Stress-induced cervical lesions

Abfraction: Etiopathogenesis, clinical aspect, and diagnostic-treatment modalities: A review

Background

Abfraction is a loss of tooth structure along the gingival margin and manifests with different clinical appearances. It has multifactorial etiology and may occur due to normal and abnormal tooth function and may also be accompanied by pathological wear, such as abrasion and erosion. The theory behind the abfraction is that the tooth flexure in the cervical area is caused due to occlusal compressive forces and tensile stresses. This results in the fractures in the hydroxyapatite (HA) crystals. It is also caused by the low packing density of the Hunter-Schreger band (HSB) at the cervical area. Unfortunately, there is a lack of evidence regarding the outcome of abfraction with or without intervention. The aim of this review is to collect clinical information from the literature and discuss the etiology, pathogenesis, clinical representation, and management. Also, search databases for clinical studies that describe the role of sclerotic dentine in non-carious cervical lesions (NCCLs) are becoming a clinical challenge.

Methods

The literature was searched that described the etiology, pathogenesis, clinical representation, and management of the abfraction lesions. Also, a specific question regarding the formation of sclerotic dentin in the NCCL lesion was described and searched for evidence that challenges etching, bonding, and successfully restoring NCCLs. The databases PUBMED, SCOPUS, MEDLINE, WEB of SCIENCE, and EMBASE were searched using the key terms. The inclusion criteria were the randomized controlled clinical trial, cohort studies, and cross-sectional studies that aimed at determining the role of sclerotic dentine in NCCLs and its effect on etching, bonding.

Results

One clinical study was retrieved according to the PRISMA flowchart and PICO format. The longer etching time, total-etch adhesive system, and EDTA pre-treatment of the sclerotic dentin of cervical wedge-shaped defects could improve the bonding strength in lesions like NCCL's.

Conclusion

In conclusion, clinical challenges that occur due to NCCLs are better managed by a proper understanding of factors like etiopathogenesis, ultra-structure of enamel, and dentine and their effect on the bonding of restorations of the tooth.

Microshear bond strength of composite resin to demineralized dentin after remineralization with sodium fluoride, CPP-ACP and NovaMin containing dentifrices

Background

Bonding composite to remineralized dentin is challenging. The aim of this study was to evaluate the microshear bond strength (μSBS) of composite to demineralized dentin, which had been remineralized with sodium fluoride (NaF), CPP-ACP and NovaMin containing dentifrices.

Materials and methods

108 extracted human premolars or molars were sectioned longitudinally into buccal and lingual halves (n = 216). Dentin (3 × 3 mm) was exposed on the cervical aspect of teeth and the samples were allotted randomly to six groups (n = 36) according to the remineralizing agent used namely, group 1 (sound dentin), group 2 (demineralized dentin), group 3 (NaF), group 4 (CPP-ACP), group 5 (NovaMin) and group 6 (non-fluoridated). The type of bonding system (total-etch or self-etch) formed the subgroups. Samples in groups 2-6 were submitted to an acid challenge for 3 days followed by remineralization in groups 3-6 for 90 days. Etching pattern (n = 3) was observed under SEM. μSBS of the bonded samples (n = 15) were evaluated. The data were statistically analyzed using Kruskal Wallis and Dunn's Post Hoc tests (p < 0.05).

Results

SEM micrographs of remineralized samples showed varying degrees of partially occluded and exposed dentinal tubules. Under both the adhesives, the mean μSBS of composite in groups 2-6 was lesser than that of group 1. Among self-etch subgroups, μSBS of NaF group was not significantly different from that of normal dentin.

Conclusion

Composite forms a weaker bond to remineralized dentin. Self-etch bonding system is capable of achieving acceptable bond strength to dentin remineralized with NaF and NovaMin.

Status of occlusal contact during sleep bruxism in patients who visited dental clinics - A study using a Bruxchecker®

OBJECTIVE

Bruxism-induced mechanical load causes various dental problems, and its treatment is challenging. The present study analyzed upper and lower tooth contacts to determine actual occlusal contact during sleep bruxism.

METHODS

Tooth contact patterns were analyzed in 49 patients attending dental clinics, using a Bruxchecker®, cephalograms, and condylographs.

RESULTS

Approximately 80% of individuals demonstrated contact from the anterior teeth to the molar region (ICPM); about 96% had mediotrusive grinding and contact. The tooth contact area increased with the flatness of the anterior occlusal plane. The ratio of the contact area of the anterior teeth to the overall tooth contact area increased with overbite. Bilateral ICPM and mediotrusive contact patterns were associated with a high frequency of temporomandibular disorder symptoms, clicking, and/or pain.

DISCUSSION

The tooth contact area, anterior occlusal plane, and overbite are closely related, suggesting that tooth contact with the anterior teeth should be controlled with occlusal therapy.

