628 Comparison of Facial Measurements Using 2D and 3D Photography

Friday, March 23, 2012: 8 a.m. - 9:30 a.m.
Presentation Type: Oral Session
B.E. LARSON1, V. LEON-SALAZAR1, A.J. SODERHOLM2, and P.R. GAILLARD3, 1Division of Orthodontics, University of Minnesota, Minneapolis, MN, 2Oral and Maxillofacial Surgery, Gundersen Lutheran Medical Foundation, La Crosse, WI, 3Clinical and Translational Science Institute, University of Minnesota, Minneapolis, MN
Objective: Although non-ionizing three-dimensional systems (3D) are currently available for facial analysis, two-dimensional digital photographs are still the most common record used in orthodontics for quantitative and qualitative analysis of facial soft-tissue. The aim of this study was to compare linear measurements and facial proportions obtained using direct anthropometry, 2D photographs, and  a 3D stereophotogrammetry system.

Method: Six linear measurements [total facial height (N-Gn), face width (Zy-Zy), lower face width (Go-Go), nasal width (Al-Al), nose height (N-Sn), and lower lip height (Sto-Gn)], and six facial proportions (N-Gn/Zy-Zy, Al-Al/N-Sn, Sto-Gn/Go-Go, Go-Go/Zy-Zy, Go-Go/N-Gn, Sto-Gn/N-Gn) were obtained from facial moulages of orthodontic patients (n=37) by each of the three techniques. The Bland-Altman method was used to test the equivalence between these techniques. Linear measurements and facial proportions were considered equivalent if the differences did not exceed 1mm and 5%, respectively (p<0.05).

Result: The results showed that 3D and direct anthropometry were equivalent with differences smaller than 0.52 mm and 3% (p<0.0001) in all measurements except in nasal width which showed a mean difference of 1mm. In contrast, the 2D technique  showed underestimation greater than 2mm in linear measurements when compared to 3D and direct anthropometry; however, most of the facial proportions were equivalent with the two other methods (p<0.0001) except for Al-Al/N-Sn and Sto-Gn/Go-Go which showed differences between 6% and 9%.

Conclusion: The accuracy of 3D measurements of facial soft-tissue structures is comparable to direct caliper-based anthropometry. On the other hand, conventional 2D facial assessment underestimates linear measurements and should be limited to qualitative facial analysis.

Keywords: Digital image analysis, Facial Anthropometry and Orthodontics