British Journal of Orthodontics
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Residual Lower First Premolar Extraction Space Margaret E. Richardson To cite this article: Margaret E. Richardson (1990) Residual Lower First Premolar Extraction Space, British Journal of Orthodontics, 17:3, 229-234, DOI: 10.1179/bjo.17.3.229 To link to this article: http://dx.doi.org/10.1179/bjo.17.3.229
Published online: 21 Jun 2016.
Submit your article to this journal
View related articles
Citing articles: 2 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yjor19 Download by: [Cornell University Library]
Date: 03 July 2017, At: 23:51
British Journal of Ortlwdomicsf Vol. 17/ /990(229-234
Residual Lower First Premolar Extraction Space MARGARET E. RICHARDSON, M.DENT. Se., D.ORTH. Orthodontic Department, School of Dentistry, Grosvenor Road, Belfast BTI2 6BA
Received for publication June 1989
Abstract. Residuallowerfirst premolar extraction space was examined in 43 subjects, 16 male and 27 female, 5 years after extraction; 16 subjects were treated mechanically, 27 had no active treatment. Forty per cent of extraction sites had residual spaces averaging 0·62 mm left and 0·71 mm right. Various param~ters were measured to try to establish reasons for non-closure of spaces. These included buccal space condition and incisal space condition measured on the pre-extraction models, and alveolar atrophy assessed on final models. The angulation of second premolars and canine to the maxillary plane and molar space were measured on 60'' cephalograms. Changes in these three parameters were measured ajier superimposing a tracing of the pre-extraction.film on the finalfilm. Angulation of lower incisors to the maxillary plane was measured on pre-extraction 90" cephalograms, and change in lower incisor angulation and position measured after superimposing a tracing on the final 90u film. Index words: Premolar Extraction, Residual Space, Alveolar Atrophy
Introduction When lower first premolars are extracted in orthodontic treatment there is often complete spontaneous closure of the extraction space, the principle upon which the procedure of serial extraction is based (Kellgren, 1947). Clinical experience suggests that, at least in some cases, lower first premolar extraction provides some space in the molar region. Faubion (1968) found that extraction of lower first premolars reduced the incidence of lower third molar impaction. Richard son ( 1989) noted a reduction in lower third molar impaction from 34 per cent in nonextraction cases to 28 per cent in first premolar extraction cases and a significantly greater increase in molar space in extraction cases, compared with non-extraction cases. Change in molar space in extraction cases was correlated significantly with the original space condition, suggesting that if anterior crowding is severe, most of the first premolar space will be used in treatment and little, if any, space will be gained in the molar region. If anterior crowding is mild, however, it was noted that excess first premolar extraction space will generally allow forward movement of the buccal teeth making more room in the molar region and helping to prevent third molar impaction. Sometimes lower first premolar extraction spaces 030 1·228X/90/008000 + 00502.00
do not close completely or reopen at the end of retention following mechanical treatment. Bredy and Jungto (1970) found complete closure of 82 of I00 lower premolar extraction sites approximately 5 years after extraction. Some of their cases were treated with removable appliances including activators. Cookson ( 1970) found that 83 per cent of lower first premolar spaces in 118 cases closed completely without mechanical treatment. Oftedal and Wisth ( 1982) found complete space closure in 75 per cent of extraction sites in the post-retention period following treatment with fixed appliances. In Cookson's study (Cookson, 1970) space closure was related to the degree of crowding of the whole arch but not to incisor crowding. Wisth and Oftedal ( 1982) found crowding to be an important factor in space closure during active treatment and retention, but not to continued space closure afterwards. They also noted that the presence of third molars resulted in smaller residual spaces at the end of retention. Crossman and Reed (1978) and Cookson (1970) reported no association between the presence of third molars and the degree of space closure. Cook son ( 1970) found that 90 per cent of lower first premolar space closure was due to forward movement of buccal teeth. A similar figure (91 per cent) was found by Robertson et al. (1979). Berg and Gebauer (1982) found that 80 per cent of lower ll.J 1990 British Society for the Study of Orthodontics
230 M. E. Richardson
first premolar space closure during the first 6 months following extraction was due to distal movement of canines. Mills ( 1964) found little change in the position of the lower incisors in a labio-lingual direction after lower first premolar extraction. Another factor contributing to incomplete space closure is atrophy of the alveolar process or lack of bone in the extraction site. Wisth and Oftedal ( 1982) found that this was responsible for re-opening of space in extraction sites in the post-retention period. The following investigation was undertaken to try to identify factors contributing to closure or non-closure of lower first premolar extraction spaces.
