Comparison of Implant Survival Rates and Biologic and Mechanical Complications with Implant-Supported Fixed Complete Dental Prostheses Using Four and Six Implants.

This study aims to compare the incidence of biologic and mechanical complication rates and the survival rates after at least 5 years of implants and implant-supported fixed complete dental prostheses (IFCDPs) placed during second-stage surgery using four and six implants. A total of 77 patients (33 men, 44 women) with a mean age of 60.6 ± 8.8 years (range: 39 to 80 years) were included, and the total of 92 IFCDPs were classified into two groups: 51 received four implants, and 41 received six implants. No implant failed in the four-implant group (0/204), and one implant failed in the six-implant group (1/246), with no statistically significant differences (P > .05). One prosthetic failure occurred in the four-implant group (1/51), and one failure occurred in the six-implant group (1/41). Both groups experienced some technical and biologic complications, with no statistically significant differences between the groups (P > .05). For both groups, veneer or resin fracture was the most frequent mechanical complication, and mucositis was the most frequent biologic complication. The use of four or six implants may represent a predictable treatment option in the rehabilitation of completely edentulous patients with IFCDPs in the medium-term.

Prosthetic complications with mandibular bar-retained implant overdentures having distal attachments and metal frameworks: A 2- to 12-year retrospective analysis.

STATEMENT OF PROBLEM: Long-term reports on 2-implant-retained overdentures having metal frameworks and bars containing distal attachments are scarce. PURPOSE: The purpose of this retrospective study was to evaluate prosthetic complications with 2-implant-retained mandibular overdentures with metal frameworks having either screw- or cement-retained cantilevered bars with distal attachments. MATERIAL AND METHODS: Seventy-three edentulous study participants who had been treated with mandibular overdentures with 2 implants were included. The parameters assessed were acrylic resin fractures (base fracture, fracture at midline), debonding of teeth, opposing prosthesis fracture, need for relining or rebasing, abutment and bar screw loosening and fracture, ball or bar attachment or clip wear, fracture or detachment, bar fracture, and implant loss. Statistical analysis was performed by using the Mann-Whitney U test as the data were not normally distributed. The categorical variables between the groups were analyzed by using the Fisher exact test (α=.05). RESULTS: Twenty-seven prostheses had a cement-retained bar, and 46 bars were screw-retained. Of 73 overdentures, 68 were metal-reinforced. The mean observation time was 5.9 years with a range between 2 and 12 years. The most common complication was wear of the Rhein 83 polymer attachment followed by bar screw loosening. The cumulative survival rate for overdentures was 91.9% at 6.8 years. The service life of cement-retained prostheses was significantly longer (P<.05). Bar, resin base, and mid-line fractures were only seen with cement-retained prostheses. The number of times an attachment change was required did not differ between cement- and screw-retained bars. Of 191 implants, 3 were lost, and the cumulative survival rate was 93.5% at 7.5 years. No significant difference was found between retention types in terms of implant loss (P>.05). CONCLUSIONS: Based on the participant population observed, the survival rates of 2-implant-retained mandibular overdentures and their implants in the medium term were high. Wear of the polymer attachment was commonly seen. Overdentures with cement-retained bars had bar or acrylic resin fractures. Mandibular 2-implant-retained overdentures with a screw-retained bar containing bilateral distal attachments had fewer prosthetic complications and high implant survival in the medium term.

Color change during the surface preparation stages of metal ceramic alloys.

STATEMENT OF PROBLEM: Even though metal ceramic restorations (MCRs) are widely used by clinicians, the influence of the metal on the color of overlaying porcelain is unknown. PURPOSE: The purpose of this study was to analyze the color alterations of different types of metal ceramic alloys during several stages of metal surface preparation and to determine the effect of those changes on the resulting color of opaque porcelain (OP). MATERIAL AND METHODS: Seven different types of alloys (3 base metal, 3 noble, and 1 high noble) were used to prepare disk-shaped specimens (1 mm × 10 mm, n=3), followed by OP application (0.1 mm). L*a*b* values of specimens were recorded after different stages of metal surface preparation (ingot, after casting, after oxidation, and after the OP application) in addition to the shade tab of OP B1 (target shade). L*a*b* values of alloys were measured from the ingot structure to the OP application stage and statistically analyzed (Repeated measures ANOVA, and Bonferroni corrected paired t test, α=.05). L*a*b* values of OP applied groups and the OP shade tab (target shade) were analyzed (1-way ANOVA with Dunnett's multiple comparison test, α=.05). The color differences of the target shade both before and after OP application were calculated and statistically analyzed (1-way ANOVA, Ryan-Einot-Gabriel-Welsch Multiple Range Test, α=.05). RESULTS: The L* values of all alloys changed significantly after each stage except for 2 alloys (V-Deltaloy SF (N-VDSF)) and (Gnathos Plus (HN-GP)) after casting and airborne-particle abrasion (P<.05). The a* value of all alloys increased after casting. Changes in the a* coordinate were significant except for one of the base metal alloys (P<.05). The a* coordinate changes of alloys showed variation in direction after oxidation and OP application (P<.05). The b* coordinate changes of alloys showed variation in direction after each stage (P<.05). The L*a*b* values of some OP applied alloys were significantly different from that of the OP shade tab (P<.05). Color difference values (ΔE (OP applied alloy-target shade)) of 2 OP-applied alloys (Cerapall 2 (N-CP2) and Ceradelta (N-CD)) were significantly different (P<.05) and higher than the other OP-applied alloys. CONCLUSIONS: The achromatic color behavior of different alloys was all in the same direction at all metal surface preparation stages. The chromatic behavior of the different alloys was primarily towards the same direction after casting and airborne-particle abrasion, whereas it varied after oxidation and OP application. The color difference of OP for all alloys, regardless of their type, was not visually perceivable when compared to the target shade (ΔE<2.6).

