Lateral pterygoid muscle activity in mandibular retrognathism and response to mandibular advancement surgery

Electromyographic patterns of muscle activity were recorded in 11 patients with mandibular retrognathism and compared with ten normal subjects. Categorization of facial morphology was based on standard cephalometric data. Seven patients in the retrognathic group have been studied 1 year after mandibular-lengthening surgery. A computer-based data acquisition and analysis system with a Selspot movement monitoring system was used to record and quantify simultaneously both mandibular movement patterns and associated electromyographic data. Of particular interest was the pattern of activity for the lateral pterygoid muscles of all patients in the retrognathic group compared with controls. Both the ipsilateral and contralateral lateral pterygoids contracted during either right or left lateral excursions for eight of the 11 patients in the retrognathic group compared to aphasic activity during this movement as expected in the control group. However, all seven of the patients tested 1 year after mandibular lengthening demonstrated normal aphasic firing patterns of the lateral pterygoid muscles (inferior belly) during right and left lateral excursions. The retrognathic group of patients also demonstrated abnormal recruitment patterns of the lateral pterygoid muscles during border movements of the mandible in the preoperative stage. Recruitment patterns approached normal levels after mandibular advancement surgery. The number of patients studied did not permit accurate statistical analysis. However, a trend is apparent that demonstrates previously unreported abnormal activity patterns of the lateral pterygoid muscles and an adaptive response of these muscles to orthognathic surgery.     

Mixed facial reanimation technique to treat paralysis in medium-term cases

Recent facial paralyses, in which fibrillations of the mimetic muscles are still detectable by electromyography (EMG), allow facial reanimation based on giving new neural stimuli to musculature. However, if more time has elapsed, mimetic muscles can undergo irreversible atrophy, and providing a new neural stimulus is simply not effective. In these cases function is provided by transferring free flaps into the face or transposing masticatory muscles to reinstitute major movements, such as eyelid closure and smiling.In a small number of cases, patients affected by paralysis are referred late — more than 18 months after onset. In these cases, reinnervating the musculature carries a high risk of failure because some or all of the mimetic muscles may atrophy irreversibly while axonal ingrowth is taking place. A mixed reanimation technique to address this involves a neurorrhaphy between the masseteric nerve and a facial nerve branch for the orbicularis oculi, to ensure a stronger innervation to that muscle, associated with the transposition of the temporalis muscle to the nasiolabial sulcus. This gives good symmetry in the rest of the midface, while smiling movement is achievable, but not guaranteed. This one-time facial reanimation is particularly indicated for those who refuse major free-flap surgery or when that may be risky, as in previously operated and irradiated fields. More extensive procedures based on utilizing a free flap to recover smiling, while adding a cross-face nerve graft to restore blinking, may be proposed for motivated patients.Between 2010 and 2015, five patients affected by complete unilateral facial palsy underwent this technique in the Maxillofacial Surgery Department, San Paolo Hospital (Milan, Italy).Symmetry of the middle-third of the face at rest and recovery of smiling was quite good. Complete voluntary eyelid closure was obtained in all cases.Combining temporalis flap rotation and a masseteric-to-orbicularis-oculi-facial-nerve branch neurorrhaphy seems to be a valid solution for those medium-term referred patients.     

Muscle reorientation following superior repositioning of the maxilla

In facial reconstructive surgery the importance of the orofacial muscles on form, function, and esthetics must be recognized. Once this fact is acknowledged, these muscles may be manipulated to advantage by the surgeon; thus, undesirable effects in the perioral area following superior repositioning of the maxilla can be avoided. A V-Y advancement-closure of the horizontal maxillary vestibular incision is advocated. This successfully repositions the lip muscles in a predictable manner and maintains normal lip form pout, and amount of exposed vermilion. Alar width and unesthetic widening of the alar bases may also be controlled by the proper repositioning of the transverse nasalis muscles. The validity of these surgical procedures is supported by a statistical analysis of the lip and nasal structures in patients whose dentofacial deformities were corrected by superior repositioning of the maxilla and concomitant facial muscle reorientation.     

