title: A practice-based clinical evaluation of the survival and success of metal-ceramic and zirconia molar crowns: 5-year results.
abstract: This practice-based study evaluates the survival and success of conventionally luted metal-ceramic and zirconia molar crowns fabricated by using a prolonged cooling period for the veneering porcelain. Fifty-three patients were treated from 07/2008 to 07/2009 with either metal-ceramic crowns (MCC) or zirconia crowns (ZC). Forty-five patients (26 female) with 91 restorations (obser-vational period: 64.0 ± 4.8 months) participated in a clinical follow-up examination and were included in the study. Estimated cumulative survival (ECSv), success (ECSc) and veneering ceramic success (ECVCSc) were calculated (Kaplan-Meier) and analysed by the crown fabrication technique and the position of the restoration (Cox regression model) (P < 0.05). Five complete failures (MCC: 2, ZC: 3) were recorded (5-year ECSv: MCC: 97.6%, (95% confidence interval (95%-CI): [93%; 100%]/ZC: 94.0%, (95%-CI): [87%; 100%]). Of the MCCs (n = 41), 85.0%, [95%-CI: (77%; 96%)] remained event-free, whereas the ECSc for the ZCs (n = 50) was 74.3% (95%-CI): [61%; 87%]. No significant differences in ECSv (P = 0.51), ECSc (P = 0.43) and ECVCSc (P = 0.36) were detected between the two fabrication techniques. Restorations placed on terminal abutments (n = 44) demonstrated a significantly lower ECVCSc (P = 0.035), (5-year VCF-rate: 14.8%) than crowns placed on tooth-neighboured abutments (n = 47), (5-year VCF-rate: 4.3%). In the present study, zirconia molar crowns demonstrated a 5-year ECSv, ECSc and ECVCSc comparable to MCCs. Irrespective of the fabrication technique, crowns on terminal abutments bear a significantly increased risk for VCFs. Clinical investigations with an increased number of restorations are needed.
authors.affiliation: Private Practice, Hanau, Germany.|Department of Prosthodontics, Georg-August-University, Göttingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Rinke
authors.affiliation: Department of Medical Statistics, Georg-August-University, Göttingen, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Kramer
authors.affiliation: Department of Prosthodontics, Georg-August-University, Göttingen, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Bürgers
authors.affiliation: Department of Prosthodontics, Georg-August-University, Göttingen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Roediger
mesh_terms: D000328:Adult; D003442:Crowns / Q000009:adverse effects*; D003764:Dental Materials / Q000009:adverse effects*; D003776:Dental Porcelain / Q000009:adverse effects*; D017267:Dental Prosthesis Design / Q000009:adverse effects*; D019232:Dental Restoration Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008963:Molar; D016896:Treatment Outcome; D015040:Zirconium / Q000009:adverse effects*
chemical_list: D003764:Dental Materials; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
keywords: clinical trial; crown; metal-ceramic; success rate; veneering ceramic; zirconia