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A cephalometric evaluation of Class I serial extraction treatment
Volume Number
Reviews and abstracts
53 2
Measurement Protrusive
of Labiolingual Positions
Forces
on
Central
incisors
in
Normal
137 and
By Edwat+a C. McNulty, Clement S. C. Lear, and Coenraad F. A. Moorrees, Forsyth Dental Center, Harvard School of Dental Medicine, Boston, Mass. The adaptability of the labiolingual musculature to changes in incisor POsition has been studied to test the long-held assumption that teeth are in homeostasis with, and their position is determined by, the enveloping and opposing forces of the lips and tongue. Four partial dentures, replacing missing maxillary central and lateral incisors, were constructed for each of three subjects. The dentures were identical except that in two, the incisor position of the patient’s original denture was reproduced. In the other pair, the incisors were positioned in 3 mm. protrusion. The size, shape, and inclination of the central incisors was the same in each denture. One denture from each pair, worn only during recording sessions, contained transducers which registered the force on the entire labial or lingual tooth surface. The other denture, lacking transducers, was worn between test sessions. Transducers only 1.4 mm. thick were placed in the recording dentures by removing the central incisors, splitting the crowns lengthwise, and cementing the transducers into place. The adapted tooth thus consisted of a force-sensitive surface facing the musculature and a rigid section attached to the denture. PROTOCOL FOR RECORDING SESSIONS. The patient received the “normal” (0 mm. protrusion) denture to record labial and lingual force patterns during various physiologic oral activities on the first, second, and seventh days. After the third test of the normally positioned incisors, the “protrusive” denture (3 mm. labioversion of incisors) was inserted, tested immediately, and retested again on the eighth and fourteenth days. The “normal” partial denture was reinserted and muscle forces were again quantitated. Preliminary results indicate that muscle forces increase labially and decrease lingually when the orofacial musculature first experiences the incisors in labioversion. Within as little as 24 hours, however, the musculature appears to have largely adapted to the new hard-tissue architecture.
A Cephalometric
Evaluation
of Class
I Serial
Extraction
By George Smolen, D.D.S., Saint Louis Uwiversity,
Treatment
St. Louis, MO.
This study was designed to evaluate cephalometrically changes produced during orthodontic treatment by serial extraction procedures. An experimental group was treated by serial extraction procedures and compared pre- and postoperatively with a control group. The treatment procedures and mechanical therapy used were otherwise alike for both groups. The findings show that no significant difference was found at the start of treatment, which proves that the samples originally were similar. The final measurements show that desirable results were achieved in both
138
Keviews and a,bstracts
groups at the 1 per cent level 01 c:odidence. Comparison of the tinisld results in the experimental and control groups showed that differences were not. significant at the 5 per cent level of confidence. Retardation of growth due t.o serial extraction procedures was not evident. Treatment was completed a year carlicr in the experimenta, group, which a(.counts for the lesser amount of growt,h in this group. This study supports serial extra&ion as a good clinical procedure offering the following ad,vantages : 1. It lessens degree of difficulty in banding 2. It allows physiologic movement of teeth 3. It permits earlier alignment of anterior teet,h 4. It lessens active appliance therapy 5. It decreases probability of root resorption 6. It decreases the retention period 865 Med. Group APO San Francisco,
An
Evaluation
Calif.
of Cephalometric
By G. V. Mueller, Jr., D.M.D.,
Magnification
Saint Louis University,
St. Louis, MO.
