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PubMed2004

Effect of dentinal fluid composition on dentin demineralization in vitro.

Dentin demineralization is reduced by perfusion with water. We hypothesized that a simulated dentinal fluid (SDF) that contains albumin, in addition to electrolytes, would be more effective in reducing dentin demineralization than water alone, and this effect would increase with increasing flow rate of SDF. Perfusion rate in tooth segments that carried buccal cervical dentin windows was measured in a fluid transport set-up. These windows were then demineralized under perfusion with water, or SDF at 1.47 kPa for 31 days. We analyzed integrated mineral loss and lesion depth with the use of transverse microradiography (TMR), which revealed that 38% more mineral dissolved from dentin lesions perfused with water than from those perfused with SDF. The former were also 18% deeper. Flow rate of dentinal fluid showed no correlation with demineralization. We concluded that composition of dentinal fluid is an important determinant of the rate of lesion formation and progression in dentin.

Albumins↗
PubMed2005

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.

Dental Stress Analysis↗
PubMed2006

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.

Dental Enamel↗
PubMed2006

Increased Young's modulus and hardness of Col1a2oim dentin.

Mice harboring the Col1a2(oim) mutation (oim) express dentinogenesis imperfecta. To determine the effect of Col1a2 genotype on tissue mechanical properties, we compared Young's modulus and hardness of dentin in the 3 Col1a2 genotypes. Upper incisors were tested by nanoindentation. Genotype had a significant effect on Young's modulus, but there was not a simple mutant allele dosage relationship. The effect of genotype on hardness did not reach significance. Hardness and Young's modulus were greater near the dento-enamel junction than near the pulp chamber. Greater hardness and Young's modulus values near the dento-enamel junction reflected continued mineralization of the dentin following its initial synthesis. Analysis showed the mechanical data to be consistent with Fourier transform infrared and backscattered electron microscopy studies that revealed increased mineralization in oim bone. Analysis of the data suggests that clinical fragility of teeth in oim mice is not due to deficiencies of hardness or Young's modulus, but may be due to defects in post-yield behavior or resistance to fatigue damage.

Animals↗
PubMed2006

Influence of alveolar support on stress in periodontal structures.

The influence of alveolar bone support on the functional capability of a tooth remains unclear. It was hypothesized that a reduction in alveolar support causes an increase of maximum stress in the periodontal structures. Mathematical models of the maxillary incisor to simulate in vivo tooth movement were constructed with periodontium of normal or reduced bone height, and normal or widened periodontal ligament (PDL) space. Under simulated bite force, the maximum tensile stress at the lingual cervical region in the PDL increased with bone height reduction, but decreased with PDL widening. The compressive stress at the cervical region in the cortical bone was no more than 22% of the yield strength of bone, and did not increase by the height reduction with widened PDL. The result suggests that the height reduction potentially causes mechanical damage to the PDL, but, of itself, is not likely to have a negative effect on the bone.

Alveolar Bone Loss↗
PubMed2005

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.

Bicuspid↗
PubMed2006

The biomechanics of abfraction.

The role of occlusal loading in the development of non-carious cervical lesions is becoming increasingly prominent. It is suggested that high occlusal loads result in large stress concentrations in the cervical region of the teeth. These stresses may be high enough to cause disruption of the bonds between the hydroxyapatite crystals, eventually resulting in the loss of cervical enamel. This article reviews the evidence to support the thesis that occlusal loading can contribute to the process of non-carious cervical tooth loss or abfraction. It also reviews the potential interactions between occlusal loading and erosion that may contribute to non-carious cervical tooth loss.

Animals↗
PubMed2004

Conventional and digital radiographic methods in the detection of simulated external root resorptions: a comparative study.

OBJECTIVES: The purpose of this study was to evaluate and to compare the efficacy of a conventional and a digital radiographic method in diagnosing simulated external root resorption cavities. METHODS: Human dry mandibles containing teeth were covered with bovine muscle slices in order to simulate the soft tissues. Nine teeth from each dental group were investigated. Three periapical radiographs of each tooth were taken in an orthoradial, mesioradial and distoradial aspect using conventional film (Insight Kodak F-speed; Eastman Kodak, Rochester, NY) and a digital sensor (DRS Gnatus System; Gnatus, Ribeirao Preto, Brasil). The teeth were extracted using a forceps and had 0.7 mm and 1.0 mm deep cavities prepared on their vestibular, mesial and distal surfaces at the cervical, middle and apical thirds. Following preparation, each tooth was replaced in its alveolus and new radiographs were taken. Three dental professionals, an endodontist, a radiologist and a general practioner, evaluated the images. RESULTS: A larger number of cavities (P<0.05) were detected by the digital method when compared with the conventional method, for all depths of lesions. CONCLUSIONS: The results of this study suggest that the digital radiographic method is more sensitive than conventional radiography to detect simulated external root resorption cavities.

