Teaching posterior composite resin restorations in the United Kingdom and Ireland: consensus views of teachers

Teaching posterior composite restorations: A survey of dental schools in Palestine

Aim

This study aimed to assess different aspects of teaching posterior composite restorations in two dental schools in Palestine.

Materials and methods

A questionnaire was emailed to the heads of the operative and conservative dentistry departments to collect detailed information on the teaching practices related to posterior composite restorations. The questionnaire comprised 22 questions structured to collect information on the time dedicated to teaching the topic, competency assessments, future plans for allocating time for each restoration type, relevant indications and contraindications, specific materials and techniques utilized in the application, and fees charged for posterior restorations. The gathered responses were collated in Excel and analyzed.

Results

Both dental schools allocated similar teaching times to posterior composites and amalgam in their preclinical operative dentistry courses. However, there was a greater emphasis on composites in the clinical course than in the preclinical course at both institutions. Despite these differences, both institutions expressed a shared intention to allocate more time to teaching posterior composites while reducing the emphasis on teaching amalgam procedures. Consistency was observed across competency testing, cavity design preferences, and contraindications, with both schools favoring slot-type cavities. Furthermore, uniformity was noted in the management of operatively exposed dentin and matrix techniques, although variations existed in moisture isolation. Notably, both schools taught circumferential and sectional metal matrices but did not teach clear sectional matrices or use of bulk-fill composites. Additionally, the adhesive and light-curing practices remained consistent across both institutions.

Conclusion

The findings of this study indicate that the teaching of posterior composite restorations is consistent across both Palestinian dental schools. Their curricula are aligned with contemporary international practices, demonstrating a strong commitment to modern operative dentistry and adherence to global standards. These findings offer valuable insights for educators and researchers and emphasize the need for ongoing adaptations to maintain high clinical standards.

Preparing students for primary dental care in the Republic of Ireland

There are two dental schools in the Republic of Ireland, graduating approximately 90 new dentists annually following successful completion of a five-year undergraduate course. Currently, once these graduates have been awarded their degree, they have no legal requirement to complete post-graduation training, foundation training or continuing professional development. While the vast majority will do this voluntarily, it sets a high bar for dental educators to prepare these students to practice independently in primary dental care. As in other jurisdictions, there can often be a disconnect between the ethos taught to students for delivering primary dental care in dental schools and remuneration systems once graduates enter the workforce. Changing demographics will need to be reflected in our undergraduate curricula with explicit teaching in the area of gerodontology.

Current trends in placing posterior composite restorations: Perspectives from Palestinian general dentists: A questionnair study

Aim

The success of composite restorations relies on material selection and practitioner-related factors that shape the overall outcome. This study explores the practices of Palestinian general dental practitioners in placing posterior composites, examining the impact of work sector, experience, and gender on their choices.

Materials and Methods

The study was conducted as an online cross-sectional questionnaire and involved 351 participants, with a response rate of 69.8%. The survey comprised 18 closed-ended questions covering demographics, material selection, and composite placement in special cases, techniques, and factors influencing the choices. Statistical analyses included descriptive statistics, chi-squared tests, and Fisher's exact tests.

Results

Composite was the predominant choice for small-size (83.7%) and large-size posterior cavities (60.4%). Practitioners commonly opted for composite restorations in cases involving occlusal parafunctional activity (60%), poor oral hygiene (78%), and subgingival cavities (72.2%). Only 19.6% and 5.3% reported occlusal and gingival beveling, respectively. Rubber dams for isolation stood at 30%, one-step self-etch adhesives at 44.9%, and the oblique layering technique at 51%. Light-emitting diode curing units were popular (97.55%), but monitoring output with a radiometer was infrequent (93.5%). Tofflemire metal matrix usage was 46.1%, whereas a sectional matrix system was employed by 29.8%. A 2 mm layer exposure to light curing for 20 s was reported by 62%, and 27.75% utilized additional light-curing postmatrix band removal.

Conclusion

The study highlights the need for Palestinian dental professionals to update their clinical approaches in placing composite restorations in posterior teeth. Gender, work sector, and experience influence practitioners' choices, emphasizing the importance of tailored continuing education programs for improving clinical practices.

