Linping Zhao

Application of Virtual Surgical Planning with Computer Assisted Design and Manufacturing Technology to Cranio-Maxillofacial Surgery

Computer aided design and manufacturing (CAD/CAM) technology today is the standard in manufacturing industry. The application of the CAD/CAM technology, together with the emerging 3D medical images based virtual surgical planning (VSP) technology, to craniomaxillofacial reconstruction has been gaining increasing attention to reconstructive surgeons. This article illustrates the components, system and clinical management of the VSP and CAD/CAM technology including: data acquisition, virtual surgical and treatment planning, individual implant design and fabrication, and outcome assessment. It focuses primarily on the technical aspects of the VSP and CAD/CAM system to improve the predictability of the planning and outcome.

Three-dimensional cephalometric study of upper airway space in skeletal class II and III healthy patients

Because the pharynx and the dentofacial structures have close relationship, a mutual interaction can be expected to occur between them. The literature presents skeletal malocclusion as etiology for airway morphology changes and/or vice versa. The present three-dimensional cephalometric study from computed tomography scans was carried out to investigate upper airway space in normal nasal breathing patients presenting skeletal pattern of classes II and III. In addition, the statistical analysis was done according to gender criterion. The results revealed that the majority of the airway measurements have not been affected by type of malocclusion. The three-dimensional technology used in this study also allowed the volume and surface area calculations, and no statistical significance was found. The retroglossal width and posterior nasal cavity height mean were larger in males than females in the class II group, but volume and cross-section area were not statistically significant. However, in class III group, although the differences in linear and angular measures means were not significant, the retropalatal volume and retroglossal volume and cross-section area were larger in males. The authors highlight that the evaluation of upper airway space should be an integral part of diagnosis and treatment planning to achieve functional balance and stability of the results.

CT analysis after distraction osteogenesis in Pierre Robin Sequence.

Early mandibular lengthening by distraction osteogenesis provides an alternative to traditional methods of airway management in infants with Pierre Robin sequence (PRS). Little evidence in the medical literature quantitatively demonstrates the changes in skeletal, soft tissue, and hypopharyngeal spaces with mandibular distraction.

Measuring Progressive Soft Tissue Change With Nasoalveolar Molding Using a Three-dimensional System

Background: For craniofacial orthodontics and surgery to progress, accurate temporal evaluation of soft tissue and skeletal change with treatment is necessary. Evolution in three-dimensional imaging eliminates certain inherent challenges in making such measurements in infants with facial clefts. Objective: The aim of this pilot study was to measure progressive three-dimensional changes in nasal form in a series of infants with facial clefts during the course of presurgical nasoalveolar molding. Materials and Methods: In 5 infants with unrepaired cleft lip and palate, three-dimensional photographs were obtained using the 3dMD system (3dMD, Inc, Atlanta, GA) at 2-week intervals during nasoalveolar molding treatment. Using the 3dMD Vultus software, temporal soft tissue changes were evaluated quantitatively based on three-dimensional linear measurements of 3 landmarks in the nasal area and qualitative changes in the surface shell. Results: Increase in columellar length on the cleft side and decrease of the nostril floor on the noncleft side were observed in all subjects. Progressive changes were observed most significantly in week 4 (T3) into treatment. Conclusions: This pilot study describes an approach using the 3dMD photo system with Vultus software for measuring the progressive change in the nasal soft tissues. The 3dMD system was believed to be valuable for facial analysis in this setting.

Biomechanical response of the maxillofacial skeleton to transpalatal orthopedic force in a unilateral palatal cleft

OBJECTIVES To assess the skeletal and dental effects of rapid maxillary expansion in a patient with unilateral cleft deformity of secondary palate and alveolus using the finite element method. MATERIALS AND METHODS A patient-specific composite skull model was developed from a patient computed tomographic scan and a surface scan of the patients maxillary cast using MIMICS imaging analysis software. For volumetric meshing and the finite element analysis, Abaqus (6.7) was used. RESULTS The typical wedge-shaped opening that occurs after RME, seen in non-cleft patients, is not seen in cleft patients. A clockwise rotation of the maxilla as a result of maxillary expansion was evident. The areas of maximum stress were the intact primary palate region, inferior orbital foramen of the non-cleft and the cleft sides, and the zygomatic buttress of the cleft side. During expansion, the intact primary palate showed high stress and acted as a region of major resistance, followed by the zygomatic buttress on the cleft side. CONCLUSIONS Clinicians should consider a need for customization of expansion therapy for cleft patients depending on the patients age, the type of cleft present (primary or secondary palate), and the desired area of expansion (anterior or posterior).

Arthrogryposis: diagnosis and therapeutic planning for patients seeking orthodontic treatment or orthognathic surgery.

