Left Orbits Research Articles

Comparative study of orbital volumes according to multispiral computed tomography data

BACKGROUND: It is believed that accurate reconstruction of the correct anatomy of the orbital bony walls, restoration of symmetry and volume are necessary for a favorable functional prognosis and elimination of an aesthetic defect. The main problem when estimating orbital volume is its complex anatomy. Scientists use various methods to determine orbital volume, and in reviews comparing various methods for calculating orbital volumes, there is no data on which orbital volumetric method is the most accurate, since each of them has both advantages and disadvantages. AIM: The aim of this study is the analysis and the comparison of orbital volumes according to multispiral computed tomography data of healthy patients without bone-traumatic changes of orbital walls. MATERIALS AND METHODS: To measure the volume of orbits, 50 random patients were selected who were examined in the radiology department No. 2 of the University Clinical Hospital No. 1 of the Sechenov University from 2023 to 2024 and who underwent multispiral computed tomography of the facial skeleton for indications unrelated to orbital conditions. Computed tomography data from 25 women and 25 men of different ages (from 18 to 85 years old) were analyzed. A total of 8 groups were formed depending on gender and age: group 1 — women 18–25 years old, group 2 — men 18–25 years old, group 3 — women 26–35 years old, group 4 — men 26–35 years old, group 5 — women 36–50 years old, group 6 — men 36–50 years old, group 7 — women 51 and older, group 8 — men 51 and older. Multispiral computed tomography of the facial skeleton was performed using the Aquilion One 640 CT scanner (Japan) with 0.5 slice thickness in bone and soft tissue windows, to be able to calculate orbital volumes at the workstation, all bone contours of the orbits were marked on each axial slice, starting from the upper wall to the bottom of the orbit with a representation of the orbital volumes in ml. RESULTS: The difference in the volumes of the right and left orbits of 0.5 ml or more was detected in 5 women out of 25 cases, among men the difference was present in 12 cases out of 25; a difference in volumes of more than 1 ml was noted in 1 woman and 2 men; a difference of more than 1.5 ml was not observed in any study group. The orbital asymmetry coefficient in women ranged from 0 ml to 1.21 ml, in men — from 0.08 ml to 1.19 ml, in women, the average volume of both orbits is less than in men. It was also detected that the volume of orbits increases with age, both in men and women. CONCLUSIONS: Considering that the majority of patients had differences in orbital volumes of up to 1.0 ml, we agree with studies that indicate the possibility of using a healthy contralateral orbit as a guideline when planning reconstructive surgery. However, for planning surgical treatment, it is recommended to use manual contouring, as this allows the most accurate reproducibility of the bone boundaries of the orbit, although it requires more time than semi- and automatic segmentation. Also, the advantages of the used method for calculating the volumes of orbits in this study include reproducibility on any workstation from different manufacturers, since the method is carried out on a standard tomograph workstation and does not require any additional software.

Effect of retrobulbar prostaglandin analog injection on orbital fat in rats.

Periorbital fat atrophy is a known side effect of topical prostaglandin analogs (PA). This side effect may have implications in the treatment of diseases like thyroid orbitopathy. In this in vivo study we aimed to evaluate the effects of retrobulbar injection of three different PAs on orbital fat. Eighteen adult male Wistar-albino rats were divided into three groups of six animals. 0.1ml of 0.03% bimatoprost, 0.005% latanoprost, or 0.005% travoprost was injected into the right orbits and saline was injected into the left orbits, as controls. Both orbits were exenterated after 3weeks. Histological cross-sections were analyzed using ImageJ image analysis software. Intraconal adipocyte density was calculated. There was no significant difference in the adipocyte density between the PA injected orbits and the control side in each of the three groups. When calculations from all three groups were analyzed together, again the difference in the adipocyte density between the PA injected orbits and the control side was not significant. No significant fat atrophy was noted in this rat model three weeks after retrobulbar injection of PAs. To evaluate retrobulbar injection of PA as a potential therapy for orbital diseases with fat proliferation, in vivo studies in different animal models, higher concentrations of PA, or longer follow-up duration are required.

