Effects of solvent type and UV post-cure time on 3D-printed restorative polymers.

OBJECTIVES: This study evaluated the impact of different solvents and UV post-curing times on properties of 3D printing resins for provisional restorations. METHODS: The post-processing methods were tested using two solvents (isopropyl alcohol or absolute ethanol) and three UV times (5, 10, or 30 min). The resins tested were Resilab 3D Temp, Printax Temp, and Prizma Bioprov. Microhardness (kgf/mm2), fracture toughness (KIC, MPa√m), surface roughness (Ra, µm), gloss (gloss units), and degree of CC conversion (%DC) were measured (n = 8). All response variables were collected from the same specimen. The specimens were 3D printed using an SLA/LCD printer (150° angulation, 50 µm layer thickness). Light exposure times were adjusted for each material, and the post-processing methods were applied using an all-in-one machine immediately after printing. Data were analyzed using Three-Way ANOVA (α = 0.05). RESULTS: Microhardness was affected by UV post-cure time and 3D resin. Resilab showed higher microhardness with isopropyl alcohol and 30-min UV time, while Printax had higher microhardness with absolute ethanol. KIC was influenced by solvent type, UV time, and 3D resin, with varying effects on different resins. Roughness was affected by 3D resin and UV time, but no significant differences were seen for Resilab or Prizma. Gloss was influenced by 3D resin, and for Prizma, it was lower with specific solvent/UV time combinations. DC was influenced by 3D resin, with each resin behaving differently. SIGNIFICANCE: Tailoring the combination of 3D resin, solvent washing type, and UV post-curing time is important to achieve optimal mechanical and aesthetic outcomes for restorations.

Influence of pigment Solutions on color stability and surface properties in low-shrinkage and conventional composites.

Color stability is among the most frequent causes of restoration failures, and influences surface properties. Aim: The aim of this study was to investigate the influence of pigment solutions on low-shrinkage and conventional composites regarding changes in the physical properties of composite surfaces. Materials and Method: Specimens of four composites (Filtek Z350 XT, Point 4, N'Durance and Venus Diamond) were randomly distributed into three groups to be submitted to each of three pigment solutions (red wine, tomato sauce and coffee) in fifteen-minute daily cycles, for twenty-eight days. There were 12 groups altogether (n = 10). Color, surface roughness and hardness tests were performed. Statistical analysis includedAnalysis of variance (ANOVA) and Tukey's significance test (a = 0.05). Results: Color changes caused by the solutions did not differ significantly among Filtek Z350 XT, Venus Diamond and N'Durance. Hardness decreased significantly in Filtek Z350 XT and Venus Diamond after chemical challenge with each solution. For the composite independent factor, roughness was highest in Venus Diamond, followed by Filtek Z350 XT, Point 4 and N'Durance. Conclusions: Treatment with different pigment solutions (red wine, tomato sauce or coffee) increased stainability and decreased hardness of both low-shrinkage and conventional composites, while roughness was unaffected.

A estabilidade de cor está entre as causas mais frequentes de falhas de restauragoes, que também influenciam suas propriedades superficiais. Objetivo: O objetivo do presente estudo foi investigar a influencia de solugoes de pigmentos em compósitos convencionais e de baixa retragao, bem como alteragoes naspropriedades físicas da superficie dos compósitos. Materiais eMétodo: Amostras de cada compósito (Filtek Z350XT, Point 4, N'Durance e Venus Diamond) foram distribuidas aleatoriamente em grupos submetidos a cada solugao pigmentante (vinho tinto, molho de tomate e café) em ciclos diários de quinze minutos, durante vinte e oito dias. Assim, totalizando 12 grupos (n = 10). Foram realizados testes de cor, rugosidade superficial e dureza. A Análise Estatistica foi realizada usando Análise de variáncia (ANOVA) e o teste de significáncia de Tukey (a = 0.05). Resultados: As alteragoes de cor desencadeadas pelas solugoes investigadas nao mostraram diferenga estatisticamente significativa entre os compósitos Filtek Z350 XT, Venus Diamond e N'Durance. Os valores de dureza registrados para Filtek Z350XT e Venus Diamond diminuiram significativamente após o desafio químico com cada uma das solugoes pigmentantes. Para o fator independente compósito, Venus Diamond registrou a maior rugosidade; foi seguido por Filtek Z350XT, Point 4 e N'Durance. Conclusoes: Os tratamentos das amostras com diferentes solugoes pigmentantes (vinho tinto, molho de tomate e café) aumentaram a manchabilidade dos compósitos convencionais e de baixa retragao e diminuiram sua dureza, embora nao tenham afetado a rugosidade dos compósitos.

