Wet-bonding technique with ethanol may reduce protease activity in dentin-resin interface following application of universal adhesive system.

Background: Greater degradation of the hybrid layer is expected when a universal adhesive system is used, especially in the conventional application strategy. Therefore, it would important to evaluate the effect of the ethanol (ETH) and a potential matrix protease inhibitor (caffeic acid phenethyl ester/ CAPE) to maximize the ability to achieve stable dentin bond strength. The aim of this study was to evaluated the effect of ETH on a wet-bonding technique, and dentin pretreatments with different concentrations of CAPE in ethanolic solution, followed by application of a universal adhesive system (Single Bond Universal) to inhibit proteolytic activity. Material and Methods: Dentin blocks were allocated to eight experimental groups according to the strategy (total-etch our self-etch) and treatments: ETH, or dentin pretreatment with CAPE (at 0.5%, 2.5%; and 5.0%). Half of each block (each hemiblock) served as the control (without dentin pretreatments) for the same group. The bonding strategy was performed (adhesive system/ restoration with composite resin). Two slices were obtained from each hemiblock and evaluated using in situ zymography. The proteolytic activity was analyzed by quantifying the green photons of the images obtained under a fluorescence microscope in three dentin locations close to the dentin-resin interface: hybrid layer (HL), underlying dentin (UD) and deep dentin (DD). Results: Wilcoxon tests (for comparison between experimental and control groups) and Friedman and Nemenyi tests (for comparisons between interface locations) showed that there was no difference between the groups with different CAPE concentrations and the respective control groups (p>0.05). ETH reduced the proteolytic activity at the HL and UD (p<0.05). Conclusions: The wet-bonding technique with ETH proved effective in reducing the proteolytic activity. The use of CAPE in different concentrations solubilized in ethanol did not have a favorable effect on proteolytic inhibition. Key words:Adhesives, Hybrid layer, Dentin, Metalloproteinases.

Titanium dioxide nanotubes in a hydrogen peroxide-based bleaching agent: physicochemical properties and effectiveness of dental bleaching under the influence of a poliwave led light activation.

OBJECTIVES: The effects of different concentrations of titanium dioxide (TiO2) into 40% hydrogen peroxide (HP) were evaluated as regards the effectiveness of dental color change either associated with activation by polywave LED light or not. MATERIALS AND METHODS: TiO2 (0, 1, 5, or 10%) was incorporated into HP to be applied during in-office bleaching (3 sessions/40 min each). Polywave LED light (Valo Corded/Ultradent) was applied or not in activation cycles of 15 s (total time of 2 min). The color of 80 third molars separated into groups according to TiO2 concentration and light activation (n = 10) was evaluated at baseline and at time intervals after the 1st, 2nd, and 3rd bleaching sessions. RESULTS: WID value was significantly higher when using HP with 5% TiO2 in the 2nd session than the values in the other groups (p < 0.05). After the 2nd and 3rd sessions, the ΔEab value was significantly higher when activated with light (p < 0.05) for all agents containing TiO2 or not. Zeta potential and pH of the agents were not modified by incorporating TiO2 at the different concentrations. CONCLUSIONS: The 5% TiO2 in the bleaching agent could enhance tooth bleaching, even without light application. Association with polywave LED light potentiated the color change, irrespective of the presence of TiO2 in the bleaching gel. CLINICAL SIGNIFICANCE: HP with 5% TiO2 could lead to a greater tooth bleaching response in the 2nd clinical session, as well as the polywave light can enhance color change.

Implant-Abutment Misfit after Cyclic Loading: An In Vitro Experimental Study.

