Composite Resin Systems Research Articles

Comparative Assessment of the Shear Bond Strength of Ceramic Brackets Bonded to the Enamel Surface with a Self-adhesive System.

Objectives: This study aimed to evaluate the shear bond strength of ceramic brackets bonded to the enamel surface using Vertise Flow, with or without the application of phosphoric acid. Materials and Methods: Forty-five extracted human premolar teeth were randomly assigned to three groups (N=15) based on the adhesive used for bonding: 1) Transbond XT, etch, and bond; 2) Vertise Flow; 3) Etch and Vertise Flow. After a 500-round thermocycling procedure, the shear bond strength was measured using a universal testing machine. The samples were then evaluated under a stereomicroscope to determine failure modes, and the Adhesive Remnant Index (ARI) was measured for each group. The data were analyzed with one-way ANOVA and post-hoc Tamhane at a significance level of P<0.05. Results: The highest shear bond strength values were observed in the Transbond XT (13.5±5.38MPa), acid etch and Vertise Flow (11.2±2.89MPa), and Vertise Flow (6.2±3.16MPa) groups, respectively, in descending order. The Vertise Flow group exhibited a significantly lower shear bond strength value compared to the other two groups, with no significant difference between the latter two. Conclusion: While all three study groups demonstrated clinically acceptable shear bond strength values, Vertise Flow showed lower values compared to the other two adhesives. The Vertise Flow composite resin system, whether used alone or with acid etching, remains a suitable choice for bonding ceramic brackets, offering the advantage of a simplified bonding procedure.

Evaluation of bond strength in customizing fiber post using translucent resins photoactivated by different light-emitting diodes.

The objective of the study was to evaluate two translucent resin composite systems for customizing light-polymerized fiber posts with light-emitting diode (LED) curing units regarding adhesion using conventional cement at 24 h and 6 months. This was an experimental in vitro study. Forty roots were prepared and divided into four groups (n = 10): ZV-Z350 resin and LED Valo; ZR-Z350 resin and LED Radii-Cal; OV-Opallis resin and LED Valo; and OR-Opallis resin and LED Radii-Cal. The fiber post was customized and cemented with conventional resin cement and was photoactivated by two different sources. The data were subjected to two-way ANOVA and Tukey's post hoc tests (P = 0.05). The data regarding the pattern of adhesive failures were described in terms of the frequency of occurrence in each third of the postspace. Both at 24 h and 6 months, bond strength among groups was similar, regardless of the analyzed postspace 3rd (P > 0.05). Adhesive failure Type 4 was the most frequent in all thirds. Customizing the fiber post with Z350 and Opallis has the same effect on bond strength and adhesive failure pattern, regardless of the LED curing units used for photopolymerization.

Clinical performance of different bulk-fill composite resin systems in class II cavities: A 2-year randomized clinical trial.

This study evaluated the clinical performance of bulk-fill resin composite systems with different viscosities in class II cavities. A total of 80 class II restorations were performed with a single operator in 50 patients using four different bulk-fill resin composite materials: Filtek™ Bulk Fill, Heated Filtek™ Bulk Fill, G-ænial™ BULK Injectable, and SonicFill3. A double-blinded randomized clinical trial was designed to evaluate the two-year clinical performance of the four bulk-fill composite resins using modified FDI criteria. Data were analyzed descriptively. Level of significance was set at 0.05. Differences between groups were tested using Wilcoxon-signed-rank and Mann-Whitney-U test as nonparametric tests. Data were analyzed using Kruskal-Wallis, Mann-Whitney U, and Wilcoxon signed rank tests (p < 0.05). Eighty restorations were available for evaluation, with a survival function of 100%. No statistically significant differences were observed between the four groups regarding assessing esthetic, functional, and biological properties during different follow-up periods. After 2 years of clinical follow-up, the bulk-fill composite systems with different viscosities seem to be esthetically, functionally, and biologically acceptable, with a promising clinical performance in class II cavities.

Effect of ultra-fast high-intensity light-curing on the properties of a new bulk-fill restorative resin composite system: A Scoping Review.

