Effect of Er:Yag laser on dentin demineralization around restorations.

The aim of this study was to evaluate the effect of cavity preparation with Er:YAG laser on dentin adjacent to restorations submitted to cariogenic challenge in situ, by subsuperficial microhardness analysis. Bovine incisors were sectioned, flattened, and polished, resulting in 40 dentin slabs. The slabs were randomly assigned to four groups (n = 10), according to the cavity preparation method: I-high-speed handpiece (control); II-Er:YAG laser (160 mJ; 3 Hz); III-Er:YAG laser (260 mJ; 3 Hz); IV-Er:YAG laser (300 mJ; 3Hz). Cavities were restored with composite resin, and the specimens were fixed in intra-oral appliances, which were worn by 10 volunteers for 14 days for simulating cariogenic challenge in situ. During the experimental period, 20% sucrose solution was dripped over each specimen 6 times a day. Samples were removed, sectioned, and examined for subsuperficial Knoop microhardness at 100, 200, and 300 µm from the restoration and at 30 µm from dentin surface. Split-plot analysis of variance showed no significant difference among the cavity preparation techniques (p = 0.1129), among distances (p = 0.9030), as well as no difference in the interaction between the main factors (p = 0.7338). It was concluded that the cavity preparation with Er:YAG laser did not influence on dentin microhardness submitted to cariogenic challenge in situ.

Caries removal in deciduous teeth using an Er:YAG laser: a randomized split-mouth clinical trial.

OBJECTIVES: The aim of the present clinical randomized split-mouth study was to evaluate the effectiveness and efficiency of an Er:YAG laser for caries removal in primary molars, microbiological dentin analysis, and clinical restorations after 1 year in 29 children. MATERIALS AND METHODS: The children's teeth were randomized into two groups: (I) an Er:YAG laser group and (II) a bur preparation group. The efficiency of the treatments (the time necessary for the removal of carious tissue) was evaluated based on the time spent on caries removal in the deciduous molars. The effectiveness (caries removal capacity) of the caries removal was determined by means of a blind test in which the examiner performed a tactile and visual examination of the dentin. Microbiological analysis was performed by counting the Streptococcus mutans and Lactobacillus sp in the remaining dentin. Clinical analysis of restorations was performed using the USPHS method in combination with photographs of restored teeth, 7 days after the restorative procedure and again after 1 year. All cavities were restored with the Adper Single Bond 2/Filtek Z350 system. The obtained data were analyzed with a significance level of 5 %. RESULTS: The Er:YAG laser was less effective and had the same efficacy as bur preparation during caries removal at the pulpal wall of deciduous molars. In the surrounding walls, bur preparation was the more effective method. Regardless of the method employed, the affected dentin in the pulpal wall had similar amounts of S. mutans and Lactobacillus sp. The restorations were clinically accepted by the USPHS method over a 1-year period. CONCLUSION: It can be concluded that caries removal with an Er:YAG laser has no influence on the clinical behavior of restorations. CLINICAL RELEVANCE: Irradiation with an Er:YAG laser is appropriate for caries removal in primary teeth.

Effect of Er:YAG laser on enamel demineralization around restorations.

This study evaluates in situ the effect of erbium-doped yttrium aluminum garnet (Er:YAG) laser parameters on the development of caries-like lesions adjacent to dental restorations. One hundred fifty bovine enamel slabs were randomly allocated among 15 volunteers. The specimens were subdivided into ten groups: nine experimental groups prepared with Er:YAG laser (300 mJ output, frequency of 2, 4 or 6 Hz, water flow rate of 2.0, 5.0, or 8.0 mL/min) and one control group (high-speed handpiece). The prepared cavity was restored with a composite resin, and the slabs were mounted on palatal appliance to be installed in the volunteers to the cariogenic challenge. After this, the specimens were sectioned to the longitudinal microhardness measurements. Data were submitted to Friedman and Wilcoxon paired tests. All groups prepared with Er:YAG laser demonstrated microhardness values higher than those prepared with high-speed handpiece, which showed the lowest microhardness values (24.86). The group prepared with Er:YAG laser (2 Hz-2.0 mL/min) showed the highest microhardness values (152.43), followed by those prepared with Er:YAG laser (2 Hz-5.0 mL/min) (133.08) and Er:YAG laser (2 Hz-8.0 mL/min) (91.61), respectively. The groups Er:YAG laser with 4 and 6 Hz of frequency and water flow rates of 2.0, 5.0, and 8.0 mL/min showed microhardness values lower than the groups cited above and showed statistical similarity among them. The Er:YAG laser parameters employed to cavity preparation influenced the acid resistance of the irradiated substrate, and the Er:YAG laser was capable to control the development of caries-like lesions around composite resin restorations.

