Synthesis and evaluation of novel dental monomer with branched aromatic carboxylic acid group

Abstract

A new glycerol-based dimethacrylate monomer with an aromatic carboxylic acid, 2-((1,3-bis(methacryloyloxy)propan-2-yloxy)carbonyl)benzoic acid (BMPB), was synthesized, characterized, and proposed as a possible dental co-monomer for dentin adhesives. Dentin adhesives containing 2-hydroxyethyl methacrylate (HEMA) and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (BisGMA) in addition to BMPB were formulated with water at 0, 5, 10, and 15 wt % to simulate wet, oral conditions, and photo-polymerized. Adhesives were characterized with regard to viscosity, real-time photopolymerization behavior, dynamic mechanical analysis, and microscale 3D internal morphologies and compared with HEMA/BisGMA controls. When formulated under wet conditions, the experimental adhesives showed lower viscosities (0.04-0.07 Pa s) as compared to the control (0.09-0.12 Pa s). The experimental adhesives showed higher glass transition temperature (146-157°C), degree of conversion (78-89%), and rubbery moduli (33-36 MPa), and improved water miscibility (no voids) as compared to the controls (123-135°C, 67-71%, 15-26 MPa, and voids, respectively). The enhanced properties of these adhesives suggest that BMPB with simple, straightforward synthesis is a promising photocurable co-monomer for dental restorative materials.

Keywords: dental monomer; dentin adhesives; dynamic mechanical property; photopolymerization; water miscibility.

FIGURE 1

Reaction scheme for synthesis of 2-((1,3-bis(methacryloyloxy)propan-2-yloxy)carbonyl)benzoic acid (BMPB).

FIGURE 2

¹H (A) and ¹³C (B) NMR spectra in DMSO of new monomer, BMPB. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIGURE 3

The viscosities of control (A: C0, C5, C10, C15) and experimental adhesives (B: E0, E5, E10, E15) as a function of shear rate at 25°C. Control (C): BisGMA/HEMA: 55/45 wt %. Experimental (E): BisGMA/HEMA/BMPB: 30/45/25 wt%. Abbreviations: C, C5, C10, C15 represent control adhesive with 0, 5, 10, 15 wt % water; E, E5, E10, E15 represent experimental adhesive with 0, 5, 10, 15 wt % water. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIGURE 4

Real-time conversion of control (A: C0, C5, C10, C15) and experimental adhesives (B: E0, E5, E10, E15). The adhesives were light-cured for 40 s at room temperature using a commercial visible-light curing unit (Spectrum^® 800, Dentsply, Milford, DE) at an intensity of 550 mW cm⁻². *Significantly (p < 0.05) different from the corresponding control. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIGURE 5

Maximal polymerization rate of control and experimental adhesives polymerized in the presence of 0, 5, 10, and 15 wt % water. N = 3 ± SD. *Significantly (p < 0.05) different from the corresponding control. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]

FIGURE 6

The microscale morphologies of control (A: the left = CT slice at x-y plane from 3D image; the right = 3D image) and experimental (B: the left = CT slice at x-y plane; the right = 3D image) adhesives cured in the presence of 11 wt % water. The morphologies were observed using three-dimensional (3D) MicroXCT (Xradia Inc. Concord, CA). [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.]