Abstract
Unilateral posterior crossbite is a malocclusion disease that involves morpho-functional characteristics of masseter muscle; a normal or increased activity of contralateral muscle and a reduced activity of the ipsilateral muscle during unilateral crossbite have been shown. Since the extracellular matrix plays a key role in in mechano-transduction of transmitting forces during muscle contraction, the aim of the present study was to analyse the behaviour of extracellular matrix in this type of malocclusion through immunofluorescence reactions against laminin, collagen IV, MMP-2 and MMP-9. Our results show an increased expression of Laminin, Collagen IV, and MMP-9 in the contralateral side if compared to the ipsilateral side. No differences have been found in MMP-2 expression between contralateral and ipsilateral muscles. Since the increased expression of Laminin, Collagen IV and MMP-9 is associated with muscle hypertrophy and MMP-2 is associated with muscle atrophy, our results support the existence of a hypertrophic response of contralateral muscle during unilateral posterior crossbite that probably aims to compensate the altered function of the ipsilateral one.
Highlights
Unilateral posterior crossbite is a widespread malocclusion where it is possible to observe an inverse relationship of the upper and lower buccal dental cusps on one side only of the dental arch [1,2]
It has been shown that the contralateral muscle presents an increased expression of sarcoglycans and integrins, which are proteins that usually play a key role in sarcolemma stabilisation during muscle activity [7,8,9,10]
Interactions between muscle fibres and extracellular matrix are fundamental in mechanotransduction of transmitting forces and during muscular development [14,15,16,17]. On this basis and since important morphological changes have been already demonstrated during unilateral posterior crossbite, the aim of the present study was to analyse the behaviour of extracellular matrix in this type of malocclusion through immunofluorescence reactions against laminin, collagen IV, MMP-2, and MMP-9
Summary
Unilateral posterior crossbite is a widespread malocclusion where it is possible to observe an inverse relationship of the upper and lower buccal dental cusps on one side only of the dental arch [1,2]. Several studies have observed morphological features of masticatory muscle during unilateral posterior crossbite [5,6]. Most of them focused on the behaviour of muscle fibres showing different changes in protein expression and size between the ipsilateral and the contralateral muscles. It has been shown that the contralateral muscle presents an increased expression of sarcoglycans and integrins, which are proteins that usually play a key role in sarcolemma stabilisation during muscle activity [7,8,9,10].
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