Effect of over- and underexposure on the sharpness of the image of a marker in computer-assisted dental implant tomography.

In dental implant tomography, a clinician typically makes several tomograms of cross-sectional and sagittal slices at and near the intended implantation site. The slice with the sharpest image of the metal marker is deemed to be the correct implantation site; the other slices with blurred images of the marker are those made either mesially or distally to the marker. However, if the images were over- or underexposed, the marker will be blurred on all the slices and a dentist may be wrongly accused of having placed a dental implant at an improper site with possible medico-legal ramifications.

Interrelationship between cross-sectional and sagittal imaging in computer-assisted dental implant tomography.

OBJECTIVE: To determine what changes may occur in computer-assisted dental tomography to cross-sectional and sagittal slices when the positions of one or both slices are adjusted. METHODS: A human skull with a ball bearing attached to the mandibular first molar was positioned off-centre in a CommCAT (Imaging Sciences International, Hatfield, PA, USA) tomographic machine. An occlusal projection of the mandibular dental arch was scanned into the computer. Correction measurements obtained from scout cross-sectional and sagittal slices were used to 'customize' cross-sectional and sagittal slices simultaneously and also individually. RESULTS: The resulting changes in position and blur of the ball bearing were analysed. When simultaneously and correctly customized, the resultant slices were at the correct locations with a sharp image of the marker. When the sagittal slice only was adjusted, the blur of the marker changed, but its position remained unchanged; at the same time, the blur of the marker in the cross-sectional slice remained unchanged, but its position changed. When the cross-sectional slice only was adjusted, the blur changed, but its position remained unchanged; at the same time, the blur of the marker in the sagittal slice remained unchanged, but its position changed. CONCLUSIONS: It is important for dentists evaluating tomograms for implant placement to be aware that with the CommCAT tomographic machine an interrelationship exists between cross-sectional and sagittal slices and that adjustment in one type of slice produces changes in either the blur or position of the marker in the adjusted and unadjusted slices.

Everything you wanted to know about radiographic duplication.

If dental radiographs are not duplicated correctly, the resulting duplicates will be of inferior quality. This article discusses the characteristics of a duplicating film, the principle of radiographic duplication, a description of dental duplicators, the selection of optimum duplicating time, a technique of duplicating radiographs, an alternate technique of duplicating radiographs, errors in duplication and their correction, and the maintenance of duplicators.

Differential diagnosis of pericoronal radiolucencies with and without radiopacities.

Pericoronal radiolucencies, by definition, surround the crown of a tooth. They are encountered not only in pediatric patients but also in adults of all ages. It is likely that all clinicians, at some time or another, will be confronted with a radiograph showing a pericoronal radiolucent lesion. The differential diagnosis of such lesions is reviewed.

Radiographic/surgical template incorporating metal telescopic tubes for accurate implant placement.

The dental literature is replete with information on various implant surgical template designs and imaging techniques for presurgical assessment of dental implant sites. Seldom are these two aspects combined in a practical and effective manner to fabricate a guide for precise implant placement. Unless detailed, three-dimensional images of the underlying bone are obtained, the use of a template is ineffective. This article describes a radiographic/surgical template that utilizes a series of telescoping metal tubes as radiographic markers and as implant drill guides.

Diseases of the maxillary sinus.

Dentists often encounter patients whose signs and symptoms are not related to any dental disease, but rather originate in the maxillary sinuses. To distinguish when dental care is appropriate, dentists must be familiar with the anatomic, physiologic, clinical, and radiographic aspects of the maxillary sinuses.

Film-screen systems: sensitometric comparison of Kodak Ektavision system to Kodak T-Mat/RA system.

