Noncarious cervical lesions and abfractions: a re-evaluation

Deep Margin Elevation: Current Concepts and Clinical Considerations: A Review

Dietschi and Spreafico first proposed deep margin elevation (DME) in 1998 to address the multiple clinical problems associated with sub-gingival margins, where sub-gingival margins will be repositioned coronally using composite resin restorations. Given that dentistry is directing towards conservatism, its use is currently trending. Materials and Methods: a search was performed through PubMed, Scopus, and Google Scholar search engines to obtain relevant articles with no time restriction. Results: With biological width taken into consideration, well-defined and polished sub-gingival restorations are compatible with periodontal health. Marginal integrity in the DME technique seems to be affected by the type of adhesive, restoration, and incremental layering of the restoration. Regarding fracture resistance, DME has no significant effects. Conclusion: The DME technique seems to be a minimally invasive alternative to surgical crown lengthening (SCL) and orthodontic extrusion (OE) with respect to biological width. Well-controlled clinical trials are limited in this field; further long-term follow-up studies emphasizing the periodontal outcomes and prevention of complications are needed.

Evaluation of Dentin Tubule Plugging Efficiencies and Effects on Dentin Surface Roughness of Dentin Desensitizing Agents, the Er,Cr:YSGG Laser, and Their Combination After Erosion-Abrasion Cycles: An In Vitro Study

OBJECTIVES

The purposes of this in vitro study were to evaluate the tubule plugging efficiencies and effects on the surface roughness of dentin of different dentin desensitizing agents (DDAs; Teethmate Desensitizer, Kuraray; Gluma Desensitizer, Kulzer; Clinpro White Varnish, 3M ESPE; Enamelast, Ultradent) and the Er,Cr:YSGG laser (Biolase, Waterlase), both alone and in combination with DDAs, after application and after an erosion-abrasion cycle.

METHODS AND MATERIALS

For surface roughness examinations, superficial buccal dentin specimens were divided into 10 groups: the control, Teethmate Desensitizer, Gluma Desensitizer, Enamelast, Clipro White Varnish, Er,Cr:YSGG Laser, Teethmate Desensitizer-Laser, Gluma Desensitizer-Laser, and Enamelast-Laser, and Clinpro White Varnish-Laser groups. Profilometric analyses and scanning electron microscopy (SEM) examinations were performed after applications and after a 5-day erosive-abrasive cycle. For the statistical analysis of surface roughness measurements, 2-way analysis of variance (ANOVA), 1-way ANOVA, and Tukey post hoc test were used.

RESULTS

Among the treatments, only DDAs alone did not cause increase in surface roughness after application. All of the laser applications increased the surface roughness of dentin, and after the erosion-abrasion cycle, all of the test groups had increased surface roughness. However, SEM images showed that morphological changes were less frequently observed in all of the experimental groups than in the control group. In addition, all of the laser-DDA combinations had stronger tubule occlusion effects than did DDAs alone, even after erosion-abrasion.

CONCLUSIONS

All of the test treatments showed protective effects on dentin surfaces against the negative effects of erosion-abrasion. The addition of the laser to DDA applications increased tubular plugging efficiencies of DDAs, and the tubule plugs of the combination treatments were resistant to the erosion-abrasion cycle.

Pathophysiology of Demineralization, Part I: Attrition, Erosion, Abfraction, and Noncarious Cervical Lesions

PURPOSE OF THE REVIEW

Compare pathophysiology for infectious and noninfectious demineralization disease relative to mineral maintenance, physiologic fluoride levels, and mechanical degradation.

