Can a single composite resin serve all purposes?

Color Matching of Universal Shade Resin-Based Composite with Natural Teeth and Its Stability before and after In-Office Bleaching

Objectives

Esthetics is an essential issue for the long-term success of composite resin restoration. Therefore, this study aimed to view the esthetics of universal shade composite resin restorations and to assess its color matching before and after bleaching.

Materials and Methods

Overall, 40 freshly extracted premolars were mounted in an acrylic resin mold, and Class V cavities were then prepared and restored by OMNICHROMA composite (Tokuyama Dental, Tokyo, Japan) and polished with 2-step polishing system. Baseline color analysis was performed using VITA Easyshade V digital spectrophotometer, and another color analysis was carried out 24 hours after storage in distilled water. In-office bleaching was carried out, and color measurements were taken after bleaching and 2 weeks postbleaching. The data were statistically analyzed using SPSS 26.0 Windows version statistical software. Changes were considered statistically significant at P = 0.05.

Results

ΔE value of OMNICHROMA restoration before and after restoration was 6.474, 3.529 before and after bleaching, and 3.651 two-weeks postbleaching. In-office bleaching was effective in bleaching the OMNICHROMA specimens as the restoration showed positive ΔL^∗ values, which indicated that the specimens were lighter in color after bleaching; however, the bleaching effect was not maintained after 2 weeks.

Conclusion

OMNICHROMA universal shade composite resin restoration showed different color matching values with the adjacent enamel of class Vs. The material appeared lighter in shade postbleaching, and the color change was not maintained 2 weeks postbleaching.

Placement of Posterior Composite Restorations: A Cross-Sectional Study of Dental Practitioners in Al-Kharj, Saudi Arabia

Dental practitioner-related factors can affect the quality of composite restorations. This study aimed to investigate the clinical techniques used by dental practitioners (DPs) while placing direct posterior composite restorations. Methods: A questionnaire survey that sought information related to the placement of posterior composite restorations was delivered to 161 DPs working in the Al-Kharj area, Saudi Arabia. The collected data were statistically analyzed using Pearson’s Chi-square test and Fisher’s exact test considering the DP’s working sector and the answered questions. Results: A total of 123 DPs completed the survey (76.4% response rate). There was a statistically significant difference between DPs working in the private sector and those working in the governmental sector in 7 out of 17 questionnaire items namely: preparing a minimum depth of 2 mm, (p = 0.001); mechanical means of retention, (p = 0.003); operative field isolation, (p = 0.004); adhesive strategy, (p < 0.001); light-curing unit used, (p = 0.013); the use of radiometer, (p = 0.023), and dental matrix selection, (p < 0.001). Conclusion: The clinical techniques applied by DPs working in the private sector in Al-Kharj, Saudi Arabia when placing posterior composite restorations, including the specifications of cavity preparation, operative field isolation, and selection of the dental matrix system, may be substandard compared to those applied by DPs working in the governmental sector.

Comparison of mechanical and optical properties of a newly marketed universal composite resin with contemporary universal composite resins: An in vitro study

The purpose of this study was to evaluate the surface roughness, microhardness, color change, and translucency of a newly marketed universal nanohybrid composite resin (CR) (G-aenial A'CHORD) comparing with four contemporary universal CRs including two nanofilled (Filtek and Estelite Asteria) and two nanohybrid CRs (Charisma Dimond and Neo Spectra ST HV in vitro). Sixty-five specimens (8.0 mm × 2.0 mm) were fabricated (n = 13, per group). After finishing and polishing, specimens were subjected to surface roughness and microhardness tests. Color and translucency of the specimens were evaluated at baseline and after darkening with coffee solution at day 1 and day 7. A representative specimen from each group was investigated under scanning electron microscopy (SEM). Data was analyzed statistically (p < .05). There were significant differences among the groups in terms of surface roughness, microhardness, color, and translucency. The surface roughness was recorded as: Charisma Diamond > Neo Spectra ST HV, Filtek > Estelite Asteria, G-aenial A'CHORD, whereas Vickers Hardness number was as: Filtek, Charisma Diamond > Neo Spectra ST HV > G-aenial A'CHORD, Estelite Asteria. Color change was as: Charisma Diamond > Neo Spectra ST HV, Filtek, G-aenial A'CHORD > Estelite Asteria and the translucency was as: Neo Spectra ST HV > G-aenial A'CHORD, Filtek > Estelite Asteria, Charisma Diamond. SEM examinations revealed smooth surfaces for G-aenial A'CHORD, Neo Spectra ST HV and Estelite Asteria. Mechanical and optical properties of universal composite resins with different compositions show variations.