Arthrogryposis is the name given to a group of musculoskeletal disorders characterized by multiple joint contractures through the body that are present at birth. There are many causes for congenital limitations of the range of motion of a joint. However, the most common form of arthrogryposis, present in 40% of cases, is a condition called amyoplasia. In many cases, abnormal nerve, muscle, and connective tissue development is involved. Hands, wrists, elbows, shoulders, hips, feet, knees, back, and jaws are affected. Because of the complexity of tissue alterations and implications in normal facial growth, the authors of this article address the aspects related to clinical manifestations and therapeutic planning for patients with this condition who seek orthodontic treatment or orthognathic surgery.

Three-dimensional Facial Surface Analysis of Patients With Skeletal Malocclusion

Three-dimensional (3D) laser surface scanning analysis has taken hold in orthodontics, as well as craniomaxillofacial and plastic surgery as a new tool that can navigate away from the limitations of conventional two-dimensional methods. Various techniques for 3D reconstruction of the face have been used in diagnosis, treatment planning and simulation, and outcomes follow-up. The aim of the current prospective study was to present some technical aspects for the assessment of facial changes after orthodontic and orthognathic surgery treatment using 3D laser surface scanning. The technique proposed for facial surface shape analysis represented three-dimensionally the expected surgical changes, and the reduction of the postoperative swelling was verified. This study provides technical information from the data collection to the 3D virtual soft-tissue analysis that can be useful for diagnostic information, treatment planning, future comparisons of treatment stability or facial postoperative swelling, and soft-tissue profile assessment.

Determining the osteotomy pattern in surgically assisted rapid maxillary expansion in a unilateral palatal cleft: A finite element model approach

OBJECTIVES To evaluate the stress pattern in the craniofacial skeleton in a patient with unilateral cleft deformity of the secondary palate and alveolus in response to various techniques of surgically assisted rapid maxillary expansion (SARME). MATERIALS AND METHODS Three patient-specific composite skull models were developed for finite element model analysis. The details of the modeling procedure have been described in Part I of this series. The finite element analysis was performed on each model with a specified SARME technique in combination with RME using Abaqus (6.7). RESULTS The ideal form of surgery in SARME for patients with unilateral cleft deformity of the secondary palate and alveolus would be complete unilateral LeFort I with pterygoid dysjunction in combination with midpalatal split, followed by isolated midpalatal split and zygomatic buttress osteotomies. CONCLUSIONS A more invasive SARME technique can significantly reduce the resultant stresses. However, this benefit should be weighed against the risk of increasing complications associated with more extensive surgeries. When a more conservative surgical technique is selected, it would be preferable to perform a midpalatal split rather than zygomatic buttress osteotomies, as indicated by the stress-strain distribution and displacement pattern associated with different SARME techniques.

The Structural Implications of a Unilateral Facial Skeletal Cleft: A Three-Dimensional Finite Element Model Approach

Objective: For children born with a unilateral facial skeletal cleft, oral motor function is impaired and skeletal development and growth are asymmetrical with regard to the midsagittal plane. This study was designed to verify that a unilateral skeletal cleft and its dimensions (i.e., depth and width) affect the severity of the asymmetric stress and strain distribution within the maxilla. Methods: A three-dimensional finite element model of a normal maxilla was developed from pediatric, subject-specific computerized tomography scan data. A clefting pattern then was introduced to simulate varying degrees of deformity in geometry, with the bone properties and boundary conditions held constant. The asymmetric index was introduced to quantify the asymmetrical stress and strain distribution within the maxilla with regard to the midsagittal plane. Results: The unilateral skeletal cleft led to a nonuniform, asymmetric stress and strain distribution within the maxilla: intensified on the noncleft side and weakened on the cleft side. As the depth of the unilateral cleft increased, the stress and strain distribution became increasingly asymmetric as measured by the asymmetric index. In contrast, the width of the cleft had minimal effect on the asymmetrical stress and strain distribution. Interpretation/conclusion: These results implied that a child born with a unilateral cleft would be expected to have an asymmetric skeletal development between the noncleft and the cleft sides as a consequence of an asymmetric functional loading pattern.

Virtual surgical planning and 3D printing in prosthetic orbital reconstruction with percutaneous implants: a technical case report

Osseointegrated titanium implants to the cranial skeleton for retention of facial prostheses have proven to be a reliable replacement for adhesive systems. However, improper placement of the implants can jeopardize prosthetic outcomes, and long-term success of an implant-retained prosthesis. Three-dimensional (3D) computer imaging, virtual planning, and 3D printing have become accepted components of the preoperative planning and design phase of treatment. Computer-aided design and computer-assisted manufacture that employ cone-beam computed tomography data offer benefits to patient treatment by contributing to greater predictability and improved treatment efficiencies with more reliable outcomes in surgical and prosthetic reconstruction. 3D printing enables transfer of the virtual surgical plan to the operating room by fabrication of surgical guides. Previous studies have shown that accuracy improves considerably with guided implantation when compared to conventional template or freehand implant placement. This clinical case report demonstrates the use of a 3D technological pathway for preoperative virtual planning through prosthesis fabrication, utilizing 3D printing, for a patient with an acquired orbital defect that was restored with an implant-retained silicone orbital prosthesis.