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This study investigated the marginal fit of the prefabricated crowns for the Ha-Ti implant system using scanning electron microscopy. The results demonstrated that the mean gap between the crown margin and the implant base was less than 3 micrometers following simulated ceramic firing and continuous loading in vitro.
Regardless of whether CVK is used qualitatively for RGP lens design selection or quantitatively in RGP parameter selection, it has a significant role in contact lens practice. Further advancements and testing on CVK-based RGP fitting modules and fluorescein simulations will make CVK an invaluable tool for the RGP lens fitter. Soft lens applications of CVK data are already being tested [42,43]. This technology will become the standard of care for all contact lens patients and will most likely replace the keratometer.
The PediPump is a new ventricular assist device with a hydraulic output range designed for children from newborn infants to adolescents. The design is based on a mixed-flow rotary pump; the rotating assembly consists of a front impeller, front and rear radial magnetic bearings, and a central motor magnet. Two different implantable pumps were designed initially: an intravascular pump measuring 7 x 75 mm and an extravascular pump measuring 14 x 85 mm. Current prototypes are substantially smaller: The current intravascular version measures 4.5 x 55 mm, whereas the current extravascular version measures 11 x 70 mm. Both devices provide pressure and flows capable of supporting adults, far exceeding the initially defined physiologic requirements for children weighing 2 to 25 kg. This basic pump design may be used in acute or chronic clinical settings to provide right ventricular, left ventricular, or biventricular support. There are three objectives for the PediPump development program: 1) determination of basic engineering requirements for hardware and control logic including design analysis for system sizing, evaluation of control concepts, and bench testing of prototypes; 2) performance of preclinical anatomic fitting studies using CT-based 3D modeling; and 3) animal studies to provide characterization and reliability testing of the device.
The authors report the results obtained with the use of the Montgomery silicone prosthesis for the prevention or treatment of thick and sometimes partially stenosing synechiae of the anterior commissure following bilateral cordectomy by median thyrotomy. The umbrella-shaped prosthesis consists of two silicone sheets which are perpendicular to each other. The vertical sheet is of variable length and, once placed in position, it separates at the anterior commissure the two portions of larynx operated on, so that they may be adequately reepithelized. This procedure was used in three patients undergoing internal subperichondral cordectomy by median thyrotomy, due to a malignancy in both vocal folds which, however, was not extended to the anterior commissure. In two patients the prosthesis was fitted in during the main surgical procedure to prevent an excess of scar tissue; in the third patient, by contrast, it was used to treat a thick, partially stenosing synechia in the commissure secondary to cordectomy, which had already been unsuccessfully managed under direct microlaryngoscopy. In the three patients the prostheses were left in place for 2 and a half, 3, and 3 and a half months, respectively, with no major irritation or inflammation inside the larynx. No supportive tracheotomy had to be performed, and only in one case was the prosthesis secured externally by percutaneous stitching. On indirect laryngoscopy several months after the prosthesis was removed, two patients showed a perfectly healed larynx; in the third patient a very small amount of scar tissue in excess was still present, but it did not affect his respiratory function.
The literature on self-assessed outcomes from bilateral and unilateral hearing aid fitting is reviewed. The nature, aims, and design of different studies are quite varied, and limitations attend many of them. Nonetheless, certain indications can be extracted from the pattern of reported results. Thus, greater measured impairment, greater self-rated disability, and/or more critical contexts of listening emerge as candidate predictors of preference for, or persistence with, a bilateral fitting profile. Two matters are briefly critiqued regarding one vs two hearing aids: 1) the analogue with binocular optical correction; 2) the unaided ear ("deprivation") effect. Questions are raised about the adequacy of the range of hearing functions addressed by previous investigations of bilateral vs. unilateral fitting-and a broadened range of functions is outlined. A recent self-report-based comparison of one versus two hearing aids (Noble & Gatehouse, International Journal of Audiology, 2006) reveals that the benefit of two lies in contexts of more demanding and dynamic listening and in reduced listening effort.