This scoping review aims to analyze the impact of rapid high-intensity light-curing on a new bulk-fill resin-based composites (RBCs) designed for this type of polymerization. This scoping review was reported according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) and Joanna Briggs Institute Manual of Evidence Synthesis. The methods were registered on the Open Science Framework (<osf.io/pq57t>). The literature search was conducted in PubMed/MEDLINE, Embase, Web of Science, Scopus and Cochrane Library databases. Eligibility was considered for in vitro and clinical studies evaluating the effects of ultra-fast high-intensity light-curing on a new system of bulk-fill RBCs. Of 1.688 articles identified, 27 were included in the qualitative synthesis. All studies were conducted in vitro. A total of 2.432 specimens were evaluated. The studies have shown that shortness light-curing may result in similar properties (stress generated by polymerization shrinkage, marginal integrity, and bond strength to dental interface) for the new bulk-fill RBCs. Therefore, the new bulk-fill RBCs can be light-cured with a short exposure time and high intensity, providing a time-saving benefit in clinical practice, with similar results to standard light-curing in conventional composites, although, its use should be approached with caution in the flowable composite. Key words:Resin composites, polymerization, dental materials, review.

Polymer-induced liquid precursors: How are they being used and what is the effect on dentin remineralization? A scoping review

To identify the effectiveness of polymer-induced liquid precursors (PILP) on dentin remineralization and the assessment approaches used to evaluate remineralization. The analyses were done into six stages: (1) Identifying the research question; (2) Identifying the studies; (3) Selecting relevant studies; (4) Plotting the data; (5) Reporting results; and (6) Risk of bias. The searches were carried out in the following databases: PubMed, Web of Science, and Scopus. A total of 247 articles were identified in the electronic database search. After applying the eligibility criteria, only 12 articles were included for data extraction. The outcomes of dentin remineralization patterns were plotted in association to PILP agent type and application mode. The intrafibrillar mineralization occurred in 78% of studies where polyaspartic acid (pAsp) was used, and 50% when the polyacrylic acid (PAA) was used. All the studies where PILP was used in a restorative material (resin composite, glass ionomer, and adhesive system)—extra and intrafibrillar mineralization pattern was found. The association of PILP agents with other materials with potential for mineralization showed beneficial results in remineralization, since they provide a medium to high concentration of calcium and phosphate. The pAsp showed better results for interfibrillar remineralization when compared to PAA. The association with Ca/P release materials or solution Ca P are essentials for mineralization via PILP agent. Further studies are needed to assess the effectiveness of remineralization through PILP agents because the level of evidence of the studies was low.

Preparation of HNTs‐e‐POSS hybrid nanoparticles and modification of gallic acid epoxy resin

AbstractGallic acid is a renewable plant phenolic resource, and the polyphenolic bio‐based epoxy resin prepared from it can be used as a substitute for bisphenol A epoxy resin in certain fields. However, bio‐based epoxy resins used in the field of high‐performance composite material matrices often require modification. In this paper, firstly, γ‐(2,3‐epoxypropoxy)propyl trimethoxysilane (KH560) was used as the raw material to prepare epoxy‐based cage silsesquioxanes (E‐POSS). Then, E‐POSS was grafted onto γ‐aminopropyltriethoxysilane (KH550) modified halloysite nanotubes (m‐HNTs) to prepare a novel hybrid nanoparticle HNTs‐e‐POSS. Experimental analysis shows that ring opening reactions of amino and epoxy groups can occur between m‐HNTs and E‐POSS, forming a hybrid nanoparticle system of POSS aggregates on the surface of HNTs. Bio‐based nanocomposites were prepared by adding different mass fractions of hybrid nanoparticles HNTs‐e‐POSS into polyphenol type gallic acid epoxy resin matrix (GAER) and using methyltetrahydrophthalic anhydride as curing agent. The properties and micromorphology of the composite were analyzed and characterized. The research showed that with the addition of HNTs‐e‐POSS nanoparticles, the strength and toughness of the composite resin system show a pattern of first increasing and then decreasing, while the storage modulus(E′), glass transition temperature (Tg), and thermal stability of the composite material increased. Mechanical performance analysis shows that the introduction of 0.5 wt% HNTs‐e‐POSS would increase the tensile strength of the composite by 25.46%, while adding 0.75 wt% HNTs‐e‐POSS can increase the impact strength by 15%. The E′(30°C) increased by 24.2% and Tg increased by 7.7°C when the HNTs‐e‐POSS addition was 0.25 wt%.Highlights Prepared hybrid nanoparticle HNTs‐e‐POSS by grafting POSS onto the HNTs surface. Application of HNTs‐e‐POSS in modification of bio‐based gallic acid epoxy resin. HNTs‐e‐POSS can co‐cured with epoxy matrix to increase the crosslinking degree. The strength, toughness, and modulus of gallic acid epoxy resin are improved. Tg and thermal stability of gallic acid epoxy resin are enhanced.

