Quantitative investigation of the esthetic impact of lip prominence in relation to the esthetic line.

INTRODUCTION: The purpose of this quantitative investigation was to assess the influence of lip prominence in relation to the esthetic line (E-line) on perceived attractiveness and threshold values of desire for treatment. METHODS: The lip prominence of an idealized silhouette male white profile image was altered incrementally between -16 mm to 4 mm from the E-line. The images were rated on a Likert scale by pretreatment orthognathic patients (n = 75), laypeople (n = 75), and clinicians (n = 35). RESULTS: In terms of perceived attractiveness, lips to E-line distance within the ranges of -12 mm to -16 mm and 0-4 mm in relation to the E-line was associated with a reduction in median attractiveness scores to below 4 in the patient and clinician groups of observers; for the lay group, the corresponding ranges were -14 mm to -16 mm and 2-4 mm. Relative lip prominence appears to be viewed as more attractive than lip retrusion. Clinicians were generally least likely to suggest treatment for varying levels of bilabial position. For a number of the images, there was reasonable agreement among clinicians and laypeople regarding whether treatment is required. For the clinician group, the only categories for desire for treatment were at a lip to E-line distance within the ranges of -14 mm to -16 mm and 2-4 mm. CONCLUSIONS: It is recommended that the range of normal variability of the prominence of the lips and threshold values of the desire for treatment be considered in planning.

The Opinion of Different Observer Groups About the Esthetic Impact and Need for Surgical Correction of Varying Submental Lengths.

PURPOSE: This study evaluated the opinion of different observer groups about the influence of the submental length on perceived attractiveness and when surgical correction was deemed necessary. MATERIALS AND METHODS: The submental length of an idealized silhouette of a white male profile was altered incrementally between 5 and 95 mm. Images were rated for attractiveness on a Likert scale by pretreatment orthognathic surgery patients (n = 75), laypersons (n = 75), and clinicians (maxillofacial surgeons and orthodontists) (n = 35). RESULTS: For perceived attractiveness, the ideal submental length was approximately 50 mm (range, 40 to 75 mm). A submental length shorter than or equal to 30 mm was deemed unattractive by all 3 groups. Overall, a submental length less than 40 mm generally was judged less attractive than a comparable increase in length. Clinicians were generally least likely to suggest surgery for varying submental lengths. For this group, the cutoff at which the majority suggested surgery was a submental length of 25 mm or less. For the patient and layperson groups, the corresponding cutoff values were a length shorter than or equal to 30 mm or equal to 95 mm. CONCLUSIONS: A submental length of approximately 50 mm (range, 40 to 75 mm) was viewed by most observers as attractive. At 30 mm or less, it was generally deemed progressively less attractive. Clinicians were less likely to suggest corrective surgery than were the patient and layperson groups. For comparative proportional relationships, the submental length should be between the lower lip-chin height and lower facial height, assuming an otherwise proportional facial profile.

The aesthetic impact of upper lip inclination in orthodontics and orthognathic surgery.

BACKGROUND: The nasolabial angle, particularly its lower component, i.e. the upper lip inclination (ULI), is an important keystone in treatment planning. Normative data for this parameter are not available. OBJECTIVES: A quantitative evaluation of the aesthetic impact of ULI on perceived attractiveness and threshold values of desire for treatment was undertaken. METHODS: The ULI of an idealized silhouette profile image was altered incrementally between 61 and 100 degrees. Images were rated on a Likert scale by pre-treatment orthognathic patients (n = 75), laypeople (n = 75), and clinicians (n = 35). RESULTS: An ULI between 79 and 85 degrees is viewed as ideal, with a range of 73-88 degrees deemed acceptable. Angles above or below this range, down to 67 degrees and up to 94 degrees are perceived as slightly unattractive, and anything outside the range of 67-94 degrees is deemed very unattractive. For patients the threshold value of desire for treatment was 91 degrees and above and 64 degrees and below, and for both clinicians and lay people the threshold value was 94 degrees and above and 64 degrees and below. Patients appear to be more critical than lay and clinician groups. This stresses the importance of using patients as observers, as well as laypeople and clinicians, in facial attractiveness research. LIMITATIONS: The results are based on an idealized male Caucasian profile. CONCLUSIONS: It is recommended that in treatment planning, the range of normal variability of the ULI, in terms of observer acceptance, is taken into account as well as the threshold values of the desire for treatment.