A Critical Review of the Durability of Adhesion to Tooth Tissue: Methods and Results

The immediate bonding effectiveness of contemporary adhesives is quite favorable, regardless of the approach used. In the long term, the bonding effectiveness of some adhesives drops dramatically, whereas the bond strengths of other adhesives are more stable. This review examines the fundamental processes that cause the adhesion of biomaterials to enamel and dentin to degrade with time. Non-carious class V clinical trials remain the ultimate test method for the assessment of bonding effectiveness, but in addition to being high-cost, they are time- and labor-consuming, and they provide little information on the true cause of clinical failure. Therefore, several laboratory protocols were developed to predict bond durability. This paper critically appraises methodologies that focus on chemical degradation patterns of hydrolysis and elution of interface components, as well as mechanically oriented test set-ups, such as fatigue and fracture toughness measurements. A correlation of in vitro and in vivo data revealed that, currently, the most validated method to assess adhesion durability involves aging of micro-specimens of biomaterials bonded to either enamel or dentin. After about 3 months, all classes of adhesives exhibited mechanical and morphological evidence of degradation that resembles in vivo aging effects. A comparison of contemporary adhesives revealed that the three-step etch-and-rinse adhesives remain the ‘gold standard’ in terms of durability. Any kind of simplification in the clinical application procedure results in loss of bonding effectiveness. Only the two-step self-etch adhesives approach the gold standard and do have some additional clinical benefits.

A finite element study to determine the occurrence of abfraction and displacement due to various occlusal forces and with different alveolar bone height

Background:

Noncarious cervical lesions (NCCLs) are rarely described in the periodontal literature, perhaps because no direct link between NCCLs and periodontal lesions has been demonstrated.

Aim:

The aim of this study is to determine the stress and displacement produced in the tooth at different bone levels under different occlusal load using finite element model (FEM) study.

Materials and Methods:

Four FEMs of maxillary incisor were designed consisting of the tooth, pulp, periodontal ligament, and alveolar bone at the various level of bone height (25%, 50%, and 75%). Different occlusal load (5 kg, 15 kg, 24 kg, and 29 kg) at an angle of 50° to the long axis of the tooth was applied on the palatal surface at the level of middle third of the crown. All the models were assumed to be isotropic, linear and elastic, and the analysis was performed on a Pentium IV processor computer using the ANSYS software.

Results:

The maximum stress in the tooth was seen in the cervical region and to a greater extent at the apex for all models. The maximum tooth displacement for all the occlusal loads applied in this study was at the incisal edge with the minimum tooth displacement at the cervical third of the root which shifted apically with the reduction of alveolar bone support.

Conclusion:

The cumulative effect of increased stress and displacement at the cervical region of the tooth would result in abfraction as the age advances along with other wasting diseases.

Factors influencing the progression of noncarious cervical lesions: A 5-year prospective clinical evaluation

STATEMENT OF PROBLEM

The etiology (chemical, friction, abfraction) of noncarious cervical lesion (NCCL) progression is poorly understood.

PURPOSE

The purpose of this 5-year prospective clinical trial was to measure the relationship between NCCLs and various etiologic factors.

MATERIAL AND METHODS

After review board approval, 29 participants with NCCLs were enrolled. Polyvinyl siloxane impressions were made of each NCCL, and casts were poured at baseline, 1, 2, and 5 years. The casts were scanned with a noncontact profilometer, and 1-, 2-, and 5-year scans were superimposed over baseline scans to measure volumetric change in NCCLs. T-scan and Fujifilm Prescale films were used to record relative and absolute occlusal forces on teeth with NCCLs at the 5-year recall. Participant diet, medical condition, toothbrushing, and adverse oral habit questionnaires were given at the 5-year recall. Occlusal analysis was completed on mounted casts to determine the presence of wear facets and group function. Volumetric lesion progression from 1 to 5 years was correlated to absolute and relative occlusal force using mixed model analysis. The Kruskall-Wallis and Mann-Whitney analyses compared lesion progression with diet, medical condition, toothbrushing, adverse oral habits, wear facets, and group function.

RESULTS

The NCCL progression rate over 5 years was 1.50 ±0.92 mm(3)/yr. The rate of progression of NCCLs was related to mean occlusal stress (P=.011) and relative occlusal force (P=.032) in maximum intercuspation position. No difference was seen in NCCL progression between participants with any other factors.

CONCLUSION

Heavy occlusal forces play a significant role in the progression of NCCLs.

Dentine sensitivity: past, present and future

OBJECTIVE

This review defines dentine sensitivity (DS), its prevalence, its aetiology, the mechanism(s) responsible for DS, its diagnosis and its treatment. The review then examines the modes of action of various treatments for DS including potassium salts, strontium salts, bioglasses, arginine/calcium carbonate and professional treatments such as adhesives and oxalates. The methods used to evaluate the various treatment modalities are discussed, including laboratory studies and randomised controlled clinical trials.

DATA SOURCES AND STUDY SELECTION

A literature search was conducted using PubMed, Ovid Medline and Cochrane reviews for information on DS and its treatments, as well as laboratory and clinical studies used to evaluate the efficacy of various DS treatments. With regard to efficacy of treatments for DS only reports of clinical studies that were randomised, controlled and blinded were reviewed. The authors offer new insights into the shortcomings of the recent systematic review of the use of oxalates for DS.