RECENT FINDINGS

Environmental acidity, biomechanics, and intercrystalline percolation of endemic fluoride regulate resistance to demineralization relative to osteopenia, noncarious cervical lesions, and dental caries. Demineralization is the most prevalent chronic disease in the world: osteoporosis (OP) >10%, dental caries ~100%. OP is severely debilitating while caries is potentially fatal. Mineralized tissues have a common physiology: cell-mediated apposition, protein matrix, fluid logistics (blood, saliva), intercrystalline ion percolation, cyclic demineralization/remineralization, and acid-based degradation (microbes, clastic cells). Etiology of demineralization involves fluid percolation, metabolism, homeostasis, biomechanics, mechanical wear (attrition or abrasion), and biofilm-related infections. Bone mineral density measurement assesses skeletal mass. Attrition, abrasion, erosion, and abfraction are diagnosed visually, but invisible subsurface caries <400μm cannot be detected. Controlling demineralization at all levels is an important horizon for cost-effective wellness worldwide.

An in vitro evaluation of microleakage of resin based composites bonded to chlorhexidine-pretreated dentin by different protocols of a universal adhesive system

Purpose

This study compared microleakage of different resin based composite (RBC) materials bonded to dentin, after chlorhexidine (CHX) application, by different adhesion protocols of a universal adhesive system.

Methods

Class V cavities were prepared on the buccal and lingual surfaces of 40 premolar teeth. The “etch-and-rinse” technique of a universal bond adhesive system (Single Bond Universal Adhesive) was used on buccal preparations, while the “self-etch” protocol was used on the lingual surfaces. Two RBCs, one bulk fill (Filtek Bulk Fill [FBF]) and one conventional (Filtek Z350 XT [Z350XT]), were used. Teeth were divided into two groups of 20 teeth each, 10 per each RBC (n = 10): (1) control; and (2) pretreatment with 2% CHX. For FBF groups, teeth were restored with a single increment; however, for Z350XT, a layering technique was used. Teeth were aged by thermo-cycling and prepared for microleakage testing. Dye penetration was evaluated and scored from 0 to 4. Data were analyzed at a significance level of P < 0.05.

Results

The highest microleakage mean scores were found in the control group of the etched margins for both RBCs (2.80 ± 1.033 FBF and 2.10 ± 1.370 Z350XT). The CHX-pretreated group showed significantly lower microleakage than the control for FBF only (P = 0.008). No significant difference was found between groups for the “self-etch” protocol (χ² = 0.884, P = 0.08). No significant differences were found between FBF and Z350XT in all study groups (P > 0.2).

Conclusions

When the “self-etch” protocol of the universal adhesive system was used, dentin microleakage was not affected by CHX-pretreatment when teeth were restored with bulk fill or conventional RBCs. In the “etch-and-rinse” protocol, CHX application improved the marginal seal before restoration with bulk fill material. However, in the absence of CHX, the “etch-and-rinse” protocol negatively affected marginal integrity.

Effect of proximal box elevation on fracture resistance and microleakage of premolars restored with ceramic endocrowns

Background

Restoration of endodontically treated premolar is in high risk for biomechanical failure, and often presents with subgingival margins. Proximal box elevation (PBE) has been used to relocate subgingival cavity outlines.

Objective

To evaluate the influence of PBE on fracture resistance and gingival microleakage of premolars with endodontic access cavities following ceramic endocrown.

Methods

Eighty sound maxillary premolars with standardized Class II cavities on mesial surfaces were randomly assigned to four groups (n = 20 in each group). Groups E1, E2 and E3, with proximal margins located in dentin/cementum, 2 mm below the cemento-enamel junction (CEJ), simulated subgingival location. Group E4 (supragingival group), with proximal margins located in enamel, 1 mm above the CEJ, was used as the positive control. For margin elevation of the proximal cavities, bulk-fill Smart Dentin Replacement (SDR), a visible light cured resin composite, was applied in group E1, and conventional resin composite (3M Z350 XT, a light-activated composite) was placed in group E2. Group E3 was only treated with a ceramic crown and served as the negative control. In all groups, computer-aided design (CAD) ceramic endocrowns were adhesively inserted, and fracture resistance, failure mode and microleakage were evaluated.