Fluoride plus CO2 laser against the progression of caries in root dentin.

PURPOSE: To evaluate the effect of a 1.23% acidulated phosphate fluoride (APF) gel combined with CO2 laser in protecting carious root dentin against further cariogenic challenges. METHODS: After a 7-day lead-in period, 12 volunteers wore an intraoral palatal device containing four carious root dentin slabs, treated with APF and APF+CO2 or placebo and placebo+CO2. After a 14-day wash-out period, volunteers were crossed-over to the other treatment arm. During both intraoral phases, specimens were submitted to cariogenic challenges and then evaluated for cross-sectional Knoop microhardness. RESULTS: Two-way ANOVA demonstrated that there was significant effect for both main factors: CO2 laser irradiation (P < 0.0001) and gel treatment (P < 0.0001), and that there was no interaction between them (P = 0.4706). Protection of carious root dentin against further cariogenic challenges may be provided by APF fluoride gel and CO2 laser, but no additive benefit was found by combining such strategies.

Effect of dentifrices against hydrochloric acid-induced erosion.

PURPOSE: This in vitro investigation assessed whether different dentifrices would be capable of controlling the enamel erosion progression caused by HCl. MATERIALS AND METHODS: Sixty bovine enamel slabs were covered with acid-resistant varnish, except for a 2.5-mm2 circular area on the labial surface. According to a complete block design, the experimental units were immersed in HCl solution (pH 1.2; 0.1M). After storage in artificial saliva for 1 h, specimens (n = 15) were exposed to different dentifrices: Sensodyne Cool Gel (1100 ppm F), Sensodyne ProNamel (1450 ppm F), and PrevDent 5000 (5000 ppm F). The control group was immersed in deionised water. Following five cycles of erosive challenge, the slabs were prepared for porosity evaluation using solutions of copper sulfate and rubeanic acid. RESULTS: ANOVA demonstrated no difference in the enamel porosity as a function of the dentifrice employed (P = 0.5494). CONCLUSION: The damage caused by a simulated intrinsic erosive challenge seems unable to be controlled by fluoridated dentifrices, even when this ion is found in elevated concentrations.

Effect of a bleaching agent on abrasion of resin-based restoratives.

PURPOSE: To evaluate the effect of a 10% carbamide peroxide-containing bleaching agent on brushing abrasion of esthetic restorative materials. METHODS: Using a randomized complete block design, 150 specimens (n = 15) measuring 3 x 3 x 2 mm were fabricated into acrylic resin cylinders, using one of the restorative materials: a microfilled resin composite (Al), a hybrid resin composite (Ch), a flowable resin composite (Wa), a resin-modified glass-ionomer cement (Fj) and a polyacid-modified resin composite (Dy). The bleaching agent or artificial saliva (control) was applied for 2 hours/day. After that, 120 brushing strokes were simulated automatically and the samples were kept in artificial saliva. Such bleaching/brushing cycle was performed daily for 21 days. Wear depth was assessed using profilometry. RESULTS: Bleaching did not show significant effect on wear depth. There was a significant difference among the restorative materials. Tukey's test showed that (Al = Ch) < (Wa) < (Fj) and that Dy was only different from Fj.

Potential effect of sodium bicarbonate-containing dentifrice in controlling enamel erosion in situ.