This study aimed to evaluate the influence of thermomechanical cycling (TMC) and type of abutment on the misfit and compressive strength of the implant−abutment interface. Forty 3.75-mm external hexagon implants with 25° angled abutments were divided into four groups (N = 10). Group A: overcast plus TMC; Group B: overcast without TMC; Group C: completely cast plus TMC; Group D: completely cast without TMC. Abutments were fixed to the implants with 32-Ncm torque, and groups A and C specimens were cyclically loaded at 80 N with 2 Hz for 1 million cycles. The misfit on the implant−abutment interface was evaluated by optical microscope (100×) and the compressive strength test was performed in a universal test machine. For statistical analysis, a two-way ANOVA and post hoc Tukey test were used. There was no difference in misfit presented by all the abutments in the absence of TMC (p > 0.05). When TMC was performed, the completely cast abutments showed greater misfit than overcast ones (p = 0.001). Regarding compressive strength, irrespective of TMC performed, the overcast abutments showed higher compressive strength values than completely cast abutments (p = 0.003). Moreover, disregarding the type of abutment used, the absence of TMC provided higher compressive strength values (p < 0.001). It was concluded that thermomechanical cyclic loading aggravated the misfit, especially in completely cast abutments, regardless of material or fabrication technique, and reduced the compressive strength of the two types of abutments tested.

The use of desensitizing agents during in-office bleaching might not decrease tooth bleaching sensitivity: a randomized clinical trial.

BACKGROUND: Due to controversial results in relation to the influence of desensitizing agents on sensitivity during bleaching, the present study evaluated the degree of tooth bleaching sensitivity, color change, and patient acceptability of desensitizing agents containing potassium nitrate/sodium fluoride (PNF) or nanostructured calcium phosphate (N) associated with in-office bleaching with 35% hydrogen peroxide (HP). MATERIALS AND METHODS: Seventy-five patients were randomly distributed into three groups (n = 25): 1) Group W - in-office bleaching (Whiteness HP Maxx - three sessions of 45 min); 2) Group WD - associated with PNF desensitizing gel (Desensibilize KF 2%) applied for 10 min before each session; 3) Group WDN - associated with N desensitizing paste (Desensibilize Nano P) applied after bleaching for 5 min. The degree of sensitivity and patient acceptability of the desensitizing treatments were evaluated using a visual analog scale. Color change evaluations were made over different time intervals. RESULTS: The three groups showed no significant difference in sensitivity between the time intervals throughout the evaluation, except for the one of 24 h after the second bleaching session, in which group WD showed lower bleaching sensitivity than group W (P < 0.05; Kruskal-Wallis and Dunn tests). The use of PNF gel and N paste did not interfere with the color change during dental bleaching. CONCLUSIONS: Although the use of desensitizing agents during bleaching did not interfere with the color change during dental bleaching, it was shown that these agents were not effective in the treatment of tooth bleaching sensitivity, despite being acceptable to the patients.

Assessment of frictional resistance and surface roughness in orthodontic wires coated with two different nanoparticles.

Several mechanical and biological factors may change the orthodontic wire frictional resistance (FR). Titanium dioxide (TiO2 ) and silica dioxide (SiO2 ) nanoparticle (NP) coatings may be used to improve the characteristics of materials, reducing FR between archwire and bracket. This in vitro study aimed to evaluate the FR of orthodontic wires with and without coating in both dry and wet environments and measure the surface roughness (SR). One hundred and eighty segments of rectangular Cr-Ni orthodontic wires (Morelli Co, Brazil) were divided into three groups according to the NP coating applied: TiO2 group; SiO2 group; and control group. The SR parameters were measured in an optical profilometer, the surface morphology was analyzed with scanning electron microscopy (SEM), and FR was performed in a universal testing machine in dry and wet environments (n = 30). The statistical analysis was performed using the Generalized Estimated Equations model with a Bonferroni post-test (α = 0.05). It was observed that SiO2 NP coating decreased FR significantly when compared to the TiO2 and control groups, in both environments (p < .001). The SiO2 and TiO2 groups presented statistically lower SR than the control group and were similar to each other (p < .001). The SiO2 group presented the lower depth of Valley parameter than the TiO2 group (p < .001). The SEM showed that the TiO2 coating had the most heterogeneous surface morphology than the SiO2 and control groups. The orthodontic wires with NP coating modified the FR and morphology. The SiO2 coating reduced FR in both dry and wet environments and decreased SR. Titanium dioxide (TiO2 ) and silica dioxide (SiO2 ) nanoparticles coatings may be used to reduce frictional resistance (FR) between archwire and bracket as well as to improve surface morphology. The SiO2 coating reduced FR in both dry and wet environments and decreased the SR of Cr-Ni orthodontic wire. The TiO2 coating promoted the most heterogeneous surface morphology of Cr-Ni orthodontic wire.

