Bond strength of prefabricated and CAD-CAM milled glass fiber post-and-cores luted with conventional, universal, and self-adhesive composite resin cement.

STATEMENT OF PROBLEM: Little is known about the effect of different composite resin cements on the bond strength of prefabricated and milled glass fiber post-and-cores. PURPOSE: The purpose of this in vitro study was to compare the push-out bond strengths of root dentin and standard, relined, or computer-aided design and computer-aided manufacturing (CAD-CAM) glass fiber post-and-cores luted with conventional, universal, or self-adhesive composite resin cement. MATERIAL AND METHODS: Post spaces were prepared in 90 premolars. Standard and relined prefabricated and CAD-CAM-milled glass fiber post-and-cores were luted with conventional (RelyX ARC; 3M ESPE), universal (RelyX Ultimate; 3M ESPE), and self-adhesive (RelyX U200; 3M ESPE) composite resin cement (n=10). All specimens were thermally aged (5000 cycles at 5°C and 55°C with a 20-second dwell time) and mechanical fatigue (1 000 000 cycles at 2 Hz, 50-N load). The specimens were sectioned perpendicularly to the root long axis into 1-mm-thick sections (apical, middle, and cervical root thirds), the push-out bond strength was determined, and the mode of failure recorded. Data were submitted to the Kruskal-Wallis test followed by the Bonferroni-Dunn multiple comparison test (α=.05). RESULTS: Push-out bond strength values did not differ (P>.05) among posts at the same root thirds. Standard posts showed higher bond strength than CAD-CAM at the apical third for data grouped by composite resin cements (P<.001). The cervical root thirds had higher bond strength than the apical thirds (P<.05). The cervical, middle, and apical root thirds showed decreasing bond strength values for each type of post for data grouped by composite resin cement (P<.001). Adhesive failures at the dentin-cement interface were predominant. CONCLUSIONS: The type of posts and cements did not affect the bond strength of glass fiber posts. The cervical root thirds had better bonding performance than the apical thirds.

Clinical efficacy of bioactive restorative materials in controlling secondary caries: a systematic review and network meta-analysis.

BACKGROUND: This systematic review and network meta-analysis aimed to compare the clinical efficacy of bioactive and conventional restorative materials in controlling secondary caries (SC) and to provide a classification of these materials according to their effectiveness. METHODS: A search was performed in Pubmed, Web of Science, Embase, BBO, Lilacs, Cochrane Library, Scopus, IBECS and gray literature. Clinical trials were included, with no language or publication date limitations. Paired and network meta-analyses were performed with random-effects models, comparing treatments of interest and classifying them according to effectiveness in the permanent and deciduous dentition and at 1-year or 2/more years of follow-up. The risk of bias and certainty of evidence were evaluated. RESULTS: Sixty-two studies were included in the qualitative syntheses and 39 in the quantitative ones. In permanent teeth, resin composite (RC) (RR = 2.00; 95%CI = 1.10, 3.64) and amalgam (AAG) (RR = 1.79; 95%CI = 1.04, 3.09) showed a higher risk of SC than Glass Ionomer Cement (GIC). In the deciduous teeth, however, a higher risk of SC was observed with RC than with AAG (RR = 2.46; 95%CI = 1.42, 4.27) and in GIC when compared to Resin-Modified Glass Ionomer Cement (RMGIC = 1.79; 95%CI = 1.04, 3.09). Most randomized clinical trials studies showed low or moderate risk of bias. CONCLUSION: There is a difference between bioactive restorative materials for SC control, with GIC being more effective in the permanent teeth and the RMGIC in the deciduous teeth. Bioactive restorative materials can be adjuvants in the control of SC in patients at high risk for caries.

Enamel erosion control by strontium-containing TiO2- and/or MgO-doped phosphate bioactive glass.

