Open Sandwich Technique Research Articles

Long term clinical performance of 'open sandwich' and 'total-etch' Class II composite resin restorations showing proximal deterioration of glass-ionomer cement.

To compare clinical performance of resin composite posterior Class-II restorations placed with etch-and-rinse adhesive or open sandwich technique using glass-ionomer cement. Data on Class II restorations placed by one dentist between 1990 and 2016 were collected from patient files, including caries risk, tooth related variables, applied materials and dates of last check-up visit and restoration placement. Open sandwich restorations were placed before 2001, while after 2001, a total-etch technique using etch-and-rinse 3-step adhesive was used when placing a Class II composite restoration. For statistical analysis, Kaplan-Meier statistics and a multilevel Cox-Regression was conducted (p<0.05). Annual Failures Rates (AFR) were calculated. 675 Class II restorations were placed in 91 patients, 491 total-etch restorations (observation time 2-18y), and 184 open sandwich restorations (observation time 19-29y) showing AFRs at 15 years as 2.9% for total-etch and 9.7% for open sandwich restorations. Secondary caries as failure was equally distributed among the 2 groups and 27% of the failures in the open sandwich group were due to proximal deterioration of glass-ionomer cement. The Cox-regression showed a significant higher risk for failure for the open sandwich technique compared to total-etch class-II composite restorations (HR=2.9; p<0.001). Application of glass-ionomer cement using the open sandwich technique cannot be recommended for class-II restorations as being more complex and showing poorer clinical performance.

Effect of RMGI Roughness and Dentin Bonding Primer on Shear Bond Strength of Sandwich-type Restorations.

The open sandwich technique is a reliable alternative to amalgam placement in deep proximal box preparations, where proper isolation and enamel bonding may not be possible. It is often difficult to prepare the box for composite placement without affecting the resin-modified glass ionomer (RMGI) that has been placed in the gingival portion. We hypothesized that RMGI surfaces that are roughened or those that use all steps in the manufacturing bonding protocol, including the priming solution, applied before placing a bonded composite increment, would have greater composite/RMGI shear bond strength. Shear bond strengths (SBS) of RMGI tested in the presence and absence of SiC roughening and primer-coating were tested using a fourth-generation dentin bonding agent to composite after thermocycling. Twenty specimens for four test conditions were fabricated and investigated. Data were subjected to a two-way ANOVA and the Holm-Sidak post-hoc test. Placing dentin primer on unabraded RMGI provided a statistically significant improvement in SBS, but only modestly. Furthermore, because bond failure consistently occurred within the RMGI itself, none of the surface modifications have a clinically relevant impact on SBS at the RMGI to the composite interface. Clinicians should be aware that they need not avoid RMGI abrasion and do not need to incorporate all components of a fourth-generation bonding system when covering an RMGI sandwich layer with composite.

Evaluation of the Outcome of Modified Open Sandwich Technique and Conventional Composite Resin Restoration: For Managing Class II Cavity of Primary Molars Among 4- 8 years Old Children

