Influence of a proximal margin elevation technique on marginal adaptation of ceramic inlays

Deep margin elevation in restorative dentistry: A scoping review

OBJECTIVES

Deep margin elevation (DME) is a restorative approach offering the possibility of performing stepwise elevation of deep proximal cavities to create more favourable margins for direct or indirect restorations. The objectives of this scoping review were to explore what is known or unknown about DME by describing a wide ranging evidence base including peer reviewed literature and non-traditionally published information on the web.

DATA

Data were extracted from the included evidence in order to describe the following: the extent and nature of the evidence base; the situations which are appropriate for DME; the materials and techniques which are used; the outcomes which have been measured in empirical studies; the risks which have been reported; and the findings which have been reported in studies which compared DME to surgical crown lengthening.

SOURCES

This scoping review included a wide range of published evidence and extensive web searching for grey literature, including CPD, training and multimedia information.

STUDY SELECTION

The findings revealed a range of published literature as well as freely available, online information advising practitioners about DME. Most empirical evidence was based on in vitro studies, and there were few clinical studies comparing DME to crown lengthening. Online information included recent, multimedia sources.

CONCLUSIONS

DME is a technique that can be used with motivated patients with good oral hygiene if rubber dam isolation is achieved, if there is no invasion of the connective tissue space, and if a strict restorative protocol is adhered to.

CLINICAL SIGNIFICANCE

With phasing out of amalgam and adhesive dentistry increasing in popularity, DME addresses multiple clinical problems associated with sub-gingival margins prior to restoration.

Enhancing subgingival margin restoration: a comprehensive review and meta-analysis of deep margin elevation's impact on microleakage

INTRODUCTION

Restorative dentistry faces complex challenges with deep proximal surface destruction, requiring novel approaches like DME (Deep Margin Elevation). In order to achieve the best results while treating severe tooth damage, this study examines the advantages, disadvantages, and possible collaborations of different treatments.

AIMS

This systematic review investigates the efficacy of DME as an adjunctive procedure in restorative dentistry, specifically focusing on its impact on microleakage.

METHODS

The study adheres to PRISMA guidelines and employs the PICOS framework for eligibility criteria. 394 potentially qualifying studies were discovered and thorough literature search was carried out via databases. After applying inclusion criteria, 7 studies were included in the analysis. Articles were selected based on criteria that included indirect restoration and performing DME and were compared with indirect restorations without DME. Composite resin was used for DME. Other materials for DME performing, including GI and composite flow, were systematically reviewed. Data analysis was done by biostat software (α = 0.05).

RESULTS

The meta-analysis of selected studies reveals a statistically significant positive effect of DME on reduction of microleakage (p = 0.001).

CONCLUSION

The results of this study underscore the potential of DME in addressing subgingival margin challenges and provide valuable insights for restorative dentistry practices.

Is Deep margin elevation a reliable tool for cervical margin relocation? - A comparative review

The permanence of deep subgingival restorations are questionable both functionally and biologically. Crown lengthening is one of the traditionally performing procedures to visualize and relocate the deep margins, but the limitations of the invasive surgical procedure are anatomical complications like exposure of root concavities or furcation, violation of biological width, post operative discomfort because of sutures or periodontal packs; and less patient compliance. Other than crown lengthening, researchers tried some other techniques like modified matrix adaptation technique, using retraction cord, making holes in matrix band and flowing resin modified glass ionomer cement (RMGIC) to the root or cervical caries, orthodontic extrusion. But most of these procedures are failed to give adequate clinical success. Deep margin elevation (DME) is one of the minimally invasive and successful procedure performing in deep subgingival caries. But the evidences and knowledge in this technique is limited among practitioners. This review is to evaluate the applicability of DME, the current clinical concepts, techniques and materials for DME; and a comparison with traditionally used various techniques for cervical margin relocation also concluding that currently available various clinical parameters with this technique.

M-i-M for DME: matrix-in-a-matrix technique for deep margin elevation

Deep margin elevation is a solution to the problem of localized subgingival margins when preparing a tooth for direct, semidirect, or indirect restorations. The technique focuses on the local isolation of the deep margin by using a modified circumferential matrix. An evolution of the technique is presented, the matrix-in-a-matrix technique, to facilitate the isolation and fit of the subgingival matrix by adding a sectional band inside the circumferential matrix and packing Teflon tape between the 2 bands. Resective surgeries, invasive restorative procedures, and even sometimes extractions can all potentially be avoided by this modified deep margin elevation, allowing ideal conditions for scanning or impression making.

Fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: Cervical margin relocation and crown lengthening with complete and partial ferrule with three different post and core systems

PURPOSE

To assess the fracture resistance and failure mode of endodontically treated premolars reconstructed by different preparation approaches: cervical margin relocation (CMR) and crown lengthening (CL) with complete ferrule (CLF) and partial ferrule (CLPF) with three different post and core systems.