PURPOSE: To assess, by a crossover 2 x 2 in situ study, the speculated protective role of a sodium bicarbonate-containing toothpaste in controlling erosive lesions. METHODS: Bovine enamel slabs were sterilized, and submitted to baseline Knoop microhardness measurements. After a 3-day lead-in period, 14 volunteers wore palatal acrylic appliances containing six enamel slabs (three on each side), for 4 consecutive days. On the first day, appliances with contained specimens were placed in the oral cavity to allow salivary pellicle formation. On the subsequent days, half of the enamel slabs were immersed extraorally in a lemonade-like soft drink for 90 seconds, twice daily. On both of these occasions, the appliance was dipped in toothpaste slurry of either a sodium bicarbonate-containing toothpaste or a regular counterpart for 60 seconds. Following a 3-day washout period, a new set of enamel slabs were mounted and the volunteers started the second period using the alternate dentifrice. RESULTS: ANOVA (alpha = 0.05) showed no statistically significant difference between enamel treated with regular and sodium bicarbonate-based dentifrices, regardless of whether specimens were eroded or not (P = 0.8430). Acid-challenged specimens revealed lower microhardness values than uneroded samples.

Feasibility of using sodium bicarbonate solution as a damage-limiting strategy for erosion lesions.

PURPOSE: One of the recommended measures to prevent and control dental erosion is the oral rinse with sodium bicarbonate solution, which would neutralise the dietary acids. However, the prescription of this aqueous suspension has been made on an empirical basis. The aim of this in vitro study was to evaluate whether the demineralisation caused by erosive episodes could be controlled by the potential neutralising effect exerted by a sodium bicarbonate solution. MATERIALS AND METHODS: Bovine enamel slabs were embedded in epoxy resin, ground/polished and tested for initial surface microhardness. Twice daily for 2 days, specimens were subjected to an erosive challenge with orange juice in an orbital shaker. Following each erosive episode, specimens (n = 15) were immersed for either 30 or 60 seconds in a sodium bicarbonate solution or deionised water. The negative control group was left untreated. For the remaining daily time, specimens were kept in artificial saliva. New microhardness indentations were then made as described for the initial measurements. RESULTS: ANOVA applied to the percentage of surface microhardness change (%deltaSMH) showed no statistically significant difference among treatments (P = 0.5810). CONCLUSION: The use of sodium bicarbonate solution, at least under in vitro conditions, may not be a feasible strategy for managing enamel erosion.

Effects of a potentially erosive antiasthmatic medicine on the enamel and dentin of primary teeth: An in situ study.

This study evaluates, in situ, the effect of an anti-asthmatic medicine on the enamel and dentin of primary teeth. Twenty-eight specimens of enamel and dentin were prepared, selected, sterilized, and stored. Microhardness, microscopic morphology, and initial surface roughness were evaluated. Fourteen volunteers wore palatal devices containing two dentin specimens and two enamel specimens. Volunteers underwent surface treatment three times a day for 5 days, with the dripping of 5 ml of salbutamol sulfate for 1 min, only on specimens from one side of the device. At the end of the experiment the microscopic morphology, roughness, surface loss, and microhardness were ascertained. For enamel surfaces exposed to the medicine, erosion was observed in the microscopy images, along with a significant increase in roughness (p = .0325) and tissue loss (p = .03251) and a significant decrease in microhardness (p = .0325). For the dentin surfaces, erosion was observed in the microscopy images, but there was no significant increase in roughness (p = .593) or tissue loss (p = .285) nor any decrease in microhardness (p = .1088). In conclusion, the salbutamol sulfate had an in situ erosive effect on primary teeth enamel and this effect was observed morphologically on primary dentin. RESEARCH HIGHLIGHTS: Asthma is considered a global health problem, and its prevalence has increased in many countries, especially among children, as well as dental erosion. This study has clinical relevance because provides data on the erosive effect of a commonly prescribed anti asthmatic drug on deciduous teeth.

Micromorphology and surface roughness of sound and demineralized enamel and dentin bleached with a 10% carbamide peroxide bleaching agent.

