Use of the Clark Twin Block functional appliance with and without an upper labial bow: a randomized controlled trial

Abstract

Objectives: To compare dentoalveolar and skeletal changes in two groups of Class II division 1 patients treated with different designs of Clark's Twin Block (CTB), with (Group 1) or without (Group 2) an upper labial bow.

Materials and methods: A randomized controlled trial was conducted in the Department of Orthodontics at the East Kent Hospitals University NHS Foundation Trust, UK. Sixty-two white subjects (aged 10-14 years at the start of treatment, minimum overjet > 6 mm, molar relationship at least ½ unit Class II) were recruited. Subjects were divided into age- and sex-matched pairs, were randomly allocated to treatment with either appliance design, and were treated for 12 months, at which time additional data were collected.

Results: Sixty participants were available for final data collection. The two groups were well matched with respect to age (mean 12.5 years in Group 1; 12.3 years in Group 2). No statistical difference was noted between groups for any dentoalveolar or skeletal variables measured. Both groups experienced a reduction in overjet as a result of maxillary incisor retroclination, mandibular incisor proclination, and forward positioning of the pogonion. Maxillary molar distalization, mandibular molar mesialization, and ANB reduction also occurred in both groups.

Conclusions: The addition of a maxillary labial bow to the CTB has no influence on dentoalveolar or skeletal changes, or on rate of overjet reduction, in relation to appliance therapy.

Figure 1

Subjects were allocated for treatment with a CTB-LB (upper panels) or a CTB-NLB (lower panels).

Figure 2

CONSORT flow diagram of subjects through each stage of the study.

Figure 3

Eastman analysis. (1) Sella-nasion-A point (SNA). (2) Sella-nasion-B point (SNB). (3) A point-nasion-B point (ANB). (4) Maxillary-mandibular planes angle (MMPA). (5) Upper incisor-maxillary plane (UI). (6) Lower incisor-mandibular plane (LI). (7) Nasion-menton anterior face height (AFH).

Figure 4

Pancherz analysis. OL: line drawn tangent to disto-buccal cusp of maxillary first permanent molar and bisecting the incisal vertical overbite. OLp: a line perpendicular to OL through sella. Sp: (subspinale) deepest point on the anterior contour of the maxillary alveolar projection by tangent perpendicular to OL. Ii (incision inferius): the incisal tip of the most prominent mandibular central incisor. Is (incision superius): the incisal tip of the most prominent maxillary central incisor. Ms (molar superius): the mesial contact point of the maxillary permanent first molar determined by a tangent to OL. Mi (molar inferius): the mesial contact point of the mandibular permanent first molar determined by a tangent perpendicular to OL. Pg (pogonion): the most prominent point on the bony chin determined by a tangent perpendicular to OL. (1) Sp/OLp. (2) Li/OLp. (3) Ms/OLp. (4) Mi/OLp. (5) Pg/OLp.

Figure 5

Rate of overjet reduction between groups during the study.