Occlusal Contacts of Milled Polyurethane Casts Mounted in a Proprietary and Semi-adjustable Articulator

Abstract

Digital impressions utilize digital images of the dentition from multiple intraoral scans that are stitched together. A digital bite scan records a static, MI occlusion of the patient and orients the digital casts into the indicated occlusal relationship. This information is transferred to a milling machine that carves casts from a solid polyurethane block using a subtractive process. The completed arches can be ‘snapmounted’ in a proprietary articulator for restoration fabrication at a lab. Digital acquisition of the tooth preparation is comparable to traditional impression methods for many of the intraoral scanners on the market today. However, few studies have demonstrated the potential discrepancies of milled or rapid-prototyped casts from an occlusal aspect. The purpose of this study was to compare the actual occlusal contact (AC, 0-50um) and near occlusal contact (NC, 51-350um) areas of iTero® milled polyurethane casts articulated in a proprietary articulator, and a semi-adjustable articulator, by using trans-illumination of inter-occlusal records.

A statistically significant difference was found between the actual contact of milled casts in the proprietarily-mounted (PM) and semi-adjustable (SA) articulator groups, but not with near contact. PM casts’ NC was significantly different from the control while the AC was not. The SA casts showed no statistical significant difference from the control patient in terms of AC or NC. Occlusal contact of milled casts from the same subject are not identical, and these differences may be compounded or minimized depending on the articulation method.