Dimensional accuracy of stone casts obtained with multiple pours into the same mold.

Area of Science:

• Dental Materials Science
• Prosthodontics
• Manufacturing and Material Processing

Background:

• Accurate dental stone casts are crucial for fabricating fixed prostheses.
• The double-impression technique with vinyl polysiloxane (VPS) is commonly used.
• Understanding the dimensional stability of casts from multiple pours into the same VPS mold is essential for clinical success.

Purpose of the Study:

• To evaluate the dimensional accuracy of dental stone casts.
• To compare casts produced by multiple pours (three) into the same VPS impression mold.
• To assess the impact of pour timing (1, 6, and 24 hours) on cast accuracy.

Main Methods:

• A stainless steel master model simulating a three-unit fixed prosthesis was used.
• Twelve VPS double impressions were made.
• Three pours of Type IV gypsum were made into each mold at 1, 6, and 24 hours post-impression; measurements were taken using a coordinate measuring machine.

Main Results:

• No statistically significant difference in dimensional accuracy was found between the first and second pours (P > 0.05).
• The third pour showed statistically significant differences in abutment height and interabutment distance.
• The waiting time (1 and 6 hours) before pouring did not significantly impact the dimensional accuracy of the casts.

Conclusions:

• Multiple pours into the same VPS impression mold can affect dimensional accuracy, particularly by the third pour.
• The timing of the pour (1, 6, or 24 hours) did not introduce significant dimensional inaccuracies.
• Clinicians should be aware of potential dimensional changes when performing multiple pours from a single impression.