2007 Fiscal Year Final Research Report Summary
Comparative anatomical study of oromaxillary region shape associated with mastication and swallowing form in marsupial
| Project/Area Number |
16590156
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General anatomy (including Histology/Embryology)
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| Research Institution | The Nippon Dental University College at Tokyo (2005-2007)
The Nippon Dental University (2004) |
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Principal Investigator |
UENO Ryuji The Nippon Dental University College at Tokyo, Others, Associate Professor (10160201)
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| Co-Investigator(Kenkyū-buntansha) |
TOMO Soichiro St. Marianna University School of Medicine, Department of Anatomy, Associate Professor (10227639)
IIMURA Akira Kanagawa Dental College, Department of Anatomy, Lecturer (30211022)
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| Project Period (FY) |
2004 – 2007
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| Keywords | koala / brushtail possum / masticatory and swallowing movement / temporomandibular joint / molar / masseter muscle / morphology / comparative anatomy |
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| Research Abstract |
Although there have been many general descriptions of the skull, muscles and teeth having an intimate involvement in masticatory and swallowing movement of mammals, detailed investigations of the relationship between jaw movement form and morphological characteristic of oromaxillary region are still needed. In this research brushtail possum and koala, Australian marsupials, were used and investigated by comparative anatomical methods.
The mandibular condyle shapes in the koala were classified into four types and maximal height was observed to occur in the middle and the lateral of the condyle. These findings contrast with the result for the brushtail possum in whom the condyle shape was classified into three types and the flat type was found most frequently. Maximal height were observed most often in the lateral third of the condyle.
As for the relationship with composite tooth wear class and the shape of temporomandibular joint, a strong correlation was found in koala but there was no correlation coefficients significantly in brushtail possum.
In the odontometric study of the maxillary molars, there were no significant differences in crown diameters between the first and second molars in koala. On the contrary, in the brushtail possum, there was a trend for the second molar to be larger than the other three molars in lingual mesiodistal and mesial buccolingual diameters, and the first molar was smaller than the second and third molar in mesial buccolingual diameters.
As for the muscles for the mastication, in the koala the thickness of the buccinator muscle increased the same rate as the lower part of the masseter muscle in milk stage group but hardly increased in masticatory stage group,. Upper width and thickness of muscle indicated high correlation coefficients with mandibular fossa thickness.
These results suggested that specific morphological characteristics of oromaxillary region was highly associated with jaw movement form.
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