Fatigue behavior of dental resin composites: flexural fatigue in vitro versus 6 years in vivo.
OBJECTIVE
To evaluate fatigue behavior of direct resin composite restorations (Tetric Ceram vs. Grandio) in vitro and in vivo over an observation period of 6 years.


METHODS
For the in vitro part, Young's moduli (YM) were calculated and both initial (FS: flexural strength) and fatigue flexural strength (FFL: flexural fatigue limit) were evaluated in a four-point bending setup (n = 15) in distilled water at 37°C. For the in vivo part, 30 patients received 68 direct resin composite restorations of the same materials (Grandio bonded with Solobond M; Tetric Ceram bonded with Syntac). Patients revealed a minimum of two different class II restorations in different quadrants. Epoxy replicas of restored teeth were analyzed under a scanning electron microscope (SEM) at 30× magnification for fatigue characteristics, and 11 selected restorations per group were assessed for marginal fatigue characteristics at 200×.


RESULTS
In vitro, YM was 15.7 GPa (Grandio) and 8.7 GPa (Tetric Ceram; p < 0.05), FS was 115.0 MPa (Grandio) versus 101.5 MPa (Tetric Ceram; p > 0.05), and FFL was 63.0 MPa (Grandio) versus 44.3 MPa (Tetric Ceram; p < 0.05). In vivo, no significant difference in fatigue behavior (cracks, chippings) was evaluated for the different materials under investigation. However, marginal breakdown was more pronounced under the SEM for Tetric Ceram (7.9% vs. 4.8% for Grandio; p < 0.05), but without being clinically relevant. SEM analysis exhibited distinct wear patterns after 6 years with no significant differences among materials as well.


CONCLUSIONS
Despite higher in vitro values for YM, FS, and FFL for Grandio, clinical outcome for both resin composite materials over 6 years of clinical service was similar. Higher FFLs in vitro seem to be related to less marginal composite fractures in vivo but without any influence on clinical outcome until the 6 years recall.
College of Dentistry, University of Tennessee, Memphis, Tennessee 38163, USA.
Franklin
F
Garcia-Godoy
Roland
R
Frankenberger
Ulrich
U
Lohbauer
Albert J
AJ
Feilzer
Norbert
N
Krämer
D000180:Acrylic Resins / Q000737:chemistry*; D000328:Adult; D001672:Biocompatible Materials / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D055119:Elastic Modulus; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008855:Microscopy, Electron, Scanning / Q000379:methods; D008875:Middle Aged; D015233:Models, Statistical; D011140:Polyurethanes / Q000737:chemistry*; D011312:Pressure; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014070:Tooth / Q000502:physiology
D000180:Acrylic Resins; D001672:Biocompatible Materials; C029012:Composite Dental Resin; D003188:Composite Resins; C509998:Grandio; D011140:Polyurethanes; C121818:Tetric ceram