Temperature increase beneath etched dentin discs during composite polymerization.
OBJECTIVE
The purpose of this in vitro study was to measure the temperature increase during the polymerization of a composite resin beneath acid-etched or laser-etched dentin discs.


BACKGROUND
The irradiation of dentin with an Er:YAG laser may have a positive effect on the thermal conductivity of dentin. This technique has not been studied extensively.


METHODS
Forty dentin discs (5 mm in diameter and 0.5 or 1 mm in height) were prepared from extracted permanent third molars. These dentin discs were etched with 20% orthophosphoric acid or an Er:YAG laser, and were then placed on an apparatus developed to measure temperature increases. The composite resin was polymerized with a high-intensity quartz tungsten halogen (HQTH) or light-emitting diode unit (LED). The temperature increase was measured under the dentin disc with a J-type thermocouple wire that was connected to a data logger. Five measurements were made for each dentin disc, curing unit, and etching system combination. Differences between the initial and the highest temperature readings were taken, and the five calculated temperature changes were averaged to determine the value of the temperature increase. Statistical analysis was performed with a three-way ANOVA and Tukey HSD tests at a 0.05 level of significance. Further SEM examinations were performed.


RESULTS
The temperature increase values varied significantly, depending on etching systems (p < 0.05), dentin thicknesses (p < 0.05), and curing units (p < 0.05). Temperature increases measured beneath laser-etched discs were significantly higher than those for acid-etched dentin discs (p < 0.05). The HQTH unit induced significantly higher temperature increases than the LED unit (p < 0.05). The LED unit induced the lowest temperature change (5.2°C) in the 1-mm, acid-etched dentin group. The HQTH unit induced the highest temperature change (10.4°C) for the 0.5-mm, laser-etched dentin group.


CONCLUSIONS
The risk of heat-induced pulpal damage should be taken into consideration during the polymerization of composite resin after laser etching when the dentin thickness is less than 0.5 mm.
Department of Operative Dentistry, Gaziantep University, Gaziantep, Turkey.
Emine Sirin
ES
Karaarslan
Asli
A
Secilmis
Mehmet
M
Bulbul
Cihan
C
Yildirim
Aslihan
A
Usumez
D003188:Composite Resins; D045662:Dental Etching; D003804:Dentin / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D053844:Lasers, Solid-State; D010756:Phosphoric Acids / Q000494:pharmacology; D058105:Polymerization; D013696:Temperature
D003188:Composite Resins; D010756:Phosphoric Acids; C030242:phosphoric acid