Animals↗
PubMed2002

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.

Acids↗
PubMed2002

Direct restorative material use of selected practitioners in the United Kingdom.

PURPOSE OF THE INVESTIGATION: To investigate, by questionnaire, the direct restorative materials used by a sample of practitioners from the United Kingdom. BASIC PROCEDURES: A postal questionnaire was distributed to a group of self-selected practitioners, who volunteered to participate in the study. In all 110 practitioners participated in the study. MAIN FINDINGS: The most used material for the restoration of occlusal (Class I) and approximal (Class II) lesions was amalgam with 61% and 73% of practitioners indicating that they used amalgam in this situation. Adhesive tooth-coloured materials, specifically composites and compomers, were preferred by the majority of practitioners for anterior approximal (Class III) and incisal (Class IV) restorations with compomer preferred for Class V restorations including non-carious cervical lesions and for the restoration of primary teeth. PRINCIPAL CONCLUSIONS: It is concluded that the general practitioners surveyed in this study tend to use amalgam for the restoration of Class I and II lesions as opposed to resin composite. The majority of practitioners in this study used compomers, a relatively new group of restorative materials, with little evidence of traditional glass-ionomer cements being used routinely.

Adult↗
PubMed2001

Examining the prevalence and characteristics of abfractionlike cervical lesions in a population of U.S. veterans.

BACKGROUND: Abfraction is believed to be caused by biomechanical loading forces. It may be due to flexure and ultimate fatigue of tooth tissues that occur away from the point of occlusal loading. Other possible causes of cervical lesions include toothbrush abrasion and erosion. The purpose of this study was to investigate the characteristics and prevalence of abfraction-like lesions in a population of U.S. veterans. METHODS: The authors evaluated 103 teeth with noncarious cervical lesions in 32 subjects and characterized them based on the surface on which the lesion was located, history of toothbrush abrasion, size of the lesion, presence of plaque, surface texture, and presence and size of occlusal wear facets. RESULTS: Clinical examination revealed that adjacent control teeth had a significantly lower percentage of surfaces with plaque than did teeth with cervical lesions. Control teeth also had significantly less gingival recession than did affected teeth. Seventy-five percent of subjects reported a history of using a firm toothbrush, and 78.1 percent reported using a brushing technique that is known to cause toothbrush abrasion in the affected area. Affected teeth had neither significantly different occlusal wear facets nor occlusal contacts than control teeth. No significant correlations were found between cervical lesion dimensions and facet area. CONCLUSIONS: Toothbrush abrasion is strongly suspected as contributing to the formation of the majority of wedge-shaped lesions in this group of subjects. A small subset of lesions is thought to have resulted from some other phenomenon. Although the presence or contribution of occlusal stresses in the direct formation of these lesions could not be measured directly, the possibility of abfraction could not be eliminated. CLINICAL IMPLICATIONS: Because the existence of abfraction could not be ruled out in about 15 percent of the cases, teeth with noncarious, wedge-shaped lesions warrant careful occlusal evaluation, with the possible need for occlusal adjustment or bitesplint therapy to treat bruxism.

Adult↗
PubMed2001

Clinical evaluation of two one-bottle dentin adhesives at three years.

BACKGROUND: The method currently used to adhere resin to dentin involves etching, priming and bonding. Many commercial adhesives now combine priming and bonding functions in a single solution, and these are frequently called one-bottle adhesives. The purpose of this study was to compare the 36-month clinical performance of two commercial one-bottle adhesives. METHODS: The authors enrolled 33 patients with noncarious cervical lesions in the study. A total of 101 lesions were restored with either a filled, ethanol-based adhesive (OptiBond Solo, SDS Kerr) or an unfilled, acetone-based adhesive (Prime & Bond 2.1, Dentsply Caulk) and a hybrid resin-based composite. Enamel margins were not beveled, and no mechanical retention was placed. The restorations were evaluated at baseline and six months, 18 months and 36 months after placement using modified Cvar/Ryge criteria. RESULTS: The retention rates at 36 months were 93.3 percent for the ethanol-based adhesive and 89.4 percent for the acetone-based adhesive. The difference in retention rates was not statistically significant. In both groups, 12 percent of the retained restorations had marginal staining, but no recurrent caries was detected around any restoration. Other restoration characteristics such as marginal adaptation and color match remained excellent three years after placement. CONCLUSIONS: The performance of both adhesives was excellent during this 36-month clinical trial. At the most recent recall evaluation (that is, 36 months), the filled, ethanol-based adhesive exhibited slightly better bond durability, but the difference between the two materials was not statistically significant. CLINICAL IMPLICATIONS: The one-bottle adhesives evaluated in this study provided excellent clinical retention of Class V restorations without mechanical retention. When the materials are used properly, restorations are retained at a high rate during at least three years of clinical service.

