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At least 379 records · Page 21Linked to original sources
PubMed1995

Accuracy of implant-supported prostheses in the edentulous jaw: analysis of precision of fit between cast gold-alloy frameworks and master casts by means of a three-dimensional photogrammetric technique.

Distortions of 15 routine implant-supported prostheses were measured in relation to the master casts after completion by means of a 3-dimensional (3-D) photogrammetric technique. All prostheses were designed as one-piece gold-alloy castings with resin teeth. Five of the prostheses were placed in the edentulous maxilla, and the remaining were placed in the lower jaw. Distortion of the cylinders was mostly observed in the horizontal plane (x- and y-axis) while the vertical aspect seemed to be more stable. The mean 3-D center point distortion was 42 (SD 15) and 74 (SD 38) microns for the upper and lower jaws, respectively. The measurements revealed a range of 3-D center point distortion from 16 to 80 and 15 to 165 microns for the different jaws, respectively. The corresponding 3-D mean angular distortion of the cylinders was 51 (SD 35) microns in lower and 70 (SD 75) microns in the upper jaws. A correlation was found between 3-D center point distortion and the width as well as the curvature of the implant arch, indicating more displacement the wider and the more curved the arch was. The 3-D center point distortion was also significantly higher in the upper jaws which could possibly be explained by the curvature of the implant arch and higher numbers of implants in the upper jaws. Further problems with the fit of upper jaw castings could be related to more alloy in the castings and poor alignment of implants.

Dental Prosthesis Design↗
PubMed2001

Hearing aid fitting procedures--state-of-the-art and current issues.

The increasing degree of sophistication in hearing aid technology calls for appropriate fitting strategies, as otherwise hearing aid users cannot receive the full benefit from the most modern technological achievements. This paper describes the state of the art in hearing aid fitting procedures and offers a look into possible future developments. Currently, threshold-based fitting formula compete with loudness- and sound-based fitting procedures. Whereas threshold-based approaches are straightforward and timesaving, they do not consider loudness growth and the sound preferences of the listener. On the other hand, loudness- and sound-based procedures do take these aspects into account, but they are time consuming and it is not yet proven that they provide higher benefit for the end user. This may be due to the fact that either there is actually no extra benefit or more likely that the evaluation tools or study designs have to be improved. Concerns about how to fit more advanced future hearing instruments seem to be inappropriate, as an analysis of possible future signal processing algorithms shows that they probably do not need extra fitting to the individual hearing impairment but rather need optimization according to the acoustical environment.

Hearing Aids↗
PubMed1998

Standardized range of conformers and symblepharon rings.

Conformers and symblepharon rings are routinely used to keep fornices formed after socket surgery or in the presence of conjunctival cicatricial disease. However, there is no accepted standard size or shape of conformers or symblepharon rings. We measured the ideal conformer and symblepharon sizes in patients undergoing socket surgery and designed six conformer and symblepharon sizes. The full set of six conformers and symblepharon rings is available to the surgeon at the end of surgery. We have successfully used these conformers and symblepharon rings in over 600 cases during the last 7 years. These standardized sizes allow more accurate fitting of conformers and symblepharon rings.

Eye Enucleation↗
PubMed1997

Grinding precision and accuracy of fit of CEREC 2 CAD-CIM inlays.

The authors conducted research to determine the grinding precision and accuracy of fit of ceramic inlays generated with the completely redesigned CEREC 2 computer-assisted design/computer-integrated manufacturing, or CAD-CIM, unit. They found that the grinding precision of the CEREC 2 unit was 2.4 times greater than that of CEREC 1. With CEREC 2, the mean (+/-standard deviation) luting interfaces were 56 +/- 27 micrometers, which is a 30 percent improvement in the accuracy of fit compared with that of CEREC 1.

Computer-Aided Design↗
PubMed1995

Finite element stress analysis of the wrist joint without and with an endoprosthesis.