Reflections from undergraduate teaching experiences: some problems and solutions of restoring teeth with dental resin composite instead of dental amalgam

This is a simple personal reflection on some of the problems and solutions related to the increasing use of composite resin to replace dental amalgam when dental students learn to place restorations at the start of their careers. To the author, much seems common sense. Much is not, or cannot, be backed up by ideal science and some may still be considered outdated to the more progressive practitioner. Unfortunately, prospective, ideally-designed clinical trials may no longer be possible to seek the answers we lack due to ethical, organisational, financial or other constraints.

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.

Current and future trends in the teaching of direct posterior resin composites in Malaysian dental schools: a cross-sectional study

OBJECTIVE

To investigate the current and future teaching of posterior composite restorations in undergraduate curricula in Malaysian dental schools.

METHODS

A 24-item validated questionnaire including closed and open questions on the teaching of posterior composites was emailed to faculty members in all 13 Dental Schools in Malaysia. Responses were compiled on Excel and analysed.

RESULTS

All 13 dental schools responded to the survey yielding a 100 % response. All schools indicated the use of posterior composites for 2- and 3-surface cavities in premolars and molars. The didactic teaching time devoted to composites was greater than for amalgam (38 h vs 29 h). Clinically, most posterior restorations placed by students were composites (average 74.1 %, range 10 %-100 %); the remaining 25.9 % were amalgams (range, 0 %-50 %). Slot-type cavities were the preparation techniques most commonly taught (n = 11,84.6 %). The use of rubber dam for moisture control was mandatory in most schools (n = 11, 84.6 %). History of adverse reaction to composites was found to be the most common contraindication to composite placement. The phase down of teaching and use of amalgam in Malaysia is expected to occur within the next six years.

CONCLUSION

The trend to increase the teaching of posterior composites reported for other countries is confirmed by the findings from Malaysian dental schools. Notwithstanding this trend, the use of amalgam is still taught, and future studies are required to investigate the implications of the phase down of amalgam in favour of posterior composites.

CLINICAL SIGNIFICANCE

Notwithstanding the increase in the teaching of posterior composites there is a pressing need to update and refine clinical guidelines for the teaching of posterior composites globally.

Dental educators' attitudes towards the teaching of dental amalgam

OBJECTIVE

To ascertain dental educators' attitudes towards the teaching of dental amalgam at dental schools in Australia and identify preferred curricular approaches in a potentially "amalgamless" profession.

METHODS

A mixed methods analysis was employed based on an open-ended response survey followed by a closed-ended questionnaire. Identification of key issues from the survey helped frame the questionnaire. Participants included those with expertise in operative and restorative dentistry, with direct involvement in curriculum development or delivery, at Australian dental schools.

RESULTS

Participants numbered fifteen and represented seven of the nine dental schools in Australia. Key themes identified and explored included the following: (in)consistency of approach to teaching restorative dentistry; a perceived disconnect between undergraduate study and the "real world"; a need for a focus on teaching of alternatives to dental amalgam (80 per cent (strongly) agreeing); the contradictory nature of the evidence base and literature that is not readily understood; the need for more post-graduate education relating to adhesive restorative materials (86 per cent (strongly) agreeing); the need for dental amalgam to continue to be available; formal understandings (guidelines) as to the use of dental amalgam; dental schools in Australia being heard on these issues; and the relevance of this issue (100 per cent (strongly) agreeing the issue is topical and important).

CONCLUSION

There is a broad consensus of dental educators at Australian dental schools as how best to approach the teaching of amalgam if a phase-down is to occur and the issues any such approach may face.

Leadership in dental education

Dental school education continues to evolve at a significant pace. The challenge for those in leadership positions in dental education is to deliver a curriculum which is contemporary, evidence-based, and at the same time meeting the expectations of regulators and the established dental workforce - the latter being professional colleagues, including employers of future graduates. An important change in recent years is the acceptance that dental education itself is no longer a 'start-stop process', beginning at entry to dental school and concluding at graduation. Rather, dental education should be viewed as a continuous and life-long continuum. Perhaps one of the greatest attributes we can develop in our students is the desire and ability to seek to update, refresh and develop their knowledge and skills in the ever-advancing world of dental practice.

Dental cavity liners for Class I and Class II resin-based composite restorations

BACKGROUND

Resin-based composite (RBC) is currently accepted as a viable material for the restoration of caries for posterior permanent teeth requiring surgical treatment. Despite the fact that the thermal conductivity of the RBC restorative material closely approximates that of natural tooth structure, postoperative hypersensitivity is sometimes still an issue. Dental cavity liners have historically been used to protect the pulp from the toxic effects of some dental restorative materials and to prevent the pain of thermal conductivity by placing an insulating layer between restorative material and the remaining tooth structure. This is an update of the Cochrane Review first published in 2016.

