Mandibular Response After Maxillary Orthopedic Expansion in Class II Growing Subjects

Mandibular Response After Rapid Maxillary Expansion in Class II Growing Patients: a Pilot Randomized Controlled Trial

the effectiveness of RME (Rapid Maxillary Expander) on the sagittal dental or skeletal parameters is still controversial because very little has been written regarding the behavior of antero-posterior mandibular changes in Class II growing subjects who underwent RME as the phase 1 treatment intervention. The reported significant occlusal improvement could be attributed to other reasons, ie, skeletal growth or the use of additional appliances during transition from mixed to permanent dentition. Moreover, the majority of the studies show some limits: they are not randomized, they are not prospective, and they have no control group or they use patients from growth studies as a source for the control group. The primary objective of the present investigation was to conduct a pilot randomized controlled trial (RCT) evaluating the changes in the antero-posterior mandibular position induced by bonded or banded RMEs compared with an untreated Class II control group

Class II malocclusions are commonly observed in orthodontic patients. During treatment planning among the several dento-skeletal pattern combinations of Class II malocclusion, it is important to consider the maxillary transverse deficiency, which is often overlooked. it has been showed showed an underlying posterior interarch transverse discrepancy of 3 to 5 mm in subjects in early mixed dentition with Class II malocclusions without posterior crossbites in centric occlusion. When these Class II patients are asked to posture their lower jaw forward in a Class I molar relationship, this transverse discrepancy (ie, maxillary constriction) can be observed clinically. It was postulated that in these subjects the mandible is kept in a distal position relative to centric relation because the constricted maxilla is holding it back. The presence of a primitive transverse discrepancy between the dental arches induces a backward position of the mandible, as the occlusal goal is to obtain the highest number of functional contacts. As reported by several authors, widening the maxilla with rapid maxillary expansion often leads to spontaneous forward posturing of the mandible during the retention period. The orthopedic expansion removes occlusal interferences, allowing the mandible to posture forward, thus improving the sagittal relationships. The mandibular arch acts as a ''foot'' that moves forward after the ''shoe'' is widened. However, the effectiveness of RME on the sagittal dental or skeletal parameters is still controversial because very little has been written regarding the behavior of antero-posterior mandibular changes in Class II growing subjects who underwent RME as the phase 1 treatment intervention. The reported significant occlusal improvement could be attributed to other reasons, ie, skeletal growth or the use of additional appliances during transition from mixed to permanent dentition. Moreover, the majority of the studies show some limits: they are not randomized, they are not prospective, and they have no control group or they use patients from growth studies as a source for the control group. Considering that it was not possible to estimate from previous studies the standard deviation to be used for sample size calculation of the main trial with special regards to type of intervention and observation intervals, the primary objective of the present investigation was to conduct a pilot randomized controlled trial (RCT) evaluating the changes in the antero-posterior mandibular position induced by bonded or banded RMEs compared with an untreated Class II control group. To evaluate the sagittal mandibular response induced by RME therapy in mixed dentition patients with Class II malocclusion, comparing the effects of bonded RME and banded RME with a matched untreated Class II control group This is a single center, prospective 3-arm parallel group randomized clinical trial with a 1:1:1allocation ratio. 30 (thirty) of subjects are planned. Each subject in the treated groups will be treated with a Rapid Maxillary Expander (RME), bonded or banded respectively. Subjects will be assigned to the groups in random order. Evaluations will be taken at baseline and at the end of the retention period/follow up (for a total of 12 months). Subjects who meet all inclusion criteria and none of the exclusion criteria will be entered into the study. Allocation of patients to the three groups in a 1:1:1 ratio was determined by a computer-generated randomization list using Rv.0.1 software and by a block size of 4. Then, the allocation information (randomization results) was concealed in opaque and sealed envelopes by the statistician. The study was blinded in regard of the statistical analysis. Data were recorded and blinded for the statistician: blinding was obtained by eliminating from the elaboration file every reference to patient group assignment To determine the reliability of the method 15 radiographs chosen at random were traced and digitized by the same investigator on 2 separate occasions at least one month apart. A paired t-test was used to compare the two measurements (systematic error). The magnitude of the random error was calculated by using the method of moment's estimator (MME). Exploratory statistics revealed that not all cephalometric variables were normally distributed (Kolmogorov-Smirnov test) with equality of variances (Levene's test).Kruskal-Wallis test or ANOVA with Tukey's post-hoc tests were used to compare the T2-T1 changes in the three groups. All changes were considered significant at P<0.05. All statistical computations were performed with Statistical Package for the Social Sciences software (Version 12, Chicago, IL).. 10 randomized subjects will be included in the treated group 1, 10 randomized patients will be included in the treated group 2 and 10 randomized patients will be used as untreated control group. The baseline age was 8.1 ± 0.6 years (range 6.6-9.1 years). Sample size for this pilot trial was calculated according to the method proposed by Whitehead et al. For a standardized effect size of 1 (a clinically relevant change of 2.0 mm with a combined Standard Deviation of 2.0 mm derived from Guest et al.) for the 8 primary outcome variable Pogonion to Nasion perpendicular, a sample size of 10 subjects per group was required for a Type I error rate of 5% and a power of 80%.

