Effect of various surface coating methods on surface roughness, micromorphological analysis and fluoride release from contemporary glass ionomer restorations.

OBJECTIVE: To evaluate the effect of various surface coating methods on surface roughness, micromorphological analysis and fluoride release from contemporary resin-modified and conventional glass ionomer restorations. MATERIALS & METHODS: A total of 72 permanent human molars were used in this study. The teeth were randomly assigned into 2 groups according to type of restorative materials used; resin modified glass ionomer cement and conventional glass ionomer (SDI Limited. Bayswater Victoria, Australia). Each group was subdivided into 3 subgroups according to the application of coat material; Sub-group1: without application of coat; Sub-group2: manufacturer recommended coat was applied and sub-group3: customized (vaseline) coat was applied. Each group was then subdivided into two divisions according to the time of testing; immediate (after 24 h) and delayed (after 6 months of storage). Three specimens from each sub-group were selected for surface roughness test (AFM) and another 3 specimens for the micromorphological analysis using scanning electron microscope (SEM). For the fluoride release test, a total of 60 cylindrical discs were used (n = 60). The discs were randomly split into 2 groups according to type of restorative materials used (n = 30); resin modified glass ionomer cement and conventional glass ionomer. Each group was subdivided into 3 subgroups (n = 10) according to the application of the coat material; Sub-group1: without application of coat; Sub-group2: with the manufacturer recommended coat and sub-group3: with application of customized (vaseline) coat. Data for each test was then collected, tabulated, were collected, tabulated, and tested for the normality with Shapiro-Wilk test. Based on the outcome of normality test, the significant effects of variables were assessed using appropriate statistical analysis testing methods. RESULTS: Regarding the data obtained from surface roughness test, Shapiro-Wilk test showed normal distribution pattern of all values (p > 0.05). Accordingly, Two-way ANOVA outcome showed that the 'type of restoration' or 'test time' had statistically significant effect on the AFM test (p < 0.05). Regarding Fluoride specific ion electrode test 2-way ANOVA followed by Least Significant Difference (LSD) Post-hoc test revealed significant difference among the groups (p < 0.05). It showed that SDI GIC group after 14 days of measurement had the highest mean of fluoride release (36.38 ± 3.16 PPM) and SDI RMGIC after 30 days of measurement had the second highest mean of fluoride release (43.28 ± 1.89 PPM). Finally, regarding the micromorphological analysis using SEM, a slight difference was observed between the studied groups. CONCLUSIONS: Based on the results of this study, various coatings enhance surface roughness in the initial 24 h of restoration insertion. Different coat types seems that have no influence on fluoride release and the micromorphological features of the restoration/dentin interface.

Clinical performance of two ion-releasing bulk-fill composites in class I and class II restorations: A two-year evaluation.

OBJECTIVES: This randomized clinical trial evaluated and compared the 2-year clinical performance of two ion-releasing bulk-fill composites (Cention N and Surefil One) with that of a conventional bulk-fill resin composite (Powerfil) in Class I and II cavities. METHODS: Thirty-two patients, each with 3 Class I and/or Class II cavities under occlusion, were enrolled in this trial. A total of 96 restorations were placed, 32 for each material, as follows: a self-adhesive composite; Surefil-one, alkasite; Cention N, and a bulk-fill resin composite; Powerfil. The restorations were placed by a single operator. Clinical evaluation was performed at baseline (1-week), 6-months, 1-year, and 2-years by two independent examiners using the FDI criteria. Intergroup and intragroup comparisons were analyzed using the Kruskal-Wallis and Friedman Tests. Multiple comparisons between groups were analyzed using the Mann-Whitney and Wilcoxon-rank tests. The level of significance was set at α = 0.05. RESULTS: Twenty-seven patients with a total of 81 restorations were evaluated at the end of the 2-years with 84.35% recall rates. Clinical success rates were 100%, 100%, and 96.3% for Powerfil, Surefil-one, and Cention N, respectively. Cention N showed a statistically significant (p < 0.05) decreased marginal integrity in comparison with resin composite at the 2-year evaluation. No recurrent decay was detected in any restoration. CONCLUSIONS: Both ion-releasing bulk-fill composites provided acceptable clinical performance similar to bulk-fill composite in Class I and II restorations over a 2-year period. CLINICAL RELEVANCE: The results of this trial suggests that there is a promising evidence supporting the use of ion-releasing composites.

