Effect of preheating on the physicochemical properties and bond strength of composite resins utilized as dental cements: An in vitro study.

STATEMENT OF PROBLEM: Little is known regarding the use of preheated composite resins to bond indirect restorations and its impact on mechanical properties when compared with resin cements. PURPOSE: The purpose of this in vitro study was to compare the chemical and physical properties and bond strength to enamel and ceramics of preheated composite resins and resin cements. MATERIAL AND METHODS: Two composite resins, the microhybrid Filtek Z250XT and the nanoparticulate Z350XT were tested, and 2 commercially available resin cements, the dual-polymerized Rely-X ARC and the light-polymerized Rely-X Veneer were used as controls. A device (HotSet) was used to preheat the composite resins to 69 °C before light-polymerization. The following properties were tested: flexural strength, modulus of elasticity, fracture toughness, microshear bond strength to enamel and ceramics, degree of conversion, flow, sorption and solubility, and color stability. Statistical analysis was done with ANOVA and Holm-Sidak for multiple comparisons (α=.05). RESULTS: Preheating had no significant effect on the degree of conversion, flexural strength, fracture toughness, solubility, or microshear bond strength to the enamel of the tested composite resins (P>.05). However, preheating increased the sorption and reduced the microshear bond strength to the ceramic (P<.05). The flowability of the composite resins increased with heating but showed lower values when compared with both resin cements (P<.05). Color stability was more affected in the preheated composite resins than in the resin cements. CONCLUSIONS: The preheating process resulted in little to no benefit in the evaluated properties for the composite resins. Resin cements appear to be the best option for cementing indirect restorations.

Physicochemical, Mechanical, and Esthetic Properties of the Composite Resin Manipulated with Glove Powder and Adhesive as a Modeling Liquid.

Composite resins with low flowability are usually handled and manipulated before insertion into the tooth preparation with gloved hands and/or using an instrument covered with a little amount of adhesive to facilitate modeling. We investigated if the modeling techniques (combined or not) affected physicochemical and esthetic properties of a composite resin. Specimens were fabricated and divided into groups according to the handling/modeling technique: Gloved-hands (composite was hand-manipulated with powdered latex gloves); Adhesive (adhesive was used in between the composite layers); Gloved-hands + Adhesive; Control (no adhesive and no touch with gloved-hands). The highest values for flexural strength (MPa), modulus of elasticity (GPa), and fracture toughness (MPa.m0.5) were obtained for Adhesive and Gloved-hands + Adhesive (p < 0.05); the lowest values were obtained for Control and Gloved-hands (p < 0.05). The Control group had the highest sorption. The Gloved-hands (p < 0.05) group had the highest solubility. Adhesive and Gloved-hands + Adhesive had a similar solubility (p > 0.05). The Control group (p < 0.05) had the lowest solubility. There was no statistical interaction between translucency vs. handling/modeling techniques and color stability vs. handling/modeling techniques. Adhesive as a modeling liquid protected the composite against sorption and solubility (if powdered gloves were used) and improved its physical/mechanical properties. Translucency and color stability were not correlated with modeling techniques.

Effect of Glass Fiber Post Surface Treatment on Bond Strength of a Self-Adhesive Resin Cement: An "In Vitro" Study.

OBJECTIVE: This study evaluated the influence of different mechanical and chemical surface treatments alone and combined with silane on the bond strength (BS) of glass fiber posts (GFPs) using self-adhesive resin cement. METHODS: Eighty-four single-rooted bovine teeth (six groups, n = 14) were submitted to BS analysis after GFP cementation. The treatments applied in the studied groups were no surface treatment (control), silane (S), 24% hydrogen peroxide (PER), 24% hydrogen peroxide and silane (PER + SIL), blasting with 50 µm aluminum oxide particles (BLAST), and blasting with 50 µm aluminum oxide particles and silane (BLAST + SIL). RESULTS: BS differed significantly among groups (p < 0.001). It was higher in the SIL (10.5 ± 3.5 MPa), BLAST + SIL (11.5 ± 3.2 MPa), and PER + SIL (11.6 ± 4.6 MPa) groups than in the control (6.5 ± 2.9 MPa), BLAST (8.6 ± 4.0 MPa), and PER (7.1 ± 2.8 MPa) groups, with no significant difference among groups receiving silanization. Cement post adhesive failure was more common in the SIL, BLAST, and PER + SIL groups, and cement-dentin adhesive failure was more common in the control, BLAST + SIL, and PER groups. CONCLUSION: These results show that silane application alone increases BS.

