Rehardening of acid-softened enamel and prevention of enamel softening through CO(2) laser irradiation

Objectives: The aims of the present study were to investigate whether irradiation with a CO(2) laser could prevent surface softening (i) in sound and (ii) in already softened enamel in vitro. Methods: 130 human enamel samples were obtained and polished with silicon carbide papers. They were divided into 10 groups (n = 13) receiving 5 different surface treatments: laser irradiation (L), fluoride (AmF/NaF gel) application (F), laser prior to fluoride (LF), fluoride prior to laser (FL), non-treated control (C); and submitted to 2 different procedures: half of the groups was acid-softened before surface treatment and the other half after. Immersion in 1% citric acid was the acid challenge. Surface microhardness (SMH) was measured at baseline, after softening and after treatment. Additionally, fluoride uptake in the enamel was quantified. The data were statistically analysed by two-way repeated measurements ANOVA and post hoc comparisons at 5% significance level. Results: When softening was performed either before or after laser treatment, the L group presented at the end of the experiments SMH means that were not significantly different from baseline (p = 0.8432, p = 0.4620). Treatment after softening resulted for all laser groups in statistically significant increase in SMH means as compared to values after softening (p < 0.0001). Enamel fluoride uptake was significantly higher for combined laser-fluoride treatment than in control (p < 0.0001). Conclusion: Irradiation of dental enamel with a CO(2) laser at 0.3J/cm(2) (5 mu s, 226 Hz) not only significantly decreased erosive mineral loss (97%) but also rehardened previously softened enamel in vitro. (C) 2011 Elsevier Ltd. All rights reserved.

Treatment of infrabony defects with or without enamel matrix proteins: A 24-month follow-up randomized pilot study

Objective: To evaluate a comparison of open-flap debridement (OFD) with or without the use of enamel matrix proteins (EMP) for the treatment of infrabony defects. Method and Materials: Ten volunteers (38 infrabony defects) were randomized to receive OFD + EMP (test site) and OFD (control site). Clinical outcomes included mean changes in Plaque Index, Gingival Index, probing pocket depth (PPD), relative attachment level (RAL), gingival recession, width of keratinized tissue, and dental mobility at baseline and at 24 months. Results: A significant reduction of 4.21 +/- 0.97 mm was observed in PPD for the OFD + EMP group (from 6.30 +/- 0.99 mm to 2.09 +/- 0.97 mm) and of 3.28 +/- 1.23 mm for the OFD group (from 6.13 +/- 0.88 mm to 2.85 +/- 1.42 mm) (P < .001). The reduction in PPD was statistically significantly greater for OFD + EMP compared to OFD (P = .03). The mean RAL decreased from 13.26 +/- 1.88 mm to 7.57 +/- 2.05 mm for the OFD + EMP group (a gain of 5.69 +/- 1.96 mm) and from 13.37 +/- 1.71 mm to 8.13 +/- 1.34 min (P < .001) for the OFD group (a gain of 5.24 +/- 1.55 mm). Gingival recession was higher it) the OFD + EMP group than in the OFD group. The mean keratinized tissue significantly decreased from 4.41 +/- 1.39 mm to 3.63 +/- 1.54 mm for OFD flap group (P < .01). Conclusion: Both treatment modalities were efficient in improving RAL and PPD. Within groups, there was a significant reduction in keratinized tissue for OFD and a significant postoperative recession for the OFD + EMP group. Infrabony defects treated with OFD + EMP showed significantly more PPD reduction when compared to OFD. (Quintessence Int 2010;41:125-134)

Influence of Cavity Preparation with Er:YAG Laser on Enamel Adjacent to Restorations Submitted to Cariogenic Challenge In Situ: A Polarized Light Microscopic Analysis

