Ternary Phase Diagram of Model Dentin Adhesive Exposed to Over-wet Environments

Good

et al. 2014

Acta Biomaterialia

Current dental resin undergoes phase separation into hydrophobic-rich and hydrophilic-rich phases during infiltration of the over-wet demineralized collagen matrix. Such phase separation undermines the integrity and durability of the bond at the composite/tooth interface. This study marks the first time that the polymerization kinetics of model hydrophilic-rich phase of dental adhesive has been determined. Samples were prepared by adding varying water content to neat resins made from 95 and 99wt% hydroxyethylmethacrylate (HEMA) and 5 and 1wt% (2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl1]-propane (BisGMA) prior to light curing. Viscosity of the formulations decreased with increased water content. The photo-polymerization kinetics study was carried out by time-resolved FTIR spectrum collector. All of the samples exhibited two-stage polymerization behavior which has not been reported previously for dental resin formulation. The lowest secondary rate maxima were observed for water content of 10-30%wt. Differential scanning calorimetry (DSC) showed two glass transition temperatures for the hydrophilic-rich phase of dental adhesive. The DSC results indicate that the heterogeneity within the final polymer structure decreased with increased water content. The results suggest a reaction mechanism involving both polymerization-induced phase separation (PIPs) and solvent-induced phase separation (SIPs) for the model hydrophilic-rich phase of dental resin.

Section: Discussionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Polymerization- and solvent-induced phase separation in hydrophilic-rich dentin adhesive mimic

Good

et al. 2014

Acta Biomaterialia

“…To prepare samples at the miscibility limit, D Hydrophilic-rich mimics with reduced photoinitiator concentration were prepared similarly, but the photoinitiator was not refilled after the addition of the D 2 O, causing the concentration of the photoinitiator to decrease (Table 2). More D 2 O was added to the neat resins with increased hydrophilicity (Ye et al 2011). Figure 1 indicates the composition of all the formulations studied on the ternary phase diagram of HEMA, BisGMA, and D 2 O.…”

Section: Composition and Preparation Of Hydrophobicand Hydrophilic-rimentioning

confidence: 99%

“…This study gives insight into the polymerization behavior of the dentin adhesive when exposed to an excessive hydrated condition. The in situ polymerization kinetics of dilute dentin adhesive solutions was investigated; these solutions could be mimics for the hydrophilic-rich phase arising within the hybrid layer (Ye et al 2011). The 2-fold objectives of the current investigation were 1) to understand the difference between the polymerization kinetics of hydrophobic and hydrophilic-rich phases and 2) to determine which factor, cross-linker or photoinitiator concentration, has a greater influence on polymerization of the hydrophilic-rich phase.…”

Section: Introductionmentioning

confidence: 99%

Polymerization Behavior of Hydrophilic-Rich Phase of Dentin Adhesive

Parthasarathy

et al. 2015

J Dent Res

Self Cite

The 2-fold objectives of this study were 1) to understand whether model hydrophobic-and hydrophilic-rich phase mimics of dentin adhesive polymerize similarly and 2) to determine which factor, the dimethacrylate component, bisphenol A glycerolate dimethacrylate (BisGMA) or photoinitiator concentration, has greater influence on the polymerization of the hydrophilic-rich phase mimic. Current dentin adhesives are sensitive to moisture, as evidenced by nanoleakage in the hybrid layer and phase separation into hydrophobic-and hydrophilic-rich phases. Phase separation leads to limited availability of the cross-linkable dimethacrylate monomer and hydrophobic photoinitiators within the hydrophilic-rich phase. Model hydrophobic-rich phase was prepared as a single-phase solution by adding maximum wt% deuterium oxide (D 2 O) to HEMA/BisGMA neat resins containing 45 wt% 2-hydroxyethyl methacrylate (HEMA). Mimics of the hydrophilicrich phase were prepared similarly but using HEMA/BisGMA neat resins containing 95, 99, 99.5, and 100 wt% HEMA. The hydrophilic-rich mimics were prepared with standard or reduced photoinitiator content. The photoinitiator systems were camphorquinone (CQ)/ethyl 4-(dimethylamino)benzoate (EDMAB) with or without [3-(3, 4-dimethyl-9-oxo-9H-thioxanthen-2-yloxy)-2-hydroxypropyl]trimethylammonium chloride (QTX). The polymerization kinetics was monitored using a Fourier transform infrared spectrophotometer with a time-resolved collection mode. The hydrophobic-rich phase exhibited a significantly higher polymerization rate compared with the hydrophilic-rich phase. Postpolymerization resulting in the secondary rate maxima was observed for the hydrophilic-rich mimic. The hydrophilic-rich mimics with standard photoinitiator concentration but varying cross-linker (BisGMA) content showed postpolymerization and a substantial degree of conversion. In contrast, the corresponding formulations with reduced photoinitiator concentrations exhibited lower polymerization and inhibition/delay of postpolymerization within 2 h. Under conditions relevant to the wet, oral environment, photoinitiator content plays an important role in the polymerization of the hydrophilic-rich phase mimic. Since the hydrophilic-rich phase is primarily water and monomethacrylate monomer (e.g., HEMA as determined previously), substantial polymerization is important to limit the potential toxic response from HEMA leaching into the surrounding tissues.

“…6 To determine quantitatively the components in the hydrophobic-rich and hydrophilic-rich phases when exposed to over-wet environments, our group used high-performance liquid chromatography (HPLC) to analyze the well-separated phases of model dentin adhesive. 7,8 …”

Section: Introductionmentioning

confidence: 99%

Multivariate Analysis of Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopic Data to Confirm Phase Partitioning in Methacrylate-Based Dentin Adhesive

Ranganathan

et al. 2013

Appl Spectrosc

Water is ubiquitous in the mouths of healthy individuals and is a major interfering factor in the development of a durable seal between the tooth and composite restoration. Water leads to the formation of a variety of defects in dentin adhesives; these defects undermine the tooth-composite bond. Our group recently analyzed phase partitioning of dentin adhesives using high-performance liquid chromatography (HPLC). The concentration measurements provided by HPLC offered a more thorough representation of current adhesive performance and elucidated directions to be taken for further improvement. The sample preparation and instrument analysis using HPLC are, however, time-consuming and labor-intensive. The objective of this work was to develop a methodology for rapid, reliable, and accurate quantitative analysis of near-equilibrium phase partitioning in adhesives exposed to conditions simulating the wet oral environment. Analysis by Fourier transform infrared (FT-IR) spectroscopy in combination with multivariate statistical methods, including partial least squares (PLS) regression and principal component regression (PCR), were used for multivariate calibration to quantify the compositions in separated phases. Excellent predictions were achieved when either the hydrophobic-rich phase or the hydrophilic-rich phase mixtures were analyzed. These results indicate that FT-IR spectroscopy has excellent potential as a rapid method of detection and quantification of dentin adhesives that experience phase separation under conditions that simulate the wet oral environment.