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Postpubertal facial growth in Class II males
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Reviews and abstracts
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both jaws moving around their centers of rotation. To avoid these negative effects the protraction elastics should always leave the arch in the canine area. Basically Class III cases are due to either a short maxilla and/or a long mandible with variations in the vertical. Approximately 60% of all Class III cases have a short maxilla indicating the need for protraction. About 50% of the total Class III patient population would need surgery to finish with an ideal occlusion. However, many types of compromise treatments can be acceptable. A good occlusion can only be accomplished in the presence of normal function. In Class III patients special attention should be given to possible nasal obstruction as well to tongue posture and function. ENT cooperation and tongue spikes are often necessary to resolve these problems. Class III elastics tend to rotate the maxilla and the mandible upward and forward. The resulting change in molar relationship is only due to the rotation of the occlusal plane, which is unstable. Also because of the extrusional side effect there is an increase in vertical dimensions, which usually is undesirable. Intraorally the protraction device can either be attached to a bonded acrylic expansion appliance or to a cemented Hyrax depending on the development stage of the dentition. To avoid traumatic occlusion conditions, a modified splint should be used with the protraction gear in adults. In all growing Class III patients overcorrection of overjet and overbite is very important. This way not only possible relapse is prevented but also the chance of a posteriorly displaced mandible is avoided that could be a later cause for TMJ derangement. When deciding whether the deformity is in the maxilla or in the mandible, the individualized Jacobson templates are very helpful. Alex Jacobson
Thesis abstracts
Am. J. Orthod. Dentofac. Orthop. September 1992
ment and retention for a group of treated Class I/patients with untreated controls, and (2) to investigate the relationship between the MGD during treatment and the pretreatmet~t skeletal morphology. Pretreatment, posttreatment, and 2 years posttreatment lateral cephalograms of 26 Class II, Division 1 subjects, who were treated 'nonextraction' with low or straight pull headgears were compared with an untreated control group of 15 subjects. Mandibular growth direction was interpreted as the movement of gnathion relative to the SN line when successive tracings were superimposed on the S-N line at S. On average, MGD was more vertical during treatment than after. Posttreatment MGD was generally more horizontal than that during treatment, but was also extremely variable. Three of the pretreatment skeletal measures studied, especially the articular angle (SArG0), were significantly related to in-treatment MGD. The inclination of the mandibular ramus is also an important indicator of how mandibular growth will respond to Class II treatment mechanics.
Postpubertal facial growth in Class II males Lesley E. Pollard, MCID Orthodontics, The University of Western Ontario, 1991.
With lateral cephalograms, postpubertal maxillary and mandibular growth was assessed for 39 untreated males ages 16 to 20 years. All subjects exhibited Class II skeletal characteristic (ANB > 4.0~ Significant increases in mean maxillary and mandibular measurements were observed over the age period studied. Mean mandibular growth (Co-Gn) was approximately three times that of maxillary growth (CoA). Growth from 16 to 18 years was greater than that from 18 to 20 years. The mandible appeared to rotate anteriorly-superiorly, reflected by a mean reduction in mandibular plane angle of 1.47 ~ and a greater increase in posterior versus anterior face height. There were no statistically significant changes in incisor angulation. Mean growth changes in this Class II sample were comparable to those previously reported (8) for Class I males over the same age period, suggesting a similarity in postpubertal development between these two groups.
Mandibular growth direction with convention Class II nonextraction treatment Anthony Mair, MCID
Predicting growth direction in cervical and highpull headgear subjects Paul K. Kyle, MCID
Orthodontics, The UniverMty of Western Ontario, 1990.
Orthodontics, The University of Western Ontario, 1991.
The purposes of this study were: (1) to compare the direction of mandibular growth (MGD) during treat-
The objectives of this study were (1) to determine if a relationship exists between pretreatment skeletal
Reviews and abstracts
5.
6.
7.
8.
9.
10.
both jaws moving around their centers of rotation. To avoid these negative effects the protraction elastics should always leave the arch in the canine area. Basically Class III cases are due to either a short maxilla and/or a long mandible with variations in the vertical. Approximately 60% of all Class III cases have a short maxilla indicating the need for protraction. About 50% of the total Class III patient population would need surgery to finish with an ideal occlusion. However, many types of compromise treatments can be acceptable. A good occlusion can only be accomplished in the presence of normal function. In Class III patients special attention should be given to possible nasal obstruction as well to tongue posture and function. ENT cooperation and tongue spikes are often necessary to resolve these problems. Class III elastics tend to rotate the maxilla and the mandible upward and forward. The resulting change in molar relationship is only due to the rotation of the occlusal plane, which is unstable. Also because of the extrusional side effect there is an increase in vertical dimensions, which usually is undesirable. Intraorally the protraction device can either be attached to a bonded acrylic expansion appliance or to a cemented Hyrax depending on the development stage of the dentition. To avoid traumatic occlusion conditions, a modified splint should be used with the protraction gear in adults. In all growing Class III patients overcorrection of overjet and overbite is very important. This way not only possible relapse is prevented but also the chance of a posteriorly displaced mandible is avoided that could be a later cause for TMJ derangement. When deciding whether the deformity is in the maxilla or in the mandible, the individualized Jacobson templates are very helpful. Alex Jacobson
Thesis abstracts
Am. J. Orthod. Dentofac. Orthop. September 1992
ment and retention for a group of treated Class I/patients with untreated controls, and (2) to investigate the relationship between the MGD during treatment and the pretreatmet~t skeletal morphology. Pretreatment, posttreatment, and 2 years posttreatment lateral cephalograms of 26 Class II, Division 1 subjects, who were treated 'nonextraction' with low or straight pull headgears were compared with an untreated control group of 15 subjects. Mandibular growth direction was interpreted as the movement of gnathion relative to the SN line when successive tracings were superimposed on the S-N line at S. On average, MGD was more vertical during treatment than after. Posttreatment MGD was generally more horizontal than that during treatment, but was also extremely variable. Three of the pretreatment skeletal measures studied, especially the articular angle (SArG0), were significantly related to in-treatment MGD. The inclination of the mandibular ramus is also an important indicator of how mandibular growth will respond to Class II treatment mechanics.
Postpubertal facial growth in Class II males Lesley E. Pollard, MCID Orthodontics, The University of Western Ontario, 1991.
With lateral cephalograms, postpubertal maxillary and mandibular growth was assessed for 39 untreated males ages 16 to 20 years. All subjects exhibited Class II skeletal characteristic (ANB > 4.0~ Significant increases in mean maxillary and mandibular measurements were observed over the age period studied. Mean mandibular growth (Co-Gn) was approximately three times that of maxillary growth (CoA). Growth from 16 to 18 years was greater than that from 18 to 20 years. The mandible appeared to rotate anteriorly-superiorly, reflected by a mean reduction in mandibular plane angle of 1.47 ~ and a greater increase in posterior versus anterior face height. There were no statistically significant changes in incisor angulation. Mean growth changes in this Class II sample were comparable to those previously reported (8) for Class I males over the same age period, suggesting a similarity in postpubertal development between these two groups.
Mandibular growth direction with convention Class II nonextraction treatment Anthony Mair, MCID
Predicting growth direction in cervical and highpull headgear subjects Paul K. Kyle, MCID
Orthodontics, The UniverMty of Western Ontario, 1990.
Orthodontics, The University of Western Ontario, 1991.
The purposes of this study were: (1) to compare the direction of mandibular growth (MGD) during treat-
The objectives of this study were (1) to determine if a relationship exists between pretreatment skeletal