"Association between posterior unilateral functional crossbite and asymmetrical spinal flexion: A prospective study".

Background: Unilateral posterior crossbite (UPC) with functional shift is a malocclusion that may have the potential to affect the masticatory function and the flexibility of the spine due to intrinsic occlusal, structural and functional asymmetries sustained by marked asymmetrical muscular activation. Research question: To investigate whether the presence of UPC with functional shift is associated with reverse chewing pattern and altered spine flexion. Methods: Patients with UPC and a control group of patients with normal occlusion were recorded when chewing soft and hard boluses using a Kinesiograph (Myotronics-Noromed Inc., USA) and spine alignment was assessed with an electronic inclinometer Spinal Mouse® system (Idiag AG, Switzerland). Results: There were 87 children with UPC in the patients' group among whom 38, with median (IQR) age 8.0 (7.3-9.3) years, had measurements before and after treatment. The UPC patients showed a higher percentage of anomalous/reverse chewing patterns on the crossbite side compared with a control group (p < 0.001). Moreover, a clear difference was observed between left and right flexion angles of the spine in the patients' group (p < 0.001 and p = 0.001, paired t-test) with the crossbite side being more flexible compared to the non-crossbite side. No such differences were seen in the control group, nor post-treatment for right and left crossbite (p = 0.44 and p = 0.15 respectively, paired t-test). Significance: This study suggests an association between UPC, asymmetrical chewing patterns and asymmetrical flexion of the spine. These results may help improve understanding of any association between dental malocclusions and spine posture and hence aid diagnosis and treatment strategies.

Mandibular shape prediction using cephalometric analysis: applications in craniofacial analysis, forensic anthropology and archaeological reconstruction.

BACKGROUND: The human mandible is variable in shape, size and position and any deviation from normal can affect the facial appearance and dental occlusion. OBJECTIVES: The objectives of this study were to determine whether the Sassouni cephalometric analysis could help predict two-dimensional mandibular shape in humans using cephalometric planes and landmarks. MATERIALS AND METHODS: A retrospective computerised analysis of 100 lateral cephalometric radiographs taken at Kingston Hospital Orthodontic Department was carried out. RESULTS: Results showed that the Euclidean straight-line mean difference between the estimated position of gonion and traced position of gonion was 7.89 mm and the Euclidean straight-line mean difference between the estimated position of pogonion and the traced position of pogonion was 11.15 mm. The length of the anterior cranial base as measured by sella-nasion was positively correlated with the length of the mandibular body gonion-menton, r = 0.381 and regression analysis showed the length of the anterior cranial base sella-nasion could be predictive of the length of the mandibular body gonion-menton by the equation 22.65 + 0.5426x, where x = length of the anterior cranial base (SN). There was a significant association with convex shaped palates and oblique shaped mandibles, p = 0.0004. CONCLUSIONS: The method described in this study can be used to help estimate the position of cephalometric points gonion and pogonion and thereby sagittal mandibular length. This method is more accurate in skeletal class I cases and therefore has potential applications in craniofacial anthropology and the 'missing mandible' problem in forensic and archaeological reconstruction.

Nasolabial angle and nasal tip elevation changes in profile view following a Le Fort I osteotomy with or without the use of an alar base cinch suture: a long-term cohort study.

