Evaluation of changes following advancement genioplasty using finite element analysis

This study examined skeletal stability and the remodelling process following advanced pedicled genioplasty. Twenty patients who had advancement genioplasty concomitant with other adjunctive orthognathic surgery were evaluated. A finite element analysis method was used to assess these changes. The stability of the advanced segment was excellent after 6 months. At 6 months bone remodelling was observed in the form of bone apposition at B point and Pogonion with bone resorption at the superior aspect of the advanced segment. The genial segment rotated about 12 degrees antero-superiorly which was thought to be due to the action of the mentalis muscle. Finite element analysis is a sensitive tool for assessing changes after genioplasty and was able to separate them from the effects of other adjunctive orthognathic surgery

A three-dimensional imaging system for archiving dental study casts: a preliminary report

Dental study casts form an essential part of patient records for both diagnostic and medicolegal purposes. Storage of study casts poses major problems because of inconvenience and cost of mass storage. Various methods for recording and storage of study casts are discussed. A new biostereometric technique for digitally recording and storing dental casts, and using the recent advances in stereophotogrammetry, is presented. Archiving dental casts in a digital format would reduce problems of mass storage and provide new benefits such as duplication of casts and use in clinical and research studies

The stability of bimaxillary osteotomy after correction of skeletal Class II malocclusion

This study investigates changes following bimaxillary osteotomy for correction of Class II malocclusion. The records of 15 patients who had simultaneous maxillary impaction and sagittal split ramus osteotomy with rigid fixation are evaluated. Traditional cephalometric analysis as well as finite element and Euclidean distance matrix analyses are used to assess the changes. The maxilla was relatively more stable than the mandible; the maxilla stayed within 1 mm of its immediate postoperative position, whereas the mandible was 2 mm from the achieved surgical changes. The mandible rotated in a clockwise direction during the first 6 months after surgery. The mandibular plane angle increased by 2.9 degrees. This is, in part, believed to be due to posterior condylar displacement during surgery. Theories of mandibular relapse following sagittal split advancement osteotomy are discussed. The new methods of morphometric analysis do not require the superimposition of cephalograms and are able to separate maxillary from mandibular changes

A three dimensional modelling for modern diagnosis and planning in maxillofacial surgery

The existing methods of recording the face in three dimensions are reviewed, and a new method for three-dimensional facial modeling is introduced. The technique utilizes two stereo pairs of videocameras, a stereo pair at each side of the patient's face. The system allows rapid capture of the face in three dimensions and precise measurement of anatomic landmarks. The system can be used to capture the facial image and a cephalogram almost simultaneously, allowing more accurate superimposition of soft and hard tissues. This precision will facilitate development of the surgical treatment plan. A computer program in the early stages of development will use the data generated by this biostereometric measurement system to predict soft tissue changes following orthognathic surgery

Stability of sagittal split advancement osteotomy: single- versus double-jaw surgery

The effect of Le Fort I maxillary impaction on the stability of the sagittal split advancement osteotomy is debatable. The aim of this study was to compare the stability of mandibular advancement in two groups of patients: those that had simultaneous Le Fort I maxillary impaction and sagittal split advancement osteotomy and those that had only sagittal split advancement osteotomy. Lateral cephalograms taken immediately after surgery, 6 months postoperatively, and at 1-year follow-up were used in the assessment. In addition to routine cephalometric analysis, the Euclidean Distance Matrix method was also used. The magnitude of mandibular relapse was similar in both groups in the form of mandibular clockwise rotation and posterior settling. The mandible rotated by 2.2 degrees in the single-jaw surgery group and 2.5 degrees in the bimaxillary osteotomy group. The mandible settled posteriorly by 1.0 degree in the single-jaw surgery group and 1.2 degrees in the bimaxillary osteotomy group. The differences were not statistically significant. In all the patients, Le Fort maxillary osteotomy was more stable than was mandibular advancement. The counter-clockwise rotation of the distal mandibular segments and the distraction of the condylar segments during surgery were responsible for mandibular relapse

A comparison of wire osteosynthesis and screw fixation in the stability of bimaxillary osteotomies

