M J Tyas

University of Melbourne, Melbourne, Victoria, Australia

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Publications (122)209.23 Total impact

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    ABSTRACT: Oral health-related quality of life of removable partial denture wearers and related factors S. SHAGHAGHIAN*, M. TAGHVA† , J. ABDUO‡ & R. BAGHERI§ *Oral Public Health Department, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, , †Prosthodontic Department, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran, ‡Restorative Department, Melbourne Dental School, Melbourne University, Melbourne, Vic., Australia and §Dental Material Department and Biomaterial Research Centre, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran SUMMARY This study aims to investigate the oral health-related quality of life (OHRQoL) in a group of removable partial denture (RPD) wearers in Shiraz (Iran), using the Persian version of the Oral Health Impact Profile (OHIP-14). Two hundred removable partial denture wearers had completed a questionnaire regarding patients’ demographic characteristics and denture-related factors. In addition, the OHIP-14 questionnaire was filled out by interviewing the patients. Two measures of interpreting the OHIP-14 scales were utilised: OHIP-14 sum and OHIP-14 prevalence. The relationship of the patients’ demographic characteristics and denture-related factors, with their OHRQoL was investigated. The mean OHIP- 14 sum and OHIP-14 prevalence of RPD wearers were 13�80 (�10�08) and 44�5%, respectively. The most problematic aspects of OHIP-14 were physical disability and physical pain. Twenty-seven percentage and 24% of participants had reported meal interruption and eating discomfort, respectively. OHIP-14 prevalence and OHIP-14 sum were found to be significantly associated with factors representing RPD wearer’s oral health such as self-reported oral health and frequency of denture cleaning. Furthermore, OHIP-14 prevalence and OHIP-14 sum were significantly associated with factors related to frequency of denture use such as hours of wearing the denture during the day and wearing the denture while eating and sleeping. Therefore, it can be concluded that the OHRQoL of the patients of the study was generally not optimal and found to be strongly associated with oral health. KEYWORDS: oral health, quality of life, removable, partial, denture Accepted for publication 30 July 2014
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    ABSTRACT: Objective: To determine Australian dentists’ attitudes to the United Nations Environment Programme approach to a ‘phase-down’ of the use of amalgam. Method: A survey was carried out based on literature and a qualitative study. Likert Scale questions included demographics, usage of amalgam in practice and specific aspects of a phase-down of amalgam. The survey was validated by six volunteer dentists. Members of the Australian Dental Association were invited to complete the survey online. Data were analysed by percentage. Results: Responses were received from 381 dentists – with 14,890 dentists in Australia this represents a confidence level of 95% ± 4.96. Key findings included that 44% of respondents strongly disagreed (SD) or disagreed (D) with the statement that a phase-down of amalgam is a ‘good thing’, and 50% who strongly agreed (SA) or agreed (A) that a phase-down would make ‘no significant difference’ to their practise. Responses diverged when asked if adequate materials alternative to amalgam existed: there were 50% SD plus D and 40% SA plus A. 62% ‘cared’ if amalgam was phased-down or not. Results were comparable when filtered by gender or place of primary dental qualification, but differed between respondents who did or did not use amalgam in practice and year of primary dental qualification. Respondents were neutral or undecided as to a phase-down being a ‘good thing’ (30%) and whether or not they trusted policy-makers to make the ‘right decision’ (22%). Conclusion: There is a divergence in attitudes of Australian dentists to a phase-down of amalgam, which is influenced by current amalgam practises and years since obtaining a primary dental qualification. Neutral or undecided response rates suggest the possible need for formulation and dissemination of information on this issue.