Minimally invasive direct restorations: a practical guide

The primary objectives of minimum intervention dentistry (MID) are to prevent or arrest active disease using non-operative management techniques. However, patients commonly present with cavitated caries lesions or failed restorations that are in need of operative intervention. Although much of clinical practice is devoted to preventing and managing the effects of caries and subsequent failure of the tooth-restoration complex, the clinical survival of restorations is often poor and becomes significantly worse as they increase in size and complexity. Minimally invasive (MI) restorative techniques present a range of well-documented advantages over more tissue-destructive traditional restorations by minimising unnecessary tooth tissue loss, insult to the dentine-pulp complex and reducing the risk of iatrogenic damage to adjacent hard and soft tissues. They also maximise the strength of the residual tooth structure by use of optimal adhesive restorative materials designed to restore function and aesthetics with durable, long-lasting restorations that are easy for the patient to maintain. In contemporary oral healthcare practice, if patients are to give valid consent for operative interventions, minimally invasive options must be offered, and may be expected to be the first choice of fully informed patients. This paper describes concepts of MID and provides an update of the latest materials, equipment and clinical techniques that are available for the minimally invasive restoration of anterior and posterior teeth with direct restorations.

Bioinspired Catecholic Primers for Rigid and Ductile Dental Resin Composites

In the construction of dental restorative polymer composite materials, surface priming on mineral fillers is essential to improve the mechanical performance of the composites. Here we present bioinspired catechol-functionalized primers for a tougher dental resin composite containing glass fillers. The catecholic primers with different polymerizable end groups were designed and then coated on glass surfaces using a simple drop-casting or dip-coating process. The surface binding ability and possible cross-linking (coupling or chemical bridging between the glass substrate and the dental resin) of the catecholic bifunctional primers were evaluated using atomic force microscopy, contact angle measurements, and the knife shear bonding test and compared to a state-of-the-art silane-based coupling agent. Various mechanical tests including shrinkage and compression tests of the dental resin composites were also conducted. Compression tests of the composites containing the catecholic primed fillers exhibited enhanced mechanical properties, owing to the bidentate hydrogen bonding of catechol moieties to the oxide mineral surface. Furthermore, the superior biocompatibility of the primed surface was confirmed via cell attachment assay, thus providing applicability of catecholic primers for practical dental and biomedical applications.

Comparative evaluation of the bond strength of posterior composite with different cavity configurations and different liners using a two-step etch and rinse adhesive system: In vitro study

Introduction:

Conventional Class II cavity preparations used for restoring small lesions with amalgam may be inappropriate for composite resin restorations due to the extensive cavity form, large occlusal contact area, and thin or missing margins of the tooth. Cavity preparation in the proximal areas as per the precepts of Clark is a conservative method of caries excavation and tooth preparation.

Materials and Methods:

Conventional Class II and Clark's Class II cavities were prepared on the mesial surfaces of 60 molars. All cavities were given a standard buccolingual width of 2 mm, an occlusogingival height of approximately 3.5 mm and an axial depth of 1.5 mm. These were then restored using flowable composites or resin-modified glass-ionomer cement liners and nanohybrid composites. The compressive bond strength was tested with a universal testing machine.

Results:

The compressive bond strength was the highest for Clarks Class II cavity preparation with a lining of flowable composites. Conventional Box only Class II cavities restored with flowable liners showed the next best result.

Conclusion:

Clark's class II cavity preparation can be used as efficiently as the conventional Class II box preparation with the advantage of preserving more tooth structure, more precise tooth preparation, good bond strength and better esthetics.

