Open Sandwich Technique Research Articles

Comparative evaluation of microleakage in Class II restorations using open vs. closed centripetal build-up techniques with different lining materials.

Background:Evaluation of microleakage is important for assessing the success of new restorative materials and methods.Aim and Objectives:Comparative evaluation of microleakage in Class II restorations using open vs. closed centripetal build-up techniques with different lining materials.Materials and Methods:Standardized mesi-occlusal (MO) and distoocclusal (DO) Class II tooth preparations were preparedon 53 molars and samples were randomly divided into six experimental groups and one control group for restorations. Group 1: Open-Sandwich technique (OST) with flowable composite at the gingival seat. Group 2: OST with resin-modified glass ionomer cement (RMGIC) at the gingival seat. Group 3: Closed-Sandwich technique (CST) with flowable composite at the pulpal floor and axial wall. Group 4: CST with RMGIC at the pulpal floor and axial wall. Group 5: OST with flowable composite at the pulpal floor, axial wall, and gingival seat. Group 6: OST with RMGIC at the pulpal floor, axial wall, and gingival seat. Group 7: Control — no lining material, centripetal technique only. After restorations and thermocycling, apices were sealed and samples were immersed in 0.5% basic fuchsin dye. Sectioning was followed by stereomicroscopic evaluation.Results:Results were analyzed using Post Hoc Bonferroni test (statistics is not a form of tabulation). Cervical scores of control were more than the exprimental groups (P < 0.05). Less microleakage was observed in CST than OST in all experimental groups (P < 0.05). However, insignificant differences were observed among occlusal scores of different groups (P > 0.05).Conclusion:Class II composite restorations with centripetal build-up alone or when placed with CST reduces the cervical microleakage when compared to OST.

Microleakage of Nanofilled Resin-modified Glass-ionomer/Silorane- or Methacrylate-based Composite Sandwich Class II Restoration: Effect of Simultaneous Bonding

Microleakage of composite restorations at the cervical margin placed apically to the cementoenamel junction (CEJ) is still a concern. This study evaluated the effect of simultaneous bonding application on cervical sealing of nano-ionomer/silorane- or methacrylate-based composite open sandwich Class II restorations in the modified technique compared with that of conventional bonding. In 60 sound maxillary premolars, two standardized Class II cavities were prepared with cervical margins 1 mm below the CEJ. The teeth were randomly divided into six groups of 10 teeth each. In the first three groups (groups 1-3), Clearfil SE Bond and Clearfil APX (Kuraray) were used for restoration in the total bonding technique (group 1), conventional open sandwich technique associated with a nano-ionomer (Ketac N100, 3M ESPE) (group 2), and modified open sandwich technique with simultaneous bonding application for both nano-ionomer and composite (group 3). In the second three groups (groups 4-6), Silorane Adhesive and Filtek Silorane composite (3M ESPE) were used in the same manner as in the first three groups, respectively. The simultaneous bonding application in the modified sandwich restorations (with SE Bond or Silorane Adhesive) resulted in a significant reduction of the cervical microleakage compared with that of the conventional bonding (p<0.05). However, microleakage of the modified technique was similar to that of the total bonding (with SE Bond or Silorane Adhesive) (p>0.05), both showing good marginal seal.

Effect of open-sandwich vs. adhesive restorative techniques on enamel and dentine demineralization: An in situ study

ObjectivesTo assess in situ the effect of different restorative techniques used with fluoride-releasing materials on enamel and dentine demineralization in the presence of a cariogenic challenge. MethodsThirty human molars were prepared for 60 Class V cavities, with enamel and dentine margins. The teeth were divided into four groups (n=15): L1 – open sandwich technique with a conventional glass ionomer cement (GIC), L2 – open sandwich technique with a resin-modified GIC, A1 – total-etch bonding with a fluoride-containing adhesive, A2 – total-etch bonding with a nonfluoride-containing adhesive. All the cavities were restored with a nanofilled composite. Fifteen volunteers used appliances containing one specimen from each group. The cariogenic challenge was carried out with a 20% sucrose solution 8×/day for 7 days. The specimens were sectioned for microhardness test and EDS analysis at different depths below the enamel and dentine margins (25, 50 and 100μm) and distances from the tooth-restoration interfaces (25 and 75μm). The data were analyzed by ANOVA and Games–Howell test (α=5%). ResultsBoth GICs produced higher hardness in enamel at all depth-and-distance combinations, but only L1 produced higher hardness in dentine (p<0.05). L2 and A1 exhibited similar dentine hardness at 25μm distance for all depths (p>0.05). L1 demonstrated significantly higher amounts of calcium in dentine than the other groups, but had similar amounts in enamel to L2 and A1. ConclusionsThe open sandwich technique using conventional GIC proved more effective in reducing enamel and dentine demineralization at depths of up to 100μm under a cariogenic challenge. Clinical significanceConventional GICs should be considered the materials of choice for lining of cavities not having all margins in enamel, particularly using the open sandwich technique.

