Ana Maria Spohr

Surface Modification of In-Ceram Zirconia Ceramic by Nd:YAG Laser, Rocatec System, or Aluminum Oxide Sandblasting and Its Bond Strength to a Resin Cement

OBJECTIVE The purpose of this study was to evaluate the effect of different surface treatments on bond strength between In-Ceram Zirconia ceramic and Panavia Fluoro Cement. BACKGROUND DATA Although several surface treatments have been used on In-Ceram Zirconia, no study has been conducted to investigate the effect of the Nd:YAG laser. MATERIALS AND METHODS Nine In-Ceram Zirconia blocks (10 x 10 x 6 mm) received three different surface treatments (n = 3 per group): group 1-Al2O3 sandblasting + silane; group 2-Al2O3 sandblasting + Rocatec Plus + silane; and group 3-Al2O3 sandblasting + Nd:YAG laser + silane. Resin cement was applied and light-cured, followed by the application of composite resin. The blocks were sectioned to obtain square rods with a cross-sectional dimension of 1.0 mm2 (n = 12 per group). Microtensile bond strength (muTBS) was recorded using a universal testing machine at a cross-head speed of 0.5 mm/min and expressed in megapascals (MPa). RESULTS All groups yielded statistically significantly different muTBS mean values: group 1 (11.81 +/- 3.12 MPa); group 2 (15.75 +/- 4.45 MPa); group 3 (18.70 +/- 5.14 MPa) (ANOVA and Tukeys test; alpha = 0.05). CONCLUSION Nd:YAG laser irradiation is an effective surface treatment for bonding between In-Ceram Zirconia and Panavia Fluoro Cement.

Effect of polyacrylic acid on the interface and bond strength of self-adhesive resin cements to dentin.

PURPOSE To examine the influence of 11.5% polyacrylic acid pretreatment on the interface and bond strength of self-adhesive resin cements (Maxcem Elite, RelyX Unicem, SeT) to dentin. MATERIALS AND METHODS Fifty-six third molars were randomly divided into seven groups: RelyX ARC as control (ARC), RelyX Unicem (RLXU), Maxcem Elite (MCE), SeT (ST), polyacrylic acid+RelyX Unicem (RLXU-P), polyacrylic acid+Maxcem Elite (MCE-P), and polyacrylic acid+SeT (ST-P). Resin composite blocks were luted to flat dentin. After storage in distilled water for 24 h, sticks with a cross-sectional area of ca 0.80 mm2 were obtained (n = 24 per group) and submitted to a microtensile bond strength (µTBS) test in a universal testing machine at a crosshead speed of 0.5 mm/min. Two sets from each group were sectioned mesiodistally in the center of the crown and observed with a scanning electron microscope at 4000X magnification. RESULTS The mean results of the µTBS test (MPa) followed by the same letter do not differ statistically significantly according to ANOVA and Tukeys post-hoc test (p < 0.05): ARC = 24.19 (± 6.90)a, RLXU-P = 23.12 (± 6.18)a, MCE-P = 13.09 (± 5.87)b, RLXU = 10.23 (± 2.88)b,c, and MCE = 8.14 (± 4.63)c. All SeT specimens failed during the cutting procedure. The hybrid layer was not observed for the self-adhesive resin cements, and resin tags were observed for RelyX Unicem and Maxem Elite when dentin was pretreated with polyacrylic acid. CONCLUSION Pretreatment with 11.5% polyacrylic acid was effective for bonding RelyX Unicem and Maxcem Elite to dentin.