Audiometric measurements are traditionally made in dB HL, which by definition are specified relative to the sound pressure level (SPL) in a coupler. Real-ear dB SPL is then estimated by applying an average ear transform to the coupler value. However, individual variation in ear canal acoustics and variations in transducer placement strongly influence the dB SPL of signals arriving at the eardrum. In this paper, data from 1814 ears are presented, showing that the distribution of eardrum dB SPL for a fixed signal level varies across ears and across frequency by as much as 40 dB. The impact of this variance upon hearing aid targets computed with the NAL-NL1 fitting algorithm is examined by comparing the targets obtained from using an average transform with those obtained when audiometric data in dB SPL are obtained by applying individually measured real-ear-to-coupler difference (RECD) values to dB HL thresholds. The impact can be considerable.
AIM: The purpose of this in vitro study was to investigate the marginal accuracy and internal fit of complete cast crowns and three-unit fixed partial dentures (FPDs) cast with commercially pure titanium (CPTi) and Titanium-Aluminum-Vanadium alloy (Ti-6Al-4V). METHODS AND MATERIALS: CPTi and Ti-6Al-4V alloy were used to cast twelve single crowns and twelve three-unit FPDs. A traveling microscope was used to measure marginal gap and discrepancies in internal fit. Two and one-way analysis of variance (ANOVA) analyses were used to determine the effects of the marginal and internal fit discrepancies. RESULTS: The Ti-6Al-4V alloy demonstrated a significantly smaller marginal gap than CPTi (P<0.0001). The recorded marginal discrepancies for both metals were within a clinically accepted range (<100 microm). The single crown fit discrepancy was significantly smaller than the three-unit FPD for both the CPTi and the Ti-6Al-4V alloy (P<0.0001). For the internal fit discrepancy, the occlusal surface showed the greatest gaps. CONCLUSIONS: The Ti-6Al-4V alloy demonstrated a better fit than CPTi. Single crowns showed an improved fit when compared with the three-unit FPD. Mid-occlusal internal gap demonstrated greater values than the axial internal gap. CLINICAL IMPLICATIONS: This in vitro study suggested marginal fit of complete crowns and three-unit FPDs cast by CPTi or Ti-6Al-4V alloy were within the range of what is clinically acceptable for longevity of restorations.
PURPOSE: To assess the efficacy of computerized corneal topography in (1) fitting cosmetic rigid gas permeable contact lenses on normal corneas and (2) patients who have keratoconus. METHODS: In study 1, 26 patients were fitted with cosmetic contact lenses. In 13 patients, the first rigid gas permeable lens was chosen on the basis of corneal topography using the EyeSys videokeratoscope and contact lens software version 2.11w. Thirteen control patients were fitted with rigid gas permeable contact lenses by means of diagnostic contact lenses. The number of parameter changes required in each group to reach the best fit were compared. In study 2, the records of 28 patients (41 eyes) with keratoconus who had been successfully fit with rigid gas permeable lenses were reviewed. Topographic analysis using the EyeSys videokeratoscope was conducted. The following 8 data points were analyzed: maximum dioptric curvature with respect to the central visual axis, the power at the visual axis (VK), the average keratometry readings within the 3-mm zone, the average flat K at 3-mm central and 5-mm paracentral regions, and the K reading at 1.5, 2.0, and 2.5 mm superior to the visual axis. RESULTS: Study 1: In 10 eyes (38%) fitted with cosmetic contact lenses utilizing corneal topography and the EyeSys contact lens program, the first lens chosen by the computer program was correct with no additional changes in lens parameters required. In the other 16 eyes, 21 parameter changes were required. In the control group, 14 eyes (53%) required no additional change in parameters from the original contact lens that was fitted using diagnostic lenses. In the other 12 eyes, 12 parameter changes were required. Study 2: In the keratoconus group, of the 9 measurements analyzed, the final base curve of patients' rigid gas permeable lenses was correlated most closely with the average flat corneal curvature at the 3-mm central zone. CONCLUSION: Study 1: In fitting cosmetic rigid gas permeable contact lenses, the videokeratoscope with the EyeSys software 2.11w contact lens program proved to be inferior to diagnostic lenses in selecting the final correct contact lens parameters. However, it may be useful in selecting an initial diagnostic lens with which to begin rigid gas permeable fitting. Study 2: In patients with irregular corneas such as keratoconus, corneal topography is helpful in determining the initial base curve of the contact lens. In patients with keratoconus, it appears to be the average flat corneal curvature at the 3.0-mm zone.