Colorimetric analysis of opaque porcelain fired to different base metal alloys used in metal ceramic restorations.

STATEMENT OF PROBLEM: The popularity of base metal alloys has considerably increased in recent years because of their superior mechanical properties as well as the high cost of noble alloys. However, there is disagreement about their effect on the opaque porcelain color and the color differences among base metal alloys. PURPOSE: The purpose of this in vitro study was to determine and compare the influence of various commercially available base metal alloys (excluding titanium-based systems) on the resulting color of opaque porcelain with the use of a colorimetric device. MATERIAL AND METHODS: Fourteen different types of Ni-Cr and 3 different types of Co-Cr porcelain bonding alloys were selected with a Au-Pd alloy (V-Delta SF) as the control group for colorimetric measurements and determination of color shift after opaque application. Shade B1 of an opaque porcelain (IPS d.SIGN Opaquer) was applied (0.1 mm) to all specimens (16 mm x 1 mm). The color coordinates of each specimen were measured with a chromameter. The data were displayed in L*, a*, and b* values according to the CIELAB system, and the color differences (DeltaE) between base metal alloys and the control group were calculated. Data were statistically analyzed with 1-way ANOVA (alpha=.05). The ANOVA was followed by Dunnett's multiple comparison test for comparisons with the control group to determine specifically which groups were significantly different from the control group. RESULTS: The L* value of only 1 base metal alloy was significantly different from the control group (P<.001). All base metal alloy groups except 3 had a* values which were significantly different from the control group a* value (P=.001 for Rexillium III, P=.008 for Heracles N, and P<.001 for the remaining 12 alloys), whereas only 3 base metal alloys were not statistically significantly different from the control group in the means of b* values (P<.001). All base metal alloys to which opaque porcelain was applied had significantly different DeltaE values in comparison with the control group (P<.001). CONCLUSIONS: The data of the study indicated that a 0.1-mm-thick layer of opaque porcelain applied on the Ni-Cr and Co-Cr alloys did not reliably reproduce the color of opaque porcelain. However, within the limitations of this study, the color differences of base metal alloys measured according to the control group are within clinically acceptable limits (DeltaE<3.5).

Effects of silicon coating on bond strength of two different titanium ceramic to titanium.

OBJECTIVES: This study investigated the effect of silicon coating (SiO2) by magnetron sputtering on bond strength of two different titanium ceramics to titanium. METHODS: Sixty cast titanium specimens were prepared following the protocol ISO 9693. Titanium specimens were divided into two test and control groups with 15 specimens in each. Test groups were silicon coated by the magnetron sputtering technique. Two titanium ceramics (Triceram and Duceratin) were applied on both test (coated) and control (uncoated) metal specimens. The titanium-ceramic specimens were subjected to a three point flexural test. The groups were compared for their bond strength. SEM and SEM/EDS analyses were performed on the delaminated titanium surfaces to ascertain bond failure. RESULTS: The mean bond strength of Ti-Duceratin, Ti-Triceram, Si-coated Ti-Duceratin and Si-coated Ti-Triceram were 17.22+/-2.43, 23.31+/-3.18, 23.21+/-3.81 and 24.91+/-3.70 MPa, respectively. While the improvement in bond strength was 30% for Duceratin, it was statistically insignificant for Triceram. An adhesive mode of failure was observed in the Duceratin control group. In the silicoated Duceratin specimen, the bonded ceramic boundaries were wider but less than in the silicoated Triceram specimen. In the coated Triceram specimen, the ceramic retained areas were frequent and the failure mode was generally cohesive. SIGNIFICANCE: Silicon coating was significantly effective in both preventing titanium oxide layer formation and in improving bond strength for Duceratin. However, it was of less value for Triceram.