Effects of surface treatment and joint shape on microtensile bond strength of reattached root dentin segments.
BACKGROUND
An effective bonding technique for reattaching vertical root fracture segments has not yet been established.


OBJECTIVE
The purpose of this study was to investigate the effects of surface treatment and joint shape on bond strength of reattached root dentin segments.


METHODS
Microtensile dentin specimens (n=120, cross-sectional area=1.5 mm2) were obtained from 12 bovine teeth roots, and fractured under a tensile force. The segments of each group (n=6) were reattached by a 4-META/MMA-TBB adhesive resin after different treatments (etching or polishing, a 50-microm or 500-microm gap space, butt or wedge joint). The group with a 50-microm gap space and butt joint, which was not etched or polished, served as the control. After 24 hours of storage in 0.9% normal saline solution or thermal cycling (3000 cycles, 4 degrees C and 60 degrees C), the specimens were fractured in a universal testing machine at a crosshead speed of 1.0 mm/min. The microtensile bond strengths (MPa) were recorded. The bonded interface and fractured surface were observed by SEM (original magnification x 1000). The results were analyzed by a 2-way analysis of variance and the Fisher protected least significant difference post-hoc test (alpha=.05).


RESULTS
Significantly higher bond strengths (P=.0001) were shown for the nonpolished group (9.78 +/- 4.44 MPa) and the etched group (9.31 +/- 1.23 MPa) than for the polished group (fractured before test). The wedge-shaped joint exhibited the highest bond strength (18.57 +/- 3.40 MPa, P=.0017). SEM observations showed that the penetration of resin tags along the oblique dentinal tubules was within the wedge joint.


CONCLUSIONS
Etching and oblique tubule orientation contributed to significantly high bond strength of reattached segments to dentin after vertical root fracture.
Liu
Jia
J
Department of Dental Materials Science, Tokyo Dental College, Chiba, Japan.
Kawada
Eiji
E
Oda
Yutaka
Y
D000134:Acid Etching, Dental; D000704:Analysis of Variance; D000818:Animals; D001896:Boron Compounds / Q000737:chemistry; D002417:Cattle; D001840:Dental Bonding; D003775:Dental Polishing; D003793:Dental Restoration, Permanent / Q000379:methods*; D003804:Dentin / Q000293:injuries* / Q000648:ultrastructure; D008768:Methylmethacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry; D012965:Sodium Chloride; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D013997:Time Factors; D014082:Tooth Fractures / Q000628:therapy*; D019246:Tooth Preparation; D014092:Tooth Root / Q000293:injuries* / Q000648:ultrastructure
C476988:4-methacryloxyethyltrimellitic acid-methylmethacrylate-tributylborane; D001896:Boron Compounds; D008768:Methylmethacrylates; D019279:Resin Cements; D012965:Sodium Chloride