Addition of zinc methacrylate in dental polymers: MMP-2 inhibition and ultimate tensile strength evaluation.

This study evaluated the effect of zinc methacrylate (ZM) on the inhibition of matrix metalloproteinase 2 (MMP-2) and the ultimate tensile strength (UTS) of an experimental polymer. Enzymes secreted from mouse gingival tissues were analyzed by gelatin zymography in buffers containing 5 mM CaCl(2) (Tris-CaCl(2)) in 50 mM Tris-HCl buffer with various concentrations of ZM (0.5, 1, 2, 4, 8, and 16 mM). The matrix metalloproteinases present in the conditioned media were characterized by immunoprecipitation. The polymer UTS evaluation was performed in eight groups with various concentrations of ZM (0, 0.5, 1, 2.5, 5, 10, 20, and 30 wt.%), in a mechanical testing machine. MMP-2 (62 kDa) was detected in the zymographic assays and inhibited by ZM in all tested concentrations. UTS data were submitted to one-way ANOVA and Tukey's test (α = 0.05), and no significant differences were observed among groups, except in the polymer containing 30% ZM, presenting a significantly lower value when compared with the control group (p < 0.05). The results suggest that ZM inhibits MMP-2 expression in all concentrations tested, while small concentrations did not affect the ultimate tensile strength of the polymer. Zinc methacrylate is a metalloproteinase inhibitor that can be copolymerized with other methacrylate monomers. Yet, the addition of ZM did not affect the resin bond strength. Thus, in vivo tests should be performed to evaluate the performance of this material.

Characterization of an antimicrobial dental resin adhesive containing zinc methacrylate.

This study evaluates the effect of zinc methacrylate (ZM) on the degree of conversion (DC), cytotoxicity and antimicrobial activity (AA) of an experimental resin. Tetraethyleneglycol dimethacrylate was used as the experimental resin and it was photo activated using camphoroquinone and ethyl 4-dimethylamine benzoate. Additionally, 1.0, 2.5, 5.0, 10, 20 and 30 wt% of ZM was added to the various experimental resins. The DC was accessed by Fourier Transform infrared spectroscopy. For cytotoxicity, immortalized mouse fibroblasts were exposed to the experimental resin extracts. An MTT assay was used to access the cytotoxicity. The AA against Streptococcus mutans UA159 was accessed by the agar diffusion method. An improvement in the DC in all concentrations of ZM was observed. The greater the amount of ZM on the experimental resin, the less the cytotoxicity was provoked. Three ZM concentrations showed AA that exhibited various inhibition growth zones with 10, 20 (10 mm) and 30 wt% (15 mm).

Clareamento dental caseiro por meio de fitas adesivas: relato de caso / Home bleaching using whitening strips: a case report

O clareamento caseiro, com peróxido de carbamida a 10%, aplicado por meio de moldeiras personalizadas, ainda é o protocolo de tratamento mais utilizado, quando se quer branquear os dentes. No entanto, está disponível técnica mais recente, que consiste na utilização de fitas adesivas pré-contornadas, impregnadas com agente clareador, que contêm diferentes concentrações de peróxido de hidrogênio. Aplicadas uma ou duas vezes ao dia, as fitas são facilmente adaptadas aos dentes anteriores. O objetivo deste artigo é apresentar relato de clareamento dental caseiro com utilização de fitas adesivas impregnadas com peróxido de hidrogênio a 6%, abordando suas principais características, indicações e limitações.

Vital bleaching using 10% Carbamide Peroxide and custom-made trays is still the most used technique for dental bleaching. However, there is a novel technique for bleaching vital teeth using whitening strips containing different concentrations of hydrogen peroxide. The strips are easily adapted in a QD or BID regimen over the anterior teeth. The aim of this paper is to present a clinical case where 6% hydrogen peroxide strips were used, and to discuss the main characteristics, indications and limitations.

Factors influencing the microhardness of a microhybrid composite.

This study investigated how different photocuring units, exposure times, and ethanol storage affected the depth of cure in a microhybrid composite. Forty composite specimens (each with a depth of 4 mm) were prepared and divided randomly into four groups (n = 10) to receive treatment from a quartz-tungstenhalogen (QTH) curing unit (400 mW/cm2) or a light-emitting-diode (LED) curing unit (180 mW/cm2). The specimens were photocured for either 20 or 40 seconds and stored in the dark for 24 hours at room temperature. Knoop hardness was measured by making three indentations at each depth interval of 1 mm (up to 4 mm) with a 50 g load for 30 seconds. The specimens were stored in ethanol for 24 hours; at that time, hardness was measured again. Data were submitted to three-way ANOVA, Tukey's test, and Student's t-test (p < 0.05). Statistical analysis revealed that hardness was significantly affected by depth, exposure time, and storage in ethanol (p < 0.001). No differences were observed between the curing units tested.

