Showing papers in "American Journal of Dentistry in 2011"

Strength and wear resistance of a dental glass-ionomer cement with a novel nanofilled resin coating.

Abstract: PURPOSE To evaluate the influence of different resin coating protocols on the fracture strength and wear resistance of a commercial glass-ionomer cement (GIC). METHODS A new restorative concept [Equia (GC Europe)] has been introduced as a system application consisting of a condensable GIC (Fuji IX GP Extra) and a novel nanofilled resin coating material (G-Coat Plus). Four-point fracture strength (FS, 2 x 2 x 25 mm, 14-day storage, distilled water, 37 degrees C) were produced and measured from three experimental protocols: no coating GIC (Group 1), GIC coating before water contamination (Group 2), GIC coating after water contamination (Group 3). The strength data were analyzed using Weibull statistics. Three-body wear resistance (Group 1 vs. Group 2) was measured after each 10,000 wear cycles up to a total of 200,000 cycles using the ACTA method. GIC microstructure and interfaces between GIC and coating materials were investigated under SEM and CLSM. RESULTS The highest FS of 26.1 MPa and the most homogenous behavior (m = 7.7) has been observed in Group 2. The coated and uncoated GIC showed similar wear resistance until 90,000 cycles. After 200,000 wear cycles, the coated version showed significantly higher wear rate (ANOVA, P< 0.05). The coating protocol has been shown to determine the GIC fracture strength. Coating after water contamination and air drying is leading to surface crack formation thus significantly reducing the FS. The resin coating showed a proper sealing of GIC surface porosities and cracks. In terms of wear, the coating did not improve the wear resistance of the underlying cement as similar or higher wear rates have been measured for Group 1 versus Group 2.

Incomplete caries removal in deep lesions: a 10-year prospective study.

Abstract: Purpose To follow-up teeth with deep caries lesions submitted to incomplete caries removal over a 10-year period. Methods 27 subjects (32 permanent posterior teeth) with deep caries lesions composed the sample. In this single-arm long-term prospective study, the inclusion criteria were risk of pulp exposure during caries excavation, positive response to the cold test, absence of spontaneous pain or sensitivity during percussion, and radiographic absence of a periapical lesion. Subjects were submitted to the following procedures: complete caries removal from the surrounding cavity walls, incomplete caries removal from the pulpal wall, capping with a calcium hydroxide cement, and sealing with a modified zinc oxide-eugenol cement. After 6-7 months, the temporary sealing was removed for methodological purposes (no further excavation was performed), and teeth were capped with a calcium hydroxide cement and filled with resin composite. Clinical and radiographic assessments were conducted after 6-7 months, 1.5, 3, 5 and 10 years. Success was defined as clinical and radiographic signs and symptoms of pulp sensitivity while failure was defined as endodontic treatment need. Results Over 10 years, one tooth was excluded from the sample (pulp exposure during treatment), five were lost to recall, 10 had therapy failure (five fractures and four necroses leading to endodontic treatment need, and one extraction) and 16 had therapy success (pulp sensitivity). Overall survival rates were 97%, 90%, 82% and 63% at 1.5-, 3-, 5- and 10-year follow-ups, respectively. Teeth with two or more restored surfaces failed significantly more than teeth with one restored surface (P= 0.01).

The Featherstone laboratory pH cycling model: a prospective, multi-site validation exercise.

Abstract: Purpose To demonstrate the robustness of the Featherstone pH cycling model when tested in three independent laboratories and to evaluate the use of "non-inferiority" testing at those laboratories. Methods The fundamental principles for the Featherstone laboratory pH cycling model to be an appropriate alternative to animal testing is that it must demonstrate equivalent accuracy to the "Gold Standard" (rat caries model) by: (1) providing a meaningful representation of the caries process; (2) demonstrating a proportionate response to fluoride dose (or concentration); (3) being able to show that clinically proven formulations perform similarly relative to the controls; and (4) differentiating products that have attenuated fluoride activity. Results This cross-validation study confirmed the ability of the three independent laboratories to discriminate between various concentrations of fluoride-containing dentifrice formulations, demonstrated that clinically proven formulas perform as expected and identified an attenuated fluoride formulation (NaF/CaCO3 dentifrice - 1100 ppm NaF) as inferior compared to the 1100 ppm F (NaF/silica) positive control.

Enamel protection: a comparison of marketed dentifrice performance against dental erosion.

