Cephalometric studies of the mandible, its masticatory muscles and vasculature of growing Göttingen Minipigs-A comparative anatomical study to refine experimental mandibular surgery.

Over many decades, the Göttingen Minipig has been used as a large animal model in experimental surgical research of the mandible. Recently several authors have raised concerns over the use of the Göttingen Minipig in this research area, observing problems with post-operative wound healing and loosening implants. To reduce these complications during and after surgery and to improve animal welfare in mandibular surgery research, the present study elucidated how comparable the mandible of minipigs is to that of humans and whether these complications could be caused by specific anatomical characteristics of the minipigs' mandible, its masticatory muscles and associated vasculature. Twenty-two mandibular cephalometric parameters were measured on CT scans of Göttingen Minipigs aged between 12 and 21 months. Ultimately, we compared this data with human data reported in the scientific literature. In addition, image segmentation was used to determine the masticatory muscle morphology and the configuration of the mandibular blood vessels. Compared to data of humans, significant differences in the mandibular anatomy of minipigs were found. Of the 22 parameters measured only four were found to be highly comparable, whilst the others were not. The 3D examinations of the minipigs vasculature showed a very prominent deep facial vein directly medial to the mandibular ramus and potentially interfering with the sectional plane of mandibular distraction osteogenesis. Damage to this vessel could result in inaccessible bleeding. The findings of this study suggest that Göttingen Minipigs are not ideal animal models for experimental mandibular surgery research. Nevertheless if these minipigs are used the authors recommend that radiographic techniques, such as computed tomography, be used in the specific planning procedures for the mandibular surgical experiments. In addition, it is advisable to choose suitable age groups and customize implants based on the mandibular dimensions reported in this study.

Observation of Effects of Different Surgical Treatments on Unilateral Masticatory Muscle Spasm.

BACKGROUND: Unilateral masticatory muscle spasm is a rare disease without a generally accepted and efficacious treatment plan. OBJECTIVE: We sought to compare the effects of different surgical treatments on unilateral masticatory muscle spasm. METHODS: A retrospective analysis of the surgical treatment and effects of 10 cases of unilateral masticatory muscle spasm occurred between February 2010 and September 2016. Three cases underwent complete amputation of the trigeminal motor branch, 3 cases underwent partial amputation of the trigeminal motor branch, and 4 cases received only vascular decompression. All patients were followed up by telephone interview after surgery. RESULTS: In the simple vascular decompression group, 3 cases were cured and 1 was cured after a delay. Of these 3 cases, 1 case became aggravated 2 years after the operation, 1 case became aggravated 5 years after the operation, and 1 case showed no change during the follow-up period. In the partial amputation group, 2 cases were cured and 1 case was alleviated. Of the 2 patients who were cured, 1 suffered recurrence 2 years later, while the other case showed no recurrence during the follow-up period. In the complete amputation group, 1 case was cured with a delay and 2 cases were cured immediately with no recurrence during the follow-up. Mild atrophy of the temporal muscle occurred gradually with no restriction of the mouth opening in 2 cases. CONCLUSIONS: Complete amputation of the trigeminal nerve did achieve better effects than pure microvascular decompression and partial amputation of the trigeminal motor branch, but it may lead to mild temporal muscle atrophy.

Collateral circulation prevents masticatory muscle impairment in rat middle cerebral artery occlusion model.

The rat suture middle cerebral artery occlusion (MCAO) is a frequently used animal model for investigating the mechanisms of ischemic brain injury. During suture MCAO, transection of the external carotid artery (ECA) potentially restrains blood flow and impairs masticatory muscle and other ECA-supported territories, consequently influencing post-operation animal survival. This study was aimed at investigating the effect of ECA transection on the hemodynamic alterations using a novel synchrotron radiation (SR) angiography technique and magnetic resonance imaging in live animals. Fifteen male adult Sprague-Dawley rats were used in this study. Animals underwent MCAO, in which the ECA was transected. SR angiography was performed before and after MCAO. Rats then underwent magnetic resonance imaging (MRI) to detect the tissue lesion both intra- and extra-cranially. Animals with SR angiography without other manipulations were used as control. High-resolution cerebrovascular morphology was analyzed using a novel technique of SR angiography. The masticatory muscle lesion was further examined by hematoxylin and eosin staining. MRI and histological results showed that there was no masticatory muscle lesion at 1, 7 and 28 days following MCAO with ECA transection. In normal condition, the ECA and its branch external maxillary artery were clearly detected. Following ECA transection, the external maxillary artery was still observed and the blood supply appeared from the anastomotic branch from the pterygopalatine artery. SR angiography further revealed the inter-relationship of hemisphere extra- and intra-cranial vasculature in the rat following MCAO. Transection of the ECA did not impair masticatory muscles in rat suture MCAO. Interrupted blood flow could be compensated by the collateral circulation from the pterygopalatine artery.

