Incremental versus maximum bite advancement during twin-block therapy: A randomized controlled clinical trial

Burnley General Hospital, Burnley, United Kingdom.
American Journal of Orthodontics and Dentofacial Orthopedics (Impact Factor: 1.38). 12/2004; 126(5):583-8. DOI: 10.1016/S088954060400602X
Source: PubMed


The aim of this study was to evaluate the effectiveness of incremental and maximum bite advancement during treatment of Class II Division 1 malocclusion with the Twin-block appliance in the permanent dentition. It was performed at 3 district general hospitals in the United Kingdom with 4 operators. Two hundred three patients, 10-14 years old, were randomized. Control patients had the initial bite taken edge-to-edge for appliance construction with a standard Twin-block. Experimental patients had 2 mm initial bite advancement and subsequent 2 mm advancements at 6 weekly intervals with a Twin-block appliance incorporating advancement screws. Data were collected at the start and the finish of Twin-block treatment. The use of incremental advancement of the Twin-block did not confer any advantages in terms of process and outcome of the treatment. However, patient compliance was influenced by operator and patient age. The duration of treatment was influenced by operator and initial overjet. Incremental bite advancement produced no advantages over maximum advancement.

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    • "Early in the study the age range was extended to recruit a greater number of patients more rapidly. Although it is commonly perceived that the degree of maturity influences the skeletal response recent prospective studies have found that stage of maturity of the cervical spine did not influence outcome [31] [32]. "

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    • "Since the variance of the outcome variable was not known, the size of the sample was calculated to identify a difference between the appliance groups of 1 standard deviation (SD). The limitation of this assumption is that if the SD is large, the study will identify only large differences ( Altman, 1991 ). The Statistical Package for the Social Sciences for Windows (SPSS Inc., Chicago, Illinois, USA) was used. "
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    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.
    The European Journal of Orthodontics 07/2007; 29(3):272-82. DOI:10.1093/ejo/cjm004 · 1.48 Impact Factor
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