Korean J Orthod.  2018 Jan;48(1):11-22. 10.4041/kjod.2018.48.1.11.

Predictors of favorable soft tissue profile outcomes following Class II Twin-block treatment

Affiliations
  • 1Department of Orthodontics, College of Dentistry, Kyung Hee University, Seoul, Korea. deodor94@khu.ac.kr
  • 2Department of Orthodontics, Dental Hospital, Kyung Hee University Hospital at Gangdong, Seoul, Korea.
  • 3Department of Orthodontics, College of Dentistry, Seoul National University, Seoul, Korea.

Abstract


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.

Keyword

Class II Twin-block; Soft-tissue profile; Cephalometric predictors

MeSH Terms

Dental Occlusion
Humans
Incisor
Malocclusion
Orthodontists
Overbite
Retrospective Studies

Figure

  • Figure 1 The Class II Twin-block appliance used in this study.

  • Figure 2 An example of a pair of pre-treatment (left) and post-treatment (right) silhouettes used for evaluation by the panels.

  • Figure 3 Cephalometric analysis. A, Cephalometric landmarks (and the vertical reference plane) recorded: Nasion (N), sella point (S), condylion (Cd), articulare (Ar), basion (Ba), gonion (Go), anterior nasal spine (ANS), posterior nasal spine (PNS), point A (A), point B (B), pogonion (Pog), gnathion (Gn), menton (Me), upper incisor edge (UIE), upper incisor apex (UIA), lower incisor edge (LIE), lower incisor apex (LIA), infradentale (Id), upper molar mesial cusp tip (UM), lower molar mesial cusp tip (LM), glabella (Gb), soft-tissue nasion (sN), subnasale (Sn), labrale superius (Ls), labrale inferius (Li), soft-tissue pogonion (sPog), and the vertical reference plane perpendicular to the horizontal plane at 7° to the SN plane (VRP). B, Cranial base, facial height, and vertical measurements: (1) S-Ar, (2) S-N, (3) Ba-N, (4) N-S-Ar, (5) UAFH, (6) LAFH, (7) UPFH, (8) LPFH, (9), S-Ar-Go, and (10) maxillary plane angle (MxP)-mandibular plane angle (MnP). C, Anteroposterior mandibular dimension measurements: (1) SNA, (2) SNB, (3) VRP-Cd, (4) VRP-ANS, (5) VRP-A, (6) VRP-B, (7) VRP-Pog, (8) B-Pog, (9) S-N-Pog, (10), Cd-Go, (11) Cd-Gn, (12) Go-Gn, (13) Ar-Gn, (14) Ar-Go-Me, and (15) symphysis inclination. D, Dento-alveolar and soft-tissue measurements: (1) U1-MxP, (2) L1-MnP, (3) interincisal angle, (4) UM-MxP, (5) LM-MnP, (6) VRP-UM, (7) VRP-LM, (8) VRP-Gb, (9) VRP-sN, (10) VRP-Sn, (11) VRP-Ls, (12) VRP-Li, and (13) VRP-sPog. Terms and definitions are listed in Tables 1 and 2.


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