The concept of measuring pressure at the interface between the stump and the prosthetic socket could provide valuable information in the process of prosthetic socket fabrication, modification, and fit. Two systems, the Rincoe Socket Fitting System (SFS) and Tekscan's F-Socket Pressure Measurement System, have been commercially designed for in situ interface pressure measurement over the past decade. Their use is not common in prosthetic practice, perhaps due to questions of cost effectiveness and the difficulties of interpreting the data. Another concern is the use of sensors for pressure measurements in areas of high contour and complex geometries such as the stump. Before these systems can be used in a clinical setting, it is necessary to determine the reliability and accuracy of each system. In order to assess the clinical validity of the Rincoe SFS and F-Socket systems, a series of trials was conducted to evaluate different aspects of sensor performance, namely; accuracy, hysteresis, drift and the effect of curvature. The sensors were subjected to tests in flatbed and custom-designed pressure vessels. Overall results indicated an accuracy error for the Rincoe SFS system of 25% (flatbed) and 33% (mould), with a corresponding 15% (flatbed) and 23% (mould) error in hysteresis, and 7% (flatbed) and 11% (mould) drift errors. The F-Socket system demonstrated an 8% (flatbed) and 11% (mould) accuracy errors, 42% (flatbed) and 24% (mould) hysteresis errors, and 12% (flatbed) and 33% (mould) drift errors. These findings indicate favourable results for the F-Socket Pressure Measurement System compared to the Rincoe Socket Fitting System with respect to its accuracy errors only. Nevertheless, it is the authors' belief that these systems are adequate in indicating areas of high pressure at the stump socket interface for clinical purposes, but both systems should be used with caution.
PURPOSE: Spectral optical coherence tomography (SOCT) is a new non-invasive, non-contact, high-resolution technique, which provides cross-sectional images of objects that weakly absorb and scatter light. The aim of this article is to demonstrate the application of SOCT to imaging of eyes fitted with contact lenses. METHODS: Nine eyes of six different subjects fitted with various contact lenses have been examined with a slit-lamp and a prototype SOCT instrument. RESULTS: Our SOCT system provides high-resolution (4-6 mum longitudinal, 10 mum transversal) tomograms composed of 3000-5000 A-scans with acquisition time of 100-250 ms. The quality of the images is adequate for detailed evaluation of contact lens fit. Design, shape and lens edge position were assessed, and complications of contact lens wear could be visualized. Thickness of the lens, corneal epithelium and stroma as well as the space between the lens and the eye surface have been measured. CONCLUSIONS: SOCT allows high-resolution, cross-sectional visualization of the eye fitted with a contact lens. The ability to carry out a detailed evaluation of the fitting relationship between the lens and the ocular surface might be useful in research and optometric practice. SOCT can also be helpful in diagnosis, evaluation and documentation of contact lens complications.
PURPOSE: To describe reverse geometry rigid gas permeable (RGP) contact lens fitting in eyes with irregular surface induced by complications after myopic corneal refractive surgery. METHODS: Reverse geometry RGP contact lenses were fit in nine eyes that underwent myopic corneal refractive surgery and experienced a reduction in best spectacle-corrected visual acuity (BSCVA) Snellen lines postoperatively. RESULTS: Comparing the BSCVA with contact lenses, 5 (55.6%) eyes improved > or = 2 lines of BSCVA, 2 (22.2%) eyes improved 1 line, and 2 (22.2%) eyes maintained the same BSCVA as the one eye with spectacles (P < .004). No eye lost lines of BSCVA. All patients reported excellent tolerance and subjective visual quality with the contact lenses. The mean time of contact lens wear was 10.44 +/- 0.88 hours per day (95% confidence interval, 9.76 to 11.12). CONCLUSIONS: Reverse geometry RGP contact lens fitting is effective in correcting surgically induced irregular surfaces with improved visual acuity and comfortable wear. These lenses may be the best choice in cases in which surgical retreatment is unfeasible or undesirable.
PURPOSE: Globe luxation, characterized as the anterior dislocation of the eyeball beyond retracted lids, presents a dramatic clinical picture. It is an uncommon event and can produce anxiety in both the patient and the physician. The purpose of this article is to present a case of spontaneous globe luxation which occurred with attempted contact lens placement. METHODS: A case report and literature review are presented. RESULTS: Manual reduction of the globe required conscious sedation in the emergency room. Diffuse superficial punctate keratitis resolved completely with no visual sequelae. DISCUSSION: The clinical features, epidemiology, risk factors, complications and treatments of globe luxation are presented. Eye care specialists who fit and dispense contact lenses should be aware of risk factors associated with globe luxation. A step-wise plan for management is presented, in hope of limiting patient discomfort, recurrence, and perhaps long-term visual impairment.
