Development of toothpaste formulations containing mineral clays as abrasive agents and their effects on the physical properties of dental enamel.

To assess the physical properties and topographical aspect of dental enamel's surface microhardness (KHN), surface roughness (Ra), and color parameters CIELAB (∆Eab*), CIEDE 2000 (∆E00), and whiteness index for dentistry (∆WID) after toothbrushing with experimental toothpaste formulations with the following mineral clay types: kaolin, Sparclay SGY, and Tersil CGY used as abrasive component. Scanning electron microscopy (SEM) was performed for topographical analyses purposes. A total of 96 bovine incisors were used in the experiment. They were divided into eight experimental groups (n = 12), namely: NC-negative control (no treatment), CT12-Colgate Total 12®, CMP-Colgate® Máxima Proteção Anticáries, K-kaolin experimental toothpaste, SGY-Sparclay SGY experimental toothpaste; CGY-Tersil CGY experimental toothpaste, SD-SiO2 experimental toothpaste, and CC-CaCO3 experimental toothpaste. All samples were subjected to mechanical brushing protocol with 5000 cycles and kept in artificial saliva with daily exchanges. KHN was analyzed through the mixed linear model for repeated measures over time. Ra was analyzed through nonparametric Kruskal Wallis and Dunn tests to compare the groups. Paired Wilcoxon test was run to compare experimental times. ∆WID, ∆Eab*, and ∆E00 were analyzed through Kruskal Wallis and Dunn tests. All analyses were performed in R* software, at 5% significance level. EXP_SGY recorded higher KHN than EXP_SiO2 and EXP_CaCO3, whereas EXP_K showed increased Ra in comparison to CMP (p = 0.0229). ∆Eab and ∆E00 were significantly higher in the CT12, EXP_SiO2, and EXP_CaCO3 groups than in the NC and EXP_K (p < 0.0001). There were no significant changes in ∆WID (p = 0.0852). According to SEM results, toothbrushing with experimental toothpastes added with mineral clay types did not have significant impact on enamel's polishing and smoothness. CLINICAL RELEVANCE: Mineral clays have a broad application in the cosmetic industry, and recently, they have been used in the formulation of vegan toothpaste.

Maintenance of enamel properties after bleaching with high-concentrated hydrogen-peroxide gel containing calcium polyphosphate sub-microparticles.

OBJECTIVE: To assessed the physical and chemical properties of human-enamel after treatment with an experimental bleaching gel containing 35%-hydrogen peroxide (HP) and calcium polyphosphate sub-microparticles (CaPP). MATERIALS AND METHODS: Enamel/dentin specimens (4 × 4 × 3 mm) were obtained (n = 120) and allocated to different groups: control (saliva only); experimental (HP35%); commercial (whiteness-HP-Maxx); CaPP0.5% (HP35% + CaPP0.5wt%); CaPP1.5% (HP35% + CaPP1.5wt%). Three sessions were performed. The specimens' color was assessed using a spectrophotometer and the color (ΔE/ΔE00) and bleaching index (ΔWID) determined. The surface roughness and microhardness were assessed with a roughness tester and Knoop indenter. Raman spectroscopy was performed to obtain the ratios between the areas under the 431, 580, and 1070 cm-1 and the 960 cm-1 bands (430:960, 580:960, 1070:960). Kruskal-Wallis and Dunn compared the color, Ra, and SMH data. The Raman data was analyzed with Kruskal-Wallis and Dunn (α = 5%). RESULTS: The ΔE, ΔE00, and ΔWID were similar among the bleached groups (p > 0.05). The roughness was not different between the groups (p > 0.05). After the 3rd session, CaPP0.5% had higher microhardness than the experimental (p < 0.05). The 1070:960 was higher in the experimental than in the CaPP1.5% and control (p < 0.05). CONCLUSIONS: In human enamel, CaPP did not alter the bleaching effectiveness or roughness, and additionally, CaPP-containing gels increased the microhardness and preserved the mineral content when compared to the experimental without CaPP. CLINICAL RELEVANCE: Experimental bleaching gels containing calcium polyphosphate sub-microparticles as a mineral source reduce the mineral content alteration and superficial microhardness reduction, known potential side effects of the in-office bleaching treatments.