Synthesis of phosphate monomers and bonding to dentin: esterification methods and use of phosphorus pentoxide.

OBJECTIVES: The aim of this study was to synthesize an acidic monomer using an alternative synthetic pathway and to evaluate the influence of the acidic monomer concentration on the microtensile bond strength to dentin. METHODS: The intermediary 5-hydroxypentyl methacrylate (HPMA) was synthesized through methacrylic acid esterification with 1,5-pentanediol, catalyzed by p-toluenesulfonic acid. To displace the reaction balance, the water generated by esterification was removed by three different methods: anhydrous sodium sulfate; molecular sieves or azeotropic distillation. In the next step, a phosphorus pentoxide (4.82 mmol) slurry was formed in cold acetone and 29 mmol of HPMA was slowly added by funnel addition. After the reaction ended, solvent was evaporated and the product was characterized by 1HNMR and FTIR. The phosphate monomer was introduced in a self-etch primer at concentrations of 0, 15, 30, 50, 70 and 100 wt%. Clearfil SE Bond was used as commercial reference. Microtensile bond strength to dentin was evaluated 24h after the bonding procedures, followed by fracture analysis (n=20). Data was submitted to ANOVA and Tukey's post hoc test. RESULTS: The highest yield was obtained (62%) when azeotropic distillation was used, while the reaction with molecular sieves was not feasible. The phosphoric moiety attachment to the monomer was successfully performed with a quantitative yield that reached around 100%. The acidic monomer concentration significantly affected the bond strength and the highest mean (55.1+/-12.8 MPa) was obtained when 50% of acidic monomer was used. CONCLUSION: The synthesis pathways described in the present study appear to be a viable alternative for developing phosphate monomers.

Papain-based gel for biochemical caries removal: influence on microtensile bond strength to dentin.

This study investigated the influence of a papain-based gel (Papacárie) for chemo-mechanical caries removal on bond strength to dentin. Human molars were assigned to the following groups: Group 1: sound teeth were flattened to expose dentin; Group 2: after flattening of surfaces, the papain-based gel was applied on the sound dentin; Group 3: overlying enamel from carious teeth was removed and mechanical excavation of dentin was conducted; Group 4: chemo-mechanical excavation of carious dentin was conducted using the papain-based gel. The Prime&Bond NT or Clearfil SE Bond adhesive systems were used for restorative procedures. A microtensile bond strength test was performed, and the modes of failure were determined under SEM. The data were submitted to two-way ANOVA and Tukey's test (p < or = 0.05). No significant differences were observed between the sound dentin groups. For both excavation methods, Clearfil presented a significantly higher bond strength than Prime&Bond NT. Also, for Clearfil, the mechanically excavated samples disclosed a significantly higher bond strength than the chemo-mechanically ones. For Prime&Bond NT, no significant differences were detected between the excavation methods. Predominance of mixed failures for the sound substrate and of adhesive failures for the carious dentin one was detected. The bond strength to carious dentin of the self-etching system was negatively affected by chemo-mechanical excavation using the papain-based gel.

Papain-based gel for biochemical caries removal: influence on microtensile bond strength to dentin

This study investigated the influence of a papain-based gel(Papacárie) for chemo-mechanical caries removal on bond strength todentin. Human molars were assigned to the following groups: Group 1:sound teeth were flattened to expose dentin; Group 2: after flattening ofsurfaces, the papain-based gel was applied on the sound dentin; Group3: overlying enamel from carious teeth was removed and mechanical excavationof dentin was conducted; Group 4: chemo-mechanical excavationof carious dentin was conducted using the papain-based gel. ThePrime&Bond NT or Clearfil SE Bond adhesive systems were used forrestorative procedures. A microtensile bond strength test was performed,and the modes of failure were determined under SEM. The data weresubmitted to two-way ANOVA and Tukey’s test (p ≤ 0.05). No significantdifferences were observed between the sound dentin groups. Forboth excavation methods, Clearfil presented a significantly higher bondstrength than Prime&Bond NT. Also, for Clearfil, the mechanically excavatedsamples disclosed a significantly higher bond strength than thechemo-mechanically ones. For Prime&Bond NT, no significant differenceswere detected between the excavation methods. Predominance ofmixed failures for the sound substrate and of adhesive failures for thecarious dentin one was detected. The bond strength to carious dentinof the self-etching system was negatively affected by chemo-mechanicalexcavation using the papain-based gel.