Yasas S. N. Jayaratne

Three-dimensional cephalometric norms of Chinese adults in Hong Kong with balanced facial profile

OBJECTIVE The objectives of this study were (1) to develop a 3D cephalometric analysis scheme applicable to assessing dentofacial deformities; and (2) to create a normative database of 3D cephalometric measurements for adult Chinese in Hong Kong. STUDY DESIGN A cross-sectional study was conducted on 50 male and 50 female adults with normal balanced facial profile and occlusion. Cone-beam computed tomography and stereo photogrammetry imaging were performed on all subjects. Three-dimensional virtual models were generated from imaging data, and cephalometric analysis was performed using specialized software. A new 3D cephalometric analysis scheme appropriate for orthognathic surgery as well as a new reference plane (supraorbital margin plane) for midfacial assessment was used in this study. RESULTS The cephalometric norms generated in this study were comparable with those reported in the literature for conventional 2D cephalometric analysis and the unique features of Chinese faces. The results also showed significant differences between males and females in most of the facial height measurements (P < .01). CONCLUSIONS This is the first database of 3D cephalometric norms based on CBCT and 3D photogrammetry of the Chinese population in Hong Kong. This can be a useful reference for characterizing facial deformities in 3 dimensions. Moreover, 3D cephalometric analysis has the potential of incorporating new measurement methods that are difficult if not impossible in 2D cephalometric analysis.

How Accurate Are the Fusion of Cone-Beam CT and 3-D Stereophotographic Images?

Background Cone-beam Computed Tomography (CBCT) and stereophotography are two of the latest imaging modalities available for three-dimensional (3-D) visualization of craniofacial structures. However, CBCT provides only limited information on surface texture. This can be overcome by combining the bone images derived from CBCT with 3-D photographs. The objectives of this study were 1) to evaluate the feasibility of integrating 3-D Photos and CBCT images 2) to assess degree of error that may occur during the above processes and 3) to identify facial regions that would be most appropriate for 3-D image registration. Methodology CBCT scans and stereophotographic images from 29 patients were used for this study. Two 3-D images corresponding to the skin and bone were extracted from the CBCT data. The 3-D photo was superimposed on the CBCT skin image using relatively immobile areas of the face as a reference. 3-D colour maps were used to assess the accuracy of superimposition were distance differences between the CBCT and 3-D photo were recorded as the signed average and the Root Mean Square (RMS) error. Principal Findings: The signed average and RMS of the distance differences between the registered surfaces were −0.018 (±0.129) mm and 0.739 (±0.239) mm respectively. The most errors were found in areas surrounding the lips and the eyes, while minimal errors were noted in the forehead, root of the nose and zygoma. Conclusions CBCT and 3-D photographic data can be successfully fused with minimal errors. When compared to RMS, the signed average was found to under-represent the registration error. The virtual 3-D composite craniofacial models permit concurrent assessment of bone and soft tissues during diagnosis and treatment planning.

Computer-Aided Maxillofacial Surgery: An Update

Introduction. Recent developments in technology have revolutionized medicine and surgery. This article aims at providing an update on the current trends in computer-aided maxillofacial surgery and illustrates these advances with clinical cases. Methods. The PubMed database was searched for articles published during the past 5 years using the keywords “maxillofacial” and “surgery, computer-assisted.” Full texts of relevant articles were retrieved, and their study details were extracted. Results. Among the 133 articles, most focused on cone-beam computed tomography (CBCT), stereophotography, surgical panning software, and intraoperative navigation. Stereophotography produces 3D facial photographs with natural color and texture, whereas CBCT generates excellent hard-tissue images with a substantially lower radiation than conventional CT scans. Information gathered from CBCT and stereophotography can be used for accurate diagnosis, virtual planning, and simulation of surgery with the aid of specialized software. The preplanned treatment can be executed accurately via intraoperative surgical navigation. Conclusion. Tremendous potential exists for computer-aided maxillofacial surgery as it moves from research to clinical care.

Facial soft tissue response to anterior segmental osteotomies: A systematic review

Bimaxillary protrusion is prevalent among Asians and anterior segmental osteotomies are commonly used for its surgical correction. The objective of this study was to evaluate the soft tissue changes resulting from anterior segmental osteotomies. The electronic databases PubMed, Scopus and ISI Web of knowledge were searched for potentially eligible studies using a set of predetermined keywords. Full texts meeting the inclusion criteria were retrieved and their references were manually searched for additional relevant articles. The study details and outcome data of these reports were extracted using spreadsheets for comparison. The methodological quality of each study was assessed. Eleven studies met the inclusion criteria. Lateral cephalometry was used in all studies. A reduction of the labial prominence with an increase in the nasolabial angle was noted subsequent to anterior segmental osteotomies. The magnitude of the reported soft tissue changes and their ratios corresponding to the osseous movements varied among studies. Long-term, prospective, methodologically sound clinical trials with larger samples and three-dimensional quantification are required to provide sufficient information for predicting the soft tissue response to anterior segmental osteotomies.