Results

A higher fracture resistance value was observed in PBE groups E1 and E2, regardless of the materials used (P = 0.038, and 0.010, respectively, vs E3), and fracture resistance in group E1 was higher than that in group E2. In teeth without PBE, the percentage of catastrophic failures reached 70%. Compared to group E3, a lower frequency distribution of microleakage was detected in supragingival group E4 (P = 0.031). No increased percentage of microleakage was observed in groups treated with PBE.

Conclusion

For endodontically treated maxillary premolars restored with ceramic endocrowns, PBE increases fracture resistance but not microleakage.

The prevalence of non-carious cervical lesions (NCCLs) with or without erosive etiological factors among adults of different ages in Tokyo

OBJECTIVES

To evaluate the prevalence of non-carious cervical lesions (NCCLs) on teeth with or without erosive etiological factors across a broad range of ages of Japanese adults.

MATERIALS AND METHODS

The study sample consisted of a total of 1108 subjects aged 15 to 89 years in Tokyo, Japan. Two examiners evaluated NCCLs and dental erosion (DE) during a full-mouth examination. Subjects were asked to complete a self-administered daily diet, habits, and health condition questionnaire. Subjects who had frequent acid consumption or gastric reflux and at least one tooth with initial enamel wear were placed in the erosion present (EP) group, and the remainder of subjects were placed in the erosion not present (EN) group. Logistic regression analyses were carried out to identify etiological factors of NCCLs associated with DE.

RESULTS

Overall prevalence of NCCLs was 60.2%; the prevalence increased with age. There were no statistical differences in the prevalence of NCCLs between the EP and EN groups, except for the 60-69 years group. Multiple logistic regression analysis showed the frequency of consumption of carbonated soft drinks, citrus juice, and acidic fruits such as oranges; tooth brushing pressure; and bruxism were associated with the presence of NCCLs.

CONCLUSION

There were no statistical differences in the prevalence of NCCLs with or without erosive etiological factors except for the 60-69 years group.

CLINICAL RELEVANCE

NCCL distribution increased with age, and erosive risk factors caused by change in dietary habits might affect the incidence of NCCLs for elders.

TRIAL REGISTRATION

UMIN000041982.

Evaluation of the relationship between non-caries cervical lesions and the tooth and periodontal tissue: An ex-vivo study using micro-computed tomography

The purpose of this study was to analyze the relationship between the height and depth of buccal non-carious cervical lesions (NCCLs) and the relationship between the size of buccal NCCLs and clinical crown-root ratio of both buccal and lingual (palatal) sides using micro-computed tomography (micro-CT) images of the teeth and periodontal tissues from the cadavers. The micro-CT images of 56 teeth and their supporting tissues were obtained from 17 cadavers. From these images, the height and depth of NCCLs and the length of the buccal and lingual (palatal) clinical crowns were measured, and the conventional/modified clinical crown-root ratios were calculated. The height and depth ratio of NCCLs were analyzed statistically with the conventional/modified crown-root ratios by Pearson's correlation and multiple regression. According to the Pearson's correlation, the height and depth of buccal NCCLs were positively correlated with the modified buccal clinical crown-root ratio (p < 0.001 and p = 0.013, respectively). The regression model composed of variables of crown-root ratios explained the height of buccal NCCLs, and the prominent factor of the model was the modified buccal clinical crown-root ratio (p < 0.001). Moreover, the depth of buccal NCCLs was also explained by the regression model, and its prominent factor was the proportion of modified buccal and lingual (palatal) clinical crowns (p = 0.004). The buccal NCCLs were related to the crown-root ratios; particularly, the level of buccal gingival margin could be associated with the formation of buccal NCCLs.

