Eduardo Gonçalves Mota

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.

Maximum occlusal force and medial mandibular flexure in relation to vertical facial pattern: a cross-sectional study.

BackgroundVertical facial pattern may be related to the direction of pull of the masticatory muscles, yet its effect on occlusal force and elastic deformation of the mandible still is unclear. This study tested whether the variation in vertical facial pattern is related to the variation in maximum occlusal force (MOF) and medial mandibular flexure (MMF) in 51 fully-dentate adults.MethodsData from cephalometric analysis according to the method of Ricketts were used to divide the subjects into three groups: Dolichofacial (n = 6), Mesofacial (n = 10) and Brachyfacial (n = 35). Bilateral MOF was measured using a cross-arch force transducer placed in the first molar region. For MMF, impressions of the mandibular occlusal surface were made in rest (R) and in maximum opening (O) positions. The impressions were scanned, and reference points were selected on the occlusal surface of the contralateral first molars. MMF was calculated by subtracting the intermolar distance in O from the intermolar distance in R. Data were analysed by ANCOVA (fixed factors: facial pattern, sex; covariate: body mass index (BMI); alpha = 0.05).ResultsNo significant difference of MOF or MMF was found among the three facial patterns (P = 0.62 and P = 0.72, respectively). BMI was not a significant covariate for MOF or MMF (P > 0.05). Sex was a significant factor only for MOF (P = 0.007); males had higher MOF values than females.ConclusionThese results suggest that MOF and MMF did not vary as a function of vertical facial pattern in this Brazilian sample.

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.

Can we add chlorhexidine into glass ionomer cements for band cementation

OBJECTIVE To test if the addition of chlorhexidine digluconate (CHD) might influence the mechanical properties and antibacterial properties of two different conventional glass ionomer cements (GICs) used for band cementation. MATERIALS AND METHODS Two commercial brands of conventional GICs were used: Ketac Cem Easymix (3M/ESPE, St Paul, Minn) and Meron (Voco, Cuxhaven, Germany). The cements were manipulated in their original composition and also with 10% and 18% CHD in the liquid to create a total of six groups. Diametral tensile strength, compressive strength, microhardness, shear bond strength, and antibacterial effects in 5, 45, and 65 days against Streptococcus mutans were tested in all groups, and the data were submitted to statistical analyses. RESULTS There were no significant differences between the groups of the same material in diametral tensile, compressive strength, and shear bond strength (P > .05). There was significant improvement in the microhardness to the Ketac Cem Easymix (P < .001). GICs with the addition of CHD showed significant inhibition of S. mutans growth in comparison with the control groups at the three time points evaluated (P < .001). The addition of 18% CHD resulted in higher bacterial inhibition (P < .001). CONCLUSIONS The addition of chlorhexidine digluconate to conventional GICs does not negatively modify the mechanical properties and may increase the antibacterial effects around the GICs even for relatively long periods of time.

Effect of whitening dentifrices on the surface roughness of commercial composites.

PURPOSE Our study aimed to test the null hypothesis that whitening and non-whitening dentifrices affect similarly the surface roughness of commercial microhybrid composites, independent of the brushing time. MATERIALS AND METHODS One hundred and ninety-two disc-shaped specimens of Filtek Z250 (3 M/ESPE, St. Paul, MN, USA) and Rok (SDI, Australia) were built up and randomly assigned to 24 groups, based on the dentifrices used (two whitening dentifrices: Colgate Max White-Colgate-Palmolive, São Bernardo do Campo, São Paulo, Brazil and Close Up Extra Whitening-Unilever, Brasil Higiene Pessoal e Limpeza Ltda, Ipojuca, Pernambuco, Brazil; and one non-whitening dentifrice: Colgate Total 12 Clean Mint-Colgate-Palmolive), and on the simulated brushing times (24 hours, 6, 12 and 24 months). The specimens were submitted to the toothbrushing regimens after which the surface roughness (Ra) was measured. Data was submitted to analysis of variance and Tukey test (α=0.05). RESULTS The composites surface roughness was significantly affected by the composites (p=0.0007), the dentifrices (p=0.0001), and the simulated brushing time (p=0.0001). Higher roughness was observed when the whitening dentifrices were used and when the brushing time increased. Filtek Z250 was more affected than Rok, especially after 24 months of simulated brushing. CONCLUSION Whitening dentifrices produced higher surface roughness in the composites tested. The degree of surface compromising increased with brushing time and depends on the composites microstructure and composition.

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

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.

