A study on the fracture strength of collarless metal-ceramic fixed partial dentures.
OBJECTIVE
The objective of this study was to evaluate fracture strength of collarless metal-ceramic FPDs according to their metal coping designs.


METHODS
Four different facial margin design groups were investigated. Group A was a coping with a thin facial metal collar, group B was a collarless coping with its facial metal to the shoulder, group C was a collarless coping with its facial metal 1 mm short of the shoulder, and group D was a collarless coping with its facial metal 2 mm short of the shoulder. Fifteen 3-unit collarless metal-ceramic FPDs were fabricated in each group. Finished FPDs were cemented to PBT (Polybutylene terephthalate) dies with resin cement. The fracture strength test was carried out using universal testing machine (Instron 4465, Instron Co., Norwood MA, USA) at a cross head speed of 0.5 mm/min. Aluminum foil folded to about 1 mm of thickness was inserted between the plunger tip and the incisal edge of the pontic. Vertical load was applied until catastrophic porcelain fracture occurred.


RESULTS
The greater the bulk of unsupported facial shoulder porcelain was, the lower the fracture strength became. However, there were no significant differences between experimental groups (P > .05).


CONCLUSIONS
All groups of collarless metal-ceramic FPDs had higher fracture strength than maximum incisive biting force. Modified collarless metal-ceramic FPD can be an alternative to all-ceramic FPDs in clinical situations.
Department of Prosthodontics, Graduate School, Seoul National University, Seoul, Korea.
Jong-Wook
JW
Yoon
Sung-Hun
SH
Kim
Jai-Bong
JB
Lee
Jung-Suk
JS
Han
Jae-Ho
JH
Yang
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