MATERIALS AND METHODS

In this in vitro study, 100 maxillary premolars were assigned to the following 10 groups according to their preparation approach and type of post and core system (n = 10): (I) control (intact teeth), (II) prefabricated fiber post (PFP) and composite core with CMR (PFP-CMR), (III) polyethylene fiber-reinforced composite (PEFRC) with CMR (PEFRC-CMR), (IV) casting post (CP) and core with CMR (CP-CMR), (V) PFP-CLPF, (VI) PEFRC-CLPF, (VII) CP-CLPF, (VIII) PFP-CLF, (IX) PEFRC-CLF, and (X) CP-CLF. After thermomechanical loading, the fracture resistance and failure mode were assessed. Data were analyzed statistically (α = 0.05).

RESULTS

In all post and core systems, the CLPF approach had lower fracture resistance than CMR (p < 0.05); CLF showed higher fracture resistance than CLPF only in the PFP system (p = 0.038). In PEFRC and CP systems, the difference between CLF and CLPF was not significant (p > 0.05). No significant difference was found in fracture resistance of different post and core systems with the same preparation approach (p > 0.05). CLPF showed the highest frequency of favorable, and CLF showed the highest frequency of unfavorable fractures.

CONCLUSION

CLPF yielded lower fracture resistance than CMR. The difference in fracture resistance was not significant between CLF and CMR but the frequency of unfavorable fractures was higher in CLF than in other groups.

Quality of CAD-CAM inlays placed on aged resin-based composite restorations used as deep margin elevation: a laboratory study

OBJECTIVES

To assess the impact of the age of resin-based composite (RBC) restorations used for deep margin elevation (DME) on the marginal quality and fracture resistance of inlays.

MATERIALS AND METHODS

Permanent human molars with direct RBC restorations, involving the mesial, occlusal, and distal surface (MOD), were allocated to four groups (each n = 12). Half of the teeth underwent thermomechanical loading including 240,000 occlusal load cycles and 534 thermal cycles (TML, 5 °C/55 °C; 49 N, 1.7 Hz). With RBC left in one proximal box as DME, all teeth received MOD inlays, made from lithium disilicate (LDS) or a polymer-infiltrated ceramic network material (PICN). The restored teeth underwent TML including 1.2 million occlusal cyclic loadings and 2673 thermal cycles. The marginal quality was assessed at baseline and after both runs of TML. Load-to-fracture tests were performed. The statistical analysis comprised multiple linear regressions (α = 0.05).

RESULTS

Simulated aging of RBC restorations had no significant effect on the marginal quality at the interface between the RBC and the tooth and the RBC and the inlay (p ≥ 0.247). Across time points, higher percentages of non-continuous margin were observed between the inlay and the tooth than between the tooth and the RBC (p ≤ 0.039). The age of the DME did not significantly affect the fracture resistance (p ≥ 0.052).

CONCLUSIONS

Artificial aging of RBC restorations used for DME had no detrimental effect on the marginal quality and fracture resistance of LDS and PICN inlays.

CLINICAL RELEVANCE

This laboratory study suggests that-in select cases-intact, direct RBC restorations not placed immediately before the delivery of an indirect restoration may be used for DME.

Deep Margin Elevation: Current Concepts and Clinical Considerations: A Review

Dietschi and Spreafico first proposed deep margin elevation (DME) in 1998 to address the multiple clinical problems associated with sub-gingival margins, where sub-gingival margins will be repositioned coronally using composite resin restorations. Given that dentistry is directing towards conservatism, its use is currently trending. Materials and Methods: a search was performed through PubMed, Scopus, and Google Scholar search engines to obtain relevant articles with no time restriction. Results: With biological width taken into consideration, well-defined and polished sub-gingival restorations are compatible with periodontal health. Marginal integrity in the DME technique seems to be affected by the type of adhesive, restoration, and incremental layering of the restoration. Regarding fracture resistance, DME has no significant effects. Conclusion: The DME technique seems to be a minimally invasive alternative to surgical crown lengthening (SCL) and orthodontic extrusion (OE) with respect to biological width. Well-controlled clinical trials are limited in this field; further long-term follow-up studies emphasizing the periodontal outcomes and prevention of complications are needed.

A Comparison of Microtensile Bond Strength, Film Thickness, and Microhardness of Photo-Polymerized Luting Composites

The aim of this study was to evaluate the effect of CAD/CAM composite thickness on micro-tensile bond strength (µTBS), microhardness (HV), and film thickness (FT) of different luting composites. Composite blocks (6.8 mm × 6.8 mm) were divided into 12 groups according to: CAD/CAM thickness and luting composite. For each group, 21 rods (1 mm × 1 mm) were tested in tension at crosshead speed of 1 mm/min. Fracture modes were categorized as adhesive, mixed, and cohesive. Microhardness (n = 5/group) was assessed using microhardness tester. Film thickness (12-rods/group) was evaluated using a stereomicroscope (×40). Data were analyzed using the two-way ANOVA/Tukey’s HSD test (p = 0.05). Parameters “thickness”, “cement”, and “thickness x cement” showed significant difference on µTBS and HV (p < 0.05). At 2 mm, heated x-tra fil composite showed the highest µTBS (45.0 ± 8.5 MPa), while at 4 mm thickness, Grandio Flow revealed the lowest µTBS (33.3 ± 6.3 MPa). Adhesive, mixed, and cohesive failures were reported. The HV of all composites decreased when photo-polymerized through 4 mm thickness (p < 0.05). Regardless of CAD/CAM thickness, photo-polymerized composites can be successfully used for luting CAD/CAM composite.

