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At least 19 recordsLinked to original sources
PubMed1987

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.

Adult↗
PubMed1997

Muscle activity during mandibular movements in normal and mandibular retrognathic subjects.

PURPOSE: The masticatory muscles function as a unit during precise mandibular positioning movements that occur during such activities as speech, singing, or playing musical instruments. This investigation was designed to assess jaw muscle recruitment patterns during controlled mandibular movement in normal subjects and in patients with mandibular retrognathism. PATIENTS AND METHODS: A computer-integrated electromyography (EMG) and movement monitoring (Selspot) system was used to collect data over 7 seconds of a sagittal border movement (Posselt envelope) of the mandible and 4 seconds each of rest position, light tooth contact, and maximum clench. Fine wire bipolar electrodes were placed into the inferior belly of the lateral pterygoid muscles bilaterally and surface electrodes were placed bilaterally over the anterior belly of the temporalis muscles and the masseter muscles. Ten subjects with Class I occlusion, normal cephalometric values, and an absence of temporomandibular joint (TMJ) dysfunction were compared with 12 patients with mandibular retrognathism, Class II malocclusion, and an absence of clinical signs of TMJ internal derangement before and after a bilateral sagittal split and advancement of the mandible. RESULTS: There was a wide variation in standard deviations of EMG activity for the lateral pterygoid muscles in the retrognathic patients compared with normal controls before surgery (P < .05). In light tooth contact, temporalis muscle activity increased after surgery with respect to both control and the presurgical levels (P < .05, P < .005, respectively). In maximum clench, activity in all muscle groups in the retrognathic patients, both before and after surgery, were below that of control subjects (P < .005). The lateral pterygoid muscles showed late recruitment, with low EMG activity levels during the forward movement phase of the envelope, before surgery compared with controls (P < .001). After surgery, the lateral pterygoid muscle showed early recruitment in the forward movement similar to control levels. CONCLUSION: The masticatory muscles function as a unit during mandibular positioning movements. Patients with mandibular retrognathism have different muscle recruitment patterns from those of normal subjects with the mandible at rest and during mandibular movement. After orthognathic surgery, adaptation occurs in the phasic timing of jaw muscle activity.

Adaptation, Physiological↗
PubMed2006

Herbst treatment of Class II division 1 malocclusions in retrognathic and prognathic facial types.

OBJECTIVE: The aim of this retrospective pilot study was to analyze and compare the short-term and long-term changes of Herbst treatment in Class II division 1 subjects of the retrognathic and prognathic facial type. MATERIALS AND METHODS: The subject material comprised 10 retrognathic (mean SNA = 74.5 degrees, SNB = 70.4 degrees, ML/NSL = 41.1 degrees) and 16 prognathic (mean SNA = 86.7 degrees, SNB = 81.5 degrees, ML/NSL = 25.1 degrees) Class II division 1 subjects treated with the Herbst appliance for an average period of 7 months. Lateral head films from before (T1), immediately after (T2), 12 months after (T3), and 39 months after (T4) Herbst treatment were analyzed with the SO-analysis (analysis of changes in sagittal occlusion) and standard cephalometrics. RESULTS: During the treatment period (T2-T1) the two facial type groups showed similar favorable changes for all variables. During the posttreatment periods of 12 months (T3-T2) and 39 months (T4-T2) recovering changes occurred. In the long-term, a tendency of more unfavorable growth changes was stronger (not significant) for retrognathic subjects than for prognathic subjects. CONCLUSION: On a long-term basis, retrognathic subjects are prone to exhibit more unfavorable mandibular growth changes than prognathic subjects and, thus, might exhibit a greater risk for an occlusal relapse when a stable Class I occlusion is not attained after treatment.

Adolescent↗
PubMed2004

Masticatory function in retrognathic patients, before and after mandibular advancement surgery.

