Applicability of vital staining and tissue clearing to vascular anatomy and melanocytes' evaluation of temporal bone in six laboratory species.

The purpose of the present study was to define the applicability of tissue clearing to the field of otology. We combined tissue clearing with vital staining perfusion via a pumping system to examine the vascular anatomy of temporal bones in laboratory animals. We used six different types of species including Korean wild mouse, mouse, Mongolian gerbil, hamsters and Guinea pigs. A mixture of Alcian blue reagent and 4% paraformaldehyde was circulated throughout the entire circulatory system of the animal via a perfusion pump system. Transparency images were obtained from the temporal bones according to the protocol of the SunHyun 3D Imaging Kit. In examining the inner surface of the tympanic membrane, flaccid part (pars flaccida) was positioned along the entire marginal area in Guinea pig. In the Guinea pig, unlike the other species, the cortical bone of the mastoid (bullae) was easily removed using cold instruments, allowing a direct approach to the enclosed structures. The distribution and pattern of cochlea melanocytes were compared among the species. "Mobius strip"-like accumulated melanocytes in vestibules were shown in both the Korean wild mouse and mouse. The collateral blood supply to the cochlea in six different species was checked in various pattern. Combining dye infusion with tissue-clearing techniques, we documented the middle ear and transparent inner ear structures in six different species. The information and associated images will help other researchers to develop hypotheses and design experimental investigations.

3 D printed replica of the human temporal bone intended for teaching gross anatomy.

The anatomy of the human temporal bone is complex and, therefore, poses unique challenges for students. Furthermore, temporal bones are frequently damaged from handling in educational settings due to their inherent fragility. This report details the production of a durable physical replica of the adult human temporal bone, manufactured using 3D printing technology. The physical replica was printed from a highly accurate virtual 3D model generated from CT scans of an isolated temporal bone. Both the virtual and physical 3D models accurately reproduced the surface anatomy of the temporal bone. Therefore, virtual and physical 3D models of the temporal bone can be used for educational purposes in order to supplant the use of damaged or otherwise fragile human temporal bones.

Comparison of unbiased stereological estimation of total number of cresyl violet stained neurons and parvalbumin positive neurons in the adult human spiral ganglion.

Estimation of total number of neurons in the spiral ganglion (SG) at various ages and their functional status is important as these neurons are constantly exposed to noise and other environmental factors that may lead to neuronal loss with aging due to excitotoxic damage. Parvalbumin (PV) is a calcium-binding protein (CBP), found in highly metabolically active neurons. It helps in buffering cytosolic calcium, which is essential for neurotransmitter release. The neurons in the adult human SG express PV more strongly than other CBPs like calbindin and calretinin. These CBPs can be used as signatures to recognise neurons. In the present study, we quantified the number of neurons expressing PV by unbiased stereology and compared it to the number of neurons stained by cresyl violet (CV), which is a Nissl stain, in the adult human SG. Five adult human cadaveric temporal bones were obtained from the forensic science mortuary, after due clearance from the institute ethics committee. Independent CV stained and PV immunostained sections were used to estimate the total number of neurons (optical fractionator), with StereoInvestigator (SI) software. The estimated total number of SG neurons was 27,485±3251 and 26,705±1823 in the PV and CV stained sections, respectively. There was no significant difference between the estimates (p=0.552). Therefore, CV staining is simpler and more cost effective when estimating neuronal number. Although PV stains spiral ganglion neurons (SGNs) with a greater intensity and provides a functional status, its tedious protocol limits its use for quantification.

Laser-Modified Surface Enhances Osseointegration and Biomechanical Anchorage of Commercially Pure Titanium Implants for Bone-Anchored Hearing Systems.

