Dentine bond strength and microleakage of flowable composite, compomer and glass ionomer cement

Effect of Bonding Agents on the Shear Bond Strength of Tooth-colored Restorative Materials to Dentin: An In Vitro Study

AIM

The aim of the study is to determine the difference in the shear bond strengths to dentin among dental composite (Filtek Z350®, 3M), compomer (Dyract Flow®, Dentsply) and Giomer (Beautifil®, Shofu) with 3MTM Single BondTM Universal Adhesive (SBU) (7th generation, self-etch, single solution adhesive) and AdperTM Single Bond 2 Adhesive (ASB) (5th generation, total-etch, two solution adhesive).

MATERIALS AND METHODS

Sixty extracted human permanent teeth were collected, cleansed of debris, and placed in distilled water. The samples were segregated into two groups depicting the two bonding agents-AdperTM (ASB) and 3MTM Single Bond Universal (SBU) and sub-grouped into three groups depicting the three restorative materials (Composite, Giomer, and Compomer) used. Groups were respresented as follows: Group I-ASB + Composite; Group II-ASB + Giomer; Group III-ASB + Compomer; Group IV-SBU + Giomer; Group V-SBU + Compomer; Group VI-SBU + Composite. After applying the bonding agent as per the manufacturer's instructions, following which the restorative material was placed. A Universal Testing Machine (Instron 3366, UK) was employed to estimate the shear bond strength of the individual restorative material and shear bond strengths were calculated.

RESULTS

Composite bonded with SBU (group VI) displayed the greatest shear strength (11.16 ± 4.22 MPa). Moreover, Giomers and flowable compomers displayed better bond strengths with ASB compared with their SBU-bonded counterparts.

CONCLUSION

These results mark the importance of careful material selection in clinical practice and the bonding agent used to achieve optimal bond strength and enhance the clinical longevity and durability of dental restorations.

CLINICAL SIGNIFICANCE

From a clinical perspective, to avoid a compressive or a shear failure, it would be preferrable to use a direct composite restorative material with SBU (Single bond universal adhesive, 7th generation) to achieve maximum bond strength. How to cite this article: Kuchibhotla N, Sathyamoorthy H, Balakrishnan S, et al. Effect of Bonding Agents on the Shear Bond Strength of Tooth-colored Restorative Materials to Dentin: An In Vitro Study. J Contemp Dent Pract 2024;25(3):245-249.

Evaluation of the amount of residual monomer released from different flowable composite resins

Today, resin materials are used in the restoration of permanent and deciduous teeth or as fissure sealants. The materials can contain different types of monomers (Bis-GMA, UDMA, TEGDMA). These monomers can be released into the oral cavity after polymerization. Residual monomers released from resin-containing restorative materials after polymerization have been reported to have negative effects on mechanical properties. The aim of our study is to evaluate the amount of residual monomers released after polymerization of different flowable composite resin materials using two different modes of LED light source. Composite disc samples (8 mm diameter/2 mm depth) prepared for each material group were polymerized using two different modes of the LED light device (Standard mode and extra power mode). HPLC (High Performance Liquid Chromatography) device was used to measure the amount of residual monomer release at 1 h, 1 day, 3 days and 7 days periods. Pairwise comparison of the differences between the materials was performed by Post-hoc test. For each residual monomer, the Kruskal Wallis test was used to analyze the difference between the materials in standard mode and the difference between the materials in extra power mode. According to the results of the study; Grandio flow flowable composite showed the highest release of TEGDMA and Bis-GMA while SDR® Flow flowable composite showed the lowest release of TEGDMA, Bis-GMA and UDMA. For all materials, the extra power mode resulted in more residual monomer release. TEGDMA and Bis-GMA release was detected in all tested flowable composites at all time periods.

Comparative evaluation of shear bond strength of three different glass ionomer cement (conventional, zirconium-reinforced and advanced glass hybrid) in primary molars: an in vitro study

PURPOSE

The success of restorative materials is largely dependent on their capacity to adhere to the tooth structure and withstand the various forces present in the oral cavity. So, the aim of present study was to evaluate and compare the shear bond strength (SBS) of Type IX Glass Ionomer Cement (GIC), Zirconomer, and Gold Label Hybrid GIC in primary molars.