Abstract: PURPOSE To determine the relative ability of various marketed toothpastes formulated with either stabilized stannous fluoride (SnF2), sodium fluoride (NaF), or sodium monofluorophosphate (SMFP) to protect human enamel against the initiation and progression of damage due to dietary acid attack, using a laboratory erosion cycling model. METHODS Cores of ground and polished enamel from extracted human teeth were soaked in pooled, human saliva (pellicle formation) and then subjected to erosion cycling conditions that included exposure of tooth specimens to: (1) treatments in a 1:3 slurry (w/w) of toothpastes and saliva; and (2) acid challenges using either citric acid (Study 1) or both citric and phosphoric acids (Study 2). These acids represent potentially damaging acids found in common food and drinks. Upon completion of treatments, specimens were analyzed with regard to the depth of tooth mineral removed from exposed areas of the treated specimens over the course of the study. Two studies were conducted: Study 1 included a marketed, stabilized SnF2 toothpaste vs. marketed NaF toothpastes; Study 2 tested the same stabilized SnF2 product compared to a marketed SMFP toothpaste and a NaF control. RESULTS The stabilized SnF2 toothpaste included in these studies demonstrated a highly significant reduction in enamel surface loss, relative to the control, in each study: Study 1 = 65% reduction; Study 2 = 58% reduction when using citric acid and 84% reduction when using phosphoric acid. Products formulated with NaF resulted in a net loss of between +1% and -21%, with none of the NaF toothpastes performing significantly different from the control (P<0.05, ANOVA). For the SMFP product included in Study 2, results were also not significantly different from the NaF control. In both studies, the stabilized SnF2 paste demonstrated a highly significant level of protection compared to all other test groups included in the study, regardless of the type of dietary acid challenge considered.

Evaluation of silica-coating techniques for zirconia bonding.

Abstract: PURPOSE To evaluate silica-coating/silane treatment techniques for zirconia bonding. METHODS 19 groups of zirconia disks were subjected to different surface treatments: polished or sandblasted by CoJet or alumina, and treatment with silane or zirconia primers (containing phosphate- or phosphonate-monomer). After surface treatments, the zirconia disks were cemented with resin cements and stored in deionized water for 2 hours at 370 degrees C prior to shear bond strength testing. Zirconia surface (polished and unpolished), CoJet sand, Cojet-treated zirconia surface (before and after water rinsing) and representative debonded surfaces were examined by scanning electron microscopy (SEM). The zirconia surface after silica-coating was examined by Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) spectroscopy. RESULTS A non-phosphate-containing resin cement (Choice 2) had almost no bond strength on polished zirconia, while MDP-containing cements (Panavia F2.0) had mild bond strength. After zirconia was sandblasted with CoJet or alumina, bond strengths were slightly increased. Silane treatment did not increase bond strength, while phosphate/carboxylate-based primer (i.e. Exp Z-Prime) doubled the bond strengths. Silica nanoparticles identified by FTIR-ATR spectra, were observed by SEM on the zirconia surface after CoJet treatment. However, these nanoparticles were removed by forceful water stream.

Noncarious cervical lesions (NCCL)--a clinical concept based on the literature review. Part 2: restoration.

Abstract: To present an updated knowledge on the restorative options and their performance in the particular environment of non-carious cervical lesions (NCCL).

Fluoride release and recharge behavior of a nano-filled resin-modified glass ionomer compared with that of other fluoride releasing materials

Abstract: PURPOSE To compare the long-term fluoride release kinetics of a novel nano-filled two-paste resin-modified glass-ionomer (RMGI), Ketac Nano (KN) with that of two powder-liquid resin-modified glass-ionomers, Fuji II LC (FLC) and Vitremer (VT) and one conventional glass-ionomer, Fuji IX (FIX). METHODS Fluoride release was measured in vitro using ion-selective electrodes. Kinetic analysis was done using regression analysis and compared with existing models for GIs and compomers. In a separate experiment the samples of KN and two conventional glass-ionomers, FIX and Ketac Molar (KM) were subjected to a treatment with external fluoride source (Oral-B Neutra-Foam) after 3 months of fluoride release and the recharge behavior studied for an additional 7-day period. RESULTS The cumulative amount of fluoride released from KN, VT and FLC and the release profiles were statistically similar but greater than that for FIX at P < 0.05. All four materials, including KN, showed a burst of fluoride ions at shorter times (t) and an overall rate dependence on t1/2 typical for glass-ionomers. The coating of KN with its primer and of DY with its adhesive did not significantly alter the fluoride release behavior of the respective materials. The overall rate for KN was significantly higher than for the compomer DY. DY showed a linear rate of release vs. t and no burst effect as expected for compomers. The nanoionomer KN showed fluoride recharge behavior similar to the conventional glass ionomers FIX and KM. Thus, it was concluded that the new RMGI KN exhibits fluoride ion release behavior similar to typical conventional and RMGIs and that the primer does not impede the release of fluoride.

Clinical effects of at-home bleaching along with desensitizing agent application.

Abstract: PURPOSE To evaluate whether the use of a desensitizing agent before at-home vital bleaching decreased this sensitivity. METHODS After informed consent, 60 subjects, 18-31 years of age, participated in the study and were divided into desensitizer and placebo groups. Before bleaching treatment with 16% carbamide peroxide (CP), a placebo or desensitizer gel (DG; 5% potassium nitrate and 2% sodium fluoride) was applied in the tray and used by patients for 10 minutes. Color was evaluated at the baseline, second and fourth week following the initial delivery of bleaching trays. Color change was measured using the Vita Classic Shade Guide arranged by value. The subjects recorded their perception of tooth sensitivity on a 0-4 scale. The bleaching treatment at each week recall was evaluated by repeated measures ANOVA. The percentage of patients with tooth sensitivity was evaluated by Chi-square test. The tooth intensity ratio (% of days with tooth sensitivity) as well as the tooth sensitivity intensity between groups were analyzed using chi-square and the Mann-Whitney tests, respectively (alpha = 0.05). RESULTS The use of DG did not affect the bleaching efficacy of the CP (P > 0.05). The prevalence and intensity of tooth sensitivity was similar for both groups (P > 0.05). However, participants from the placebo group had sensitivity in 33.6% of the bleaching days, which was significantly higher than the DG experimental group (20.1%) (P < 0.05).