Deep Margin Elevation: A Literature Review

A conservative approach for restoring deep proximal lesions is to apply an increment of composite resin over the preexisting cervical margin to relocate it coronally, the so-called “deep margin elevation” (DME). A literature search for research articles referring to DME published from January 1998 until November 2021 was conducted using MEDLINE (PubMed), Ovid, Scopus, Cochrane Library and Semantic Scholar databases applying preset inclusion and exclusion criteria. Elevation material and adhesive system employed for luting seem to be significant factors concerning the marginal adaptation of the restoration. This technique does not affect bond strength, fatigue behavior, fracture resistance, failure pattern or repairability. DME and subgingival restorations are compatible with periodontal health, given that they are well-polished and refined. The available literature is limited mainly to in vitro studies. Therefore, randomized clinical trials with extended follow-up periods are necessary to clarify all aspects of the technique and ascertain its validity in clinical practice. For the time being, DME should be applied with caution respecting three criteria: capability of field isolation, the perfect seal of the cervical margin provided by the matrix, and no invasion of the connective compartment of biological width.

Effect of Deep Margin Elevation on Interfacial Gap Development of CAD/CAM Inlays after Thermomechanical Cycling

The aim of this study was to evaluate interfacial gap formation of CAD/CAM lithium disilicate inlay margins before and after thermomechanical loading.

METHODS AND MATERIALS

Mesio-occlusal-distal cavities were prepared on 12 extracted mandibular molars. The gingival margin of one proximal box was elevated with resin modified glass ionomer (RMGI) by a height of 2 mm (Group E [elevation]), and the margin of the other side served as a control (Group NE [no elevation]). Lithium disilicate computer-aided design and computer-aided manufacturing (CAD/CAM) inlays were fabricated and bonded with a self-adhesive resin cement. An aging process was simulated on the specimens under thermomechanical cycling by using a chewing simulator. Marginal integration was evaluated under scanning electron miscroscopy (SEM) using epoxy resin replicas before and after cycling. Marginal areas were stained with silver nitrate solution, and the volumetric gap was measured at the bonded interfaces using microcomputed tomography (CT) before and after cycling. Statistical analyses were performed using paired t-tests, the Wilcoxon signed rank test, and the Mann-Whitney test (a<0.05).

RESULTS

SEM showed marginal discontinuities in Group NE that increased after thermomechanical cycling. Micro-computed tomography exhibited three-dimensional dye-penetrating patterns at the interfaces before and after cycling. Interfacial disintegration was larger in Group NE before cycling (p<0.05). Thermomechanical cycling increased the gaps in both Groups NE and E (p<0.05). The gap increment from thermomechanical cycling was larger in Group NE (p<0.05).

CONCLUSIONS

Thermomechanical cycling induced interfacial disintegration at the lithium disilicate CAD/CAM inlays, with deep proximal margins. Margin elevation with RMGI placement reduced the extent of the interfacial gap formation before and after the aging simulation.

Fatigue behavior and stress distribution of molars restored with MOD inlays with and without deep margin elevation

OBJECTIVES

This study evaluated the effect of deep margin elevation (DME) and restorative materials (leucite-reinforced glass-ceramics [C] vs. indirect resin composite [R]) on the fatigue behavior and stress distribution of maxillary molars with 2-mm deep proximal margins restored with MOD inlay.

METHODS

Fifty-two extracted human third molars were randomly assigned into four groups (n = 13): C; DME + C; R; and DME + R. Inlays were fabricated in CAD-CAM and bonded to all teeth. The fatigue behavior was assessed with the stepwise stress test (10,000 cycles/step; step = 50 N; 20 Hz; initial load = 200 N). Fatigue failure loads and the number of cycles were analyzed with 2-way ANOVA and Tukey's test (p < 0.05) and Kaplan-Meier survival plots. The stress distribution was assessed with finite element analysis. The models were considered isotropic, linear, and homogeneous, and presented bonded contacts. A tripod axial load (400 N) was applied to the occlusal surface. The stress distribution was analyzed with the maximum principal stress criterion.

RESULTS

For fatigue, there was no difference for DME factor (p > 0.05). For the material factor, the load and number of cycles for failure were statistically higher in the R groups (p < 0.05). The finite element analysis showed that resin composite inlays concentrated more stress in the tooth structure, while ceramic inlays concentrated more stress in the restoration. Non-reparable failures were more frequent in the resin composite inlays groups.

CONCLUSIONS

DME was not negative for fatigue and biomechanical behaviors. Resin composite inlays were more resistant to the fatigue test, although the failure mode was more aggressive.

CLINICAL SIGNIFICANCE

DME does not impair mechanical behavior. Resin composite inlays failed at higher loads but with a more aggressive failure mode.

Influence of the adhesive strategy in the sealing ability of resin composite inlays after deep margin elevation

Background

The aim of this study was to determine the influence of the gingival margin position and the adhesive strategy selected to perform deep margin elevation (DME) in marginal sealing of resin composite inlays by a nanoleakage test.