OBJECTIVES

The objective of this review was to assess the effects of using dental cavity liners in the placement of Class I and Class II resin-based composite posterior restorations in permanent teeth in children and adults.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 12 November 2018), the Cochrane Central Register of Controlled Trials (CENTRAL; 2018, Issue 10) in the Cochrane Library (searched 12 November 2018), MEDLINE Ovid (1946 to 12 November 2018), Embase Ovid (1980 to 12 November 2018) and LILACS BIREME Virtual Health Library (Latin American and Caribbean Health Science Information database; 1982 to 12 November 2018). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

We included randomized controlled trials assessing the effects of the use of liners under Class I and Class II posterior resin-based composite restorations in permanent teeth (in both adults and children). We included both parallel and split-mouth designs.

DATA COLLECTION AND ANALYSIS

We utilized standard methodological procedures prescribed by Cochrane for data collection and analysis. Two review authors screened the search results and assessed the eligibility of studies for inclusion against the review inclusion criteria. We conducted risk of bias assessments and data extraction independently and in duplicate. Where information was unclear we contacted study authors for clarification.

MAIN RESULTS

Eight studies, recruiting over 700 participants, compared the use of dental cavity liners to no liners for Class I and Class II resin-based composite restorations.Seven studies evaluated postoperative hypersensitivity measured by various methods. All studies were at unclear or high risk of bias. There was inconsistent evidence regarding postoperative hypersensitivity (either measured using cold response or patient-reported), with a benefit shown at some, but not all, time points (low-quality evidence).Four trials measured restoration longevity. Two of the studies were judged to be at high risk and two at unclear risk of bias. No difference in restoration failure rates were shown at 1 year follow-up, with no failures reported in either group for three of the four studies; the fourth study had a risk ratio (RR) 1.00 (95% confidence interval (CI) 0.07 to 15.00) (low-quality evidence). Three studies evaluated restoration longevity at 2 years follow-up and, again, no failures were shown in either group.No adverse events were reported in any of the included studies.

AUTHORS' CONCLUSIONS

There is inconsistent, low-quality evidence regarding the difference in postoperative hypersensitivity subsequent to placing a dental cavity liner under Class I and Class II posterior resin-based composite restorations in permanent posterior teeth in adults or children 15 years or older. Furthermore, no evidence was found to demonstrate a difference in the longevity of restorations placed with or without dental cavity liners.

An ex-vivo model to determine dental pulp responses to heat and light-curing of dental restorative materials

AIM

Based on histological studies from the 1960s, it is recommended that dental pulp temperature increases should not exceed 5.5 °C. However, no contemporary reliable models exist to explore the effects of heat on living dental pulp. The aim of this project was to develop a clinically valid model for studying temperature increases caused by three commonly-used light curing units (LCUs).

METHODS

Temperature increases caused by LCUs at varying exposure times and via various thicknesses of dentine were recorded using traditional approaches (i.e. thermocouple device on a laboratory bench) and an ex-vivo tooth slice model. Histomorphometric and immunohistochemical (IL-1β, HSP70, caspase-3) analysis was performed of the tooth slice model following varying exposure and culture times.

RESULTS

Reduced dentine thickness and increased exposure time led to increases in temperature. Whilst the majority of temperature increases recorded using the traditional approach (53 of 60) were greater than the recommended 5.5 °C, 52 of the 60 reference points recorded using the ex-vivo tooth slice model resulted in temperature increases of less than 5.5 °C. Temperature increases of 5.5 °C or more that are prolonged for 40 s caused an immediate decrease in cell number. IL-1β was not detected in any samples, while HSP70 was detectable immediately after exposure to a temperature increase of 6 °C or more. Higher levels of HSP70 were detected after 24 h culture in tooth slices that experienced a temperature increase of 7.5 °C or more. Low levels of caspase-3 were detected in tooth slices exposed to temperature increase of 7.5 °C or more.

CONCLUSION

Experimental arrangements for assessing LCU performance that measure temperature increases using a thermocouple device on a laboratory bench should no longer be used. Future studies in this area should include replication of the clinical environment using greater sophistication, such as the use of an ex-vivo tooth slice model as described here. Temperature increases of 5.5 °C or more for 40 s caused an immediate decrease in cell number, which supports previous findings. However, complex interactions at an immunohistochemical level suggest that while temperature increases of 5 °C or less are ideal, there may be some cell damage between 5-7 °C which might not result in pulpal death. Further investigations are indicated.