OBJECTIVES: To evaluate the effect of strontium-containing titanium- and/or magnesium-doped phosphate bioactive glass on the control of dental erosion. MATERIALS AND METHODS: Fifty fragments of human enamel were divided into five groups: negative control, 45S5 bioglass, strontium-containing Ti-doped phosphate bioactive glass (PBG-Ti), strontium-containing Mg-doped phosphate bioactive glass (PBG-Mg), and strontium-containing Ti- and Mg-doped phosphate bioactive glass (PBG-TiMg). The specimens underwent cycles of erosive challenge twice daily for 5 days with 1 mL of citric acid for 2 min followed by 1 mL of the suspension with bioactive substances for 3 min. After the cycles, profilometry, roughness and microhardness testing, and scanning electron microscopy (SEM) were performed. The following statistical tests were used: one-way ANOVA (profile, roughness, and surface microhardness (%VMS) data variation), Tukey's HSD (%VMS), Games-Howell test (profilometry), Student's t test (roughness), and Pearson's correlation between the variables. RESULTS: The lower loss of enamel surface and lower %VMS was observed in the PBG-Mg and PBG-TiMg groups, and only the PBG-Mg group showed similar roughness between baseline and eroded areas (p > 0.05). On SEM micrographs, PBG-Ti and PBG-Mg groups showed lower apparent demineralization. CONCLUSION: All bioactive materials protected the enamel against erosion. However, strontium-containing phosphate bioactive glasses showed lower enamel loss, and the presence of Mg in these bioactive glasses provided a greater protective effect. CLINICAL RELEVANCE: Experimental strontium-containing phosphate bioactive glasses are effective in controlling enamel erosion. The results obtained in this study will guide the development of new dental products.

Effect of CAD/CAM glass fiber post-core on cement micromorphology and fracture resistance of endodontically treated roots.

PURPOSE: To investigate the fracture resistance of weakened roots restored with prefabricated or CAD/CAM-customized posts and cores as well as the thickness of the cement film and the presence of voids in the cement. METHODS: The roots of 40 human premolars were weakened by removing internal dentin with a diamond bur (2.5 mm in the coronal third and 1.5 mm in the apical third) and restored with prefabricated posts (PPs) or customized posts (CPs) with or without a zirconia crown (n= 10). Posts and crowns were cemented with resin cement. Microtomography was used to determine the thickness of the cement film and whether voids were present. After fatigue testing (1 million cycles, 50 N, 5 Hz, 36.5°C), the specimens underwent compression testing with an oblique load (30°, 1 mm/minute) and fracture strengths were recorded (N). Fracture strength and film thickness were analyzed with ANOVA and the Games-Howell test; the variable presence of voids was analyzed with the Mann-Whitney test (α= 5%). RESULTS: Mean fracture strengths varied between 640.4 and 792.9 N and did not differ significantly between groups. The CP group had a thinner cement film and fewer voids than the PP group. There was a positive, statistically significant correlation (Spearman, R=0.488, P= 0.029) between these variables. CLINICAL SIGNIFICANCE: CAD/CAM-manufactured glass-fiber posts and cores do not affect the fracture strength of flared root canals or cause catastrophic failure of the root when used with zirconia crowns.

Performance of Dental Students in Shade Matching: Impact of Training.

