The impact of methylene blue photosensitizer, aPDT and a calcium hydroxide-based paste on the physicochemical and mechanical characteristics of root canal dentin and the bonding interface of fiberglass posts

PURPOSE

To investigate the influence of methylene blue (MB)-mediated antimicrobial photodynamic therapy (aPDT) and calcium hydroxide (CH) medication on the mechanical characteristics, degree of conversion (DC), quantification, and volume of gaps at the adhesive interface of glass fiber posts (GFPs) luted to distinct thirds of root canal dentin. Additionally, the microhardness (MH), elastic modulus (Eit), morphology, and chemical structure of the intraradicular dentin were assessed.

MATERIALS AND METHODS

6 experimental groups were formed by sorting 102 bovine incisors. Canals receiving deionized water irrigation as a negative control; canals receiving deionized water irrigation and filled with CH as a positive control; groups treated with CH + MB at 50 and 100 mg/L without irradiation; and groups treated with CH + MB at 50 and 100 mg/L irradiated by red laser for 60 s (660 nm; 100 mW; 6.5 J; 72 J/cm2). MH, Eit, and DC properties were evaluated for both the resin cement layer and root dentin substrate (n = 8). Volume and quantification of gaps at the bonding interface (n = 6), and dentin morphology and chemical content were investigated (n = 3). Data were analyzed using a repeated-measures 2-way ANOVA followed by Tukey post hoc analysis (α = 0.05).

RESULTS

The distinct intraradicular thirds and treatment with MB-mediated aPDT, whether activated or not, in combination with CH, had a significant impact on the mechanical characteristics of the root dentin. This effect was also observed in the MH, Eit, DC, quantification, and volume of gaps at the luting interface (P < .05). In general, a higher concentration of MB, whether activated by a red laser or not, led to lower values in the mechanical properties of the root dentin, as well as in MH, Eit, and DC at the adhesive interface (P < .05). Additionally, these groups exhibited higher values for quantification and volume of gaps at the luting substrate (P < .05). Scanning electron micrographs and energy dispersive X-ray spectra showed qualitative similarity among all groups, except for the negative experimental control group.

CONCLUSIONS

MB-mediated aPDT at 50 mg/L, in combination with CH, demonstrated favorable physico-chemical and mechanical characteristics in intraradicular dentin, along with satisfactory mechanical features and the adhesive interface integrity for GFPs at all intraradicular depths.

CLINICAL SIGNIFICANCE

MB-mediated aPDT at a concentration of 50 mg/L combined to CH medication represents a suitable choice for photosensitization in the context of intracanal disinfection following the biomechanical procedure and prior to luting of intraradicular restorations.

Adhesion and sealing of different universal adhesive systems associated with bulk-fill resins after using endodontic irrigation solutions: An in vitro study

This study aimed to evaluate the interface of universal adhesive (UA) with bulk-fill resin (BF) and dentin, after endodontic irrigation. The pulp chamber of 96 molars was irrigated with chlorhexidine 2% (CHX) or sodium hypochlorite 5.25% (NaOCl) and restored according to three restorative protocols. Microtensile bond strength (μTBS) and nanoleakage tests were performed after 24 h of thermocycling. Kruskal Wallis, Mann-Whitney and Wilcoxon were performed (p < 0.05). Comparing restorative systems, a difference was found only when irrigated with CHX after 24 h. CHX provided higher μTBS than NaOCl after 24 h for two restorative protocols; after thermocycling, NaOCl provided the greatest μTBS than CHX for one group. Decreased μTBS was observed for all restorative systems when CHX was used after thermocycling. NaOCl demonstrated the highest nanoleakage. The composition of UA influenced the immediate adhesion and sealing to BF when CHX was used; ageing has a deteriorating effect on adhesion and sealing for all restorative systems.

Fluorescence intensity of composite resin for direct veneer removal using a fluorescence-aided identification technique

OBJECTIVES

This laboratory study evaluated the influence of the fluorescence intensity of composite resins on additional tooth wear and the presence of restorative material in different dental thirds during the retreatment of direct veneers.

MATERIALS AND METHODS

The crown dimensions of 60 bovine incisors were reduced to 10 × 8 mm. The teeth were classified according to the fluorescence intensity of the composites: low (LOW) (TPH Spectra), medium (MED) (Opallis), and high (HIGH) (Essentia) groups. The teeth were divided according to the removal methods: conventional (CON) and fluorescence-aided identification technique (FIT). The specimens were scanned (T0), received veneer preparation, and scanned again (T1). After restorations, the composites were removed and the teeth were scanned (T2). Measurement assessments between T1 and T2 were performed to determine additional wear, presence of residual areas, and the average between additional wear and the presence of residual areas. Kruskal Wallis, Mann-Whitney, Friedman, 2-way ANOVA, and post-Tukey tests were performed (α < 0.05).

RESULTS

The comparison of composite resins indicated a smaller area of additional wear and greater residue presence in the HIGH group than the LOW group for both techniques in the cervical third. Regarding removal methods, the FIT produced greater additional wear than the CON method for the LOW and MED groups in the middle and cervical thirds. The incisal third exhibited greater additional wear than the other thirds.

CONCLUSIONS

Composite resins with high fluorescence intensity removed using FIT had less tooth wear. The incisal third was the most affected area for direct veneer removal procedures.

CLINICAL SIGNIFICANCE

A FIT has been proposed for composite resin removal; however, the different fluorescence intensities of composite resins can influence tooth wear caused during this procedure.

Influence of bioceramic sealers on dentinal tubule penetration and antimicrobial effectiveness: a systematic review and meta-analysis of in vitro studies

The aim of this systematic review and meta-analysis (SRM) was to evaluate whether bioceramic sealers have better penetration capacity in dentinal tubules and antimicrobial activity when compared to AH Plus® sealer. This SRM was recorded in the Open Science Framework database and followed the guidelines of the PRISMA 2020. Five databases were searched by two independent reviewers. Only in vitro studies that evaluated the effects of bioceramic sealers on dentinal tubule penetration and antimicrobial activity outcomes compared to AH Plus® sealer were included. Meta-analysis was conducted using R software, using the effect measure of the standardized mean difference (SMD) and inverse variance method. A modified Joanna Briggs Institute's Checklist was used for the risk of bias assessment. A total of 1486 studies were identified, and only 54 studies that fulfilled our eligibility criteria were included in this review. There was no statistical difference between the sealers evaluated for dentinal tubule penetration, in the thirds evaluated: coronal SMD 0.58 [0.14; 1.31], p = 0.12; middle SMD 0.07 [0.54; 0.39], p = 0.75; and apical SMD 0.08 [0.73; 0.56], p = 0.80. Both sealers demonstrated similar antimicrobial action (SMD [3.42; 5.32], p = 0.67 and SMD 0.67 [1.89; 0.55], p = 0.28). The studies presented a low risk of bias. Based on the in vitro studies included and according to the limitations of the present review, the data suggest that bioceramic and AH Plus® sealers present similar penetration capacity in dentinal tubules and antimicrobial effect, making them suitable materials to be considered in clinical practice.

Morphological and biomechanical characterization of long bones and peri-implant bone repair in type 2 diabetic rats treated with resveratrol

Type 2 diabetes interferes with bone remodeling mechanisms, requiring studies to reverse this damage, and resveratrol is a polyphenol with rich properties. This study aimed to characterize the long bone morphology and peri-implant biomechanics of normoglycemic and type 2 diabetic animals treated with resveratrol. Thirty-two male Wistar rats were used and divided into normoglycemic and diabetic with or without treatment. They had the installation of implants in the tibia and treatment with oral resveratrol within 45 days. Resveratrol was responsible for weight homeostasis and decreased glycemic levels in rats with type 2 diabetes. The three-point bending testing, resveratrol showed positive effects on the biomechanics of long bones, corroborating a more resistant bone in comparison to untreated diabetics. Micro-ct revealed how bone metabolism is affected by systemic disease, decreasing bone quality. The counter-torque of normoglycemic animals showed superior osseointegration to diabetes, with no differences in the administration of the polyphenol, showing the sovereignty of the deleterious effects of the disease when there is a tissue lesion and an inflammatory picture installed. Overall, resveratrol acted positively in the etiopathogenesis of type 2 diabetes and revealed positive effects on the strength of long bones.

Postoperative pain after root canal filling with bioceramic sealers: a systematic review and meta-analysis of randomized clinical trials

The aim of this systematic review and meta-analysis (SRM) was to assess postoperative pain (PP) after endodontic treatment with bioceramic root canal sealer compared to AH Plus® sealer. This SRM was carried out in accordance with the items on the PRISMA 2020 checklist and Cochrane guidelines and registered in PROSPERO (CRD42021259283). Only randomized clinical trials (RCTs) were included. Meta-analysis was conducted using R software, the standardized means difference (SMD) measure of effect was calculated for quantitative variables, and the odds ratio (OR) for binary variables. The Cochrane tool (RoB 2.0) was used to assess the risk of bias, and the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to assess the quality of evidence. Qualitative and quantitative analysis included 18 and 17 studies, respectively. For quantitative variables, the bioceramic root canal sealer presented less occurrence of postoperative pain than the AH Plus® sealer in 24 h (SMD - 0.17 [- 0.34; - 0.01], p = 0.0340). For binary variables, there was no difference observed between the sealers evaluated, except for sealer extrusion where the bioceramic group had lower post-filling material extrusion (OR 0.52 [0.32; 0.84], p = 0.007). Regarding the risk of bias analysis, low risk was observed for most domains, except allocation that was considered unclear, while the certainty of evidence ranged from moderate to low. The results showed that bioceramics sealers reduced postoperative endodontic pain only after 24 h and showed less sealer extrusion compared to the AH Plus® sealer. However, more robust and standardized clinical trials are needed to confirm the results with less heterogeneity and higher quality of evidence.

Does the use of antioxidant agents after dental bleaching compromise the aesthetic results of ceramic laminate veneers?

