Entrance Of Canal Research Articles

Influence of lasing parameters on the cleaning efficacy of laser-activated irrigation with pulsed erbium lasers.

Laser-activated irrigation (LAI) using erbium lasers is an irrigant agitation technique with great potential for improved cleaning of the root canal system, as shown in many in vitro studies. However, lasing parameters for LAI vary considerably and their influence remains unclear. Therefore, this study sought to investigate the influence of pulse energy, pulse frequency, pulse length, irradiation time and fibre tip shape, position and diameter on the cleaning efficacy of LAI. Transparent resin blocks containing standardized root canals (apical diameter of 0.4 mm, 6% taper, 15 mm long, with a coronal reservoir) were used as the test model. A standardized groove in the apical part of each canal wall was packed with stained dentin debris. The canals were filled with irrigant, which was activated by an erbium: yttrium aluminium garnet (Er:YAG) laser (2940 nm, AT Fidelis, Fotona, Ljubljana, Slovenia). In each experiment, one laser parameter was varied, while the others remained constant. In this way, the influence of pulse energy (10-40 mJ), pulse length (50-1000 μs), frequency (5-30 Hz), irradiation time (5-40 s) and fibre tip shape (flat or conical), position (pulp chamber, canal entrance, next to groove) and diameter (300-600 μm) was determined by treating 20 canals per parameter. The amount of debris remaining in the groove after each LAI procedure was scored and compared among the different treatments. The parameters significantly (P < 0.05, Kruskal-Wallis) affecting debris removal from the groove were fibre tip position, pulse length, pulse energy, irradiation time and frequency. Fibre tip shape and diameter had no significant influence on the cleaning efficacy.

Effectiveness of three methods for evaluating root canal anatomy of mandibular incisors.

This study compared the effectiveness of clinical observation, clinical microscopic observation, and tooth-clearing technique in determining the number of canals in mandibular incisors. Root canal ramifications were also analyzed. Using clinical and microscopic analyses, we determined the number of canal entrances in 277 mandibular incisors. In addition, tooth-clearing technique was used to determine the number of canals and frequency of ramifications in the samples. The kappa coefficient was used to compare the different methods with regard to frequency of canals. Most teeth had one canal entrance. The proportion of teeth with two canals was 23.5% by tooth-clearing analysis, 5.8% by clinical microscopy, and 1.1% by clinical analysis. A large number of samples had some type of ramification (40.1%), and most ramifications were present in teeth with two canals. The most frequent ramification was lateral canals (8.3%). Clinical microscopy improved identification of a second canal in mandibular incisors. However, it did not identify second canals in all teeth with two canals. (J Oral Sci 58, 347-351, 2016).

Pudendal Nerve Entrapment Syndrome due to a Ganglion Cyst: A Case Report.

Pudendal nerve entrapment syndrome is an unusual cause of chronic pelvic pain. We experienced a case of pudendal neuralgia associated with a ganglion cyst. A 60-year-old male patient with a tingling sensation and burning pain in the right buttock and perineal area visited our outpatient rehabilitation center. Pelvis magnetic resonance imaging showed the presence of multiple ganglion cysts around the right ischial spine and sacrospinous ligament, and the pudendal nerve and vessel bundle were located between the ischial spine and ganglion cyst at the entrance of Alcock's canal. We aspirated the lesions under ultrasound guidance, and consequently his symptoms subsided during a 6-month follow-up. This is the first report of pudendal neuralgia caused by compression from a ganglion cyst around the sacrospinous ligament.