Are Neoclassical Canons Valid for Southern Chinese Faces

Background Proportions derived from neoclassical canons, initially described by Renaissance sculptors and painters, are still being employed as aesthetic guidelines during the clinical assessment of the facial morphology. Objective 1. to determine the applicability of neoclassical canons for Southern Chinese faces and 2. to explore gender differences in relation to the applicability of the neoclassical canons and their variants. Methodology 3-D photographs acquired from 103 young adults (51 males and 52 females) without facial dysmorphology were used to test applicability of four neoclassical canons. Standard anthropometric measurements that determine the facial canons were made on these 3-D images. The validity of the canons as well as their different variants were quantified. Principal Findings The neoclassical cannons seldom applied to these individuals, and facial three-section and orbital canons did not apply at all. The orbitonasal canon was most frequently applicable, with a frequency of 19%. Significant sexual dimorphism was found relative to the prevalence of the variants of facial three-section and orbitonasal canons. Conclusion The neoclassical canons did not appear to apply to our sample when rigorous quantitative measurements were employed. Thus, they should not be used as esthetic goals for craniofacial surgical interventions.

Three-Dimensional Color Maps: A Novel Tool for Assessing Craniofacial Changes

Introduction. Three-dimensional (3D) color maps are useful for analyzing data acquired by laser scanning, stereophotography, or computed tomography (CT). The authors aim to illustrate the different applications of color maps in the craniomaxillofacial region. Methods. The images obtained from the above techniques at 2 different time points are superimposed based on a common area unaffected by the surgical intervention or growth. Using specialized software, the distance differences between the 2 superimposed images are depicted in a graphical format as a 3D color map. A color-coded scale indicating the distances accompanies these maps. Results. 3D color maps can be manipulated and viewed in a variety of angles to extract the maximum diagnostic information. They facilitate the critical evaluation of facial asymmetry, accuracy of fusing CT and 3D photo data sets, and postsurgical changes. Conclusion. 3D color maps aid the objective assessment of craniofacial structures while enhancing visual comprehension and communication with patients.

Normative findings for periocular anthropometric measurements among Chinese young adults in Hong Kong

Measurement of periocular structures is of value in several clinical specialties including ophthalmology, optometry, medical and clinical genetics, oculoplastic surgery, and traumatology. Therefore we aimed to determine the periocular anthropometric norms for Chinese young adults using a noninvasive 3D stereophotography system. Craniofacial images using the 3dMDface system were acquired for 103 Chinese subjects (51 males and 52 females) between the ages of 18 and 35 years. Anthropometric landmarks were identified on these digital images according to standard definitions, and linear distances between these landmarks were calculated. It was found that ocular measurements were significantly larger in Chinese males than females for intercanthal width, biocular width, and eye fissure lengths. No gender differences were found in the eye fissure height and the canthal index which ranged between 43 and 44. Both right and left eye fissure height-length ratios were significantly larger in females. This is the first study to employ 3D stereophotogrammetry to create a database of anthropometric normative data for periocular measurements. These data would be useful for clinical interpretation of periocular pathology and serve as reference values when planning aesthetic and posttraumatic surgical interventions.

Nasal Morphology of the Chinese: Three-Dimensional Reference Values for Rhinoplasty

Objective To determine normative nasal measurements for Chinese young adults, conditioned on demographics. Study Design A cross-sectional descriptive study. Setting A university hospital. Subjects and Methods Three-dimensional (3D) photographs were captured from 103 Chinese subjects between 18 and 35 years of age using a commercial stereophotographic system. Anthropometric landmarks were identified on these 3D surface images, and measurements suitable for nasal analysis were performed and contrasted against established Caucasian norms. Gender differences in anthropometric dimensions were also analyzed. Results Normative data for these measurements are made available. Linear nasal measurements, except those for mid-columella length, were significantly larger in men than in women; further, the nasal tip angle and nasofrontal angle were significantly larger in Chinese women. Contrasts of these new data against published Caucasian norms revealed dimensions that differ for these 2 groups. The Chinese normative mean values for morphological nose width, nasal tip angle, nasofrontal angle, and alar slope angle exceeded those reported for North American Caucasians. Conclusions Gender-specific normative data for the Chinese nose were established in this study to provide a useful tool for surgeons in dealing with rhinoplasty. Moreover, the Chinese nasal anthropometric measurements in this study are broader and flatter than those reported for North American Caucasians.

Integration of 3-dimensional surgical and orthodontic technologies with orthognathic “surgery-first” approach in the management of unilateral condylar hyperplasia

Recent innovations in technology and techniques in both surgical and orthodontic fields can be integrated, especially when treating subjects with facial asymmetry. In this article, we present a treatment method consisting of 3-dimensional computer-aided surgical and orthodontic planning, which was implemented with the orthognathic surgery-first approach. Virtual surgical planning, fabrication of surgical splints using the computer-aided design/computer-aided manufacturing technique, and prediction of final orthodontic occlusion using virtual planning with robotically assisted customized archwires were integrated for this patient. Excellent esthetic and occlusal outcomes were obtained in a short period of 5.5 months.

A 3D anthropometric analysis of the orolabial region in Chinese young adults

The orolabial region undergoes considerable changes after orthognathic surgery or orthodontic treatment. Ethnicity, age, and sex-specific norms are needed during the planning of interventions in this region. In 2008 the Br J Oral Maxillofac Surg published anthropometric measurements of the lips of Chinese children, but to our knowledge such reference data for young Chinese adults are not currently available. We therefore used digital anthropometry on 3-dimensional craniofacial images acquired from 103 healthy young Chinese adults with Class I skeletal pattern. Anthropometric landmarks were identified, which provided linear and angular measurements. All orolabial measurements were significantly larger in men than women, with the exception of the labiomental angle. In contrast, there were no sex differences in the anthropometric proportions. We therefore provide what we think are the first cross-sectional norms available for young Chinese adults. These norms can be used to evaluate the morphology of the lips objectively for preoperative diagnosis, planning of treatment, and assessment of postoperative outcomes.