Controversy of Retention after Dento-Alveolar Expansion (Clinical Study)

Arkan Muslim Al Azzawi
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Keywords : Dento-alveolar expansion,bilateralcross bite, Hyrax, Trans-palatal bar, Relapse
Medical Journal of Babylon  13:1 , 2016 doi:1812-156X-13-1
Published :10 April 2016

Abstract

Maxillary constriction whether unilateral or bilateral still one of the most important problem in orthodontics thus aim of this articleto test hypothesis that Maxillary expansion may be combined with or without retainers for complete treatment due to expansion treatment taken a couple of months while the expander was not removed for several more months to keep teeth from relapse. Twenty patients with an age ranged between 17-22 years old, had posterior bilateral buccal cross bite 5 mm or less based on Angle classification malocclusion were selected in this study. All of them were white Iraqi Arab in origin and had full permanent dentition regardless the wisdom teeth with minimal crowding (1-2mm). Sample classified in to two groups (A) and (B) of 10 patient and study model was taking preoperatively, after 4 month and after 12 month respectively. Transpalatalbarconstructed and cementedat the same time of hyrax removal, this is procedure prepared for group (B), while for group (A) Hyrax removed and just take impression without TPB and at that time sequence of main arch wire continue and all cases finished with 019*025 mil Nickel Titanium arch wire.Inter-cuspal premolar distance showed significant relapse (1.79 mm) occurred in none retention group (A) between 4 and 12 month this is not present in retention group(B) amount of relapse was none significant (0.05). While there was significant difference in inter-cuspalmolar group A equaled to (1.48mm) and group B equaled to (1.38).Analysis of relapse in group A and group B clarifying that the use of Trans-Palatal arch as retention after hyrax expander didn’t increasedento-alveolar stability.

Introduction

Posterior crossbite described according to the position of the upper molars, Therefore a bilateral maxillary lingual (or palatal) crossbite means that the maxillary molars were lingual to their normal position on both sides, while a unilateral mandibular buccal crossbite means that the mandibular molars were buccally positioned on one side. This terminology specifies which teeth (maxillary or mandibular) are displaced from their normal position[1,2]. Expansion studies recommended several indications, involving correction of crossbite, elimination of dental crowding, leveling of the curve of Wilson, facilitation of eruption of the permanent canines, increasing the size of the nasal airway, and reduction of unaesthetic buccal corridors[3,4]. The major focus of rapid maxillary expansion(RME) treatment was related to crossbite correction and reduction in tooth size/arch size discrepancies and control of the vertical dimension. The hyrax or Beidermanappliance is a common type of RME. It is tooth borne and composed of a jack screw and an all metal framework soldered to bands on the first maxillary premolars and molars. RME appliances cause increase in vertical dimension, downwarddisplacement of maxilla, dental extrusion, lateral rotation of maxillary segments and cuspal interferences attributed to bite opening characteristic of RME[5,8]. Following expansion by any means, a retainer is needed even after bone fill-in seems complete. The expansion appliance should remain in place for 3 to 4 months and then can be replaced with a removable retainer or other retention device[1,5]. The TPA shown to lack a significant effect in improving anchorage in extraction cases,although it may be effective as a space maintenance device to assist the improvement in molar relationships induced by the RME[1,5,9]. Total relapse into crossbite is unlikely in the absenceof a skeletal problem, and mixed dentition expansion reducesthe incidence of posterior crossbite in the permanent dentition,so early correction also simplifies future diagnosis andtreatment by eliminating at least that problem from the list[1,9]. The aim of this study was to evaluate the hypothesis that stability of expansion of the maxilla with and without using TPB as a retainer after expansion accomplished to see amount of relapse after treatment.