METHODS

Thirty primary molars were selected based on inclusion and exclusion criteria. The molars were polished to provide a flat dentin surface after being inserted in auto polymerizing acrylic resin. The samples were randomly divided into three groups, equally and were bonded to GIC. On the dentin surface, restoration cylinders were made using a plastic mould that had an internal diameter and height of 5 mm and 3 mm, respectively. The cement was manipulated according to the manufacturer's directions through the plastic mould. Then, the samples were stored at room temperature for 10 days to mimic oral conditions. The Universal Testing Machine was used to test SBS. One-way ANOVA and the post hoc Tukey test were used to statistically assess the collected data.

RESULTS

A statistically significant difference was found in all three groups (p < 0.01), with Zirconomer demonstrating highest SBS, followed by Type IX GIC and Gold Label Hybrid GIC.

CONCLUSION

The SBS value of Zirconomer was better when compared to Type IX GIC and Gold Label Hybrid GIC.

Intelligent pH-responsive dental sealants to prevent long-term microleakage

OBJECTIVES

Microleakage is a determinant factor of failures in sealant application. In this study, DMAEM (dodecylmethylaminoethyl methacrylate), a pH-responsive antibacterial agent, was incorporated into resin-based sealant for the first time. The objectives of this study were to: (1) investigate the long-term performance of DMAEM-modified sealants against oral microbial-aging; and (2) investigate the long-term preventive effect of DMAEM-modified sealants on microleakage.

METHODS

Depth-of-cure and cytotoxicity of DMAEM-modified sealants were measured. Then, an aging model using biofilm derived from the saliva of high caries experience children was conducted. After aging, microhardness and surface roughness were measured. Biofilm activity, lactic acid production and exopolysaccharide (EPS) production were measured. 16S rRNA gene sequencing were also performed. The effects of DMAEM on microleakage were tested using an in vitro microleakage assessment.

RESULTS

The addition of DMAEM with a mass fraction of 2.5-10% did not affect depth-of-cure values and cytotoxicity of sealants. Adding 2.5-10% DMAEM did not affect the surface roughness and microhardness after aging. Compared to control, adding 2.5-10% DMAEM reduced biofilm metabolic activity by more than 80%. The lactic acid production and EPS production were reduced by 50% in DMAEM groups. DMAEM-modified sealants maintained the microbial diversity of biofilm after aging, they also inhibited the growth of lactobacillus. The 5% and 10% DMAEM groups exhibited a significant reduction in microleakage compared to control.

SIGNIFICANCE

The long-term antibacterial activities against oral microbial-aging and the long-term microecosystem-regulating capabilities enabled DMAEM-modified sealant to prevent microleakage in sealant application and thus prevent dental caries.

Meta-Analysis of In-Vitro Bonding of Glass-Ionomer Restorative Materials to Primary Teeth

Restoration of primary teeth is among the main clinical applications of glass-ionomer cements (GIC). The aim of the study was to review and summarize existing evidence of in vitro bond strength of glass-ionomer (GI) restoratives to enamel and dentin of primary teeth. A literature search was performed in PubMed/Medline, Scopus, Web of Science, Cochrane, and Google Scholar databases to identify studies published until April 2021. The search strategy was: (“glass”) and (“ionomer”) and (“primary” or “deciduous”) and (“bond” or “tensile” or “shear”). Two researchers independently retrieved articles that reported on the bond strength of GIC to primary dentin and/or enamel. The meta-analysis was performed to compare the bond strength values of conventional (C) GIC and resin-modified (RM) GIC to different substrates. From 831 potentially eligible articles, 30 were selected for the full-text examination, and 7 were included in the analysis. Studies were rated at high (3), medium (3), and low (1) risk of bias. RM-GIC showed higher bond strength to primary enamel and dentin compared to the C-GIC. Meta-analysis of in vitro studies, evaluating bonding properties of GI restoratives to primary teeth, suggests the superior performance of RM-GIC. However, there is a lack of studies that examine the properties of novel GI formulations.