OBJECTIVE: The present study evaluated the effect of training on dental students' ability for matching two different shade guides. MATERIALS AND METHODS: The study was conducted in 2012. The participants were 88 male and female undergraduate dental students from Brazil and Portugal, with or without previous color education and vision refractive errors (response rate of 73.33%). They were asked to match a pair set of the shade guides Vita Classical (VC) and Vitapan 3D Master (3DM), with a 20-minutes' rest between each match. The sets were assembled over a neutral gray background and under controlled light. About 7-10 days later, all participants watched a video lecture on color education and repeated the matching procedure. The percentage of matches was calculated and submitted to statistical analysis for the variables gender, geographic region, shade guide and previous color education (Mann-Whitney tests), vision refractive errors (Kruskal-Wallis), and training (Wilcoxon signed rank). All tests were performed at a confidence level of 95%. RESULTS: Training increased the percentage of matches for all groups, except for Portuguese and hyperopic individuals (VC and 3DM) and men (3DM). Previous color education affected VC shade matching before training. Gender, refractive errors, and geographic region did not affect shade matching ability. CONCLUSIONS: Previous education and training in color positively affected shade-matching ability of dental students on shade guide pairing tests. CLINICAL SIGNIFICANCE: The subjectivity of the visual method might not be a clinical concern in daily practice. The human eye can detect small differences in color and visualize the tooth with all its complex geometry, multilayered tissues, and secondary color parameters. Therefore, any color-matching task will be judged by the patient and/or other observers with consideration to this complexity. In other words, visual assessment is paramount to the success/failure of esthetic restorative procedures. The efficiency of the visual color method may be improved by color education through the development of professional color discrimination ability. This would make the students responsible for color selection, reproduction, and evaluation and lead to increased capability over a layperson observer receiving the restorative treatment. (J Esthet Restor Dent 29:E24-E32, 2017).

Effect of desensitizing agents on the microtensile bond strength of two-step etch-and-rinse adhesives to dentin.

Desensitizers can be used to control postoperative sensitivity in adhesive restorations. The aim of this study was to evaluate the effect of desensitizing agents on the bond strength of two-step etch-and-rinse adhesive systems to dentin. Forty-two human molars were sectioned to obtain 3-mm-thick dentin discs. The discs were divided into three groups (n = 14 in each) - no-treatment control group (CT), and oxalic acid [BisBlock (BB)] and calcium phosphate [Desensibilize Nano-P (NP)] desensitizers - before the application of two adhesive systems [Adper Single Bond Plus (SB) and One-Step Plus (OSP)]. A nanoparticle composite resin was used to create a 3-mm-thick build-up. The specimens were stored in distilled water for 24 h before a microtensile bond-strength test was performed. The failure modes were determined using a stereomicroscope at 100 × magnification. Specimens were sectioned perpendicular to the interface for scanning electron microscopy analyses. The CT-SB group exhibited the highest bond strength, differing significantly from BB-SB and BB-OSP groups. Mixed failures were prevalent for all groups. Scanning electron microscopy revealed a continuous hybrid layer and resin tags in all groups. Dentin bond strength of etch-and-rinse adhesive systems was reduced by an oxalic acid desensitizer but was not affected by a calcium phosphate-containing desensitizer.

Effect of urbanization and water quality on microplastic distribution in Conceição Lagoon watershed, Brazil.

Urbanization in watersheds leads to the introduction of sources of microplastics and other pollutants in water bodies. However, the effect of urbanization on microplastic pollution and the relationship between microplastics and water quality are not well understood. We assessed the distribution of microplastics in tributaries urbanized, non-urbanized and in the receiving lagoon body of Conceição Lagoon watershed. The results show that urbanization significantly affects water quality but does not differentiate tributaries in terms of microplastic concentrations. Microplastic concentrations were lower in the receiving lagoon body compared with the tributaries, highlighting their importance in microplastic pollution in the studied lagoon. Microplastic concentration was correlated with low N:P ratios in the lagoon and associated with high levels of total phosphorus, which indicate the discharge of effluents. The correlations between microplastic concentration, water temperature, and dissolved oxygen in the lagoon were based on the temporal variations of these variables. Precipitation and wind velocity had influence on microplastic distribution in the watershed. Our findings underscore the importance of evaluating water quality parameters and meteorological variables to comprehend the microplastic distribution at small watersheds.

Porcelain laminate veneer on a highly discoloured tooth: a case report.

Esthetic treatment of a single darkened tooth represents a great challenge to the dental practitioner. The properties of dental ceramic-colour stability, mechanical strength, clinical longevity, esthetic appearance and compatibility with periodontal tissues-make this material a good choice for such treatment. We present a case of restoration of a single, highly darkened anterior tooth with a feldspathic porcelain veneer. Resolution involved preparation of the dental structure guided by orientation grooves and provisional restoration using composite resin, a silicone impression and adhesive luting. Conservative use of porcelain laminate veneers provides satisfactory esthetic outcomes and preserves sound tooth structure. The patient was very satisfied with the result and had no complaints during 2 years of follow-up.