The finite element analysis method was used to obtain the lateral deformation profile and values of the von Mises stress in the cortical and cancellous regions of the various bones in models of a selected space in the coronal plane of a human wrist joint, without and with a prosthesis. The prosthesis was the metacarpal component of the Trispherical design of the total wrist joint arthroplasty. The models included all the bones, the associated network of ligaments, and the intervening soft muscle tissue. Each type of model was completely constrained along its entire proximal surface and subjected to either a static point force (in the axial compressive or anteroposterior tensile direction) acting at the center of the distal tip of the third metacarpal cortical bone. For the models containing the prosthesis, a parametric study was conducted involving the method of anchorage of the prosthesis to the contiguous bones and the material of fabrication of the prosthesis. It was found that: (1) the axial force produces lower stresses in the bones compared with the anteroposterior one; (2) no clear-cut case can be advanced, from the stress viewpoint, for press-fitting the prosthesis to the contiguous bones rather than using bone cement for such anchorage; and (3) any alloy with modulus of elasticity in the 79 to 196 GPa range and Poisson's ratio of about 0.3 may be used to fabricate the prosthesis. The approximations used and the associated limitations of the work are fully discussed, as are the design implications and clinical significance of the results.

Humans↗
PubMed2000

Evaluation of the ZEBRA 2000 (Z-10) Breger Vision bifocal contact lens.

PURPOSE: Evaluate the ZEBRA 2000 (Z-10) bifocal contact lens on presbyopic and aphakic patients. METHODS: Thirty-eight patients, 37 presbyopes and one aphake, were fit in the Z-10 and evaluated for 6 months. RESULTS: Twenty patients (53%) completed 6 months of contact lens wear. Ten (26%) discontinued due to lens related problems, three (8%) discontinued due to other health problems, and five (13%) were lost to follow-up. Average refits per eye were 1.75. Average distance visual acuity was 20/25; average near visual acuity was J1.6; average wear time, 11 hours. Patient satisfaction was rated good in comfort and vision and fair in nighttime glare by patients' subjective evaluation. CONCLUSIONS: The ZEBRA 2000 (Z-10) can be a useful addition in fitting the general presbyopic patient population.

Adult↗
PubMed1995

Comparisons of fit of CAD-CAM restorations using three imaging surfaces.

One of the factors that influences the overall fit of a Cerec restoration is the thickness of the optical powder. The objective of this study was to compare the measurement of the fit of glass inlays produced with the Cerec instrument after each preparation had been coated, in separate trials, with imaging powder applied with an aerosol; imaging powder applied with air from a dental unit; and a water-soluble paint applied with a brush. Ten inlay preparations were made in extracted teeth. Each preparation was coated with one of the three imaging media and an inlay was made. This was repeated until each preparation received each imaging surface. Each inlay was measured at eight different points by using an image analysis system interfaced to a stereoscopic measuring microscope. The inlays fabricated on the two powder surfaces were not significantly different, but the painted surfaces were found to result in a significantly better-fitting inlay.

Analysis of Variance↗
PubMed1995

Computed tomography analysis of proximal tibial coverage.

Researchers of this study used computed tomographic studies of the proximal tibia for patients undergoing total knee arthroplasty to determine basic morphologic data of size, shape, and area of varying levels from the articular surface. Five off-the-shelf tibial component shapes (4 symmetric, 1 asymmetric) were templated to determine the fit of the components at the various resection levels. Seventy-two knees were assessed at 2-mm, 68 at 5-mm, 40 at 8-mm, and 17 at 11-mm resection levels. Significant differences in fit and percentage of total area of coverage were identified. Fit was significantly better for asymmetric as compared with the symmetric components (p = 0.001) at all levels of resection. Fit was significantly worse for each component as the resection depth increased. This information can serve as a bridge to clinical and laboratory data in identifying the importance of tibial component fit to the overall performance of a total knee arthroplasty design.

Female↗
PubMed1998

The importance of occlusal balance in the control of complete dentures.

OBJECTIVE: The importance of occlusal balance to the control of complete dentures during function was assessed. METHODS AND MATERIALS: The complete dentures of five patients who were having difficulty controlling their prostheses were accurately duplicated. The artificial teeth were replaced with occlusally balanced teeth. No other changes were made. Patients were asked to report their experiences with the new dentures after 1 week, 3 weeks, and 6 weeks. RESULTS: By the end of 6 weeks, improvement in denture stability and eating comfort were reported by all patients. CONCLUSION: Improvements occurred when the occlusion was balanced, despite existing jaw relationship errors, fitting inaccuracies, and peripheral extension errors.

