Tertiary amine and tooth mineral hydroxyapatite facilely trigger self-cure of 10-MDP based adhesives

Abstract

The present work aims to investigate if a novel self-cure system, mediated by tertiary amine ethyl 4-(dimethylamino)-benzoate (4E) and tooth mineral hydroxyapatite (HAp), would trigger polymerization of model adhesives based on a popular self-etch monomer, 10methacryloyloxydecyl dihydrogen phosphate (10-MDP). The effect of 4E and HAp contents on degree of conversion (DC), polymerization rate (Rp), and induction period (IP) was investigated. The occurrence of such self-cure phenomenon in adhesives that underwent prior inadequate light cure was also evaluated. Model self-etch adhesives were prepared by using a monomer mixture of 10-MDP with 2-hydroxyethyl methacrylate at1:1 wt. ratio. 4E (0.3-1.3 wt%), and HAp (0.5-2 wt %) were added to the mixture. Benzoylperoxide and N,N-dihydroxyethyl-p-toluidine were used as conventional chemical-cure system, and trimethylbenzoyl-diphenylphosphine oxide as light-curing photoinitiator. The polymerization processes and mechanical properties of model adhesives were evaluated by real time ATR/FT-IR and nanoindentation, respectively. The 4E-HAp system successfully triggered self-cure of 10-MDP based model adhesives. DC, Rp and IP were apparently affected by both 4E and HAp contents. DC of self-cure of the model adhesives was much higher than that of the conventional chemical-cure system. 4E-HAp initiated self-cure further boosted DC to ~100% regardless of prior light exposure, and significantly improved elastic modulus and hardness, thus provided a novel polymerization method to effectively salvage curing of the adhesives after inadequate light-cure.

Bis[2-(Methacryloyloxy) Ethyl] Phosphate as a Primer for Enamel and Dentine

“…Earlier studies by Liu et al (2016) also reported a secondary cure of BMEP via chemical initiation, which enhanced degree of cure within similar systems using FTIR and Raman line mapping. Time-resolved FTIR spectra of 10-MDP–HA interaction reported similar findings, the process being dependent on concentration of HA and acidity of the monomer ( Liu and Wang 2019 ). The formation of tertiary amine-acid complexes is known to initiate radical polymerization, but this self-curing is triggered only in presence of a base such as HA when the acidity is high as in BMEP primers.…”

Evaluation of drug release, monomer conversion and surface properties of resin composites containing chlorhexidine‐loaded mesoporous and nonporous hydroxyapatite nanocarriers

“…Similar to the results of the presented study, in a study conducted by Jalalian et al (2019), HAP at different concentrations was placed in a dental resin, and the researchers reported that concentrations below 7% did not change the DC of the resin, but high concentrations reduced DC. In the previous study, Liu and Wang (2019) combined tertiary amine ethyl 4-(dimethylamino)-benzoate and HAP (4 E-HAP), and they reported that this structure triggered the polymerization of the adhesive resin. However, in the present study, the DC did not change in any group.…”