Effect of curing time on the bond strength of a bracket-bonding system cured with a light-emitting diode or plasma arc light

The purpose of this study was to assess the influence of two light units, a light-emitting diode (LED) and a plasma arc light (PAC), on the shear bond strength (SBS) of brackets bonded to enamel. Ninety bovine teeth were divided into six groups, according to the light-curing unit and exposure times used. In the LED (Ortholux; 3M-Unitek) group, the specimens were light cured for 5, 10, and 15 seconds. In the PAC (Apollo 95E; DenMed Technologies) group, the specimens were light cured for 3, 6, and 9 seconds. The brackets were bonded with Transbond XT (3M-Unitek), stored in distilled water at 37 °C for 24 hours and then submitted to SBS testing in a universal testing machine. The adhesive remnant index (ARI) was used to evaluate the amount of adhesive remaining on the teeth. According to analysis of variance and Tukey multiple comparisons test, the highest mean SBS was obtained with the LED at 15 seconds (16.68 MPa), which did not significantly differ from the LED 10 (14.76 MPa) or 5 (13.92 MPa) second groups (P > 0.05). The LED 10 and 5 second groups were not significantly different from the PAC 9 second group (12.66 MPa) or from the PAC 6 second group (9.96 MPa). The lowest mean SBS was obtained with the PAC 3 second group (8.29 MPa), which did not differ significantly from the PAC 6 second group. The method of light curing did not influence the ARI, with score 3 predominant. The LED at 5 seconds and the PAC at 3 seconds provided sufficient mean SBS to resist either orthodontic or masticatory forces.

Effect of the Nd:YAG and the Er:YAG Laser on the Adhesive–Dentin Interface: A Scanning Electron Microscopy Study

OBJECTIVE This study analyzed the adhesive-dentin interface when Nd:YAG and Er:YAG lasers were applied to dentin. BACKGROUND DATA Lasers applied to dentin cause morphological changes of this tissue. Because adhesive systems bond to dentin through the hybrid layer, it is important to investigate the adhesive-dentin interface when dentin is irradiated with lasers. METHODS The occlusal dentin of 12 human molars was exposed and polished with 400 and 600 grit silicon carbide abrasive paper. Teeth were randomly divided into six groups: Group 1, adhesive system Adper Single Bond 2 (SB); Group 2, adhesive system Clearfil SE Bond (CSB); Group 3, Nd:YAG laser (60 mJ, 15 Hz, 0.9 W) and SB; Group 4, Nd:YAG laser (60 mJ, 15 Hz, 0.9 W) and CSB; Group 5, Er:YAG (200 mJ, 4 Hz, 0.8 W) and SB; Group 6, Er:YAG (200 mJ, 4 Hz, 0.8 W) and CSB. Blocks of composite resin were built upon the adhesive system. Tooth-resin sets were cut in a mesio-distal direction, resulting in four samples for each group. Surfaces were polished until 1200 grit silicon carbide abrasive paper, followed by diamond pastes. Samples were demineralized, deproteinized, dried, metalized, and evaluated by scanning electron microscopy. RESULTS SB formed a thicker hybrid layer, with resin tags longer than CSB. Nd:YAG laser application on the dentin surface, prior to the adhesive procedures, resulted in a thinner hybrid layer with fewer resin tags. Er:YAG laser application on the dentin surface, prior to the adhesive procedures, did not allow the formation of a hybrid layer but formed resin tags. CONCLUSION Nd:YAG and Er:YAG laser changed the adhesive-dentin interface.

Degree of conversion and hardness of an orthodontic resin cured with a light-emitting diode and a quartz - tungsten - halogen light

The purpose of this study was to assess the influence of two light units, a quartz-tungsten-halogen (QTH) and a light-emitting diode (LED), on the hardness and degree of conversion of an orthodontic composite resin. Sixty specimen disks were prepared from Transbond XT composite resin (3M Unitek) and light cured for 10, 20, and 30 seconds with a QTH (Curing Light XL 3000, 3M Unitek) or a LED (Ortholux, 3M Unitek) light-curing unit for 5, 10, and 15 seconds. Composite resin polymerization was evaluated by Fourier-transform infrared (FTIR) spectrophotometry and Knoop hardness number (KHN). The results were statistically analysed using analysis of variance and Tukeys multiple comparisons test (alpha = 0.05). The highest KHN was obtained with the QTH at 30 (25.19 KHN) and 20 (24.01) seconds, which did not differ statistically, and in the LED 15 second (21.86) group. The QTH 10 second group (20.53) did not differ statistically from the QTH 20 second or the LED 5 (19.96) and 15, or 10 second (18.95) groups. According to FTIR, there was no statistical difference for the degree of conversion among the groups, QTH 10 (43.42 per cent), QTH 20 (46.12 per cent), QTH 30 (45.30 per cent), LED 10 (47.02 per cent), or LED 15 (47.24 per cent) seconds. The lowest degree of conversion was obtained for the LED 5 second group (38.97 per cent), which did not differ statistically from the QTH 10 second group. Light curing with the LED resulted in a reduction of 50 per cent in the time recommended for use of the QTH light with the composite resin, Transbond XT.

