Korean J Orthod.  2020 Mar;50(2):120-128. 10.4041/kjod.2020.50.2.120.

Changes in maximum lip-closing force after extraction and nonextraction orthodontic treatments

• Choi TH
• Kim SH
• Kim C
• Kook YA
• Larson BE
• Lee NK

• KMID: 2471872
• DOI: http://doi.org/10.4041/kjod.2020.50.2.120

Abstract

OBJECTIVE
The aims of the present study were to evaluate the changes in the maximum lip-closing force (MLF) after orthodontic treatment with or without premolar extractions and verify the correlation of these changes with dentoskeletal changes.
METHODS
In total, 17 women who underwent nonextraction orthodontic treatment and 15 women who underwent orthodontic treatment with extraction of all four first premolars were included in this retrospective study. For all patients, lateral cephalograms and dental models were measured before (T0) and after (T1) treatment. In addition, MLF was measured at both time points using the Lip De Cum LDC-110R® device. Statistical analyses were performed to evaluate changes in clinical variables and MLF and their correlations.
RESULTS
Both groups showed similar skeletal patterns, although the extraction group showed greater proclination of the maxillary and mandibular incisors and lip protrusion compared to the nonextraction group at T0. MLF at T0 was comparable between the two groups. The reduction in the arch width and depth and incisor retroclination from T0 to T1 were more pronounced in the extraction group than in the nonextraction group. MLF in the extraction group significantly increased during the treatment period, and this increase was significantly greater than that in the nonextraction group. The increase in MLF was found to be correlated with the increase in the interincisal angle and decrease in the intermolar width, arch depth, and incisor-mandibular plane angle.
CONCLUSIONS
This study suggests that MLF increases to a greater extent during extraction orthodontic treatment than during nonextraction orthodontic treatment.

Keyword

Dental arch morphology; Nonextraction orthodontic treatment; Premolar extraction; Lip-closing force

MeSH Terms

Bicuspid
Dental Models
Female
Humans
Incisor
Lip
Retrospective Studies

Figure

• 

  Figure 1 Landmarks, reference planes, and measurements in cephalometric analyses.A, Dentoskeletal variables. S, Sella; N, nasion; Por, porion; Or, orbitale; Me, menton; Go, gonion; A, A point; B, B point; U1, upper central incisor; L1, lower central incisor; SN plane (S-N); FH plane, Frankfort horizontal plane (Or-Por); mandibular plane (Go-Me); 1, angle between FH plane and mandibular plane (FMA); 2, S to Go (posterior facial height, PFH); 3, N to Me (anterior facial height, AFH); 4, angle between the SN plane and N-A line (SNA); 5, angle between the SN plane and N-B line (SNB); 6, angle between the N-A line and N-B line (ANB); 7, angle between the long axis of U1 and the FH plane (U1-FH); 8, angle between the long axis of L1 and the mandibular plane (IMPA); 9, angle between the long axis of U1 and the long axis of L1 (interincisal angle); 10, overbite; 11, overjet. B, Soft tissue variables. Pn, Pronasale; Cm, columella; Sn, subnasale; Ls, labrale superius; ULP, upper lip point; LLP, lower lip point; Stms, lowest point on the upper lip; Stmi, highest point on the lower lip; Pog', soft tissue pogonion; Me', soft tissue menton; 1, Rickett's E line (Pn-Pog'; EL) to ULP; 2, EL to LLP; 3, Sn to Stms; 4, Stmi to Me’; 5, interlabial gap (distance from Stms to Stmi); 6, nasolabial angle (angle between the Sn-Cm line and the Sn-Ls line).

• 

  Figure 2 Measurements of the dental arch morphology on study models.UICW/LICW, Distance between both canine cusp tips in the maxillary/mandibular arch; UIMW/LIMW, distance between the mesiobuccal cusp tips of both first molars in the maxillary/mandibular arch; UAD/LAD, distance from the contact point between the central incisors perpendicular to a line connecting the mesial contact points of both first molars in the maxillary/mandibular arch.

• 

  Figure 3 Measurement of the lip-closing force using a lip holder (Ducklings®) connected to a sensor in the Lip De Cum LDC-110R® device.

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