Validation of a new method for building a three-dimensional physical model of the skull and dentition.

We present a new method for replicating the skull and occlusal surface with an accurate physical model that could be used for planning orthognathic surgery. The investigation was made on 6 human skulls, and a polyvinyl splint was fabricated on the dental cast of the maxillary dentition in each case. A cone beam computed tomogram (CBCT) was taken of each skull and a three-dimensional replica produced. The distorted dentition (as a result of magnification errors and streak artefacts) was removed from the three-dimensional model and replaced by new plaster dentition that was fabricated using the polyvinyl splint and a transfer jig replication technique. To verify the accuracy of the method the human skulls and the three dimensional replica model, with the new plaster dentition in situ, were scanned using a laser scanner. The three-dimensional images produced were superimposed to identify the errors associated with the replacement of the distorted occlusal surface with the new plaster dentition. The overall mean error was 0.72 and SD was (0.26)mm. The accuracy of the method encouraged us to use it clinically in a case of pronounced facial asymmetry.

Evaluation of an improved orthognathic articulator system. 2. Accuracy of occlusal wafers.

The errors produced by occlusal wafers constructed on casts of the teeth mounted on a standard articulator and an improved orthognathic articulator were investigated by carrying out simulated orthognathic surgery on plastic skulls. The wafers were used to relocate the position of the maxillae of the skulls. The vertical and horizontal displacements of the maxillae were determined from measurements of the positions of markers on the skull and teeth. Comparison of the magnitudes of the actual and intended movements showed that wafers constructed on the standard articulator had systematic prediction errors of up to 5mm, but the improved orthognathic articulator showed much smaller random errors. There was a statistically significant improvement in overall accuracy in predicting maxillary Le Fort I position with the use of the improved orthognathic articulator which the authors recommend for clinical use.

Evaluation of an improved orthognathic articulator system: 1. Accuracy of cast orientation.

A systematic study was carried out using plastic model skulls to quantify the accuracy of the transfer of face bow registration to the articulator. A standard Dentatus semi-adjustable articulator system was compared to a purpose built orthognathic articulator system by measuring the maxillary occlusal plane angles of plastic model skulls and of dental casts mounted on the two different types of articulators. There was a statistically significant difference between the two systems; the orthognathic system showed small random errors, but the standard system showed systematic errors of up to 28°.

Errors in orthognathic surgery planning: the effect of inaccurate study model orientation.

The results of orthognathic surgery may differ significantly from the planned outcome using dental models. The orientation of dental models mounted on articulators using conventional face bows does not accurately replicate the orientation of the patients' teeth and jaws, but introduces a systematic error. A mathematical analysis showed that the misalignment of the maxillary model introduces errors in the perioperative wafers, which may lead to the incorrect surgical positioning of the maxilla reported in the literature. The results of the mathematical analysis were validated by image analysis of photographs of mounted maxillary models, used to simulate five orthognathic procedures. No significant difference between the experimental results and the theoretical predictions from the mathematical equations was noted. Planning for maxillary forward and upward movement produced more advancement and only 50% of maxillary impaction. Planning for maxillary forward and downward movement produced less advancement and more inferior displacement in relation to horizontal and vertical reference planes.

3D assessment of morbidity associated with lower eyelid incisions in orbital trauma.

This study compared the morbidity associated with transconjunctival and transcutaneous approaches for orbital floor exploration with respect to the position of the lower eyelid following surgery. Two groups of 32 volunteers and 32 patients (12 transconjunctival and 20 transcutaneous) were recruited and three-dimensional (3D) imaging was carried out at 6 months following surgery. In the transcutaneous group, there were significant variations in the shape of the lower eyelid, with more medial displacement of the exocanthion. No significant differences were detected in the transconjunctival group compared to controls. The use of a 3D imaging system provided an objective method of assessing this aspect of morbidity associated with the use of lower eyelid incisions.

Bridging and dimensions of sella turcica in subjects treated by surgical-orthodontic means or orthodontics only.

The aim of the study was to compare the incidence of sella turcica bridging and sella turcica dimensions in 150 Caucasian subjects who had combined surgical-orthodontic correction of their malocclusion with a randomly selected group of 150 Caucasian subjects who were treated contemporaneously by orthodontic means only. Pretreatment lateral cephalometric radiographs were scanned and analyzed. A sella turcica bridge was identified as a continuous band of bony tissue extending from the anterior cranial fossa to the posterior cranial fossa. The dimensions of the sella turcica were measured. In the group treated by combined surgical-orthodontic means, the incidence of bridging was 16.7%, whereas it was 7.3% in the orthodontics-only group (P = .012). Significant increases in the mean surface area (P = .02) and mean perimeter of the sella turcica (P = .01) were found for the combined surgical-orthodontic group compared with the orthodontics-only group. The mean interclinoid distance was significantly smaller in the surgical-orthodontic group (P = .02). These findings appear to indicate the greater likelihood of sella turcica bridging and abnormal sella turcica dimensions in subjects treated by combined surgical-orthodontic means rather than by orthodontics only.