Clinical evaluation of subgingival open sandwich restorations: 3-year results of a randomized double-blind trial.

OBJECTIVES: To provide a 3-year follow-up of previously treated patients to assess and compare the periodontal responses and clinical performance of proximal subgingival open sandwich restorations. MATERIALS AND METHODS: Ninety-five adults participated in the study, with a combined total of 120 compound Class II cavities. These cavities had gingival margins located below the CEJ. Four different restorative materials were used to elevate the dentin/cementum gingival margins of the cavities: resin-modified glass ionomer, glass hybrid, flowable bulk-fill composite, or ion-releasing material, which were then completed with the same overlaying composite. Different periodontal and clinical evaluations, based on the criteria set by the World Dental Federation (FDI) criteria, were performed at different time intervals, including baseline, 6 months, 1, 2, and 3 years. RESULTS: The type of base material did not affect the periodontal evaluations. There were no statistically significant differences between different time intervals or base material groups in any of the evaluated FDI parameters. However, the ion-releasing material scored significantly worse in the radiographic evaluation than any of the other groups. CONCLUSIONS: All tested materials are suitable for proximal subgingival open sandwich restorations, as long as the restoration/tooth margin is at least 2-mm away from the bone crest. CLINICAL SIGNIFICANCE: Clinicians can confidently choose any of the tested materials for proximal subgingival open sandwich restorations, as they have shown good outcomes from both periodontal and clinical perspectives.

Periodontal Evaluation of Subgingival Open Sandwich Restorations: 2-Year Results of a Randomized Double-Blind Trial.

This study aimed to evaluate the periodontal responses of subgingival proximal margins elevated using different restorative materials. A total of 120 proximal cavities with dentin/cementum gingival margins were elevated using one of four materials (resin-modified glass ionomer, glass hybrid, flowable bulk-fill resin composite, or bioactive ionic resin) and completed with the same overlaying resin composite. At 2 weeks (baseline), 6 months, 1 year, and 2 years postrestoration, periodontal parameters and the radiographic distance between the restoration margin and bone crest were evaluated. Appropriate statistical analyses were performed. The values of all periodontal parameters increased with time, although only the increases in Plaque Index and probing depth within each material group were statistically significant. There were no statistically significant differences in any of the periodontal parameters between the different materials within the same evaluation period, nor between different time points or material groups in the radiographic distances. Both glass ionomer-based and resin-based materials were periodontally safe as subgingival open sandwich restorations.

Inhibition of Caries around Restoration by Ion-Releasing Restorative Materials: An In Vitro Optical Coherence Tomography and Micro-Computed Tomography Evaluation.

The objective of this study was firstly to assess the demineralization inhibitory effect of ion-releasing restorations in enamel adjacent to restoration using a biofilm caries model and secondly to compare the effect to that in a chemical caries model. Fifty-six bovine incisors were filled with either Surefil one (SuO), Cention N (CN) (both ion-releasing materials), Ketac-Molar (GIC) or Powerfill resin composite (RC). The restored teeth were then randomly divided into 2 groups according to the used caries model (biofilm or chemical caries model). The micro-computed tomography (MicroCt) and optical coherence tomography (OCT) outcome measures used to evaluate demineralization inhibition effects were lesion depth, LD and increase in OCT integrated reflectivity, ΔIR, at five different depths. It was observed that all outcome measures of CN were statistically the same as those of GIC and conversely with those of RC. This was also the case for SuO except for LD, which was statistically the same as RC. When comparing the two caries models, LD of the biofilm model was statistically deeper (p < 0.05) than the chemical model for all four materials. In conclusion, CN and SuO have similar demineralization inhibitory effects as GIC, and the biofilm caries model is more discriminatory in differentiating demineralization inhibitory effects of ion-releasing restorative material.