BACKGROUND: In 1995, Eastman Kodak Company (Rochester, N.Y.) marketed the Ektavision Extraoral Imaging Film and Screen System. It produced high-resolution images by keeping the light emitted by intensifying screens from "punching through" one emulsion layer on the film to another. OBJECTIVES: The objectives of the experiment were (1) to compare the sensitometric properties of the Ektavision system to its predecessor, the T-Mat/RA system and (2) to determine whether films and screens of the Ektavision and the T-Mat/RA systems could be interchanged without clinically changing the sensitometric properties. Ektavision and Lanex Regular intensifying screens were used in combination with Ektavision, T-Mat G/RA, T-Mat L/RA, and T-Mat H/RA films. RESULTS: The results showed that the Ektavision film was slightly slower than the T-Mat G/RA film no matter what type of screen was used. The type of screen used had little effect on inherent contrast or exposure latitude. The Ektavision film had approximately similar inherent contrast as the T-Mat G/RA film but less than that of the T-Mat H/RA film; its latitude was less than that of the T-Mat L/RA film. The manufacturer does not recommend combining T-Mat/RA film with Ektavision screens or Lanex Regular screens with Ektavision film because of a possible reduction in image resolution. But this mismatch did not clinically affect inherent contrast and exposure latitude; however, film speed was slightly affected. CONCLUSIONS: The Ektavision system is the result of advanced technology that produces images of high resolution. The high-resolution Ektavision film is slightly slower than the T-Mat G/RA film but is equivalent to it in its contrast and latitude. Therefore when changing from the combination of T-Mat/RA film plus Lanex Regular screens to that of Ektavision film plus Ektavision screens, a slight increase in x-radiation exposure should be made.

Effects of tomographic motion, slice thickness, and object thickness on film density.

The experiment used the computer-aided CommCat model IS 2000 tomographic machine (Imaging Sciences International, Roebling, N.J.). The objective of the experiment was to study the influence of tomographic tube motion, tomographic slice thickness, and object thickness on film density. The experiment was conducted by x-radiating an aluminum step-wedge placed along the x-axis. Exposures were made for different tube motions and for different slice thicknesses. In linear horizontal and linear vertical motions, an increased slice thickness decreased film density. Slice thickness had a stronger effect on film density when the object to be x-radiated was thinner. In circular, elliptical, spiral, and hypocycloidal motions, changes in slice thickness had no noticeable effect on film density because the manufacturer had programmed the machine to produce approximately similar exposure times by increasing the x-ray tube velocity thickness had a greater effect on film density for circular, elliptical, spiral, and hypocycloidal tube motions than for linear horizontal and linear vertical tube motions. Clinical observation showed that except for the linear vertical motion (motion that was oriented in the same direction as that of the tube travel) all other motions produced a zone of diffusion along the edges of the steps of the step-wedge. An increase in slice thickness had an effect on film density. Slice thickness had a noticeable effect on film density in linear but not in multidirectional tomography. Object thickness had a greater effect on film density in multidirectional than in linear tomography.

Effects of developer exhaustion on Kodak EKTASPEED Plus, Ektaspeed, and Ultra-speed dental films.

In 1994, Eastman Kodak Co. (Rochester, N.Y.) replaced its Ektaspeed film with the EKTASPEED Plus film. The manufacturer claims that one of the advantages of the new film is that it is not strongly affected by exhausted (depleted plus aged) processing solutions. The objective of the experiment was to test this claim. In exhausted solutions, EKTASPEED Plus film lost its speed more rapidly than Ultra-speed film but less rapidly than Ektaspeed film; that is, Ultra-speed film had the most stable speed. EKTASPEED Plus film lost contrast for 2 weeks before stabilizing, whereas Ultra-speed and Ektaspeed films continued to lose contrast for 3 weeks. Overall, EKTASPEED Plus film held its contrast over the other two films. EKTASPEED Plus film stopped increasing its film latitude after 2 weeks, whereas Ultra-speed and Ektaspeed films continued to increase film latitudes. In conclusion, for the three films studied, EKTASPEED Plus maintained the most constant levels of contrast and latitude in progressively exhausted solutions. All three films lost speed in exhausted solutions; EKTASPEED Plus film was the fastest but Ultra-speed film had the most stable speed.

Sensitometric comparison of Kodak EKTASPEED Plus, Ektaspeed, and Ultra-speed Dental Films.

In 1994, Eastman Kodak Co. (Rochester, N.Y.) marketed EKTASPEED Plus dental film to combine the advantages of the contrast of Ultra-speed film and the speed of Ektaspeed film. EKTASPEED Plus film uses T-Grain Emulsion technology similar to that used in the manufacture of the light-sensitive indirect exposure Kodak T-Mat film. This study compared the sensitometric properties of Ultra-speed, Ektaspeed, and EKTASEED Plus dental films. EKTASPEED Plus film was faster than Ektaspeed film at all film densities. Ektaspeed film became slower at higher densities and around a density of 1.9 became even slower than the Ultra-speed film. EKTASPEED Plus film had high inherent contrast and narrow exposure latitude similar to that of Ultra-speed film, whereas Ektaspeed film had low inherent contrast and wide exposure latitude. In conclusion, EKTASPEED Plus film had the advantages of the high contrast of Ultra-speed film and the high speed of Ektaspeed film. It maintained its high speed at high densities.