PURPOSE: Mandibular retrognathia is a dentofacial deformity that can be surgically corrected. The purpose of this study was to evaluate the influence of orthognathic surgery on masticatory function in a sample of retrognathic patients and to compare these findings with those of controls. PATIENTS AND METHODS: Eleven retrognathic patients were tested before and 1 to 1.5 years after mandibular advancement surgery and compared with 12 controls. The median particle size after chewing a silicon rubber test food, the maximum bite force, and the electromyographic activity (EMG) of the anterior temporalis and the masseter muscles during isometric clenching and during chewing were determined. Patients, before and after treatment, and controls were statistically compared by analysis of variance. RESULTS: Surgical correction of mandibular retrognathia did not change chewing efficiency, maximum bite force, EMG during maximal clenching, EMG during chewing, or the EMG/bite-force relationship. Compared with controls, the chewing efficiency, maximum bite force, EMG during maximal clenching, and EMG during chewing values were lower. No difference for the EMG/bite-force ratio at maximal clenching was found, indicating similar muscle efficiency for patients and controls. However, in the range of 10% to 40% of the maximum bite force, the slope of the EMG/bite-force regression line was steeper for the patients than for the controls, indicating decreased muscle efficiency for patients. CONCLUSIONS: The results of this study suggest that in retrognathic patients, function of the masticatory system is impaired. Oral function was not influenced by mandibular advancement surgery.

Adult↗
PubMed2006

The influence of mandibular advancement surgery on oral function in retrognathic patients: a 5-year follow-up study.

PURPOSE: Previous studies have shown that patients with mandibular retrognathism who were scheduled for orthognathic surgery have a lower maximum bite force and an impaired chewing performance. Surgical correction of this deformity is supposed to lead to an improvement of these oral functions. One year after surgery, no significant changes could be shown in these patients. However, a longer follow-up might demonstrate an improvement after all. PATIENTS AND METHODS: Maximum bite force and chewing performance were determined in 12 patients with a mandibular retrognathism before mandibular advancement surgery and at least 5 years after surgery. Chewing performance (median particle size) was determined with a sieving method after chewing 15 strokes on an artificial test food. Maximum bite force was recorded bilaterally at the level of the first molars. RESULTS: Five years after surgery, chewing performance was improved, especially in patients with a poor performance before treatment. An increase of the maximum bite force could not be shown. CONCLUSION: Surgical correction of mandibular retrognathism had a positive effect on oral function 5 years after surgery, although it could not be detected 1 year after surgery. However, the function of the masticatory system was still impaired when compared with controls.

Adult↗
PubMed1977

Severe mandibular retrognathism: orthodontic versus surgical orthodontic treatment.

1. Treatment of Class II, Division 1 malocclusions should be accomplished by normalization of the abnormal structures that are identified diagnostically. 2. In the presence of mandibular retrognathism and unfavorable growth potential (limited amount, undesirable direction), surgical mandibular lengthening should be incorporated into the treatment plan. 3. Compensation for mandibular retrognathism by conventional orthodontic and facial orthopedic treatment incurs the risk of (a) increase in nasolabial angle, (b) reduction in upper lip support, (c) increase in lower facial concavity, (d) excessive proclination of lower incisors with compromise of labial periodontal support, and (e) protracted duration of appliance therapy and accompanying detrimental periodontal and root resorption effects.

Adolescent↗
PubMed1975

Vertical osteotomy of the ascending rami in mandibular retrognathism.

The authors present their experience and conclusions regarding surgical lengthening of the mandible in retrognathism due to bone hypo-development. Thus, in hypotrophies of the ascending ramus, especially in temporo-mandibular ankylosis, they use a longitudinal osteotomy (Popescu 1949); various technical adaptations of this method, in different situations, are described, as well as their association with osteoplasty, utilizing iliac bone grafts or the hypertrophic chin prominence. In retrognathism due to hypo-development of the mandible, when the ascending rami have a good conformation, sagittal osteotomy (Obwegeser 1957, Dal Pont 1961) is preferred.

Ankylosis↗
PubMed1976

A variation in the vertical osteotomy of the rami for correction of retrognathism: preliminary report.

A new method for the surgical correction of mandibular retrognathism is proposed. With this method, the ascending ramus is osteotomized vertically from an extra-oral incision. The condylar segment is then inserted in a step, which has been cut in the mandibular segment, so that the mandible is fixed in its new advanced position. This step-like support of the segments obviates the tendency to relapse. This surgical procedure is a modification of the technique for vertical osteotomy of the ascending ramus described by Robinson (1957) for the correction of retrognathism.

