Effect of tooth surface preparation on the bonding of self-etching primer adhesives.

The aim of this study was to determine the bonding effectiveness of four self-etching primer adhesives after various tooth preparation protocols. Enamel/dentin specimens were prepared from 84 permanent molars, divided into three enamel preparation groups (silicon carbide paper [SiC1; erbium, chromium:yttri-um, scandium, gallium, garnet [Er,Cr:YSGG] laser [EL] and diamond bur [DB]) and five dentin preparation groups (SiC, EL, DB, steel[SB], and ceramic burs [CBs]). In each group,specimens were equally divided into four sub-groups and were bonded using Clearfil SEBond (CSE, Kuraray), Xeno IV (XE, Dentsply),Tokuyama Bond Force (TK, Tokuyama) and Filtek Silorane System Adhesive (FS, 3MESPE), as well as a hybrid resin composite(Clearfil Majesty Esthetic, Kuraray) for CSE,XE, and TK, and Filtek Posterior Restorative(3M ESPE) for FS). After 24 hours of water storage at 370C, microshear bond strength(iSBS) testing was carried out. Data were analyzed using analysis of variance (ANOVA)-Tukey test at a=0.05 and bond failure modes assessed. Representative debonded specimens were prepared and examined under the scanning electron microscope (SEM). All adhesives exhibited no significant differences in 1SBS on enamel and dentin under the clinical cavity preparation protocols, except for TK on den-tin. SEM revealed areas of altered subsurface enamel/dentin following EL ablation.

Mapping a non-carious cervical lesion using stereoimagery and dental casts incorporating optical texture.

OBJECTIVES: Recent advances in digital photogrammetry have enabled a new approach to high resolution mapping of tooth surfaces. The aim of this study was to assess the accuracy and the precision of a new system using automatic digital stereo-photogrammetry combined with an experimental casting material and to measure tooth surface loss in a non-carious cervical lesion. METHODS: A test object and tooth replicas incorporating optical texture obtained at baseline, one and 2 years were imaged with a pre-calibrated stereocamera. The stereoimagery was then processed with digital photogrammetric software to automatically generate digital surface models. Test object models were analysed for accuracy and precision and tooth surface models were aligned with point cloud analysis software and tooth surface loss determined. RESULTS: Replicas were mapped to an accuracy of (6+/-13)microm. The sensitivity of change detection on tooth replicas was 40 microm with change ranging from 40 to 70 microm per annum in a discrete part of the lesion. CONCLUSIONS: In the case examined, the change detection data were of sufficient accuracy and resolution to draw meaningful conclusions about the spatial distribution and quantum of tooth hard tissue loss. The results of this investigation suggest that annual change detection studies will provide a clearer picture of the pattern of tooth surface loss and, in combination with other analytical techniques, a more detailed explanation of the natural history of these lesions.

Dentine bonding after CPP-ACP paste treatment with and without conditioning.

OBJECTIVES: To evaluate microshear bond strength (MSBS) to dentine following application of a casein phosphopeptide amorphous calcium phosphate paste (Tooth Mousse (TM)), and the effect of smear layer removal before paste application and preconditioning. METHODS: Specimens of polished human dentine were divided into two groups: 1, smear layer retained; 2, smear layer removed using 15% EDTA for 90 s. In each group, half the specimens were left untreated and half treated with TM for 60 min daily x 7 days. Each subgroup was divided into three further subgroups for conditioning (Primer only; 30-40% phosphoric acid (PA)+primer; 20% polyacrylic acid (CC)+primer). Two self-etching/priming adhesives (Clearfil SE Bond (CSE) and G-Bond (GB)) were used for bonding resin composite to superficial/deep dentine and after 24h, stressed in shear until failure. Maximum loads at failure and bond failure modes were recorded. Group means were compared using one-way ANOVA and Tukey's post hoc test at alpha=0.05. RESULTS: TM did not significantly affect MSBS in group 1. In group 2, there was a statistically significant increase in MSBS for CSE on deep dentine (P=0.002) and a reduction for GB (P=0.013) on superficial dentine. PA conditioning did not significantly affect MSBS for CSE and GB while CC significantly reduced MSBS for GB. CONCLUSIONS: TM application did not reduce MSBS for CSE but significantly reduced MSBS for GB when the smear layer was removed before paste treatment. Preconditioning did not improve or worsen dentine MSBS for CSE or GB with/without TM, except when CC was used with GB.

