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ORIGINAL ARTICLE
Year : 2022  |  Volume : 25  |  Issue : 3  |  Page : 325-335

Differences in hard and soft tissue profile after orthodontic treatment with and without extraction


1 Department of Preventive Dental Sciences, College of Dentistry, Prince Sattam bin Abdulaziz University, Al-Kharj, Saudi Arabia
2 Hotat Bani Tamim General Hospital, Ministry of Health, Riyadh, Saudi Arabia
3 Private Practice, Riyadh, Saudi Arabia
4 Department of Restorative and Prosthetic Dental Sciences, College of Dentistry, Dar Al uloom University, Riyadh, Saudi Arabia; Department of Prosthodontics, College of Dentistry, Ibb University, Ibb, Yemen
5 Department of Oral and Maxillofacial Surgery and Diagnostic Science College of Dentistry, Prince Sattam Bin Abdullaziz University, Al-Kharj, Saudi Arabia
6 Department of Preventive Dental Science, Dar Al Uloom University, Riyadh, Saudi Arabia

Date of Submission31-May-2021
Date of Acceptance20-Aug-2021
Date of Web Publication16-Mar-2022

Correspondence Address:
Dr. A Alqerban
Department of Preventive Dental Sciences, College of Dentistry, Prince Sattam Bin Abdulaziz University, Al-Kharj
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njcp.njcp_1562_21

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   Abstract 


Aims and Background: Premolar extraction is often associated with variations in the soft tissue profile that lead to considerable improvements in the facial profile. This study compared the changes in the facial profile of hard and soft tissues and investigated possible differences in the various facial parameters between patients who were treated with and without premolar extraction. Materials and Methods: A total of 98 orthodontically treated patients were divided into two groups with an equal number of participants. Premolar extraction was performed in the test group only. A total of 33 landmarks were identified on each cephalometric radiograph. The intraclass correlation coefficient was calculated. We evaluated changes in measurements between pre- and post-treatment by performing the signed-rank test. We used the Kruskal–Wallis test to compare changes between the groups. Results: No significant differences were observed in the treatment outcomes of skeletal and soft tissue variables in class I and class II participants between the test and control groups (P > 0.01). However, significant differences were noted in the treatment outcomes of dental variables in class II participants between the groups. Dental variables did not show any significant difference in class III patients between the groups. Conclusion: This study showed that skeletal and soft tissue changes were similar in skeletal except for few dental parameters following orthodontic treatment with and without premolar extraction.

Keywords: Class I, class II, class III, malocclusion, facial profile, premolar extraction


How to cite this article:
Alqerban A, Alaskar A, Alnatheer M, Samran A, Alqhtani N, Koppolu P. Differences in hard and soft tissue profile after orthodontic treatment with and without extraction. Niger J Clin Pract 2022;25:325-35

How to cite this URL:
Alqerban A, Alaskar A, Alnatheer M, Samran A, Alqhtani N, Koppolu P. Differences in hard and soft tissue profile after orthodontic treatment with and without extraction. Niger J Clin Pract [serial online] 2022 [cited 2022 Aug 19];25:325-35. Available from: https://www.njcponline.com/text.asp?2022/25/3/325/339716




   Introduction Top


Facial esthetics has gained prominence in the modern community and is a major reason to seek orthodontic treatment.[1] Professionals may encounter difficulties in predicting soft tissue changes with various orthodontic devices and techniques for correcting malocclusion, especially while deciding whether to perform an extraction.[2],[3],[4],[5],[6],[7],[8] Diversity of available orthodontic treatments has made it difficult for orthodontists to choose the best alternative for their patients while maintaining the harmony of soft tissues components.

In the 1970s, orthodontic treatment commonly avoided premolar extraction because of its possible adverse effects. The supporters of Angle's “old school” believed the face to be in accord if teeth were in harmony.[9],[10] However, the “rational school” claimed that extraction was necessary to treat malocclusion because the bone cannot grow beyond its inherent potential. Case et al.[11] thought that malocclusion was hereditary, subsequent to the mixing of races and facial forms.

Premolars are the most commonly extracted teeth for orthodontic reasons as this leads to differences in the soft tissue contour, specifically in the proclination of the incisors. Occasionally, these deviations cause significant improvements in the soft tissue profile that validate the extraction of teeth in patients without other signs. Several studies have reported the association between incisor and lip retraction.[12],[13],[14],[15] Oliver[16] examined the effect of the lip structure on incisor retraction and reported that patients with thin lips or high strain showed a significant association between incisor and lip retraction, although patients with thick lips or low strain showed no such association. A relationship was found between high mandibular plane angle and lip retraction in extraction and nonextraction cases; when compared with extraction cases, the lips retracted in nonextraction cases. Therefore, Stromboni[17] reported that lip prominence reduces with an increase in the vertical dimension which tends to stretch the lip.