In vitro elemental and micromorphological analysis of the resin-dentin interface of bioactive and bulk-fill composites.

PURPOSE: To evaluate the bonding interface and the remineralization potential of a bioactive restorative material on demineralized dentin compared to a conventional bulk-fill resin composite restoration. METHODS: Twelve caries-free human molars were used in this study. Specimens were randomly divided into two groups according to the type of restorative material used (n=12); an injectable resin-modified glass-ionomer restorative [Activa BioActive-Restorative (ABR) ] and a bulk-fill composite [3M Filtek One Bulk Fill Restorative, (BFC) ]. Each restored specimen was sectioned in two semi-equal halves along the long axis of the teeth perpendicular to the resin dentin interface with a water-cooled diamond disk at low speed. The restoration-dentin interfaces were scanned under SEM to observe micromorphological analysis; then an elemental analysis of the interface was performed using an energy dispersive X-ray (EDX) spectroscopy. RESULTS: Quantitative data were described using median (minimum and maximum) after testing normality using the Shapiro-Wilk test. Mann-Whitney U test was used to compare the BFC and ABR. Higher mean values of Ca were identified and related to the ABR material, which provided more Ca ions than BFC. The comparison of Ca and P between materials showed a significant difference in the amount of Ca provided by ABR versus BFC. ABR restorations presented a thicker, and superior remineralization interface compared to the bulk-fill resin composite. CLINICAL SIGNIFICANCE: Activa BioActive Restorative restorations presented a thicker and superior remineralization interface compared to the bulk-fill resin composite.

Periodontopathic bacterial adhesion to different restorative materials used to elevate proximal subgingival margins.

This study compared the periodontopathic bacterial adhesion to four restorative materials used for deep margin elevation at 2, 24, and 48-h after incubation. Discs were produced from four restorative materials: resin modified glass ionomer, glass hybrid, flowable bulk fill resin composite, and bioactive ionic resin. Root dentin was used as control. Specimens were coated with saliva and used to culture a biofilm comprised of three strains of periodontopathic bacteria; Porphyromonas gingivalis, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans. Bacterial adherence was assessed by colony count assay, crystal violet staining, and visualized using confocal laser scanning microscopy. Data were analyzed by two-way ANOVA followed by Tukey's post hoc tests. The adhesion values for the control specimens were significantly higher than for other materials, while those for the flowable bulk fill were significantly lower than for any other material within all evaluation assays. The 2-h incubation period showed the lowest adhesion values regardless of the group. The 48-h adhesion values were higher than the 24-h results in all groups except the flowable bulk fill. Microscopic imaging partially supported the findings of the measurements. In terms of periodontopathic bacterial adhesion, the tested flowable bulk fill may be preferable for subgingival use over other tested materials.

Correlation between different methodologies used to evaluate the marginal adaptation of proximal dentin gingival margins elevated using a glass hybrid.

Objectives: This study aimed to evaluate the effect of aging on the marginal quality of glass hybrid (GH) material used to elevate dentin gingival margins, and to analyze the consistency of the results obtained by 3 in vitro methods. Materials and Methods: Ten teeth received compound class II cavities with subgingival margins. The dentin gingival margins were elevated with GH, followed by resin composite. The GH/gingival dentin interfaces were examined through digital microscopy, scanning electron microscopy (SEM) using resin replicas, and according to the World Dental Federation (FDI) criteria. After initial evaluations, all teeth were subjected to 10,000 thermal cycles, followed by repeating the same marginal evaluations and energy dispersive spectroscopy (EDS) analysis for the interfacial zone of 2 specimens. Marginal quality was expressed as the percentage of continuous margin at ×200 for microscopic techniques and as the frequency of each score for FDI ranking. Data were analyzed using the paired sample t-test, Wilcoxon signed-rank test, and Pearson and Spearmen correlation coefficients. Results: None of the testing techniques proved the significance of the aging factor. Moderate and strong significant correlations were found between the testing techniques. The EDS results suggested the presence of an ion-exchange layer along the GH/gingival dentin interface of aged specimens. Conclusions: The marginal quality of the GH/dentin gingival interface defied aging by thermocycling. The replica SEM and FDI ranking results had stronger correlations with each other than either showed with the digital microscopy results.