Color Stability, Gloss Retention, and Surface Roughness of 3D-Printed versus Indirect Prefabricated Veneers.

The long-term color stability and surface properties of anterior laminate veneers are among the crucial factors affecting the clinical longevity of aesthetic restorations. Novel 3D-printed materials are being introduced as definitive restorative treatment. In light of the existing variety of indirect yet minimally invasive composite resin veneers, research on their surface properties is warranted. This in vitro study evaluated the effect of artificial aging by immersion in different staining solutions on the color changes, gloss, and surface roughness (Ra) of 3D-printed veneers compared to the prefabricated resin composite veneer systems (PRCVs) manufactured by Componeer and Edelweiss. Moreover, this study compared the effects of two methods for stain removal: repolishing with Sof-Lex disks and in-office bleaching with 40% hydrogen peroxide. The veneers (n = 24) were randomly divided according to the immersion solutions used, i.e., tea and coffee. Colorimetric measurements, surface roughness, and surface gloss were determined before and after staining and surface treatment with either in-office bleaching or surface polishing. The data were statistically analyzed using two-way ANOVA followed by the Tukey's post hoc test (α = 0.05). Artificial aging with immersion in staining solutions led to significant color changes, increased surface roughness, and gloss reduction in all materials (p < 0.05). The 3D-printed veneers showed higher ΔE values (coffee = 10.112 ± 0.141) and (tea = 10.689 ± 0.771) compared to baseline after 7 days of aging. The 3D-printed veneers had a statistically significant surface roughness Ra (0.574 µm ± 0.073). The gloss was >70% in all groups at baseline; these values dropped in all groups after 7 days of artificial aging. After the stain-removing procedures, the ΔE values decreased in all tested veneers. That being said, they failed to return to the baseline values, and both stain-removing methods were found to have an adverse effect on surface roughness and gloss retention in all tested veneers.

Is surface roughness of direct resin composite restorations material and polisher-dependent? A systematic review.

Direct resin composite bonding offers a highly esthetic, minimally invasive option for the treatment of anterior teeth however the challenge to improve their longevity remains. Direct resin composite restorations are limited by the risk of staining which may be influenced by the final surface roughness (Ra) of composite achieved. The purpose of this review is to investigate, using a systematic approach, whether the final surface roughness of anterior composite restorations is affected by the interaction between resin composite and polishing systems. The review was conducted by 3 independent reviewers and included articles published up to January 21, 2021. Three electronic databases were searched: Medline, Embase, and Web of Science. Studies assessing a quantitative effect of polishing methods on the Ra of direct composite resin materials published after the year 2000 and restricted to the English language were included. The database search for the effect of polishing systems on composite materials retrieved 125 eligible studies. Twelve duplicate records were removed. The resulting records were screened using title and abstract leading to 38 reports which were sought for retrieval. Application of eligibility criteria led to 11 studies included in the review. Hand searching of these studies yielded no additional papers. There is insufficient evidence to determine whether combination of composite and polisher influences final Ra. More research is required to determine if there is an optimum combination of polisher and composite. Polishing should be completed following planned finishing procedures. The approximation to the final surface and which finishing burs to use, if any, should be considered when planning a restoration. Durafill VS predictably achieves an acceptable Ra by different polishers.

The Effect of Blocker Application on Color Matching of Different Colored Composite Resin Systems.

