Mechanical behaviors of dental class V restorations under occlusal loading

摘要

Dental class V cavities are common tooth lesions but their failure rates are high due to complicated margin locations on enamel and dentin and occlusal loading The occlusal force leads to stress at the resin-tooth interfaces which may cause marginal and interfacial debonding This study is aimed to investigate the effects of restorative materials on deformation stress distributions and debonding of class V composite restorations under mechanical loading by an experimental-numerical analysis Forty-eight premolars were collected Each tooth was prepared with one box-cavity These teeth were divided into six groups (n=8) to receive different composite material restorations: a nanofill composite Filtek Z350 filling (Z350); a packable composite Filtek P60 filling (P60); Filtek Z350 filling with a flowable composite (Filtek Z350 Flowable) lining (Z350F); P60 filling with Filtek Z350 Flowable lining (P60F); and two bulkfill composite filling FB and SDR The elastic modulus of these five composites were measured by dynamic material analysis (DMA) A mechanical load was applied on the buccal cusps of the restored teeth During two-step loading to 250N and 500N the acoustic emission (AE) sensor recorded the signal of interfacial debonding and a CCD camera captured their deform images A digital-image-correlation (DIC) program Vic-2990 was used to calculate the full-field deformation A corresponding finite element analysis (FEA) simulated the loading by a static structural module accordingly to analyze the stress distribution The elastic moduli of P60 Z350 Z350 Flowable Filtek Bulkfill and SDR were 13 4 8 8 4 5 5 5 and 7 GPa respectively In the displacement analysis P60 showed the smallest y-displacements on the top and bottom margins but great x-displacements on the axial margin FB showed the greatest y-displacements under both 250N and 500N In the strain analysis P60 showed less y-strain while Z350 Z350F and P60F showed increased y-strain on the bottom area FB and SDR showed uniformly great y-strain (0 003-0 005) Z350 showed greater shear strain on the bottom margin while FB showed the greatest shear strain on the axial margin The lined groups showed more AE hits than the unlined groups and the FB showed the most hits FEA showed that the flowable lining could decrease the principal stress on the tooth-composite interface The highest von-Mises stress and maximum shear stress located close to cervical region With these results P60 showed less horizontal deformation low shear stress and debonding Flowable linings buffered stress only in Z350F but increased AE hits compared to unlined groups Bulk fill composites presented various responses but could not sustain the large force on class V restorations

獎項日期	2015 12月 15
原文	English
監督員	Terry Yuan-Fang Chen (Supervisor)