Effect of impression holding time and tray removal speed on the dimensional accuracy of impressions for artificial abutment tooth inclined.

Oral scanners allow dental impressions to be taken in a short time without the use of an impression material. However, it has been noted that high impression accuracy cannot be obtained in cases where the abutment is inclined or in cases where the span is long. Consequently, in daily clinical practice, impressions are often created using silicone impression material. When taking an impression using silicone impression material, the curing time or the removal time of the impression material are often based on the intuition of the dental staff. This study investigated the effects of impression holding time and impression tray removal speed on the dimensional accuracy of impressions. A specimen with an abutment inclined 30° to the removal direction of an impression was prepared. Four types of silicone rubber impression materials were used. Impressions were taken with two levels of holding time and two levels of removal speed using an autograph. The diameter of stone models was measured at 3, 6, and 9 mm from the baseline of each. The height of the inclined and opposite sides was also measured. Two-way analysis of variance was used to analyze data regarding the assessment of the effects of holding time and tray removal speed. The reproducibility of the impressions was affected by the volume of undercut caused by the inclined abutment. For a large undercut, longer holding times and faster tray removal speeds are recommended to reduce the deformation of silicone rubber impressions.