Evaluation of the Bond Strength of Densely Sintered Ceramics Subjected to Extended Firing.

INTRODUCTION: Critical failures in ceramic materials can be caused by the processing mode, which includes all steps taken in the manufacture of a ceramic part, from molding to firing. PURPOSE: To evaluate the effect of extended firing on bond strength in densely sintered ceramics of the zirconium reinforced lithium silicate, lithium disilicate, and feldspathic ceramic. MATERIALS AND METHODS: Three types of ceramics were evaluated: zirconium reinforced lithium silicate, lithium disilicate, feldspathic ceramic. A total of 6 ceramic blocks, two for each material were used in the study. Each block was cut into four square sections. A total of 24 ceramic surfaces were randomly distributed into 6 groups (n = 4 surfaces per group) divided according to the variables: heat treatment: conventional firing or extended firing; test time: immediate (24 hours after cementation) or longevity (after 1000 cycles of thermocycling). The bond strength tests were performed in a semi-universal test machine for microshear bond strength. For data analysis, the Shapiro-Wilk test was performed to evaluate the normality between the groups measured, and regarding homoscedasticity (homogeneity of variances) by the Bartlett test. The comparisons between the groups were made using the nonparametric Kruskal-Wallis test. RESULTS: There was no statistically significant difference of the resistance values in relation to the thermal treatment methods (conventional firing and extended firing) in any ceramic group (p <0.05). Among the times (immediate and long), there was a statistically significant difference (p <0.05), with higher resistance values for immediate time. CONCLUSION: Extended firing did not influence the micro-shear bond strength of zirconium reinforced lithium silicate, lithium disilicate, feldspathic ceramic.

Influence of delay between dental bleaching with 35% hydrogen peroxide and orthodontic brackets on the bond strength at the enamel/adhesive interface.

BACKGROUND: The aim of this study was to evaluate the influence of waiting time between the bleaching with 35% hydrogen peroxide and orthodontic brackets bonding on shear bond strength (SBS) in enamel. MATERIAL AND METHODS: Eighty bovine teeth were randomly divided into four groups (G): G1(negative control) and G2, G3 and G4 (experimental groups). The experimental groups were submitted to bleaching. Prior to orthodontic brackets bonding to enamel the procedure was adopted different waiting times, as follows: G2 (1 day); G3 (7 days) and G4 (14 days). It was performed enamel etching (30s), washing water (30s), application of adhesive system followed by photoactivation (20s). A thin layer of composite resin was placed between the adhesive and the brackets. The applied pressure was measured by tensiometer (300N/40s). The composite resin was light-cured (40s). After 24 hours the shear test was held (0.5mm/min). To compare the SBS it was used ANOVA one-way followed by Tukey test (α = 0.05). The Adhesive Remaining Index (ARI) was analyzed using the Kruskal-Wallis test. RESULTS: The SBS values were significantly lower in G2 (15.51 MPa) and G3 (17.77 MPa) compared to G1 (30.14 MPa) and G4 (28.50 MPa) (p<0.05). The ARI revealed significant difference between the G3 and the other groups (p<0.05). CONCLUSIONS: It was concluded that the bond strength in enamel in the interfaces/adhesive system/composite resin/orthodontic brackets was more effective 14 days after the bleaching with 35% hydrogen peroxide. Key words:Dental materials, teeth bleaching, orthodontic brackets.

Effect of Sonic Application of Self-Adhesive Resin Cements on Push-Out Bond Strength of Glass Fiber Posts to Root Dentin.

