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Impaired masticatory behavior in subjects with reduced periodontal tissue support.
Umeå University, Faculty of Medicine, Department of Odontology. Umeå University, Faculty of Medicine, Department of Odontology, Oral and Maxillofacial Surgery.
2006 (English)In: Journal of Periodontology, ISSN 0022-3492, Vol. 77, no 9, 1491-7 p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Mechanoreceptors situated in the periodontal ligament provide detailed information about intensive and spatial aspects of tooth loads, which support the neural control of masticatory forces. We asked whether a reduced periodontal ligament due to periodontitis, and, thus, an altered mechanoreceptive innervation of the teeth, would affect masticatory behavior when subjects used incisors to hold and split food. METHODS: We tested 11 subjects with reduced periodontal tissue support that rendered 30% to 70% alveolar bone loss for at least one pair of opposing anterior incisors. Forces were recorded when subjects used their affected incisors to hold half of a peanut for approximately 4 seconds and then split it. Age- and gender-matched healthy subjects served as the control group. None of the participants showed acute oral symptoms or massive periodontal inflammation. RESULTS: The test group used greater force when holding food between the teeth (1.1+/-0.4 N [ mean+/-1 SD]) compared to the control group (0.4+/-0.2 N). Hold forces used by subjects in the test group were also more variable, both within and between trials. The increase in bite force applied to split the peanut was slower and more hesitant for subjects in the test group compared to the control group. CONCLUSIONS: Reduced periodontal tissue support accompanies impaired regulation of masticatory forces. Faulty mechanoreceptive innervation of the periodontal ligament explains the elevated hold force, whereas a change in biting strategy due to the weakened support of the teeth may account for the more defensive food-splitting behavior.

Place, publisher, year, edition, pages
2006. Vol. 77, no 9, 1491-7 p.
URN: urn:nbn:se:umu:diva-22651DOI: 10.1902/jop.2006.050355PubMedID: 16945024OAI: diva2:217517
Available from: 2009-05-14 Created: 2009-05-14 Last updated: 2014-08-13
In thesis
1. Context dependent adaptation of biting behavior in human
Open this publication in new window or tab >>Context dependent adaptation of biting behavior in human
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The focus of this thesis was to study an action that humans perform regularly, namely, to hold a morsel between the teeth and split it into smaller pieces. Three different issues related to this biting behavior were addressed:  (1) the effect of redu­c­ed perio­dontal tissues on food holding and splitting behavior; (2) the behavioral conse­quences of performing different bite tasks with different functional requirements, i.e., to split a peanut half resting on a piece of chocolate or to split both the peanut and the chocolate; and (3) the reflex modulations resul­ting from such a change in the intended bite action. The main conclusions from the experi­mental studies were the following:

First, perio­dontitis, an inflam­matory disease that destroys the peri­o­dontal ligaments and the embedded perio­dontal mechanoreceptors, causes significant impairments in the masticatory abili­ty: the manipulative bite forces when holding a morsel are elevated compared to a matched control population and the bite force development prior to food split is altered. These changes are likely due to a combination of reduced sensory informa­tion from the damaged ligaments and to changes in the bite stra­tegy secon­d­ary to the unstable oral situation.

Second, people exploit the anatomy of jaw-closing muscles to regulate the amount of bite force that dissipates following a sudden unloading of the jaw. Such control is necessary because without mechanisms that quickly halt jaw-closing movements after sudden unloading, the impact forces when the teeth collide could otherwise damage both the teeth and related soft tissues. Splitting a piece of chocolate, for instance, regularly requires >100N of bite force and the jaws collide within 5 ms of a split. On the other hand, when biting through heterogeneous food, the bite force needs to be kept high until the whole morsel is split. The required regulation is achieved by differen­tial­ly engaging parts of the masseter muscles along the anteroposterior axis of the jaw to exploit differences between muscle portions in their bite force generating capa­ci­ty and muscle shortening velocity.

Finally, the reflex evoked by suddenly unloading the jaw—apparent only after the initial bite force dissipation—is modulated according to the bite intention. That is, when the intention is to bite through food items with multiple layers, the reflex response in the jaw opening muscles following a split is small, thus minimizing the bite force reduction. In contrast, when the intention is to rapidly decrease the bite force once a split has occurred, the reflex response is high. This pattern of reflex modulation is functionally beneficial when biting through heterogeneous food in a smooth manner.

The presented studies show the significance of integrating cogni­tive, physiological and anatomical aspects when attempting to understand human masticatory control.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2014. 35 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1666
EMG, bite force, human, mastication, muscles, jaw opening reflex, motor control, reflex modulation, periodontal attachment loss, periodontitis
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Research subject
urn:nbn:se:umu:diva-91664 (URN)978-91-7601-096-9 (ISBN)
Public defence
2014-09-03, Biologihuset, BiA 201, Umeå Universitet, Umeå, 09:00 (English)
Swedish Research Council, 2011-3128
Available from: 2014-08-15 Created: 2014-08-13 Last updated: 2014-08-13Bibliographically approved

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