Evaluation of experimental resin infiltrant containing nanohydroxyapatite on color stability and microhardness in demineralized enamel.

OBJECTIVE: The aim of the study was to evaluate the effect of the addition of 10% nanohydroxyapatite in an experimental resin infiltrant on color stability and mineral loss. MATERIAL AND METHODS: Bovine enamel blocks were randomized into five groups (n = 27/group): SE (sound enamel); ICL (initial caries lesion); I (Icon®); E (experimental infiltrant); EH (experimental infiltrant containing 10% nanohydroxyapatite). Color evaluation (n = 15) was performed and CIEL*a*b* values were obtained at points T0 (baseline), T1 (14 days immersed on coffee solution), and T2 (28 days immersed) and data were calculated ∆E00, ∆WID, ∆L*, ∆a*, and ∆b*. Cross-sectional microhardness (n = 12) was performed and lesion area (∆S) was calculated. Images were obtained with polarized light optical microscopy at 40 × magnification (n = 5). RESULTS: In color stability results, there was significant difference between time (14 and 28 days); ICL demonstrated significant difference among treated groups in all measures (∆L*, ∆a*, ∆b*, ∆E00, ∆WID) regardless of time; I and E demonstrated similar behavior on those measures and EH differed from I in ∆L*. For ∆S, ICL group showed a significant difference compared to I and EH groups, but did not differ from E. CONCLUSION: The nanohydroxyapatite incorporation suggested an effective mineral recovery on initial caries lesion in depth; however, it showed high color variation, such as Icon. In terms of ∆S, I and EH had lower mineral loss, suggesting a reinforcement on initial caries lesion. CLINICAL RELEVANCE: Commercial and experimental infiltrants containing nanohydroxyapatite present low color stability and might reinforce mineral in initial caries lesion.

Effect of incorporation of calcium polyphosphate sub-microparticles in low-concentration bleaching gels on physical properties of dental enamel.

AIM: To evaluate the bleaching efficacy and effects on enamel properties of experimental gels with carbamide peroxide (CP; 10%) or hydrogen peroxide (HP; 6%) containing calcium polyphosphate sub-microparticles (CaPPs). METHODS: A total of 216 bovine tooth specimens were divided for microhardness and color analyses (n = 108) and block randomized into nine groups (n = 12): (G1) commercial CP (Whiteness Perfect, FGM; Brazil); (G2) experimental CP; (G3) CP-0.5%CaPPs; (G4) CP-1.5%CaPPs; (G5) commercial HP (Potenza Bianco, PHS; Brazil); (G6) experimental HP; (G7) HP-0.5%CaPPs; (G8) HP-1.5%CaPPs; (G9) artificial saliva. The gels' pH values were determined with a bench pH meter. Color (ΔE, ΔE00, ΔWID) and microhardness variation were evaluated before and after the therapy. Part of the specimens used for microhardness was submitted to the scanning electron microscopy (SEM) (n = 3) and energy-dispersive X-ray spectroscopy EDX (n = 3) analyses. Statistical analyses were performed in the R statistical software (α = 0.05). Linear mixed models for repeated measures in time were used to analyze microhardness and L* values. Generalized linear models were used to analyze the a*, b*, ΔE, ΔE00, and ΔWID, considering a group effect. The EDX data were analyzed using a one-way ANOVA with Tukey's test. RESULTS: The gels' pH remained over 6,0. All gels effectively bleached the specimens and did not differ significantly. When compared to the control group, the hardness was significantly lower in the G1, G2, G6, and G7 groups. The G3, G4, G5, and G8 groups did not differ significantly (p > 0.05). CONCLUSION: The incorporation of CaPPs in low-concentration whitening gels reduces its negative effects on microhardness without interfering with their bleaching efficacy.

Influence of alveolar bone height on the biomechanical behavior of roots restored with custom-made posts-and-cores.

