Efst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinnInngangur: Tilgangur rannsóknarinnar var að kanna samdráttarálag hefðbundinna og magnfyllingar- (e. bulk-fill) plastblendifyllingarefna á tannvef með því að mæla kúspaspennu. Efniviður og aðferðir: Fimmtíu efri góms forjaxlar voru steyptir niður í plasthringi og þeim skipt niður í fimm hópa (n=10). Staðlaður MOD tannskurður var skorinn í hverja tönn. Tveggja þátta sjálfætandi bindiefni (OptiBond XTR) var borið á tannskurðinn og fyllingar gerðar með aðstoð sílíkon matrixu sem hér segir: Filtek Supreme Ultra í tveggja millimetra þykkum lögum (FSUI); Filtek Supreme Ultra með magnfyllingaraðferð (FSUB); SonicFill með magnfyllingaraðferð (SF); SureFil SDR flow með magnfyllingaraðferð, hulið tveggja millimetra þykku lagi af Filtek Supreme Ultra (SDR/FSU); Tetric EvoCeram Bulk Fill með magnfyllingaraðferð (TEBF). Spennunemar (e. strain gages) festir á kinn- og gómafleti mældu kúspaspennu (e. microstrain, µε) í rauntíma á meðan plastblendifyllingarefnum var komið fyrir og þau fjölliðuð. Gögn voru greind með one-way ANOVA prófi og hópar bornir saman með Least-Squares Means prófi. Niðurstöður: Meðal kúspaspenna hópanna (µε±SD) var sem hér segir: FSUI: 730.6±104.8, FSUB: 1264.2±1418.8, SF: 539±75.9, SDR-FSU: 506.3±69.3, TEBF: 624.1±147.4. Hópur FSUI mældist með marktækt meiri kúspaspennu en allir magnfyllingarplastblendihóparnir. Einnig mældist hópur TEBF með marktækt meiri kúspaspennu en hópur SDR/FSU. Nauðsynlegt var að útiloka hóp FSUB frá tölfræðilegri úrvinnslu sökum þess hversu frábrugðin meðaltal og stalaðfrávik hans voru miðað við aðra hópa. Ályktun: Ísetning allra magnfyllingarplastblenda leiddi til marktækt minni kúspaspennu en ísetning hefðbundins plastblendis í tveggja millimetra lögum, þó svo að nokkur breytileiki hafi mælst milli hópa magnfyllingarplastblenda. Notkun hefðbundins plastblendis í magnfyllingaraðferð er varasöm og getur leitt til kúspabrota.Objective: : To compare the polymerization shrinkage stress exerted on tooth structure by bulk-fill and conventional composite resin materials, by measuring cuspal strain. Materials and methods: Fifty extracted maxillary premolars were mounted into ring molds and divided into five groups (n=10). Strain gages were attached to the buccal and lingual cusps. Custom proximal matrices were made using poly vinylsiloxane. Large MOD cavity preparations were performed with the following dimensions: the width of the occlusal isthmus was 40% of the maximum buccopalatal width of the specimen, the pulpal floor was 3.5 mm below the palatal cusp tip, the axial wall was 2 mm high, and the axial wall depth was 25% of the maximum mesiodistal width of the specimen. A 2-step universal self-etching adhesive (Optibond XTR) was applied. Two high-viscosity (SonicFill and Tetric EvoCeram Bulk Fill) and one low-viscosity (SureFil SDR flow) were used for the experimental groups. As a control, a conventional nanofilled composite resin (Filtek Supreme Ultra) was used. The specimens were restored as follows: SonicFill in bulk (SF); SureFil SDR flow in bulk, covered with a 2-mm occlusal layer of Filtek Supreme Ultra (SDR-FSU); Tetric EvoCeram Bulk Fill in bulk (TEBF). As positive and negative control groups, Filtek Supreme Ultra was placed in 2mm increments (FSUI), and in bulk (FSUB), respectively. Strain gages recorded cuspal strain in real-time as the restorations were performed, and mean maximum strain values for buccal and lingual cusps were calculated for each group. Data were subjected to one-way ANOVA and pairwise comparisons using LS Means. Results: Mean maximum strain values and standard deviations (in µε) were: SF: 539±75.9, SDR-FSU: 506.3±69.3, TEBF: 624.1±147.4, FSUI: 730.6±104.8, FSUB: 1264.2±1418.8. A significant difference was found between group FSUI and groups SF, SDR-FSU and TEBF, as well as between groups SDR-FSU and TEBF. The FSUB group was excluded from the statistical analysis due to excessively high mean and standard deviation strain values resulting from cuspal fractures. Conclusions: All tested bulk-fill composites exerted less contraction stress on tooth structure than the incrementally placed conventional composite resin. Shrinkage stress generated by bulk-fill materials seems to be product-dependent. Bulk-filling with conventional composite resins is unpredictable and contraindicated and can have detrimental effects on both the tooth structure and the adhesive interface
