Convexity Angle Research Articles

Downs cephalometric norms for Iraqi adolescents in Mosul City

The purpose of this study is to develop cephalometric standards for Iraqi adolescents in Mosul City, using Downs' analysis, and to compare them with those of white Americans. The lateral cephalometric radiographs (108) Iraqi adolescents (57 males and 51 females) with age range was (12) to (15) years (with a mean of 13.7 years) were carried out. The subjects were chosen on the bases of having class I normal occlusion and well-balanced faces. Measurements were taken for all dento-skeletal variables in Downs' analysis. Norms were established for the Iraqi sample and the comparison between both sexes was carried out. No significant difference was demonstrated between males and Females. When the measurements of this study were compared with Downs' original data for white Americans, the Iraqi adolescents showed a highly significant greater values of facial convexity angle, mandibular plane angle, Y-axis angle, occlusal plane angle, lower incisors inclination to the occlusal plane and to the mandibular plane and the distance of upper incisors to Apog line. The interincisal angle and facial angle were significantly higher in Downs' original standards than the present study

Seven parameters describing anteroposterior jaw relationships: Postpubertal prediction accuracy and interchangeability

Seven parameters describing anteroposterior jaw relationships (the A-B plane angle, the angle of convexity, the ANB angle, the SN-AB angle, the Wits appraisal, the AF-BF distance, the APDI) were measured on pairs of prepubertal and postpubertal cephalograms of 44 normal occlusion subjects (20 males and 24 females). The mean ages at prepubertal and postpubertal stages were 10 years 5 months and 14 years 5 months in males and 8 years 10 months and 12 years 10 months in females, respectively. The purpose of this study was to compare prediction accuracy of future relationships by regression analysis and to evaluate interchangeability among the 7 parameters by correlation analysis. In the prepubertal assessment, the ANB angle and the angle of convexity showed better prediction accuracy for postpubertal jaw relationships. Higher interchangeability among the parameters was statistically substantiated between the SN-AB angle and the AF-BF distance, as well as among the ANB angle, the angle of convexity, and the A-B plane angle. The Wits appraisal and the APDI were less interchangeable with other parameters. The ANB angle, the Wits appraisal, and the APDI would complement each other for the geometrically distorting factors because of the low interchangeability due to their different geometric basis. The conjunctive use of the ANB angle, the Wits appraisal, and the APDI is recommended as a clinically appropriate method for assessment of jaw relationships in individuals. (Am J Orthod Dentofacial Orthop 2000;117:714-20)

Sagittal changes after maxillary protraction with expansion in Class III patients in the primary, mixed, and late mixed dentitions: A longitudinal retrospective study

The purpose of this study was to determine the sagittal response of Class III patients in the primary, mixed, and late mixed dentition phases fitted with a protraction mask and expansion. The before-and-after cephalometric records of 112 patients divided by gender were analyzed at age groups 3 to 6, 6 to 9, and 9 to 12 years to assess the maxillary, mandibular, and intermaxillary sagittal changes. Data were correlated by means of paired t tests and Scheffé multiple contrasts. The study showed: (1) descriptive statistics and the before-and-after results in males and females in the different age groups; (2) the changes in males and females, disregarding age; and (3) the changes at the different ages, disregarding gender. Results show no significant differences between males and females in most of the angular and linear measurements at different ages. Greater significant changes were seen in patients treated in the primary and mixed dentition phases. Females showed highly significant changes in most linear and angular measurements between the ages of 3 and 6 years ( P < .0001) compared with males ( P < .05 ) at the same age. Significant changes were seen in the angle between the anterior part of the maxilla and the base of the skull (SNA), the maxillary depth, and the facial convexity angles, being more active in females than males. In contrast, the angle between the anterior part of the mandible and the base of the skull (SNB) showed no significant changes in all age groups, with the exception of males between 3 and 6 years. Even if correction can be achieved in all age groups, we recommend that treatment be started as soon as the diagnosis is made and cooperation allows for it. Young patients show greater and faster results in less time. Esthetics are greatly enhanced, compliance is improved, and the possible psycho-social scars can be greatly reduced. (Am J Orthod Dentofacial Orthop 2000;117:669-80)