Phenolic extract of Libidibia ferrea inhibits dentin endogenous enzymatic activity depending on the adhesive system strategy.

This study evaluated the influence of Libidibia ferrea (Lf) extract used as dentin pretreatment on the resin-dentin bond strength stability and dentin endogenous enzymatic activity. The phytochemical profile (PP) of the Lf extract was evaluated by liquid chromatography; particle size, polydispersity index (PdI), and zeta potential (ZP) were evaluated by dynamic light scattering. The tested groups were ER-Scotchbond Universal (SBU) in the etch-and-rinse (ER) mode; ERLf-SBU in the ER mode + Lf after etching; SE- SBU in the self-etch (SE) mode; and LfSE-Lf before SBU in the SE mode. Sticks were obtained for microtensile bond strength tests and failure mode (24 hr and 12 months). The hybrid layer was evaluated using scanning electron microscopy. The endogenous enzymatic activity of the underlying dentin was analyzed by in situ zymography with the same treatments. The PP showed the presence of quercetin (2.6% w/w). Lf particles were considered large after the analysis of the PdI. The ZP remained stable over time. The ER and ERLf groups had lower bond strength after 12 months, but SE and LfSE remained stable. The predominant failure mode was adhesive for both times. ER and ERLf had longer resin tags and a thicker hybrid layer. The ER and LfSE groups showed higher enzymatic activity than the ERLf and SE groups after 12 months. The Lf extract may contribute to inhibit the dentin endogenous enzymatic activity when associated with an adhesive system in the ER mode.

Biomechanical behavior of atrophic maxillary restorations using the all-on-four concept and long trans-sinus implants: A finite element analysis.

Background. Maxillary bone atrophy with a considerable amount of pneumatization and anterior expansion of the maxillary sinus might be a situation limiting oral rehabilitation with osseointegrated implants. Therefore, the present study aimed to biomechanically evaluate two rehabilitation techniques for maxillary bone atrophy: all-on-four and long trans-sinus implants. Methods. Two three-dimensional models consisting of atrophic maxilla with four implants were simulated. In the M1 model, two axially inserted anterior implants and two tilted implants, 15 mm in length, placed tangential to the maxillary sinus's anterior wall were used. In the M2 model, two axially inserted anterior implants and two trans-sinus tilted implants, 24 mm in length, were used. For the finite element analysis (FEA), an axial load of 100 N was applied on the entire extension of the prosthesis, simulating a rehabilitation with immediate loading. The peri-implant bone and the infrastructure were analyzed according to the Mohr-Coulomb and Rankine criteria, respectively. Results. The results were similar when the stresses on peri-implant bone were compared: 0.139 and 0.149 for models 1 and 2, respectively. The tension values were lower in the model with trans-sinus implants (27.99 MPa). Conclusion. It was concluded that the two techniques exhibited similar biomechanical behavior, suggesting that the use of long trans-sinus implants could be a new option for atrophic maxilla rehabilitation.

Effect of whitening dentifrices on color, surface roughness and microhardness of dental enamel in vitro.

