Randomized clinical trial of four adhesion strategies in posterior restorations-18-month results.

PURPOSE: To evaluate the 18-month clinical performance of four adhesive strategies in posterior composite restorations placed in private practice. MATERIALS AND METHODS: Upon approval by an institutional review board, 144 restorations were inserted in 45 subjects (average age = 32.6) to treat caries lesions or to replace existing restorations in vital molars and premolars. The adhesives OptiBond FL (three-step etch-and-rinse), OptiBond SOLO Plus (two-step etch-and-rinse), OptiBond XTR (two-step self-etch), and OptiBond All-in One (one-step self-etch) were applied as per manufacturer's (Kerr Co.) instructions followed by a nanofilled resin composite (Filtek Z350XT, 3M ESPE) under rubber dam isolation. Restorations were evaluated at baseline and at 18 months using United States Public Health Service (USPHS)-modified criteria and high-resolution digital photographs. Statistical analyses included the McNemar and the Mann-Whitney non-parametric tests (p < 0.05). RESULTS: A total of 137 restorations were evaluated after 18 months. The number of alfa ratings did not change significantly from baseline to 18 months for any of the adhesion strategies. When the 18-month evaluation criteria were pooled by pairs of adhesives, none of the adhesives resulted in a significantly different number of alfa ratings for any of the criteria compared with the other adhesives. CONCLUSION: Bonding strategy did not influence the clinical performance of posterior composite restorations under the clinical conditions used in this study. CLINICAL SIGNIFICANCE: When used in ideal clinical conditions, the composition of current dentin adhesives may be more clinically relevant than their adhesion strategy.

Colour stability and opacity of resin cements and flowable composites for ceramic veneer luting after accelerated ageing.

OBJECTIVES: Colour changes of the luting material can become clinically visible affecting the aesthetic appearance of thin ceramic laminates. The aim of this in vitro study was to evaluate the colour stability and opacity of light- and dual-cured resin cements and flowable composites after accelerated ageing. METHODS: The luting agents were bonded (0.2 mm thick) to ceramic disks (0.75 mm thick) built with the pressed-ceramic IPS Aesthetic Empress (n=7). Colour measurements were determined using a FTIR spectrophotometer before and after accelerated ageing in a weathering machine with a total energy of 150 kJ. Changes in colour (ΔE) and opacity (ΔO) were obtained using the CIE L*a*b* system. The results were submitted to one-way ANOVA, Tukey HSD test and Student's t test (α=5%). RESULTS: All the materials showed significant changes in colour and opacity. The ΔE of the materials ranged from 0.41 to 2.40. The highest colour changes were attributed to RelyX ARC and AllCem, whilst lower changes were found in Variolink Veneer, Tetric Flow and Filtek Z350 Flow. The opacity of the materials ranged from -0.01 to 1.16 and its variation was not significant only for Opallis Flow and RelyX ARC. CONCLUSIONS: The accelerated ageing led to colour changes in all the evaluated materials, although they were considered clinically acceptable (ΔE<3). Amongst the dual-cured resin cements, Variolink II demonstrated the highest colour stability. All the flowable composites showed proper colour stability for the luting of ceramic veneers. After ageing, an increase in opacity was observed for most of the materials.

Reaction kinetics of sodium ascorbate and dental bleaching gel.

OBJECTIVE: The aim of this study was to establish the reaction kinetics of 35% hydrogen peroxide and sodium ascorbate and to determine the mass of antioxidant required to neutralize the bleaching gel. METHODS: The method used to quantify sodium ascorbate was based on the United States Pharmacopeia (1995)(26). Oxidation-reduction titration was used to confirm the concentration of hydrogen peroxide and sodium ascorbate and to determine the reaction kinetics between them. RESULTS: The results indicated a direct correlation between the mass of hydrogen peroxide and that of the antioxidant agent. In addition, 5 min of contact was sufficient to neutralize the hydrogen peroxide used. CONCLUSION: This in vitro study showed that the amount of sodium ascorbate required for reduction of hydrogen peroxide is directly related to the concentration of the latter. In addition, the reaction kinetics between oxidant and antioxidant showed that a longer application time for sodium ascorbate does not influence the effectiveness of the reaction and that 5 min is sufficiently long for this antioxidant to exert an antioxidant effect.

Fracture loads of all-ceramic crowns under wet and dry fatigue conditions.