Influence of Diode Laser for the Treatment of Dentin Hypersensitivity on Microleakage of Cervical Restorations

Noncarious cervical lesions (NCCLs) are a common clinical finding often linked with dentin hypersensitivity (DH). Aim. The aim of the study was to evaluate the influence of diode laser for the treatment of DH on microleakage of subsequent NCCL restorations. Materials and Methods. Forty-eight extracted human premolars were collected. All teeth received standardized cervical preparation on both the buccal and palatal surfaces and were randomly divided into three groups (n = 16) according to the restorative material used: nanohybrid composite resin (CR), resin-modified glass ionomer (RMGI), and conventional glass ionomer (GIC). The prepared cavities on the palatal surfaces were treated by diode laser using SIROlaser Blue (Sirona Dental Systems, Bensheim, Germany) prior to restoration, while preparations on the buccal surfaces were directly restored. After thermocycling, the teeth were immersed in methylene blue dye for microleakage evaluation under 40x magnification at both occlusal and cervical margins. The Kruskal-Wallis test followed by the Bonferroni tests was conducted to determine inter- and intragroup differences (P < 0.05). Results. All restorative materials tested showed some degree of microleakage with no statistically significantly different scores with or without the use of laser desensitization prior to restorative treatment. Group CR showed the least microleakage, followed by group RMGI, while group GIC showed the highest. Cervical margins showed greater microleakage than the occlusal margins where the difference was statistically significant in the RMGI group without laser pretreatment (P = 0.006) and in both groups CR (P = 0.02) and RMGI (P = 0.006) with the laser pretreatment. Conclusion. Application of diode laser for the treatment of DH prior to the restoration of teeth with NCCL did not affect the microleakage of all the restorative materials tested. All the materials showed some degree of microleakage, which was higher in gingival margins compared to occlusal margins. The resin composite shows the least microleakage among all the tested materials.

The management of a complicated crown-root fracture incorporating modified crown-lengthening surgery

Anterior teeth with subgingival fractures require a multidisciplinary management approach with regards to biological, functional and aesthetic factors. This case report emphasises the use of a minimally invasive technique combined with a sequence of therapies to treat a complicated crown-root fracture and reviews the critical factors to ensure predictable outcomes. Endodontic treatment was undertaken due to exposure of the pulp in a complicated crown-root fracture of the maxillary right central incisor. Extrusion of the fractured fragment was performed to expose the fracture margin under the alveolar bone. Modified crown-lengthening surgery was used to reconstruct the biologic width. The traumatised tooth was restored with a glass fibre post and resin core, which fit the biological requirements. Finally, an all-ceramic crown fulfilled biomimetic aesthetics. This multidisciplinary approach achieved a good long-term prognosis with regards to periodontal and periapical healing.

A comparative evaluation of the fracture resistance of endodontically treated teeth with simulated invasive cervical resorption cavities restored with different adhesive restorative materials: An in vitro study

Aim:

The aim of the study was to compare the fracture resistance of endodontically treated teeth with simulated invasive cervical resorption cavities, restored with different restorative materials, namely, conventional glass-ionomer cement (CGIC), resin-modified glass-ionomer cement (RMGIC), flowable composite (FC), and giomer.

Methods:

Sixty extracted human permanent maxillary central incisor teeth were assigned to six groups,which were, Group 1 (intact teeth, control), Group 2 (teeth with biomechanical preparation and resorption cavity), Group 3 (CGIC), Group 4 (RMGIC), Group 5 (FC), and Group 6 (giomer). Except for Group 1, other groups were subjected to endodontic treatment. Teeth of Group 2 were left unobturated and teeth of Groups 3–6 were obturated. A simulated resorption cavity was prepared labially in the specimens belonging to Groups 2–6 and restored with respective restorative materials. The specimens were subjected to compressive load until failure in an Instron testing machine and the load at failure was recorded in Newtons.

