Biomedical subjects

A F Ayoub

Publications and source records attributed to A F Ayoub.

At least 19 recordsLinked to original sources

PubMed2003

Preliminary assessment of skeletal stability after sagittal split mandibular advancement using a bioresorbable fixation system.

We studied skeletal stability during the first year after mandibular advancement and fixation with bioresorbable self-reinforced poly-L-lactide (SR-PLLA) screws in 11 patients by cephalometric measurements. We compared these with a cohort of 11 patients, in whom titanium screws were used for fixation. We found no significant difference between the two groups in the median preoperative cephalometric values and the median changes after operation. There was also no significant difference between the two groups regarding the median extent of relapse 1-year after operation. We conclude that bioresorbable SR-PLLA screws are comparable to metallic screws for fixation of bone after sagittal split mandibular advancement.

Absorbable Implants↗

PubMed2003

Are facial expressions reproducible?

OBJECTIVES: To determine the extent of reproducibility of five facial expressions. DESIGN: Thirty healthy Caucasian volunteers (15 males, 15 females) aged 21 to 30 years had 20 landmarks highlighted on the face with a fine eyeliner pencil. Subjects were asked to perform a sequence of five facial expressions that were captured by a three-dimensional camera system. Each expression was repeated after 15 minutes to investigate intrasession expression reproducibility. To investigate intersession expression reproducibility, each subject returned 2 weeks after the first session. A single operator identified 3-dimensional coordinate values of each landmark. A partial ordinary procrustes analysis was used to adjust for differences in head posture between similar expressions. Statistical analysis was undertaken using analysis of variance (linear mixed effects model). RESULTS: Intrasession expression reproducibility was least between cheek puffs (1.12 mm) and greatest between rest positions (0.74 mm). The reproducibility of individual landmarks was expression specific. Except for the lip purse, the reproducibility of facial expressions was not statistically different within each of the two sessions. Rest position was most reproducible, followed by lip purse, maximal smile, natural smile, and cheek puff. Subjects did not perform expressions with the same degree of symmetry on each occasion. Female subjects demonstrated significantly better reproducibility with regard to the maximal smile than males (p =.036). CONCLUSIONS: Under standardized conditions, intrasession expression reproducibility was high. Variation in expression reproducibility between sessions was minimal. The extent of reproducibility is expression specific. Differences in expression reproducibility exist between males and females.

Adult↗

PubMed2002

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.

Absenteeism↗

PubMed2001

A new device for microincremental automatic distraction osteogenesis.

We have invented a distraction device that can be placed intraorally and provides autodistraction. The device consists of two units: an implantable component that is applied directly on the bone, and an external component that is distant from the surgical site. The external component is mounted on a standard, battery-driven portable syringe driver or infusion pump. A fine flexible non-compressible tube connects the two. The compression of the bellows in the external component causes fluid to be forced through the connecting tube into the distraction component. The combination of the sealed system and incompressible fluid guarantees expansion of the bellows of the distraction component and gradually separates the bone segments.

Electric Power Supplies↗

PubMed2001

Segmental mandibular reconstruction by microincremental automatic distraction osteogenesis: an animal study.

We investigated the reconstruction of a surgically created critical size mandibular defect in sheep using a newly developed automatic distraction device. The device has an implantable component, which is fixed to the mandible to allow the transfer of the transport disc across the created defect, and an external component which is mounted on the activation pump and secured away from the site of bone distraction. Compression of the bellows in the external component causes fluid to be forced through the connecting tube into the distraction component. Distraction at a rate of 1 mm over 24 h was achieved in six sheep. New bone generated at the site of the created defects both anterior (compression side) and posterior (tension side) to the transport disc and had similar radiodensity to the adjacent mandibular bone eight weeks after the completion of distraction.

Angiography↗

PubMed2001

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.

Adolescent↗

PubMed2000

Evaluation of skeletal stability following surgical correction of mandibular prognathism.

This retrospective study was designed to assess skeletal stability after the correction of mandibular prognathism by sagittal split osteotomy (SSO) and intraoral vertical subsigmoid osteotomy (VSO). We used lateral cephalographs of 31 patients taken before, immediately after, and at least one year after the operation. We recorded euclidean distance matrix analysis, linear and angular measurements, and x and y co-ordinates of cephalometric landmarks for each cephalograph. There were no significant differences in extent of the mandibular retrognathia or magnitude of change between the two groups. The main significant changes in both groups were reduction of the total mandibular length, and posterior shifting in the mandible. One year after the operation the main change was the mean forward relapse of 2.5 mm in the SSO group and the mean posterior relapse of 0.5 mm in the VSO group. The difference in skeletal stability between the groups was significant (P< 0.05), and we conclude that VSO is the more effective technique for correcting mandibular prognathism.

Adolescent↗

PubMed2000

Assessment of zygomatico-orbital complex fractures using ultrasonography.