Impact of Material Shade and Distance from Light Curing Unit Tip on the Depth of Polymerization of Composites

Abstract This study aimed to evaluate the effect of the composite shade and distance from the light-curing unit (LCU) tip on the irradiance reaching the bottom of composite disks and on the depth of polymerization. Composites of three shades (opaque - OXDC, bleach - BXL, and A2) were inserted into molds with 3-mm of thickness positioned over a spectrometer and photo-activated with the LCU (Bluephase) tip placed at 0 or 1 cm from the composite surface. The mean irradiance reaching the bottom of composite was recorded during the entire photo-activation (30 s). Specimens (2 x 2 x 4 mm) were polymerized and used to map the degree of conversion achieved in different depths from irradiated surface. Specimens were sectioned into slices that were positioned over the platform of the infra-red microscope connected to the spectrometer to map the conversion. The conversion was measured in eight different depths every 500-µm. Increasing the distance of LCU tip reduced the irradiance only for A2. Interposing OXDC disks resulted in lowest values of irradiance and A2 the highest one. A tendency to decrease the conversion was observed towards the bottom of specimens for all experimental conditions, and the slope was more accentuated for OXDC. Differences among shades and distances from LCU tip were evident only beyond 1.5-2.0 mm of depth. In conclusion, both composite shade and distance from LCU tip might affect the light-transmission and depth of polymerization, while the effect of last was more pronounced.

Dental cavity liners for Class I and Class II resin-based composite restorations

BACKGROUND

Resin-based composite (RBC) is currently accepted as a viable material for the restoration of caries for posterior permanent teeth requiring surgical treatment. Despite the fact that the thermal conductivity of the RBC restorative material closely approximates that of natural tooth structure, postoperative hypersensitivity is sometimes still an issue. Dental cavity liners have historically been used to protect the pulp from the toxic effects of some dental restorative materials and to prevent the pain of thermal conductivity by placing an insulating layer between restorative material and the remaining tooth structure.

OBJECTIVES

The objective of this review was to assess the effects of using dental cavity liners in the placement of Class I and Class II resin-based composite posterior restorations in permanent teeth in children and adults.

SEARCH METHODS

Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 25 May 2016), the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 4) in the Cochrane Library (searched 25 May 2016), MEDLINE Ovid (1946 to 25 May 2016), Embase Ovid (1980 to 25 May 2016) and LILACS BIREME Virtual Health Library (Latin American and Caribbean Health Science Information database; 1982 to 25 May 2016). We searched ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform for ongoing trials. No restrictions were placed on the language or date of publication when searching the electronic databases.

SELECTION CRITERIA

We included randomized controlled trials assessing the effects of the use of liners under Class I and Class II posterior resin-based composite restorations in permanent teeth (in both adults and children). We included both parallel and split-mouth designs.

DATA COLLECTION AND ANALYSIS

We utilized standard methodological procedures prescribed by Cochrane for data collection and analysis. Two review authors screened the search results and assessed the eligibility of studies for inclusion against the review inclusion criteria. We conducted risk of bias assessments and data extraction independently and in duplicate. Where information was unclear we contacted study authors for clarification.

MAIN RESULTS

Eight studies, recruiting over 700 participants, compared the use of dental cavity liners to no liners for Class I and Class II resin-based composite restorations.Seven studies evaluated postoperative hypersensitivity measured by various methods. All studies were at unclear or high risk of bias. There was inconsistent evidence regarding postoperative hypersensitivity (either measured using cold response or patient-reported), with a benefit shown at some, but not all, time points (low-quality evidence).Four trials measured restoration longevity. Two of the studies were judged to be at high risk and two at unclear risk of bias. No difference in restoration failure rates were shown at one year follow-up, with no failures reported in either group for three of the four studies; the fourth study had a risk ratio (RR) 1.00 (95% confidence interval (CI) 0.07 to 15.00) (low-quality evidence). Three studies evaluated restoration longevity at two years follow-up and, again, no failures were shown in either group.No adverse events were reported in any of the included studies.

AUTHORS' CONCLUSIONS

There is inconsistent, low-quality evidence regarding the difference in postoperative hypersensitivity subsequent to placing a dental cavity liner under Class I and Class II posterior resin-based composite restorations in permanent posterior teeth in adults or children 15 years or older. Furthermore, no evidence was found to demonstrate a difference in the longevity of restorations placed with or without dental cavity liners.