CONCLUSION

The authors introduce the concept of a novel desensitising mouthrinse containing 1.4% potassium oxalate: Listerine® Advanced Defence Sensitive mouthrinse. Readers of this supplement issue of the Journal of Dentistry are invited to review the significance of managing the clinical problem of DS. They are also invited to assess data from laboratory and randomised controlled clinical studies in order to understand the advantages offered by regular use of 1.4% potassium oxalate-containing mouthrinse, Listerine Advanced Defence Sensitive, in particular its resistance to daily erosive and/or abrasive challenges.

Abfraction: A review

Abfraction (AF) is the pathological loss of tooth substance caused by biomechanical loading forces that result in flexure and failure of enamel and dentin at a location away from the loading. The theory of AF is based primarily on engineering analyses that demonstrate theoretical stress concentration at the cervical areas of the teeth. However, the theory is not yet proven and there are explanations against it. AF lesions present primarily at the cervical region of the dentition and are typically wedge-shaped, with sharp internal and external line angles. Diagnosis of AF plays a very important role in the management of patients. The aim of the present narrative review is to comprehensively discuss the historical, etiopathogenetic, clinical, and diagnostic and treatment aspects of AF.

An Investigation Into the Relationship Between Noncarious Cervical Lesions and Premature Contacts

The aim of the present study was to investigate the relationship between noncarious cervical lesions (NCCL) and dental premature contacts (PC). Following examination of 1,974 teeth from 77 patients referred to the Department of Oral Medicine, Faculty of Dentistry, Mashad University of Medical Science, Iran, a total of 167 teeth were identified to have the criteria set for noncarious cervical lesions (regarded as NCCL group). Also, 167 teeth exhibiting no such lesions were selected randomly from the same population (regarded as control group). The results indicated that within the NCCL group, the frequency of noncarious cervical lesions differed significantly among the various teeth; the first premolar teeth showed the greatest number of cervical lesions, followed by the canine teeth, and the second molar teeth had the least number of lesions. A similar trend was detected in the total number of premature contacts among the seven types of teeth. The results revealed a highly significant and positive correlation between the incidence of NCCL and the PC. The NCCL group and the control group differed significantly in the number of premature contacts in centric relation (CR) and working side, but not in balancing and protrusion.

Clinical evaluation of the association between noncarious cervical lesions and occlusal forces

STATEMENT OF PROBLEM

Noncarious cervical lesions (NCCLs) are a frequent challenge in clinical dental practice, given the variety of opinions regarding their etiology, diagnosis, and treatment.

PURPOSE

The purpose of this study was to assess the potential relationship between occlusal forces and the occurrence of NCCLs.

MATERIAL AND METHODS

The participant population consisted of 111 volunteers (30 male and 81 female, mean age 23.6 years). General personal information was recorded, after which participants were examined for the presence and location of NCCLs, gingival recession, fracture lines, dental and restoration fractures, presence and location of tooth wear, type of occlusal guidance scheme for lateral mandibular movements, and existence of occlusal interference or premature contacts. The participants were divided according to the presence or absence of NCCLs, and data were statistically analyzed with the Independent t test, the Chi-square test, and the Fisher exact test (α=.05).

RESULTS

A significant association was found between the presence of NCCLs and age (P=.008), gingival recession (P<.001), occlusal trauma (P<.001), presence (P<.001) and location of tooth wear, and group function as occlusal guidance scheme in lateral excursive movements (P<.001).

CONCLUSIONS

A strong relationship between the presence of NCCLs and occlusal overload was found.

Dental erosion and its growing importance in clinical practice: from past to present

Since the mid-1990s, the focus of studies on tooth wear has steadily shifted from the general condition towards the more specific area of dental erosion; equally, a shift has occurred from studies in adults to those in children and adolescents. During this time, understanding of the condition has increased greatly. This paper attempts to provide a critical overview of the development of this body of knowledge, from earlier perceptions to the present. It is accepted that dental erosion has a multifactorial background, in which individual and lifestyle factors have great significance. Notwithstanding methodological differences across studies, data from many countries confirm that dental erosion is common in children and young people, and that, when present, it progresses rapidly. That the condition, and its ramifications, warrants serious consideration in clinical dentistry, is clear. It is important for the oral healthcare team to be able to recognize its early signs and symptoms and to understand its pathogenesis. Preventive strategies are essential ingredients in the management of patients with dental erosion. When necessary, treatment aimed at correcting or improving its effects might best be of a minimally invasive nature. Still, there remains a need for further research to forge better understanding of the subject.

Noncarious Cervical Lesions and Their Association With Toothbrushing Practices: In Vivo Evaluation

Knowledge of the characteristics and etiologies of noncarious cervical lesions assists dentists in selecting an appropriate treatment and improving the prognosis.

