British Journal of Orthodontics
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Second Molar Extraction in the Treatment of Lower Premolar Crowding Margaret E. Richardson M.Dent.Sc.D.Orth. & Donald J. Burden B.D.S., F.D.S., F.F.D., M.Orth. To cite this article: Margaret E. Richardson M.Dent.Sc.D.Orth. & Donald J. Burden B.D.S., F.D.S., F.F.D., M.Orth. (1992) Second Molar Extraction in the Treatment of Lower Premolar Crowding, British Journal of Orthodontics, 19:4, 299-304, DOI: 10.1179/bjo.19.4.299 To link to this article: http://dx.doi.org/10.1179/bjo.19.4.299
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: [Tufts University]
Date: 20 November 2016, At: 01:45
British Journal of Orthodontics/ Vol. 19/1991/199-304
Second Molar Extraction in the Treatment of Lower Premolar Crowding MARGARET E. RICHARDSON, M.DENT.Sc.D.ORTH. CBlinical Department of Orthodontics, School of Clinical Dentistry, Royal Victoria Hospital, Grosvenor Road, elfast BTI2 6BA DONALD J. BURDEN, B.D.S., F.D.S., F.F.D., M.ORTH. Clinical Department of Orthodontics, School of Clinical Dentistry, Queens University, Belfast BT12 6BP Received for publication November 1991
Abstract. Thirty-four children with lower premolar crowding were treated by extraction of second molars. Thirteen cases had mechanical lower arch treatment started not less than 6 months after extractions. The remainder had no treatment in the lower arch. The change in premolar crowding was measured, and the reasons why spontaneous alignment occurred in some cases and not in others were examined. Index words: Second Molar Extraction, Premolar Crowding, Spontaneous Alignment.
One of the advantages attributed to the extraction of second molars in orthodontic treatment is the Provision of space for the spontaneous relief of lower premolar crowding (McBride and Huggins, 1970; Huggins and McBride, 1978; Broadbent, 1986). Crowding in the lower premolar region occurs as a result of premature loss of deciduous molars in cases where a degree of arch length discrepancy al~eady exists (Seipel, 1946; Lundstrom, 1955; Chnch, 1959; Richardson, 1965). That is to say Primary crowding is transferred from the incisor and molar regions to create secondary crowding in the premolar region. In these circumstances, if no teeth are extracted, the force of eruption of the second premolar may cause malignment elsewhere. If_premolars are extracted, fixed appliance therapy Will often be required in both arches. Second molar extraction may provide space to relieve premolar crowding with little or no mechanical treatment. Dacre ( 1987) reported on 51 subjects whose treatment involved extraction of second permanent molars. He noted spontaneous alignment in five quadrants where lower premolars were crowded. Cryer ( 1967) considered relief of lower premolar crowding to be one of the aims of treatment in extracting second molars but found that appliance therapy was sometimes necessary and that the degree of crowding which could be relieved by such means was limited. 030 1·228X/92/004000+00S02.00
The object of the present investigation was to quantify the degree of lower premolar crowding which could be successfully treated by extraction of second molars and to identify the circumstances in which spontaneous improvement might be expected.
Materials and Methods Thirty-four subjects, 11 boys and 23 girls, with varying degrees of crowding in the lower premolar region were treated by extraction of second molars. No mechanical treatment was started until at least 6 months after extractions. Subsequently 13 subjects, who showed no sign of spontaneous alignment of premo1ars, were treated either with simple removable appliances incorporating a screw or finger spring to move the first molar distally, or in two cases with fixed Edgewise or straight wire appliances. Many of these cases and those who had no lower appliances had mechanical treatment in the upper arch, either with removable or fixed appliances, and in some cases including extra-oral traction. The age at extraction ranged from 10·5 to 16·5 years with an average of 13·9 years. Records included plaster models taken before extraction and at the end of treatment or observation. Orthopantomograms, lateral oblique or 60 degree cephalometric radiographs were taken before extraction. '!) 1992 British Society for the Study of Onhodontics
300
M. E. Richardson
BJO Vol. /9 No. 4
Measurements On pre-extraction models
Original premolar space was measured from the mesial surface of the lower first molar to the distal surface of the canine. Original premolar space condition (crowding) was calculated as the difference between premolar space, and the sum of the mesio-distal widths of the first and second premolars. If the size of a premolar could not be measured on these models because of incomplete eruption the measurement was taken from the final model. Negative values indicated crowding. On final models, final premolar space was measured as above. Change in premolar space (space gain) and residual premolar crowding were calculated. Positive values for change in premolar space indicated space gain. Negative values for residual premolar crowding indicated space gain in excess of the size of the premolars. Measurements were made with a Baker Vernier microscope on 2 separate occasions by one observer. If the difference in replicate measurements exceeded 0·5 mm a third measurement was made and the aberrant one discarded. A mean of the two measurements was used in calculations. When premolar crowding was unilateral only the crowded side was included in the study (11 left, 8 right, in the treated group and IS left, 13 right in the untreated group). Differences in measurements between treated and untreated lower arch groups were tested for significance using independent sample t-tests. In order to examine reasons for spontaneous premolar alignment in some cases, but not in others, three of the untreated cases (four quadrants) showing little or no spontaneous improvement and who refused appliance therapy were combined with the treated group. This combined group (n= 16) was compared with the spontaneous alignment group (n = 18) in respect of: l ... Age at the time of second molar extraction. 2. Stage of dental development. 3. First molar occlusion, assessed subjectively on models as either good inter-digitation or poor inter-digitation. Normal molar occlusion or a full unit pre or post-normal were considered to be good inter-digitation. Cusp to cusp relationship of half a unit pre- or post-normality was considered to be poor inter-digitation. 4. Mesial tipping of the first molar assessed subjectively on radiographs as either present (Fig. I) or absent. 5. Mechanical treatment of the upper arch.
