Mandibular Space Research Articles

Structural adaptations of the beak and oropharyngeal cavity roof in migratory Anas crecca: Distinctive scanning electron microscopic pattern of its filter feeding apparatus

There is insufficient data about the migratory duck Anas crecca, especially the beak and oropharyngeal cavity roof. This study aimed to characterize the beak and palatine adaptations and relate the morphological features with the species-specific feeding behavior of A. crecca collected near Lake Nasser (Egypt). Our study was carried out with the help of gross, scanning electron microscopy (SEM), and morphometric analysis. The lower median papillary teeth-like region corresponded to the lower papillary region in terms of food particle capture. The serrated gnathotheca surface exhibited transverse, wedge-like, cap-like, and serrated border-like processes. The lower mandibular space had four spaces: the rostral smooth, the middle folded, the long sublingual, and the caudal sublaryngeal space. The palate showed two major regions, the rostral long beak (beak nail, middle part, and the caudal papillary part) and the connecting region. The choana consists of the rostral narrow part, which has rostral non-papillated and caudal papillated parts, and the caudal papillated wide part, which has three papillary rows. The infundibular plate had numerous small papillae and sphenopterygoid salivary gland openings. Functionally, the beak plays an important role in the sieving filter feeding mechanism, and the palate is involved in the fixation of the captured food particles inside the oral cavity. Consequently, beak and palate structures exhibit anatomical adaptations for efficiently filtering feeding mechanisms.

Effect of orthodontics combined with fibre-reinforced composite resin-bonded fixed partial denture on anterior dentition defects with minimal vertical intermaxillary space.

Prosthodontics are often performed to treat patients with malocclusion and dentition defects. However, single prosthodontics cannot properly correct the disharmony of teeth, dental arch and other parts affected by malocclusion, and some patients may have difficulty in recovering the occlusal function due to poor prosthodontics. This study aims to investigate the effect of orthodontics combined with fibre-reinforced composite resin-bonded fixed partial denture (FRC-RBFPD) on anterior dentition defects with minimal vertical intermaxillary space. Sixty-two patients with anterior dentition defects with minimal vertical mandibular space admitted to our hospital between March 2021 and May 2023 were enrolled in this study. The participants were divided into the observation group (31 cases) and the control group (31 cases), according to the treatment plan. The control group was treated with traditional therapy, and the observation group was treated with orthodontic combined FRC-RBFPD therapy. Periodontal conditions (periodontal pocket depth [PD], the plaque index [PLI], the sulcus bleeding index [SBI]), levels of inflammatory factors in gingival crevicular fluid (high mobility group box 1 [HMGB1]), myeloid cell triggering receptor-1 (TREM-1), monocyte chemoattractant protein-1 (MCP-1), pain (visual analogue scale [VAS]), the clinical response rate and the incidence of adverse reactions were collected and compared. After 1, 3, 5 and 9 months following treatment, the scores of the PD, PLI, SBI, HMGB1, VAS, TREM-1 and MCP-1 in the observation group were found to be lower than those in the control group (FPD treatment= 352.532, FPLI score treatment= 112.341, FSBI score treatment= 79.479, FVAS score treatment= 96.132, FHMGB1 treatment= 52.532, FTREM-1 score treatment= 64.593, FMCP-1 score treatment= 53.582, and they were all statistically significant P< 0.05). There was a statistically significant difference in the response rate between the two groups (97.77% vs. 80.65%, χ2= 4.026, P= 0.045). No statistically significant difference was observed in the incidence of adverse reactions between the two groups (6.45% vs. 16.13%, χ2= 1.449, P= 0.229). Orthodontics combined with FRC-RBFPD shows an ideal restorative effect on patients with anterior dentition defects and minimal vertical intermaxillary space.