Patients' responses to distraction osteogenesis: a multi-centre study.

This investigation aimed to compare and contrast practical difficulties experienced by 54 children from three different centres (Mexico City, New York, Paris) treated with either extra-oral or intra-oral distraction devices. The possible effect of distraction osteogenesis on pain/sleeping difficulty, speech and eating problems and disturbance of recreational activities and alteration in sensation were investigated. It was expected that intra-oral devices would reduce the difficulties associated with the distraction process and their psychological effect on the child. Some benefits resulting from the use of intra-oral devices were identified, these included fewer sleeping problems (P = 0.006) and less disturbance of recreational activities (P = 0.002). However, eating and maintaining oral hygiene were more problematic with intra-oral devices the differences between the intra-oral and extra-oral groups was approaching significance at P = 0.07. A major disadvantage of the extra oral device was scarring. In both groups the alteration of lip sensation was temporary, pain was limited to the time of activation of the distraction device. A high level of patients' cooperation was mandatory for successful completion of the treatment.

Extra-oral craniofacial endosseous implants and radiotherapy.

This paper discusses the use of extra-oral endosseous craniofacial implant (EOECI) therapy in irradiated bone. The survival rate of EOECIs in irradiated bone is reviewed and the controversy over the optimal time prior to place implants is described. The advantages and disadvantages of pre- and post-implant radiotherapy are addressed. The EOECI rehabilitation and osteoradionecrosis and the evidence of the potential role of hyperbaric oxygen are reviewed. Strategies for improving the clinical outcome of EOECIs are suggested.

Miniplate removal in trauma and orthognathic surgery--a retrospective study.

Records of patients undergoing the surgical removal of miniplates placed during the management of maxillofacial trauma (n=49) and orthognathic surgery (n=16) in a single unit, over a 2-year period have been analysed. Data concerning indications for plating, age and sex distribution, site of plating, time between insertion and removal, antibiotic prophylaxis, general medical factors and clinical indications for plate removal were evaluated for all patients. In addition, data for trauma patients included the site of fracture, and time delay between injury and plate insertion. Infection and/or wound dehiscence were the predominant causes for plate removal in both groups, in spite of the routine use of prophylactic antibiotics in a predominantly young, healthy cohort of patients.A removal rate of approximately 10% was found in the two groups of patients. This low rate would seem to imply that the routine removal of miniplates is not clinically indicated.

Extra-oral endosseous craniofacial implants: current status and future developments.

The published experience of extra-oral endosseous craniofacial implants (EOECIs) is reviewed. The definition of osseointegration, concept of success, the relative merit of one- or two-stage implant placement, EOECI design and control of peri-abutment skin infection are discussed. A plea is made for more consistent and objective reading of clinical experience of this technique.

Response of patients and families to lengthening of the facial bones by extraoral distraction osteogenesis: a review of 14 patients.

Fourteen patients or their immediate family were interviewed about their experiences of having either unilateral or bilateral external distraction osteogenesis of the mandible. The patients showed a high level of co-operation with treatment. Six of the 14 patients required repeat distractions, and had been informed and accepted that this was a possibility before the initial distraction. However, patients or their parents expressed some reservations about the extraoral distractors, which prevented them from practising their favourite sport and made them vulnerable to bullying by their friends and colleagues. Patients had moderate pain when the appliances were removed. They all expressed their satisfaction with the results and would recommend this treatment to others. Problems, including speech, eating, pain, and sleeping difficulties, were encountered by patients at all stages of treatment. Of considerable concern was the disruption of education when the child was treated during the school term.

Complications following orthognathic surgery that required early surgical intervention: fifteen years' experience.

The aim of this study was to assess complications following various orthognathic surgical procedures that required early surgical intervention. This study was carried out on 821 patients who had undergone surgical treatment for correction of dentofacial deformities between 1985 and 2000. Only patients who required a second procedure to deal with immediate or early postoperative complications (i.e., those occurring within 4 weeks of surgery) were investigated in this study. Twelve patients underwent a second surgical procedure; 9 had undergone conventional osteotomy surgery, and 3 had undergone distraction osteogenesis. Three Le Fort I cases had to be further impacted and repositioned, and 4 vertical subsigmoid osteotomies had to be reexplored. The details of the complications are presented, and possible methods by which these problems could be reduced and/or prevented are discussed.

