Original article
Periodontal effects of rapid maxillary expansion with tooth-tissue-borne and tooth-borne expanders: A computed tomography evaluation

https://doi.org/10.1016/j.ajodo.2006.02.021Get rights and content

Introduction: The force delivered during rapid maxillary expansion (RME) produces areas of compression on the periodontal ligament of the supporting teeth. The resulting alveolar bone resorption can lead to unwanted tooth movement in the same direction. The purpose of this study was to evaluate periodontal changes by means of computed tomography after RME with tooth-tissue-borne and tooth-borne expanders. Methods: The sample comprised 8 girls, 11 to 14 years old, with Class I or II malocclusions with unilateral or bilateral posterior crossbites Four girls were treated with tooth-tissue-borne Haas-type expanders, and 4 were treated with tooth-borne Hyrax expanders. The appliances were activated up to the full 7-mm capacity of the expansion screw. Spiral CT scans were taken before expansion and after the 3-month retention period when the expander was removed. One-millimeter thick axial sections were exposed parallel to the palatal plane, comprising the dentoalveolar area and the base of the maxilla up to the inferior third of the nasal cavity. Multiplanar reconstruction was used to measure buccal and lingual bone plate thickness and buccal alveolar bone crest level by means of the computerized method. Results and Conclusions: RME reduced the buccal bone plate thickness of supporting teeth 0.6 to 0.9 mm and increased the lingual bone plate thickness 0.8 to 1.3 mm. The increase in lingual bone plate thickness of the maxillary posterior teeth was greater in the tooth-borne expansion group than in the tooth-tissue-borne group. RME induced bone dehiscences on the anchorage teeth’s buccal aspect (7.1 ± 4.6 mm at the first premolars and 3.8 ± 4.4 mm at the mesiobuccal area of the first molars), especially in subjects with thinner buccal bone plates. The tooth-borne expander produced greater reduction of first premolar buccal alveolar bone crest level than did the tooth-tissue-borne expander.

Section snippets

Material and methods

Our study sample (n = 8) was selected from a larger group of 87 young subjects with Angle Class I or Class II malocclusions with unilateral or bilateral posterior crossbites who sought orthodontic treatment at the Department of Orthodontics, Bauru Dental School, University of São Paulo. The exclusion criteria were (1) age below 11 and above 14 years, (2) persistence of any deciduous teeth, (3) absence of maxillary posterior permanent teeth, (4) metallic restorations on maxillary posterior

Results

No variable had a statistically significant systematic error. The casual errors ranged from 0.09 to 0.20.

Evaluation of the pooled groups showed that RME reduced the BBPT of the supporting teeth by 0.6 to 0.9 mm (Table I). The Haas-type (Table II) and hyrax (Table III) expanders showed the same results, reducing alveolar bone thickness on the buccal aspect of the banded teeth, whereas the bone plate of adjacent teeth—canines and second premolars—remained almost unchanged. Therefore, there were

Discussion

The use of a small sample in this study was justified by ethical considerations, which limit radiation exposure for research purposes. CT images are not part of routine orthodontic records, and the ethics committee approved the project only because CT scanning can provide RME information not obtainable from other methods, mainly the periodontal findings. To overcome the small study sample, patient age and sex were homogenized, and all subjects were carefully treated and controlled by the same

Conclusions

  • 1

    RME orthodontic effect reduced the BBPT of maxillary posterior teeth and increased the LBPT.

  • 2

    The tooth-tissue-borne expander caused less of an increase to the LBPT of the maxillary posterior teeth than did the tooth-borne expander.

  • 3

    RME induced bone dehiscences on the anchorage teeth’s buccal aspect, especially in subjects with thinner buccal bone plates.

  • 4

    The tooth-borne expander produced more reduction of first premolar BACL than did the tooth-tissue-borne expander.

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    Based on research by Dr Daniela G. Garib in partial fulfillment of the requirements for the PhD degree in orthodontics at Bauru Dental School, University of São Paulo.

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