Local adverse effects of amalgam restorations.

Amalgam has been used for the restoration of teeth for well over 100 years, and is the most successful of the direct restorative materials with respect to longevity. Despite the increasing use of tooth-coloured materials, with advantages of aesthetics and adhesion, amalgam is one of the most widely used dental restorative materials. One of the principal disadvantages of amalgam, apart from aesthetics, is that it may have adverse biological effects, both locally and systemically. Locally, it can cause an erythematous lesion on the adjacent oral soft tissues (tongue and buccal mucosa), and systemically free mercury in the amalgam may give rise to a hypersensitivity reaction. The purpose of this paper is to review the literature concerning the local adverse reactions to dental amalgam. The focus will be on the reactions of the oral mucosa, and brief consideration will be given to laboratory cytotoxicity of dental amalgam and its components, and to the 'amalgam tattoo'.

A clinical trial comparing two all-in-one adhesive systems used to restore non-carious cervical lesions: results at one year.

BACKGROUND: Few data exist with respect to the clinical performance of all-in-one adhesive systems. However, their clinical use is increasing. The aim of this study was to evaluate the retention and marginal staining of resin composite restorations bonded with Clearfil S(3) Bond or G-Bond all-in-one systems placed in non-carious cervical lesions. MATERIALS AND METHODS: Sixty restorations were placed in 11 subjects, mean age 62.5 years. Approval for the clinical trial was obtained from the Human Ethics Committee of The University of Melbourne. Restorations were bonded and placed according to the manufacturers' instructions. No enamel etching was performed on the enamel margins prior to restoration placement. Patients were recalled at six months, and one year for evaluation of presence and marginal staining. Photographic records were obtained prior to restoration, immediately after and at recall. RESULTS: All patients could be recalled. All restorations were present at both recall periods. A 100 per cent retention rate was obtained. Slight marginal staining was observed on four restorations for S(3) and three restorations for G-Bond. CONCLUSIONS: The early results of this clinical evaluation showed good outcomes for both materials.

Bond strength test: role of operator skill.

BACKGROUND: Test method, substrate material and operator variability are factors known to affect bond strength test outcomes. The aim of this study was to determine if, with increasing experience, individual operator skill in material handling influenced microshear bond strength outcomes. METHODS: This retrospective study used data collected from six preliminary tests carried out successively on enamel microshear bond strength for two adhesives: Clearfil SE Bond (Kuraray) and Adper Single Bond 2 (3M ESPE) by one operator. Mean and median microshear bond strength values, standard deviations and coefficients of variation for each adhesive test group were calculated and assessed. RESULTS: A gradual increase in mean microshear bond strengths, a decrease in standard deviations and coefficients of variation over time for both adhesives and a progressively more uniform distribution of microshear bond strength results recorded in individual test sets was observed. The results suggest an improvement in bonding reliability as experience is gained. CONCLUSIONS: Operator skill in material handling appears to play a critical role in determining the outcome of bond strength testing. This same skill is probably relevant when using an adhesive for the first time clinically. It is important that clinicians become familiar with new adhesives in order to achieve optimal outcomes.

Effects of conditioners on microshear bond strength to enamel after carbamide peroxide bleaching and/or casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) treatment.

OBJECTIVES: To evaluate (a) the enamel microshear bond strength (MSBS) of a universal adhesive and (b) the effects of conditioning with a self-etching primer adhesive with/without prior bleaching and/or casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) application. METHODS: Thirty-five molars were cut into four sections, assigned randomly to four groups (no treatment; 16% carbamide peroxide bleaching; CPP-ACP-containing paste (Tooth Mousse, TM); bleaching and TM) and treated accordingly. Specimens were divided into two for bonding with either a self-etching primer (Clearfil SE Bond, CSE) or a total-etch adhesive (Single Bond, SB). Specimens for CSE bonding were subdivided for one of four preconditioning treatments (no conditioning; 30-40% phosphoric acid (PA); 15% EDTA; 20% polyacrylic acid conditioner (Cavity conditioner, CC) and treated. The adhesives were applied and resin composite bonded to the enamel using microtubes (internal diameter 0.75mm). Bonds were stressed in shear until failure, mean MSBS calculated and data analysed using ANOVA with Tukey's HSD test (alpha=0.05). The modes of bond failure were assessed and classified. RESULTS: Two-way ANOVA revealed significant differences between treatments (P<0.0001), conditioners (P<0.0001) and a significant interaction between treatments and conditioners (P=0.001). One-way ANOVA revealed no significant differences in MSBS following any of the treatments for SB; following TM application for CSE without preconditioning; and significant differences in MSBS following bleaching with and without TM application for CSE. With preconditioning, applying PA before CSE post-bleaching and either PA or CC before CSE post-TM application, resulted in significant differences in MSBS (P<0.05). CONCLUSIONS: The use of conditioners prior to bonding with the self-etching primer adhesive system on treated enamel may significantly improve bond strengths.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 5: knowledge factors.