Coupling image processing and stress analysis for damage identification in a human premolar tooth

Non-carious cervical lesions are characterized by the loss of dental hard tissue at the cement-enamel junction (CEJ). Exceeding stresses are therefore generated in the cervical region of the tooth that cause disruption of the bonds between the hydroxyapatite crystals, leading to crack formation and eventual loss of enamel and the underlying dentine. Damage identification was performed by image analysis techniques and allowed to quantitatively assess changes in teeth. A computerized two-step procedure was generated and applied to the first left maxillary human premolar. In the first step, dental images were digitally processed by a segmentation method in order to identify the damage. The considered morphological properties were the enamel thickness and total area, the number of fragments in which the enamel is chipped. The information retrieved by the data processing of the section images allowed to orient the stress investigation toward selected portions of the tooth. In the second step, a three-dimensional finite element model based on CT images of both the tooth and the periodontal ligament was employed to compare the changes occurring in the stress distributions in normal occlusion and malocclusion. The stress states were analyzed exclusively in the critical zones designated in the first step. The risk of failure at the CEJ and of crack initiation at the dentin-enamel junction through the quantification of first and third principal stresses, von Mises stress, and normal and tangential stresses, were also estimated.

Rehabilitation of the worn dentition

The purpose of this review was to evaluate the literature on the rehabilitation of tooth wear, with some pertinent historical, epidemiological and aetiological aspects of tooth wear provided as background information. In historical skull material, extensive tooth wear, assumed to be the result of coarser diets, was found even in relatively young individuals. Such wear is seldom seen in current populations. Although many of the factors associated with extensive tooth wear in historical material are no longer present or prevalent, new risk factors have emerged. In the young individual, the literature points to a global rise in soft drink consumption as the most significant factor in the development of tooth wear through dental erosion. Among older individuals, lifestyle changes and chronic diseases that are controlled with medications that may, in turn, result in regurgitation and/or dry mouth, are possible reasons amongst others for the widespread clinical impression of an increasing prevalence of tooth wear. The aetiology of tooth wear is multifactorial and the role of bruxism is not known. Clinical controlled trials of restorative and prosthodontic approaches for the range of clinical conditions that wear can give rise to, are limited in number and quality. Equally, the striking lack of evidence regarding the long-term outcomes of treatment methods and materials calls for caution in clinical decision-making. Notwithstanding these observations, clinicians have provided and continue to provide rehabilitative strategies for managing their patients' worn dentitions that range traditionally from extensive prosthodontics to an increasing reliance on adhesive techniques.

Identification of the occurrence and pattern of masseter muscle activities during sleep using EMG and accelerometer systems

BACKGROUND

Sleep bruxism has been described as a combination of different orofacial motor activities that include grinding, clenching and tapping, although accurate distribution of the activities still remains to be clarified.

METHODS

We developed a new system for analyzing sleep bruxism to examine the muscle activities and mandibular movement patterns during sleep bruxism. The system consisted of a 2-axis accelerometer, electroencephalography and electromyography. Nineteen healthy volunteers were recruited and screened to evaluate sleep bruxism in the sleep laboratory.

RESULTS

The new system could easily distinguish the different patterns of bruxism movement of the mandible and the body movement. Results showed that grinding (59.5%) was most common, followed by clenching (35.6%) based on relative activity to maximum voluntary contraction (%MVC), whereas tapping was only (4.9%).

CONCLUSION

It was concluded that the tapping, clenching, and grinding movement of the mandible could be effectively differentiated by the new system and sleep bruxism was predominantly perceived as clenching and grinding, which varied between individuals.

Non-carious cervical tooth surface loss: a literature review

OBJECTIVES

As the population ages and teeth are increasingly retained for life the incidence of non-carious cervical tooth surface loss is increasing but little is understood about the aetiology and management of these lesions. The purpose of this literature review was to review and critically appraise the literature as it relates to the prevalence, aetiology and treatment of non-carious cervical tooth surface loss.

SEARCH STRATEGY

An electronic search, using OVID electronic bibliographic databases was performed with no restriction on the language of publication.

CONCLUSIONS

Despite the paucity of research into non-carious cervical tooth surface loss it was concluded that the number and size of lesions increases with age, lesions are more common on the facial aspects of teeth and the formation of lesions appears to be multi-factorial with lesion shape not being a predictor of aetiology. It was also concluded that the value of restoring these lesions, where indicated, is unclear and that occlusal adjustment to increase the retention of restorations placed to restore lesions or to halt lesion progression cannot be supported.

Incidence of noncarious cervical lesions and their relation to the presence of wear facets

PROBLEM

Noncarious cervical lesions are characterized by loss of tooth structure in the cervical area, compromising its integrity and resulting in esthetic problems for the patient.

PURPOSE

The purpose of this study was to assess noncarious cervical lesions in young patients in an attempt to establish a possible relationship to the presence of wear facets.

MATERIALS AND METHODS

First-year dental students of Bauru Dental School were studied to verify the prevalence of noncarious cervical lesions and their relationship to the presence of wear facets. After 3 years, the students were examined again to verify the incidence of new lesions, trying to establish a correlation to the previous existence of wear facets.