OBJETIVE: This study evaluated the influence of alveolar bone height and post type on compressive force resistance, fracture pattern, and stress distribution in endodontically treated teeth. MATERIALS AND METHODS: Bovine roots were endodontically treated and divided into eight groups (n = 10) according to alveolar bone height (normal alveolar bone and alveolar bone loss - 2 and 5 mm from the margin of the crown, respectively) and post type (prefabricated glass fiber post, anatomic glass fiber post, customized milled glass fiber post-and-core and customized milled polyetheretherketone (PEEK) post-and-core). Mechanical fatigue was simulated (300.000 cycles/50 N/1.2 Hz). Compression force resistance (N) was analyzed by two-way ANOVA and Tukey test (α = 0.05). Fracture patterns were described as percentages. Stress distribution was analyzed by finite element analysis. RESULTS: Significant diferences were found for alveolar bone height (P < 0.0001): normal alveolar bone groups showed higher mean values of compression force resistance compared to alveolar bone loss groups, while no significant differences were found for post type (P = 0.4551), and there was no double interaction between them (P = 0.5837). Reparable fractures were more predominant in normal alveolar bone groups, especially in the milled glass fiber and PEEK post-and-core groups. Stress distribution was similar in groups with prefabricated glass fiber posts and milled PEEK posts-and-cores, and the alveolar bone loss condition significantly increased stress concentration and strain values, mainly on apical dentin. CONCLUSIONS: Alveolar bone loss due to physiological aging and/or periodontal disease may lead to increased risk of restored tooth failure, although milled glass fiber and PEEK posts-and-cores provide more reparable fractures. CLINICAL SIGNIFICANCE: Custom-made glass fiber and PEEK post-and-cores are interesting options, since they enable clinicians to work with a single-body post-and-core system that avoid several materials interfaces and fits well in the root canal provided promising results to improve the failure behavior of restored roots, as they offer more reparable fractures even in situations of alveolar bone loss.

In-office tooth bleaching with chitosan-enriched hydrogen peroxide gels: in vitro results.

OBJECTIVE: This study aimed to evaluate the effects of adding chitosan to 35% hydrogen peroxide gels (for in-office bleaching), with or without calcium gluconate, on tooth properties and bleaching efficacy. METHODS: Bovine enamel/dentin specimens (4 × 4 × 2.5 mm) were randomly allocated into groups (n = 10): negative control (unbleached), bleaching with 35% hydrogen peroxide gel (35% HP, commercial gel); 35% HP with 2% chitosan (% wt) (35% HP + chitosan), 35% HP and calcium (35% HP + Ca, commercial gel), and 35% HP + Ca + 2% chitosan. Variation of surface profile (ΔRa) and color analyses (ΔL*, Δa*, Δb*, ΔE*ab, ΔE00, and ΔWID) were performed comparing specimens at baseline (initial) and 24 h after of storage in artificial saliva (final). Surface microhardness (KHN) values and scanning electron microscopy (SEM) images were obtained on conclusion. The data were analyzed by ANOVA and Tukey's tests (KHN), generalized linear models (ΔL*, ΔEab, ΔE00, ΔWID, ΔRa), and Kruskal-Wallis and Dunn tests (Δa*, Δb*) (α = 0.05). RESULTS: Considering ΔL*, Δa*, Δb*, ΔE*ab, ΔE00, and ΔWID values, the bleached groups differed from negative control. For ΔRa, chitosan-based groups showed lower variation in surface roughness compared to 35% HP, without significant difference from negative control. For KHN, chitosan groups did not differ from negative control (unbleached control = chitosan groups > 35% HP + Ca > 35% HP). For SEM, slight surface changes were observed in all bleached groups, but the intensity varied according to gel used (35% HP > gels with Ca > gels with chitosan). CONCLUSION: Chitosan-enriched hydrogen peroxide gels can reduce negative impacts on tooth properties without affecting bleaching efficacy. CLINICAL RELEVANCE: Although commercial gels containing remineralizing agents such as calcium reduce the negative effects on the properties of teeth, the addition of chitosan appears to be a promising approach to preservation of dental properties without interfering in bleaching efficacy.

PEEK and fiberglass intra-radicular posts: influence of resin cement and mechanical cycling on push-out bond strength.