Three-dimensional radiographic features of craniometaphyseal dysplasia—a comparative CBCT study

PurposeCraniometaphyseal dysplasia (CMD) is a rare skeletal disorder that has progressive thickening and increased density of the craniofacial bones along with abnormal metaphyses of the long bones. Other features include a wide nasal bridge, paranasal bossing, hypertelorism, and an increase in the zygomatic width. We present a series of cases that showcase the three-dimensional radiographic features of this rare condition and compare it with an age and gender-matched controlled group using cone beam computed tomography (CBCT).ObjectiveTo evaluate the three-dimensional radiographic features of craniometaphyseal dysplasia (CMD).Materials and methodsRetrospective analysis of CBCT scans of 7 patients who were diagnosed with the rare condition craniometaphyseal dysplasia was evaluated. Radiographic features of the craniofacial bones, the paranasal sinuses prominently maxillary, and frontal and sphenoid sinuses were evaluated. Skull bones were also evaluated, and the size and shape of the sella turcica and external auditory meatus were measured. Retained primary teeth and impactions were evaluated using a panoramic reformatted image. The type of occlusion and buccolingual dimensions of jaw bones were also assessed. Age and gender-matched control samples were used to measure the same features for comparing CMD patients to healthy controls. The quality of normal and syndromic patients’ cortical and trabecular bone was determined by measuring pixel intensity values (PIV) generated by CBCT scans.ResultsCone beam CT images of patients with CMD were analyzed to evaluate cranial bones, their density, and any abnormalities associated with the sinuses and foramina. Patients with CMD had bones increased in size. A significant increase in the amount of bone formed was found in the inner table of the frontal and occipital bones. All seven patients with CMD had smaller foramina due to the deposition of sclerosed bone in the foramina of the skull base. The paranasal sinuses, prominently maxillary and frontal and sphenoid sinuses, were smaller than the age and gender-matched controls. The buccolingual dimensions of jawbones were increased. The maxillary and mandibular arch relationship ranged from class II to class III. The mean nasal bridge measurement for the CMD patients was 26.77 mm, while in the controls, the mean nasal bridge measurement was 19.48 mm. The mean measurements of the right and left orbits of CMD patients were 30.6 mm and 31.07 mm respectively, and the mean measurements of the right and left orbits of controls were 32.45 mm and 32.04 mm. Pixel intensity values (PIVs) representing density ranged between 100 and 1000 PIVs for cortical bone and between − 60 and 258 for trabecular bone suggesting a densely sclerotic texture, while in the control group patients, the PIVs for cortical bone were > 1000 and 150–300 for trabecular bone.ConclusionCMD patients had significantly larger bone widths, a lower density of the bone, and smaller sinuses compared to the control group.

Radiologic Assessment of Orbital Dimensions among Omani Subjects: A computed tomography imaging-based study at a single tertiary centre.

This study aimed to determine the orbital dimensions of Omani subjects who had been referred for computed tomography (CT) of the brain at Sultan Qaboos University Hospital, Muscat, Oman. Good knowledge of the normal orbital dimensions is clinically essential for successful surgical outcomes. Racial, ethnic and regional variations in the orbital dimensions have been reported. A total of 273 Omani patients referred for CT scans of the brain were retrospectively evaluated using an electronic medical records database. The orbital dimensions were recorded using both axial and sagittal planes of CT images. The mean orbital index (OI) was found to be 83.25 ± 4.83 mm and the prevalent orbital type was categorised as the mesoseme. The mean orbital index was 83.34 ± 5.05 mm and 83.16 ± 4.57 mm in males and females, respectively, with their difference not being statistically significant (P = 0.76). However, a statistically significant association was observed between the right and left orbits regarding horizontal distance (P <0.05) and vertical distance (P <0.01) of orbit and OI (P <0.05). No significant difference between the OI and age groups was observed in males and females. The mean interorbital distance and interzygomatic distance were found to be 19.45 ± 1.52 mm and 95.59 ± 4.08 mm, respectively. These parameters were significantly higher in males (P <0.05). Results of the present study provide reference values of orbital dimensions in Omani subjects. Mesoseme, a hallmark of Caucasian people, is discovered to be the prevalent orbital type of Omani subjects.