    IADR General Session and Exhibition 2014; 06/2014
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    ABSTRACT: Objective: To compare the shear bond strength (SBS) and failure mode of a self-adhesive resin-based luting cement to five different metals using three different de-bonding methods. Method: A self-adhesive resin luting cement (RelyX Unicem; 3M, St Paul, MN)) was bonded to five metals using two ‘unsupported’ and one ‘supported’ specimen and an adhesive area diameter of 2.36 mm. For each of the 15 groups, n = 15. The bond was stressed to failure at 1 mm/min using flat shear knife and wire loop methods. The distance of the shear force from the interface was 0 mm for the shear knife method, and for the wire loop method the wire was placed directly against the bonding surface. Failure mode was assessed by stereomicroscope and SEM analysis. Result: ANOVA and post hoc Tukey tests within each metal demonstrated significant differences between the unsupported and supported mean SBSs. SBS, MPa (SD) Metal Type Supported; Shear knife Unsupported; Shear knife Unsupported; Wire loop Wironit Cobalt-based 11.7 (2.5)a 9.4 (2.1) a 10.9 (3.3) a Titanium Ti 14.3 (2.7)b 9.5 (1.0) a 11.2 (3) a Rexillium III Nickel-based 10.8 (2.1)b 13.0 (1.8) c 6.8 (1.1) a Argenco 68 Gold-based 13.2 (2.5)b 7.8 (1.3) a 7.0 (2.1) a SS 316 Stainless steel 12.1 (1.3)c 8.5 (1.6) b 5.1 (1.7) a In all cases, except for cobalt-based metal, the SBS of supported specimens were significantly higher (p<0.05) than specimens that were not supported. Mean SBS ranged from (5.1 ± 1.7) MPa to (14.3 ± 2.7) MPa. Failure mode for each method was adhesive for 96% for supported specimens and between 77 - 68% for unsupported specimens. Conclusion: Supported (i.e., mold enclosed) specimens exhibited higher mean SBS and higher instances of adhesive failure than unsupported specimens.
    IADR General Session and Exhibition 2014; 06/2014
  • O A Adebayo, M F Burrow, M J Tyas
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    ABSTRACT: This study aimed to evaluate the association between the fracture toughness of two nanofilled-hybrid resin composites (Clearfil Majesty Esthetic [CME], Kuraray Medical, Japan; Estelite Σ [ES], Tokuyama, Japan) and their bond strengths to enamel and dentine mediated by a self-etching primer system (Clearfil SE Bond [CSE]; Kuraray). Twenty-four permanent human molars were sectioned into enamel and dentine specimens and finished with 600-grit silicon carbide paper, bonded with CSE and either CME or ES, for μ-shear bond strength (μSBS) and μ-tensile bond strength (μTBS). The specimens were tested until failure at a cross-head speed of 1 mm/min, failure loads recorded, bond strengths calculated and results analysed using independent samples t-tests. Eight single-notched bar-shaped specimens, 30 mm × 5.2 mm × 2.2 mm, were prepared for each resin composite and fracture toughness measured using four-point bending at a cross-head speed of 0.5 mm/min. Results were analysed using independent samples t-tests. For μSBS and μTBS, there was no significant difference between the resin composites for enamel or dentine. The fracture toughness of CME was significantly higher than that of ES. For both enamel and dentine, resin composite fracture toughness affected neither μTBS nor μSBS to enamel or dentine.
    Australian Dental Journal 09/2012; 57(3):319-24. · 1.37 Impact Factor
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    ABSTRACT: 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.
    Operative Dentistry 09/2011; 37(2):137-49. · 1.31 Impact Factor
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    ABSTRACT: Introduction: Aim - to evaluate the clinical performance of G-Bond (GC Corporation, Japan) dentine-enamel bonding agent, over 5 y in unprepared non-carious cervical lesions (NCCL). Materials and Methods: Ethics Committee approval was obtained, and 47 restorations were placed (30 anteriors, 13 premolars, 4 molars) in 10 patients aged 45-75 y (mean 62 y), using Gradia resin composite (GC) and G-Bond. Patients were recalled at 6 mo, 1 y, then annually to 5 y, and photographs taken for assessment of marginal discoloration. Results: Over 5-y , one restoration was lost, however, 20 restorations were unavailable for assessment. Survival analysis indicated loss rates of: 1 y, 0%; 2 y, 0%; 3 y, 0%; 4 y, 3%; 5 y, 3%. At the 1-, 2- and 3-y recalls, 2-3 restorations showed slight marginal discolouration; at 4 y, 12 restorations showed marginal discolouration, and at 5 y seven of the 27 restorations examined had some degree of marginal discolouration. G-Bond is an all-in-one' bonding agent, i.e., etching, priming and bonding are carried out simultaneously. The functional monomer 4-MET and a phosphate ester achieve bonding by hybridization. G-Bond is HEMA-free, which precludes possible hypersensitivity. However, the pH of the solution applied is such that the manufacturers recommend pre-etching of uncut enamel with phosphoric acid. A key requirement when using G-Bond is to dry the adhesive aggressively in order to evaporate the acetone solvent and thus prevent phase separation. The mainly mild staining could indicate bond degradation, or a remaining flash of resin at the margins. This appears to be the only 5-year study of G-Bond; other shorter term studies are available with similar retention results at comparable recall times. Conclusion: G-Bond shows good clinical performance in NCCL after 5 y. (Supported by GC Corp, Japan.)
