Marginal and internal adaptation of milled cobalt-chromium copings.

STATEMENT OF PROBLEM: The application of computer-aided design and computer-aided manufacturing (CAD/CAM) systems to produce complete coverage restorations with different materials continues to increase. To date, insufficient information is available regarding the adaptation of recently introduced milled cobalt-chromium (Co-Cr) copings for metal ceramic restorations. PURPOSE: The purpose of this in vitro study was to evaluate the marginal and internal fit of milled Co-Cr copings produced by CAD/CAM with 2 different marginal preparation designs. MATERIAL AND METHODS: Four master dies were developed from 2 ivorine central incisors and 2 ivorine maxillary molars, 1 of each prepared with a 0.8-mm chamfer and a 1.2-mm rounded shoulder. These 4 groups of teeth were replicated with polyvinyl siloxane and used as templates to fabricate epoxy dies (n=10) for each of the 4 groups; a total of 40 epoxy resin dies. Cobalt-chromium copings of standard thickness (0.4 mm) were fabricated for each die with CAD/CAM technology. Next, the working dies were scanned with a 5-axis laser scanner to produce a 3-dimensional model. A thin layer of low-viscosity polyvinyl siloxane material was placed inside each coping and seated on the die until the material set. Copings were removed from the dies, leaving the polyvinyl siloxane intact, and these silicone-coated dies were scanned. The software superimposed the 2 scans, and the marginal openings and internal fit were measured at multiple locations. The marginal opening was determined at 4 locations: mid-buccal (mB), mid-lingual (mL), mid-mesial (mM), and mid-distal (mD), and the mean of these 4 measurement locations was referred to as the group variable "edge." The internal occlusal adaptation was measured at the midpoint from buccal to lingual and mesial to distal locations and referred to as mid-occlusal (mO). Means and standard deviations for edge (marginal adaptation) and mO were calculated for each of the 4 groups. A 2-sample t test was performed to detect differences among groups. A regression analysis was done to evaluate the interaction between the variables mO and edge (α=.05). RESULTS: Significantly smaller mean marginal openings (P=.017) were observed overall for the chamfer marginal design (anterior chamfer: 61 ±41 µm; posterior chamfer: 52 ±27 µm) compared with the shoulder design (anterior shoulder 103 ±49 µm, posterior shoulder 113 ±110 µm). The anterior chamfer had a statistically significant (P=.055) smaller mean marginal opening (61 ±41 µm) than the anterior shoulder (103 ±49 µm). No statistically significant differences (P=.119) were found between the posterior chamfer and posterior shoulder. The internal adaptation at the mO location was not significantly different among all 4 groups (P>.05). However, a regression analysis demonstrated a strong correlation (R=.842; P<.001) between the occlusal seat (mO) and marginal opening, with the smaller mean marginal opening of the chamfer design coinciding with the smaller occlusal seat values (61µm; mO: 182 µm) anterior chamfer; (52 µm; mO: 172 µm) posterior chamfer versus (103 µm; mO: 235 µm) anterior shoulder; (113 µm; mO: 242 µm) posterior shoulder. CONCLUSIONS: The milled Co-Cr copings produced with a CAD/CAM system in this study demonstrated clinically acceptable marginal fit in the range of 52 to 113 µm before ceramic application.

Material options for restoring intentionally misaligned implants on maxillary edentulous arch: a clinical report.

Without major bone grafting procedures, anatomic challenges may dictate less than ideal implant placement. When surgical correction is impossible, it may be possible to place implants on an angle and use angled abutments to compensate. This article presents 2 patient treatments where angled abutments were used to facilitate the fabrication of an implant-supported fixed complete-arch prosthesis. In both scenarios the supporting bars for the prostheses were milled in titanium. Soft tissue shaded ceramic was used to simulate the soft tissues for one patient and soft tissue shaded composite resin was used for the second. The prostheses were completed by cementing 12 individual crowns on each bar.

Nonrigid connection of tooth with implants in the esthetic zone with a ceramic restoration: a clinical report.

Restoring edentulous areas with fixed prostheses can be challenging, especially when key abutment teeth are missing and implant placement is not an option. Sometimes, clinicians are faced with situations where teeth have to be connected with implants even though long-term prognosis of those connections may be questionable. This clinical report presents a connection of 2 implants with 1 tooth in the esthetic zone with a nonrigid connection. Two zirconia custom abutments and 1 zirconia coping definitively cemented on the tooth were used. A zirconia superstructure, veneered with porcelain, was cemented with provisional cement on the abutments and the coping.

Maxillary implant-supported bar overdenture and mandibular implant-retained fixed denture using CAD/CAM technology and 3-D design software: a clinical report.

The implant-supported bar overdenture and the implant-retained fixed complete denture are appropriate treatment choices for patients with inadequate bone volume in the posterior maxilla and mandible, respectively. Computer-aided design/computer-aided manufacturing (CAD/CAM) technology has broadened the scope and application of those treatment options, allowing for prosthodontically-driven implant placement and ideal substructure design for optimal esthetics and biomechanics. This report describes the fabrication of a maxillary implant-supported milled titanium bar with attachments and an overdenture, and a mandibular implant-retained fixed complete denture with milled titanium substructure.