Root Canal Morphology and Configuration of 179 Maxillary First Molars by Means of Micro–computed Tomography: An Ex Vivo Study

IntroductionThe objective of this study was to propose a root canal configuration description method and to investigate the root canal system morphology of the maxillary first molar by means of micro–computed tomographic imaging. MethodsThe root canal configuration, foramina, and accessory canal frequency of 179 maxillary first molars were investigated by means of micro–computed tomographic imaging and 3-dimensional software imaging. The root canal configuration and main foramina number are described from coronal to apical with a 4-digit system. ResultsThe most frequent root canal configurations were 1-1-1/1 (45.8%), 2-2-2/2 (25.1%) and 2-2-1/1 (10.1%) in mesiobuccal roots and 1-1-1/1 in distobuccal (97.2%) and palatal (98.9%) roots. The first mesiobuccal (MB1) root canal had 1 accessory canal in 26.3% of the teeth, the distobuccal root canal had 12.3%, and the palatal root canal had 9.5%; in the second mesiobuccal root canal, there was rarely 1 accessory canal. There was 1 accessory canal in 26.3%, 12.3%, and 9.5% in the MB1, distobuccal, and palatal root canals, respectively. The MB1, distobuccal, and palatal root canals had 1 main foramen. The MB2 had 1 main foramen in 39.0% of the teeth and no main foramen in 61.0%. ConclusionsThe root canal configuration of maxillary first molars is quite diversified. Contrary to our expectations in this research, the mesiobuccal root has predominantly 1 root canal entrance and only 1 main foramen. Anatomic variations including connecting and accessory canals occur in any third of root.

Eficácia de protocolos de medicação intracanal sobre o biofilme de Enterococcus faecalis em um modelo de dentes bovinos – estudo in vitro

Aim: The purpose of study was to evaluate, in vitro, the effectiveness of intracanal dressing protocols in root canals infected with E.faecalis. Methods: Eighty eight bovine incisors were contaminated with E. faecalis, remaining in culture for 30 days for biofilm formation. The teeth were divided into ten groups according to presence of disinfectant penetration (DP), intracanal dressing and medication placement site: G1 (CHX gel) – 2% chlorhexidine (CHX) gel (cervical third), G2 (CHX liq) – 2% CHX liquid (cervical third), G3 (TC) – tricresol formalin (canal entrance). In these groups (n=10), DP was not performed. G4 (DP+CHX gel) – 2% CHX gel (all thirds), G5 (DP+CHX liq) – 2% CHX liquid (all thirds), G6 (DP+TC) – tricresol formalin (canal entrance), G7 (DP+Ca(OH)2) – calcium hydroxide paste (all thirds). In these groups (n=10) DP with 2% NaOCl was performed. Groups G8 (DP NaOCl) – DP with 2% NaOCl, G9 (DP H2O) – DP with distilled water, and G10 – (no treatment) were considered controls (n=6). Microbiological test (CFUs counting) and scanning electron microscopy (SEM) were performed to evaluate and illustrate respectively the effectiveness of proposed treatments. Results: Microbiological test demonstrated that groups G4 (DP+CHX gel), G5 (DP+CHX liq), G6 (DP+TC) and G7 (DP+Ca(OH)2) showed no bacterial growth, being statistically different from all other groups (p<0.05). Conclusion: 2% chlorhexidine gel, 2% chlorhexidine liquid and calcium hydroxide paste in all root canal thirds, as well as tricresol formalin on root canal entrance, are effective intracanal dressings against E. faecalis, when associated to previous DP with 2% NaOCl.

Pulp revascularization for immature replanted teeth: a case report.

Immature avulsed teeth are not usually treated with pulp revascularization because of the possibility of complications. However, this therapy has shown success in the treatment of immature teeth with periapical lesions. This report describes the case of an immature replanted tooth that was successfully treated by pulp revascularization. An 8-year-old boy suffered avulsion on his maxillary left lateral incisor. The tooth showed incomplete root development and was replanted after 30minutes. After diagnosis, revascularization therapy was performed by irrigating the root canal and applying a calcium hydroxide paste and 2% chlorhexidine gel for 21days. In the second session, the intracanal dressing was removed and a blood clot was stimulated up to the cervical third of the root canal. Mineral trioxide aggregate was placed as a cervical barrier at the entrance of the root canal and the crown was restored. During the follow-up period, periapical repair, apical closure and calcification in the apical 4mm of the root canal was observed. An avulsed immature tooth replanted after a brief extra-alveolar period and maintained in a viable storage medium may be treated with revascularization.