PURPOSE

This in vitro study aimed to evaluate the aesthetic compromise generated in adhesive interface of ceramic laminate veneer luted after tooth bleaching and the use of antioxidant agents. Thus, the chromatic coordinates and whitening index (WID) were evaluated, comparing whiteness changes (ΔWID) results to perceptibility and acceptability thresholds.

MATERIAL AND METHODS

In total, 88 bovine enamel samples (7 × 8 × 4 mm; n = 8) were submitted to the ceramic laminate veneer luting protocol according to surface treatment (unbleached and bleached enamel), antioxidant agents (control; 10% ascorbic acid and 10% α-tocopherol), and luting periods (after 24 h and after 14 days). To lute IPS e.max ceramic restorations (7 × 8 × 0.6 mm), Tetric N-Bond Universal adhesive system and Variolink Aesthetic LC resin cement were used. An ultraviolet-visible spectrophotometer (UV-VIS) was utilized to measure CIE L*a*b* coordinates prior to and after UV-B artificial accelerated aging for 252, 504, and 756 h. L*, a*, and b* axes were evaluated separately, and the whitening stability (ΔWID) effect was assessed by varying the whiteness index for dentistry (WID). The 50:50% visual threshold was used to evaluate ΔWID values (whiteness perceptibility [WPT] and whiteness acceptability [WAT]). Color parameters changes (ΔL*Δa*Δb*), WID, and ΔWID data were subjected to 2-way repeated measures ANOVA followed by Tukey's test (α = 0.05).

RESULTS

Different UV-aging periods influenced the chromatic coordinates, WID, and ΔWID of the ceramic restorations regardless of the bleaching treatment, antioxidant solutions and luting periods (P < .05). In general, ΔWID values after UV-aging periods were above perceptibility and acceptability thresholds (WPT = 0.72 and WAT = 2.62, respectively) for all experimental groups (P < .05). Unbleached and 10% ascorbic acid-treated enamels luted after 14 days of the antioxidant action exhibited lower ΔL* and Δb* values, while control group showed lower Δa* values. All experimental groups showed similar performance on ΔWID compared to the control group, regardless of the UV-aging period analyzed (P > .05).

CONCLUSION

α-tocopherol is a suitable antioxidant solution to be used 24 h post enamel bleaching not compromising clinical acceptability of ceramic laminate veneers.

CLINICAL RELEVANCE

The adhesive interface of ceramic laminate veneers may appear darker after the use of antioxidant agents affecting the clinical acceptability of the restorations.

Effects of Different Toothpastes on the Nanomechanical Properties and Chemical Composition of Resin-Modified Glass Ionomer Cement and Composite Resin Restorations

PURPOSE

This study evaluates the effects of different toothpastes on the nanohardness and chemical compositions of restorative materials and dental surfaces.

METHODS

Bovine enamel (n = 72) and dentin (n = 72) blocks were obtained and restored using RMGIC (n = 36) or CR (n = 36) to create the following surfaces: dentin adjacent to RMGIC (DRMGIC), enamel adjacent to RMGIC (ERMGIC), dentin adjacent to CR (DCR), and enamel adjacent to CR (ECR). After restoration, one hemiface of each specimen was coated with an acid-resistant varnish to facilitate the creation of control (C) and eroded (E) sides; the latter were achieved by erosion-abrasion cycles as follows: erosion with 1% citric acid: 5 days, four times for 2 min each day; 1% citric acid/abrasion, two times for 15 s, followed by immersion in a toothpaste slurry for 2 min. Toothpastes without fluoride (WF; n = 12), with sodium fluoride (NaF; n = 12), and with stannous fluoride (SnF₂; n = 12) were used for RMGIC or CR. The specimens were analyzed for nanohardness (H), and chemical composition using energy-dispersive X-ray spectroscopy and Raman microscopy. The data were statistically analyzed using two-way repeated measures ANOVA and Tukey's test (α = 0.05).

RESULTS

Lower H values were obtained with NaF for DRMGIC-C, with a statistically significant difference from the H value obtained with WF (p < 0.05). The calcium and phosphorus concentrations in DCR-E were significantly lower with WF than with the other types of toothpaste (p < 0.05). Fluoride-containing toothpastes are capable of preserving the main chemical components of the dentin adjacent to the restorative materials under erosive-abrasive conditions.

Influence of thickness and degree of opacity of lithium disilicate on the degree of conversion and bond strength of resin cements

The aim of this study was to evaluate the influence of various opacities and thicknesses of lithium disilicate on the degree of conversion (DC) of two resin cements and on their bond strength (BS) to the ceramic. Two hundred and forty ceramic samples of lithium disilicate with high translucency (HT), low translucency (LT), and medium opacity (MO) were obtained from IPS e. max CAD in five different thicknesses. Light-cured and dual-cured resin cements were used for DC (n = 9) and BS (n = 8). Cement samples were light-cured under ceramic samples and analyzed using a Raman confocal spectrometer to determine the DC. For BS, resin cement cylinders were fabricated using ceramic samples which were thsen subjected to a microshear bond strength test. The mean values were provided for statistical analysis. The increase in thickness resulted in a decrease in DC for both cements under all experimental conditions, but only affected the BS of the light-cured cement for the MO ceramic. Comparing the opacities, the most translucent ceramics with particular thicknesses exhibited higher DC values than the less translucent ceramics. The LT and MO ceramics with certain thicknesses exhibited the highest BS values than the HT. The dual-cured cement generally showed highest values in both analyses than the light-cured cement. A thicker and more opaque ceramic material can reduce the DC of the cement. The BS decreases with the increasing thickness of the more-opaque ceramics.

In vitro study on how photodynamic therapy and calcium hydroxide medication influence adhesive interface properties of glass-fiber posts to intraradicular dentin

PURPOSE

This in vitro study evaluated the influence of antimicrobial photodynamic therapy (aPDT), using methylene blue (MB) as photosensitizer (PS) and calcium hydroxide (CH) as intracanal medication on adhesive bond strength, sealing, and integrity of the luting interface of glass-fiber posts to different thirds of endodontically treated root canal dentin.

MATERIAL AND METHODS

102 incisors were sorted into 6 groups: a negative control irrigated with deionized water; a positive control irrigated with deionized water and filled with CH; CH + MB 50 mg/L without laser radiation; CH + MB 100 mg/L without laser radiation; CH + MB 50 mg/L radiated by red laser; and CH + MB 100 mg/L radiated by red laser. Push-out bond strength (n = 8), adhesive interface sealing (n = 3), and volume and quantification of voids (n = 6) were assessed using a universal testing machine, confocal laser scanning microscope, and computerized microtomography, respectively. Scanning electron micrographs were obtained from representative samples to qualify the fracture patterns. Push-out bond strength and adhesive interface integrity data were subjected to 2-way ANOVA for repeated measures followed by Tukey's test (α = 0.05). Adhesive interface sealing was evaluated by the inter-examiner Kappa test and submitted to Kruskal-Wallis and Dunns tests (α = 0.05).

RESULTS

Assessing the apical region, the positive control and MB_100WA + Ca(OH)₂ groups showed lower adhesive bond strength compared to the MB_100A + Ca(OH)₂ group (P < 0.05). The cervical third showed higher bond strength than the apical third for the positive control, MB_50WA + Ca(OH)_2, MB_100WA + Ca(OH)_2, and MB_50A + Ca(OH)₂ groups (P < 0.05). A prevalence of mixed failure was observed in all experimental groups. There were no statistically significant differences in adhesive interface sealing for any of the parameters assessed (P > 0.05). MB_100WA + Ca(OH)₂ and MB_100A + Ca(OH)₂ groups promoted a higher volume and quantification of voids compared to the negative control group evaluating the cervical third (P < 0.05). In general, there were no differences in the quantification of voids comparing the intraradicular thirds (P > 0.05), differently to the volume of voids in which, in general, the cervical third promoted higher values compared to the middle and apical thirds (P < 0.05).

CONCLUSION

aPDT with methylene blue PS at 50 mg/L associated with calcium hydroxide as intracanal medication demonstrated satisfactory bond strength, sealing, and integrity of the adhesive interface at any intraradicular depth.

Antimicrobial effectiveness of ultrasonic irrigation in root canal treatment: a systematic review of randomized clinical trials and meta-analysis

OBJECTIVE

The objective of this systematic review and meta-analysis (SRM) was to answer the question as to whether the use of ultrasonic irrigation (UI) results in better antimicrobial activity in root canal disinfection compared to conventional irrigation (CI).

METHODS

A literature search was performed in the main scientific databases, carried out until October 2021. The eligibility criteria were randomized clinical trials (RCTs). Two meta-analyses were conducted using R software with the "META" package. The mean difference (MD) and odds ratio (OR) measure of effect were calculated. The fixed effect model was applied with a 95% confidence interval. The Cochrane collaboration scale was used to assess risk of bias and the GRADE tool to assess the quality of evidence.

RESULTS

A total of 1782 records were screened, and 12 studies meeting the criteria were included in this review. A low risk of bias was observed for most domains, except allocation concealment that was considered unclear. The certainty of evidence was classified as moderate in the OR meta-analyses and low in the MD meta-analyses. Ultrasonic irrigation resulted in a better antimicrobial effect in both meta-analyses, MD 1.42 [1.60; 1.23] p < 0.0001, I² = 80%; and OR 3.86 [1.98; 7.53] p< 0.0001, I² = 28.7%.

CONCLUSION

Within the limitations of this SRM, UI presented better antimicrobial efficacy than CI.

CLINICAL RELEVANCE

UI should be used by clinicians as it promotes better antimicrobial efficacy in patients undergoing endodontic treatment.

Biomechanical performance of three fiberglass post cementation techniques: Imaging, in vitro, and in silico analysis

PURPOSE

The structural integrity of the resin cement layer, the bond strength, and the biomechanical behavior of different fiberglass post cementation techniques were evaluated.