PURPOSE: To evaluate the micromorphology and surface roughness of sound and demineralized enamel and dentin treated with a 10% carbamide peroxide bleaching agent in situ for 3 weeks. METHODS: A 10% carbamide peroxide bleaching agent, Opalescence (OPA) was evaluated and a placebo agent (PLA) not containing carbamide peroxide, was used as a control group. Forty dental slabs [10 sound enamel slabs (SE), 10 demineralized enamel slabs (DE), 10 sound dentin slabs (SD) and 10 demineralized dentin slabs (DD)] were randomly fixed on the facial surface of the first maxillary molars and second maxillary premolars of 10 volunteers. Demineralized enamel and dentin fragments were obtained by a dynamic model using demineralizing and remineralizing solutions. The volunteers were divided into two groups that received the bleaching or the placebo agent in different sequences and periods in a double blind 2 x 2 cross-over study with a wash-out period of 2 weeks. Roughness was performed on the slab surfaces followed by scanning electron microscope (SEM) evaluations. The images were evaluated by three calibrated examiners in duplicate in two different periods at x1500 (SE and DE) and x2000 original magnification (SD and DD). RESULTS: The Wilcoxon test showed significant differences in roughness for SE and DE treated with OPA or PLA, with rougher surfaces treated with OPA. No differences in roughness were observed for SD or DD treated with OPA or PLA. As the Kappa value for the inter-examiner agreement of SEM evaluations showed "moderate" reproducibility (0.41 < k< 0.60) in Period 1 and "substantial" (0.61 < k < 0.8) in Period 2, the latter was considered for the statistical analysis. The McNemar test showed no significant differences between SE, DE, SD or DD treated with OPA or PLA.

Concentration-dependent effect of bleaching agents on microhardness and roughness of enamel and dentin.

PURPOSE: To evaluate the microhardness and surface roughness of enamel and root dentin bleached with 10%, 15% and 22% carbamide peroxide agents. METHODS: 52 slabs of enamel and root dentin (6 x 3 x 2 mm) were cut from bovine incisors, ground flat and polished. According to a randomized complete block design, enamel and root dentin slabs (n = 13) were independently allocated to be bleached with one of the following carbamide peroxide-containing agents (CP): 10% (Rembrandt Bleaching Gel Plus), 15% (Rembrandt Xtra Comfort), or 22% (Rembrandt Xtra Comfort Ultra Strength). The control groups were mock-treated with artificial saliva. The bleaching procedures consisted of daily application of the agents on dental substrate surfaces for 2 hours, followed by immersion in artificial saliva for 22 hours over 21 days. Knoop microhardness and surface roughness were measured initially, on sound dental tissues, and at the postbleaching phase. RESULTS: In enamel, microhardness attained after bleaching with 10% CP and 15% CP were similar and significantly lower than that observed for the control group. Specimens bleached with CP 22% did not differ from any of the other groups tested. In root dentin, microhardness changes were indistinguishable. ANOVA showed no significant difference among treatments with respect to surface roughness.

Susceptibility of bleached enamel and root dentin to artificially formed caries-like lesions.

PURPOSE: To evaluate in vitro the susceptibility of caries-like lesion formation on enamel and root dentin that had been bleached with carbamide peroxide agents. METHODS: 150 slabs of bovine enamel and root dentin were ground flat and polished. According to a randomized complete block design, the specimens were then allocated to be bleached with agents (Rembrandt) containing 12% [CP12], 16% [CP16], 22% [CP22] or 30% [CP30] of carbamide peroxide over 21 days. The control group remained unbleached. Afterwards, all specimens were randomly distributed between two subgroups (n= 15): one was subjected to alternating demineralizing and remineralizing solutions to induce caries-like lesions and the other was not. Enamel specimens were cycled four times in demineralizing (pH 5.0) and remineralizing solutions (pH 7.0), while root dentin specimens were cycled twice. Microhardness measurements were carried out at the post-bleaching and at the post-caries lesion formation phases. RESULTS: In the post-bleaching condition, microhardness values for both enamel and root dentin were dependent on the bleaching agent used. At the post-caries formation stage, there was a significant interaction between the bleaching treatment and substrate condition (carious or noncarious) for enamel and root dentin. Regardless of the bleaching agent, carious enamel and root dentin presented significantly lower microhardness values as compared to the noncarious counterparts. For carious enamel, those specimens exposed to CP16 exhibited higher microhardness values than the subset group formed by CP22, CP30 and unbleached samples. Both subsets did not differ from CP12. For carious root dentin, no difference was observed among the microhardness values attained as a result of the different bleaching treatments.