OBJECTIVES: Cinch sutures attempt to counteract alar base widening but may lead to unintended increases in the nasolabial angle and nasal tip elevation. The aim of this investigation was to assess nasolabial angle changes after maxillary osteotomies with and without alar base cinch sutures in the short and long terms. STUDY DESIGN: Seventy-eight patients were assessed, with 51 in the cinch group (38 females, 13 males; age range 16-39 years) and 27 in the no-cinch group (12 females, 15 males; age range 17-27 years). The upper component (nasal tip elevation), lower component (lower lip inclination), and the overall nasolabial angle were measured on preoperative, postoperative, and long-term follow-up lateral cephalometric radiographs. RESULTS: The overall nasolabial angle (P = .006) and its upper component (P < .001) increased significantly in the cinch group immediately postoperatively but resolved by 6 to 12 months for the overall nasolabial angle and by 12+ months (up to 5.7 years) for the upper component. There were no significant changes in the no-cinch group. CONCLUSIONS: In the short term, the alar base cinch suture increases nasal tip elevation and the overall nasolabial angle. In the long term, there was no significant difference, suggesting that the initial nasal tip elevation resolves over time and that the cinch suture may have a limited effect on nasal tip elevation in the longer term.

Analysing chin prominence in relation to the lower lip: The lower lip-chin prominence angle.

The purpose of this investigation is to describe a potentially useful analysis in assessing the required extent of sagittal chin augmentation or set-back, by relating chin prominence to lower lip position using the 'lower lip-chin prominence angle'. The secondary aim was to quantitatively evaluate the influence of this angle on perceived attractiveness and desire for surgery. Having described this angular analysis, a quantitative evaluation was undertaken by incrementally altering the angle on an idealised profile image to create a range of images that were rated on a 7-point Likert scale by a pre-selected group of pre-treatment orthognathic patients, clinicians and laypeople. In treatment planning alterations in chin prominence, an 'ideal' sagittal position with soft tissue pogonion on or just behind a true vertical line through the most prominent point of the lower lip may be used. Chin retrusion or prominence up to an angle of 15° retrusion to -5° prominence is deemed acceptable. Surgery is desired from chin prominence of greater than -15° and retrusions greater than 25°. The greater the retrusion or prominence of the chin from an angle of 0°, the less the perceived attractiveness and the greater the desire for surgical correction.

Normative anthropometry and proportions of the Kenyan-African face and comparative anthropometry in relation to African Americans and North American Whites.

BACKGROUND: There is no normative craniofacial anthropometric data for the Kenyan-African population. The purpose of this investigation was to determine normative anthropometric craniofacial measurements and proportional relationships for Kenyans of African descent and to compare the data with African Americans (AA), North American Whites (NAW), and neoclassical canons. METHODS: Twenty-five direct facial anthropometric measurements, and 4 angular measurements, were taken on 72 Kenyan-African participants (age range 18-30 years) recruited at the University of Nairobi in Kenya. The data were compared with AA and NAW populations, and neoclassical canons. Descriptive statistics of the variables were computed for the study population. RESULTS: Significant differences between both Kenyan males and females were detected in forehead height (~ 5 mm greater for males, ~ 4.5 mm for females), nasal height (reduced by ~ 4 mm in males, ~ 3 mm in females), nasal width (8-9 mm greater), upper lip height (> 3 mm), and eye width (greater by ~ 3 mm) compared to NAW subjects. All vertical measurements obtained were significantly different compared with NAW. Differences were observed in comparison with AA subjects, but less marked. Mouth width was similar in all groups. Angular measurements were variable. Neoclassical canons did not apply to the Kenyan population. CONCLUSIONS: Anthropometric measurements of NAW showed clear differences when compared with the Kenyan population, and variations exist with comparative AA data. The anthropometric data in terms of linear measurements, angular measurements, and proportional values described may serve as a database for facial analysis in the Kenyan-African population.

Characterisation of the macroporosity of polycaprolactone-based biocomposites and release kinetics for drug delivery.