RESULTS

Of the 1,131 teeth analyzed, 129 had noncarious cervical lesions. Twenty-nine of the 40 students had at least one tooth with one lesion. After 3 years, the incidence of new lesions was 57. Mandibular first molars (22.3%), mandibular first premolars (13.2%), mandibular second premolars (13.2%), and maxillary first molars (12.4%) showed the highest prevalence of lesions. On final analysis, 86.8% of all teeth presenting lesions showed wear facets. The identification of new lesions associated with the presence of wear facets identified during the first exam 3 years earlier was statistically significant (p < 0.01).

CONCLUSIONS

The patterns of wear facets found in the study population examined were associated with an increased occurrence of noncarious cervical lesions.

CLINICAL SIGNIFICANCE

Occlusal factors, especially the presence of wear facets, should be considered in the management of noncarious cervical lesions.

In vivo evaluation of noncarious cervical lesions in sleep bruxism subjects

STATEMENT OF PROBLEM

Occlusal load has frequently been suggested to be involved in the development of a noncarious cervical lesion (NCL). However, there is a lack of clinical studies evaluating NCLs and occlusal parameters in sleep bruxism (SB) subjects.

PURPOSE

The purpose of this clinical study was to assess the frequency of NCLs and determine potential occlusal differences between SB subjects and healthy control subjects.

MATERIAL AND METHODS

A total of 91 volunteers, 58 women and 33 men, with a mean (SD) age of 28.37 (4.89) years (range of 20 to 39 years), participated in this investigation. The clinical assessment of SB was based on the criteria of the American Academy of Sleep Medicine. The participants were divided into 2 groups; 58 subjects were assigned to the SB group and 33 subjects to the control group, following a thorough dental examination that was performed by a single trained dentist. Additionally, the following parameters were recorded: mean number of teeth present, existence/absence of NCLs, frequency of NCLs relating to the type of tooth, type of occlusal guidance scheme, existence of a slide from centric occlusion (CO) to maximum intercuspation (MI), length of the slide, and report of tooth hypersensitivity. Group differences were statistically analyzed using chi-square tests for the qualitative variables and Mann-Whitney U tests for the quantitative variables (alpha=.05).

RESULTS

NCLs were significantly more prevalent in SB subjects (39.7%) than in the control subjects (12.1%) (P=.006). In SB subjects, the first premolars were the teeth most affected, and in control subjects, the first molars were most affected. Tooth hypersensitivity was reported in 62.1% of the SB subjects and in 36.4% of the control subjects (P=.018). The evaluation of occlusal guidance schemes revealed no significant difference between the groups. In SB subjects (70.7%), a slide from CO to MI was significantly more prevalent than in control subjects (42.4%) (P=.008). Moreover, SB subjects demonstrated a significantly longer mean (SD) slide of 0.77 (0.69) mm compared to that of control subjects of 0.4 (0.57) mm (P=.008).

CONCLUSIONS

Within the limitations of this study, SB subjects demonstrated significantly more NCLs than the control group; whereas, the type of occlusal guidance scheme seems to be of minor importance in the development of NCLs.

Fatigue of dentin-composite interfaces with four-point bend

OBJECTIVES

The objective was to determine the fracture and cyclic fatigue properties of composite-dentin beams bonded with a self-etching adhesive in four-point bend.

METHODS

Beams of rectangular cross-section were shaped to a size of approximately 0.87mmx0.87mmx10mm and placed in a four-point bending apparatus, with the loading points 1.8 and 7.2mm apart, with the interface centered between the inner rollers. Cyclical loading was performed in Hanks' Balanced Salt Solution at 25 degrees C, with forces between 54% and 99% of the bending strength of the bonded beams.

RESULTS

Solid dentin and solid composite beams [n=6] had bending strengths of 164.4 and 164.6MPa, respectively, under monotonically increasing loads. Bonded beams [n=6] had strengths of 90.6MPa. No significant difference was found between solid composite and solid dentin beams, the bonded beams were different (ANOVA, p<0.0001) With long-term cycling, stresses below 49MPa were tolerated for 10(6) cycles, but with increasing stress up to 90MPa, beams failed earlier, demonstrating that subcritical fatigue cycling will eventually cause failure.

SIGNIFICANCE

Fatigue may be a significant mechanism of dentin-composite bond degradation.

Restoring cervical lesions with flexible composites

OBJECTIVES

Flexure at the tooth cervix has been suggested to dislodge cervical restorations more rapidly. The objective of this randomized controlled clinical trial was to test the hypothesis that a higher composite flexibility better withstands tooth flexure stress.

METHODS

One hundred and forty-two non-carious cervical lesions were restored with composites with contrasting stiffness. Seventy-one patients randomly received two cervical restorations placed following two out of the three experimental groups: (1) the three-step etch-and-rinse adhesive Permaquick applied with the stiff micro-hybrid composite Amelogen Hybrid (PMQ/A-Hy, Ultradent), (2) Permaquick applied with the more flexible micro-filled composite Amelogen Microfill (PMQ/A-Mi, Ultradent), or (3) the 'golden standard' three-step etch-and-rinse adhesive Optibond FL applied with the micro-hybrid composite Prodigy (O-FL/Pro, Kerr).