Obliteration of mastoid cavities: 30 years of experience with recommendations for surgical strategy

The obliteration of mastoid cavities is an appropriate intervention to sustainably improve patients' quality of life. After 30 years, 843 cases of mastoid obliteration were analyzed from the pool of data resulting from 16,000 surgical procedures on the ear. The materials used by the authors included cartilage/bone, Palva flaps, and bone pâté; as well as alloplastic material such as hydroxyapatite (HA) and bioactive glass granules (BAG S53P4) from BonAlive® (BonAlive Biomaterials Ltd., Turku, Finland). Pathological findings included rejection with inflammation, granulation of the auditory canal reconstruction, unclear retraction pockets, as well as shrinkage and cicatricial contraction. The follow-up interval was at least 4 months, with an average of 33 months (standard deviation ± 27.8 months). Use of HA was discontinued after 18 cases, because rejection and retraction occurred in 33% of patients. The same applied for bone pâté after 33 cases, with a pathological finding in 21%. The Palva flaps (145 cases) showed pathological findings in 21% of cases, primarily in the form of shrinkage (7%) and retractions (10%). Cartilage/bone pieces (516 cases) and BAG S53P4 (133 cases) only showed abnormal postoperative findings in 8% and 3%, respectively. It is recommended to focus particularly on auditory canal and canal entrance expansion during mastoid obliteration surgery. When using the bioactive glass granules, postoperative use of a mini-drain for 1-2 days is beneficial, in order to avoid accumulation of seroma fluid in the mastoid. In our experience, a combination of BAG S53P4 and cartilage as cover is a suitable material for cavity obliteration.

Numerical simulation of wave propagation in a realistic model of the human external ear

In this study, a numerical investigation is performed to evaluate the effects of high-pressure sinusoidal and blast wave's propagation around and inside of a human external ear. A series of computed tomography images are used to reconstruct a realistic three-dimensional (3D) model of a human ear canal and the auricle. The airflow field is then computed by solving the governing differential equations in the time domain using a computational fluid dynamics software. An unsteady algorithm is used to obtain the high-pressure wave propagation throughout the ear canal which is validated against the available analytical and numerical data in literature. The effects of frequency, wave shape, and the auricle on pressure distribution are then evaluated and discussed. The results clearly indicate that the frequency plays a key role on pressure distribution within the ear canal. At 4 kHz frequency, the pressure magnitude is much more amplified within the ear canal than the frequencies of 2 and 6 kHz, for the incident wave angle of 90° investigated in this study, attributable to the ‘4-kHz notch’ in patients with noise-induced hearing loss. According to the results, the pressure distribution patterns at the ear canal are very similar for both sinusoidal pressure waveform with the frequency of 2 kHz and blast wave. The ratio of the peak pressure value at the eardrum to that at the canal entrance increases from about 8% to 30% as the peak pressure value of the blast wave increases from 5 to 100 kPa for the incident wave angle of 90° investigated in this study. Furthermore, incorporation of the auricle to the ear canal model is associated with centerline pressure magnitudes of about 50% and 7% more than those of the ear canal model without the auricle throughout the ear canal for sinusoidal and blast waves, respectively, without any significant effect on pressure distribution pattern along the ear canal for the incident wave angle of 90° investigated in this study.

Ballast tank biofilms resist water exchange but distribute dominant species

Shipping in the Laurentian Great Lakes includes numerous “lakers” and a group of international vessels arriving via the St. Lawrence Seaway. It was expected that ballast water exchange techniques, or eventual volumetric ballast water treatment, would eliminate the risks of transfer of ballast tank nuisance aquatic and aerosol organisms to Great Lakes ports and other parts of the world. New and important information is that ballast water exchanges and current ballast water treatments are not effective in destroying biofilms on tank walls and sediments that provide living micro-organisms for new biofilms and bioaerosols. Our Ballast Organic Biofilm (BOB) studies of around-theworld ships associated with multiple ballasting events in the continuous presence of BOB samplers showed that dominant microorganisms are acquired and persist, and can be spontaneously transferred to fresh surfaces and also delivered as bioaerosols from discharged ballast water plumes. This communication uses such studies to infer that a port-based ballast tank water-exchange and cleaning procedure can mitigate such biofilm risks to health and existing biodiversity. A useful site would be the Port of Buffalo, just opposite the Welland Canal entrance for international shipping to the upper Great Lakes.