A Review of Mercury Exposure and Health of Dental Personnel

Considerable effort has been made to address the issue of occupational health and environmental exposure to mercury. This review reports on the current literature of mercury exposure and health impacts on dental personnel. Citations were searched using four comprehensive electronic databases for articles published between 2002 and 2015. All original articles that evaluated an association between the use of dental amalgam and occupational mercury exposure in dental personnel were included. Fifteen publications from nine different countries met the selection criteria. The design and quality of the studies showed significant variation, particularly in the choice of biomarkers as an indicator of mercury exposure. In several countries, dental personnel had higher mercury levels in biological fluids and tissues than in control groups; some work practices increased mercury exposure but the exposure levels remained below recommended guidelines. Dental personnel reported more health conditions, often involving the central nervous system, than the control groups. Clinical symptoms reported by dental professionals may be associated with low-level, long-term exposure to occupational mercury, but may also be due to the effects of aging, occupational overuse, and stress. It is important that dental personnel, researchers, and educators continue to encourage and monitor good work practices by dental professionals.

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.

Managing the phase-down of amalgam: part II. Implications for practising arrangements and lessons from Norway

The announcement of the Minamata Convention has triggered the lead into a phase-down in the use of dental amalgam. This paper considers aspects of this development in the context of the experience of banning the use of dental amalgam in Norway. It is suggested that strong top-down leadership and joined-up working by all relevant stakeholders, including patients, may be one of the most important keys to an effective, seamless transition to the provision of preventatively orientated, patient-centred, minimally interventive operative dentistry, based on state-of-the-art selection and application of tooth-coloured restorative materials. The benefits of such a transition are considered to be an important goal for dentistry in the UK.

Survival of direct resin restorations in posterior teeth within a 19-year period (1996-2015): A meta-analysis of prospective studies

OBJECTIVES

The aim of this study is to analyze the survival of posterior composite restorations published within the last 19 years (1996-2015).

METHODS

In this study only prospective, clinical trials with specification of the failure rate according to Class I/II composite fillings were included. Studies were analyzed according to the observation period (all studies vs. short-term vs. long-term studies). Retrospective studies and/or open laminate studies, tunnel restorations and Class V restorations were excluded. The following variables possibly influencing the failure rate were extracted from the studies: observation period, recall rate, average age of patients, number of patients, ratio of Class I/II fillings, number of restorations, ratio of premolars/molars, operator, method of isolation, bonding generation and filler size.

RESULTS

A total of 88 studies were included for statistical analysis. The observation period of the studies varied between 1 and 17 years, while most of the studies did not last longer than 5 years. Fracture of the restorations, secondary caries and marginal gap are the main causes for failure in the first 5 years (in descending order), while fracture and secondary caries are similarly distributed in long-term studies. Variables of investigation differed greatly in significance according to the respective observation period. The observation period, the recall rate, the ratio of Class I/II fillings and the number of restorations and patients had a significant influence on the overall failure rate when including all studies (short- and long-term). A linear correlation between the observation period and the failure rate was observed. In long-term studies these variables were not significant any longer. No significant difference in the failure rates between the materials per study was observed. The most common commercial composites investigated were: Tetric Ceram, Surefil, Filtek Supreme (incl. XT), Filtek Z250. The mean annual failure rate was 1.46% (±1.74%) for short-term studies and 1.97% (±1.53) for long-term studies. There is still a big need for clinical studies lasting longer than 5 years, as failure rates of composite restorations in posterior teeth increases with longer observation periods.

SIGNIFICANCE

A decreasing failure rate with an increasing recall rate as observed in our study suggests a patient selection in regard to availability and dental awareness. Internationally standardized evaluation criteria are mandatory in order to allow comparisons of the outcomes of clinical studies.

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.

Are dentine pins obsolete?

Dentine pins have been used in operative dentistry for many years to retain a non-adhesive restorative material (such as dental amalgam) in a cavity which has little or no inherent mechanical retention. However, dentine pin placement can be a hazardous procedure and there are a number of problems associated with their use. Alternative techniques have been described which may be utilized and are effective at retaining the restorative material without the shortcomings of dentine pins. There is a strong argument therefore that dentine pins have no place in contemporary dental practice and have consequently become obsolete.

