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Treatment timing for Twin-block therapy.
Am J Orthod Dentofacial Orthop 2000; 118(2):159-70AJ

Abstract

This cephalometric study evaluated skeletal and dentoalveolar changes induced by the Twin-block appliance in 2 groups of subjects with Class II malocclusion treated at different skeletal maturation stages in order to define the optimal timing for this type of therapy. Skeletal maturity in individual patients was assessed on the basis of the stages of cervical vertebrae maturation. The early-treated group was composed of 21 subjects (11 females and 10 males). Mean age of these subjects at time 1 (immediately before treatment) was 9 years +/- 11 months, and at time 2 (immediately after discontinuation of the Twin-block appliance) was 10 years 2 months +/- 11 months. According to the cervical vertebrae maturation staging at times 1 and 2, the peak in growth velocity was not included in the treatment period for any of the subjects in the early group. The late-treated group consisted of 15 subjects (6 females and 9 males). Mean age of this group was 12 years 11 months +/- 1 year 2 months at time 1 and 14 years 4 months +/- 1 year 3 months at time 2. In the late group, treatment was performed during or slightly after the onset of the pubertal growth spurt. Both treated samples were compared with control samples consisting of subjects with untreated Class II malocclusions also selected on the basis of the stage in cervical vertebrae maturation. A modification of Pancherz's cephalometric analysis was applied to the lateral cephalograms of all examined groups at both time periods. Linear and angular measurements for mandibular dimensions, cranial base angulation, and vertical relationships were added to the original analysis. Annualized differences for all the variables from time 1 to time 2 were calculated for both treated groups and contrasted to the annualized differences in the corresponding untreated groups by means of nonparametric statistics. The findings of this short-term cephalometric study indicate that optimal timing for Twin-block therapy of Class II disharmony is during or slightly after the onset of the pubertal peak in growth velocity. When compared with treatment performed before the peak, late Twin-block treatment produces more favorable effects that include: (1) greater skeletal contribution to molar correction, (2) larger increments in total mandibular length and in ramus height, and (3) more posterior direction of condylar growth, leading to enhanced mandibular lengthening and to reduced forward displacement of the condyle in favor of effective skeletal changes. The importance of the biological evaluation of skeletal maturity in individual patients with Class II disharmony to be treated with functional appliances is emphasized.

Authors+Show Affiliations

Department of Orthodontics, University of Florence, Italy. condax@tin.it

Pub Type(s)

Comparative Study
Journal Article

Language

eng

PubMed ID

10935956

Citation

Baccetti, T, et al. "Treatment Timing for Twin-block Therapy." American Journal of Orthodontics and Dentofacial Orthopedics : Official Publication of the American Association of Orthodontists, Its Constituent Societies, and the American Board of Orthodontics, vol. 118, no. 2, 2000, pp. 159-70.
Baccetti T, Franchi L, Toth LR, et al. Treatment timing for Twin-block therapy. Am J Orthod Dentofacial Orthop. 2000;118(2):159-70.
Baccetti, T., Franchi, L., Toth, L. R., & McNamara, J. A. (2000). Treatment timing for Twin-block therapy. American Journal of Orthodontics and Dentofacial Orthopedics : Official Publication of the American Association of Orthodontists, Its Constituent Societies, and the American Board of Orthodontics, 118(2), pp. 159-70.
Baccetti T, et al. Treatment Timing for Twin-block Therapy. Am J Orthod Dentofacial Orthop. 2000;118(2):159-70. PubMed PMID: 10935956.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Treatment timing for Twin-block therapy. AU - Baccetti,T, AU - Franchi,L, AU - Toth,L R, AU - McNamara,J A,Jr PY - 2000/8/10/pubmed PY - 2000/9/2/medline PY - 2000/8/10/entrez SP - 159 EP - 70 JF - American journal of orthodontics and dentofacial orthopedics : official publication of the American Association of Orthodontists, its constituent societies, and the American Board of Orthodontics JO - Am J Orthod Dentofacial Orthop VL - 118 IS - 2 N2 - This cephalometric study evaluated skeletal and dentoalveolar changes induced by the Twin-block appliance in 2 groups of subjects with Class II malocclusion treated at different skeletal maturation stages in order to define the optimal timing for this type of therapy. Skeletal maturity in individual patients was assessed on the basis of the stages of cervical vertebrae maturation. The early-treated group was composed of 21 subjects (11 females and 10 males). Mean age of these subjects at time 1 (immediately before treatment) was 9 years +/- 11 months, and at time 2 (immediately after discontinuation of the Twin-block appliance) was 10 years 2 months +/- 11 months. According to the cervical vertebrae maturation staging at times 1 and 2, the peak in growth velocity was not included in the treatment period for any of the subjects in the early group. The late-treated group consisted of 15 subjects (6 females and 9 males). Mean age of this group was 12 years 11 months +/- 1 year 2 months at time 1 and 14 years 4 months +/- 1 year 3 months at time 2. In the late group, treatment was performed during or slightly after the onset of the pubertal growth spurt. Both treated samples were compared with control samples consisting of subjects with untreated Class II malocclusions also selected on the basis of the stage in cervical vertebrae maturation. A modification of Pancherz's cephalometric analysis was applied to the lateral cephalograms of all examined groups at both time periods. Linear and angular measurements for mandibular dimensions, cranial base angulation, and vertical relationships were added to the original analysis. Annualized differences for all the variables from time 1 to time 2 were calculated for both treated groups and contrasted to the annualized differences in the corresponding untreated groups by means of nonparametric statistics. The findings of this short-term cephalometric study indicate that optimal timing for Twin-block therapy of Class II disharmony is during or slightly after the onset of the pubertal peak in growth velocity. When compared with treatment performed before the peak, late Twin-block treatment produces more favorable effects that include: (1) greater skeletal contribution to molar correction, (2) larger increments in total mandibular length and in ramus height, and (3) more posterior direction of condylar growth, leading to enhanced mandibular lengthening and to reduced forward displacement of the condyle in favor of effective skeletal changes. The importance of the biological evaluation of skeletal maturity in individual patients with Class II disharmony to be treated with functional appliances is emphasized. SN - 0889-5406 UR - https://www.unboundmedicine.com/medline/citation/10935956/Treatment_timing_for_Twin_block_therapy_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0889-5406(00)38675-9 DB - PRIME DP - Unbound Medicine ER -