Relationship between filler content and selected mechanical properties of six microhybrid composites

OBJETIVO: O objetivo deste estudo foi avaliar a influencia do conteudo de carga, em peso, de seis resinas compostas microhibrida sobre determinadas propriedades mecânicas. METODOLOGIA: A resistencia a compressao, modulo de elasticidade, microdureza Vickers (VHN) e conteudo de carga de peso foram avaliados nas seguintes resinas compostas: Admira (AD), Charisma (CH), InTen-S (IN), Tetric Ceram (TC), Point 4 (P4) e Z250 (Z2). RESULTADOS: Os valores medios de resistencia a compressao (MPa) variaram de P4 76,60 a Z2 222,33. Os modulos de elasticidade (GPa) variou de IN 2,56 a Z2 4,59. A microdureza VHN variou de P4 50,53 a Z2 87,88. O conteudo de carga em peso (Wt%) variou de IN 72,51 a TC 79,56. Foram encontradas diferencas significativas entre as resinas compostas (ANOVA/Tukeys, P<0,05). CONCLUSAO: A resina Z2 teve a maior resistencia a compressao; Z2 e TC apresentaram maiores modulo de elasticidade, VHN e conteudo de carga em peso. O conteudo de carga em peso teve uma forte influencia nas propriedades mecânicas avaliadas (0,78

Fracture resistance of root filled molar teeth restored with glass fibre bundles

AIM To evaluate the effect of unidirectional or woven glass fibre tapes inserted into MOD cavity preparations on the fracture resistance of root filled molar teeth. METHODOLOGY Extracted human molar teeth were randomly divided into six groups (n = 15) : G1 - sound teeth, control; G2 - MOD cavity preparation; G3 - MOD + root canal treatment (Endo); G4 - MOD + Endo + composite resin restoration (Resin); G5 - MOD + Endo + unidirectional fibre (UF) + Resin; G6 - MOD + ;Endo + woven fibre (WF) + Resin. The teeth were subjected to a compressive fracture test in a universal testing machine. After testing, two failure modes were classified: pulp chamber floor or cusp. RESULTS The highest and the lowest mean fracture strengths were found in sound teeth (G1) (4960N) and MOD + root canal treatment (G3) (612.84N), respectively, with significant differences from the other groups (P < 0.05). The remaining groups had statistically similar means. In G5 and G6, there was a tendency for fracture to occur in the pulp chamber floor compromising tooth integrity. CONCLUSIONS The insertion of glass fibres into MOD cavity preparations and restoring them with composite resin was not different than molar teeth filled with composite resin only in terms of fracture resistance. Fibres placed into MOD cavities do not reinforce teeth.

Bond Strength of a Novel One Bottle Multi-mode Adhesive to Human Dentin After Six Months of Storage

