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Biomedical subjects

A F Ayoub

Publications and source records attributed to A F Ayoub.

35 records · Page 2Linked to original sources
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↗
PubMed1993

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.

Bone Remodeling↗
PubMed1993

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.

Adult↗
PubMed1992

Aberrant mandibular growth: theoretical implications.

There is a multiplicity and variety of studies investigating mandibular growth. The exact role of the mandibular condyle in influencing mandibular growth is still a point of conflict. This study was conducted with six subjects who had different condylar defects. The cranium and the skeletal profile, as well as the position of the maxilla and the mandible, were investigated. In all cases, the mandible showed a tendency toward posterior rotation. The total mandibular length was reduced with deficient corpus length and ramus height. The influence of the integrity of the condylar head and its normal articulation in the temporal fossa on mandibular growth were emphasized.

Adult↗
PubMed1991

Soft tissue response to anterior maxillary osteotomy.

The soft tissue profile adaptation to anterior maxillary intrusion was evaluated by comparing preoperative and 6-month postoperative cephalograms of ten adult patients. Holdaway's soft tissue analysis was the method utilized for profile evaluation. Lip protrusion and interlabial gap were decreased significantly and acceptable lip competency was provided postoperatively. Other factors also played a role in controlling the final soft tissue appearance.

Adolescent↗