Epithelial attachment and downgrowth on dental implant abutments--a comprehensive review.

UNLABELLED: The soft tissues around dental implants are enlarged compared with the gingiva because of the longer junctional epithelium and the hemidesmosonal attachments are fewer, suggestive of a poorer quality attachment. Inflammatory infiltrates caused by bacterial colonization of the implant-abutment interface are thought to be one of the factors causing epithelial downgrowth and subsequent peri-implant bone loss. Gold alloys and dental ceramics as well as the contamination of the implant surface with amino alcohols, appear to promote epithelial downgrowth. Physical manipulaton of the abutment surfaces, including concave abutment designs, platform switching, and microgrooved surfaces are believed to inhibit epithelial downgrowth and minimizes bone loss at the implant shoulder. This paper reviews the factors that are believed to influence the migration of epithelial attachment the dental implant and abutment surfaces. Exploration of innovative computer-aided design/computer-aided manufacturing-based concepts such as "one abutment-one time" and their effect on epithelial downgrowth are discussed. CLINICAL SIGNIFICANCE: Based on the review of current literature, the authors recommend inserting definitive abutments at the time of surgical uncovering. To implement this concept, registration of the implant position should to be taken at the time of surgical implant placement.

Shear bond strengths of pressed and layered veneering ceramics to high-noble alloy and zirconia cores.

STATEMENT OF PROBLEM: Heat-pressed ceramics to metal alloys and zirconia have been available for some time. However, information regarding their shear bond strengths is limited. PURPOSE: The purpose of this study was to evaluate the shear bond strengths of heat-pressed and layered ceramics with regard to their corresponding high-noble alloy and zirconia cores. MATERIAL AND METHODS: Forty cylinders (approx. 5 mm in diameter) of high-noble alloy (Olympia) were cast and divided into 4 groups (n=10). Metal cylinders were veneered with ceramics to produce shear test specimens: Group PMI with IPS InLine POM; Group LMI with IPS InLine; Group PMC with Pulse press-to-metal; and Group LMC with Authentic Pulse Metal ceramic. Forty cylinders (approx. 5 mm in diameter) of zirconia (Lava) were obtained and divided into 4 groups (n=10). These cylinders were veneered with ceramics to produce shear test specimens: Group PZI with IPS e.max ZirPress; Group LZI with IPS e.max. Ceram; Group PZV with VITA PM9; and Group LZV with VITA VM9. The veneering ceramics, 3 mm in thickness, were either pressed or layered to their corresponding cylinders. Thermal cycling was performed at 5°C and 55°C for 20,000 cycles with a 20 second dwell time. Shear bond strength testing was conducted in a universal testing machine, and the failure strengths were recorded. Fracture surfaces were characterized visually, under a stereomicroscope, and with a scanning electron microscope (SEM). Data were analyzed using rank-based Kruskal-Wallis and Mann-Whitney tests with Bonferroni correction to adjust for multiple comparisons (α=.05). RESULTS: For metal ceramic specimens, the mean (SD) shear bond strengths ranged from 37.8 (20.6) MPa to 66.4 (22.1) MPa. There were significant differences between Groups PMI and PMC and between Groups LMI and PMC, in which Groups PMI and LMI had significantly higher strength values than Group PMC (P=.041). For zirconia ceramic specimens, the mean (SD) shear bond strengths ranged from 30.03 (9.49) MPa to 47.2 (13.0) MPa, with Group LZV having a significantly higher shear bond strength value than Group LZI (P=.012). Half of the Group PZV specimens failed during thermal cycling, and Group PZV was, therefore, excluded from statistical analysis. For all shear bond strength testing specimens, cohesive failures in the veneering ceramics were observed. CONCLUSIONS: For shear bond strength of veneering ceramics to high-noble alloy, there was no significant difference between pressing and layering with the same manufacturer. For shear bond strength of veneering ceramics to zirconia, there was no significant difference between the pressed and layered groups.

Interdisciplinary treatment of cervical lesions.

Soft tissue grafting is an integral part of treatment of cervical lesions due to the common lack of adequate attached gingiva and root exposure associated with these lesions. Complete root coverage is a predictable outcome for Miller Class I and II recession defects, and partial root coverage can be achieved in Miller Class III defects. In the esthetic zone, it is desirable to cover as much of the root as possible, and all sites require an adequate zone of attached gingiva, especially adjacent to a restoration. Restorations are required for cervical lesions with excessive depth and significant involvement of the enamel, but they should be avoided where the lesion is shallow and the enamel involvement is minimal. Of course, some sites will require both soft-tissue grafting and placement of a restoration. An interdisciplinary approach to treating cervical lesions will create the most biologically appropriate, stable, and esthetic outcome. Establishing the appropriate tooth form first in treatment planning and sequencing will determine the gingival level and extent of periodontal procedures necessary to achieve the desired outcome.

Use of magnification in dental technology.

UNLABELLED: Binocular stereoscopic microscopes have been used in dental technology for decades to improve visual acuity during the fabrication process. Technicians endeavor to produce a restoration that has marginal discrepancies of < 50 microm and to polish the surface of the restorative material so that there is minimal bacterial accumulation. There are six key areas in which the use of magnification is critical to fabricating high-quality restorations: inspection of the impression; trimming and marking of the margin on the die; waxing of the margin; fitting of the initial casting, pressing, or milled unit; final fitting of the restoration; and polishing of the restoration. This article explains some of the specific areas in which dental technicians rely on magnification to increase the probability of a long-term biologically acceptable restoration. CLINICAL SIGNIFICANCE: Precision in the dental laboratory during fabrication of indirect restorations is crucial to long-term clinical success. An intimate but passive fit to the restoration ensures complete seating at the time of cementation with excellent marginal integrity and subsequent minimal occlusal adjustments. A restorative surface that is smooth and well polished in the gingival third results in minimal bacterial accumulation and a healthy periodontium.