Background: Dental caries is the most prevalent disease in humans, especially during early childhood. The restoration of such an extensive carious lesion should be done properly to reestablish their anatomy and hence their masticatory, phonetic, esthetic, and space-maintainer functions in the dental arches. Composite resins are the most commonly used tooth-colored restorative material, but many difficulties occur particularly when used directly in posterior restorations. The objective of the study was to compare the clinical effectiveness of the Modified Open Sandwich Technique and Conventional Composite Resin Restoration for managing class II caries on primary molars. Material &amp; Methods: This was a randomized control trial and was conducted in the Department of Pedodontics, Faculty of Dentistry, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka, Bangladesh during the period from October, 2021 to September, 2022. In our study we included 68 patients with proximal dental caries of primary molars with reversible pulpitis. The patients were divided by using random sampling technique into two groups – Group A (The modified open sandwich technique, n=34) and Group B (The conventional composite resin restoration, n=34). Results: In total 68 patients from both the groups completed the study. In our study we found mean±SD of age was 5.37±1.24 years. 76.5% of cases of the modified open sandwich technique restorations were &amp; 82.4% of the conventional composite resin restoration were &lt; 6 years. Mandibular primary molars were 64.7% and 53% for the modified open sandwich technique and conventional composite resin restoration respectively. Conventional composite resin restorations showed 32.4% postoperative sensitivity and the modified open sandwich technique restorations showed 11.8%. After 12 months of follow-up, no secondary caries developed. Good marginal adaptation in 100% of cases were found in the modified open sandwich technique and 88.2% for conventional composite restorations. Conclusion: In our study we found that postoperative sensitivity developed more in conventional composite restorations in comparison to the modified open sandwich technique. Initially marginal adaptation showed better in the modified open sandwich method technique. So, conventional and modified open sandwich composite resin techniques were acceptable for primary molar teeth considering secondary caries and marginal adaptation.

Comparative Evaluation of Microleakage in Class II Restorations Using Open- and Closed-Sandwich Techniques With Zirconomer as an Intermediate Material: An In-Vitro Study.

Aim To evaluate and compare the microleakage In class II restorations using open- and closed-sandwich techniques with zirconomer as an intermediate material. Material and method Twenty-six non-carious mandibular first molars were selected and randomly divided into two groups (groups 1 and 2 where n=13). A standardized Class II preparation was made with the cervical margin 1 mm below the cementum-enamel junction. Samples of group 1 were restored using the open-sandwich technique and samples of group 2 with the close-sandwich technique, and zirconomer was used as an intermediate restorative material. Following that, the restorations underwent 200 heat cycles with dwell times of 20 seconds at 5°C and 55°C. Dye penetration and scanning electron microscope (SEM) analysis using the replica approach were used to assess adaptation at the cervical margin.The data were statistically analyzed using the Paired T-test(p<0.05). Results Lower dye penetration was seen in the open-sandwich technique compared to the closed-sandwich technique (p<0.001). Conclusion When comparing the open-sandwich technique with the closed one, it was observed that less microleakage was seen in the open-sandwich technique as it has better marginal adaptation and fewer voids.

Comparison of Marginal Compliance and Microleakage of CL V Restorations in Deciduous Anterior Teeth Using Two Different RMGI Liners

Introduction: Microleakage has always been a problem in restorative dentistry. To decrease microleakage, different restorative techniques and materials have been recommended. The purpose of this study was to evaluate micro leakage of the composite restoration in deciduous anterior teeth using the open sandwich technique by two different liners.&#x0D; Materials &amp; Methods: This cross-sectional experimental study was conducted at Khorasgan University in 2019. A total of sixty intact deciduous canine teeth were divided into 3 groups of 20. At the buccal surface of the specimens, the Class V cavity was extracted at 1 mm below the CEJ (Cementoenamel junction) and in groups 1 and 2, ionoseal liner and Fuji II ionomer glass were placed at the buccal floor. Cavities were restored with Z250 composite resin. In group 3 which served as the control, restorations was perfromed without liners. All samples are prepared for establishment after dying in methylene blue 0.5% solution. The buccal lingual incisions with a thickness of 1 mm were inspected under stereo microscope for micro leakage. A total of 5 samples were extracted from each group via random sampling to examine the marginal compliance under SEM (Scanning electron microscope). The intergroup comparisons were made using the chi-square and Kruskal-Wallis tests. Besides, intra-group comparisons were performed using the Mann-Whitney U test. All statistical procedures were performed at a significance level of less than 0.05 (p value &lt; 0.05) using Gpower software.&#x0D; Results: The outcome of this study showed that microleakage of gingival margin in open sandwich techniques with ionoseal and Fuji II (group 1, 2) was significantly higher than in control group (p value = 0.033).but in comparison between group 1,2 there was no significant difference (p value = 0.795). In SEM evaluation there was no significant difference in gingival microleakage (p value = 0.232).&#x0D; Conclusion: Use of two liners: Ionoseal and Fuji II in Class V cavities restored by opensandwich technique in deciduce anterior teeth can reduce gingival microleakage.