Aerobic Microorganisms in Nonspecific Neck Abscess - A Prospective Study in A Tertiary Level Hospital

Background: The knowledge of the local pattern of infection and microorganisms in non-specific neck abscess is essential to enable efficacious treatment for it. Objective: To find out the pattern of bacteria responsible for developing non-specific neck abscess and to analyze the coverage rate of different empiric antimicrobial agents. Materials and methods: It is prospective observational type of study carried out into Department of Otolaryngology &amp; Head Neck Surgery, Dhaka Medical College Hospital, Dhaka and Department of Clinical Microbiology, ICDDR,B, Dhaka from1st January,2016 to 30th June, 2016. Total 100(Hundred) patients were included in this study. Data were analyzed using computer based programmed statistical package for social science (SPSS). Results: This study was done among 100 patients. In this study 42 cases (42%) were in the (31- 45) years age group. The male patients were 60 (60%) and female were 40 (40%). Majority of patients 70(70%) came from poor class family with 70 (70%) patients came from rural area, 50 (50%) patients had dental infection, 40(40%) patients were smoker, 35 (35%) patients had diabetes mellitus, all the cases (100%) presented with dysphagia and fever. The major complication was necrotizing fasciitis 8 (8%), common space was sub mandibular space (45%), Streptococcus 30 (30%) was the most common organism. Conclusion: The most frequently isolated organism in neck abscess is Streptococcus. J Dhaka Med Coll. 2021; 29(1): 31-37

Novel Approach for Management of Deep Space Neck Infections: a Case Report

When patients present with deep space neck infections, typically the treatment involves Incision and Drainage (I&amp;D) with an extraoral incision that could measure several centimeters in length, as well as antibiotic administration. While this approach is effective in managing these types of infections, it is not without limitations. Most notably, patients treated with I&amp;Ds often are subject to prolonged hospitalization due to sepsis and they complain of a permanent, unsightly scar in the facial or cervical region once healed. In this case report, a 28-year-old male patient presenting to the emergency room with a right mandibular space collection of suppuration is treated with a modified version of the Seldinger technique which provided adequate abscess drainage and a more cosmetically-pleasing outcome once healed. Furthermore, this patient was treated bedside under local anesthesia as opposed to in an operating room under general anesthesia. While this technique may not be indicated for every patient presenting with deep space neck infections, it is a less-invasive approach that was effective for this patient.

Diagnostic Accuracy of Hyomental Distance Ratio (HMDR) for Prediction of Difficult Laryngoscopy in Patients Undergoing Surgery Under General Anesthesia Using Tracheal Intubation

Background: To keep the airway open, a flexible plastic tube (ETT) is inserted into the trachea during tracheal intubation. Even when done correctly, tracheal intubation requires much clinical experience, and catastrophic problems can occur. Mandibular space has been estimated using hyomental distance (HMD), although HMD has only been found to provide a limited amount of diagnostic accuracy on its own. In order to determine how well the Hyomental Distance Ratio (HMDR) predicts difficult laryngoscopy, we conducted this study. Objectives: Using the Cormack and Lehane classification as the gold standard, the objective is to assess the diagnostic validity of the Hyomental Distance Ratio (HMDR) for the prediction of challenging laryngoscopy in patients undergoing surgery under general anaesthesia. Materials &amp; Methods: The department of anesthesiology and the general surgery operating rooms at Sir Ganga Ram Hospital in Lahore conducted this cross-sectional study over the course of six months in 2015–2016. The approach of non-probability purposive sampling was applied. Informed consent was acquired, and patient demographics were recorded. The researcher herself then assessed patients for HDMR. In order to determine if a patient had a difficult or normal laryngoscopy, HDMR was determined. After that, the researcher performed a laryngoscopy on the patients. If the vocal cords were visible, the mouth was opened, and the case was assessed using the Cormack and Lehane classification (CL), with easy or difficult laryngoscopy being designated. SPSS version 20 was used to enter and analyse all of the data. Results: The patients in our study had a mean age of 43.23 11.63 years and a male to female ratio of 1.5:1. In this study, 43.91% of patients had an HDR difficult intubation. HDR's difficult intubation has a sensitivity of 95.05%, a specificity of 96.12%, and a diagnostic accuracy of 95.65% when using CL as the gold standard. Practical Implication: According to this study, this strategy can be applied accurately in other hospitals. Government should establish guidelines for using the most trustworthy techniques as the benchmark in healthcare settings. Conclusion: According to the findings of our study, the HMDR is a viable diagnostic tool for anticipating challenging laryngoscopy in patients having general anaesthesia with tracheal intubation. According to this study, this strategy can be applied accurately in other hospitals. Government should establish guidelines for using the most trustworthy techniques as the benchmark in healthcare settings. Keywords: Laryngoscopy, difficult intubation, Cormack Classification, difficult surgery

Current challenges faced by transgender and gender-diverse patients and providers in anesthesiology.