Adult↗
PubMed2002

Abfraction.

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Dental Enamel↗
PubMed2002

Characteristics of noncarious cervical lesions: a clinical investigation.

BACKGROUND: The purpose of the authors' in vivo investigation was to analyze the characteristics of noncarious cervical lesions, or NCCLs, in adult patients who had a high incidence of them. METHODS: The patient pool consisted of a total of 57 patients and 171 teeth (three teeth per patient), with one NCCL per tooth. The characteristics the authors evaluated were shape, dimensions, sensitivity, sclerosis and occlusion. RESULTS: In terms of lesion characteristics, 91 percent of the lesions had axial depths of 1 to 2 millimeters, 49 percent had occlusogingival widths of 1 to 2 mm, 74 percent had an angular shape of 45 to 135 degrees, 76 percent had mild or moderate sclerosis, and 73 percent had no or mild sensitivity. In terms of occlusion, 75 percent of teeth had an Angle Class I occlusion on the involved side, 60 percent had group function or mixed excursive guidance, 82 percent had wear facets, and 99 percent had Type 0 or I mobility. In terms of tooth location, 70 percent of NCCLs were on posterior teeth, 65 percent were on maxillary teeth, and 46 percent were on premolars. CONCLUSIONS: The evaluated NCCLs were found mainly to have small dimensions of depth and width (< 2 mm) and to be roughly right-angled in shape, and many had sclerosis and low sensitivity. A majority of the dentitions studied had Class I occlusion, with group function, prevalent wear facets, and little or no mobility. Cervical lesions were more common with posterior maxillary teeth and premolars, especially first premolars, which had the highest prevalence of lesions. Older patients were more likely to exhibit noncarious cervical lesions, but no great difference in incidence was found between men and women. Clinical Implications. A knowledge of the NCCL characteristics and etiologic covariables aids in proper case selection for treatment, aids in selection of appropriate treatment protocols and improves assessment of prognosis.

Adult↗
PubMed2004

Attrition, abrasion, corrosion and abfraction revisited: a new perspective on tooth surface lesions.

OVERVIEW: The authors propose updated and revised nomenclature, definitions and classification for tooth surface lesions. Their objective is standardization, clarity and clinical utility for the dental practitioner. The article presents a schema of the pathodynamic mechanisms in the formation of tooth surface lesions--three basic physical and chemical mechanisms, their interactions and their dental manifestations. CONCLUSIONS AND CLINICAL IMPLICATIONS: The use of precise definitions will assist the practitioner in determining the etiology of various tooth surface lesions. Understanding the pathodynamic mechanisms and their many possible interactions, as set forth in the schema, will enable the practitioner to make an accurate differential diagnosis and to provide effective prevention and treatment. It also will assist dentists in communicating more effectively with their colleagues as well as with their patients. In addition, the schema helps identify areas in which future research is indicated.

Bite Force↗
PubMed2005

The two-year clinical performance of esthetic restorative materials in noncarious cervical lesions.

BACKGROUND: Materials used in restoration of cervical lesions include resin-modified glass ionomer cements, polyacid-modified resin-based composites and resin-based composites. In this study, the authors evaluated the clinical performance of these materials over a two-year period. METHODS: Thirty patients were enrolled in this study. The authors placed in these patients 130 restorations, 24 of which were Vitremer (3M Dental Products, St. Paul, Minn.), 38 were F2000 Compomer (3M Dental Products), 46 were Dyract AP (Dentsply DeTrey, Konstanz, Germany) and 22 were Valux Plus (3M Dental Products). Enamel margins were not beveled, and no mechanical retention was placed. Two independent, calibrated examiners evaluated the restorations baseline and at one and two years after placement using modified U.S. Public Health Service criteria. RESULTS: Retention rates at the end of two years were 100 percent for Vitremer, 67 percent for F2000 Compomer, 68 percent for Dyract AP and 70 percent for Valux Plus. The retention rate of Vitremer was significantly higher than that of the others (P < .05). In other categories, however, Valux Plus had the most favorable performance (P < .05). No secondary caries was detected around any restoration. CONCLUSION: Vitremer, with its high retention rate, seems to be the most appropriate material for restoration of noncarious cervical lesions, though it does not have the esthetic properties of resin-based composites. All materials used in this study were in need of improvements. CLINICAL IMPLICATIONS: Resin-modified glass ionomer cement, polyacid-modified resin-based composite and resin-based composite behaved differently in the restoration of noncarious cervical lesions. Therefore, clinicians should take factors such as esthetic needs and localization into account in selecting materials for such restorations.

Adult↗