At the start of the treatment there were no statistically significant differences in maxillary and mandibular intercanine widths in both groups .At the end of Treatment in both the groups anterior and posterior arch width changes were not significant except for the intercanine dimension which was 0.82 mm larger (P<0.05) in the extraction group.
Conclusion :
The extraction treatment does not result in narrower dental arches than non extraction treatment in intercanine and intermolar region.
Clinical significance:
It is documented that the arch widths determine smile esthetics and treatment stability. According to the findings of the present study the arch widths in extraction treatments are not narrower than non extraction so there will not be any compromising effects on esthetics and treatment stability .
Key words: Arch width Changes, Intercanine and Intermolar width , extraction and Non Extraction Treatment.
Introduction:
The extraction versus non extraction dilemma still exists in orthodontics ..
Angle1 believed that all 32 teeth could be accommodated in the jaws, in an ideal occlusion with the first molar in Class I occlusion, extractions was against his ideals as he believed bone would form around the teeth in their position according to Wolff's law2. However this was criticised by Case who stated that extractions were necessary in order to relieve crowding and aid stability of treatment.3
However with accurate diagnosis the extraction decision should be taken. Crowding and protrusion of teeth are observed in Class I malocclusion which can be treated by extraction or non-extraction treatment depending upon space discrepancy .However the long term stability in both treatments is surrounded by a controversy.
One of the criticism of extraction treatment is that it results in narrower arches as compared to non-extraction treatment.4It is believed that the pre-treatment values of intercanine and intermolar widths present a position of muscular balance so it is suggested that the maintaince of these values provide postretention stability 5,6.
In the past many studies have been carried out to study the effects of extraction and non-extraction treatment but the conclusions vary a lot which could be because of different treatment techniques ,malocclusion types and sample size examined during these studies.
So the aim of present study was to compare dental arch widths changes in Angle Class I malocclusion after extraction of first premolar and non-extraction with in a study group with same type of malocclusion and treated with same mechanics.
Materials and methods
In this retrospective study orthodontic study models of 30 patients who had first premolar extractions and 30 patients treated without extractions were selected In the extraction group there were 17 girls and 13 boys with mean age 14.7+-2.7 years and in the non-extraction group had 16 boys and 14 girls with mean age 14.6+_2.3 years All the patients were treated with preadjusted edgewise appliance by various instructors in a dental institute
While selection the following criteria were applied
All patients had skeletal Class I malocclusion
All patients had full complement of teeth upto second molars without any missing teeth ,supernumerary teeth, or congenitally missing teeth.
None of the patients had a adjunctive appliances for expansion of the arches during treatment.
In the extraction group all patients had first premolar extraction as a part of orthodontic treatment.
With a digital caliper, dental arches were measured in the canine and the first molar regions from the most labial aspect of the buccal surfaces of these teeth. The caliper was placed at right angle to the palatal suture in the maxillary arch and to a line bisecting the incisor segment in the mandibular arch4.The average of first three measurements was considered the final value
The random error of measurement was assessed by Dahlberg's formula:7
Sx =
where D is the difference between duplicate measurements, and N is the number of double determinations.
The range of error of measurement was 0.22 to 0.50.
The collected data was treated statistically by using two tailed t test (P<0.05)
Results
The mandibular intercanine and intermolar widths did not show statistical differences at the start of the treatment in both the groups.(Table 1)
At the end of treatment the arch widths of both the groups were also statistically similar except in mandibular canine region .(Table 2)
The average mandibular intercanine dimension was 0.82 mm larger in extraction sample than non-extraction sample. During treatment the mean mandibular canine width increase was 1.28mm in extraction group and the 0.66mm increase in non-extraction group which was not statistically significant.(Table 3&4)
The mandibular intermolar widths for both extraction and non-extraction group were not changed.
Table 1. Pretretment mandibular intercanine and intermolar arch widths : means and SD (mm)
Extraction
(n=30 )
Non-extraction
(n=30 )
Significance
Intercanine
30.47 ± 2.09
30.27 ± 1.82
NS
Intermolar
59.25 ±2.92
59.05± 1.67
NS
NS-Not Significant P<0.05-S
Table 2. post treatment maxillary and mandibular arch intercanine and intermolar widths: means and SD (mm)
Extraction
(n=30 )
Non-extraction
(n=30 )
Difference
Significance
Mx Intercanine
39.12 ± 1.98
39.84 ± 1.81
0.72
NS
Md Intercanine
31.75 ± 1.84
30.93 ± 1.92
0.82
0.01
Mx Intemolar
61.01 ± 1.98
60.98 ± 2.09
0.03
NS
Md Intemolar
59.81 ± 1.25
59.01 ±1.98
0.80
NS
Mx- Maxillary ;Md- Mandibular; NS-Not Significant P<0.05-S
Table 3.Mandibular intercanine and intermolar width changes : means and SD (mm)
Extraction
(n=30 )
Pre-Treatment
Post- Treatment
Difference
Md Intercanine
30.47± 2.09
31.75 ± 1.84
1.28
Md
Intermolar
59.25 ± 2.92
59.81 ± 1.25
0.56
Md-Mandibular; NS-Not Significant.
