Influence of resin cements on cuspal deflection and fracture load of endodontically-treated teeth restored with composite inlays.

OBJECTIVES: To evaluate the influence of resin cements on cuspal deflection, fracture load and failure mode of endodontically-treated teeth restored with composite resin inlays. MATERIALS AND METHODS: Forty maxillary premolars were randomly divided into four groups: G1 (sound teeth, control), G2 (RelyX ARC), G3 (RelyX Unicem) and G4 (Maxcem Elite). The teeth from groups 2, 3 and 4 received mesial-occlusal-distal preparations and endodontic treatments. Impressions were taken with vinyl polysiloxane and poured using type IV die stone. Inlays with Z250 composite resin were built over each cast and luted with the resin cements. A 200-N load was applied on the occlusal surface and the cuspal deflection was measured using a micrometer. The specimens were then subjected to an axial load until failure occurred. The resulting failure mode was analyzed. RESULTS: The means for cuspal deflection (µm) and fracture load (N) followed by the same letter represent no statistically significant difference based on ANOVA and Tukey's test (p < 0.05). Cuspal deflection: G1 = 4.7 (± 1.7)(a), G2 = 12.0 (± 8.9)(a), G3 = 39.0 (± 27.0)(b) and G4 = 56.8 (± 18.2)(b). Fracture load: G1 = 1982 (± 893)(a), G2 = 690.9 (± 225.5)(b), G3 = 679 (± 193.6)(b) and G4 = 465.5 (± 121.6)(b). G1 presented cusp fractures only at the cement-enamel junction (CEJ). There was a high frequency of cusp fractures below the CEJ in G2, G3 and G4. CONCLUSIONS: Composite resin inlays luted with resin cements do not recover the strength of sound teeth. However, teeth restored with composite resin inlays and luted with RelyX ARC can withstand mechanical fatigue longer before failure occurs than those luted with RelyX Unicem and Maxcem Elite.

Optical X-ray density of composite resin luting agents.

This study verified the optical density of four composite resin luting agents - RelyX ARC (RY), Enforce (E), C&B Cement (CB) and Flow it (FI), at thicknesses of 2, 3, and 4 mm. The optical density of the luting agents was compared with that of enamel and dentin at the same thicknesses. Fifteen tooth crowns were embedded in PVC cylinders with self-cured acrylic resin. In addition, acrylic resin was poured into 5 PVC cylinders and four equidistant 5 mm diameter holes were prepared, with one luting material inserted in each. A laboratory cutting machine was used to prepare 4-, 3- and 2-mm thick slices of the tooth crowns and materials. Digital images were obtained with a Digora system. Three radiographs of each thickness were obtained, totalizing 135 radiographs of the crowns and 45 of the materials. Three readings were carried out on each radiograph: three in enamel, three in dentin and three in each material, totalizing 1350. According to Students t-test (p

Selective masking for thin indirect restorations: can the use of opaque resin affect the dentine bond strength of immediately sealed preparations?

PURPOSE: Evaluate the dentine bond strength using different methods of application of opaque resins to mask dentine discoloration. MATERIALS AND METHODS: Dentine was exposed on 21 extracted molars which were assigned to 3 groups: G1: immediate dentine sealing (IDS). G2: IDS+opaque. G3: IDS with adhesive resin mixed with opaque. After 1 week, teeth were restored and beams were fabricated for microtensile testing. Optical microscopy was used to analyse the failure mode. RESULTS: Bond strength mean values were statistically different: G1 55.20MPa>G2 45.79MPa>G3 18.96MPa. Failure modes were mostly adhesive for G1 and G3. G2 presented mostly mixed failures. CONCLUSION: The use of opaque resin to mask discoloured dentine results in a decrease of bond strength.

Effect Of Nd:YAG laser and CO2 laser treatment on the resin bond strength to zirconia ceramic.

OBJECTIVE: this study evaluated the effect of surface treatments (Nd:YAG laser, CO2 laser, Al203 airborne-particle abrasion, and silica-coating) on the zirconia-to-resin shear bond strength (SBS). METHOD AND MATERIALS: eighty-one Lava (3M ESPE) blocks (13 x 4 x 2 mm) were embedded in acrylic resin, polished, and randomly divided into three groups, which received the following surface treatments: no abrasion, Al203 airborne-particle abrasion (50 Μm), or silica-coating (Cojet, 3M ESPE). Each group was divided into three subgroups that were treated with Nd:YAG laser, CO2 laser, or no laser irradiation. Following application of a monomer phosphate-containing primer, cylinders of resin cement (Panavia F, Kuraray) (n = 18) were built on the surface. SBS testing was carried out after 24 hours of storage in water. Surface roughness and topography (SEM) after treatments were evaluated. RESULTS: according to ANOVA and Tukey test ( α = 0.05), mean SBS after Nd:YAG laser treatment ranged from 14.09 to 16.20 MPa and was statistically higher than CO2 laser (6.24 to 10.51 MPa) and no laser treatment (4.65 to 8.79 MPa). The Nd:YAG laser created more roughness on zirconia when compared to the CO2 laser and abrasion treatments. Silica-coating increased the SBS of lased and nonlased zirconia. Significant microcracks were found on specimens treated with CO2. CONCLUSION: Nd:YAG laser pretreatment, whether associated with abrasion methods or not, created consistent roughness on the zirconia surface and significantly increased zirconia SBS to Panavia F. Silica-coating could potentially increase the SBS of lased and nonlased zirconia. Significant microcracks were found on specimens treated with the CO2 laser.

