ReviewThermal cycling procedures for laboratory testing of dental restorations
Introduction
Restorative materials are routinely used to obturate dental cavities but later pain, marginal staining and caries often occur. These conditions may be associated with an inadequate cavity seal [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], which is thought to be exacerbated by the effects of thermal changes [18]. Intraoral temperature changes may be induced by routine eating [19], drinking [18], [20], [21], [22], [23], [24] and breathing [25]. Thermal stresses can be pathogenic in two ways. Firstly, mechanical stresses induced by differential thermal changes can directly induce crack propagation through bonded interfaces [18], [26], [27]. Secondly, the changing gap dimensions are associated with gap volume changes which pump pathogenic oral fluids in and out of the gaps. This cyclical flow has been incorrectly termed `percolation' [18].
Laboratory simulations of clinical service are often performed because clinical trials are costly and time-consuming. Thermal cycling is an in vivo process often represented in these simulations, but the regimens used vary considerably and, with few exceptions [28], [29], [30], [31], [32], [33], are always proposed without reference to in vivo observations. Standardization of conditions is necessary to allow comparison of reports. The aim now is to analyse the limited number of reported in vivo observations, summarize previous thermal cycling regimens, and recommend a single substantiable regimen to enable comparability between the results of future tests.
Section snippets
Temperatures recorded in vivo
Some experimental work has attempted to measure the routine limits of temperature change induced by eating and drinking. It is difficult to be precise about such events, as eating and drinking are very erratic habits and large variations are expected between occasions, subjects [22] and locations in the mouth [22], [24]. Air temperature, humidity and air velocity when breathing can radically alter even resting mouth temperature [25]. However, with no thermal load and no mouth breathing,
Temperature regimens previously used for in vitro tests
Thermal cycling is common in tracer penetration, shear bond strength and tensile bond strength tests of dental materials. Some 130 thermal cycling experimental reports from 25 journals with 99 first authors made up the sample reviewed here (Table 2). Of these, 110 involved a tracer penetration test, 26 a shear bond strength test, nine a tensile bond strength test and one recorded enamel crack length. The mean low-temperature point was 6.6°C (range 0–36°C, median 5.0°C). The mean
Investigation of effects of thermal cycling regimens
Various aspects of a thermal cycling regimen have been tested experimentally. The dependent variable was often some measure of tracer penetration. Comparison of cycled and uncycled specimens [56], [62], [69], [77], [83], [86], [109], [121], [128], [167], temperature range [168], number of temperatures in the cycle [57], [69], number of cycles [3], [9], [49], [53], [99], [118], [168], dwell times [57], [69] and whether the cycles were in tracer [9] have all been made. Gage and Clarke [87] used
Recommendations for thermal cycling simulation for in vitro interface testing
Past thermal cycling regimens are almost all unreferenced to in vivo observations [171], despite the general expectation that methods are substantiated in publications. In addition, despite great variations in temperature fluctuations and their tolerance in vivo, a standard thermal cycling simulation is required to allow comparison of materials and procedures between reports. The essential element is ordinarily assumed to be the generation of mechanical stresses and fluid flows. The thermal
The usefulness of thermal cycling
It is to be noted that there is no concrete evidence that failures in practice occur because of thermal stresses, notwithstanding the theoretical expectation. However, the distinction must be made between the equivalent static stress test (i.e., increase steadily until collapse occurs) and fatigue failure, where repeated loading to a stress below the static strength occurs. A less severe test would in fact improve discrimination of this point, so long as stresses were below those which would
Acknowledgements
Financial assistance in the form of a postgraduate studentship for Martin Gale from The University of Hong Kong is gratefully acknowledged. This work was done in partial fulfilment of the requirements for the degree of Ph.D. for the first author.
References (177)
- et al.
The control of marginal microleakage in amalgam restorations using dentin adhesive: a pilot study
Dent Mater
(1987) - et al.
Microleakage: the effect of storage and cycling duration
J Prosthet Dent
(1987) A lining system for composite resin fillings
J Prosthet Dent
(1990)- et al.
