Anas Aaqel Salim Salim Al-Ani1, Thiago Henrique Scarabello Stape2, Murat Mutluay3, Leo Tjäderhane4, Arzu Tezvergil-Mutluay5. 1. Finnish Doctoral Program in Oral Sciences (FINDOS), University of Turku, Institute of Dentistry, Turku, Finland; Department of Cariology and Restorative Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Adhesive Dentistry Research Group, Biomaterials and Medical Device Research Program, Biocity, Turku, Finland. Electronic address: aassal@utu.fi. 2. Finnish Doctoral Program in Oral Sciences (FINDOS), University of Turku, Institute of Dentistry, Turku, Finland; Department of Cariology and Restorative Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Adhesive Dentistry Research Group, Biomaterials and Medical Device Research Program, Biocity, Turku, Finland. 3. Department of Cariology and Restorative Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Adhesive Dentistry Research Group, Biomaterials and Medical Device Research Program, Biocity, Turku, Finland; Department of Prosthetic Dentistry, Institute of Dentistry, University of Eastern Finland, Kuopio, Finland. 4. Department of Oral and Maxillofacial Diseases, University of Helsinki, Helsinki, Finland; Research Unit of Oral Health Sciences, and Medical Research Center Oulu (MRC Oulu), Oulu University Hospital and University of Oulu, Oulu, Finland; Helsinki University Hospital, Helsinki, Finland. 5. Department of Cariology and Restorative Dentistry, Institute of Dentistry, University of Turku, Turku, Finland; Adhesive Dentistry Research Group, Biomaterials and Medical Device Research Program, Biocity, Turku, Finland; Turku University Hospital, TYKS, University of Turku, Turku, Finland.
Abstract
OBJECTIVE: To understand dimethyl sulfoxide (DMSO) interaction with distinct methacrylate monomer blends and the impact on polymer formation by investigating the combined relationship among degree of resin hydrophilicity, presence of DMSO and specific physico/mechanical properties. METHODS: One hydrophobic (R2) and one hydrophilic (R5) methacrylate-based resins with different monomer compositions were solvated in ascending DMSO concentrations (0, 0.01, 0.1, 1, 5, and 10 w/w %). Neat resins (0 w/w % DMSO) were used as controls. The degree of conversion was determined by Fourier-transform infrared spectroscopy. Polymer crosslinking density was indirectly measured by a modified ethanol-water two-stage solvation technique and the biaxial flexural strength was measured after 24 h and 30 days of water storage at 37 ̊C. Water sorption and solubility were gravimetrically assisted during 28 days of water storage to determine the kinetics of water-polymer interactions. Data were analyzed by ANOVA and Tukey test (α = 0.05). RESULTS: Incorporation of high DMSO-concentrations significantly increased the degree of conversion of all tested formulations, specifically for the hydrophobic resin (p < 0.05). Despite the increase in degree of monomer conversion, higher water sorption/solubility values and lower biaxial flexure strengths were detected as a result of reductions in polymer crosslink density (p < 0.05). In general, low DMSO-concentrations had no impact on the biaxial flexural strength, crosslinking density and water sorption/solubility (p < 0.05). CONCLUSION: DMSO-monomer ratio and monomer composition are critical for new dental methacrylate-based adhesive formulations. High DMSO incorporation hampers physico/mechanical properties of methacrylate bonding resins, albeit to a lesser extend when hydrophilic resins are employed. Nonetheless, DMSO-solvated hydrophobic adhesives extensively outperform their hydrophilic correspondents. DMSO incorporation of 1w/w % may constitute a secure threshold regardless of monomer composition.
OBJECTIVE: To understand dimethyl sulfoxide (DMSO) interaction with distinct methacrylate monomer blends and the impact on polymer formation by investigating the combined relationship among degree of resin hydrophilicity, presence of DMSO and specific physico/mechanical properties. METHODS: One hydrophobic (R2) and one hydrophilic (R5) methacrylate-based resins with different monomer compositions were solvated in ascending DMSO concentrations (0, 0.01, 0.1, 1, 5, and 10 w/w %). Neat resins (0 w/w % DMSO) were used as controls. The degree of conversion was determined by Fourier-transform infrared spectroscopy. Polymer crosslinking density was indirectly measured by a modified ethanol-water two-stage solvation technique and the biaxial flexural strength was measured after 24 h and 30 days of water storage at 37 ̊C. Water sorption and solubility were gravimetrically assisted during 28 days of water storage to determine the kinetics of water-polymer interactions. Data were analyzed by ANOVA and Tukey test (α = 0.05). RESULTS: Incorporation of high DMSO-concentrations significantly increased the degree of conversion of all tested formulations, specifically for the hydrophobic resin (p < 0.05). Despite the increase in degree of monomer conversion, higher water sorption/solubility values and lower biaxial flexure strengths were detected as a result of reductions in polymer crosslink density (p < 0.05). In general, low DMSO-concentrations had no impact on the biaxial flexural strength, crosslinking density and water sorption/solubility (p < 0.05). CONCLUSION:DMSO-monomer ratio and monomer composition are critical for new dental methacrylate-based adhesive formulations. High DMSO incorporation hampers physico/mechanical properties of methacrylate bonding resins, albeit to a lesser extend when hydrophilic resins are employed. Nonetheless, DMSO-solvated hydrophobic adhesives extensively outperform their hydrophilic correspondents. DMSO incorporation of 1w/w % may constitute a secure threshold regardless of monomer composition.