[Effect of composite restoration on the reinforcement of teeth].
OBJECTIVE
To determine the effect of composite restoration on reinforcement of weakened tooth structure and the possible mechanism.


METHODS
Sixty freshly extracted non-carious maxillary premolars were collected and divided into 6 groups with 10 specimen in each group. MOD cavities (buccolingual width: 2.8 to 3.2 mm; palatal cusp width: 2.0 mm; cusp height: 5.0 mm) were prepared individually. Group 1 was prepared and not restored (control). The other 5 groups were restored with silver amalgam alloy (group 2), Z250 without bonding (group 3), F2000 (group 4), Z250 (group 5) and Z350 nanocomposite (group 6) (3M ESPE) respectively. The fracture resistance of the tested teeth was determined by applying a vertical splitting load through a specially shaped steel rod at a crosshead speed of 1 mm/min. The data were analyzed by ANOVA.


RESULTS
The average fracture resistance of the 6 groups was: (245.29 +/- 39.49) N (group 1), (255.09 +/- 42.14) N (group 2), (267.34 +/- 31.56) N (group 3), (293.90 +/- 33.42) N (group 4), (337.81 +/- 32.63) N (group 5) and (349.08 +/- 32.93) N (group 6). There was no significant difference between the group 1, group 2 and group 3. The fracture resistance of group 4, group 5 and group 6 was higher than that of group 1 and group 2 (P < 0.05). Significant difference was noted between group 5 and group 3 (P < 0.01). The fracture resistance of group 4 was much lower than that of group 5 and group 6 (P < 0.01). No significant difference was found between group 5 and group 6.


CONCLUSIONS
The use of composite increased the fracture resistance of the tooth with an MOD restoration. This effect was related to the adhesive force, polymerization shrinkage stress and the elastic modulus of the composite.
He
Yuan
Y
Department of Cariology and Endodontology, School of Stomatology, Tongji University, Shanghai, China.
Zhao
Shou-Liang
SL
Zhang
Xiao-Lei
XL
Liu
Hai-Jiang
HJ
Zhang
Xiao-Ying
XY
D001641:Bicuspid; D003188:Composite Resins; D019245:Compressive Strength; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D012387:Root Canal Filling Materials; D014082:Tooth Fractures / Q000517:prevention & control
D003188:Composite Resins; D012387:Root Canal Filling Materials