Materials A group of 43 subjects, 16 male and 27 female, who had one or both lower first premolars extracted for othodontic reasons was selected from the records of a longitudinal study of third molar development (Richardson, 1977). Thirty had bilateral extraction and 13 unilateral, so that 35 left and 38 right quadrants were available for investigation. Third molars were present in all extraction quadrants. The records used included plaster models, and 60" left and right, and 90° left lateral cephalometric radiographs, taken just before extraction of first premolars and repeated 5 years later. First premolars were extracted just before or soon after second premolar eruption. Twenty-seven subjects (23 left quadrants and 25 right) had no mechanical treatment, the remaining 16 (12left and 13 right) were treated with single arch round wire fixed appliances.
BJO Vol. 17 No. 3
Alveolar atrophy: judged subjectively and classified as I =no atrophy. 2=moderate atrophy, and 3 =severe atrophy (Fig. I). Tracings of the 60" rotated cephalometric radiographs, taken before extraction of premolars, provided the following data. Original angulation of the second premolar: measured as the angle formed between the long axis of the second premolar and the maxillary plane (A.N.S.-P.N.S.) (Fig. 2). Original angulation of the canine: measured as the angle formed between the long axis of the canine and the maxillary plane (Fig. 2). Original molar space: measured as the distance between projections of the distal contact point of the first molar and the junction of the anterior border of the ramus with the body of the mandible onto the maxillary plane (Fig. 3). Changes in these last three variables were measured or calculated when a tracing of the first film was superimposed on the film taken at the end of the observation period registering on mandibular structures (Figs 2 and 3). Change in the position of the second premolar and change in the position of the canine: measured along the maxillary plane when the tips of the cusps of the
Measurements taken on the pre-extraction models using a Baker vernier microscope Buccal space condition: calculated as arch length, from the distal surface of the first molar to the mesial surface of the canine, minus the size of premolars and canine. Incisor space condition: calculated as the difference between the distance from the mesial surface of the canine to the mid-point between the central incisors and the size of the central and lateral incisors. Negative values for these two variables indicated crowding. Data from models taken at the end of the observation period. Residual first premolar space: measured directly with the Vernier microscope.
FIG. I Alveolar atrophy. Left-no atrophy I; centre-moderate atrophy 2; right-severe atrophy 3.
Extraction Space
BJO August NW!
FIG. 2 Measurement of angulation, change in angulation, and change in position of lower second premolars and canines with a tracing of the first film superimposed on the second registering on mandibular structures. Solid lines-first film. Broken linessecond film.
231
FIG. 4 Measurements of angulation, change in angulation, and change in position of the most procumbent lower incisor with a tracing of the first film superimposed on the second register!ng on mandibular structures. Solid lines-first film. Broken linessecond film.
Change in angulation of the lower incisors: measured when a tracing of the first film was superimposed on the second as before (Fig. 4). Change in position of the lower incisors: measured along the maxillary plane when the incisal edge of the most proclined lower incisor was projected unto the maxillary plane with a tracing of the first film superimposed on the second as before (Fig. 4).
FIG. 3 Measurement of original molar space and change in molar space with a tracing of the first film superimpo~ed on _the second registering on mandibular structures. Sohd hnes-hrst film. Broken lines-second film.
All measurements were made on two separate occasions by one observer, with an accuracy of +0·5 mm or +OS'. Alveolar atrophy was assessed ~ two separ;te occasions. In all cases the same grade was recorded at both assessments. Results
second premolar and canine were projected onto the maxillary plane with a tracing of the first film superimposed on the second as shown in Fig. 2. For changes in angulation and position of second premolars positive values indicated mesial tipping and forward movement; for canines, negative values indicated distal tipping and distal movement. Tracings of the 90" left lateral cephalometric radiographs, taken before extraction, were used for measuring the following. Original angulation of lower incisors: the angle formed between the long axis of the most procumbent lower incisor to the maxillary plane (Fig. 4).