METHODS

Thirty-three bovine incisors were divided into three groups (n = 11): conventional fiberglass post (CFP), conventional fiberglass post in flared root canals (CFL), and relined fiberglass post (RFP). Six specimens from each group were submitted for high-resolution microcomputed tomography (μCT) to evaluate the integrity and presence/volume of voids at the resin cement layer. Finite element analysis (FEA) of two three-dimensional (3D) models of each group were conducted, one considered ideal (without interface defects) and another containing the conditions identified in the μCT analysis. Push-out bond strength tests were conducted for all specimens.

RESULTS

The CFL group had the greatest mean values of void (Thirds cervical: 73.67; middle: 95.67; apical: 47.33) and gap concentration (Thirds cervical: 14.67; middle: 15.83; apical: 8.33) compared with CFP and RFP. A significant difference in bond strength was observed between the cervical (1.33 MPa) and middle thirds (1.85 MPa) compared with the apical third (4.85 MPa) of the CFL. A significant difference was observed in the bond strength in the CFL (1.33 MPa) and RFP (3.29 MPa) in the cervical third, which were statistically similar to the bond strength of the CFP. The tensile stress distributions were similar in most structures, localized in the cervical region on the lingual surface.

CONCLUSIONS

Structural defects in the interface layer might influence the bond strength and biomechanical behavior under the different fiberglass post cementations.

Surface characterization of indirect restorative materials submitted to different etching protocols

OBJECTIVES

This in vitro study aimed to evaluate the effect of different times and concentrations of hydrofluoric acid etching on the surface of indirect restorative materials obtained from blocks used in CAD-CAM technology.

METHODS

Specimens (4 mm × 4 mm × 0.8 mm) were obtained for each indirect restorative material: zirconia-reinforced lithium monosilicate ceramic (Celtra Duo), nanoceramic resin (Lava Ultimate), and polymer-infiltrated ceramic network material (Vita Enamic). The materials were submitted to etching with 5% or 10% hydrofluoric acid for 20, 40, 60, or 90 s. A control group for each material was evaluated without any surface treatment, totaling nine experimental groups for each material (n = 10). The specimens were evaluated for surface roughness (R_a and R_z), confocal optical microscopy, the contact angle (θ), surface free energy (γs), total free interaction energy (∆G) using a goniometer, and microshear bond strength to resin cement. Specimen images were obtained using scanning electron microscopy, confocal optical microscopy, and atomic force microscopy. Data on the surface roughness, the contact angle, surface free energy, total free interaction energy, and bond strength were subjected to two-way ANOVA and Tukey´s test (α=0.05).

RESULTS

In general, Celtra Duo showed better results after etching with 10% hydrofluoric acid for 40 or 60 s. Lava Ultimate showed better performance after etching with 10% hydrofluoric acid for 20 or 40 s, whereas Vita Enamic showed better results after etching with 5% hydrofluoric acid for 90 s.

CONCLUSION

Each material showed different characteristics after etching with hydrofluoric acid. Knowledge of the proper protocol for each material is essential to ensure improvements in the adhesion process and durability of indirect restorations. In general, Celtra Duo presented mechanical properties superior to those of Lava Ultimate and Vita Enamic.

CLINICAL SIGNIFICANCE

Specific etching protocols must be recommended for each indirect material because longer exposure to hydrofluoric acid can jeopardize the surface, thus affecting the mechanical and bond strength properties.

Antimicrobial photodynamic therapy in endodontic reintervention: A systematic review and meta-analysis

BACKGROUND

To evaluate the effectiveness of the use of antimicrobial photodynamic therapy (aPDT) in root canals disinfection in cases of endodontic retreatments.

METHODS

This Systematic Review was registered in PROSPERO (CRD42021260013) and followed the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). Searches were performed in the electronic databases PubMeb, Scopus, Web of Science, Embase, Web of Science, Clinical Trials and Cochrane Library. Methodological quality and risk of bias were assessed by the Cochrane Risk of Bias tool for randomized clinical trials (RCT) and by the Newcastle-Ottawa (NOS) qualifier for non-RCT (prospective) studies. Meta-analysis was performed using R software, version 3.6.3 with the "META" package assistant by the RStudio platform. The odds ratio (OR) measure of effect was calculated and the random effect model was applied with a 95% confidence interval, and heterogeneity tested by the I2 index. The certainty of evidence was rated using GRADE.

RESULTS

Regarding the 1513 studies screened, 10 met the eligibility criteria and were included, and 8 used in the quantitative synthesis. Meta-analysis showed that all of studies data presented a significant difference before and after of antimicrobial photodynamic therapy in the microbial load reduction in secondary endondontic infections (OR 0.15 [0.07; 0.32], p < 0.0001). Overall, the studies had a low risk of bias and, the analysis of evidence by GRADE assessment was rated as moderate.

CONCLUSION

It is suggested that aPDT is a beneficial and promising tool, showing efficacy in reducing the microbial load in cases of endodontic retreatment.

In vitro study on how antioxidant solutions affect enamel surface characteristics and bonding interface of ceramic laminate veneers luting after dental bleaching

PURPOSE

This in vitro study aimed to determine the effect of antioxidant solutions used after dental bleaching on the shear bond strength and adhesive interface sealing of ceramic laminate veneer luting. Additionally, effects on the enamel surface characteristics of hydrogen peroxide neutralization, surface energy, total free interaction energy, morphology, and chemical composition of enamel were assessed.

MATERIAL AND METHODS

Total 127 bovine incisors were divided into experimental groups, according to the surface treatment (unbleached and bleached enamel), antioxidant types (control; 10% ascorbic acid and 10% α-tocopherol), and periods of luting of ceramic laminates (24 h and after 14 days). Shear bond strength was assessed using microtensile test before and after thermal cycling (5760 cycles, 5-55 °C) (n = 6). The sealing of the adhesive interface was assessed using a confocal laser scanning microscope (n = 3). Hydrogen peroxide neutralization analysis was performed using a spectrophotometer (n = 5). The surface energy and total free interaction energy (n = 10) were measured using an automatic goniometer, while enamel morphology and chemical composition were assessed by scanning eletron microscopy (n = 3). Shear bond strength and enamel surface properties data were subjected to ANOVA followed by Tukey's test (α = 0.05). Adhesive interface micrographs were evaluated by the inter-examiner Kappa test and subjected to Kruskal-Wallis and Dunn's tests (α = 0.05).

RESULTS

In general, thermal aging decreased the shear bond strength values of the luting agents to enamel (P < .05). The α-tocopherol solution was able to reverse the oxidizing effect from dental bleaching, increasing the shear bond strength values and preserving the integrity of the adhesive interface sealing (P < .05). Moreover, the α-tocopherol antioxidant agent promoted higher hydrogen peroxide neutralization after dental bleaching (P < .05). Dental bleaching influenced the enamel surface, decreasing the surface energy and total free interaction energy values (P < .05).

CONCLUSION

α-tocopherol was able to reverse the oxidizing effects of dental bleaching, improving the enamel surface properties, as well as the adhesion and interface sealing of ceramic laminate veneer restorations.

Randomized prospective clinical trial of class II restorations using flowable bulk-fill resin composites: 4-year follow-up

OBJECTIVES

This randomized, prospective, and split-mouth study aimed to evaluate flowable bulk-fill resin composites in class II restorations, comparing it with a conventional layering technique after 4-year follow-up.

MATERIALS AND METHODS

Fifty-three subjects received three class II restorations according to the restorative systems: conventional microhybrid composite resin (PA - Peak Universal + Amelogen Plus, Ultradent); flowable bulk-fill and nanoparticulate composite resins (ABF - Adper Single Bond 2 + Filtek Bulk Fill Flow + Filtek Z350XT, 3M/Espe); and flowable bulk-fill and microhybrid composite resins, (XST - XP Bond + SDR + TPH3, Dentsply). The clinical performance and interproximal contacts were evaluated. Statistical analyses were performed using the Kaplan-Meier, equality test of two proportions, Friedman, Wilcoxon, Kruskal-Wallis, Mann-Whitney, and Logistic regression analysis tests (alpha = 0.05).

RESULTS

In total, 106 restorations were evaluated at 4 years. Both systems with bulk-fill composites presented higher marginal discoloration than PA. About surface texture, ABF restorative system showed superior bravo scores being statistically similar to XST. Better performance for wear and surface staining was found for XST restorative system. All restorative systems resulted in the decreased interproximal contacts, occurring early for XST.

CONCLUSIONS

The restorative systems that used flowable bulk-fill resin composites showed satisfactory clinical performance compared with conventional resin composite after 4 years. All restorative systems had decreased proximal contact after 4 years.

CLINICAL RELEVANCE

Initial marginal discoloration was observed in more than 50% of class II restorations performed with restorative systems that used flowable bulk-fill resin composite. All restorative systems had decreased proximal contact strength over time.

Cytotoxicity of root canal irrigating solutions and photodynamic therapy using curcumin photosensitizer

BACKGROUND

Photodynamic therapy (PDT) has shown satisfactory antibacterial effects. However, few information regarding the cytotoxicity potential of PDT using curcumin as a photosensitizer (PS) on fibroblasts are found. The aim of this in vitro study was to evaluate the cytotoxicity of root canal irrigating solutions and photodynamic therapy with curcumin PS on the L-929 cell line.

METHODS

Healthy mouse skin fibroblast cells were distributed into the following 7 experimental groups: G1 - culture medium DMEM (control group); G2 - 0.9% sodium chloride; G3 - 2.5% sodium hypochlorite (NaOCl); G4 - 5% NaOCl; G5 - PDT with curcumin PS at 500 mg/L + blue LED; G6 - PDT with curcumin PS at 750 mg/L + blue LED; and G7 - PDT with curcumin PS at 1000 mg/L + blue LED. All experimental groups which underwent PDT action were submitted to blue LED for 4 minutes, with a wavelength of 480 nm and energy fluency of 75 J/cm². The cultures were maintained under standard cell culture conditions (37°C, 100% humidity, 5% CO₂). Cell viability analysis was performed using the colorimetric method to evaluate the periods of 6, 24, and 48 hours. Data were subjected to the Kruskal-Wallis test, followed by the Dunn test to compare groups and Friedman test to compare periods (α = 0.05).