Noncarious cervical lesions--a clinical concept based on the literature review. Part 1: prevention.

Abstract: Due to an increased prevalence of non-carious cervical lesions (NCCL), a clinical strategy for this lesion type should be considered. Previous reviews focused mainly on etiology and prevalence. In Part 1 of this paper, an evidence-based support for a preventive strategy of NCCL was elaborated.

Comparative evaluation of mechanical characteristics of nanofiller containing resin composites.

Abstract: Purpose To determine basic mechanical characteristics of six commercially available nanofiller containing resin composites compared to a microhybrid and a microfilled reference material. The tested hypothesis was that there are no differences in mechanical properties between the materials. Methods Durafill VS (DUR) and Filtek Z250 (Z250) were used as microfilled and microhybrid references. The nanofiller containing products were: Filtek Supreme XT (FIL), Grandio (GRA), Kalore (KAL), MI Flow (MIF), Tetric EvoCeram (TET), and Venus Diamond (VED). The following material characteristics were determined after 24 hours water storage (n = 6): Flexural strength and modulus (FM), yield stress (0.02%), tensile strength and modulus (TM), diametral tensile strength, Knoop hardness (KHN), and fracture toughness (KIC). Results The microfilled composite DUR consistently showed the lowest values for each property investigated. The group of nanofiller containing products could be subdivided into two groups: the nanohybrid products GRA and VED and the nanofilled FIL with higher values, on the one hand, and the flowable MIF, and the prepolymer containing composites KAL and TET, on the other. The mechanical performance of the microhybrid reference material Z250 was overall slightly better or in line with the nanohybrid and nanofilled materials. Stringent linear relationships were found between KHN and the moduli FM and TM, respectively (r > 0.95). Linear relations between the other materialvalues investigated were moderate to high.

The whole is greater than the sum of its parts: dental plaque bacterial interactions can affect the virulence properties of cariogenic Streptococcus mutans.

Abstract: It has been well established that dental caries results from the accumulation of dental plaque on tooth surfaces. Several decades of in vitro and as well as clinical studies have identified Streptococcus mutans as an important etiological agent in carious lesion formation. In addition, a variety of approaches have suggested that interactions between the bacterial components of biofilms can influence the properties of such polymicrobial structures. Therefore, it is likely that the mere presence of S. mutans in dental plaque does not alone account for the cariogenic potential of such biofilms. Recent studies have indicated that several bacteria commonly found in dental plaque can influence either the viability and/or virulence properties of S. mutans. This review will summarize some of the more recent findings in this regard as well as their implications for the development of novel anti-caries strategies.

Occlusal caries prevention in high and low risk schoolchildren. A clinical trial.

Abstract: PURPOSE To evaluate the caries-preventive effect of a resin-modified glass-ionomer cement used as occlusal sealant (Vitremer) compared with fluoride varnish (Duraphat) application on occlusal surfaces of permanent first molars (OSPFM) in 6-8 year-old schoolchildren (n=268) at high (HR) and low (LR) caries risk. METHODS The children were followed-up for 24 months after being systematically allocated into six groups as follows: Control Groups HRC and LRC: children receiving oral health education (OHE) every 3 months; Groups HRV and LRV: children receiving OHE plus varnish application biannually; and Groups HRS and LRS: children receiving OHE plus a single sealant application . The baseline and follow-up examinations were performed by the same calibrated dentist under natural light, using CPI probes and mirrors, after toothbrushing and air-drying. The DMFS was used to record dental caries, in addition to the detection of initial lesions (IL). Data analysis was performed with two primary outcome measures: DMF and DMF+ IL on the OSPFM. RESULTS After 24 months, only the HRS group showed statistically lower DMF and DMF+IL increments on OSPFM compared with HRC group. HRV group did not differ from HRC and HRS groups. For LR groups, no statistical difference (P> 0.05) was observed among the treatments.

Removal of dental plaque from different regions of the mouth after a 1-minute episode of mechanical oral hygiene.

Abstract: PURPOSE To assess dental plaque on different regions of the dentition prior to and immediately after toothbrushing. METHODS Subjects refrained from oral hygiene for 22-26 hours prior to baseline whole mouth plaque assessments by the Turesky modification of the Quigley-Hein Index (TMQH). All subjects brushed with a marketed soft-bristled toothbrush and a fluoride dentifrice for 1 minute prior to post-brushing plaque assessments similar to baseline. One calibrated clinical examiner conducted all measurements. RESULTS 30 subjects (mean age 23 years) completed the study. Irrespective of arch, posterior teeth harbored higher frequencies for scores of 3-5 than corresponding anterior teeth prior to brushing. In comparison to the pre-brushing examination, scores of 0-1 were more common in the post-brushing evaluation, however, greater frequencies of higher plaque were observed on posterior than on anterior regions. Irrespective of gender, subject or arch, anterior teeth harbored lower mean amounts of plaque than posterior teeth by ANOVA at both clinical examinations (P < 0.0001). Additionally, irrespective of arch, lower mean scores for plaque were observed on anterior teeth than from posterior teeth or the whole mouth at both examinations (P < 0.001). Lingual and molar surfaces consistently harbored large densities of plaque and represented areas with the least plaque removal after toothbrushing. Mid-vestibular sites represented the areas with the highest percent removal of plaque at 65% and harbored significantly lower levels of plaque than proximal sites during all phases of the study (P < 0.0059).