OBJECTIVES: To evaluate the bond strength of four types of posts (pre-fabricated fiberglass post, fiberglass post anatomized with composite resin, milled fiberglass post, and milled polyetheretherketone (PEEK) post), and two types of resin cements (conventional and self-adhesive) by assessing immediate bond strength and post-mechanical aging at each root third. MATERIALS AND METHODS: Bovine endodontically treated roots (16 groups, n = 8) were prepared and the posts were produced and luted; the specimens of aging groups were cycled (300,000 cycles under 50 N load at 1.2 Hz frequency); six slices of each root were obtained; push-out test was performed by using a universal testing machine (500 N load at 1 mm/min cross speed); fracture pattern was classified into five levels. The statistical analyses used were three-way ANOVA, Tukey's test (for bond strength), and Fisher's test (for fracture pattern) (α < 0.05). RESULTS: Differences were found between the cements for posts (conventional: p < 0.001; self-adhesive: p = 0.002), whereas no difference was found for root region (p = 0.941; p = 0.056, respectively); analysis of each root showed significant differences for cements (p < 0.001), posts (p < 0.001), and mechanical cycling (p = 0.001); in terms of double interaction, differences were found for posts and mechanical cycling (p = 0.005); no other interactions were observed (double or triple); the fracture pattern showed difference between the groups for both cements. CONCLUSIONS: Milled PEEK posts seem to be a good clinical option, but they require improvement of CAD-CAM technology and advances towards their adhesion. CLINICAL RELEVANCE: Milled posts are promising and can reduce clinical time for rehabilitation of extensively destroyed teeth.

Altered physical-chemical properties of home bleaching gels after an accelerated stability study and their effects on tooth enamel.

OBJECTIVES: To investigate the physical-chemical properties of home bleaching gels based on Carbamide Peroxide (CP) and Hydrogen Peroxide (HP) after accelerated stability (AS) and its effects on enamel. MATERIALS AND METHODS: A total of 360 bovine teeth blocks were divided (n = 12): Control, CP10%-Whiteness Perfect, CP10%-Pola Night, HP7.5%-Pola Day, and HP7.5%-White Class Calcium. Microhardness (KHN), roughness (Ra), color (ΔE and ΔE00), hardness, compressibility, elasticity, cohesiveness, adhesiveness, weight, pH, and calcium (Ca) quantification in enamel were analyzed without storage of the bleaching gels and after AS at 1 and 3 months. Data of Ca, KHN, and Ra were analyzed through mixed models for repeated measurements and the Tukey-Kramer test. Values of weight, hardness, compressibility, and elasticity were analyzed with two-way ANOVA and Tukey's test. ΔE/ΔE00 data, cohesiveness, and adhesiveness were analyzed with Kruskal-Wallis and Dunn tests (α = 0.05). RESULTS: Groups subject to AS had lower ΔE and ΔE00 compared to those without storage. Lower KHN and higher Ra values were found after bleaching treatment in all groups compared to controls. Higher amounts of Ca were found on the first day of evaluation in the gels subject to AS for 3 months, regardless of the bleaching agent used. CONCLUSIONS: Incorrectly stored bleaching gel accentuates adverse effects on enamel. Temperature and humidity interfere directly with the chemical stability of bleaching agents, reducing their properties. CLINICAL RELEVANCE: HP is an unstable oxidizing agent when stored at high temperatures. Therefore, pH becomes more acidic and potentiates the demineralizing effect on enamel.

Nano-hydroxyapatite-induced remineralization of artificial white spot lesions after bleaching treatment with 10% carbamide peroxide.

OBJECTIVE: To assessed in vitro the effect of nanohydroxyapatite (n-HA) to improve the aesthetic appearance and microhardness of white spot lesions (WSL) when associated with a low-concentration bleaching agent (carbamide peroxide-CP10%). MATERIAL AND METHODS: Enamel/dentin specimens (n = 60) of 5 × 5 × 2.2 mm were prepared, of these, 48 were submitted to pH-cycling to create artificial WSL. Subsequently, these were allocated into five groups (n = 12): n-HA; n-HA + CP10%; CP10%; WSL control (WSLC ); sound control (Sound). The color was assessed at baseline, pre-treatment, and post-treatment using a spectrophotometer, and the color (ΔE/ΔE00 ) and whiteness index (ΔWID) alterations were determined. The enamel cross-sectional microhardness (CSMH) was evaluated (post-treatment) with a Knoop indenter, 25gf/5 s, 20-200 µm. The data was analyzed through generalized linear models (α = 5%). RESULTS: ΔE and ΔE00 were significantly higher for the bleached groups (n-HA + CP10% and CP10%), and the n-HA was higher than the WSLC group (p < 0.05). ΔWID was significantly higher for the bleached groups (p < 0.05). The CSMH values were significantly higher in the sound group than in the n-HA, CP10%, and WSLC groups (p < 0.05). The WSLC had lower microhardness than the n-HA + CP10% and sound groups (p < 0.05). CONCLUSION: n-HA is suitable to remineralize and recover the color of the WSL. However, its association with CP10% maintains the esthetical outcome while increasing its in-depth remineralizing effect. CLINICAL SIGNIFICANCE: Considering the aesthetic and functional repercussions of the WSL persistence, treatments that tend to improve its physical appearance and reinforce its weakened substructure in a non-invasive way are ideal. For this associating low-concentration, bleaching agents to the remineralizing treatments is promising to treat this type of lesions.