Evaluation of Marginal Microleakage in Class II Composite Restorations Using Open Sandwich and Snowplow Techniques

Introduction: Adaptation of posterior composites to dental walls has been questioned for various reasons and polymerization shrinkage is one example. Thus, the present study investigated microleakage ocurring from different class II composite restorations techniques.&#x0D; Materials and Methods: In this in-vitro study class II cavities with cervical margins 1 mm below the CEJ (Cementoenamel junction) were prepared in 64 extracted human premolars. The teeth were randomly divided into two groups. Group 1 (open sandwich): Glass ionomer was injected on the floor of the cavity and the rest of the cavity was restored using composite resin using incremental technique. Group 2 (Snowplow) one layer of flowable composite was placed in the bottom of the cavity and was co-cured with the first layer of composite resin. The rest of the cavity was restored the same as group 1. To evaluate the microleakage, the specimens were thermocycled for up to 3000 cycles and immersed in 1% methylene blue solution for 72 hours. Then they were sectioned mesiodistally and evaluated under a stereomicroscope. Data were analyzed via Mann-Whitney and Fishers exact test and p value &lt; 0.05 was considered significant.&#x0D; Results: The mean value for microleakage in group 1 (795.74 ± 494.04 mμ) was lower than group 2 (972.99 ± 457.8 mμ), but the results were not statistically significant (p value = 0.117).&#x0D; Conclusion: It appears that microleakage in both open sandwich technique and Snowplow technique did not portray statistical significance, so both of them can be used.

In vitro marginal and internal adaptation of four different base materials used to elevate proximal dentin gingival margins.

BackgroundThere is still debate about the most appropriate restorative material category to relocate the proximal deep cervical margins, thus, this study aimed to compare the marginal and internal adaptation of four base materials used for deep margin elevation, and to evaluate each base material/overlying composite interface. Material and MethodsFifty six molars received class II cavities with dentin/cementum gingival margins. They were divided into four groups and their gingival margins were elevated using either; resin modified glass ionomer (RMGI), highly viscous conventional glass ionomer (HV-GIC), flowable bulk fill resin composite (Bulk Flow) and bioactive ionic resin (Activa). The rest of the cavities were completed with the same overlying composite. Half of each group was either; kept in sterile water for 1 week, or subjected to 18 months water storage and 15,000 thermal cycles. Base materials/gingival dentin interfaces were examined under a scanning electron microscope at different magnifications, and percentage of continuous margin (% CM) and maximum gap width (MGW) were analyzed, in addition to base materials/overlying composite interfaces evaluations. % CM values were statistically analyzed using Two-way analysis of variance, Tukey post hoc tests (at p<0.05) and Pearson’s correlation while MGW values were analyzed using Kruskal–Wallis, Mann–Whitney U tests and Spearmen correlation ResultsBoth Bulk Flow and Activa had better marginal integrity than RMGI and HV-GIC. All base materials were adversely affected by aging. All base materials/overlying composite interfaces were continuous and age defying. ConclusionsIn terms of marginal integrity, Bulk Flow and Activa might be preferable for proximal dentin margin elevation under direct restoration compared to the other tested base materials. Key words:Deep proximal margin, interface analysis, marginal quality, open sandwich technique.

Deep proximal margin rebuilding with direct esthetic restorations: a systematic review of marginal adaptation and bond strength.