BACKGROUND: A phase-down of amalgam in Australia is possible given the Australian Government intends to ratify the Minamata Convention. There is little research as to the influence of a dentist's knowledge on decision-making, which may be of use when determining the impact of any change. METHODS: An online survey relating to aspects of and attitudes to use of direct restorative materials was distributed to all dentists who were members of the Australian Dental Association or Members or Fellows of the Royal Australasian College of Dental Surgeons. RESULTS: There were 408 respondents. Fifty-eight per cent agreed that there was consistency in undergraduate teaching. Fifty-two per cent stated that there was a difference between undergraduate teaching and the 'real world'. Postgraduate education was ranked the most important influence on decision-making. Ninety-six per cent stated that knowledge of the evidence base is important and 89% believed that they practised evidence-based dentistry. CONCLUSIONS: Dental schools need to maintain teachers' and students' understanding of the evolving technology of direct restorative materials. There is a perceived disconnect between undergraduate teaching and the 'real' world. The evidence base is viewed as confusing, contradictory and not readily understandable. The creation of clinical guidelines would be useful.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 4: clinical factor.

BACKGROUND: The Minamata Convention embodies a worldwide reduction in the production and use of mercury and mercury-containing products and processes, including a phase-down of dental amalgam. This will change the approach to the use of direct restorative materials in the near future. There is little research as to the influence of clinical factors on dentists' decision-making which may be of use when determining the impact of any change. METHODS: An online survey relating to aspects of and attitudes to the use of direct restorative materials was distributed to all dentists who were members of the Australian Dental Association and/or members or fellows of the Royal Australasian College of Dental Surgeons. Data were statistically analysed. RESULTS: There were 408 respondents to the survey. Eighty-seven per cent of respondents (strongly) disagreed that amalgam was a technically more difficult material to place compared with resin composite, 82% (strongly) disagreed that placement time for amalgam was longer than that for resin composite and 69% (strongly) disagreed that amalgam was more difficult to finish than resin composite. Eighty-three per cent of respondents stated they were confident in their ability to place amalgam restorations. Where physical properties were of importance, indirect restorations were preferred (e.g. parafunction) 54%. The factors considered most important when choosing a direct restorative material included moisture control and aesthetics; least important factors were cost and time to place. CONCLUSIONS: There is consensus that amalgam is not more technically difficult to use, place or finish than resin composite and vice versa. There is recognition that both amalgam and resin composite have limitations in terms of physical properties. When choosing a direct restorative material, clinical factors considered to be of greatest importance are moisture control, aesthetics and the need to apply minimally invasive approaches. There is little difference in the opinions of users and non-users of amalgam with respect to these findings.

Tooth morphology and characteristics of non-carious cervical lesions.

OBJECTIVES: Two 3-dimensional models, one of a lower second premolar and one of a lower central incisor were used to investigate effects of load on the location and magnitude of cervical strains. METHODS: Point loads of 100 N were applied to the model premolar (at the cusp tip, parallel and 45 degrees to the long axis of the tooth) and incisor (at the mid-buccal point on incisal edge, parallel and 45 degrees to the long axis of the tooth). Outputs were presented in the form of tensile-strain contours and vector plots. RESULTS: Strains were concentrated near the cementoenamel junction (CEJ) regardless of load direction, and oblique loading showed higher tensile strains, opposite to the point of loading, than vertical loading for both models. For the premolar model, regardless of loading direction, strains were concentrated at the mid- buccal CEJ. In contrast, under vertical loading on the incisor model, tensile strains were concentrated at the line-angle of CEJ. From oblique loads, vector plots of both models showed tensile vectors in vertical directions while vertical loads showed tensile vectors in horizontal directions. CONCLUSION: Mechanisms of non-carious cervical lesions (NCCLs) may in part be due the changing orientation of tensile strains as well as their magnitude. Stress concentration at the CEJ related well to the common location of clinical NCCLs. The crown-root morphology may have an influence on the initial location of non-carious cervical lesions.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 3: Dentists' attitudes.

