Correlation between degree of conversion, resin-dentin bond strength and nanoleakage of simplified etch-and-rinse adhesives.

OBJECTIVES: The aim of this study was to correlate the degree of conversion measured inside the hybrid layer (DC) with the microtensile resin-dentin bond strength (µTBS) and silver nitrate uptake or nanoleakage (SNU) for five simplified etch-and-rinse adhesive systems. METHODS: Fifty-five caries free extracted molars were used in this study. Thirty teeth were used for µTBS/SNU [n=6] and 25 teeth for DC [n=5]. The dentin surfaces were bonded with the following adhesives: Adper Single Bond 2 (SB), Ambar (AB), XP Bond (XP), Tetric N-Bond (TE) and Stae (ST) followed by composite resin build-ups. For µTBS and SNU test, bonded teeth were sectioned in order to obtain stick-shaped specimens (0.8mm(2)), which were tested under tensile stress (0.5mm/min). Three bonded sticks, from each tooth, were not tested in tensile stress and they were immersed in 50% silver nitrate, photo-developed and analyzed by scanning electron microscopy. Longitudinal 1-mm thick sections were prepared for the teeth assigned for DC measurement and evaluated by micro-Raman spectroscopy. RESULTS: ST showed lowest DC, µTBS, and higher SNU (p<0.05). All other adhesives showed similar DC, µTBS, and SNU (p>0.05), except for TE which showed an intermediate SNU level. The DC was positively correlated with µTBS and negatively correlated with SNU (p<0.05). SNU was also negatively correlated with µTBS (p<0.05). SIGNIFICANCE: The measurement of DC inside the hybrid layer can provide some information about bonding performance of adhesive systems since this property showed a good correlation with resin-dentin bond strength and SNU values.

Improvement of exposure times: effects on adhesive properties and resin-dentin bond strengths of etch-and-rinse adhesives.

PURPOSE: This study evaluated the effect of prolonged polymerization times on the microtensile resin-dentin bond strength (µTBS), degree of conversion of adhesive films (DC) and silver nitrate uptake (SNU) for an ethanol/water- (Adper Single Bond 2, [SB]) and an acetone-based (One Step Plus, [OS]) etch-and-rinse adhesive. MATERIALS AND METHODS: Thirty caries-free extracted molars were included in this study. The occlusal enamel of all teeth was removed by wet grinding the occlusal enamel on 180-grit SiC paper. Adhesives were applied according to the manufacturer's instructions, but they were light cured for 10, 20 and 40 s at 600 mW/cm2. Bonded sticks (0.6 mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in an ammoniacal solution of silver nitrate (24 h), photodeveloped (8 h), and analyzed by SEM. The DC of the adhesives was evaluated under Fourier Transformed Infra-Red spectroscopy (FTIR). Data for each property were analyzed by two-way ANOVA and Tukey's test (α = 0.05). RESULTS: Statistically higher µTBS and DC were observed for SB and OS when both adhesives were light cured for 40 s in comparison with 10 s. For OS, the µTBS in the 20- and 40-s groups did not differ statistically, while for SB it did. Higher prolonged exposure times did not prevent nanoleakage within the hybrid layer for all groups regardless of the adhesive. CONCLUSION: This study supports the hypothesis that exposure times longer than those recommended can improve the degree of conversion of adhesive films and the immediate resin-dentin bonds. The prolonged curing times (20 and 40 s) for polymerization of simplified adhesives resulted in an increase in the degree of conversion of the adhesive films and resin-dentin bond strengths but did not reduce the nanoleakage within the hybrid layer.

Effects of adhesive temperature on the early and 6-month dentin bonding.