This review aimed to characterize the effect of direct restorative material types and adhesive protocols on marginal adaptation and the bond strength of the interface between the material and the proximal dentin/cementum. An electronic search of 3 databases (the National Library of Medicine [MEDLINE/PubMed], Scopus, and ScienceDirect) was conducted. Studies were included if they evaluated marginal adaptation or bond strength tests for proximal restorations under the cementoenamel junction. Only 16 studies met the inclusion criteria and were included in this review. These studies presented a high degree of heterogeneity in terms of the materials used and the methodologies and evaluation criteria of each test; therefore, only a descriptive analysis could be conducted. The included studies were individually evaluated for the risk of bias following predetermined criteria. To summarize the results of the included studies, the type of restorative material affected the test results, whereas the use of different adhesive protocols had an insignificant effect on the results. It could be concluded that various categories of resin-based composites could be a suitable choice for clinicians to elevate proximal dentin/cementum margins, rather than the open sandwich technique with resin-modified glass ionomers. Despite challenges in bonding to proximal dentin/cementum margins, different adhesive protocols provided comparable outcomes.

Comparing the Ability of Various Resin-Based Composites and Techniques to Seal Margins in Class-II Cavities.

Background: Resin-based composites (RBCs) provide excellent esthetics but the marginal micro-leakage in the proximal cavities remains a major concern. The aim of the present study was to assess the ability of various dental RBCs and techniques utilized for sealing deep dentin margin in class-II cavities. Methods: Box-cavities (class-II) on the distal and mesial surfaces of extracted (premolar) teeth were prepared with a gingival margin placed 1mm apical to the cemento-enamel junction. Teeth with prepared class II cavities were randomly divided into four study groups according to the type of restorative materials (conventional RBC; bulk-fill RBC; conventional RBC lined with flowable RBC and conventional RBC lined with resin-modified glass-ionomer-cement (GIC) as open sandwich-technique). Each group was further subdivided into a total-etch subgroup in which a separate etching step was performed before applying the bonding agent and a self-etch subgroup in which a self-etch adhesive system was used (n = 10). For each group, cavities were restored using the respective restorative materials and techniques, subjected to 1000 thermocycles, and placed in the methylene-blue dye. The specimen teeth were sectioned for further microscopic examination for micro-leakage. Results: The least dye penetration values were reported for group 4 (GIC) followed by the group Bulk-fill using the self-etch adhesive system (group 2b). The highest dye penetration was reported for the group Bulk-fill using the total-etch adhesive system (2a), followed by the group conventional RBC using the total-etch adhesive system). The total-etch adhesive system had significantly greater micro-leakage compared to the self-etch adhesive system (1a) (p = 0.026). Conclusions: The self-etch adhesive system significantly reduced the micro-leakage compared to the total-etch system. Bulk-fill RBC when bonded with the self-etch adhesive provided good marginal sealing ability comparable to open sandwich-technique using GIC.

Effects of Resin-modified Glass Ionomer Cement and Flowable Bulk-fill Base on the Fracture Resistance of Class II Restorations: An Original Laboratory Experimental Study

The purpose of this study was to investigate the fracture resistance of marginal ridges restored using different techniques (amalgam, open sandwich technique, and incremental placement) and to compare these with smart dentin replacement (SDR) bulk-fill. Amalgam, dispersalloy; a nanohybrid resin composite (Tetric N Ceram), a resin-modified glass ionomer cement (RMGIC) base (Fuji II LC), and flowable bulk-fill composites (SureFil SDR) were used. Standardized class II (occluso-distal) OD cavities were prepared on 60 (n = 12) extracted premolars, and five different protocols were used to restore the teeth: group 1, dispersalloy; group 2, dispersalloy with 4 mm Fuji II LC base; group 3, incrementally placed Tetric N Ceram; group 4, Tetric N Ceram with 4 mm Fuji II LC base; and group 5, Tetric N Ceram with SureFil SDR. The restorations were thermocycled then fractured using a universal testing machine, the maximum fracture load of the specimens was measured (N), and the type of fracture was recorded. Statistical analysis was carried out using one-way analysis of variance. Amalgam groups showed the lowest fracture resistance, with no significant difference between the based and nonbased groups. The highest fracture resistance was displayed by Tetric N Ceram with SDR base, and it was significantly higher than all the groups except the Tetric N Ceram nonbased group. The RMGIC based Tetric N Ceram displayed intermediate fracture resistance. The majority of the restorations showed mixed types of fracture except for nonbased amalgam, which mostly failed cohesively through amalgam. SDR-based composite was the only group that showed severe tooth failures. The use of a 4 mm thick RMGIC base had no detrimental effect on the fracture resistance of class II amalgam and composite restorations. Bulk-fill SureFil SDR placed under a conventional resin-based composite had similar fracture resistance to incrementally placed composite but higher than amalgam and composite restorations based on RMGIC.

