Does Classification of Composites for Network Meta-analyses Lead to Erroneous Conclusions?

Objectives: 

Composites can be classified differently, according to manufacturer information, filler particle size, resin-monomer base, or viscosity, for example. Using clinical trial data, network meta-analyses aim to rank different composite material classes. Dentists then use these ranks to decide whether to use specific materials. Alternatively, annual failure rates (AFRs) of materials can be assessed, not requiring any classification for synthesis. It is unclear whether different classification systems lead to different rankings of the same material (ie, erroneous conclusions). We aimed to evaluate the agreement of material rankings between different classification systems.

Methods: 

A systematic review was performed via MEDLINE, Cochrane Central Register of Controlled Trials, and EMBASE. Randomized controlled trials published from 2005-2015 that investigated composite restorations placed in load-bearing cavitated lesions in permanent teeth were included. Network meta-analyses were performed to rank combinations of composite classes (according to manufacturer, filler particle size, resin-monomers, viscosity) and adhesives. Material combinations were additionally ranked using AFRs.

Results: 

A total of 42 studies (6088 restorations, 2325 patients) were included. The ranking of most material class combinations showed significant agreement between classifications (R2 ranged between 0.03 and 0.56). Comparing material combinations using AFRs had low precision and agreement with other systems. AFRs were significantly correlated with follow-up periods of trials.

Conclusion: 

There was high agreement between rankings of identical materials in different classification systems. Such rankings thus allow cautious deductions as to the performance of a specific material. Syntheses based on AFRs might lead to erroneous results because AFRs are determined by follow-up periods and have low precision.

Margin Integrity and Secondary Caries of Lined or Non-lined Composite and Glass Hybrid Restorations After Selective Excavation In Vitro

OBJECTIVES

For deep carious lesions, selective carious tissue removal (leaving soft dentin close to the pulp) is suggested. Afterward, different restoration materials, such as resin composites or glass hybrids (GHs), can be placed. Many dentists also apply setting or non-setting calcium hydroxide liners before restoration. We compared margin integrity and susceptibility for secondary caries in differently restored premolars in vitro.

METHODS

In 48 extracted human premolars, artificial residual lesions were induced on pulpo-axial walls of standardized cavities. Teeth were restored using a GH (Equia Forte) or adhesively placed resin composite restoration (OptiBond FL and Tetric EvoCeram) without any liner (RC), resin composite restoration with a non-setting calcium hydroxide liner (RC_NCH), or resin composite restoration with a setting calcium hydroxide liner (RC_SCH). After thermomechanical cycling, groups (n=12) were compared regarding their gingivocervical margin integrity (proportion of irregularities, microgaps, gaps >5 μm, overhangs). Teeth were then submitted to a continuous culture Lactobacillus rhamnosus biofilm model. After 14 days, bacterial numbers in biofilms, along tooth-restoration margins and mineral loss (ΔZ) of secondary lesions, were determined.

RESULTS

GH and RC_NCH showed significantly higher proportions of irregularities than RC and RC_SCH (p<0.05/Mann-Whitney). GH also showed significantly more gaps than alternative restorations (p<0.05). Bacterial numbers and ΔZ did not differ significantly between groups (p>0.05).

CONCLUSIONS

GH and composites lined with non-setting calcium hydroxide showed reduced margin integrity compared with non-lined composites or composites lined with setting calcium hydroxide. This did not increase susceptibility for secondary caries.