Means, standard deviations and ranges for all the variables were calculated (Table 1). Correlation analyses of residual first premolar space and all the other variables except alveolar atrophy and mechanical treatment were carried out for left and right sides separately. Only those correlation coefficients which were significant are shown in Table 2. The 5 per cent level of significance was used. With residual first premolar space as the dependent variable, regression analyses were made including all the original variables plus alveolar atrophy.
232 M. E. Richardson
BJO Vol. 17 No. 3
Means, standard deviations, and ranges of the TABLE I variables in this study Range Variable Res. 4 sp. (mm)
S.D.
Mean L R
L R L R L R L R L R Original L angle~ (degrees) R Change L angle ] (degrees) R Change L position ] (mm) R Original L molar sp. (mm) R Change L molar sp. (mm) R Original angle T(degrees) Buccal sp. cond. (mm) Incisor sp. cond. (mm) Original angle 3 (degrees) Change angle 3 (degrees) Change position 3 (mm)
0·62 0·71 -1·36 -1·39 -1·01 -0·68 76·46 78·05 8·76 7·69 5·92 5·61
Min.
Max.
1·03 1·12 2-47 2·39 1·12 0·81 8·76 7·52 9·24 8·02 2·69 2·57 76·11 8·78 77-60 8·49 -4·31 6·27 -5·10 6·62 -1·20 2-23 -1·55 2·34 12·06 2·67 11·79 2-80 7·31 1·85 7·43 1·56
0·0 0·0 -5-82 -6·88 -4·86 -2·78 59· 50 66·25 -10·50 -10·50
3·34 5·20 3·42 2-45 0·00 0·30 103·00 107·00 34·75 31·00
0·75 1·00 60·25 56·25 -20·50 -20·00 -7·00 -7·00 7·00 4·00 2·75 4·00
11·50 10·00 95·00 96·00 9·50 5·50 2·75 3·00 17·75 17·00 11·00 11·25
59·59 6·67
45·00
71·00
Change angle T(degrees)
-2-81
3·73
-9·50
7·00
Change position
-0·62
1·37
-4·00
2·50
T(mm)
TABLE 2 Significant zero order correlation coefficients
Residual4 space
r Original molar space
Left Right
Change angulation 3
Left Right
-0·33* -0·48** 0·32*
*Denotes significance P
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Residual Lower First Premolar Extraction Space Margaret E. Richardson To cite this article: Margaret E. Richardson (1990) Residual Lower First Premolar Extraction Space, British Journal of Orthodontics, 17:3, 229-234, DOI: 10.1179/bjo.17.3.229 To link to this article: http://dx.doi.org/10.1179/bjo.17.3.229
Published online: 21 Jun 2016.
Submit your article to this journal
View related articles
Citing articles: 2 View citing articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=yjor19 Download by: [Cornell University Library]
Date: 03 July 2017, At: 23:51
British Journal of Ortlwdomicsf Vol. 17/ /990(229-234
Residual Lower First Premolar Extraction Space MARGARET E. RICHARDSON, M.DENT. Se., D.ORTH. Orthodontic Department, School of Dentistry, Grosvenor Road, Belfast BTI2 6BA
Received for publication June 1989
Abstract. Residuallowerfirst premolar extraction space was examined in 43 subjects, 16 male and 27 female, 5 years after extraction; 16 subjects were treated mechanically, 27 had no active treatment. Forty per cent of extraction sites had residual spaces averaging 0·62 mm left and 0·71 mm right. Various param~ters were measured to try to establish reasons for non-closure of spaces. These included buccal space condition and incisal space condition measured on the pre-extraction models, and alveolar atrophy assessed on final models. The angulation of second premolars and canine to the maxillary plane and molar space were measured on 60'' cephalograms. Changes in these three parameters were measured ajier superimposing a tracing of the pre-extraction.film on the finalfilm. Angulation of lower incisors to the maxillary plane was measured on pre-extraction 90" cephalograms, and change in lower incisor angulation and position measured after superimposing a tracing on the final 90u film. Index words: Premolar Extraction, Residual Space, Alveolar Atrophy
Introduction When lower first premolars are extracted in orthodontic treatment there is often complete spontaneous closure of the extraction space, the principle upon which the procedure of serial extraction is based (Kellgren, 1947). Clinical experience suggests that, at least in some cases, lower first premolar extraction provides some space in the molar region. Faubion (1968) found that extraction of lower first premolars reduced the incidence of lower third molar impaction. Richard son ( 1989) noted a reduction in lower third molar impaction from 34 per cent in nonextraction cases to 28 per cent in first premolar extraction cases and a significantly greater increase in molar space in extraction cases, compared with non-extraction cases. Change in molar space in extraction cases was correlated significantly with the original space condition, suggesting that if anterior crowding is severe, most of the first premolar space will be used in treatment and little, if any, space will be gained in the molar region. If anterior crowding is mild, however, it was noted that excess first premolar extraction space will generally allow forward movement of the buccal teeth making more room in the molar region and helping to prevent third molar impaction. Sometimes lower first premolar extraction spaces 030 1·228X/90/008000 + 00502.00