Microporous, biocomposite matrices comprising a continuous phase of poly(epsilon-caprolactone) (PCL) and a dispersed phase of lactose or gelatin particles with defined size range (45-90, 90-125 and 125-250 microm) were produced by precipitation casting from solutions of PCL in acetone. Scanning electron microscopy (SEM) analysis revealed a characteristic surface morphology of particulates interspersed amongst crystalline lamellae of the polymer phase. Rapid release of around 80% of the lactose content occurred in PBS at 37 degrees C in 3 days, whereas biocomposites containing gelatin particles of size range 90-125 and 125-250 microm, respectively, displayed gradual and highly efficient release of around 90% of the protein phase over 21 days. A highly porous structure was obtained on extraction of the water-soluble phase. Micro-computed tomography (Micro-CT) and image analysis enabled 3-D visualisation and quantification of the internal pore size distribution. A maximum fractional pore area of 10.5% was estimated for gelatin-loaded matrices. Micro-CT analysis confirmed the presence of an extensive system of macropores, sufficiently connected to permit protein diffusion, but an absence of high volume, inter-pore channels. Thus tissue integration would be confined to the matrix surface initially if the designs investigated were used as tissue-engineering scaffolds, with the core potentially providing a depot system for controlled delivery of growth factors.

Production and in vitro evaluation of macroporous, cell-encapsulating alginate fibres for nerve repair.

The prospects for successful peripheral nerve repair using fibre guides are considered to be enhanced by the use of a scaffold material, which promotes attachment and proliferation of glial cells and axonal regeneration. Macroporous alginate fibres were produced by extraction of gelatin particle porogens from wet spun fibres produced using a suspension of gelatin particles in 1.5% w/v alginate solution. Gelatin loading of the starting suspension of 40.0, 57.0, and 62.5% w/w resulted in gelatin loading of the dried alginate fibres of 16, 21, and 24% w/w respectively. Between 45 and 60% of the gelatin content of hydrated fibres was released in 1h in distilled water at 37°C, leading to rapid formation of a macroporous structure. Confocal laser scanning microscopy (CLSM) and image processing provided qualitative and quantitative analysis of mean equivalent macropore diameter (48-69µm), pore size distribution, estimates of maximum porosity (14.6%) and pore connectivity. CLSM also revealed that gelatin residues lined the macropore cavities and infiltrated into the body of the alginate scaffolds, thus, providing cell adhesion molecules, which are potentially advantageous for promoting growth of glial cells and axonal extension. Macroporous alginate fibres encapsulating nerve cells [primary rat dorsal root ganglia (DRGs)] were produced by wet spinning alginate solution containing dispersed gelatin particles and DRGs. Marked outgrowth was evident over a distance of 150µm at day 11 in cell culture, indicating that pores and channels created within the alginate hydrogel were providing a favourable environment for neurite development. These findings indicate that macroporous alginate fibres encapsulating nerve cells may provide the basis of a useful strategy for nerve repair.

Validation of a new three-dimensional imaging system using comparative craniofacial anthropometry.

BACKGROUND: The aim of this study is to validate a new three-dimensional craniofacial stereophotogrammetry imaging system (3dMDface) through comparison with manual facial surface anthropometry. The null hypothesis was that there is no difference between craniofacial measurements using anthropometry vs. the 3dMDface system. METHODS: Facial images using the new 3dMDface system were taken from six randomly selected subjects, sitting in natural head position, on six separate occasions each 1 week apart, repeated twice at each sitting. Exclusion criteria were excess facial hair, facial piercings and undergoing current dentofacial treatment. 3dMDvultus software allowed facial landmarks to be marked and measurements recorded. The same measurements were taken using manual anthropometry, using soluble eyeliner to pinpoint landmarks, and sliding and spreading callipers and measuring tape to measure distances. The setting for the investigation was a dental teaching hospital and regional (secondary and tertiary care) cleft centre. The main outcome measure was comparison of the craniofacial measurements using the two aforementioned techniques. RESULTS: The results showed good agreement between craniofacial measurements using the 3dMDface system compared with manual anthropometry. For all measurements, except chin height and labial fissure width, there was a greater variability with the manual method compared to 3D assessment. Overall, there was a significantly greater variability in manual compared with 3D assessments (p < 0.02). CONCLUSIONS: The 3dMDface system is validated for craniofacial measurements.

Submental-Cervical Angle: Perceived Attractiveness and Threshold Values of Desire for Surgery.

