Clinical outcomes of full arch fixed implant-supported zirconia prostheses: A systematic review.

AIM: The primary aim of this systematic review was to study the clinical outcomes of one-piece fixed complete dentures (complete arch fixed implant-supported prostheses) made of zirconia for edentulous patients. The secondary aim was to compare the clinical outcomes of monolithic zirconia vs zirconia veneered with porcelain (conventional, minimal or gingival) for fixed complete dentures. MATERIALS AND METHODS: Two investigators conducted an independent electronic search of the literature, using PubMed and Scopus search engines from January 1, 2000, to August 31, 2016. After application of pre-determined inclusion and exclusion criteria, the final list of articles was reviewed to meet the aims of this review. RESULTS: A total of 12 observational studies were identified that satisfied the inclusion criteria of this systematic review. Short-term results from a combined 223 patients with 285 one-piece zirconia fixed complete dentures showed a mean failure rate of 1.4% due to the fracture of four prostheses. Prosthetic complications occurred in 46 prostheses (16.1%). Out of these, 42 prostheses (14.7%) had minor complications exclusive to fracture of veneered porcelain. CONCLUSIONS: Current evidence indicates that zirconia fixed complete dentures have a very low failure rate in the short term, but have a substantial rate of minor complications related to chipping of veneered porcelain. Use of monolithic zirconia with only gingival stains, or zirconia that is veneered only at the gingiva may offer promising results, but will need to be validated by future long-term studies. Conflict-of-interest statement: All authors report no conflict of interest.

The effect of static load on dental implant survival: a systematic review.

PURPOSE: The purpose of this study was to systematically review the current evidence related to the effects of static loading on the long-term stability of the osseointegrated interface. MATERIALS AND METHODS: The literature search was conducted using Medline supplemented by SCOPUS and the Cochrane databases as well as hand searching from references of reviewed papers. Relevant studies were selected according to predetermined inclusion and exclusion criteria. Key words used in the search included: dental implant passive fit, dental implant misfit, dental implant static load, dental implant overload, orthodontic forces, and dental implants. RESULTS: The initial database search yielded 192 relevant titles. After the subsequent filtering process, 36 studies were finally selected. Twenty-eight articles involved animal studies and eight articles involved human studies. CONCLUSIONS: The results of this systematic review demonstrate that there is no apparent detrimental effect of static loading on osseointegrated dental implants.

Clinical outcomes of implant abutments in the anterior region: a systematic review.

STATEMENT OF PROBLEM: The clinical outcomes of anterior implant abutments are not well reported. Purpose of the Study To systematically review the existing literature to identify survival, mechanical, biological, and esthetic outcomes of anterior implant abutments. MATERIAL AND METHODS: An electronic search was performed using PubMed/MEDLINE with specific search terms and predetermined criteria. After application of inclusion and exclusion criteria, the final list of articles was reviewed in-depth to meet the objectives of this review. RESULTS: Systematic application of inclusion and exclusion criteria resulted in identification of 27 studies that described outcomes of anterior implant abutments. Because of substantial heterogeneity of data, true survival, or cumulative survival of abutments could not be calculated. However, the mean failure of abutments was 1.15%, attributable to fractures restricted to ceramic abutments. Mechanical complications included abutment screw loosening, primarily restricted to external hex implants. Biological complications included fistulas and mucosal recession. Esthetic outcomes showed lesser gingival discoloration for zirconia abutments compared with metal abutments. CONCLUSIONS: Minimal anterior abutment fractures have been reported and are restricted to ceramic abutments. Studies using spectrophotometry showed lesser gingival discoloration with zirconia abutments, but there is no evidence for difference in patient's esthetic satisfaction between ceramic and metal abutments. CLINICAL SIGNIFICANCE: For the anterior region, selection of an implant with internal connection and a customized metal abutment (titanium or cast metal) can have the least mechanical complications. Limited existing clinical data indicate reduced peri-implant mucosal discoloration from zirconia abutments, which may be preferable over metal abutments, in patients with thinner mucosal tissues or patients with high or gummy smiles.

Insights into "bonding" of all-ceramics influenced by cement, sandblasting and water storage time.