The aim of this study was to evaluate the influence of a sonic application of self-adhesive resin cements on the bond strength of glass fiber posts to root dentin. Eighty bovine incisors were randomly divided into eight groups (n = 10). Four self-adhesive resin cements were used-RelyX U200 (3M/ESPE), Bifix SE (Voco), seT PP (SDI), and Panavia SA (Kuraray). The cements were inserted into the root canal in two different modes-Centrix syringe (control) or with a sonic device (Sonic Smart). The roots were sectioned and taken to a universal test machine (Instron 3342) to perform the push-out test. The fracture pattern was evaluated by stereomicroscope and scanning electron microscope. The bond strength data were analyzed by two-way ANOVA and Tukey tests (α = 0.05). The interaction between the main factors was significant (p = 0.002). The sonic application increased the bond strength in comparison with the conventional application for the RelyX U200 (p < 0.001) and Bifix SE (p < 0.017) cements. However, for the seT PP and Panavia SA cements, the bond strength values did not differ significantly (p > 0.05). The fracture pattern showed adhesive at the interface between the luting cement and the dentin. Using a sonic device in the application of self-adhesive resin cement helpedpromote an increase in the bond strength for RelyX U200 and Bifix SE.

Polymerization Shrinkage of Bulk Fill Composites and its Correlation with Bond Strength.

The present study aimed to evaluates polymerization shrinkage (PS) using microcomputed tomography (µCT) and microtensile bond strength (µTBS) in bulk fill composites (BFC) and conventional class I restorations as well as the correlation between these factors. Class I cavities (4 x 5 x 4 mm), factor-C = 4.2, were created in third molars that were free of caries, which were randomly divided in 4 groups (n = 6): XTI (Filtek Supreme XTE: incremental technique); XTB (Filtek Supreme XTE: single fill technique); TBF (Tetric Bulk Fill); and SF (SonicFill). Each tooth was scanned twice in µCT: T0 was after filling the cavity with composite, and T1 was after light curing. The data were analyzed by subtracting the composite volume for each time (T1 - T0). After 1 week, the teeth were sectioned crosswise in the buccolingual and mesiodistal directions to obtain specimens with approximately 1 mm² thickness and fixed in a universal testing machine to perform µTBS. The Kruskal-Wallis and Dunn tests showed a statistically significant difference for shrinkage in µCT among the XTI and XTB and between the SF and XTB. Regarding the µTBS, all the groups differed from XTB. Bulk fill composites type presents a PS similar to that of the conventional nanoparticulate composite inserted using the incremental technique, but the bond strength was higher for the incremental group, which presented a lower number of pre-test failures when compared to BFC. No correlation was observed between the polymerization shrinkage and bond strength in the studied composites.

Polymerization shrinkage of bulk fill composites and its correlation with bond strength

Abstract The present study aimed to evaluates polymerization shrinkage (PS) using microcomputed tomography (μCT) and microtensile bond strength (μTBS) in bulk fill composites (BFC) and conventional class I restorations as well as the correlation between these factors. Class I cavities (4 x 5 x 4 mm), factor-C = 4.2, were created in third molars that were free of caries, which were randomly divided in 4 groups (n = 6): XTI (Filtek Supreme XTE: incremental technique); XTB (Filtek Supreme XTE: single fill technique); TBF (Tetric Bulk Fill); and SF (SonicFill). Each tooth was scanned twice in μCT: T0 was after filling the cavity with composite, and T1 was after light curing. The data were analyzed by subtracting the composite volume for each time (T1 - T0). After 1 week, the teeth were sectioned crosswise in the buccolingual and mesiodistal directions to obtain specimens with approximately 1 mm² thickness and fixed in a universal testing machine to perform μTBS. The Kruskal-Wallis and Dunn tests showed a statistically significant difference for shrinkage in µCT among the XTI and XTB and between the SF and XTB. Regarding the μTBS, all the groups differed from XTB. Bulk fill composites type presents a PS similar to that of the conventional nanoparticulate composite inserted using the incremental technique, but the bond strength was higher for the incremental group, which presented a lower number of pre-test failures when compared to BFC. No correlation was observed between the polymerization shrinkage and bond strength in the studied composites.

