Temperature mediated coefficient of dimensional change of dental tooth-colored restorative materials.
OBJECTIVE
Restorative materials are constantly subjected to thermal challenges in the oral environment. Such challenges, if significant, can have unfavorable effects on the margins of restorations in terms of the seal between the material and the tooth structure. This study aimed to assess the Coefficient of Dimensional Change (CDC) of tooth-colored restorative materials.


METHODS
Five cylindrical specimens (6 mm x 4 mm) were made (using a stainless steel mold) of each of the following: the compomers Dyract AP (Dentsply), or F2000 Compomer (3M); a resin composite, Z100 MP (3M); a resin-modified glass-ionomer, Fuji II LC Capsule (GC); the conventional glass-ionomers Fuji IX GP Fast (GC) or Ketac Fil Aplicap (ESPE). The light-cured materials were cured for 40 s at each end and also around the 'waist' after removal from the mold. All specimens were stored in distilled water at 37 degrees C for 24 h, before testing. The CDC for each specimen was determined using a thermal mechanical analyser, by heating the sample from 25 to 70 degrees C at 10 degrees C min(-1).


RESULTS
All materials except the glass-ionomers showed expansion on heating. The temperature response was non-linear in each case and values of CDC were therefore calculated between 25 and 50 degrees C and between 50 and 70 degrees C. The mean values of CDC (x 10(-6) degrees C(-1)) between 25 and 50 degrees C were Dyract: 83.4, F2000: 66.1, Z100: 64.5. The glass-ionomer materials showed contraction, which was non-linear in nature and was associated with a loss of water on heating. ANOVA and Tukey's pairwise comparisons of mean CDC values for the other materials indicated significant differences between all pairs of materials.


CONCLUSIONS
The compomers and resin composite tested had similar values of CDC. The conventional and resin-modified glass-ionomers contracted on heating. For one glass-ionomer the dimensional change on heating was minimal as thermal expansion appeared to be compensated by water loss.
Sidhu
Sharanbir K
SK
Restorative Dentistry, School of Dental Sciences, University of Newcastle, Framlington Place, Newcastle upon Tyne NE2 4BW, UK. s.k.sidhu@ncl.ac.uk
Carrick
Thomas E
TE
McCabe
John F
JF
D000704:Analysis of Variance; D020770:Compomers; D003188:Composite Resins; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis; D005899:Glass Ionomer Cements; D006358:Hot Temperature; D008422:Materials Testing; D018709:Statistics, Nonparametric
D020770:Compomers; D003188:Composite Resins; D005899:Glass Ionomer Cements