Tensile bond characteristics between composite resin and resin-modified glass-ionomer restoratives used in the open-sandwich technique

The clinical success of large class II resin-modified glass-ionomer cement/composite resin (RMGIC/CR) 'open-sandwich' restorations in permanent or primary molars may be influenced by certain bonding parameters. To examine in vitro the effect of placing/curing mode on the RMGIC/CR bond strength. Two restoratives, a CR (Z250), a RMGIC (Vitremer) and a bonding agent (Adper Single Bond 2), all of 3M ESPE, were used for preparing five groups of seven specimen sticks each. The bond between the two restorative materials at the stick centre was created in the three test groups by: (A) 1-step placing RMGIC in contact with CR, then photocuring; (B) 2-step RMGIC placing/curing, then CR placement/curing; (C) 3-step RMGIC placing/curing, bonding agent placing/curing, CR placing/curing. Control groups consisted of sticks made of CR alone (D, positive) and RMGIC alone (E, negative). The specimens were subjected to tensile stress measurements in an Instron dynamometer and examined by scanning electron microscope for type of failure. Tensile bond strength, tensile strain and elastic modulus differences were examined with one-way ANOVA and Tukey test. Among experimental groups, Group C exhibited significantly higher tensile strength (MPa) means (A=12.11±4.72, B=15.69±5.18, C=19.08±4.05) and significantly higher tensile strain (%) means (A=0.50±0.11, B=0.64±0.19, C=0.98±0.24), compared to Group A, at p=0.05. Group D had significantly higher tensile strength and strain than all other groups. No statistically significant differences were observed in the elastic modulus. The use of bonding agent (Group C) resulted in absence of adhesive failures as seen by SEM. The use of bonding agent improved the CR/RMGIC bond by tensile strength and strain tests.

Role of delayed light polymerization of a dual-cured composite base on marginal adaptation of class II posterior composite open-sandwich restoration

To determine the effect of delayed light polymerization of a dual-cured composite base material on the marginal adaptation of class II composite restoration. 35 extracted human molar teeth were used to prepare class II mesio-occlusal or disto-occlusal slot preparations with gingival margins at the CEJ. The teeth were restored using an open-sandwich technique with a 2mm base increment of dual-cured composite, and divided into 5 groups based on the mode of the polymerization of the dual-cured composite base: Group A - self-cured after placement (5 mins), Group B - light-cured immediately after placement, Group C - light-cured 30 seconds after placement, Group D - light-cured 60 seconds after placement, Group E - light-cured 120 seconds after placement. Then a top layer of a light-cured composite resin is placed to complete the restoration. The teeth were thermocycled and immersed in 1% aqueous solution of methylene blue for 24 hours. Sectioning of the teeth and scoring under stereomicroscope was done. Data will be statistically evaluated using the kruskal wallis 1-way ANOVA. Statistical analysis using kruskal wallis 1-way ANOVA showed that the dual-cured composite light polymerized 1 minute after placement exhibited the least microleakage. Delayed light polymerization of the dual-cured composite base reduced the microleakage in class II open-sandwich restorations.

Microleakage in Class II Restorations: Open vs Closed Centripetal Build-up Technique

This study evaluated whether a Class II restoration in a flowable resin composite has to be placed prior to (open-sandwich technique) or after (closed-sandwich technique) construction of the interproximal wall in the centripetal build-up technique in order to reduce microleakage. Thirty non-carious molars were selected and randomly divided into two groups (n = 15). A standardized Class H preparation was made with the cervical margin 1 mm below the cementum-enamel junction. In Group 1, flowable resin composite was applied as a 1 mm base, remaining exposed at the cervical margin. In Group 2, the hybrid resin composite was applied to the interproximal wall, followed by a layer of flowable composite on the pulpal floor, away from the margins. The restorations were then subjected to 500 thermal cycles, each with a dwell time of 20 seconds at 5 degrees C and 55 degrees C. Adaptation at the cervical margin was evaluated by dye penetration and SEM analysis using the replica technique. The data were statistically analyzed using the Mann-Whitney U-test (p < 0.05). The centripetal open-sandwich technique led to significantly lower dye penetration than the centripetal closed-sandwich technique (p < 0.001). Flowable resin composite placed under hybrid resin composites in Group 1 provided better marginal adaptation and fewer voids. However, neither Group 1 nor Group 2 was able to completely prevent microleakage.