Resumo O presente estudo teve por objetivo avaliar a contração de polimerização (CP) usando microtomografia computadorizada (µCT) e a resistência de união por microtração (µTBS) em restaurações classe I de compósitos bulk fill (CBF) e convencional, assim como a correlação entre esses fatores. Cavidades classe I (4 x 5 x 4 mm), fator C=4,2, foram feitas em terceiros molares livres de cárie que foram randomizados e divididos em 4 grupos (n = 6): XTI (Filtek Supreme XTE: técnica incremental); XTB (Filtek Supreme XTE: técnica de preenchimento único); TBF (Tetric Bulk Fill); E SF (SonicFill). Cada dente foi escaneado duas vezes em μCT: T0 -após o preenchimento da cavidade com compósito, e T1 - após a cura à luz. Os dados foram analisados subtraindo o volume do compósito para cada tempo (T1 - T0). Após 1 semana, os dentes foram seccionados transversalmente no sentido vestíbulo-palatino e mesio-distal para obter espécimes com aproximadamente 1 mm² de espessura e fixados em uma máquina de ensaio universal para teste de μTBS. Os testes de Kruskal-Wallis e Dunn mostraram diferença estatisticamente significante para a contração em μCT entre XTI e XTB, e entre SF e XTB. Em relação à μTBS, todos os grupos diferiram do XTB. Compósitos do tipo bulk fill apresentam uma CP similar ao compósito convencional nanoparticulado inserido usando a técnica incremental, porém a resistência de união foi maior para o grupo incremental, que apresentou um menor número de falhas pré-teste quando comparado aos CBF. Não foi observada correlação entre a contração de polimerização e a resistência de união nos compósitos estudados.

Evaluation of several clinical parameters after bleaching with hydrogen peroxide at different concentrations: A randomized clinical trial.

OBJECTIVE: This randomized double-blind clinical trial compared tooth sensitivity (TS), bleaching efficacy, and cytokine levels after applying in-office bleaching treatments containing 15% and 35% hydrogen peroxide (HP15% and HP35%, respectively). METHODS: Twenty-five volunteers were randomly assigned to receive HP15% or HP35% treatment. The bleaching agent was applied in three 15-min applications per session. Two bleaching sessions were separated by a 1-week interval. The participants scored TS using a visual analog scale and numerical rating scale. Bleaching efficacy was determined by subjective and objective methods. Gingival crevicular fluid was collected from three jaws sites per patient for the analysis of fluid volume. Flow cytometry was used to analyze gingival crevicular fluid levels of interleukin (IL)-1ß, IL-2, IL-4, IL-6, IL-10, tumor necrosis factor, and interferon-gamma. All measurements were obtained before and after bleaching. All data were statistically analyzed (α=0.05). RESULTS: The absolute risk and intensity of TS was higher for HP35% than for HP15% (p>0.002). One month post-bleaching, HP35% produced more bleaching than HP15% (p=0.02). However patient perception (p=0.06) and patient satisfaction (p=0.53) with regard to bleaching were not significantly different. No significant differences existed in the gingival fluid volume (p>0.38) or in any cytokine level (p>0.05) for either HP concentration. CONCLUSION: Treatment: with HP35% is more effective than HP15%, but generates a greater risk and intensity of TS. No inflammatory changes occurred despite the difference in the HP concentrations. CLINICAL SIGNIFICANCE: Hydrogen peroxide at a lower concentration (e.g., 15%) should be considered a good treatment alternative for in-office bleaching because the higher concentration for in-office bleaching generates a greater risk and intensity of TS for patients.

Is there correlation between polymerization shrinkage, gap formation, and void in bulk fill composites? A µCT study.