Effect of different surface treatments on resin-matrix CAD/CAM ceramics bonding to dentin: in vitro study.

BACKGROUND: Evaluating the effect of different surface treatment methods on the micro-tensile bond strength (µTBS) of two different resin-matrix computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics (RMCs). METHODS: A standardized inlay preparations were performed on 100 intact maxillary premolars. According to the type of the restorative material, the teeth were randomly divided into two equally sized groups (n = 50): (polymer-infiltrated ceramic (Vita Enamic) and resin-based composites (Lava Ultimate)). The inlays were fabricated using CAD/CAM technology. In each group, the specimens were randomly assigned to five subgroups (n = 10) according to the surface treatment method: group 1 used was the control group (no surface treatment); group 2, was treated with air abrasion with 50 µm Al2O3 (A) and universal adhesive (UA); group 3, was treated with air abrasion with 50 µm Al2O3 (A) and silane coupling agent (S); group 4, was treated with hydrofluoric acid (HF) and universal adhesive (UA) and group 5, was treated with Hydrofluoric acid (HF) + silane coupling agent (S). The inlays were then cemented to their respective preparations using dual-cure self-adhesive resin cement (RelyX U200, 3 M ESPE) according to the manufacturer's instructions. The µTBS test was conducted in all groups, and stereomicroscope and scanning electron microscope were used to inspect the failure mode. The data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey's post-hoc multiple comparison tests at a significance level of p < 0.05. RESULTS: Surface treatments significantly increased the µTBS of the materials compared to the control group (p < 0.05). For CAD/CAM RBCs, the µTBS value highest in group 2 whereas, for PICN, the µTBS value was highest in group 3. Cohesive failure of CAD/CAM restorative material was the most predominant mode of failure in all treated groups, whereas adhesive failure at restoration-cement interface was the most predominant failure mode in the control group. CONCLUSION: Surface treatments increase the µTBS of resin-matrix CAD/CAM ceramics to tooth structure. Air abrasion followed by universal adhesive and hydrofluoric acid followed by silane application appears to be the best strategies for optimizing the bond strength of CAD/CAM RBCs and PICN respectively.

Secondary caries and marginal adaptation of ion-releasing versus resin composite restorations: a systematic review and meta-analysis of randomized clinical trials.

This systematic review was aimed to evaluate occurrence of secondary caries and marginal adaptation in ion-releasing materials versus resin composite. Electronic search of PubMed, Scopus, and Open Grey databases with no date or language restrictions until May 21st, 2021, was conducted. Randomized clinical trials that compared ion-releasing restorations versus resin composite were included. For quantitative analysis, a random-effects meta-analysis with risk difference as an effect measure and a 95% confidence interval was used. Quality of evidence was assessed using The Grading of Recommendations, Assessment, Development, and Evaluation criteria. The risk of bias was evaluated using the Cochran Collaboration Risk of Bias tool. The inclusion criteria were met by 22 studies, and 10 studies were included in the meta-analysis. Three follow-up periods (1 year, 18 months-2 years, and 3 years) were evaluated. The overall quality of evidence for secondary caries and marginal adaptation outcomes was low. The results of the meta-analysis showed no significant difference (p > 0.05) in both outcomes between ion-releasing materials and resin composite. The occurrence of secondary caries was not dependent on the nature of the restorative material. It is more likely a complex process that involves the same risk factors as primary carious lesions.

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

Background: There 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 Methods: Fifty 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. Results: Both 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. Conclusions: In 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.

Clinical performance of resin-matrix ceramic partial coverage restorations: a systematic review.