Influence of different restorative techniques on marginal seal of class II composite restorations

ObjectiveTo evaluate the gingival marginal seal in class II composite restorations using different restorative techniques.Material and MethodsClass II box cavities were prepared in both proximal faces of 32 sound human third molars with gingival margins located in either enamel or dentin/cementum. Restorations were performed as follows: G1 (control): composite, conventional light curing technique; G2: composite, soft-start technique; G3: amalgam/composite association (amalcomp); and G4: resin-modified glass ionomer cement/ composite, open sandwich technique. The restored specimens were thermocycled. Epoxy resin replicas were made and coated for scanning electron microscopy examination. For microleakage evaluation, teeth were coated with nail polish and immersed in dye solution. Teeth were cut in 3 slices and dye penetration was recorded (mm), digitized and analyzed with Image Tool software. Microleakage data were analyzed statistically by non-parametric Kruskal-Wallis and Mann-Whitney tests.ResultsLeakage in enamel was lower than in dentin (p<0.001). G2 exhibited the lowest leakage values (p<0.05) in enamel margins, with no differences between the other groups. In dentin margins, groups G1 and G2 had similar behavior and both showed less leakage (p<0.05) than groups G3 and G4. SEM micrographs revealed different marginal adaptation patterns for the different techniques and for the different substrates.ConclusionThe soft-start technique showed no leakage in enamel margins and produced similar values to those of the conventional (control) technique for dentin margins.

Stainless steel crown versus modified open‐sandwich restorations for primary molars: a 2‐year randomized clinical trial

The aim of this study was to investigate the clinical performance and survival of stainless steel crown (SSC) restoration and modified open-sandwich technique using resin-modified glass ionomer cement. Randomized clinical trial. General dental practice. A total of 87 children aged 4-7 years at baseline with one or more primary molars that have undergone pulp therapy were randomly assigned to receive either SSC or modified open-sandwich restoration. One hundred and sixty restorations were placed and evaluated after 6, 12, 18, and 24 months using the Ryge criteria. Comparable survival rates were observed for both SSC and modified open-sandwich restoration. With only four SSCs and six modified open-sandwich restorations failing over 24 months, the survival rates were high for both materials (2-year survival rate: 95.0% for SSCs and 92.5% for modified open-sandwich restorations). Significantly better gingival health (P < 0.05) was observed for the modified open-sandwich restorations compared with SSCs, as only one modified open-sandwich restoration was rated Charlie compared to 13 SSCs. No significant differences were observed between the two materials for marginal integrity, proximal contact, occlusion, or recurrent caries. The 2-year results indicated that the modified open-sandwich restoration is an appropriate alternative to SSC in extensive restorations, particularly where aesthetic considerations are important.

CLASS II COMPOSITE RESIN RESTORATIONS WITH GINGIVAL MARGINS IN DENTIN

The rising demand for esthetic restorations has considerably increased the number of direct composite restorations being placed in private practices. While composite resin is often selected primarily for its esthetic qualities, another significant advantage of direct composite restorations is the ability to perform conservative cavity preparations. The traditional configuration used for amalgam restorations is no longer mandatory; thus, more sound tooth structure can be preserved. The technique of composite placement is complex when compared to amalgam placement. The use of adhesive systems prior to placement of composite restorations requires not only excellent isolation to avoid contamination, but also precise manipulation of the adhesive system. While stable bonds to enamel are routinely obtained, the heterogeneous composition and intricate morphology of dentin makes this substrate more challenging to restore. In addition, the cavity configuration (C‐factor) and inherent polymerization shrinkage of composite resin play an important role in the durability of the composite–dentin interface. Class II preparations often have gingival margins in root surfaces because of the location of the caries lesion. Clinicians are then faced with a preparation that is challenging to isolate, has a relatively high C‐factor, and relies on optimal bonding to dentin to secure long‐lasting marginal integrity. Various restorative techniques, such as incremental placement or the use of an intermediate layer (flowable composite or resin‐modified glass ionomer cements—open sandwich technique), have been some of the methods proposed to increase the longevity of composite restorations, especially those with margins in dentin. This review evaluates some of the published research on Class II composite resin restorations with margins in the dentin/cementum.

Nine-year evaluation of a polyacid-modified resin composite/resin composite open sandwich technique in Class II cavities

The aim of this study was to evaluate in an intraindividual comparison the durability of a polyacid-modified resin composite/resin composite open sandwich restoration in a 9 years follow-up. A polyacid-modified resin composite (PMRC; compomer, Dyract) was placed as an intermediate layer and covered with resin composite (RC, Prisma TPH). A direct RC restoration was used as control. Each of 57 patients, received at least one pair of Class II restorations, one open sandwich and one resin composite control. In total 75 pairs of Class II restorations, 68 premolars and 82 molars, all in occlusion, were placed by two dentists. Most of the cavities were surrounded by enamel. The restorations were evaluated at baseline, 6, 12, 24, 36 months and 9 years by slightly modified USPHS criteria. Survival of restorations grouped on the two different techniques was determined using Kaplan-Meier survival curves. After 9 years, 14 of 135 evaluated restorations were estimated as unacceptable, 6 in the sandwich group and 8 in the control group. Over all annual failure rate during the 9-year period was 1.1%. The survival rate was not significant different between the two techniques (p=0.604). Reasons of failure were: secondary caries (8), fracture of tooth (1), fracture of restoration (2), endodontic treatment (3). Both restorative techniques showed good durability during the 9-year period. No clinical advantage was observed for the sandwich technique.