Showing papers by "Marco Antonio Bottino published in 2004"

Vertical marginal discrepancy of ceramic copings with different ceramic materials, finish lines, and luting agents: an in vitro evaluation.

Abstract: Statement of problem Prosthetic restorations that fit poorly may affect periodontal health and occlusion Studies that have evaluated the accuracy of fit of ceramic restorations before and after cementation assessed primarily intracoronal restorations Purpose This in vitro study evaluated the effect of different finish lines, ceramic manufacturing techniques, and luting agents on the vertical discrepancy of ceramic copings Material and methods Two stainless steel molars were prepared for complete crowns with 2 different finish lines (heavy chamfer and rounded shoulder); each molar was duplicated to fabricate 90 copings A total of 180 copings generated 18 groups (n=10 for each finish line–coping material–luting agent combination) Luting agents tested included zinc phosphate, resin-modified glass ionomer (Fuji Plus), and resin composite cements (Panavia F) A metal frame was developed on which to screw the stainless steel model and a ceramic coping; the distance (μm) between 2 predetermined points was measured before and after cementation by a profile projector under a torquing force A 4-way ANOVA with repeated measurements was performed to assess the influence of each factor in the vertical marginal discrepancy: 3 between-coping factors (finish line–coping material–luting agent) and 1 within-coping factor (before and after cementation) (α=05) Results Procera copings presented the lowest mean values ( P Conclusion Considering each factor separately, the ceramic manufacturing technique appeared to be the most important factor tested for the definitive vertical discrepancy of all-ceramic copings, with lower mean values for Procera copings

Evaluation of the shear bond strength of the union between two CoCr-alloys and a dental ceramic

Abstract: INTRODUCTION: Based on the importance of the integrity of the metal/ceramic interface, the purpose of this work was to evaluate the shear bond strength of the metal-ceramic union of two Co-Cr alloys (Wirobond C, Bego; Remanium 2000, Dentaurum) combined with Omega 900 ceramic (Vita Zahnfabrik). MATERIAL AND METHOD: Eleven cylindrical matrixes were made for each alloy, and the metallic portion was obtained with the lost wax casting technique with standardized waxing of 4mm of height and of 4mm of diameter. The ceramic was applied according to the manufacturer's recommendations with the aid of a teflon matrix that allowed its dimension to be standardized in the same size as the metallic portion. The specimens were submitted to the shear bond test in an universal testing machine (EMIC), with the aid of a device developed for such intention, and constant speed of 0.5mm/min. RESULTS AND CONCLUSIONS: The mean resistance was 48.387MPa for Wirobond C alloy, with standard deviation of 17.718, and 55.956MPa for Remanium 2000, with standard deviation of 17.198. No statistically significant difference was observed between the shear strength of the two metal-ceramic alloys.

Effect of ceramic surface treatment on the microtensile bond strength between a resin cement and an alumina-based ceramic.

Abstract: Department of Restorative Dentistry School of Dentistry Federal University of Santa Maria, Santa Maria/RS

Evaluation of shear bond strength at the interface of two porcelains and pure titanium injected into the casting mold at three different temperatures

Abstract: Statement of problem Titanium has physical and mechanical properties, which have led to its increased use in dental prostheses despite casting difficulties due to high melting point and formation of oxide layers which affect the metal-ceramic bond strength. Purpose This in vitro study evaluated the shear bond strength of the interface of 2 dental porcelains and pure titanium injected into a mold at 3 different temperatures. Material and methods Using commercially pure (cp) titanium bars (Titanium, Grade I) melted at 1668°C and cast at mold temperatures of 430°C, 700°C or 900°C, 60 specimens were machined to 4 × 4 mm, with a base of 5 × 1 mm. The 4-mm surfaces were airborne-particle abraded with 100 μm aluminum oxide before applying and firing the bonding agent and evaluating the 2 porcelains (Triceram/Triline ti and Vita Titankeramik). Ten specimens were prepared for each temperature and porcelain combination Shear bond testing was performed in a universal testing machine, with a 500-kg load cell and crosshead speed of 0.5 mm/min. The specimens were loaded until failure. The interfaces of representative fractured specimens of each temperature were examined with a scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Data for shear bond strength (MPa) were statistically analyzed by 2-way ANOVA and the Tukey test (α=.05). Results The results showed significant differences for the metal/porcelain interaction effect ( P =.0464). There were no significant differences for the 2 porcelains ( P =.4250). The Tukey test showed a significant difference between the pair cp Ti 430°C Triceram and cp Ti 900°C Triceram, with respective mean values and SDs of 59.74 ± 11.62 and 34.03 ± 10.35 MPa. Conclusion Triceram porcelain showed a bond strength decrease with an increase in the mold temperature for casting titanium. The highest bond strength for Vita porcelain and the best metal-ceramic interface observed with the SEM were found with the mold temperature of 700°C.