PURPOSE: To evaluate the color, surface roughness and microhardness of human dental enamel subjected to brushing with whitening dentifrices. METHODS: The enamel samples (4 x 4 x 2 mm) were darkened using 0.2% chlorhexidine and black tea, and were randomly divided into seven groups (n= 15) for brushing cycles with only water; control; conventional dentifrice (Colgate Maximum Anticaries Protection); dentifrice containing 2% hydrogen peroxide (Colgate Luminous White Advanced); dentifrice containing sodium tripolyphosphate (Sensodyne True White); dentifrice containing activated charcoal (Black is White); and dentifrice containing blue covarine (Close Up White Now). The samples were submitted to 1,000 and 30,000 brushing cycles. The color values (CIE L*a*b*), surface roughness (Ra) and microhardness (Knoop) were recorded at four time points: baseline, after staining, after 1,000 and after 30,000 brushing cycles. The data were submitted to statistical analyses using paired t-test, ANOVA and Tukey. RESULTS: The color analysis, roughness and microhardness results showed interaction between the effect of the dentifrices and the time point (P< 0.001). The bleaching dentifrices brought about color changes (ΔE) significantly greater than those obtained with conventional dentifrices and the control; however, there were no significant color changes among the bleaching dentifrices. When the color coordinates were evaluated individually, the L* values increased and the a* and b* values decreased throughout the experiment. The conventional toothpaste and the toothpastes containing blue covarine, activated charcoal or hydrogen peroxide promoted a statistically significant increase in the surface roughness of the samples after the last brushing cycle. The sodium tripolyphosphate dentifrice caused a progressive reduction in roughness. The microhardness increased statistically after 30,000 cycles for the conventional toothpaste, blue covarine and hydrogen peroxide. It was concluded that the whitening dentifrices lightened the samples, which evidenced greater luminosity and reduction in reddish and yellow tones. Moreover, they did not have deleterious effects on microhardness, and caused acceptable changes in surface roughness. CLINICAL SIGNIFICANCE: Dentifrices with different whitening strategies changed the color of the samples, resulting in samples with greater luminosity and reduced reddish and yellowish tones. They also caused changes in surface roughness within the acceptable clinical limit and did not have a deleterious effect on the microhardness of dental enamel.

Polyphenol-enriched extract of Arrabidaea chica used as a dentin pretreatment or incorporated into a total-etching adhesive system: Effects on bonding stability and physical characterization.

The aim of this paper was to evaluate the physical properties and the long-term bond strength of a 2.5% polyphenol-enriched extract of Arrabidaea chica (AC) incorporated into both the phosphoric acid and the primer of a three-step total-etch adhesive, or into an aqueous solution as a dentin pretreatment. Fifty dentin surfaces received the treatments (n = 10): CON (control) - application of the three-step adhesive system (Adper Scotchbond Multipurpose, 3M ESPE); WAT - distilled water used as a pretreatment after dentin etching and before application of the adhesive system; ACPA - AC incorporated into the phosphoric acid; ACW - dentin pre-treatment with AC incorporated into an aqueous solution after etching; ACP - AC incorporated into the primer. Microtensile bond strength tests were performed after 24 h, 6 and 12 months of storage. Slices from the resin-dentin interface were obtained for scanning electron microscopy analysis of the hybrid layer. Degree of conversion of AC incorporated into the primer was evaluated. The particle size, polydispersity index and zeta potential of all the solutions prepared by incorporating AC (phosphoric acid, primer and distilled water) were measured by dynamic light scattering, which brought about changes after incorporation. Degree of conversion of the primer was not affected after incorporating AC. ACP showed lower microtensile bond strength values than the other groups. Bond strength decreased after 6 months of storage, stabilizing at the 12-month evaluation. Therefore, use of AC incorporated into the primer led to lower bond strength values, since AC modified the physical properties (particle size, polydispersity index and zeta potential) of the primer, but did not change the degree of conversion. Application of AC as a dentin pretreatment did not affect bond strength or the micromorphological characteristics of the hybrid layer.

Resin-dentin bond stability and physical characterization of a two-step self-etching adhesive system associated with TiF4.