PURPOSE: The aim of this study was to test the hypothesis that fracture loads of fatigued dental ceramic crowns are affected by testing environment and luting cement. MATERIALS AND METHODS: One hundred and eighty crowns were prepared from bovine teeth using a lathe. Ceramic crowns were prepared from three types of ceramic systems: an alumina-infiltrated ceramic, a lithia-disilicate-based glass ceramic, and a leucite-reinforced ceramic. For each ceramic system, 30 crowns were cemented with a composite resin cement, and the remaining 30 with a resin-modified glass ionomer cement. For each ceramic system and cement, ten specimens were loaded to fracture without fatiguing. A second group (n = 10) was subjected to cyclic fatigue and fracture tested in a dry environment, and a third group (n = 10) was fatigued and fractured in distilled water. The results were statistically analyzed using one-way ANOVA and Tukey HSD test. RESULTS: The fracture loads of ceramic crowns decreased significantly after cyclic fatigue loading (p

Microtensile bond strength of adhesive systems of single and multiple steps / Resistência à microtração dos sistemas adesivos de única e múltipla etapas

OBJECTIVE: To evaluate the microtensile bond strength of ten dentin adhesive systems. MATERIAL AND METHOD: Sixty human molars were cut to the dentine level and restored with a hybrid composite and one of the adeshive systems. Each teeth were sectioned to obtain sticks measuring 1.0 ± 0.2 mm2, which were then stressed at a crosshead speed of 1mm/min in auniversal testing machine until failure. The failure modes were verified using optical microscopy. RESULTS: One Up Bond FTM, All Bond 2TM, One Step PlusTM, Adper Prompt L-PopTM, OneStepTM, Single BondTM and Clearfil SE BondTM presented no statistically significant differences (p>0.05); the lowest bond strength values were obtained with Scotchbond MPTM, Prime&Bond NTTM and ExciteTM (p<0.05). CONCLUSION: The self etch primer systems and conventional systems exhibited the highest bond strength to dentin, except for Scotchbond MPTM, Prime&BondNTTM and ExciteTM. Adhesive fractures accounted for 69% of the total fractures.

OBJETIVO: Avaliar a resistência adesiva de dez sistemas adesivos. MATERIAIS E MÉTODOS: Os dentes foram seccionados em forma de palitos com tamanho de 1.0 ± 0,2 mm2 e tracionados com velocidade de 1mm/min. Os tipos de fraturas foram verificados utilizando o microscópio óptico. RESULTADOS: Os sistemas adesivos (One Up Bond FTM, All Bond 2TM, One Step PlusTM, Adper Prompt L-PopTM, One StepTM, Single BondTM e Clearfil SE BondTM apresentaram os maiores valores de resistência adesiva em dentina. Os sistemas ScotchbondMPTM, Prime&Bond NTTM e ExciteTM apresentaram menor resistência. CONCLUSÃO: Os sistemas autocondicionantes e os convencionais apresentaram maior resistência adesiva em dentina. Os sistemas Scotchbond MPTM, Prime&Bond NTTM e ExciteTM apresentaram menor resistência adesiva. As fraturas adesivas representaram 69% do total das fraturas.

Impact of refrigeration on the surface hardness of hybrid and microfilled composite resins.

This in vitro study evaluated the Knoop hardness of the composite resins Charisma (C) and Durafill VS (D) polymerized in 3 different conditions: at room temperature (A) (23 +/- 1 degrees C); refrigerated at 4 +/- 1 degrees C and immediately photo-activated after removal from the refrigerator (0); and, refrigerated at 4 +/- 1 degrees C and photo-activated after a bench time of 15 min at room temperature (15). One hundred and twenty specimens (4 mm diameter and 2 mm depth) were made using a stainless steel mold and following manufacturer's instructions. All specimens were tested immediately after polymerization (I) and after 7 days of water storage in the dark at room temperature (7d). The data were subjected to ANOVA and post-hoc Tukey's test (alpha=0.05). On the top surface, C(AI) was statistically similar to C(15I) and D(AI) to D(15I) (p>0.05). On the bottom surface, C(AI) presented higher hardness values when compared to COI and C(15I) (p<0.05). The D groups showed no significant differences (p>0.05) on the bottom surfaces for any tested polymerization condition. After 7 days of storage, the Knoop hardness decreased significantly (p<0.05) for groups C(7d) and D(7d) except for C(07d), which was not different from C(OI) at either surface (p>0.05). D(07d) showed higher Knoop hardness (p<0.05) values on the top surface when compared to the other groups.

