A controlled clinical trial of the effects of the Twin Block and Dynamax appliances on the hard and soft tissues

Abstract

The aim of this controlled trial was to identify and quantify skeletal, soft tissue and dental changes during treatment, and immediately post-treatment with Twin Block (TB) or Dynamax appliance using the techniques of three-dimensional (3D)optical surface laser scanning, cephalometric, and clinical measurements. Sixty-two Caucasian subjects, 36 males aged 11-14 years and 26 females aged 10-13 years were enrolled in the study. The patients were placed in two groups, matched for gender and age and subsequently allocated randomly for treatment with either a TB or Dynamax appliance. Active treatment lasted 9 months followed by 3 months' post-treatment observation. Laser scanning and clinical measurements were taken at 3-monthly intervals and final cephalometric records after 12 months. Statistical analysis was performed using Wilcoxon's matched-pairs signed-rank tests. The non-compliance rates were the same for both groups (9 per cent), but a greater incidence of breakages was found in the Dynamax group. The TB was found to produce slightly more antero-posterior skeletal change, median ANB reduction, TB=2 degrees, Dynamax 1.1 degree (P=0.006), and similar forward movements of the chin and was associated with larger increases in the vertical facial dimension, median total anterior face height increase; TB=3.2 mm, Dynamax = 2.8 mm (P=0.03). The soft tissue vertical cephalometric increases were 3.6 mm with the TB, 2.0 mm with the Dynamax (P=0.036), and with laser scanning 5.05 and 2.6 mm, respectively, a difference which is likely to be more clinically relevant. The median post-treatment changes in soft tissue pogonion were -0.65 mm in the TB and +0.22 mm in the Dynamax group. The optical surface scanning mark and measure system is a valid method for quantifying soft tissue changes.

Dentoskeletal Changes in Class II Subjects following Treatment with Twin Block and Herbst Appliance

“…15 It has been proved in the literature that functional appliances do not produce long term skeletal changes and most of their effects are dentoalveloar. 16 In a prospective controlled trial with twin blocks and controls to investigate the skeletal and dental effects showed that the ANB angle reduced by 2° which was almost entirely due to mandibular length increase which was 2.4 mm compared to the controls and there was no evidence of a restriction in maxillary growth. 17 Limitations of this study are sample size and single centre approach.…”

Biological basis for functional appliance therapy

“…50,51 A study on rats by Chayanupatkul et al 52 reported on the histological changes when functional appliances were removed early or following more protracted periods of treatment. The authors found that bone formation is not complete at the condyle following 5 to 7 months of treatment with a Type III collagen remaining.…”

Clinical use of the Twin Block appliance

“…19,20 In both circumstances the lateral open bite consistently closed spontaneously and it was felt that any habitual postural ele ments from the appliances would no longer be present. If the lower first molar erupts differentially ahead of the lower second premolar, there is a risk of reducing the avail able space for the second premolar, predisposing to localized crowd ing and displacement of the second premolar.…”