Directly Placed Restorative Materials

For restoring cavitated dental lesions, whether carious or not, a large number of material combinations are available. We aimed to systematically review and synthesize data of comparative dental restorative trials. A systematic review was performed. Randomized controlled trials published between 2005 and 2015 were included that compared the survival of ≥2 restorative and/or adhesive materials (i.e., no need for restorative reintervention). Pairwise and Bayesian network meta-analyses were performed, with separate evaluations for cervical cavitated lesions and load-bearing posterior cavitated lesions in permanent and primary teeth. A total of 11,070 restorations (5,330 cervical, 5,740 load bearing) had been placed in 3,633 patients in the included trials. Thirty-six trials investigated restoration of cervical lesions (all in permanent teeth) and 36 of load-bearing lesions (8 in primary and 28 in permanent teeth). Resin-modified glass ionomer cements had the highest chance of survival in cervical cavitated lesions; composites or compomers placed via 2-step self-etch and 3-step etch-and-rinse adhesives were ranked next. Restorations placed with 2-step etch-and-rinse or 1-step self-etch adhesives performed worst. For load-bearing restorations, conventional composites had the highest probability of survival, while siloranes were found least suitable. Ambiguity remains regarding which adhesive strategy to use in load-bearing cavitated lesions. Most studies showed high risk of bias, and several comparisons were prone for publication bias. If prioritized for survival, resin-modified glass ionomer cements might be recommended to restore cervical lesions. For load-bearing ones, conventional or bulk fill composites seem most suitable. The available evidence is quantitatively and qualitatively insufficient for further recommendations, especially with regard to adhesive strategies in posterior load-bearing situations. Moreover, different material classifications might yield different findings on the same materials. Future trials should aim for sufficient power, longer follow-up times, and high internal validity to prove or refute differences between certain material combinations. An agreed material classification for future syntheses is desirable.

Effect of Industry Sponsorship on Dental Restorative Trials

Industry sponsorship was found to potentially introduce bias into clinical trials. We assessed the effects of industry sponsorship on the design, comparator choice, and findings of randomized controlled trials on dental restorative materials. A systematic review was performed via MEDLINE, CENTRAL, and EMBASE. Randomized trials on dental restorative and adhesive materials published 2005 to 2015 were included. The design of sponsored and nonsponsored trials was compared statistically (risk of bias, treatment indication, setting, transferability, sample size). Comparator choice and network geometry of sponsored and nonsponsored trials were assessed via network analysis. Material performance rankings in different trial types were estimated via Bayesian network meta-analysis. Overall, 114 studies were included (15,321 restorations in 5,232 patients). We found 21 and 41 (18% and 36%) trials being clearly or possibly industry sponsored, respectively. Trial design of sponsored and nonsponsored trials did not significantly differ for most assessed items. Sponsored trials evaluated restorations of load-bearing cavities significantly more often than nonsponsored trials, had longer follow-up periods, and showed significantly increased risk of detection bias. Regardless of sponsorship status, comparisons were mainly performed within material classes. The proportion of trials comparing against gold standard restorative or adhesive materials did not differ between trial types. If ranked for performance according to the need to re-treat (best: least re-treatments), most material combinations were ranked similarly in sponsored and nonsponsored trials. The effect of industry sponsorship on dental restorative trials seems limited.

Guidelines for the preparation of CAD/CAM ceramic inlays and partial crowns

Ceramic inlays and partial crowns have become scientifically recognized posterior restorations. Their clinical effectiveness depends on the development of durable dental ceramics and luting materials as well as an effective bonding system. Therefore, these factors were in the focus of interest in the past. In contrast, only little attention was given to preparation techniques. However, current studies show that special preparation rules should be followed to ensure best fitting CAD/CAM ceramic restorations and long-lasting clinical success. This paper describes preparation requirements by means of detailed three-dimensional schematic drawings and then deduces the clinical procedure for the preparation of ceramic inlays and partial crowns with standardized preparation instruments.

The influence of a simplified application technique for ceramic inlays on the margin quality

The adhesive luting technique for ceramic inlays requires a sequence of multiple steps that are cumber-some and time consuming. Furthermore, modifications of dentin bonding procedures may negatively influence the margin quality of ceramic inlays with cervical dentin finishing lines.

PURPOSE

The objective of this study was to test the effect of a new, simplified procedure for dentin bonding on the margin quality of ceramic inlays.

MATERIALS AND METHODS

Thirty-two MOD inlay cavities with cervical finishing lines in dentin were prepared into premolars. They were randomly divided into four groups (n = 8): In the balanced design, one parameter was the inlay material (Empress/Cerec) and the other the polymerization of the dentin bonding agent, before insertion of the inlay (P+) and after insertion of the inlay (P-). All inlays were inserted with Variolink II in combination with an enamel and dentin conditioning universal bonding agent (Etch & Prime 3.0). Two parameters were used to determine the inlay quality: (1) the fit, measured by the difference of the insertion depth into the cavity between try-in and cementation, and (2) a quantitative margin analysis in the SEM at a magnification of 200x, performed for the cervical segment before and after thermocycling, using epoxy replicas.

