Relationship between composite contraction stress and leakage in Class V cavities.
OBJECTIVE
The purpose of this study was to determine the relationship between polymerization contraction stress and leakage in Class V composites.


METHODS
A microfill (Heliomolar) and two minifill hybrid composites (Herculite, Z100) were tested. Maximum contraction stress (n = 5) for the composites was evaluated in a MTS machine at a C-factor of 3 (ratio of bonded to non-bonded surface area). Composite was placed in the gap between the surfaces of glass stubs that had been air abraded, silane treated and coated with a layer of resin adhesive. Specimens were light-cured through the top glass stub for 60 seconds and maximum force was recorded during the first 10 minutes. Leakage (n = 10) was evaluated by cutting cylindrical cavity preparations with all enamel margins (C-factor = 3) in bovine incisors. The cavities were treated with two layers of Scotchbond MP adhesive. Composites were applied in one increment, light-cured at the same intensity used in the stress tests, and immediately finished on SiC paper. After 1 day in water, the restorations were placed in silver nitrate, developed and evaluated as a single cross-section (2-D) and multiple cross-sections (3-D) for leakage: 0 (none), 1 (minimal leakage), 2 (to the DEJ), 3 (to line angle), 4 (along the pulpal wall).


RESULTS
The maximum stresses (MPa) recorded were lowest for Heliomolar (7.0 +/- 0.4), intermediate for Herculite (10.5 +/- 0.6) and greatest for Z100 (11.6 +/- 1.3). 3-D leakage was as follows: Heliomolar--two specimens scored 1, seven scored 2 and one scored 3; Herculite--six scored 2 and four scored 3; Z100--eight scored 3 and two scored 4. The Kruskal-Wallis test showed a significant difference in leakage for the three composites (P < 0.05), and leakage was greater when evaluated in 3-D. The leakage results correlated with the stress values, i.e. composites with higher contraction stress showed more extensive marginal leakage.
Ferracane
Jack L
JL
Department of Biomaterials and Biomechanics, Oregon Health & Science University, 611 S.W. Campus Drive, Portland, Oregon 97239, USA. ferracan@ohsu.edu
Mitchem
John C
JC
D000180:Acrylic Resins / Q000737:chemistry; D000818:Animals; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D002417:Cattle; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding; D003737:Dental Cavity Preparation / Q000145:classification*; D003763:Dental Leakage / Q000145:classification*; D003775:Dental Polishing; D044367:Phase Transition; D011140:Polyurethanes / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D017655:Silicon Compounds / Q000737:chemistry; D012822:Silicon Dioxide; D016622:Silver Staining; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D015040:Zirconium
D000180:Acrylic Resins; D017554:Carbon Compounds, Inorganic; C029012:Composite Dental Resin; D003188:Composite Resins; C513708:Heliomolar; D011140:Polyurethanes; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D012821:Silanes; D017655:Silicon Compounds; C083568:Z100 composite resin; C065770:Herculite XR; D012822:Silicon Dioxide; D015040:Zirconium; C022088:silicon carbide