Significant Performance Enhancement of Polymer Resins by Bioinspired Dynamic Bonding

Marine mussels use catechol-rich interfacial mussel foot proteins (mfps) as primers that attach to mineral surfaces via hydrogen, metal coordination, electrostatic, ionic, or hydrophobic bonds, creating a secondary surface that promotes bonding to the bulk mfps. Inspired by this biological adhesive primer, it is shown that a ≈1 nm thick catecholic single-molecule priming layer increases the adhesion strength of crosslinked polymethacrylate resin on mineral surfaces by up to an order of magnitude when compared with conventional primers such as noncatecholic silane- and phosphate-based grafts. Molecular dynamics simulations confirm that catechol groups anchor to a variety of mineral surfaces and shed light on the binding mode of each molecule. Here, a ≈50% toughness enhancement is achieved in a stiff load-bearing polymer network, demonstrating the utility of mussel-inspired bonding for processing a wide range of polymeric interfaces, including structural, load-bearing materials.

Randomized Controlled Trial of Postoperative Sensitivity with Warm and Room Temperature Composite

Physical properties of composite improve when it is preheated prior to polymerization. However, postoperative sensitivity may be considered a potential complication. A review of the literature revealed no reported randomized controlled trials (RCTs) of postoperative sensitivity when using preheated composite resin. The objective of the study was to determine if preheating composite leads to changes in postoperative sensitivity in a parallel RCT. In total, 120 eligible, consenting adults were recruited in private dental practice and randomized into 2 groups of 60 patients. One group had room temperature composite restorations placed and the second had composite preheated to 39°C. The primary outcome was sensitivity after 24 h by the visual analog scale (VAS), recorded blind by patients. Secondary outcomes were VAS scores recorded over a month. Blind statistical analysis used the Mann-Whitney U test to compare the 24-h VAS score between groups and repeated-measures analysis of variance to assess the change over time. Potential confounders were tested using regression models. A total of 115 patients completed the trial: 57 in the heated composite group and 58 in the room temperature group. Analysis of 24-h VAS scores found no statistically significant difference between the 2 groups ( P = 0.162). Examining the potential confounders confirmed the nonsignificant difference between heated and room temperature groups on the 24-h VAS score, after controlling teeth type and preoperative pulp test (effect size = 0.173, P = 0.317). Analysis of the secondary outcomes found significant changes (within-subject effect) in VAS scores over the review period ( F statistic = 4.7, P = 0.002) but not a significant (between-subject effect) difference between heated and room temperature groups over time (effect size = 0.102, P = 0.197). There was a significant correlation between preoperative VAS score and postoperative VAS score ( P < 0.001). For the restorations in this study, there was no detectable difference in postoperative VAS score between preheated and room temperature composite. Postoperative sensitivity decreased throughout the first month. Postoperative sensitivity was correlated to preoperative sensitivity (ISRCTN 76727312). Knowledge Transfer Statement: The results of this study can be used by clinicians when considering the advantages and disadvantages of preheated composite. The study found no evidence of any change in postoperative sensitivity when using preheated composite. Since preheated composite has superior physical properties, its use for routine care can be considered good practice.

Mercury Amalgam Diffusion in Human Teeth Probed Using Femtosecond LIBS

In this work the diffusion of mercury and other elements from amalgam tooth restorations through the surrounding dental tissue (dentin) was evaluated using femtosecond laser-induced breakdown spectroscopy (fs-LIBS). To achieve this, seven deciduous and eight permanent extracted human molar teeth with occlusal amalgam restorations were half-sectioned and analyzed using pulses from a femtosecond laser. The measurements were performed from the amalgam restoration along the amalgam/dentin interface to the apical direction. It was possible to observe the presence of metallic elements (silver, mercury, copper and tin) emission lines, as well as dental constituent ones, providing fingerprints of each material and comparable data for checking the consistence of the results. It was also shown that the elements penetration depth values in each tooth are usually similar and consistent, for both deciduous and permanent teeth, indicating that all the metals diffuse into the dentin by the same mechanism. We propose that this diffusion mechanism is mainly through liquid dragging inside the dentin tubules. The mercury diffused further in permanent teeth than in deciduous teeth, probably due to the longer diffusion times due to the age of the restorations. It was possible to conclude that the proposed femtosecond-LIBS system can detect the presence of metals in the dental tissue, among the tooth constituent elements, and map the distribution of endogenous and exogenous chemical elements, with a spatial resolution that can be brought under 100 µm.