Tensile and flexural moduli for human orbital wall bones – comparative study

Purpose The main aims of the current research were: (1) to analyze in detail tensile modulus and ultimate tensile strength (UTS) of orbital wall bones separately for the left and right orbits of the same cadaver and (2) to compare the obtained results with a flexural modulus of the left and right orbits reported earlier by A. C. van Leeuwen et al. [14]. Methods A set of 54 specimens of orbital superior and/or medial walls harvested from 16 human skulls (4 female, 12 male) were tensioned at 0.01 mm/s till fracture. The samples were taken always from both orbits of the same cadaver. For each sample, cross-section area, apparent density, tensile modulus and UTS were identified. Results There were no statistical difference between left and right orbit for pooled male and female group for (a) apparent density (T-Student test p=0.567), (b) UTS (Mann-Whitney U-test p=0.350) and (c) tensile modulus (Mann-Whitney U-test p=0.716). There were no statistical difference between left and right orbit for pooled male and female group for (a) orbital wall thickness (T-Student test p=0.811) and (b) flexural modulus (Mann-Whitney U-test p=0.206). Conclusions The comparison between tensile and flexural moduli for pooled left and right group revealed no statistical significant difference (Mann-Whitney U-test p=0.074). The maximum tensile modulus was 7279 MPa and 9913 MPa for right and left orbit, respectively, and was similar to maximum flexural moduli of 6870 MPa and 9170 MPa reported in an earlier study.

Comparison of orbital volume measured using computed tomography and fluid displacement: A comparative study using dry skull

Objectives: The purpose of the study was as follows: (1) To compare orbital volume calculated using computed tomography (CT) scans with real-time measurements. (2) To evaluate if the orbital volume of the adjacent orbit can be taken as a tool of comparison for orbital volume correction in orbital fractures. Materials and Methods: A prospective study was conducted on 30 orbital cavities with intact orbital walls. The foramina and fissures were sealed using molding wax. Alginate impressions of the orbital cavity were taken to determine the orbital volume using the Archimedes principle. GE light speed 64 slices CT scanner was used to scan the orbits with 0.8 mm sections. Orbital volume was calculated using the CT software GE ADW 4.5 workstation. Results: The comparison of CT measurement and Archimedes principle measurement shows a mean and standard error of 0.2333 mm and 0.09794, respectively, on the right orbits and a mean and standard error of 0.10011 mm and 0.0981, respectively, on the left orbits. The comparison of the right and left orbits shows a mean and standard error of 0.4067 mm and 0.2771 mm, respectively, using the Archimedes principle and a mean and standard error of 0.3300 mm and 0.2775, respectively, using CT scans. Conclusion: It was found that the difference in orbital volume between CT and real-time measurement is very negligible. The study shows that CT is a reliable tool for the orbital volume measurement and the adjacent orbit can be taken as a comparative tool for the orbital volume corrections.

Differences in anthropometric measures of the orbit between Serbian and Roma populations of the Central Serbia

Introduction/Objectives. The shape and size of the orbital cavity are important parameters in planning surgical interventions and have significance in anthropology and forensic medicine. The aim of this study was to determine the morphometric characteristics of orbital cavity in Serbian population and to examine if there are differences in examined parameters between Serbs and the Roma Community of Serbia. Methods. Using computer tomography and subsequent multiplanar reconstruction we analyzed orbits from 76 Serbian and 18 Roma healthy volunteers. There was no significant difference in age between the ethnicities. Results. The height and width of the left orbit and the height of the right orbit were significantly higher in Roma group, whereas the width of the right orbit was not statistically different between ethnicities. Orbital indices, however, for both left and right orbit did not significantly differ between Serbian and Roma examinees. Right orbital volume did not differ between the groups, but left orbits had significantly larger volumes in Roma population. Finally, biorbital and interorbital width were both significantly higher in Roma than in Serbian examinees. We could not show differences between sexes except for the biorbital width, which had lower values in Serbian, but not Roma women than in men. Conclusion. Taken together, our results indicate larger orbits, as well as greater distances between the eyes in Roma than in Serbian examinees.