Patient treated with bonded RME (Rapid Maxillary Expander) with a 13-mm screw. The acrylic splints of the bonded expander extended from the first deciduous molars through the first permanent molars.

Patients treated with banded RME (Rapid Maxillary Expander) in the form of a butterfly palatal expander with a 13-mm screw cemented through bands on the second deciduous upper molars.

The expansion screw was activated 1 quarter of a turn per day (0.25 mm per turn) until the palatal cusps of the maxillary posterior teeth approximated the lingual cusps of the mandibular posterior teeth. The expander was kept in place as a passive retainer for 8 months. After expander removal, patients were followed without performing any additional treatment for 4 months.

The expansion screw was activated 1 quarter of a turn per day (0.25 mm per turn) until the palatal cusps of the maxillary posterior teeth approximated the lingual cusps of the mandibular posterior teeth. The expander was kept in place as a passive retainer for 8 months. After expander removal, patients were followed without performing any additional treatment for 4 months.

Mandibular displacement after RME appliance therapy (linear measurement in millimeters) when compared with a matched untreated control group

The primary outcome was the change in the position of point Pogonion to the Nasion perpendicular (Pg to N perp). The objective is to evaluate the changes in the sagittal mandibular position induced by bonded or banded RMEs compared with an untreated control group. For each treated patient, standard lateral cephalograms were obtained before treatment and after 1 year to evaluate the dento-skeletal changes. The Control Group was followed up without treatment for 1 year and had lateral cephalograms before and after a one-year interval. Cephalograms were scanned using a professional table scanner (Epson Perfection V700 Photo, CA, USA), with resolution set to 150 dots per inch (dpi) gray scale and were digitized by 1 investigator., followed by a customized digitization regimen and analysis (Viewbox 3.1; dHAL Software, Kifissia, Greece). All cephalograms were at a magnification of 0%. The examiner was blinded to the origin of the films and the group to which each subject belonged

Occlusal improvement of Class II molar relationship after RME appliance therapy (linear measurement in millimeters) when compared with a matched untreated control group

The secondary outcome is to evaluate if maxillary expansion corrects or improves a Class II molar relationship (the mesiobuccal cusp of the maxillary permanent 1st molar must occlude in the embrasure between the mandibular 2nd premolar and the mandibular permanent 1st molar) when compared with an untreated control group. For each treated patient, lateral cephalograms were obtained before treatment and after 1 year to evaluate the dento-skeletal changes. Untreated patients had lateral cephalograms before and after a 1 year interval. Cephalograms were scanned using a professional table scanner (Epson Perfection V700 Photo, CA, USA), with resolution set to 150 dots per inch (dpi) gray scale and were digitized by 1 investigator., followed by a customized digitization regimen and analysis (Viewbox 3.1; dHAL Software, Kifissia, Greece). All cephalograms were at a magnification of 0%. The examiner was blinded to the origin of the films and the group to which each subject belonged

Treatment effects on vertical dimension (SN-Go Me; angular measurement) and on Gonial Angle (Ar-Go-Me, angular measurement) and vertical growth pattern after RME appliance therapy when compared with a matched untreated control group

The objective is to verify if the treatment determined a reduction of the facial divergency (SN-Go Me°) and of the gonial angle (Ar-Go-Me°) when both subjects, treated respectively with banded RME and bonded RME, are compared with untreated subjects. For each treated patient, standard lateral cephalograms were obtained before treatment and after 1 year to evaluate the dento-skeletal changes. The Control Group was followed up without treatment for 1 year and had lateral cephalograms before and after a one-year interval. Cephalograms were scanned using a professional table scanner (Epson Perfection V700 Photo, CA, USA), with resolution set to 150 dots per inch (dpi) gray scale and were digitized by 1 investigator., followed by a customized digitization regimen and analysis (Viewbox 3.1; dHAL Software, Kifissia, Greece). All cephalograms were at a magnification of 0%. The examiner was blinded to the origin of the films and the group to which each subject belonged

Inclusion Criteria: early mixed dentition with first molars fully erupted, Class II malocclusion (full-cusp or end-to-end molar relationships), negative posterior transverse interarch discrepancy ≥ 4 mm, Overjet ≥ 5 mm, and prepubertal stage of development (Cervical Stage 1 - Cervical Stage 2 in cervical vertebral maturation) Exclusion Criteria: previous orthodontic treatment, extracted or congenitally missing teeth, craniofacial syndromes or clefts, use of additional orthodontic devices during the observation period

Research Fellow, Department of Clinical Sciences and Translational Medicine, University of Rome "Tor Vergata," Rome, Italy, and research Fellow, Department of Dentistry, University Nostra Signora del Buon Consiglio, Tirana, Albania

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