Material and Methods

12 sound third molars were selected and expulsive MOD cavities for inlays were prepared. Experimental groups were established according to gingival margin location (enamel: 1 mm above cemento-enamel junction (CEJ), dentin: 1 mm below CEJ, or DME, and the adhesive strategy used to lute inlays and elevate the gingival margin. Therefore, the six experimental groups were: 1) Enamel + etch-and-rinse adhesive (ERA) Adper Scotchbond 1XT (SB1XT); 2) Dentin + SB1XT; 3) DME + SB1XT; 4) Enamel + self-etching adhesive (SEA) with enamel selective etching Clearfil SE Bond (CSE); 5) Dentin + CSE; 6) DME + CSE. Resin composite inlays were constructed (Gradia Indirect) and all luted with the same resin cement (RelyX ARC). Specimens were submitted to nanoleakage test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests with Bonferroni correction (p<0.05).

Results

A perfect sealing ability was evidenced for experimental groups with gingival margins on enamel. Similar nanoleakage values were determined when CSE adhesive was applied regardless the gingival margin position. The highest silver nitrate infiltration was detected for elevated margins with the ERA SB1XT.

Conclusions

The SEA Clearfil SE Bond showed higher sealing ability than the ERA Adper Scotchbond 1XT when margins were located on dentin, regardless margin elevation. Gingival margins on enamel together with enamel acid etching provided an excellent sealing with both adhesive systems. Key words:Adhesion, composite inlays, gingival margin, deep margin elevation, marginal seal, nanoleakage test.

Assessment of knowledge, attitude, and practice regarding Deep Margin Elevation (DME) among dental practitioners in Riyadh, Saudi Arabia

Objectives:

To evaluate Knowledge, Attitude, and Practice (KAP) regarding deep margin elevation (DME) among dental practitioners in Riyadh city.

Materials and Methodology:

A cross-sectional study that comprised a total number of 535 dental practitioners: 255 (47.7%) were males and 280 (52.3%) females. A self-constructed 21 close-ended self-administered questionnaire was utilized in the study. The data were entered and analyzed by Chi-square test and descriptive analysis using Statistical Package for the Social Sciences (SPSS) software.

Results:

Although the majority of the respondents have heard about DME, only 30.4% have utilized this technique in their clinical practice by having general practitioners and specialists utilize this technique more often than consultants. Among the participants, 65.4% of them have agreed that adhesion by bonding to deep cervical dentin is predictable and related to the success of the final restoration.

Conclusion:

The knowledge level of DME among the study participants was adequate. The findings of this study revealed that the total number of dentists who utilize the technique in restoring large subgingival defects of posterior teeth with proximal caries is very minimal. Thus, it is recommended that dental practitioners have this technique introduced in their dental clinics as an alternative to surgical crown lengthening. Although years of experience and dentist rank may influence the clinical decision, in-depth factorial analysis with a greater sample size is necessary.

Investigating inlay designs of class II cavity with deep margin elevation using finite element method

Background

This study evaluates the mechanical performance of deep margin elevation technique for carious cavities by considering the shape designs and material selections of inlay using a computational approach combined with the design of experiments method. The goal is to understand the effects of the design parameters on the deep margin elevation technique and provide design guidelines from the biomechanics perspective.

Methods

Seven geometric design parameters for defining an inlay’s shape of a premolar were specified, and the influence of cavity shape and material selection on the overall stress distribution was investigated via automated modelling. Material selection included composite resin, ceramic, and lithium disilicate. Finite element analysis was performed to evaluate the mechanical behavior of the tooth and inlay under a compressive load. Next, the analysis of variance was conducted to identify the parameters with a significant effect on the stress occurred in the materials. Finally, the response surface method was used to analyze the stress responses of the restored tooth with different design parameters.

Results

The restored tooth with a larger isthmus width demonstrated superior mechanical performance in all three types of inlay materials, while the influence of other design parameters varied with the inlay material selection. The height of the deep margin elevation layer insignificantly affected the mechanical performance of the restored tooth.

Conclusions

A proper geometric design of inlay enhances the mechanical performance of the restored tooth and could require less volume of the natural dentin to be excavated. Furthermore, under the loading conditions evaluated in this study, the deep margin elevation layer did not extensively affect the strength of the tooth structure.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01630-z.

Effect of Deep Margin Elevation on CAD/CAM-Fabricated Ceramic Inlays

CLINICAL RELEVANCE

Using the deep margin elevation technique in preparations extending beyond the cemento-enamel junction appears to be beneficial in maintaining structural integrity of CAD/CAM-fabricated feldspathic ceramic inlays.

