Morphology and mechanical performance of dental crown designed by 3D-DCGAN

OBJECTIVES

This study utilised an Artificial Intelligence (AI) method, namely 3D-Deep Convolutional Generative Adversarial Network (3D-DCGAN), which is one of the true 3D machine learning methods, as an automatic algorithm to design a dental crown.

METHODS

Six hundred sets of digital casts containing mandibular second premolars and their adjacent and antagonist teeth obtained from healthy personnel were machine-learned using 3D-DCGAN. Additional 12 sets of data were used as the test dataset, whereas the natural second premolars in the test dataset were compared with the designs in (1) 3D-DCGAN, (2) CEREC Biogeneric, and (3) CAD for morphological parameters of 3D similarity, cusp angle, occlusal contact point number and area, and in silico fatigue simulations with finite element (FE) using lithium disilicate material.

RESULTS

The 3D-DCGAN design and natural teeth had the lowest discrepancy in morphology compared with the other groups (root mean square value = 0.3611). The Biogeneric design showed a significantly (p < 0.05) higher cusp angle (67.11°) than that of the 3D-DCGAN design (49.43°) and natural tooth (54.05°). No significant difference was observed in the number and area of occlusal contact points among the four groups. FE analysis showed that the 3D-DCGAN design had the best match to the natural tooth regarding the stress distribution in the crown. The 3D-DCGAN design was subjected to 26.73 MPa and the natural tooth was subjected to 23.97 MPa stress at the central fossa area under physiological occlusal force (300 N); the two groups showed similar fatigue lifetimes (F-N curve) under simulated cyclic loading of 100-400 N. Designs with Biogeneric or technician would yield respectively higher or lower fatigue lifetime than natural teeth.

SIGNIFICANCE

This study demonstrated that 3D-DCGAN could be utilised to design personalised dental crowns with high accuracy that can mimic both the morphology and biomechanics of natural teeth.

Restoration of localised erosive wear using a combination of dental materials: a conservative approach

Objectives To present the treatment approach for the restoration of localised anterior erosive wear using a combination of dental materials.Clinical considerations A patient presented in a private dental practice concerned about the aesthetics of his anterior teeth. The patient's history and clinical examination revealed erosive wear on the labial and palatal aspects of his maxillary central incisors and right lateral incisor. The formulated treatment plan was to restore the teeth in a conservative way. A diagnostic wax-up was performed and confirmed with the patient with chairside mock-up. The treatment provided included direct composite restorations, replacement of a porcelain-fused-to-metal crown on his left lateral incisor with a porcelain-fused-to-zirconia crown, and lithium disilicate ceramic veneers on the worn labial surfaces of the central incisors and the right lateral incisor. The preparations for the ceramic veneers were carried out with the aid of the diagnostic mock-up, thus minimising the need for tooth removal of the worn teeth.Conclusions Pre-operative planning for tooth surface loss cases can help to ensure that little or no remaining tooth structure is removed during the restorative procedures. A strict bonding protocol is crucial to ensure longevity of the restorations.