Textural characterization of finished and polished composites over time of intraoral exposure.

This in situ study sought to evaluate the surface roughness evolution of resin composites finished and polished by different methods. A total of 108 rectangular-shaped specimens of a microfilled and a hybrid composite were cured against a Mylar matrix strip and left unpolished or instrumented with diamond burs, Al2O3-coated disks, Al2O3-impregnated UDMA disk, or with diamond burs followed by either one of the disks. After specimens had been profiled for the average surface roughness (Ra, microm), 18 volunteers wore a removable palatal appliance, which accommodated one specimen of each one of the 12 groups investigated. Surface roughness for up to 28 days of intraoral exposure was then measured at 1- or 7-day intervals. A split-plot ANOVA (alpha = 0.05) revealed a significant interaction between group and time. Tukey's test and regression analyses ascertained that initially finishing with burs only provided the roughest surface to both composites. Unpolished surfaces and those specimens polished with Al2O3-coated disks, regardless of previous use of diamond burs, attained smoother surface. The Al2O3-impregnated UDMA disk was capable of smoothening the surface of the hybrid material previously finished with diamond burs. The roughness achieved after finishing and polishing composites may be either smoothened or roughened after intraoral exposure. On the basis of the roughness range, it is advisable to use Al2O3-coated disks, regardless of whether diamond burs were previously used. Al2O3-impregnated UDMA disks (with or without previous application of diamond burs) may be also suitable for instrumenting hybrid restoratives.

Effect of bleaching agents on enamel permeability.

PURPOSE: To evaluate enamel permeability after external bleaching procedures. METHODS: The coronal portion of 75 human canines were covered with an acid resistant varnish, except for a 7.1 mm2 circular area on the labial surface and, according to a randomized complete block design, specimens were allocated to bleaching treatments using carbamide peroxide-containing agents (CP): 10%, 16% or 37%; or a 35% hydrogen peroxide product (HP). The control group was exposed to artificial saliva. The bleaching agents were applied following the manufacturer's recommendations over 21 days. In between bleaching exposures, specimens were stored in artificial saliva. Samples were then prepared according to a histochemical coloring method based on copper sulfate and dithiooxamide solutions. Digital images captured in an optical microscope were used to measure the percentage of copper ion penetration over the total enamel thickness on three sections taken from the exposed area. RESULTS: Analysis of Deviance showed a significant difference for the permeability values among groups (P = 0.046). Likelihood ratio test revealed that the use of the CP10% and HP35% agents caused significantly greater enamel permeability than did the control treatment. No significant differences in percentage of copper ion penetration were found among CP10%, CP16%, CP37% and HP35%. This in vitro study demonstrated that depending on the external bleaching procedure, enamel permeability may be increased.

The effect of 10% carbamide peroxide, carbopol and/or glycerin on enamel and dentin microhardness.

