title: Does the degree of advancement during functional appliance therapy matter?
abstract: The aim of this study was to assess the effect of varied degrees of mandibular advancement on condylar growth. Three hundred and thirty five 35-day-old female Sprague-Dawley rats were randomly divided into 10 experimental groups (n = 10) and five control groups (n = 5) for analysis of new bone formation and 10 experimental groups (n = 14) and five control groups (n = 14) for molecular analysis. The experimental animals were fitted with bite-jumping appliance to advance the mandible 2 and 4 mm. The rats were sacrificed on days 3, 7, 14, 21, and 30. A computer-assisted image analysing system was used to assess the quantity of new condylar bone formation. Molecular analysis utilizing real-time reverse transcription-polymerase chain reaction was used to assess the different levels of mRNA expression of different growth markers in the condyle. One-way analysis of variance (ANOVA), with a Bonferroni multiple comparison test, showed significantly more newly formed bone in the 4 mm group compared with the 2 mm and control groups on days 21 and 30 (P < 0.05). Most of the examined growth markers demonstrated a significant increase during the 4 mm advancement (P < 0.05). Indian hedgehog (Ihh) mRNA showed a 7- and 5-fold change, parathyroid hormone-related peptide (PTHrP) a 5.2- and 3-fold change and type II collagen a 9.6- and 3.7-fold change in the 4 and 2 mm advancement groups, respectively. Varied degrees of mandibular advancement result in different quantities of new bone formation and levels of expression of growth members: Ihh, PTHrP, and type II collagen.
authors.affiliation: Department of Orthodontics, Faculty of Dentistry, The University of Hong Kong, SAR, China. rabie@hkusua.hku.hk
authors.forename: A Bakr M
authors.initials: AB
authors.lastname: Rabie
authors.forename: Abdullah
authors.initials: A
authors.lastname: Al-Kalaly
mesh_terms: D000222:Adaptation, Physiological; D000704:Analysis of Variance; D000818:Animals; D001857:Bone Matrix / Q000378:metabolism; D024043:Collagen Type II / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D005260:Female; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism; D008310:Malocclusion / Q000628:therapy; D019186:Mandibular Advancement / Q000295:instrumentation / Q000379:methods*; D008335:Mandibular Condyle / Q000254:growth & development* / Q000378:metabolism; D017289:Orthodontic Appliances, Functional; D010012:Osteogenesis / Q000502:physiology*; D044162:Parathyroid Hormone-Related Protein / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical
chemical_list: D024043:Collagen Type II; D053823:Hedgehog Proteins; D044162:Parathyroid Hormone-Related Protein; D012333:RNA, Messenger