Influence of pigment solutions on color stability and surface properties in low-shrinkage and conventional composites / Influência de soluções pigmentantes na estabilidade de cor e propriedades de superfície em compósitos convencionais e de baixa contração

ABSTRACT Color stability is among the most frequent causes of restoration failures, and influences surface properties. Aim: The aim of this study was to investigate the influence of pigment solutions on low-shrinkage and conventional composites regarding changes in the physical properties of composite surfaces. Materials and Method: Specimens of four composites (Filtek Z350 XT, Point 4, N'Durance and Venus Diamond) were randomly distributed into three groups to be submitted to each of three pigment solutions (red wine, tomato sauce and coffee) in fifteen-minute daily cycles, for twenty-eight days. There were 12 groups altogether (n = 10). Color, surface roughness and hardness tests were performed. Statistical analysis includedAnalysis of variance (ANOVA) and Tukey's significance test (a = 0.05). Results: Color changes caused by the solutions did not differ significantly among Filtek Z350 XT, Venus Diamond and N'Durance. Hardness decreased significantly in Filtek Z350 XT and Venus Diamond after chemical challenge with each solution. For the composite independent factor, roughness was highest in Venus Diamond, followed by Filtek Z350 XT, Point 4 and N'Durance. Conclusions: Treatment with different pigment solutions (red wine, tomato sauce or coffee) increased stainability and decreased hardness of both low-shrinkage and conventional composites, while roughness was unaffected.

RESUMO A estabilidade de cor está entre as causas mais frequentes de falhas de restauragoes, que também influenciam suas propriedades superficiais. Objetivo: O objetivo do presente estudo foi investigar a influencia de solugoes de pigmentos em compósitos convencionais e de baixa retragao, bem como alteragoes naspropriedades físicas da superficie dos compósitos. Materiais eMétodo: Amostras de cada compósito (Filtek Z350XT, Point 4, N'Durance e Venus Diamond) foram distribuidas aleatoriamente em grupos submetidos a cada solugao pigmentante (vinho tinto, molho de tomate e café) em ciclos diários de quinze minutos, durante vinte e oito dias. Assim, totalizando 12 grupos (n = 10). Foram realizados testes de cor, rugosidade superficial e dureza. A Análise Estatistica foi realizada usando Análise de variáncia (ANOVA) e o teste de significáncia de Tukey (a = 0.05). Resultados: As alteragoes de cor desencadeadas pelas solugoes investigadas nao mostraram diferenga estatisticamente significativa entre os compósitos Filtek Z350 XT, Venus Diamond e N'Durance. Os valores de dureza registrados para Filtek Z350XT e Venus Diamond diminuiram significativamente após o desafio químico com cada uma das solugoes pigmentantes. Para o fator independente compósito, Venus Diamond registrou a maior rugosidade; foi seguido por Filtek Z350XT, Point 4 e N'Durance. Conclusoes: Os tratamentos das amostras com diferentes solugoes pigmentantes (vinho tinto, molho de tomate e café) aumentaram a manchabilidade dos compósitos convencionais e de baixa retragao e diminuiram sua dureza, embora nao tenham afetado a rugosidade dos compósitos.

Effect of a Self-Assembly Peptide on Surface Roughness and Hardness of Bleached Enamel.