OBJECTIVES: To evaluate the bond strength to superficial (SD) and deep (DD) dentin after the use of 2.5% (T2.5%) or 4% (T4%) titanium tetrafluoride (TiF4) in aqueous solution as a dentin pretreatment, or when incorporated into the primer (T2.5%P and T4%P) of an adhesive system (Clearfil SE Bond/CL). Degree of conversion (DC), particle size (PS), polydispersity index (PI) and zeta potential (ZP) of the solutions were evaluated. METHODS: Fifty molars were sectioned longitudinally to obtain two slices of each tooth, which were demarcated into SD and DD. Treatments were applied (n=10): CL; T2.5%; T4%; T2.5%P; T4%P. After 24h or 180days storage, microshear bond strength tests were performed. The DC values of T2.5%P and T4%P were evaluated by FTIR. PS, PI and ZP were measured using dynamic light scattering. RESULTS: Analysis of mixed models showed significant effect of concentration of TiF4 * solution * storage time (p=0.0075). There were higher bond strength values in SD than in DD (p=0.0105) for all treatments in both times. The failure mode showed adhesive failures in the majority of groups, irrespective of depth and time (p=0.3746). The bond strength values were not affected by treatments. Lower average particle size was observed for T2.5%P and T4%P at baseline. T2.5% and T4% showed a trend towards agglomeration. SIGNIFICANCE: Higher bond strength values were achieved at SD for all treatments and times. The failure modes observed were adhesive. TiF4 incorporation did not affect DC. T2.5%P and T4%P presented excellent stability over time.

Inhibition of demineralization around the enamel-dentin/restoration interface after dentin pretreatment with TiF4 and self-etching adhesive systems.

OBJECTIVES: The objective of this study was to evaluate the inhibition of demineralization around enamel-dentin/restoration interface after dentin pretreatment with 2.5% titanium tetrafluoride (TiF4). MATERIALS AND METHODS: Forty dental class V cavities at the cementoenamel junction were distributed into four groups (n = 10), according to the presence or absence of TiF4 and to the adhesive system (Clearfil SE Bond/CL and Adper EasyOne/AD), and restored with a resin composite. A dynamic pH cycling model was used to induce the development of artificial caries lesions. After sectioning the dental blocks, Knoop microhardness tests were performed at different depths (20, 40, and 60 µm from the occlusal margin of the restoration) and at different distances (100, 200, and 300 µm from the adhesive interface). Repeated measures three-way analysis of variance (ANOVA) and Tukey's test were used (α = 0.05). RESULTS: For enamel, there were no differences in the microhardness values for CL, AD, and TiF4-AD at depths, regardless of the distances. Considering each depth, there were no significant differences among treatments. For dentin, ANOVA showed no significant interaction among the independent variables treatment*distance*depth (p = 0.994), no significant interaction between treatment*depth (p = 0.722), no significant interaction between treatment*distance (p = 0.265), no significant interaction between depth*distance (p = 0.365), and no significant effect on treatment (p = 0.151), depth (p = 0.067), or distance (p = 0.251). CONCLUSIONS: Dentin pretreatment of the cavity walls with TiF4 before self-etching adhesive systems was not effective in inhibiting demineralization around the enamel-dentin/restoration interfaces. CLINICAL RELEVANCE: The mechanism of incorporating fluoride in enamel and dentin of the cavity walls to inhibit demineralization around restorations seems ineffective when using TiF4 as a dentin pretreatment.

Antimicrobial Potential of Papain Chemomechanical Agent on Streptococcus Mutans and Lactobacillus Casei Followed by the Use of Self-Etching Adhesive Systems.