AERODYNAMICS AND AEROACOUSTICS OF AIRFLOW OVER A HUMAN HEAD

Airflow should be affected by ear, nose, etc, and aerodynamic sound could be brought when the human head and the airflow occurs at a relative speed movement. Because the drag force of the head is large, in cycling competitions and other high-speed sport the diversion hats should be worn. After the speed of airflow reaches to a certain speed, due to the strong airflow interference, the aerodynamic noise could be brought and it could greatly impact on the athletes to make action decisions. In this paper, computational fluid dynamics (CFD) method is used for solving the aerodynamic behavior of a human head under different air velocities, and the pressure on head surface and the airflow around the head are calculated. Then, the above-mentioned conditions of different aerodynamic sound are solved by the finite element/infinite element method (FEM/IFEM), the points in the canal entrance of the two ears are picked up for collecting the SPL spectral curves, and the sound distribution of the horizontal plane and the median plane are drawn. Previous studies showed that the aerodynamic noise brought by head spoiler is obvious at low frequencies, because the influence of the head, if the airflow speed is greater than a certain value, the aerodynamic noise could not only increase, but also should be substantially reduced. The results are useful for athlete diversion cap design and spatial hearing research in which the influence of the airflow should be considered.

Correlation of lateral stenosis in MRI with symptoms, walking capacity and EMG findings in patients with surgically confirmed lateral lumbar spinal canal stenosis.

BackgroundTo evaluate the clinical significance of lateral lumbar spinal canal stenosis (LLSCS), found by magnetic resonance imaging (MRI), through correlating the imaging findings with patient symptoms, walking capacity and electromyography (EMG) measurements.Method102 patients with symptoms of LSS referred for operative treatment were studied in this uncontrolled study. Of these patients, subjects with distinct only lateral LSS were included. Accordingly, 140 roots in 14 patients (mean age 58, range 48-76 years, male 43%) were evaluated. In MR images the entrance and mid zones of the lateral lumbar nerve root canal were graded as normal, narrowed but not compressed, or compressed. In quantitative analysis, the minimal widths of the lateral recess and mid zone area were measured. Clinical symptoms were recorded with the Oswestry Disability Index (ODI), overall Visual Analogue Scale (VAS), specific low back pain (LBP; NRS-11), specific leg pain (LP NRS-11), Beck Depression Inventory (BDI) and walking distance in the treadmill test. Lumbar paraspinal (L2- L5) and lower limb (L3 – S1) needle EMG studies were performed. The findings were classified root by root as 1 = normal, 2 = abnormal. The associations between radiological, EMG and clinical findings were tested with each other.ResultsEMG findings were normal in 92 roots and abnormal in 48 roots. All of the patients had at least one abnormal nerve root finding. Severity of the mid zone stenosis in MRI correlated with abnormal EMG findings (p = 0.015). Patients with abnormal EMG had also higher scores in the VAS (41.9 ± 25.7 vs 31.5 ± 18.1; p = 0.018), NRS leg pain (7.5 ± 1.5 vs 6.3 ± 2.1; p = 0.000) and BDI (9.8 ± 3.8 vs 8.0 ± 3.9; p = 0.014). However, no statistically significant correlations between MRI findings and clinical symptoms or walking capacity were found.ConclusionsAmong persons previously selected for surgery, lateral stenosis seen on MRI correlates with EMG, and thus may be a clinically significant finding. Our EMG findings were also associated with patient symptoms. However, no relationships between the MRI findings and symptoms or walking capacity were found, suggesting their multifactorial etiology.

An in-situ calibration method and the effects on stimulus frequency otoacoustic emissions.

