Biomechanical Behavior Evaluation of Resin Cement with Different Elastic Modulus on Porcelain Laminate Veneer Restorations Using Micro-CT-Based Finite Element Analysis.

The aim of this study is to evaluate the biomechanical behavior of the porcelain laminate veneer restorations (PLV) of the maxillary central incisor luted with two types of resin cements having different incisal preparations: butt joint and palatal chamfer. Biomechanical analyses were performed using the micro-CT-based finite element models, and von Mises stress and strain values of the PLV, resin cement, adhesive layer, and tooth structure were computed. The PLV with butt joint preparation showed larger stress values than those of restored with palatal chamfer preparation, regardless of the elasticity of the cement and loading conditions. An increase in the elasticity modulus of the resin cement induced slightly larger stresses on the adhesive layer, tooth tissues, and restorative materials. Overall, this study demonstrates the role of the preparation design and luting materials on the mechanical behavior of the PLV restorations and discusses the potential failure mechanisms of the PLV restorations under different loading mechanisms.

Effect of black tea and matrix metalloproteinase inhibitors on eroded dentin in situ.

Purpose of this in situ study was to evaluate the surface properties of eroded dentin specimens activated with three different matrix metalloproteinase (MMP) inhibitors (chlorhexidine [CHX], fluoride, green tea), black tea, and water. One hundred eighty dentin samples were prepared from extracted third molars and then samples divided into six groups. Ten volunteers were carried three specimens of each group, on acrylic palatal appliances, which were fabricated exactly for them (n = 3). Erosive cycles were done by immersing appliances in cup containing Cola and was followed by rinsing with test solutions. Microhardness values were measured. Surface properties were investigated by atomic force microscopy (AFM). Lowest change in microhardness was shown in fluoride group whereas negative control group (water) had the highest change. There were no statistically significant differences among surface roughness changes (p > .05). The least change in microhardness was seen in the fluoride group (13.05 ± 8.07), while the control group showed the highest change (33.80 ± 12.42) and was statistically significant when compared to other groups (p < .05). Besides lowest depth, values were shown in fluoride group as well. AFM evaluations showed macromolecular deposits on surfaces of fluoride, CHX, and black tea groups. No superior results were detected in CHX + fluoride group and black tea showed similar surface characteristics as green tea. Mouthrinses containing not only green tea but also black tea could be beneficial for patients with exposed dentin surfaces. Catechines and theaflavins in teas could be useful for improving surface quality.

Effects of different kinds of beers on the surface roughness of glazed and polished methacrylate and Silorane-based composites: a 1-month study.

BACKGROUND: The aim of this in vitro study was to evaluate the effect of different kind of beers on the surface roughness of glazed and polished methacrylate- and Silorane-based resin composites after different immersion periods. METHODS: Methacrylate-based resin composites (Tetric N-Ceram, Ceram-X) and a Silorane-based resin composite (Filtek Silorane) were tested in the study. A total of 126 specimens (n=42 for each composite) were fabricated using a cylindrical custom metal mould. Surface roughness measurement was performed using a profilometer at baseline and after a 1-week and 1-month immersion in different kind of beers or distilled water. The results were analysed using repeated measure ANOVA and Tukey's HSD test (α=0.05). RESULTS: Repeated measure ANOVA results revealed that immersion period was a significant factor in the surface roughness of the tested specimens (p<0.001). The lowest surface roughness values were obtained with the specimens' polished Optidisc+BisCover LV. Regardless of the polishing systems used, Tetric N-Ceram showed the statistically lowest surface roughness values (p<0.05), whereas Filtek Silorane showed the highest surface roughness (p<0.001). CONCLUSION: The surface roughness values of the tested resin composites were affected by the polishing procedure used, the exposure time in the solutions and the type of composite resin.

Prevalence of dental injuries and awareness regarding mouthguards among basketball players and coaches.

