Kyung Seok Hu

Relationships between Dental Roots and Surrounding Tissues for Orthodontic Miniscrew Installation

OBJECTIVEnTo elucidate relationships between the dental roots and surrounding tissues in order to prevent complications after placement of a miniscrew.nnnMATERIALS AND METHODSnTwenty human mandibles and maxillas were used for this study. In the 200 sections of each mandible and maxilla, nine items were measured to investigate the relationships between the dental roots.nnnRESULTSnThe interroot distance increased from anterior to posterior teeth and from the cervical line to the root apex in both the maxilla and the mandible. In the maxilla, the greatest interroot distance was between the second premolar and the first molar. In the mandible, the greatest interroot distance was between the first and second molars. The maxillary buccolingual bone width exceeded 10 mm from 7 mm (between canine and first premolar), 5 mm (between second premolar and first molar), and 4 mm (between first and second molars) above the cervical line. The mandibular buccolingual bone width exceeded 10 mm from 7 mm (between second premolar and first molar) and 4 mm (between first and second molars) below the cervical line.nnnCONCLUSIONSnThe safest zone for placement of a miniscrew in the maxilla was between the second premolar and the first molar, from 6 to 8 mm from the cervical line. The safest zone for placement of a miniscrew in the mandible was between the first and second molars, less than 5 mm from the cervical line.

Anatomical considerations regarding the location and boundary of the depressor anguli oris muscle with reference to botulinum toxin injection.

Background: Hyperactivity of the depressor anguli oris muscle can lead to a drooping of the mouth corner, which can give a sad, tired, or almost angry look in some patients. Botulinum toxin type A has recently been used to relax these hyperactive muscles. However, it is difficult to inject botulinum toxin type A into the depressor anguli oris muscle because its medial border overlaps with the depressor labii inferioris, and its lateral border is adjacent to the risorius, zygomaticus major, and platysma muscles. The aims of this study were to determine the topography of the facial muscles at the mouth corner and to provide critical information for determining the safest and most effective depressor anguli oris muscle botulinum toxin type A injection site. Methods: Forty-two hemifaces from Korean and Thai adult cadavers were dissected. Results: The location of the modiolus was 11.0 ± 2.6 mm (mean ± SD) lateral and 8.9 ± 2.8 mm inferior to the cheilion. The angle formed by the sagittal line passing through the modiolus (LV) and the line connecting the modiolus and the intersection point of the lateral border of the depressor anguli oris muscle and the mandibular border (LP2) was 44.7 ± 13.7 degrees. The angle formed by LV and the line connecting the modiolus and the most concave point of the medial border of the depressor anguli oris muscle (LP3) was 31.8 ± 8.5 degrees. Conclusion: These results suggest that the fan-shaped area bounded by LP2, LP3, and the mandibular border is the safest and most effective depressor anguli oris muscle injection site.

Clinical and anatomical approach using Sihler's staining technique (whole mount nerve stain)

Sihlers staining allows visualization of the nerve distribution within soft tissues without extensive dissection and does not require slide preparation, unlike traditional approaches. This technique can be applied to the mucosa, muscle, and organs that contain myelinated nerve fibers. In particular, Sihlers technique may be considered the best tool for observing nerve distribution within skeletal muscles. The intramuscular distribution pattern of nerves is difficult to observe through manual manipulation due to the gradual tapering of nerves toward the terminal end of muscles, so it should be accompanied by histological studies to establish the finer branches therein. This method provides useful information not only for anatomists but also for physiologists and clinicians. Advanced knowledge of the nerve distribution patterns will be useful for developing guidelines for clinicians who perform operations such as muscle resection, tendon transplantation, and botulinum toxin injection. Furthermore, it is a useful technique to develop neurosurgical techniques and perform electrophysiological experiments. In this review, Sihlers staining technique is described in detail, covering its history, staining protocol, advantages, disadvantages, and possible applications. The application of this technique for determining the arterial distribution pattern is also described additionally in this study.