Resin Bonding to a Hybrid Ceramic: Effects of Surface Treatments and Aging

The aim of this study was to verify the effects of different surface treatments on the microtensile bond strength between resin cement and a hybrid ceramic. Thirty-two hybrid ceramic slices (8 × 10 × 3 mm) were produced and allocated among four groups according to the surface treatment: Cont = no treatment, HA = 10% hydrofluoric acid applied for 60 seconds, PA = 37% phosphoric acid applied for 60 seconds and CJ = air abrasion with silica particle coated alumina (Cojet Sand, 3M ESPE, 30 μm/2.8 bar). As a control group, eight blocks of feldspathic ceramic (8 × 10 × 3 mm) were etched by hydrofluoric acid for 60 seconds (VMII). After the surface treatments, the ceramic slices were silanized (except the Cont group) and adhesively cemented to composite resin blocks (8 × 10 × 3 mm ) with a load of 750 g (polymerized for 40 seconds each side). The cemented blocks were cut into beams (bonded surface area of ∼1 mm2). Half of the beams were aged (thermocycling of 5°C-55°C/6000 cycles + water storage at 37°C/60 days), and the other half were tested immediately after being cut. Data were analyzed by Kruskal-Wallis and Dunn tests (non-aged groups) and by one-way analysis of variance and Tukey test (aged groups; α=0.05%). The mode of failure was classified by stereomicroscopy. The surface treatment significantly affected the bond strength in each set of groups: non-aged (p=0.001) and aged (p=0.001). Before being aged, samples in the CJ, HA, and PA groups achieved the highest bond strength values. However, after being aged, only those in the HA group remained with the highest bond strength values. Adhesive failure was found most often. In conclusion, hydrofluoric acid etching should be used for surface conditioning of the studied hybrid ceramic.

Managing the phase-down of amalgam: Part I. Educational and training issues

Following the recently agreed Minamata Convention, a phase-down in the use of dental amalgam will become a priority for the profession. With a lead-in period of a number of years, important changes in the mind-set of the profession are required to ensure that patient safety is not compromised. Posterior composites have been a viable, and in many cases preferable, alternative to amalgam for many years. However, notwithstanding considerable developments in dental school teaching on the application and placement of posterior composites, growing evidence to support the use of composites in the restoration of posterior teeth and advances in composite systems, many practitioners remain reluctant to place composite rather than amalgam. This paper considers the present and future use of posterior composites and highlights ways in which dental school teaching and continuing professional development (CPD) may contribute to the successful phase-down, and now inevitable discontinuation, in the use of dental amalgam.

Knowledge and attitudes of general dental practitioners towards posterior composite restorations in northern saudi arabia

INTRODUCTION

The restoration of posterior teeth with composite restoration is a common clinical practice nowadays. Opinions regarding posterior composite restorations vary among dentists. The aim of the present study was to determine the knowledge and opinions of general dental practitioners towards composite resins for posterior teeth restorations.

MATERIALS AND METHODS

A questionnaire was devised to elicit information regarding placement of composite restoration in posterior teeth in northern Saudi Arabia. It was distributed to 230 dentists by hand and e-mail. A response rate 136 (59%) was obtained. The questionnaire sought details about case selection criteria for composite restoration, problems associated with composites and reasons for selecting composite restoration in posterior teeth. The data was processed and analysed by SPSS statistical software 19. Frequencies and percentages were calculated for various responses of the participants.

RESULTS

Regarding the selection of composite restoration in posterior teeth, 97% of the dentists did not prefer composite placement for class I restoration with heavy occlusal contacts. 83% of the participants did not select composite for class II restoration. 78% of the respondents opted for restoring composites in small defects. Patients' aesthetic demands (90%), amalgam replacement (22%) and restoration of endodontically treated teeth (42%) were the contributing factors. Regarding the problems associated with posterior composite restorations. Recurrent caries (87%), post-operative sensitivity (84%), restoration fracture (83%) and polymerization shrinkage (73%) were the major problems reported by respondents associated with composite restorations. The other minor concerns were wear (60%), contact build up in case of class II cavity restorations (51%) and isolation for composite restorations (36%). Conservative cavity preparation (78%), aesthetics (73%) and patient preference (65%) were the main reasons for choosing composite restoration for the posterior teeth.

CONCLUSION

Posterior composites are not popular among dentists practicing in northern Saudi Arabia and there is a need of continued professional education and clinical training for the dentists for posterior composite restorations.