Statistical Analysis:

The data obtained were statistically analyzed using one-way ANOVA, pair-wise comparison was made with Tukey's multiple comparison test, and P < 0.05 was considered statistically significant.

Results:

There was a statistically significant difference in the fracture resistance of intact teeth and endodontically treated teeth with simulated invasive cervical resorption cavities restored with different adhesive restorative materials. Among the restored teeth, there was no significant difference.

Conclusion:

Intact teeth were found to have the highest resistance to fracture followed by those restored with giomer, FC, RMGIC, and CGIC in that order.

The forgotten merits of GIC restorations: a systematic review

Objective

To reevaluate proven strengths and weakness of glass ionomer cements (GICs) and to identify agreement versus conflicting evidence in previous reports regarding the transition between GIC and the tooth, and the existence of an “interphase”.

Materials and methods

Relevant electronic databases (PubMed, Embase via Ovid and Medline via Web of science) were searched for publications of evidence relating to the transition zone at the GIC-tooth interphase. Studies were examined and grouped according to characteristics of GIC-tooth attachment area quantified by X-ray and optical microscopy techniques in 2D and 3D.

Results

Inclusion criteria comprised of in vitro studies that showed images of the conventional GIC-tooth substrate attachments using at least one of the following techniques: SEM, CLSM, or μCT. The search identified 419 studies, from which 33 were included. Ten studies demonstrated the existence of an interphase layer and five studies quantified the layer thickness (1–15 μ). Twenty-nine publications studied different failure modes of the GIC-tooth interphase. Eleven studies described discontinuities inside the GIC bulk.

Conclusion

The GIC-tooth interphase attributes evolve with time. Good attachment is evident even under compromised surface preparation. The GIC-tooth attachment area is resistant to acidic dissolution as compared to both tooth and GIC bulk. In general, studies revealed mostly intact GIC-tooth interphases with only some cracked interphases.

Clinical significance

GIC bonds to the tooth structure and forms an acid resistant attachment zone that might enhance caries inhibition. Due to fluoride release and ease of use, GIC provides a cost effective treatment, ideal for low income or high caries populations.

Evaluation of Four Different Restorative Materials for Restoration of the Periodontal Condition of Wedge-Shaped Defect: A Comparative Study

BACKGROUND This study aimed to conduct a clinical evaluation of four restorative materials for restoration of dental wedge-shaped defect (WSD) and their impacts on periodontal tissues. MATERIAL AND METHODS A total of 280 maxillary premolars with dental WSD were selected from 106 patients; the patient cases were divided into eight groups according to different combinations of restorative materials (flowable resin composites, Dyract compomers, glass ionomer cement (GIC), light-curing composite resin), and WSD positions (approaching gingival and subgingival positions). Gingival crevicular fluid (GCF) volume, levels of aspartate aminotransferase (AST), alkaline phosphatase (ALP), and interleukin-1β (IL-1β) in GCF were analyzed, while probing depth (PD), plaque index (PLI), and sulcus bleeding index (SBI) were also measured. The periodontal conditions of all patients were followed prior to restoration, as well as six months and 12 months after restoration. RESULTS After six months of restoration, the overall clinical success rates of flowable resin composites, Dyract compomers, and light-curing composite resin were greater than those of GIC. GCF volume, GCF-AST, IL-1β levels, PD, PLI, and SBI of cases restored by GIC were higher than those restored by the other three materials. After 12 months of restoration, the overall clinical success rates of flowable resin composites and Dyract compomers were greater than those of light-curing composite resin and GIC. GCF volume, GCF-AST, GCF-ALP, IL-1β levels, PD, PLI, and SBI of cases restored by GIC were higher than those restored by the other three materials. CONCLUSIONS Our study provided evidence that the clinical efficacy of flowable resin composites, Dyract compomers, and light-curing composite resin was greater than that of GIC for restoration of dental WSD.