Can brushing with regular and whitening dentifrices influence changes in color and micromorphologic surfaces of ceramic brackets subjected to coffee staining?

The aim of the present study was to evaluate the influence of brushing with regular or whitening dentifrices on the change in color and micromorphologic surface of ceramic orthodontic brackets subjected to coffee staining. Fifty ceramic brackets were subjected to cycles of coffee staining followed by brushing according to the following groups (n = 10): C, control (no brushing); DW, brushing with distilled water; CT, brushing with Colgate Total 12 Clean Mint (regular toothpaste); COW, brushing with Colgate Optic White (containing 1% hydrogen peroxide); and CUWA, brushing with Close-Up White Attraction (containing blue covarine). The color of the brackets was assessed using the Commission Internationale de l'Eclairage (CIE) L*a*b* system at 5 different timepoints: prior to staining (baseline) and after 1, 7, 14, and 21 days of staining and brushing cycles. The surface micromorphology of the brackets was assessed at the baseline timepoint and after 21 days. Kruskal-Wallis, Dunn, Friedman, and Nemenyi tests were applied (α = 0.05) for the statistical analysis. The C group demonstrated a significant reduction in L* and a significant increase in a* and b* values over time. For the DW group, the L* value was reduced but was higher than in the C group, and there were also significant increases in a* and b* from baseline values. A significant increase in the a* and b* values was observed in all groups (P < 0.05). Total color change (∆E*) increased over the period of evaluation for all whitening groups, although only the CT group presented significantly lower ∆E* than the other dentifrices. At the end of the test period, only the COW group exhibited a surface with higher porosity. None of the dentifrices prevented the brackets from staining, but they did reduce the magnitude of color change caused by coffee. The most significant difference was found in the CT group. Micromorphologic surface changes were observed when COW was employed.

Restoration of teeth with customized CAD/CAM glass fiber posts: report of 2 cases.

This article presents 2 cases in which computer-aided design/computer-aided manufacturing (CAD/CAM) was used to fabricate glass fiber posts to restore an anterior tooth and a posterior tooth with severe coronal destruction. In the past decade, CAD/CAM technology has improved, allowing high-precision milling of customized glass fiber posts. This can enhance the biomechanical behavior of the restoration, as the post and core are milled in a single unit, decreasing the risk of failure near the core junction or in the body of the core. The customized post also provides better adaptation and requires a thinner layer of cement, thus minimizing voids. In case 1, the patient had a severely damaged maxillary right canine with a ferrule from a previous restoration. In case 2, the patient presented with a mandibular left first molar exhibiting severe coronal destruction. In both cases, impressions of the root canal were scanned with a bench scanner, and the posts were fabricated using a glass fiber material designed for CAD/CAM technology. A self-adhesive resin cement was used to cement the posts in the root canals, and a metal-free crown (case 1) and overlay (case 2) were fabricated and placed. Satisfactory retention and esthetics were achieved, and both patients was pleased by the final results. These cases demonstrate the viability of CAD/CAM to restore endodontically treated teeth, and this technology can be an option for dentists interested in using a digital workflow. The longevity of the posts produced via this technique needs to be evaluated in clinical trials.

Effect of ammonium acryloyldimethyltaurate copolymer on the physical and chemical properties of bleached dental enamel.

