < 0.0001). However, neither chronic blockade of dopaminergic receptors with haloperidol, nor its withdrawal, modified attrition. In addition, since emotional disturbances are considered to be causal factors of bruxism, we tested whether experimental stress might accelerate tooth wear. Exposure to two different chronic stress regimes did not induce significant changes in incisal attrition. Moreover, exposure to chronic stress after the withdrawal of chronic haloperidol treatment did not alter attrition either. These results partially support the role of the central dopaminergic system in bruxism and suggest that stress, in general, may not be a relevant factor in tooth wear.

Restoration of the severely worn dentition using a systematized approach for a predictable prognosis

Dental literature supports the concept that vertical dimension of occlusion is normally not lost in severely worn dentition, and the bite should generally not be opened to facilitate dental reconstruction. However, restoration of a periodontally sound but severely worn dentition, at existing vertical dimension, frequently presents unique challenges in patient management, diagnosis, treatment planning, and restorative methodology. This report reviews and demonstrates an integrated and planned approach to this complex treatment situation that can lead to a favorable and predictable prognosis. The approach also allows a practitioner free use of various techniques if certain goals of occlusion are followed.

The epidemiology of tooth wear

There is a perception within the dental profession that the problem of pathological loss of tooth tissue is increasing. However, methods used to measure tooth wear are often complex and not reproducible. This fact, together with the lack of information on 'normal' loss of tooth tissue suggests that conclusions from current prevalence studies should be treated with caution.

The prevalence, etiology and management of tooth wear in the United Kingdom

STATEMENT OF PROBLEM

Recent epidemiologic evidence suggests that tooth wear is now a significant problem in both children and adults. There is growing evidence that a major cause of severe wear in patients is regurgitation erosion due to a variety of factors including gastroesophageal reflux disease.

PURPOSE

The purpose of this article is to discuss the prevalence of tooth wear in the United Kingdom. Emphasis in management should be on accurate diagnosis, and in some patients, long-term monitoring before embarking on any irreversible, interventive treatment. Even when treatment is necessary, a period of monitoring is helpful to assess the rate of progress of the wear, the effectiveness of preventive measures, and therefore the extent of the treatment necessary.

Midface collapse: an overlooked disease

Midface collapse is a disease caused by occlusal interferences leading to excessive tooth attrition and loss of vertical dimension. Although it can cause premature aging, it can be prevented or treated.

Clinical diagnosis of enamel defects: pitfalls and practical guidelines

Changes in enamel during its development are permanently recorded, and commonly present as either demarcated opacity, diffuse opacity, or enamel hypoplasia. Developmental enamel defects may provide clues regarding their aetiology, and this may have application in clinical dentistry, dental epidemiology and anthropology. However, the usefulness of these applications may be hampered by many pitfalls encountered in the detection and diagnosis of developmental enamel defects. The defects may be masked by saliva, dental plaque, and incorrect lighting. In addition, confounding effects of post-eruptive changes such as dental caries, attrition, and traumatic loss of tooth structure may impair the detection of developmental enamel defects. The non-specificity of appearance of enamel defects may make aetiologic diagnosis of enamel hypoplasia difficult. Furthermore, difficulty is often encountered in the relative timing of events in enamel hypoplasia, due to limited data on the chronology of development of the human dentition. In this review, pitfalls in the clinical assessment of enamel defects are discussed, and guidelines to overcome some of these difficulties are presented.

Measurement of tooth wear in patients with palatal erosion

AIM

To develop a reproducible method for the assessment of tooth wear in vivo using a laser profilometer.

DESIGN

A controlled study to measure tooth wear.

SUBJECTS AND METHODS

Wear was measured over a 6-month period in 13 patients with unexplained palatal dental erosion and compared with a group of 7 controls without any evidence of abnormal wear.

MAIN OUTCOME MEASURES

Metal disks were cemented to the tooth surface and impressions taken at 6-month intervals. Wear was estimated by scanning the impressions with a contacting laser profilometer and measuring a change in depth around the disk over a 6-month period using fixed reference points on the metal disks.

RESULTS

A statistically significant difference was observed between patients with palatal erosion and the controls. Patients with erosion had a median of 36.5 microns of wear over 6 months (range 17.6-108.2) and the controls had a median of 3.7 microns (range 0.5-15.8).

CONCLUSIONS

This paper presents a novel method for measuring erosion using fixed reference points cemented to the palatal surfaces of upper incisor teeth.

Development of a novel system for assessing tooth and restoration wear

OBJECTIVES

This investigation sought to develop a mapping apparatus for use in the assessment of both tooth and restoration wear.

METHODS

A computer controlled mapping device, capable of scanning a suitably prepared electroconductive tooth replica by means of an electrical feedback mechanism, was constructed and its accuracy assessed by measuring the thicknesses of four engineers' slip gauges 12 times each. The reproducibility of three potential methods of rendering a die stone replica electroconductive was also investigated. Finally, tooth replicas were surface profiled and compared empirically with the originals using a commercial surface mapping program.

RESULTS

The overall mean accuracy of the mean thicknesses of the slip gauges was 4.4 (2.8) microns. Surface deposition of either nickel spray or gold leaf, upon a ready formed replica, did not give a reproducible thickness. Precoating silicone impressions with nickel spray prior to replica production overcame this problem. On an empirical basis the instrument yielded accurate digital terrain models of tooth replicas.

CONCLUSIONS

A surface mapping device has been developed which is both accurate and reproducible. A satisfactory electroconductive surface may be produced upon a tooth replica by precoating a silicone impression with nickel spray before casting the replica. The technique should prove invaluable for monitoring both tooth and restoration wear but further work is necessary to examine how such an approach will perform clinically.