Biomedical subjects

Hong-Po Chang

Publications and source records attributed to Hong-Po Chang.

10 recordsLinked to original sources

PubMed2006

Treatment of mandibular prognathism.

Mandibular prognathism (MP) or skeletal Class III malocclusion with a prognathic mandible is one of the most severe maxillofacial deformities. Facial growth modification can be an effective method of resolving skeletal Class III jaw discrepancies in growing children with dentofacial orthopedic appliances including the chincup, face mask, maxillary protraction combined with chincup traction and the Fränkel functional regulator III appliance. Orthognathic surgery in conjunction with orthodontic treatment is required for the correction of adult MP. The two most commonly applied surgical procedures to correct MP are sagittal split ramus osteotomy (SSRO) and intraoral vertical ramus osteotomy. Both procedures are suitable for patients in whom a desirable occlusal relationship can be obtained with a setback of the mandible, and each has its own advantages and disadvantages. In bilateral SSRO, the intentional ostectomy of the posterior part of the distal segment can offer long-term positioned stability. This may be attributable to reduction of tension in the pterygomasseteric sling that applies force in the posterior mandible. While various environmental factors have been found to contribute to the development of MP, heredity plays a substantial role. The relative contributions of genetic and environmental components in the etiology of MP are unclear. The recent identification of the genetic susceptibilities to MP constitutes the first step toward understanding the molecular pathogenesis of MP. Further studies in molecular biology are needed to identify the gene-environment interactions associated with the phenotypic diversity of MP and the heterogenic developmental mechanisms thought to be responsible for them.

Humans↗

PubMed2006

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.

Case-Control Studies↗

PubMed2006

Morphometric analysis of the mandible in subjects with Class III malocclusion.

This study evaluated the deformations that contribute to Class III mandibular configuration, employing geometric morphometric analysis. Lateral cephalograms of male and female groups of 100 young adults and 70 children with Class III malocclusion were compared to those of counterparts with normal occlusion. The sample included an equal number of both genders. The cephalographs were traced, and 12 homologous landmarks were identified and digitized. Average mandibular geometries were generated by means of Procrustes analysis. Thin-plate spline analysis was then applied to mandibular configurations to determine local form differences in male and female groups of adults and children with normal occlusion and Class III mal-occlusion. The mandibular morphology was significantly different between these two groups of male and female adults, and children (p < 0.0001). This spline analysis revealed an anteroposterior elongation of the mandible along the condylion-gnathion axis, showing an extension in the regions of the mandibular condyle and ramus, and of the anteroinferior portion of the mandibular symphysis in Class III groups. More extension was evident in Class III adults. The deformations in subjects with Class III malocclusion may represent a developmental elongation of the mandible anteroposteriorly, which leads to the appearance of a prognathic mandibular profile.

Adolescent↗

PubMed2005

Canine transposition.

Transposition is described as an interchange in the position of two teeth within the same quadrant of the dental arch. Canine transposition is reportedly the most common transposition in human dentition. The incidence of maxillary canine-premolar transposition is reported to be 0.135-0.510%. Although the exact mechanism of canine transposition is unclear, it seems to be closely related to genetically influenced, retained deciduous canine, and a history of trauma. In this article, we focus on the classification, incidence, etiology, and treatment modalities of tooth transposition. We hope this information will help clinicians treating patients with this kind of dental anomaly.

Bicuspid↗

PubMed2005

Cranial-base morphology in children with class III malocclusion.

The association between cranial-base morphology and Class III malocclusion is not fully understood. The purpose of this study was to investigate the morphologic characteristics of the cranial base in children with Class III malocclusion. Lateral cephalograms from 100 children with Class III malocclusion were compared with those from 100 subjects with normal occlusion. Ten landmarks on the cranial base were identified and digitized. Cephalometric assessment using seven angular and 18 linear measurements was performed by univariate and multivariate analyses. The results revealed that the greatest between-group differences occurred in the posterior cranial-base region. It was concluded that shortening and angular bending of the cranial base, and a diminished angle between the cranial base and mandibular ramus, may lead to Class III malocclusion associated with Class III facial morphology. The association between cranial-base morphology and other types of malocclusion needs clarification. Further study of regional changes in the cranial base, with geometric morphometric analysis, is warranted.

Cephalometry↗

PubMed2005

Maxillofacial growth in children with unilateral cleft lip and palate following secondary alveolar bone grafting: an interim evaluation.

This study evaluates the effect of alveolar bone grafting on the maxillofacial growth in children of mixed dentition with unilateral complete cleft lip-cleft palate. Twenty patients received an iliac crest alveolar bone graft between the ages of 6 years 10 months and 10 years 10 months, whereas 20 matched controls between the ages of 6 years 11 months and 10 years 6 months did not. Geometric morphometric assessments were used to localize alterations between the initial and final cephalographs in the two groups of cleft children, using Procrustes analysis and thin-plate spline analysis, in addition to conventional cephalometric techniques. It is concluded that no statistically significant difference in maxillofacial growth was found between the cleft children having received secondary alveolar bone grafting and the nongraft controls in general during the first to third postoperative years. Further investigation will be undertaken to determine the long-term effects after the age of skeletal maturity.