Effect of potential remineralizing agents on acid softened enamel.

Abstract: PURPOSE To assess whether pastes containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and calcium sodium phosphosilicate (CSP) protect acid softened enamel against further erosive episodes. METHODS Enamel slabs of bovine teeth with preformed erosion-like lesions were randomly assigned to five treatment groups (n = 15): A) CPP-ACP (MI Paste, GC America); B) CPP-ACP+Fluoride (CPP-ACP+F, MI Plus Paste, GC America); C) CSP (Tooth Revitalizing Paste, Oravive); D) fluoridated dentifrice (FD, Sensodyne Cool Gel, GSK); E) control (CO, unexposed to any product). Paste treatments (1:3 slurry in deionized water or undiluted product in the case of the CPP-ACP formulae) were performed between five cycles of alternating erosive challenge (0.3% citric acid, pH = 3.2) and remineralization in artificial saliva. Specimens were analyzed by Knoop surface microhardness (SMH). RESULTS ANOVA indicated a significant (P< 0.0001) difference among the SMH values attained by acid softened enamel following the exposure to the pastes interspersed with erosion-remineralization cycles. Tukey's test ascertained that SMH values observed for the CPP-ACP+F and CSP groups did not differ from that of FD group, which were significantly higher than that found for the CO group. Specimens treated with CPP-ACP did not differ from any of the other groups.

Degree of conversion of dual-cure resins light-cured through glass-fiber posts.

Abstract: PURPOSE: To evaluate the degree of conversion (DC) of dual-curing materials used to lute glass-fiber posts in a simulated root canal polymerized by two different modalities. METHODS: Artificial root canals were used to simulate a clinical condition to lute 45 posts by three different dual curing luting cements (Calibra, Multilink Automix and Variolink II). Two light cure modalities were chosen for each luting cement: standard (S group) 400 mW/cm2 for 120 seconds and high-power (H group) 1200 mW/cm2 for 40 seconds. Raman spectra were collected at different positions in the post surface (1, 3, 5 and 7 mm from the coronal-most portion of the post covered in cement) and the percentage degree of conversion was computed. The data were analyzed using ANOVA and post-hoc Student-Neuman-Keuls t-test (P = 0.05). RESULTS: The DC of the tested luting composites decreased progressively while increasing the distance from the light tip. Regardless of the polymerization modality (H or S) applied. Conversely, the curing modality significantly influenced the DC of the tested materials, evidencing different responses to the same energy density: Calibra seemed to be less dependent on light-curing than the other tested materials, showing a constant behavior. Multilink Automix reached the highest DCs in the S group compared to the H mode. Variolink II showed an interesting drawback in DC at 7 mm when cured in the H model. Dual-cure materials show adequate monomer conversion but when the distance from the curing light increased, a variable, but significant lowering in conversion rate was observed. In addition, the time and power of curing appeared to be material-dependent and should be calibrated individually.

Morphology and microtensile bond strength of adhesive systems to in situ-formed caries-affected dentin after the use of a papain-based chemomechanical gel method.

Abstract: Purpose To evaluate the microtensile bond strength of adhesive systems to caries-affected dentin formed in situ after the use of a papain-based chemomechanical removal method. Methods 84 human dentin specimens (5 x 5 x 3 mm) were sterilized and randomly distributed on palatal devices of 14 volunteers. Each palatal device, containing six dentin slabs, was used for 14 days according to a caries induction design involving plaque accumulation and sucrose use. After this, fragments were removed from devices and randomly assigned to two groups according to the caries removal method: (1) Chemomechanical (papain-based gel followed by curette), or (2) Mechanical (curette--control group). Specimens were subdivided into three subgroups according to the adhesive system tested: (SB) a two-step etch-and-rinse (Adper Single Bond 2); (SE) a two-step self-etching adhesive (Clearfil SE Bond) and (TriS) a one-step self-etching adhesive (Clearfil Tri-S Bond) and subsequently restored with microhybrid composite resin. After 24 hours, resin-tooth blocks were sectioned into 0.9 mm thick slabs, with one slab of each block being prepared for adhesive interface analysis by scanning electron microscopy, and the remaining blocks were sectioned into 0.8-mm2 sticks that were subjected to tensile stress (0.5 mm/minute). Data were subjected to two-way ANOVA and Tukey's test at a 5% level of significance. Results The application of the chemomechanical and mechanical methods to demineralized dentin did not affect the bond strength values. SB and SE adhesives promoted statistically similar and significantly higher bond strength values than the TriS. SEM analysis showed no interference of papain-based gel in the formation of hybrid layer; SB showed the thickest hybrid layer with presence of numerous tags; SE showed an intermediate hybrid layer thickness and quantity of tags and the TriS showed no evidence of tag formation.