Table 4 .Mandibular intercanine and intermolar width changes : means and SD (mm)
Non-extraction
(n=30 )
Pre-treatment
Post- Treatment
Difference
Md Intercanine
30.27 ± 1.82
30.93 ±
1.92
0.66
Md
Intermolar
59.05 ± 1.67
59.01 ± 1.98
0.04
Md-Mandibular; NS-Not Significant.
Discussion
The two reasons for which the extraction treatments are criticised are that they result in narrow dental arches which are unesthetic because of large black triangles in buccal corridors and it is stated that the intercanine and intermolar widths tend to decrease during post retention period ,6,8
According to findings of the present study the arch widths in both canine and molar region in the mandibular arches did not show any statistical significant results.in fact the arches in extraction group were approximately 0.82mm wider than non-extraction group. The results of this study can be compared with studies in which post treatment long term stability of in mandibular intercanine width stability was found acceptable. The mandibular intercanine width increased 1.07mm in an extraction sample9 .While non-extraction subjects where the increase in mandibular intercanine dimension was less than 1mm in Class I 10,11 and Class II patients..
In borderline cases the long term increase in intrecanine width was 1mm in extraction treatments and 0.5mm in non-extraction 12 treatments.Luppanapornlarp and Johnston found that mandibular intercanine width of extraction subjects was greater at all stages of treatment in extraction cases than in non-extraction cases which indicate that extraction of 4 first premolars does not indicate narrowing of arches.13 BeGole et al 14 found 1.58mm increase in extraction sample as compared to 0.95mm in non-extraction sample.Udhe et al 15 found a larger increase in extraction group than in non-extraction group.
Gianelly 4 studied inter arch changes of extraction and non-extraction groups and found that the changes in maxillary and mandibular arch widths indicated that extraction treatment does not result in narrower arches than non-extraction groups. This finding is in accordance with the present study.On the basis of concepts documented in the literature one might expect narrower arches after extraction.However Kim and Gianelly 16 suggested that the widths of the both the arches were 1-2mm larger when compared with the arch widths of non-extraction group at a standardised arch depth.The intermolar widths of both the groups were same after treatment this finding supports the view of Johnson and smith17. Who stated that arch width at any particular location is maintained or slightly increased after extraction.
Weinberg and sadowsky18 found significant increase in mandibular intercanine and intermolar width in class1 malocclusion treated non-extraction and stated that the expansion of buccal segments in the mandibular arches helped in resolution of Class I crowding. However 16 out of 30 patients had some kind of palatal expander which might have contributed to mandibular expansion In the present study no treatments were given for expansion.
To some investigators maxillary arch width is determinant of smile esthetics 19, ,the maxillary arch widths in extraction and non-extraction groups were same so it can be expected that the treatment effects in maxillary arches will be the same,and there will be no difference in esthetic scores in both the groups.In fact the intercanine widths in extraction groups were wider than non-extraction group. However the future studies in the maxillary arches in various malocclusion classifications with various treatment mechanics will be productive.
It is stated that expansion more than 1-1.5mm in intercanine expansion is unstable so appliances designed to increase arch width more than this were not used in the present study.
On the basis of findings of the present study it can be said that extraction cases do not result in narrow dental arches than non-extraction cases and thereby do not have compromising effect on smile esthetics and stability of orthodontic treatment. However future studies with various malocclusion groups, treatment mechanics, larger sample size and long term changes in arch dimensions will be useful.
Conclusions
The present study findings indicate that the premolar extractions to relieve crowding does not result in narrowing of dental arches in extraction treatments when compared to non-extraction treatments. A proper treatment plan and treatment mechanics in accurately diagnosed case can result in treatment success regardless of extraction or non-extraction treatment.
Clinical significance
The cases which require extraction of teeth for correction of crowding and protrusion of teeth do not have narrow dental arches than the cases which do not require extraction of teeth. So these extraction cases can be treated without any compromising effects on esthetics and treatment stability.