    IADR General Session 2011; 03/2011
  • O. ADEBAYO, M. BURROW, M. TYAS
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    ABSTRACT: Introduction: The aim of this study was to evaluate the association between the fracture toughness of two nanofilled-hybrid resin composites (Clearfil Majesty Esthetic (CME); Kuraray Medical, Japan; Estelite " (ES); Tokuyama, Japan) and their bond strengths to enamel and dentine mediated by a self-etching primer system (Clearfil SE Bond (CSE); Kuraray). Materials and Methods: 22 permanent human molar teeth were sectioned into enamel and dentine specimens and finished with 600-grit silicon carbide paper, bonded with CSE and either CME or ES, using microtubes for -shear bond strength (SBS) and dumbbell-shaped specimens for -tensile bond strength (TBS). The specimens were tested until failure at a cross-head speed of 1 mm/min, failure loads recorded, bond strengths calculated and results analysed using t-tests. Eight single-notched bar-shaped specimens, 30 mm x 5.2 mm x 2.2 mm, were prepared for each resin composite and fracture toughness measured using four-point bending at a cross-head speed of 0.5 mm/min. Results were analysed using independent samples t-tests. Results: For SBS, there was no significant difference between the resin composites for enamel (CME 21.1 MPa; ES 22.7 MPa) or for dentine (CME 12.7 MPa; ES 11.8 MPa). For TBS, there was no significant difference between the resin composites for enamel (CME 13.7 MPa; ES 15.8 MPa) or for dentine (CME 18.0 MPa; ES 15.5 MPa). The fracture toughness of CME, 1.18 MPa(m0.5); was significantly higher than that of ES (0.87 MPa(m0.5). Conclusion: For both enamel and dentine, resin composite fracture toughness affected neither TBS nor SBS to enamel or dentine.
    IADR General Session 2010; 07/2010
  • O A Adebayo, M F Burrow, M J Tyas
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    ABSTRACT: To evaluate the quality of bonded resin-dentine interfaces produced by two self-etching primer adhesives after casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) treatment, in comparison to untreated dentine. Thirty-four adult molar teeth were sectioned to obtain dentine with tubule orientations parallel/oblique or perpendicular to the surface. The specimens were divided into 'smear layer' (1A, 1B) and 'no smear layer' groups, after treatment with 15% EDTA (2A, 2B). The specimens were then left either untreated (1A, 2A) or treated (1B, 2B) with CPP-ACP paste (Tooth Mousse, GC Corp.) for 60 min x 7 days. Each treatment group was divided into three subgroups and specimens etched/conditioned (no conditioning; 30-40% phosphoric acid (H(3)PO(4)); 20% polyacrylic acid) and bonded with either a 2-step self-etching primer adhesive (Clearfil SE Bond, Kuraray Medical) or an 'all-in-one' adhesive (G-Bond, GC Corp.) and a hybrid resin composite. After 24-h water storage, the bonded specimens were sectioned, polished up to 4000-grit abrasive silicon carbide paper and 0.25-microm diamond paste, prepared for FE-SEM using the acid-base technique, critical point-dried, gold-coated and examined. Bonded and fractured dentine interfaces were also prepared and examined. The 2-step adhesive produced a similar appearance of bonded resin-dentine interface irrespective of smear layer group, treatment or etching/conditioning. After polyacrylic acid conditioning, the 'all-in-one' adhesive exhibited more areas with bond failures. The bond failures were within the hybrid layer and more pronounced following CPP-ACP treatment. The quality of the bonded resin-dentine interface produced after CPP-ACP treatment may depend on the adhesive system used.
    Journal of dentistry 09/2009; 38(2):96-105. · 3.20 Impact Factor
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    ABSTRACT: 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. 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. 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. 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.