Current challenges faced by transgender and gender-diverse patients and providers in anesthesiology.

Iatrogenically Displaced Lower Wisdom Tooth Into Submandibular Space: A Case Report And Review On Retrieval Approaches

Accidental displacement of wisdom tooth and its elements are one of the uncommon complications. The common facial spaces involved during the displacement of lower wisdom teeth are Sub mandibular, Sublingual and Pterygomandibular spaces. Such complications have adverse physical and psychological impact over the patients. The management can vary from conservative observation to surgical retrieval; depending on the presenting clinical conditions, location and the relationship of the displaced elements with respect to the anatomic structures. Retrieval of a displaced root tip from these spaces may be complex due to poor visualization, limited access and under limited experience. This is a case report with a review on approaches for surgical retrieval, of a young male patient aged 28 years, who presented with a displaced mandibular third molar root into the Submandibular space during unsuccessful surgical removal by a general practitioner 2 weeks earlier. The presenting complaints were Limited mouth opening and pain during chewing on the right lower jaw. The case was managed surgically through extra oral approach under local anesthesia and MAC.

Positional and dimensional TMJ characteristics in different temporomandibular disorders: A cross-sectional comparative study

ABSTRACT Objective To investigate the morphological and positional temporomandibular joint (TMJ) characteristics of different temporomandibular disorders (TMDs). Methods One hundred forty-three TMD patients were divided into three groups: Group 1: Myalgia (M), Group 2: Disc displacement with reduction (DDWR), and Group 3: Disc displacement without reduction (DDWOR). Three-dimensional positional and dimensional parameters of the TMJ, including mandibular fossa, condyle, and TMJ spaces were evaluated using cone beam computed tomography (CBCT). The significance level was p < 0.05. Results Mandibular condyles were significantly positioned in more vertical, posterior, and medial directions, with the reduced condylar width in the DD groups (p < 0.001). Anterior joint space was significantly higher in the DDWR group than the myalgia group; the superior joint spaces were more reduced in DD groups than the myalgia group. Conclusion Patients diagnosed with disc displacement showed significantly different condylar positions and joint spaces compared to the myalgia group in a skeletally comparable sample.

How to predict a difficult airway

According to The American Society of Anaesthesiologists Task Force, a difficult airway is defined as a clinical situation in which a conventionally– trained anaesthesiologist experiences difficulty with face mask ventilation and/or difficulty with tracheal intubation. Failing at efficient airway management is a source of major apprehension for physicians. Predicting difficult airway management is a mandatory part of clinical practice for paediatric and adult patients so as to avoid unexpected difficult airway management and adverse outcomes. Predicting a difficult airway is based on a focused medical history, review of prior medical records, physical examination, and specific tests for airway assessment. Each feature or airway test has its own sensitivity and specificity for the prediction of a difficult airway. All airway assessment tests are characterised by low sensitivity, reasonable specificity, and a low positive predictive value. Several scoring system models have been developed by multivariate analysis with multiple different integrated tests or risk factors to improve the prediction of a difficult airway, but with considerably different effectiveness to predict a difficult airway. According to the European Society of Anaesthesiology, systematic multimodal screening before airway management should include the Mallampati classification and thyromental distance, mouth opening or interincisor distance, range of motion of head and neck, compliance of the mandibular space, and the upper lip bite test.

Effects of Gender and Age in Mandibular Leeway Space for Taiwanese Children.

Purpose: Leeway space is clinically crucial in pediatric dentistry because it is utilized to resolve tooth crowding and allow the first molars to drift mesially to establish a Class I molar relationship in the later stages of mixed dentition. This study investigated leeway space in the mixed dentition of Taiwanese children of different sexes and ages. Materials and Methods: The digital panoramic dental films of 182 lower arches of 119 boys and 63 girls aged 5–10 years were analyzed in this retrospective study. The mesiodistal crown widths of the primary canines and first and second molars and the permanent canines and first and second premolars were measured using medical imaging software. Differences in leeway space were statistically analyzed. Results: The average leeway space was 1.29 ± 1.48 mm on each side of the lower arch. The leeway space of children aged 5–6 years was significantly greater than that of children aged 7–8 years. No gender difference in crown width was discovered, except with regard to the primary first molar. Although no gender difference in leeway space was observed, permanent teeth affected leeway space more for girls than for boys. Conclusion: In Taiwanese children, although leeway space does not differ by sex, age affects leeway space. However, permanent tooth size has an influence on the leeway space of girls.