Impact of refrigeration on the surface hardness of hybrid and microfilled composite resins

This in vitro study evaluated the Knoop hardness of the composite resins Charisma® (C) and Durafill VS® (D) polymerized in 3 different conditions: at room temperature (A) (23 ± 1°C); refrigerated at 4 ± 1°C and immediately photo-activated after removal from the refrigerator (0); and, refrigerated at 4 ± 1°C and photo-activated after a bench time of 15 min at room temperature (15). One hundred and twenty specimens (4 mm diameter and 2 mm depth) were made using a stainless steel mold and following manufacturer's instructions. All specimens were tested immediately after polymerization (I) and after 7 days of water storage in the dark at room temperature (7d). The data were subjected to ANOVA and post-hoc Tukey's test (a=0.05). On the top surface, CAI was statistically similar to C15I and DAI to D15I (p>0.05). On the bottom surface, CAI presented higher hardness values when compared to COI and C15I (p<0.05). The D groups showed no significant differences (p>0.05) on the bottom surfaces for any tested polymerization condition. After 7 days of storage, the Knoop hardness decreased significantly (p<0.05) for groups C7d and D7d except for C07d, which was not different from COI at either surface (p>0.05). D07d showed higher Knoop hardness (p<0.05) values on the top surface when compared to the other groups.

O objetivo do presente estudo in vitro foi avaliar a dureza Knoop das resinas compostas, uma resina híbrida (Charisma - C) e uma de micropartículas (Durafill VS - D) quando polimerizadas à temperatura ambiente (A) (23 ± 1°C); refrigeradas (4 ± 1°C) e fotoativadas imediatamente após a remoção do refrigerador (0); e refrigeradas (4 ± 1°C), com tempo de espera de 15 min após a remoção do refrigerador para fotoativação (15). Cento e vinte corpos-de-prova com 4 mm de diâmetro por 2 mm de altura foram confeccionados em uma matriz de aço inoxidável. Cada corpo-de-prova foi testado imediatamente após a fotoativação (I) e, após 7 dias de armazenamento (7d) em ambiente escuro com umidade relativa a 100 por cento, à temperatura do ambiente (23 ± 1°C). Quando testada imediatamente após a polimerização, na superfície de topo CAI foi estatisticamente semelhante à C15I e DAI à D15I. Na base, a resina composta CAI, teve maiores valores de dureza quando comparados à COI e C15I. Os grupos do material D não mostraram diferenças significantes com relação ao efeito da refrigeração na base. Sete dias após, os valores de dureza Knoop caíram tanto para C7d quanto para D7d com exceção de C07d que não diferiu de C07d nas diferentes superfícies, e D07d que mostrou maiores valores de dureza no topo.

Sorption and solubility of composites cured with quartz-tungsten halogen and light emitting diode light-curing units.

AIM: The objective of this study was to evaluate the effect of light polymerization on water sorption and solubility of hybrid composites. METHODS AND MATERIALS: Three composite resins were used to make discs cured with either quartz-tungsten halogen (QTH) or light emitting diode (LED) curing units. The specimens were stored in a desiccator at 37 degrees C and weighted to a constant mass, then immersed in deionized water for different periods of time, and reconditioned until achieving a constant mass. Sorption and solubility were calculated and subjected to analysis of variance (ANOVA) and Tukey tests (p<0.01). RESULTS: There were no statistically significant differences between the light sources. Water sorption increased with storage time for all the composites. The lowest sorption was observed for Herculite XRV, followed by Tetric Ceram, and Filtek Z250. Increased storage times reduced the solubility of Filtek Z250 but did not affect the solubility of Herculite XRV and Tetric Ceram. CONCLUSION: Water sorption and solubility of composites are not affected by the type of polymerization when the same intensity and exposure times are used. Thus, the differences found are probably related to the composition of the materials. CLINICAL SIGNIFICANCE: Water sorption and solubility of composites can lead to a shortened service life. However, these properties are not correlated to the type of polymerization.

Influence of curing tip distance on resin composite Knoop hardness number, using three different light curing units.

This in vitro study evaluated the influence of curing tip distance on the Knoop Hardness Number (KHN) of a resin composite when using three different light curing units: (1) a halogen light (XL 1500 curing unit-3M), (2) a "softstart-polymerization" (Elipar Trilight curing in an exponential mode-ESPE) and (3) a PAC (Apolo 95E curing unit-DMD). The resin composite, Filtek Z250 (3M), was cured by these curing units at three light-tip distances from the resin composite: 0 mm, 6 mm and 12 mm. The resin composite specimens were flattened to their middle portion and submitted to 18 KHN measurements perspecimen. The results showed that for the Elipar Trilight unit, the hardness of the resin composite decreased as the light tip distance increased. The XL 1500 unit presented a significant decrease in hardness as the depth of cure of the resin composite increased. Apolo 95E caused a decrease in the resin composite hardness values when the depth of cure and light tip distance increased.