Humans↗
PubMed2005

Effects of camouflage treatment on dentofacial structures in Class II division 1 mandibular retrognathic patients.

The aims of this study were to determine the changes in the dentofacial structures of Class II division 1 mandibular retrognathic patients treated with bilateral extraction of the upper first premolars, and to compare pre- and post-treatment values with the cephalometric norms of Anatolian Turkish adults. The Class II division 1 subjects included 20 males and 33 females (mean age: 17.08 +/- 1.03 years). All received comprehensive orthodontic treatment using an edgewise appliance and appropriate headgear. Lateral cephalograms were taken at the beginning and end of treatment. Twenty-five (14 linear and 11 angular) measurements were analysed on each radiograph. Each cephalogram was traced and digitized. For statistical evaluation, paired and independent-samples t-tests were performed. When the pre- and post-treatment measurements were compared, statistically significant differences were found for nine of 25 measurements. During treatment the facial axis, U1-SN ( degrees ), U1-NA (mm), U1-NA ( degrees ), H angle and upper lip to E plane measurements decreased, while N-ANS, interincisal angle and upper lip to Steiner S line increased. No statistically significant gender differences were found. Significant improvements were determined in ANS-Me and L1-APo measurements compared with Turkish norms. However, statistically significant deterioration was found in values related to point A, upper incisor and lower lip measurements. The findings demonstrates that camouflage treatment in Class II, mandibular retrognathic subjects has characteristic skeletal, dental and soft tissue effects on the dentofacial complex.

Adolescent↗
PubMed2000

Harmonization of free mandibular movements by orthodontic-surgical treatment of patients with mandibular retrognathism.

The aim of the following study was to investigate whether adult patients with mandibular retrognathism combined with a dental Class II relationship without craniomandibular pain show a characteristic structure of free mandibular movements caused by the neuromuscular system compared to patients with neutral skeletal and dental relationships. The authors also analyzed whether these characteristic structures changed following orthodontic-surgical treatment. To record the spatial movement of the mandible, an ultrasound measurement system was chosen and diagnostic software was developed for computer analysis of the recorded movements based on physical and biomechanical concepts. Clinically complaint-free, adult patients with mandibular retrognathism and distal bite exhibited a structure of mandibular movement that was markedly displaced as compared to patients with neutral skeletal and dental alignment. After completion of orthodontic and surgical treatment, it is apparent that the entire neuromuscular system of movement was transformed from one characterized by massive dysco-ordination to one of harmonized, coordinated motion, as is seen in patients with nonpathologic, neutral relation.

Adolescent↗
PubMed1982

Surgical advancement of the retrognathic mandible in growing children.

Orthodontists and surgeons may occasionally decide that there are compelling reasons for correcting a retrognathic mandible surgically before facial growth is completed. The literature implies that there will be no untoward effects. This study on twenty-two growing children demonstrated that there are severe growth disturbances after surgery. The response varied with the amount of surgical correction: Type A cases (those advanced more than 10 mm.) showed either resorption of the condyle, bizarre bony outgrowths in the posterior symphysis, or both. Relapse may continue in these cases for several years. Once condylar resorption occurred, there was no recovery. Type B cases (those advanced less than 9 mm.) had a milder response. Even in Type B cases, however, there was no clinically significant increase in mandibular length subsequent to surgery. There is a one-year recovery period, after which further growth and remodeling of the condyle are directed (if our hypothesis is correct) towards achieving an equilibrium of forces and a return to the preoperative growth pattern. We found that movement of the Y point (intersection of the posterior surface of the symphysis with the inferior border of the mandible) reflected a stable growth pattern prior to surgery and returned to the same pattern, usually within 2 years after surgery.

Adolescent↗
PubMed1976

The retrognathic mandible--surgical correction.