Twenty-two patients were referred to the maxillofacial surgical unit for assessment and management of suspected fractures of the zygomatico-orbital complex. In each case, both routine plain radiographic and ultrasound examinations were made. The aim of the study was to investigate the sensitivity and reliability of ultrasound to detect such fractures. Imaging with ultrasound was carried out at five areas: the infraorbital margin; lateral wall of the maxillary sinus; zygomatic arch; frontozygomatic process; and orbital floor. Both radiographic and ultrasound findings were correlated with the findings at operation. An overall agreement of 85% between radiographs and ultrasound scans was found. Ultrasound imaging was most reliable at the lateral wall of the maxillary sinus, where the sensitivity was 94% and specificity 100%. The positive predictive value at this area was 100% compared with radiographic findings. We conclude that ultrasound is a useful tool in imaging facial trauma as an initial investigation, and can help to reduce the total number of radiographs required for the diagnosis of fractures of the zygomatico-orbital complex.

Acute Disease↗

PubMed2000

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.

Adolescent↗

PubMed1998

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.

Algorithms↗

PubMed1997

Stability of bimaxillary osteotomy following surgical correction of class II skeletal deformities: a two-centre study.

This study compares the stability following bimaxillary osteotomy for correction of class II skeletal deformities between two groups of patients. One group (15 patients) were treated at Canniesburn Hospital, West of Scotland Regional Plastic and Maxillofacial Unit, UK. The other group (15 patients) were treated at Ann Arbor Michigan University Hospital, USA. All cases were treated by Le Fort I maxillary advancement/impaction and bilateral sagittal split advancement osteotomy. In all cases Le Fort I maxillary osteotomy was more stable than sagittal split advancement osteotomy. The maxilla stayed within 1 mm of its immediate postoperative position. The average mandibular advancement in Canniesburn cases was 6 mm and about 4 mm in Michigan cases. During surgery the condyles were displaced about 2 mm posteriorly in Canniesburn cases, but remain in their anatomic position in Michigan cases. At 6 months following surgery, Canniesburn patients showed a clockwise mandibular relapse. This increased both the mandibular plane angle and ramus angle by 2.7 degrees and 2.9 degrees respectively. The mandible settled posteriorly 1.7 mm and inferiorly 1.5 mm. In Michigan cases the mandible stayed within 1 mm of its immediate postoperative position. The difference in mandibular relapse between the two groups was statistically significant (P < 0.05). The differences in the stability between the two groups are investigated and the theories of mandibular relapse following sagittal split osteotomy are discussed.

Adult↗

PubMed1997

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.

Archives↗

PubMed1996

Management of asymptomatic impacted wisdom teeth: a multicentre comparison.

This study was carried out to assess the opinions of clinicians (general practitioners and oral and maxillofacial surgeons) regarding the management of unerupted Mandibular Asymptomatic Impacted Wisdom Teeth (MAIWT) at two centres: Glasgow Dental Hospital and School and its affiliated institutions and Prince Philip Dental Hospital and its affiliated institutions in Hong Kong. Twenty four clinicians, twelve from each centre, of whom six were oral and maxillofacial surgeons (OMS) and six general dental practitioners (GDP) participated in this investigation. The orthopantomographs of 21 cases were used in the study and were examined by each clinician to investigate the management of unerupted MAIWT was recorded using a custom written questionnaire. Hong Kong clinicians showed a greater tendency towards extraction of MAIWT in comparison to Glasgow clinicians. The difference was statistically significant. The data indicates a significant difference between Hong Kong OMS and Glasgow OMS and between Hong Kong OMS and Hong Kong GDP, with Hong Kong OMS showing a greater tendency towards extraction. This study proved the diversity of opinions in one of the most common dento-alveolar procedures. The dilemma to extract or retain MAIWT still exists and controversy is likely to remain. The difference in the rationale of management regimes between the centres are discussed. The medico-legal and financial issues are investigated.

General Practice, Dental↗

PubMed1996

Three-dimensional modeling 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.

Cephalometry↗

PubMed1995

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.

Cephalometry↗

PubMed1994

Assessment of chin surgery by a coordinate free method.

A quantitative description of the changes and stability after genioplasty in a cross-sectional sample of 19 patients who had advancement genioplasty is presented. Euclidean distance matrix analysis (EDMA) of five cephalometric landmarks was used to assess these changes. During the first 6 months after surgery, bone deposition occurred at B point and pogonion, with bone resorption at the superior and posteroinferior aspects of the advanced segment. The genial segment rotated slightly anticlockwise. The authors believe this to be due to the action of the mentalis muscles. The stability of the advanced segment was excellent when assessed 1 year after surgery. The Euclidean distance matrix method can be used to assess shape changes and does not require cephalographic superimposition. It can also distinguish repositioning from remodelling and the changes of genioplasty from those of concomitant orthognathic surgery.

Cephalometry↗

PubMed1994

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.

Bone Plates↗

PubMed1993

The practicability of finite-element analysis for assessing changes in human craniofacial morphology from cephalographs.

The usefulness of a finite-element analytical (FEA) method for studying changes in facial form was investigated. The material was lateral cephalographs of 19 patients who had undergone surgical correction of the chin. FEA was used to assess changes in bony form brought about by surgery. Replicate digitization of cephalographic landmarks was used to minimize measurement error. Random and systematic errors were examined and their influence on the finite-element method was assessed. However, the sensitivity of FEA is such that the level of residual measurement error affects the reliability of the method and makes the technique unsuitable for individual cases. However, for pooled data from a group of cases the effect of measurement error is reduced and the reliability of the analysis is satisfactory for intergroup comparison.

Cephalometry↗