Effects of Preheated Composite on Micro leakage-An in-vitro Study

INTRODUCTION

Resin composites have been the pinnacle of direct esthetic restorations ever since its discovery. However, it comes with its own disadvantages. Post-operative sensitivity and marginal discoloration frequently occur due to polymerization shrinkage and micro leakage, which is the major cause of failure in resin composite restorations.

AIM

To evaluate the effects of preheated composite at different temperatures on microleakage.

MATERIALS AND METHODS

A total of 60 extracted non-carious human premolars were collected and class 1 cavity (1.5x4x 3mm) was prepared in each and were randomly divided into three groups. Group 1 (n=20) was filled with microhybrid resin composite (Heraeus Charisma Smile) at room temperature. Group 2 (n=20) was filled with the same resin composite which was preheated to 50°C and Group 3 (n=20) was filled with resin composite preheated to 60°C. Teeth were subjected to a thermocycling regime (500X, 5 - 55°C), followed by a dye infiltration by immersing in basic fuschin for 24 hours. The tooth was sectioned longitudinally and the extent or absence of micro-leakage was determined by the amount of dye penetration along the resin composite-tooth interface using a confocal microscope.

RESULTS

There was minor micro-leakage detected at the occlusal margin of the control tooth specimen. The sample with preheated composite restoration at 50°C showed an intact tooth-restoration interface with no micro leakage. However, the preheated composite at 60°C showed large amount of microleakage.

CONCLUSION

Under the current limitation of the study, preheated composite at 50°C showed the least micro-leakage.

Glass-ionomer Cements in Restorative Dentistry: A Critical Appraisal

Glass-ionomer cements (GICs) are mainstream restorative materials that are bioactive and have a wide range of uses, such as lining, bonding, sealing, luting or restoring a tooth. Although the major characteristics of GICs for the wider applications in dentistry are adhesion to tooth structure, fluoride releasing capacity and tooth-colored restorations, the sensitivity to moisture, inherent opacity, long-term wear and strength are not as adequate as desired. They have undergone remarkable changes in their composition, such as the addition of metallic ions or resin components to their composition, which contributed to improve their physical properties and diversified their use as a restorative material of great clinical applicability. The light-cured polymer reinforced materials appear to have substantial benefits, while retaining the advantages of fluoride release and adhesion. Further research should be directed towards improving the properties, such as strength and esthetics without altering its inherent qualities, such as adhesion and fluoride releasing capabilities.

Flowable Resin Composites: A Systematic Review and Clinical Considerations

BACKGROUND

Little is known about flowable composite materials. Most literature mentions conventional composite materials at large, giving minimal emphasis to flowables in particular. This paper briefly gives an in depth insight to the multiple facets of this versatile material.

AIM

To exclusively review the most salient features of flowable composite materials in comparison to conventional composites and to give clinicians a detailed understanding of the advantages, drawbacks, indications and contraindications based on composition and physical/mechanical properties.

METHODOLOGY

DATA SOURCES

A thorough literature search from the year 1996 up to January 2015 was done on PubMed Central, The Cochrane Library, Science Direct, Wiley Online Library, and Google Scholar. Grey literature (pending patents, technical reports etc.) was also screened. The search terms used were "dental flowable resin composites".

SEARCH STRATEGY

After omitting the duplicates/repetitions, a total of 491 full text articles were assessed. As including all articles were out of the scope of this paper. Only relevant articles that fulfilled the reviewer's objectives {mentioning indications, contraindications, applications, assessment of physical/mechanical/biological properties (in vitro/ in vivo /ex vivo)} were considered. A total of 92 full text articles were selected.

CONCLUSION

Flowable composites exhibit a variable composition and consequently variable mechanical/ physical properties. Clinicians must be aware of this aspect to make a proper material selection based on specific properties and indications of each material relevant to a particular clinical situation.