Effect of Mechanical Load Cycling on Microleakage of Restorative Glass Ionomers Compared to Flowable Composite Resin in Class V Cavities

Objectives:

Microleakage is the most important factor responsible for the destruction of restoration margins. The aim of this study was to assess the effect of mechanical load cycling on microleakage of four types of glass ionomer cement (GIC) in comparison with a flowable composite resin.

Materials and Methods:

In this in-vitro experimental study, 100 Class V cavities were prepared on the buccal and lingual surfaces of 50 intact premolars. The prepared cavities were divided into five groups of (A) Z350, (B) Equia Forte, (C) encapsulated Fuji II LC, (D) hand-mixed Fuji II LC, and (E) Ketac Molar. All the samples were thermocycled (×2,000, 5–55°C), and half of the samples in each group were load cycled. All the teeth were then immersed in 0.5% basic fuchsine for 24 hours, sectioned, and observed under a stereomicroscope. Data were analyzed with Kruskal-Wallis and Mann-Whitney-U tests. Comparison between the incisal and gingival microleakage was made with Wilcoxon test. P<0.05 was considered statistically significant.

Results:

Load cycling and type of restorative material had a significant effect on microleakage. Gingival microleakage was significantly higher than occlusal microleakage with Equia Forte, encapsulated Fuji II LC, hand-mixed Fuji II LC, and Ketac Molar in the absence of loading, and with Z350 after loading.

Conclusion:

The sealing ability of Z350 under load cycling was better than that of Equia Forte, hand-mixed Fuji II LC, and Ketac Molar. The marginal integrity of encapsulated Fuji II LC was not significantly different than that of Z350.

Root caries on a Paranthropus robustus third molar from Drimolen

OBJECTIVES

Dental caries is often perceived as a modern human disease. However, their presence is documented in many early human groups, various nonhuman primates and, increasingly, our hominin ancestors and relatives. In this study, we describe an antemortem lesion on the root of a Paranthropus robustus third molar from Drimolen, South Africa, which likely represents another example of caries in fossil hominins.

MATERIALS AND METHODS

The molar, DNH 40, is dated to 2.0-1.5 Ma and displays a lesion on the mesial root surface, extending from the cementoenamel junction 3 mm down toward the apex. The position and severity of the lesion was macroscopically recorded and micro-CT scanned to determine the extent of dentine involvement.

RESULTS

A differential diagnosis indicates root caries, as the lesion is indistinguishable from clinical examples. Although necrotic in appearance, external tertiary dentine is evident on a micro CT scan. Gingival recession and/or continuous eruption of the tooth as a result of extensive occlusal wear would have occurred to facilitate caries formation. Therefore, the lesion is likely linked to relative old age of this individual.

DISCUSSION

This new example increases the total number of carious lesions described in P. robustus teeth to 10, on occlusal, interproximal, and now, root surfaces. Beyond the consumption of caries-causing food, caries formation would have also required the presence of requisite intraoral cariogenic bacteria in this individual and the species. Of interest, the presence of tertiary dentine on the outward surface suggests the DNH 40 lesion may have been arrested, that is, no longer active, perhaps relating to a change in diet or oral microbiome just prior to the individual's death.

Associated factors to cervical dentin hypersensitivity in adults: a transversal study

Background

This cross-sectional study aimed to identify the factors associated to the cervical dentin hypersensitivity (DH) in Brazilian adult population.

Methods

Three hundred and eighty patients (67.2% women and 32.8% men) were assessed by questionnaire and thermal test with ice. Participants marked in a visual analogue scale (VAS) the intensity of pain, and a calibrated examiner (ICC 0.990) measured the scores using a caliper. Pain scores above 0.5 mm were considered sensitive teeth. The DH associated factors were investigated by clinical examination. The association between variables was assessed by Spearman correlation and the Chi-square test. Logistic regression was used to determine the variables that predict DH (p < 0.05).