BackgroundThe interference between the incoming sound wave and the acoustic energy reflected by the tympanic membrane (TM) forms a standing wave in human ear canals. The existence of standing waves causes various problems when measuring otoacoustic emissions (OAEs) that are soft sounds closely related with the functional status of the inner ear. The purpose of this study was to propose an in-situ calibration method to overcome the standing-wave problem and to improve the accuracy of OAE measurements.MethodsIn this study, the sound pressure level (SPL) at the TM was indirectly estimated by measuring the SPL at the entrance of the ear canal and the acoustic characteristics of the earphone system, so that sound energy entering the middle ear could be controlled more precisely. Then an in-situ calibration method based on the estimated TM SPL was proposed to control the stimulus level when measuring the stimulus frequency otoacoustic emissions (SFOAEs) evoked by swept tones. The results of swept-tone SFOAEs with the in-situ calibration were compared with two other calibration methods currently used in the clinic.ResultsOur results showed that the estimate of the SPL at the TM was rather successful with the maximal error less than 3.2 dB across all the six subjects. With the high definition OAE spectra achieved by using swept tones, it was found that the calibration methods currently used in the clinic might over-compensate the sound energy delivered to the middle ear around standing-wave frequencies and the SFOAE amplitude could be elevated by more than 7 dB as a consequence. In contrast, the in-situ calibration did not suffer from the standing-wave problem and the results could reflect the functional status of the inner ear more truthfully.ConclusionsThis study suggests that calibration methods currently used in the clinic may produce unreliable results. The in-situ calibration based on the estimated TM SPL could avoid the standing-wave problem and might be incorporated into clinical OAE measurements for more accurate hearing loss screenings.

Wideband detection of middle ear muscle activation using swept-tone distortion product otoacoustic emissions.

The measurement of efferent-induced suppression of otoacoustic emissions (OAEs) using contralateral acoustic stimulation (CAS) is complicated by potential contamination by the middle ear muscle reflex (MEMR), particularly at moderate to high CAS levels. When logarithmically sweeping primaries are used to measure distortion product otoacoustic emissions, the level and phase of the primaries at the entrance of the ear canal may be monitored simultaneously along with the OAEs elicited by the swept-tones. A method of detecting MEMR activation using swept-tones is presented in which the differences in the primaries in the ear canal with and without CAS are examined, permitting evaluation of MEMR effects over a broad frequency range. A range of CAS levels above and below expected contralateral acoustic reflex thresholds permitted evaluation of conditions with and without MEMR activation.

Correlation of Lateral Stenosis in MRI with Symptoms, Walking Capacity, and EMG Findings in Patients with Surgically Confirmed Lateral Lumbar Spinal Canal Stenosis

Introduction The aim of this study is to evaluate the clinical significance of lateral lumbar spinal canal stenosis (LLSCS), found by magnetic resonance imaging (MRI), through correlating the imaging findings with patient symptoms, walking capacity and electromyographic (EMG) measurements. Materials and Methods A total of 80 patients with symptoms of LSS severe enough to indicate operative treatment were studied with MRI. Of these patients, subjects with distinct lateral LSS were included. Accordingly, 140 roots in 14 patients (mean age, 58 years; range, 48-76 years; male, 43%) were evaluated. In MR images, the entrance and midzones of the lateral lumbar nerve root canal were graded as normal, narrowed but not compressed, or compressed. In quantitative analysis, the minimal widths of the lateral recess and midzone area were measured. Clinical symptoms were recorded with the oswestry disability index (ODI), overall visual analogue scale (VAS), specific low back pain (LBP; NRS-11), specific leg pain (LP NRS-11), beck depression inventory (BDI), and walking distance in the treadmill test. Lumbar paraspinal (L2-S1) and lower limb needle EMG studies were performed. The findings were classified root by root as 1 = normal, 2 = abnormal. The associations between radiological, EMG, and clinical findings were tested with each other. Results LLSCS was confirmed in all patients during surgery. EMG findings were normal in 92 roots and abnormal in 48 roots. All of the patients had at least one abnormal nerve root finding. Severity of the midzone stenosis in MRI correlated with abnormal EMG findings ( p = 0.015). Patients with abnormal EMG had also higher scores in the VAS (41.9 ± 25.7 vs. 31.5 ± 18.1; p = 0.018), NRS leg pain (7.5 ± 1.5 vs. 6.3 ± 2.1; p = 0.000), and BDI (9.8 ± 3.8 vs. 8.0 ± 3.9; p = 0.014). However, no statistically significant correlations between MRI findings and clinical symptoms or walking capacity were found. Conclusion MRI findings correlated with abnormal EMG, indicating that a lateral stenosis seen by MRI is a clinically significant finding. However, no relationships between the MRI findings and symptoms or walking capacity were found, suggesting their multifactorial etiology. MRI and EMG may be useful in the workup of patients with suspected LLSCS. Disclosure of Interest None declared