Background and Objectives: Er:YAG laser has been used for caries removal and cavity preparation, using ablative parameters. Its effect on the margins of restorations submitted to cariogenic challenge has not yet been sufficiently investigated. The aim of this study was to assess the enamel adjacent to restored Er:YAG laser-prepared cavities submitted to cariogenic challenge in situ, under polarized light microscopy. Study Design/Materials and Methods: Ninety-one enamel slabs were randomly assigned to seven groups (n = 13): I, II, III-Er:YAG laser with 250 mJ, 62.5 J/cm(2), combined with 2, 3, and 4 Hz, respectively; IV, V, VI-Er:YAG laser with 350 mJ, 87.5 J/cm(2), combined with 2, 3, and 4 Hz, respectively; VII-High-speed handpiece (control). Cavities were restored and the restorations were polished. The slabs were fixed to intra-oral appliances, worn by 13 volunteers for 14 days. Sucrose solution was applied to each slab six times per day. Samples were removed, cleaned, sectioned and ground to polarized light microscopic analysis. Demineralized area and inhibition zone width were quantitatively assessed. Presence or absence of cracks was also analyzed. Scores for demineralization and inhibition zone were determined. Results: No difference was found among the groups with regard to demineralized area, inhibition zone width, presence or absence of cracks, and demineralization score. Inhibition zone score showed difference among the groups. There was a correlation between the quantitative measures and the scores. Conclusion: Er:YAG laser was similar to high-speed handpiece, with regard to alterations in enamel adjacent to restorations submitted to cariogenic challenge in situ. The inhibition zone score might suggest less demineralization at the restoration margin of the irradiated substrates. Correlation between the quantitative measures and scores indicates that score was, in this case, a suitable complementary method for assessment of caries lesion around restorations, under polarized light microscopy. Lasers Surg. Med. 40:634-643, 2008. (c) 2008 Wiley-Liss, Inc.

Micro-Shear Bond Strength of Different Adhesives to Human Dental Enamel

The aim of this study was to evaluate the micro-shear bond strength of 5 adhesive systems to enamel, one single-bottle acid-etch adhesive (O), two self-etching primers (P) and two all-in-one self-etching adhesives (S). Method: Sixty premolar enamel surfaces (buccal or lingual) were ground flat with 400- and 600-grit SiC papers and randomly divided into 5 groups (n=12), according to the adhesive system.. SB2 - Single Bond 2 (O); CSE - Clearfil SE Bond (P); ADS - AdheSE (P); PLP - Adper Prompt L-Pop (S); XE3 - Xeno III (S). Tygon tubing (inner diameter of 0.8mm) restricted the bonding area to obtain the resin composite (Z250) cylinders. After storage in distilled water at 37 degrees C for 24h and thermocycling, micro-shear testing was performed (crosshead speed of 0.5mm/min). Data were submitted to one-way ANOVA and Tukey test (a=5%). Samples were also subjected to stereomicroscopic and SEM evaluations after micro-shear testing. Mean bond strength values (MPa +/- SD) and the results of Tukey test were: SB2: 36.36(+/- 3.34)a; ADS: 33.03(+/- 7.83)a; XE3: 32.76(+/- 5.61)a; CSE: 30.61(+/- 6.68)a; PLP: 22.17(+/- 6.05)b. Groups with the same letter were not statistically different. It can be concluded that no significant difference was there between SB2, ADS, XE3 and CSE, in spite of different etching patterns of these adhesives. Only PLP presented statistically lower bond strengths compared with others. J Clin Pediatr Dent 35(3): 301-304, 2011

Does Adhesive Thickness Affect Resin-dentin Bond Strength After Thermal/Load Cycling?

This study evaluated the influence of adhesive layer thickness (ADL) on the resin-dentin bond strength of two adhesive systems (AS) after ther-mal and mechanical loading (TML). A flat superficial dentin surface was exposed with 600-grit SiC paper on 40 molars. After primer application, the adhesive layer of Scotchbond Multipurpose (SBMP) or Clearfil SE Bond (CSEB) was applied in one or two layers to a delimited area (52 mm(2)) and resin blocks (Filtek 2250) were built incrementally: Half of the sample was stored in distilled water (37 C, 24 hours) and submitted to thermal (1,000; 5 degrees-55 degrees C) and mechanical cycles (500,000; 10kgf) [TML]. The other half was stored in distilled water (72 hours). The teeth were then sectioned to obtain sticks (0.8 mm(2)) to be tested under tensile mode (1.0 mm/minute). The fracture mode was analyzed at 400x. The BS from all sticks from the same tooth was averaged for statistical purposes. The data was analyzed by three-way ANOVA. The x(2) test was used (p<0.05) to compare the frequency of pre-testing failure specimens. Higher BS values were observed for SBMP regardless of the ADL. The TML reduced the BS values irrespective of the adhesive employed and the ADL. A higher frequency of pre-testing failure specimens was observed for the cycled groups. A thicker adhesive layer, acting as an intermediate flexible layer, did not min-imize the damage caused by thermal/mechanical load cycling for a three-step etch-and-rinse and two-step self-etch system.