RESULTS

When comparing the periods, no significant differences were observed for any of the experimental groups analyzed (p > 0.05), except for the NaOCl_2.5 group that exhibited higher cell viability at 6 hours compared to the period of 48 hours (p = 0.0489). In the comparisons of the experimental groups, there were no statistically significant differences between the control group compared to all disinfection protocols, regardless of the period evaluated (p > 0.05), except for the PDT + C₁₀₀₀ group that showed lower cell viability (p < 0.05).

CONCLUSIONS

PDT with curcumin at 1000 mg/L was cytotoxic on L-929 fibroblast cell culture. However, laser-activated curcumin at a concentration of 500 mg/L presented no influence on L-929 fibroblast cell viability in in vitro conditions.

Effects of methylene blue and curcumin photosensitizers on the color stability of endodontically treated intraradicular dentin

BACKGROUND

Photodynamic therapy with photosensitizers can reduce the microbial load. However, few studies have evaluated the effects of photosensitizers on the color stability of endodontically treated intraradicular dentin. This in vitro study investigated the effects of methylene blue and curcumin photosensitizers used in photodynamic therapy on the color stability of intraradicular dentin.

METHODS

Sixty human incisors were divided into three experimental groups according to the photosensitizer solutions used and their concentrations: methylene blue (25 mg/L), curcumin (1000 mg/L), and curcumin (1500 mg/L). The color stability of endodontically treated intraradicular dentin was evaluated using a portable reflectance spectrophotometer before and after the samples been storage in 2 mL of the photosensitizer solutions during 5 min (n = 20). Color stability data were subjected to a normality test, and statistical analysis was performed using the one-way analysis of variance and Tukey least significant difference test (α = 0.05).

RESULTS

Samples treated with 25 mg/L methylene blue photosensitizer showed a higher level of color alteration than those stored in 1000 mg/L curcumin (p = .03322). However, there was no significant difference in the color alteration profiles between the samples treated with 25 mg/L methylene blue and 1500 mg/L curcumin (p = .36428). Furthermore, there was no difference in the color alteration profiles between the dentin samples immersed in 1000 mg/L and 1500 mg/L curcumin photosensitizer solutions (p = .45321).

CONCLUSIONS

Methylene blue and curcumin photosensitizers influenced the color stability of endodontically treated intraradicular dentin, and this color alteration exceeded the clinical acceptability threshold. Samples treated with 25 mg/L methylene blue showed the highest level of color alteration.

Performance of different abutment/implant joints as a result of a sealing agent

Purpose This in vitro study aimed to evaluate the effectiveness of a sealing agent in sealing the abutment/implant interface and the preload maintenance of retaining screws after mechanical cycling.Methods Six groups (n = 12) were evaluated according to the abutment/implant system (external-hexagon implant and UCLA abutments, EHU; Morse taper implant and UCLA abutments, MTU; and Morse taper implant and flexcone abutments, MTF) and the presence of an anaerobic gel sealing agent (control group, no sealing agent; experimental group, sealing agent). Toluidine blue (0.7 μL) was inserted into each implant and the abutments were attached to the implants using a digital torque wrench to evaluate the sealing of the abutment/implant interface. The specimens were tested through mechanical cycling (1 × 10⁶ cycles, 2 Hz, and 130 N). Dye release from the abutment/implant interface was analyzed using a spectrophotometer, and the reverse torque values were obtained using a digital wrench. Reverse torque and dye release data were measured after mechanical cycling and analyzed using ANOVA and Tukey's test (α =.05).Results All experimental groups showed higher reverse torque values than the control groups (P <.05). In general, the MTU and MTF experimental groups, as well as the MTF control group, showed no significant dye release at different periods (P >.05).Conclusions The use of a sealing agent improved the preload maintenance of screw-retained implant-supported prostheses. The sealing agent was effective in sealing the Morse taper connection.

Influence of photodynamic therapy and intracanal medication on Martens hardness, elastic modulus and bond strength of glass-fiber posts to endodontically treated root dentin

BACKGROUND

The purpose of this in vitro study was to evaluate the influence of photodynamic therapy (PDT) with methylene blue photosensitizer (PS) and calcium hydroxide intracanal medication on Martens hardness (MH), elastic modulus (Eit) and adhesive bond strength of glass-fiber posts in different thirds of intraradicular dentin.

METHODS

Ninety-six bovine teeth were distributed into the following 6 experimental groups: a negative control irrigated with deionized water; a positive control irrigated with deionized water and filled with calcium hydroxide intracanal medication (Ca[OH]₂); Ca[OH]₂ + methylene blue 50 mg/L without activation; Ca[OH]₂ + methylene blue 100 mg/L without activation; Ca[OH]₂ + methylene blue 50 mg/L activated by red laser; and Ca[OH]₂ + methylene blue 100 mg/L activated by red laser (n = 16). MH and Eit were measured using an ultramicrodurometer under load action of 3 mN (n = 8). Adhesive bond strength was measured using the push-out test in a universal testing machine (n = 8), and representative samples underwent scanning electron microscopy. Data on MH, Eit, and bond strength were subjected to normality tests and analyzed by ANOVA and Tukey's test (α = 0.05).

RESULTS

Methylene blue PS, activated or not by red laser, associated with calcium hydroxide medication did not promote significant difference as compared to the control groups irrigated with deionized water, associated or not with the use of intracanal medication, regarding mechanical properties and bond strength (p > 0.05). Experimental groups showed no difference between the thirds regarding root canal depth (p > 0.05), except for the positive control group, in which the apical third showed higher Eit values than the middle third (p = 0.0324). There was a predominance of mixed failure in all experimental groups, excepted the red laser-activated group treated with the highest concentration of methylene blue, which showed predominance of adhesive failure.

CONCLUSIONS

PDT with methylene blue PS at 50 mg/L, associated with intracanal calcium hydroxide medication is a satisfactory alternative for endodontic treatment as there is no interference in the mechanical properties and bond strength among glass-fiber posts to intraradicular dentin at any depth of the root canal.

In vitro study on how cold plasma affects dentin surface characteristics

PURPOSE

Studies evaluating different features of cold plasma action on dentin surface characteristics are lacking. Thus, this in vitro study aimed to determine the effect of cold plasma under different protocols of exposure time, distance to plasma source, and the association of argon gas with distinct concentrations of oxygen on the wettability, surface energy, total free interaction energy, surface roughness, morphology and chemical composition of dentin.

MATERIAL AND METHODS

One hundred and twenty-five bovine dentin samples were used and divided into twenty-five groups according to the exposure time to plasma (15, 30, or 60 s); distance between plasma source and dentin surface (3 or 6 mm); argon gas without plasma generation; and plasma generated by argon gas and association of argon gas with distinct concentrations of oxygen (2 % or 3 %) (n = 5). Contact angle (θ), surface energy (γs) and total free interaction energy (ΔG) were measured using a goniometer (Krüss), while surface roughness (Ra) was evaluated by a profilometer (Mitutoyo). Representative samples were submitted to scanning electron microscopy (JEOL) to ilustrate the morphology and chemical composition of dentin. Data comparing control group with all experimental groups were submitted to ANOVA followed by Tukey's test (α = .05). Data comparing oxygen gas action at different concentrations and argon gas on dentin characteristics were submitted to non-parametric Kruskal-Wallis test, followed by Dunn test for comparison between the groups and methods (α = 0.05).

RESULTS

In general, argon gas without plasma generation promoted no significant difference on dentin surface characteristics compared to control group (P > .05), differently for the cold plasma that significantly reduced contact angle values and increased total free interaction energy of dentin surface (P < .05). Overall, feeding of oxygen at distinct concentrations promoted significant difference on dentin surface characteristics compared to control group (P < .05). Exposure time and distance protocols interfered with contact angle, surface energy and total free interaction energy analyses for each gas. There was no significant difference on surface roughness (P > .05), morphology and chemical composition of dentin submitted to argon gas, cold plasma, and distinct concentrations of oxygen.

CONCLUSION

In conclusion, plasma generated by argon gas and its feeding with 2 % and 3 % oxygen gas improved the dentin surface characteristics about wettability, surface energy and total free interaction energy. Such treatments preserved the surface roughness, morphology and chemical composition of dentin. The protocols of groups Ar-6mm-15sec, ArO2-3mm-30sec and ArO3-3mm-15sec are recommended for improvement of dentin surface characteristics.

Analysis of permeability and biological properties of dentin treated with experimental bioactive glasses

OBJECTIVES

To evaluate obliterating capability and biological performance of desensitizing agents.

METHODS

50 dentin blocks were distributed according to the desensitizing agent used (n = 10): Control (Artificial saliva); Ultra EZ (Ultradent); Desensibilize Nano P (FGM); T5-OH Bioactive Glass (Experimental solution); F18 Bioactive Glass (Experimental solution). Desensitizing treatments were performed for 15 days. In addition, specimens were subjected to acid challenge to simulate oral environment demineralizing conditions. Samples were subjected to permeability analysis before and after desensitizing procedures and acid challenge. Cytotoxicity analysis was performed by using Alamar Blue assay and complemented by total protein quantification by Pierce Bicinchoninic Acid assay at 15 min, 24-h and 48-h time points. Scanning electron microscopy and energy dispersion X-ray spectroscopy were performed for qualitative analysis. Data of dentin permeability was analyzed by two-way repeated measures ANOVA and Tukey's test. For cytotoxicity, Kruskal-Wallis and Newman-Keuls tests.

RESULTS

for dentin permeability there was no significant difference among desensitizing agents after treatment, but control group presented highest values (0.131 ± 0.076 Lp). After acid challenge, control group maintained highest values (0.044 ± 0.014 Lp) with significant difference to other groups, except for Desensibilize Nano P (0.037 ± 0.019 Lp). For cytotoxicity, there were no significant differences among groups.

CONCLUSION

Bioglass-based desensitizers caused similar effects to commercially available products, regarding permeability and dentin biological properties.