MRI-Based Normative Measurement of the Ocular Globe Position in Relation to Inter-Zygomatic Line among Nepalese Subjects

Introduction: Proptosis and enophthalmos are cardinal signs of many orbito-ocular and systemic diseases. The need for an imaging parameter that will aid its early detection is necessary, as visual compromise is a major consequence if they are not diagnosed and managed early. Methodology: This prospective study was performed in a tertiary center. Data were collected over the period of January to April 2021 with total of 300 normal ocular globes. The measurement was done at the level of lens (midglobe section) on T2-weighted axial image. Results: The distance between the anterior margin and inter zygomatic line of the right ocular globe was 16.95 ± 1.48 mm (ranged 14.2 - 20.5 mm) and that of left was 16.86 ± 1.38 mm (ranged 14.2 - 20.3 mm). The position of the globes showed no statistically significant differences among gender groups in our study and the position of the right globe within the orbit was significantly different from that of the left orbit. Conclusion: The position of the globes showed higher values in males than in female. However, a statistically significant difference in globe position was observed between right and left orbits. The distance between the posterior margin of the globe and the inter zygomatic line was found to be lower among the Nepalese population compared with other population.

Dynamical height growth: left, right, and total orbits

Let $S$ be a set of dominant rational self-maps on $\mathbb{P}^N$. We study the arithmetic and dynamical degrees of infinite sequences of $S$ obtained by sequentially composing elements of $S$ on the right and left. We then apply this insight to dynamical Galois theory.

Investigation of the Orbital Arterial Distribution Using Image Superimposition to Determine Safe Zones for Retrobulbar Injection and to Prevent Filler Complications.

Retrobulbar filler injection has recently been considered an ideal method for orbital volume enhancement due to its nontoxic, easily reversible, and noninvasive characteristics. This study determined the arterial distribution in the orbit with the aim of defining a safety zone for retrobulbar filler injections used to enhance the orbital volume. Twenty-seven orbits of 24 formalin-embalmed cadavers were dissected. The orbital arteries were identified after removal of the eyeball, extraocular muscles, and connective tissues. The course of each orbital artery was then recorded in each specimen, and all of the courses were then superimposed to determine the arterial distribution in the orbit. The superimposition of lined images based on the orbital vasculature of each specimen revealed that the arterial density was highest in the superonasal region and lowest in the inferotemporal region. In particular, orbital arteries were scarce at 8 o'clock and 4 o'clock in the right and left orbits, respectively, and an artery-free zone was demonstrated in the outer part of those directions. When performing a transcutaneous retrobulbar injection of filler for orbital volume enhancement, the relative safety zone could be considered to be located at 8 o'clock and 4 o'clock in the right and left orbits, respectively. The detailed topographic information about the arterial distribution in the orbit, provided by the present study, may help oculofacial surgeons to avoid injury to major vessels and decrease the risk of retrobulbar hemorrhage and vision-threatening complications.

Assessment of the orbital structures using computed tomography in healthy adults.

In this study, we retrospectively evaluated the orbital and ocular dimensions using computed tomography (CT) scans in healthy adults. This retrospective study included 302 Turkish adult individuals aged 20-76 years (158 males and 144 females), who underwent paranasal sinus or craniofacial CT due to headache or suspicion of sinusitis, but abnormal orbital or cranial CT findings were not detected. Linear and volumetric measurements of the orbital structures were performed in the sagittal, coronal, and axial planes on CT slices. The volume was estimated in cubic centimeters using the equation of the ellipsoid method. A total of 34 parameters were measured from both eyes of each individual using 14 different anatomical landmarks and analyzed by gender and age. Parameter values of orbital structures in males and females are shown in millimeters or cubic centimeters. In most of the 34 parameters that we evaluated, it was seen that males had statistically significant higher mean values than females (P < 0.05). Also, there was no statistically significant difference between the measurements of right and left orbits. The correlation with age was varied according to the 34 parameters. Interestingly enough, there were no statistically significant differences between the two genders for extraocular muscles thickness (except superior muscles group thickness-SMT) and left optic nerve thickness (LOT) (p > 0.05). The mean right superior muscles group thickness was 5.35 ± 0.85 mm in the male subjects and 4.64 ± 1.10 mm in the female subjects (P < 0.001). The mean left superior muscles group thickness (LSMT) was 5.28 ± 0.88 mm in the male subjects and 4.67 ± 1.16 mm in the female subjects (P < 0.001). The mean LOT was 6.15 ± 0.97 and 5.88 ± 1.07 mm in males and females, respectively (P = 0.099). This study can be applied to the standardization of orbital morphometry in healthy adults.