RESULTS

The recall rate at 7 years was 80%. No statistically significant difference was found for any of the parameters evaluated neither between both adhesives, nor between both composites (McNemar, p>0.05). Eleven percent of the O-FL/Pro restorations were clinically unacceptable due to loss of retention (5.5%) and severe marginal discoloration (5.5%). In the PMQ-group, 22% of the PMQ/A-Mi restorations (8% loss of retention, 5% severe enamel margin defects, 3% severe dentin margin defects, 6% severe marginal discoloration, 3% extreme sensitivity) and 19% of the PMQ/A-Hy restorations (13% loss of retention, 3% severe enamel margin defects, 3% severe marginal discoloration) needed repair or replacement.

SIGNIFICANCE

The clinical performance of the three adhesive/composite combinations was good and reliable during the 7-year clinical trial. It was concluded that the composite stiffness does not affect the clinical longevity of cervical composite restorations.

A critical review of non-carious cervical (wear) lesions and the role of abfraction, erosion, and abrasion

The terms 'abfraction' and 'abrasion' describe the cause of lesions found along the cervical margins of teeth. Erosion, abrasion, and attrition have all been associated with their formation. Early research suggested that the cause of the V-shaped lesion was excessive horizontal toothbrushing. Abfraction is another possible etiology and involves occlusal stress, producing cervical cracks that predispose the surface to erosion and abrasion. This article critically reviews the literature on abrasion, erosion, and abrasion, and abfraction. The references were obtained by a MEDLINE search in March, 2005, and from this, hand searches were undertaken. From the literature, there is little evidence, apart from laboratory studies, to indicate that abfraction exists other than as a hypothetical component of cervical wear.

Epidemiological evaluation of the multifactorial aetiology of abfractions

The purpose of this study was to determine risk indicators for the aetiology of abfractions (cervical wedge-shaped defects) on teeth using dental and medical variables obtained in a population-based sample of the cross-sectional epidemiological 'Study of Health in Pomerania' (SHIP). Medical history, dental, and sociodemographic parameters of 2707 representatively selected subjects 20-59 years of age with more than four natural teeth were checked for associations with the occurrence of abfractions using a two-level logistic regression model on a tooth and a subject level. The estimated prevalence of developing abfractions generally increased with age. The following independent variables were associated with the occurrence of abfractions: buccal recession of the gingiva, odds ratio (OR) = 6.7; occlusal wear facets of scores 1, 2 and 3, OR = 1.5, 1.9, 1.9; tilted teeth, OR = 1.4; inlays, OR = 1.6; toothbrushing behaviour, OR = 1.9 to 2.0 (two and three times a day versus once a day). First premolars had the highest estimated risk for developing abfractions, followed by the second premolars. Maxillary and mandibular teeth behaved similarly in terms of abfractions, with the exception of mandibular canines, which had a much lower estimated risk of incurring abfractions than did maxillary canines. The results of this analysis indicated that abfractions are associated with occlusal factors, like occlusal wear, inlay restorations, altered tooth position and tooth brushing behaviour. This study delivers further evidence for a multifactorial aetiology of abfractions.

Pattern of disocclusion in patients with complete cleft lip and palate

Objective:

to analyze the pattern of disocclusion during excursive mandibular movements and presence or absence of occlusal interferences and occlusal pathologies (gingival recession and abfraction).

Method:

examination of 120 individuals divided into two groups, as follows: Group 1-90 patients with complete cleft lip and palate (study group), subdivided into 30 patients with complete left unilateral cleft lip and palate, 30 patients with complete right unilateral cleft lip and palate and 30 patients with complete bilateral cleft lip and palate; Group 2-30 individuals without clefts (control group).

Results:

58.8% of patients in Group 1 presented unilateral or bilateral canine guidance, 26.6% presented unilateral or bilateral group function and 54.4% presented lateral movements through the posterior teeth. Regarding protrusive movements, 80% presented anterior guidance and 20% presented posterior guidance. In Group 2, 69.6% of individuals presented unilateral or bilateral canine guidance, 43.2% presented unilateral or bilateral group function and only 13.3% presented lateral movements through the posterior teeth; 3.4% presented protrusion through the posterior teeth.

Conclusions:

there was no difference in the pattern of disocclusion between subgroups of patients with clefts. Group 2 presented predominance of bilateral group function, whereas Group 1 presented a higher prevalence of posterior guidance during lateral movements. Protrusion occurred primarily through anterior guidance in Group 2 and through the posterior teeth in Group 1. There was high prevalence of occlusal interferences at the molar area for both groups, yet with no correlation with occlusal pathologies (recession and abfraction).

Dentin erosion simulation by cantilever beam fatigue and pH change

Exposed root surfaces frequently exhibit non-carious notches representing material loss by abrasion, erosion, and/or abfraction. Although a contribution from mechanical stress is often mentioned, no definitive proof exists of a cause-effect relationship. To address this, we examined dimensional changes in dentin subjected to cyclic fatigue in two different pH environments. Human dentin cantilever-beams were fatigued under load control in pH = 6 (n = 13) or pH = 7 (n = 13) buffer, with a load ratio (R = minimum load/maximum load) of 0.1 and frequency of 2 Hz, and stresses between 5.5 and 55 MPa. Material loss was measured at high- and low-stress locations before and after cycling. Of the 23 beams, 7 withstood 1,000,000 cycles; others cracked earlier. Mean material loss in high-stress areas was greater than in low-stress areas, and losses were greater at pH = 6 than at pH = 7, suggesting that mechanical stress and lower pH both accelerate erosion of dentin surfaces.