CLINICAL SIGNIFICANCE

There is no gold standard protocol for dentin sensitivity. The study of novel desensitizing agents that can obliterate dentinal tubules in a faster-acting and long-lasting way may help meet this clinical need.

Evaluation of material waste, dimensional stability, and detail reproduction of polyvinyl siloxane impression materials mixed with different mixing tips

STATEMENT OF PROBLEM

Redesigned mixing tips, promising less impression material waste, have been marketed. However, whether their use adversely affects the dimensional stability and detail reproduction of the impression material is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the dimensional stability, detail reproduction, and material waste of different polyvinyl siloxane impression materials (regular and light-body) mixed with 2 different mixing tips (MIXPAC T-Mixer mixing tip and MIXPAC helical mixing tip).

MATERIAL AND METHODS

Six different polyvinyl siloxane impression materials were used in 2 different consistencies: Virtual Monophase and Virtual Light Body (Ivoclar Vivadent AG), Express XT Regular and Express XT Light Body (3M ESPE), and Panasil initial contact Regular and Panasil initial contact Light (Kettenbach). The polyvinyl siloxane impression materials were mixed with 2 different mixing tips: conventional helical and T-Mixer (n=10). The specimens were prepared in a metal matrix as per specification #19 of the American National Standards Institute/American Dental Association (ANSI/ADA) and International Organization for Standardization (ISO) 4823:2015. The materials were mixed with both mixing tips as per the manufacturer's instructions, inserted into a perforated custom tray on the matrix, and allowed to polymerize completely. The dimensional stability was calculated based on the measurement of the reproduction of lines engraved in the metal matrix. Detail reproduction was evaluated through analysis of continuity and reproducibility of those lines, immediately, 7 days, and 14 days after polymerization. Material waste was assessed by the difference between the initial (before mixing) and final weight (after complete polymerization) of both mixing tips. The data on dimensional stability and detail reproduction among the materials were submitted to the Kruskal-Wallis test, followed by the Student-Newman-Keuls test (α=.05). Comparison between the mixing tips was carried out with the Mann-Whitney test (α=.05), while the comparison among the periods of analysis (immediate, 7 days, and 14 days) was carried out with the Friedman test (α=.05). The data on material waste between the mixing tips were submitted to 1-way ANOVA, followed by the Tukey honestly significant difference tests (α=.05).

RESULTS

The T-Mixer mixing tip resulted in reduced material waste. For dimensional stability, Virtual Light mixed with T-Mixer resulted in lower dimensional change (0.53 ±0.58%) compared with the helical mixing tip (1.09 ±0.43%). Among the materials, Panasil Light presented higher values of dimensional change at immediate and 7-day analysis when mixed with T-Mixer tip with a statistical difference compared with Express Light, Virtual Light, and Panasil Regular (P<.05). In general, both mixing tips provided similar results in all periods of analysis (P>.05) for qualitative analysis of detail reproduction.

CONCLUSIONS

The T-Mixer tip resulted in less material waste compared with the helical mixing tip. In general, light-body materials showed higher dimensional stability when the T-Mixer tip was used compared with the conventional tip. In general, reduced detail reproduction was observed after periods longer than 7 days after impression making.

Dental bleaching with violet LED: Effects on dentin color change, resin-dentin bond strength, hybrid layer nanohardness and dentinal collagen biostability

BACKGROUND

The purpose of this study was to investigate the effect of a novel dental bleaching technique with Violet LED on enamel color change, bond strength and hybrid layer nanomechanical properties in resin-dentin restoration, and dentin biostability.

METHODS

A total of 125 bovine incisors were distributed into a control group, violet LED group (LED), and 35 % peroxide hydrogen bleaching gel (BLG) groups (n = 15). Three 45-minute sessions were performed for both bleaching procedures every week. Enamel color change (ΔE, ΔL, and Δb) was determined after every bleaching session. After color analysis, dentin was exposed for the resin-dentin bond strength analysis using microtensile test and evaluation of the nanomechanical properties at the hybrid layer (nanohardness). While half of the specimens were tested immediately, the remaining were evaluated after 10,000 thermal cycles (TC). Thirty additional teeth were used to investigate dentin ultimate tensile strength (UTS) after the bleaching treatments. UTS was evaluated before and after an enzymatic challenge. Two-way repeated measures ANOVA and Tukey's post-test were used for the statistical analysis (α = 0.05).

RESULTS

Enamel bleaching effect was observed in the LED and BLG groups with significant alterations in the ΔE, ΔL, and Δb in the BLG group. No difference was observed in the resin-dentin bond strength among the groups (p > 0.05), however, TC negatively affected the bond strength values for all the groups. Nanomechanical properties ​​remained unchanged when comparing immediate and after TC results (p > 0.05). Bleaching with BLG reduced significantly the dentin UTS, while all groups showed major decrease in UTS after the enzymatic challenge.

CONCLUSIONS

Although violet LED was able to promote a bleaching effect, less color changes was observed when compared to BLG. None of the bleaching techniques effected the resin-bond strength or the nanomechanics of the hybrid layer. Violet LED did negatively effect dentin biostability as observed for BLG and it may promote less changes to the organic content of dentin.

Effects of different toothpastes on the prevention of erosion in composite resin and glass ionomer cement enamel and dentin restorations

Objective

This study aimed to evaluate the effects of different toothpastes on the surface wear of enamel, dentin, composite resin (CR), and resin-modified glass ionomer cement (RMGIC), and to perform a topographic analysis of the surfaces, based on representative images generated by atomic force microscopy (AFM) after erosion-abrasion cycles.

Methodology

One hundred and forty bovine incisors were collected and divided into two groups: 72 enamel and 72 dentin blocks (4×4 mm). Half of the specimens were restored with CR (Filtek Z350 XT) and the other half with RMGIC (Fuji II LC). Then, samples were submitted to a demineralization cycle (5 days, 4×2 min/day, 1% citric acid, pH 3.2) and exposed to three different toothpastes (2×15 s/day): without fluoride (WF, n=12), sodium fluoride-based (NaF, n=12), and stannous fluoride-based (SnF₂, n=12). Surface wear, as well as restoration interfaces wear, were investigated by profilometry of the dental substrates and restorative materials. All representative surfaces underwent AFM analysis. Data were analyzed by two-way analysis of variance and Tukey’s tests (α=0.05).

Results

NaF-based toothpaste caused the greater dentin surface wear (p<0.05). Toothpastes affected only enamel-restoration interfaces. AFM analysis showed precipitate formation in dentinal tubules caused by the use of fluoride toothpastes.

Conclusions

NaF-based toothpastes had no protective effect on enamel adjacent to CR and RMGIC against erosion-abrasion challenges, nor on dentin adjacent to RMGIC material. SnF2-based toothpastes caused more damage to interfaces between enamel and RMGIC.

Clinical outcomes of minimally invasive ceramic restorations executed by dentists with different levels of experience. Blind and prospective clinical study

PURPOSE

To evaluate the clinical outcomes of minimally invasive ceramic restorations executed by dentists with different levels of experience.

METHODS

Sixteen professionals were divided into 4 groups according to their experience levels. These included G1: up to 2 years since graduation, G2: 2-5 years, G3: 5-10 years, and G4: more than 10 years. All professionals were trained to follow the same standardized clinical protocol, but were unaware of the research objectives. A single evaluator followed the clinical treatments and recorded the complications and errors that occurred during the execution of the protocol. Ninety-one full crowns, 137 veneers, and 46 no-preparation veneers were prepared from lithium disilicate. Follow-ups were performed immediately and at 30, 180, and 360 days after the cementation and the evaluation based on the modified United States Public Health Service criteria. Ceramic chipping/fracture and debonding were considered failures. Fractures were replicated and submitted to fractographic analysis.

RESULTS

The highest number of failures were found in G1 followed by G3 and the lowest number of failures were found in G2. The level of success was 94% after 360 days. The fractographic analysis demonstrated the external surface of restorations as the critical area and suggested that failures might occur due to noncompliance with the clinical protocol. There was no correlation between professional experience and number of failures or patient satisfaction.

CONCLUSIONS

Professional experience was not a decisive for patient satisfaction and success of minimally invasive ceramic restorations, and noncompliance with the clinical protocol was associated with early ceramic restoration failures.

Efficacy of Polyacrylic Acid as a Conditioning Agent on the Bond Strength of Self-adhesive Resin Cements to Dental Enamel

PURPOSE

This in vitro study evaluated the effectiveness of polyacrylic acid as an acid etchant similar to phosphoric acid and its effect on the microtensile bond strength of self-adhesive resin cement to enamel.

MATERIALS AND METHODS

Ninety Te-Econom Plus resin blocks (11 x 4 mm) were cemented onto bovine enamel and distributed into 10 groups according to the surface treatments (no surface treatment; etching with 37% phosphoric acid; etching with 20% polyacrylic acid; etching with 37% phosphoric acid + dental adhesive, and etching with 20% polyacrylic acid + dental adhesive) and the self-adhesive resin cements used (RelyX U200 and MaxCem Elite) (n = 9). After bonding, the specimens were sectioned into sticks, subjected to thermocycling (5760 cycles, 5°C and 55°C) and microtensile bond strength testing (n = 6). Images of representative specimens were obtained using a scanning electron microscope. Enamel penetration evaluation of different surface treatments was analysed by confocal laser scanning microscopy (n = 3). Data on bond strength were subjected to 2-way ANOVA and Tukey's least significant difference test (α = 0.05).

RESULTS

Both 37% phosphoric acid and 20% polyacrylic acid yielded the same microtensile bond strength between self-adhesive resin cement and enamel, independent of the application of dental adhesives (p > 0.05). MaxCem Elite showed higher bond strength values than RelyX U200 just for the 20% polyacrylic acid group (p = 0.001).

CONCLUSION

Acid pre-conditioning of dental enamel may influence the bond strength of self-adhesive resin cement to enamel, and 20% polyacrylic acid showed efficacy similar to that of 37% phosphoric acid.