Sensitivity of digital dental photo CIE L*a*b* analysis compared to spectrophotometer clinical assessments over 6 months.

Abstract: PURPOSE To assess the sensitivity of digital dental photo CIE L*a*b* analysis compared to clinical spectrophotometer assessments over 6 months. METHODS CIE L*a*b* values for the upper right central incisors of 14 predoctoral dental students subjected to certain color-relevant exclusion criteria were recorded at baseline (T0), after 6 months (T1), and 1 week later (T2), using (Method 1) a spectrophotometer and (Method 2) a method of digital photo analysis. Statistical analysis of color and lightness data between both methods and time points were assessed using the Shapiro-Wilk test, Pearson's correlation coefficient (r), Dahlberg's formula for method error calculation, and paired samples t-tests, adopting a level of significance alpha = 0.05. RESULTS Between T0 - T1, the spectrophotometer recorded significant changes in lightness (75.51 > 77.75) and color values (a*: 3.25 > 2.38; b*: 18.47 > 17.31), whereas significant changes with Method 2 were only seen for b* (21.51 > 20.57). No significant changes for overall color and lightness changes deltaE to deltaE2 were found for either of the methods. The error of the method (T1-T2) and corresponding correlation coefficients r for values L*a*b* were found to be 1.44 / 0.43 / 0.62 (r: 0.69; P = 0.007/0.64; P = 0.14/0.9; P < 0.001) for Method 1 and 0.97/0.67/1.25 (r : 0.87; P < 0.001/0.63; P = 0.17/0.57, P = 0.04) for Method 2, respectively.

Influence of curing rate on softening in ethanol, degree of conversion, and wear of resin composite

Abstract: PURPOSE: To investigate the effect of curing rate on softening in ethanol, degree of conversion, and wear of resin composites. METHOD: With a given energy density and for each of two different light-curing units (QTH or LED), the curing rate was reduced by modulating the curing mode. Thus, the irradiation of resin composite specimens (Filtek Z250, Tetric Ceram, Esthet-X) was performed in a continuous curing mode and in a pulse-delay curing mode. Wallace hardness was used to determine the softening of resin composite after storage in ethanol. Degree of conversion was determined by infrared spectroscopy (FTIR). Wear was assessed by a three-body test. Data were submitted to Levene's test, one and three-way ANOVA, and Tukey HSD test (alpha = 0.05). Results: Immersion in ethanol, curing mode, and material all had significant effects on Wallace hardness. After ethanol storage, resin composites exposed to the pulse-delay curing mode were softer than resin composites exposed to continuous cure (P< 0.0001). Tetric Ceram was the softest material followed by Esthet-X and Filtek Z250 (P< 0.001). Only the restorative material had a significant effect on degree of conversion (P< 0.001): Esthet-X had the lowest degree of conversion followed by Filtek Z250 and Tetric Ceram. Curing mode (P= 0.007) and material (P< 0.001) had significant effect on wear. Higher wear resulted from the pulse-delay curing mode when compared to continuous curing, and Filtek Z250 showed the lowest wear followed by Esthet-X and Tetric Ceram.

Polymerization characteristics, flexural modulus and microleakage evaluation of silorane-based and methacrylate-based composites.

Abstract: Purpose To compare the behavior of a new low-shrinkage silorane-based composite (P90) with two conventional methacrylate-based composites, in terms of polymerization shrinkage, polymerization stress, gel point, flexural modulus and microleakage. Methods The materials tested were P90 (3M ESPE), AP-X (Kuraray), Quixfil (Dentsply). Polymerization shrinkage was measured using the Accuvol method. Polymerization stress was assessed using a stress-strain analyzer. Polymerization shrinkage (%) and force (N) were continuously recorded for 300 seconds. Polymerization shrinkage and stress after 300 seconds and gel point were recorded. Flexural modulus was obtained by three-point bending. A laboratory microleakage test was performed. Class V cavities prepared on labial surfaces of 70 freshly extracted human teeth were randomly assigned to the seven groups (N=10): P90/PSA (P90 System Adhesive), AP-X/CBA (Clearfil SE Bond Adhesive), Quixfil/XBA (XP Bond Adhesive), P90/CBA, P90/XBA, AP-X/PSA, Quixfil/PSA. The teeth were immersed in 1% basic fuchsin dye for 24 hours at room temperature. All teeth were cut in a labial-lingual direction and the penetration of dye along the wall of cavities was observed under a stereoscopic light microscope. Statistical analysis was performed with one-way ANOVA, Kruskal-Wallis ANOVA test and post hoc tests (P Results The low-shrinkage silorane-based composite (P90) exhibited significantly lower polymerization shrinkage, polymerization stress, flexural modulus and a later gel point than the conventional methacrylate-based composites. In the microleakage test, P90/PSA, AP-X/CBA, AP-X/PSA demonstrated the lowest microleakage scores without a significant difference among them (P> 0.05). Quixfil/XPA exhibited the highest microleakage scores.

