The examination includes:
Study models are most commonly used in the digital form in orthodontics today. Good impressions of the upper and lower arch (typically with alginate) and a bite registration in centric occlusion can be sent to companies (ex: OrthoCAD) to generate digital models. The preferred material for bite registration is polyvinyl siloxane due to its improved accuracy.11 Several digital scanners (ex: iTero, 3Shape Trios) can also be used to create digital models. The digital models can be used to generate a stereolithography (.stl) file that can be used to 3D print models when needed. Most laboratories accepting digital files can now provide this service for practitioners that do not have 3D printers readily available. Digital models have served to improve storage capability, communication among dental practitioners, and ease in diagnosis.12 Research shows similar accuracy of linear measurements using digital models or stone models,13 making them useful for evaluation of tooth size and arch discrepancy, occlusal characteristics, and relationships of the teeth within the arch and between the arches (Figure 9). In-office scanners also exist to generate digital models from stone models and impressions, but are expensive and less commonly found in offices. Lastly, CBCT images can be used to generate digital models using companies such as Anatomage or CareStream, although the accuracy of CBCT generated models remains to be fully explored. Alternatively, stone models can be poured from the alginate impressions to perform the analyses. Study models, either digital or stone, are used to validate occlusal characteristics assessed from the intraoral examination and to generate a space analysis.