Development of noncarious cervical notch lesions in vitro

Composite vs. ionomer vs. mixed restoration of wedge-shaped dental cervical lesions: Marginal quality relative to eccentric occlusal loading

Dental cervical restorations may be impacted by resultants of occlusal loads that may have already contributed to the development of the lesion and should rely on materials' favorable properties to bear the stresses. The marginal quality of cervical restorations made with materials of different moduli of elasticity in essence, isolated, or in combination, was evaluated relative to eccentric occlusal loading. Cervical wedge-shaped cavities, prepared in extracted premolars, were restored with a composite resin (CR), a restorative ionomer (GIC), or the composite in combination with a lining ionomer (Mixed restoration: M). Half of the teeth in each group were subjected to eccentric occlusal loading (eol; 150 N / 10⁶ cycles / 2.5 Hz; CReol / GICeol / Meol, n = 10), and the others were stored in 37 °C distilled water (Control: c; CRc / GICc / Mc, n = 10). A fluorescein-modified adhesive favored delimitation of formed gaps, which were evaluated by confocal laser scanning microscopy regarding their presence, location related to the cavity walls, and width and depth (µm), at a 5% significance level. From a comprehensive perspective, neither the loading nor the materials were significantly associated with the qualitative response variables or exerted any influence over the quantitative variables. More specifically, the use of the different materials was significantly associated with the frequency of gaps exclusively when loading was applied (Chi-square test, p = 0.029, CR > M > GIC). Though the marginal quality of cervical restorations may not be influenced by eccentric occlusal loading or the use of different materials, even in association in general, the unfavorable aspects of the use of the composite may be relevant, particularly in face of the existence of eccentric occlusal loads.

Characteristics of non-carious cervical lesions--an ex vivo study using micro computed tomography

The aetiology of non-carious cervical lesions (NCCLs) is not well understood and still controversial. The aim of this ex-vivo study was to examine the morphological characteristics of NCCLs for clinical evidence of enamel loss above the cemento-enamel junction (CEJ) as suggested by the abfraction theory. Fifty extracted human teeth with various types of NCCLs were collected and scanned by micro computed tomography. The reconstructed three-dimensional models were evaluated from multiple aspects, including longitudinal cross-section series. The location of internal line angle and proximal exits of the lesions were evaluated in relation to the level of CEJ. The coronal margins of the lesions were inspected for evidence of enamel loss above the CEJ using the bucco-lingual longitudinal sectional images. Coronal margins of the lesions were located along and/or under the CEJ for all of the 50 samples. In most of the lesions, regardless of lesion type, the proximal exits and internal line angles were located below the CEJ. This study did not detect clinical evidence of enamel loss above the occlusal margin of NCCLs as would have been expected according to the general abfraction mechanism.

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.

A qualitative assessment of non-carious cervical lesions in extracted human teeth

BACKGROUND

Opinions vary about the causes of non-carious cervical lesions (NCCLs). They have been attributed to toothbrush abrasion, acid corrosion (commonly termed dental erosion), and abfraction. The purpose of this study was to examine the microwear details of NCCLs in a collection of extracted human teeth using scanning election microscopy (SEM).

METHODS

Negative replicas of large NCCLs in 24 extracted human teeth were obtained in polyvinylsiloxane impression material (Light Body Imprint II, 3M ESPE) and viewed under SEM.

RESULTS

All NCCLs extended from the cemento-enamel junction to the root surface and they displayed a variety of wedge-shaped appearances. There was evidence of both abrasion and corrosion in 18 of the 24 teeth (75.0 per cent), abrasion only in one tooth (4.2 per cent) and corrosion only in five teeth (20.8 per cent). Horizontal furrows with smooth edges and minor scratch marks, characteristic of abrasion and corrosion, were noted in 13 teeth (54.2 per cent).

CONCLUSIONS

Based on microscopic assessment of a sample of extracted teeth, it appears that abrasion and corrosion are common associated aetiological factors in the formation of NCCLs.

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.

Symmetry of non-carious cervical lesions in canines and premolars

OBJECTIVES

Clinically non-carious cervical lesions (NCCLs) are frequently seen. The aim of this study was to investigate the relationship between the shape and symmetry of NCCLs, wear of cuSPS and triangular ridge, and the curvature of the tooth root.

METHODS

One hundred and twenty-nine extracted human upper canine teeth and 274 extracted human upper premolar teeth with NCCLs were used in this study. The specimens were studied using photographs and three-dimensional scanning.

RESULTS

Asymmetric NCCL was observed in 69.0% of the canines and 44.5% of the premolars. Wear of cusp and lingual ridges was observed in 82.9% and 93.0% of the canines, respectively. Wear of the buccal cusp and buccal triangular ridge was observed in 85.4% and 89.8% of the premolars, respectively. On the other hand, the wear of lingual cusp and lingual triangular ridge was observed in 89.1% and 93.8% of the premolars, respectively. The curvature of the root was observed in 48.1% of the canines and 43.4% of the premolars.

CONCLUSIONS

There was no relationship between the symmetry of NCCLs, and the wear of cuSPS and triangular ridges for either canines or premolars. Although there was a relationship (p < 0.05) between the symmetry of NCCL and the curvature of the root in the canines, no relationship was observed between the symmetry of NCCL and the curvature of the root in the premolars.

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.

Attrition, abrasion, corrosion and abfraction revisited

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.

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.

Abfraction Lesions: Myth or Reality?

Loss of tooth substance in the cervical region is usually attributed to toothbrush abrasion, erosion, or a combination of both factors. Recently the role of occlusal loading has become increasingly prominent. It is suggested that high occlusal loads cause large cervical stress concentrations, resulting in a disruption of the bonds between the hydroxyapatite crystals and the eventual loss of cervical enamel. This process has been called noncarious cervical tooth loss or abfraction. This article reviews the available evidence to support the thesis that occlusal loading can contribute to the process of abfraction. It also reviews the potential interactions between occlusal loading and erosion that may contribute to abfraction lesion formation.

CLINICAL SIGNIFICANCE

It is important to recognize the potential role of occlusal loading in the loss of cervical tooth tissue so that management of the occlusion can be incorporated into a treatment plan for a patient with abfraction lesions.

Noncarious cervical lesions and abfractions: a re-evaluation

BACKGROUND

The concept of abfraction is controversial. The authors present the fundamental basis of abfraction and review studies that describe the condition.

TYPES OF STUDIES REVIEWED

The authors used data on masticatory forces, enamel and dentin properties, as well as stress studies related to abfraction, for background information. They also analyzed the genesis of the abfraction theory, experimental evidence, case presentations, clinical investigations and restorative studies.

RESULTS

The theory of abfraction is based primarily on engineering analyses that demonstrate theoretical stress concentration at the cervical areas of teeth. While some recent stress studies support earlier findings, others have provided significant deviating information. Few controlled studies exist that demonstrate the relationship between occlusal loading and abfraction lesions. The role of occlusal loading in noncarious cervical lesions (as shown by clinical data) appears to be part of a multifactorial event that may not necessarily follow the proposed classic abfraction mechanism, and other mechanisms or factors may explain cervical restoration failure just as well.

CLINICAL IMPLICATIONS

There is little direct evidence supporting the theory of abfraction as the primary factor in the formation of noncarious cervical lesions. Controlled clinical trials are necessary to elucidate more fully the etiology of those lesions.