do not close completely or reopen at the end of retention following mechanical treatment. Bredy and Jungto (1970) found complete closure of 82 of I00 lower premolar extraction sites approximately 5 years after extraction. Some of their cases were treated with removable appliances including activators. Cookson ( 1970) found that 83 per cent of lower first premolar spaces in 118 cases closed completely without mechanical treatment. Oftedal and Wisth ( 1982) found complete space closure in 75 per cent of extraction sites in the post-retention period following treatment with fixed appliances. In Cookson's study (Cookson, 1970) space closure was related to the degree of crowding of the whole arch but not to incisor crowding. Wisth and Oftedal ( 1982) found crowding to be an important factor in space closure during active treatment and retention, but not to continued space closure afterwards. They also noted that the presence of third molars resulted in smaller residual spaces at the end of retention. Crossman and Reed (1978) and Cookson (1970) reported no association between the presence of third molars and the degree of space closure. Cook son ( 1970) found that 90 per cent of lower first premolar space closure was due to forward movement of buccal teeth. A similar figure (91 per cent) was found by Robertson et al. (1979). Berg and Gebauer (1982) found that 80 per cent of lower ll.J 1990 British Society for the Study of Orthodontics
230 M. E. Richardson
first premolar space closure during the first 6 months following extraction was due to distal movement of canines. Mills ( 1964) found little change in the position of the lower incisors in a labio-lingual direction after lower first premolar extraction. Another factor contributing to incomplete space closure is atrophy of the alveolar process or lack of bone in the extraction site. Wisth and Oftedal ( 1982) found that this was responsible for re-opening of space in extraction sites in the post-retention period. The following investigation was undertaken to try to identify factors contributing to closure or non-closure of lower first premolar extraction spaces.
Materials A group of 43 subjects, 16 male and 27 female, who had one or both lower first premolars extracted for othodontic reasons was selected from the records of a longitudinal study of third molar development (Richardson, 1977). Thirty had bilateral extraction and 13 unilateral, so that 35 left and 38 right quadrants were available for investigation. Third molars were present in all extraction quadrants. The records used included plaster models, and 60" left and right, and 90° left lateral cephalometric radiographs, taken just before extraction of first premolars and repeated 5 years later. First premolars were extracted just before or soon after second premolar eruption. Twenty-seven subjects (23 left quadrants and 25 right) had no mechanical treatment, the remaining 16 (12left and 13 right) were treated with single arch round wire fixed appliances.
BJO Vol. 17 No. 3
Alveolar atrophy: judged subjectively and classified as I =no atrophy. 2=moderate atrophy, and 3 =severe atrophy (Fig. I). Tracings of the 60" rotated cephalometric radiographs, taken before extraction of premolars, provided the following data. Original angulation of the second premolar: measured as the angle formed between the long axis of the second premolar and the maxillary plane (A.N.S.-P.N.S.) (Fig. 2). Original angulation of the canine: measured as the angle formed between the long axis of the canine and the maxillary plane (Fig. 2). Original molar space: measured as the distance between projections of the distal contact point of the first molar and the junction of the anterior border of the ramus with the body of the mandible onto the maxillary plane (Fig. 3). Changes in these last three variables were measured or calculated when a tracing of the first film was superimposed on the film taken at the end of the observation period registering on mandibular structures (Figs 2 and 3). Change in the position of the second premolar and change in the position of the canine: measured along the maxillary plane when the tips of the cusps of the
Measurements taken on the pre-extraction models using a Baker vernier microscope Buccal space condition: calculated as arch length, from the distal surface of the first molar to the mesial surface of the canine, minus the size of premolars and canine. Incisor space condition: calculated as the difference between the distance from the mesial surface of the canine to the mid-point between the central incisors and the size of the central and lateral incisors. Negative values for these two variables indicated crowding. Data from models taken at the end of the observation period. Residual first premolar space: measured directly with the Vernier microscope.