Bonding Ability of Paste-Paste Glass Ionomer Systems to Tooth Structure: In Vitro Studies

This study investigated the effect of nonrinse conditioners (ie, Ketac Nano Primer [KNP] and GC Self Conditioner [SC]) used as substrate pretreatment and their respective paste-paste resin-modified glass-ionomer cement (RMGIC) (ie, Ketac Nano [KN] and Fuji Filling LC [FF]) on microtensile bond strength to dentin and marginal sealing when compared with traditional RMGIC (ie, Photac Fil [PF] and Fuji II LC [FII]) used in association with polyacrylic acid (ie, Ketac Cavity Conditioner [KC] and GC Cavity Conditioner [CC]). A total of 192 extracted human molars were allocated into eight groups: KNP-KN, KC-KN, KNP-PF, KC-PF, SC-FF, CC-FF, SC-FII, and CC-FII. For microtensile bond strength, the teeth were sectioned to expose occlusal dentin and restored according to the group. After 24 hours the teeth were cut to yield nine beams per tooth (±0.8 mm2). Testing was done using a universal testing machine followed by failure mode classification. For microleakage testing, standardized cavity preparations were made on the buccal cementoenamel junction and restored according to the group. The teeth were thermocycled (500 cycles, 8°C to 48°C), sealed, immersed in methylene blue for 24 hours, and then assessed for microleakage using a stereomicroscope. Microtensile bond strengths in megapascals (mean±SE) were KNP-KN: 14.9 ± 1.6, KC-KN: 17.2 ± 1.5, KNP-PF: 31.2 ± 1.6, KC-PF: 26.2 ± 1.2, SC-FF: 23.6 ± 1.5, SC-FII: 31.2 ± 1.5, and CC-FII: 21.9 ± 1.5. Cervical margins showed more microleakage compared with occlusal margins. Overall, the use of nonrinse conditioners in association with traditional RMGICs demonstrated superior microtensile bond strengths to dentin when compared with the paste-paste RMGICs. Meanwhile, the association between polyacrylic acid (CC) and a traditional RMGIC (FII) led to the least microleakage for cervical locations when compared with all other groups.

Does the use of a novel self-adhesive flowable composite reduce nanoleakage?

Objective

The aim of the study reported here was to evaluate the performance of a self-adhesive flowable composite and two self-etching adhesive systems, when subjected to cyclic loading, in preventing the nanoleakage of Class V restorations.

Methods

Wedge-shape Class V cavities were prepared (4×2×2 mm [length × width × depth]) on the buccal surfaces of 90 sound human premolars. Cavities were divided randomly into three groups (n=30) according to the used adhesive (Xeno^® V [self-etching adhesive system]) and BOND-1^® SF (solvent-free self-etching adhesive system) in conjunction with Artiste^® Nano Composite resin, and Fusio™ Liquid Dentin (self-adhesive flowable composite), consecutively. Each group was further divided into three subgroups (n=10): (A) control, (B) subjected to occlusal cyclic loading (90N for 5,000 cycles), and (C) subjected to occlusal cyclic loading (90N for 10,000 cycles). Teeth then were coated with nail polish up to 1 mm from the interface, immersed in 50% silver nitrate solution for 24 hours and tested for nanoleakage using the environmental scanning electron microscopy and energy dispersive analysis X-ray analysis. Data were statistically analyzed using two-way analysis of variance and Tukey’s post hoc tests (P≤0.05).

Results

The Fusio Liquid Dentin group showed statistically significant lower percentages of silver penetration (0.55 μ) compared with the BOND-1 SF (3.45 μ) and Xeno V (3.82 μ) groups, which were not statistically different from each other, as they both showed higher silver penetration.

Conclusion

Under the test conditions, the self-adhesive flowable composite provided better sealing ability. Aging of the two tested adhesive systems, as a function of cyclic loading, increased nanoleakage.

Efficacy of four lining materials in sandwich technique to reduce microleakage in class II composite resin restorations

OBJECTIVES

The aim of the present study was to evaluate the effect of four different sandwich techniques on gingival microleakage of Class II direct composite resin restorations.

