GP3d - Development of Elaborate 3D-Printed Training Skulls for Local Anesthesia Instruction: Highlighting Angle’s Classifications of Malocclusion

Abstract: Dental students learn to give local anesthesia injections during their preclinical dental school years. This experience relies on practice with cadavers and fellow classmates. This does not give the students experience nor a comprehensive understanding for variances in skeletal anatomy including pediatric patients and various adult malocclusions that are encountered during clinical treatment. In developing a proper training model, highlighting the inferior alveolar nerve (IAN) block is advantageous to help students better appreciate these variances, minimize risk for improper administration of local anesthesia, and foster active, engaging, and immersive learning.

A collaborative effort was fostered with the Case Western Reserve University (CWRU) Sears think[box], the CWRU Oral and Maxillofacial Radiology Department, and the CWRU Oral and Maxillofacial Surgery Department. Initially, cone-beam computer tomography (CBCT) images were captured utilizing an iCAT FLX unit set to a field of view of 17 cm x 23 cm. Digital Imaging and Communications in Medicine (DICOM) reconstruction was performed at 0.3 mm voxel size. CBCT images were acquired for a pediatric patient, a patient with Class I occlusion, Class II malocclusion, and Class III malocclusion.
Materialize Mimics software was used to segment DICOM scan data using thresholding, while isolating and refining desired areas using editing tools and establishing 3D geometry. Zbrush software was used to fuse mesh and eliminate topological errors for printing. The mandible was digitally opened 25 degrees. Digital attachments were applied to facilitate later mucosal attachment and structures were exported as individual stereolithography (STL) files. GrabCad software was used to import multiple STL files as Assembly and the following model material settings was assigned: Mandible – Musculoskeletal > Skull > Dense; Inferior alveolar canal – Gel Support; Medial pterygoid muscle and tongue – Digital Materials > TissueMatrix and Agilus30 > DM600; Mucosa – Digital Materials > Agilus30 and Vero Magenta Vivid > FLXA-MT-S50. Anatomy assets include the following: Mandible (BoneMatrix), Inferior alveolar canal (GelMatrix as support), Medial pterygoid muscle (TissueMatrix and Agilus30), Tongue (TissueMatrix and Agilus30), and Mucosa (Agilus30 and Vero Magenta Vivid). Tray layout was optimized and model orientated for printing. A Stratasys J750 Digital Anatomy printer was used to print 3D models and a Clean Station DT3 lye bath used to remove support materials.

The 3D-printed pediatric, Class I, Class II, and Class III skulls were assembled and tested for durability, anatomic accuracy, and ability to simulate IAN injections. Initial feedback suggests a significant appreciation for the anatomic variations and changes in injection technique required to accommodate these variations.

An elaborate 3D training skull model was successfully created in collaboration with the world-class innovation center at the CWRU think[box]. Four different skeletal jaw relationships were established and revealed anatomically accurate and elaborate models to innovate local anesthesia education in our institution. The study will be expanded to include 200 preclinical and clinical students for further assessment and determination of educational efficacy for the 3D models.

References
Brand HS, Baart JA, Maas NE, Bachet I. Effect of a training model in local anesthesia teaching. J Dent Educ. 2010 Aug;74(8):876-9. PMID: 20679457.

Sayahpour B, Nucci L, Eslami S, Talaeipour A, Ahmadi Ranani S, Mafi R, Jamilian A. Three-dimensional evaluation of mandibular lingula: Comparisons of skeletal angle classifications and growth patterns. Orthod Craniofac Res. 2024 Jan 21. doi: 10.1111/ocr.12757. Epub ahead of print. PMID: 38247222.