Dental Articulators↗
PubMed2005

Acclimatization in first-time hearing aid users using three different fitting protocols.

OBJECTIVE: To study auditory acclimatization and outcome in first time hearing aid users fitted with state of the art hearing aids as a function of different hearing aid fitting protocols. METHODS: Twenty-eight adult subjects participated in the study. Each subject was assigned to one of three study groups (named audiologist driven, AD; patient driven, PD; set-to-target, STT according to the fitting protocol used) and fitted with digital hearing aids (Bernafon Symbio). Speech recognition scores were measured in aided and unaided conditions over a 6-month period. RESULTS: Five subjects (three from the PD-group, two from the STT group) decided to withdraw from the study during the 6-month-study period, leaving a total of 23 complete data sets for analysis. Aided speech understanding increased significantly over this time period in all three groups. However, average hearing aid insertion gain changes were small over the same period. There were no statistically significant differences in aided or unaided speech recognition scores between the three groups after 2 weeks or after 6 months. On average, twice as many fine tunings of the hearing aids were requested by the patients in the AD and the STT group than in the PD group and subjects in the AD and STT group used their hearing aids approximately twice as much as subjects in the PD group. CONCLUSIONS: The substantial increase in speech intelligibility without significant changes of the insertion gain of the hearing aids over a 6-month period in all three groups suggests a significant acclimatization effect. Although the speech recognition with hearing aids did not differ significantly among the three study groups after 6 months, the lower average wearing time and the higher number of withdrawals from the study in the PD group suggest that the patients' needs are not adequately met. In terms of aided speech recognition scores and hearing aid wearing time the STT group and the AD group were very similar. However, comments of the patients and the higher rate of withdrawals in the STT group suggest an over-all advantage for the AD fitting protocol.

Adaptation, Psychological↗
PubMed1996

The effect of soldering, electrowelding, and cast-to procedures on the accuracy of fit of cast implant bars.

The effect of three different connecting procedures on the accuracy of fit of cast implant bars over their supporting abutments was investigated. Thirty Hader implant bars were waxed on a master cast over two abutment analogs and cast in a type IV gold alloy. The bars were sectioned and divided into three groups of ten implant bars according to the connecting procedure that was to be followed. Group 1 bars were connected by soldering, Group 2 bars were connected by electrowelding, and Group 3 bars were connected with the cast-to procedure. The accuracy of fit of each group of bars was measured at the gold cylinder-abutment interface in microns using a stereomicroscope. The use of the cast-to procedure resulted in a more accurate fit as compared with the soldering and the electrowelding techniques.

Analysis of Variance↗
PubMed1994

Bitoric rigid contact lens with prism fitting in rare cases of moderate corneal and residual astigmatism.

We reviewed all records of bitoric rigid gas permeable (RGP) contact lenses with prism ballast fittings performed at Tulane University Hospital and affiliated clinics from 1985 to 1993. We found eight eyes of six patients fit were fit with this lens, which is indicated for the patient with a moderately astigmatic cornea in addition to residual refractive astigmatism. In this design, a small amount of prism is added to a standard bitoric design to achieve rotational stability. All patients achieved 20/25 or better vision. We provide an outline for fitting bitoric RGP contact lenses with prism ballast.

Adult↗
PubMed2002

Porcelain veneers. Problems and solutions.

Porcelain veneer restorations require close attention to detail from beginning to end. It is often prudent to go slowly when working with these cases. Patients receiving them have high expectations that go beyond considerations of function alone. Many problems are encountered when porcelain veneers are used to improve the appearance of the teeth. Avoiding and overcoming these problems first requires identification of the causes of the problems, followed by changes in clinical techniques. Success is the result of careful selection of teeth to receive veneers; preparing teeth in a manner that optimizes the aesthetic potential of the veneer; employing techniques that maximize the strength of both the veneer and its adhesive bond to the tooth; utilizing high-quality provisional veneers; insisting on a precision fit; and paying attention to the details of adhesive bonding protocols.

Contraindications↗
PubMed1998

The role of computerized corneal topography in rigid gas permeable contact lens fitting.

