Kim, Ji-Eun
(Department of Orthodontics, College of Dentistry, Kyung Hee University)
,
Mah, Su-Jung
(Department of Orthodontics, Dental Hospital, Kyung Hee University Hospital at Gangdong)
,
Kim, Tae-Woo
(Department of Orthodontics, College of Dentistry, Seoul National University)
,
Kim, Su-Jung
(Department of Orthodontics, College of Dentistry, Kyung Hee University)
,
Park, Ki-Ho
(Department of Orthodontics, College of Dentistry, Kyung Hee University)
,
Kang, Yoon-Goo
(Department of Orthodontics, College of Dentistry, Kyung Hee University)
Objective: The aim of this study was to determine cephalometric factors that help predict favorable soft-tissue profile outcomes following treatment with the Class II Twin-block appliance. Methods: Pre- and post-treatment lateral cephalograms of 45 patients treated with the Class II Twin-block appli...
Objective: The aim of this study was to determine cephalometric factors that help predict favorable soft-tissue profile outcomes following treatment with the Class II Twin-block appliance. Methods: Pre- and post-treatment lateral cephalograms of 45 patients treated with the Class II Twin-block appliance were retrospectively analyzed. Profile silhouettes were drawn from the cephalograms and evaluated by three orthodontists in order to determine the extent of improvement. Samples were divided into a favorable group (upper 30% of visual analogue scale [VAS] scores, n = 14) and an unfavorable group (lower 30% of VAS scores, n = 14). Skeletal and soft-tissue measurements were performed on the cephalograms and an intergroup comparison was conducted. Results: An independent t-test revealed that the following pre-treatment values were lower in the favorable group compared to the unfavorable group: lower incisor to mandibular plane angle, lower incisor to pogonion distance, point A-nasion-point B angle, sella-nasion line (SN) to maxillary plane angle, SN to mandibular plane angle, gonial angle, and symphysis inclination. The favorable group had a larger incisor inclination to occlusal plane. Moreover, the favorable group showed larger post-treatment changes in gonial angle, B point projection, and pogonion projection than did the unfavorable group. Conclusions: Class II malocclusion patients with a low divergent skeletal pattern and reduced lower incisor protrusions are likely to show more improvement in soft-tissue profile outcomes following Class II Twin-block treatment.
Objective: The aim of this study was to determine cephalometric factors that help predict favorable soft-tissue profile outcomes following treatment with the Class II Twin-block appliance. Methods: Pre- and post-treatment lateral cephalograms of 45 patients treated with the Class II Twin-block appliance were retrospectively analyzed. Profile silhouettes were drawn from the cephalograms and evaluated by three orthodontists in order to determine the extent of improvement. Samples were divided into a favorable group (upper 30% of visual analogue scale [VAS] scores, n = 14) and an unfavorable group (lower 30% of VAS scores, n = 14). Skeletal and soft-tissue measurements were performed on the cephalograms and an intergroup comparison was conducted. Results: An independent t-test revealed that the following pre-treatment values were lower in the favorable group compared to the unfavorable group: lower incisor to mandibular plane angle, lower incisor to pogonion distance, point A-nasion-point B angle, sella-nasion line (SN) to maxillary plane angle, SN to mandibular plane angle, gonial angle, and symphysis inclination. The favorable group had a larger incisor inclination to occlusal plane. Moreover, the favorable group showed larger post-treatment changes in gonial angle, B point projection, and pogonion projection than did the unfavorable group. Conclusions: Class II malocclusion patients with a low divergent skeletal pattern and reduced lower incisor protrusions are likely to show more improvement in soft-tissue profile outcomes following Class II Twin-block treatment.
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문제 정의
To date, no studies have investigated the predictors of successful Class II Twin-block appliance treatment based on softtissue profile outcomes. Therefore, the aim of this retrospective study was to determine factors related to the successful outcomes of Class II Twin-block appliance treatment based on the evaluation of soft-tissue profile changes in growing patients with skeletal Class II malocclusion.