This study evaluated the effects of 10% carbamide peroxide, carbopol and glycerin and their associations on microhardness over time on enamel and dentin. Eight treatment agents were evaluated: a commercial bleaching agent containing 10% carbamide peroxide (Opalescence 10% Ultradent), 10% carbamide peroxide, carbopol, glycerin, 10% carbamide peroxide + carbopol, 10% carbamide peroxide + glycerin, carbopol + glycerin and 10% carbamide peroxide + carbopol + glycerin. Three hundred and twenty human dental fragments, 80 sound enamel fragments (SE), 80 demineralized enamel fragments (DE), 80 sound dentin fragments (SD) and 80 demineralized dentin (DD) fragments, were exposed to the treatment agents (n=10). These agents were applied onto the surface of the fragments eight hours a day for 42 days. After eight hours, they were washed from the dental fragment surfaces after five back-and-forth movements with a soft bristle toothbrush under distilled and deionized running water. During the remaining time (16 hours per day), the fragments were kept in individual vials in artificial saliva. After the 42-day treatment period, the specimens were kept individually in artificial saliva for 14 days. Knoop microhardness measurements were performed at baseline, after eight hours, and 7, 14, 21, 28, 35 and 42 days, and 7 and 14 days post-treatment (corresponding to 49 and 56 days after the initial treatment agent applications). The non-parametric Kruskal-Wallis analysis showed significant differences among the agents at each time interval, except at baseline for sound and demineralized enamel and dentin. For SE, SD and DD, there was a decrease in microhardness values during treatment with all agents. There was a tendency towards lower microhardness values after treatment with carbopol and its associations for sound tissues. DD showed low microhardness values during and after treatment with CP and its associations. For DE, there was an increase in microhardness values during treatment with all agents and in the post-treatment phase. The baseline microhardness values were not recovered during the 14-day post-treatment phase. Opalescence 10%, carbamide peroxide, carbopol, glycerin and their associations may change the microhardness of sound and demineralized dental tissues, even in the presence of artificial saliva.

Role of dentifrices on abrasion of enamel exposed to an acidic drink.

PURPOSE: To evaluate in vitro the abrasive potential of different dentifrices on enamel previously exposed to an acidic soft drink. METHODS: 150 bovine enamel slabs measuring 6 x 3 x 2 mm were grounded flat and polished. Surface roughness was measured to obtain Ra (microm) baseline values using a profilometer. The slabs' outer surface was covered with a tape except for a 3 x 4 mm window. According to a randomized complete block design, specimens were exposed to an acidic drink or distilled water (control) for 5 minutes, and then to artificial saliva for 1 minute. Next, the experimental units were submitted to 5,000 brushing strokes using one of four dentifrices - regular (RE), baking soda (BS), tartar control (TC) or whitening (WT) - or distilled water as control (CO) (n=15). At the end of five repetitions of this erosive/abrasive cycle, the tape was removed and final readings of surface roughness were carried out. Roughness gain consisted of the subtraction of the baseline values from the post-treatment measurements. Also, the enamel wear due to erosive/abrasive challenges was profilometrically determined. RESULTS: ANOVA did not show significant interaction between enamel condition (eroded and sound) and dentifrice (P> 0.05) for both roughness gain and wear. No significant effect was found for enamel condition and dentifrice in the wear analysis. The exposure of enamel to the acidic drink provided higher roughness gain than did distilled water. Tukey's test evidenced that TC yielded significantly greater increase in surface roughness than did both CO and WT, whereas BS and RE induced an intermediate roughness gain.

Visual evaluation of in vitro cariostatic effect of restorative materials associated with dentifrices.

This study evaluated in vitro the cariostatic effect of 6 restorative materials with and without fluoride release (Fuji II LC, F-2000, Degufil Mineral, Sure Fil and Z-250) associated with a fluoridated and a non-fluoridated dentifrice (Sensodyne Original Formula and Sensodyne Sodium Bicarbonate), on human enamel. Class V-like cavities were prepared on 240 enamel slabs, assigned to 12 groups (6 materials and 2 dentifrices). After cavity restoration, the slabs were submitted to a thermocycling regimen of 1000 thermal cycles and demineralization/remineralization cycles. During pH cycles, slurries of fluoridated and non-fluoridated dentifrices were applied for 5 min. Formation of artificial caries-like lesions was scored independently and blindly by 5 calibrated examiners according to an ordinal scale ranked 0 to 3 by visual examination. The results were analyzed statistically by the Kruskal-Wallis test and pair-wise comparisons (alpha=0.05). There were no significant differences (p>0.05) among the restorative materials associated with the fluoridated dentifrice. When used in association with the non-fluoridated dentifrice, Ketac-Fil showed the highest cariostatic effect followed by Fuji II LC and the other materials. Ketac-Fil was the only material that did not differ statistically when combined with either the fluoridated or the non-fluoridated dentifrice. In conclusion, under the tested experimental conditions, the association of restorative materials and fluoridated dentifrice yielded higher cariostatic effect, except for the conventional glass ionomer cement, whose cariostatic effect was not influenced by the type of dentifrice.