MATERIALS AND METHODS

Fifty sound human premolars were selected and randomly divided into five groups (n=10). Class II box only cavities were prepared in one of the proximal surfaces of each tooth with a gingival margin located approximately 0.5 mm below the cemento-enamel junction. Group A (control) was restored incrementally with composite resin (Tetric Ceram). Groups B, C, D, and E were restored with the sandwich technique using a compomer (Compoglass F), flowable composite resin (Tetric Flow), self-cure composite resin (Degufill SC), or resin modified glass ionomer (Fuji II LC), respectively. After thermal-load cycling, the specimens were immersed in 0.5% basic fuschin for 24 hours. Dye penetration (10(-1) mm) was detected using a sectioning technique. Data were analyzed with repeated measurements and Duncan test at α=0.05.

RESULTS

The least amount of microleakage was detected in the incremental group (1.28 ± 0.98). The sandwich technique using resin modified glass ionomer (7.99 ± 9.57) or compomer (4.36 ± 1.78) resulted in significantly more leakage than did the sandwich technique using flowable (1.50 ± 1.97) or self-cure composite (2.26 ± 1.52).

CONCLUSION

According to the results of this study, none of the four sandwich technique composite resin restorations used in this study could reduce gingival microleakage to a greater degree than the incremental technique.

Microleakage in Class II composite restorations with margins below the CEJ: in vitro evaluation of different restorative techniques

OBJECTIVES

The purpose of this in vitro study was to evaluate the microleakage in "deep" Class II composite restorations with gingival cavosurface margin below the CEJ (cemento-enamel junction) and restored with different techniques.

STUDY DESIGN

Fifty human teeth were used. In each tooth two standardized Class II slot cavities (on mesial and on distal surfaces) were prepared: the buccolingual extension of the cavities was 4 mm; the gingival wall was located in dentin/cementum (2 mm beyond the CEJ). The prepared teeth were randomly assigned to 5 experimental groups (of 10 specimens and 20 cavities each) and restored. Group 1: Filtek TM Supreme XTE Flowable (3MESPE) + Universal Filtek Supreme XTE (3MESPE), Group 2: GrandioSO Heavy Flow (Voco) + GrandioSo (Voco), Group 3: SDR™ (Dentsply Caulk) + Esthet-X® HD (Dentsply Caulk), Group 4: SonicFill (Kerr), Group 5: Grandio (Voco). After thermocycling, the specimens were immersed in a 0.5% basic fuchsine dye solution and incubated at 37°C for 24 hours. The teeth were subsequently sectioned mesiodistally. All specimens were examined at 25 in a stereomicroscope and standardized digital images were obtained. Dye penetration was measured from gingival margins.

RESULTS

The results demonstrated no significant leakage differences between Group 4 and Group 5, that both showed significantly higher frequency distribution of Score 0. Group 2 and Group 3 showed a significant prevalence of Score 1, whereas Group 1 showed significantly higher frequency of Score 2.

CONCLUSIONS

None of the restorative techniques tested completely eliminated microleakage dye penetration in dentin margins; marginal adaptation in Class II composite restorations with gingival wall below the CEJ varied in both substrates and from different restorative techniques used.

The use of bur and laser for root caries treatment: a comparative study

This research analyzed the influence of bur and erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser caries removal on cavity characteristics and marginal seal of composite resin restorations. One hundred and forty human dental root samples were used. After in vitro root caries induction using Streptococcus mutans, the carious lesions were removed either by a conventional technique using burs (G1=control) or by using an Er,Cr:YSGG laser (λ=2.78 μm, 20 Hz, pulse duration is approximately equal to 140 μs, noncontact mode using a 600-μm tip) with the following power outputs: G2: 1.0 W; G3: 1.25 W; G4: 1.5 W; G5: 1.75 W; G6: 2.0 W; G7: 2.25 W; G8: 2.5 W; G9: 2.75 W; G10: 3.0 W; G11: 3.25 W; G12: 3.5 W; G13: 3.75 W; and G14: 4.0 W. Samples in the 14 groups (n=10) were conditioned with Clearfil SE Bond and restored with a flowable composite. They were then thermocycled (1000 cycles) and immersed into a 2% methylene blue solution for microleakage analysis. The data were statistically compared (analysis of variance or Spearman correlation tests; p≤0.05). The lased groups showed significantly greater microleakage indexes, cavity depths, and presence of residual caries than did those of the control group. There was a strong positive correlation between residual caries and microleakage. The results indicate that Er,Cr:YSGG laser irradiation is not a good alternative to the use of burs for root caries removal since it may cause a significant loss of marginal sealing in composite resin restorations.