Interaction of LED light with coinitiator-containing composite resins: effect of dual peaks

OBJECTIVES

Recently the colour stability of composite resins has been an issue due to the emphasis on the aesthetics of restored teeth. The purpose of the present study was to investigate how dual-peak LED units affect the polymerization of coinitiator-containing composite resins.

MATERIALS AND METHODS

Five composite resins [coinitiator-containing: Aelite LS Posterior (AL), Tetric EvoCeram (TE), and Vit-l-escence (VI); only CQ-containing: Grandio (GD) and Filtek Z350 (Z3)] were light cured using four different light-curing units (LCUs). Among them, Bluephase G2 (BP) and G-light (GL) were dual-peak LED LCUs. Microhardness, polymerization shrinkage, flexural, and compressive properties were measured.

RESULTS

BP and GL had no consistent effect on the microhardness of AL, TE, and VI on the top and bottom surfaces of resin specimens. Among the specimens, AL and VI showed the least (9.86-10.41 μm) and greatest (17.58-19.21 μm) polymerization shrinkage, respectively. However, the effect of BP and GL on the shrinkage of specimens was not consistent. Among the specimens, GD showed the greatest flexural properties [strength (FS) and modulus (FM)] and TE showed the lowest flexural and compressive properties [strength (CS) and modulus (CM)]. In same resin product, maximum FS and CS differences due to the different LCUs were 10.3-21.0% and 3.6-9.2%, respectively. Furthermore, the influences of BP and GL on FS and CS were not consistent.

CONCLUSION

The tested dual-peak LED LCUs had no consistent synergic effect on the polymerization of coinitiator-containing composite resins as compared with QTH and single-peak LED LCUs.

CLINICAL SIGNIFICANCE

The dual-peak LED LCUs achieve a similar degree of polymerization in coinitiator-composite resins as QTH and single-peak LED LCUs did. Choice of LCU does not appear to be a determinant of the light curing of coinitiator-composite resins.

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.

Assessment of laminate technique using glass ionomer and resin composite for restoration of root filled teeth

OBJECTIVE

To evaluate the open laminate technique using glass ionomer cements (GIC) in association with a low shrink composite for restoring root filled premolars.

METHODS

Extensive MOD cavities plus endodontic access and root filling were performed in intact extracted maxillary premolars. Three restoration types were evaluated: (1) resin composite alone; (2) resin-modified GIC (RM-GIC) open laminate plus resin composite; (3) conventional GIC open laminate plus resin composite (n=8 for all groups and tests). Three tests were conducted to assess restorations: (A) inward cusp deflection during light curing, using DCDTs; (B) fracture strength using a ramped oblique load at 45° to the long axis in a servohydraulic testing machine in comparison with intact and unrestored teeth; (C) proximal marginal leakage using methylene blue dye and the effect of thermocycling. Data were analysed using 1-way ANOVA for cuspal deflection and fracture strength and Fisher's exact test for leakage.

RESULTS

Laminate restorations resulted in significantly less cuspal deflection compared with resin composite (4.2±1.2 μm for RM-GIC and 5.1±2.3 μm for conventional GIC vs. 12.2±2.6 μm for composite, P<0.001). Fracture strength was not significantly different among all groups. Failure with all restorations was predominantly adhesive at the tooth-restoration interface. The two laminate groups showed significantly better marginal seal than composite alone, but sealing ability of conventional GIC deteriorated after thermocycling.

CONCLUSIONS

Laminate restoration of root filled teeth had beneficial effects in terms of reducing cuspal deflection and marginal seal, with acceptable fracture strength.

Bonded amalgams and their use in clinical practice

There has been a move in recent years for operative dentists to use the benefits of adhesive technology when placing dental amalgam restorations. This paper describes the potential advantages of the bonded amalgam technique. These benefits include decreased microleakage between the cavity wall and the restorative material. This, in turn, may decrease post-operative sensitivity, pulpal inflammation and the incidence of recurrent caries. Extra retention for the restoration may also be provided and the need for cavities to rely on traditional retention and resistance form may be decreased or even eliminated, thus conserving precious tooth tissue. If the restoration is bonded then flexure during function in teeth may be decreased and, in the case of teeth exhibiting a cracked cusp, this may alleviate or eliminate symptoms. Bonding may also provide support to weakened tooth tissue which otherwise would have to be removed, so rendering cavities more conservative, and may increase the fracture resistance of the tooth. Clinical examples are included to illustrate some of these benefits.

