Linda Cheng DDS, FAGD, ABGD
Short-term clinical data suggests that zirconia-based fixed dental prostheses (FDPs) may be acceptable restorations in both the anterior and posterior regions with limited data suggesting better clinical outcomes with pressed-to-zirconia technique than conventional layering.
Survival rates of FDPs with zirconia frameworks range from 73.9 percent to 100 percent within 11 prospective cohort studies and one randomized controlled trial over a 2- to 5-year period.
In patients who have zirconia-based FDP restorations, what are the clinical survival and complications rates?
The authors searched PubMed and hand-searched for peer-reviewed clinical studies published in English from January 1999 through June 2011. They included studies in which the zirconia-based FDPs were examined clinically at regular intervals and that provided data on survival, failure, and a description of biological and technical complications with their time of occurrence. They excluded retrospective, in-vitro, partial coverage or implant-supported FDP studies. A final search of the references of the retrieved articles found no additional articles.
The authors identified 12 studies: one randomized controlled trial and 11 prospective cohort studies with follow-up ranging 2-5 years. They grouped the studies by different zirconia-ceramic systems, veneering techniques (layered or pressed), and connector dimensions (>9 mm2 or <9mm2) used to fabricate the FDPs. The FDP framework varied in design (non-anatomic or anatomic) and fabrication technique (fully sintered or partially sintered). Five studies reported 100 percent survival rates, one reported 73.9 percent survival of the framework, and the remaining six studies reported 88.2 to 96.6 percent survival rates. Less than 10 percent had complete failures resulting from framework fracture or loss of retention. Chipping of the veneering porcelain was the most common technical complication, followed by framework fracture, loss of retention and marginal discrepancies. One of the three studies that used the pressed-to-zirconia technique reported no chipping of the veneered ceramic. The included studies reported the main biological complications as secondary caries, abutment teeth fracturing or requiring endodontic treatment, and periodontal disease.
Zirconia FDPs may be viable restorations, but larger studies with more long-term follow-up and standardized parameters of evaluation are needed.
Source of Funding:
Partially supported by NIDCR R25 DE018436
Importance and Context:
Consumer demand for esthetics has led to an increased use of zirconia as a metal-free restorative material that can mimic natural dentition with high mechanical strength and biocompatibility. Based on data reported in the relatively short time (18-20+ years) they have been in use, zirconia-based FDPs may be clinically acceptable restorations.
Strengths and Weaknesses of the Systematic Review:
A major weakness of this systematic review arises from the clinical question that was posed; they did not include a comparison group making it impossible to ascertain the relative survival of zirconia FDPs versus other dental prostheses. The authors used both MeSH terms and key words to search one database for clinical studies in the English language. The review did not disclose the original number of studies screened, if studies were selected independently or how they resolved disagreements to reach a final consensus of reviewing the 12 retrieved studies. They hand-searched but had no personal communication with any of the studies’ authors. Because of the few similarities and comparable procedures between the studies, the authors did not perform a meta-analysis.
Strengths and Weaknesses of the Evidence:
Because of the small sample size in many of the studies as well as differences in the outcome variables and how they were defined, a direct comparison of the selected studies was not possible. The authors did not define and explain how the survival rates were calculated based on the data given. Individual studies were presented in tables by fabrication techniques, size of the studies, and results of the studies. Some of the studies had subjects with more than one FDP restoration. Three studies included long-span FDPs ranging from four to seven units. Only two studies involved FDPs in both the anterior and posterior region, but these did not identify their location in the arch. Not all the studies provided information on the connector size. The design of the framework, zirconia-ceramic system, and veneering technique varied among all 12 clinical studies with no statistical analyses provided in the individual studies.
Implications for Dental Practice:
As technological advances in metal-free restorations such as zirconia evolve and improve, limited data indicate zirconia-based FDPs may be viable alternatives to traditional metal-ceramic FDPs1. The prognosis of zirconia FDPs may be improved by proper tooth reduction that allows for anatomical framework design, and case selection that allows for shorter span2 and sufficient connector size. Larger randomized controlled trials with longer follow-up times and standardized outcome measures distinguishing between survival and success rates are needed to assess zirconia FDPs as a definitive alternative to metal-ceramic FDPs. 1. Lops D, Mosca D, Casentini P, et al. Prognosis of zirconia ceramic fixed partial dentures: a 7-year prospective study. Int J Prosthodont 2012;25:21-3. 2. Schley JS, Heussen N, Reich S, et al. Survival probability of zirconia-based fixed dental prostheses up to 5 yr: a systematic review of the literature. Eur J Oral Sci 2010; 118(5): 443-50.