AIM: The submental-cervical angle may alter as a result of mandibular orthognathic surgery and/or the ageing process and is therefore an important facial aesthetic parameter for comparative diagnosis and treatment planning. The purpose of this study was to undertake a quantitative evaluation of the influence of the submental-cervical angle on perceived attractiveness and threshold values of desire for surgery. STUDY DESIGN: The submental-cervical angle of an idealized profile silhouette image was altered incrementally between 90° and 130°. The images were rated on a seven-point Likert scale by pre-treatment orthognathic patients (n = 75), laypeople (n = 75), and clinicians (n = 35). RESULTS: A submental-cervical angle of 90°-105° was deemed acceptable. Angles up to 120° were deemed slightly unattractive by the lay and clinician groups, but very unattractive by the patient group. By 125°-130° all groups perceived the angle as very unattractive. The threshold value of desire for surgery was 110° for patients, 115° for lay people and 125° for clinicians. Patients appear to be more critical than lay and clinician groups. CONCLUSIONS: These ranges of normal variability of the submental-cervical angle and threshold values of desire for surgery, in terms of observer acceptance, should be considered by clinicians in planning mandibular orthognathic surgery and aesthetic surgical procedures of the submental-cervical region.

Pressure oscillation amplitude after interruption of tidal breathing as an index of change in airway mechanics in preschool children.

Bronchodilator reversibility testing using change in airway resistance during interruption (Rint) is feasible in preschool children. Analysis of postocclusion oscillations of the mouth pressure-time transient (Pmo(t)), recorded during airflow interruption, may offer an alternative index of change in airway mechanics. We analyzed Pmo(t) oscillation amplitude in three different ways: 1) difference between the first relative maximum and minimum (AMxMn); 2) detection of the dominant frequency using Fourier analysis (AFS); and 3) curve-fitting based on a mathematical model (ACurv). In 25 asymptomatic asthmatic children, aged 2.5-5.6 years, who had undertaken reversibility testing, the correlation coefficients between baseline Rint and amplitude were: AMxMn r = -0.84, AFS r = -0.82, ACurv r = -0.84. The coefficient of variation (CoV) of readings contributing to baseline Rint measurement, as median (range), was 12% (5-24%), which was not significantly different from AFS or ACurv (P > 0.05). All parameters were significantly different postbronchodilator (P < 0.001). Using the sensitivity index, i.e., the change after intervention divided by the baseline standard deviation, ACurv was the most sensitive and Rint the least sensitive, with median (range) at 2.72 (-0.84 to 12.10) and 1.91 (-1.17 to 9.50), respectively (P = 0.005). Our results suggest that oscillation amplitude analysis may provide a sensitive index of change in airway mechanics in preschool children undertaking bronchodilator reversibility testing.

Analysis of retrieved growth guidance sliding LSZ-4D devices for early onset scoliosis and investigation of the use of nitinol rods for this system.

STUDY DESIGN: Analysis of volumetric wear loss of retrieved growth guidance sliding devices LSZ-4D for treatment of early onset scoliosis and laboratory in vitro wear test for comparison of wear resistance of alloys Nitinol, Ti, and cobalt chromium (CoCr). OBJECTIVE: To evaluate quantitatively the amount of wear debris from the sliding LSZ-4D device and to investigate the potential of using Nitinol for replacing Ti alloys in spinal instrumentation. To do that, wear resistance of Nitinol, Ti, and CoCr was compared. SUMMARY OF BACKGROUND DATA: There are little data regarding the amount of wear debris associated with growth guidance sliding devices for patients with early onset scoliosis and the wear resistance of superelastic Nitinol compared with Ti and CoCr. METHODS: Volumetric wear loss was measured on LSZ-4D devices made from titanium alloy Ti6Al4V and each consisted of 2 rectangular section (6 × 4 mm) rods and 40 ± 8 fixture elements (20 ± 4 hooks and 20 ± 4 clips) retrieved from 3 patients (implantation period, 3.5-5.8 yr). Images of wear scars were taken on Bruker interferometer microscope and incorporated into MATLAB software. Wear resistance of Nitinol, Ti, and CoCr was studied using reciprocation pin-on-disk wear test in bovine serum at 37°C ± 1°C. RESULTS: The volume wear rate of LSZ-4D device was found to be 12.5 mm per year from which 5 mm³ per year is the wear debris of the rod and 7.5 mm per year is the contribution of fixtures. Wear resistance of Nitinol is 100 times higher than that of Ti and comparable with that of CoCr. CONCLUSION: Application of wear-resistant coatings on Ti components in growth guidance sliding devices for the treatment of early onset scoliosis will be useful. High wear resistance of Nitinol combined with its superelastic and shape memory properties could make application of Nitinol rods for spinal instrumentation beneficial.