Efficacy of vertical lid split versus lateral canthotomy and cantholysis in the management of orbital compartment syndrome

ABSTRACT Purpose: To compare the efficacy of the vertical lid split (VLS) to the standard lateral canthotomy and cantholysis (LC/C) for orbital compartment syndrome (OCS) in the cadaveric model. Methods: Simulated OCS was achieved in seven fresh frozen cadaveric orbits. Orbital pressure (OP) was monitored in one control orbit and six interventional orbits. Initial OP was recorded before three right orbits underwent lateral canthotomy with superior and inferior cantholysis, and three left orbits underwent vertical lid split of the upper and lower eyelids. In all 7 orbits, OP was recorded for a total of 16 min. The main outcome measure was the amount of OP reduction at timed intervals. Results: Beginning OP in the control orbit was 109 mmHg, and average initial OP of the LC/C and VLS orbits were 90 and 103 mmHg, respectively. The control orbit maintained high OP without intervention. One minute after LC/C, OP decreased an average of 58.7 mmHg (65.2%; range 48–65 mmHg). One minute following VLS, OP decreased an average of 63 mmHg (61.0%; range 39–102 mmHg). At 16 min, OP reduction in the LC/C orbits averaged 65.3 mmHg (72.6%; range 56–71 mmHg), and OP reduction in the VLS orbits averaged 78 mmHg (75.5%; range 54–121 mmHg). Both interventions produced a comparable reduction in OP. Conclusions: Vertical lid split was found to be as effective as LC/C in reducing OP. The technical simplicity of the VLS lends itself well to utilization by physicians who are unfamiliar with eyelid surgery.

Anatomic Variability of the Human Orbit

Knowledge of the bony orbit and how its volume changes are clinically important in addressing traumatic injuries. Restoration of orbital volume in some patients is critical to achieving successful outcomes after such injuries. In this large cadaveric study, we aimed to assess the average volume, range of bony orbit volumes, degree of volume discrepancy between the right and left orbits, and percentage of skulls with 1- and 1.5-mL orbital volume differences via alginate impressions and volume displacement. This study used 121 skulls (242 orbits) from the University of Texas Southwestern Department of Cell Biology/Anatomy.Seal-press wrap was first adapted to each bony orbit to ensure no damage to the internal orbits, foramina, or fissures. Alginate impressions were then taken and trimmed to encompass the bony orbit. The volume of each impression was calculated via the volume-displacement method. The average orbital volume was 26.75mL for the right side and 26.65mL for the left. The average right-to-left difference between orbits was 0.8mL, with a range from 0.02 to 3.64mL. The calculated methodologic error was 0.91% for the right orbit and 1.05% for the left.Approximately 14% and 21% of skulls showed normal left-to-right orbital volume differences of 1.5mL or greater and 1.0mL or greater, respectively. Our data suggest that the average normal asymmetry between the right and left orbital volumes is 0.8mL, which is 50 to 80% of the orbital volume increase implicated in traumatic enophthalmos. Of the skulls, 17 (14%) showed a right-to-left orbital volume asymmetry of 1.5mL or greater and 25 (21%) showed an asymmetry of 1.0mL or greater. The skull-to-skull orbital volume range approached 200%. Thus, this study provides surgeons with important information to consider when reconstructing a traumatized orbit using a computed tomography scan of the unaffected, contralateral orbit.

Diagnosis and surgical management of orbital sparganosis.

Orbital sparganosis represents an extremely rare condition with only a few cases being reported in literature. Here we describe cases of orbital sparganosis, including their etiology, clinical findings, and surgical outcomes. A retrospective review was performed on patients with orbital sparganosis, who were treated at Zhongshan Ophthalmic Center, of Sun Yat-sen University, China between 2000 and 2012. Five patients (three males and two females, one right orbit and four left orbits) were identified. Their mean age was 14.8 years (range = 6-33 years). Four cases were contracted from eating raw snakes and fishes, or placing poultices of frog on open wounds. All cases showed a swelling and/or redness of the eyelid and conjunctiva, and a migrating inflammation was present in one of the cases. High levels of blood eosinophils were observed in three of these cases. Of the two patients examined using computed tomography, one showed a diffuse soft tissue infiltration and a punctate calcification, while one of the three patients examined using magnetic resonance imaging displayed an annular "tunnel sign" within the lesion. All patients underwent an anterior orbitotomy and the entire worm was removed with no surgical complications. Orbital sparganosis should be highly suspected in patients with a history of eating raw snakes and frogs, a migrating orbital inflammation and the presence of eosinophilia. Orbital imaging examinations play an important role in the diagnosis of orbital sparganosis. Surgical removal of the entire worm is required.