OBJECTIVES: The aim of this study was to test the effect of adhesive temperature on the bond strength to dentin (muTBS) and silver nitrate uptake (SNU) of an ethanol/water (Adper Single Bond 2 [SB]) and an acetone-based (Prime&Bond 2.1 [PB]) etch-and-rinse adhesive system. METHODS: The bottles of each adhesive were kept in various temperatures (5 degrees C, 20 degrees C, 37 degrees C and 50 degrees C) for 1h previously to its application in the occlusal demineralized dentin of 40 molars. Bonded sticks (0.8 mm(2)) were tested in tension (0.5 mm/min) immediately (IM) or after 6 months (6 M) of water storage. Two bonded sticks from each hemi-tooth were immersed in silver nitrate and analyzed by SEM. Data were analyzed by two-way repeated measures ANOVA and Tukey's test (alpha=0.05). RESULTS: No significant difference in muTBS was detected for both adhesives at 5 degrees C and 20 degrees C. The highest bond strength for PB was observed in the 37 degrees C group while for SB it was in the 50 degrees C. Significant reductions of bond strengths were observed for PB at 37 degrees C and SB at 50 degrees C after 6 M of water storage. Silver nitrate deposition was seen in all hybrid layers, irrespective of the group. Lower silver nitrate deposition (water trees) in the adhesive layer was seen for PB and SB at higher temperatures. CONCLUSIONS: The heating or refrigeration of the adhesives did not improve their resin-dentin bond resistance to water degradation over time.

Evaluation of mineral trioxide aggregate and calcium hydroxide cement as pulp-capping agents in human teeth.

This study evaluated the histomorphologic response of human dental pulps capped with mineral trioxide aggregate (MTA) and Ca(OH)2 cement (CH). Pulp exposures were performed on the occlusal floor of 40 human permanent premolars. After that, the pulp was capped either with CH or MTA and restored with composite resin. After 30 and 60 days, teeth were extracted and processed for histologic exam and categorized in a histologic score system. The data were subjected to Kruskal-Wallis and Conover tests (alpha = .05). All groups performed well in terms of hard tissue bridge formation, inflammatory response, and other pulpal findings. However, a lower response of CH30 was observed for the dentin bridge formation, when compared with MTA30 and MTA60 groups. Although the pulp healing with calcium hydroxide was slower than that of MTA, both materials were successful for pulp capping in human teeth.

Effects of hemostatic agents on the histomorphologic response of human dental pulp capped with calcium hydroxide.

OBJECTIVE: To evaluate the response of human pulps capped with a calcium hydroxide [Ca(OH)2] cement after bleeding control with 2 hemostatic agents. METHOD AND MATERIALS: Pulps were exposed on the occlusal floor, and the bleeding was controlled either with saline solution (SS) or 2.5% sodium hypochlorite (NaOCl) (SH). After that, the pulp was capped with Ca(OH)2 cement and restored with resin composite. After 30 (groups SS30 and SH30) and 60 (groups SS60 and SH60) days, the teeth were extracted and processed with hematoxylin-eosin and categorized in a histologic score system. The data were subjected to Kruskal-Wallis and Mann-Whitney tests (alpha = .05). RESULTS: Regarding dentin bridge formation, an inferior response of SH60 group was observed when compared to SS60 (P < .05). The response of the SH30 group generally was similar to that of the groups treated with saline solution. However, after 60 days, 2.5% NaOCl showed a trend toward having an inferior response. CONCLUSION: Using saline solution as a hemostatic agent before pulp capping with Ca(OH)2 resulted in a significantly better histomorphologic response than using 2.5% NaOCl as a hemostatic agent before capping with Ca(OH)2.

Influence of adhesive systems on interfacial dentin gap formation in vitro.