Micro-CT in drug delivery.

Micro-computed tomography (micro-CT) has not to date been fully exploited in the area of controlled drug delivery despite its capability for providing detailed, 3-D images of morphology and the opportunity this presents for exploring the relationships between delivery device formulation, structure and performance. Micro-CT was used to characterize the internal structure of polycaprolactone (PCL) matrix-type devices incorporating soluble particulates (lactose Mw 342.30, gelatin Mw 20-25kDa) as models of hydrophilic bioactives or pore-forming excipients. Micro-CT images confirmed that the lactose and gelatin particles were uniformly dispersed throughout the PCL phase and that efficient delivery of 95-100% of each species in 9days involved transport from the matrix core. Quantitative analysis of micro-CT images provided values for matrix macroporosity, which were within 15% of the theoretical value and revealed uniform porosity throughout the samples. Total release of protein occurred in 9days (PBS, 37 degrees C) from matrices containing a high protein load (44%w/w) and was independent of particle size. Measurements of equivalent pore diameter and frequency distribution identified a large population of sub-40microm pores in each material, indicative of a high density of connecting channels between particles which facilitates protein transport through the matrices.

Micro-CT analysis of matrix-type drug delivery devices and correlation with protein release behaviour.

A series of matrix-type drug delivery devices comprising a continuous phase of microporous poly(epsilon-caprolactone) (PCL) and a dispersed phase of protein particles (gelatin) with defined size ranges (45-90, 90-125 and 125-250 microm) were produced by rapidly cooling suspensions in dry ice followed by solvent extraction from the hardened material. High protein loadings (38-44%, w/w) were achieved and highly efficient protein release (90% of the initial load) was obtained over time periods of 3-11 days depending on particle loading and size range. The duration of protein release was extended from 3 to 11 days by reducing the protein load. Quantitative analysis of Micro-CT images identified a three to four times increase in the population of sub-40 microm pores in those matrices which gave rise to accelerated protein release in 24 h (40% rising to 80%) and reduced duration of protein release (11-3 days). Formation of a high density of channels and fissures (connects) between the particles is indicated, which facilitate fluid ingress and diffusion of solubilised protein molecules. Micro-CT analysis also confirmed the uniformity of particle distribution in the matrices and provided measurements of macroporosity within 5-30% of the theoretical value for materials displaying irregular shaped macropores larger than 90 microm. These findings demonstrate the utility of Micro-CT for optimising the formulation and performance of matrix-type delivery devices for macromolecular entities.

A computerized photographic assessment of the relationship between skeletal discrepancy and mandibular outline asymmetry.

The aim of this study was to investigate the relationship between mandibular outline asymmetry and skeletal discrepancy in a sample of orthodontic patients (33 females, 33 males) aged from 8 to 19 years. Skeletal discrepancy was assessed in both the anteroposterior and vertical planes, using standard cephalometric analyses. All were photographed under standardized conditions and the photographs were then digitized for analysis using a computerized system to assess differences in four variables (area, perimeter, compactness and moment-ratio) between the right and left sides of the mandibular outline. The results showed good repeatability of the photographic, cephalometric and digitization methods. A statistically significant relationship was found between mandibular outline asymmetry and both anteroposterior and vertical skeletal discrepancy in this sample, when compared with patients with an average skeletal pattern. There appeared to be a statistically significant relationship between a reduced ANB angle (< 3 degrees) and mandibular outline asymmetry (P = 0.051), as well as between an increase in lower face height and mandibular asymmetry (P = 0.023).