The effects of thermal and occlusal stresses on the microleakage of Scotchbond 2 dentinal bonding system
Dent Mater
(1991) Clinical correlations of dentin structure and function
J Prosthet Dent
(1991)- et al.
Fluid exchanges at the margins of dental restorations
J Amer Dent Assoc
(1952) - et al.
A comparison of the physical properties of four restorative resins
J Amer Dent Assoc
(1966) - et al.
Temperature extremes produced orally by hot and cold liquids
J Prosthet Dent
(1992) - et al.
Evaluation of two methods for assessing marginal leakage
J Prosthet Dent
(1981) - et al.
The effect on marginal leakage, in vitro, of curing a composite material at elevated temperatures with or without marginal etching of the cavity
J Dent
(1987)
Thermocycling and dwell times in microleakage evaluation for bonded restorations
Dent Mater
In vivo measurements of thermal diffusion through restorations of various materials
J Prosthet Dent
Thermal conductivity of cement base materials
Dent Mater
The influence of cavity geometry on heat transmission in restored teeth
J Dent
Effect of post preparation on the apical seal
J Prosthet Dent
Comparison of the marginal integrity of in vitro class II composite restorations
J Dent
Marginal leakage of several acid-etch composite resin restorative systems
J Prosthet Dent
Marginal seal of new generation dental bonding agents
J Prosthet Dent
Significance of thermal cycling in microleakage analysis of root restorations
J Dent
A comparison of four in vitro marginal leakage tests applied to root surface restorations
J Dent
In vitro evaluation of two microleakage detection tests
J Dent
Microleakage comparisons of dentin bonding systems with glass ionomer
Dent Mater
The effects of sealants placed over composite resin restorations
J Prosthet Dent
Comparison of four thermocycling techniques
J Prosthet Dent
Bond durability between dentinal bonding agents and tooth structure
J Prosthet Dent
The durability of dental glazes
J Prosthet Dent
Microleakage measurement of selected restorative materials: a new in vitro method
J Prosthet Dent
A comparison between the microleakage of direct and indirect composite restorative systems
J Dent
Effect of a resin lining and rebonding on the marginal leakage of amalgam restorations
J Dent
Effect of bonded amalgam on the fracture resistance of teeth
J Prosthet Dent
Composition, wetting properties and bond strength with dentin of 6 new dentin adhesives
Dent Mater
Marginal closure of composite restorations with the gingival wall in cementum/dentin
J Prosthet Dent
Effect of storage media on microleakage of five dentin bonding agents
Dent Mater
Microleakage and bond strength of resin restorations with various bonding agents
Dent Mater
Quantitative microleakage of some dentinal bonding restorative systems
Dent Mater
Marginal leakage of class II glass ionomer–composite resin restorations: an in vitro study
J Prosthet Dent
A fluorescent dye method for demonstrating leakage around dental restorations
J Dent Res
Prepolymerization of Gluma 4 sealer: effect on bonding
Amer J Dent
Polymeric adhesion to dentin: contrasting substrates
Amer Dent J
Microleakage in three designs of glass ionomer under composite resin restorations
J Oral Rehab
The effect on microleakage of four dentin–enamel bonding systems
Quintessence Int
Microleakage of glass ionomer/composite laminate class V restorations
Amer J Dent
Dentine bonding in perspective
Amer J Dent
Microleakage at gingival margins of class V composite resin restorations rebonded with various low-viscosity resin systems
Quintessence Int
The evaluation of materials: relationship between laboratory investigations and clinical studies
Oper Dent
Penetration around the margins of restorations: 1. Review and experiments
J Can Dent Assoc
The caries status of occlusal amalgam restorations with marginal defects
J Dent Res
In vitro microleakage of class V composite resin restorations with and without light-cured glass–ionomer (polyalkenoate) cement lining
Eur J Pros Rest Dent
A preliminary report on the solubility of decalcified dentine in water
Austral J Dentistry
The heat evolved and temperatures attained during setting of restorative materials
Brit Dent J
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