A study of cephalometric magnification was made by taking lateral cephalograms of a 100 mm. aluminum rule scaled in millimeters. By varying the position and direction of the rule on the head holder, the ear-rod width, and the position of the film, the effects of growth and head size on magnification were studied on different planes of the face, using two different techniques of film placement. When using a 60 inch target-object distance, per cent magnification was found to be the same as the periphery of the film as at t,he central ray. Also, no difference was found between magnification in a horizontal or vertical direction. Since there was a gross distortion in magnification between the two sides of the face, a recommendation was made to bisect the images of all bilateral landmarks, thus projecting their average magnification onto the midsagittal plane. Average magnification at the midsagittal plane was found to be 6.00 prr cent ? 0.50 per cent with the film placed against the left ear rod and 9.00 per cent with the film 15 cm. from the midsagittal plane. Depending on the location of measured structures, the range of increased magnification was from 2 per cent to 3.5 per cent when the latter film-placement technique was used. Because of this increased magnification and its undesirable effect on cephalometric superimpositioning in growth studies, positioning of the film against the left. ear rod was deemed the preferred technique. A method of correction for magnification was suggested in which a projection was made of the aluminum rule at the midsagittal plane with a 110 mm. ear-rod width and film against the left ear rod. A photographic contact print of the projected rule could be cut out and used for 1inea;r measurements of all
Reviews and abstracts
53 2
Measurement Protrusive
of Labiolingual Positions
Forces
on
Central
incisors
in
Normal
137 and
By Edwat+a C. McNulty, Clement S. C. Lear, and Coenraad F. A. Moorrees, Forsyth Dental Center, Harvard School of Dental Medicine, Boston, Mass. The adaptability of the labiolingual musculature to changes in incisor POsition has been studied to test the long-held assumption that teeth are in homeostasis with, and their position is determined by, the enveloping and opposing forces of the lips and tongue. Four partial dentures, replacing missing maxillary central and lateral incisors, were constructed for each of three subjects. The dentures were identical except that in two, the incisor position of the patient’s original denture was reproduced. In the other pair, the incisors were positioned in 3 mm. protrusion. The size, shape, and inclination of the central incisors was the same in each denture. One denture from each pair, worn only during recording sessions, contained transducers which registered the force on the entire labial or lingual tooth surface. The other denture, lacking transducers, was worn between test sessions. Transducers only 1.4 mm. thick were placed in the recording dentures by removing the central incisors, splitting the crowns lengthwise, and cementing the transducers into place. The adapted tooth thus consisted of a force-sensitive surface facing the musculature and a rigid section attached to the denture. PROTOCOL FOR RECORDING SESSIONS. The patient received the “normal” (0 mm. protrusion) denture to record labial and lingual force patterns during various physiologic oral activities on the first, second, and seventh days. After the third test of the normally positioned incisors, the “protrusive” denture (3 mm. labioversion of incisors) was inserted, tested immediately, and retested again on the eighth and fourteenth days. The “normal” partial denture was reinserted and muscle forces were again quantitated. Preliminary results indicate that muscle forces increase labially and decrease lingually when the orofacial musculature first experiences the incisors in labioversion. Within as little as 24 hours, however, the musculature appears to have largely adapted to the new hard-tissue architecture.
A Cephalometric
Evaluation
of Class
I Serial
Extraction
By George Smolen, D.D.S., Saint Louis Uwiversity,
Treatment
St. Louis, MO.
This study was designed to evaluate cephalometrically changes produced during orthodontic treatment by serial extraction procedures. An experimental group was treated by serial extraction procedures and compared pre- and postoperatively with a control group. The treatment procedures and mechanical therapy used were otherwise alike for both groups. The findings show that no significant difference was found at the start of treatment, which proves that the samples originally were similar. The final measurements show that desirable results were achieved in both
138
Keviews and a,bstracts
groups at the 1 per cent level 01 c:odidence. Comparison of the tinisld results in the experimental and control groups showed that differences were not. significant at the 5 per cent level of confidence. Retardation of growth due t.o serial extraction procedures was not evident. Treatment was completed a year carlicr in the experimenta, group, which a(.counts for the lesser amount of growt,h in this group. This study supports serial extra&ion as a good clinical procedure offering the following ad,vantages : 1. It lessens degree of difficulty in banding 2. It allows physiologic movement of teeth 3. It permits earlier alignment of anterior teet,h 4. It lessens active appliance therapy 5. It decreases probability of root resorption 6. It decreases the retention period 865 Med. Group APO San Francisco,
An
Evaluation
Calif.
of Cephalometric
By G. V. Mueller, Jr., D.M.D.,
Magnification
Saint Louis University,
St. Louis, MO.
A study of cephalometric magnification was made by taking lateral cephalograms of a 100 mm. aluminum rule scaled in millimeters. By varying the position and direction of the rule on the head holder, the ear-rod width, and the position of the film, the effects of growth and head size on magnification were studied on different planes of the face, using two different techniques of film placement. When using a 60 inch target-object distance, per cent magnification was found to be the same as the periphery of the film as at t,he central ray. Also, no difference was found between magnification in a horizontal or vertical direction. Since there was a gross distortion in magnification between the two sides of the face, a recommendation was made to bisect the images of all bilateral landmarks, thus projecting their average magnification onto the midsagittal plane. Average magnification at the midsagittal plane was found to be 6.00 prr cent ? 0.50 per cent with the film placed against the left ear rod and 9.00 per cent with the film 15 cm. from the midsagittal plane. Depending on the location of measured structures, the range of increased magnification was from 2 per cent to 3.5 per cent when the latter film-placement technique was used. Because of this increased magnification and its undesirable effect on cephalometric superimpositioning in growth studies, positioning of the film against the left. ear rod was deemed the preferred technique. A method of correction for magnification was suggested in which a projection was made of the aluminum rule at the midsagittal plane with a 110 mm. ear-rod width and film against the left ear rod. A photographic contact print of the projected rule could be cut out and used for 1inea;r measurements of all