Staggers[18] observed increased lower lip retraction in patients who underwent four first premolar extractions when compared with nonextraction group; higher lower lip retraction was reported in patients who underwent four first premolar extractions than in those who underwent four second premolars extractions.

With appropriate treatment planning, adverse effects of extraction on the facial profile can be eliminated.[1],[3],[5],[6] Contrarily, some studies have indicated that orthodontic treatment with extraction can blight the facial profile because of excessive retrusion.[4],[7] Only a few studies have examined soft tissue changes that occur with specific treatments.[19]

It was hypothesized that extraction would exert no effect on hard and soft tissues in patients treated for different malocclusions. Therefore, the present study compared changes in the hard and soft tissue facial profile between patients who underwent orthodontic treatment with and without premolar extraction.


   Materials and Methods Top


The present study was approved by the institutional ethics committee of the College of Dentistry, Dar Al Uloom University (REC 14/2021) on 14 Jan 2021. The study sample was retrospectively selected from orthodontic clinics. Inclusion criteria were patients who treated and finished orthodontic treatment and had their pre- and post-treatment lateral cephalometric radiographs available. Patients with agenesis (exclusion of third molars), significant asymmetries, craniofacial anomalies, syndromic anomalies, and missing teeth without an orthodontic indication and those with orthognathic surgery planned were excluded. All patients' sex and age were ascertained at the start and end of the treatment. A power analysis (set at ≥80%) was utilized to determine a statistically acceptable sample size comparable to previously published data in the dental literature.

A total of 98 patients were collected who had completed the orthodontic treatment. The patients were divided into two groups: test and controlled groups that were matched by gender and age. The test group consisted of 49 patients (14 male and 35 female patients) orthodontically treated with the extraction of premolars. The control group consisted of 49 patients (14 male and 35 female patients) treated without the removal of premolars. The mean age, gender, and treatment duration of patients are given in [Table 1]. The mean treatment duration of the control and treatment groups were 2 years 4 months and 2 years 11 months, respectively. Both the groups were treated at the same hospital by postgraduate residents, under the supervision of an orthodontist, by using a preadjusted 0.022-inch slot Roth prescription orthodontic fixed appliance (3M Unitek, Monrovia, CA, USA).
Table 1: The mean age and treatment time in different patient groups

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Pre- and post-treatment lateral cephalometric radiographs were taken in the upright posture with the Frankfort horizontal plane parallel to the floor, the teeth in occlusion, and the lips at rest. The patients were told not to stress on the lips and bite down on the molars. Lateral cephalometric radiographs were used because they are the most commonly used radiographs for diagnosis and treatment planning in patients with ongoing orthodontic treatment. For all patients, lateral cephalometric radiographs were collected and considered clinically acceptable preceding the study to outline the orthodontic treatment plan. Pretreatment lateral cephalometric radiographs were taken approximately 2 weeks before the start of the treatment, and post-treatment radiographs were taken immediately at the end of the treatment. No additional radiographs were taken for this study. Digital lateral cephalometry was performed using Orthophos XG5 (Sirona Dental Systems, Bensheim, Germany) equipped with a digital charge-coupled device line sensor with exposure parameters of 14.1 S, 64 kV, and 8 mA. Furthermore, all images were extracted and stored as JPG format files (resolution: 2503 × 1244; 24 bit).

Overall, 33 landmarks were identified on each cephalometric radiograph: 14 skeletal, 13 soft tissue, and 6 dental landmarks [Table 2].[20],[21],[22],[23] All the landmarks were recognized by a single investigator and re-evaluated for the precision of location by an additional investigator. All the landmarks were traced using a software program named FACAD Copyright Ilexis AB 2016, version 3.9.2. The probability of magnification was eliminated by calibrating the actual length of the ruler on the head positioner. The following 49 measurements were obtained: 21 anteroposterior vertical skeletal, 17 soft tissue, and 11 linear and angular dental variables [Table 2].
Table 2: Skeletal, soft tissue, and dental linear and angular measurements

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Statistical analysis

To evaluate the reproducibility of the measurements, the data of 30 patients (15 patients with extraction and 15 patients without extraction) were randomly selected and remeasured by the same investigator after a minimum of 1-month interval. The intraclass correlation coefficient (ICC) was calculated to determine reproducibility. The error of the method was calculated using the Dahlberg's formula, , where ME is the method error, d is the difference between the first and second measurement, and n is the sample of repeated measurements. Changes in variables between pre- and post-treatment within the same group were evaluated using the paired t-test and signed-rank test based on the normality test. Differences were examined as the post-treatment value minus the pre-treatment value.