Esthetic noncarious Class V restorations: a case report

When restoring anterior and posterior teeth affected by noncarious cervical lesions, many clinicians overlook the etiologic factors responsible for the lesions' development, resulting in frequent restorative failures. The treatment approach for noncarious cervical lesions must not be based only on restorative procedures since a variety of causative and aggravating factors are related to their formation. This article discusses a treatment protocol and techniques for the restoration of noncarious Class V lesions and presents a clinical case in which esthetic restorations are achieved.

CLINICAL SIGNIFICANCE

Treatment options for noncarious Class V lesions can range from simply eliminating the causative factors of the lesions and regularly monitoring their progression to specific restorative procedures. Resin composites are the best materials for restoring cervical defects owing to their bonding ability, physical properties, and esthetic potential. A straightforward technique for the successful restoration of noncarious Class V lesions is presented.

Update on the etiology of tooth resorption in domestic cats

Based on recent findings of increased vitamin D activity in cats with feline odontoclastic resorptive lesions (FORL), the present article provides further clues on the possible etiology of FORL. Microscopic features of FORL and other peculiarities of feline permanent teeth are compared with pathologic findings obtained from experimental studies in other species. Administration of excess vitamin D or vitamin D metabolites in laboratory animals caused changes to dental and periodontal tissues that resemble histopathologic features of teeth from cats with FORL. Chronic excess dietary vitamin D may be the long-sought cause of multiple tooth resorption in domestic cats. It may also provide a basis for future research on idiopathic hypercalcemia and renal disease in the same species.

3D finite element model and cervical lesion formation in normal occlusion and in malocclusion

The aim of this study was to develop a three-dimensional (3D) finite element model (FEM) of the first maxillary premolar in order to compare the stress profiles in the buccal and palatal cervical regions. The 3D geometry of the tooth was reconstructed, the solid model was transferred into a finite element program where a 3D mesh was created, and the stress distribution analysis was performed. Two typical cases have been considered: the tooth under normal occlusion (case I) and the tooth under malocclusion (case II). In case I, larger compressive stresses were found in the cervical enamel and dentine. Tensile stresses were found in the fissure system, adjacent area, and at the vestibular surface of the buccal cusp. The peak values for the principal stress ranged from -259 to +2.25 MPa in the cervical areas. In the case II, larger compressive stresses were found in the palato-cervical enamel and dentine. Tensile stresses were found inside the enamel in the fissure system, adjacent area, at the vestibular surface of the buccal cusp, and in the bucco-cervical enamel. The peak values for the principal stress ranged from -501.947 MPa in palatal region to +82.4 MPa in the buccal region This study implies a role of occlusal forces in development of non-carious lesions. In the case of malocclusion, tensile stresses generated on the cervical areas were higher compared with the stresses generated in the case of normal occlusion and it is probably capable of producing non-carious cervical lesion.

In vivo correlation of noncarious cervical lesions and occlusal wear

STATEMENT OF PROBLEM

The etiology of noncarious cervical lesions is not well understood. An understanding of the etiology helps the clinician determine appropriate treatment and management strategies. Purpose This study evaluated the relationship between noncarious cervical lesions and occlusal (or incisal) wear.

MATERIAL AND METHODS

Casts (n = 299) made from dental students were articulated in a semi-adjustable articulator and evaluated. Data included the presence and contour of noncarious cervical lesions (NCLs) and the presence, location, and severity of any occlusal/incisal wear facets. Also included were Angle's classification, occlusal guidance patterns, midline, presence of tori, tooth restoration, reverse articulation (crossbite), open occlusal relationship, and posterior excursive contacts where present. Following a calibration procedure, 2 evaluators made independent observations on the casts. The first evaluator recorded for each tooth in each subject: presence and severity of NCLs, presence and extent of occlusal/proximal restorations, and presence of reverse articulation and open occlusal relationship. Following the first evaluation red rope wax was placed at the cervical margins of each tooth for the purpose of blinding the second evaluator from NCL observations. The second evaluator recorded severity and location of occlusal/incisal wear, presence or absence of posterior excursive contacts, Angle's classification, occlusal guidance pattern, any midline discrepancy, and presence or absence of tori. The Spearman correlation coefficient and chi 2 tests were used to analyze the data (alpha=.05).

RESULTS

There was no relationship between noncarious cervical lesions and occlusal/incisal wear. There was also no correlation between NCLs and other parameters examined.

CONCLUSIONS

Under the conditions of this study, noncarious cervical lesions are not related to occlusal wear.