Effect of storage temperature on pH of in-office and at-home dental bleaching agents.

The aim of this study was to determine the pH of several commercially available in-office and at-home dental bleaching products stored at room temperature and refrigerated. The products were divided into in-office (n=09) and at-home (n=12) bleaching gels and submitted to two different temperatures, namely, room temperature (23 degrees C +/- 1 degree C) and refrigeration temperature (4 degrees C +/- 1 degree C). The pH was measured using a portable pH meter with a direct electrode, which was calibrated with standard buffer solutions at pH 4.0 and 7.0 and recalibrated for each new product. The pH of the dental bleaching products tested ranged from 2.39 +/- 0.10 to 6.52 +/- 0.09, and was found to vary significantly both with temperature and between bleaching agents. Most of the bleaching gels were found to be acidic, especially the in-office bleaching products, and the refrigerated at-home gels had the highest pH values. Thus, we conclude that the storage temperature affected the pH of the products tested.

Influence of simplified, higher-concentrated sodium ascorbate application protocols on bond strength of bleached enamel.

BACKGROUND: Bleaching procedures performed before restorative procedures, due to the oxygen released, affects the quality of bonding restorations. The application of an lower-concentrated antioxidant for one-hour or more can reversal the compromised bonding to bleached enamel, but it was not effective according to the bleaching concentrations applied. The aim of the present study was to evaluate simplified protocol of higher-concentrated sodium ascorbate (35%SA) in bond strength values of enamel bleached with 10%, 16%, 22% carbamide peroxide (CP) or 35% hydrogen peroxide (HP). MATERIAL AND METHODS: Three hundred and forty enamel surfaces of 85 human third molars were used, divided into 17 groups (n=20), according to the following groups: control = no bleaching and no ascorbic acid application; bleaching (CP10%, CP16%, CP22% at-home and HP 35% in-office) and 35%SA application (no application; 35%SA applied twice for 1-min each [SA2×1], twice for 5-min each [SA2×5] and; twice for 10-min each [SA2×10]). After that, adhesive was applied and composite cylinders were made with Filtek Z350 composite. Microshear test was performed in a universal testing machine. BS values were statistically evaluated using ANOVA and Tukey's and Dunnet's (against control) tests, with 5% level of significance. RESULTS: All bleaching concentrations significantly decrease the enamel bond strength results when compared to control group (p<0.05). More concentrated PC (PC22% and PH35%) showed lower enamel bond strength results when compared to lower concentrated PC (PC10% and PC16%; p<0.05). A significant increase of the enamel bond strength results were only observed when SA2×5 and SA2×10 were applied (p<0.05). CONCLUSIONS: The application of 35% sodium ascorbate for twice 5- and 10-min each was an efficient protocol to reverse the bond strength in bleached enamel at the same level as the no bleaching enamel, independently of the bleaching concentration used. Key words:Tooth bleaching, hydrogen peroxide, sodium ascorbate, bond strength.

Lysmata arvoredensis nov. sp. a new species of shrimp from the south coast of Brazil with a key to species of Lysmata (Caridea: Lysmatidae) recorded in the southwestern Atlantic.

Lysmata arvoredensis sp. nov. inhabits temperate waters in the south coast of Brazil and is named in tribute to the Marine Protected Area REBIO Arvoredo. This is the fourth species belonging to the genus Lysmata recorded for the region and the ninth for Brazil. L. arvoredensis sp. nov. can be distinguished from other species of Lysmata by the presence of a nearly completely fused accessory branch with a single free unguiform segment on the outer antennular flagellum; a rostrum with seven dorsal (2+5) and three ventral teeth; a stylocerite with a pointed tip bearing mesial setae; a second pereiopod with 22-24 carpal subsegments and 14-16 subsegments in the merus; a merus of the third pereiopod with five ventrolateral and 12 ventral spines on the propodus; and its color pattern, with red bands and patches in pleonites 2-3 that resemble a mask in dorsal view. Molecular characters demonstrate that L. arvoredensis sp. nov. is most closely related to other species of Lysmata belonging to the Neotropical and Cleaner clades. To support future ecological studies in the region, identification keys to the species of Lysmata recorded in the southwestern Atlantic Ocean are provided.