After bleaching, enamel surfaces are damaged, contributing to erosion and tooth sensitivity. Although fluoride is used after bleaching to try and revert alterations, it is not capable of repairing tooth structure. This study compared the effect of a self-assembly peptide (P11-4), with and without fluoride, and sodium fluoride (NaF 2%) on the Knoop microhardness (KHN) and surface roughness (Ra (µm)) of bleached enamel with an in-office bleaching regimen. Enamel blocks of bovine teeth (5 × 5 × 2 mm) with standardized surface hardness were bleached with 35% carbamide peroxide, following the manufacturer's instructions. The teeth were randomly divided into the following groups (n = 7) according to post-bleaching treatment: no treatment (negative control) (C-); 2% NaF (NaF); Curodont™ Repair (Repair); and Curodont™ Protect (Protect). Specimens were stored in artificial saliva at 37 °C. To evaluate the effect of the post-bleaching treatments, KHN and Ra were measured before bleaching (baseline) and 24 h and 7 days after bleaching. Data were submitted to repeated measures ANOVA and Bonferroni tests (α = 0.05). There were significant interactions between the study factors (p = 0.001). After 7 days, Repair (572.50 ± 79.04) and Protect (583.00 ± 74.76) specimens showed increased surface KHN, with values higher than the NaF (465.50 ± 41.50) and C- (475.22 ± 58.95) baseline values. There was no significant difference in KHN at 24 h among groups (p = 0.587). At 24 h after bleaching, Repair was significantly different from all groups (p < 0.05). Repair showed the lowest Ra (µm) values (0.133 ± 0.035). After seven days, there was no significant difference in Ra values among groups when compared to the baseline. The use of P11-4-based materials after bleaching resulted in the fastest recovery to baseline enamel properties.

Degradation of Adhesive-Dentin Interfaces Created Using Different Bonding Strategies after Five-year Simulated Pulpal Pressure.

PURPOSE: To compare after five-year simulated pulpal pressure (SPP) the degradation of adhesive-dentin interfaces created using two simplified adhesives applied with different bonding strategies. MATERIALS AND METHODS: A two-step self-etch (CSE: Clearfil SE Bond) adhesive was used as a control multistep adhesive. The tested experimental materials were two simplified adhesives, a one-step self-etch (CS3: Clearfil S3 Bond) and a self-priming etch-and-rinse adhesive (SB2: Adper Single-Bond 2). Half of the bonded specimens were submitted to microtensile bond strength (µTBS) testing after 24 h. The other half submitted to SPP for five years before µTBS testing. Nonfractured sticks were evaluated using transmission electron microscopy (TEM). Scanning electron microscopy (SEM) was used to evaluate silver-nitrate nanoleakage within the interface. Data were statistically analyzed by two-way ANOVA and Tukey's test (p < 0.05). RESULTS: Prolonged SPP induced bond-strength reduction for both SB2 and CS3. All bonding approaches showed increased nanoleakage after aging. The two simplified adhesives showed severe degradation at the resin-dentin interface. TEM revealed that the main degradation patterns for the etch-and-rinse adhesive SB2 was collagen breakdown, while polymer hydrolysis along with filler debonding was mainly observed in CS3. CONCLUSIONS: Simplified adhesives applied in etch-and-rinse mode are mainly characterized by hydrolysis and collagen degradation. In self-etch mode, simplified adhesives may principally show hydrolysis of the polymeric matrix and/or at the interface of fillers and coupling agent. The use of multistep self-etching adhesives may guarantee greater dentin bond durability compared to simplified adhesives.

Influence of nanogel additive hydrophilicity on dental adhesive mechanical performance and dentin bonding.