FIG. I Alveolar atrophy. Left-no atrophy I; centre-moderate atrophy 2; right-severe atrophy 3.
Extraction Space
BJO August NW!
FIG. 2 Measurement of angulation, change in angulation, and change in position of lower second premolars and canines with a tracing of the first film superimposed on the second registering on mandibular structures. Solid lines-first film. Broken linessecond film.
231
FIG. 4 Measurements of angulation, change in angulation, and change in position of the most procumbent lower incisor with a tracing of the first film superimposed on the second register!ng on mandibular structures. Solid lines-first film. Broken linessecond film.
Change in angulation of the lower incisors: measured when a tracing of the first film was superimposed on the second as before (Fig. 4). Change in position of the lower incisors: measured along the maxillary plane when the incisal edge of the most proclined lower incisor was projected unto the maxillary plane with a tracing of the first film superimposed on the second as before (Fig. 4).
FIG. 3 Measurement of original molar space and change in molar space with a tracing of the first film superimpo~ed on _the second registering on mandibular structures. Sohd hnes-hrst film. Broken lines-second film.
All measurements were made on two separate occasions by one observer, with an accuracy of +0·5 mm or +OS'. Alveolar atrophy was assessed ~ two separ;te occasions. In all cases the same grade was recorded at both assessments. Results
second premolar and canine were projected onto the maxillary plane with a tracing of the first film superimposed on the second as shown in Fig. 2. For changes in angulation and position of second premolars positive values indicated mesial tipping and forward movement; for canines, negative values indicated distal tipping and distal movement. Tracings of the 90" left lateral cephalometric radiographs, taken before extraction, were used for measuring the following. Original angulation of lower incisors: the angle formed between the long axis of the most procumbent lower incisor to the maxillary plane (Fig. 4).
Means, standard deviations and ranges for all the variables were calculated (Table 1). Correlation analyses of residual first premolar space and all the other variables except alveolar atrophy and mechanical treatment were carried out for left and right sides separately. Only those correlation coefficients which were significant are shown in Table 2. The 5 per cent level of significance was used. With residual first premolar space as the dependent variable, regression analyses were made including all the original variables plus alveolar atrophy.
232 M. E. Richardson
BJO Vol. 17 No. 3
Means, standard deviations, and ranges of the TABLE I variables in this study Range Variable Res. 4 sp. (mm)
S.D.
Mean L R
L R L R L R L R L R Original L angle~ (degrees) R Change L angle ] (degrees) R Change L position ] (mm) R Original L molar sp. (mm) R Change L molar sp. (mm) R Original angle T(degrees) Buccal sp. cond. (mm) Incisor sp. cond. (mm) Original angle 3 (degrees) Change angle 3 (degrees) Change position 3 (mm)
0·62 0·71 -1·36 -1·39 -1·01 -0·68 76·46 78·05 8·76 7·69 5·92 5·61
Min.
Max.
1·03 1·12 2-47 2·39 1·12 0·81 8·76 7·52 9·24 8·02 2·69 2·57 76·11 8·78 77-60 8·49 -4·31 6·27 -5·10 6·62 -1·20 2-23 -1·55 2·34 12·06 2·67 11·79 2-80 7·31 1·85 7·43 1·56
0·0 0·0 -5-82 -6·88 -4·86 -2·78 59· 50 66·25 -10·50 -10·50
3·34 5·20 3·42 2-45 0·00 0·30 103·00 107·00 34·75 31·00
0·75 1·00 60·25 56·25 -20·50 -20·00 -7·00 -7·00 7·00 4·00 2·75 4·00
11·50 10·00 95·00 96·00 9·50 5·50 2·75 3·00 17·75 17·00 11·00 11·25
59·59 6·67
45·00
71·00
Change angle T(degrees)
-2-81
3·73
-9·50
7·00
Change position
-0·62
1·37
-4·00
2·50
T(mm)
TABLE 2 Significant zero order correlation coefficients
Residual4 space
r Original molar space
Left Right
Change angulation 3
Left Right
-0·33* -0·48** 0·32*
*Denotes significance P