Multiple-unit implant frames: one-piece casting vs. laser welding and brazing

Abstract: The linear distortion of prostheses over implants, one-piece casting and cast in sections followed by laser welding by laser and brazing was evaluated in an edentulous mandibular model with five parallel abutments, with a distance of 10mm from center to center. Seventy five gold cylinders were tightened with screws on the abutments with 10Ncm torque. The cylinder/analogue assemblies were measured by microscopic examination (0.001mm accuracy) and the obtained results were compared with the GC (control group). Fifteen metal frames were waxed and cast in a gold alloy (Stabilor, Degussa Hulls, Brazil) and divided into three groups with five elements each, as followed: GM (one-piece casting), GB (section and brazing) and GL (section and laser welding). In all groups, measurements were taken at the right, left, buccal and lingual sides of the cylinder/analogue interface and the results were submitted to analysis of variance (ANOVA) and to the Tukey test (5%). The smallest amount of distortion was seen in the laser group (GL with a mean value of 13.58), followed by the brazing group (GB with a mean value of 24.33) and one-piece (GM with a mean value of 40.00). The greatest distortion was found in the one-piece group (GM).

Marginal fit of electroformed copings before and after the coction of the porcelain

Abstract: The aim of this study was to evaluate the marginal discrepancy of electroforming copings, before and after the porcelain application, varying the cervical preparation of the crownsTwo master die were prepared with stainless steel to complete crown margin designs: chamfer and rounded shoulder The impressions were taken with a polyvinylsiloxane by the double impression technique and, the insertion and removal axis were standardized by a dental surveyor Ten type IV plaster dies from each cervical margin were obtained, on which a die spacer was applied before duplicate The duplicated dies received a silver layer and connected to a copper wire to enable the gold electrodeposition After cleaning and adjustments all specimens were examined under a microscope (magnificatio X 30) The marginal gap was measured before and after ceramic application The results were elaborated by descriptive statistical and two-way analysis of variance (ANOVA) The ANOVA revealed no significant difference between marginal gap before and after the ceramic application (p=5%) It was concluded that the porcelain application does not influence the marginal fit of copings, therefore the two marginal endings can be used with the electroforming system

Evaluation of marginal adaptation of ceramic crowns depending on the marginal design and the addition of ceramic

Abstract: This study evaluates the marginal adaptation of ceramic copings front of two finish lines and addition of ceramic. Hence, two master steel dies were milled with all-ceramic crowns preparation, one with a round shoulder finish line margin design, and the other with a deep chamfer. From each one of them, 15 copings were made, and the marginal discrepancy was evaluated in measuring microscope. The ceramic addition was accomplished in both groups with aid of a silicone matrix, and the discrepancies were measured again, obtaining the final mean gap values. The initial measurements resulted means of 44,0µm for deep chamfer and 24,0µm for the round shoulder, and the final measurements were 53,3µm for the deep chamfer and 27,4µm for the round shoulder. The data were submitted to the analysis of variance for verification of influence of the finish lines and application of the ceramic. When analyzed the interaction among the variables it was not observed statistical differences, but when comparing the two types of finish lines or the groups before and after ceramic addition, statistical differences were found. It is was concluded that the round shoulder finish line presents better values of marginal gap than deep chamfer and the addition of ceramic influences in the final gap values of marginal adaptation.

Mechanical properties and micro structural analysis of a NiCr alloy cast under different temperatures

Abstract: The purpose of this study was to evaluate the chemical and metallurgical aspects, mechanical properties and hardness of the NiCr dental alloy when it was submitted to different castings temperatures. An NiCr alloy was cast, with lost wax technique, 20 specimens, separated in two groups of 10 each one, in two different casting temperatures: a) in accordance with the manufactures instructions (T1); b) above manufactures instructions (T2). It was done chemical and metallographic analysis witch scanning electron microscope in the alloy in these conditions: no cast, T1 and T2. It was determined mechanical properties and hardness, too. The microstructures were similar to no cast, T1 and T2. There was no significant difference between chemical analysis and to mechanical properties. The hardness of the T1 and T2 groups was greater than no cast group. Clinically, it may predict that when elevated temperatures were used, above manufacture s recommendations (more than 100oC), there will be failures in the prosthesis, like porosities, fissures or cracks.

The fitness of copings constructed over UCLA abutments and the implant, constructed by different techniques: casting and casting with laser welding