OBJECTIVE: To assess the influence of hydrophilicity of reactive nanogels on the mechanical performance of dental adhesives and microtensile bond strength (µTBS) to dentin after 24h or 3 months of aging. METHODS: A series of three nanogels were synthesized: NG1-IBMA/UDMA; NG2-HEMA/BisGMA; NG3-HEMA/TE-EGDMA. The nanogels were dispersed in solvent, HEMA or BisGMA/HEMA. The degree of conversion (DC) of the materials was measured and the flexural modulus of these polymers was evaluated in dry or wet conditions. For µTBS analysis, a model adhesive was used without nanogel (control) or with the incorporation of nanogels. µTBS was evaluated after storage in distilled water for 24h or 3 months. The analysis of the fracture was performed after µTBS testing. Data were analyzed using ANOVA and Tukey's test (α=0.05). RESULTS: Water significantly increased the modulus of NG1 and NG2 dispersed in solvent, while significantly decreased the stiffness of NG3. All polymers dispersed in HEMA and BisGMA/HEMA had significantly lower modulus when stored in water. NG2 showed the highest DC in solvent and BisGMA/HEMA. In HEMA, NG1 and NG3 produced the highest DC. After three months, NG2 showed the best µTBS. The µTBS of NG2-containing adhesive resin significantly increased after 3 months, while storage had no effect in the control group, NG1 and NG3. SIGNIFICANCE: The more hydrophobic IBMA/UDMA nanogel showed higher bulk material mechanical property results, but the best dentin bond strength values, and notably strength values that improved upon storage, were obtained with the amphiphilic nanogel based on BisGMA/HEMA.

Effect of antioxidants on the dentin interface bond stability of adhesives exposed to hydrolytic degradation.

PURPOSE: This study assessed the effect of antioxidants vitamin C (Vit. C), vitamin E (Vit. E) and quercetin (Querc) on the dentin bonding performance, degree of conversion, and rate of polymerization of three commercial adhesive systems (Adper Single Bond 2 [SB], Clearfil SE Bond [CSE], Adper Easy Bond [EB]). MATERIALS AND METHODS: Human premolars were restored using antioxidant-doped adhesives. The samples were stored for 24 h in distilled water or 6 months under simulated pulpal pressure. Teeth were cut into sticks and the microtensile bond strength (µTBS) to dentin was tested in a universal testing machine. Qualitative nanoleakage analysis was performed from a central stick of each restored tooth. Degree of conversion and rate of polymerization of adhesive systems were evaluated in triplicate using real-time FT-IR. RESULTS: Although the inclusion of the antioxidants negatively affected the µTBS over 24 h, the antioxidant-doped adhesives maintained (SB-Vit. C, SB-Vit. E, CSE-Vit. C, EB-Querc) or increased (SB-Querc, CSE-Vit. E, CSE-Querc, EB-Vit. E, and EB-Vit. C) their µTBS during 6 months of storage. Only the µTBS of Adper Single Bond 2 dropped significantly after 6 months among the control groups. Slight changes in the nanoleakage pattern after aging were observed in all groups, except for the EB-control group, which showed a noteworthy increase in nanoleakage after 6 months, and for EB-Vit. C, which presented a remarkable decrease. A lower degree of conversion was obtained with all antioxidants in SB and EB, except for the EB-Vit. E group. Similar degrees of conversion were attained in control and experimental groups for CSE. The rate of polymerization was reduced in antioxidant-doped adhesives. CONCLUSION: The performance of antioxidants changed according to the adhesive system to which they were added, and antioxidant-doped adhesives appear to have a positive effect on the adhesive interface durability, since their bond strength obtained after 24 h was maintained or increased over time.

Impact of hydrophilicity and length of spacer chains on the bonding of functional monomers.