BACKGROUND: Dental injuries are frequently occurred by an impact to facial area among basketball players. In fact, mouthguards are able to absorb the power of impacts and protect teeth from excessive forces, it is crucial for players even at training to wear mouthguards. To determine the prevalence of dental injuries and investigate the awareness about the use of mouthguards among basketball players and coaches. METHODS: A 14-item questionnaire was designed and tested among licensed basketball players and coaches, all of whom were continuously exposed to the risk of dental injuries. The questions focused on the prevalence of dental injuries and attitudes and knowledge regarding the use of mouthguards among the players and coaches. Data were calculated using descriptive statistics and χ2 tests. RESULTS: A total of 53 coaches (18-69 years) and 351 players (12-38 years) participated. Of these, 124 players (35% of the total sample) had experienced oral injuries, including soft tissue lacerations (80.6%), fractures (17.7%) and avulsions (1.6%). Although the players had sustained dental injuries, 95% of them found mouthguards to be protective, and only 6.3% (N.=22) actually used a mouthguard. The rate of mouthguard use among players who had experienced an oral injury was significantly higher than that among players without any history of injury (P<0.05). Although 98% of the coaches believed that mouthguards could prevent dental injuries, only 47% of them suggested their use to their players. The most common reasons for not using a mouthguard were discomfort (37.7%) and difficulty in breathing (7.3%) or talking (6.4%). CONCLUSIONS: This study showed that the use of mouthguards among basketball players is very rare, with inadequate knowledge among the coaches. Consequently, more information is required through sports associations and dentists.

Effect of surface sealing on stain resistance of a nano-hybrid resin composite.

PURPOSE: This study investigated the influence of sealant application on stain resistance of a nanohybrid resin composite compared to the efficacy of a bonding agent used as a surface sealant on prolonging color stability of the resin composite. MATERIALS AND METHODS: 28 disc-shaped materials were prepared from a nano-hybrid resin composite Filtek Z550 and assigned to four groups: G1K: nonsealed; G2:Adper Single Bond; G3: Fortify ; G4: Biscover LV. After 24 h storage in distilled water at 37˚C, all specimens were subjected to thermocycling and immersed into coffee solution. Color measurements were performed using spectrophotometer (VITA Easyshade; Vident) according to CIEL*a*b* system. RESULTS: Color change values were significantly different among the groups in each evaluation period except for after thermocycling (p<0.05). For 7 days evaluation period, the difference between G3 and G4 group was statistically significant while G4 exhibited statistically significant differences (p<0.05 and p<0.0001 respectively) compared to control (G1) in 14 day whereas no significant difference was found between GI and GII in 28-day evaluation period. However, ΔE values of sealed specimens (GIII, GIV) differed significantly from non-sealed (GI) specimens after 28 days of immersion in coffee solution (p<0.05 and p<0.0001 respectively). CONCLUSION: It may be concluded that using a bonding agent as a surface sealant does not increase stain resistance of resin composites of the sealants evaluated. Biscover LV showed the highest efficacy to prolong color stability of the resin composite.

Effect of Different Antioxidants on the Microtensile Bond Strength of an Adhesive System to Sodium Hypochlorite-treated Dentin.

PURPOSE: To evaluate the effects of different antioxidant treatments on the microtensile bond strength of an adhesive system to sodium hypochlorite (NaOCl)-treated dentin. MATERIALS AND METHODS: Thirty extracted third molars were sectioned 3 mm below the occlusal surface and divided into six groups according to the antioxidant treatment received: control group: distilled water; NaOCl group: 5.25% NaOCl and distilled water; proanthocyanidin (PA) group: 5.25% NaOCl, 5% PA and distilled water; 1-week storage group: 5.25% NaOCl and storage for 1 week in distilled water; Accel group: 5.25% NaOCl, Accel, and distilled water; noni group: 5.25% NaOCl, noni fruit juice, and distilled water. NaOCl, PA, Accel, noni, and distilled water were administered for 30 s, 10 min, 30 s, 10 min, and 30 s, respectively. A self-etching adhesive system (Single Bond Universal Adhesive) was applied to each specimen and a resin composite (Filtek Z550) was built up to a height of 5 mm on the dentin surface. Each specimen was serially sectioned to obtain sticks with a cross-sectional area of 1 mm2, and their microtensile bond strength was determined. Statistical differences between groups were analyzed using one-way ANOVA and Tamhane's T2 test. RESULTS: Microtensile bond strength in the NaOCl group was significantly lower than in all other groups. However, there were no significant differences in the bond strength between the groups treated with different antioxidants. CONCLUSIONS: NaOCl significantly reduced the microtensile bond strength of the adhesive system. The application of PA, Accel, and noni fruit juice to NaOCl-treated dentin significantly improved the microtensile bond strength.