Length of orbital margins of dry skulls in a local Pakistani population

Orbit is an important bony cavity which lodges eyeball and associated structures for our fundamental sense of vision. Knowledge regarding accurate morphometric measurements of its margins and depth will help in diagnosis and treatment plans of various optic functions. Previous studies showed racial differences in different populations we want to collect data in local population of Asian region as we are lacking data in this region. This study was carried out on 64 bony orbits of 32 dry Asian human skulls. Measurements from right and left bony orbits were taken by digital vernier calipers in millimeters and entered in SPSS 18.0 for calculation of mean and standard deviation.Results were obtained from different orbital margins. Right superior, inferior, medial and lateral orbital margins showed results as 31.30 ± 2.329 mm, 33.59 ± 3.35 mm, 29.57 ± 2.28 mm and 28.37 ± 2.023 mm respectively. While left superior, inferior, medial and lateral orbital margins were 30.944 ± 2.1080 mm, 31.19 ± 2.54 mm, 29.567 ± 2.36 mm and 28.14 ± 2.286 mm respectively. Right sided depth from optic canal to frontomaxillary suture was 41.40 ± 2.88 and left sided depth was 39.93 ± 3.33 mm. Data collected in Asian population showed differences from other races. This study covers important area regarding helpful in surgeries of this region as precise measurements could avoid injuries and postoperative complications.Key Words: Orbital Margin, Pakistan

How Symmetrical Are Bony Orbits in Humans?

Establishing the symmetry of intraindividual orbital volumes is crucial for radiologic assessment, preoperative planning, and postoperative outcome evaluation. However, no reliable method exists to measure orbital volume because of problems in defining the bony boundaries of the orbit. Therefore, the purpose of this study was to propose a new approach to analyze human orbits and determine its application for quantifying bony symmetry in a cohort of patients. Computed tomography scans of 93 patients were retrospectively collected from our institutional database. The intraindividual volume difference was quantified using a surface model derived from manual segmentations. The average shape of the orbit was calculated iteratively and nonrigidly registered to both orbits of all patients. After registration, the surface reconstructions of all orbits had an identical mesh topology and vertices at corresponding anatomic locations. The volume difference was calculated locally based on the relative position of the vertices at equivalent locations in the left orbit and right orbit. This approach was used to quantify the volume difference between the left and right orbits for all patients. Interobserver sensitivity was assessed in 5 randomly chosen patients and was measured independently by 3 specialists. An average difference of 600±500μL between the volumes of the left and right orbits was found, representing a difference of 2.1%.Although the difference in volume was small, the volumes were significantly different (P=.039). The largest asymmetries were found in the roof and floor area. The method proposed to measure the difference in volume between the left and right orbits is automated and does not rely on a closed orbital volume, which provides more objective volume measurements. With the help of modern computed tomography techniques and the coherent point drift method, it was possible to show that the intraindividual volume difference in the orbits is approximately 2%, not 7 to 8% as often cited in the literature.

The importance of upper first permanent molars position for the orthognatic occlusion

