Application of magnetic resonance imaging and ultrasonography to preoperative evaluation of masseteric hypertrophy

Clinical investigation of botulinum toxin (prabotulinumtoxin A) for bruxism related to masseter muscle hypertrophy: A prospective study

This study aims to confirm the effectiveness and safety of a prabotulinumtoxin type A (praBTX-A) injection in patients with bruxism and masseter hypertrophy. The study included patients who ground or clenched their teeth while sleeping and had computed tomography (CT) scans that showed a maximum thickness of the masseter muscle of 15 mm or more. The praBTX-A was administered bilaterally into the masseter muscles; 15 U/side for group 1, 25 U/side for group 2, and 35 U/side for group 3. CT scans and bruxism questionnaires were conducted before and eight weeks after the injection. Thirty-seven patients were enrolled, but three dropped out due to loss of follow-up. After injection, masseter thickness decreased to 15.1 ± 2.0 mm for group 1, 14.3 ± 2.9 mm for group 2, and 13.4 ± 1.8 mm for group 3 (p = 0.043). Group 3 showed a statistically significant lower masseter thickness compared to group 1 (p = 0.039). Both subjective and objective frequencies of bruxism decreased for all groups, but there were no significant differences in either subjective (p = 0.396) or objective frequencies (p = 0.87) between the groups after the injection. The results of this study suggest that praBTX-A injection is a safe and effective treatment for bruxism and masseter hypertrophy. A dosage of 35 IU/side can effectively decrease masseter thickness and relieve bruxism symptoms. Even the minimum dosage of 15 IU/side can contribute to improvements in bruxism symptoms. This investigation provides valuable information for managing bruxism that is associated with hypertrophic masseter muscles.

Application of botulinum toxin in maxillofacial field: part I. Bruxism and square jaw

The application of botulinum in oral and maxillofacial surgery begins in 1982, where Jan Carruthers started using it for reducing the muscle mass and smoothing the skin, and since then it has been used for cosmetic purposes. In Korea, it is already being used by various specialties including dentistry (oral and maxillofacial surgery, oral medicine), plastic surgery, dermatology, ophthalmology, general surgery, and orthopedic surgery, etc. Each specialty approaches to Botox with its own medical indications. In this article, we will discuss the maxillofacial application of botulinum toxin, which includes theoretical and practical aspects of such as bruxism and square jaw.

Three-dimensional vector analysis of mandibular structural asymmetry

OBJECTIVES

The three-dimensional (3D) asymmetric structure of the mandible makes it necessary to analyze both its size and angle. Currently the developing 3D analysis techniques are not able to perform the simultaneous linear and angular measurements. Our aim was to evaluate mandibular asymmetry using a vector-based system by constructing 3D vectors for the mandibular functional units.

MATERIAL AND METHODS

We analyzed the 3D computed tomography images of normal control (N = 27) and asymmetric mandibles (N = 40). We created 3D vectors for the condylar, coronoid, body, gonial, and symphyseal functional units and compared the corresponding pairs of 3D vectors by calculating vector operations.

RESULTS

The vector difference and other vector components represented the individual 3D architectural pattern and severity of the asymmetric mandible. The body unit contributed most to mandibular asymmetry followed by the condylar unit.

CONCLUSIONS

The results indicate that 3D vector analysis can improve our understanding of the 3D architecture of asymmetric mandibles. This type of 3D vector analysis can be a useful tool for the comprehensive evaluation of its asymmetric mandibular structure.

The use of ultrasound in the investigation of the muscles of mastication

The aim of this article was to review the literature concerning ultrasonography imaging (US) of the muscles of mastication and to discuss its use, advantages and disadvantages and the findings of the authors. A web search was performed using the terms "ultrasound" and "muscles". US has been shown to be a reliable method of great utility in the field of diagnosis of alterations in the muscles of mastication and for the study of changes during growth and aging. It should be preferred in comparison to computerized axial tomography (CT) and magnetic resonance imaging (MRI) because of its safety and cost advantages since it is as reliable and precise as these other techniques. Although various techniques have been used in ultrasonographic scanning, this article discusses those techniques most commonly adopted by the authors.

Ultrasound-guided drainage of submasseteric space abscesses

PURPOSE

The oral approach for incision and drainage (I and D) in patients presenting with submasseteric space (SMS) abscesses and marked trismus is more difficult and requires a general anesthetic, necessitating an anesthetist experienced in fiberoptic-guided nasal intubation. In such patients, ultrasound-guided drainage (USGD) has been attempted to obviate this need. The purpose of this trial was to report our experience with the surgical management of 11 SMS abscesses, with special reference to their USGD.