BACKGROUND: The Minamata Convention has agreed to a worldwide reduction in the production and use of mercury-containing products and processes. This will change the approach to use of direct restorative materials in the future. There is little research exploring the attitudes of dentists to any change. METHODS: A survey relating to the use of direct restorative materials was distributed to dentists who were members of the Australian Dental Association or Members and Fellows of the Royal Australasian College of Dental Surgeons. Data were statistically analysed. RESULTS: There were 408 respondents. Responses to statements concerning attitudes toward a phase-down of amalgam depended on whether the respondent used amalgam, year of primary dental qualification and association with academia. Thirty per cent of respondents indicated they do not use amalgam. The mean use of amalgam for all direct restorative procedures was 18%. CONCLUSIONS: Dentists are concerned over potential implications of a phase-down of amalgam and much should be done to address these concerns. Many dentists are undecided as to what are the implications, which may reflect a lack of understanding of the issues. It is incumbent on policy-makers to produce and disseminate information relating to the issues identified by this research.

Two-year clinical evaluation of One-Up Bond F in noncarious cervical lesions.

PURPOSE: To evaluate the retention of restorations placed in non-undercut, noncarious cervical lesions using One-Up Bond F and Palfique Estelite resin composite. MATERIALS AND METHODS: Fifty-one non-undercut, noncarious cervical lesions were restored with One-Up Bond F and Palfique Estelite in 15 patients (mean age 57.7 years). Teeth were cleaned with pumice and water and restored following the manufacturer's instructions. Restorations were evaluated at 6 months, 1 and 2 years for presence or absence, and for the degree of marginal staining using standardized colour photographs for comparison. RESULTS: At 1 year, 42 restorations were evaluated, and all were intact. Slight marginal staining was observed in three restorations. At 2 years, 37 restorations were evaluated from 11 patients, and all were intact. Marginal staining was observed around nine restorations. ANOVA for marginal staining showed a significant increase of staining at both the enamel and cervical margins over the 2 years of the study. No caries was detected in association with any restoration. CONCLUSION: Although a number of restorations could not be evaluated, the retention of 100% at 2 years showed very good promise for the treatment of noncarious cervical lesions. The marginal staining was limited to a small number of patients.

Placement and replacement of restorations by selected practitioners.

BACKGROUND: There are few Australian data on the reasons for placement and replacement of restorations, and the extent to which these are carried out in general practice. METHODS: A survey was carried out of approximately 100 consecutive restorations placed by each of 28 general dental practitioners. The data were coded and statistically analyzed for various associations. RESULTS: Resin composite was used twice as frequently as amalgam as a restorative material, and nearly four times as often as glass-ionomer cement. Secondary caries was the principal reason for replacing restorations, affecting predominantly amalgam restorations in Class I and Class V cavities. Teeth restored with amalgam fractured nearly twice as often as teeth restored with resin composite. The average ages of amalgam, resin composite and glass-ionomers at replacement were 13.6, 7.1 and 5.7 years respectively. CONCLUSIONS: Amalgam has the longest clinical service life, but is associated with more tooth fracture. Secondary caries is the main reason for replacing restorations. The anti-cariogenic effect of glass-ionomer cement is equivocal.

Microhardness and Ca:P ratio of carious and Carisolv treated caries-affected dentine using an ultra-micro-indentation system and energy dispersive analysis of x-rays--a pilot study.

BACKGROUND: This study aimed to evaluate microhardness and chemical analysis of carious and caries-affected dentine. The hypothesis tested was that calcium:phosphorous (Ca:P) ratios correlate with microhardness values. METHODS: Four carious human third molars were sectioned through the caries lesion in the mesiodistal longitudinal plane. One half of each lesion underwent carious dentine removal using Carisolv gel. The cut surfaces were polished, microhardness tested using an Ultra-Micro-Indentation System (UMIS) and elemental analysis performed using energy dispersive analysis of x-rays (EDAX). RESULTS: The microhardness of carious dentine decreased gradually towards the cavity floor, but that for caries-affected dentine showed more variation with depth, having a mean hardness of (0.63 +/- 0.18) GPa. Ca:P ratios of carious dentine varied among the four specimens. The mean Ca:P ratio of caries-affected dentine was 1:2.03 +/- 0.08. The hypothesis was accepted for active lesions. CONCLUSIONS: The use of Carisolv to excavate carious tissue can be as effective as rotary instrumentation.