To evaluate the effect of blocker on color matching of different shaded composite systems on natural teeth, 120 anterior teeth were divided into two groups as light and dark shades (n = 60). Round cavities (7 mm in diameter; 2 mm in depth) were prepared on labial surfaces of the teeth. They were restored using three types of resin composites: multi-shaded (Estelite Sigma Quick, Tokuyama Dental, Japan), single-shaded (Omnichroma, Tokuyama Dental, Japan) and group-shaded (Neo Spectra ST, Dentsply Sirona, Germany) (n = 20). Blocker (Omnichroma) was applied to half of the samples in each group (n = 10). Color matching of the restorations with the surrounding tissues were evaluated either by visual analysis or an instrumental method. The resin composites tested did not yield acceptable results instrumentally. Using blocker with single-shade resin composite on dark-colored teeth yielded a minimal change in color in 2 mm deep cavities in the visual evaluation by dentists. Similarly, applying blocker with group-shaded and multi-shaded resin composite on light-colored teeth caused minimal change in color of 2 mm deep cavities in the visual evaluation by dentists. As the application of blocker had no effect on the color matching of different shaded resin composites in the visual evaluations by all observers, except by dentists, blocker may be used as a dentin shade in 2 mm deep cavities of anterior teeth.

Assessment of Intra-Oral Repair Systems for Veneered Zirconia and Zirconia Only.

The aim of this study was to compare bond strength resin composites to porcelain laminate veneers in the indirect repair method to composite resins used in the direct repair method for cases of porcelain veneer fracture of zirconia-based fixed dental prostheses. In the study, the groups were formed with different percentages of areas to be repaired to mimic porcelain fractures in the mouth. The experimental group of veneered zirconia were as follows: Group A = 100% Zr surface; Group B = 70% Zr, 30% porcelain surface; Group C = 50% Zr, 50% porcelain surface; Group D = 30% Zr, 70% porcelain surface; Group E = 100% porcelain surface. The repairs of the specimens were made using composite resin systems in half of the groups and using porcelain laminate veneers in the other half. Specimens were embedded in acrylic blocks before surface treatments and repairs were applied. After surface conditioning, laminate veneers were applied to the first half of the groups, and composite repair systems were applied to the second half of the groups. After all specimens were aged by thermal cycling, their bond strength values were measured using a Universal Testing Machine, and the obtained data were recorded. The specimens were examined with a stereomicroscope and classified according to failure types (adhesive/cohesive/mixed). Bond strength values were evaluated based on independent-samples t-test statistics. According to the comparisons among the groups, the bond strength of the indirect repairs made with the laminate material was higher than the bond strength of the repairs made with the composite. There was a statistically significant difference in favor of the indirect repair groups among all groups except for Group C. The highest bond strength was found in Group A in the indirect repair method, while the lowest bond was found in the direct repair method in Group E. Adhesive failure was mostly seen in the groups that were repaired with the composite.

The Effect of Pre-Heating on Fracture Toughness in Three Distinct Composite Resin Systems at Two Different Temperatures: A Protocol for an In-vitro Study

Introduction: Composite resins are considered the pinnacle of esthetic restorations, but they have their own disadvantages, such as polymerization shrinkage, low fracture toughness, and the formation of microcracks, all of which eventually results in failure of the restoration. Fracture toughness is an important factor for failure. Warming the same composites to certain temperatures will show drastic improvements in the abovementioned flaws, especially the fracture toughness. Need for the study: Therefore, the objective of this study is to evaluate and compare the fracture toughness of three different types of composite resin systems at two different pre-heating temperatures. The study aims to provide valuable information to clinicians in choosing the most appropriate restorative material for posterior composite restorations, which can ultimately improve the treatment's success rate and reduce the risk of complications such as secondary caries, postoperative sensitivity and ultimately restoration failure. Objective: In summary, this study will compare and evaluate the fracture toughness of nanohybrid, micro-hybrid, and bulkfill composite resins pre-heated at 50 degrees Celsius and 60 degrees Celsius. Methodology: The methodology involves dividing 72 freshly extracted premolars with intact occlusal anatomy and fully developed apical foramina into three main groups based on three different composites and further dividing each group into two sub-groups based on two different pre-heating temperatures, with 12 teeth in each group. Each tooth will then be prepared with a Class-II Mesio-Occlusal-Distal (MOD) cavity and receive pre-heated composite restoration according to its assigned group and sub-group. The prepared samples will be tested for fracture toughness using a universal testing machine.

