Thermal conductivity through various restorative lining materials.
OBJECTIVE
Traditional teaching has advocated the placement of insulating materials under restorations to protect against 'thermal shock'. Often this involves placement of a thick zinc-oxide eugenol cement lining. The purpose of this in vitro study was to assess the heat transfer through four lining materials and dentine and to relate these findings to the temperature exposures that may be experienced in the oral environment.


METHODS
Two 'traditional' linings, zinc oxide eugenol cement (ZNOE) and calcium hydroxide paste (CAOH), and two more contemporary materials, a resin modified glass polyalkenoate (RMGP) and dentine bonding system (DBS) were studied in addition to dentine itself. Seven samples of each material were tested by utilising a Lees' Disc apparatus. Incorporation of thermocouples allowed heat transfer through the sample to be recorded. Thermal conductivity (J/m/s/ degrees C) was calculated for individual samples and a mean value obtained for each material. One way ANOVA and post hoc Tukey's tests were applied to the data obtained.


RESULTS
In ascending order of thermal conductivity, DBS<CAOH<RMGP<DENTINE<ZNOE. Statistical analysis revealed that the thermal conductivity of DBS was significantly less than RMGP, DENTINE and ZNOE (p<0.05); CAOH was significantly less than DENTINE and ZNOE (p<0.05); RMGP was significantly higher than DBS and significantly less than DENTINE and ZNOE (p<0.05).


CONCLUSIONS
Thermal insulation is not a major consideration in cavity lining and therefore other criteria for selection of a lining material should be applied.
Little
Peter A G
PA
Division of Restorative Dentistry, Leeds Dental Institute, Leeds LS2 9LU, UK.
Wood
David J
DJ
Bubb
Nigel L
NL
Maskill
Stuart A
SA
Mair
Lawrence H
LH
Youngson
Callum C
CC
D000704:Analysis of Variance; D002126:Calcium Hydroxide; D003736:Dental Cavity Lining; D003804:Dentin; D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements; D018709:Statistics, Nonparametric; D013814:Thermal Conductivity; D015035:Zinc Oxide-Eugenol Cement
D017220:Dentin-Bonding Agents; D005899:Glass Ionomer Cements; D019279:Resin Cements; D015035:Zinc Oxide-Eugenol Cement; C067790:Vitrabond; C041330:Scotchbond; D002126:Calcium Hydroxide