Review article

Jaw relation records for fixed prosthodontics

Although intraoral scanners (IOSs) are popular, few studies have evaluated the accuracy of digital mounting by using IOSs.

The purpose of this in vitro study was to compare the accuracy of digital mounting by using 2 IOSs and 2 occlusal scanning methods.

Fourteen Ø5-mm zirconia balls were attached approximately 5 mm apical to the free gingival margin of both second molars, second premolars, and canines and between the central incisors in maxillary and mandibular epoxy casts. A polyetheretherketone hexagonal cube with a 10-mm-long edge was attached to the buccal side of the missing mandibular right first molar area, and the cube was used to set a part coordinate system. Two IOSs (TRIOS 3, Primescan) were used to assess the intra-arch and interarch accuracies. For intra-arch assessment, each IOS was used to digitally scan the mandibular epoxy cast 15 times and fabricate 15 datasets. The deviation of each zirconia ball centroid was statistically compared between the IOSs. For interarch assessment, each IOS was used to digitally scan the maxillary and mandibular epoxy casts, and the data were digitally mounted by using a single anterior occlusal scan (A) or bilateral posterior occlusal scan (P). Both occlusal scans were performed 15 times; therefore, 4 groups (15 datasets per group) of mounted digital datasets were assigned. The deviation of each maxillary zirconia ball centroid, as well as the interarch distance between the corresponding maxillary and mandibular zirconia ball centroids, were compared among the 4 groups. For statistical analysis, the Mann–Whitney U test and Kruskal–Wallis test with Bonferroni correction were used (α=.05).

Primescan had less deviation than TRIOS 3 in the complete arch scan. When the zirconia balls were close to the origin, the bilateral posterior occlusal scan produced less deviation of their centroids. Primescan produced decreased interarch distance in the anterior and posterior dentition, while TRIOS 3 produced increased interarch distance in the anterior dentition and decreased interarch distance in the posterior dentition.

A significant difference was noted in intra-arch accuracy between the IOSs, and the difference influenced the digital mounting accuracy. The type of occlusal scan and IOS significantly influenced the accuracy of digital mounting. Both IOSs produced decreased interarch distances in the second molar area.

Fabricating an immediate complete denture in the conventional manner may be complicated and difficult. The purpose of this article was to describe a fully digital workflow used to fabricate an immediate complete denture before removing the teeth and without the use of conventional impressions or stone casts. The digital data for the workflow were acquired using an intraoral scanner and were then used to design the denture base and teeth after deleting any remaining tooth images from the virtual 3-dimensional image of the jaw. The resulting data were exported to a milling machine for denture fabrication.

Fabricating an immediate denture (ID) in the conventional manner may be complicated and difficult. An alternative technique is described for the fabrication of an ID that eliminates the need for an interim prosthesis and reduces treatment time.