OBJECTIVE: This study evaluated the antimicrobial effect of papain-based gel (Papacárie/ P) followed by self-etching adhesive systems with MDPB monomer (Clearfil Protect Bond/ PB) and without (Clearfil SE Bond/ Cl) on Streptococcus mutans (Sm) and Lactobacillus casei (Lc). STUDY DESIGN: The dentin of twenty human teeth was exposed to prepare four cylindrical cavities in each tooth. The cavities were incubated with Sm or Lc. One cavity from each tooth served as contamination control (positive control group); the other three were treated with P, P+CL and P+PB. The cavities were sealed and after 72 h, dentin samples were collected and microbial cultivation was performed. Microbial count was undertaken (CFUs/mg) according to the morphological characteristics for Sm and Lc. Analysis of variance and Tukey's test were applied (α=5%). RESULTS: For Sm, groups P+Cl and P+PB had lower microbial count than group P (no statistical differences between P+Cl and P+PB). For Lc, group P+Cl had microbial count similar to group P. There was statistical difference between cavities treated with P and P+PB but none between groups P+Cl and P+PB. After using P, both self-etching adhesives showed antimicrobial potential, although Clearfil Protect Bond proved better against Lc. CONCLUSIONS: Both self-etching adhesives used after application of Papacárie showed antimicrobial potential, although Clearfil Protect Bond proved more effective against Lactobacillus casei.

Influence of translucence/opacity and shade in the flexural strength of lithium disilicate ceramics.

BACKGROUND: Lithium disilicate ceramic system consists of glass ceramic ingots with different grades of translucence which may influence its flexural strength. AIMS: To assess the three-point flexural strength of the different lithium disilicate-based ceramic ingots (IPS e.max Press/Ivoclar Vivadent) with different levels of translucence and shade. MATERIALS AND METHODS: Six groups of ceramic ingots were selected to represent different levels of translucence and shade (HTA1, HTBL2, LTA2, LTB2, MO2, and HO). They measured 25 mm × 5 mm × 2 mm (n = 10), according to ISO 6872 specifications, and tested on a universal test machine (EMIC). STATISTICAL ANALYSIS USED: A one-way analysis of variance (ANOVA) was used (α = 0.05). RESULTS: The results (in MPa) were: HTA1 = 392.98; HTBL2 = 390.74; LTA2 = 390.46; LTB2 = 389.92; MO2 = 390.43; HO = 391.96. ANOVA showed no significant difference among groups (P = 0.1528). CONCLUSIONS: Different levels of translucence, opacity and shade of ingots did not affect their mechanical strength, and the use of these ceramics should be guided by the esthetic demands of each clinical situation.

In vitro evaluation of calcium and phosphorus concentrations in enamel submitted to an in-office bleaching gel treatment containing calcium.

The aim of this in vitro study was to evaluate the calcium and phosphorus concentrations in enamel surfaces before, during, and after treatment with in-office 35% hydrogen peroxide bleaching agents with 2% calcium gluconate (WCa) or without calcium gluconate (W). Twenty sound human third molars were divided into 2 groups of 10. The bleaching agents were applied to the tooth surfaces in accordance with the manufacturer's instructions: WCa, 40 minutes per day at 3 sessions with 7-day intervals; W, 3 × 15 minutes per day at 3 sessions with 7-day intervals. Enamel microbiopsies were performed prior to the bleaching treatment, immediately after each bleaching session (first, second, and third applications), and 7 and 14 days following the last bleaching treatment. The concentration levels of calcium and phosphorus in the microbiopsy specimens were recorded spectrophotometrically. There was a statistically significant decrease in the calcium concentration 7 days after the last bleaching treatment, but there was a recovery to baseline values at 14 days, regardless of the bleaching agent used (WCa and W). When W was used, there was no difference in the phosphorus concentration over time. The phosphorus concentration in the WCa group decreased after the third application, showing a significant difference from the W group at this time. However, an increase in the phosphorus concentration was observed in the posttreatment period, and no significant differences were observed between values at baseline and those at 14 days posttreatment. The in-office bleaching gel containing 2% calcium gluconate did not affect the calcium and phosphorus concentrations in enamel as compared to a calcium-free bleaching agent.

Microhardness and color monitoring of nanofilled resin composite after bleaching and staining.

