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RME ON PERMANENT VS RME ON DECIDUOUS TEETH: COMPARISON OF SKELETAL AND DENTO-ALVEOLAR EFFECTS BY VOLUMETRIC TOMOGRAPHY ENRICO ALBERTINI REGGIO EMILIA, ITALY ABSTRACT Objective: the aim of this study was to evaluate skeletal and dento-alveolar effects of RME on permanent and on deciduous teeth by means of volumetric tomography. Materials and Methods: The sample included 12 patients with transverse maxillary hypoplasia (6 treated with RME on permanent first molars, 6 treated with RME on deciduous second molars) in the mixed dentition. Beginning and post-expansion CBCTs were compared to analyze skeletal and dento-alveolar effects of the two devices. Results: RME treatment significantly increased palatal volume in both groups (10.78% for RME on permanent teeth and 9.89% for RME on deciduous teeth). Intermolar width increased for both skeletal and dental measurements. Greater maxillary first molar tipping was observed on first permanent molars when RME was anchored on deciduous teeth than when anchored on permanent teeth (4.02° vs 2.13°). Mandibular molar decompensation was higher in patients treated with RME on permanent teeth than on deciduous teeth (4.58° vs 1.71°). Conclusions: RME treatment significantly increased palatal volume. RME anchored on permanent teeth determined a higher dental intermolar width variation and significant difference in mandibular molar decompensation. RME anchored on decidous teeth was more effective in increasing skeletal intermolar width and had more effect on molar inclination. INTRODUCTION Rapid maxillary expansion (RME) is the most common treatment employed for the correction of transverse maxillary hypoplasia. Many studies have demonstrated its benefits in terms of posterior crossbite resolution 1 , breathing improvement 2 , arch length increase 3 and impacts on permanent teeth retention 4 . Side effects of maxillary expansion include downward displacement of the maxilla, dental extrusion, lateral rotation of the maxillary segment, opening of the bite, gingival recession 5,6 and nasal width increase 7,8,9 . Dental tipping also occurs during maxillary expansion and leads to subsequent alveolar bone changes 5 . Orthopedic maxillary expansion is the result of skeletal (173 sutural openings), dental (tipping), and alveolar (bending and remodelling) changes. As a child matures, more force is required, less skeletal expansion and more dental tipping occur. In his study, Krebs 10 demonstrates that children have 50% skeletal and 50% dental expansion, whereas the adolescent showed 35% skeletal and 65% dental expansion. Many studies have shown the effectiveness of maxillary expansion both on skeletal and dental structures. Prior research 11,12,13,14,15 utilized dental casts, two- 25
dimensional lateral and posteroanterior cephalograms, and occlusal radiographs to assess the effects of RME. Although these studies were able to highlight changes with bidimensional measures, a tridimensional evaluation of the dento-skeletal changes is needed. The diffusion in clinical orthodontic practice of the employment of cone beam computed tomography (CBCT) has led to the development of several studies aimed at evaluating the RME effects in a tridimensional view. During the last few years, the author investigated variations in oropharyngeal airway volume 16 , suture opening 17 , skeletal and dentoalveolar expansion components 18 , radicular resorption 19 , airway and breathing 20 , comparison between Haas and Hyrax devices 21 and variation of palatal volume 22 . The Hyrax type “New REP” 23 was cemented on maxillary deciduous second molars or on permanent first molars depending on the availability of root support. Whenever possible, it was anchored on deciduous second molars in order to avoid side effects on permanent teeth and to minimize dental effects on trasverse correction 24 . (Fig. 1 - Fig. 2) The expansion protocol included 1 activation per day (0.2mm) until the achievement of a slight overcorrection, with maxillary palatal cusps in contact with mandibular vestibular cusps (meantime of 4 weeks). The aim of this study was to assess the dentoalveolar and skeletal effects by means of CBCT of an RME appliance anchored either on permanent or on decidous teeth. MATERIALS AND METHODS A sample of 53 patients actively treated in the School of