Roughness of Human Enamel Surface Submitted to Different Prophylaxis Methods

The purpose of this in vitro study was to evaluate alterations in the surface roughness and micromorphology of human enamel submitted to three prophylaxis methods. Sixty-nine caries-free molars with exposed labial surfaces were divided into three groups. Group I was treated with a rotary instrument set at a low speed, rubber clip and a mixture of water and pumice; group II with a rotary instrument set at a low speed, rubber cup and prophylaxis paste Herjos-F (Vigodent S/A Industria e Comercio, Rio de Janeiro, Brazil); and group III with sodium bicarbonate spray Profi II Ceramic (Dabi A dante Indtistrias Medico Odontologicas Ltda, Ribeirao Preto, Brazil). All procedures were performed by the same operator for 10 s, and samples were rinsed and stored in distilled water. Pre and post-treatment surface evaluation was completed using a surface profilometer (Perthometer S8P Marh, Perthen, Germany) in 54 samples. In addition, the other samples were coated with gold and examined in a scanning electron microscope (SEM). The results of this study were statistically analyzed with the paired t-test (Student), the Kruskal-Wallis test and the Dunn (5%) test. The sodium bicarbonate spray led to significantly rougher surfaces than the pumice paste. The use of prophylaxis paste showed no statistically significant difference when compared with the other methods. Based on SEM analysis, the sodium bicarbonate spray presented an irregular surface with granular material and erosions. Based on this study, it can be concluded that there was an increased enamel stuface roughness when teeth were treated with sodium bicarbonate spray when compared with teeth treated with pumice paste.

Effect of Different Fluoride Concentrations of Experimental Dentifrices on Enamel Erosion and Abrasion

It has been suggested that fluoride products are able to reduce erosive tooth wear. Thus, the purpose of this in vitro study was to evaluate the effect of dentifrices with different fluoride concentrations as well as of a low-fluoridated dentifrice supplemented with trimetaphosphate (TMP) on enamel erosion and abrasion. One hundred twenty bovine enamel blocks were assigned to the following experimental dentifrices: placebo, 1,100 mu g F/g, 500 mu g F/g plus 3% TMP and 5,000 mu g F/g. The groups of enamel blocks were additionally subdivided into conditions of erosion (ERO) and of erosion plus abrasion (ERO + ABR). For 7 days, the blocks were subjected to erosive challenges (immersion in Sprite (R) 4 times a day for 5 min each time) followed by a remineralizing period (immersion in artificial saliva between erosive challenges for 2 h). After each erosive challenge, the blocks were exposed to slurries of the dentifrices (10 ml/sample for 15 s). Sixty of the blocks were additionally abraded by brushing using an electric toothbrush (15 s). The alterations of the enamel were quantified using the Knoop hardness test and profilometry (measurements in micrometers). The data were analyzed using a 2-way ANOVA test followed by a Bonferroni correction (p < 0.05). In in vitro conditions, the 5,000 mu g F/g and 500 mu g F/g plus 3% TMP dentifrices had a greater protective effect when compared with the 1,100 mu g F/g dentifrice, under both ERO and ERO + ABR conditions. The results suggest that dentifrices alone are not capable of completely inhibiting tooth wear. Copyright (C) 2010 S. Karger AG, Basel

Cross-Sectional Microhardness of Human Enamel Subjected to Erosive, Cariogenic or Combined Erosive/Cariogenic Challenges

This in situ study evaluated the interaction between caries and erosion processes. In the first phase, enamel specimens were subjected to erosion without dental plaque (EO) or to erosion with plaque (EP); in the second phase, they were subjected to erosion plus cariogenic challenge (EC) or cariogenic challenge (CO), both with plaque accumulation. Cross-sectional hardness data (10-330 mu m depth) were tested using ANOVA (alpha = 0.05). EO and EP showed surface softening to 10 mu m depth. CO and EC produced subsurface lesions, of similar depth (up to 220 mu m), with CO showing higher integrated loss of hardness than EC, indicating that cariogenic and erosive challenges did not have an additive effect. Copyright (C) 2010 S. Karger AG, Basel