Osseointegrated implants inserted in the temporal bone are a vital component of bone-anchored hearing systems (BAHS). Despite low implant failure levels, early loading protocols and simplified procedures necessitate the application of implants which promote bone formation, bone bonding and biomechanical stability. Here, screw-shaped, commercially pure titanium implants were selectively laser ablated within the thread valley using an Nd:YAG laser to produce a microtopography with a superimposed nanotexture and a thickened surface oxide layer. State-of-the-art machined implants served as controls. After eight weeks' implantation in rabbit tibiae, resonance frequency analysis (RFA) values increased from insertion to retrieval for both implant types, while removal torque (RTQ) measurements showed 153% higher biomechanical anchorage of the laser-modified implants. Comparably high bone area (BA) and bone-implant contact (BIC) were recorded for both implant types but with distinctly different failure patterns following biomechanical testing. Fracture lines appeared within the bone ~30-50 µm from the laser-modified surface, while separation occurred at the bone-implant interface for the machined surface. Strong correlations were found between RTQ and BIC and between RFA at retrieval and BA. In the endosteal threads, where all the bone had formed de novo, the extracellular matrix composition, the mineralised bone area and osteocyte densities were comparable for the two types of implant. Using resin cast etching, osteocyte canaliculi were observed directly approaching the laser-modified implant surface. Transmission electron microscopy showed canaliculi in close proximity to the laser-modified surface, in addition to a highly ordered arrangement of collagen fibrils aligned parallel to the implant surface contour. It is concluded that the physico-chemical surface properties of laser-modified surfaces (thicker oxide, micro- and nanoscale texture) promote bone bonding which may be of benefit in situations where large demands are imposed on biomechanically stable interfaces, such as in early loading and in compromised conditions.

Importance of Stereoscopy in Haptic Training of Novice Temporal Bone Surgery.

UNLABELLED: We investigate the effects of stereoscopic simulation on novice trainee surgical performance. METHODS: 20 first year medical students were randomized into a stereo or non-stereo group. Each participant viewed a 13 minute instructional video and then performed 3 mastoidectomy procedures with an in-house haptic temporal bone simulation, using a 3D-capable display with either active (stereo) or inactive (non-stero) shutter glasses. Following training, participants performed an actual mastoidectomy on a single 3D-printed bone model. The printed models were evaluated by 3 blinded neurotologic surgeons using a 7 point grading system. RESULTS: Two-tailed t-tests showed no significant difference in overall performance (mean score across test categories over all subjects) between stereo (M=3.8, SD=1.1) and non-stereo (M=4.4, SD=1.5) conditions (p=0.163). No significant differences existed in any of the assessed sub-domains. CONCLUSIONS: The addition of stereo-vision to haptic training may not affect temporal bone surgical skill acquisition in novice users.

Anti CD163+, Iba1+, and CD68+ Cells in the Adult Human Inner Ear: Normal Distribution of an Unappreciated Class of Macrophages/Microglia and Implications for Inflammatory Otopathology in Humans.

HYPOTHESIS: Identification, characterization, and location of cells involved in the innate immune defense system of the human inner ear may lead to a better understanding of many otologic diseases and new treatments for hearing and balance-related disorders. BACKGROUND: Many otologic disorders are thought to have, as part of their disease process, an immune component. Although resident macrophages are known to exist in the mouse inner ear, the innate immune cells in the human inner ear are, to date, unknown. METHODS: Primary antibodies against CD163, Iba1, and CD68 (markers known to be specific for macrophages/microglia) were used to immunohistochemically stain celloidin embedded archival temporal bone tissue of normal individuals with no known otologic disorders other than changes associated with age. RESULTS: Cells were positively stained throughout the temporal bone within the connective tissue and supporting cells with all three markers. They were often associated with neurons and on occasion entered the sensory cell areas of the auditory and vestibular epithelium. CONCLUSIONS: We have immunohistochemically identified an unappreciated class of cells in the normal adult inner ear consistent in staining characteristics and morphology with macrophages/microglia. As in other organ systems, it is likely these cells play an essential role in organ homeostasis that has not yet been elucidated within the ear.

The viability of perilabyrinthine osteocytes: a quantitative study using bulk-stained undecalcified human temporal bones.