This study compared stability of rigid and nonrigid fixation in patients who underwent simultaneous sagittal split mandibular advancement and Le Fort I maxillary impaction. Immediately postoperative, 6-month, and 1-year follow-up cephalograms were used in the assessment. Slight inferior settling of the posterior end of the maxilla was detected in the nonrigid fixation group, but the maxilla generally stayed within 1 mm of its immediately postsurgical position in both groups. At the 6-month follow-up, the rigid fixation group averaged 2.5 degrees of clockwise mandibular rotation without any change in the gonial angle. In the nonrigid fixation group, the distal segment had rotated in a clockwise direction with an increase in the gonial angle of 3.0 degrees. No further changes were detected in the rigid fixation group, whereas the mandible continued its clockwise rotation in the nonrigid fixation group. These results support the belief that rigid fixation is more stable than wire osteosynthesis. The merits of assessing cephalograms with finite element and Euclidean distance matrix analyses to evaluate surgical changes and stability are discussed

The stability of bimaxillary osteotomy after correction of skeletal Class II malocclusion

This study investigates changes following bimaxillary osteotomy for correction of Class II malocclusion. The records of 15 patients who had simultaneous maxillary impaction and sagittal split ramus osteotomy with rigid fixation are evaluated. Traditional cephalometric analysis as well as finite element and Euclidean distance matrix analyses are used to assess the changes. The maxilla was relatively more stable than the mandible; the maxilla stayed within 1 mm of its immediate postoperative position, whereas the mandible was 2 mm from the achieved surgical changes. The mandible rotated in a clockwise direction during the first 6 months after surgery. The mandibular plane angle increased by 2.9 degrees. This is, in part, believed to be due to posterior condylar displacement during surgery. Theories of mandibular relapse following sagittal split advancement osteotomy are discussed. The new methods of morphometric analysis do not require the superimposition of cephalograms and are able to separate maxillary from mandibular changes

A comparison of wire osteosynthesis and screw fixation in the stability of bimaxillary osteotomies

This study compared stability of rigid and nonrigid fixation in patients who underwent simultaneous sagittal split mandibular advancement and Le Fort I maxillary impaction. Immediately postoperative, 6-month, and 1-year follow-up cephalograms were used in the assessment. Slight inferior settling of the posterior end of the maxilla was detected in the nonrigid fixation group, but the maxilla generally stayed within 1 mm of its immediately postsurgical position in both groups. At the 6-month follow-up, the rigid fixation group averaged 2.5 degrees of clockwise mandibular rotation without any change in the gonial angle. In the nonrigid fixation group, the distal segment had rotated in a clockwise direction with an increase in the gonial angle of 3.0 degrees. No further changes were detected in the rigid fixation group, whereas the mandible continued its clockwise rotation in the nonrigid fixation group. These results support the belief that rigid fixation is more stable than wire osteosynthesis. The merits of assessing cephalograms with finite element and Euclidean distance matrix analyses to evaluate surgical changes and stability are discussed

Euclidean distance matrix analysis of surgical changes in prepubertal craniofacial microsomia patients treated with an inverted L osteotomy

OBJECTIVES Correction of craniofacial microsomia (CFM) presents several challenges concerning the modality of surgical intervention. The aim of this study was to assess early and late surgical outcome, by undertaking Euclidean distance matrix analysis (EDMA) of CFM patients exhibiting an unilateral mandibular deformity that was surgically corrected by an inverted L osteotomy and autogenous bone graft. DESIGN Longitudinal study. Preoperative, approximately =1-year postoperative and approximately 3-year postoperative assessments of 14 consecutive children (mean age 9 years) with CFM. Posteroanterior cephalographs were scanned and five homologous mandibular landmarks were digitized in triplicate (< 1% digitization error). Average mandibular geometries, scaled to an equivalent size, were generated using a generalized rotational fit program (Procrustes superimposition) and subjected to EDMA. RESULTS The mean pre- and both postoperative mandibular configurations differed statistically (p < .01). Early postoperative improvements in mandibular form were noted; increases in length arising in the treated mandibular body (approximately =19%) and ramus (approximately =13%). Comparing early and late postoperative configurations, a decrease of approximately =22% in the late postoperative mandibular body length was evident, but the ramus maintained steady vertical growth (approximately =7%). Comparing the preoperative and late postoperative configurations, the decrease observed in the mandibular body on the treated side was reduced to approximately =8% while the ramus maintained good growth (approximately =20%) on that side. CONCLUSION Mandibular morphology is improved significantly in CFM patients surgically treated by an inverted L osteotomy, but relapse in the mandibular body is evident after approximately =3 years. Nevertheless, ramus growth proceeds well after the surgical reconstruction