This in vitro study aimed to evaluate the volume of polymerization shrinkage (VS), gap (VG), and void (VV) using computerized microtomography (µCT) in bulk fill resin composites and conventional class I restorations, and to establish a correlation between these factors. Class I cavities (4 x 5 x 4 mm), C-factor = 4.2, were performed on caries-free human third molars and randomly divided into five groups (n = 6): FSI (Filtek Supreme XTE incremental insertion); FSS [(Filtek Supreme XTE single insertion(SI)]; TBF [(Tetric Bulk Fill: SI and manual filling (MF)]; SFM (Sonic Fill: SI/MF); and SFS (SonicFill: SI and sonic filling). The teeth were scanned and analyzed by µCT at T0, after filling the cavity with resin, and at T1, after polymerization for VG and VV, and for VS (T1-T0). There was statistically significant difference in VS in µCT for the FSI and FSS groups and between SFS and FSS as well as some difference in VV for FSI and bulk fill resin composites and no difference in VG between the conventional technique and bulk fill composites. Bulk fill resin composites presented similar VS and gap formation to those of incrementally inserted conventional resin composites. There is a moderate and weak positive correlation between polymerization shrinkage and gap formation and void, respectively. The final gap formation was more dependent on the initial gap than on polymerization shrinkage or void volume.

Effect of Ceramic Barriers of Different Thicknesses on Microhardness of Light-Cured Resin Cements.

This study evaluated the microhardness of two resin cements and a low-viscosity resin composite when light-cured under different ceramic thicknesses. A total of 20 samples (10.0 × 1.0 mm) of each material were polymerized by means of a LED light source with an intensity of 1,100 mW/cm2 for 20 seconds. For each experimental group, different ceramic thicknesses (0.5 mm, 1.0 mm, and 1.5 mm) were applied to each sample. For the control group, the samples were polymerized without the presence of ceramics. Each material was then stored in dry vials that inhibited the passage of light for a period of 24 hours. After that time, each sample underwent Vickers hardness test (HMV, Shimadzu: 25 g/10 seconds). The data were collected and analyzed using analysis of variance and Tukey test (P < .05). For the control group, RelyX Veneer (3M ESPE), Filtek Flow Z350XT (3M ESPE), and Allcem Veneer (FGM) showed mean microhardness values and standard deviations of 44.42 ± 4.9, 44.25 ± 2.4, and 31.71 ± 2.4, respectively. The lowest microhardness value (24.13) was found when the greatest ceramic thickness (1.5 mm) was used on the Allcem Veneer cement (P < .01). The microhardness of resin-based materials was affected when the 1.5-mm-thick ceramic material was interposed during photoactivation.

Chlorhexidine Prevents Root Dentine Mineral Loss and Fracture Caused by Calcium Hydroxide over Time.

Purpose. To evaluate the mineral ion loss of root dentine after treatment with 2% chlorhexidine solution (CHX) and to compare its yield and flexural strength (fs) after exposure to calcium hydroxide [Ca(OH)2]. Materials and Methods. Dentine bars (DB) were made from 90 roots of bovine incisors and randomized into three groups: GControl: distilled/deionized water (DDW), GNaOCl: 2.5% sodium hypochlorite + 17% EDTA, and GCHX: CHX + DDW. The release of phosphate (PO4) and calcium (Ca) ions was measured by spectrophotometry. The DB were exposed to Ca(OH)2 paste for 0, 30, 90, and 180 days. DB were subjected to the three-point bending test to obtain yield and fs values. The fracture patterns were evaluated (20x). Data were analyzed using Kruskal-Wallis and Dunn's post hoc tests or one- and two-way ANOVA followed by Tukey's post hoc test (α = 0.05). Results. GCHX showed lower PO43- and Ca2+ ionic release than GNaOCl (p < 0.001). For yield and fs, GCHX > GNaOCl in all periods (p < 0.001), except for yield strength values on 90 days (p = 0.791). A larger frequency of vertical fractures was observed in GNaOCl and that of oblique fractures in GCHX (p < 0.05). Conclusions. CHX prevented PO43- and Ca2+ loss and showed a tendency to preserve the yield and fs of root dentine over time following exposure to Ca(OH)2 paste.

Two-Year Follow-up of Multidisciplinary Treatment Using Digital Smile Design as a Planning Tool for Esthetic Restorations on Maxillary Midline Diastema.

One of the challenges posed by diastema closure treatment in the presence of tooth size discrepancy is to achieve adequate distribution of the spaces between the teeth. The use of the Digital Smile Design can assist the clinician in visualizing and measuring dentogingival discrepancies with maximum predictability. The present clinical case describes an approach to space distribution with assistance of the digital tool, allowing adequate restorative procedures. The protocol used was shown to be efficient, achieving the esthetics desired by the patient both during and after multidisciplinary treatment, as well as having adequate stability.