SUMMARY

Objective: To evaluate the effect of deep margin elevation on structural and marginal integrity of ceramic inlays.Methods and Materials: Forty extracted human third molars were collected and randomly separated into four groups (n=10/group). In group 1 (enamel margin group), the gingival margin was placed 1 mm supragingival to the cemento-enamel junction (CEJ). In group 2 (cementum margin group), the gingival margin was placed 2 mm below the CEJ. In group 3 (glass ionomer [GI] margin group), the gingival margin was placed 2 mm below the CEJ, and then the margin elevated with GI to the CEJ. In group 4 (resin-modified glass ionomer [RMGI] margin group), the gingival margin was placed 2 mm below the CEJ, and then the margin elevated with RMGI to the CEJ. Standardized ceramic class II inlays were fabricated with computer-aided design/computer-aided manufacturing and bonded to all teeth, and ceramic proximal box heights were measured. All teeth were subjected to 10,000 cycles of thermocycling (5°C/55°C) and then underwent 1,200,000 cycles of vertical chewing simulation at 50 N of force. Ceramic restorations and marginal integrity were assessed with a Hirox digital microscope. The Fisher exact test (two-tailed) with adjusted p-values (α=0.05) and logistic regression were used for statistical analysis.Results: The cementum margin group had a significantly higher ceramic fracture rate (90%) compared to other groups (10% in enamel margin and GI margin groups, p=0.007; 0% in RMGI group, p<0.001). Logistic regression showed that with increased ceramic proximal box heights, the probability of ceramic fracture increased dramatically.Conclusion: Deep marginal elevation resulted in decreased ceramic fracture when preparation margins were located below the CEJ. There was no difference found between margin elevation with GI or RMGI. Increased heights of ceramic proximal box may lead to an increased probability of ceramic fracture.

Tridimensional Evaluation of the Interfacial Gap in Deep Cervical Margin Restorations: A Micro-CT Study

CLINICAL RELEVANCE

Using a material that optimizes marginal seal when using a margin elevation technique to manage deep class II cavities should enhance clinical outcomes.

SUMMARY

Objectives: The purpose of this laboratory study was to perform a tridimensional interfacial gap evaluation of class II cavities with enamel and dentin cervical margins, before and after cyclic fatigue, restored with different nanohybrid resin composites.Methods and Materials: Standardized class II cavities were performed on 48 intact maxillary premolars, placing the mesial cervical margin 1 mm above the cement-enamel junction (CEJ) and the distal cervical margin 1 mm below the CEJ. Specimens were treated with two-step self-etch adhesive (Clearfil SE Bond2) and divided into six groups according to the restoration technique. Microcomputed Tomography imaging was executed before and after 1,000,000 cycles of chewing simulation at 50 N. Tridimensional interfacial gaps, expressed as cubic millimeters, were analyzed through a standardized software flowchart (Mimics). Data were analyzed with a two-way analysis of variance and Tukey post hoc tests (α=0.05).Results: Restoration technique (p=0.001) and chewing simulation (p=0.00001) significantly influenced interfacial gap on dentin but not on enamel. The post hoc test showed that, on dentin margins, flowable resins had a lower gap at baseline but a higher gap after chewing simulation, especially when a 2-mm-thick layer was applied, compared with nanohybrid and bulk-fill composites.Conclusions: Based on the obtained results, no differences in interfacial gap volume were found on enamel margins. On dentin margins, flowable resins showed better marginal seal at baseline, but they seem to be more prone to interfacial degradation during chewing simulation than traditional composites.

No correlation between two methodological approaches applied to evaluate cervical margin relocation

The study evaluated the quality of gingival margins created by cervical margin relocation (CMR) technique using different materials and assessed the consistency of the results obtained by two in vitro methods: microleakage test and scanning electron microscopy (SEM). Mesio-occlusal-distal cavities with subgingival proximal margins were prepared. Mesial margins were elevated supragingivally with total-etch adhesive and flowable composite (Group 1) or with universal adhesive and bulk-fill flowable composite (Group 2). Distal margins were not elevated. Teeth were restored with CAD/CAM overlays. Marginal quality was evaluated by microleakage test and SEM observation of epoxy resin replicas. Statistical analyses showed no significant correlations between microleakage scores and percentage of marginal integrity observed under SEM at CMR margins, lower microleakage scores at margins without CMR compared to CMR margins, lower microleakage scores in Group 2 than in Group 1 and no difference in SEM integrity between groups at CMR margins.

Efficacy of Direct Restorative Materials in Proximal Box Elevation on the Margin Quality and Fracture Resistance of Molars Restored With CAD/CAM Onlays

PURPOSE

The purpose of this study was to investigate the effect of four direct restorative materials that can be used in the proximal box elevation (PBE) technique.

METHODS AND MATERIALS

Seventy-five molar teeth were randomly assigned to one of five groups (n=15): type II glass ionomer (GI), type II resin-modified glass ionomer (RMGI), resin-based composite (RBC), bulk-fill (BF) resin-based composite, and a control with no box elevation procedure. Specimens were prepared for a standard mesio-occlusal-distal, computer-aided design/computer-aided manufactured (CAD-CAM) resin, nanoceramic onlay with mesial cervical margins located 1 mm above the cementoenamel junction (CEJ) and distal cervical margins located 2 mm below the CEJ. PBE was used to elevate the distal margins to 1 mm above the CEJ in all groups except the control group. For the control group the onlay margin was placed directly on the prepared distal tooth structure without PBE. A Lava Ultimate CAD/CAM resin, nanoceramic onlay restorative was manufactured and bonded on all specimens with RelyX Ultimate adhesive resin cement. The quality of the tooth-PBE material and PBE material-onlay interface was evaluated with scanning electron microscopy using epoxy resin replicas before and after cyclic loading (100,000 cycles, 1.2 Hz at 65N and 37°C). In addition to margin quality, the fracture resistance of each group was measured using a universal testing machine. Fracture pattern was recorded by visual examination. The Levene test for homogeneity and the Welch analysis of variance were completed for fracture resistance and margin quality. A χ² test was completed for break mode.