Materials and methods

Twenty patients with an age ranged between 17-22 years old, had posterior bilateral buccal cross bite 5 mm or less based on Angle classification malocclusion were selected in this study. All of them were white Iraqi Arab in origin with minimal crowding (1-2mm.).Diagnostics aids like study models, intraoral and extraoral  photographs with natural head position using Canon Power shot SD750 digital Elph (7.1 Megapixel, Japan) camera, O.P.G were taken prior to the orthodontic treatment and hyrax cementation.
Sample classified in to two groups A (none retention group) and B (retention group) of 10 patients each and study model was taking preoperatively, after 4 months and 12 month respectively.
 Elastic separators placed mesial and distal to the maxillary first molars and maxillary first premolars for 28 hours and then orthodontic bands with Roth prescription is placed on maxillary first molars and maxillary first premolars then alginate impression taken and study model produced to make hyrax appliance after that Roth stainless steel braces (Bionic, Orthotechnology Co., USA) with 0.022" slot were bonded on the maxillary and mandibular teeth using no-mix orthodontic composite (Orthotechnology Co., USA). Hyrax appliance were cemented using glass ionomer cement, then patient supplied with orthodontics brush, relieving wax, and driver screw to activate Hyrax, slow expansion by activation of   hyrax  to gain 1 mm per week and follow up each month to change sequence of arch wire (Figure.1).




Results

Descriptive statistics in table 1 showed that the mean values for premolar inter-cusp (PID) distance in 4 month larger than that of 12 month and that preoperative respectively in both groups. While analytics statistics that representative by ANOVA test showed that there is significant difference related to relapse in PID in group A.PI measurement demonstrate an interaction effect between groups over the time frame with P value= 0.03. Descriptive statistics in table 2 clarified that the mean values of Molar inter-cusp distance (MID) in 4 month more than 12 month and preoperative respectively in both groups. ANOVA test clarified high significant difference with P value <0.001 and no significant interaction between groups over time period. PIDshowed significant relapse (1.79 mm) occurred in none retention group (A) between 4 and 12 month this is not present in retention group (B) amount of relapse was none significant (0.05), as shown in table 1. While there was significant difference in MID in group A equaled to (1.48mm) and group B equaled to (1.38), as clearly stated in table 2. All assessment values significantly increased at the 4 month over time frame in comparison to preoperative assessment with P value <0.05 as shown in table 3.

Discussions

Relapse determination must be accounted for the effect of expansion which differed in anterior area and posterior area [11].Assessment of stability depended on relapse amount in millimeter after removal of fixed expander [11,12].Then relapse might be evaluated by average difference between 4 and 12 months. PID measurement increased between 4 and 12 months subsequently this result come in accordance with Sokucu et al[13], on the other hand significant relapse (1.79) found in 12 month time frame in group A only, this is may be due to lack of anterior extension of Trans-Palatal bar[10]. MID measurement was different between 4 and 12 months time frame in about 1.48 and 1.38 in group A and group B respectively and this amount of relapse logically accepted because in orthodontics overcorrection of 2mm always recommended to overcome relapse, this may be due to uses of TPB didn’t increase alveolar bone stability, and this result completely come in agreement with Prado et al[10]. In conclusion of this study the analysis of relapse in group A and group B clarifying that the use of Trans-Palatal arch as retention after fixed retainer didn’t increase dento-alveolar stability.

References

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5. McNamara JA Jr. Maxillary transverse deficiency. Am J OrthodDentofacOrthop. 2000;117:567–570.
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10. Prado GP, Furtado F, Aloise AC, Bilo JP, Ferreira LM and Pereira MD. Stability of surgically assisted rapid palatal expansion analyzed by 3 –dimensional imaging. Am J OrthodDentofacOrthop 2014; 145;5: 610-616.
11. Aloise AC, Pereira MD,Hino CT,Filho AG, Ferreira LM. Stability of the transverse dimension of the maxilla after surgically assisted rapid expansion. J CranifacSurg 2007;18:860-5.
12. Koudstaal MJ, Wolvius EB, Schulten AG, Hop WC, Van der wal KG.Stability, tipping and relapse of bone-borne versus tooth –borne surgically assisted rapid palatal expansion; aprospective randomized patient trial. Int. J. Oral MaxillofacSurg 2009; 38-15.
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