Effect of organic solvents compared to sandblasting on the repair bond strength of nanohybrid and nanofilled composite resins.

BACKGROUND: This study evaluated the effect of different surface treatments on the repair bond strength of nanohybrid (Empress Direct) and nanofilled (Filtek Z350 XT) composite resins. MATERIALS AND METHODS: A total of 120 specimens of each material (7.5 x 4.5 x 3 mm) were prepared and polished with SiC paper. Half of the specimens were kept in water for seven days and the other half for six months; they were then divided into six groups according to the type of surface treatment: negative control (no treatment), Al2O3sandblasted, liquid acetone, acetone gel, liquid alcohol and alcohol gel. Following application of the silane coupling agent and the adhesive system, composite resin cylinders were fabricated on the specimens and light cured (20 seconds). The same composite resins were used for the repair. Additionally, ten intact specimens of each composite resin (without repair) were prepared (positive control). The specimens were then loaded to failure in the microshear mode. Three additional specimens were fabricated in each group, and the surface treatments were analyzed by atomic force microscopy, energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). RESULTS: The nanofilled composite resin showed higher cohesive strength and repair bond strength than the nanohybrid composite resin. The aging process affected the repair bond strength of the nanofilled composite resin. Al2O3sandblasting was more efficient for the nanofilled composite resin and promoted greater surface roughness in both materials. The solvents demonstrated higher efficacy for the nanohybrid composite resin. CONCLUSION: The strengths resulting from the solvents were material dependent, and Al2O3sandblasting resulted in superior repair bond strength in both materials.

Assessing the use of 35 percent sodium ascorbate for removal of residual hydrogen peroxide after in-office tooth bleaching.

BACKGROUND: The authors conducted a study to quantify the amount of hydrogen peroxide remaining after in-office bleaching and to investigate the effectiveness of 35 percent sodium ascorbate (SA) on removal of the bleaching agent from dentin. METHODS: The authors sectioned 70 extracted human third molars to form 4×4×2-millimeter blocks of dentin and then categorized them into eight groups as follows: group 1, no bleaching; group 2, bleaching (35 percent hydrogen peroxide) and daily measurement; group 3, bleaching plus one application of 35 percent SA for 60 minutes; group 4, bleaching plus one application of SA for 10 minutes; group 5, bleaching plus two applications of SA for 10 minutes each; group 6, bleaching plus two applications of SA for five minutes each; group 7, bleaching plus three applications of SA for one minute each; and group 8, bleaching plus two applications of SA for one minute each. They quantified the amount of residual hydrogen peroxide by using a colorimetric assay with horseradish peroxidase and o-phenylenediamine dihydrochloride as the enzyme and substrate, respectively. RESULTS: The authors analyzed the data by using the Kruskal-Wallis test (α = .05). The results showed that no hydrogen peroxide remained after 120 hours in group 2 and at their respective measurement points in groups 5, 6, 7 and 8, whereas hydrogen peroxide had been removed only partially in groups 3 and 4. CONCLUSION: Two applications of 35 percent SA for one minute each produced the same result--complete removal of the bleaching agent--as that observed five days after tooth bleaching with 35 percent hydrogen peroxide without any application of SA. CLINICAL IMPLICATIONS: In an appropriate concentration, SA facilitates rapid elimination of residual peroxide up to two minutes after bleaching with 35 percent hydrogen peroxide. This finding suggests that clinicians can perform bonding procedures shortly after the bleaching procedure.

Colour stability and opacity of resin cements and flowable composites for ceramic veneer luting after accelerated ageing.