Intramuscular nerve distribution pattern of ankle invertor muscles in human cadaver using sihler stain

Introduction: We sought to the ideal sites for botulinum toxin injection by examining the intramuscular nerve patterns of the ankle invertors. Methods: A modified Sihler method was performed on the flexor hallucis longus, tibialis posterior, and flexor digitorum longus muscles (10 specimens each). The muscle origins, nerve entry points, and intramuscular arborization areas were measured as a percentage of the total distance from the most prominent point of the lateral malleolus (0%) to the fibular head (100%). Results: Intramuscular arborization patterns were observed at 20–50% for the flexor hallucis longus, 70–80% for the tibialis posterior, and 30–40% for the flexor digitorum longus. Conclusions: These findings suggest that treatment of muscle spasticity of the ankle invertors involves botulinum toxin injections in specific areas. These areas, corresponding to the areas of maximum arborization, are recommended as the most effective and safest points for injection. Muscle Nerve 53: 742–747, 2016

Neurovascular structures of the mandibular angle and condyle: a comprehensive anatomical review

BackgroundVarious surgical interventions including esthetic surgery, salivary gland excision, and open reduction of fracture have been performed in the area around the mandibular angle and condyle. This study aimed to comprehensively review the anatomy of the neurovascular structures on the angle and condyle with recent anatomic and clinical research.Methods and resultsWe provide detailed information about the branching and distributing patterns of the neurovascular structures at the mandibular angle and condyle, with reported data of measurements and proportions from previous anatomical and clinical research. Our report should serve to help practitioners gain a better understanding of the area in order or reduce potential complications during local procedures. Reckless manipulation during mandibular angle reduction could mutilate arterial branches, not only from the facial artery, but also from the external carotid artery. The transverse facial artery and superficial temporal artery could be damaged during approach and incision in the condylar area. The marginal mandibular branch of the facial nerve can be easily damaged during submandibular gland excision or facial rejuvenation treatment. The main trunk of the facial nerve and its upper and lower distinct divisions have been damaged during parotidectomy, rhytidectomy, and open reductions of condylar fractures.ConclusionBy revisiting the information in the present study, surgeons will be able to more accurately prevent procedure-related complications, such as iatrogenic vascular accidents on the mandibular angle and condyle, complete and partial facial palsy, gustatory sweating (Frey syndrome), and traumatic neuroma after parotidectomy.

Regulation of root patterns in mammalian teeth

Mammalian teeth have diverse pattern of the crown and root. The patterning mechanism of the root position and number is relatively unknown compared to that of the crown. The root number does not always match to the cusp number, which has prevented the complete understanding of root patterning. In the present study, to elucidate the mechanism of root pattern formation, we examined (1) the pattern of cervical tongues, which are tongue-like epithelial processes extending from cervical loops, (2) factors influencing the cervical tongue pattern and (3) the relationship among patterns of cusp, cervical tongue and root in multi-rooted teeth. We found a simple mechanism of cervical tongue formation in which the lateral growth of dental mesenchyme in the cuspal region pushes the cervical loop outward, and the cervical tongue appears in the intercuspal region subsequently. In contrast, when lateral growth was physically inhibited, cervical tongue formation was suppressed. Furthermore, by building simple formulas to predict the maximum number of cervical tongues and roots based on the cusp pattern, we demonstrated a positive relationship among cusp, cervical tongue and root numbers. These results suggest that the cusp pattern and the lateral growth of cusps are important in the regulation of the root pattern.

Anatomical recommendations for safe botulinum toxin injection into temporalis muscle: a simplified reproducible approach

PurposeThe objective of this study was to simplify the anatomically safe and reproducible approach for BoNT injection and to generate a detailed topographic map of the important anatomical structures of the temporal region by dividing the temporalis into nine equally sized compartments.MethodsNineteen sides of temporalis muscle were used. The topographies of the superficial temporal artery, middle temporal vein, temporalis tendon, and the temporalis muscle were evaluated. Also evaluated was the postural relations among the foregoing anatomical structures in the temporalis muscle, pivoted upon a total of nine compartments.ResultsThe temporalis above the zygomatic arch exhibited an oblique quadrangular shape with rounded upper right and left corners. The distance between the anterior and posterior margins of the temporalis muscle was equal to the width of the temporalis rectangle, and the distance between the reference line and the superior temporalis margin was equal to its height. The mean ratio of width to height was 5:4.ConclusionsWe recommend compartments Am, Mu, and Pm (coordinates of the rectangular outline) as areas in the temporal region for BoNT injection, because using these sites will avoid large blood vessels and tendons, thus improving the safety and reproducibility of the injection.