OBJECTIVES: The present study aimed to investigate the effect of staining solutions on microhardness and shade changes of a nanofilled resin composite, which had been previously in contact with bleaching agents. MATERIALS AND METHODS: A total of 135 disk-shaped specimens (10 mm × 2 mm) were fabricated with a nanofilled resin (Filtek Supreme) and photocured with a Light Emission Diode (LED) unit and then allocated into three groups to be bleached with 10% or 16% carbamide peroxide (CP) bleaching agents or a 35% hydrogen peroxide (HP) product. Following bleaching, specimens within each group were subdivided into three groups to be immersed in coffee, red wine or distilled water. Microhardness and color were monitored at baseline, after bleaching and after staining. RESULTS: Analysis of variance for split-plot design showed lower microhardness values when the composite had been in contact with HP (P < 0.0001). The specimens immersed in red wine and coffee provided lower microhardness values than those immersed in distilled water, regardless of the bleaching agent to which the composites were previously exposed. Kruskal Wallis and Dunn tests demonstrated that the composite was lighter after bleaching with a 35% HP agent (P < 0.0500). CONCLUSION: The composite was darker as a result of being immersed either in red wine or coffee, regardless of the bleaching agent.

Effect of double coating of one-step self-etching adhesive on micromorphology and microtensile bond strength to sound vs demineralized dentin.

AIM: The purpose of the present study was to evaluate (1) the one-step adhesive system application method (doubling the adhesive coatings) in regard to microtensile bond strength (MTB) and (2) the interfacial morphology of one-step adhesives to sound vs demineralized dentin. MATERIALS AND METHODS: Forty dentin fragments were randomly allocated to 2 groups: D. demineralized dentin and S. sound dentin. Specimens were also subdivided into 2 groups (n = 10), according to the one-step adhesive [AEO (Adper Easy One), 3M ESPE] application method: M, According to the manufacturer's instructions, and D, based on the application of two consecutive layers. After adhesive light polymerization, a resin composite block (Filtek Z250, 3M ESPE) was built on the dentin surface. Resin-tooth blocks were sectioned into 0.9 mm thick slabs, and one slab of each block was prepared for adhesive interface analysis by scanning electron microscopy (SEM). The remaining slabs were sectioned into 0.8 mm(2) sticks that were subjected to tensile stress (0.5 mm/min). Data were subjected to two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The application of two consecutive layers of AEO adhesive system did not Influence MTB values for sound dentin. When two consecutive layers of one-step adhesive system were applied, MTB was statistically greater in demineralized vs sound dentin. SEM analysis demonstrated that the application of two consecutive adhesive layers to sound and demineralized dentin produced longer resin tags. CONCLUSION: It can be concluded that the application of two consecutive adhesive layers improved bond strength to deminera-lized dentin, but no such effect was observed for sound dentin. CLINICAL SIGNIFICANCE: Application of double coats of one-step self-etching adhesive improved bond strength to demineralized dentin.

Influence of preheating the bonding agent of a conventional three-step adhesive system and the light activated resin cement on dentin bond strength.

AIMS: to evaluate the influence of preheating the bonding agent (Scotchbond Multipurpose Adhesive/3M ESPE) and the light-activated resin cement (RelyX Venner/3M ESPE) on dentin microtensile bond strength. MATERIALS AND METHODS: The exposed flat dentin surface of 40 human third molars were randomly distributed into four groups for cementation (SR Adoro/Ivoclar Vivadent) (n = 10): G1-bond and resin cement, both at room temperature (22°C), G2-bond preheated to 58°C and cement at room temperature (22°C), G3-bond at room temperature (22°C) and the cement preheated to 58°C, G4-bond preheated to 58°C and cement preheated to 58°C. Sticks of dentin/block set measuring approximately 1 mm(2) were obtained and used for the microtensile bond strength test. All sticks had their failure mode classified. STATISTICAL ANALYSIS USED: Factorial analysis of variance was applied, 2 × 2 (bond × cement) (P < 0.05). RESULTS: Preheating the bonding agent (P = 0.8411) or the cement (P = 0.7155), yielded no significant difference. The interaction bond × cement was not significant (P = 0.9389). CONCLUSIONS: Preheating the bond and/or the light-activated resin cement did not influence dentin bond strength or fracture failure mode.

The effects of home-use and in-office bleaching treatments on calcium and phosphorus concentrations in tooth enamel: an in vivo study.