RESULTS

For dentin margins, a statistically significant difference was detected between the RMGI and control groups at baseline (p=0.0442). All other groups-GI, RBC, and BF-showed no difference from the control at baseline (p>0.05). No statistical significance was observed among groups for post-cyclic fatigue (p=0.8735). For onlay margins, no statistical significance was observed among groups for pre-cyclic fatigue, post-cyclic fatigue, or change (p=0.9713, p=0.528, p=0.4385, respectively). No significant difference was observed for the fracture resistance among groups or for the type of break by material used (p=0.1593, p=0.77, respectively).

CONCLUSION

Within the parameters of this study, after mechanical fatigue, the materials used for PBE: RMGI, RBC, and BF, did not influence results in terms of margin quality and fracture resistance. Therefore, collective findings suggest that these materials might be suitable for PBE procedures. Nevertheless, clinical caution is recommended with any PBE procedure and further testing of GI materials is needed.

Marginal and internal fit of CAD-CAM inlay/onlay restorations: A systematic review of in vitro studies

STATEMENT OF PROBLEM

Different parameters can influence the adaptation of computer-assisted design and computer-assisted manufacturing (CAD-CAM) inlay/onlay restorations. However, systematic reviews to identify and discuss these parameters are lacking.

PURPOSE

The purpose of this systematic review was to summarize the scientific literature investigating all parameters that can influence both the marginal and internal adaptation of CAD-CAM inlay/onlay restorations.

MATERIAL AND METHODS

An electronic search was conducted by 2 independent reviewers for studies published in English between January 1, 2007 and September 20, 2017 on the PubMed/MEDLINE, Scopus, and Web of Science databases and in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Factors investigated in the selected articles included the type of CAD-CAM system, virtual space parameters, version of the software, type of block, luting procedure, type of restoration, sample size and aging procedure, evaluation method, and number of measurement points per specimen.

RESULTS

A total of 162 articles were identified, of which 23 articles met the inclusion criteria. Nine studies investigated adaptation with different restorative materials, 2 evaluated adaptation according to the type of preparation design, 9 compared adaptation before/after thermomechanical loading, and 2 before/after cementation, 1 study investigated marginal adaptation based on whether the optical scan was made intraorally or extraorally, 1 compared adaptation with 5 and 3 axis CAM systems, and 1 assessed adaptation with 4 different intraoral scanners. The risk of bias was high for 7, medium for 15, and low for 1 of the studies reviewed. The high level of heterogeneity across the studies excluded meta-analysis.

CONCLUSIONS

Most of the studies reported clinically acceptable values for marginal adaptation. The performance of a CAD-CAM system is influenced by the type of restorative material. A nonretentive cavity preparation exhibited better adaptation than a retentive preparation. Most studies showed that thermomechanical loading affected the quality of marginal adaptation. Cementation increased marginal discrepancies. No statistically significant difference was found for marginal fit of onlays between intraoral and extraoral optical scans using a stone die. The number of milling axes, the type of digital camera, and the region measured were statistically significant in relation to marginal/internal adaptation. Values of adaptation recorded failed to reproduce the preestablished spacer parameters in the software. Clarification is needed concerning adaptation according to the type of preparation design, the type of material, the choice of intrinsic parameters for the CAD process, the type and shape of milling instruments, and the behavior of the material during milling. Adaptation of CAD-CAM inlay/onlays should be evaluated under clinical conditions.

Shear bond strength and interface analysis between a resin composite and a recent high-viscous glass ionomer cement bonded with various adhesive systems

OBJECTIVE

This study investigated the shear bond strength (SBS) and interface between a resin composite and a new high-viscous glass ionomer cement (HV-GIC), a HV-GIC, a resin-modified glass ionomer cement (RM-GIC), a bulk-fill flowable composite, and a regular flowable composite bonded with various adhesive systems.

METHODS AND MATERIALS

A resin composite (Filtek Z350) was bonded to a new HV-GIC (EQUIA Forte Fil) using various adhesive systems, including a universal adhesive in self-etch and etch-and-rinse mode (Scotchbond Universal), a two-step etch-and-rinse adhesive (Scotchbond 1-XT), a one-step self-etch adhesive (Optibond All-in-one) tested also after silane application (Monobond Plus), and a coating material (EQUIA Forte Coat). The resin composite was also bonded to a HV-GIC (Fuji IX GP), a RM-GIC (Fuji II LC), a bulk-fill flowable composite (SDR), and a regular flowable composite (Tetric Evo Flow) with the universal adhesive in self-etch mode (Scotchbond Universal). Two-way ANOVA followed by Dunnett's post hoc test was used to investigate the difference in SBS. Failures were analyzed by chi-square test. Bonding interfaces were examined by environmental scanning electron microscopy (E-SEM).