Soft tissue profile changes from 5 to 45 years of age

The purpose of this study was to describe the changes in five soft tissue parameters that are commonly used by orthodontic practitioners in their diagnosis and treatment planning as well as in their evaluation of profile changes that occur with growth and orthodontic treatment. The subjects in this study were 20 males and 15 females for whom lateral cephalograms were available between 5 and 45 years of age. The parameters evaluated were two angles of facial convexity, the Holdaway soft tissue angle, and the relationship of the upper and lower lips to Rickett’s esthetic line. Descriptive statistics for the absolute and incremental changes were collected on a yearly basis between 5 and 17 years of age as well as at early (25 years) and middle (45 years) adulthood. Growth profile curves were constructed for each parameter to describe the age-related changes in the five parameters for both males and females. The analysis of variance was used to compare the absolute and incremental changes both longitudinally and cross-sectionally. Significance was predetermined at P ≤ .05. The present findings indicated that (1) in general, the changes in males and females were similar in both magnitude and direction. On the other hand, the timing of the greatest changes in the soft tissue profile occurred earlier in females (10 to 15 years) than in males (15 to 25 years); (2) the angle of soft tissue convexity that excludes the nose expressed little change between 5 and 45 years; (3) the upper and lower lips became significantly more retruded in relation to the esthetic line between 15 and 25 years of age in both males and females; the same trends continued between 25 and 45 years of age; (4) the Holdaway soft tissue angle progressively decreased between 5 and 45 years of age. It is important for clinicians to be aware of these changes when planning the orthodontic treatment of the still growing adolescent patients because the changes might influence the extraction/nonextraction decision. (Am J Orthod Dentofacial Orthop 1998;114:698-706)

Longitudinal evaluation of growth changesin class II division 1 subjects

Longitudinal records from the Ohio State University Growth Study were used to compare the skeletal growth changes between Class II division 1 and Class I female subjects between ages 7 and 14. Tensor analysis was used to determine the yearly growth rate and direction. No significant difference was found in cranial base dimension between the Class I and Class II subjects. In Class II subjects, the maxilla (S-N-A) was found to be normally related to the cranial base. However, mandibular position (S-N-B and S-N-Pog) was found to be significantly more retrusive in Class II when compared with Class I subjects. Mandibular length (Ar-Gn) and corpus length (Go-Gn) were found to be shorter in Class II subjects. The ratio of PFH to AFH was found to be smaller in Class II subjects. This is particularly apparent during the pubertal growth period. The y-axis and mandibular plane angle were more open in Class II subjects which also contributed to the retrusive position of the mandible. Maxillo-mandibular difference (A-N-B) between Class I and II subjects was present at age 7 and persisted through puberty, maintaining a greater angle of convexity (A-N-Pg) in Class II subjects. These results suggest that Class II malocclusion can be detected early. The majority of the Class II cases showed mandibular skeletal retrusion or a combination of horizontal and vertical abnormalities of the mandible rather than maxillary protrusion. These skeletal differences remain through puberty without orthodontic intervention. Individual variations were found within each type of malocclusion

Perceptions of a balanced facial profile

This research deals with the assessment of the role of the nose, lips, and chin in achieving a balanced facial profile. A survey instrument of constructed androgynous facial silhouettes was evaluated by 545 professionals. The silhouettes had varied nose, lips, and chin relationships, as well as changes in facial angle and angle of convexity. The varied facial profiles were graded on the basis of most preferred to least preferred. The data was computed, and it was found that in males, a straighter profile was preferred in comparison with a slightly convex profile for the females. Among the various unfavorable combinations, the worst ones were either with an extremely recessive chin or those with excessively convex faces. More lip protrusion was found acceptable for both male and female faces when either a large nose or a large chin was present. It is suggested that orthodontic treatment goals should be attuned to the achievement of balanced and harmonious facial features rather than rigid adherence to standard average dental and skeletal parameters. Treatment of adolescent children should also take into account the changes in the thickness of the soft tissue integument at the nose, lips, and chin.

Skeletal stability after surgical correction of mandibular prognathism by vertical ramus osteotomy

The purpose of the study was to assess skeletal stability following combined surgical-orthodontic management of 52 adults with severe mandibular prognathism. Lateral cephalograms taken 1 week before surgery, within 1 week post-surgery and approximately 1 year after operation were studied by means of eight variables and a constructive stable reproducible reference system. The surgical procedure of choice was a bilateral vertical ramus osteotomy through an extra-oral approach. In all cases the condyles were left passively in the articular fossa and no attempt at their active repositioning was made. The patients were randomly allocated to an osteosynthesis or non-osteosynthesis group with regard to intramandibular fixation. Intermaxillary fixation lasted 6 weeks and an interocclusal wafer was used in all cases during this period. The findings of this study showed that during the post-operative period there was a trend for posterior rotation of the mandibular corpus (P less than 0.001). This pattern was also characterized by an increase (P less than 0.001) of the lower anterior face height and an improvement of the angle of convexity (P less than 0.001). These changes occurring in a direction so that the dentoskeletal profile became less concave, did not tend to reverse the goal of operation and cannot be considered as detrimental. No significant differences (P greater than 0.05) were found between the groups without and with osteosynthesis.