Sensitometric and archival evaluation of Kodak RA films in dental automatic processing.

The Kodak Rapid Access System is an extension of the T-grain technology (T-Mat film). Unlike the T-Mat film, the T-Mat/Rapid Access film is forehardened by the addition of more hardener to the film emulsion. It can thus be processed rapidly in a Kodak Rapid Access medical processor in only 45 seconds dry-to-dry cycle by using the Kodak X-Omat RA/30 developer that does not contain a hardener. The absence of the hardener, glutaraldehyde, in the developer also makes this solution environmentally safer. In medical radiography, the T-Mat film has been replaced by the T-Mat/Rapid Access film. However, in dental extraoral radiography the T-Mat film is still being used because the processing solutions and the comparatively low temperatures of dental automatic processors are different from those used in medical radiography. This report shows that, for panoramic and other dental extraoral radiography, T-Mat films can be replaced by T-Mat/RA films by processing them in conventional Kodak X-Omat RP solutions using a dental automatic processing cycle. The differences in the sensitometric properties of the T-Mat and T-Mat/rapid Access films were negligible and therefore clinically insignificant. All films tested well for archival quality.

Sensitometric comparison of direct- and indirect-exposure films used in intraoral radiography.

In Japan, some dentists use indirect-exposure (screen) films for intraoral radiography, without the use of intensifying screens. The purpose of the present investigation was to determine whether film speed, inherent contrast, and latitude of Japanese indirect-exposure films used without intensifying screens were comparable to those of direct-exposure (non-screen) films used for intraoral radiography. The characteristic curves of Kodak Ektaspeed ("E" speed) and Ultra-speed ("D" speed) films were used as standards for comparison. Indirect-exposure films without intensifying screens were extremely slow compared with direct-exposure "E" and "D" speed films. Therefore, they should not be used for intraoral radiography because they needlessly expose the patient to excessive X-ray radiation. The direct-exposure films Hanshin Hi-Fi and Hanshin New Silver were equivalent in speed, higher in contrast, and narrower in latitude than Kodak Ektaspeed film. In general, the indirect-exposure films had lower speed, lower contrast and wider latitude than the direct-exposure films. Their speed and contrast would have been increased if intensifying screens had been used. Therefore, indirect-exposure films without intensifying screens should not be used for intraoral radiography.

Automatic processing: effects of temperature and time changes on the sensitometric properties of light-sensitive films.

The effects of changes in the processing temperature and time of automatic processors were studied with three light-sensitive Kodak films: (1) blue-sensitive X-Omat RP film, (2) green-sensitive T-Mat G film, and (3) ultraviolet-sensitive X-Omat duplicating film. Speed and inherent contrast were derived for each of the three films from sensitometric curves at six different temperatures and at five different processing times. The T-Mat G film (T-grain technology) was comparatively less sensitive than conventional films (X-Omat RP) to increases in processing temperature or time. Unlike dental intraoral films, which cannot be processed at low processing time or temperature, the light-sensitive films were of archival storage quality even at a low processing time of 2.5 minutes or at a low processing temperature of 21 degrees C. Therefore the processing time of an automatic processor may be decreased for light-sensitive films.

Automatic processing: effects of temperature and time changes on sensitometric properties of ULTRA-SPEED and EKTASPEED films.

The effects of changes in the processing temperature and time of automatic processors were studied with Kodak ULTRA-SPEED and EKTASPEED dental x-ray films. Speeds and inherent contrasts were derived for the two films from sensitometric curves at seven different temperatures and at five different processing times. As opposed to manual processing, only a slight change in film fog was observed with increases in automatic processing temperature or time. Film speed and contrast could be increased by increasing the processing temperature or time. The EKTASPEED film was more sensitive to these changes than was the ULTRA-SPEED film. Temperature had a stronger influence than processing time. All films were of archival storage quality except those processed at the low processing times of 2.5 or 3.5 minutes, and at the low processing temperature of 21 degrees C.