Differences in treatment outcomes between with and without extraction groups were evaluated by performing the independent t-test and Mann–Whitney U test as appropriate. ANOVA and Kruskal–Wallis test were performed, as appropriate, to compare changes between different classifications based on the cephalometric analysis of the A point, nasion, B point (ANB) angle, which indicates whether the skeletal relationship belonged to skeletal class I, class II, or class III (class I if the ANB angle ranged from 2° ± 2; class II if the ANB angle was >4°; and class III if the ANB angle was <0°). Given a large number of verified relationships, P values were only considered significant if they were <0.01 (instead of the classical 0.05) to reduce the probability of false-positive results. All statistical tests were performed using Statistical Package for Social Sciences (SPSS Version 25, IBM).


   Results Top


The number of cases who had skeletal classification was 25 patients with class I (15 with extraction, 11 without extraction), 62 class II (29 with extraction, 33 without extraction), and 10 patients with class III (5 with extraction, 5 without extraction).

The reliability of the measurements indicated a favorable agreement between the first and second readings (ICC > 0.73, > 0.85, and > 0.90 for skeletal, soft tissue, and dental variables, respectively). The test–retest reliability (ICC) of skeletal variables ranged from 0.736 (angle around the center S between marker N and Gn [NSGn]) to 0.976 (ANB 1). The results of the Dahlberg's formula revealed small measurement errors between the readings obtained for soft tissue variables (most errors <3), dental variables (most errors <1), and skeletal variables (most errors <2). The ICC of soft tissue and dental variables ranged from 0.893 (interla bial space) to 0.994 (distance between H Line and most anterior point on nose[H-PRN]) and 0.914 (angle between the cranial baseline and occlusal plane line [OL/NSL]) to 0.990 (lower incisor inclination [Ii-Iia/N-B]), respectively.

Skeletal variables

Significant differences were not observed in treatment consequences of skeletal variables in class I and class II participants between the extraction and no extraction groups (P > 0.01). Furthermore, a significant difference was observed in the treatment outcome of the sella–nasion–pogonion (SNPg) angle in class III participants between the extraction and no extraction groups with the mean value being higher in the nonextraction group, and the mean difference being −8.88 (P = 0.009; [Table 3]).
Table 3: Differences in treatment outcomes of skeletal variables between extraction and none-extraction groups among participants for class I, class II and class III skeletal relationship

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Soft tissue variables

No significant differences were noted in the treatment outcomes of soft tissue variables in class I and class II participants between the extraction and nonextraction groups (P > 0.01). Significant variances were observed in the treatment outcomes of the soft tissue facial angle (GL-SN-PGs) and the angle centered by the nose tip and point GL PGs (GL-PRN-PGs) in class III participants between the extraction and nonextraction groups (mean difference of −23.56 and −16.24 respectively; P = 0.009; [Table 4]).
Table 4: Differences in treatment outcomes of soft tissue variables between extraction and none-extraction groups among participants for class I, class II, and class III skeletal relationship

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Dental variables

Significant differences were not observed in the treatment outcomes of dental variables in class I or class III participants between the extraction and nonextraction groups (P > 0.01). Significant differences were noted in the treatment outcomes of the interincisal angle, upper incisor inclination, distance between the most anterior point of the crown of the maxillary incisor and NA line, distance between the most anterior point of the crown of the mandibular incisor and NB Line, distance between the upper incisor and pogonion–A Point line (Is: A-Pog), distance between the lower incisor and pogonion–B Point Line, and the upper incisor and cranial base angle (ILs/NSL) in class II participants among the extraction and nonextraction groups [Table 5].
Table 5: Differences in treatment outcomes of dental variables between extraction and none-extraction groups among participants for class I, class II and class III skeletal relationship

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Differences in treatment outcomes between the extraction and nonextraction groups

No significant changes were observed in the treatment outcomes of skeletal and soft tissue variables between the extraction and nonextraction groups (P > 0.05). However, significant changes were observed in the treatment outcomes of the following dental variables: interincisal angle (mean difference = −13.27, P = 0.000), lower incisor inclination (mean difference = 5.08, P = 0.002), distance between upper incisor to pogonion-A Point Line (mean difference = 1.84, P = 0.003), and upper incisor to cranial base angle (mean difference = 6.15, P = 0.002; [Table 6]).
Table 6: Differences between extraction and none-extraction groups