BACKGROUND: Because the effects of dental bleaching on enamel needs to be clarified in vivo, the authors conducted a study to determine calcium and phosphorus concentrations in enamel after the application of different bleaching treatments. METHODS: The authors applied four agents (10 percent and 20 percent carbamide peroxide [both recommended for home use], 38 percent and 35 percent hydrogen peroxide [both applied in the dental office]) to the enamel of 80 participants, who were divided into four groups of 20. The authors collected enamel microbiopsy specimens from incisors before (baseline), during (seven, 14 and 21 days) and after (seven and 14 days) the bleaching treatments. They analyzed calcium and phosphorus concentrations by using a spectrophotometer. RESULTS: The authors analyzed data by using the Friedman test and the Kruskal-Wallis test, followed by the Dunn test (α= .05). There were no statistical differences between the evaluation results, regardless of which bleaching gel was used, for determining the concentration of either calcium or phosphorus. CONCLUSIONS: Home-use and in-office bleaching gels did not alter the concentrations of calcium and phosphorus concentrations on the enamel surface in vivo. CLINICAL IMPLICATIONS: In vivo, different dental bleaching techniques did not alter the inorganic composition of enamel.

Effects of water flow on ablation rate and morphological changes in human enamel and dentin after Er:YAG laser irradiation.

PURPOSE: To investigate the laboratory effect of Er:YAG laser on ablation rate and morphological changes in human enamel and dentin with varying water flow. METHODS: 23 human third molars were sectioned in mesio-distal and buccal-lingual directions. The slabs were flattened and weighted on an analytical laboratory balance (control). A 4-mm2 area was demarcated and the samples were randomly assigned into three groups according to water flow employed during the laser irradiation (1.0, 1.5, and 2.0 mL/minute). An Er:YAG laser was used to ablate enamel (80.22-J/cm2, 300 mJ/4Hz) and dentin (96.26-J/cm2, 250 mJ/4Hz). After irradiation, the samples were immersed in distilled water for 1 hour and then weighted again. The final mass was obtained and laser-irradiated substrate mass loss was calculated by the difference between the initial and final mass. Afterwards, specimens were prepared for SEM. RESULTS: Data were submitted to ANOVA and Tukey's test (P < 0.05). It was observed that the 2.0 mL/minute resulted in a higher mass loss, 1.0 mL/minute showed a lower mass loss, and 1.5 mL/minute demonstrated intermediate results (P < 0.05). The increase of water flow promoted less melting areas and cracks. Furthermore, dentin was more ablated than enamel. It may be concluded that the water flow of Er:YAG laser and the substrates affected the ablation rate. Among the tested parameters, 2.0 mL/minute improved the ability of ablation in enamel and dentin, with less morphologic surface alteration.

Surface roughness evaluation and shade changes of a nanofilled resin composite after bleaching and immersion in staining solutions.

PURPOSE: To investigate the effect of bleaching and staining solutions on roughness and shade changes in a nanofilled resin composite [Filtek Supreme (FS)]. METHODS: FS specimens (n = 135) were light cured and separated into groups (n = 45) that were bleached with 10% carbamide peroxide (CP) agent or 16% or 35% hydrogen peroxide (HP). In the first two groups the bleaching gel was used for 4 hours a day, during 14 days, and for the third group in three sessions of 45 minutes. Each group was subdivided (n = 15) and immersed in coffee, red wine or distilled water for 3 hours a day during 40 days. The roughness values (Ra) and shade (parameter CLELab) were evaluated at baseline, after bleaching and after staining. The data was analyzed by ANOVA and Tukey test or Kruskal Wallis. RESULTS: The effects on specimens varied depending on the bleaching product and staining solution. FS after bleaching and after staining presented higher roughness. In the evaluation of shade changes after bleaching, it was observed that resin color changed and that 35% hydrogen peroxide bleached the resin more than the others. After staining in three solutions, all specimens changed color and wine showed the higher staining capacity.