Monomer-to-polymer conversion and micro-tensile bond strength to dentine of experimental and commercial adhesives containing diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide or a camphorquinone/amine photo-initiator system.

OBJECTIVES To compare the degree of conversion (DC) of adhesives initiated by diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) or a camphorquinone/tertiary amine system (CQ/Amine) as well as their 'immediate' micro-tensile bond strength (μTBS) to bur-cut dentine. METHODS DC of Scotchbond Universal ('SBU'; 3M ESPE), its experimental counterpart containing TPO as photo-initiator system, an experimental G-aenial Bond ('Ga-B'; GC) adhesive formulation, and an experimental LUB-102 adhesive formulation ('LUB', Kuraray Noritake), containing as photo-initiatior system either 2wt% CQ along with 2wt% tertiary amine ('SBU_CQ/Amine'; 'Ga-B_CQ/Amine'; 'LUB_CQ/Amine'), or 2wt% TPO ('SBU_TPO'; 'Ga-B_TPO'; 'LUB_TPO'), was determined using Fourier-transform infrared spectroscopy (FTIR), after being cured with a dual-wavelength light-curing unit (bluephase 20i, Ivoclar Vivadent). The same adhesive formulations were applied to bur-cut mid-coronal dentine of intact human molars, and subjected to a μTBS test after 1-week water storage. Besides being applied following a self-etch (SE) application mode, the adhesive formulations SBU_CQ/Amine and SBU_TPO were also applied following an etch-and-rinse (E&R) mode, this both for DS and μTBS measurement. RESULTS No significant difference in DC was found for any of the adhesive formulations, except for SBU_CQ/Amine_SE and SBU_TPO_SE. For both SBU formulations, a significantly higher DC was reached for the E&R than the SE approach. Regarding μTBS, no significant differences were recorded, except for the significantly higher μTBS measured for SBU_CQ/Amine_E&R and SBU_TPO_E&R. CONCLUSIONS In self-etch adhesives, the photo-initiator TPO may be used instead of CQ/Amine. The curing and 'immediate' bonding efficiency depended on the application protocol (E&R versus SE), but not on the photo-initiator system. CLINICAL SIGNIFICANCE The photo-initiator TPO may be used in self-etch adhesives instead of CQ/Amine with similar curing and 'immediate' bonding efficiency.

[1]  S. Ban,et al.  Effect of various visible light photoinitiators on the polymerization and color of light-activated resins. , 2009, Dental materials journal.

[2]  A. Santini.  Current status of visible light activation units and the curing of light-activated resin-based composite materials. , 2010, Dental update.

[3]  A. Mine,et al.  Effect of dentin location and long-term water storage on bonding effectiveness of dentin adhesives. , 2011, Dental materials journal.

[4]  R. Hickel,et al.  Can CQ be completely replaced by alternative initiators in dental adhesives? , 2008, Dental materials journal.

[5]  M. Radišić,et al.  Mathematical modeling of cross-linking monomer elution from resin-based dental composites. , 2013, Journal of biomedical materials research. Part B, Applied biomaterials.

[6]  W. D’hoore,et al.  Concise Review Biomaterials & Bioengineering: Meta-analytical Review of Factors Involved in Dentin Adherence , 2001, Journal of dental research.

[7]  P. Marquis,et al.  Cure width potential for MOD resin composite molar restorations. , 2008, Dental materials : official publication of the Academy of Dental Materials.

[8]  S. Inoue,et al.  New concept of resin-dentin interfacial adhesion: the nanointeraction zone. , 2006, Journal of biomedical materials research. Part B, Applied biomaterials.

[9]  E. Leite,et al.  Effects of the solvent evaporation technique on the degree of conversion of one-bottle adhesive systems. , 2008, Operative dentistry.

[10]  B. Codan,et al.  Influence of different initiators on the degree of conversion of experimental adhesive blends in relation to their hydrophilicity and solvent content. , 2010, Dental materials : official publication of the Academy of Dental Materials.

[11]  T. Endo,et al.  A review of the development of radical photopolymerization initiators used for designing light-curing dental adhesives and resin composites. , 2010, Dental materials journal.

[12]  F. Rueggeberg,et al.  Molar extinction coefficients and the photon absorption efficiency of dental photoinitiators and light curing units. , 2005, Journal of dentistry.

[13]  V. Miletic,et al.  Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units. , 2012, Journal of dentistry.

[14]  N. Moszner,et al.  Chemical aspects of self-etching enamel-dentin adhesives: a systematic review. , 2005, Dental materials : official publication of the Academy of Dental Materials.

[15]  S. H. Dickens,et al.  Interpretation of bond failure through conversion and residual solvent measurements and Weibull analyses of flexural and microtensile bond strengths of bonding agents. , 2005, Dental materials : official publication of the Academy of Dental Materials.

[16]  S. Demoustier‐Champagne,et al.  A physico-chemical explanation of the post-polymerization shrinkage in dental resins. , 2006, Dental Materials.

[17]  Yong Wang,et al.  Improved degree of conversion of model self-etching adhesives through their interaction with dentine. , 2012, Journal of dentistry.

[18]  M. Bradley,et al.  Degree of conversion and microhardness of TPO-containing resin-based composites cured by polywave and monowave LED units. , 2012, Journal of dentistry.

[19]  Yoshiharu Nakamura,et al.  Effects of functional monomers and photo-initiators on the degree of conversion of a dental adhesive. , 2012, Acta biomaterialia.

[20]  P. Marquis,et al.  Monomer conversion versus flexure strength of a novel dental composite. , 2003, Journal of dentistry.

[21]  H. Lygre,et al.  Identification of organic eluates from four polymer-based dental filling materials. , 2003, European journal of oral sciences.

[22]  M. A. Garrido,et al.  Effect of thermal aging on the tensile bond strength at reduced areas of seven current adhesives , 2012, Odontology.

[23]  P. Lambrechts,et al.  A Critical Review of the Durability of Adhesion to Tooth Tissue: Methods and Results , 2005, Journal of dental research.

[24]  P. Spencer,et al.  Adhesive phase separation at the dentin interface under wet bonding conditions. , 2002, Journal of biomedical materials research.

[25]  P. Lambrechts,et al.  Influence of three specimen fixation modes on the micro-tensile bond strength of adhesives to dentin. , 2007, Dental materials journal.

[26]  S. Prahl,et al.  Curing efficiency of dental resin composites formulated with camphorquinone or trimethylbenzoyl-diphenyl-phosphine oxide. , 2012, Dental materials : official publication of the Academy of Dental Materials.

[27]  C. Vallo,et al.  Effect of different photoinitiator systems on conversion profiles of a model unfilled light-cured resin. , 2007, Dental materials : official publication of the Academy of Dental Materials.

[28]  P. Cesar,et al.  Direct comparison of the bond strength results of the different test methods: a critical literature review. , 2010, Dental materials : official publication of the Academy of Dental Materials.

[29]  J. Ferracane,et al.  Photoinitiator type and applicability of exposure reciprocity law in filled and unfilled photoactive resins. , 2011, Dental materials : official publication of the Academy of Dental Materials.

[30]  P. Lambrechts,et al.  Microtensile bond strength and interfacial characterization of 11 contemporary adhesives bonded to bur-cut dentin. , 2010, Operative dentistry.