Clinical management of microstomia due to the static treatment of facial paralysis and oral rehabilitation with dental implants

Facial-nerve paralysis is seldom seen and may occur because of a broad spectrum of causes. The most commonly seen cause of facial paralysis is the Bell palsy; iatrogenic causes and tumors are relatively rare. Facial asymmetry, drooling, garbled speech, and difficulty in feeding: all adversely affect the psychosocial conditions of the patients. Fascial and tendon sling procedures may be performed for the static treatment of the unilateral permanent facial paralysis. These techniques are used both for the correction of the asymmetry of the face, especially by providing static support for the corner of the mouth, and to prevent drooling. Microstomia after a sling procedure is not a previously observed complication in the literature. A patient is presented with the surgical management of the complication of microstomia that had risen because of a static treatment of his unilateral facial paralysis via a tendon that passes circularly through his orbicularis oris muscle. Oral rehabilitation thereafter was maintained with the support of dental implants and fixed prosthodontics. The most efficient treatment protocol was decided with an interdisciplinary consultation of the oral and maxillofacial surgeon, the plastic surgeon, and the prosthodontist.     

Biomechanics of differences in lower facial height

A two-dimensional model which allows calculation of mechanical advantage of the human temporalis and masseter muscles is presented. The model is manipulated to demonstrate how selected differences in facial morphology affect the mechanical advantage of the muscles. The model is then used to evaluate the differences in mechanical advantage between patients with the long face syndrome and those with the short face syndrome. Differences in facial morphology between these two groups result in significant differences in the mechanical advantages of their muscles. Mechanical advantage may, in part, explain observed differences in bite force between the two groups. The model suggests that some surgical procedures used to correct facial disharmonies may have a significant effect on the mechanical advantage of the jaw muscles.     

Orthognathic treatment for a patient with facial asymmetry associated with unilateral scissors-bite and a collapsed mandibular arch

Subapical mandibular surgeries have been used to correct vertical malocclusion and interdental problems associated with mandibular deformity. Subapical surgery to the anterior part of the mandible is applicable in many patients with anterior open bite and deepbite. Surgery of the posterior part of the mandible is needed less frequently than surgery of the anterior part. This case report describes the surgical-orthodontic treatment of a 21-year-old woman who underwent posterior subapical mandibular surgery. Her chief complaint was facial asymmetry, and she had a collapsed mandibular arch with a scissors-bite of the right premolars and molars. After subapical osteotomy, surgically assisted correction of the collapsed right mandibular arch was performed with a lingual arch appliance. Comprehensive orthodontic treatment was initiated in both arches after this correction. Le Fort I osteotomy and sagittal split ramus osteotomy were used to correct the facial asymmetry. Her facial appearance and temporomandibular problems were markedly improved, and she achieved a functional and stable occlusion after these treatments. This case report demonstrates the efficiency of posterior subapical mandibular surgery for a patient with a collapsed mandibular arch and a scissors-bite.     

The results of using extraoral traction in children with a prognathic bite

Primary and repeated lateral teleroentgenograms of the head of 37 children aged 4-8 with prognathic occlusion were analyzed, recorded on an average in 2 years after employment of a chin sling with extraoral traction. Analysis has shown normalization of the jaws and occlusion in the sagittal plane, resultant from limitation of mesial transposition of the mandible in the skull in the course of facial skeleton growth. This has been achieved at the expense of inhibition of longitudinal growth of the mandibular body and ascending branches more than twofold as against the reference values and was also a result of mandibular shift due to traction and of enhanced vertical transposition of the mandible in the skull due to distal rotation. The principal indications for the employment of chin sling in the management of prognathic occlusion are intensive growth of the mandible or a tendency to such growth, mesial position of the mandible in the skull, and a combination of these disorders, that may be the principal or additional factors contributing to the pathogenesis of this abnormality.     

Facial growth and oral function in a case of juvenile rheumatoid arthritis during an 8-year period

The present report is a detailed analysis of facial growth and oral function in a girl with juvenile rheumatoid arthritis of the temporomandibular joints. She was followed from 9 to 17 years of age prior to and after orthognathic surgery. Facial growth was assessed by facial photographs, dental casts, and roentgencephalometry, and oral function was assessed clinically by electromyography, kinesiography, and bite force. In addition, histological and histochemical analysis was performed on biopsy material from her masseter muscle obtained at the time of surgery. The study showed a clear relationship between facial growth and oral function. Dysplastic growth of the mandible led to an increasingly unstable occlusion with poor working conditions for the masticatory muscles. The muscles became weak, and even revealed marked structural histological and histochemical changes. Based on these observations it is suggested that the conventional treatment strategy with postponement of orthodontic or orthognathic surgical treatment until cessation of growth is abandoned and that early treatment should be undertaken to maintain occlusal stability throughout the growth period.     