OBJECTIVE: To analyze the effect of bioadhesive polymer, Aristoflex® AVC, on enamel physical and chemical properties. MATERIALS AND METHODS: Bovine enamel blocks were divided into CP 10% with carbopol-Whiteness Perfect® (WP-FGM), CP 10% with Aristoflex (A + CP 10%), CP 10% with carbopol (C + CP 10%), Aristoflex (A), carbopol (C), carbamide peroxide 10% (CP 10%) and control (no treatment). The treatment was performed for 4 h during 14 days. The colour (ΔE, ΔL*, Δa* and Δb*), profilometry (Ra) and surface microhardness (KHN) were performed before and after the bleaching treatment. The concentrations of Ca and P were performed on the 1st, 3rd, 7th and 14th days by inductively coupled plasma optical emission spectrometry for the groups WP, A + CP 10%, C + CP 10%, A, C and CP 10% (control without thickener) and the morphology by scanning electron microscopy. RESULTS: All groups with CP 10%, regardless of polymer, differing statistically to ΔE, ΔL*, Δa* and Δb* compared to control group. The group A + CP 10% maintained low values of roughness and microhardness after bleaching. Higher concentration of Ca and P was found in the 1st day of treatment for the WP group compared to the groups A + CP 10% and C + CP 10%. CONCLUSION: The 10% CP associated with the bioadhesive polymer Aristoflex® AVC was effective on the bleaching treatment without changing the physical properties of the dental enamel. Also, this experimental gel caused less mineral loss than the group CP 10% with carbopol (WP-FGM). CLINICAL RELEVANCE: Because the change of Carbopol by Aristoflex, a bioadhesive polymer, does not interfere with the effectiveness of bleaching treatment, it is a promising agent associated to carbamide to maintain the physical properties of enamel after bleaching.

Influence of different thickeners in at-home tooth bleaching: a randomized clinical trial study.

OBJECTIVES: To evaluate the effects of 10% carbamide peroxide (CP) with two different thickeners, carbopol (CPc) and natrosol (CPn), on color variation (CV), tooth sensitivity (TS), and cytotoxicity (CC). METHODS: Seventy subjects were distributed into the CPc or CPn groups (n = 35), in a parallel group, randomized, controlled, single-blind clinical trial. Bleaching gels were used by volunteers for 4 h daily for 2 weeks. Color evaluation was performed using a reflectance spectrophotometer, before bleaching treatment (BT), immediately after the first and second weeks of BT, and 1 week and 1 month after BT ended. TS was evaluated using two pain scales, before, during, and after BT. CC was evaluated using MTT after exposure of MDPC-23 cells to the bleaching gels for 4 h. Epoxy replicas of the subjects teeth were made before and after BT and analyzed using a scanning electronic microscope. The data was analyzed using statistical methods. RESULTS: CV and TS showed similar variation between both bleaching gels (p ≤ 0.05). None of the protocols affected cellular metabolism or the surface morphology of enamel. CONCLUSIONS: Bleaching gels with carbopol and natrosol as thickening agents produced similarly effective tooth bleaching and TS, but did not cause cytotoxicity. CLINICAL RELEVANCE: Natrosol could be an alternative as a thickener used in bleaching gels due to its similar bleaching effect and TS when compared with Carbopol.

Effect of diphenyliodonium hexafluorophosphate salt on experimental infiltrants containing different diluents.

Non-invasive treatments for caries lesions are increasingly required for oral health; resin infiltration is one possible conservative option. In this study, we evaluated the effects of diphenyliodonium hexafluorophosphate salt (DPI) on experimental resin infiltrants with either (hydroxyethyl)methacrylate (HEMA) or ethanol as the diluent. A monomeric base with diglycidyl methacrylate ethoxylated (BisEMA, 25 wt%) and triethylene glycol dimethacrylate (TEGDMA, 75 wt%), 0.5 mol% of camphorquinone, and 1 mol% of ethyl-4-(dimethylamino)benzoate (EDAB) was prepared. The mixtures were divided into 12 groups according to DPI concentration (0; 0.25; 0.5; 1 mol%) and diluents (10 wt% HEMA, 10 wt% ethanol, or none). Degree of conversion (DC), water sorption (Ws), solubility (Sol), contact angle (CA), and cohesive strength (CS) tests were performed and compared to a commercial infiltrant control group (Icon). Only ethanol negatively affected DC and Sol, but both diluents negatively affected Ws and CS. Nevertheless, the presence of DPI, mainly at the 0.5 mol% concentration, compensated for the negative effects of the diluents. The commercial control group was less effective only for CS. In conclusion, 0.5% DPI seems to be the most suitable concentration to compensate for the negative effects of diluents.