Bone remodeling is highly inhibited around the inner ear space, most likely by the anti-resorptive action of the inner ear cytokine osteoprotegerin (OPG) entering perilabyrinthine bone through the lacuno-canalicular porosity (LCP). This extracellular signaling pathway depends on the viability of individual osteocytes. The objective of this study was to evaluate the patency of the LCP at different ages. Sixty-five bulk-stained undecalcified human temporal bones and 19 ribs were selected to span the ages from the 30th gestational week to 95 years. Osteocytes from inside a 2-mm wide perilabyrinthine zone of bone were identified by 3D vector calculations and the numerical densities estimated with an optical dissector and compared to age-matched ribs. From a high fetal count of 90,000 cells/mm(3), the density of viable capsular osteocytes declined rapidly to 73,000 cells/mm(3) at three years of age, and non-viable osteocytes increased inversely. After 3 years, this decline/increase continued at a much slower rate. The densities of viable as well as non-viable osteocytes and the rates of change were much higher in perilabyrinthine bone compared to ribs. Only after the age of 80 years had the density of viable capsular osteocytes declined to the level of ribs. The bi-phasic osteocyte kinetics reflects different development stages. The high initial density of viable osteocytes may secure a life-long anatomical route for inner-ear OPG despite the unique accumulation of non-viable osteocytes. Clustering of non-viable osteocytes may cause local aberrations in the signaling system by closure of the LCP.

Spiral and vestibular ganglion estimates in archival temporal bones obtained by design based stereology and Abercrombie methods.

The objective of this study was to make direct comparisons of the estimates of spiral and vestibular neuronal number in human archival temporal bone specimens using design-based stereology with those using the assumption-based Abercrombie method. Archival human temporal bone specimens from subjects ranging in age from 16 to 80 years old were used. The number of spiral and vestibular ganglia neurons within the counting areas was estimated using the stereology-optical disector technique and compared with estimates obtained using the assumption-based Abercrombie method on the same specimens. Using the optical disector method, there was an average of 41,480 (coefficient of variation=0.12) spiral ganglia neurons and 28,930 (coefficient of variation=0.15) vestibular ganglia neurons. The mean coefficient of error was 0.076 for the spiral ganglion estimates, and 0.091 for the vestibular ganglion estimates. Using the Abercrombie correction method of two-dimensional analysis, an average of 23,110 (coefficient of variation of 0.08) spiral ganglia neurons, and 16,225 vestibular ganglia neurons (coefficient of variation of 0.15) was obtained. We found that there was a large disparity between the estimates with a significant 44% underestimation of the spiral and vestibular ganglion counts obtained using the Abercrombie method when compared with estimates using the optical disector method.

[A novel cryo-grinding technique for evaluating new cochlear implant electrodes after ex vivo insertions in temporal bone specimens]. / Entwicklung einer Kryo-Schlifftechnik für Felsenbeinpräparate: eine neue Möglichkeit zur Beurteilung ex vivo implantierter CI-Test-Elektroden.

BACKGROUND: Prior to clinical application, newly developed prototypes of cochlear implant electrode arrays must prove their suitability with the smallest possible tissue damage in ex vivo temporal bones. So far, after insertion of the electrodes the temporal bone specimens have to be processed in a rather intricate technique, including embedding, sectioning or grinding prior to histological evaluation. The question remains whether for special indications this time-consuming method, which even causes artifacts, can be replaced by a new technique based on cryo-grinding. MATERIALS AND METHODS: The main principle of the method described is to grind the temporal bone with the inserted electrode in a frozen state, provided by a fixation device filled with dry ice. After creating a plane surface and staining it (still in a frozen state), the specimen can be examined and photographed with a projection microscope. This procedure is continued by subsequently grinding and examining new surfaces in defined distances. RESULTS: In numerous trial runs the method proved feasible, saving much time and manpower. After grinding, each plane could be examined sufficiently; the site of the electrodes and the corresponding tissue damage could be documented properly. DISCUSSION: The new concept of cryo-grinding provides relatively easy and fast examinations of temporal bones after inserting test electrodes. The examiner is enabled to correlate his "sensations" during the insertion (e.g., smoothness, resistances) almost directly with the morphologic findings, without having to wait a long time while the temporal bone specimens are being processed conventionally. Furthermore, this method avoids artifacts due to soft tissue shrinking during drying. In further steps of development, the grinding device will be optimized for standard use.