Outcome of extra-oral craniofacial endosseous implants.

We report our experience of endosseous implants designed to retain various types of facial prostheses that were inserted by the West of Scotland Oral and Maxillofacial Surgery Service between January 1988 and September 1998. Forty-seven patients were given a total of 150 implants, most of which were auricular (n= 85) or orbital (n= 53). The functioning success rates were 100% and 75%, respectively. Soft tissue infection was the commonest complication, and could occur at any time after exposure of the implant, suggesting that life-long follow-up is required.

The microflora associated with extra-oral endosseous craniofacial implants: a cross-sectional study.

Infection of soft tissues surrounding extra-oral craniofacial endosseous implants is a common clinical problem. The aim of this study was to analyse the microflora associated with such implants, in both health and disease. Eighteen patients with a total of 49 implants were studied. Each patient was seen on two occasions for both a clinical examination and for collection of microbiological samples, using swabs and paper points, from the peri-abutment soft tissues. Specimens were cultured on blood agar and on agars selective for staphylococci and yeasts. Isolates were identified and selective antibiotic susceptibility testing undertaken. No single organism emerged as a predominant cause of peri-abutment skin infection but Staphylococcus aureus, Gram-negative bacilli and yeasts were all present as potential pathogens in this context. Culture and sensitivity results should therefore guide the treatment of these infections.

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.

Randomized prospective study of the influence of steroids on postoperative eye-opening after exploration of the orbital floor.

OBJECTIVE: To find out if giving steroids reduces postoperative swelling in orbital surgery. DESIGN: Prospective, randomized, double-blind trial. SETTING: Regional unit, teaching hospital, UK. SUBJECTS AND INTERVENTIONS: 20 patients who require orbital floor exploration after injuries. Patients were given methylprednisolone 250 mg (or placebo identically packaged) at induction of anaesthesia, with a further three doses at 6-hourly intervals postoperatively. MAIN OUTCOME MEASURE: Differences in interpalpebral width before and after operation. RESULTS: Those given steroids (n=11) had a significantly increased interpalpebral width compared with placebo (n=9) postoperatively (P < 0.01, 95% confidence intervals of the difference = 1 mm-6 mm). CONCLUSION: Short courses of steroids therapy should be considered in orbital surgery for appropriate patients. There is an advantage in being able to assess the globe postoperatively.

Does diplopia persist after blow-out fractures of the orbital floor in children?

Blow-out fractures of the orbital floor are comparatively rare in children, particularly those less than 8 years old. Published reports have suggested that the long-term outcome in children is worse than that in adults with similar injuries. In this study, we examine this question in the light of data from 45 children from Birmingham and Glasgow who were divided into three age ranges: 0-9 years (n = 9), 10-12 years (n = 11) and 13-15 years (n = 25). Fourteen were treated conservatively and 31 were treated surgically. The 0-9-year-old group were more likely to have small- or medium-sized defects in the anterior part of the orbital floor, which were of a linear 'trapdoor' type. The 13-15-year-olds tended to have larger 'open-door' defects. More than half the 0-9-year-olds had persistent diplopia compared with just under a third of the two other age groups. This diplopia took twice as long to resolve in the younger group compared with the other two groups. Our results confirm the view that younger patients have more persistent problems than adults after blow-out fractures of the orbital floor.

Skull reconstruction with a two-part interlocking custom-made titanium plate.

We have used a two-part interlocking titanium plate for cranioplasty in two patients with large skull defects in which reconstruction with a titanium plate was required and extensive contouring of the plate was necessary.

A vision-based three-dimensional capture system for maxillofacial assessment and surgical planning.

We describe a vision-based three-dimensional facial data capture system designed for the planning of maxillofacial operations. We describe the system requirements and outline the methods used to develop a complete three-dimensional facial capture system. Our approach is based upon imaging the face using two stereo-pair sets of cameras. Scale-space-based stereo-matching is then used to recover correspondences between each of the captured stereo-pairs. Photogrammetric routines based on adjustment of bundles are used off-line to calibrate the system by imaging a single object that references all cameras to the same co-ordinate frame. This calibration scheme allows us to convert stereo correspondences to world points for each pair of cameras without the need for any subsequent fusion of data. Initial results show that we are able to capture key facial landmarks to within 0.5 mm.