Influence of an arginine-containing toothpaste on bond strength of different adhesive systems to eroded dentin.

The aim of this study was to evaluate the bond strength of different adhesive systems to eroded dentin following toothbrushing with an arginine-containing toothpaste. Sixty standardized 3 × 3 × 2-mm fragments of root dentin (n = 10) were prepared. After all surfaces except the buccal surfaces were impermeabilized, specimens were subjected to an erosive wear protocol and stored for 24 hours at 37°C. The specimens underwent 1000 toothbrushing cycles with an arginine-containing toothpaste, an arginine-free toothpaste (positive control group), or artificial saliva (negative control group). Following application of a self-etching or an etch-and-rinse adhesive to the buccal surfaces of the specimens, 6-mm-high composite resin blocks were built up in 2-mm increments. After 24 hours' storage in 100% relative humidity, microtensile test specimens with an approximate area of 1 mm² were prepared. The test was performed at a speed of 0.5 mm/min until specimen fracture, and the failure patterns were evaluated using a stereoscopic loupe. Two-way analysis of variance revealed no significant difference between the toothpastes, the adhesive systems, or the interactions between toothpaste and adhesive system in terms of the bond strength to eroded dentin (P > 0.05). The predominant failure pattern was adhesive in all groups. It was concluded that a toothpaste containing arginine did not interfere with the bond between either the self-etching or the etch-and-rinse adhesive system and eroded dentin.

Effect of 7.5% hydrogen peroxide containing remineralizing agents on hardness, color change, roughness and micromorphology of human enamel.

PURPOSE: To determine the microhardness, color change, surface roughness, and micromorphology of tooth enamel submitted to bleaching treatment with 7.5% hydrogen peroxide (HP) with added calcium, amorphous calcium phosphate, sodium fluoride (NaF), and hydroxyapatite (HA). METHODS: 80 enamel slabs were used (n = 10). Three commercial agents [Pola Day 7.5%, Day White ACP 7.5% (DW-ACP), and White Class Calcium 7.5% (WC-Calcium)], three experimental (7.5% HP+NaF, 7.5% HP+HA, and 7.5% PH+NaF+HA), a positive control (with HP), and a negative control (without HP) groups were assessed. The commercial products were applied according to manufacturers' recommendations and the experimental ones were applied for 1.5 hours daily. During and after treatment, specimens were stored in artificial saliva. Tests were performed at baseline, 7, 14, 21, 28, and 35 days. Data were analyzed by ANOVA and Tukey's test (α = 0.05). RESULTS: DW-ACP presented lower microhardness and HP+HA presents the highest values (P < 0.05); only the experimental group presented color change similar to the commercial agents (P > 0.05). Overall, roughness increased with time (P < 0.05) and porosities, and deposition of crystalline structures in groups HP+HA and HP+NaF+HA were noted. The HP+HA agent was capable of reducing the loss of enamel microhardness due to bleaching and also present color change similar to the commercial products.

Influence of successive light-activation on degree of conversion and Knoop hardness of the first layered composite increment.

PURPOSE: To evaluate the influence of light-activation of second, third and fourth increments on degree of conversion (DC) and microhardness (KHN) of the top (T) and bottom (B) surface of the first increment. MATERIALS AND METHODS: Forty samples (n = 5) were prepared. In groups 1-4, after each increment light-activation (multiple irradiation), T and B of the first increment were measured in DC and KHN. In groups 5-8, only the first increment was made (single irradiation) and measurements of DC and KHN were taken at 15 min intervals. The light-activation modes were (XL) 500 mW/cm(2) × 38 s (G1/G5); (S) 1000 mW/cm(2) × 19 s (G2/G6), (HP) 1400 mW/cm(2) × 14 s (G3/G7); (PE) 3200 mW/cm(2) × 6 s (G4/G8). Data for DC and KHN were analyzed separately by using PROC MIXED for repeated measures and Tukey-Kramer test (α = 0.05). RESULTS: For KHN, B showed lower values than T. PE resulted in lower values of KHN in B surface. For single and multiple irradiations, T and B of first measurement showed the lowest KHN and the fourth measurement showed the highest, with significant difference between them. For single irradiation, first and second increments presented similar KHN, different from the third and fourth increment, which did not differ between them. For multiple irradiations, the second light-activation resulted in KHN similar to first, third and fourth increments. For DC, except QTH, T presented higher DC than B. CONCLUSION: The light-activation of successive increments was not able to influence the KHN and DC of the first increment.