The effects of age and sex on the expression of oestrogen and its receptors in rat mandibular condylar cartilages.

OBJECTIVE: Oestrogen expression may indicate a difference in resistance potential to mechanical strain. The purpose of this study was to investigate the expression of oestrogen and oestrogen receptors in mandibular condylar cartilages in male and female Sprague-Dawley rats at different ages. MATERIALS AND METHODS: One-hundred SD rats at the age of 2, 4, 8 weeks and 4, 12 months in both sexes, 10 in each age-sex group, were enrolled in this study. The expression of oestradiol, ERalpha and ERbeta was detected in mandibular condylar cartilages by the method of immunohistochemistry, and enzyme-linked immunosorbent assay or western blot. RESULTS: Oestradiol and ERs immunoreactivity were obvious in mandibular condylar cartilages of SD rats. Oestradiol and ERalpha were observed in hypertrophic and mature layers, while ERbeta only in hypertrophic layer. There was no sex difference of same age (except 8-week age group) in the expression of oestradiol. The expression of both ERs, however, was usually higher in male than in age-matched female rats (P<0.05), except that the 8-week-old female rats showed a higher ERalpha expression and the 4- and 8-week-old female rats showed a higher ERbeta expression than the age-matched male ones in western blot results (P<0.05). CONCLUSIONS: The results that oestradiol, ERalpha and ERbeta are co-expressed in rat mandibular condylar cartilage, indicate that mandibular condylar cartilage is a target for oestrogen. The age and sex related differences in ERs expression may indicate a difference in potential to resist mechanical loading between genders at different ages.

Effects of fixative and embedding medium on morphology and immunostaining of the cochlea.

The localization of proteins by immunostaining is a powerful method to investigate otologic disorders. However, the use of fixatives and embedding media (necessary for the preservation of morphology) can obscure antigens, making it difficult to perform immunoassays. We performed a systematic investigation of the effects of fixative and embedding medium on morphology and immunostaining of the mouse cochlea. Three different fixative solutions [4% formaldehyde (F), 4% formaldehyde + 1% acetic acid (FA), and 4% formaldehyde + 1% acetic acid + 0.1% glutaraldehyde (FGA)] and 3 different embedding media (paraffin, polyester wax, and celloidin) were used. Morphology was assessed using light microscopy. Immunostaining was studied using a panel of 6 antibodies (to prostaglandin D synthase, aquaporin 1, connective tissue growth factor, 200-kDa neurofilament, tubulin and Na(+),K(+)-ATPase). Preservation of morphology was suboptimal with paraffin, adequate with polyester wax and superb with celloidin. Immunostaining was successful using all 6 antibodies in all 3 fixatives and all 3 embedding media. While there were differences in strength of signal and localization of antigen between the 3 fixatives, overall, FA and FGA gave the most uniform results. For a given fixative and antibody, there was surprisingly little difference in the quality of immunostaining between celloidin and paraffin, while results in polyester wax were not as good in some cases. These results suggest that celloidin may be the embedding medium of choice for both morphological and pathological studies, including immunostaining when morphology must be optimized.

Scalar localization of the electrode array after cochlear implantation: a cadaveric validation study comparing 64-slice multidetector computed tomography with microcomputed tomography.

HYPOTHESIS: Improved resolution available with 64-slice multidetector computed tomography (MDCT) could potentially be used clinically to localize the cochlear implant (CI) electrode array within the basal turn. BACKGROUND: In CI surgery, the electrode array should be inserted into and remain within the scala tympani to avoid injury to Reissner's membrane and the scala media. Correlating the position of the electrode in the basal turn with surgical technique and implant design could be helpful in improving outcomes. METHODS: After a standard left mastoid exposure of the round window niche through the facial recess performed on a cadaver head, an electrode array from a Nucleus Softip Contour CI was fully inserted through a cochleostomy. The head was then scanned axially on a 64-slice MDCT with 0.4-mm slice thickness and reconstructed into the oblique axial, oblique coronal, and oblique sagittal planes of the cochlea. The temporal bone was then harvested and imaged on a microcomputed tomographic scanner using 20-microm slice thickness. Identical reconstructions were made and compared with the 64-slice images to confirm exact location of the electrode array. RESULTS: The 64-slice MDCT accurately localized the electrode array to the scala tympani. This was best demonstrated in the oblique sagittal plane, identifying the electrode array in the posterior inferior portion of the basal turn, posterior to the spiral lamina. CONCLUSION: This ex vivo validation study suggests that 64-slice MDCT has the potential to allow accurate localization of the CI electrode array within the basal turn of the cochlea.