Effect of foods and drinks on primary tooth enamel after erosive challenge with hydrochloric acid.

The aim of this study was to evaluate the effect of industrialised foods and drinks on primary tooth enamel previously eroded with hydrochloric acid (HCl). The crowns of one hundred two specimens were subjected to an erosive challenge with HCl and randomly divided into six groups (n = 17): Chocolate Milk (Toddynho® - Pepsico) - negative control; Petit Suisse Yogurt (Danoninho® - Danone); Strawberry Yogurt (Vigor); Apple puree (Nestlé); Fermented Milk (Yakult® - Yakult); and Home Squeezed Style Orange Juice (del Valle) - positive control. The 28-day immersion cycles for the test products were performed twice daily and were interspersed with exposure of the test substrate to artificial saliva. Measurements of enamel surface microhardness (SMH) were performed initially, after immersion in HCl and at 7, 14, 21 and 28 days of experimentation. A two-way ANOVA, according to a split-plot design, followed by the sum of squares decomposition and Tukey's test, revealed a significant effect for the interaction between Foods and Drinks and Length of Exposure (p < 0.00001). Orange juice resulted in greater mineral loss of enamel after 28 days. None of the test products was associated with recovery of tooth enamel microhardness.

In situ study of the anticariogenic potential of fluoride varnish combined with CO2 laser on enamel.

OBJECTIVE: This in situ study evaluated the effect of fluoride varnish combined with CO2 laser in controlling enamel demineralization caused by cariogenic challenges. DESIGN: In a crossover study conducted in 2 phases of 14 days each, 14 volunteers (n = 14) wore palatal appliances with bovine enamel slabs treated with fluoride varnish + CO2 laser (FV + CO2), fluoride varnish (FV), nonfluoride placebo varnish (PV) and nonfluoride placebo varnish + CO2 laser (PV + CO2). Drops of sucrose solution were dripped onto enamel slabs allowing the accumulation of biofilm. At the first phase, half of the volunteers received 4 enamel slabs treated with FV while the remainders received slabs exposed to the PV with and without CO2 laser. In the second phase, the vonlunteers were reversed treatments. The slabs were evaluated for cross-sectional microhardness (CSMH) and the concentration of loosely bound fluoride (CaF2) and firmly bound fluoride (FAp). The concentration of fluoride in biofilm were also determined. RESULTS: Two-way ANOVA showed that the CSMH values were higher in laser-irradiated enamel, regardless of the fluoride varnish. Friedman test showed that FV group presented significantly larger amount of fluoride in biofilm (P < 0.05). In the enamel, the largest amount of fluoride was found in the groups FV + CO2, which was not different from FV (P > 0.05). CONCLUSION: The synergistic effect of fluoride varnish and CO2 laser on enamel demineralization was not observed, however, CO2 laser reduces enamel demineralization. CLINICAL SIGNIFICANCE: CO2 laser might reduce the demineralization of subsurface enamel, although its association with a high concentrated fluoride therapy may not result in a positive synergistic interaction.

Wear of dental resin composites: insights into underlying processes and assessment methods--a review.

Given the increased aesthetic demands of patients, along with improvements in the formulation of resin composites, the ability of these materials to bond to tooth structures, and concerns about dental amalgam fillings, the applicability of resin composites in dentistry has become increasingly widespread. As resistance to wear represents an important factor in determining the clinical success of resin composite restoratives, the aim of this article was to define what constitutes wear; the major underlying phenomena involved in this process-adhesion, abrasion, fatigue, and corrosion-being described. Discussions were also focused on factors that contribute both to the magnitude and minimization of resin composite wear. Finally, insights were included on both in vivo and laboratory studies used to determine wear resistance.