In vivo validation of the historical in vitro thermocycling temperature range for dental materials testing

Abstract

In dental research, restorative materials have been regularly subjected to alternating in vitro thermal stress in investigations since the 1950s, in order to simulate in vivo alternating temperature stress and to artificially stress them in vitro. The provocation temperature is mostly 5 degrees C for cold provocation, and 55 degrees C for hot provocation. These temperatures are determined quite arbitrarily based on very few examinations in vivo. Extensive temperature data for the approximal space of teeth, which is decisive for the success of fillings adhesively attached to dentin, has so far not been addressed. The objective of this study was to examine the interproximal temperature characteristics created in the space of all teeth in vivo with thermal alternating stress, and therefore to validate the in vitro standardized thermal alternating stress of 5-55 degrees C. Fifteen study participants with healthy teeth were used to determine the temperature in each inter-dental space, resulting from hot/cold provocation in the upper and lower jaw, from the central incisor to the second molars. This was performed by a thermal element (cable sensor GTF 300, Greisinger Electronic GmbH, Regenstauf, Germany). The temperature sensor was attached with dental floss into the interproximal space and the temperature was recorded by the computer. The participants in the pilot test had to state when they were able to sip an 85 degrees C hot drink. That particular temperature value was taken for hot provocation as maximum temperature reference. Cold ice water (0 degrees C) was used for cold provocation as minimum temperature reference. The respective recordings with a total of 14 measurements for each individual were performed simultaneously in the upper and lower jaw. The study participants were to start with hot provocation, followed by cold provocation. This cycle was repeated at least once with an individual dwell time. The highest recorded approximal space temperature was 52.8 degrees C in the lower jaw, between the first and the second premolar. The lowest temperature of 13.7 degrees C was recorded in two participants in the upper jaw, between the 1st and 2nd incisor, and between the two central incisors. The mean of the maximum temperatures was 43.8+/-3.7 degrees C, and the mean of the minimum temperatures 24.2+/-4.6 degrees C. The mean initial temperature was 35.2+/-1.3 degrees C. None of the recordings reached either the upper threshold (55 degrees C) or the lower threshold (5 degrees C). This study showed that the actual thermal stress in the interproximal space of teeth is slightly lower than the one used in in vitro examinations. For class II cavities, most of the alternating temperature stress limits selected at 5-55 degrees C cover the actually occurring temperature interval quite well.

Influence of Curing Rate of Resin Composite on the Bond Strength to Dentin

“…[20][21]32 Thermocycling may still be considered a valuable means to stress the adhesive interface. 19 It must be noted, however, that the influence of thermocycling on bond strength may depend on the specific test set-up or adhesive used. 20,32 …”

“…Thermocycling is a widely accepted artificial mode of aging used to simulate alternating in vivo temperatures. 19 Although thermocycling does not always influence the mechanical properties of resin composite materials, it may result in the decreased bonding of resin composite to enamel 20 or dentin, particularly when increasing the number of cycles. 21 Since the curing rate and curing mode may affect the polymer structure, [22][23][24] thermocycling may have an influence on shear bond strength.…”

The effect of preparation order on the crystal structure of yttria-stabilized tetragonal zirconia polycrystal and the shear bond strength of dental resin cements

“…2b). All specimens were stored in distilled water for 24 h at 37 • C, followed by thermocycling (5000 cycles at 5 • C and 55 • C, with a 30 s dwelling time in each bath and 2 s of transferring time) [23].…”

Effect of Thermocycling on Nickel Release from Orthodontic Arch Wires: an In Vitro Study

“…Corrosion, the graded degradation of materials by electrochemical attack, is of concern particularly when orthodontic appliances are placed in the hostile electrolytic environment provided by the human mouth [36]. Investigators have shown that thermocycling regimen comprising a minimum of 500 cycles in water between 5 and 55°C is an appropriate artificial aging test [26,35]. The results of the current study revealed that thermocycling has a significant effect on the release of Ni from orthodontic appliances.…”

“…Thermocycling process has been introduced as an artificial aging methodology [35], which is utilized for evaluating the influence of thermal stresses on dental materials. Orthodontic appliances are subject to larger temperature variations than most other parts, coping with ice-cold temperatures (0°C) through to hot coffee and soup (60°C).…”