Intravoxel incoherent motion imaging of masticatory muscles: pilot study for the assessment of perfusion and diffusion during clenching.

OBJECTIVE: The purpose of this study was to evaluate intravoxel incoherent motion (IVIM) imaging for assessing perfusion and diffusion of masticatory muscles during clenching. SUBJECTS AND METHODS: A prospective study was performed to assess the perfusion and diffusion of masticatory muscles during clenching. The masseter and medial pterygoid muscles participate in clenching, and the lateral pterygoids do not. IVIM parameters (microvascular volume fraction, f; pure diffusion coefficient, D; and perfusion-related incoherent microcirculation, D*) were determined on both the clenching and the balancing sides in 24 volunteers. The Wilcoxon test was used to compare the IVIM parameters at rest and during clenching. RESULTS: The f and D* values of the masseters significantly increased on the clenching side (f = 0.17 ± 0.10 vs 0.29 ± 0.11, p < 0.001; D* = 21.3 ± 18.5 × 10(-3) mm(2)/s vs 42.1 ± 33.3 × 10(-3) mm(2)/s, p = 0.0008). However, the D values did not change during clenching (1.26 ± 0.23 × 10(-3) mm(2) vs 1.21 ± 0.35 × 10(-3) mm(2)). The f values of the medial pterygoids also increased on the clenching side (0.20 ± 0.09 vs 0.30 ± 0.09, p < 0.001). On the balancing side, the f values of the masseters (0.19 ± 0.12 vs 0.30 ± 0.12, p < 0.001) and medial pterygoids (0.20 ± 0.09 vs 0.29 ± 0.11, p = 0.0007) significantly increased during clenching. In contrast, the IVIM values of the lateral pterygoids did not change. CONCLUSION: IVIM imaging may be useful for assessing perfusion and diffusion of the masticatory muscles.

[Application of near infrared spectroscopy in study of occlusal splints and resistance of masticatory muscles to fatigue pain].

OBJECTIVE: To analyze the influence of occlusal splint on resistance capability of masticatory muscles to fatigue. METHODS: In the study, 25 young male volunteers were randomly divided to 5 groups according to different splint placements: (1) no splint, (2) 1.5 mm thick soft splint, (3) 2 mm thick resin stability splint, (4) 4 mm thick resin stability splint, (5) buccolingual mock splint. Near infrared spectroscopy (NIRS) was used to measure blood oxygen content in human masticatory muscles during constant strong biting before and after the splint placement at seven time points: before, baseline after, 1 week after, and 2 weeks after splint placement, and immediately after, 1 week after, and 5 weeks after removing of splints. The strength of the biting force was maintained constantly at 30% level of the maximum biting force of each subject by biofeedback to the displayed value of an electro-myographic monitor. The time points of muscular fatigue and pain that appeared were recorded and the correlation between the subjective feeling and the NIRS measurement result was analyzed. RESULTS: The NIRS measurement curve had a point of inflection that had no significant difference with the time point of the muscle pain that appeared. Two weeks after placement of soft splint, the time point of the muscular fatigue and pain that appeared were 2.75 s and 8.00 s delayed respectively compared with that before placement of splint (P<0.01) while they were earlier in the groups of hard splints and there was no significant difference (P>0.05) in the group of mock splint. CONCLUSION: The metabolic status of human masticatory muscles could be monitored in real time by using NIRS; soft splint delayed the appearing of muscle fatigue and muscle pain after two weeks of placement.

Jaw claudication in the era of carotid stenting.

Jaw claudication could result from external carotid artery (ECA) occlusive disease. Carotid artery stenting (CAS) has been shown to worsen the disease in the ECA. This could potentially worsen the symptoms in patients with pre-existing jaw claudication undergoing CAS. Meanwhile, ECA endarterectomy is routinely done during internal carotid artery endarterectomy (CEA). This has been shown to alleviate jaw claudication symptoms. We report a case of a high-risk patient for CEA who presented with symptomatic carotid disease as well as bilateral jaw claudication. Both symptoms resolved after CEA. We also present the case of another patient treated for recurrent high-grade carotid disease with CAS resulting in acute ECA occlusion and jaw claudication. High-risk patients with symptomatic carotid disease and jaw claudication should be considered for CEA and not only CAS.