Study of a temporal bone of Homo heildelbergensis.

CONCLUSIONS: The characteristic features of the Hh specimen conformed to those of other Pleistocene human fossils, indicating strong cranial structures and a heavy mandible. The mastoid was large and suggested a powerful sternocleidomastoid muscle. The inner ear and tympanic cavities were similar in size and orientation, suggesting that their functions were probably similar. Our observations suggest that the left ear of this Hh specimen was healthy. The large canaliculo-fenestral angle confirms that this ancestor was bipedal. It also strongly suggests that Hh individuals were predisposed to develop certain pathologies of the labyrinth capsule associated with bipedalism, in particular otosclerosis. OBJECTIVE: We studied a temporal bone of Homo heidelbergensis (Hh) in order to investigate the clinical and physiological implications of certain morphological features, especially those associated with the evolutionary reorganization of the inner ear. MATERIAL AND METHODS: The bone, found in a breach of a cave near MAáaga in southern Spain, together with Middle Upper Pleistocene faunal remains, is >300000 years old. Four analytical methods were employed. A 3D high-resolution surface laser scan was used for anatomical measurements. For the sectional analysis of the middle and inner ears of Hh we used high-resolution CT, simultaneously studying a normal temporal bone from Homo sapiens sapiens (Hss). To study the middle and inner ear spaces we used 3D reconstruction CT preceded by an intra-bone air shielding technique. To examine the tympanic cavities and measure the canaliculo fenestral angle, we used a special minimally invasive endoscopic procedure. RESULTS: The surface, sectional and 3D CT examinations showed that the Hh specimen was generally more robust and larger than the Hss specimen. It had a large glenoid fossa. The external meatus was wide and deep. The middle ear, and especially the mastoid, was large and widely pneumatized. There were no appreciable differences in the position and size of the labyrinthine spaces and tympanic cavity. The dimensions of the semicircular canals were similar to those of the Hss specimen. Endoscopy revealed normal, healthy tympanic walls and an ossicle fragment in the atticum that probably belonged to the body of the malleus. The diameters of the fallopian duct and the tympanic opening of the Eustachian tube were large. The canaliculo-fenestral angle was approximately 114 degrees

Detection of mitochondrial DNA from human inner ear using real-time polymerase chain reaction and laser microdissection.

CONCLUSIONS: In this study we were able to amplify and analyze extremely small amounts of template DNA from only a few individually dissected cells. We anticipate that this approach will facilitate the detection and analysis of mitochondrial (mt) DNA mutations in specific cell types in the inner ear, which should shed new light on genetic disorders leading to hearing loss. OBJECTIVE: To isolate mtDNA from selected tissues in the inner ear. Although several methods for extracting DNA from formalin-fixed, celloidin-embedded, archival human temporal bones have been reported, the isolation of DNA from the inner ear by means of laser microdissection has not been previously demonstrated. MATERIAL AND METHODS: This was a retrospective study. Temporal bones were obtained from subjects with no known otological history at autopsy. The combined method of laser microdissection and real-time polymerase chain reaction was used to isolate mtDNA from selected tissues in the inner ear. RESULTS: mtDNA could be isolated from the stria vascularis, spiral ligament, spiral ganglion cells and organ of Corti.

Prevalence and variations of pneumatized articular eminence: a study from Turkey.