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   Discussion Top


The foremost goal of an orthodontist is to preserve harmony among the various facial parameters by predicting the outcome of orthodontic treatment. It is a common dilemma among orthodontists whether or not to perform a tooth extraction. The controversy regarding the detrimental effects of premolar extraction on treatment outcomes is age-old. The premolars are commonly extracted to overcome tooth size-arch length discrepancy. Several studies have compared hard and soft tissue changes following treatment with and without premolar extractions.[12],[13],[14],[15] The current retrospective study intended to assess the soft and hard tissue profiles of patients before and after orthodontic treatment. Standard cephalometry was performed to assess facial soft and hard tissue changes between the extraction and nonextraction groups. All cephalometric radiographs obtained before and after treatment were of high quality and clearly showed skeletal, soft tissue, and dental parameters.

The results of the current study are in agreement with those reported by Zierhut et al.,[4] Finnoy et al.,[24] and Janson et al.,[6] who did not find any significant differences in cephalometric skeletal variables between the extraction and nonextraction groups. However, in contrast to our study findings, Bishara et al.,[3] reported a significant change in N-Me between the extraction and nonextraction groups. In the current study, the extraction group showed significant differences pre- and post-treatment in N-Me, Co-Gn, and NAPog. No significant difference was observed in skeletal variables pre- and post-treatment in the nonextraction group.

The findings of our study regarding soft tissue changes are in accordance with those reported by Verma et al.,[8] Janson et al.,[6] and Finnoy et al.,[24] wherein the authors did not find any significant difference in soft tissue changes between the extraction and nonextraction groups.

In the extraction group, significant differences were noticed pre- and post-treatment in four variables, namely the upper and lower lip to the esthetic line, distance between H Line and most anterior point on the nose, distance between the lower lip to subnasal soft tissue pogonion plane and H angle. No significant differences were observed in few variables among the extraction and nonextraction groups. Class I and class II patients did not show any significant change in soft tissue variables between the groups, whereas class III patients showed a significant difference in the total facial convexity angle and facial profile angle between the groups.

In the nonextraction group, the enhancement in the nose lip chin relationship represented by Z angle significantly differed pre- and post-treatment. This finding is in accordance with those of Saelens et al.,[19] Finnoy et al.,[24] James et al.,[25] and Drobocky et al.,[26] who noticed that the nonextraction group had a protrusive lip profile compared with the extraction group.

The findings of our study indicate that the extraction of premolars facilitates more retraction of the upper and lower incisors when compared with the nonextraction group. The extraction group presented significant differences in all variables except for the distance between the mandibular plane to lower incisor tip and occlusal plane angle. However, the nonextraction group did not show any significant changes in any considered variable. We found statistically significant differences in variables such as the interincisal angle, upper incisal inclination, and upper incisal cranial base angle between the groups, in accordance with those reported by Bishara et al.,[3] Finnoy et al.,[24] and Zierhut et al.[4]

Kocadereli et al.[2] found that the mandibular and maxillary incisors displayed more retroclination after the treatment than before the treatment in the extraction group. Nevertheless, forward tipping of the incisors after the treatment was noted in the nonextraction group. The deviations in incisor inclination were shown to be significant. Alqahtani et al.[27] had found an adequate amount of upper incisor retraction and a positive correlation between upper incisor retraction and protrusion of upper and lower lips.

In addition, this study specified dentoalveolar and soft tissue measurements that can demonstrate the correlation between hard and soft tissues. Among the 29 dentoalveolar and soft tissue variables studied, the current study identified the seven most influential cephalometric measurements that can aid the clinician in the diagnosis and assessment of post-treatment changes.

The study carried some limitations derived from its retrospective nature. The limitations as the samples were recruited based on the availability of the pre and post on lateral cephalometric radiographs, the effect of confounding factors could not be prevented. Moreover, the choice of sample collections was limited to the extraction decision and matched by the age and gender of the subject. Lack of this standardization caused a small number of cases with class I and class III subjects compared to class II that were included in the study. It would be ideal to standardize each skeletal classification as the evaluation of the hard and soft tissue changes response to orthodontic treatment is complex. Further research with large and ideal sample distribution could lead to a greater understanding if there are any changes in the soft and hard tissue after orthodontic treatment.


   Conclusion Top


This study demonstrated that no changes were observed in skeletal and soft tissue variables between the extraction and nonextraction groups. A significant difference was observed in the treatment outcomes of the dental variables mainly interincisal angle, upper and lower incisor inclinations. Dental variables were changed significantly in class II skeletal patients, whereas skeletal and soft tissue changes were mainly seen in class III patients.

Acknowledgements

The authors extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research work through the project number (IF-PSAU-2021/03/18524).

Financial support and sponsorship

Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

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