The optimal toll scheme for ships queuing at the entrance of Panama Canal

As the insufficiency of watercourses and the limitation of breadth are leading to long queues at Panama Canal, the plan of canal expansion is undertaken by the authorities to increase the service capacity. In order to avoid ships queuing at the entrance of the canal, this research establishes an optimal toll scheme, which will effectively disperse ship arrival times and eliminate long queues. The research shows all ship arrival rates at the entrance of canal before and after implementing the optimal toll scheme.

Irrigant transport into dental microchannels

The root canal system of a tooth is a complex geometrical entity, consisting not only of the main root canal, but also of accessory and lateral canals. Bacteria can reside up to hundreds of micrometers inside those channels and may be difficult to reach for the antimicrobial agents with which root canals are irrigated during a root canal treatment. A combined numerical and experimental study was performed to assess the penetration rate of a root canal irrigant into the lateral canals and tubules, considering both diffusion and convection. The numerical model was validated experimentally using a fluorescent dye. Convection was studied separately using a Computational Fluid Dynamics model, validated with Particle Imaging Velocimetry experiments. Both diffusion and convection were found to be slow on the timescale of an irrigation procedure. The contribution of convection was limited to two canal diameters from the canal entrance, making diffusion the main irrigant transport mechanism. More than 10 min of fresh irrigant delivery was required to obtain an 86 % concentration of the irrigant at the far end of a tubule, in the ideal case of a straight tubule without reaction taking place. Diffusion was even slower when the concentration at the lateral canal entrance was not kept constant, as in the case of a single delivery, which suggests that frequent irrigant replenishment and/or irrigant activation during a root canal treatment are beneficial. Alternative methods should be considered to improve irrigant penetration into lateral canals and tubules.

Morphological study of the asymmetrical buccal cavity of the flatfish common solea (Solea solea) and its relation to the type of feeding

ObjectiveTo investigate the surface architecture of the asymmetrical buccal cavity of Solea solea which are considered one of the most important predators in benthic communities. MethodsAdult Solea solea were obtained from Mediterranean Sea near Damietta. The heads were removed and processed for scanning electron microscopy. Its buccal cavity is asymmetrical and divided into roof and floor and the tongue for histological studies. ResultsThe buccal cavity roof is formed from upper jaw, velum and the palate. The upper jaw has several wing like processes with teeth arranged in several rows which may help in cutting and pushing the food to the entrance of the digestive canal while the floor is formed from the lower jaw and the tongue. The tongue is divided into apex, body and root. There is a gradual decrease of goblet cells in the tongue from anterior to posterior. These goblet cells function in protection of the epithelium. ConclusionsTeeth in the floor of the buccal cavity and taste buds can be considered adaptive changes of the oral cavity related to the feeding habits and was a source to identify new and better methods of nutrition in aquaculture of Solea solea.