OBJECTIVES: 10-Methacryloyloxy-decyl-dihydrogen-phosphate (10-MDP) is currently considered as one of the most effective functional monomers for dental bonding, this in part thanks to its long and relatively hydrophobic spacer chain, adequately separating the polymerizable from the phosphate functionalities. This study compared functional monomers with different spacer chains' length and hydrophilicity to 10-MDP on their dentin and enamel bonding performance. METHODS: Atomic absorption spectroscopy (AAS) was used to characterize the chemical interaction. Micro-tensile bond strength (µTBS) and fractographic analyses were performed after 24h and one year. Confocal micro-permeability and SEM nanoleakage assessments were also undertaken. The tested functional monomers were 2-MEP (2-carbon spacer), 10-MDP (10-carbon), 12-MDDP (12-carbon), MTEP (high hydrophilic polyether spacer chain) and CAP-P (intermediate hydrophilic ester spacer). RESULTS: AAS revealed clear differences (p<0.05) in monomer-calcium salt formation in this order: 12-MDDP=10-MDP>CAP-P>MTEP>2-MEP. The highest initial dentin µTBS was obtained using 10-MDP or 12-MDDP. After 1-year aging, a significant drop (p<0.05) in µTBS was observed for the adhesives with MTEP (enamel and dentin), 2-MEP (enamel) and CAP-P (enamel). MTEP presented the highest micro-permeability, while 2-MEP, CAP-P and MTEP showed increased nanoleakage after aging. SIGNIFICANCE: These outcomes showed that more hydrophilic and shorter spacer chains may compromise the chemical interaction with calcium and the dentin/enamel bonding performance.

The role of spacer carbon chain in acidic functional monomers on the physicochemical properties of self-etch dental adhesives.

OBJECTIVES: To evaluate the effects of acidic functional monomers with different hydrophilicity and spacer carbon chain length on the degree of conversion (DC), wettability (contact angle), water sorption (WS) and ultimate tensile strength (UTS) of experimental one-step self-etch adhesives (1-SEAs). METHODS: A series of standard resin blends was prepared with each formulation containing 15mol% of each acidic monomer. The structural variations of the acidic monomers were MEP (spacer chain with 2 carbons), MDP (10-carbons), MDDP (12-carbons), MTEP (more hydrophilic polyether spacer) and CAP-P (intermediate hydrophilicity ester spacer). Dumbbell-shaped and disc specimens were prepared and tested for UTS and WS, respectively. DC was assessed by FTIR, while the wettability of each 1-SEA was evaluated on glass slides and flat dentine surfaces. Results were analysed with one-way ANOVA and Tukey's test (p<0.05). RESULTS: The outcomes showed lower UTS for CAP-P, control blend and MEP than MTEP, MDDP and MDP (p<0.05). The degree of conversion was statistically similar for all resins (p=0.122). On dentine, the wettability was higher (lower contact angle) with the most hydrophilic monomer MTEP. Higher WS was attained using MTEP. Different lengths of the spacer chains did not result in different wettability and WS (p>0.05). CONCLUSION: At similar molar percentage, different acidic functional monomers induced similar degree of conversion and different UTS when included in a 1-SEA. However, the inclusion of highly hydrophilic monomer may increase the wettability on dentine and the WS.

Chemical interaction of 10-MDP (methacryloyloxi-decyl-dihydrogen-phosphate) in zinc-doped self-etch adhesives.

OBJECTIVES: Zinc-doped dentine adhesives have been recently advocated to interfere with metallo-proteinases-mediated collagen degradation. Nevertheless, there is a little information about the effects of zinc ions on the chemical interaction of self-etch functional monomers to dentine. The aim of this study was to assess if the inclusion of zinc into the primers of self-etch adhesives containing MDP (10-methacryloyloxi-decyl-dihydrogen-phosphate) may interfere with their chemical interaction to calcium/dentine. METHODS: Caries-free human molars were bonded using two commercial self-etching adhesives [Clearfil SE bond (CSE) and S3 bond (S3)] doped with zinc nitrate and submitted to microtensile bond strength (µTBS) and interface nanoleakage evaluation. Moreover, MDP was synthesised to evaluate the chemical interaction with calcium/dentine through atomic absorption spectroscopy (AAS) and SEM-EDX in the presence or absence of zinc ions. RESULTS: AAS showed increasing formation of MDP-zinc rather than MDP-calcium salts (p=0.002) in the presence of zinc. SEM-EDX confirmed the formation of zinc-rich phosphate deposits that were probably responsible for the significant reduction in µTBS and increased interfacial nanoleakage attained with zinc-doped CSE and S3. CONCLUSION: These outcomes demonstrated that the excessive presence of zinc ions may jeopardise the bonding performance of MDP-containing self-etch adhesives.