An In-depth Analysis of the Effects of Preheating Three Different Composite Resin Systems at Two Different Temperatures on Their Microhardness

Abstract Background: Composite restorations often have inferior physical properties compared to natural enamel and dentin, leading to early failure. Preheating the traditional composite before its placement and curing seems to enhance all its physical characteristics magically. The objective of the current research was to assess the impact of preheating on the surface microhardness of commonly used composite resin materials, specifically FILTEK P60, FILTEK Z250XT, and Tetric-N-Ceram Bulk fill. Materials and Methods: The resin composite tubes were either left at the ambient room temperature (24°C ± 1°C) or preheated in a commercial preheating device to 50°C and 60°C for 40 min. By inserting uncured preheated composite resin into class II Mseio-Occluso-Distal (MOD) cavities with specifications of 2 ± 0.3 mm axial height, 2 ± 0.3 mm pulpal depth, parallel proximal walls with a 3 ± 0.3 mm buccolingual width, 1.5 ± 0.3 mm gingival width, and an occlusal isthmus width equal to one-third of the intercuspal distance from composite resin tubes, a total of 99 class II MOD cavities on premolars were established. Each specimen’s Vicker’s hardness number (VHN) was determined. The gathered information was examined utilizing a two-way ANOVA and Tukey’s post hoc test with a significance threshold of 0.05. Results: When preheated to the temperatures of 50°C and 60°C, a remarkable rise in the mean Vickers hardness numbers (VHNs) of all the resin composites compared to those maintained at the room temperature (P &lt; 0.05) was seen. The mean VHNs at the room temperature for FILTEK P60, FILTEK Z250XT, and Tetric-N-Ceram were 47.27 ± 9.08, 59.63 ± 1.56, and 75.69 ± 0.80, respectively, with a significant variation between all of them (P &lt; 0.05). The mean VHNs were, respectively, 108.45 ± 2.42, 103.45 ± 1.29, and 113.00 ± 4.35 at 50°C, with a significant variation between them all. At 60°C, the mean VHNs were, respectively, 121.09 ± 1.30, 128.00 ± 0.89, and 135.00 ± 2.04, with a significant variation between all of them (P &lt; 0.05). Conclusion: The surface microhardness of all investigated composite resins was greatly increased by preheating, with Tetric N-Ceram Bulk Fill showing the greatest value at a preheating temperature of 60°C.

Clinical study of different composite resin systems in Class I cavities (an 18-month randomized clinical trial)

Clinical study of different composite resin systems in Class I cavities (an 18-month randomized clinical trial)

Marginal integrity of composite resin restoration in class I cavities prepared by hydro-abrasion

Aim To evaluate and compare the marginal integrity of composite resin restorations made by two different preparation techniques: conventional drill and hydro-abrasion. Materials and methods Forty extracted human premolars with simple occlusal caries were used. The teeth were fixed with sticky wax to the base of plastic cylinder. The cylinder was filled with self-curing acrylic resin so that only root was embedded within the self-curing acrylic resin. The teeth were randomly divided into two main groups (n = 20) according to the preparation technique. Group I: class I cavity preparation was done by the conventional drill method using a #245 Carbide bur and contra angle high-speed hand piece with water coolant. Cavity design was restricted to remove caries with no undercuts, and no beveling. Group II: class I cavity preparation was done by Aquacut Quattro air hydro-abrasion unit which uses a gamma irradiated aluminum oxide particle as abrasives (29 μm), cutting fluid and a hand piece of 0.6 mm diameter tip. The preparation in both groups was restored by the same composite resin (Grandio) and adhesive systems (Futurabond U) following the manufacturer's instructions. All specimens were thermocycled. Impressions for each tooth was made using a polyvinyl Siloxane material. The impressions were then poured with epoxy resin. These replicas were examined under scanning electron microscope. Scanning electron microscope photographs of tested samples were used for the gap evaluation. Results It was found that, group I recorded higher mean value of marginal gap length (157.57 ± 35.15 μm) than group II that recorded (69.55 ± 20.02 μm). Also, group I recorded higher mean value of marginal gap length ratio (10.72 ± 2.47) than group II that recorded (7.44 ± 2.69). Conclusion Conventional drilling technique was faster than the hydro-abrasion technique for cavity preparation. Hydro-abrasion technique showed more marginal adaptation than conventional drilling technique.

