Effect of the curing mode on the clinical performance and properties of acrylic resin overdenture bases

Abstract EN

This study was two folded : an in-vivo study aimed to compare between the clinical efficiency of heat-cured and microwave-cured over denture bases, and an in-vitro study to relate the chemical, physical and mechanical properties, to the clinical performance of these over dentures.

Fourteen mandibular over dentures were constructed for edentulous patients with remaining two natural mandibular canines.

Over dentures were divided equally according to the curing mode into two groups using heat cured acrylic resin material.

Group I was processed in water bath for 1 ½ hrs at 74ºC and then for another 1 hr at 100 ºC.

Group II was processed using dry heat of microwave energy at 550 W for 3 minutes.

In-vivo study, the mandibular over dentures were weighed and their thicknesses were measured at predetermined fixed points on denture bases at delivery, 6monhts and 12 months follow-up periods to evaluate the wear resistance.

In-vitro study involved preparing of twenty rectangular specimens assigned to two equal divisions with respect to the processing technique.

A 4-point loading bending test was used to determine the flexural characteristics under static and cyclic loading.

Hardness was evaluated using Vickers's hardness tester.

Uncured, water bath (heat) cured and microwave cured solid samples were analyzed using Fourier Transform Infrared spectral analysis (FTIR) to determine the degree of conversion.

The porosity was also assessed using stereomicroscope for samples cured by both investigated modes.

Although heat cured acrylic resins exhibited higher wear resistance, their over denture bases decreased in weight in contrast to microwave cured bases which showed slight increase in weight over the follow up periods.

Significant decrease in thickness either for heat or microwave cured over denture bases over periods ; however, this change was insignificant regarding the mode of curing.

Heat cured acrylic resin showed significantly higher flexural characteristics than microwave ones except for flexural modulus which was insignificantly different.

The degree of conversion using microwave irradiation resulted in (67.21 % DC) but it was (52.17 % DC) for heat curing.

Microwave cured specimens showed widely spread porosity accompanied with lower significant hardness.

Depending on the mode of curing, the clinical efficiency could be related to the chemical, physical and mechanical properties of acrylic resin.

Water bath method showed favorable results in processing heat cured resin material than microwave irradiation, however, the curing conditions of the latter should be considered.