Effect of lip line and registration method on the accuracy of 3-dimensional patient representation using professional and smartphone based facial scanners: A clinical study.

OBJECTIVES

To evaluate the impact of smile line and registration method on the accuracy of 3D virtual patient representations.

METHODS

Ten participants were scanned using 3 professional (MetiSmile, Rayface, Morpheus) and 3 smartphone based (EM3D, Heges, Qlone) facial scanners. For each scanner, 3 subgroups were created: 2 with patient in high and medium smile line respectively, and 1 with lips retracted. Four fiducial landmarks had been placed on each participant's face. To generate virtual patient representation for high and medium smile line subgroups, the acquired facial models were directly superimposed onto the corresponding intraoral scans. For retracted subgroup, facial models were aligned with intraoral scans, followed by superposition of smiling onto the retracted model. Twenty linear measurements between predefined facial landmarks and tooth-based reference points were obtained manually using a digital caliper to establish control values.

RESULTS

For professional facial scanners, the use of medium smile models led to VPR with significantly lower trueness compared to those composed from high smile line or retracted smile models (P<.05).When a retracted smile was involved, intraoral scans were first superimposed onto the facial scan, followed by alignment with a smiling facial scan, smartphone based FSs produced VPRs with significantly lower trueness compared to those based on a single facial scan with either high or medium smile lines (P<.05).

CONCLUSIONS

To achieve optimal accuracy in virtual patient representation, both patient's smile line and type of facial scanner should be taken into consideration when assessing the necessity of acquiring additional facial scan with lip retraction.

CLINICAL SIGNIFICANCE: When smartphone based facial scanners are used for constructing virtual patient representations in dentate patients with high or medium smile lines, a digital integration workflow incorporating the smiling facial scan should be implemented. For professional facial scanners, a registration protocol that includes an additional facial scan with lip retraction is recommended.