Changes in masticatory performance during the retention period following extraction and non-extraction orthodontic treatment

다국어 초록 (Multilingual Abstract)

Orthodontic treatment is the process of acquiring an optimal occlusion by modifying the initial malocclusion through space closure after extraction or space gain without extraction using various techniques. The functional benefits of modifying the occlusion while treating malocclusion remain controversial due to the lack of long-term studies evaluating the outcomes after orthodontic treatment.
This study aimed was (1) to evaluate change in masticatory performance (MP) during retention period after extraction and non-extraction orthodontic treatment in adult patients and compare it with the MP in the participants with normal occlusion by measuring the mixing ability (MA) using a two-color chewing gum and (2) to evaluate whether extraction affects the MP after orthodontic treatment.
Adult patients who had completed orthodontic fixed appliance treatment comprised the non-extraction group (mean age 25.33±5.26) and extraction group (mean age 29.14±7.00), and those with normal occlusion(mean age 28.3±6.57) comprised the control group.
Mixing ability (MA), maximum bite force (MBF), and occlusal contact area (OCA)were recorded one week after debonding the fixed appliance, the day when the wrap-around retainer was delivered (T0), 1-month post-treatment(T1), 6 months post-treatment(T2),
1-year post-treatment(T3). MA were measured with two-color chewing gum MA test using ViewGum software, and MBF and OCA were measured using Dental Prescale II system.
The results are follows
1. The MA immediately after orthodontic treatment was lower than that observed in normal occlusion group but showed a time-dependent gradual increase during 1-year retention period (P<0.01).
2.The MA at 1-month post-treatment was not significantly different from that in the normal occlusion group (P>0.05), but the MBF and OCA at 1-year post-treatment were significantly lower than those in the normal occlusion group (P<0.01).
3. The MA showed a significant correlation with the MBF and OCA (P<0.05).
4. No significant difference was observed in MA between the non-extraction group and extraction group (P>0.05).
In conclusion, the MP immediately after orthodontic treatment in the experimental groups was lower than that in the normal occlusion group but increased gradually over time during the retention period and improved to levels similar to those in the normal occlusion group at 1-month post-treatment. Further, extraction did not affect the MP after orthodontic treatment.

국문 초록 (Abstract)

본 연구의 목적은 ViewGum-software를 이용한 두가지 색깔 껌의 혼합능력을 평가하는 방법으로 발치, 비발치 교정치료 후 유지기간 1년동안에 시간에 따르는 저작효율의 변화를 정상교합과 비교 평가하는 것과 동시에 발치가 교정치료 후 저작효율에 영향을 미치는가를 평가하는 것이다.
실험군은 총 32명의 고정성교정장치를 이용하여 교정치료를 끝낸 환자들 중 비발치군 18명(남, 여 각각 9명씩, 평균나이: 25.33±5.26)과 발치군 14명(남, 여 각각 7명씩, 평균나이: 29.14±7.00)으로 나누고 대조군으로는 정상교합군 20명(남, 여 각각 10명씩, 평균나이: 28.3±6.57)으로 구성하였다.
저작효율은 두가지 색상의 껌을 씹은 후 스캔한 이미지를 ViewGum-software를 이용하여 혼합정도를 평가하는 방법으로 측정하였고 최대교합력과 교합면적은 압력감지필름 시스템II를 이용하여 측정하였다.
고정식 교정장치 제거 1주일 후 가철성 유지장치를 장착하는 날과 그 후 1개월, 6개월, 1년이 되는 시기에 각각 측정하여 다음과 같은 결과를 얻었다.
1. 교정치료 직후 교정치료군의 혼합능력은 정상교합군보다 낮은 값을 보이지만 유지기간 1년동안에 시간에 따르는 증가를 보여주었다 (P<0.01).
2. 교정치료군의 혼합능력은 교정치료 1개월 후 정상교합군과 유의한 차이가 없었으나(P>0.05) 교정치료 1년 후 교정치료군의 최대교합력과 교합면적은 정상교합군보다 여전히 낮은 값을 보여주었다 (P<0.01).
3. 교정치료 후 혼합능력은 최대교합력, 교합면적과 유의한 상관관계를 보여주었다 (P<0.05).
4. 발치군과 비발치군의 혼합능력을 비교한 결과 어느 시기에도 유의한 차이를 보이지 않았다(P>0.05).

본 연구를 통하여 교정치료 후 1년간의 유지기간 동안에 교합력과 교합면적은 정상교합수준에 이르지 못하는 것과는 달리 저작효율은 치료 1개월 후 정상교합과 비슷한 수준으로 개선되며 더욱이 발치는 교정치료 후 저작효율에 영향을 주지 않는다는 결론을 내릴 수 있었다

목차 (Table of Contents)

• TABLE OF CONTENTS
• List of Tables ························································································· iii
• List of Figures ························································································ iv
• Abstract (English) ··················································································· v
• I. Introduction ························································································ 1
• II. Materials and Methods ······································································ 4
• 1. Participants ···················································································· 4
• 2. Measurements ··············································································· 5
• 3. Statistical analysis ··········································································· 8
• III. Results ······························································································ 10
• 1. Participant characteristics ······························································ 10
• 2. Changes in the MA during the retention period ····························12
• 3. Changes in the MBF and OCA during the retention period ·········· 13
• 4. Correlation between the MA, MBF, and OCA ······························· 18
• IV. Discussion ······················································································· 19
• V. Conclusion ························································································25
• References ···························································································· 26
• Abstract (Korean) ················································································· 30

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