Objective: The aim of the study was to evaluate the microtensile bond strength (µTBS) of Scotchbond Universal to dentin using the etch-and-rinse or the self-etch technique after 24 h and 6 months of storage. Materials and Methods: Flat dentin surfaces were obtained in 24 third molars. The teeth were divided into four groups: G1 – Scotchbond Universal applied in the etch-and-rinse mode; G2 – Scotchbond Universal applied in the self-etch mode; G3 – Scotchbond Multi-Purpose; G4 – Clearfil SE Bond. A block of composite was built on the adhesive area. The tooth/resin sets were cut parallel to the long axis to obtain 40 beams (~0.8 mm2) for each group. Twenty specimens were immediately submitted to the µTBS test, and the remaining 20 were stored in water for 6 months. Failures and the adhesive interface were analyzed by SEM. Results: According to two-way ANOVA, the interaction between adhesive and storage time was significant (p=0.015).The µTBS (MPa) means were the following: 24 h – G1 (39.37±10.82), G2 (31.02±13.76), G3 (35.09±14.03) and G4 (35.84±11.06); 6 months – G1 (36.99±8.78), G2 (40.58±8.07), G3 (32.44±6.07) and G4 (41.75±8.25). Most failures were mixed. Evidence of hybrid layer and numerous resin tags were noted for Scotchbond Universal applied with the etch-and-rinse mode and Scotchbond Multi-Purpose. A thinner hybrid layer and fewer resin tags were noted for Scotchbond Universal applied in the self-etch mode and Clearfil SE Bond. Conclusion: The results indicate that the µTBS for Scotchbond Universal is comparable to the gold-standard adhesives. Scotchbond Universal applied in the self-etch mode and Clearfil SE Bond revealed higher bond stability compared to the etch-and-rinse mode.

Clinical Evaluation of Indirect Composite Resin Restorations Cemented with Different Resin Cements.

PURPOSE To clinically evaluate the performance of indirect composite resin restorations cemented with conventional and self-adhesive resin cements over a 12-month period. MATERIALS AND METHODS Ten patients fulfilled all the inclusion criteria. Twenty-four composite resin restorations were performed using an indirect technique and cemented with a resin cement (RelyX ARC) or a self-adhesive resin cement (RelyX U100). Two independent evaluators analyzed the restorations using modified USPHS criteria after periods of two weeks and 6 and 12 months. Statistical significance between the cements at each timepoint was evaluated with the Wilcoxon test and between timepoints with the Mann-Whitney test, both at a significance level of 5%. Fishers exact test was used to assess the occurrence of absolute failures. RESULTS No statistically significant differences were found between the groups at the same timepoint nor between groups at different timepoints. The only significant difference was found for color match for both groups after 12 months. CONCLUSION After 12 months, indirect composite resin restorations cemented with self-adhesive resin cement performed similarly to those cemented with conventional resin cement.

The influence of postpouring time on the roughness, compressive strength, and diametric tensile strength of dental stone

STATEMENT OF PROBLEM The optimum time after pouring a dental impression before removing the dental cast is unknown with regard to the strength and roughness of the stone. Setting times and the commercial products used are important variables. PURPOSE The purpose of this study was to evaluate the effect of postpouring time on the surface roughness, compressive strength, and diametric tensile strength of Type IV dental stone. MATERIAL AND METHODS A total of 270 specimens were prepared from 3 commercial brands of dental stone (Durone, Fuji Rock, and Tuff Rock). Surface roughness, compressive strength, and diametric tensile strength were assessed at 1 hour, 24 hours, and 7 days after pouring. Specimens 6 mm in diameter and 3 mm in height were produced for roughness and diametric tensile strength tests. Specimens 3 mm in diameter and 6 mm in height were used to measure compressive strength. The results were analyzed with the general linear model and Tukey honestly significant difference test (α=.05). RESULTS The surface roughness measured for the different types of dental stone tested varied from 0.3 μm (Durone, 1 hour) to 0.64 μm (Tuff Rock, 7 days). The diametric tensile strength ranged from 3.94 MPa (Tuff Rock, 1 hour) to 9.20 MPa (Durone, 7 days). The compressive strength varied from 26.67 MPa (Durone, 1 hour) to 65.14 MPa (Fuji Rock, 7 days). CONCLUSIONS Surface roughness (P=.005), diametric tensile strength (P=.001), and compressive strength (P=.001) increased significantly with time after pouring. The commercial brand used affected roughness (P=.001), diametric tensile strength (P=.004), and compressive strength (P=.001). Tuff Rock exhibited the highest surface roughness. The highest diametric tensile strength values were recorded for Durone and Fuji Rock. Fuji Rock exhibited the highest compressive strength.