Alveolar Bone Loss↗

PubMed2005

Evaluation of the changes in midfacial configuration after face mask therapy in skeletal Class III growing patients by morphometric analysis techniques.

BACKGROUND AND PURPOSE: The prevalence of Angle Class III malocclusion is relatively high in Taiwan. For children who suffer from maxillary retrognathia, face mask therapy is a promising treatment modality. The purpose of this study was to evaluate the changes in midfacial configuration after face mask therapy in skeletal Class III growing patients by morphometric analysis techniques. METHODS: Thirty children who had been treated with face masks were compared with a group of 30 gender-matched, age-matched, observation period-matched, and craniofacial configuration-matched subjects with untreated Class III malocclusions. Average geometries, scaled to an equivalent size, were generated by means of Procrustes analysis. Graphical analysis, utilizing thin-plate spline analysis and strain tensor methods, was performed for localization of differences in shape and size changes. Maximum and minimum principal extensions were drawn to express the directions of shape change. RESULTS: Maxillary protraction-induced changes resulted from a combination of both orthopedic and dental effects. A significant increase in size (7.7% to 9.9%) was noted at the supero-anterior region of the midfacial configuration (rhinion-orbitale-midpalatal point-anterior nasal spine) when subjected to an extraoral traction force; 7.7% to 12.1% of increase in size and 14.4% to 33.4% of change in shape were found at the anterior portion of the maxillary alveolar bone. The directions and amount of principal strain tensors could express the magnitudes and directions of morphological changes within the midfacial complex in an efficient way. CONCLUSIONS: We conclude that morphometric analysis techniques can be used to evaluate the changes in midfacial configuration after face mask therapy and can provide a valuable supplement for conventional cephalometric analysis.

Case-Control Studies↗

PubMed2004

Tooth morphometry in lingual orthodontics.

Lingual orthodontics is used clinically. This study investigated the lingual crown angulation and inclination of optimal occlusion in Taiwanese people. The sample included 45 sets of dental study casts from 28 males and 17 females with optimal occlusion selected from approximately 5,000 young adults. Mesial tipping occurred in all teeth except the upper second molars, the lower central incisors, and the lower lateral incisors. The greatest mesial tipping was observed in the lower second molars. The greatest distal tipping was observed in the lower lateral incisors. Labial (buccal) inclination was observed in all teeth except the lower first molars and the lower second molars. Maximum labial inclination occurred in the upper central incisors. Maximum lingual inclination was observed in the lower first molars.

Adolescent↗

PubMed2004

Treatment effects of chin cup appliance on mandible in Class III malocclusion: strain tensor analysis. A pilot study.

OBJECTIVE: The effects of chin cup therapy on the mandible in Class III malocclusions have been investigated extensively via cephalometric analyses. However, the actual sites of mandibular skeletal change are not detectable with conventional cephalometric analysis. It is important to elucidate the association between remodeling of the mandible with the mechanical stress applied with chin cup therapy. METHOD AND MATERIALS: In this study, the geometric morphometric changes in the mandible from chin cup force and/or growth were investigated using strain tensor analysis. RESULTS: This geometric morphometric analysis reveals that mandibular deformation arises partly due to a size change and partly due to a shape change. The direction and magnitude of principal vectors of the strain tensors may provide more information about this deformation. CONCLUSION: Strain tensor analysis may show the degree of transformation within the mandibular geometric configuration due to treatment effects and/or growth changes as seen on lateral cephalometric radiographs.

Bone Remodeling↗

PubMed2002

Thin-plate spline graphical analysis of the mandible in mandibular prognathism.

The chin cup has been used to treat skeletal mandibular prognathism in growing patients for 200 years. The pull on the orthopedic-force chin cup is oriented along a line from the mandibular symphysis to the mandibular condyle. Various levels of success have been reported with this restraining device. The vertical chin cup produces strong vertical compression stress on the maxillary molar regions when the direction of traction is 20 degrees more vertical than the chin-condyle line. This treatment strategy may prevent relapse due to counter-clockwise rotation of the mandible. In this report, we describe a new strategy for using chin-cup therapy involving thin-plate spline (TPS) analysis of lateral cephalometric roentgenograms to visualize transformation of the mandible. The actual sites of mandibular skeletal change are not detectable with conventional cephalometric analysis. A case of mandibular prognathism treated with a chin cup and a case of dental Class III malocclusion without orthodontic treatment are described. The case analysis illustrates that specific patterns of mandibular transformation are associated with Class III malocclusion with or without orthopedic therapy, and that visualization of these deformations is feasible using TPS graphical analysis.

Cephalometry↗