Localisation of deformations of the midfacial complex in subjects with class III malocclusions employing thin-plate spline analysis

A retrospective analysis of dentofacial deformities and orthognathic surgeries using the index of orthognathic functional treatment need (IOFTN)

OBJECTIVES

To assess the functional needs of orthognathic cases treated in Northampton General Hospital using the index of orthognathic functional treatment need (IOFTN).

MATERIALS AND METHODS

A retrospective study was conducted on 78 subjects (54 female and 24 males, 10-54 years, mean (SD) age=21.88 (6.98) years) who had orthognatic surgery in Northampton General Hospital or were in preparation for it (5 case). The sample represents a period between February 1997 and December 2014. The components of IOFTN and Dental Health Component (DHC) of the Index of Orthodontic Treatment Need (IOTN) as well as Malocclusion type were recorded.

RESULTS

Class III malocclusion/skeletal pattern was the most prevalent type (approximately 49%). There were 1, 36, 3, and 38 subjects with Class I, Class II Division I, Class II Division II, and Class III malocclusions, respectively. In terms of sagittal skeletal relationship, there were 2, 37, and 39 subjects with Class I, Class II, and Class III skeletal bases, respectively. The most prevalent IOFTN score in our sample was the 5.2 (29.5%), followed by 5.3 (15.5%), 4.2 (13%), 4.3 (11.5%). Overall, 92.3% were classified as in great and very great functional needs according to the IOFTN. Similarly, 84.6% scored as grade 4 or 5, according to the IOTN (DHC). The bimaxillary type osteotomy was the most prevalent type (61.5%).

CONCLUSIONS

Using IOFTN, 92.3% of our sample were classified as having great and very great functional needs. IOFTN is a simple and reliable tool to identify patients in need of orthognathic surgery and can be used in resource allocation for patients with highest functional needs.

Phenotypic diversity in white adults with moderate to severe Class III malocclusion

INTRODUCTION

Class III malocclusion is characterized by a composite of dentoskeletal patterns that lead to the forward positioning of the mandibular teeth in relation to the maxillary teeth and a concave profile. Environmental and genetic factors are associated with this condition, which affects 1% of the population in the United States and imposes significant esthetic and functional burdens on affected persons. The purpose of this study was to capture the phenotypic variation in a large sample of white adults with Class III malocclusion using multivariate reduction methods.

METHODS

Sixty-three lateral cephalometric variables were measured from the pretreatment records of 292 white subjects with Class II malocclusion (126 male, 166 female; ages, 16-57 years). Principal component analysis and cluster analysis were used to capture the phenotypic variation and identify the most homogeneous groups of subjects to reduce genetic heterogeneity.

RESULTS

Principal component analysis resulted in 6 principal components that accounted for 81.2% of the variation. The first 3 components represented variation in mandibular horizontal and vertical positions, maxillary horizontal position, and mandibular incisor angulation. The cluster model identified 5 distinct subphenotypes of Class III malocclusion.

CONCLUSIONS

A spectrum of phenotypic definitions was obtained replicating results of previous studies and supporting the validity of these phenotypic measures in future research of the genetic and environmental etiologies of Class III malocclusion.

Statistical Shape Analysis of Differences in the Shape of the Corpus Callosum Between Genders

Sexual dimorphic characteristics, which play an important role in human evolution studies and biological research, can be studied morphologically and metrically. Geometric morphometrics allows a better assessment of morphological characteristics. Statistical shape analysis has a long history in neuroanatomical and other research. The aim of this study was to identify shape differences of the corpus callosum between genders. Landmark coordinate data were collected from two-dimensional magnetic resonance imaging scans of 93 homogeneously aged patients, 45 men and 48 women. These data were analyzed using Euclidean distance matrix analysis and thin plate spline analysis. The general shape variability of the corpus callosum of men was greater than that of women (men, 0.134; women, 0.097). We found no significant difference between sexes in the general shape of the corpus callosum, but we did find significant differences in the distances between some landmarks. Deformation of the corpus callosum between men to women was mainly detected in the posterior of the corpus callosum. These results serve as a reference for future studies on shape alterations of the corpus callosum associated with certain conditions.