Digital subtraction angiography-guided percutaneous sclerotherapy of venous malformations with pingyangmycin and/or absolute ethanol in the maxillofacial region.

PURPOSE: The present study evaluated the safety and efficacy of digital subtraction angiography-guided percutaneous sclerotherapy of venous malformations (VMs) with pingyangmycin and/or absolute ethanol in the maxillofacial region. We present our safe and novel method for treating venous malformations. PATIENTS AND METHODS: A total of 20 patients (21 locations) diagnosed with VMs were enrolled in the present trial. Evaluated by preoperative digital subtraction angiography, the lesions were categorized into 4 types according to the venous drainage features. Of the 20 patients, 5 had type I VMs, 5 had type II, 6 had type III and 3 had type IV VMs. One patient had type I and type III VMs in different locations of the maxillofacial region. For types I and II lesions, pingyangmycin sclerotherapy was performed. Multistage sclerotherapy with absolute ethanol and pingyangmycin was performed on types III and IV lesions. RESULTS: After evaluation and guided by preoperative digital subtraction angiography, all the patients were treated successfully and safely. Of the 20 patients, the clinical outcome was excellent in 13, good in 6, and fair in 1. No disease recurrence was noted during the follow-up evaluations (range 6 to 25 months, median 13.55). The complications were fever in 5 patients after the first session of sclerotherapy, incomplete facial paralysis in 1, swelling in 1, and ulceration in 3. No major complications were observed. CONCLUSIONS: Digital subtraction angiography-guided phlebography of VMs in the maxillofacial region is one of the approaches to classify VMs using anatomic and hemodynamic features. A strong association was seen between the type of VM and the approach of sclerotherapy. Percutaneous sclerotherapy using pingyangmycin and/or absolute ethanol is a safe and effective method of treating symptomatic VMs.

Parasympathetic vasodilator fibers in rat digastric muscle.

The present study examined whether parasympathetic vasodilator fibers exist in rat jaw-opening muscles such as the digastric muscle. The mental nerve was stimulated to activate the parasympathetic vasodilator nerve in the digastric muscle. Electrical stimulation of the mental nerve elicited intensity- and frequency-dependent increases of blood flow in this muscle. These increases were markedly reduced by hexamethonium in dose- and time-dependent manners, but pretreatment with phentolamine or propranolol had no effect. Pretreatment with atropine also attenuated the increase in blood flow in digastric muscle. When retrograde fluorogold was injected into the digastric muscle, labeled neurons were observed in the otic ganglion only on the ipsilateral side, but not in the pterygopalatine ganglion of either side. These results indicate that parasympathetic vasodilator fibers originate from cell bodies in the otic ganglion in rat digastric muscle.

A case of a divided maxillary artery in the infratemporal fossa.

A divided maxillary artery was found in the left infratemporal fossa of a 63-year-old male cadaver during a student dissection practice. The maxillary artery, which arose from the external carotid artery at the posterior border of the ramus of the mandible, was divided into two branches in the infratemporal fossa. The deep branch of the maxillary artery was deep to the lateral pterygoid muscle and the inferior alveolar, buccal and lingual nerves, giving off the anterior tympanic, middle meningeal, anterior deep temporal, buccal, and posterior superior alveolar arteries. The deep branch passed through the pterygomaxillary fissure. On the other hand, the superficial branch of the maxillary artery, which was superficial to the lateral pterygoid muscle, gave off the inferior alveolar artery and other branches. The maxillary artery on the right side displayed a normal branching pattern within the infratemporal fossa. These findings indicate that the deep and superficial branches of the maxillary artery remained without disappearing during the development of the maxillary artery originated from the stapedial artery.

Orofacial muscle pain: new advances in concept and therapy.

This manuscript focuses on chronic myogenous pains affecting the masticatory muscles. The differentiation of myogenous masticatory pain into subcategories is proposed by separating myogenous pains according to their location and anatomic extent. Focal myalgia, regional myalgia, myofascial pain, and fibromyalgia are classified based on specific historical and clinical examination criteria. The probable mechanisms underlying chronic myogenous pains and trigger points phenomena are discussed. Treatment options of the myogenous masticatory pain conditions including physical medicine modalities, as well as several types of pharmacologic agents, are presented.

[Chewing gum influence upon blood supply of mastication muscles].

A total of 27 volunteers 16-26 years of age participated in the study of the influence of chewing gum use in different regimens upon velocity parameters of blood supply of mastication muscles at dopplerography (MM-D-K dopplerograph made in Russia). It was established that regular and continuous (30 min) chewing the gum and also of big volume (in two) but short-term chewing (5 min) equalizes blood supply of mastication muscles on both working and non-working sides.

