Abstract
Tooth-coloured plastic dental fillings secured by adhesives to tooth structures are widely used to fix decayed teeth. Whereas laboratory tests demonstrate rapid deterioration of the ability of the adhesives to stick to dentine, clinical studies show that these fillings are relatively durable. This discrepancy suggests that the parameters used for simulating bond degradation in the laboratory setting do not correlate well with clinical outcomes. The present study examined the long-term tensile bond strength of resin composite fillings performed in real life and under different laboratory-simulated bonding conditions to identify parameters that may be used to forecast the durability of adhesive bonds created in dentine. Fillings placed in vivo were subjected to different periods of intraoral function. In vitro specimens were bonded based on whether simulated pulpal pressure (SPP) or thermomechanical cycling was implemented, and how long the completed fillings were stored in water. Thermomechanical cycling used in combination with long-term water ageing are useful in forecasting the decline in strength of resin-dentine bonds created in vivo. These parameters should be adopted for future evaluations. Conversely, the use of SPP does not appear to be a significant parameter in the simulation of long-term clinical deterioration of bond integrity.
Highlights
It is not always possible to conduct clinical trials on adhesive plastic tooth fillings due to operator variations, lack of patient cooperation and cost constraints from the manufacturers’ perspective
Three null hypotheses were tested: 1) the time of intraoral functioning has no adverse effect on the bond strength to dentine in fillings performed in vivo; 2) the use of simulated pulpal pressure (SPP), thermomechanical ageing and an extended storage period for in vitro bond testing have no adverse effect on the bond strength to dentine; 3) In vitro testing conditions are incapable of reproducing the long-term dentine bond strength of plastic fillings performed in vivo after functional challenges
Bond strength tests are helpful for predicting clinical outcomes, the exact laboratory testing conditions that are useful in reflecting clinical outcome had not been elucidated
Summary
It is not always possible to conduct clinical trials on adhesive plastic tooth fillings due to operator variations, lack of patient cooperation and cost constraints from the manufacturers’ perspective. Far from being the gold standard, laboratory testing has frequently been utilised to fulfil pre-launching criteria of new dental adhesive products These in vitro tests should faithfully reproduce the oral conditions to provide greater reliability in predicting clinical performance[20]. Whereas laboratory tests frequently demonstrate rapid deterioration of the ability of the adhesives to stick to dentine[6], clinical evaluations of plastic fillings indicated that the fillings appear to be relatively durable[19,21,22]. A miniature technique for challenging the adhesive joint to failure under tension, known as the microtensile bond strength (MTB) test, was used for testing standardised segments obtained from the filled cavities[23] Both short-term (24 hours) and long-term (6 months) bond strengths of those fillings to dentine were evaluated. Three null hypotheses were tested: 1) the time of intraoral functioning has no adverse effect on the bond strength to dentine in fillings performed in vivo; 2) the use of simulated pulpal pressure (SPP), thermomechanical ageing and an extended storage period for in vitro bond testing have no adverse effect on the bond strength to dentine; 3) In vitro testing conditions are incapable of reproducing the long-term dentine bond strength of plastic fillings performed in vivo after functional challenges
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