OBJECTIVE: It was the objective of this study, to analyze the influence of the marginal design on the marginal accuracy of a casting in a clinical setup in patients. METHODS: Ninety volunteer patients' teeth-which were intended for extraction due to medical reasons-were prepared prior to extraction. Three different types of finishing line-chamfer, 135 degrees shoulder and 90 degrees shoulder-were employed. Two each c-silicone and pvs impressions were taken of each tooth using either a two-stage or a one-stage putty-wash technique. After preparation and impression taking the teeth were extracted. Gypsum casts were poured from the impressions and high precious alloy castings fabricated on the dies and marginal discrepancies were determined on the extracted teeth. RESULTS: The median value of marginal discrepancies was lower than 150 microm for all groups. The difference between the three different preparation types was significant (H-test, p<0.05). The lowest median values were obtained for the chamfer preparations, while the 90 degrees shoulders always produced the highest median values. Preparations at gingva level exhibited more accurate marginal fit than subgingival preparations. No significant differences could be observed between the pvs and c-silicone materials or the one-step and two-step putty-wash techniques. CONCLUSIONS: The marginal designs of the preparations had much less influence on the marginal fit of high precious alloy castings than expected. There is considerable reason to assume that technical but clinical parameters influence the quality of fixed prosthodontics much more than has been believed in the past.
BACKGROUND: Rigid gas permeable (RGP) contact lenses have numerous benefits; however, RGP lens use is not increasing in the United States. An important factor for this trend has been initial comfort. Studies have demonstrated that how RGPs are presented to patients, in addition to lens design, can play an important role in the initial comfort process. Another important factor could be the use of a topical anesthetic during the fitting and dispensing visits. The purpose of this study was to use a multicenter format to determine if topical anesthetic use increased the likelihood of patient satisfaction and success. METHODS: A total of 80 subjects, with no previous rigid lens wear experience, was entered into this 1-month study, including 20 subjects from each of 4 institutions. Subjects were randomly divided into the following two groups: (A) anesthetic or (B) placebo, with the former group receiving one drop of a topical anesthetic before lens insertion at both the diagnostic fitting and dispensing visits, whereas the latter group received a placebo. Subjects completed a questionnaire on their perception of rigid lens wear both immediately before fitting and at the 1-month visit. After diagnostic fitting with rigid lenses, subjects completed an adaptation questionnaire after 15 min, 1 week, 2 weeks, and 1 month of lens wear. RESULTS: Seventy of the 80 subjects completed the study and, of the 10 subjects who discontinued, 8 were in the placebo group. In all categories evaluated, the anesthetic group experienced a more optimum adaptation experience at each visit vs. the placebo group. Specifically, overall comfort was rated significantly higher at both dispensing and 2 weeks. In addition, the anesthetic group exhibited significantly greater overall satisfaction with rigid lens wear at 2 and 4 weeks. Also, the anesthetic group perceived their adaptation, sensitivity, and adaptation time to be significantly better at the 1-month visit. There was no significant difference in corneal staining between these two groups at each visit, with the exception of a greater amount of staining in the central quadrant for the placebo group at the 1-month visit. CONCLUSIONS: The use of a topical anesthetic at the fitting and dispensing visits for first-time wearers of RGP lenses resulted in significantly fewer dropouts, improved initial comfort, an enhanced perception of the adaptation process, and greater overall satisfaction after 1 month of lens wear as compared to the use of a nonanesthetizing placebo at those visits. This result, in combination with both presenting RGP lenses in a nonthreatening manner and optimizing the lens design and fitting relationship, should result in a positive adaptation process and successful wear of RGP contact lenses.