Evaluation of microleakage in Class II composite restorations: Bonded-base and bulk-fill techniques

This study compared microleakage of Class II cavities restored using bonded-base and bulk-fill techniques with different bases. In this in vitro study, in 60 extracted human molars, standardized (4 mm × 2 mm × 8 mm) Class II cavities were prepared, such that the gingival floor was located 1 mm below the CEJ. The teeth were randomly divided into five groups and filled with: (1) Fuji II LC + x-tra fil, (2) Ionoseal + x-tra fil, (3) x-tra base + x-tra fil, (4) Grandio Flow + x-tra fil, and (5) x-tra fil only [control group]; in open-sandwich technique, the base thickness was 1 mm. The bases were coated all gingival floor. Except for the first group, where dentin conditioner was used, the Clearfil SE bond was applied before application of the bases and restorative materials as a bonding agent. After 500 thermocycles between 5°C and 55°C, the specimens were immersed in 0.5% basic fuchsine solution for 24 h. The restored teeth were sectioned, and the dye penetration in gingival floor was observed by a stereomicroscope at ×32. The data were analyzed using Kruskal-Wallis and Mann-Whitney tests in SPSS software. The significance was determined at 0.05 confidence interval. The statistical analysis revealed a significant difference in microleakage among the study groups (P < 0.001). The Ionoseal group followed by the control group (x-tra fil composite) had the greatest microleakage. Except for the Ionoseal group, all other groups had significantly less microleakage than the control group. The use of bonded-base techniques could reduce microleakage, including those in bulk-fill composite restorations.

Cervical Microleakage in Giomer Restorations: An In Vitro Study

The purpose of this in vitro study was to determine the effect of different composite placement techniques on gingival microleakage of giomer restorations. Sixty class II preparations were created in 30 extracted molar teeth with cervical margins 1 mm below the cementoenamel junction. The teeth were divided into three groups of 10 teeth each. In group I, teeth were restored with open sandwich technique using Beautifil II and Beautifil II Flow. In group II, teeth were restored with snowplow technique using Beautifil II and Beautifil Flow. In group III, teeth were restored with oblique increment technique using Beautifil II. After thermocycling and immersion in 2% methylene blue, the teeth were sectioned and dye penetration was evaluated. Statistically significant reduction in microleakage was found along the gingival walls in snowplow restorations compared to sandwich restoration and oblique increment restorations. Microleakage was reduced along the gingival walls in snowplow restorations. Microleakage was significantly lower in the snowplow restorations.

Evaluation of Dental Composite Resin Interface and Adhesion Using Laser Scanning Confocal Microscopy

The aim of the study was to evaluate and to compare the interface and marginal leakage of dental composite resins using confocal laser scanning biological microscopy (CM). Ten class II cavities were prepared on the proximal surfaces of 10 extracted teeth, previously kept in 10% formalin to preserve the bonding properties of the tooth structures. Cavities were restored with dental composite resin using the �open sandwich� technique and then assessed using CM. Open marginal adaptations at the interfaces inside the composite resins were identified. The results obtained with CM helped to eliminate and reduce the background information collected from a distance from the focal plane and allowed for the acquisition of serial optical sections from thick tooth specimens. In vitro assessments were thus made using CM on the teeth structure, regarding the occurrence of potential micro-leakages at the restoration interface.