The preceding case reports demonstrate the excellent results available to the patient with a retrognathic mandible. Etiology, adverse effects, and the modalities used in evaluation of the underdeveloped mandible have been discussed. The age at which surgical intervention is undertaken needs additional input by clinicians. Several surgical procedures have been and are employed to advance the mandible. The C osteotomy is recommended since the final result has been excellent and consistent. The surgeon has constant surgical control and vision. The advanced portion of the mandible can be firmly held by intraosseous wires. There is minimak disturbance of muscle position and the inferior alveolar nerve. We have not encountered unusual loss of blood, immediate postoperative problems with the airway, infection, or unfavorable relapse. A postoperative regimen that has been found rewarding is discussed. We have come to the conclusion that most patients can tolerate lengthy surgical procedures with few adverse side effects. Our colleagues in anesthesia and nursing provide superb operative and postoperative care. When the preoperative work-up indicates that more than one procedure is indicated, we recommend that the total surgical treatment plan be carried through at one operation, although occasionally this approach may be contraindicated. We should strive for perfection and can fall short of this goal when a patient will not return for additional surgical procedures which could have been accomplished during the first operation. Although good results have been experienced with both the C osteotomy and the sagittal split osteotomy, we believe that the C osteotomy is a superior procedure. However, this does not imply that the sagittal split osteotomy should not be a part of the armamentarium of the oral surgeon. In conclusion, the C osteotomy, the sagittal split osteotomy, genioplasty, and additional procedures--such as a mandibular alveolar osteotomy to intrude supraerupted teeth--when indicated, can provide very favorable results in cases of retrognathia or micrognathia of the mandible.

Adolescent↗
PubMed1995

Functional characteristics of retrognathic patients before and after mandibular advancement surgery.

PURPOSE: The purpose of this investigation was to compare morphologic parameters and functional performance between controls and a sample of patients with mandibular retrognathia prior to surgical correction, and to examine how oral motor function adapts after treatment. PATIENTS AND METHODS: Twenty-four retrognathic female patients were compared with 26 female controls before and up to 3 years after mandibular advancement surgery. Measures of skeletal morphology, mandibular range of motion, maximum isometric bite force, and levels of electromyographic activity in the anterior and posterior temporalis and masseter muscles during isometric bites were made on all subjects over time. One-way analysis of variance was used to compare the controls, the patients before surgery, and the patients after surgery. RESULTS: Surgical lengthening of the mandible averaged 7.3 mm, bringing most skeletal measures into the normal range. There were no significant differences in jaw muscle mechanical advantage between patients and controls before surgery, but surgery significantly reduced mechanical advantage of the anterior temporalis and masseter muscles. Jaw hypomobility was apparent at 6 weeks after surgery, but returned to normal values within 12 to 24 months. Before surgery the patients had maximum isometric bite forces less than half those of controls. Bite forces steadily increased after surgery, approaching normal values within 2 years. Before surgery the patients' muscle activity levels per unit of bite force were equivalent to those of controls or somewhat higher. After surgery some of the patients' muscles had significantly lower levels of muscle activity per unit of bite force than did controls. CONCLUSION: The results of this study suggest that correction of mandibular retrognathia by mandibular advancement surgery produces some significant functional benefits.

Adolescent↗
PubMed2004

Effects of food processing on masticatory strain and craniofacial growth in a retrognathic face.

Changes in the technology of food preparation over the last few thousand years (especially cooking, softening, and grinding) are hypothesized to have contributed to smaller facial size in humans because of less growth in response to strains generated by chewing softer, more processed food. While there is considerable comparative evidence to support this idea, most experimental tests of this hypothesis have been on non-human primates or other very prognathic mammals (rodents, swine) raised on hard versus very soft (nearly liquid) diets. Here, we examine facial growth and in vivo strains generated in response to raw/dried foods versus cooked foods in a retrognathic mammal, the rock hyrax (Procavia capensis). The results indicate that the hyrax cranium resembles the non-human primate cranium in having a steep gradient of strains from the occlusal to orbital regions, but differs from most non-anthropoids in being primarily twisted; the hyrax mandible is bent both vertically and laterally. In general, higher strains, as much as two-fold at some sites, are generated by masticating raw versus cooked food. Hyraxes raised on cooked food had significantly less growth (approximately 10%) in the ventral (inferior) and posterior portions of the face, where strains are highest, resembling many of the differences evident between humans raised on highly processed versus less processed diets. The results support the hypothesis that food processing techniques have led to decreased facial growth in the mandibular and maxillary arches in recent human populations.