Bonding orthodontics brackets to enamel using experimental composites with an iodonium salt.

OBJECTIVES: This study investigated whether the addition of diphenyliodonium chloride (DPC) to experimental resin bonding agents would allow fixation of brackets to enamel using shorter light exposure times. METHODS: Photoactivated dimethacrylate-based composites were prepared containing DPC molar concentrations of 0 (control), 0.5 (R05), or 1 per cent (R1). Metallic brackets were bonded to bovine incisors and the bond strengths were evaluated using a shear test. In total, 18 groups were tested (n = 15 per group) defined by three bonding materials (control, R05, or R1), three light-activation time (8, 20, or 40 seconds), and two storage periods (10 minutes or 24 hours). The adhesive remnant index (ARI) was scored under magnification. Data were statistically analysed at a 5 per cent significance level. RESULTS: At 10 minutes, the control composite showed lower bond strengths than the DPC-modified bonding agents for all light-activation times. Differences in bond strengths between both DPC-modified agents were not significant. Lower bond strengths at 10 minutes were generally observed for groups light activated for 8 seconds compared with groups light activated for 20 and 40 seconds. At 24 hours, no significant differences were observed among the light-activation times. The bond strengths at 24 hours were higher than the bond strengths at 10 minutes for all groups. A predominance of ARI scores 2 and 3 was generally observed. CONCLUSION: The use of a ternary photoactivation system containing an iodonium salt in bonding composites may allow bonding brackets to enamel using reduced light exposure times.

Evaluation of the micro-mechanical strength of resin bonded-dentin interfaces submitted to short-term degradation strategies.

The aim of this study was to evaluate the microtensile bond strength (µTBS) and confocal micropermeability of resin bonded-dentin specimens created using two representative two-step/self-etch adhesives submitted to short-term period degradation strategies such as simulated pulpal pressure, thermo- or mechanical-cycling challenges. Clearfil SE Bond (CSE) and Silorane adhesive (SIL) were bonded to flat deep dentin from seventy extracted human molars and light-cured for 10 s. Composite build-ups were constructed using with Filtek Z350 XT and Filtek P90 respectively. The specimens of each adhesive group were subjected to three different accelerated aging methods: (1) thermo-cycling challenge (5000 cycles); (2) mechanical-cycling load (200,000 cycles); (3) experiment and (4) conventional method for simulated pulpal pressure (20 cm H2O). Control resin-bonded specimens were stored in distilled water for 24 h. µTBS and confocal microscopy (CLSM) micropermeability evaluation were performed and the results were analyzed using Two-way ANOVA and Tukey's tests (α=0.05). The CLSM evaluation revealed micro-cracks within the Silorane-bonded dentin subsequent to mechanical-cycling load, whereas, the simulated pulpal pressure induced evident micropermeability in both bonding agents. Mechanical loading provides discernible bonding degradation in a short-term period in resin-bonded dentin created using two-step/self-etch adhesives. However, simulated pulpal pressure may reduce the sealing ability of self-etch adhesives causing greater water uptake within the resin-dentin interface.

Hydrolytic degradation of the resin-dentine interface induced by the simulated pulpal pressure, direct and indirect water ageing.