Effectiveness of Sealing Gel on Vertical Misfit at the Implant-Abutment Interface and Preload Maintenance of Screw-Retained Implant-Supported Prostheses

PURPOSE

This in vitro study evaluated the effectiveness of a sealing agent on vertical misfit of the implant-abutment interface in an external hexagon implant system before and after mechanical cyclic loading. Effects on preload maintenance of retaining screws after mechanical cycling were also assessed.

MATERIALS AND METHODS

External hexagon implant systems were divided into two groups (n = 12) according to the presence of an anaerobic sealing gel (control group-no sealing gel; experimental group-sealing gel applied). A prefabricated UCLA abutment was attached to the external hexagon implant with a digital torque wrench in accordance with the recommendations of the manufacturer. Specimens were tested through mechanical cyclic loading (1 × 10⁶ cycles, 2 Hz, and 130 N). Vertical misfit of the implant-abutment interface was analyzed using a stereomicroscope, and reverse torque values were obtained using a digital wrench. Misfit and reverse torque data were measured and analyzed via analysis of variance (ANOVA) and the Tukey least significant difference test (α = .05).

RESULTS

The sealing gel promoted lower vertical misfit values in the test group after mechanical cycling compared with before cycling (P = .009). The control group showed lower reverse torque values for retaining screws compared with the initial torque after mechanical cyclic loading (P < .0001). However, sealing gel application promoted higher reverse torque values in the test group postcycling (P = .0003).

CONCLUSION

Anaerobic sealing agent application improved vertical misfit of the implant-abutment interface and preload maintenance of screw-retained implant-supported prostheses post-mechanical cycling.

Effect of acidic beverages on surface roughness and color stability of artificial teeth and acrylic resin

PURPOSE

The aim was to evaluate the effect of four acidic beverages on the roughness (Ra) and color change (ΔE_ab) of two brands of artificial teeth and a heat-polymerized acrylic resin (HPAR) for use in a prosthetic base.

MATERIALS AND METHODS

All materials were divided into 5 groups, according to the used acidic beverage (artificial saliva - control, red wine, orange juice, coke-based, and lemon juice-based soft drink). The immersion process was divided into two stages: T1 - immersion in the acidic solutions for 10 minutes for 14 days; T2 - after T1, the samples were immersed in grape juice for 14 days. The Ra of the samples was evaluated in a rugosimeter and the ΔE_ab in a spectrophotometer, before and after the immersions. The analysis of variance of one (ΔE_ab) and two factors (Ra) and Tukey were performed (α=.05).

RESULTS

There was a statistical difference for roughness after immersion (T1) for Trilux and Tritone teeth, regardless of the acid solution. For Trilux teeth, all acid solutions increased Ra (P<.05). For Tritone teeth, only the coke-based soft drink did not statistically change Ra. Grape juice (T2) altered Ra only of artificial teeth (P<.05). The color was changed for all materials, after T1 and T2.

CONCLUSION

In general, the acidic solutions changed the Ra and ΔE_ab of HPAR and artificial teeth after T1. The grape juice altered the roughness only of the artificial teeth, promoting a clinically acceptable color change in the materials.

Do Different Pretreatments of Dentine Surface Affect the Bond Strength with a Self-adhesive Resin Cement?

PURPOSE

To evaluate the microtensile bond strength of dentine/self-adhesive resin cement interface after several treatments on a dentine surface.

MATERIALS AND METHODS

Twenty-eight human molars were selected and divided into four groups: no treatment (control (C)); 2% chlorhexidine digluconate (CHX); 25% polyacrylic acid (PA); and 23 ppm dispersive solution of silver nanoparticle (SN). Prepolymerised TPH resin composite (Dentsply) blocks were luted on the dentine surface using RelyX U200 self-adhesive resin cement (3M ESPE). Microtensile bond strength was measured (MPa) in a universal testing machine 24 h and 6 months after the bonding process. The fractured specimens were examined in an optical microscope and classified according to the fracture pattern. A representative sample of each group was observed by scanning electronic microscope. Data were submitted to analysis of variance (ANOVA) and Tukey's test to compare the mean among the groups (p <0.05).

RESULTS

The highest microtensile bond strength values after 24 h were found for the PA group (13.34 ± 6.36 MPa), with no statistically significant difference for the C group (9.76 ± 3.11 Mpa). After 6 months, the highest microtensile bond strength values were found for the C group (9.09 ± 3.27 Mpa), with statistically significant difference only for the CHX group (2.94 ± 1.66 MPa). There was statistically significant difference only for the PA group when comparing the periods studied. Regardless of the surface treatment applied, there were more adhesive failures in both periods of time.

CONCLUSION

Dentinal pretreatment with PA, as well as use of SN before the bonding procedure of self-adhesive resin cement to dentine, may be alternative bonding protocols.

Materials Sealing Preventing Biofilm Formation in Implant/Abutment Joints: Which Is the Most Effective? A Systematic Review and Meta-Analysis

The purpose of this systematic review was to evaluate the literature available for materials exhibiting the best efficacy in preventing biofilm formation in the interior of implants. We searched PubMed/MEDLINE, Scopus, and Cochrane databases. This review is registered with the PROSPERO database and followed the suitability of the PRISMA protocol. The initial search resulted in 326 articles from the databases. After they were read, 8 articles remained, and the inclusion and exclusion criteria were applied. Six of these 8 articles were classified as in vitro and 2 were classified as in situ. The regions of the implants evaluated ranged from the interface of the pieces to the occlusal upper access of the abutment. The implant connections evaluated the Morse taper, external connection, and internal connection. Meta-analysis of the quantitative data was performed at a significance level of .05. Cotton exhibited poor control of infiltration, even in combination with other materials. Isolated gutta-percha (GP) and polytetrafluoroethylene (PTFE) tape with composite resin (CR) or GP performed better as physical barriers. The best results for chemical barriers were observed by the application of 1% chlorhexidine gluconate (CG) gel, thymol varnish, and the deposition of Ag films onto the surface. The applied meta-analysis did not show a significant difference in comparison between the different types of implant connections (P > .05). The application of CG and thymol varnish antimicrobials was effective in preventing biofilm formation and easy clinical execution; these could be used in combination with CR, GP, and PTFE.

Degree of conversion of resin cements polymerized under different ceramic systems

The aim of this study was to evaluate the degree of conversion of resin cements polymerized under different ceramic systems. Forty specimens of RelyX ARC (3M ESPE) and Maxcem Elite (Kerr) resin cements were polymerized under 5 types of dental ceramics: feldspathic, aluminum oxide-reinforced, aluminum oxide-based strengthened with zirconium oxide, leucite-reinforced, and lithium disilicate-reinforced. Measurements of the degree of conversion of the resin cements were performed 10 minutes, 1 hour, and 24 hours after curing using a Fourier transform infrared spectrophotometer. The values were subjected to a 3-way repeated-measures analysis of variance, and the means were compared with the Fisher protected least significant difference test (α = 0.05). The study findings showed that RelyX ARC resin cement displayed a higher degree of conversion than Maxcem Elite (P < 0.05). The degree of conversion was significantly lower for RelyX ARC polymerized under aluminum oxide ceramic and aluminum oxide ceramic strengthened with zirconium oxide (P < 0.05). For Maxcem Elite, there was no significant difference in the degree of conversion attained under the various ceramics (P > 0.05). For both cements, the degree of conversion increased gradually up to 24 hours after curing (P < 0.05). The ceramic system used directly influenced the degree of conversion of RelyX ARC. Both resin cements displayed an increase in the degree of conversion over time.

Effect of dental bleaching on the microhardness and surface roughness of sealed composite resins

Objectives

The aim of this in vitro study was to evaluate the microhardness and surface roughness of composite resins before and after tooth bleaching procedures.

Materials and Methods

Sixty specimens were prepared of each composite resin (Filtek Supreme XT and Opallis), and BisCover LV surface sealant was applied to half of the specimens. Thirty enamel samples were obtained from the buccal and lingual surfaces of human molars for use as the control group. The surface roughness and microhardness were measured before and after bleaching procedures with 35% hydrogen peroxide or 16% carbamide (n = 10). Data were analyzed using 1-way analysis of variance and the Fisher test (α = 0.05).

Results

Neither hydrogen peroxide nor carbamide peroxide treatment significantly altered the hardness of the composite resins, regardless of surface sealant application; however, both treatments significantly decreased the hardness of the tooth samples (p < 0.05). The bleaching did not cause any change in surface roughness, with the exception of the unsealed Opallis composite resin and dental enamel, both of which displayed an increase in surface roughness after bleaching with carbamide peroxide (p < 0.05).

Conclusions

The microhardness and surface roughness of enamel and Opallis composite resin were influenced by bleaching procedures.

Sensitivity of hyperparasitic fungi to alternative products for use in the control of papaya black spot

The use of more than one control technique can maximize the reduction of the damages caused by the fungus Asperisporium caricae causal agent of the black spot in the papaya crop. The objective of this work was to evaluate the sensitivity of the fungi Hansfordia pulvinata and Acremonium spp. to alternative products with potential for use in the control of the black-spotted ptarmigan. Three isolates of Acremonium spp. (A-598, A-602 and A-617) and an isolate of H. pulvinata (H-611) were grown in BDA medium containing Agro-Mos®, Bion®, Ecolife®, Hortifospk®, Matriz G®, Vitaphol® separately. The Amistar 500WG ® fungicide was used as a positive control and pure BDA as a negative control. The toxicity of the tested products was determined based on the values of the biological index, derived from the means of mycelial growth, sporulation and germination of conidia, in each experimental unit. In this way it was possible to select the products classified as compatible for all isolates, and to test them in vivo. In the greenhouse, only the isolates and isolates with selected products, were applied in papaya plants with foliar symptoms of black-spotted. The incidence of leaves with hyperparasites and the percentage of black-painted lesions colonized by the tested isolates were evaluated. Thus, the H-611 isolate proved to be compatible with most of the alternative products tested, except with Hortifos®. Bion® and Matrix® products were compatible with all tested isolates and could be used in conjunction with Acremonium spp. and H. pulvinata to control the papaya black spot, since these products did not present toxicity on the hyperparasitic fungi.