RESULTS

In all four groups the inlays were > 5 microns deeper in the cavities than at the try-in session. This is explained by the substance loss from the etching. The measured difference for Cerec inlays inserted in cavities, where the bonding agent was not polymerized prior to insertion, was significantly larger. Margin analysis of the cervical segment revealed no statistical differences (P < 0.01) for both criteria tested. The median values for all groups were 100% for clinical acceptable margin and 0% for marginal opening.

CONCLUSION

By using the universal bonding agent, high margin qualities on dentin and enamel are obtained with ceramic inlays even with the simplified approach.

Marginal adaptation of compomer Class V restorations in vitro

PURPOSE

The purpose of this in vitro study was to determine the marginal adaptation of different adhesives, including recently developed self-etching primers, in combination with compomers in Class V cavities.

MATERIALS AND METHODS

In 80 extracted human teeth, divided into 10 groups of 8, Class V cavities were prepared (ca. 4 mm high, 3 mm wide, and 1.5 mm deep) with one half of the margin length in dentin. The one-bottle adhesives Prime & Bond 2.1, Syntac SC, and Espe OSB, and the self-etching primers Rasant F 2000 and Prompt L Pop were used in combination with compomers. Before and after thermocycling (TC), replicas were taken and a quantitative margin analysis using the SEM was performed at a magnification of 200x using defined criteria.

RESULTS

The statistical analysis using Kruskal-Wallis and Bonferroni tests showed a significantly (p < 0.05) better marginal adaptation in enamel and dentin for the self-etching primers, and when the one-bottle adhesives were used in combination with the total-etch technique.

CONCLUSION

Self-etching primers improve the marginal adaptation of compomer restorations in enamel.

Improving cervical restorations: a review of materials and techniques

INTRODUCTION

There is a great variety of cervical lesions and an increased need for treatment because patients complain either about esthetics, hypersensitivity, or even food impaction. The cumulative effects of noncarious dental tissue loss are increasingly evident within any population. The prevalence of these noncarious lesions has been estimated at between 31% and 56%, with 85% of the population showing some loss of tooth structure in the cervical area. Since more elderly patients will keep their teeth for a longer time, the problems regarding the cervical areas of the teeth will increase. Therefore, the challenge for the dentist is rather substantial, since it has been shown that the longevity of these cervical restorations is not as great as that of other restorations. The purpose of this review is to summarize some facts about cervical lesions, the different tooth-colored restorative materials and their application, and the assessment of the clinical performance of these materials.

Influence of incorrect application of a water-based adhesive system on the marginal adaptation of Class V restorations

PURPOSE

To determine the influence of incorrectly performed steps during the application of the water-based adhesive system OptiBond FL on the marginal adaptation of Class V composite restorations.

MATERIALS AND METHODS

In 96 extracted human teeth Class V cavities were prepared. Half of the margin length was situated in dentin. The teeth were randomly divided into 12 groups. The cavities were filled with Prodigy resin-based composite in combination with OptiBond FL according to the manufacturer's instructions (Group O) and including several incorrect application steps: Group A: prolonged etching (60 s); Group B: no etching of dentin; Group C: excessive drying after etching; Group D: short rewetting after excessive drying; Group E: air drying and rewetting; Group F: blot drying; Group G: saliva contamination; Group H: application of primer and immediate drying; group I: application of only primer; group J: application of only adhesive; Group K: no light curing of the adhesive before the application of composite. After thermocycling, replicas were taken and the margins were quantitatively analyzed in the SEM. Statistical analysis of the results was performed using non-parametric procedures.

RESULTS

With exception of the "rewetting groups" (D and E) and the group with saliva contamination (G), all other application procedures showed a significantly higher amount of marginal openings in dentin compared to the control group (O). Margin quality in enamel was only affected when the primer was not applied.