Specialization in Orthodontics (University of Ferrara, Italy) for the correction of trasverse maxillary hypoplasia was submitted to the following inclusion criteria: unique treatment with RME, mixed dentition phase and pre-treatment CBCT availability (T0). Patients respondent to the following criteria were excluded: treatment with other appliances, attendance of “dental anomalies”, presence of hereditary syndromes. The final sample was made up of 12 patients, 6 treated with RME on deciduous second molars (4 males, 9 females; average 9 years 4 months), 6 treated with RME on permanent first molars (1 male, 3 females; average 10 years 1 month). The CBCTs were repeated after an interval of 10 months (T1): this time interval was chosen after considering the extent of the active and passive phases of rapid maxillary expansion (9 months of retention). Fig. 1: “New REP” anchored on maxillary first permanent molar Fig. 2: “New REP” anchored on maxillary second deciduous molar 26
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RME ON PERMANENT VS RME ON DECIDUOUS TEETH: COMPARISON OF SKELETAL AND<br />
DENTO-ALVEOLAR EFFECTS BY VOLUMETRIC TOMOGRAPHY<br />
ENRICO ALBERTINI<br />
REGGIO EMILIA, ITALY<br />
ABSTRACT<br />
Objective: <strong>the</strong> aim of this study was to evaluate skeletal<br />
and dento-alveolar effects of RME on permanent<br />
and on deciduous teeth by means of volumetric tomography.<br />
Materials and Methods: <strong>The</strong> sample included 12 patients<br />
with transverse maxillary hypoplasia (6 treated<br />
with RME on permanent first molars, 6 treated with<br />
RME on deciduous second molars) in <strong>the</strong> mixed<br />
dentition. Beginning and post-expansion CBCTs were<br />
compared to analyze skeletal and dento-alveolar effects<br />
of <strong>the</strong> two devices.<br />
Results: RME treatment significantly increased palatal<br />
volume in both groups (10.78% for RME on permanent<br />
teeth and 9.89% for RME on deciduous teeth).<br />
Intermolar width increased for both skeletal and dental<br />
measurements. Greater maxillary first molar tipping<br />
was observed on first permanent molars when RME<br />
was anchored on deciduous teeth than when anchored<br />
on permanent teeth (4.02° vs 2.13°). Mandibular<br />
molar decompensation was higher in patients treated<br />
with RME on permanent teeth than on deciduous teeth<br />
(4.58° vs 1.71°).<br />
Conclusions: RME treatment significantly increased<br />
palatal volume. RME anchored on permanent teeth<br />
determined a higher dental intermolar width variation<br />
and significant difference in mandibular molar decompensation.<br />
RME anchored on decidous teeth was more<br />
effective in increasing skeletal intermolar width and<br />
had more effect on molar inclination.<br />
INTRODUCTION<br />
Rapid maxillary expansion (RME) is <strong>the</strong> most common<br />
treatment employed for <strong>the</strong> correction of transverse<br />
maxillary hypoplasia. Many studies have demonstrated<br />
its benefits in terms of posterior crossbite<br />
resolution 1 , breathing improvement 2 , arch length<br />
increase 3 and impacts on permanent teeth retention 4 .<br />
Side effects of maxillary expansion include downward<br />
displacement of <strong>the</strong> maxilla, dental extrusion, lateral<br />
rotation of <strong>the</strong> maxillary segment, opening of <strong>the</strong> bite,<br />
gingival recession 5,6 and nasal width increase 7,8,9 . Dental<br />
tipping also occurs during maxillary expansion and<br />
leads to subsequent alveolar bone changes 5 .<br />
Orthopedic maxillary expansion is <strong>the</strong> result of skeletal<br />
(173 sutural openings), dental (tipping), and alveolar<br />
(bending and remodelling) changes. As a child matures,<br />
more force is required, less skeletal expansion<br />
and more dental tipping occur. In his study, Krebs 10<br />
demonstrates that children have 50% skeletal and 50%<br />
dental expansion, whereas <strong>the</strong> adolescent showed 35%<br />
skeletal and 65% dental expansion.<br />
Many studies have shown <strong>the</strong> effectiveness of maxillary<br />
expansion both on skeletal and dental structures.<br />
Prior research 11,12,13,14,15 utilized dental casts, two-<br />
25
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