제안 방법
A modified form of Dr. Clark’s Twin-block appliance comprising two separate, upper and lower, removable appliances was used in this study (Figure 1).
The association of the inclination of symphysis with mandibular growth direction has also been reported in a previous study.15In that study, metallic implants were used to discriminate the forward mandibular rotator from the backward rotator; cephalometric characteristics were also investigated. In the forward rotating type, the symphysis swung forward in the face and the chin was prominent, while in the backward rotating type, the symphysis swung back and the chin receded.
Patients were then divided into two groups based on their VAS scores: a favorable group comprising the upper 30% of VAS scores, and an unfavorable group comprising the lower 30%. Pre- and post-treatment lateral cephalograms of each group were traced and analyzed by one operator.
Other patients also showed profile improvement however, it was not enough to classify as a straight profile. The objective of this study was to determine factors related to favorable soft-tissue profile outcomes following Class II Twin-block treatment.
The panel was provided with an explanation of the study and allowed 10 seconds to view each silhouette pair. The panel then recorded the extent of the silhouette improvement following treatment by using an unmarked 100-mm visual analogue scale (VAS) from 0 (no improvement of facial profile) to 100 (facial profile improved close to Class I).
13 The tracings were arranged with the Frankfort line parallel to the horizontal aspect of the computer monitor and were saved as JPEG images. Using a photo editor program, the profile tracings were filled in black, against a white background, and were standardized for size and range, from the soft-tissue glabella to slightly below the throat point.
대상 데이터
For each patient, the silhouette pairs (pre- and post- treatment) were randomly assigned a number (1–45) and were inserted on the same sheet: pre-treatment image on the left side and post-treatment image on the right (Figure 2). The extent of silhouette improvement was evaluated by a panel comprised of three orthodontists, each with an orthodontic experience of more than 10 years. The panel was provided with an explanation of the study and allowed 10 seconds to view each silhouette pair.
데이터처리
Statistical comparison of the pre-treatment measurements between the favorable and unfavorable groups was performed using an independent t-test. A logistic regression test was performed to determine the most highly correlated factor among the pretreatment variables and an intra-class correlation coefficient was used to determine intra-panel reliability; a high correlation coefficient (0.895) was recorded between the orthodontists within the panel.
A normal distribution of the variables was confirmed using the KolmogorovSmirnov test. Statistical comparison of the pre-treatment measurements between the favorable and unfavorable groups was performed using an independent t-test. A logistic regression test was performed to determine the most highly correlated factor among the pretreatment variables and an intra-class correlation coefficient was used to determine intra-panel reliability; a high correlation coefficient (0.
이론/모형
, Armonk, NY, USA). A normal distribution of the variables was confirmed using the KolmogorovSmirnov test. Statistical comparison of the pre-treatment measurements between the favorable and unfavorable groups was performed using an independent t-test.
The error of the first and second measurements was compared using Dahlberg’s formula.
성능/효과
Table 3 presents the comparative data for pre-treatment cephalometric measurements in both groups. An independent t-test indicated that there were statistically significant pre-treatment cephalometric differences in symphysis inclination, lower incisor to mandibular plane angle (IMPA), lower incisor to occlusal plane angle (L1 to Occ), lower incisor to pogonion distance (L1 to pogonion), ANB, SN to MxP, SN to mandibular plane angle (MnP), and gonial angle between the two groups. With the exception of L1 to Occ, the favorable group had the lowest cephalometric measurements.
후속연구
23 Therefore, if fixed-appliance treatment seems inevitable, initial Twinblock application may not be justified. Consequently, when patients are expected to have an unfavorable profile after Twin-block treatment, the application of a Twin-block appliance is not recommended; however, further studies with long-term follow-up profiles are required to confirm this finding.
According to these authors, the increase in the gonial angle after Class II Twin-block treatment is a positive indication of mandibular morphogenetic change, resulting in an improved jaw relation. This could be one of the reasons for the improvement in soft-tissue profile outcomes in the favorable group reported in the present study; however, further research is required to elucidate the precise mechanism.
참고문헌 (24)
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