Morphofunctional compensation of masseter muscles in unilateral posterior crossbite patients

Abstract

Unilateral posterior crossbite is a widespread, asymmetric malocclusion characterized by an inverse relationship of the upper and lower buccal dental cusps, in the molar and premolar regions, on one side only of the dental arch. Patients with unilateral posterior crossbite exhibit an altered chewing cycles and the crossbite side masseter results to be less active with respect to the contralateral one. Few studies about morphological features of masticatory muscle in malocclusion disorders exist and most of these have been performed on animal models. The aim of the present study was to evaluate morphological and protein expression characteristics of masseter muscles in patients affected by unilateral posterior crossbite, by histological and immunofluorescence techniques. We have used antibody against PAX-7, marker of satellite cells, and against α-, β-, γ-, δ-, ε- and ζ-sarcoglycans which are transmembrane glycoproteins involved in sarcolemma stabilization. By statistical analysis we have evaluated differences in amount of myonucley between contralateral and ipsilateral side. Results have shown: i) altered fibers morphology and atrophy of ipsilateral muscle if compared to the contralateral one; ii) higher number of myonuclei and PAX-7 positive cells in contralateral side than ipsilateral one; iii) higher pattern of fluorescence for all tested sarcoglycans in contralateral side than ipsilateral one. Results show that in unilateral posterior crossbite hypertrophic response of contralateral masseter and atrophic events in ipsilateral masseter take place; by that, in unilateral posterior crossbite malocclusion masticatory muscles modify their morphology depending on the function. That could be relevant in understanding and healing of malocclusion disorders; in fact, the altered balance about structure and function between ipsilateral and contralateral muscles could, long-term, lead and/ or worsen skeletal asymmetries.

Microscopic reconstruction and immunohistochemical analysis of discomalleolar ligament

“…For the detection of images, Laser Argon (458 e 488 nm) was utilized. All images were digitized at a resolution of 8 bits into an array of 2048 × 2048 pixels [ 34 , 35 ].…”

Human Dental Pulp Tissue during Orthodontic Tooth Movement: An Immunofluorescence Study

“…The size of the biological response depends on the application time, force magnitude and force distribution [ 3 ]; in fact, different force distribution patterns could determine different type of tissue reactions. By that, several studies focused on evaluating tissue reaction to force appliance [ 4 , 5 ] and iatrogenic sequelae to orthodontic force have been detected.…”

Immunofluorescence Evaluation of Myf5 and MyoD in Masseter Muscle of Unilateral Posterior Crossbite Patients

“…Piancino et al [ 1 ] have shown by electromyography that when chewing on the crossbite side, the ipsilateral masseter presents a reduced activity, while on the contralateral side, the masseter contractile activity is unaltered or increased. Our previous morphological investigations have shown in contralateral masseter an increase in muscle proteins, as sarcoglycans and integrins, and an increase in number of myonuclei and satellite cells, if compared to the ipsilateral one [ 9 ]. Satellite cells are muscle stem cells interposed between the sarcolemma and the basement membrane of the muscle fibres; these are cells in a quiescent state [ 27 ], but they are induced to proliferate by injury or by increased muscle activity [ 28 ].…”

“…Little morphological data exist on masticatory muscles during crossbite disease, and most of them have been performed on animal models [ 5 , 6 , 7 ]. Our morphological investigations, performed on humans, have demonstrated—in contralateral muscles—an increased thickness of muscle fibres and an increase in integrins and sarcoglycan expression [ 8 , 9 ]. Integrins are proteins that guarantee a correct muscular development during somitogenesis [ 10 , 11 ], and sarcoglycans are transmembrane glycoproteins that play a key role in sarcolemma stabilization during muscle contraction [ 12 , 13 , 14 , 15 , 16 ].…”