FIG. I
Mesially inclined lower first molar.
The difference in age at extraction between the combined and spontaneous alignment groups was tested for significance with an independent sample t-test. The eruptive status and position of the lower second premolar was used to assess the stage of dental development. First molar occlusion and mesial tipping were assessed on two separate occasions by one observer and the differences between the two groups tested for significances using chisquared tests.
Results Means, standard deviations and mean differences between treated and untreated groups for original premolar crowding, premolar space gain and residual premolar crowding are shown in Table I. None of these differences was statistically significant at the 5 per cent level (used throughout). However, there was, on average, slightly more original premolar crowding and space gain in the treated group compared with the untreated group and the treated group showed a small excess space gain compared with minimal residual premolar crowding in the untreated group. The average age of the combined group (14·6 years, SD 1·62), at the time of second molar extraction, was significantly greater than the spontaneous alignment group (13· 3 years, SD 1·25) {1=2·58, P
ISSN: 0301-228X (Print) (Online) Journal homepage: http://www.tandfonline.com/loi/yjor19
Second Molar Extraction in the Treatment of Lower Premolar Crowding Margaret E. Richardson M.Dent.Sc.D.Orth. & Donald J. Burden B.D.S., F.D.S., F.F.D., M.Orth. To cite this article: Margaret E. Richardson M.Dent.Sc.D.Orth. & Donald J. Burden B.D.S., F.D.S., F.F.D., M.Orth. (1992) Second Molar Extraction in the Treatment of Lower Premolar Crowding, British Journal of Orthodontics, 19:4, 299-304, DOI: 10.1179/bjo.19.4.299 To link to this article: http://dx.doi.org/10.1179/bjo.19.4.299
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: [Tufts University]
Date: 20 November 2016, At: 01:45
British Journal of Orthodontics/ Vol. 19/1991/199-304
Second Molar Extraction in the Treatment of Lower Premolar Crowding MARGARET E. RICHARDSON, M.DENT.Sc.D.ORTH. CBlinical Department of Orthodontics, School of Clinical Dentistry, Royal Victoria Hospital, Grosvenor Road, elfast BTI2 6BA DONALD J. BURDEN, B.D.S., F.D.S., F.F.D., M.ORTH. Clinical Department of Orthodontics, School of Clinical Dentistry, Queens University, Belfast BT12 6BP Received for publication November 1991
Abstract. Thirty-four children with lower premolar crowding were treated by extraction of second molars. Thirteen cases had mechanical lower arch treatment started not less than 6 months after extractions. The remainder had no treatment in the lower arch. The change in premolar crowding was measured, and the reasons why spontaneous alignment occurred in some cases and not in others were examined. Index words: Second Molar Extraction, Premolar Crowding, Spontaneous Alignment.