Crystal precipitation on dentin by poly(acrylic acid) solutions containing SO4(2-) ions

The ability of four different 40% poly(acrylic acid) (PAA) solutions, containing 4 or 6 wt-% of either Na2SO4 or (NH4)2SO4, to cause precipitation of CaSO4 on dentin surfaces was investigated. Each treatment consisted of exposing the dentin to one of the four solutions for either 1 or 2 min and was followed by a water rinse (1 min) and air drying (30 sec). The treated dentin surfaces were then evaluated in a scanning electron microscope (SEM), which showed that crystals precipitated on the dentin with these solutions. Of the four investigated PAAs, one performed better than the others with regard to crystal precipitation and blockage of the tubules. This solution was selected for additional studies of the effects of different PAA concentrations (10%, 20%, 30%, 40%, and 50%). In these solutions, 4 and 6 wt-% of either Na2SO4 or (NH4)2SO4 were dissolved. Additional dentin surfaces were then treated with these solutions as described earlier and evaluated in an SEM. This evaluation showed that solutions containing 30-50% PAA resulted in optimized crystal formation for all the different sulfate solutions and that the optimization occurred within 1 min. Besides optimizing crystal precipitation, these mixtures also minimized the frequency of open dentinal tubules.

[Effects of dentin bonding agents on the proximal margins of ceramic inlays]

Ceramic inlays have shown good marginal seal as long as the margins of the cavities are located in enamel. The purpose of this study was to investigate the marginal seal of ceramic inlays with the cervical margins situated in dentin and to determine the effectiveness of dentin bonding agents. Sintered ceramic inlays were adhesively luted either without dentin bonding agents or with the use of Gluma or Miragebond. After thermocycling and incubation in a colored dye the penetration depth of the dye was measured on sequential sections. The used dentin bonding agents did not improve marginal seal. The glass ionomer cement base was able to prevent further penetration in most of the cases when deep leakage occurred. Unless a tight marginal seal in dentin can be achieved, the indication for adhesively luted inlays must be limited to cavities with margins located in enamel.

[Time of extraction and cavity position in in-vitro tests of dentin adhesives]

Cylindrical cavities were prepared in different tooth segments (coronal, cervical and radicular) and at different times (1 hour, 1 day, 1 week and 1 month) after extraction into face-ground dentin surfaces of extracted teeth. The cavities were filled with composite resin materials using different dentin adhesives. Before and after thermocycling (TC) the marginal adaptation was evaluated using defined criteria. The statistical evaluation did not show any significant differences (p greater than 0.01) after TC within the different groups of dentin adhesives. For in vitro tests of dentin adhesives neither the position nor the time of extraction decisively influences the process.

[Comparison of two cavity preparations to examine the efficacy of dentin adhesives]

Cylindrical cavities and class V cavities were treated with six different dentin adhesives before filling them with composites. Cavity margins were studied quantitatively with defined criteria before and after alternating thermal stress tests in a scanning electron microscope. In both cavity preparations groups of dentin adhesives with significantly different efficacies (p 0.05) were identified. The efficacy of dentin adhesives and their effect on marginal adaptation of composite materials in dentin can be determined rather easily in cylindrical cavities.

Quantitative margin analysis in the scanning electron microscope

Interface between restorative materials and tooth hard substances must be morphologically as perfect as possible to avoid plaque accumulation and subsequent secondary caries or pulpal diseases. Therefore the marginal behavior of restorations is an important parameter to predict their longevity. Morphologically, the quality of margins is characterized by different well defined criteria. Using a replica technique it is possible to assess the complete marginal circumference of restorations in the SEM. Margins of restorations show a large variety of their morphology. This publication describes a method to quantify the quality of dental restorations. The restoration margins are traced on the SEM screen with a digitizer and an interface to measure the margin's length. Simultaneously the margin quality is assessed and assigned to the corresponding lengths. The % distribution of the quality criteria for each restoration is then calculated. Using a comparative light microscope, the replicas are aligned and mounted identically in the SEM for longitudinal studies. The results presented are limited to tests for the accuracy of the method. Using 5 criteria to characterize the margin quality, it was found that the difference between two measurements by the same operator, 4 weeks apart was 3% +/- 2.6%. The largest difference for one group was 9%. In another accuracy test where 4 criteria for margin characterization were used, the difference between two measurements was 1.9% +/- 0.9%. The largest difference between two groups found was 3.4%. This method can be used for longitudinal studies in vivo, but also for in vitro screening tests with new materials.