Thursday, January 15, 2015

Prospective evaluation of zirconia based tooth- and implant-supported fixed dental prostheses: 3-Year results

Journal of Dentistry 2015, 43 (1): 87-93
 
OBJECTIVES:
This prospective clinical study compared the performance of implant-retained (study group) and tooth-retained (control) zirconia based fixed dental prostheses (FDPs) with at least 4 units. The null-hypothesis stated that complication rates in both groups are equally distributed.

METHODS:
 The study included patients in need of one 4- to 6-unit implant- or tooth-retained FDP each. All patients were examined 2 weeks after insertion (baseline) and then at 6 month intervals up to 3 years. At follow-up all restorations were examined for framework fracture, chipping, marginal integrity, surface roughness and biological complications. Kaplan-Meier estimation was used for data analysis.

RESULTS:
  20 patients received tooth-retained and 7 patients implant-retained FDPs. The study was halted early when differences in chipping rates reached a statistically significant level. One FDP in the study group was lost due to implant abutment failure. FDP related chipping rates were 71% in the study group (mean observation time 32 months) and 15% in the control (mean observation time 34 months). Unit (abutment crown/pontic) related chipping rates were 32% in the study group and 6% in the control. Chipping rates differed statistically significant (log-rank test, p<.05). However, all ceramic defects could be corrected by grinding and polishing. No framework fracture was detected.

CONCLUSIONS:
Within the study limitations, survival rates seem satisfactorily in both implant- and tooth retained long-span zirconia based FDPs. However, implant-supported FDPs seem more susceptible to veneering ceramic chippings.

CLINICAL SIGNIFICANCE:
  The high chipping rates found in this study discourage the use of long-span implant-retained FDPs with zirconia frameworks. The study was registered in ClinicalTrials.gov with the ID Number NCT02220764.

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