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The reliability of mandibular radiographic superimposition
DEPARTMENT OF REVIEWS AND ABSTRACTS Edited by
Alex dacobson, DMD, MS, MDS, PhD Birmingham, Ala. All inquiries regarding information on reviews and abstracts should be directed to the respective authors. Articles or books for review in this department should be addressed to Dr. Alex Jaeobson, University of Alabama School of Dentistr~y, University Station~Birmingham, Alabama 35294.
Posterior Discrepancy S. Sato and Y. Suzuki J. Jpn. Orthod. Soc. 1988;47:796-810
The purpose of the article (well illustrated and written in English) was an endeavor to explain the relationship between the development of skeletal Class III malocclusion and vertical discrepancy in the posterior region of the jaws. Four unsuccessfully treated orthodontic cases were evaluated to demonstrate possible causative factors. The forward displacement of the mandible was associated with inferiofly positioned maxillary molars and/or superiorly positioned mandibular molars caused by the "squeezing out" effect of posterior molar height discrepancy, which in turn will cause the occlusal plane to be increased. The authors contend that it is possible for continuous forward displacement of the mandible (because of increased molar height posteriorly) to induce vertical condylar elongation, which establishes the characteristics of skeletal Class Ill malocclusion. A new approach to the orthodontic treatment of skeletal Class HI malocclusion was achieved bY controlling the cant of the occlusal plane through extraction of four second molars in an effort to eliminate the posterior vertical discrepancy. Alex Jacobson
Relation Between Sucking Habits and Dental Characteristics in Preschool Children With Unilateral Cross-bite Anders Lindner and Thomas Modder Scand. J. Dent. Res. 1989;97:278-83
The relationship between sucking habits and dental characteristics of unilateral crossbite in 4-year-old children (N = 76) was studied. The crossbites were classified on the variables, such as number of teeth involved, incisor overjet, incisor overbite, terminal plane shift, midline shift, maxillary arch asymmetry, and maxillary/mandibular arch width difference. Type of sucking habit (dummy, finger) and its duration and intensity were analyzed from a questionnaire answered
by the parents. The maxillary/mandibular arch width difference in' the canine region was found to be negatively related to the intensity and duration of the sucking habit, and also negatively related to sucking a dummy as compared with finger sucking, The study indicates that the "duration" and "intensity" of the sucking habit have a negative influence by reducing the transverse width of the maxilIary arch in children with a unilateral crossbite. Dummy sucking was more detrimental to the transverse dimension in the canine region than finger sucking. Alex Jacobson
The Reliability of Mandibular Radiographic Superimposition P. A. Cook and P. J. Southall Br. J. Orthod. 1989;16:25-30
With tracings from 30 pairs of serial cephalaometric radiographs, the reliability of three outlines commonly used for mandibular positioning was investigated, The mandibular outlines compared were (1) between cephalometric points menton and gonian, (2) the mandibular outline, and (3) mandibular structures as defined by Bjrrk (1969). The findings reflected sizable errors associated with all three groups, but the Bj6rk structures showed a highly significant degree of error in comparison to superimposition using either mandibular plane or the mandibular outline. The conclusion reached by the authors advocates the use of Bj6rk's structures for mandibular superimposition for studies involving a growing patient, especiaally when a marked degree of mandibular rotation is expected. They further recommend that either the mandibular plane or mandibular outline be used in those studies in which growth has ceased, or in cases in which the time between radiographs is short and identification of the internal structures of the mandible may be unclear. Alex Jacobson
451
Alex dacobson, DMD, MS, MDS, PhD Birmingham, Ala. All inquiries regarding information on reviews and abstracts should be directed to the respective authors. Articles or books for review in this department should be addressed to Dr. Alex Jaeobson, University of Alabama School of Dentistr~y, University Station~Birmingham, Alabama 35294.
Posterior Discrepancy S. Sato and Y. Suzuki J. Jpn. Orthod. Soc. 1988;47:796-810
The purpose of the article (well illustrated and written in English) was an endeavor to explain the relationship between the development of skeletal Class III malocclusion and vertical discrepancy in the posterior region of the jaws. Four unsuccessfully treated orthodontic cases were evaluated to demonstrate possible causative factors. The forward displacement of the mandible was associated with inferiofly positioned maxillary molars and/or superiorly positioned mandibular molars caused by the "squeezing out" effect of posterior molar height discrepancy, which in turn will cause the occlusal plane to be increased. The authors contend that it is possible for continuous forward displacement of the mandible (because of increased molar height posteriorly) to induce vertical condylar elongation, which establishes the characteristics of skeletal Class Ill malocclusion. A new approach to the orthodontic treatment of skeletal Class HI malocclusion was achieved bY controlling the cant of the occlusal plane through extraction of four second molars in an effort to eliminate the posterior vertical discrepancy. Alex Jacobson
Relation Between Sucking Habits and Dental Characteristics in Preschool Children With Unilateral Cross-bite Anders Lindner and Thomas Modder Scand. J. Dent. Res. 1989;97:278-83
The relationship between sucking habits and dental characteristics of unilateral crossbite in 4-year-old children (N = 76) was studied. The crossbites were classified on the variables, such as number of teeth involved, incisor overjet, incisor overbite, terminal plane shift, midline shift, maxillary arch asymmetry, and maxillary/mandibular arch width difference. Type of sucking habit (dummy, finger) and its duration and intensity were analyzed from a questionnaire answered
by the parents. The maxillary/mandibular arch width difference in' the canine region was found to be negatively related to the intensity and duration of the sucking habit, and also negatively related to sucking a dummy as compared with finger sucking, The study indicates that the "duration" and "intensity" of the sucking habit have a negative influence by reducing the transverse width of the maxilIary arch in children with a unilateral crossbite. Dummy sucking was more detrimental to the transverse dimension in the canine region than finger sucking. Alex Jacobson
The Reliability of Mandibular Radiographic Superimposition P. A. Cook and P. J. Southall Br. J. Orthod. 1989;16:25-30
With tracings from 30 pairs of serial cephalaometric radiographs, the reliability of three outlines commonly used for mandibular positioning was investigated, The mandibular outlines compared were (1) between cephalometric points menton and gonian, (2) the mandibular outline, and (3) mandibular structures as defined by Bjrrk (1969). The findings reflected sizable errors associated with all three groups, but the Bj6rk structures showed a highly significant degree of error in comparison to superimposition using either mandibular plane or the mandibular outline. The conclusion reached by the authors advocates the use of Bj6rk's structures for mandibular superimposition for studies involving a growing patient, especiaally when a marked degree of mandibular rotation is expected. They further recommend that either the mandibular plane or mandibular outline be used in those studies in which growth has ceased, or in cases in which the time between radiographs is short and identification of the internal structures of the mandible may be unclear. Alex Jacobson
451