Results

The mean age of participants was 24.08 years. In this population, 8958 teeth were evaluated, of those 3037 (33.9%) were diagnosed sensitive. The most prevalent associated factors to DH were abnormal tooth positioning (9.0%), occlusal trauma (6.5%) and gingival recession (5.6%). The erosion predicted significantly the DH on both simple (OR 7.85, p < 0.001) and multiple(OR 4.36, p < 0.001) analysis.

Conclusion

The exposure of dentinal tubules by erosion is probably the major predictor of dentin hypersensitivity. The healthy tooth is able to protect against DH.

Root grooves on two adjacent anterior teeth of Australopithecus africanus

Tooth root grooves and other ante-mortem dental tissue loss, not associated with caries found on or near the cementoenamel junction (CEJ), are commonly termed non-carious cervical lesions. Three main processes are implicated in forming these lesions: abrasion, dental erosion, and abfraction. As yet, these lesions have not been described in non-Homo hominins. In this study, South African fossil hominin collections were examined for evidence of any type of non-carious cervical lesion. Only one individual shows ante-mortem root grooves consistent with non-carious cervical lesions. Two teeth, a mandibular right permanent lateral incisor (STW 270) and canine (STW 213), belonging to the same Australopithecus africanus individual, show clear ante-mortem grooves on the labial root surface. These lesions start below the CEJ, extend over a third of the way toward the apex, and taper to a point towards the lingual side. The characteristics of these grooves suggest the predominant aetiology was erosive wear. In addition, they are extremely similar to clinical examples of dental erosion. These are the oldest hominin examples of non-carious cervical lesions and the first described in a genus other than Homo. Further, the lesions suggest that this individual regularly processed and consumed acidic food items.

Synergistic degradation of dentin by cyclic stress and buffer agitation

Secondary caries and non-carious lesions develop in regions of stress concentrations and oral fluid movement. The objective of this study was to evaluate the influence of cyclic stress and fluid movement on material loss and subsurface degradation of dentin within an acidic environment. Rectangular specimens of radicular dentin were prepared from caries-free unrestored 3rd molars. Two groups were subjected to cyclic cantilever loading within a lactic acid solution (pH = 5) to achieve compressive stresses on the inner (pulpal) or outer sides of the specimens. Two additional groups were evaluated in the same solution, one subjected to movement only (no stress) and the second held stagnant (control: no stress or movement). Exterior material loss profiles and subsurface degradation were quantified on the two sides of the specimens. Results showed that under cyclic stress material loss was significantly greater (p ≤ 0.0005) on the pulpal side than on the outer side and significantly greater (p ≤ 0.05) under compression than tension. However, movement only caused significantly greater material loss (p ≤ 0.0005) than cyclic stress. Subsurface degradation was greatest at the location of highest stress, but was not influenced by stress state or movement.

A comparative evaluation of microleakage in class v composite restorations

Aim. To compare and evaluate the microleakage in class V lesions restored with composite resin with and without liner and injectable nanohybrid composite resin. Materials and Methodology. 60 class V cavities were prepared in 30 freshly extracted teeth. After etching and application of bonding agents these cavities were divided into three groups: Group A (n = 20)—restored with composite resin, Group B (n = 20)—flowable composite resin liner + composite resin, and Group C (n = 20)—restored with injectable composite resin. After curing all the specimens were subjected to thermocycling and cyclic loading. Specimens were stained with 0.5% basic fuchsin and evaluated for dye penetration. Results. Results are subjected to Kruskal Wallis and Wilcoxon test. Conclusion. Within the limitations of this study, none of the three materials were free from microleakage. All the three materials showed more microleakage at gingival margins compared to occlusal margins. Among all the groups G-ænial Flo showed the least microleakage at the gingival wall.

Dental wear: a scanning electron microscope study

Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.

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.

Microleakage in Class II composite restorations with margins below the CEJ: in vitro evaluation of different restorative techniques

OBJECTIVES

The purpose of this in vitro study was to evaluate the microleakage in "deep" Class II composite restorations with gingival cavosurface margin below the CEJ (cemento-enamel junction) and restored with different techniques.