Preventive Effect of Commercial Desensitizing Toothpastes on Bovine Enamel Erosion in vitro

This study evaluated in vitro commercial desensitizing toothpastes with respect to the prevention of erosion and explored the effect of their agents alone or in combination with fluoride. Bovine enamel blocks were randomly allocated to five groups of 20 and exposed to: Sensodyne ProNamel (1,425 ppm F as NaF, 5% KNO(3)), Sensodyne Original (no fluoride, 10% SrCl(2)), Colgate Sensitive (1,450 ppm F as sodium monofluorophosphate, 5% K citrate), Crest (fluoride-only toothpaste, 1,100 ppm F as NaF) and water (negative control). A second experiment was conducted with experimental dentifrices containing fluoride (NaF, 1,100 ppm F), 10% SrCl(2), 5% KNO(3) or 5% K citrate alone or the latter three combined with F. The samples were submitted to four cycles, alternating demineralization (cola, 10 min) and remineralization (artificial saliva, 1 h). Before and between cyclic de- and remineralization, blocks were treated with slurries of the respective toothpastes or water (1 min). Erosive tissue loss was analyzed by profilometry. Data were analyzed by Kruskal-Wallis and Dunn`s tests (p < 0.05). The mean erosion depth (+/- SE, mu m) was significantly less for Colgate Sensitive (0.04 +/- 0.00), Sensodyne Original (0.06 +/- 0.01) and Crest (0.07 +/- 0.01) than for Sensodyne ProNamel (2.36 +/- 0.25) or water (2.92 +/- 0.24), which did not significantly differ from each other. Both F and the desensitizing agents alone reduced erosion, but no additive effect was found. In addition, the combination of F and KNO(3) did not reduce erosion. These in vitro results suggest that the presence of fluoride or desensitizing substances in toothpastes, alone or in combination, can reduce erosion of enamel, but this is not valid for all the formulations. Copyright (C) 2010 S. Karger AG, Basel

Comparison of Cross-Sectional Hardness and Transverse Microradiography of Artificial Carious Enamel Lesions Induced by Different Demineralising Solutions and Gels

The aims of this study were: (1) to correlate surface (SH) and cross-sectional hardness (CSH) with microradiographic parameters of artificial enamel lesions; (2) to compare lesions prepared by different protocols. Fifty bovine enamel specimens were allocated by stratified randomisation according to their initial SH values to five groups and lesions produced by different methods: MC gel (methylcellulose gel/lactic acid, pH 4.6, 14 days); PA gel (polyacrylic acid/lactic acid/hydroxyapatite, pH 4.8, 16 h); MHDP (undersaturated lactate buffer/methyl diphosphonate, pH 5.0, 6 days); buffer (undersaturated acetate buffer/fluoride, pH 5.0, 16 h), and pH cycling (7 days). SH of the lesions (SH(1)) was measured. The specimens were longitudinally sectioned and transverse microradiography (TMR) and CSH measured at 10- to 220-mu m depth from the surface. Overall, there was a medium correlation but non-linear and variable relationship between mineral content and root CSH. root SH(1) was weakly to moderately correlated with surface layer properties, weakly correlated with lesion depth but uncorrelated with integrated mineral loss. MHDP lesions showed the highest subsurface mineral loss, followed by pH cycling, buffer, PA gel and MC gel lesions. The conclusions were: (1) CSH, as an alternative to TMR, does not estimate mineral content very accurately, but gives information about mechanical properties of lesions; (2) SH should not be used to analyse lesions; (3) artificial caries lesions produced by the protocols differ, especially considering the method of analysis. Copyright (C) 2009 S. Karger AG, Basel