Thin-plate spline analysis of the effects of face mask treatment in children with maxillary retrognathism

BACKGROUND

Face mask therapy is indicated for growing patients who suffer from maxillary retrognathia. Most previous studies used conventional cephalometric analysis to evaluate the effects of face mask treatment. Cephalometric analysis has been shown to be insufficient for complex craniofacial configurations. The purpose of this study was to investigate changes in the craniofacial structure of children with maxillary retrognathism following face mask treatment by means of thin-plate spline analysis.

METHODS

Thirty children with skeletal Class III malocclusions who had been treated with face masks were compared with a group of 30 untreated gender-matched, age-matched, observation period-matched, and craniofacial configuration-matched subjects. Average geometries, scaled to an equivalent size, were generated by means of Procrustes analysis. Thin-plate spline analysis was then performed for localization of the shape changes.

RESULTS

Face mask treatment induced a forward displacement of the maxilla, a counterclockwise rotation of the palatal plane, a horizontal compression of the anterior border of the symphysis and the condylar region, and a downward deformation of the menton. The cranial base exhibited a counterclockwise deformation as a whole.

CONCLUSION

We conclude that thin-plate spline analysis is a valuable supplement to conventional cephalometric analysis.

Mandibular transformations in prepubertal patients following treatment for craniofacial microsomia: thin-plate spline analysis

To analyze correction of mandibular deformity using an inverted L osteotomy and autogenous bone graft in patients exhibiting unilateral craniofacial microsomia (CFM), thin-plate spline analysis was undertaken. Preoperative, early postoperative, and approximately 3.5-year postoperative posteroanterior cephalographs of 15 children (age 10+/-3 years) with CFM were scanned, and eight homologous mandibular landmarks digitized. Average mandibular geometries, scaled to an equivalent size, were generated using Procrustes superimposition. Results indicated that the mean pre- and postoperative mandibular configurations differed statistically (P<0.05). Thin-plate spline analysis indicated that the total spline (Cartesian transformation grid) of the pre- to early postoperative configuration showed mandibular body elongation on the treated side and inferior symphyseal displacement. The affine component of the total spline revealed a clockwise rotation of the preoperative configuration, whereas the nonaffine component was responsible for ramus, body, and symphyseal displacements. The transformation grid for the early and late postoperative comparison showed bilateral ramus elongation. A superior symphyseal displacement contrasted with its earlier inferior displacement, the affine component had translocated the symphyseal landmarks towards the midline. The nonaffine component demonstrated bilateral ramus lengthening, and partial warps suggested that these elongations were slightly greater on the nontreated side. The affine component of the pre- and late postoperative comparison also demonstrated a clockwise rotation. The nonaffine component produced the bilateral ramus elongations-the nontreated side ramus lengthening slightly more than the treated side. It is concluded that an inverted L osteotomy improves mandibular morphology significantly in CFM patients and permits continued bilateral ramus growth.

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.

Morphologic determinants in the etiology of class III malocclusions: a review

Morphospatial disharmony of the craniomaxillary and mandibular complexes may yield apparent mandibular prognathism, but Class III malocclusions can exist with any number of aberrations of the craniofacial complex. Deficient orthocephalization of the cranial base allied with a smaller anterior cranial base component has been implicated in the etiology of Class III malocclusions. Whereas the more acute cranial base angle may affect the articulation of the condyles resulting in their forward displacement, the reduction in anterior cranial size may affect the position of the maxilla. As well, intrinsic skeletal elements of the maxillary complex may be responsible for maxillary hypoplasia that may exacerbate the anterior crossbite seen in the Class III condition. Conversely, with an orthognathic maxilla, condylar hyperplasia and anterior positioning of the condyles at the temporo-mandibular joint may produce an anterior crossbite. Aside from the skeletal components, soft tissue matrices, particularly labial pressure from the circumoral musculature, may influence the final outcome of craniofacial growth of a child skeletally predisposed to Class III conditions. Indeed, as some Asian ethnic groups demonstrate an increased prevalence of Class III malocclusions, it is likely that the skeletal components and soft tissues matrices are genetically determined. Presumably, the co-morphologies of the craniomaxillary and mandibular complexes are likely dependent upon candidate genes that undergo gene-environmental interactions to yield Class III malocclusions. The identification of such genes is a desirable step in unraveling the complexity of Class III malocclusions. With this knowledge, the clinician may elect an early course of dentofacial orthopedic and orthodontic treatments aimed at preventing the development of Class III malocclusions.