STUDY DESIGN

Fifty human teeth were used. In each tooth two standardized Class II slot cavities (on mesial and on distal surfaces) were prepared: the buccolingual extension of the cavities was 4 mm; the gingival wall was located in dentin/cementum (2 mm beyond the CEJ). The prepared teeth were randomly assigned to 5 experimental groups (of 10 specimens and 20 cavities each) and restored. Group 1: Filtek TM Supreme XTE Flowable (3MESPE) + Universal Filtek Supreme XTE (3MESPE), Group 2: GrandioSO Heavy Flow (Voco) + GrandioSo (Voco), Group 3: SDR™ (Dentsply Caulk) + Esthet-X® HD (Dentsply Caulk), Group 4: SonicFill (Kerr), Group 5: Grandio (Voco). After thermocycling, the specimens were immersed in a 0.5% basic fuchsine dye solution and incubated at 37°C for 24 hours. The teeth were subsequently sectioned mesiodistally. All specimens were examined at 25 in a stereomicroscope and standardized digital images were obtained. Dye penetration was measured from gingival margins.

RESULTS

The results demonstrated no significant leakage differences between Group 4 and Group 5, that both showed significantly higher frequency distribution of Score 0. Group 2 and Group 3 showed a significant prevalence of Score 1, whereas Group 1 showed significantly higher frequency of Score 2.

CONCLUSIONS

None of the restorative techniques tested completely eliminated microleakage dye penetration in dentin margins; marginal adaptation in Class II composite restorations with gingival wall below the CEJ varied in both substrates and from different restorative techniques used.

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.

Clinical evaluation of self-etch and total-etch adhesive systems in noncarious cervical lesions: a two-year report

OBJECTIVE

The purpose of this study was to compare the clinical performance of two self-etch dental adhesives with Single Bond Plus, a traditional one-bottle total-etch dental adhesive, for the restoration of noncarious cervical lesions.

MATERIALS AND METHODS

A total of 156 restorations were placed in noncarious cervical lesions with a minimum depth of 1.5 mm. Patients had no chronic periodontal disease and had normal salivary function. Each patient received restorations on three teeth, each bonded with either Adper Single Bond Plus, Adper Easy Bond, or Adper Scotchbond SE dental adhesive. All lesions were restored with Filtek Supreme Plus composite resin. All teeth were isolated with a rubber dam, received a short enamel bevel, and were cleaned with flour of pumice. The adhesives and resin composite were applied following the manufacturers' instructions. Restorations were clinically evaluated at baseline, six months, one year, and two years using modified US Public Health Service criteria.

RESULTS

Two-year retention was recorded as 97.3%, 90.5%, and 95.2%, for Single Bond Plus, Scotchbond SE, and Easy Bond, respectively. Statistical analysis did not show a significant difference (p>0.05) in clinical performance between any of the three adhesives after a period of two years.

Influence of periodontal ligament simulation and splints on strains developing at the cervical area of a tooth crown

Many in vitro tooth models do not incorporate periodontal ligament (PDL) simulation. This study presents the influence of physiologically loaded occlusal splints on cervical strains in a model incorporating roots and PDL. Four sets (N = 10) of occlusal splints differing in material (hard/soft) and location (upper/lower) were prepared for first maxillary and mandibular anatomic molars. Two strain gauges were bonded to the buccal and lingual aspects of the lower molar. Teeth were embedded in acrylic resin with/without a PDL-simulating material. Force vs. strain data were acquired during loading and the maximal strains at 500 N were analyzed. When PDL was incorporated into the model without splints, buccal compressive strains were significantly decreased. Usage of a soft splint resulted in compressive strains on both tooth aspects. Usage of a hard splint on the lower tooth resulted in higher compressive strains on the lingual side compared with the buccal side, whereas usage of this splint on the upper tooth resulted in tensile strains on the lingual side. Bending towards the buccal side occurred when the splints were located on the upper tooth. Soft splints reduce buccal bending, but do not reduce cervical strains. Periodontal ligament stimulation materials should therefore be incorporated in models involving teeth.