OBJECTIVE: To evaluate clinical performance of the new CAD/CAM resin-matrix ceramics and compare it with ceramic partial coverage restorations. MATERIALS AND METHODS: An electronic search of 3 databases (The National Library of Medicine (MEDLINE/PubMed), Scopus, and the Cochrane Central Register of Controlled Trials) was conducted. English clinical studies published between 2005 and September 2020 that evaluated the clinical performance of CAD/CAM resin-matrix ceramics inlays, onlays, or overlays were selected. The primary clinical question was applied according to PICOS strategy (Population, Intervention, Comparison, Outcome, Study design). The included studies were individually evaluated for risk of bias according to the modified Cochrane Collaboration tool criteria. RESULTS: A total of 7 studies were included according to the established inclusion and exclusion criteria. From the included studies, 6 were randomized clinical trials while one study was longitudinal observational study without control group. According to the results of the included studies, the success rate of CAD/CAM resin-based composite ranged from 85.7 to 100% whereas the success rate reported for ceramic partial coverage restorations ranged from 93.3 to 100%. Fractures and debondings are found to be the most common cause of restorations failure. CONCLUSION: CAD/CAM resin-based composite can be considered a reliable material for partial coverage restorations with clinical performance similar to glass ceramic restorations. However, this result needs to be confirmed in long-term evaluations. CLINICAL RELEVANCE: CAD/CAM resin-based composites provide a potential alternative to ceramic indirect restorations. However, clinicians must be aware of the lake of knowledge regarding long-term outcome.

Indirect Resin Composite Inlays Cemented with a Self-adhesive, Self-etch or a Conventional Resin Cement Luting Agent: A 5 Years Prospective Clinical Evaluation.

OBJECTIVE: The aim of this study was to clinically evaluate the 5-years clinical performance of indirect resin composite inlays luted with three different resin cement strategies in MOD Class II restorations. MATERIALS AND METHODS: A randomized clinical trial was conducted following CONSORT guidelines. Forty patients with three large cavities indicated for indirect MOD Class II restorations were enrolled in the current study. Then, 120 indirect resin composite inlay restorations (SR Nexco) were placed and luted with three different resin cement strategies (n=40); an etch-and-rinse (Variolink N), self-etch (Panavia F2.0) and self-adhesive (RelyX Unicem). These restorations were evaluated to the periods of 1 week (baseline), 1, 3 and 5 years using modified USPHS criteria. Statistical analyses were performed with Wilcoxon and Friedman tests with level of significance set at 0.05. RESULTS: The outcome of the clinical trial showed that, there was neither loss of restorations nor recurrent caries after 5 years for all luting cements groups. Both self-etch Panavia F2.0 and self-adhesive RelyX Unicem resin cements exhibited significant differences between the evaluation periods regarding to marginal discoloration and marginal adaptation (p=0.03). At baseline, only 8 cases of etch-and-rinse (Variolink N) resin cement group exhibited post-operative sensitivity which were relieved after short time (p=0.04). CONCLUSION: All the three resin cement strategies tested, showed acceptable clinical performance after 5-years recall period. In time, etch-and-rinse resin cement group showed better clinical performance regarding marginal discoloration and marginal adaptation at 5-years recall period. Clinical Relevance statement:In vitro and in vivo studies reveal contradictory evidence of the clinical performance of indirect resin composite inlays luted with different resin cement strategies. Thus, this study revealed that etch-and-rinse resin cement still has the best prognosis for adhesive luting of indirect resin composite inlays.

Influence of material type, thickness and storage on fracture resistance of CAD/CAM occlusal veneers.

