Volumetric Loss of Plastic Teeth on Intracoronal and Extracoronal Posterior Preparations

Objectives: This study measured and compared the volume loss associated with different extracoronal and intracoronal tooth preparations (MO Inlay, MOD Inlay, MODL Onlay, 90° Margin Overlay, Short Bevel Overlay, Chamfer Overlay, Shoulder Overlay).
Methods: After proper training and calibration, a participant (RI) performed all experimental procedures. Non-prepared adult mandibular right first molar typodont teeth were scanned digitally (Planmeca, Hoffman Estates, IL). Subsequently, samples (n=10) were allocated and prepared for the next intracoronal preparations: MO inlay, MOD inlay, MODL onlay. In addition, samples (n=10) were prepared for the next extracoronal preparations: 90^o margin overlay, overlay bevel, overlay chamfer, overlay shoulder. All preparations were made according to standard preparations utilized for the preclinical curriculum teaching of a fully accredited U.S. dental School. Pre-op and post-op preparation scans were evaluated and compared using MeshMixer (San Francisco, United States), GOM (Braunschweig, Germany, and MeshLab (Pisa, Italy). Descriptive statistics were analyzed to determine mean volume loss (VL) and standard deviations.
Results: Volume loss among different intracoronal and extracoronal preparations varied (Table 1). The highest volume loss recorded was a shoulder overlay preparation, followed by a chamfer overlay, short bevel overlay, 90^o margin overlay, MODL onlay, MOD inlay, and lastly MO inlay.
Conclusions: Volume loss is dependent on the preparation design of different conventional intracoronal and extracoronal preparations.