Abstract
BackgroundThe purpose of this controlled study was to investigate indirect effects on mandibular arch dimensions, 1 year after rapid palatal expansion (RPE) therapy.MethodsThirty-three patients in mixed dentition (mean age 8.8 years) showing unilateral posterior crossbite and maxillary deficiency were treated with a RPE (Haas type) cemented on the first permanent molars. Treatment protocol consisted of two turns per day until slight overcorrection of the molar transverse relationship occurred. The Haas expander was kept on the teeth as a passive retainer for an average of 6 months. Study models were taken prior (T1) and 15 months on average (T2) after expansion. A control group of 15 untreated subjects with maxillary deficiency (mean age 8.3 years) was also recorded with a 12-month interval. Stone casts were digitized with a 3D scanner (3Shape, DK).ResultsIn the treated group, both mandibular intermolar distance (+1.9 mm) and mandibular molar angulation (+9°) increased. Mandibular incisor angulation showed an increase of 1.9°. There was little effect on intercanine distance and canine angulation. Controls showed a reduction in transverse arch dimension and a decrease in molar and canine angulation values.ConclusionsRPE protocol has indirect widening effects on the mandibular incisors and first molars.
Highlights
The purpose of this controlled study was to investigate indirect effects on mandibular arch dimensions, 1 year after rapid palatal expansion (RPE) therapy
Normal transversal arch growth was modified by crossbite malocclusion: the patients showed a tendency towards contraction of the transverse mandibular dimension and a decrease in molar, canine, and incisor angulation values
We found that the decrease in intercanine and intermolar width and part of arch perimeter reduction were mainly caused by the decrease in mandibular teeth angulation value
Summary
The purpose of this controlled study was to investigate indirect effects on mandibular arch dimensions, 1 year after rapid palatal expansion (RPE) therapy. If the crossbite affects one side of the McNamara has speculated that the position of the mandibular dentition might be influenced more by Ugolini et al Progress in Orthodontics (2016) 17:1 maxillary skeletal morphology than by the size and shape of the mandible [4]. This hypothesis could explain why some mandibular arch decompensation happened during rapid maxillary expansion therapy, but very few published researches support this thesis [5,6,7,8,9,10]. While some recent investigations reviewed the palatal expansion and its effects on the palatal vault and the lower third of the face in a three-dimensional perspective, an evaluation of the effects on the mandible with a 3D noninvasive analysis is still missing [11, 12]
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