    Journal of Dentistry 02/2009; 37(3):191-7. · 3.20 Impact Factor
  • O A Adebayo, M F Burrow, M J Tyas
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    ABSTRACT: The study aimed to evaluate, (a) the surface morphology of acid etched/conditioned enamel following carbamide peroxide bleaching with/without casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) (Tooth Mousse (MI Paste); GC Corp., Tokyo, Japan) treatment; and b) the nature of the bonded resin-enamel interfaces formed with a self-etching primer adhesive. Twenty-four human adult molars were each sectioned into four, the specimens divided and treated according to four experimental groups: 1, no treatment; 2, 16% carbamide peroxide bleaching; 3, CPP-ACP paste; 4, bleaching and CPP-ACP paste. A self-etching primer adhesive (Clearfil SE Bond, CSE) was used. The specimens were further divided into four subgroups for etching/conditioning: A, CSE Primer only; B, 30-40% phosphoric acid and CSE primer; C, 15% EDTA and CSE primer; D, 20% polyacrylic acid and CSE primer. Bonded specimens were also prepared. The morphology of the etched/conditioned enamel surfaces and polished resin-enamel interfaces of the bonded specimens were observed by field-emission scanning electron microscopy (FE-SEM). Treatment with CPP-ACP did not inhibit phosphoric acid etching of enamel. Poorly defined enamel etch patterns were observed with the other conditioners in all the groups. The morphology of the bonded resin-enamel interfaces observed on FE-SEM for each acid etching/conditioning subgroup was similar in all the experimental groups, except after bleaching. Resin infiltration into enamel was observed with prior phosphoric acid etching and polyacrylic acid conditioning and was unaffected by experimental group treatments. The use of a CPP-ACP paste with or without prior bleaching did not inhibit enamel etching. Enamel etching/conditioning may help improve bonding efficiency of the self-etching primer adhesive after CPP-ACP treatment.
    Journal of dentistry 02/2009; 37(4):297-306. · 3.20 Impact Factor
  • O A Adebayo, M F Burrow, M J Tyas
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    ABSTRACT: 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. 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. 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. 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.
    Journal of Dentistry 11/2008; 36(12):1013-24. · 3.20 Impact Factor
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    M F Burrow, M J Tyas
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    ABSTRACT: 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. 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. 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. The early results of this clinical evaluation showed good outcomes for both materials.
    Australian Dental Journal 10/2008; 53(3):235-8. · 1.37 Impact Factor
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    O A Adebayo, M F Burrow, M J Tyas
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    ABSTRACT: 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. 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. 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. 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.
    Australian Dental Journal 07/2008; 53(2):145-50. · 1.37 Impact Factor
  • M J McCullough, M J Tyas
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    ABSTRACT: 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'.
    International Dental Journal 03/2008; 58(1):3-9. · 1.04 Impact Factor
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    ABSTRACT: About 35 years ago, Ryge provided a practical approach to evaluation of clinical performance of restorative materials. This systematic approach was soon universally accepted. While that methodology has served us well, a large number of scientific methodologies and more detailed questions have arisen that require more rigor. Current restorative materials have vastly improved clinical performance and any changes over time are not easily detected by the limited sensitivity of the Ryge criteria in short term clinical investigations. However, the clinical evaluation of restorations not only involves the restorative material per se but also different operative techniques. For instance, a composite resin may show good longevity data when applied in conventional cavities but not in modified operative approaches. Insensitivity, combined with the continually evolving and non-standard investigator modifications of the categories, scales, and reporting methods, has created a body of literature that is extremely difficult to meaningfully interpret. In many cases, the insensitivity of the original Ryge methods is misinterpreted as good clinical performance. While there are many good features of the original system, it is now time to move to a more contemporary one. The current review approaches this challenge in two ways: (1) a proposal for a modern clinical testing protocol for controlled clinical trials, and (2) an in-depth discussion of relevant clinical evaluation parameters, providing 84 references that are primarily related to issues or problems for clinical research trials. Together, these two parts offer a standard for the clinical testing of restorative materials/procedures and provide significant guidance for research teams in the design and conduct of contemporary clinical trials. Part 1 of the review considers the recruitment of subjects, restorations per subject, clinical events, validity versus bias, legal and regulatory aspects, rationales for clinical trial designs, guidelines for design, randomization, number of subjects, characteristics of participants, clinical assessment, standards and calibration, categories for assessment, criteria for evaluation, and supplemental documentation. Part 2 of the review considers categories of assessment for esthetic evaluation, functional assessment, biological responses to restorative materials, and statistical analysis of results. The overall review represents a considerable effort to include a range of clinical research interests over the past years. As part of the recognition of the importance of these suggestions, the review is being published simultaneously in identical form in both the "Journal of Adhesive Dentistry" and the "Clinical Oral Investigations." Additionally an extended abstract will be published in the "International Dental Journal" giving a link to the web full version. This should help to introduce these considerations more quickly to the scientific community.
    International Dental Journal 11/2007; 57(5):300-2. · 1.04 Impact Factor
  • O A Adebayo, M F Burrow, M J Tyas
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    ABSTRACT: 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. 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. 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). The use of conditioners prior to bonding with the self-etching primer adhesive system on treated enamel may significantly improve bond strengths.