OBJECTIVES: The present study aimed to evaluate the effect of restoration thickness, CAD/CAM material, and 6 months of artificial saliva storage on the fracture resistance of occlusal veneers. MATERIALS AND METHODS: A total of 84 intact maxillary molars were sectioned 4.0 mm occlusal to the cementoenamel junction to expose the dentine. The teeth were assigned into 3 main groups according to the type of restorative material (e.max CAD, Vita Enamic, and Lava Ultimate). In each group, the teeth were allocated into 2 subgroups (n = 14) according to restoration thickness (1.0 and 1.5 mm). The veneers were adhesively bonded using dual-cure self-adhesive luting agent. A total of 42 specimens comprising half the tested subgroups were stored in distilled water for 24-h before the test. The remaining half was stored in artificial saliva at 37 ± 1 °C in an incubator for 6 months. All specimens (n = 84) were subjected to 5000 thermal cycles between 5 and 55 °C ± 2 before the fracture resistance test. The maximum force at fracture was recorded in Newton. Failure mode was analyzed using a stereomicroscope. The results were analyzed using a parametric Three-way ANOVA test. RESULTS: The results of the Three-way ANOVA test revealed that material type and restoration thickness significantly affected fracture resistance values (p < 0.5), while 6 months of storage in artificial saliva had no significant effect on mean fracture resistance values (p˃0.5). The most common failure patterns in CAD/CAM resin composite and polymer-infiltrated ceramics were scores I and score II. For glass ceramic groups, score IV and III were more dominant. CONCLUSIONS: All the tested CAD/CAM restorations in both thicknesses exhibited fracture resistance values exceeding normal and parafunctional bite forces. Polymer-infiltrated ceramics and CAD/CAM resin composite veneers showed more favorable fracture patterns.

Effect of Different Polishing Systems on the Surface Roughness and Gloss of Novel Nanohybrid Resin Composites.

OBJECTIVES: To evaluate the surface roughness and gloss of three nanohybrid resin composites after polishing with three different polishing systems. MATERIALS AND METHODS: A total number of 112 disc specimens (10 × 3 mm) were prepared from nanohybrid-Empress Direct (ID), Grandio (GR), Filtek Z350 (Z350) and a microhybrid resin composite restorative materials-Filtek Z250 (Z250). Following 24-hour storage in 37°C distilled water, each composite group (n = 28) was assigned into four groups (n = 7) according to finishing/polishing (F/P) system: Mylar strip, Optrapol, Politip, and Sof-Lex (SL). The surface roughness (Ra, mm) was measured by a novel three-dimensional method using an image analysis software attached to an environmental scanning electron microscope. A glossometer was used to measure the surface gloss. RESULTS: Statistical analysis used was ANOVA test. Two-way Anova test revealed that the "type of composite" and "F/P techniques" had a significant effect on both surface roughness and gloss of the tested resin composite materials (p < 0.05). Tukey's post hoc test showed that ID, GR, and Z350 revealed lower surface roughness and higher surface gloss than Z250 within the same polishing system (p < 0.05). Sof-Lex polishing discs produced the lowest surface roughness and highest surface gloss values compared with Optrapol and Politip (p < 0.05). CONCLUSION: The tested F/P systems provided comparable surface roughness and gloss for nanohybrid composites. The Sof-Lex system provided the best surface roughness and gloss for nanohybrid composites.

Fracture resistance of CAD/CAM occlusal veneers: A systematic review of laboratory studies.

OBJECTIVE: The purpose of this systematic review was to summarize scientific evidence that evaluates in vitro fracture and fatigue strength of occlusal veneers in different thicknesses, CAD/CAM materials, and under different aging methodologies. MATERIALS AND METHODS: An electronic search of 3 English databases (The National Library of Medicine (MEDLINE/PubMed), ScienceDirect, and EBSCOhost) was conducted. Laboratory studies published between September 2009 and October 2019 that evaluated fracture or fatigue strength of CAD/CAM occlusal veneers and used human teeth were selected. The included studies were individually evaluated for the risk of bias following a predetermined criterion. The outcomes assessed included the types of the restorative material, the thickness of the veneers, and aging methods. RESULTS: A total of 12 studies fulfilled the inclusion criteria. Most of the included studies (86%) evaluated the fracture strength of occlusal veneers. Two studies evaluated fatigue resistance. There was a significant relationship between the choice of materials and fracture strength. Polymeric materials performed better in fatigue testing in comparison to ceramics. Lithium silicate-based glass ceramics showed more favorable outcomes in a thickness of 0.7-1.0 mm. Fracture resistance values in all the included studies exceeded maximum bite forces in the posterior region. CONCLUSIONS: The outcomes of this systematic review suggest that occlusal veneers can withstand bite forces in the posterior region, whereas the measurement of thickness should be standardized in order to have a fair comparison. Further research needs to be conducted to evaluate the longevity of this type of restorations clinically.