Dentists' restorative decision-making and implications for an 'amalgamless' profession. Part 1: a review

The Minamata Convention has agreed to a worldwide reduction and ultimate elimination in the production and use of mercury containing products. This will have implications for the practice of dentistry. Australian organizations' pronouncements on the issue are limited and research examining the Australian context dated. The restoration of teeth with direct materials has changed significantly since the 1980s. Up to this time amalgam was the material of choice for direct posterior restorations. Its properties and guidelines for placement were, and remain, well established. Resin composite has replaced amalgam as the material of choice in many clinical situations. Despite inherent clinical disadvantages compared to amalgam, there continues to be a shift toward greater use of resin composite. There is consensus worldwide that the restoration of posterior teeth using resin composite now exceeds that of amalgam. The reasons for this are reviewed in this article along with current evidence and commentary relating to direct restorative and evidence-based decision-making, minimally invasive approaches, and approaches to education. The implications for these in an 'amalgamless' profession are identified.

The Management of Defective Resin Composite Restorations: Current Trends in Dental School Teaching in Japan

Aim:

The aim of this article is to investigate the contemporary teaching of the management of defective direct resin composite restorations in dental schools in Japan.

Methods:

A questionnaire relating to the teaching of the management of defective resin composite restorations was developed and e-mailed to 29 dental schools in Japan in 2010.

Results:

Completed responses were received from 19 of the 29 invited schools (response rate = 66%). Eighteen schools (95%) report that they included the teaching of repair of direct defective resin composite restorations in their dental school programs. Thirteen schools reported that they included both clinical and didactic instruction on the repair of direct resin composite restorations. Fourteen schools did not teach any mechanical roughening of the exposed resin composite restoration surface before undertaking a repair. The most commonly reported treatment was acid etching with phosphoric acid (12 schools). The most commonly taught material for completing repairs was a flowable resin composite (16 schools).

Conclusion:

The teaching of repair of defective resin composite restorations is well established within many Japanese dental schools, to a greater extent than in some other regions of the world. The impact of this teaching on subsequent clinical practices in Japan should be investigated. Furthermore, it is concluded that there is a need for much stronger leadership in operative and conservative dentistry, ideally at the global level, to resolve differences in key aspects of operative procedures such as repairs.

Teaching the placement of posterior resin-based composite restorations in Spanish dental schools

Objectives: In an area of esthetic dentistry such as posterior composites, in which new materials and techniques are being devolved continuously, it is important to confirm that dental students have a clear understanding of the basic principles of clinical application of this knowledge. Considering that the preparation of dental graduates in Spain may be of interest to competent dental authorities and employers with whom they can work worldwide, this study investigated the teaching of posterior composite restorations in Spanish dental schools. Study design: In late 2009⁄ early 2010, a questionnaire seeking information on the teaching of posterior composites was emailed to the professor responsible for teaching operative dentistry in each of the fifteen dental schools having complete undergraduate dental degree programs in Spain. Results: The response rate was 100%. Most investigated topics did not show noteworthy differences depending on whether the schools were public or private. Variations were found among Spanish dental schools in both the amount and content of the teaching programs concerning posterior composite restorations. Differences were recorded in the teaching of cavity design, contraindications to composite placement, indications for liners and bases, matrix and wedging techniques, composite and bonding systems, light curing and finishing procedures for composite restorations. More consistency was observed in teaching methods of moisture-control, indirect composites and amalgam bonding. Conclusions: As recommended in previously surveyed countries, efforts must be made to promote harmonization of dental curricula to make it easier for graduates to work elsewhere, and to ensure they meet the needs of their patients on entering independent practice.

Key words:Aesthetic dentistry, composite restoration, dental education, teaching program, undergraduate dental student.

In Vivo and In Vitro Evaluations of Microleakage Around Class I Amalgam and Composite Restorations

The lining of amalgam restorations showed no significant effect on microleakage around restoration margins. In vivo and in vitro evaluations confirmed that microleakage was higher in resin composite restorations than in amalgam.

Material properties and fractography of an indirect dental resin composite

OBJECTIVES

Determination of material and fractographic properties of a dental indirect resin composite material.

METHODS

A resin composite (Paradigm, 3M-ESPE, MN) was characterized by strength, static elastic modulus, Knoop hardness, fracture toughness and edge toughness. Fractographic analyses of the broken bar surfaces was accomplished with a combination of optical and SEM techniques, and included determination of the type and size of the failure origins, and fracture mirror and branching constants.