Impact of the distance of light curing on the degree of conversion and microhardness of a composite resin.

OBJECTIVE: This study evaluated the impact of the distance between the light guide tip of the curing unit and material surface on the degree of conversion and Knoop microhardness of a composite resin. MATERIALS AND METHODS: Circular samples were carried out of a methacrylate micro-hybrid resin-based composite and light cured at 0, 2 and 4 mm distance. Monomer conversion rate was measured using a Fourier-transform Raman spectrometer and Knoop hardness number was obtained using a microhardness tester on the top and bottom surfaces. Data were statistically analyzed by analysis of variance and Tukey's test (α=0.05). RESULTS: Overall, the increase of curing distance reduced the microhardness (p≤0.05), but did not influence the carbon double bond conversion rate (p>0.05) of the composite resin tested; and the top surface showed better properties compared to the bottom (p≤0.05). CONCLUSIONS: The light curing at distance can reduce mechanical properties and could affect long-term durability of the composite restorations. Thus, the use of a curing device with high irradiance is recommended.

In vitro effects of hydrogen peroxide combined with different activators for the in-office bleaching technique on enamel.

OBJECTIVE: The aim of this study was to evaluate the alteration of human enamel bleached with high concentrations of hydrogen peroxide associated with different activators. MATERIALS AND METHODS: Fifty enamel/dentin blocks (4 × 4 mm) were obtained from human third molars and randomized divided according to the bleaching procedure (n = 10): G1 = 35% hydrogen peroxide (HP - Whiteness HP Maxx); G2 = HP + Halogen lamp (HL); G3 = HP + 7% sodium bicarbonate (SB); G4 = HP + 20% sodium hydroxide (SH); and G5 = 38% hydrogen peroxide (OXB - Opalescence Xtra Boost). The bleaching treatments were performed in three sessions with a 7-day interval between them. The enamel content, before (baseline) and after bleaching, was determined using an FT-Raman spectrometer and was based on the concentration of phosphate, carbonate, and organic matrix. Statistical analysis was performed using two-way ANOVA for repeated measures and Tukey's test. RESULTS: The results showed no significant differences between time of analysis (p = 0.5175) for most treatments and peak areas analyzed; and among bleaching treatments (p = 0.4184). The comparisons during and after bleaching revealed a significant difference in the HP group for the peak areas of carbonate and organic matrix, and for the organic matrix in OXB and HP+SH groups. Tukey's analysis determined that the difference, peak areas, and the interaction among treatment, time and peak was statistically significant (p < 0.05). CONCLUSION: The association of activators with hydrogen peroxide was effective in the alteration of enamel, mainly with regards to the organic matrix.

Effect of light polymerization time, mode, and thermal and mechanical load cycling on microleakage in resin composite restorations.

This study evaluated the effect of polymerization mode and time and thermal and mechanical loading cycling (TMC) on microleakage in composite resin restorations. One hundred and eighty cavities were prepared and randomly divided according to the light curing time (20, 40, or 60 s), modes (quartz-tungsten-halogen (QTH)-420 mW/cm(2), LED 2 (2nd degree generation)-1,100 mW/cm(2), or LED 3 (3rd degree generation)-700 mW/cm(2)), and TMC. Following standard restorative procedures, the samples were prepared for analysis in an absorbance spectrophotometer. All results were statistically analyzed using the three-way ANOVA and Tukey test (p ≤ 0.05). The results revealed that the groups QTH and LED 3 submitted to TMC showed higher microleakage than those that were not submitted to TMC. Only for LED 3, 60 s showed higher microleakage than 20 s. For LED 2 and QTH, there were no differences between the times. QTH showed lower microleakage means than LED 2, when photoactivated for 20 s, without TMC. When photoactivated for 60 s, QTH showed lower microleakage means than LED 3, for the groups with or without TMC. It was concluded that TMC, the increase in polymerization time, and the irradiance were factors that may increase the marginal microleakage of class II cavities.