OBJECTIVES: Bonding of all-ceramic restorations has become routine practice mainly due to results from clinical studies. Sandblasting has been advocated for surface treatment of many ceramics, based on results from numerous in vitro studies. This present work examines the influence of bonding on fracture loads of a veneered alumina ceramic using both chemical and sandblasting treatments. METHODS: Veneered tabs (In-Ceram alumina) were cemented (50 µm; ZnPO(4) or Panavia 21) to dentin-analog bases designed to allow water penetration to the cement/dentin interface. 60 specimens were fabricated for 2 weeks storage and another 80 specimens for 6 months storage (water, 37°C). Half of each group was tested "as-finished" and the other half "as-sandblasted", each divided between two cements. Specimens were loaded cyclically (20 Hz, 500,000) cycles in water beneath a 3mm diameter piston. A staircase sensitivity protocol was followed, using a step size of 25 N. Specimens were examined for cracking by transillumination (10×). RESULTS: Mean failure loads differed significantly between (1) as-finished Panavia versus zinc phosphate at 2 weeks; (2) as-finished versus sandblasted at 2 weeks; and (3) as-finished at 6 months versus 2 weeks (ANOVA, 95% post hoc test). Sandblasted groups did not differ among themselves at either time period or between 2 weeks and 6 months. CONCLUSION: Sandblasting was important for maintaining failure loads after 6 months of water storage. Zinc phosphate was equally protective as Panavia for sandblasted groups. Adhesion testing may not replicate clinical stresses important for investigating protective cement effects.

The slippery slope: critical perspectives on in vitro research methodologies.

OBJECTIVES: This paper attempts to provide critical perspectives on common in vitro research methodologies, including shear bond testing, wear testing, and load-to-failure tests. Origins of interest in high-quality laboratory data is reviewed, in vitro data is categorized into property and simulation protocols, and two approaches are suggested for establishing clinical validity. It is hoped that these insights will encourage further progress toward development of in vitro tests that are validated against clinical performance and/or by producing clinically validated failure or damage mechanisms. MATERIALS AND METHODS: Published shear and tensile bond data (macro and micro) is examined in light of published finite element analyses (FEA). This data is subjected to a Weibull scaling analysis to ascertain whether scaling is consistent with failure from the bonded interface or not. Wear tests results are presented in light of the damage mechanism(s) operating. Quantitative wear data is re-examined as being dependent upon contact pressure. Load-to-failure test results are re-analyzed by calculating contact stresses at failure for 119 tests from 54 publications over more than 25 years. RESULTS: FEA analyses and reported failure modes (adhesive, mixed, cohesive) are consistent with failure not involving interfacial "shear stresses" as calculated in published work. Weibull scaling clearly suggests failure involving external surfaces of specimens, not interfacial origins. Contact stresses (pressures) are clearly an important variable in wear testing and are not well-controlled in published work. Load-to-failure tests create damage not seen clinically due to excessively high contact stresses. Most contact stresses in the 119 tests examined were calculated to be between 1000MPa and 5000MPa, whereas clinical contact stresses at wear facets have been measured not to exceed 40MPa. CONCLUSIONS: Our community can do a much better job of designing in vitro tests that more closely simulate clinical conditions, especially when contact is involved. Journals are encouraged to thoughtfully consider a ban on publishing papers using bond tests and load-to-failure methods that are seriously flawed and have no clinical relevance.

Two imaging techniques for 3D quantification of pre-cementation space for CAD/CAM crowns.

OBJECTIVES: Internal three-dimensional (3D) "fit" of prostheses to prepared teeth is likely more important clinically than "fit" judged only at the level of the margin (i.e. marginal "opening"). This work evaluates two techniques for quantitatively defining 3D "fit", both using pre-cementation space impressions: X-ray microcomputed tomography (micro-CT) and quantitative optical analysis. Both techniques are of interest for comparison of CAD/CAM system capabilities and for documenting "fit" as part of clinical studies. METHODS: Pre-cementation space impressions were taken of a single zirconia coping on its die using a low viscosity poly(vinyl siloxane) impression material. Calibration specimens of this material were fabricated between the measuring platens of a micrometre. Both calibration curves and pre-cementation space impression data sets were obtained by examination using micro-CT and quantitative optical analysis. Regression analysis was used to compare calibration curves with calibration sets. RESULTS: Micro-CT calibration data showed tighter 95% confidence intervals and was able to measure over a wider thickness range than for the optical technique. Regions of interest (e.g., lingual, cervical) were more easily analysed with optical image analysis and this technique was more suitable for extremely thin impression walls (<10-15µm). Specimen preparation is easier for micro-CT and segmentation parameters appeared to capture dimensions accurately. CONCLUSIONS: Both micro-CT and the optical method can be used to quantify the thickness of pre-cementation space impressions. Each has advantages and limitations but either technique has the potential for use as part of clinical studies or CAD/CAM protocol optimization.