RESULTS

The flexure test mean strength+/-standard deviation was 145+/-17 MPa, and edge toughness, T(e), was 172+/-12N/mm. Knoop hardness was load dependent, with a plateau at 0.99+/-0.02 GPa. Mirrors in the bar specimens were measured with difficulty, resulting in a mirror constant of approximately 2.6 MPa m(1/2). Fracture in the bar specimens initiated at equiaxed material flaws that had different filler concentrations that sometimes were accompanied by partial microcracks. Using the measured flaw sizes, which ranged from 35 to 100 microm in size, and using estimates of the stress intensity shape factors, fracture toughness was estimated to be 1.1+/-0.2 MPa m(1/2).

SIGNIFICANCE

Coupling the flexure tests with fractographic examination enabled identification of the intrinsic strength limiting flaws. The same techniques could be useful in determining if clinical restorations of similar materials fail from the same causes. The existence of a strong load-dependence of the Knoop hardness of the resin composite is not generally mentioned in the literature, and is important for material comparisons and wear evaluation studies. Finally, the edge toughness test was found promising as a quantitative measure of resistance to edge chipping, an important failure mode in this class of materials.

Review: Resin Composite Filling

The leading cause of oral pain and tooth loss is from caries and their treatment include restoration using amalgam, resin, porcelain and gold, endodontic therapy and extraction. Resin composite restorations have grown popular over the last half a century because it can take shades more similar to enamel. Here, we discuss the history and use of resin, comparison between amalgam and resin, clinical procedures involved and finishing and polishing techniques for resin restoration. Although resin composite has aesthetic advantages over amalgam, one of the major disadvantage include polymerization shrinkage and future research is needed on reaction kinetics and viscoelastic behaviour to minimize shrinkage stress.

Resin-based composites and dentine-bonding agents. Which, who and why? A study in the East of Scotland

AIMS

To determine which resin-based composite (RBC) and dentine-bonding agent (DBA) systems were most widely used by a random convenience sample of dentists in the East of Scotland, by whom they were used, and what influenced the dentists' choice when buying/using a particular RBC and DBA.

METHODS

A cross-sectional questionnaire-based study was conducted from June to December 2006. A questionnaire was compiled and, following a short pilot and revision, 250 questionnaires were randomly distributed to dentists attending vocational training/general professional training study days, continuing education courses and various dental meetings. Data from the completed questionnaires were collated and analysed.

RESULTS

A total of 138 questionnaires were returned, giving a response rate of 55%, of which 101 (73%) were from practitioners working within the General Dental Services, 20 (14%) from Community Dental Service dentists, and 17 (12%) from practitioners in the hospital dental service. The most popular RBC reported by respondents 43 (31%) was Z100 (3M UK, Bracknell, UK). The most common factors that influenced respondents' choice when buying an RBC were ease of use and availability, reported by 51 (37%) and 45 (33%) respondents, respectively. Prime & Bond (DENTSPLY DeTrey, Konstanz, Germany) was reported as the most popular DBA by 58 (42%) respondents. Overall, availability, reported by 61 (44%) respondents, was the most popular reason for choice of a DBA, followed by ease of use, reported by 52 (38%) respondents, and reliability, reported by 23 (17%) respondents.

CONCLUSIONS

The most popular RBCs and DBAs used by respondents to this study and common reasons for their use were identified. However, it was found that, among those who responded, there was no discernible relationship between undergraduate training, year of qualification and choice of material. Further research is required to corroborate these findings and to identify the level of understanding of material science by dental clinicians.

Refractive Index Mismatch and Monomer Reactivity Influence Composite Curing Depth

Limited cure depth is a drawback of light-activated composites. We hypothesize that curing light transmission and cure depth are influenced by monomer reactivity and filler/resin refractive index mismatch. Light transmission throughout cure was recorded for composites based on strontium (refractive index 1.51) or barium (refractive index 1.53) glass fillers. Fillers were mixed (70 wt%) with 4 bisphenol-A diglycidyl-ether-dimethacrylate (bis-GMA):triethylene glycol dimethacrylate (TEGDMA) formulations with refractive indices ranging from 1.4703 to 1.5370. Following polymerization, cure depth and pre- and post-cure translucency parameters were determined. Transmission changes and cure depths related to monomer reactivity and filler/resin refractive index mismatch with significant interaction. Composites became more opaque or translucent on curing. Optimizing filler/resin refractive index mismatch provides increased curing depth and assists shade-matching.