Regional alterations in fiber type distribution, capillary density, and blood flow after lower jaw sagittal advancement in pig masticatory muscles.

Muscular remodeling is known to be a prerequisite for permanent correction of mandibular-maxillary malocclusion. The objective of this study was to clarify if an increase in type I fiber number is accompanied by an increased capillary density and improved muscular blood flow. Juvenile pigs received build-ups on the molars, which induced a protrusion of 7.6 + 1.5 mm. After 4 weeks of treatment, chronic lower jaw protrusion induced a marked muscle blood flow increase in the anterior and medial regions of the superficial part of the masseter and in the medial pterygoid muscle (P < 0.05). Furthermore, an increase in capillary density and in the amount of type I fibers was found in all regions of masticatory muscles with an increased muscle blood flow (P < 0.05). Finally, the capillary-to-fiber ratio increased (P < 0.05). Muscle blood flow and capillary density showed a strong linear correlation (r = 0.89, P < 0.01). These changes suggest a complex muscle adaptation for long-term, fatigue-resistant activity during the early corrective period of mandibular-maxillary malocclusion treatment.

Claudication on mastication following bilateral external carotid artery ligation for posterior epistaxis.

This case highlights a potentially disabling complication of intermittent claudication in the region of the masseter muscles on mastication, following bilateral external carotid artery ligation for epistaxis. Although there have been few reports of this complication this may be a reflection of the fact that the operation is rarely performed, and not because the complication is rare. Its potentially disabling nature, and its possible common occurrence after this procedure make awareness of it by surgeons who may carry out this procedure important.

Differences in capillary supply between human oro-facial, masticatory and limb muscles.

In this report we show that immunostaining of the capillary basement membrane with an antibody directed against laminin is a useful alternative in detecting the capillaries in human muscle. Using this method, the capillary supply of three embryologically, morphologically and functionally different muscle groups, oro-facial, masticatory and limb muscles, were analysed. Significant differences in capillarization between muscles and muscle groups were found. The oro-facial and masseter muscles showed significantly higher density of capillaries than the limb muscles, taken in consideration the muscle cross-sectional area, with the masseter having the highest capillary density ever reported for human sedentary skeletal muscles. Judged from the number of capillaries per muscle fibre, the limb muscles showed the best capillarization. However, since the three muscle groups investigated differed with respect to fibre diameter, our evaluation of number of capillaries per muscle fibre was related also to fibre diameter. Thus, capillary constants were created which take fibre diameter into account. Based on these new parameters, the oro-facial and masseter muscles were found to be relatively better supplied by capillaries than the limb muscles. These results suggest differences in tasks and functional activity between muscles, and reflect a relatively higher need and demand for blood supply in the masticatory and oro-facial muscles than in limb muscles.

Muscle-specific enzyme activity patterns of the capillary bed of human oro-facial, masticatory and limb muscles.

Enzyme-histochemical methods were used to analyse the activities of alkaline phosphatase (AP), dipeptidylpeptidase IV (DPP IV) and adenosine triphosphatase (ATPase) in capillaries of four different human oro-facial muscles, the major and minor zygomatic, the orbicularis oris and buccinator, one masticatory, the masseter and two limb muscles, the biceps brachii and first dorsal interosseus muscles. In all muscles, except for the orbicularis oris, the majority of the capillaries lacked enzyme activity. Therefore, none of these enzymes seems to be reliable as a general marker for human muscle capillaries. In general, the capillaries of the limb muscles and the major and minor zygomatic and the buccinator, were similar in their staining pattern for AP and ATPase, but differed in DPP IV staining. The orbicularis oris muscle differed from the other muscles by showing the largest proportion of capillaries with AP and ATPase activity. The masseter muscle had the largest proportion of capillaries stained for DPP IV. The muscle specific differences in enzyme activity of the capillaries are in agreement with our previous findings of specific differences between limb, oro-facial and masticatory muscles with respect to capillary supply and composition of fibre types and myosins. The results reflect functional specialization of the capillary bed of human muscles.

A case report. Jaw claudication: a sign of giant cell arteritis.

Jaw claudication is an often unrecognized sign of giant cell arteritis. The significance of this symptom has been underemphasized in the dental literature. Dentists should consider jaw claudication when making the differential diagnosis of jaw pain, especially in the elderly patient. Early diagnosis and treatment of giant cell arteritis may help save a patient's vision.