MATERIALS AND METHODS

Seven men and 4 women ranging in age from 18 to 41 years (average age, 25 years) participated in this trial. They were initially examined with US, and their abscesses were subsequently drained under US guidance using a 16-gauge intravenous catheter. An antibiotic regimen was prescribed, and arrangements were made to see the patients daily for 5 days. USGD was repeated after 24 hours, and 24 hours later the infection course was monitored in each patient. Patients with nonresolving infection had their abscesses formally incised and drained extraorally. The source of infection was removed as soon as the acute phase of infection passed and the interincisal opening (IIO) allowed. The catheter or corrugated drain was removed when the discharge ceased or became minimal. Patients were then instructed to continue a 3-day course of an antibiotic and to return after 1 week and then after 1 month.

RESULTS

Resolution of infection was successfully achieved by USGD with no need for I and D in 8 of the 11 patients (73%). In those patients, the average total amount of pus removed was 8.5 mL, and the average IIO was 17.4 mm immediately after an average initial aspirate of 4.5 mL of pus. I and D was required in the remaining 3 patients (27%). In those patients the average total amount of pus removed was 17.5 mL, and the average IIO was 7.7 mm immediately after an average initial aspirate of 9.3 mL of pus.

CONCLUSIONS

Resolution of infection with USGD is more probable if there was an immediate improvement of the IIO to about 1.5 cm or more after an initial aspiration of 5 mL of pus.

Magnetic resonance imaging in the diagnosis of asymmetrical bilateral masseteric hypertrophy

Asymmetrical bilateral masseteric hypertrophy or unilateral masseteric hypertrophy may present a diagnostic dilemma. While the history and clinical examination are important in differentiating this benign condition from parotid and dental pathology, they cannot necessarily exclude rarer malignant lesions of or within the muscle itself. We present a case where MRI provided clear and elegant confirmation of our provisional clinical diagnosis by illustrating both the soft tissue features and the logical corresponding bony features of this condition, thus obviating the need for further invasive investigations.

Isolated unilateral temporalis muscle hypertrophy. A case report

A case of isolated unilateral temporalis muscle hypertrophy is presented. A review of the literature revealed only one report of temporalis hypertrophy, probably caused by psychogenic muscle hyperactivity. The temporalis muscle hypertrophy in the patient described was idiopathic and its management was surgical.

Diagnosing protracted submasseteric abscess: the role of computed tomography

Because of its anatomical location, the submasseteric abscess mimics a parotitis. This is particularly true when the usual dental source of the infection is not present. A thorough medical history and clinical examination as well as computed tomography are important tools in the differential diagnosis.

Ultrasonographic evaluation of inflammatory changes in the masseter muscle

The ultrasonographic images of 32 patients with inflammatory change in the masseteric region were investigated to clarify the characteristic findings and to evaluate the utility of ultrasonography. Inflamed masseter muscles frequently demonstrated reduction of echo intensity and complete or partial absence of hyperechoic bands. The mean thickness of the masseter muscle on the unaffected side was 8.6 mm, whereas that on the affected side was 12.9 mm. Nine of 10 patients with heterogeneous hypoechoic area, but only 1 of 10 patients with homogeneous hypoechoic area, had received surgical treatment before ultrasonographic examination.

Quantitative analysis of masticatory muscles using computed tomography

Quantitative information on the normal size range of the masticatory muscles needed for successful treatment of facial asymmetry is sparse. Our purpose in this study was to define morphological indicators for the volume of the masticatory muscles on CT. Cross-sectional areas and volumes of the masseter and medial pterygoid muscles were measured from CT scans of 65 patients. The muscles were scanned from origin to insertion and the maximum cross-sectional area (MCSA) and its location together with the total volume were determined. The mandibular foramen was used as a landmark to determine the location of MCSA. The location of MCSA of masseter muscle was centred 8 mm above the mandibular foramen, and that of medial pterygoid muscle at the foramen. The MCSA of both muscles was highly correlated with volume suggesting that this parameter might serve as an indicator of their volume. Knowledge of the location of the MCSA would facilitate its measurement and so reduce radiation exposure. There was a positive correlation between the two muscles for both volume and MCSA. This finding could be relevant for future studies of the relationship between the morphology, biomechanics and pathology of the masticatory muscles.