Influence of laboratory degradation methods and bonding application parameters on microTBS of self-etch adhesives to dentin.

Abstract: PURPOSE To evaluate the laboratory resistance to degradation and the use of different bonding treatments on resin-dentin bonds formed with three self-etching adhesive systems. METHODS Flat, mid-coronal dentin surfaces from extracted human molars were bonded according to manufacturer's directions and submitted to two challenging regimens: (A) chemical degradation with 10% NaOC1 immersion for 5 hours; and (B) fatigue loading at 90 N using 50,000 cycles at 3.0 Hz. Additional dentin surfaces were bonded following four different bonding application protocols: (1) according to manufacturer's directions; (2) acid-etched with 36% phosphoric acid (H3PO4) for 15 seconds; (3) 10% sodium hypochlorite (NaOClaq) treated for 2 minutes, after H3PO4-etching; and (4) doubling the application time of the adhesives. Two one-step self-etch adhesives (an acetone-based: Futurabond/FUT and an ethanol-based: Futurabond NR/FNR) and a two-step self-etch primer system (Clearfil SE Bond/CSE) were examined. Specimens were sectioned into beams and tested for microtensile bond strength (microTBS). Selected debonded specimens were observed under scanning electron microscopy (SEM). Data (MPa) were analyzed by ANOVA and multiple comparisons tests (alpha= 0.05). RESULTS microTBS significantly decreased after chemical and mechanical challenges (P< 0.05). CSE showed higher microTBS than the other adhesive systems, regardless the bonding protocol. FUT attained the highest microTBS after doubling the application time. H3PO4 and H3PO4 + NaOCl pretreatments significantly decreased bonding efficacy of the adhesives.

Assessment of hypersensitivity reduction of a dentifrice containing 0.3% triclosan, 2.0% PVM/MA copolymer, 0.243% NaF and specially-designed silica as compared to a dentifrice containing 0.454% stannous fluoride, sodium hexametaphosphate and zinc lactate and to a dentifrice containing 0.243% NaF on dentin hypersensitivity reduction: an 8-week study.

Abstract: PURPOSE To evaluate the 8-week dentin hypersensitivity efficacy of three toothpastes: (1) a dentifrice containing 0.3% triclosan, 2.0% PVM/MA copolymer, 0.243% sodium fluoride and specially-designed silica (Test Dentifrice 1); (2) a commercially-available dentifrice containing 0.454% stannous fluoride in a silica base with sodium hexametaphosphate and zinc lactate (Test Dentifrice 2); and (3) a commercially-available non-sensitive dentifrice containing 0.243% sodium fluoride in a silica base (Negative Control Dentifrice). METHODS For this 8-week randomized controlled clinical study, qualifying subjects had to have at least two hypersensitive teeth with a tactile hypersensitivity score (Yeaple Probe) between 10 and 50 grams of force, and air blast hypersensitivity score of 2 or 3 (Schiff Cold Air Sensitivity Scale). Subjects brushed twice daily for 1 minute, using the assigned toothpaste and toothbrush. Dentin hypersensitivity assessments, as well as examinations of oral hard and soft tissues, were conducted at the baseline examination and after 4 and 8 weeks of brushing. RESULTS 118 subjects complied with the protocol, and completed the 8-week study. At baseline, the mean tactile sensitivity scores for toothpastes (1), (2) and (3) were 13.6, 14.1 and 13.1; at 4 weeks 28.75, 20.13, and 20.00; and after 8 weeks 33.1, 24.0 and 20.5, respectively. The mean air blast scores for toothpastes (1), (2), and (3) at baseline were 2.5, 2.5, and 2.4; at 4 weeks 1.25, 1.50 and 1.85; and after 8 weeks 0.99, 1.36 and 1.5, respectively. At all time points after the baseline examination, for both tactile and air blast sensitivity scores, the differences between Test Dentifrice 1 and the Negative Control Dentifrice were statistically significant (P < 0.05). The differences between Test Dentifrice 1 and Test Dentifrice 2 were statistically significant (P < 0.05) at 4 and 8 weeks after baseline examination for tactile sensitivity scores and at 8 weeks after baseline examination for air blast sensitivity scores.