Structure and properties of methacrylate based dental restorative materials.

The chemistry and structure of the dimethacrylate resins and the nature of the filler systems in dental composite resins are reviewed in relation to their influence on the setting behaviour, dimensional stability, aesthetics, fracture behaviour and adhesive potential. It is clear that a deeper understanding of the structure of the polymeric matrix and the mechanism of clinical wear is required. As a result of ongoing research in this area and with the development of dentine adhesives, the future prospects of composite resins are encouraging.

An in vitro study of zinc in dentine beneath cavities filled with two dental cements.

The concentrations of zinc ions in dentine in vitro beneath cavities filled with zinc oxide/eugenol and zinc phosphate cements were measured by atomic absorption spectrophotometry. No significant difference was recorded between the two materials over a period of 15 weeks. The clinical significance of this finding is discussed.

A method for the in vitro toxicity testing of dental restorative materials.

An vitro method of toxicity testing of dental restorative materials is described in which their clinical usage is closely simulated. The test material was separated from the cells by either a synthetic filter or dentine slice. Toxic effects were quantiated by determining changes in enzyme activity by scanning and integrating microdensitometry.

Incorporation of casein phosphopeptide-amorphous calcium phosphate into a glass-ionomer cement.

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) nanocomplexes have been shown to prevent demineralization and promote remineralization of enamel subsurface lesions in animal and in situ caries models. The aim of this study was to determine the effect of incorporating CPP-ACP into a self-cured glass-ionomer cement (GIC). Incorporation of 1.56% w/w CPP-ACP into the GIC significantly increased microtensile bond strength (33%) and compressive strength (23%) and significantly enhanced the release of calcium, phosphate, and fluoride ions at neutral and acidic pH. MALDI mass spectrometry also showed casein phosphopeptides from the CPP-ACP nanocomplexes to be released. The release of CPP-ACP and fluoride from the CPP-ACP-containing GIC was associated with enhanced protection of the adjacent dentin during acid challenge in vitro.

Apical dentin permeability and microleakage associated with root end resection and retrograde filling.

This study evaluated the apical leakage associated with various depths of retrograde fillings placed in root apices which had been resected at one of three different angles. Leakage was assessed with a hydraulic conductance apparatus. Teeth were divided into groups corresponding to the angle of apical resection (0, 30, and 45 degrees to the long axis of the root) and apical leakage was determined following incremental increases in the depth of the retrograde filling (Ketac Silver). Increasing the depth of the retrograde filling significantly decreased apical leakage; there was also a significant increase in leakage as the amount of bevel increased. Both the permeability of resected apical dentin and microleakage around the retrograde filling material had a significant influence on apical leakage.

Light-cured lining materials: a laboratory study.

OBJECTIVES: The purpose of this study was to compare seven light-cured lining materials (four glass ionomer and three non-glass ionomer), with a chemical-cured glass ionomer lining material. METHODS: Specimens were prepared and tested according to the methods prescribed in Australian/International Standards for compressive strength, diametral tensile strength, depth of cure, radiopacity, and acid erosion. Other tests were adhesion to dentin and adhesion to resin composite. RESULTS: Compressive strengths ranged from 48.6 MPa to 307.1 MPa, and diametral tensile strengths from 5.8 MPa to 34.8 MPa. Most of the light-cured materials were stronger than the chemical-cured glass ionomer. Depth of cure increased with increased irradiation times, with values of 0.63 mm to 6.43 mm for 60 s irradiation. Radiopacity was in the range of 0.91 mm Al to 1.07 mm Al. All materials were unaffected or only slightly affected by acid erosion. Adhesion to dentin was effectively zero for the non-glass-ionomer products. Adhesion to composite was from 6.23 MPa to 25.1 MPa, and thermocycling affected only three light-cured and the one chemical-cured glass ionomer. SIGNIFICANCE: All products complied with the requirements of standards, where available. Incremental placement and curing is necessary for some products. Adhesion to dentin is better with glass ionomers, whereas their adhesion to composite may be unreliable.