Effect of different polishing techniques on surface roughness and bacterial adhesion of three glass ionomer-based restorative materials: In vitro study.

BACKGROUND: Although many reports concluded that polishing of glass ionomers is crucial for smoother surface and limiting the adhesion of cariogenic bacteria, there is no specific surface treatment protocol recommended. A novel material in the same category was released recently claimed to have surface smoothness comparable to resin composite and bacterial adhesion less than other types of glass ionomers. In this study, different polishing systems were tested with three glass ionomers one of them is the novel material to find the most appropriate polishing protocol. Objectives: To evaluate and compare the surface roughness and bacterial adhesion to resin modified glass ionomer, bioactive ionic resin and conventional glass ionomer restorative materials after different polishing protocols in vitro. MATERIAL AND METHODS: The materials tested includes resin modified glass ionomer, bioactive ionic resin, and conventional glass ionomer. The polishing protocols were divided into four groups: group 1 = (Mylar matrix strips, Control), group 2 = (one-step, PoGo), group 3 = (two-step, Prisma Gloss) and group 4 = (three-step, Sof-Lex). From each material, eleven cylindrical specimens were prepared for each group according to the manufacturers' instructions. The surface roughness for all specimens was measured using atomic force microscope in tapping mode. the same specimens were subjected to bacterial adhesion testing after being coated with artificial saliva. Data were analyzed with two-way analysis of variance followed by Post hoc multiple comparisons. RESULTS: The highest Ra and S. mutans adhesion values were recorded for all materials in two-step group. The lowest Ra and S. mutans adhesion values were seen in one-step and three step groups. CONCLUSIONS: One-step polishing system was more effective and may be preferable for polishing of the three studied glass ionomer-based materials compared to two-step and three-step systems. Key words:Activa bioactive restorative, glass ionomer, surface roughness, bacterial adhesion, surface treatment.

The effect of four materials on direct pulp capping: An animal study.

The aim of this study was to investigate the outcomes of direct pulp capping performed with two types of tricalcium silicate-based materials (mineral trioxide aggregate/MTA and Biodentine/BD); nano-hydroxyapatite (nHAP) crystals or calcium hydroxide (CH) in dogs. Following mechanical exposure, the pulps were randomly capped with one of the four materials. Histological analyses were performed to examine the outcomes after 7 days or 3 months. At 7 days, BD and nHAP showed significantly less inflammatory cell response than MTA and CH. At 3 months, the inflammatory cell response and tissue necrosis were significantly higher in the CH group. There was no significant difference between the tested materials in the calcific bridge formation after 7 days; however, a significant difference was noticed at the 3-month period. Tricalcium silicate-based cements and nHAP are potential alternatives to CH in vital pulp therapy following accidental pulp exposure.

The effect of preheating resin composites on surface hardness: a systematic review and meta-analysis.

OBJECTIVES: This paper presents a systematic review and meta-analysis of the effect of preheating on the hardness of nanofilled, nanoceramic, nanohybrid, and microhybrid resin composites. MATERIALS AND METHODS: An electronic search of papers on MEDLINE/PubMed, ScienceDirect, and EBSCOhost was performed. Only in vitro studies were included. Non-English studies, case reports, clinical trials, and review articles were excluded. A meta-analysis of the reviewed studies was conducted to quantify differences in the microhardness of the Z250 microhybrid resin composite using the Comprehensive Meta-Analysis software. RESULTS: Only 13 studies met the inclusion criteria for this systematic review. The meta-analysis showed that there were significant differences between the non-preheated and preheated modes for both the top and bottom surfaces of the specimens (p < 0.05). The microhardness of the Z250 resin composite on the top surface in the preheated mode (78.1 ± 2.9) was higher than in the non-preheated mode (67.4 ± 4.0; p < 0.001). Moreover, the microhardness of the Z250 resin composite on the bottom surface in the preheated mode (71.8 ± 3.8) was higher than in the non-preheated mode (57.5 ± 5.7, p < 0.001). CONCLUSIONS: Although the results reported in the reviewed studies showed great variability, sufficient scientific evidence was found to support the hypothesis that preheating can improve the hardness of resin composites.