Influence of Chlorhexidine Gluconate on the Immediate Bond Strength of a Universal Adhesive System on Dentine Subjected to Different Bonding Protocols: An In Vitro Pilot Study

PURPOSE

The aim of this in vitro study was to evaluate the influence of preapplication of 2% chlorhexidine gluconate on the immediate microtensile bond strength of a universal adhesive system on dentine subjected to different bonding protocols.

MATERIALS AND METHODS

Twenty human molars were used in this study, and the tooth surface was abraded to expose the dentine. The teeth were randomly divided into four groups according to the surface treatment (n = 5): SBU group: Single Bond Universal without acid etching; SBUPA group: 37% phosphoric acid + Single Bond Universal; SBUCG group: 2% chlorhexidine gluconate + Single Bond Universal; and SBUPACG group: 37% phosphoric acid + 2% chlorhexidine gluconate + Single Bond Universal. The microtensile bond strengths were measured using a microtensile tester 24 h after bonding. The bond strength data were subjected to analysis of variance (ANOVA) and Sheffé's least statistically significant difference test (α = 0.05).

RESULTS

No statistically significant differences between the analysed groups were observed (p > 0.05). However, conditioning with phosphoric acid without the action of the chlorhexidine gluconate group resulted in higher numerical values of bond strengths than that for the chlorhexidine gluconate without the acid conditioning group.

CONCLUSION

The preapplication of 2% chlorhexidine gluconate did not reduce the immediate bond strength of the Single Bond Universal adhesive system under different bonding protocols.

Effect of glass fiber post customization on the mechanical properties of resin cement and underlying dentin

This study evaluated the Martens hardness (HM) and elastic modulus (E_IT) of resin cement and dentin underlying the bonding interface of customized glass fiber posts luted to intraradicular dentin and subjected to mechanical cycling. Two null hypotheses were tested: (1) no differences in the mechanical properties (HM and E_IT) of the resin cement and underlying dentin would be found between customized and noncustomized glass fiber post groups, with or without mechanical cycling; and (2) no differences in the mechanical properties of the resin cement or underlying dentin would be found between the cervical, middle, and apical thirds of the intraradicular dentin. Forty single-rooted premolars were divided into 4 groups: customized or noncustomized glass fiber post, with or without mechanical cycling. The noncustomized posts were cemented in their original state to prepared canals, while the customized posts were modified with composite resin according to the geometry of the root canal. The specimens in the mechanical cycling groups were positioned at a 45-degree angle in an electromechanical fatigue testing machine and subjected to loading with a steel tip with a 4-mm diameter for 1,200,000 cycles at 50 N. After the specimens were prepared according to the appropriate group protocol, they were sectioned into thirds, and HM and E_IT values of the resin cement and dentin underlying the bonding interface were determined using an ultramicrohardness tester under a load of 5 mN. A 2-way repeated-measures analysis of variance with post hoc Tukey test was performed. For resin cement in the cervical region, the highest HM and E_IT values were observed in the noncustomized group after mechanical cycling. Similarly, in the underlying dentin, specimens in the noncustomized group after mechanical cycling had the highest HM values in the cervical region. Therefore, customization of glass fiber posts with composite resin is not essential for bonding to intraradicular dentin.

Influence of Light-Curing Intensity on Color Stability and Microhardness of Composite Resins

The purpose of this study was to evaluate the intensity of light-curing units and its relationship with the color stability and microhardness of composite resins with different shades subjected to a thermocycling procedure. Eighty blocks (5.0 × 2.0 mm) of TPH Spectrum composite resin (Dentsply Sirona) were produced and distributed into four groups according to the light-curing units (EC 450, ECEL; Valo, Ultradent) and color of the resin material (A3; C3) (n = 20). Within each group, color stability was measured on half the sample (n = 10) using a UV-2450 visible UV spectrophotometer (Shimadzu), and Knoop hardness was measured on the other half (n = 10) using an HMV 2000 microhardness tester (Shimadzu) before and after thermocycling (12,000 cycles, 5°C and 55°C). Mann-Whitney test was performed on the color stability data; the microhardness data were analyzed using a three-way analysis of variance (ANOVA) and Tukey test (α = .05). The ANOVA results showed that thermocycling, distinct light intensity, and different colors of resin materials influenced the microhardness of the composite resins, which was evidenced by the A3 composite resin light-cured with a Valo polywave showing higher hardness values. There was no statistical difference in the color stability of the A3 composite resin; however, the C3 composite resin light-cured with an EC 450 singlewave light-curing unit showed higher color alteration values. In general, the Valo polywave light-curing unit imparted better mechanical property and color stability to both shades of the composite resins. The different shades of resin material influenced the hardness of the composite resins. Therefore, the light intensity of the light-curing units should be evaluated and monitored, as the amount of light intensity will interfere in the quality and longevity of resin restorations.

Is It Necessary to Photoactivate the Adhesive System Inside Ceramic Laminate Veneers in a Luting Procedure?

PURPOSE

To investigate the need for photoactivation of the adhesive system inside ceramic laminates before the luting procedure and to evaluate the color stability, nanohardness, and elastic modulus of the adhesive interface activated with singlewave and polywave light-curing units.

MATERIALS AND METHODS

A total of 44 lithium disilicate ceramic veneers (7.0 mm × 8.0 mm × 0.6 mm) were fabricated, bonded to enamel, and sorted into four experimental groups (n = 11 each) according to the type of light-curing unit (Radii-Cal [singlewave] or Valo [polywave]) and mode of adhesive system activation (with or without previous photoactivation). Two luting agents were used: the Tetric N-Bond adhesive system and Variolink Veneer resin cement. A visible ultraviolet spectrophotometer was used to evaluate the color stability before and after UVB artificial accelerated aging for 252, 504, and 756 hours (n = 8 samples from each group). A nanohardness tester under a load of 1,000 μN was used to evaluate the nanohardness and elastic modulus (n = 3 samples from each group). Data regarding the color stability and the mechanical properties (nanohardness and elastic modulus) were subjected to analysis of variance and Tukey protected least significant difference test (α = .05).

RESULTS

Prior activation of the adhesive system, the distinct light-curing units, and different aging periods exerted no significant difference on the color stability or mechanical properties of the resin cement (P > .05), except for in the group activated with Radii-Cal after 756 hours, in which the nonprevious activation showed lower color alteration compared to the previous photoactivation (P = .0285). Without prior activation of the adhesive with Valo, the polywave unit promoted higher nanohardness and elastic modulus values in the adhesive system (P < .05).

CONCLUSION

In general, singlewave and polywave light-curing units promoted no difference in color stability or the mechanical properties of the adhesive interface. The prior curing of an adhesive system inside ceramic laminate is not necessary.

Influence of the depth of intraradicular dentin on the pushout bond strength of resin materials

AIM

The aim of the present study was to evaluate the pushout bond strength between glass-fiber posts to different regions of intraradicular dentin with different materials for adhesive cementation.

METHODS

After endodontic filling, 40 teeth were divided into five groups according to adhesive cementation: Adper Single Bond 2 + RelyX ARC, Excite DSC + RelyX ARC (EXC), Adper SE Plus + RelyX ARC (SEP), RelyX Unicem, and Set. After the bonding process, roots were sectioned obtaining slices to be analyzed from each third. The bond strength was measured using the pushout test in a universal testing machine (Emic DL 3000) at a cross-head speed of .5 mm/minutes in different areas of the post space (cervical, middle, and apical). Data were subjected to analysis of variance and Fisher's test (α = .05).

RESULTS

The highest values for the pushout bond strength were found for the SEP group in all experimental conditions, without a significant difference for the EXC group in the middle and apical regions. There was a decrease in pushout bond strength in the cervical-apical direction for all groups, except the EXC group, which did not show a difference among the different regions.

CONCLUSIONS

The different interactions of the resin materials and the intraradicular depth influenced the bond strength of adhesives materials to dentin substrate.

Influence of different types of light curing units and photoinitiators in microhardness and color of composite resins after immersion in wine

Abstract Objective: the aim of this study to evaluate the microhardness and color change (?E) of composite resins, light cured with different LEDs, submitted to staining drink. Materials and Methods: Two composite resins with lucerin-TPO (Tetric N-Ceram/ Vit-l-escence) and camphorquinone (Filtek Z350) were select. Specimens (n=120) were prepared. Then were photopolymerized with LED of singlewave or polywave. Microhardness and color evaluations were performed before and after chalanges. Data were evaluated by two-way ANOVA, Tukey's test (p?0,05). Results: No statistically significant difference between the two generations of LEDs was found for microhardness data. Regarding the ?E, statistical difference between the two LEDs was observed for Tetric N- Ceram and Filtek Z350. Conclusion: Compostion of composites appears to have more influence on analyses than the type of LEDs.

Effects of dentifrices on mechanical resistance of dentin and restorative materials after erosion and abrasion

The aim of this study was to evaluate the mechanical resistance of dentin and restorative materials submitted to erosive/abrasive challenges with different dentifrices. The dentin was restored using a resin-modified glass-ionomer (RMGIC) or a composite resin (RC). One hemiface of the sample was protected, and the other was subdivided according to the applied dentifrice (n = 10): without fluoride (SF), sodium fluoride (NaF) and stannous fluoride (SnF). The specimens were submitted to erosive/abrasive cycles, the varnish was removed, and the Martens hardness (HMV) and elastic modulus (Eit) were evaluated. The data were analyzed by repeated two-way ANOVA measurements and Tukey tests (alpha = 0.05). When analyzing the HMV on the test side, there was no influence of the dentifrices in the dentin; however, the orders of NaF < SnF = SF in RC and SnF > NaF = SF in RMGIC were observed. Comparing the treated surfaces, there were no differences in the dentin, and only the SF since CR presented an HMV superior to that of RMGIC. Comparing control and test sides, both dentins obtained a decreased HMV after the erosive/abrasive challenge; for the restorative materials, superior values were found only for SnF in the RMGIC. The Eit values were influenced more by the dentifrices on the test side for the dentin adjacent to the RMGIC, with the lowest values shown for the SF, and for both materials, the highest values were shown for the SnF group. No differences were found when comparing each dentin treated with the same dentifrice; however, the RMGIC presented a superior Eit than the CR when brushed with both dentifrices with a fluoride. Comparing the control and test sides, the same results were obtained for the HMV. The dentifrices showed little influence on the dentin substrate, whereas the dentifrice with SnF enhanced the mechanical properties of the restorative materials, which was more evident in the RMGIC.