Studies on Adhesion of Composite Resins and Glass-Ionomer Cements in Open-Sandwich Technique

The aim of this study was to assess the quality of the interface between dental root cement and some restorative materials used in the open sandwich technique. Standardised cavities were prepared on the buccal and oral surfaces of 30 human molars with the gingival margin situated in root cement. The teeth were randomly divided in 3 groups. Different materials combinations were used in buccal and oral cavities. In the control group, the cavities were filled only with composite resins (Filtek Z250-3M ESPE and Zmack Comp-Zermack). In the test groups the cavities were restored using an open sandwich technique as follows: in group 1 Filtek Z250 in combination with Dyract, respectively Ketac Molar Easymix; in group 2 Zmack Comp in combination with Dyract, respectively Ketac Molar. The teeth were stored in 1% methylene blue solution, for 24 hours. The samples were longitudinally sectioned through the centre of restorations and the degree of dye penetration as well as the morphology of the interface between the root cement and the restorative material were evaluated by optical microscopy and SEM. The results showed less microleakage and and adhesive failures in open sandwich restorations with Zmack Comp and Dyract combination.

Three-year clinical evaluation of class II posterior composite restorations placed with different techniques and flowable composite linings in endodontically treated teeth.

The objective of this study is to evaluate the clinical performance of direct resin composite restorations placed with different techniques (incremental or bulk) and different flowable linings (conventional or bulk-fill) in endodontically treated teeth. Forty-seven pair class II (mesio-occlusal or disto-occlusal) composite restorations were placed in 37 patients. In all cavities, Adper Single Bond 2 was used. In one of the cavities of each pair, a conventional flowable composite, Aelite Flo, was applied in approximately 2mm thick, and the remaining cavity was restored incrementally with GrandioSO. In the second cavity, a bulk-fill flowable composite, x-tra base, was applied in approximately 4mm thick in bulk increments and the remaining 2-mm occlusal part of the cavity was restored with GrandioSO. All cavities were restored with open-sandwich technique by the same operator. At baseline and after 6-month, 1-, 2-, and 3-year follow-up visits, restorations were evaluated by modified USPHS criteria. At 3-year recall, 33 restorations with Aelite Flo lining and 33 with x-tra base lining were available. Two restorations from each group (6.0%) were scored as Bravo in terms of surface texture. One restoration's color match from x-tra base group scored as Bravo (3.0%). All other evaluated criteria were scored as Alfa (100%) for all restorations. No statistically significant difference between the two groups was found in all evaluated criteria during 3-year period (p>0.05). Bulk-filling technique showed clinically acceptable performance comparable to the incremental technique. Restorations placed with bulk-filling technique with x-tra base lining and incremental technique with a conventional flowable lining showed highly clinical performance over 3-year period.

Microleakage in Sub-Gingival Class II Preparations Restored Using Two Different Liners for Open Sandwich Technique Supplemented With or Without Ultrasonic Agitation: An In Vitro Study.