Visible-light-excited long-lived organic room-temperature phosphorescence of phenanthroline derivatives in PVA matrix by H-bonding interaction for security applications

Organic room-temperature phosphorescence (RTP) materials are very attractive, but there is still a challenge to achieve RTP for their practical applications under visible light excitation (λ > 400 nm) because of the implement for the most organic RTP is under ultraviolet light. Herein, a simple tactics for inhibiting the vibrational dissipation of three amorphous phenanthroline derivatives by doping them into polyvinyl alcohol (PVA) matrix was utilized to afford visible-light excitation RTP. By using this method, on account of the mutual H-bonding and confinement effect with PVA matrix, a series of organic RTP materials with blue-green phosphorescence emission were obtained under visible-light excitation. The afterglow colors of RTP materials can be adjusted by co-doping the available fluorescence dyes (RhB or Rh6G) into the PVA films through a triplet-to-singlet Förster resonance energy transfer. However, the H-bonding is easily broken by water molecules resulting in the RTP phenomenon disappears. Hence, Aphen-epoxy resin composite system was constructed to overcome this drawback. It is shown that the composite still has good phosphorescence properties after soaking in water for 7 days. The superior RTP of the amorphous phenanthroline derivatives in processable polymer matrices endows these materials with a highly potential for the night warning clothing coating and information encryption.

Clinical Study of Different Composite Resin Systems in Class I Cavities

Clinical Study of Different Composite Resin Systems in Class I Cavities

The Blending Effect of Single-Shade Composite with Different Shades of Conventional Resin Composites-An In Vitro Study.

Single-shade composite systems are gaining popularity among clinicians due to the claimed potential of blending with different tooth structure shades while restoring the tooth. The purpose of this study was to evaluate the blending effect of two single-shade composite with different shades of conventional resin composite systems. Seventy-two composite cylinders of B1, B2, A1, A2, A3, or A3.5 shade from CharmFil Plus (CP) and Filtek Universal Restorative (3M) were prepared using custom-made silicone mold. Single-shade composite OMNICHROMA (OC) or Beautifil II Enamel (BE) was placed in the center of each cylinder and polymerized. The color parameters, lightness (L*), chroma (C*), and hue (H*) of each composite were measured using a color chronometer. Furthermore, color stability of the samples was evaluated after 1-week staining challenge. Multivariant analysis was performed to evaluate the effect of material and shade on the color parameters. Multiple comparisons of the data were performed using post hoc test. The staining challenge data were analyzed using repeated measure analysis of variance and paired sample T-test. The multivariant analysis showed a statistically significant difference in color parameters among CP, 3M, OC, and BE (p = 0.001). Image analysis showed a visual blending effect for both OC and BE for certain shades; however, some color contrast with the darker shades was observed. The C* value of OC showed a similar pattern to CP; however, the H* of the latter was closely followed by BE. The L* value showed statistically significant difference among the shades of 3M, and in OC and BE when blended with 3M. All four materials used in this study showed color alteration after the staining challenge. Single-shade composite can blend with only certain shades of resin composites.

Coverage error of three resin composite systems to vital unrestored maxillary anterior teeth.