PURPOSE: This study measured: 1) the interfacial dentin gap formation (IGW) of 2 etch & rinse and 3 self-etch systems with different degrees of acidity and determined the correlation between the smear layer thickness and interfacial gap formation after 1 day and 6 months water storage; 2) the hybrid layer thickness (HLT) produced by the adhesives applied under different smear layer thicknesses. METHODS AND MATERIALS: Three self-etch adhesives, a mild (Clearfil SE Bond; SE), a moderate (Optibond Solo Plus Self-Etch Primer; SO) and a strong (Tyrian Self Priming Etchant + One Step Plus; TY), and 2 etch & rinse systems (Single Bond; SB and Scotchbond Multi-Purpose Plus; SBMP) were studied. After flat grinding of the occlusal surfaces, 30 molars were sectioned longitudinally in 2 halves. Dentin surfaces with thick and thin smear layers were obtained for each tooth after polishing different sections on 60- and 600-grit SiC paper, respectively. A resin composite (Z250) build-up was made on each tooth section after randomized application of the adhesives. After 24-hour storage in water, resin-dentin bonded sticks (0.8 mm2) were prepared and divided for 1-day and 6-month measurements. The IGW was measured in a stereomicroscope under 400x. SEM micrographs were also made in order to measure the HLT provided by each adhesive. RESULTS: The thickness of the smear layer did not influence the mean gap width (p>0.05). The etch & rinse systems showed the lowest mean IGW in the 1-day group. Their IGW remained unchanged after 6 months. The self-etch systems showed wider initial IGW, which diminished after 6 months water storage, to sizes similar to the etch & rinse systems. The hybrid layer was thicker when bonded to #60 SiC-treated dentin; however, this difference was only statistically different for the 3-step etch & rinse system (p=0.001). The thickest hybrid layers were observed for the 2 etch & rinse adhesive systems and the thinnest for the mild self-etch. A negative and strong correlation between IGW and HLT was observed for the self-etching adhesive systems tested (r=80.2, p=0.01).

Effect of smear layer thickness and acidity of self-etching solutions on early and long-term bond strength to dentin.

OBJECTIVES: To evaluate the effect of smear layer thickness (SL) on early and 6-month bond strength (BS) of self-etching adhesives to dentin and to measure the ultimate microtensile strength (UTS) of the adhesives. METHODS: Clearfil SE Bond; Optibond Solo Plus Self-Etch Primer; Tyrian Self Priming Etchant (TY) and as controls, Single Bond (SB) and Scotchbond Multi-Purpose Plus (SBMP) were applied on flat superficial dentin surface with thick and thin SL thicknesses. After adhesive's application (n=6) a resin build-up was made. After 24h, resin-dentin beams (0.8mm(2)) were prepared to be tested immediately and after 6-month (6M) at 0.5mm/min. For the UTS measurement, hour-glass specimens were prepared with the bonding resin alone or after mixing (1:1). BS values were analyzed by three-way repeated measures ANOVA and Tukey's multiple comparison tests. Two-way ANOVA (bonding resin and bonding resin+self-etching primer) and Tukey's test were used for the UTS values. The bonding resins were re-evaluated separately by a one-way ANOVA and Tukey's test, since Single Bond is a one-bottle adhesive (alpha=0.05). RESULTS: The SL thickness was not significant (p=0.64). BS values were reduced after 6M, except for the SBMP. TY provided the lowest BS mean while SB and SBMP the highest BS. The UTS of the SBMP was the highest. TY yielded the lowest UTS. Regression analysis revealed a linear and significant relationship between the UTS of self-etch systems and the mean BS (R=0.95, p=0.02). CONCLUSIONS: The performance of a self-etching system does not seem to be dependent on the SL thickness. The total-etch, three-step system provided the highest BS to dentin and maintained the BS stable over 6 months. The performance of the self-etching systems can be envisaged by their UTS.

Adverse effects of human pulps after direct pulp capping with the different components from a total-etch, three-step adhesive system.