Clinical T4b Squamous Cell Carcinoma Resection With Hemimandibulectomy and Temporomandibular Joint Reconstruction With Bridging Plate and Modified Dautrey Procedure

Clinical T4b oral squamous cell carcinoma is traditionally considered nonoperable. We present a case of right mandibular squamous cell carcinoma (PT4bN0M0, stage IVB). The tumor had extended to the right mandibular condylar head and masticatory space. The patient received right modified radical neck dissection and radical operation with hemimandibulectomy to remove the right mandibular condyle. Then, we reconstructed the resected portion with an anterior lateral thigh free flap and bridging plate, which was bent to form an artificial condyle and fixed using the modified Dautrey procedure. The patient had stable postoperative occlusion and normal hinge movement of the temporomandibular joint. After postoperative concurrent chemotherapy and radiotherapy, the patient is under regular out patient department follow-up with satisfactory jaw function and oral intake.

Ludwig’s Angina: Management of 32 Cases at Tertiary Care Hospital

Background: Ludwig’s angina is a rapidly expanding cellulitis involving the floor of mouth and sub mandibular space predominantly due to dental / periodontal infections. Aim: To determine the management outcomes in the patients of Ludwig’s Angina. Place and duration of study: Department of Otorhinolaryngology Bahawal Victoria Hospital Bahawalpur. Duration was two years from August 2018 to July 2020. Study design: Hospital based cross sectional descriptive type of study Methodology: Patients of any age and gender who were clinically diagnosed as Ludwig angina and required hospitalization during the study duration were included in the study. Data regarding age, gender underlying cause, mode of presentation, treatment and complications were collected and analyzed. Patients with mild infection who did not require hospital admission were excluded from the study. Results: Out of total 32 cases, 20(62.5%) were males and 12(37.5%) were females. Age range was 10 to 70 years. In 28 (87.5%) cases, the cause was dental infection. All patients presented with pain and swelling of sub mandibular region. Four (12.5%) patients were improved with conservative treatment while 28(87.5%) underwent incision and drainage. Two (6.25%) patients needed tracheostomy. One (3.1%) patient developed complication (mediastinitis) and could not revive. Conclusion: Ludwig's angina is a disease of any age and gender commonly seen among the patients of preexisting dental infection. It can be life threatening if presented late with complication. Early diagnosis and aggressive treatment decrease morbidity and mortality. Key words: Angina, Ludwing, Cellulitis, Submandibular region.

Effects of Angle classII correction with the Forsus fatigue resistant device on mandibular third molars : Aretrospective study.

The goal was to evaluate the effects of Angle classII malocclusion treatment using the Forsus fatigue resistant device (FRD, 3M, St. Paul, MN, USA) on the position and angulation of mandibular third molars and retromolar space. In all, 58classII patients (mean age 13.6 ± 1.8years) treated with the FRD (FRD group) were compared with 51classI patients (mean age 13.5 ± 1.6years) who underwent orthodontic treatment (control group). A total of 109 mandibular third molars in the FRD group and 91in the control group were evaluated. Changes in the retromolar space, angulation of the second (ɣ) and third molars (β), and the angle between these teeth (α) were assessed with panoramic radiographs taken at the beginning and the end of the treatment. Data were statistically analyzed. At the end of the treatment, there were significant increases in ɣand βin the FRD group and ɣin the control group (p < 0.05). The decrease in αin the FRD group and increase in the control group were not significant (p > 0.05); however, this change led to asmall significant change between the groups (p < 0.05). The retromolar space significantly increased in the FRD group compared to the control group (p < 0.05). No significant correlation was found between retromolar space and third molar uprighting in any of the groups (p > 0.05). ClassII correction with FRD led to mesialization of the lower arch which provided an increase in the retromolar space. Little improvement in the uprighting of the third molars occurred.