Define the color of anterior teeth of a selected population and correlate it (by using coverage error [CE] and the frequency of best match) with the final color of all possible enamel-dentine combinations of three different resin composite systems. Color of 636 vital unrestored anterior teeth (central incisors, lateral incisors and canines; n=212) and disk specimens (12 mm diameter, varying thickness) corresponding to enamel-dentin combinations of all available enamel (0.5 mm and 1.0 mm thickness) and dentin shades (3.0 mm thickness) of Essentia, Enamel Plus HRi and IPS Empress Direct composite systems was measured using a clinical dental spectrophotometer (Spectroshade Micro). CE and frequency of best match for all composite systems were calculated for the measured in-vivo teeth color space. Natural in-vivo teeth exhibit higher lightness when compared to enamel-dentin composite combinations, independently of the enamel thickness used. The best (lowest) CE was found for IPS Empress, while the highest values were found for Enamel Plus Hri independently of tooth type and enamel thickness (p < 0.001). The use of 0.5 mm instead of 1.0 mm enamel thickness within enamel-dentin composite combinations resulted in a lower CE for in-vivo tooth color (p < 0.001). The color space defined by all possible enamel-dentin combinations of the studied resin composite systems does not fully match the color range of anterior teeth. All composite systems examined lack combinations with lightness values as high as the population's. IPS Empress Direct composite system represented better the in-vivo teeth color. The use of 0.5 mm enamel shade thickness is suggested when building layered restorations, as it provided better color coverage than using 1.0 mm thickness.

Effect of C-factor on Micro-tensile Bond Strength of Bulk fill V/S Micro-hybrid Composite in Class II Restorations - An In-Vitro Study.

High Configuration factor (C-factor) results into increased polymerization shrinkage causing stress at resin-dentin interface leading to failure of the restoration. The purpose of this study was to evaluate the effect of C-factor on micro-tensile bond strength (μTBS) of bulk fill composites in class-II cavities when restored in 4mm of bulk as compared to conventional composite. A total of 90 carious, crack free extracted human mandibular permanent molars were selected and randomly divided into 3 groups (n=30). On all samples, class II cavities (3.5X 3.5cm) were made by single operator and divided as Gp1 (2.5mm), Gp2 (4mm), and Gp3 (6mm) on the basis of depth of cavities. Sampling units of 30 in each group were further randomly subdivided into 3 subgroups (n=10 each subgroup), according to the type of composite resin systems to be used for restoration. Experimental Subgroup includes SubGp1 restored with SDR Surefil (Dentsply, caulk, USA) and SubGp2 restored with Sonic fill (kerr, orange, CA, USA), whereas SubGp3 restored with FILTEK Z250 served as control. After storage in water at 37◦C, the teeth were sectioned perpendicular to the restorative tooth interface as 1×1 mm non-trimmed rectangular micro-specimens for micro-tensile bond strength (μTBS) testing. Beams (n=30 max) from each SubGp were fixed to a metal jig and subjected to micro-tensile bond strength testing. The data collected for micro-tensile bond strength (expressed in Mpa) were statistically analysed using one way ANOVA and Tukey's post hoc test. In class II cavities with high C-factor, SDR Surefil showed better μTBS than SonicFill and micro-filled composite when filled in bulk of 4mm, as compared to micro-hybrid composite filled incrementally. There is no effect of high C-factor on μTBS of tooth restored with both SDR Surefil and Sonic Fill in class II cavities as compared to microhybrid composites.

Immediate bond performance of resin composite luting systems to saliva-contaminated enamel and dentin in different curing modes.

The purpose of this study was to evaluate the immediate shear bond strength of resin composite luting systems to tooth with or without saliva contamination in different curing modes. The Knoop hardness number of the resin composite luting agents was measured. Four combinations of resin composite luting systems were used. The shear bond strength to bovine teeth was measured with and without saliva contamination in different curing modes at different storage periods. The Knoop hardness number of the resin composite luting agents was also evaluated. Significantly lower enamel and dentin shear bond strengths and Knoop hardness number values were observed in all resin composite luting systems at 5min versus 24 h, regardless of the curing mode or saliva contamination. The influence of the curing mode of the resin composite luting systems on shear bond strengths and Knoop hardness number was dependent on material. For the saliva contamination conditions, only G-CEM ONE EM did not show any significant difference in shear bond strength among the groups with and without saliva contamination, regardless of curing mode, storage period, or tooth substrate. All the resin composite luting systems showed lower shear bond strengths and Knoop hardness number values immediately after setting.