Effect of bonding application time on the microleakage of Class V sandwich restorations

BACKGROUND

The aim of this study was to assess the effect of bonding application time on the microleakage of Class V sandwich restorations.

METHODS

Eighty non-carious third molars were randomly divided into 16 groups. Two Class V cavities were prepared on the buccal and lingual surfaces of teeth. Three groups were restored with Fuji II GIC and treated with a total-etch bonding system (Stea/SDI) immediately after insertion, at 7 minutes and 15 minutes after mixing the glass ionomer cements (GICs). Another three groups were restored with Riva Self Cure GIC and treated with the total-etch system identically. The other six groups were subjected to self-etching bonding (Frog/SDI) after GIC placement in an identical procedure. The remaining groups were made using light cure GICs (Fuji II or Riva Light Cure) in conjunction with the total-etch or self-etching systems. Cavities were then restored with composite (Valux plus, 3M/ESPE). Samples were subsequently immersed in 2% methylene blue solution for 48 hours and observed under a stereomicroscope after sectioning. Four-scale grading was used to assess microleakage in occlusal and gingival walls. Data were analysed using Kruskal-Wallis and Mann-Whitney tests.

RESULTS

The self-etching bonding system exhibited more microleakage in occlusal margins regardless of time. Over time, microleakage significantly decreased in gingival margins in all self-cure groups except for Riva Self Cure treated with the total-etch system (p < 0.05).

CONCLUSIONS

Bonding application time had no effect on the microleakage of occlusal margins. However, maturation of GICs induced a decreased microleakage in gingival margins.

Effect of precuring warming on mechanical properties of restorative composites

To investigate the effect of prepolymerization warming on composites' mechanical properties, three composites were evaluated: Clearfil Majesty (CM) (Kuraray), Z-100 (3M/ESPE), and Light-Core (LC) (Bisco). Specimens were prepared from each composite at room temperature as control and 2 higher temperatures (37°C and 54°C) to test surface hardness (SH), compressive strength (CS), and diametral tensile strength (DTS). Data were statistically analyzed using ANOVA and Fisher's LSD tests. Results revealed that prewarming CM and Z100 specimens significantly improved their SH mean values (P < 0.05). Prewarming also improved mean CS values of Z100 specimens (P < 0.05). Furthermore, DTS mean value of CM prepared at 52° was significantly higher than that of room temperature specimens (P < 0.05). KHN, CS, and DTS mean values varied significantly among the three composites. In conclusion, Prewarming significantly enhanced surface hardness of 2 composites. Prewarming also improved bulk properties of the composites; however, this improvement was significant in only some of the tested materials.

Effect of the insertion and polymerization technique in composite resin restorations: analysis of marginal gap by atomic force microscopy

This in vitro study evaluated the marginal gap at the composite tooth/resin interface in class V cavities under the influence of two insertion techniques and a curing system by means of atomic force microscopy (AFM). Forty enamel and dentin cavities were prepared on the buccal surface in bovine teeth with quadratic forms measuring 2 mm × 2 mm and depth of 1.5 mm. The teeth were then divided into four groups: group A, 10 cavities were restored in one increment, light cured by halogen light; group B, 10 cavities filled with bulk filling, light cured by the light emitting diodes (LED); group C, 10 cavities were restored by the incremental technique, light cured by halogen light; group D, 10 cavities were restored by the incremental technique, light cured by the LED. The teeth underwent the polishing procedure and were analyzed by AFM for tooth/restoration interface evaluation. The data were compared between groups using the nonparametric Kruskall-Wallis and Mann-Whitney tests (p < 0.05). The results showed a statistically significant difference between groups A and B and groups A and C. It was concluded that no insertion and polymerization technique was able to completely seal the cavity.