Resin bonding to cervical sclerotic dentin: a review

Several reports have indicated that resin bond strengths to noncarious sclerotic cervical dentine are lower than bonds made to normal dentine. This is thought to be due to tubule occlusion by mineral salts, preventing resin tag formation. The purpose of this review was to critically examine what is known about the structure of this type of dentine. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralised surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridisation of the underlying sclerotic dentine. In addition, bacteria are often detected on top of the hypermineralised layer. Sometimes the bacteria were embedded in a partially mineralised matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival and deepest portions of these wedge-shaped lesions were significantly lower than similar areas artificially prepared in normal teeth. When resin bonds to sclerotic dentine are extended to include peripheral sound dentine, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention.

Effects of occlusal load on cervical lesions

Toothbrush abrasion has been considered to cause cervical lesions. However, some investigators have proposed that occlusal loading factors direct tensile stresses at the cervical area, resulting in wedge-shaped abfraction defects. The purpose of this study is to investigate the role of axial and non-axial load on the development of cervical lesions. Matched paired premolars, extracted for orthodontic purposes, were used in a custom-fabricated toothbrushing apparatus. A periodontal sulcus width of 0b1 mm with 1 mm gingival recession was simulated with denture base resin. In phase 1, eight matched premolar pairs were subjected to 80 h (1b4 million strokes) of brushing and 300 g of toothbrush force. Toothpaste slurry was applied continuously through the toothbrush. One specimen in each pair was subjected to 250 h and 45 kg of continuous axial load, while the other unloaded tooth served as a negative control. In phase 2, 10 matched premolar pairs were subjected to the same conditions; however, the experimental teeth were subjected to 250 h and 45 kg of intermittent non-axial load, directed at a 45 degrees angle to the buccal cusp. Rubber impressions were made of the cervical lesions, then trimmed, weighed, and compared to determine the amount of tooth material lost. When teeth were loaded axially, there was significantly less tooth material loss (P < 0b02); however, when teeth were loaded non-axially, there was no significant difference (P =0b80) when compared with controls. Optical and scanning electron microscopy did not reveal any significant differences in the morphology between pairs. Our data suggest that the application of occlusal load may not necessarily play a significant role in the progression of cervical tooth wear commonly referred to as abfraction.

Perioesthetic approach to the diagnosis and treatment of carious and noncarious cervical lesions: Part I

Several factors can contribute to the development of noncarious cervical lesions. Therefore, these lesions can be described and classified according to their primary etiology. Traditionally, most dentists have treated noncarious cervical lesions only with restorative methods, for example, composite resin restorations. However, in many cases, a periodontal or a combined restorative/periodontal approach provides a better esthetic and functional result. In part I of this two-part report, we provide a review of noncarious cervical lesions and a series of clinical case reports showing surgical techniques used and the importance of the periodontal aspect of lesion management.

A survey of the correspondence between abrasions and tooth brushing habits in Erzurum, Turkey

AIM

To determine whether there is a correlation between dental abrasions and the frequency and technique of tooth brushing, as well as to examine the prevalence of dental abrasion according to age and gender.

MATERIALS AND METHODS

This study was carried out on 428 adults (242 female, 186 male) 20 years of age and older, who attended the Department of Operative Dentistry, Department of Oral Diagnosis and Oral Radiology Faculty of Dentistry, Atatürk University.

RESULTS

The study revealed a statistically significant relationship between abrasive lesions and age groups as well as between abrasive lesions and gender. A statistically significant difference was determined between abrasions and tooth brushing frequency, while there was no statistically significant relation between abrasions and tooth brushing technique (p>0.05).

CONCLUSION

The prevalence of tooth brushing abrasions increases with age, and lesions are seen more frequently in males than in females. Also, tooth brushing technique is not important to the presence of abrasions, but increased tooth brushing frequency results in an increase in the number of abrasions.

Analysis of etiologic factors and periodontal conditions involved with 309 abfractions

OBJECTIVES

Non-carious cervical lesions (NCCL), also termed abfractions, have long been thought to be produced by excessive brushing. Nearly 20 years ago an occlusal etiology was proffered (Lee & Eagle 1984). Controversy still exists concerning these two concepts. The present work was carried out to verify the occurrence of signs of excessive brushing or occlusal disturbances associated with abfractions.

MATERIAL AND METHODS

All first consultants were screened for the presence of abfractions during one trimester. NCCL were found in 61 patients who consequently received a thorough examination searching for clinical evidence of excessive brushing or occlusal disturbances. The presence of plaque, calculus, periodontitis, or mobility was also noted. Simple frequency and percentage were used to describe the occurrence of different clinical signs in association with the presence of abfractions.

RESULTS

Abfractions often exist in mouths presenting plaque (40.1%), calculus (41.7%), or periodontitis (20.4%). Ulceration of the gingiva is a rare finding (1.6%). However, subgingival apical limits were frequent (32.5%). NCCL coexist almost systematically with occlusal wear facets (94.5%). Lack of canine disclusion (77.2%) was also closely associated with the presence of abfractions. Conversely, mobility was seldom found (1.9%).

CONCLUSIONS

Clinical signs of excessive brushing were lacking, whereas signs of occlusal disturbance were very consistent with the presence of abfractions.