Clinical comparison of a flowable composite and fissure sealant: a 24-month split-mouth, randomized, and controlled study.

OBJECTIVES: The aim of this clinical study was to evaluate the retention rate and caries-prevention effect of a flowable composite compared to a conventional resin-based sealant in a young population over a 24-month period. METHODS: Thirty-four patients, ranging in age from 16 to 22 years, diagnosed with at least 2 non-cavitated pit-and-fissure caries in the first and second molars were selected for this randomized split-mouth design trial. A total of 220 sealants, were placed in 117 upper molars and 103 lower molars. The teeth were sealed with a flowable resin composite (Tetric Evo Flow) or a sealant material (Helioseal F). Each restoration was independently evaluated in terms of retention and the presence of caries at baseline and at 1, 6, 12, and 24 months. Data were analyzed using non-parametric Mann-Whitney U and Friedman 1-way ANOVA tests at p<0.05. RESULTS: Tetric Evo Flow showed complete retention with 100%, 95.5%, 93.8%, and 88.5% at 1, 6, 12, and 24-month evaluations, respectively, while Helioseal F retention rates were 98.1%, 95.5%, 94.8%, and 85.4%, respectively, for the same evaluation periods. At the 24-month recall, 4 (4.2%) total losses were observed in subjects treated with Tetric Evo Flow and 2 total losses (2.1%) for Helioseal F, respectively. No significant differences were observed between the materials in retention rates or caries incidence for each evaluation period (p>0.05). CONCLUSION: Placement of flowable composite as fissure sealants in the younger population seems to be as effective as conventional fluoride containing fissure sealants for the prevention of fissure caries. CLINICAL RELEVANCE: The use of a flowable composite as a fissure sealant material, in conjunction with a total-etch, single bottle adhesive, yielded better retention than did the conventional fluoride containing resin-based fissure sealant over a 24-month period in young patients.

Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material.

PURPOSE: The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material. MATERIALS AND METHODS: A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05. RESULTS: Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001). CONCLUSION: Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used.

The efficacy of three desensitizing agents used to treat dentin hypersensitivity.

BACKGROUND: In a single-center, double-masked, split-mouth-designed, clinical short-term trial, the authors assessed the clinical responses of teeth with dentin hypersensitivity (DH) after treating the teeth with one of three desensitizing agents across four weeks. METHODS: The authors selected 131 teeth with DH in 11 participants. The authors assessed DH of the teeth by using tactile stimuli and air stimuli and had the participants record the level of sensitivity by means of a visual analog scale (VAS). The authors then treated the teeth with one of three desensitizing agents (Pain-Free [Parkell, Edgewood, N.Y.], BisBlock [Bisco, Schaumburg, Ill.], Seal & Protect [Dentsply DeTrey, Konstanz, Germany]) that they applied according to the manufacturers' instructions. The authors used a split-mouth-designed study in which the teeth in different quadrants of the participants' mouths received different desensitizing agents. The authors also conducted DH evaluations at 10 minutes after treatment and at one, two, three and four weeks. The authors analyzed data statistically by using Mann-Whitney U and Kruskal-Wallis tests. RESULTS: The results of the statistical analysis showed that all VAS scores at the posttreatment evaluation periods were reduced significantly compared with those at baseline (P<.05). More teeth were sensitive to air stimuli than to tactile stimuli. The mean VAS scores for DH in the mandibular teeth were significantly higher than for those in maxillary teeth immediately after treatment (for tactile stimuli) and two weeks after the first application (for air stimuli) (P<.05) CONCLUSIONS: All three desensitizing agents were effective in relieving DH up to four weeks, independent of their application procedures. There was, however, a significant reduction in mean sensitivity scores of teeth that had been treated with Seal & Protect and Pain-Free compared with those of BisBlock at weeks two, three and four. CLINICAL IMPLICATIONS: The study results should be considered with caution, as it is not clear how many of the pain relief effects were related to the natural desensitization of teeth over time.