Recommendation for a non-animal alternative to rat caries testing

Abstract: Purpose As a requirement of the Food & Drug Administration's final monograph on "Anticaries drug products for over-the-counter human use", the toothpaste industry has been conducting animal caries tests on every fluoride-containing toothpaste introduced into the U.S. market since 1996. The practice of testing in animals, although required by law, is in stark conflict with the corporate policy of many U.S. and global toothpaste manufacturers, in which, if possible, alternatives to animal testing are utilized. A provision does exist within the regulation which allows the use of an alternative method to demonstrate efficacy. However, to take advantage of this provision, a petition must be submitted to the FDA and in this petition data demonstrating the alternative provides results of "equivalent accuracy" must be included. After many years of research, model development and model comparisons, we have identified one particular laboratory model that demonstrated excellent correlation with the currently accepted animal caries models. This model, known as the Featherstone pH cycling model, is discussed in this paper. Methods The Featherstone pH cycling model has been shown to produce results of equivalent accuracy to the animal caries model by: (1) demonstrating a clinically relevant fluoride dose response similar to that shown in the animal caries model (including 1100 ppm F, 250 ppm F and placebo); (2) demonstrating similar results to the animal caries model for clinically proven dentifrice formulations relative to positive and negative controls; (3) demonstrating discriminating ability in strong agreement with the animal caries model for differentiating between a dentifrice formulation with attenuated fluoride activity and a USP standard; and (4) providing a clinically relevant representation of the caries process, as demonstrated by orthodontic banding studies. In addition, the model sufficiently addresses both salivary and abrasive/anticalculus agent interference concerns. Results For more than 50 years, fluoride has been the first defense in the fight against dental caries. The clinical effectiveness of fluoride is well accepted and documented extensively in the literature. The mechanism through which fluoride provides its benefit is very straightforward and well understood. The proposed laboratory model effectively simulates the effect of the caries process and has been shown to demonstrate equivalent accuracy to animal caries. This indicates that there are strong scientific grounds for the use of this model as an alternative to the animal caries test. Based on the strength of the data and the correlations noted between the two models, we recommend that the scientific community and the toothpaste industry broadly accept the Featherstone laboratory pH cycling model as an appropriate alternative to animal testing, particularly for ionic fluoride based dentifrices.

Detection of cavitated or non-cavitated approximal enamel caries lesions using CMOS and CCD digital X-ray sensors and conventional D and F-speed films at different exposure conditions.

Abstract: PURPOSE To determine the ability of digital sensors (CMOS and CCD sensors) and D and F-speed films to detect cavitated and non-cavitated enamel caries lesions at different exposure conditions compared to a gold standard. METHODS 100 extracted human molars and premolars were selected and mounted in a block between two neighboring teeth. Sensors or films were exposed with voltages of 60 or 70 kVp at varying times. Three observers assessed each approximal site independently. Lesion depth was rated according to an anatomical five-point scale (0 = no lesion to 4 = lesion reaching inner half of dentin). Serial sections of resin-embedded teeth were prepared. Gold-standard scores were established by consensus based on histological sectioning. A carious lesion was present at scores of 1 and higher. Statistical evaluation (sensitivity, specificity and receiver-operating curves) was based on caries-free surfaces and those presenting enamel caries (n=116). RESULTS The ROC curves had "area under the curve" values (Az) from 0.50 (F-speed, 70 kVp, 0.20 seconds) to 0.58 (CCD 60 kVp, 0.08 seconds). The detection percentage of cavitated lesions was generally higher (0-52%, depending on technique and observer) than that of non-cavitated lesions (3-32%). The CMOS sensor showed Az values comparable to the CCD sensors but required higher exposure times. There was no significant difference between 60 and 70 kVp.

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

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

Disinfection of toothbrushes contaminated with Streptococcus mutans.

Abstract: PURPOSE To determine the most effective method to kill Streptococcus mutans on contaminated toothbrushes. METHODS Seven toothbrushes (one for each treatment and the control) were contaminated with S. mutans. Toothbrushes were then rinsed in phosphate buffered saline (PBS) and treated as follows: (1) control without treatment; (2) air dry for 4 hours; (3) Crest Pro-Health mouthwash for 20 minutes; (4) Listerine mouthwash for 20 minutes; (5) normal cleaning cycle in a dishwasher; (6) microwave on high power for 5 minutes; and (7) ultraviolet light using the DenTek Toothbrush Sanitizer for 10 minutes. All toothbrushes were rinsed again with PBS. The bristles were cut and vortexed in PBS. Serial dilutions were performed and the number of colonies enumerated after incubation. The experiment was independently repeated seven times. RESULTS The Crest Pro-Health mouthwash and the dishwasher almost completely eliminated S. mutans. The second most effective treatment was the microwave. The Listerine mouthwash and the air dry groups were not significantly different from each other and ranked third. Although UV light significantly decreased the number of bacteria compared to the control, reduction in the number of S. mutans CFU was significantly lower than that of all the other treatments evaluated. Crest Pro-Health mouthwash for 20 minutes and a normal dishwasher cycle are the most effective methods to eradicate S. mutans from contaminated toothbrushes. Dent

Temperature rise during photo-polymerization for onlay luting.

Abstract: To measure the temperature rise during long-time irradiation needed to lute adhesive indirect restorations, with one halogen and five LED high-power lamps, in a simulated oral environment, and (2) to propose a technique to reduce heat.

The effect of 6-month water storage on the bond strength of self-etch adhesives bonded to dentin.

Abstract: PURPOSE To evaluate the microtensile bond strengths (microTBS) of 1-step vs. 2-step self-etch systems to dentin after 24 hours and after 6 months of water storage. METHODS Resin composite buildups were bonded to occlusal dentin of third molars using the following adhesives: Xeno IV (XE, Dentsply), G-Bond (GB, GC Inc), Clearfil S3 Bond (CS3, Kuraray); Adper Prompt L-Pop (AD, 3M ESPE); Go (GO, SDI), All Bond SE (ABSE 1-step or ABSE 2-step, Bisco) and Clearfil SE Bond (CSE, Kuraray). The bonded sticks (cross-sectioned area of 0.8-0.9 mm2) originated from the same teeth were randomly divided to be tested after 24 hours or after 6 months of water storage. The data was submitted to two-way repeated measures ANOVA and Tukey's test with and without the inclusion of premature failures (PF) (alpha = 0.05). RESULTS The inclusion of PF resulted in different statistically significant means for CS3, CSE and AD (P 0.05).