Effects of a fixed magnetic appliance on the dentofacial complex

The purpose of the study was to design and evaluate the effects of a fixed magnetic appliance that hinged the mandible open and exerted an intrusive force on the teeth. Ten patients between the ages of 8 years and 10 years 6 months, with Class II, Division 1 malocclusion associated with mandibular retrusion and increased lower facial height, were treated with this appliance. The length of treatment was 4 months, after which the appliance was removed and the patients were followed up for 4 months. Ten children with similar age, sex, and dentofacial characteristics acted as controls and did not receive any appliance therapy. Changes in morphology of the dentofacial complex were avaluated by use of lateral cephalograms and study models. In addition temporomandibular joint and muscle functions were assessed. During treatment mandibular length increased 3.2 mm, angle of facial convexity decreased 2.8°, the upper and lower teeth intruded an average of 1.5 mm each, and the mandibular plane angle decreased 1.3°. In the follow-up period, some rebound eruption was noted; however, all other changes were stable.

Longitudinal soft-tissue profile changes: A study of three analyses

The purpose of this study is to describe the changes in six soft-tissue parameters that are commonly used by orthodontists in their diagnosis and treatment planning as well as in the evaluation of profile changes that occur with growth and orthodontic treatment. The parameters evaluated were two angles of facial convexity, the Holdaway soft-tissue angle, Merrifield's Z angle, and Rickett's esthetic line and lip relationships. The subjects of this study consisted of 20 males and 15 females for whom lateral cephalograms taken between the ages of 5 and 25 years were available. Descriptive statistics for the absolute and incremental changes are presented on a yearly basis between the ages of 5 and 17 years and at adulthood. Growth profile curves were constructed for each parameter, and regression equations were developed to describe the age-related changes in the six parameters for both males and females. The present findings indicated that the male and female growth profile curves were significantly different, except for the angle of facial convexity (excluding the nose) and Merrifield's Z angle. One of the conclusions that can be derived from this investigation is that the two angles of soft-tissue facial convexity, the Holdaway soft-tissue angle, and Merrifield's Z angle do not behave in a similar manner with age. Therefore, the clinician needs to use a number of soft-tissue parameters to better evaluate the soft-tissue profile. A limited number of cephalometric standards have been identified for each parameter. These standards can be used by the orthodontist as representative of the change between the age of 5 years and adulthood. This should enable the orthodontist to treat the patient to soft-tissue norms that are age- and sex-specific, rather than to an adult standard.

Cephalometric analysis of the craniofacial region of the northern Foxe Basin Eskimo.

AbstractPast investigations of the Eskimo have indicated that there are marked morphological differences in the craniofacial skeleton of this relatively isolated ethnic group compared to other ethnic and racial groups. This study, using cephalometric radiography, attempted to characterize the craniofacial phenotype of the Eskimo living in the northern Foxe Basin, Northwest Territories, Canada. Age changes were examined on a cross‐sectional basis with comparisons being made with a Winnipeg Caucasian group.This investigation indicates that the Igloolik Eskimo has a phenotype, established early in life, and is distinct from the Winnipeg group. The overall size of the Eskimo craniofacial complex was significantly larger at three years of age and remained larger through the ages studied. Development of the craniofacial region, however, was fairly similar in rate and direction for both populations.The greatest differences between the Eskimo and Caucasian groups were found in the linear measurements assessing cranial width, facial width, mandibular length, facial height, protrusion of the incisors, chin point development, and nasal morphology. Differences between the two groups in the morphological relationships of the component structures include the angular relationships of the maxilla and nasal bones to the anterior cranial base, the gonial angle of the mandible, and the angle of facial convexity.

A cephalometric evaluation of 8-year-old Caucasians

1. 1. A set of mean values for twelve commonly used cephalometric angles was obtained for 8-year-old Caucasians. 2. 2. It was shown that there was no statistical difference in two readings of a single investigator at 6-month intervals. 3. 3. There was no statistical difference readings of the same film by three investigators. 4. 4. A comparison was made between the results of cephalometric readings on thirty children at the Eastman Dental Center and on fifty children in the Iowa study. A strong statistical correlation was found between these two groups. 5. 5. When the Eastman 8-year-olds were compared to Downs' teen-age group, the younger children were found to have a smaller SNB, a smaller facial angle, a larger angle of convexity, a larger mandibular plane to FH and a relatively constant Y axis.