Fatigue resistance and failure mode of novel-design anterior single-tooth implant restorations: influence of material selection for type III veneers bonded to zirconia abutments.

OBJECTIVES: This study assessed the fatigue resistance and failure mode of type III porcelain and composite resin veneers bonded to custom zirconia implant abutments. MATERIAL AND METHODS: Twenty-four standardized zirconia implant abutments were fabricated. Using the CEREC 3 machine, type III veneers of standardized shape were milled in ceramic Vita Mark II or in composite resin Paradigm MZ100. The intaglio surfaces of the restorations were hydrofluoric acid etched and silanated (Mark II) or airborne-particle abraded and silanated (MZ100). The fitting surface of the abutments was airborne-particle abraded, cleaned, and inserted into a bone level implant (BLI RC SLActive 10 mm). All veneers (n=24) were adhesively luted with a zirconia primer (Z-Prime Plus), adhesive resin (Optibond FL) and a pre-heated light-curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 40 N, followed by stages of 80, 120, 160, 200, 240, and 280 N (20,000 cycles each). Samples were loaded until fracture or to a maximum of 140,000 cycles. Groups were compared using the life table survival analysis (Logrank test at P=.05). RESULTS: Mark II and MZ100 specimens fractured at an average load of 216 N and 229 N (survival rate of 17% and 8%), respectively, with no difference in survival probability (P=.18). Among the fractured samples, 40% of the failures were at the abutment level for Mark II and 27% were at the abutment level for MZ100. No exclusive adhesive failures were observed. CONCLUSIONS: Type III Mark II and Paradigm MZ100 veneers showed similar fatigue resistance when bonded to custom non-retentive zirconia implant abutments. The bond was strong enough to induce abutment fractures. MZ100 presented a higher percentage of "friendly" failures, i.e. maintaining the restoration-abutment adhesive interface and the abutment itself intact.

Effect of endodontic irrigating solutions on the adhesive bond strength to dentin / Efeito de soluções irrigadoras endodônticas na resistência adesiva à dentina

PURPOSE: To evaluate the bond strength of a total-etching adhesive system to dentin irrigated with 1% sodium hypochlorite (NaOCl) and ethylenediaminetetraacetic acid 17% (EDTA). METHODS: Thirty human molars were sectioned 3mm below the oclusal surface and were randomly divided into 3 groups (n=10): G1, no treatment (control); G2, 1% NaOCl; G3, NaOCl followed by EDTA. The specimens received the total-etching adhesive system, restored with microhybrid composite resin, sectioned and trimmed to create 4 hourglass-shaped slabs of each tooth. The slabs were tested in microtensile bond strength in a universal testing machine (Emic DL 2000) at a crosshead speed of 0.5 mm/min until fracture. The results were analyzed statistically by ANOVA and Newman-Keuls test. G2 samples were not submitted to the test because they fractured just before testing, and its values were considered zero to the statistical analysis. RESULTS: The means and standard deviations (MPa) were: G1, 8.41 (±3.51); G2, 0.0 (±0.00); G3, 8.47 (±3.53). CONCLUSION: It was concluded that the application of the NaOCl irrigating solution significantly decreased the bond strength values. The use of NaOCl followed by EDTA resulted in bond strength values not statistically different from control group.

