A 1-year clinical report of a one-piece implant abutment.

PURPOSE: Solid one-piece standard and conical abutments, which do not involve the external implant hex when seated, have been designed. The present clinical study represents a 1-year follow-up of the use of these abutments for anchorage of implant-supported fixed prostheses for oral rehabilitation of 36 completely and eight partially edentulous patients. MATERIALS AND METHODS: After 1 year of loading, the implant-supported dentures were removed, and the seating of the 214 one-piece abutments was inspected clinically and radiographically. RESULTS: After 1 year of loading, no loose abutments were observed. One complication was reported; it involved fracture of two abutment screws within the same fixed denture. Prosthesis mobility and gold screw loosening accompanied this complication. Ninety-one percent of the patients exhibited healthy gingiva, and 9% showed erythema/edema. No periimplantitis was identified. CONCLUSION: The results of this study--healthy marginal tissue, a mean bone loss of 0.3+/-0.6 mm, and no abutment retightening 1 year after loading--support the use of the one-piece abutment design in implant-supported screw-retained restorations.

The use of a conical fixture design for fixed partial prostheses. A preliminary report.

A specially designed, TiO2-blasted titanium fixture, partially conical and microthreaded, the Astra Tech Fixture ST, was used for rehabilitation of partial edentulism in the posterior mandible. Superior to the mandibular canal 25 fixtures were placed in 10 patients. Fixed metal-ceramic bridges were then performed. After 1-year follow-up, all bridges were found to be clinically stable. The implant survival rate was 100% and the mean marginal bone resorption was 0.05 +/- 0.11 mm.

Absolute measures of image quality for the Sens-A-Ray direct digital intraoral radiography system.

To study the noise characteristics of the Sens-A-Ray (Regam Medical Systems AB, Sundsvall, Sweden) system, 20 radiographs were obtained at each of three different exposure levels at 70 and 90 kVp with a homogeneous x-ray field. Exposures were measured with an ionization chamber. Noise power spectra were calculated over three areas within each radiograph, and ensemble averages were subsequently found from 60 data files at each exposure level. Noise equivalent quanta were calculated with the noise power spectra and modulation transfer function data from previous studies. Finally, the detective quantum efficiency was calculated by dividing the noise equivalent quanta by the estimated incident photon fluence at the different exposures. The system has a maximum detective quantum efficiency of approximately 0.030 at 70 kVp and 0.025 at 90 kVp. A broad maximum exists at approximately 2 cycles/mm, indicating that the signal-to-noise ratio is most favorable at this spatial frequency.

Basic technical properties of a system for direct acquisition of digital intraoral radiographs.

The Sens-A-Ray system for direct digital intraoral radiography may be used with any computer compatible with an IBM PC/AT. The system relies on a charge-coupled device designed for direct conversion of x-ray energy to an electronic signal. It is the first such device for direct acquisition of radiographs. Technical properties of charge-coupled device detectors when exposed to radiation energies in the range of x-rays used in dental radiography have been studied. Even in the absence of light or x-radiation there is a spontaneous generation of charge within a charge-coupled device detector that gives rise to a background signal, a dark current. It was found that the dark current is a linear function of exposure time. The dose response of the charge-coupled device detector was determined at nominal kilovoltages that range from 50 to 90 kVp. The dose response was shown to be a linear function of exposure. The functions for all kVp settings were practically identical. The charge-coupled device detector is more sensitive to x-radiation than conventional dental films and, consequently, its exposure range is more narrow. The signal-to-noise ratio was calculated from the digital radiographs used for the dose response test. The ratio is above 10 for exposures higher than about 2 microC/kg. The line spread function was determined from test radiographs of a 10 microns wide slit in a test object of 1.5 mm thick tantalum. After curve fitting, the line spread function could be expressed as the sum of a Gaussian and an exponential function. Presampling modulation transfer functions valid at the detector plane and at an object plane were calculated from fitted data on the line spread function. It is concluded that the Sens-A-Ray system has such technical properties that it may replace conventional film-based systems.

Sens-A-Ray. A new system for direct digital intraoral radiography.

A new system for direct digital intraoral radiography, Sens-A-Ray, is presented. This system is based on a detector with a charge-coupled device that was designed especially for direct exposure to x-ray radiation. The system also includes interface electronics and an IBM AT-compatible personal computer with a digital I/O with frame memory, a super VGA graphics board, a high-resolution monitor, and software for the exposure, capture, storage, and enhancement of images. An external optical mass storage device is used for permanent storage of images in digital format. A video printer may be used to create hard copies. The system produces radiographic images at a significantly lower exposure than required for E-speed intraoral film. Applications of the system are exemplified, and its basic properties are discussed.

Reproducible positioning of the skull at tomography.

Description of a method for obtaining sufficient reproducibility in odontologic examinations using a vacuum pillow.