Time-resolved simultaneous measurement of group index and physical thickness during photopolymerization of resin-based dental composite

Light-activated resin-based dental composites are increasingly replacing dental amalgam. However, these materials are limited by inefficient setting reactions as a function of depth that constrain the maximum extent of cure. Insufficient curing can contribute to an overall reduction in biocompatibility of the material. We demonstrate dynamic refractive index measurements of a commercial dental composite throughout cure using spectral domain low coherence interferometry. Our results show a linear relationship between the change in refractive index and polymerization-induced reduction in physical thickness during light-activated curing. This relationship between the optical and physical density demonstrates the potential of this technique as a unique noninvasive tool for measurement of the conversion degree of curing dental composite materials.

Challenges to teaching posterior composites in the United Kingdom and Ireland

Recent surveys from general dental practice have found increased placement of direct composite resin restorations in occlusal (Class I) and occlusoproximal (Class II) cavities in permanent teeth by general dental practitioners. This has been matched, and possibly driven, at least in part, by the development of new composite resin materials and bonding technologies. Recent studies by the authors have found an increase in the teaching of Class I and Class II composite resin restorations in the UK, Ireland, the US, and Canada. The increased teaching in the UK and Ireland, however, was not as great as in North America, and several worrying trends were observed. The aim of this paper is to discuss these trends and related factors considered important to the necessary further development of the teaching of Class I and Class II direct composite resin restorations, let alone modern operative dentistry in general, in the UK and Ireland.

Teaching the placement of posterior resin-based composite restorations in U.S. dental schools

BACKGROUND

In light of the increased use of and demand for posterior resin-based composite restorations in dental practice, the authors investigated U.S. dental schools' current teaching with regard to placement of posterior composite restorations.

METHODS

In early 2005, the authors invited 52 schools to participate in an e-mailed survey.

RESULTS

The authors received 47 completed responses, for a 90 percent response rate. Although all schools provided didactic and clinical teaching in the placement of occlusal resin-based composites in posterior teeth, the survey results showed variation in teaching the use of two- and three-surface occlusoproximal composites.

CONCLUSIONS

The survey findings demonstrate a marked change in instruction in placement of posterior resin-based composite restorations in U.S. dental schools during the last five to 10 years. However, the authors found much variation in the nature and extent of the instruction and techniques taught.

CLINICAL IMPLICATIONS

Dental schools need to ensure that their graduating students are well-prepared for independent clinical practice.

Teaching of posterior composite resin restorations in undergraduate dental schools in Ireland and the United Kingdom

PURPOSE

The aim of this study was to investigate the current teaching of posterior composite resin restorations to undergraduate dental students in Ireland and the United Kingdom (UK). The investigation was a follow-up to a survey undertaken in 1997.

MATERIALS AND METHODS

A questionnaire was distributed by e-mail to the Heads of Departments of Restorative Dentistry/Units of Operative Dentistry in each of the 15 dental schools with undergraduate dental degree programmes in Ireland and the UK. The questionnaire sought information relating to the teaching of posterior composite resin restorations in each dental school.

RESULTS

Fifteen completed questionnaires were returned (response rate = 100%). All schools (n = 15) taught the placement of composite resin restorations in occlusal cavities, 14 schools taught composite resin placement in two-surface occlusoproximal cavities and nine schools taught composite resin placement in three-surface occlusoproximal cavities. Respondents anticipated that the amount of preclinical teaching of posterior composite resin placement will increase twofold over the next 5 years, whilst the corresponding teaching of amalgam will fall to two-thirds its current level. Variation was found between dental schools in the teaching of the principles of cavity design, contraindications to placement, indications for lining and basing techniques, matrix and wedging techniques, and the use of curing lights.

CONCLUSIONS

The amount of teaching of posterior composite resin restorations in undergraduate dental schools in Ireland and the UK has increased since the time of a previous survey in 1997. Composite resin may soon equal or overtake amalgam as the material of choice when restoring posterior cavities in Irish and UK dental schools. There was, however, much variation in the nature and extent of the teaching and the techniques taught.