Expression of proteins of elastic fibers and collagen type I in orthodontically rotated teeth in rats

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Introduction:The aims of this study were to investigate the expression of proteins of elastic fibers and collagen type I in the supra-alveolar structure of orthodontically rotated teeth in rats and to elucidate whether circumferential supracrestal fiberotomy diminishes relapse.Methods:The rats' maxillary left first molars were rotated by couple of force. Specimens were divided into groups according to different orthodontic procedures. A1–3 and B1–3 were blank control groups and operation control groups. Group C underwent rotation only, and group D was treated with rotation and retention. Groups E and F were treated with rotation, retention, and release of retention; additionally, circumferential supracrestal fiberotomy was performed in group F before the release of retention. The animals were killed, and the jaws were processed for histologic evaluation using the immunohistochemical method to evaluate the protein expressions of elastin, fibrillin-1, fibrillin-2, and collagen type I in supra-alveolar structures (around and below the gingival sulcus) between the maxillary left first and second molars. The degree and percentage of relapse were measured by a series of impressions.Results:The degree and percentage of relapse in group F were much lower than those in group E (P <0.05). Collagen type I was increased in group C (P <0.05) and at normal levels in groups D, E, and F. Elastin below the gingival sulcus and fibrillin-1 showed the same patterns of expression and were consistently elevated in groups C, D, E, and F (P <0.05). No positive staining for elastin was found around the gingival sulcus in any specimen. The difference in the expression of fibrillin-2 between the experimental groups (C, D, E, and F) and their matching control groups was not statistically significant (P >0.05).Conclusions:Circumferential supracrestal fiberotomy can alleviate the relapse of rotated teeth. Collagen fibers of supra-alveolar structures might contribute to relapse in a short time, whereas elastic fibers may be the reason that rotated teeth relapse to their original positions after retention.HIGHLIGHTSCircumferential supracrestal fiberotomy can alleviate relapse of rotated teeth.Supra-alveolar collagen fibers might contribute to relapse in the short term.Elastic fibers may cause rotated teeth to relapse over the long term.

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