One of the advantages attributed to the extraction of second molars in orthodontic treatment is the Provision of space for the spontaneous relief of lower premolar crowding (McBride and Huggins, 1970; Huggins and McBride, 1978; Broadbent, 1986). Crowding in the lower premolar region occurs as a result of premature loss of deciduous molars in cases where a degree of arch length discrepancy al~eady exists (Seipel, 1946; Lundstrom, 1955; Chnch, 1959; Richardson, 1965). That is to say Primary crowding is transferred from the incisor and molar regions to create secondary crowding in the premolar region. In these circumstances, if no teeth are extracted, the force of eruption of the second premolar may cause malignment elsewhere. If_premolars are extracted, fixed appliance therapy Will often be required in both arches. Second molar extraction may provide space to relieve premolar crowding with little or no mechanical treatment. Dacre ( 1987) reported on 51 subjects whose treatment involved extraction of second permanent molars. He noted spontaneous alignment in five quadrants where lower premolars were crowded. Cryer ( 1967) considered relief of lower premolar crowding to be one of the aims of treatment in extracting second molars but found that appliance therapy was sometimes necessary and that the degree of crowding which could be relieved by such means was limited. 030 1·228X/92/004000+00S02.00
The object of the present investigation was to quantify the degree of lower premolar crowding which could be successfully treated by extraction of second molars and to identify the circumstances in which spontaneous improvement might be expected.
Materials and Methods Thirty-four subjects, 11 boys and 23 girls, with varying degrees of crowding in the lower premolar region were treated by extraction of second molars. No mechanical treatment was started until at least 6 months after extractions. Subsequently 13 subjects, who showed no sign of spontaneous alignment of premo1ars, were treated either with simple removable appliances incorporating a screw or finger spring to move the first molar distally, or in two cases with fixed Edgewise or straight wire appliances. Many of these cases and those who had no lower appliances had mechanical treatment in the upper arch, either with removable or fixed appliances, and in some cases including extra-oral traction. The age at extraction ranged from 10·5 to 16·5 years with an average of 13·9 years. Records included plaster models taken before extraction and at the end of treatment or observation. Orthopantomograms, lateral oblique or 60 degree cephalometric radiographs were taken before extraction. '!) 1992 British Society for the Study of Onhodontics
300
M. E. Richardson
BJO Vol. /9 No. 4
Measurements On pre-extraction models
Original premolar space was measured from the mesial surface of the lower first molar to the distal surface of the canine. Original premolar space condition (crowding) was calculated as the difference between premolar space, and the sum of the mesio-distal widths of the first and second premolars. If the size of a premolar could not be measured on these models because of incomplete eruption the measurement was taken from the final model. Negative values indicated crowding. On final models, final premolar space was measured as above. Change in premolar space (space gain) and residual premolar crowding were calculated. Positive values for change in premolar space indicated space gain. Negative values for residual premolar crowding indicated space gain in excess of the size of the premolars. Measurements were made with a Baker Vernier microscope on 2 separate occasions by one observer. If the difference in replicate measurements exceeded 0·5 mm a third measurement was made and the aberrant one discarded. A mean of the two measurements was used in calculations. When premolar crowding was unilateral only the crowded side was included in the study (11 left, 8 right, in the treated group and IS left, 13 right in the untreated group). Differences in measurements between treated and untreated lower arch groups were tested for significance using independent sample t-tests. In order to examine reasons for spontaneous premolar alignment in some cases, but not in others, three of the untreated cases (four quadrants) showing little or no spontaneous improvement and who refused appliance therapy were combined with the treated group. This combined group (n= 16) was compared with the spontaneous alignment group (n = 18) in respect of: l ... Age at the time of second molar extraction. 2. Stage of dental development. 3. First molar occlusion, assessed subjectively on models as either good inter-digitation or poor inter-digitation. Normal molar occlusion or a full unit pre or post-normal were considered to be good inter-digitation. Cusp to cusp relationship of half a unit pre- or post-normality was considered to be poor inter-digitation. 4. Mesial tipping of the first molar assessed subjectively on radiographs as either present (Fig. I) or absent. 5. Mechanical treatment of the upper arch.
FIG. I
Mesially inclined lower first molar.
The difference in age at extraction between the combined and spontaneous alignment groups was tested for significance with an independent sample t-test. The eruptive status and position of the lower second premolar was used to assess the stage of dental development. First molar occlusion and mesial tipping were assessed on two separate occasions by one observer and the differences between the two groups tested for significances using chisquared tests.
Results Means, standard deviations and mean differences between treated and untreated groups for original premolar crowding, premolar space gain and residual premolar crowding are shown in Table I. None of these differences was statistically significant at the 5 per cent level (used throughout). However, there was, on average, slightly more original premolar crowding and space gain in the treated group compared with the untreated group and the treated group showed a small excess space gain compared with minimal residual premolar crowding in the untreated group. The average age of the combined group (14·6 years, SD 1·62), at the time of second molar extraction, was significantly greater than the spontaneous alignment group (13· 3 years, SD 1·25) {1=2·58, P