RESULTS

SBS to EQUIA Forte Fil was significantly lower with Scotchbond 1-XT than with all other adhesive systems. By using Scotchbond Universal with the self-etch technique, the SBS to EQUIA Forte Fil was significantly higher than the SBS to Fuji IX GP and significantly lower than the SBS to Fuji II LC, SDR, and Tetric Evo Flow. E-SEM images showed an intimate contact at all interfaces examined.

CONCLUSION

EQUIA Forte Fil showed satisfactory SBS and interfaces with all adhesives tested.

CLINICAL RELEVANCE

Bonding between the resin composite and HV-GIC can be achieved using a universal adhesive in self-etch mode, an easy-to-use adhesive system.

Marginal sealing of relocated cervical margins of mesio-occluso-distal overlays

We investigated the effect of cervical marginal relocation (CMR) on marginal sealing with two different viscosity resin composites, before adhesive cementation of composite computer-aided design/computer-assisted manufacture mesio-occluso-distal (MOD) overlays. Standardized MOD cavities prepared in 39 human molars were randomly assigned to three groups. The proximal margins on the mesial side were located 1 mm below the cementoenamel junction. On the distal side of the tooth, the margins were located 1 mm above the cementoenamel junction. In Groups 1 and 2, mesial proximal boxes were elevated with a hybrid composite (GC Essentia MD) and a flowable composite (GC G-ænial Universal Flo), respectively. CMR was not performed in Group 3. The overlays were adhesively cemented, and interfacial leakage was quantified by scoring the depth of silver nitrate penetration along the adhesive interfaces. Leakage score at the dentin-CMR composite interface did not significantly differ between the two tested composites but was significantly lower for Group 3. In all groups, scores were significantly higher at the dentin interface than at the enamel interface. These results indicate that the performance of flowable and microhybrid resin composites, as indicated by marginal sealing ability, is comparable for CMR.

Biological evaluation of subgingivally placed direct resin composite materials

Placement of composite resin restorations in deep subgingival cavities can damage surrounding soft tissues. In addition, commonly used resin-based composites (RBCs) might interfere with wound healing and periodontal health. To clarify cellular interactions with RBCs, we used an MTT assay to investigate adhesion of primary human gingival fibroblasts and human osteoblasts (hFOB 1.19) on five RBC materials with and without surface modifications (alumina blasting with 50- or 110-μm Al₂O₃). In addition, high-performance liquid chromatography (HPLC) was used to determine release of resin monomers from RBCs after 1 h, 1 day, and 7 days. As compared with tissue culture plastics (the control), cellular adhesion was significantly lower (P < 0.001) for human gingival fibroblasts and osteoblasts. Only minor, nonsignificant differences between individual RBCs were identified. HPLC analyses identified the release of three bifunctional methacrylates bisphenol A glycerolate dimethacrylate, triethylene glycol dimethacrylate, and diurethane dimethacrylate from RBCs and showed that monomer release increased between 1 h and 1 day but remained low. The present findings suggest that surface adhesion in the subgingival area is limited for the tested RBCs. Although residual monomer release was low for all tested RBCs, it might be sufficient to adversely affect cell adhesion.

Cervical margin relocation in indirect adhesive restorations: A literature review

PURPOSE

The aim of this review was to summarize the existing scientific literature investigating on cervical margin relocation technique (CMR) performed prior to the adhesive cementation of the indirect restorations.

STUDY SELECTION

An electronic search with no date restriction was conducted in the MEDLINE database, accessed through PubMed. The following main keywords were used: "cervical margin relocation", "coronal margin relocation", "deep margin elevation" and "proximal box elevation".

RESULTS

Seven in vitro studies and 5 clinical reports investigating on CMR are taken into consideration for the present review. The most frequently investigated parameter in almost all of the in vitro studies was the marginal adaptation of the indirect restorations. One study additionally assessed the influence of CMR on the fracture behavior of the restored teeth and one study assessed the bond strength of the indirect composite restoration to the proximal box floor. Clinical reports provided documentation with a detailed description of the treatment protocol. In the current literature no randomized controlled clinical trials or prospective or retrospective clinical studies on CMR technique could be found.

CONCLUSIONS

On the basis of the reviewed literature, it can be concluded that currently there is no strong scientific evidence that could either support or discourage the use of CMR technique prior to restoration of deep subgingival defects with indirect adhesive restorations. Randomized controlled clinical trials are necessary to provide the reliable evidence on the influence of CMR technique on the clinical performance, especially on the longevity of the restorations and the periodontal health.

Influence of proximal box elevation technique on marginal integrity of adhesively luted Cerec inlays

OBJECTIVES

This in vitro study evaluated the marginal quality of Lava Ultimate inlays in deep proximal cavities with and without proximal box elevation (PBE) before and after thermomechanical loading (TML).

