Digital 3D image of bimaxillary casts connected by a vestibular scan

The task of three-dimensionally aligning digital images of scans taken from maxillary and mandibular casts can be accomplished by scanning an interocclusal record, but vestibular scanning is also an option. The present study addressed whether this latter technique is precise enough to be used in orthodontic practice.

A total of 10 pairs of casts representing different types of tooth and jaw malposition were scanned with a photo-optical scanner (Activity 102; Smart Optics, Bochum, Germany). After obtaining detailed single scans of each upper and lower jaw, each pair of casts was rigidly aligned with instant glue. Subsequently, three vestibular scans were taken and were then merged with the single-jaw scans to form virtual bimaxillary models. These virtual models were superimposed with each other and analyzed, using the structures of the mandible as constant and documenting the highest occlusal and vestibular deviations measured on each maxillary tooth or gingival region. Descriptive analysis and a mixed linear model were performed with SPSS and SAS.

The greatest deviations between the virtual bimaxillary models averaged 37 ± 28 μm. No significant differences were seen between tooth sites along the dental arch, dentate versus edentulous sites, or occlusal versus vestibular surfaces. The mean of the greatest deviations between repeated scans were found to be 28 ± 14 μm (vestibular scans) and 15 ± 8 μm (single-jaw scans).

The presented approach of generating bimaxillary study models in a virtual environment with the help of vestibular scans meets the precision requirements for use in orthodontics and can be employed in further studies.