OBJECTIVES: Pneumatized articular eminence or tubercule (PAT) is an air cell cavity in the zygomatic process of the temporal bone that is similar to air cells in the mastoid process and ethmoid bone. The purpose of this study was to determine the prevalence and variations of PAT among an outpatient dental clinic population at Ankara University, Turkey, to make a contribution to the few current studies about PAT. STUDY DESIGN: A total of 1006 panoramic radiographs were retrospectively investigated for the prevalence and radiographic features of PAT. Meta-analysis was done for 4 large case series in the literature and our case series. Furthermore, we performed Chi-square test to evaluate age, gender, localization, and prevalence differences among 5 case series including ours. RESULTS: PAT was found in 19 (1.88%) patients with a mean age of 36.6 (SD 21.06) years. Twelve cases (63.1%) occurred in females and 7 cases (36.9%) occurred in males. Bilateral PAT was found in 7 patients (36.9%). Meta-analysis of 5 large case series revealed a total of 6669 patients, of whom 115 had PAT (1.76% prevalence) occurring over an age range of 7 to 90 years. Fifty (43.47%) occurred in males and 65 (56.53%) occurred in females. Bilateral PAT was found in 28 (24.34%) patients. The result of Chi-square test showed no statistically significant differences among the 5 studies with respect to age, gender, localization, and prevalence. CONCLUSIONS: Knowledge about these structures is helpful for the interpretation of imaging such as panoramic radiographs and provides valuable information to understand the spread and differential diagnosis of pathological entities in this region. Moreover, clinicians who are planning to perform temporomandibular joint surgery are advised to assess radiographic imaging thoroughly before the surgery to avoid intra-operative complications and reconstruction.

[Anatomohistologic study of von Oort's vestibulocochlear anastomosis]. / Etude anatomo-histologique de l'anastomose vestibulo-cochléaire de von Oort.

OBJECTIVES: The vestibulocochlear anastomosis was first described in 1918 by von Oort. It is situated deeply at the bottom of the internal acoustic meatus, and spreads from the saccular nerve before its terminal ramifications, to the cochlear nerve before its penetration into the cochlea. Nerve fibers of the cochlear efferent system are thought to pass through it. The aim of our study was to investigate the anatomy of the vestibulocochlear anastomosis and characterize its histological features. METHOD: [corrected] Ten human temporal bones were dissected. Serial sections were obtained for histological evaluation. RESULTS: The vestibulocochlear anastomosis was found in seven of the specimens, perfectly visualized in six. Average diameter was 0.5 mm with lengths varying from 0.5 to 1 mm. Serial histological sections demonstrated the nervous nature of the anastomosis and its relations with the saccular and cochlear nerves. The epinevrium of the saccular nerve was continuous with the supposed anastomosis in five of the specimens, demonstrating the distinct nature of the anastomosis from the saccular and cochlear nerves. We did not find any evidence linking these fibers to the cochlear efferent system. DISCUSSION: The vestibulocochlear anastomosis was found in seven of our ten dissections. The anastomosis is probably an anatomic reality composed of nerve fibers. The efferent function of these fibers remains to be demonstrated.

Cochlear implantation via the round window membrane minimizes trauma to cochlear structures: a histologically controlled insertion study.

OBJECTIVE: To evaluate cochlear implant trauma to intracochlear structures when inserting the electrode via the round window membrane. MATERIAL AND METHODS: Eight fresh human temporal bones were evaluated histologically after insertion using two types of cochlear implant array. Bones underwent a special fixation and embedding procedure that allowed sectioning of undecalcified bone with the electrode in situ. Insertions depths were evaluated radiologically and histologically. RESULTS: All arrays were found in the scala tympani of the cochlea. Basal trauma could be avoided in all but one specimen. The mean depth of insertion was 382.5 degrees. Apically, only one implanted bone showed cochlear trauma exceeding lifting of the basilar membrane. CONCLUSION: Insertions through the round window membrane were shown to be atraumatic, even in basal cochlear regions. This route of insertion might be very effective for combined electric and acoustic stimulation of the auditory system.

Proximity of carotid canal wall to tympanic membrane: a human temporal bone study.