MATERIALS AND METHODS

Mesio-occluso-distal cavities with proximal boxes beneath the cementoenamel junction (CEJ) were prepared in 24 human molars. Then, one of the proximal boxes was elevated with Filtek Supreme above the CEJ. The specimens were divided into three groups (n = 8). The inlays of group A were adhesively luted to the cavities with Scotchbond Universal and Rely X Ultimate, the inlays of group B with Monobond Plus, Syntac, and Variolink II, and the inlays of group C with Clearfil Ceramic Primer and Panavia SA Cement. Epoxy resin replicas were taken before and after thermomechanical loading (1,200,000 cycles, 55 °C/5 °C, max. load 50 N). Marginal integrity at the different interfaces tooth/PBE, tooth/dentine, inlay/PBE, inlay/dentine was evaluated with scanning electron microscopy (×200). The percentage of continuous margin (% of total proximal margin length) was compared between the groups before and after TML.

STATISTICS

Mann-Whitney U test (p = 0.05).

RESULTS

No significant differences (p > 0.05) before and after TML were found between the three groups for bonding the inlay to dentine or to PBE composite.

CONCLUSIONS

The marginal integrities of bonding inlays directly to dentine are not different from bonding inlays to a proximal box, which has been elevated by a composite filling material. For deep proximal cavities, the PBE technique could be an alternative technique to conventional methods. Clinical research is needed to confirm.

Influence of proximal box elevation on bond strength of composite inlays

OBJECTIVES

The objective of the present study was to evaluate the influence of proximal box elevation on microtensile bond strength (mTBS) of composite inlays to the proximal box floor, using either a total-etch or a self-adhesive resin cement.

MATERIALS AND METHODS

Twenty-five human molars were selected, and a class II OM (inlay) cavity preparation was performed in each tooth. Cavities were randomly assigned into four experimental groups, according to the location of the proximal cervical margin (located 1 mm below cementoenamel junction (CEJ), or with proximal box elevation with composite resin) and the resin cement used for luting (a total-etch resin cement RelyX ARC or a self-adhesive resin cement G-Cem). After 1-week water storage, samples were subjected to mTBS test. Results were analyzed by Kruskal-Wallis and Mann-Whitney U tests (p < 0.05).

RESULTS

Kruskal-Wallis revealed statistically significant differences among experimental groups (p = 0.007). Both resin cements showed similar bond strength values when cervical margin was located below CEJ. The proximal box elevation improved the bond strength of composite inlays for both resin cements. However, only for G-Cem was this improvement statistically significant.

CONCLUSIONS

The proximal box elevation improved the bond strength attained by G-Cem resin cement. For RelyX ARC, the position of the cervical margin did not affect composite inlays bond strength.

CLINICAL RELEVANCE

Proximal box elevation does not decline bond strength of composite inlays to the proximal floor when a total-etch or a self-adhesive resin cement is used.

Influence of proximal box elevation on the marginal quality and fracture behavior of root-filled molars restored with CAD/CAM ceramic or composite onlays

OBJECTIVES

This study investigated the influence of proximal box elevation (PBE) with composite resin when applied to deep proximal defects in root-filled molars with mesio-occluso-distal (MOD) cavities, which were subsequently restored with computer-aided designed/computer-aided manufacturing (CAD/CAM) ceramic or composite restorations.

MATERIALS AND METHOD

Root canal treatment was performed on 48 human mandibular molars. Standardized MOD cavities were prepared with the distal box located 2 mm below the cemento-enamel junction (CEJ). The teeth were randomly assigned to one of four experimental groups (n = 12). In groups G1 and G2, the distal proximal box was elevated up to the level of the CEJ with composite resin (PBE). No elevation was performed in the remaining two groups (G3, G4). CAD/CAM restorations were fabricated with feldspathic ceramic (Vita Mark II, CER) in groups G1 (PBE-CER) and G3 (CER) or with resin nano-ceramic blocks (Lava Ultimate, LAV) in groups G2 (PBE-LAV) and G4 (LAV). Replicas were taken before and after thermomechanical loading (TML; 1.2 Mio cycles; 49 N; 3,000 thermocycles between 50 °C and 5 °C). Following TML, load was applied until failure. Fracture analysis was performed under a stereomicroscope (×16). Marginal quality before and after TML (tooth restoration, composite restoration) was evaluated using scanning electron microscopy (×200).

RESULTS

After TML, lower percentages of continuous margins were observed in groups G1-G3 compared with pre-TML assessments; however, the differences were not statistically significant. For group G4-LAV, the marginal quality after TML was significantly better than in any other group. The highest mean fracture value was recorded for group G4. No significant difference was found for this value between the groups with PBE compared with the groups without PBE, regardless of the material used. The specimens restored with ceramic onlays exhibited fractures that were mainly restricted to the restoration while, in teeth restored with composite onlays, the percentage of catastrophic failures (fractures beyond bone level) was increased.

CONCLUSION

PBE had no impact on either the marginal integrity or the fracture behavior of root canal-treated mandibular molars restored with feldspathic ceramic onlays. CAD/CAM-fabricated composite onlays were more favorable than ceramic onlays in terms of both marginal quality and fracture resistance, particularly in specimens without PBE.

CLINICAL RELEVANCE

Composite onlays with or without PBE may be a viable approach for the restoration of root-filled molars with subgingival MOD cavities.