Effect of bonding application time on the microleakage of Class V sandwich restorations

BACKGROUND

The aim of this study was to assess the effect of bonding application time on the microleakage of Class V sandwich restorations.

METHODS

Eighty non-carious third molars were randomly divided into 16 groups. Two Class V cavities were prepared on the buccal and lingual surfaces of teeth. Three groups were restored with Fuji II GIC and treated with a total-etch bonding system (Stea/SDI) immediately after insertion, at 7 minutes and 15 minutes after mixing the glass ionomer cements (GICs). Another three groups were restored with Riva Self Cure GIC and treated with the total-etch system identically. The other six groups were subjected to self-etching bonding (Frog/SDI) after GIC placement in an identical procedure. The remaining groups were made using light cure GICs (Fuji II or Riva Light Cure) in conjunction with the total-etch or self-etching systems. Cavities were then restored with composite (Valux plus, 3M/ESPE). Samples were subsequently immersed in 2% methylene blue solution for 48 hours and observed under a stereomicroscope after sectioning. Four-scale grading was used to assess microleakage in occlusal and gingival walls. Data were analysed using Kruskal-Wallis and Mann-Whitney tests.

RESULTS

The self-etching bonding system exhibited more microleakage in occlusal margins regardless of time. Over time, microleakage significantly decreased in gingival margins in all self-cure groups except for Riva Self Cure treated with the total-etch system (p < 0.05).

CONCLUSIONS

Bonding application time had no effect on the microleakage of occlusal margins. However, maturation of GICs induced a decreased microleakage in gingival margins.

Restoration of noncarious tooth defects by dentists in The Dental Practice-Based Research Network

BACKGROUND

The authors conducted a study to quantify the reasons for restoring noncarious tooth defects (NCTDs) by dentists in The Dental Practice-Based Research Network (DPBRN) and to assess the tooth, patient and dentist characteristics associated with those reasons.

METHODS

Data were collected by 178 DPBRN dentists regarding the placement of 1,301 consecutive restorations owing to NCTDs. Information gathered included the main clinical reason, other than dental caries, for restoration of previously unrestored permanent tooth surfaces; characteristics of patients who received treatment; dentists' and dental practices' characteristics; teeth and surfaces restored; and restorative materials used.

RESULTS

Dentists most often placed restorations to treat lesions caused by abrasion, abfraction or erosion (AAE) (46 percent) and tooth fracture (31 percent). Patients 41 years or older received restorations mainly because of AAE (P < .001). Premolars and anterior teeth were restored mostly owing to AAE; molars were restored mostly owing to tooth fracture (P < .001). Dentists used directly placed resin-based composite (RBC) largely to restore AAE lesions and fractured teeth (P < .001).

CONCLUSIONS

Among DPBRN practices, AAE and tooth fracture were the main reasons for restoring noncarious tooth surfaces. Pre-molars and anterior teeth of patients 41 years and older are most likely to receive restorations owing to AAE; molars are most likely to receive restorations owing to tooth fracture. Dentists restored both types of NCTDs most often with RBC.

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.

Dentine bond strength and microleakage of flowable composite, compomer and glass ionomer cement

BACKGROUND

To assess in vitro the dentine bond strength and microleakage of three Class V restorations viz. flowable composite, compomer and glass ionomer cement.

