Poliklinik für Zahnärztliche Prothetik

Direktor: Prof. Dr. Gerhard Handel

Fracture resistance of different designed fibre-reinforced composite inlay bridges.

Behr M., Kolbeck C., Rosentritt M., Zappini G., Handel G.

(Department of Prosthetic Dentistry, University of Regensburg, Germany)

Objectives: Veneer fracture or bond failure between framework/veneer are typical failures of fibre-reinforced inlay fixed partial dentures (FPD). This study investigated the fracture resistance of FPDs different framework designs by an eccentric load point on the pontic. The hypothesis was stated that better support of the veneer by the fibre-framework would increase the fracture resistance. Methods: Four groups of Vectris/Adoro were manufactured. Beams (25mm length) made of Vectris pontic (parallel aligned) with a) round (Ø3mm) and b) rectangular (3x3) sectional view were directly veneered using Adoro. c) Round beams like "a)" were modified by coating the beams on the upper side with two layers of the cross-sectioned fibre mat Vectris frame. d) Vectris Pontic fibres were "anatomically" placed in the pontic area and wrapped using Vectris frame. The frameworks were constructed in a vacuum pressure process. All FPDs were mounted in a restrained-end apparatus and thermally cycled and mechanically loaded (TCML: 6000x5°C/55°C; 1.2 Mio x 50N, 1.66Hz). After TCML the FPDs were loaded to fracture. Statistics: One-way ANOVA .

Results: All FPDs surpassed TCML without any visible damage of the veneer or framework. Without enlarging the framework transversally additional cross-sectioned fibre mats alone did not ameliorate the fracture resistance. Round shaped frameworks seemed to be favourable.

Design framework

"a" round

"b" rectangular "c" round+

"d" pontic+ frame

Mean/std. dev. [N] 73766 573158 69493 902149

Fracture lines occurred only in the veneer. The fibre frameworks were never affected.

Conclusions: Anatomically enlarging of the fibre framework at the pontic area (height, width) in order to support the veneer material ameliorates effectively the fracture resistance of fibre-reinforced FPDs.