Is there correlation between polymerization shrinkage, gap formation, and void in bulk fill composites? A µCT study

Abstract: This in vitro study aimed to evaluate the volume of polymerization shrinkage (VS), gap (VG), and void (VV) using computerized microtomography (μCT) in bulk fill resin composites and conventional class I restorations, and to establish a correlation between these factors. Class I cavities (4 x 5 x 4 mm), C-factor = 4.2, were performed on caries-free human third molars and randomly divided into five groups (n = 6): FSI (Filtek Supreme XTE incremental insertion); FSS [(Filtek Supreme XTE single insertion(SI)]; TBF [(Tetric Bulk Fill: SI and manual filling (MF)]; SFM (Sonic Fill: SI/MF); and SFS (SonicFill: SI and sonic filling). The teeth were scanned and analyzed by μCT at T0, after filling the cavity with resin, and at T1, after polymerization for VG and VV, and for VS (T1-T0). There was statistically significant difference in VS in μCT for the FSI and FSS groups and between SFS and FSS as well as some difference in VV for FSI and bulk fill resin composites and no difference in VG between the conventional technique and bulk fill composites. Bulk fill resin composites presented similar VS and gap formation to those of incrementally inserted conventional resin composites. There is a moderate and weak positive correlation between polymerization shrinkage and gap formation and void, respectively. The final gap formation was more dependent on the initial gap than on polymerization shrinkage or void volume.

Influence of Relining Post on the Bond Strength of Resin Cements.

This study evaluated the influence of relining fiber posts on the bond strength (BS) of resin cements in the root canal. Forty bovine teeth were divided in four groups (n = 10): G1 (ARC)-fiber post cemented with resin cement RelyX ARC; G2 (ARC+Z350)-relined fiber post cemented with RelyX ARC; G3 (U200)-fiber post cemented with self-adhesive cement RelyX U200; G4 (U200+Z350)-relined fiber post cemented with RelyX U200. The roots were sectioned in six 1.2-mm slices and the push-out test was performed. Data were analyzed by three-way analysis of variance (ANOVA), and Tukey's test (a = 0.05). For the conventional resin cement, there was no significant difference between groups G1-ARC (15.5 ± 3.8) and G2-ARC+Z350 (16.1 ± 4.5). For the self-adhesive cement, the results revealed higher BS values for relined posts G4-U200 + Z350 (19.9 ± 7.9) as compared to non-relined posts G3-U200 (14.4 ± 4.5). For both cements, in groups of relined posts, the apical and the cervical thirds presented similar BS. Relining enhances the performance of the self-adhesive resin cement, and the interaction between relining and root third influences the BS to the conventional resin cement.

The Effect of 3% Phosphate Ascorbyl Gel on Bond Strength of Composite Resin to Enamel treated with 35% Hydrogen Peroxide.

OBJECTIVE: To evaluate the effect of 3% phosphate ascorbyl gel (PA) in different times onto the microshear bond strength of composite resin (CR) to bovine enamel treated with 35% hydrogen peroxide (HP). MATERIALS AND METHODS: Thirty enamel blocks of bovine incisors were made and divided into 5 groups (n = 6) with three specimens per group (n = 18), according to treatment: G1= No bleaching + CR; G2 = HP + CR after 15d; G3 = HP + CR after 24 hours; G4 = HP + PA (15 min) + CR after 24 hours; G5 = HP + PA (2 hours) + CR after 24 hours. The resin cylinders were made by Tygon matrices. Microshear bond strength test was performed using universal testing machine with a 50N load at a speed of 0.5 mm/min. Fracture modes were assessed by a stereomicroscope 40 ×. Microshear bond strength values were submitted to the analysis of variance (ANOVA) one-way and Tukey test (p < 0.05). RESULTS: G1 had significant results when compared to G3 and G5 (p < 0.01). However, G2, G3, G4 and G5 have showed no significant differences among groups (p > 0.05). Failure modes were categorized into adhesive (90%) and mixed (10%). CONCLUSION: The use of 3% phosphate ascorbyl gel for 15 minutes was able to improve bond strength of composite resin to bleached bovine enamel, but when 3% phosphate ascorbyl gel was applied during 40 minutes it negatively interfered in the adhesion of the resin to bleached bovine enamel.