METHODS

Eighteen dentine specimens were prepared and randomly distributed among three groups. Three kinds of restoration materials were each bonded on prepared dentine surfaces in three groups as per the manufacturers' instructions. Group Aelite: Tyrian SPE (a no-rinse, self-priming etchant) + One Step Plus (an universal dental adhesive) + Aeliteflo (a flowable composite); Group Dyract: Prime & Bond NT (a no-rinse, self-priming dental adhesive) + Dyract AP (a compomer); Group GlasIonomer: GlasIonomer Type II (a self-cured restorative glass ionomer). Fifteen dentine/restoration microtensile bond test specimens were prepared from each group and were subjected to microtensile bond strength testing. The bond interfaces were observed morphologically using a scanning electron microscope (SEM). Twenty-four cervical cavities of 4.0 mm mesiodistal length, 2.0 mm occlusogingival height and 1.5 mm depth were prepared at the cemento-enamel junction (CEJ) on both buccal and lingual surfaces of each tooth. The cavities were each filled with flowable composite (Group Aelite), compomer (Group Dyract) and glass ionomer cement (Group GlasIonomer) using the same material and methods as for the microtensile bond tests. Microleakage of each restoration was evaluated by the ratio of the length of methylene blue penetration along the tooth-restoration interface and the total length of the dentine cavity wall on the cut surface.

RESULTS

One-way ANOVA and least significant difference (LSD) tests revealed statistically significant differences among the dentine bond strength for Group Aelite (28.4 MPa), Group Dyract (15.1 MPa) and Group GlasIonomer (2.5 MPa). SEM images showed intimate adaptation in the restoration/dentine interfaces of Group Aelite and Group Dyract. All of the systems tested in this study presented microleakage. However, both Group Aelite (0.808) and Group Dyract (0.863) had significantly less microleakage than Group GlasIonomer (0.964). There were no statistically significant microleakage differences between Group Aelite and Group Dyract, and no statistically significant microleakage differences between the occlusal margin and gingival margin.

CONCLUSIONS

None of the systems tested in this study completely eliminated microleakage. However, both the flowable composite and compomer provided stronger dentine bond strengths and better margin sealing than the conventional glass ionomer cement. Occlusal forces exerted the same effects on microleakage of the occlusal margin and gingival margin in cervical cavities.

In vitro reproduction of noncarious cervical lesions

STATEMENT OF PROBLEM

A review of the dental literature indicates that noncarious cervical lesions (NCCLs) are formed by erosion, abrasion, and/or abfraction of tooth structure, but their etiology remains scientifically unsubstantiated.

PURPOSE

The purpose of this study was to reproduce noncarious cervical lesions in vitro. This study was not designed to statistically quantify the amount of lost tooth structure via abrasion, but rather to attempt to create NCCLs in the various shapes and sizes that are clinically observed.

MATERIAL AND METHODS

Three pairs of toothbrush types (generic and name-brand) with soft, medium, or firm bristles were tested with 3 different toothpastes of varying abrasive potentials (low, medium, and high) or with water only, on mounted human teeth with and without simulated gingival tissues (6 toothbrushes x 4 brushing solutions (L, M, H, dentifrices, or water only) x 2 gingival mask conditions = 48 test/control groups of 4 teeth each = 192).

RESULTS

The control sets, brushed in water only, demonstrated no visible loss of tooth structure. Each set brushed with toothpaste, regardless of the degree of abrasiveness or toothbrush bristle firmness, demonstrated visible wear at the level of the CEJ.

CONCLUSIONS

Significant noncarious cervical lesions were created via horizontal brushing with common commercial toothpaste, while brushing with water only did not create these cervical lesions.

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.

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.

Clinical Evaluation of Flowable Resins in Non-carious Cervical Lesions: Two-year Results

Different types of flowable resin materials placed in non-carious cervical lesions demonstrated acceptable clinical performance, except for the retention rates of Dyract Flow restorations, after two years.

Predictors of Non-carious Loss of Cervical Tooth Tissues

In this sample of subjects, age, premolars and the presence of corrosive factors were found to be significantly associated with NLCTT. The long-term success of treating such a lesion is dependent on properly identifying and eliminating the etiologic factors.

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.