In search of a universal and objective method to assess facial aging: The new face objective photo-numerical assessment scale

Most patients who undergo cosmetic rejuvenation treatment hope to appear younger and healthier. Although a number of scales have been put forward to assess facial aging, to date none has focused on predicting patients’ age. The purpose of our study was to validate a more complete version of the face - Objective assessment scale previously developed by the authors. Since patients with a photo-damaged skin can look older than others we created a new sub-scale: the facial photo-aging scale, in order to provide a more comprehensive method for the overall assessment of facial aging.The Rasch model was used as part of the validation process. We assigned a score to each patient based on the scales we have developed. The correlation between a patient's actual age and the obtained scores was analyzed; we also analyzed the inter-rater reliability and test-retest reliability. All the scales exceeded criteria for acceptability, reliability and validity.The facial aging scale we have developed may prove to be a valuable tool to assess patients before and after facial rejuvenation treatment or surgery, as well as for clinical research in the field of facial skin regeneration.     

面神经损伤后神经元中BCL-2、P53表达的实验研究

目的研究大鼠面神经总干压榨伤及切断伤后,BCL-2、P53在其神经元中的表达。方法将35只SD大鼠随机分为三组：组I右侧面神经总干压榨伤,组II为同体左侧面神经总干切断伤,组Ⅲ为正常对照侧。用HE染色的方法观测术后各期面神经元的形态学变化,用二步免疫组化法检测面神经元内BCL-2、P53蛋白的表达。结果面神经总干压榨伤后,其神经元未发生死亡,而总干切断伤会引起神经元死亡,面神经干切断1w后BCL-2、P53蛋白表达开始增强,3w时达到高峰,且切断后神经元数与BCL-2,P53的表达有明显相关性。结论BCL-2、P53蛋白参与面神经总干切断后诱导神经元凋亡过程的调控,BCL-2,P53的表达变化决定面神经死亡。     

Can you be too old for oral implants? An update on ageing and plasticity in the oro‐facial sensorimotor system

This review focuses on the capacity of the brain for plasticity and the utility and efficacy of oral implants in helping to restore oro‐facial sensorimotor functions, especially in elderly patients. The review first outlines the components of the oro‐facial sensorimotor system which encompasses both oro‐facial tissues and a number of brain regions. One such region is the sensorimotor cortex that controls the activity of the numerous oro‐facial skeletal muscles. These muscles are involved in a number of functions including reflexes and the more complex sensorimotor functions of mastication, swallowing and speech. The review outlines the use by the brain of sensory inputs from oro‐facial receptors in order to provide for exquisite sensorimotor control of the activity of the oro‐facial muscles. It highlights the role in this sensorimotor control played by periodontal mechanoreceptors and their sensory inputs to the brain, and how oral implants in concert with the plastic capacity of the brain may, at least in part, compensate for reduced sensorimotor functioning when teeth are lost. It outlines findings of ageing‐related decrements in oro‐facial sensorimotor functions and control. The changes in oro‐facial tissues and the brain that underlie these ageing‐related functional alterations are also considered, along with adaptive and compensatory processes that utilise the brain's capacity for plasticity. The review also notes the evidence t hat rehabilitation that incorporates adjunctive approaches such as sensorimotor training paradigms in addition to oral prostheses such as implants may enhance these processes and help maintain or facilitate recovery of sensorimotor functioning in the elderly.     

The anatomy of buccinator--insights from functional casts of the oral vestibule

OBJECTIVE: When a dental elastomer is placed in the oral vestibule and the facial muscles contracted while it sets, the functional cast produced frequently shows a deep anteroposterior groove, and marked posterosuperior and smaller anteroinferior bulges. This study investigates whether these features have a structural or a physiological basis. DESIGN: Casts of the right side of the oral vestibule of dissecting room cadavers and living volunteers were made using a polyvinylsiloxane dental elastomer. The volunteers each produced two functional casts in each of the following situations: while the teeth were clenched but the facial muscles inactive, while grimacing, and while swallowing. RESULTS: Grooves and bulges were largely absent in casts from the dissecting room cadavers and of living volunteers with the teeth clenched but the facial muscles inactive. They were present when the elastomer set while the subjects grimaced but most marked when they had been swallowing their saliva. The depth of the grooves varied between individuals and generally was greatest alongside the second molar teeth. We found that the posterosuperior bulge did not coincide with the position of the parotid duct. CONCLUSIONS: The anteroposterior groove represents a well developed horizontal part of buccinator. The regions of the casts bulging superior and inferior to the groove probably represent weaker regions of buccinator towards its maxillary and mandibular attachments. The bulge superior to the groove was not explained by a weakness in buccinator where it is pierced by the parotid duct.     