    Journal of Dentistry 11/2007; 35(11):862-70. · 3.20 Impact Factor
  • M F Burrow, M J Tyas
    Journal of Dentistry 08/2007; 35(7):623-5. · 3.20 Impact Factor
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    R Bagheri, M F Burrow, M J Tyas
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    ABSTRACT: To determine the degree of surface roughness of glass-ionomer cements (GICs) and polyacid-modified resin composite (PAMRC) after polishing and immersion in various foodstuffs. Three tooth-coloured restorative materials were used: a PAMRC (F2000), a conventional glass-ionomer cement (CGIC) (Fuji IX) and a resin-modified glass-ionomer cements (RM-GIC) (Fuji II LC). Disk-shaped specimens were prepared and tested with either a plastics matrix finish or after polishing with wet silicon carbide papers up to 2000-grit. All specimens were immersed in 37 degrees C-distilled water for 1 week, followed by three different foodstuffs (red wine, coffee or tea) for a further 2 weeks. Replicas of specimens were prepared by taking polyvinyl siloxane impressions, casting in epoxy resin, gold sputter-coating and examining using a Field-Emission Scanning Electron Microscope. The polished and matrix finish specimens of F2000 showed many microcracks at low magnification, and eroded surfaces with missing and protruding particles at high magnification in the polished specimens. The surface-polished specimens of Fuji II LC were considerably rougher than the matrix-finish specimens, with large voids and protruding filler particles. The effects of foodstuffs on Fuji II LC and F2000 were not noticeable. The CGIC became noticeably rougher after exposure to coffee and tea. All specimens had the smoothest surface when they were cured against a plastics matrix strip, and all materials had a rougher surface after polishing. None of the foodstuffs produced a perceptible increase in roughness on RM-GIC and PAMRC surfaces, whereas coffee and tea markedly increased the surface roughness of Fuji IX.
    Journal of Oral Rehabilitation 02/2007; 34(1):68-76. · 2.34 Impact Factor
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    ABSTRACT: Noncarious cervical lesions have a multifactorial etiology. Mechanical stress has been identified as one of the factors, but little evidence exists for its cause-effect relationship. This study was conducted at three different pH levels to observe the surface loss on dentin beams under tension and compression. Bovine dentin beams (10 x 3.75 x 1.45 mm) were fixed at one end and immersed in 0.1 M lactic acid solution at pH levels 4.5 (n = 20), 7 (n = 20), and 10 (n = 20) for 5 days under a load of 6.5 N (663 g). The mean surface loss was more on the surface under compression than that under tension at pH 4.5 and pH 7 than at pH 10. Also, the surface loss on the beams decreased as the distance from the fixed end increased. It was concluded that stress and lower pH both increase surface loss at the fixed end of the beam, which in a tooth represents the cervical region.
    Calcified Tissue International 01/2007; 79(6):416-21. · 2.75 Impact Factor
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    ABSTRACT: It is important to understand subsurface dentin demineralization and caries from the clinical perspective as dentin properties are modified under acidic conditions and mechanical loading. This study was conducted to observe the subsurface demineralization of dentin beams at three different pH levels under tension and compression. Bovine dentin beams (10 x 3.75 x 1.45 mm) were fixed at one end and immersed in 0.1 M lactic acid solution at pH levels 4.5, 7, and 10 for 5 days under a load of 6.5 N (663 g), and the subsurface demineralization depth was measured using a polarized light microscope. The mean subsurface demineralization depth was more subjacent to the surface under compression than that under tension at pH 4.5 and decreased as the distance from the fixed end increased. No subsurface demineralization was observed at pH 7 or 10. It was concluded that both stress and low pH are associated with increased subsurface demineralization at the fixed end of the beam.
    Calcified Tissue International 11/2006; 79(4):273-7. · 2.75 Impact Factor

Publication Stats

2k Citations
209.23 Total Impact Points

Institutions

  • 1990–2014
    • University of Melbourne
      • • Melbourne Dental School
      • • Faculty of Medicine, Dentistry and Health Sciences
      Melbourne, Victoria, Australia
  • 1998–2009
    • Victoria University Melbourne
      Melbourne, Victoria, Australia
  • 2000
    • University of Queensland 
      • School of Dentistry
      Brisbane, Queensland, Australia
  • 1995
    • Royal Melbourne Hospital
      Melbourne, Victoria, Australia