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Effects of Injury of the Posterior Belly of the Digastic Muscle on Mandibular Growth

  • Hyun, Seo-Jeong (Department of Oral and Maxillofacial Surgery, Inje University Haeundae Paik Hospital) ;
  • Lim, Hye-Youn (Department of Oral and Maxillofacial Surgery, Inje University Busan Paik Hospital) ;
  • Kim, Kyung-Hee (Department of Oral and Maxillofacial Surgery, Inje University Busan Paik Hospital) ;
  • Jung, Tae-Young (Department of Oral and Maxillofacial Surgery, Inje University Busan Paik Hospital) ;
  • Park, Sang-Jun (Department of Oral and Maxillofacial Surgery, Inje University Busan Paik Hospital)
  • Received : 2017.09.13
  • Accepted : 2017.12.27
  • Published : 2017.12.30

Abstract

Purpose: This study analyzed the effects of digastric muscle injury on mandibular growth in young rats. Methods: Fourteen 4-week-old Wistar rats were divided into 3 groups; experimental group A (n=6) with unilateral (right) shortening of the posterior digastric muscle, experimental group B (n=6) with bilateral shortening of the posterior digastric muscles, and control group C (n=2) who underwent a sham operation. Eight weeks after the operation all animals were sacrificed and the outcomes were compared using body weight evaluation, mensurations on lateral radiograph of hemimandibles and histological evaluation. Results: There was no significant difference between groups A and B in body weight gain. Comparison of the mean values of hemimandible distance on radiograph was performed. The difference in group mean value of mandible-related distances was analyzed using the Wilcoxon test (rank sum test) and a comparison of the homonymous distances of group A and B was performed using the Mann-Whitney test. There were differences between sides in mandibular length in group B and mandibular ramus height and transverse width of the condyle in group A (all, p<0.05). There were differences in condylar height and mandibular length on the left side between groups A and B (p<0.05). Histologic examination of temporomandibular joint showed similar findings in all specimens. Conclusions: Injury of the posterior belly of the digastric muscle during the rat growth period induced shortening of mandibular ramus height and transverse width of the condyle. It can be inferred that trauma to the posterior belly of the digastric muscle affects horizontal and vertical growth of the mandible.

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