下颌偏斜患者颜面与颈背部肌肌电研究

目的 探讨下颌偏斜对咀嚼机、颈、肩背部肌肌电的影响。方法 采用K6－Ⅰ系统对15例正常咬合者及12例下颌偏斜患者在最大开闭口运动、咀嚼运动、颈肩背部肌运动时咬肌、二腹肌、胸锁乳突肌与斜方肌的表面肌电进行采集分析，比较两组受试者双侧对应肌肌电平均幅值的对称性。结果 ①下合同功能性运动时颈背部肌有肌电活动；颈背部运动时咀嚼肌也有相应的肌电增强。②开闭口运动与咀嚼运动时患者组双侧咬肌、二腹肌、胸锁乳突肌肌电平均幅值的对称性明显差于正常咬合组；双侧斜方肌对称性在颈肩部运动时两组间差异显著。③正常咬合组三种运动时对应肌肌电幅值无显著性差异；患者组咀嚼运动时双侧二腹肌及颈肩部运动时双侧胸锁乳突肌、二腹肌肌电幅值有明显差异。结论 下颌偏斜影响咀嚼肌、颈肩背部肌肌电的对称性并可能导致头颈、双肩姿势的偏斜。     

Muscular equilibrium and orthognathic surgery. A preliminary electromyographic study

Few studies have been written about the effects of orthodontic preparation and of the consequences of surgical movements on mandibular motricity. The aim of this preliminary report is to evaluate the modifications of muscular activity between the pre-surgical phase and its evolution during the year after surgery, together with the skeletal modifications found. The muscular activity of six patients with serious vertical discrepancies requiring rehabilitation of the lower facial height has been studied using electromyographical recordings. A longitudinal study of the EMG data has been established in order to discover a muscular adaptation method towards physiological equilibrium following the realization of a new facial diagram. The reduction of the lower facial height obtained through a surgical procedure including a maxillary impaction, appears to indicate that, at rest, the masseter muscles activity tends to normalize, whereas that of the temporal muscles may sometimes increase. During maximal contraction, facial hyper-divergence reduction would lead to a sharp decrease in temporal and masseter muscular activity which would subsequently return to normal. The increase in vertical dimension would also cause significant changes in muscular tonus depending on the sagittal direction of the associated mandibular osteotomy. It would take longer to achieve muscular activity stability. These few results show: The existence of significant modifications following orthognathic surgery, possible reduction of high rest muscular activities, often revealing a cranio mandibular dysfunction, after vertical typology rehabilitation. The electromyographic recordings during treatment then enable to perfect the therapeutic re-evaluation of these major vertical discrepancies.     

Masticatory muscle function three years after surgical correction of class III dentofacial deformity

Individuals with dentofacial deformities have masticatory muscle changes. The objective of the present study was to determine the effect of interdisciplinary treatment in patients with dentofacial deformities regarding electromyographic activity (EMG) of masticatory muscles three years after surgical correction. Thirteen patients with class III dentofacial deformities were studied, considered as group P1 (before surgery) and group P3 (3 years to 3 years and 8 months after surgery). Fifteen individuals with no changes in facial morphology or dental occlusion were studied as controls. The participants underwent EMG examination of the temporal and masseter muscles during mastication and biting. Evaluation of the amplitude interval of EMG activity revealed a difference between P1 and P3 and no difference between P3 and the control group. In contrast, evaluation of root mean square revealed that, in general, P3 values were higher only when compared with P1 and differed from the control group. There was an improvement in the EMG activity of the masticatory muscles, mainly observed in the masseter muscle, with values close to those of the control group in one of the analyses.     

Facial palsy after inferior alveolar nerve block: case report and review of the literature

Bell's palsy is an idiopathic and acute, peripheral nerve palsy resulting in inability to control facial muscles on the affected side because of the involvement of the facial nerve. This study describes a case of Bell's palsy that developed after dental anaesthesia. A 34-year-old pregnant woman at 35 weeks of amenorrhea, with no history of systemic disease, was referred by her dentist for treatment of a mandibular left molar in pulpitis. An inferior alveolar nerve block was made prior to the access cavity preparation. 2 h later, the patient felt the onset of a complete paralysis of the left-sided facial muscles. The medical history, the physical examination and the complementary exams led neurologists to the diagnosis of Bell's palsy. The treatment and results of the 1-year follow-up are presented and discussed. Bell's palsy is a rare complication of maxillofacial surgery or dental procedures, the mechanisms of which remain uncertain.     