Probability of bond failure at sub-gingival cavosurface margin is high in class II cavity designs especially when margins are located in cementum or dentin. Previous researches have proved ultrasonics to be a beneficial tool in improving the marginal adaptation of the restorative material. Therefore, the effect of ultrasonic activation of the lining material at the gingival cavosurface margin was tested in the present research. The study aimed to evaluate the cervical micro-leakage in class II preparations with gingival margin located below cemento enamel junction and restored using open sandwich technique using two different liners and supplemented with or without ultrasonic agitation. Forty recently extracted human molars were collected, disinfected and stored in 0.9% saline solution. Standar dized class II cavities were prepared with gingival margin located 1mm below the cemento-enamel junction. Teeth were randomly divided into four groups (n=10) and restored using open sandwich technique as follows - Group A: Resin Modified Glass Ionomer Cement as liner and Beautifil II as coronal restoration; Group B: Same as group A supplemented with ultrasonic agitation; Group C: Beautifil Flow Plus as liner and Beautifil II as coronal restoration; Group D: Same as Group C supplemented with ultrasonic agitation. Prepared samples were subjected to thermo cycling, followed by immersing in 0.5% methylene blue dye solution. After 24 hours they were cleaned and sectioned in mesio-distal direction using diamond disc and evaluated for microleakage. Obtained scores were statistically analysed using one way ANOVA test and Post Hoc test. Group B showed least microleakage amongst all groups but the results were statistically insignificant (p value > 0.05). Marginal adaptation of liner with ultrasonic activation was somewhat better however, the results were statistically insignificant.

Cervical Interfacial Bonding Effectiveness of Class II Bulk Versus Incremental Fill Resin Composite Restorations.

Cervical interfacial bonding quality has been a matter of deep concern. The purpose of this study was to analyze microtensile bond strength (MTBS) and cervical interfacial gap distance (IGD) of bulk-fill vs incremental-fill Class II composite restorations. Box-only Class II cavities were prepared in 91 maxillary premolars (n = 7) with gingival margin placement 1 mm above the cementoenamel junction at one side and 1 mm below it on the other side. Eighty-four maxillary premolars were divided into self-etch and total-etch groups and further subdivided into six restorative material subgroups used incrementally and with an open-sandwich technique: group 1, Tetric Ceram HB (TC) as a control; group 2, Tetric EvoFlow (EF); group 3, SDR Smart Dentin Replacement (SDR); group 4, SonicFill (SF); group 5, Tetric N-Ceram Bulk Fill (TN); and group 6, Tetric EvoCeram Bulk Fill (TE). Groups 2-6 were bulk-fill restoratives. Tetric N-Bond Self-Etch (se) and Tetric N-Bond total-etch (te) adhesive were used in subgroups 1-5, whereas AdheSE (se) and ExciTE F (te) were used in subgroup 6. In an additional group, Filtek P90 Low Shrink Restorative (P90) was used only with its corresponding self-etch bond. The materials were manipulated, light-cured (1600 mW/cm(2)), artificially aged (thermal and occlusal load-cycling), and sectioned. Two microrods/restoration (n = 14/group) were tested for MTBS at a crosshead-speed of 0.5 mm/min (Instron testing machine). Fracture loads were recorded (Newtons), and MTSBs were calculated (Megapascals). Means were statistically analyzed by the Kruskal-Wallis test, Conover-Inman post hoc analysis for MTBS (multiple comparisons), and Mann-Whitney U test for IGD. The ends of the fractures were examined for failure mode. One microrod/restoration (n = 7/group) was investigated by scanning electron microscopy (×1200) for IGD. MTBS values for SF/te, P90 in enamel, and TC+SDR/te in enamel and cementum were significantly higher compared with those for the control TC/te and TC/se in cementum. Most of the failures were mixed. IGDs were generally smaller at enamel margins, and the smallest IGDs were found in P90 at both enamel and cementum margins. Bulk-fill and silorane-based composites might provide better cervical interfacial quality than incremental-fill restorations.