OBJECTIVES: The aim of this study was to compare the hydrolytic effects induced by simulated pulpal pressure, direct or indirect water exposure within the resin-dentine interfaces created with three "simplified" resin bonding systems (RBSs). METHODS: A two-step/self-etching (CSE: Clearfil SE Bond), one-step/self-etching (S3: Clearfil S3) and etch-and-rinse/self-priming (SB: Single-bond 2) adhesives were applied onto dentine and submitted to three different prolonged (6 or 12 months) ageing strategies: (i) Simulated Pulpal Pressure (SPP); (ii) Indirect Water Exposure (IWE: intact bonded-teeth); (iii) Direct Water Exposure (DWE: resin-dentine sticks). Control and aged specimens were submitted to microtensile bond strength (µTBS) and nanoleakage evaluation. Water sorption (WS) survey was also performed on resin disks. Results were analysed with two-way ANOVA and Tukey's test (p < 0.05). RESULTS: The µTBS of CS3 and SB dropped significantly (p < 0.05) after 6 months of SPP and DWE. CSE showed a significant µTBS reduction only after 12 months of DWE (p = 0.038). IWE promoted no statistical change in µTBS (p > 0.05) and no evident change in nanoleakage. Conversely, SPP induced a clear formation of "water-trees" in CS3 and SB. WS outcomes were CS3 > SB = CSE. CONCLUSION: The hydrolytic degradation of resin-dentine interfaces depend upon the type of the in vitro ageing strategy employed in the experimental design. Direct water exposure remains the quickest method to age the resin-dentine bonds. However, the use of SPP may better simulate the in vivo scenario. However, the application of a separate hydrophobic solvent-free adhesive layer may reduce the hydrolytic degradation and increase the longevity of resin-dentine interfaces created with simplified adhesives.

Luting glass ceramic restorations using a self-adhesive resin cement under different dentin conditions.

OBJECTIVES: The aim of this study was to investigate the bond strength of ceramic restorations luted using a self-adhesive resin cement (RelyX Unicem, 3M ESPE) under different dentin conditions. MATERIAL AND METHODS: In the experimental groups, ceramic restorations were luted to bovine incisors with RelyX Unicem under the following conditions: [Dry dentin]: surface was dried using air stream for 15 s; [Moist dentin]: excess dentin moisture was removed with absorbent paper; [Bonding agent]: Clearfil SE Bond (Kuraray) self-etching adhesive system was previously applied to dentin. In the Control group, cementation was done using an etch-and-rinse adhesive (Excite DSC) and Variolink II resin cement (Ivoclar Vivadent). Photoactivation of the resin cements was performed with UltraLume LED 5 unit (Ultradent). The restorations (n=5 per group) were sectioned into beams and microtensile testing was carried out. Data were subjected to ANOVA and Tukey's test (p<0.05). Failure modes were classified under Scanning Electron Microscopic (SEM) (x120 magnification). RESULTS: The bond strength was dependent on the moisture status of the dentin. Bond strength in the "dry dentin group" was significantly lower than that of all other groups, which showed similar results. A predominance of mixed failures was detected for the control group, while a predominance of adhesive failures was observed for the "bonding agent" and "dry dentin" groups. The "moist dentin" group presented predominantly cohesive failures within the luting material. The previous application of a self-etching adhesive showed no significant effect. CONCLUSIONS: Only excess dentin moisture should be removed for the cementation of ceramic restorations with self-adhesive resin cements.

Luting glass ceramic restorations using a self-adhesive resin cement under different dentin conditions

OBJECTIVES: The aim of this study was to investigate the bond strength of ceramic restorations luted using a self-adhesive resin cement (RelyX Unicem, 3M ESPE) under different dentin conditions. MATERIAL AND METHODS: In the experimental groups, ceramic restorations were luted to bovine incisors with RelyX Unicem under the following conditions: [Dry dentin]: surface was dried using air stream for 15 s; [Moist dentin]: excess dentin moisture was removed with absorbent paper; [Bonding agent]: Clearfil SE Bond (Kuraray) self-etching adhesive system was previously applied to dentin. In the Control group, cementation was done using an etch-and-rinse adhesive (Excite DSC) and Variolink II resin cement (Ivoclar Vivadent). Photoactivation of the resin cements was performed with UltraLume LED 5 unit (Ultradent). The restorations (n=5 per group) were sectioned into beams and microtensile testing was carried out. Data were subjected to ANOVA and Tukey's test (p<0.05). Failure modes were classifed under Scanning Electron Microscopic (SEM) (x120 magnifcation). RESULTS: The bond strength was dependent on the moisture status of the dentin. Bond strength in the "dry dentin group" was signifcantly lower than that of all other groups, which showed similar results. A predominance of mixed failures was detected for the control group, while a predominance of adhesive failures was observed for the "bonding agent" and "dry dentin" groups. The "moist dentin" group presented predominantly cohesive failures within the luting material. The previous application of a self-etching adhesive showed no signifcant effect. CONCLUSIONS: Only excess dentin moisture should be removed for the cementation of ceramic restorations with self-adhesive resin cements.