OBJETIVO: Avaliar a resistência de união de um sistema adesivo condicione-e-lave à dentina irrigada com hipoclorito de sódio 1% (NaOCl) e ácido etilenodiaminotetracético 17% (EDTA). METODOLOGIA: Trinta molares humanos foram seccionados 3mm abaixo da superficie oclusal e aleatoriamente divididos em 3 grupos (n=10): G1 (controle), nenhum tratamento; G2, NaOCl; G3, NaOCl seguido por EDTA. Os especimes foram hibridizados com um sistema adesivo condicione-e-lave, foram restaurados com resino composta microhibrida e seccionados de forma a originar 4 amplulhetas de cada dente. As fatias foram submetidas ao teste de resistência de união à microtraçnao em máquina universal de ensaios (EMIC DL 2000) à uma velocidade de 0,5 mm/min até o momento da fratura. Os resultados foram analisados estatisticamente por ANOVA seguido por Newman-Keuls. As amostras do G2 não foram submetidas aos testes de resistência de união pois fraturaram antes dos testes, e seus valores foram considerados zero para análise estatística. RESULTADOS: A média e desvios-padrão foram (MPa): G1 - 8,41 (±3,51); G2 - 0,0 (±0,00); e G3 - 8,47 (±3,53). CONCLUSÃO: Pode-se concluir que a irrigação com NaOCl diminui significativamente os valores de resistência de união. O uso de NaOCl seguido por EDTA resultaram em valores de resistência de união sem diferença estatística com o grupo controle.

The parallel stratification masking technique: an analytical approach to predictably mask discolored dental substrate.

Discolored dental substrates continue to challenge the restorative team when ultraconservative treatment modalities are chosen. An innovative laboratory concept--the parallel stratification masking technique--has been developed in order to achieve maximum preservation of dental hard tissues and predictably accomplish a desirable esthetic outcome. The major advantages of this technique are that the ceramist is able to: a)identify and map the discolored dental substrate, b)predictably mask the discolored dental substrate, and c) assess the appropriate masking efficacy of the fabricated restoration prior to laboratory delivery to the dentist in cases of bonded porcelain restorations.

Microtensile bond strength of prehybridized dentin: storage time and surface treatment effects.

PURPOSE: This study evaluated the effect of surface treatments of the prepolymerized adhesive layer in the immediate dentin sealing technique (IDS) on the microtensile bond strength of two-step etch-and-rinse adhesive systems. MATERIALS AND METHODS: The occlusal dentin surfaces of 60 human third molars were exposed and Adper Single Bond 2 (SB) or Prime & Bond NT (PB) adhesive systems were applied (control groups). Immediately afterwards, the temporary cement RelyXTemp NE was applied on the bonded dentin surface, and the teeth were stored in artificial saliva for 48 h or 4 months. After the storage time, the temporary cement layer was removed and the following surface treatments were applied: aluminum oxide (AO), 37% phosphoric acid (PA), or AO+PA. Next, a second adhesive layer was applied for each adhesive system, and a composite resin block restoration (Z250) was built. The specimens were cut and submitted to microtensile strength (microTBS) testing. The adhesive layer thickness (ALT) was evaluated in other specimens from all groups by SEM. The fracture pattern was evaluated in all sticks tested by SEM. microTBS and ALT values were analyzed with two-way ANOVA and Tukey's test (alpha = 0.05). RESULTS: The highest microTBS, similar to the control, was obtained with aluminum oxide and phosphoric acid (AO+PA) for both adhesives systems. The use of aluminum oxide alone (AO) or associated with phosphoric acid (AO+PA) showed values close to those of the control groups in relation to the ALT. The failure pattern was the same for control groups and AO +PA groups. CONCLUSION: Dentin prehybridization can improve the adhesive bond strength if the bonded surface is treated with airborne aluminum oxide particle abrasion associated with 37% phosphoric acid, followed by application of a second adhesive layer.

Influence of Nd:YAG laser irradiation on microtensile bond strength of adhesive systems to sound or carious dentin.

OBJECTIVE: To evaluate the microtensile bond strength of 2 adhesive systems (Adper Single Bond Plus [3M ESPE] and Clearfil SE Bond [Kuraray]) to carious or normal dentin, with or without previous treatment with Nd:YAG laser or Nd:YAG laser associated with fluoride. METHOD AND MATERIALS: Dentin surfaces of 60 human third molars were exposed. Teeth were divided into 12 groups; groups 1 to 6 were submitted to pH cycling for artificial caries, and groups 7 to 12 remained with normal dentin. Dentin surfaces received 3 treatments: laser Nd:YAG irradiation (60 mJ, 15 Hz, and 0.9 W) for 1 minute; laser Nd:YAG irradiation associated with fluoride in gel; and no treatment (controls). In experimental groups, adhesive systems were applied in accordance with the manufacturers' instructions, and a composite resin block (Filtek Z250, 3M ESPE) was made incrementally for the microtensile bond strength test. The teeth were sectioned serially in both x and y directions, and sticks were submitted to microtensile bond strength testing in a universal testing machine. RESULTS: According to ANOVA and Tukey (P < .05), the highest mean bond strengths were obtained in groups of normal dentin treated with Clearfil SE Bond (40.65 MPa) and Single Bond (34.2 MPa). The presence of carious dentin significantly decreased the mean bond strengths of the 2 adhesive systems whether or not they were previously laser irradiated. Nevertheless, Clearfil SE Bond presented the best microtensile bond strength on an irradiated surface. Moreover, laser irradiation associated with fluoride also decreased the bond strength values of the 2 adhesive systems. CONCLUSION: After excavating a cavity with caries-affected dentin, the use of Nd:YAG laser followed by a self-etching adhesive system is the best clinical choice when considering bond strength, compared with the total etching- based system and laser.