PURPOSE: Computerized videokeratography (CVK) has become the standard method for measuring the corneal curvature after refractive surgery. However, few resources exist on the use of CVK data for postoperative contact lens fitting, and no recommendations exist on the selection of the best topographic algorithm relevant to gas-permeable (GP) lens fitting. This study assessed the optimal use of topographic data to fit spherical GP contact lenses on patients who have undergone laser in situ keratomileusis. METHODS: A retrospective analysis of CVK maps from eight post-LASIK eyes fitted with spherical GP lenses was performed in the Contact Lens Service of the Department of Ophthalmology at Case Western Reserve University and University Hospitals of Cleveland. Axial and tangential maps from the Dicon CT 200 (version 3.50) or Humphrey Atlas (version A8) topographer were analyzed. Averaged dioptric curvatures from different locations (inferior, superior, and temporal) at various distances (2.0 mm, 2.5 mm, 3.0 mm, 3.5 mm, and 4.0 mm) from the vertex normal of each eye were compared with the base curves of the prescribed GP contact lenses. RESULTS: One-way analysis of variance, Pearson correlation analysis, and paired t tests showed that the best topographic predictors of a successful GP base curve were the average curvatures at the 4.0 mm distance on the axial maps (r=0.8078, P=0.05) and at the 2.0 mm distance on the tangential maps (r=0.9738, P=0.0002). The mean dioptric powers of the GP base curve, axial map 4.0 mm curvature, and tangential map 2.0 mm curvature were 41.50 diopters (D), 42.65 D, and 42.67 D, respectively. CONCLUSION: To simplify and guide GP fitting after LASIK, the average dioptric curvature 4.0 mm from the vertex normal on axial maps or 2.0 mm from the vertex normal on tangential maps are the best predictors of accurate GP base curve selection.
Polymethylmethacrylate (PMMA) contact lenses can alter corneal shape and induce corneal warpage or distortion. The purpose of our study was to determine the effects on the corneal topography after immediate refitting of long-term PMMA contact lens wearers into rigid gas permeable (RGP) materials. Six eyes with contact lens induced corneal warpage from PMMA contact lenses were assessed using the Topographical Mapping System-1. Statistical analysis was performed for the following variables prior to and approximately 6 months after contact lens refitting: best spectacle visual acuity, manifest refraction, surface regularity index, surface asymmetry index, keratometry, and simulated keratometry. Best spectacle visual acuity improved an average of 1.8 +/- 1.0 (mean +/- SD, P < 0.05) lines of Snellen visual acuity, while refraction did not change appreciably. The surface regularity index diminished by 0.51 +/- 0.32 (P = 0.01). The surface asymmetry index improved by 0.32 +/- 0.26 (P < 0.05). There was a good correlation between keratometry and simulated keratometry, and neither changed significantly after refitting with RGP contact lenses. All general topographic patterns remained unchanged throughout the study. Immediate refitting of long-term PMMA contact lens wearers into RGP materials of similar fit allows a slightly more regular and symmetric central corneal shape, which can result in improved spectacle visual acuity. The general corneal topographic patterns of contact lens induced corneal warpage did not change or improve after refitting to RGP material.
The effects of four sequential modifications to improve occlusion, vertical dimension, retention, and stability of poorly fitting dentures, and of placing new dentures, on the EMG activity were investigated in 21 denture wearers with a mean age of 67.7 years. Electromyographic recordings of right and left masseter muscles were made while the subjects performed masticatory and swallowing threshold tests and applied static guided forces were measured before and after each modification and at three intervals after the delivery of new dentures. A 2-week adaptation period was allowed for each denture modification. Three- and 12-week adaptation periods were allowed for the new dentures. No significant changes were found in guided static bite force or peak bite force during chewing following any modification or insertion of new dentures. Significant decreases (p < 0.05) from the original poorly fitting denture in preferred side and nonpreferred side muscle activity were found for the preferred side tests with both foods after both the correction of occlusion and 3 mm increase in vertical dimension. Concomitant decreases (p < 0.05) in the masseter closing burst and stroke durations were found and contributed to the reduction in masseter muscle effort. Further reductions (p < 0.01) in masseter closing bursts and stroke durations were observed with new dentures. The results revealed that new dentures or the stabilization of poorly fitting dentures through occlusal correction and restoration of occlusal vertical dimension permits patients to use less muscle effort while chewing and maintaining their initial masticatory performance.
Successful hearing aid fittings using high-technology features for elderly patients require consideration of factors beyond results obtained from routine audiologic evaluations. A holistic hearing aid selection, fitting, and evaluation approach that considers patient characteristics from communication, physical, psychological, and social assessment domains is presented here along with a checklist and flowcharts for matching high-tech hearing aid features to older persons who are hearing aid candidates.