Assessing changes in skeletal morphology with orthognathic surgery and postoperative stability is crucial for the proper treatment of patients with dentofacial deformity. To date, two-dimensional cephalometric analysis has been used in most cases, but three-dimensional CT images have recently started to be used for assessing the treatment of jaw deformities. However, three-dimensional analysis is not used generally because of the difficulty of establishing superimposition of three-dimensional CT images.
In this study, a definition of the coordinate system in three-dimensional assessment was proposed and a six-degrees-of-freedom search was used for clinical images. As a result, postoperative CT images were successfully superimposed, and the proposed method enabled three-dimensional evaluation of skeletal morphology.

View full abstract

The purposes of this study were to present a procedure for extracting midsagittal planes of the cranio-maxillofacial skeleton (hard tissue) and the facial soft tissue of patients with jaw deformities by using a surface-based method, and to assess whether there were differences between those two plans. Ten patients with jaw deformities who had undergone CT scanning for diagnostic purposes at pretreatment were included in this study. Three-dimensional virtualized patient models of hard and soft tissue were generated from CT scan data of the patients. The midsagittal plane for hard tissue (MSP_h) and for soft tissue (MSP_s) were extracted by using the surface-based method. The angular and distance errors between determined MSP_h and MSP_s were calculated. The average angular and distance deviation were 0.532±0.226° and 0.169±0.139 mm, respectively. From these results, the difference between MSP_h and MSP_s was considered to be minimal clinically. This study suggested that surface data of soft tissue may be useful to predict the symmetry properties of hard tissue in the diagnosis of jaw deformities.

View full abstract

The purpose of this study was to analyze three-dimensional changes in soft tissue with those in hard tissue following mandibular setback surgery in skeletal Class III patients.
Materials and methods:
The subjects comprised 11 skeletal Class III patients who had undergone BSSRO for analyzing three-dimensional changes in soft tissue.
Materials consisted of two facial three-dimensional data, dental three-dimensional data and lateral cephalograms. According to the reconstruction system previously reported, we constructed three-dimensional integration data, and set reference frames and measuring lines. The measurement regions were six areas: the upper buccal, lower buccal, subnasal, upper lip, lower lip and chin areas. Then, we calculated changes in soft tissue, hard tissue and soft tissue thickness with orthognathic surgery. To determine the ratio of soft tissue change and thickness of soft tissue change to hard tissue change, linear regression analysis was calculated and the regression parameters, a1: amount of soft tissue change/amount of hard tissue change as soft tissue change ratio, a2: amount of thickness of soft tissue change/amount of hard tissue change as thickness of soft tissue change ratio, were examined.
Results:
The thickness of soft tissue increased in the lower lip, chin and lower buccal areas and decreased in the upper lip and upper buccal regions. The soft tissue change ratio was 0.13∼0.30 in the upper lip and upper buccal regions, and 0.6∼0.78 in the lower three regions. The coefficient of determination (R²) was 0.50∼0.65 in the lower three regions. The thickness of soft tissue change ratio was -0.21 to -0.03 and 0.20∼0.23 in the upper three regions and lower three regions respectively.
Conclusion:
Integration data of facial tissue and dentition are useful for statistical analysis of three-dimensional changes in soft tissue before and after mandibular setback surgery with high accuracy. The soft tissue change ratio in the lower four regions were similar to the results of other studies, although the reconstruction system and measurement methods were different.

View full abstract

Intraoral Vertical Ramus Osteotomy (IVRO) is frequently performed as a form of mandibular osteotomy, but the process of osseous healing of the split bone fragments has not yet been reported. The purpose of this study was to clarify the process of osseous healing occurring in the tissue over time.
The subjects were 35 patients who underwent IVRO. Sixty-one rami from these patients were studied at 1 month, 6 months, 1 year, and then 2 to 3 years after surgery by computed tomography (CT). The plane passing through the mandibular foramen was designated as the upper plane, while the plane passing through the root furcation was designated as the lower plane. We examined all of the images between the two planes. We classified 5 types of bone fragments, from proximal to distal; these were classified on the basis of the CT cross-sectional images at 1 month after surgery. The 5 types were as follows: outer-side type (OS), outer-proximal type (OP), proximal type (PX), inner-proximal type (IP), and inner-side type (IS). To elucidate the types of osseous healing, the progression of bone formation and the forms of the mandibular ramus proximal bone fragments were examined.
In most cases, bone fragments were covered with callus-like structures at 6 months after surgery, and changed to cortical bone-like structures at 2 to 3 years after surgery. That is, the split bone fragments were in a transitional state at 2 to 3 years after surgery. In the majority of cases, the forms of the mandibular ramus proximal bone fragments were PX and OP. OP showed a significant difference in the amount of setback of the distal bone fragment. These aspects of osseous healing were discussed mainly because of the clinical importance of postoperative mouth opening and closing and the traction of the surrounding soft tissue.

View full abstract

We report the case of a 55-year-old woman who had a silicone implant removed from her chin because of odontogenic infection. She had undergone plastic surgery with a silicone implantation in the chin region 30 years earlier. This time, she presented with pus oozing out of her chin and around her teeth. On examination at our department, she had periapical periodontitis of the mandibular anterior teeth, which had infected the implant and caused a fistula of the chin. Surgical intervention was executed to remove the implant and eliminate the fistula.
There are two types of surgery for chin augmentation: augmentation genioplasty by osteotomy and implantation with alloplastic materials such as hydroxyapatite blocks and silicone implants. Augmentation genioplasty with silicone implantation is frequently conducted in the field of plastic surgery because it is relatively simple and can be performed under local anesthesia. However, similar to our case, this surgery carries the risk of developing secondary post-operative infection from odontogenic diseases. Therefore, regular follow-up and maintenance of oral hygiene is important for patients who undergo chin augmentation procedures using silicone implants.

View full abstract

The primary objective of surgical orthodontic treatment is to achieve occlusal function of the stomatognathic system. However, high esthetic demands have recently presented treatment providers with an additional challenge in carrying out such treatment, and occlusal function and esthetic considerations need to be balanced. Establishing the optimal treatment goal is the most critical factor in achieving high-quality results in surgical orthodontic treatment. Three-dimensional computed tomography (3-D CT) provides detailed information on maxillofacial deformation and the spatial relationship between cranial and dental structures. The use of 3-D CT in orthognathic surgery is now widespread thanks to rapid development of computers in the field of dentistry. In this case report, the patient had a discrepancy in the midline between the mandibular dentition and body. While 2-D information could be obtained by the standard cephalometric analysis, it would not have been possible to obtain 3-D morphological information. However, with 3-D CT it was possible to determine the midline discrepancy between the mandibular dentition and body. In treatment planning, 3-D CT analysis indicated that the midline of the mandibular dentition should be established between the left central incisor and the left lateral incisor, as the mandibular body midline coincided with the left central incisor and left lateral incisor in the mandibular dentition.
Presurgical orthodontic treatment and orthognathic surgery were performed according to the treatment objectives based on information obtained by 3-D CT analysis. A harmonized facial appearance in both the lateral and frontal views was accomplished. Not only intimated interdigitation but also improvement of occlusal function, namely lateral guidance and chewing movement, was observed. Thus, 3-D CT allowed the critical points in the special relationship between the various cranio-facial structures and the precise goal of surgical orthodontic treatment to be established. This case demonstrated that 3-D CT is a useful tool in diagnosis and planning not only in surgical simulation, but also in establishing pre-orthodontic treatment goals.

View full abstract