OBJECTIVE: The objective was to examine the possible risk of injury to the internal carotid artery during procedures in the middle ear, including myringotomy. STUDY DESIGN: Histopathological morphometric study of human temporal bones. METHODS: One hundred forty-two human temporal bone specimens obtained from 92 individuals without any known ear disease were prepared for light microscopic study. Using 83 bones that were available for measurement, the thickness of the carotid canal wall (CCW), which is the medial wall of the bony portion of the eustachian tube, was measured. Using 15 bones selected for three-dimensional measurement, the closest distance from CCW to the anterior tympanic annulus was measured. Using all 142 temporal bone specimens, the CCW was examined to detect the presence of partial dehiscence. In one case, the images of CCW dehiscence and its surrounding structures were reconstructed by a personal computer. RESULTS: The thickness of the CCW was 0.00 to 0.73 mm (average thickness, 0.24 mm [+/-0.12 mm]). The distance from the CCW to the anterior tympanic annulus was 1.8 to 8.1 mm (average distance, 4.9 [+/-1.7 mm]). Dehiscence of CCW was observed in 7 (4.9%) of 142 temporal bone specimens. The reconstructed image showed that the posterior half of the dehiscence of CCW could be seen from the external ear canal. CONCLUSIONS: The CCW was found to be extremely thin or even dehiscent in some cases, rendering the internal carotid artery vulnerable during transtympanic procedures. The study's findings emphasized the need for judicious care when operating in the anterior mesotympanum.

Correlation of replicating cells and osteogenesis in the glenoid fossa during stepwise advancement.

The purposes of this study were to quantify the number of replicating mesenchymal cells and to correlate it with the amount of new bone formed in the glenoid fossa during stepwise advancement. We randomly divided 250 female Sprague-Dawley rats, 35 days old, into 10 control groups (n = 5) and 20 experimental groups (n = 10). Fifty rats from the stepwise experimental group received initial advancement of 2 mm and another 1.5 mm of advancement on day 30 by the addition of veeners. On days 3, 7, 14, 21, 30, 33, 37, 44, 51, and 60, the rats were killed. One hour before that, the rats were injected with bromodeoxyuridine (BrdU) intravenously. We cut 7-microm tissue sections through the glenoid fossa sagittally and stained them with anti-BrdU antibody to evaluate the number of replicating mesenchymal cells. During the first advancement, the number of replicating cells in the posterior region of the glenoid fossa showed a significant increase compared with natural growth, but a significant decrease compared with 1-step advancement. On the second advancement, however, an increase in the number of replicating cells was observed on day 37 with a subsequent and significant increase in bone formation on day 44. Mandibular advancement conducted in a stepwise fashion increases the number of replicating mesenchymal cells in the glenoid fossa. However, a minimum threshold of strain must first be exceeded before these mesenchymal cells can differentiate to ultimately form new bone.

Replicating mesenchymal cells in the condyle and the glenoid fossa during mandibular forward positioning.

The purpose of this study was to identify and quantify the temporal sequence of replicating mesenchymal cells during natural growth and mandibular advancement in the condyle and the glenoid fossa. One hundred fifty 35-day-old female Sprague-Dawley rats were randomly divided into 10 experimental groups (10 rats each) and 10 control groups (5 rats each). The experimental groups were fitted with appliances that positioned the mandible forward. One hour before the rats were killed, bromodeoxyuridine (BrdU) was intravenously injected into them. Sections were cut and stained with anti-BrdU antibody to evaluate the number of replicating mesenchymal cells. Cellular uptake of BrdU was quantified with the Leica Qwin (Leica Microsystem Imaging Solutions, Cambridge, United Kingdom) system. The results showed that the numbers of replicating mesenchymal cells during natural growth were highest in the posterior region of the condyle and the anterior region of the glenoid fossa. In the experimental groups, the posterior region had the highest number of replicating cells for both the condyle and the glenoid fossa, with the condyle having 2 to 3 times more replicating cells than the glenoid fossa. The number of replicating mesenchymal cells, which is genetically controlled, influences the growth potential of the condyle and the glenoid fossa. Mandibular protrusion leads to an increase in the number of replicating cells in the temporomandibular joint. Individual variations in the response to growth modification therapy could be a result of the close correlation between mesenchymal cell numbers and growth.