Video created by The University of Hong Kong for the course "Materials in Oral Health". Learn online and earn valuable credentials from top universities like. Resin-modified glass ionomers (RMGIs) have been introduced to dentistry as materials which have the advantages of composite resins and glass ionomers at. Resin-modified glass ionomers (RMGI) set by at least 2 mechanisms dependent upon reactant diffusion prior to gelation. Each reaction's kinetics and setting  ‎Abstract · ‎Introduction · ‎Materials & Methods · ‎Discussion.


Author: Etha Ryan PhD
Country: Cuba
Language: English
Genre: Education
Published: 24 July 2016
Pages: 205
PDF File Size: 26.68 Mb
ePub File Size: 19.3 Mb
ISBN: 977-1-13916-623-6
Downloads: 29564
Price: Free
Uploader: Etha Ryan PhD


Resin-modified Glass-ionomer Setting Reaction Competition

Abstract Specular reflectance Fourier transform infrared SR-FTIR spectroscopy was used to study the setting reaction of dental resin-modified glass ionomer RMGI restoratives as a function of curing resin modified glass ionomer and postirradiation time.

Samples were prepared by filling the mixed materials into custom-made molds and then light-irradiating using a dental curing light. The degree of conversion and the extent of resin modified glass ionomer reaction of the materials at different depths 0, 1, 2, and 4 mm and postirradiation times 10 min, 1 day, and 7 days were determined using SR-FTIR spectroscopy in conjunction with the Kramers-Kronig K-K transformation.

The setting reaction was also investigated using microhardness measurements.

Resin-modified Glass-ionomer Setting Reaction Competition

The results showed that the depth of cure increased over time by the continuous acid-base reaction rather than photopolymerization or chemical polymerization.

Microhardness tests resin modified glass ionomer less suitable for studying the setting reaction as a function of postirradiation time, probably due to softening from the humidity. Analysis using specular reflectance in conjunction with the K-K algorithm was an easy and effective method for monitoring the setting reaction of dental RMGI materials.

Introduction Dental glass ionomers GIs are water-based materials that set by an acid-base reaction between a polyalkenoic acid and fluoroaluminosilicate glass [ 12 ]. Resin-modified glass ionomers RMGIs were developed to overcome the major drawback of conventional GIs, sensitivity to water during the initial setting, by incorporating resin monomers into an aqueous solution of polyacrylic acid [ resin modified glass ionomer ].

A discussion on how to apply resin-modified glass ionomers

The primary resin incorporated in RMGIs is a hydrophilic monomer such as 2-hydroxyethyl methacrylate HEMA [ 4 ]; a small amount of dimethacrylate monomer may be additionally incorporated to form crosslinked poly-HEMA during polymerization [ 5 ].

The setting reaction of RMGIs includes radical polymerization by either light-cure or self-cure to form a polymer network along resin modified glass ionomer a fundamental acid-base reaction to form a GI polysalt matrix [ 67 ].

Light-cure RMGI restoratives may not adequately set when placed in bulk because of the reduced penetration of light into resin modified glass ionomer deeper regions of the restoration, which may not be sufficient to initiate photopolymerization [ 8 ].

Tricure RMGI restoratives were developed in order to ensure that these deeper regions of the restoration are properly cured [ 7 — 9 ].

Journal of Spectroscopy

One of the most common methods for evaluating the setting behavior of light-cure or tricure RMGI restoratives as a function of curing depth is measuring the hardness [ 410 ].

Although microhardness tests are convenient, they fail to resin modified glass ionomer the relative contribution between radical polymerization and acid-base reaction because the two types of reactions proceed simultaneously.

A previous Fourier transform infrared FTIR spectroscopy study demonstrated resin modified glass ionomer the visible light-curing process, for either light- or tri-cure RMGIs, greatly reduces the salt formation acid-base reaction rate during the early setting stages, which is likely due to rapid polymer network formation [ 7 ].

A differential resin modified glass ionomer calorimetry DSC study showed that early light-activation of RMGIs may limit the acid-base reaction and result in a varied material structure [ 12 ].

However, there is still limited experimental and clinical information available concerning the setting reaction of RMGI restorative materials as a function of curing depth and postirradiation time.

In this in vitro study, we investigated the monomer-to-polymer conversion and the acid-base reaction of three commercial RMGI restoratives at different depths and postirradiation times using an optical microscope connected to an FTIR spectrophotometer. We also compared the FTIR analysis results with resin modified glass ionomer measured microhardness of the materials.

It was assumed that each measured microhardness value reflects the surface hardening by the contribution of both the polymerization reaction and acid-base reaction at a specified depth and postirradiation time. resin modified glass ionomer


Materials and Methods 2. To prepare samples, two types of silicone molds were fabricated: In mold A, the mixed material was transferred resin modified glass ionomer the cavities placed on a polyester strip, covered with another polyester strip, and gently pressed to expel the excess material Figure 1 a.

A discussion on how to apply resin-modified glass ionomers

Mold B was placed on a polyester strip over a glass slide that had been covered with a black adhesive paper tape black glass slide. The mixed material was filled into the cavities and then covered with another polyester strip and black glass resin modified glass ionomer.


This assembly was pressed together by means of a clamp to displace excess material.