Change in cranio-cervical angulation following orthognathic surgery.

Changes in natural head posture (NHP) were investigated in 33 patients (10 males, 23 females) with an age range of 16-40 years (median 21 years) following orthognathic surgery to change vertical face height. The reproducibility of the radiographer's technique of taking radiographs in NHP was investigated using a photographic method and found to be acceptable. The patients were divided into two groups: group 1, patients who had more than 3 mm of vertical change in anterior total face height (ATFH) and group 2, those who had less than 3 mm vertical change. For group 1 there was a significant relationship between ATFH change and cranio-cervical angulation (NSL/OPT) change (r = 0.532, P = 0.023), compared with group 2 (r = -0.247, P = 0.376). A similar relationship was revealed between lower anterior face height (LAFH)/ATFH ratio and NSL/OPT, where the correlation was also higher in group 1 (r = -0.635, P = 0.005) compared with group 2 (r = -0.182, P = 0.515). The correlation between cranio-vertical angulation (NSL/VER) and ATFH was not significant for group 1 (r = 0.406) or group 2 (r = 0.239) patients. Additionally, NSL/VER and LAFH/ATFH correlation for the two groups was not significant (r = -0.392 and -0.338, respectively). There appears to be a relationship between the reduction in vertical face height following orthognathic surgery and neck posture (as indicated by NSL/OPT). As no significant relationship was found between the reduction in face height and head posture (as indicated by NSL/VER) this suggests that neck posture, rather than head posture, had changed.

Mandibular outline assessment in three groups of orthodontic patients.

The feasibility of using computer-based parameters for quantifying mandibular asymmetry was investigated. Four methods of calculating asymmetry were used, based on the digitized facial photographs of three groups of patients: those with no observable asymmetry, a group with mild asymmetry, and a group presenting for orthognathic surgery. Three of the methods involved right/left difference ratios, namely, area, perimeter length, and compactness. The fourth, moment ratio (centre of area), was expressed as a percentage. Repeatability of both photography and digitization proved satisfactory, the standard deviation of the differences between repeated photographs being 0.016 and 0.014 for area and compactness ratios, respectively. Area, perimeter, and compactness successfully discriminated between the three groups. For area, median ratios (deviations from 1.00) for the 'normal', 'mild asymmetry', and 'surgical' groups were 0.015, 0.030, and 0.078, respectively. Those patients in the surgical group for whom asymmetry correction had been the main reason for surgery recorded higher asymmetry scores than the other subjects in that group. Moment ratio did not adequately distinguish between the three groups. Better repeatability for digitization was found when a baseline involving the ear insertions was used, than either the outer or inner canthi of the eyes. The potential uses of this approach are presented in relation to clinically relevant mild asymmetry, as well as auditing the outcome of surgical correction.

Comparison of radiographic and photographic measurement of mandibular asymmetry.

This study compared measurement of mandibular asymmetry by digitization of mandibular outlines from standardized facial photographs and posteroanterior cephalometric radiographs. Four ratios were used in calculating asymmetry: area (relative size of right and left mandibular segments), perimeter or length of outlines, compactness (shape), and moment. The records of 28 patients with varying degrees of asymmetry were used. A significant relationship was found for 3 of the ratios (area, compactness, and moment) between measurements from photographs and radiographs. A further comparison showed that measurements from the radiographs correlated more closely with those from photographs when the mastoid processes were used as a baseline, rather than latero-orbitale. Repeatability of mandibular outline digitization proved satisfactory. Although digitization from standardized photographs is the preferred approach, the results indicated that posteroanterior cephalometric radiographs can be used similarly. Unlike other cephalometric analyses for mandibular asymmetry, this method avoids problems of landmark identification, thus presenting a clinically useful method of quantifying asymmetry, eg, in auditing the surgical-orthodontic correction of asymmetry or monitoring change over time.