PURPOSE: The purpose of this study was to determine the clinical utility of computerized corneal topography (CCT) in the fitting of rigid gas permeable (RGP) contact lenses. METHODS: In this prospective study, we compared the clinically determined parameters to those obtained by CCT in 50 consecutive patients who underwent RGP lens fitting. The TMS-1 program was used for CCT, and we fit patients with Boston RGP contact lenses (type II, or Equalens). The final decision on the RGP lenses dispensed relied upon the clinical evaluation (slit lamp examination, fluorescein pattern, lens centration, and visual acuity). RESULTS: The base curve of RGP lenses proposed by CCT was similar to that selected clinically (mean: 7.74 mm versus 7.81 mm). However, the mean diameter of the CCT proposed lenses was smaller than that selected clinically (9.31 mm versus 9.6 mm, P < 0.01). Divergence was more pronounced in keratoconus. CONCLUSIONS: CCT is an important tool in RGP contact lens fitting. Clinical evaluation remains mandatory in determining the appropriate RGP lens.

Contact Lenses↗
PubMed2006

Fitting strategies and candidature criteria for unilateral and bilateral hearing aid fittings.

In this paper, hearing aid fitting strategies are reviewed and candidature criteria for unilateral and bilateral fittings are discussed. Fitting strategies are primarily governed by the objectives of hearing aid fitting that can be set in different ways. Based on common goals, fitting strategies can be broken down into three stages: (1) basic fitting, (2) fine-tuning and (3) verification and validation. A fine-tuning concept basing on so-called meta-controllers is described and the issue of bilateral fitting strategies is discussed. In a first order approach, bilateral hearing aids can be fitted in parallel as unilateral aids, followed by bilateral fine-tuning, making sure that loudness is balanced and overall loudness is accepted. Parallel fitting of bilateral aids is more favourable than sequential fitting to avoid rejection because of a negative experience with unilateral amplification due to difficulties in disadvantageous listening situations. Candidature criteria are presented by means of a flow chart structuring the decision making process and arriving at the conclusion that bilateral fitting should be considered the normal case. If there is any doubt about the benefit of bilateral fitting, a trial with bilateral aids should be performed.

Hearing Aids↗
PubMed2003

Use of a loudness model for hearing aid fitting. V. On-line gain control in a digital hearing aid.

Many researchers have proposed that hearing aids should process sounds so as to restore loudness perception to 'normal'. We describe how a model for predicting loudness for people with cochlear hearing loss can be implemented in a digital hearing aid so as to calculate the frequency-dependent gains that would be required to achieve that goal. It is assumed that the input signal is processed using brief segments or 'frames'. For each frame, the spectrum is calculated, usually via a fast Fourier transform (FFT). From the spectrum, an excitation pattern is calculated for a normal car and for the impaired ear of the patient. The loudness model is then used to calculate the gain required at the centre frequency of each channel in the aid, so as to match the specific loudness in the normal and impaired ears. The whole process is repeated for each successive frame, with overlap of frames and with smoothing of the gain changes across frames. We describe both an 'exact' model, which prescribes a 'curvilinear' compression characteristic at each frequency, and an approximation using 'straight' compression, which is computationally less intensive. Limitations of the present approach are described, and the approach is compared with more traditional approaches using multichannel compression, and with previous approaches using loudness models for fitting hearing aids.

Acoustic Stimulation↗
PubMed2000

Legal responsibilities when fitting minors with contact lenses.

BACKGROUND: Practitioners must understand their legal responsibilities in fitting minors with contact lenses, which include informed consent, contractual obligations, and the Statute of Limitations. Minors are children and teenagers who have not yet reached voting age in their state--generally 18 years of age. Informed consent requires permission from the patient before a practitioner performs any treatment. For these young people, this consent generally can only be given by a parent or legal guardian. Minors can repudiate contracts made with them; therefore, the contractual obligation to pay for a contact lens fitting should be established with a parent or legal guardian. In most states, minors have additional time beyond the usual Statute of Limitations to bring a lawsuit. If practitioners recognize their legal responsibilities in caring for these special patients, fitting youngsters with contact lenses can be a rewarding part of practice.

Adolescent↗