Surgical Removal of Orthodontic Mini-screw Accidentally Displaced Into the Pterygomandibular Space Via Intraoral Approach

The mini-screw is widely used in orthodontic treatment for anchorage reinforcement. In mild skeletal Class III patient, retraction of mandibular dentition using mini-screw has been accepted as a reliable and stable treatment approach. In addition, the mini-screw placed in the retromolar area could be used for the uprighting of the lower molar. However, the placement of the mini-screw on the retromolar trigone or anterior ramus region need to be careful because of the possible risk of the “slippage” or “displacement”. Once the mini-screw is displaced to the fascial space such as pterygomandibular space, sub- mandibular space or lateral pharyngeal space, it is difficult to remove. In this case report, we present a mini-screw removal case via an intraoral approach that was displaced into the pterygomandibular space while placing the orthodontic mini-screw on the anterior margin of mandibular ramus.

Clinical, CT scan, and laboratory changes of abscess patients with odontogenic origin admitted to Shiraz acute surgical care center, Iran.

Introduction:Rapid diagnosis of maxillofacial abscess with the odontogenic origin is effective in the treatment of patients. This study aimed to check the clinical evaluation, head, and neck computed tomography (CT) scan, and microbial sensitivity of hospitalized patients diagnosed with maxillofacial abscess admitted to the Maxillofacial Surgery Ward Shaheed Rajaie Surgical Acute Care Center of Shiraz, Iran from 2019-2021.Method:A cross-sectional study was conducted. The sample included patients diagnosed with the abscess of odontogenic origin. Data collection tools included personal profile registration form, chief complainant and clinical evaluation, laboratory test results, pus culture, antibiogram results, and head and neck CT scan changes form. Data was reported with descriptive statistics by SPSS-16 software.Results:The majority of patients were male; infection duration was 10 days; maximum mouth opening size was less than 20 mm in more than half of patients. The scan revealed 41.8% abscess, 36.4% cellulite, and 21.8% mixed abscess and cellulitis. There was 29.1% involvement of salivary glands. The majority of abscesses were unifocal involved in the submandibular space, and the least involvement was in peri mandibular space and carotid sheath. The most common organism causing was staphylococcal abscess coagulase-negative.Conclusion:In patients with maxillofacial abscess requiring hospitalization, the most common clinical features were trismus, toxic appearance, and dysphagia, and the most common source of abscess in scanning patients with mandibular molars was the most involved submandibular space and pterygomandibular space. Vancomycin, cotrimoxazole, and cefazolin had the greatest effect in the treatment of odontogenic infections in terms of antibiogram results and microbial culture.

Cheek teeth diastemata

Cheek teeth diastemata are the most common cause of quidding in the horse. They most commonly affect the most distal mandibular interdental spaces (09/10s and 10/11s) and they begin with impaction of food material, which may progress to gingivitis and periodontitis. They are diagnosed during a thorough oral examination, given under sedation. The initial assessment should include removal of the food from the diastema, which is also therapeutic. Many cases may be resolved by removing the impacted food and with good quality routine dentistry. Other proposed treatments include packing or stenting of diastemata, removing teeth from occlusion, diastema widening and extraction of cheek teeth.

Comparative study of the outcome of surgical decompression in Ludwig’s angina by conventional skin incision versus multiple interrupted skin incisions

&lt;p class="abstract"&gt;&lt;strong&gt;Background:&lt;/strong&gt; Ludwig’s angina is a potentially life threatening infection characterized by a rapidly progressing, bilateral gangrenous cellulitis of all the three primary mandibular spaces namely submental, submandibular and sublingual. If left untreated the cellulitis can progress swiftly to produce obstruction of airway and death. Despite that, no specific guidelines exist and management is greatly dependent on clinical judgement and experience.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods:&lt;/strong&gt; Forty cases of patients with Ludwig’s angina, attending the department of otorhinolaryngology were included in this study and were randomly allocated into conventional incision (CI) and multiple incisions (MI) groups. Following informed written consent, either conventional incision or multiple small incisions were used for drainage and the outcomes analysed. &lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; The mean age of patients was 28.4 years and majority of the patients belonged to 20-40 years age group. Male to female ratio was 2.3:1.The most common etiology was odontogenic. The outcome of both the conventional group and multiple small incisions group were comparable. The mean hospital stay of the conventional group was 10.25 days and multiple incisions group was 5.31 days which was statistically significant.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; Multiple small incisions for the drainage of Ludwig’s angina is a safe and less invasive alternative method, with the advantages being shorter hospital stay and better cosmesis without an increase in complications.&lt;/p&gt;