OBJECTIVES: Colour changes of the luting material can become clinically visible affecting the aesthetic appearance of thin ceramic laminates. The aim of this in vitro study was to evaluate the colour stability and opacity of light- and dual-cured resin cements and flowable composites after accelerated ageing. METHODS: The luting agents were bonded (0.2 mm thick) to ceramic disks (0.75 mm thick) built with the pressed-ceramic IPS Aesthetic Empress (n=7). Colour measurements were determined using a FTIR spectrophotometer before and after accelerated ageing in a weathering machine with a total energy of 150 kJ. Changes in colour (ΔE) and opacity (ΔO) were obtained using the CIE L*a*b* system. The results were submitted to one-way ANOVA, Tukey HSD test and Student's t test (α=5%). RESULTS: All the materials showed significant changes in colour and opacity. The ΔE of the materials ranged from 0.41 to 2.40. The highest colour changes were attributed to RelyX ARC and AllCem, whilst lower changes were found in Variolink Veneer, Tetric Flow and Filtek Z350 Flow. The opacity of the materials ranged from -0.01 to 1.16 and its variation was not significant only for Opallis Flow and RelyX ARC. CONCLUSIONS: The accelerated ageing led to colour changes in all the evaluated materials, although they were considered clinically acceptable (ΔE<3). Amongst the dual-cured resin cements, Variolink II demonstrated the highest colour stability. All the flowable composites showed proper colour stability for the luting of ceramic veneers. After ageing, an increase in opacity was observed for most of the materials.

Effect of reservoirs on gingival inflammation after home dental bleaching.

OBJECTIVE: To evaluate the influence of reservoirs on the gingival mucosa of patients submitted to at-home bleaching with 16% carbamide peroxide. METHOD AND MATERIALS: Nineteen nonsmoking male patients, 18 to 25 years of age, were submitted to home bleaching with a 16% carbamide peroxide gel for 2 consecutive hours for 21 days. The custom-made mouth trays were made with a reservoir on only the left side and cut anatomically 1 mm beyond the gingival margin. Smears of the gingival mucosa were obtained by the exfoliation cytology in liquid media technique before (control), immediately after, and 30 and 45 days after treatment. The samples were processed in the laboratory and evaluated according to Papanicolaou's criteria of malignity. Statistical analysis was carried out by McNemar test, 2 proportions test, and Wilcoxon test with a level of significance of 1%. RESULTS: The presence of a reservoir in the custom tray resulted in an increase of inflammation only immediately after the bleaching procedure. After 30 and 45 days, the difference between inflammation on the sides with and without a reservoir was not statistically significant. Significant differences were found in the degree of inflammation, classified as predominantly mild on the nonreservoir side and moderate on the reservoir side (P < .01). CONCLUSIONS: A 16% carbamide peroxide bleaching gel caused gingival inflammation immediately after the procedure and persisted until 45 days after the bleaching treatment. The use of a reservoir in the custom tray for home bleaching resulted in higher rates and higher intensity of gingival inflammation.

Reaction kinetics of sodium ascorbate and dental bleaching gel.

OBJECTIVE: The aim of this study was to establish the reaction kinetics of 35% hydrogen peroxide and sodium ascorbate and to determine the mass of antioxidant required to neutralize the bleaching gel. METHODS: The method used to quantify sodium ascorbate was based on the United States Pharmacopeia (1995)(26). Oxidation-reduction titration was used to confirm the concentration of hydrogen peroxide and sodium ascorbate and to determine the reaction kinetics between them. RESULTS: The results indicated a direct correlation between the mass of hydrogen peroxide and that of the antioxidant agent. In addition, 5 min of contact was sufficient to neutralize the hydrogen peroxide used. CONCLUSION: This in vitro study showed that the amount of sodium ascorbate required for reduction of hydrogen peroxide is directly related to the concentration of the latter. In addition, the reaction kinetics between oxidant and antioxidant showed that a longer application time for sodium ascorbate does not influence the effectiveness of the reaction and that 5 min is sufficiently long for this antioxidant to exert an antioxidant effect.