Effect of X-ray radiation dose on the bond strength of different adhesive systems to dentin.

PURPOSE: To investigate the influence of different x-ray radiation doses on the bond strength of adhesive restorations to dentin using different bonding strategies. MATERIALS AND METHODS: Flat dentin surfaces on human molars were obtained and cylinder-shaped specimens for the microshear bond test were built up with a composite (Z250, 3M ESPE), using three adhesive systems: a two-step etch-and-rinse (Single Bond 2--SB2, 3M ESPE), a two-step self-etching (Clearfil SE Bond--CSE, Kuraray), or a single-step self-etching (Adper Prompt--ADP, 3M ESPE). The specimens were assigned to 4 groups (n = 10), according to the x-ray dose: 0 (control), 5, 35, or 70 Gy. Radiation was directed to the surface of the resin cylinders. Microshear testing was conducted after 24 h, and the failure modes classified under magnification (200X). Data were submitted to two-way ANOVA and Holm-Sidak's test (p < or = 0.05). A nonlinear regression analysis was carried out with bond strength as dependent variable. RESULTS: Bond strength results were dose and material dependent. SB2: control > 5 = 35 > 70; CSE: control = 5 > 35 = 70; ADP: control = 5 = 35 = 70. Generally, SB2 > CSE > ADP. The nonlinear regression plots showed that in general, an increase in radiation dose may predict a decrease in bond strength (R2 > or = 0.905). Failure modes were dependent on the bonding system, generally with no significant influence of radiation. CONCLUSION: X-ray radiation might present a dose-dependent detrimental effect on the bond strength of resin composite restorations to dentin.

In-depth polymerization of dual-cured resin cement assessed by hardness.

This study investigates the in-depth polymerization of dual-cured resin cement (Enforce; Dentsply, shades A2, B1, and opaque). Cylindrical specimens are obtained by photo-activation through ceramic. Control samples are light-cured without using ceramic. Samples are tested after 15 min or 24 h. Knoop hardness readings are made at 100, 300, 500, and 700 microm depth. Hardness is generally dependent on the mode of activation and post-cure time. Shades A2 and B1 show higher hardness values than opaque resin. Hardness at 100 microm is higher than at 700 microm. A linear relationship between hardness and depth is observed.

Solubility and dimensional change after setting of root canal sealers: a proposal for smaller dimensions of test samples.

This study proposed smaller dimensions for samples used in solubility and dimensional change tests of root filling materials on the basis of American National Standard Institute/American Dental Association (ANSI/ADA) Specification No. 57. The volume, mass, and density of the test samples were determined, and 6 different samples of smaller dimensions were proposed for each test. Endofill and AH Plus sealers were used in the tests. For the solubility test, 2 samples were weighted, stored in distilled and dionized water for 24 hours, dried, and weighed again. Solubility was calculated by using samples' weight loss (%). For dimensional change analysis, the samples' heights were measured before and after immersion in dionized water for 30 days. For both tests, correlation between data of the different groups was observed. Kruskal-Wallis test showed that Endofill sealer presented higher solubility values than AH Plus (P < .05). The Endofill sealer presented 0.56% of shrinkage and AH Plus 0.62% expansion. Smaller dimensions for test samples used in solubility and dimensional change tests are a viable alternative, decreasing the amount of filling material necessary for executing these tests.