Dimensional accuracy of thermoformed polymethyl methacrylate

Area of Science:

• Dental materials science
• Polymer processing
• Biomaterials engineering

Background:

• Thermoforming polymethyl methacrylate (PMMA) is a common technique for fabricating dental appliances.
• Ensuring dimensional accuracy is crucial for the fit and function of these appliances.

Purpose of the Study:

• To evaluate the dimensional accuracy of thermoformed PMMA specimens.
• To quantify any linear shrinkage or expansion over time and after water immersion.

Main Methods:

• Five PMMA blanks were thermoformed on stone casts derived from a master die.
• Dimensional changes were measured using an optical comparator at various time points (24 hours, 1 week, 1 month, 3 months).
• Measurements were taken before and after water immersion.

Main Results:

• Linear shrinkage of less than 1% (0.37%–0.52%) was observed within 24 hours of thermoforming.
• Water immersion led to slight increases in dimensions (0.07%–0.18% after 3 months), remaining smaller than cast dimensions.
• The thermoformed PMMA specimens demonstrated high dimensional stability.

Conclusions:

• Thermoforming of Perspex polymethyl methacrylate can be performed with high dimensional accuracy.
• The material exhibits minimal and predictable dimensional changes, suitable for dental applications.
• Accurate fabrication of dental appliances using thermoformed PMMA is achievable.