Abstract: The alternative for the reposition of a missing tooth is the osteointegrated implant being the passive adaptation between the prosthodontic structure and the implant a significant factor for the success of this experiment, a comparative study was done between the two methods for confectioning a single prosthodontic supported by an implant. To do so a screwed implant with a diameter of 3.75mm and a length of 10.0mm (3i Implant innovations, Brasil) was positioned in the middle of a resin block and over it we screwed 15 UCLA abutments shaped and anti-rotationable (137CNB, Conexao Sistemas de Proteses, Brasil) with a torque of 20N.cm without any laboratorial procedure (control group - CTRLG). From a silicon model 15 UCLA-type calcinatable compounds (56CNB, Conexao Sistemas de Proteses, Brasil) were screwed (20 N.cm), received a standard waxing (plain buccal surface) and were cast in titanium (casting group - CG) and other 15 compounds, UCLA - type shaped in titanium (137 CNB, Conexao Sistemas de Proteses, Brasil) received the same standard waxing. These last copings were cast in titanium separated from each other and were laser-welded to the respective abutments on their border (Laser-welding group - LWG). The border adaptation was observed in the implant/compound interface, under measurement microscope, on the y axis, in 4 vestibular, lingual, mesial and distal referential points previously marked on the block. The arithmetical means were obtained and an exploratory data analysis was performed to determine the most appropriate statistical test. Descriptive statistics data (µm) for Control (mean±standard deviation: 13.50 ± 21.80; median 0.00), for Casting (36.20±12.60; 37.00), for Laser (10.50 ±12.90; 3.00) were submitted to Kruskal-Wallis ANOVA, alpha = 5%. Results test showed that distorsion median values differ statistically (kw = 17.40; df =2; p = 0.001<0.05). Dunn's (5%) test show difference between Casting and the two others. Conclusion: on the y axis, the smallest distortion values were obtained by the laser welding group.

The fitness of copings constructed over ucla abutments and the implant, constructed by different techniques: casting and casting with laser welding adaptação de copings de titânio ao implante , construídos sobre pilares ucla por duas técnicas: fundição e fundição com soldagem de bordo laser

Abstract: UNLABELLED The alternative for the reposition of a missing tooth is the osteointegrated implant being the passive adaptation between the prosthodontic structure and the implant a significant factor for the success of this experiment, a comparative study was done between the two methods for confectioning a single prosthodontic supported by an implant. To do so a screwed implant with a diameter of 3.75mm and a length of 10.0mm (3i Implant innovations, Brasil) was positioned in the middle of a resin block and over it we screwed 15 UCLA abutments shaped and anti-rotationable (137CNB, Conexão Sistemas de Próteses, Brasil) with a torque of 20N.cm without any laboratorial procedure (control group - CTRLG). From a silicon model 15 UCLA-type calcinatable compounds (56CNB, Conexão Sistemas de Próteses, Brasil) were screwed (20 N.cm), received a standard waxing (plain buccal surface) and were cast in titanium (casting group - CG) and other 15 compounds, UCLA - type shaped in titanium (137 CNB, Conexão Sistemas de Próteses, Brasil) received the same standard waxing. These last copings were cast in titanium separated from each other and were laser-welded to the respective abutments on their border (Laser-welding group - LWG). The border adaptation was observed in the implant/compound interface, under measurement microscope, on the y axis, in 4 vestibular, lingual, mesial and distal referential points previously marked on the block. The arithmetical means were obtained and an exploratory data analysis was performed to determine the most appropriate statistical test. Descriptive statistics data (µm) for Control (mean±standard deviation: 13.50 ± 21.80; median 0.00), for Casting (36.20±12.60; 37.00), for Laser (10.50 ±12.90; 3.00) were submitted to Kruskal-Wallis ANOVA, alpha = 5%. Results test showed that distorsion median values differ statistically (kw = 17.40; df =2; p = 0.001<0.05). Dunn's (5%) test show difference between Casting and the two others. CONCLUSION on the y axis, the smallest distortion values were obtained by the laser welding group.

Evaluation of the marginal fit of electroformed copings in function of the cervival preparation* Avaliação da adaptação marginal vertical de copings eletroformados

Abstract: The scope of this study was to evaluate the marginal fitness of coping made with the electroforming Gramm system. Two identical stainless steel master casts were milled simulating the tooth reduction for metal ceramic crowns; one with long chanfer and another with round shoulder preparations. The impression material used was a polivinilsyloxane silicone with the double impression technique, thus obtaining ten specimens of each master cast. To establish a pattern for impression a sheet of accetate with 1,4 mm thick was used. A dental surveyor was prepared to maintain constant the insertion and the removal axis of the master casts during all the impressions. The dies were made with gypsum type IV and after the casts were dyed with spacer, these were duplicated with laboratory silicone to obtain a second master cast with special gypsum. The casts were prepare with copper wire and coated with silver to promove the galvanic current so that a gold eletroforming is achieved. Upon adjustment and cleansing, the copings were adjusted to the master casts, which were fixed in an octagonal stainless steel table, and observed at a measuring microscope Olympus equipped with digital desk. The data obtained was submitted to “t” test and Mann-Whitney statistical test with significance level of 5%. The mean values of long chanfer and round shoulder were 29,77mm and 26,77mm, respectively, (p=0,657 and p=1,00). With the results obtained, it may be concluded that there was not a statistically significant difference, so both marginal preparations may be used.

Avaliação da influência da ciclagem mecânica na resistência à flexão de cerâmicas* Evaluation of influence of cyclic mechanical in flexural strength of ceramic

Abstract: The aim of this study was to evaluate the cyclic mechanical fatigue influence on ceramic materials using biaxial flexural strength. Forty specimens were fabricated to the final dimensions of approximated 15mm diameter and 1,2mm thickness of each ceramic material reinforced by different components: a) Procera AllCeram; b) In-