Four-year clinical performance of a lithia disilicate-based core ceramic for posterior fixed partial dentures.
OBJECTIVE
The objective of this research was to test the hypothesis that 3-unit fixed partial dentures (FPDs) made from a moderately high-strength core ceramic will adequately resist fracture in posterior regions if fabricated with a minimal connector size of 4 mm.


METHODS
Thirty ceramic FPD core frameworks were prepared using a hot-pressing technique and a lithia disilicate-based core ceramic. The maximum occlusal force was measured for each patient prior to tooth preparation. Connector heights and widths were measured for each FPD. Patients were recalled annually after cementation for 4 years and evaluated using 11 clinical criteria. All FPDs were examined by 2 independent clinicians, and rankings for each criterion were made from 1 to 4 (4 = excellent; 1 = unacceptable).


RESULTS
The fracture rate was approximately 3% per year, and the proportion of good overall ratings in the nonfractured FPDs was reduced by more than 6% per year, where a good overall rating was defined to be a rank of 3 or 4 in all 11 criteria. There was little evidence that the use of either resin-reinforced glass-ionomer cement (Protec CEM) or dual-cure resin cement (Variolink II) made any difference in terms of fracture rate or overall rating (P= .30, .63, .97, and .71 for the 4 years, respectively). From a fracture resistance perspective, 4 of the 30 ceramic FPDs fractured within the 4-year evaluation period, representing an 86.7% success rate. Another FPD was replaced because of a caries lesion on 1 abutment tooth away from the margin. One FPD fracture was associated with the subject having the greatest occlusal force (1,031 N). The other 2 fractures were associated with FPDs that exhibited connector heights of less than 3 mm. All criteria were ranked good to excellent during the 4-year period for the remaining FPDs.


CONCLUSIONS
Fractured FPDs were associated with a connector height of less than 4 mm; thus, the hypothesis was accepted.
Esquivel-Upshaw
Josephine F
JF
Department of Prosthodontics, University of Florida College of Dentistry, Gainesville, Florida 32610, USA. jesquivel@dental.ufl.edu
Young
Henry
H
Jones
Jack
J
Yang
Mark
M
Anusavice
Kenneth J
KJ
D000328:Adult; D001732:Bite Force; D002484:Cementation / Q000379:methods; D003442:Crowns; D000044:Dental Abutments; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003779:Denture Design; D003830:Denture, Partial, Fixed; D005260:Female; D005500:Follow-Up Studies; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008297:Male; D008875:Middle Aged; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D016019:Survival Analysis; D016896:Treatment Outcome
D005899:Glass Ionomer Cements; C091610:Protech glass ionomer cement; D019279:Resin Cements; C493120:lithia disilicate; D003776:Dental Porcelain; C103502:Variolink