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Conformation of the mandible
Volume 42 Number 12
ABSTRACTS
AND
REVIEWS
935
fossa. These changes are associated with the growth of the orbits and the nose. The posterior fossa and the medial portion of the anterior fossa maintain a constant angular relation throughout life. In maloecluded persons, only Class III (Angle) cases showed an altcration in angulation. This is described as an increased flexure of the base, a kyphosis. The malrelation is found between the medial portion of the anterior fossa (the planum sphenoidale) and the clivus (of the basioccipital) . A similar, but more severe, kyphosis is found in all types of cleft palate. Conformation of the Mandible: versity, College of Dentistry,
By Richard Ziegler, D.D.S., New York New York, New York.
Uni-
The purpose of this investigation is to dcterminc the quantitative relationship of ramus height, corpus length, and gonial angle in patients with malocclusion grouped according to t,he Angle classification. In this preliminary report Class III, Class II, Division 1, Class I, and those Class I cases which resemble Class III (abbreviated “Class I R 3”) have been studied. Ninety-six acceptable cephalometric roentgcnograms were chosen from the files at the New York University Orthodontic Clinic. These roentgenograms were taken with the Bolton ccphalomctcr, wit,h approximately twentyfive in each category. A line parallel to SN was drawn tangent to the left condyle of t,he mandible. From the point of tangency, a lint was dropped to gonion. This gave us the ramus height. Corpus length is represented by the line from gonion to gnathion. The enclosed angle gave the gonial angle. We found the mean of 52.07 mm. in Class I the largest and the mean of 50.8 in Class III and Class II, Division 1 the smallest in ramal height. The corpus length mean of 74.4 in Class III exceeded all the others. Among t’he Class III cases examined were included those with normal mandibles and shortened maxillae. When we exclude this latter type of Class III t,he differences a,re more startling. The gonial angle mean ranged from 117.8 degrees for Class II, Division 1 to 125.86 degrees for Class III. Here also there was the minimizing effect of the normal mandible in the Class HI cases associated with shortened maxillae. Conclusion.-The smallest ratio of ramus height over corpus lengt,h was .68 for the Angle Class III cases. The mean of 125.86 degrees for the gonial angle of the Class III cases was the most obtuse of all the means of thn classes studied. These findings confirm Hcmley’s description of the mandibular deformity found in Angle’s Class III, namely, a relatively short ramus ant1 relatively long body of thr mandible with an obtuse gonial angle. The largest rnt,io of .72 was found in Class I. In t,hc Class I R 3, or “false Class III?” the ratio .70 of ramus height over corpus length was next to the smallest. This contradicted Angle’s idea that the condyle kept on growing backward to the glenoid fossa until a true Class III was attained.
A Study Showing How the Wetzel Grid Can Be Used as a Guide to Growth and Development in Orthodontic Therapy: By A. R. Ilornbardi, D.D.S., Columbia
University,
New York, New York.
The purpose of this investigation was to determine how the Wetzel grid could be integrated into the study of occlusion in mixed dcntitions being conducted at the Columbia University Orthodontic Clinic. A Wetzel grid record was initiated on thirty-six children in the mixed dentition sta.ge of development, and a study was made of this phase of their growth pattern. Accurate recordings of height and weight appear on one
ABSTRACTS
AND
REVIEWS
935
fossa. These changes are associated with the growth of the orbits and the nose. The posterior fossa and the medial portion of the anterior fossa maintain a constant angular relation throughout life. In maloecluded persons, only Class III (Angle) cases showed an altcration in angulation. This is described as an increased flexure of the base, a kyphosis. The malrelation is found between the medial portion of the anterior fossa (the planum sphenoidale) and the clivus (of the basioccipital) . A similar, but more severe, kyphosis is found in all types of cleft palate. Conformation of the Mandible: versity, College of Dentistry,
By Richard Ziegler, D.D.S., New York New York, New York.
Uni-
The purpose of this investigation is to dcterminc the quantitative relationship of ramus height, corpus length, and gonial angle in patients with malocclusion grouped according to t,he Angle classification. In this preliminary report Class III, Class II, Division 1, Class I, and those Class I cases which resemble Class III (abbreviated “Class I R 3”) have been studied. Ninety-six acceptable cephalometric roentgcnograms were chosen from the files at the New York University Orthodontic Clinic. These roentgenograms were taken with the Bolton ccphalomctcr, wit,h approximately twentyfive in each category. A line parallel to SN was drawn tangent to the left condyle of t,he mandible. From the point of tangency, a lint was dropped to gonion. This gave us the ramus height. Corpus length is represented by the line from gonion to gnathion. The enclosed angle gave the gonial angle. We found the mean of 52.07 mm. in Class I the largest and the mean of 50.8 in Class III and Class II, Division 1 the smallest in ramal height. The corpus length mean of 74.4 in Class III exceeded all the others. Among t’he Class III cases examined were included those with normal mandibles and shortened maxillae. When we exclude this latter type of Class III t,he differences a,re more startling. The gonial angle mean ranged from 117.8 degrees for Class II, Division 1 to 125.86 degrees for Class III. Here also there was the minimizing effect of the normal mandible in the Class HI cases associated with shortened maxillae. Conclusion.-The smallest ratio of ramus height over corpus lengt,h was .68 for the Angle Class III cases. The mean of 125.86 degrees for the gonial angle of the Class III cases was the most obtuse of all the means of thn classes studied. These findings confirm Hcmley’s description of the mandibular deformity found in Angle’s Class III, namely, a relatively short ramus ant1 relatively long body of thr mandible with an obtuse gonial angle. The largest rnt,io of .72 was found in Class I. In t,hc Class I R 3, or “false Class III?” the ratio .70 of ramus height over corpus length was next to the smallest. This contradicted Angle’s idea that the condyle kept on growing backward to the glenoid fossa until a true Class III was attained.
A Study Showing How the Wetzel Grid Can Be Used as a Guide to Growth and Development in Orthodontic Therapy: By A. R. Ilornbardi, D.D.S., Columbia
University,
New York, New York.
The purpose of this investigation was to determine how the Wetzel grid could be integrated into the study of occlusion in mixed dcntitions being conducted at the Columbia University Orthodontic Clinic. A Wetzel grid record was initiated on thirty-six children in the mixed dentition sta.ge of development, and a study was made of this phase of their growth pattern. Accurate recordings of height and weight appear on one