OBJECTIVES: The objective was to evaluate the response of human pulps capped with different components from a total-etch three-step adhesive system. METHODS: Direct pulp capping was performed in 25 caries-free human premolars scheduled for extraction due to orthodontic treatment. The teeth were randomly divided in five groups, and capped with the following materials: Group 1-acid+primer+adhesive were used as recommended; Group 2-only primer was applied; Group 3-only bonding resin (light-cured for 10s); Group 4-only composite resin (light-cured for 40s); Group 5-calcium hydroxide. After capping, all teeth were restored with ScotchBond Multi Purpose Plus and Z-100 was placed incrementally. After 60 days, the teeth were extracted and processed for light microscopic examination (H/E) according to a histological score system. These were subjected to non-parametric tests (alpha<0.05). RESULTS: Overall, the histological features showed that groups 1-4 were quite similar and inferior to group 5. In groups 1-4 the pulp response varied from acute inflammatory cell infiltrate with varying degrees to necrosis. The groups 3 and 4 showed a trend towards better pulp response, since a normal connective tissue could be observed in more than half of the sample. All teeth from group 5 showed normal connective tissue below an amorphous dentin bridge. SIGNIFICANCE: Adhesive components (primer or adhesive) as well as a composite should be avoided for pulp capping. Ca(OH)(2) should be the first choice for pulp capping.

Response of human pulp capped with a bonding agent after bleeding control with hemostatic agents.

PURPOSE: This study evaluated the response of human pulps capped with a bonding agent after bleeding control with different hemostatic agents. MATERIAL AND METHODS: Twenty-five Class II cavities were prepared in 25 caries-free human premolars scheduled for extraction due to orthodontic treatment. The pulp exposures were performed on the occlusal floor. The teeth were randomly divided into five groups. Groups 1-4 were capped with an adhesive system after hemostasis with different agents: Group 1--saline solution; 2--ferric sulfate; 3--2.5% NaOCl; 4--Ca(OH)2 solution. In Group 5, after hemostasis with saline solution, the pulp was capped with calcium hydroxide (control group). Then, ScotchBond Multi Purpose Plus was applied and the resin composite Z-100 placed incrementally according to the manufacturers' directions. After 60 days, the teeth were extracted and processed for light microscopic examination (HE) and the groups were categorized in a histological score system. The data were subjected to a non-parametric test (alpha=0.05). RESULTS: Overall, the histological features showed that the pulp response from Groups 1 through 4 was inferior to the response from Group 5, where dentin bridging occurred. In all groups, where the adhesive system was used for capping, the pulp response varied from an acute inflammatory, with varying degrees, to necrosis. No dentin bridge was formed after adhesive capping.

Avaliaçäo da biocompatibilidade do hidróxido de cálcio, de agentes hemostáticos e de componentes de um sistema adesivo como capeadores diretos em polpas humanas / Biocompatibility evaluation of direct capped human pulp with calcium hydroxide, hemostatic agents and components of an adhesive system

A biocompatibilidade do sistema adesivo Scotchbond Multipurpose Plus (SBMP) foi avaliada através do capeamento direto de exposiçöes pulpares em cavidades de Classe II de 90 pré-molares, com indicaçäo para extraçäo por motivos ortodônticos. Todas as cavidades foram restauradas com resina Z100. Após o intervalo necessário de observaçäo, os pacientes foram questionados quanto à presença de sensibilidade pós-operatória e, em seguida, seus dentes foram extraídos, sendo processados para análise histológica (hematoxilina-eosina). Para os capeamentos, empregaram-se Ca(OH)² P.A., agentes hemostáticos, componentes do sistema adesivo SBMP, resina Z100 e Ca(OH)² em forma de cimento. Foi possível concluir que o hidróxido de cálcio proporcionou o maior índice de sucesso, independentemente da presença de isolamento absoluto e de agressöes prévias à polpa, necessitando de contato direto com o tecido pulpar para promover formaçäo de barreira dentinária; a forma de cimento também forneceu resultados satisfatórios. Para o SBMP, a resposta pulpar foi bastante prejudicada quando da ausência de isolamento absoluto, sendo que o fator hemostasia näo contribuiu para a melhoria dos resultados; o primer do SBMP pareceu ser o agente mais citotóxico do sistema restaurador adesivo. O hidróxido de cálcio P.A. ou na forma de cimento foi o agente de capeamento pulpar de melhor resultado. Näo se encontrou correlaçäo significante entre freqüência de dor e resultados histopatológicos