Unilateral Mandibular Space Regaining with Modified Lingual Arch and Ni&amp;ndash;Ti Open-coil Spring: A Case Report

Unilateral Mandibular Space Regaining with Modified Lingual Arch and Ni&amp;ndash;Ti Open-coil Spring: A Case Report

RELATION OF CONE BEAM COMPUTED TOMOGRAPHY ASSESSMENT OF MANDIBULAR BONE DENSITY TO DUAL ENERGY X-RAY ABSORPTIOMETRY IN TYPE 2 DIABETES MELLITUS PATIENTS

INTRODUCTION: One of the complications associated with diabetes mellitus is decrease in bone mineral density (BMD). Therefore, quantification of BMD for these patients before a dental implant procedure is essential. Cone beam computed tomography (CBCT) is an important tool that can be used for qualitative and quantitative bone assessment for treatment planning of dental implants. OBJECTIVES: Evaluation of mandibular bone mineral density measured by CBCT and its correlation to T-score obtained by dual energy xray absorptiometry (DEXA) in relation to blood glycemic control as detected by glycosylated hemoglobin (HbA1c) in type 2 diabetic patients (T2DM). MATERIALS AND METHODS: The study was conducted clinically on twenty-four patients having T2DM, referred for CBCT examination as a part of implant planning. BMD was measured for each edentulous mandibular space using CBCT scan. The patients were grouped according to the level of HbA1c into 4 groups; control group, well-controlled group, moderately controlled group and poorly controlled group. Additionally, each candidate was examined radio-graphically using DEXA. Then, a statistical correlation between HbA1c values in relation to mandibular BMD values and T-score values was investigated. RESULTS: there was a statistically significant correlation between HbA1c values and BMD variables including: mandibular edentulous quad BMD and T-score values (p <0.001), and a statistically significant correlation between T-score value and Mandibular edentulous quad BMD (p <0.001). CONCLUSIONS: Osteoporosis is a commonly underestimated problem in diabetes patients. Osteoporosis can be predicted using CBCT, so it’s the dentist responsibility to refer osteoporotic patients once being suspected.

COMPARATIVE THREE DIMENSIONAL COMPUTED TOMOGRAPHY (CT) SCANS AND ANATOMICAL INVESTIGATION OF RABBIT (Oryctolagus cuniculus) AND CAT (Felis domestica) SKULL

This study was conducted to elucidate the comparative anatomical features of the skull of rabbits and cats using CT scans. Adult healthy New Zealand rabbits and Domestic Baladi cats of both sexes, were prepared for X-ray and CT scan of the heads at different positions. The heads were also processed for bone preparation and were photographed at various views. Some measurements were taken to exhibit the main differences between the two animal species. There was a cranial pharyngeal canal in the basisphenoid bone of rabbit, which was absent in cat. The retroarticular process situated caudal to the mandibular fossa in cat and absent in rabbit. The carotid foramen was large and situated only in rabbit ventromedial to the bulla tympanica. The supraorbital process of rabbit extended anteriorly and posteriorly forming rostral and caudal supraorbital fissures. The orbit was located laterally in rabbit rostrally in cat. The facial surface of the maxilla was perforated by several formina in rabbit. A large retroalveolar foramen was found only in the mandible of rabbit. The condyloid process of the mandible was large and present longitudinally in rabbit and transversally in cat. Also, the hyoid bones and the paranasal sinuses were compared at both animals. The hyoid bone located in the mandibular space in rabbit and caudal to this space in cat. The lingual process of the hyoid bone was absent in cat. The middle and great cornuae of the hyoid bone were absent in rabbit. The paranasal sinuses of rabbit were maxillary and ethmoidal sinuses. While in cat, there were frontal, sphenoidal and maxillary sinuses. The combination between the traditional gross morphology of the skulls, X-ray and scan aimed to clarify and confirm all the points of comparison between the two animal species used, which was not achieved by using only one method of them.Key words: rabbit; cat; skull; computed tomography; anatomy