Effect of ion supplementation of a commercial soft drink on tooth enamel erosion

Acidic soft drinks are potentially erosive for dental hard tissues. This in vitro study evaluated the effect of calcium, fluoride, iron and phosphate, supplemented alone or in combination to a commercial citric acid-based carbonated beverage on dental erosion. Ninety enamel samples (4 x 4 x 3 mm) were randomly allocated to nine groups (n = 10): G1 - pure beverage (control); G2 - with 1 mM Ca; G3 - with 0.047 mM F; G4 - with 1 mM Fe; G5 - with 1 mM P; G6 - with 1 mM Ca and 0.047 mM F; G7 - with 1 mM Ca and 1 mM P; G8 - with 1 mM Fe and 0.047 mM F; and G9 - with 1 mM Ca, 1 mM P, 0.047 mM F and 1.0 mM Fe. The samples were subjected to six pH cycles over a 24-h period. In each cycle, the samples were immersed in pure or modified beverage (1 min) and in artificial saliva (59 min). During the remaining period (18 h), the samples were maintained in artificial saliva. Enamel loss was assessed by profilometry (mm). Data were tested using ANOVA and Tukey`s tests (p < 0.05). Highest enamel losses were observed in the control group (G1) and in the groups containing Fe (G4 and G8). The groups containing Ca (G2 and G6) showed significantly less wear compared to control. In conclusion, the modification of an erosive soft drink with low concentrations of Ca with or without F may reduced its erosive potential.

Effect of erosive pH cycling on different restorative materials and on enamel restored with these materials

This in vitro study evaluated the effect of erosive pH cycling on the percentage of surface micro-hardness change (%SMHC) and wear of different restorative materials and bovine enamel restored with these materials. Eighty enamel specimens were randomly divided into eight groups according to the restorative materials and immersion media used: GI/GV-resin-modifled glass-ionomer, GII/GVI-conventional glass-ionomer, GIII/GVII-resin composite and GIV/GVIII-amalgam. Over a period of seven days, groups GI to GIV were immersed in a cola drink (ERO) for 5 minutes, 3x/day and kept in artificial saliva between erosive cycles. Groups GV to GVIII were immersed in artificial saliva (SAL) throughout the entire experimental period (control). Data were tested for significant differences using ANOVA and Tukey`s tests (p < 0.05). For %SMHC, considering the restorative materials, no significant differences were detected among the materials and immersion media. Mean wear was higher for the resin modified glass ionomer cement when compared to conventional cement, but those materials did not significantly differ from the others. For enamel analyses, erosive pH cycling promoted higher wear and %SMHC compared to saliva. There were no significant differences in wear and %SMHC of enamel around the different restorative materials, regardless of the distance from the restorative material (50, 150 or 300 mu m). In conclusion, there were only subtle differences among the materials, and these differences were not able to protect the surrounding enamel from erosion.

Effect of a 4% titanium tetrafluoride (TiF4) varnish on demineralisation and remineralisation of bovine enamel in vitro

Objectives: This in vitro study assessed the effect of a 4% TiF4 varnish on demineralisation and remineralisation of sound enamel and artificial carious enamel lesions, respectively. Methods: Bovine sound and carious enamel (n = 110) were randomly allocated to each type of varnish: Duraphat (R))-D (NaF, 2.26%F, pH 4.5, Colgate-Brazil, n = 30), Duofluorid (R)-F (NaF, 2.71%F, pH 8.0, FGM-Brazil, n = 30), TiF4-T (2.45%F, pH 1.0, FGM-Brazil, n = 30) and no-fluoride-P (FGM-Brazil, pH 5.0, n = 20). For the formation of artificial enamel caries, half of the blocks were immersed in 32 mL buffer acetate solution (16 h), whereas the other half was maintained sound. The varnishes were applied onto the enamel surfaces. Thus, the samples were subjected to pH cycles (37 degrees C) for 7 days. The response variables tested were surface and cross-sectional hardness. Data were tested using Kruskal-Wallis test (p < 0.05). Results: All F varnishes significantly reduced demineralisation and increased remineralisation in comparison to placebo. The TiF4 did not significantly reduce the surface enamel softening when compared with the other F varnishes, but it decreased the loss of subsurface hardness to the same extent. In enamel blocks with previous artificial carious lesions, the TiF4 significantly improved the rehardening compared to the other varnishes up to 30 mu m depth. Conclusions: The TiF4 varnish was able to decrease the demineralisation and increase the remineralisation of previously sound and carious enamel, respectively. It was equally effective compared to NaF varnishes on reducing the demineralisation at subsurface, but it was more effective on improving the remineralisation at surface and subsurface. (c) 2007 Elsevier Ltd. All rights reserved.