Effect of airborne-particle abrasion on dentin with experimental niobophosphate bioactive glass on the microtensile bond strength of resin cements.

PURPOSE: The objective of this study was to evaluate the microtensile bond strength (µTBS) of two resin cements bonded to dentin pre-treated with experimental niobophosphate bioactive glass (NBG). METHODS: The experimental bioactive glass was prepared by mixing different amounts of NbO5; (NH4)2HP4; CaO; Na2CO3. The particle size distribution and composition of the bioactive glass powder were determined. Twenty flat dentin surfaces from sound extracted human molars were polished with 600-grit SiC paper and air-abraded using experimental bioactive glass niobium powder. The bonding procedures were accomplished by the application of two resin cements: self-etching Panavia F or self-adhesive RelyX U-100. The resin-bonded specimens were cut and the µTBS test was performed after 24h. The failure mode was determined with a stereomicroscope at 40× magnification. The results were statistically analyzed by two-way ANOVA and Tukey tests (α=0.05). RESULTS: The two-way ANOVA did not detect interactions between factors, but only a difference between the self-etching and self-adhesive cement (p=0.001). The self-etching resin cement Panavia F obtained a higher µTBS than the self-adhesive cement Relyx U-100. The predominant failure mode of the cements was adhesive/mixed between the resin cement and dentin. CONCLUSION: A new bioactive glass containing niobium did not interfere with the immediate bonding performance of self-etching and self-adhesive cements.

Human dental enamel and dentin structural effects after Er:YAG laser irradiation.

UNLABELLED: Ideally projected to be applied on soft tissues, infrared lasers were improved by restorative dentistry to be used in hard dental tissues cavity preparations--namely enamel and dentin. This paper evidentiates the relevant aspects of infrared Erbium laser's action mechanism and its effects, and characterizes the different effects deriving from the laser's beams emission. The criteria for use and selection of optimal parameters for the correct application of laser systems and influence of supporting factors on the process, such as water amount and its presence in the ablation process, protection exerted by the plasma shielding and structural factors, which are indispensable in dental tissues cavity preparation related to restorative technique, are subordinated to optical modifications caused by the interaction of the energy dissipated by these laser light emission systems in the targeted tissue substrate. CLINICAL RELEVANCE: Differences in the action of infrared Erbium laser system in regard to the nature of the ablation process and variations on the morphological aspects observed in the superficial structure of the target tissue irradiated, may be correlated to the structural optical modifications of the substrate produced by an interaction of the energy propagated by laser systems.

Evaluation of pH, ultimate tensile strength, and micro-shear bond strength of two self-adhesive resin cements.

The aim of this study was to evaluate the pH, ultimate tensile strength (UTS), and micro-shear bond strength (µSBS) of two self-adhesive resin cements to enamel and dentin. Sound bovine incisors (n = 10) and two self-adhesive resin cements (i.e., RelyX U-100 and seT PP) were used. The pH of the resin cements was measured using a pH-indicator paper (n = 3). Specimens for UTS were obtained from an hourglass-shaped mold. For µSBS, cylinders with internal diameter of 0.75 mm and height of 0.5 mm were bonded to the flat enamel and dentin surfaces. Bonded cylinders were tested in the shear mode using a loop wire. The fracture mode was also evaluated. The cement seT PP showed a low pH; U-100 showed significantly higher UTS (49.9 ± 2.0) than seT PP (40.0 ± 2.1) (p < 0.05) and high µSBS to enamel (10.7 ± 3.7). The lowest µSBS was found for seT PP to dentin (0.7 ± 0.6); seT PP to enamel (4.8 ± 1.7), and for U-100 to dentin (7.2 ± 1.9), showing an intermediate µSBS value (p < 0.05). Adhesive failure was the most frequently observed failure mode. The resin cement that presented the lowest pH and UTS also presented the lowest micro-shear bond strength to enamel and dentin.