Perioral soft-tissue rejuvenation techniques to enhance esthetic restorative dentistry

Every practitioner has the obligation to offer his or her patients the latest advances in their profession. Dentistry has made a shift over the past 50 years from caries restoration and prosthetic replacement to preventative and esthetic rejuvenation. Related dental specialties have also blossomed with new procedures and an expanded scope of practice. This shift has also included more comprehensive care and treatment of the oral and maxillofacial region. Modern esthetic dentists realize the facial soft tissues serve as a frame for their restorative artwork. Contemporary oral and maxillofacial surgery includes cosmetic facial surgery. Procedures for such surgery are taught in oral and maxillofacial surgery residency programs, are part of the oral and maxillofacial surgery board exams, and are covered by oral and maxillofacial surgery malpractice companies. Esthetic dentists should understand facial aging, as well as the basic procedures available for facial rejuvenation by the oral and maxillofacial surgeon. Contemporary esthetic dentistry goes beyond the oral cavity, and the smile is truly enhanced by simultaneous facial rejuvenation. This article discusses the process of perioral facial aging and various cosmetic facial surgery options.     

Effects of facial nerve denervation on masseter muscle of the rats

The effects of unilateral facial nerve denervation on the facial growth were studied by physiological and by histochemical examinations, using four- week- old Wistar rats. Two hundred twenty rats were divided into three groups: a control group, a group of subjects which resection of the left facial nerve, and a sham operation group. The rats were killed 1, 5, 10, 30, 60, 90, 120 days later. The superficial and deep masseter muscle fibers on both sides were classified into type I and type IIA or IIB on the basis of myosin ATPase activity and the diameter of these fibers was measured. The masseter muscles were stained with H&E and NADH-TR. Electromyogram recordings were analyzed during the rest position, stretch reflex, voluntary action and eating of solid foods in half of all groups. (1) The face of rats after denervation deviated to the right side, and the maxillo-facial skeleton was affected from the 30th day. (2) In the denervation groups the right side showed higher action potentials than the left side. (3) In the deep masseter muscles near muscle spindle in the denervated groups, the percentage of type I fibers on the right side increased on the 90th day, and that of type IIA fibers decreased on the 30th day. (4) The diameter of the deep masseter muscle fibers, of type I, IIA and IIB increased on the right side. These results prove that facial nerve denervation led to a functional disorder and a transformation of growing direction.     

Development of an intraoral device for facial muscle retraining and its clinical application

The aim of this work was to develop a facial neuromuscular retraining technique for cases of facial palsy, involving an easy-to use intraoral device that allows correcting abnormal neuromuscular patterns and improving esthetics. Facial palsy is a motor alteration of multiple origin that results in facial asymmetry. Treatment remains controversial to date and includes, surgical anastomosis and decompressive and plastic surgery, corticosteroids therapy, injection of botulinum toxin, and administration of other medicinal drugs. Physical therapy involving electrical stimulation and feedback are also used to retrain facial muscles. A removable thermopolymerized acrylic intraoral device with wrought wire clasps was developed and constructed. The device was used on a patient with facial palsy who was instructed to wear it 4 times a day during 20 minutes and perform exercises in front of the mirror, trying to coordinate the action of the device with the smile movement on the unaffected side of the face. Digital photographs of the patient were taken during smile movement and at rest with and without the device, and movements of the oral commissures were compared using specific software. Results showed anatomic and nonanatomic indices of facial motion for the lower part of the face with the device to be 1.77 and 0 respectively. The device improved facial symmetry during rest by opposing traction forces of the contralateral muscles, resulting in a better position of the filtrum during rest, and allowed the patient to exercise smile movements at home.     

Neuromuscular adaptation of craniofacial muscles to altered oral sensation

Experimentally induced changes in oral sensation to the tongue altered the use of specific craniofacial muscles. An acrylic wedge was anchored to the maxillary teeth of ten adult rhesus monkeys, providing a tactile-pressure sensation to the dorsal surface of the tongue. Fifteen craniofacial and tongue muscles were studied by electromyography during the first 6 months of adaptation. The results showed that there was an overall shift in those muscles that were normally tonically active in the craniofacial region. Muscles of the suprahyoid region, the geniohyoid and digastric, as well as the platysma muscle of the face, and the lateral pterygoid muscle were tonically active in more animals after placement of the wedge. In contrast to the enhanced activity of mandibular and facial muscles that function during mandibular depression, only the anterior temporalis muscle in the superficial and deep region demonstrated more tonic activity. The superficial and deep masseter regions, as well as the medial pterygoid muscle, demonstrated no change in their EMG activity. Only the lip muscles and mentalis demonstrated increased activity, whereas the facial muscles with more vertically oriented fibers did not demonstrate any increased activity. These findings suggest that a change in the tactile stimulation to the tongue can induce a new balance in the level of activity of specific craniofacial muscles and that this altered neuromuscular pattern can remain throughout the first 6 months of adaptation.