Relined fiberglass post: an ex vivo study of the resin cement thickness and dentin-resin interface

The aim of this study was to evaluate the thickness of resin cements in the root thirds when using conventional fiberglass posts (CP) and relined fiberglass posts (RP) in weakened roots and to evaluate the morphological characteristics of the dentin-resin interface. Forty human maxillary anterior teeth had the crown sectioned below the cemento-enamel junction. The canals were endodontically treated and weakened with diamond burs. Teeth were divided into four groups (n = 10): Group 1 - CP + RelyX ARC; Group 2 - CP + RelyX U200; Group 3 - RP + RelyX ARC; and Group 4 - RP + RelyX U200. Prior to luting, 0.1% Fluorescein and 0.1% Rhodamine B dyes were added to an adhesive and resin cement, respectively. Slices were obtained from the apical, middle, and cervical thirds of the root. Confocal laser scanning microscopy images were recorded in four areas (buccal, lingual, mesial, distal) of each third. In each area, four equidistant measures of the resin cement were made and the mean value was calculated. The interface morphology was observed. The data were submitted to three-way ANOVA and Tukeys test (α = 0.05). The interaction between fiberglass posts, resin cement, and root thirds was significant (p < 0.0001). The resin cement thicknesses were significantly lower for RP in comparison with CP, except in the apical third. There was no significant difference between the resin cements for RP. There was formation of resin cement tags and adhesive tags along the root for RP. RP favored the formation of thin and uniform resin cement films and resin tags in weakened roots.

Does immediate dentin sealing influence the polymerization of impression materials

Objectives: The objective of the following study is to evaluate the interaction between the resin materials used in immediate dentin sealing (IDS) techniques and impression materials with two different techniques to eliminate the oxygen-inhibition layer. Materials and Methods: The occlusal dentin surface of 35 human molars was exposed. The teeth were used in two Groups: Group 1 - Impression with Express XT; Group 2 - Impression with Impregum. Groups 1 and 2 were divided into 14 subgroups: Groups 1a and 2a - Control groups; 1b and 2b - IDS with Clearfil SE Bond (CSE); 1c and 2c - IDS with CSE + additional polymerization with glycerin jelly; 1d and 2d - IDS with CSE + alcohol; 1e and 2e - IDS with CSE and Protect Liner F (PLF); 1f and 2f - IDS with CSE and PLF + additional polymerization with glycerin jelly; and 1g and 2g - IDS with CSE and PLF + alcohol. Five teeth were used in each experimental group, and the tooth surface was photographed using a digital camera. Results: Small quantity of unpolymerized impression material remained attached to the CSE or to the PLF in Groups 1b and 1e. Groups 1c and 1d prevented the interaction. Small quantity of polymerized impression material remained attached to the CSE or to the PLF for Groups 2b and 2e. The same interaction was observed for Groups 2c and 2d. For Groups 2c and 2f, no interactions were observed. Conclusion: Resin materials interacted with impression materials. The application of glycerin jelly and alcohol prevented the interaction of CSE with Express XT and PLF with Impregum; however, these treatments were not completely effective in preventing the interaction of CSE with Impregum and PLF with Express XT.

Influence of ultrasound and diamond burs treatments on microtensile bond strength

OBJECTIVE To compare surface treatments with CVDentUS ultrasound tips (UT) and KGSorensen diamond burs (DB) on etched (e) and non-etched (n/e) dentin. The microtensile bond strength (μTBS) was measured and fractography was assessed by scanning electron microscope (SEM). MATERIALS AND METHODS Sixteen molars were divided into four groups of four teeth each according to treatment (DB-n/e; DB-e; UT-n/e; UT-e). The teeth were restored, sectioned into samples for μTBS (n=40) and tested on a EMIC DL-2000 universal machine (0.5 mm/min) and analyzed by SEM for fracture classification. STATISTICAL ANALYSIS For analysis of the data on μTBS, the two-way ANOVA, using treatment and acid etching as fixed factor, and the Tukey test were used (α=0.05). To failures classification in cohesive in dentin (CD); cohesive in composite resin (CC); cohesive interfacial on base or top of hybrid layer (CBT); cohesive in adhesive (CA); mixed (M); interfacial on smear layer (S) the Fishers exact test (α=0.05) was performed. RESULTS The mean values of μTBS (in MPa) in the different groups were as follows: UT-e: 45.31 ± 8.16; DB-e: 34.04 ± 9.29; UT-n/e: 15.17 ± 3.71; and DB-n/e: 9.86 ± 3.80. On analysis of the SEM micrographs, the DB-n/e group showed total obstruction of dentinal tubules; the UT-n/e group showed partial desobstruction of dentinal tubules and irregular surface; the DB-e group showed complete desobstruction of dentinal tubules; and the UT-e group showed complete desobstruction of dentinal tubules and irregular surface. CONCLUSION The combination of ultrasound treatment and acid etching provides high values of μTBS. An association exists between CA/CC failures and the UT method, CBT failure and the DB method, CBT/CC failures and etching, S failure and non-etching.