Efficacy of laser-based irrigant activation methods in removing debris from simulated root canal irregularities

In root canal therapy, irrigating solutions are essential to assist in debridement and disinfection, but their spread and action is often restricted by canal anatomy. Hence, activation of irrigants is suggested to improve their distribution in the canal system, increasing irrigation effectiveness. Activation can be done with lasers, termed laser-activated irrigation (LAI). The purpose of this in vitro study was to compare the efficacy of different irrigant activation methods in removing debris from simulated root canal irregularities. Twenty-five straight human canine roots were embedded in resin, split, and their canals prepared to a standardized shape. A groove was cut in the wall of each canal and filled with dentin debris. Canals were filled with sodium hypochlorite and six irrigant activation procedures were tested: conventional needle irrigation (CI), manual-dynamic irrigation with a tapered gutta percha cone (manual-dynamic irrigation (MDI)), passive ultrasonic irrigation, LAI with 2,940-nm erbium-doped yttrium aluminum garnet (Er:YAG) laser with a plain fiber tip inside the canal (Er-flat), LAI with Er:YAG laser with a conical tip held at the canal entrance (Er-PIPS), and LAI with a 980-nm diode laser moving the fiber inside the canal (diode). The amount of remaining debris in the groove was scored and compared among the groups using non-parametric tests. Conventional irrigation removed significantly less debris than all other groups. The Er:YAG with plain fiber tip was more efficient than MDI, CI, diode, and Er:YAG laser with PIPS tip in removing debris from simulated root canal irregularities.

Light‐based Contact Hearing Device: Characterization of Available Feedback Gain Margin at Two Device Microphone Locations

Objectives: Assistive devices compensate for hearing impairment by amplifying sounds with gain, which is limited by acoustic feedback. The light-based Contact Hearing Device (CHD) provides amplification to 10 kHz by mechanically vibrating the umbo with a wireless Tympanic Contact Actuator (TCA). Driving the eardrum mechanically generates a pressure wave, which travels laterally down the ear canal and produces feedback. Placing the microphone closer to the canal entrance may preserve more natural acoustic cues than the BTE location, although it may reduce available FGM. Our objective was to characterize the feedback gain margin (FGM) at two microphone locations using the CHD to determine if both locations are compatible with treating a broad range of hearing-impaired subjects. Methods: Thirteen subjects with bilateral mild-to-severe hearing impairment were fitted with CHDs (26 ears). The TCA was driven with light-pulses, and the feedback pressure was measured at two microphone locations: at the fossa triangularis (FT) and above the pinna at the BTE microphone location. The FGM from 1-10 kHz was computed (FGM below 1 kHz is not measureable). Results: The mean FGM varied from 32-48 dB and 38-60 dB for the FT and BTE microphone locations respectively. FGM was lowest in the 3-5 kHz range and highest at about 7 kHz. The STD of FGM varied from 5.3-13 dB due individual anatomies. Conclusions: A microphone at the BTE has 6-12 dB additional FGM over a microphone at a FT location and allows a broader inclusion range to fit impaired patients with amplification to 10 kHz.

The Narrowest Part of the Bony Nasolacrimal Canal

To determine the narrowest diameter of the bony nasolacrimal canal. Fifty-eight bony nasolacrimal canals from 29 Japanese cadavers (12 men and 17 women; average age at death, 83.4 years; range, 70-99 years) had been fixed in 10% buffered formalin before use. After exposing the medial (44 canals) or posterior half (14 canals) of the bony nasolacrimal canal, the part with the shortest anteroposterior or transverse diameter was determined on inspection. These positions from the canal entrance were measured, and the distance ratio, indicating where the shortest diameter was located in relation to the total length of the canal, was calculated. The shortest anteroposterior and transverse diameters were at the entrance to the canal in 32 of 44 canals (72.7%) and in 9 of 14 canals (64.3%), respectively. In the other canals, the shortest anteroposterior and transverse diameters were located at an average of 3.6 and 5.6 mm from the entrance, and the distance ratios were 29.0% and 46.7%, respectively. The mean shortest anteroposterior and transverse diameters were 5.6 and 5.6 mm, respectively. The shortest anteroposterior and transverse diameters were at the entrance of the canal in most of the bony nasolacrimal canals. These results are comparable with the rate of obstruction at the canal entrance in primary acquired nasolacrimal duct obstruction.