Effective Botulinum Toxin Injection Guide for Treatment of Temporal Headache

This study involved an extensive analysis of published research on the morphology of the temporalis muscle in order to provide an anatomical guideline on how to distinguish the temporalis muscle and temporalis tendon by observing the surface of the patient’s face. Twenty-one hemifaces of cadavers were used in this study. The temporalis muscles were dissected clearly for morphological analysis between the temporalis muscle and tendon. The posterior border of the temporalis tendon was classified into three types: in Type I the posterior border of the temporalis tendon is located in front of reference line L2 (4.8%, 1/21), in Type II it is located between reference lines L2 and L3 (85.7%, 18/21), and in Type III it is located between reference lines L3 and L4 (9.5%, 2/21). The vertical distances between the horizontal line passing through the jugale (LH) and the temporalis tendon along each of reference lines L0, L1, L2, L3, and L4 were 29.7 ± 6.8 mm, 45.0 ± 8.8 mm, 37.7 ± 11.1 mm, 42.5 ± 7.5 mm, and 32.1 ± 0.4 mm, respectively. BoNT-A should be injected into the temporalis muscle at least 45 mm vertically above the zygomatic arch. This will ensure that the muscle region is targeted and so produce the greatest clinical effect with the minimum concentration of BoNT-A.

The anatomical basis of paradoxical masseteric bulging after botulinum neurotoxin type A injection

The aim of this study was to determine the detailed anatomical structures of the superficial part of the masseter and to elucidate the boundaries and locations of the deep tendon structure within the superficial part of the masseter. Forty-four hemifaces from Korean and Thai embalmed cadavers were used in this study. The deep tendon structure was located deep in the lower third of the superficial part of the masseter. It was observed in all specimens and was designated as a deep inferior tendon (DIT). The relationship between the masseter and DIT could be classified into three types according to the coverage pattern: Type A, in which areas IV and V were covered by the DIT (27%, 12/44); Type B, in which areas V and VI were covered by the DIT (23%, 10/44); and Type C, in which areas IV, V, and VI were covered by the DIT (50%, 22/44). The superficial part of the masseter consists of not only the muscle belly but also the deep tendon structure. Based on the results obtained in this morphological study, we recommend performing layer-by-layer retrograde injections into the superficial and deep muscle bellies of the masseter.

Topographic Anatomy of the Inferior Medial Palpebral Artery and Its Relevance to the Pretarsal Roll Augmentation.

Background: A detailed analysis of the topography of the inferior medial palpebral artery is needed to optimize the safety and efficacy of pretarsal roll augmentation. Methods: Thirty-one hemifaces from 13 Korean and 8 Thai cadavers (15 male and six female cadavers) were dissected. The distributions of the inferior medial palpebral artery were determined with respect to the superior medial palpebral artery and the supratrochlear artery. Results: Four distribution patterns were observed. The inferior and superior medial palpebral arteries branched individually from the ophthalmic artery, with the ophthalmic artery terminating as the supratrochlear artery on the forehead (type I); a short trunk branched from the ophthalmic artery and divided into the inferior medial palpebral artery and superior medial palpebral artery, and the ophthalmic artery terminated as the supratrochlear artery (type II); the inferior and superior medial palpebral arteries arose together from the ophthalmic artery, and the ophthalmic artery terminated as the supratrochlear artery (type III); or the inferior and superior medial palpebral arteries were the terminal branches of the ophthalmic artery, with the supratrochlear artery arising from the angular artery (type IV). The diameter of the artery was 0.94 ± 0.22 mm at the entry point and 0.37 ± 0.11 mm at the lateral canthus. Conclusions: The inferior medial palpebral artery was located along the tarsal plate deep to the pretarsal part of the orbicularis oculi in the lower eyelid. Injections to augment the pretarsal roll should be made between the subcutaneous tissue and this pretarsal part of the orbicularis oculi.