Effect of CPP-ACP and APF on Streptococcus mutans biofilm: A laboratory study

Abstract: PURPOSES (1) To determine the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and acidulated phosphate fluoride (APF) on S. mutans viability, (2) to observe their effects on biofilm structure, and (3) to examine the element content of the hydroxyapatite (HA) surfaces after exposure to CPP-ACP and APF. METHODS HA discs were coated with: CPP-ACP (GC Tooth-Mousse), APF, CPP-ACP+APF (1/1). Uncoated HA discs were used as control. Following application of the materials, the discs were immersed in human saliva and incubated with S. mutans ATCC (27315) for 24 hours. Growth of bacteria on the discs was evaluated by microbial culturing methods. The structure of the biofilm was examined with confocal laser scanning microscope (CLSM). The change in element content of HA surfaces (without biofilm) was evaluated with energy-dispersive x-ray spectroscopy (EDS). The values were statistically analyzed using Kruskal-Wallis and Dunn's test. RESULTS The total number of bacteria of APF and CPP-ACP+APF applied groups were found significantly lower than the control group (P< 0.05). All specimens showed similar microbial colonization structure. No statistically significant differences were observed in O, F, Na, P, Ca content on HA surfaces after exposure to the tested agents, although fluoride concentration of the APF treated HA surfaces were increased compared to CPP-ACP, CPP-ACP +APF.

Clinical evaluation of the fast onset and sustained sensitivity relief of a 0.454% stannous fluoride dentifrice compared to an 8.0% arginine-calcium carbonate-sodium monofluorophosphate dentifrice.

Abstract: PURPOSE To evaluate the efficacy of a dentifrice containing 0.454% stannous fluoride (SnF2) in the reduction of dentin hypersensitivity immediately after use, after 3 days and after a 2-week use period as compared to a positive control dentifrice containing 8.0% arginine, calcium carbonate and 1450 ppm fluoride as sodium monofluorophosphate. METHODS 80 healthy adult subjects with moderate dentin hypersensitivity were enrolled in this clinical study, which had a controlled, randomized, examiner-blind, two-treatment (40 subjects per treatment group), parallel group design. For each subject, two sensitive bicuspid or cuspid teeth in different quadrants demonstrating reproducible sensitivity to thermal stimuli (Schiff air sensitivity score of > 1) were chosen for evaluation. Subjects were randomized to treatment with either the SnF2 dentifrice or the positive control dentifrice. At the baseline visit, subjects were assessed for sensitivity to thermal stimuli, received an oral soft tissue examination, and were instructed to brush with their assigned dentifrice according to manufacturers' usage instructions. Immediately after brushing, sensitivity to thermal stimuli for each enrolled tooth was assessed by an experienced dental examiner using the Schiff air sensitivity index and by study subjects based on air visual analog scale (VAS). After using their assigned dentifrice for 3 days and for 2 weeks, thermal sensitivity was re-assessed by both examiner and subject, and each subject received an oral soft tissue examination. RESULTS 40 subjects in the SnF2 dentifrice group and 38 subjects in the control group completed all study procedures. Both dentifrice groups showed significant sensitivity relief relative to baseline (P < 0.01). The SnF2 dentifrice provided a statistically significant (P = 0.005) 7.4% reduction in sensitivity relative to the positive control dentifrice immediately after first use and an even more significant (P = 0.001) 20% reduction at Week 2 based on the Schiff air sensitivity scale. Based on the VAS, the SnF2 dentifrice provided statistically significant (P < 0.0001) reduction in sensitivity relative to the positive control dentifrice immediately after first use, at Day 3, and Week 2, with percent reductions of 7.2%, 15.8% and 28.2%, respectively. No adverse events were reported with either dentifrice.

Release of monomers from four different composite materials after halogen and LED curing.

Abstract: PURPOSE To evaluate the release of monomers from four different composite materials (Ceram X, Filtek Supreme XT, Tetric Flow, Tetric EvoCeram), polymerized using either halogen or LED unit. METHODS Ten specimens were made for each material/unit combination. Each specimen was stored in 1 ml 75% ethanol. The storage medium was renewed after 1, 7 and 28 days. Aliquots of this medium were analyzed by LC-MS/MS. RESULTS The effect of the curing unit on monomers' release differed significantly among the materials (P 0.05). Curing with LED reduced the amount of Bisphenol A released from Ceram X compared to halogen. For Filtek Supreme XT, the type of unit exerted a significant effect on the elution of BisGMA (P < or = 0.05). LED curing resulted in a higher release of TEGDMA and UDMA compared to halogen (P < or = 0.05). For Tetric Flow, LED curing resulted in lower monomer release (P < 0.0001). For Tetric EvoCeram, the amounts of BisGMA, UDMA and Bisphenol A were higher when polymerizing with LED compared to halogen. The release of substances was more material dependent and less influenced by the curing unit used.