The influence of the Nd:YAG laser bleaching on physical and mechanical properties of the dental enamel.

BACKGROUND AND OBJECTIVES: The Nd:YAG laser can be used in Dentistry to remove soft tissue, disinfect canals in endodontic procedures and prevent caries. However, there is no protocol for Nd:YAG laser application in dental bleaching. The aims of this in vitro study were: (a) to observe the tooth shade alteration when hydrogen peroxide whitening procedures are associated with dyes with different wavelengths and irradiated with Nd:YAG laser or halogen light; (b) to measure the Vickers (VHN) enamel microhardness before and after the whitening procedure; (c) to evaluate the tensile bond strength of two types of adhesive systems applied on bleached enamel; (d) to observe the failure pattern after bond strength testing; (e) to evaluate the pulpal temperature during the bleaching procedures with halogen light or laser; (f) to measure the kinetic reaction of hydrogen peroxide. MATERIALS AND METHODS: Extracted sound human molar crowns were sectioned in the mesiodistal direction to obtain 150 fragments that were divided into five groups for each adhesive system: WL (H(2)O(2) + thickener and Nd:YAG), WH (H(2)O(2) + thickener and halogen light), QL (H(2)O(2) + carbopol + Q-switch and Nd:YAG), QH (H(2)O(2) + carbopol + Q-switch and halogen light), and C (Control, without whitening agent). Shade assessment was made with a shade guide and the microhardness tests were performed before and after the bleaching procedures. Immediately afterwards, the groups were restored with the adhesive systems Adper Single Bond 2 or Solobond M plus composite resin, and the tensile bond strength test was performed. The temperature was measured by thermocouples placed on the enamel surface and intrapulpal chamber. The kinetics of hydrogen peroxide was observed by ultraviolet analysis. RESULTS: The shade changed seven levels for Nd:YAG laser groups and eight levels for halogen light. According to the student's t-test, there was no statistical difference between the VHN before and after the whitening protocols (p > 0.05). The tensile bond strength showed no statistical significance between the test groups and the controls, considering both adhesive systems tested by ANOVA and Tukey tests (p > 0.05). The predominant failure pattern after bond strength testing was mixed. The temperature was safe for laser and halogen light. The kinetic reaction showed that after 5 min all the hydrogen peroxide had been consumed. CONCLUSIONS: Nd:YAG laser associated with hydrogen peroxide bleached the enamel, the shade being similar to that obtained with the traditional method performed with halogen light. Moreover, the Vickers' microhardness and bond strength values were not altered in comparison with those for nonbleached enamel.

Efeito do selamento dentinário imediato e de materiais restauradores provisórios na resistência de união à dentina / Effect of immediate dentin sealing and provisional restorations on bond strength to dentin

Objetivo: O objetivo do estudo foi avaliar, in vitro, o efeito da técnica do selamento dentinário imediato com um sistema adesivo de 5º geração, e da aplicação intermediária de dois materiais provisórios, na resistência de união à tração sobre a dentina. Materiais e método: A coroa de 75 dentes incisivos bovinos foram incluídas em resina acrílica quimicamente ativada, sendo a superfície vestibular desgastada até exposição da dentina. A superfície dentinária recebeu acabamento com lixas de granulação 400 e 600, sendo os dentes divididos em 5 grupos (n = 15): Grupo 1: Single Bond (controle); Grupo 2: Temp Bond NE + Single Bond; Grupo 3: Single Bond + Temp Bond NE + Single Bond; Grupo 4: Fermit + Single Bond; Grupo 5: Single Bond + Fermit + Single Bond. Os grupos 3 e 5 reproduziram a técnica de selamento imediato da dentina. Um cone de resina composta (Z250) foi construído sobre o adesivo. Após armazenamento por 24 horas a 37ºC em água destilada, os corpos-de-prova foram submetidos ao teste de resistência à tração em máquina de ensaio universal. Resultados: De acordo com a Análise de Variância, não houve diferença estatisticamente significativa nos valores médios de resistência à tração entre os grupos (p > 0,05): grupo 1 (16,84 MPa); grupo 2 (14,27 MPa); grupo 3 (17,27 MPa); grupo 4 (14,87 MPa); grupo 5 (12,97 MPa). Conclusão: A técnica de selamento imediato da dentina com o sistema adesivo Single Bond, assim como os materiais provisórios Temp Bond NE e Fermit, não influenciaram significativamente os valores de resistência de união à dentina.