Adaptation, Physiological↗
PubMed2006

Thin-plate spline analysis of the effects of face mask treatment in children with maxillary retrognathism.

BACKGROUND: Face mask therapy is indicated for growing patients who suffer from maxillary retrognathia. Most previous studies used conventional cephalometric analysis to evaluate the effects of face mask treatment. Cephalometric analysis has been shown to be insufficient for complex craniofacial configurations. The purpose of this study was to investigate changes in the craniofacial structure of children with maxillary retrognathism following face mask treatment by means of thin-plate spline analysis. METHODS: Thirty children with skeletal Class III malocclusions who had been treated with face masks were compared with a group of 30 untreated gender-matched, age-matched, observation period-matched, and craniofacial configuration-matched subjects. Average geometries, scaled to an equivalent size, were generated by means of Procrustes analysis. Thin-plate spline analysis was then performed for localization of the shape changes. RESULTS: Face mask treatment induced a forward displacement of the maxilla, a counterclockwise rotation of the palatal plane, a horizontal compression of the anterior border of the symphysis and the condylar region, and a downward deformation of the menton. The cranial base exhibited a counterclockwise deformation as a whole. CONCLUSION: We conclude that thin-plate spline analysis is a valuable supplement to conventional cephalometric analysis.

Case-Control Studies↗
PubMed2005

The influence of orthognathic surgery on masticatory performance in retrognathic patients.

Surgical correction of retrognathism may influence chewing performance and its underlying mechanisms selection and breakage of food particles. In this study we examined the hypothesis that treatment of this anomaly improves chewing performance. Furthermore, we determined to what extent this change can be attributed to selection and breakage of food particles. Eleven patients were tested before and 1-1.5 years after surgery. To determine chewing performance, eight cubes of 8 mm of a silicone rubber (Optosil) were used as a test food. Selection and breakage were determined in one-chew experiments using three particle sizes. On average, no differences were found for chewing performance, selection or breakage. However, on an individual basis, patients with a poor chewing performance before surgery tended to improve, whereas no improvement was observed for patients with a good chewing performance. The change in chewing performance was mainly due to a change in breakage of the food particles.

Adult↗
PubMed1997

[Orthodontic treatment for the surgical correction of mandibular skeletal retrognathism].

The purpose of this paper is to discuss the combining orthodontic treatment that is based on seventeen consecutive patients of severe mandibular skeletal retrognathism who have been treated by orthognathic surgery. Not only the presurgical preparation, but also the presurgical and postsurgical orthodontic treatment and the use of interocclusal splints were introduced. The goals of orthodontic treatment for patients with orthognathic surgery are (1) decompensating the teeth, expanding the upper dental arch, (2) aligning the teeth, (3) leveling the curve of Spee, (4) making the shape and width of upper and lower dental arch harmonious, (5) getting the occlusal equilibrium and fine occlusal contact. The author's experience indicates that: in order to get satisfactory results of esthetics and function, the combination of surgical and orthodontic treatment, the presurgical and postsurgical orthodontic treatment is absolutely necessary and important.

Adolescent↗
PubMed2002

Airway management of the severely retrognathic child: use of the laryngeal mask airway.

Successful airway management of an infant or child with moderate to severe retrognathia first requires recognition of a potential problem. If the child cannot be intubated in a standard fashion, the use of a laryngeal mask airway (LMA) should be considered. We describe two cases wherein a toddler and an infant with severe retrognathia failed multiple attempts at traditional intubation. Both had an anterior larynx and hypoplasia of the mandible. In both cases, a subsequent LMA was successfully placed. The severely retrognathic newborn or child presents to the physician a unique challenge in airway management. Techniques to manage this difficult pediatric airway are different from those used in the adult. Otolaryngologists should be aware of this intubation technique and include it in their armamentarium of airway-management strategies. The LMA is not recommended as the technique of choice for securing a difficult airway, but it is an effective alternative when indicated, and it might be life-saving.

Airway Obstruction↗