Color stability and surface roughness of chitosan- and nanodiamond-modified bisacrylic resin

The aim of this study is to evaluate the effect of chitosan or nanodiamond incorporation on the color stability and surface roughness of a bisacrylic resin subjected to artificial aging. Four bisacrylic resins were evaluated, namely, control, chitosan-modified material, nanodiamond-modified material, and chitosan-nanodiamond-modified material. Twenty-four specimens were prepared for each material. The surface roughness was determined using a profilometer with a cut-off of 0.25 mm. The baseline color was measured according to the CIE L*a*b* system using a reflectance spectrophotometer. After these tests, the specimens were individually immersed in cola soft drink, red wine, or distilled water (n = 8) for 28 days. After the aging, the surface roughness and final color were re-evaluated. The color stability was determined using the difference between the coordinates obtained before and after the aging process. The data on roughness and color change were evaluated using ANOVA and the Tukey test (α = 0.05). The results show that the incorporation of nanodiamonds and chitosan into a bisacrylic resin provided a better color stability to the materials (p = 0.007). The storage in red wine resulted in a higher variation in the surface roughness values, especially when only the nanodiamond was incorporated to the material (p < 0.05). The incorporation of both chitosan and nanodiamonds are promising in providing an improvement in the properties of the bisacrylic resin when they are simultaneously incorporated in the product.

Comparison of in vitro erosion protocols in bovine teeth to simulate natural erosion lesion: analysis of mechanical properties and surface gloss

OBJECTIVE

The aim of this study was to compare two in vitro erosion protocols, in which one simulates in vivo conditions experienced by patients with gastroesophageal disorders or bulimia (HCl-pepsin protocol), and the other simulates the diet of an individual who consumes a high volume of erosive beverages (citric acid protocol). In addition, the mechanical properties and surface gloss of eroded human dentin were compared with those of sound human dentin.

MATERIALS AND METHODS

Blocks of cervical dentin were used: sound human dentin (n=10), human dentin with erosive lesions (n=10), and bovine dentin (n=30). Twenty bovine blocks were subjected to either of two erosion protocols (n=10/protocol). In the first protocol, samples were demineralized using HCl-pepsin solution, then treated with trypsin solution. In the second protocol, samples were demineralized with 2% citric acid. Toothbrushing was performed in both protocols using a toothbrushing machine (15 s with a 150 g load). Ten bovine dentin blocks were not subjected to any erosive treatment. All samples of bovine and human dentin were analyzed to obtain Martens hardness values (MH), elastic modulus (Eit*) and surface gloss. One-way ANOVA and Tukey's test were performed to analyze the data (α=0.05).

RESULTS

Sound human and eroded human dentin groups showed similar MH and Eit* values (p>0.05); however, sound human dentin showed a higher surface gloss value when compared to eroded human dentin (p<0.05). Sound bovine dentin and HCl-pepsin-treated bovine dentin treatments resulted in similar values for both MH and Eit* (p>0.05), but HCl-pepsin-treated bovine dentin and citric acid-treated bovine dentin resulted in lower surface gloss than sound bovine dentin (p<0.05).

CONCLUSIONS

The HCl-pepsin protocol modified bovine dentin properties that could be similar to those that occur on human dentin surfaces with erosive lesions.

Emergence profile customization technique during implant transfer

This case report aimed to describe the clinical considerations in oral rehabilitation with prostheses on implants in the anterior region, using emergence profile customization technique during implant transfer. A patient presented with a missing left upper central incisor and with not satisfactory esthetic in the other upper incisors. After diagnosis, a treatment plan was elaborated: implant placement in this region; ceramic laminates for teeth 11 and 22, and full crown for tooth 12. During the impression procedure, the implant transfer was customized by copying the gingival profile. The prostheses were made using IPS e.max ceramic system and luted with resin cement. The patient was submitted to annual follow-up examinations that did not show any irregularity or deficiency in the prostheses. The technique performed is a viable alternative that can be used in oral rehabilitation with implants involving anterior teeth because it allows a predictable level of adaptation.

Mechanical and surface properties analysis of restorative materials submitted to erosive challenges in situ

Objective:

This study aims to evaluate the effect of acidic solutions (AS) on surface roughness (Ra) and microhardness of restorative materials (RM).

Materials and Methods:

Eight volunteers wore intraoral palatal devices (IPD) containing samples of RM: Ketac Nano (KN); Ketac Nano + Biscover LV (KN-B); Esthet-X (EX); Esthet-X + Biscover LV (EX-B); Supreme XT (SXT); Supreme XT + Biscover LV (SXT-B); and bovine enamel. The samples were submitted to three phases: (1) immersion in 0.01M hydrochloric acid (HCl) – 10 min, three times/day (14 days); (2) immersion in soft drink (Sprite®) – 10 min, three times/day (14 days); and (3) keeping in saliva (14 days). Changes in Ra/microhardness were measured before/after the three phases.

Statistical Analysis:

ANOVA (α = 0.05) and Fisher's test.

Results:

Materials sealed with Biscover LV (B) presented lowest values in all periods. KN glass ionomer cement showed highest Ra values after exposure in AS. Application of B did not reduce the Ra for the composites studied, except for EX after immersion in HCl. AS promoted changes in Ra/microhardness of RM, except for sealed materials.

Conclusions:

The acids used were able to change the Ra and microhardness of RM, except of the sealed materials. The resin-modified GIC showed the most significant changes after immersion in AS; and the composites sealed with B, even after immersion in acidic solutions (AS), showed the lowest Ra values and the least degradation in microhardness, especially when subjected to low pH solutions.

Effect of previous photoactivation of the adhesive system on the color stability and mechanical properties of resin components in ceramic laminate veneer luting

STATEMENT OF PROBLEM

The color stability and mechanical properties of luting agents influence the esthetics and longevity of ceramic restorations. However, studies evaluating the color changes and mechanical properties of luting agents under ceramic laminates activated by using different methods are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of different modes of photoactivation on the nanohardness and elastic modulus of resin cements and dental adhesives and on the color stability of ceramic laminate veneers.

MATERIAL AND METHODS

Forty-four lithium disilicate blocks (7×8×0.6 mm) were cemented onto bovine enamel and divided into 4 groups according to the polymerization light (Radii-Cal or Valo) used and the mode of activation of the dental adhesive (no previous photoactivation or previous photoactivation). Single Bond Universal dental adhesive and RelyX Veneer resin cement were used in all experimental groups. Color stability was measured using a UV-2450 ultraviolet-visible spectrophotometer before and after ultraviolet-B artificial accelerated aging (n=8). The nanohardness and the elastic modulus of the adhesive and resin cement were measured using a nanohardness tester (n=3). The color stability and mechanical properties were measured and analyzed using ANOVA and the Tukey least significant difference test (α=.05).

RESULTS

No difference in color stability or mechanical properties of the resin cement among the polymerization lights was detected (P>.05). Specimens that underwent previous photoactivation of the adhesive using the Valo polywave unit exhibited higher elastic modulus values than those that did not undergo previous photoactivation (P<.001).

CONCLUSIONS

The Valo polywave polymerization light improved mechanical properties and color stability more than the Radii-Cal unit. Previous activation of the dental adhesive in the dental enamel with the Valo polywave polymerization light yielded more satisfactory results.

Minimum intervention management of diastema closure using cordless displacement system and laminate veneers: A 2-year follow-up

This case report presents a minimally invasive diastema treatment using cordless gingival displacement system allowing a very conservative intervention. A 32-year-old female patient who presented with diastema in her upper front teeth opted for a treatment using laminate veneers to ensure achieving adequate tooth proportion and gingival levels. Having a displacement material that exerts excessive pressure during the displacement process can lead to disruption of the junctional epithelium and damage to periodontal tissues. This case report focuses on the effectiveness of the use of a minimally invasive method of gingival management. Two-year follow-up no infiltration, sensitivities, or fractures were detected on teeth, and indirect restorations, the purposed treatment allowed a quick, effective, and durable resolution for diastema.

Neurosensory analysis of tooth sensitivity during at-home dental bleaching: a randomized clinical trial

Objective The objective of this study was to evaluate dental sensitivity using visual analogue scale, a Computerized Visual Analogue Scale (CoVAS) and a neurosensory analyzer (TSA II) during at-home bleaching with 10% carbamide peroxide, with and without potassium oxalate. Materials and Methods Power Bleaching 10% containing potassium oxalate was used on one maxillary hemi-arch of the 25 volunteers, and Opalescence 10% was used on the opposite hemi-arch. Bleaching agents were used daily for 3 weeks. Analysis was performed before treatment, 24 hours later, 7, 14, and 21 days after the start of the treatment, and 7 days after its conclusion. The spontaneous tooth sensitivity was evaluated using the visual analogue scale and the sensitivity caused by a continuous 0°C stimulus was analyzed using CoVAS. The cold sensation threshold was also analyzed using the TSA II. The temperatures obtained were statistically analyzed using ANOVA and Tukey's test (α=5%). Results The data obtained with the other methods were also analyzed. 24 hours, 7 and 14 days before the beginning of the treatment, over 20% of the teeth presented spontaneous sensitivity, the normal condition was restored after the end of the treatment. Regarding the cold sensation temperatures, both products sensitized the teeth (p<0.05) and no differences were detected between the products in each period (p>0.05). In addition, when they were compared using CoVAS, Power Bleaching caused the highest levels of sensitivity in all study periods, with the exception of the 14th day of treatment. Conclusion We concluded that the bleaching treatment sensitized the teeth and the product with potassium oxalate was not able to modulate tooth sensitivity.