Microleakage in Class V Cavities Restored with Sandwich Technique: Self- Etch versus Total-Etch Bonding Systems

Objective: Microleakage has always been a problem in restorative dentistry. To decrease microleakage, modern bonding systems, different application methods and sandwich technique have been recommended. The purpose of this study was to assess the microleakage in class V cavities restored with open sandwich technique using self-etch and total-etch bonding systems. Methods: In this in vitro study, class V cavities were prepared on the buccal and lingual surfaces of 20 extracted sound human third molars and restored with sandwich technique. Fuji II LC glass ionomer (GI) was applied to the cavity floor. After curing, half the cavities received Single Bond and the other half, Clearfil SE Bond application and were all restored with Z250 composite resin. Specimens were immersed in 2% fuchsin solution for 24 hours. After copious water irrigation, specimens were sectioned and evaluated under a stereomicroscope to determine microleakage. Data were analyzed using the Mann-Whitney U test (p<0.05). Results: The microleakage at the GI-composite interface was less than that at the occlusal and gingival margins; but this difference was not significant. No significant difference was found in microleakage between the two bonding agents in neither of the two layers. Conclusion: The etch & rinse and self-etch systems are similar in terms of microleakage.

Marginal Adaptation Evaluation of Biodentine and MTA Plus in "Open Sandwich" Class II Restorations.

This study aimed at evaluation of two different commercially available calcium silicate materials (Biodentine and mineral trioxide aggregate [MTA] Plus) used as dentin substitute. Sixty Class II cavities were prepared in extracted mandibular third molars, with margins extending 1 mm below the cementum-enamel junction. The samples were divided into three groups on the basis of dentin substitute used: resin modified glass ionomer cement, Biodentine, and MTA Plus. Cavities were restored with composite resins in an "open sandwich" technique. The samples were subjected to alternate aging in phosphate buffered saline and cyclic loading. Marginal adaptation was evaluated in terms of "continuous margin" at the gingival margin, using a low vacuum scanning electron microscope. Statistical analysis was done with two-way analysis of variance with Holm-Sidak's correction for multiple comparisons. The glass ionomer group and Biodentine group presented an overall 83% and 91% of continuous margins, with no difference between them. MTA Plus showed least values of continuous margins. Granular deposits were seen over the surface of Biodentine and MTA Plus. Biodentine and resin-modified glass ionomer cement, when used as a dentin substitute under composite restorations in open sandwich technique, gave satisfactory marginal adaptation values. Contemporary calcium silicate materials can be used as dentin substitute materials in "open sandwich" Class II restorations. This study evaluates the marginal adaptation of Biodentine, MTA Plus, and resin modified glass ionomer cement used as dentin substitutes and reports better adaptation obtained with Biodentine and glass ionomer cement.

Adhesion of resin-modified glass-ionomer cements may affect the integrity of tooth structure in the open sandwich technique

ObjectiveTo study the interfaces between model cavities prepared in teeth and four glass ionomer cements (two conventional and two resin-modified). MethodsTen non-cavitated molars and premolars were used and, in each, two 3mm deep slot preparations were created on opposing sides of the tooth. The teeth were conditioned as appropriate, then restored using the open sandwich technique, using a conventional glass ionomer (Fuji IX, Ketac Molar) or resin modified glass ionomer (Fuji II LC or N100), followed by completion with composite resin. The teeth were then embedded in a transparent acrylic resin and cut parallel to the long axis through both restorations, using a low speed diamond wheel saw. Samples were evaluated using a metallographic light microscope (100×). Three areas were assessed: the axial wall, the axial gingival line angle and the cavo-surface line angle. Bonding was categorized as inadequate or adequate based on the appearance and inadequate bonding was further studied and classified. Data were analysed statistically using the McNamara analysis. ResultsThe majority of materials failed to make adequate contact with the axial wall, and there were also flaws at the axial/gingival line angle in several samples. By contrast, the cavo-surface line angle was generally soundly filled and the materials showed intimate contact with the tooth surface in this region. The most serious inadequacy, though, was not lack of intimate contact and/or adhesive bond, but the presence of perpendicular cracks in 30% of the Fuji II LC samples which extended into the underlying dentin. SignificanceThe problems of placement and dentin cracking experienced with these materials demonstrate that adhesive bond strength alone cannot be used as the criterion of success for restorative materials. In fact good adhesion can, in certain cases, promote cracking of the dentin due to stresses within the material, an outcome which is undesirable.