Accuracy of adaptation of thermoformed poly(methyl methacrylate)

Abstract

Thermoformed poly(methyl methacrylate) (PMMA) sheet is used to produce a number of different dental appliances such as stents, occlusal splints and baseplates for occlusal rims. The purpose of the present study was to measure the accuracy of adaptation of Perspex PMMA sheet and to determine the effect of annealing on the accuracy of the thermoformed specimens. The results of the study showed that PMMA can produce specimens that are accurately adapted to the cast. Immersion in water resulted in an increase in the space between the cast and the specimen for both thermoformed and thermoformed and annealed acrylic resin. Annealing of the thermoformed specimens had significantly less increase in space between the cast and the specimens when immersed in water over a period of 3 months.

Comparative adaptation accuracy of acrylic denture bases evaluated by two different methods

“…Microscopic measurements of the posterior border gap [11][12][13][14][15][16] and weighing a elastomeric material impressed under a denture base 11,[17][18][19] are one of the most frequently used methods to evaluate the denture adaptation to a master cast due to their simplicity and feasibility. The magnitude of the palatal border gap can express the ability of a border seal, and the weight of an impression material indicates the overall volume of internal space under denture base, which are all important factors in complete denture retention 8) .…”

A comparison of the fitting accuracy of thermoplastic denture base resins used in non-metal clasp dentures to a conventional heat-cured acrylic resin

“…In the present study, high-strength stone was used to re-fix the removed specimens. Thus, the evaluation method employed in our study had measurement precision advantages over the methods used in the previous study [8]. In contrast, we could not evaluate the threedimensional fitting accuracy in the current study, because the dimensional change was measured in only one dimension.…”

“…In a separate study that evaluated the fitting accuracy of denture base materials using a microscope, the specimens were removed from the master cast and subsequently re-fixed on the master cast with sticky wax applied only at the sample borders [8]. The fabrication method used in the prior study may have resulted in specimen instability, which potentially affected the reliability of the measurements of the gap between the specimens and the cast.…”

Tensile properties of denture base resin reinforced with various esthetic fibers

“…Denture fractures could result from weak mechanical properties of the denture base resin or because of the multiple factors leading to the failure of denture base material, such as increased ridge resorption, deep incisal notching at the labial frena, sharp changes at the contours of denture base or deep scratches and induced processing stress. 5,6 Dentures are subjected to various types of stress including compressive, tensile or shear stress during function, 6 and the stress intensification seems to be responsible for most of the denture fractures occurred inside the mouth. Waters 7 has described how stressed polymer chains could be distorted around stress concentrations.…”