Enhancing Dentin Bonding of Fifth-Generation Adhesive Through Experimental 10-MDP Primer: A Pilot Study on Human Teeth

Background:The study aimed to evaluate the effectiveness of an experimental primer (EP) based on the 10-MDP monomer when used with the fifth-generation adhesive system.Methods and Results: Tests were performed on tooth samples from wisdom teeth and premolars extracted for orthodontic purposes.The EP consisted of 10-MDP monomer (10%), ethanol (40%), propanol-2 (30%), water (18%), and a camphorquinone-based photoinitiator system (2%).The pH of the EP was 2.4.The adhesive resin of the fifth-generation OptiBond Solo Plus (OSP) and the universal composite Herculite XRV were the materials of choice.Two adhesive techniques were tested: the traditional total-etch technique with OSP application, and the optional technique with sequential EP and OSP applications using a selective-etch approach.Adhesive bond strength was assessed in two groups using the ultra-test technique (Ultradent Products, Inc., USA).All samples in each group underwent two sequential shear bond strength (SBS) tests.The quality of the resin composite adhesion was assessed on four specimens using an FE-SEM (Thermo Fisher Scientific Apreo 2S LoVac).Microleakage assessment was made on 10 teeth.In each tooth, two artificial cavities of similar size were prepared.Fillings were placed using two techniques in each tooth.Depth of dye penetration at tooth-composite interface was assessed using nonparametric scores.The phase composition of the dentin surface was assessed on six tooth samples divided into three groups of two using thin-film X-ray diffraction (TF-XRD).Samples from the control group were used for XRD of the dentin surface.Samples of Group 1 were used to apply EP to the dentin surface; samples of Group 2 were used for sequential application of EP and OSB to the dentin surface.A significant difference of more than three times (P=0.000)was observed between the SBS values of the first and second tests in samples from Group 1 compared with those from Group 2. SEM of the filling-to-dentin interface in samples with sequential application of EP and OSP using a selective etch approach showed a more uniform hybrid layer than with OSP application with the total-etch technique.Microleakage analysis of the dentin-composite interface revealed a significantly higher dye penetration rate in samples with the traditional OSP application.The presence of the 10-MDP calcium salt peak at diffraction angle of 2=2.54 after sequential application of EP and OSP corresponded to the longest d-spacing (3.48 nm) of the nanolayered structure on the surface of tooth dentin.

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