CLINICAL RELEVANCE

The use of adhesives to bond amalgam to tooth tissue offers potential advantages, although some of the current evidence is equivocal about their routine use.

Attitudes of some European dental undergraduate students to the placement of direct restorative materials in posterior teeth

The aim of this article was to report on the attitudes, opinions and confidences of final year dental students in three European schools towards the restoration of posterior teeth and in particular towards the use of amalgam and resin composite. One hundred and twenty-eight pre-piloted questionnaires were distributed to final year dental students in Cardiff, Dublin and Malmö. The questionnaire sought information relating to various opinions and attitudes towards the use of amalgam and resin composite in posterior teeth. Information was returned anonymously. Ninety-one completed questionnaires were returned (response rate=71%; Cardiff: n =40, Dublin: n=24, Malmö: n=27). Ninety-three per cent of Malmö students (n=24), 67% of Dublin students (n=16) and 60% of Cardiff students (n=24) reported that they feel confident when placing posterior resin composites. One hundred per cent of Malmö students (n=27), 75% of Cardiff students (n=30) and 33% of Dublin students (n=8) would prefer to have a resin composite rather than amalgam, placed in one of their own posterior teeth. Eighty-five per cent of Malmö students (n=23), 30% of Cardiff students (n=12) and 25% of Dublin students (n=6) perceive amalgam as being harmful to the environment. For the restoration of a posterior tooth in a pregnant female, 44% of students (n=40) would place a resin composite restoration, and 7% (n=6) would place an amalgam restoration, while 32% (n=29) would place a temporary restoration. Students at Malmö report that they place more posterior resin composites and have greater confidence at placing posterior resin composites than students at Cardiff or Dublin. There was confusion relating to the choice of restorative materials for pregnant females. Large variations in restorative strategies among graduates must be considered as dental professionals can practice in all countries within the European Union.

Is it the end of the road for dental amalgam? A critical review

The longevity of dental restorations is dependent on many factors, including those related to materials, the dentist, and the patient. Dental amalgams have successfully served the profession for over a century. The main reasons for restoration failure are secondary caries, fracture of the bulk of the restoration or of the tooth, and marginal deficiencies and wear. The importance of direct-placement, aesthetic, tooth-colored restorative materials is still increasing. Amalgam restorations are being replaced because of alleged adverse health effects and inferior aesthetic appearance. All alternative restorative materials and procedures, however, have certain limitations. This article will attempt to critically analyse both amalgams and resin based composites, through an evaluation of scientific literature.

Longevity of conventional and bonded (sealed) amalgam restorations in a private general dental practice

OBJECTIVE

To compare and contrast the longevity of conventionally placed dental amalgam restorations with those placed using bonding techniques.

DESIGN

Retrospective survival analysis (Kaplan Meier) of dental amalgam restorations placed by a single operator in a private general dental practice.

SUBJECTS AND METHODS

The records relating to dental amalgam restorations placed between 1 August 1996 and 31 July 2006 were sourced. The details of these were placed into a database that permitted flexible interrogation. Survival data on conventionally placed amalgams (C) and those bonded with either Panavia Ex (PE) or Rely X ARC (RX) were exported into a statistical package to permit survival analysis by the method of Kaplan and Meier.Results The number of restorations available for analysis were C = 3,854, PE = 51 and RX = 1,797. Percentage survival at one year was C = 96.29, PE = 95.65, and RX = 97.58. Percentage survival at five years was C = 86.21, PE = 76.35 and RX = 82.59. A Log Rank test demonstrated no statistically significant difference (p >0.05) in survival between the restoration types. Amalgam restorations bonded with PE or RX exhibited an acceleration of failure rate around 1,000 days post-placement. Further survival analyses of the method of restoration versus type of restored teeth (molar/premolar) and cavity preparation (Class I/II) showed no significant difference in the survival curves in respect of type of restored tooth. In the comparison of Class I and II cavities, the survival curves for the restorations differed significantly (p <0.0001), however when the curves for the Class I restorations alone were compared, no significant difference was found (p = 0.2634). This was also the case for the Class II restorations (p = 0.2260).

CONCLUSIONS

Within the limitations of the study, bonding amalgams, compared to placing them conventionally, afforded no significant benefit upon restoration longevity. This, coupled with the emerging trend of an accelerating decline in longevity of bonded amalgams from 1,000 days onwards and with the greater cost, challenges the justification for routine bonding of amalgams.