Development of the dental arches and occlusion in permanent dentition can be divided into several stages and has to be observed regularly. The first permanent molar eruption is related to the onset of significant changes in the developing occlusion. Although this tooth is seen as the `key to occlusion` its value as an anchorage is debatable. The aim of the article is to study the correct position of the upper first molars in the two planes of space - the sagittal and transverse planes. In this article the position of the first upper molar is examined with the aid of diagnostic records, such as study cast, orthopantomogram (OPG), and lateral cephalometrics. A literature review includes Bulgarian and foreigner authors. Angle, who in 1899 referred to the maxillary first permanent molars as the `key to occlusion`, was the first to mention their importance within the dentition. According to Angle, the line passing through the middle of the mesiobuccal cusp of the upper first molar coincides with the line passing through the buccal groove of the lower first molar. After Angle, other authors have discussed the position of upper molars from different point of view, such as their relation or position in the maxilla, anteroposterior axial inclination and rotation. As indicated by Lamons and Holmes molar rotations commonly exist in Class II malocclusions. The molars are usually rotated around an axis lingual to their central fossae. In an ideal occlusion the buccal surfaces of the upper first molars are usually parallel to each other. On the OPG Kurol and Bjerklin measured the axial mesial inclination of upper first molar. The tipping of the molars is measured by the angle formed between the tangent line to the mesial surfaces of the root and crown and the line through the lower margins of the left and right orbits. According to Sassouni, the mesial contour of upper first molar should to lie on the 4th arc - the temporal arc. If the molar is anterior to this arc, a treatment with distalization could be initiated. The temporal arcnasion distance measured on the radius is equal to the distance from point ANS to the upper first molar. The position of the upper first molar varies with the position of the upper central incisors. The basic hypothesis is that if the upper first molar has a fixed position in the face, any increase in the total upper dental arch length will be transferred to the incisor area. Any change in the anteroposterior position of the upper first molar could influence the position of the mandibular- leading to Class II malocclusion. Ricketts pointed out that the average distance from the pterygoid vertical (PTV) to the distal surface of upper first molar is the sum of the age of the patient + 3mm, in a growing patient. This diagnostic method can help the orthodontist to decide whether to extract teeth or to distalize the molars. Any loss of space in the arch is a justification for early orthodontic treatment. Mediopalatal rotation of the upper molar is an additional problem in the final phase as well. The rotation of upper first molars is measured by the angles formed by the intersection of lines going over the tips of the mesiopalatal and distobuccal cusps of each molar (Ricketts line) with a straight line marked over the palatine raphe. The problem of reduced arch length has an impact on the final treatment stage when the major orthodontic goal is establishing a tight teeth intercuspation. The molars influence the transfer of occlusal forces to the facial skeleton. The upper first molar tolerates more changes in the position than the lower one. The correct position of the upper molar ensures a stable occlusion with significantly low grade of relapse.

Dynamic Analysis for the Rotor Drop Process and Its Application to a Horizontal Rotor-Active Magnetic Bearing System in Helium Gas

The high-temperature gas-cooled reactor pebble-bed modular (HTR-PM) has been proposed by the Institute of Nuclear and New Energy Technology of Tsinghua University, in which the active magnetic bearings (AMBs) are equipped to support the high-speed rotor in the helium circulator system. In the case of AMB failures, emergencies, or overload conditions, the auxiliary bearing is applied as the backup protector to provide temporary mechanical support and displacement constraint for the dropping rotor. A detailed dynamic model is established to reveal the behavior of the dropping rotor. This model is able to describe the rotor displacement and inclination around each axis. The left and right rotor orbits are revealed. Dropping experiments are also carried out to reveal the actual behavior of the dropping rotor in helium. The predicted and experimental results will benefit further study, design, and application of the auxiliary bearing in HTR-PM helium circulator.

Radiologic evaluation of orbital index among Ghanaians using CT scan

BackgroundOrbital index (OI) expresses the proportion of the orbital height to the orbital width and varies with race, regions within the same race and periods in evolution. This index is useful in forensic medicine, anthropology and surgery. However, the average OI among Ghanaian adults was unknown.AimThe aim of this study was to determine the orbital index of adult Ghanaians and classify them under one of the three predetermined groups.MethodThe study design was a retrospective cross-sectional. A systematic random sampling method was used for selecting 350 adult Ghanaian head computed tomography images available from 1 January to 31 December 2015 at KBTH Hospital. The orbital height and orbital width of each orbit were measured on a 3D CT skull. Data was analysed using Microsoft Excel and Statistical Package for Social Sciences version 20.ResultsThe study had more females than men (167, 47.71%, vs 183, 52.29%). The observed orbital index of Ghanaians in the study was 81.22 ± 4.22. The mean orbital index was 80.52 ± 4.66 in males and 82.15 ± 3.83 in females with their difference being statistically significant (p value <0.05). This placed both genders in the Microseme category of orbit. There was no significant difference between the orbital index of the two orbital sides (left and right orbits).ConclusionThe study found Ghanaians in the category of the Microseme and also indicated a strong sexual dimorphism. The outcome of this study may be useful in forensic medicine for skull classification and also for better surgical approach in neurosurgery as well as cosmetic surgery.

Biphasic growth of orbital volume in Chinese children

ObjectiveThe aim of this study was to map out the developmental curve of the orbital volume of Chinese children aged 1–15 years.MethodsCT scanning was performed on 109 children and the...