Effects of Erosive, Cariogenic or Combined Erosive/Cariogenic Challenges on Human Enamel An in situ/ex vivo Study

Individuals with cariogenic diet can also consume erosive beverages. Thus, it seems necessary to investigate a possible caries/erosion interaction. To test in situ/ex vivo a combination of these challenges, 11 subjects wore intraoral appliances containing four enamel blocks randomly assigned. In the first 2-week phase, the appliances were immersed in a cola drink 3 times/day. Two blocks were free of plaque (erosion only: EO) and two blocks were covered with plaque (erosion + plaque: EP). In the second 2-week phase, four new blocks were all covered with plaque and subjected to a sucrose solution 8 times/day. Among the four new blocks, two were also subjected to the cola drink 3 times/day (erosion + caries: EC) while the other two were not (caries only: CO). Thus, in EO, the specimens were fixed at the intraoral appliance level. In EP, EC and CO they were fixed 1.0 mm under the appliance level and covered with plastic meshes for dental plaque accumulation. Changes in wear and hardness were measured. Data were tested using ANOVA and Tukey`s test (p < 0.05). Mean values of wear (mu m) and change in hardness (kp/mm(2)) were: EO 4.82/310; EP 0.14/48; EC 0.34/245; CO 0.42/309. With respect to surface softening, EP and EC differed significantly from each other and from EO and CO, which did not differ significantly. EO presented significantly higher wear than the other groups. The data suggest that the presence of dental plaque can decrease the acid attack of an erosive drink and the association of erosive and cariogenic challenges showed less enamel alterations when compared to erosive or cariogenic challenges only. Copyright (C) 2008 S. Karger AG, Basel

Influence of differently oriented dentin surfaces and the regional variation of specimens on adhesive layer thickness and bond strength

Statement of the Problem: Adhesive systems can spread differently onto a substrate and, consequently, influence bonding. Purpose: The purpose of this study was to evaluate the effect of differently oriented dentin surfaces and the regional variation of specimens on adhesive layer thickness and microtensile bond strength (MTBS). Materials and Methods: Twenty-four molars were sectioned mesiodistally to expose flat buccal and lingual halves. Standardized drop volumes of adhesive systems (Single Bond [SB] and Prime & Bond 2.1 [PB2.1]) were applied to dentin according to the manufacturer`s instructions. Teeth halves were randomly divided into groups: 1A-SB/parallel to gravity; 1B-SB/perpendicular to gravity; 2A-PB2.1/parallel to gravity; and 2B-PB2.1/perpendicular to gravity. The bonded assemblies were stored in 37 degrees C distilled water for 24 hours and then sectioned to obtain dentin sticks (0.8 mm(2)). The adhesive layer thickness was determined in a light microscope (x200), and after 48 hours the specimens were subjected to MTBS test. Data were analyzed by one-way and two-way analysis of variance and Student-Newman-Keuls tests. Results: Mean values (MPa +/- SD) of MTBS were: 39.1 +/- 12.9 (1A); 32.9 +/- 12.4 (1B); 52.9 +/- 15.2 (2A); and 52.3 +/- 16.5 (2B). The adhesive systems` thicknesses (mu m +/- SD) were: 11.2 +/- 2.9 (1A); 18.1 +/- 7.3 (1B); 4.2 +/- 1.8 (2A); and 3.9 +/- 1.3 (2B). No correlation between bond strength and adhesive layer thickness for both SB and PB2.1 (r = -0.224, p = 0.112 and r = 0.099, p = 0.491, respectively) was observed. Conclusions: The differently oriented dentin surfaces and the regional variation of specimens on the adhesive layer thickness are material-dependent. These variables do not influence the adhesive systems` bond strength to dentin. CLINICAL SIGNIFICANCE Adhesive systems have different viscosities and spread differently onto a substrate, influencing the bond strength and also the adhesive layer thickness. Adhesive thickness does not influence dentin bond strength, but it may impair adequate solvent evaporation, polymer conversion, and may also determine water sorption and adhesive degradation over time. In the literature, many studies have shown that the adhesive layer is a permeable membrane and can fail over timebecause ofits continuous plasticizing and degradation when in contact with water. Therefore, avoiding thick adhesive layers may minimize these problems and provide long-term success for adhesive restorations.