The accuracy of surgical drilling guides was assessed for placement of zygoma implants. Six zygoma fixtures of length 45 mm (Nobel Biocare, Göteborg, Sweden) were placed in three formalin-fixed human cadavers using surgical drilling guides. The fabrication of these custom-made drilling guides was based on three-dimensional computerized tomography (3D-CT) data for the maxillary-zygomatic complex. The installation of the implants was simulated preoperatively using an adopted 3D-CT planning system. In addition, anatomical measurements of the zygomatic bone were performed on the 3D images. The preoperative CT images were then matched with postoperative ones in order to assess the deviation between the planned and installed implants. The angle between the planned and actually placed implants was < 3 degrees in four out of six cases. The largest deviation found at the exit point of one of the six implants was 2.7 mm. The present study showed that the use of surgical drilling guides should be encouraged for zygoma implant placement because of the lengths of the implants involved and the anatomical intricacies of the region.

Stereognosis is the ability to recognise and discriminate forms. Oral stereognostic ability has been studied in different reports. The experimental design of the test is of primary importance as both the method used and the material applied may influence the results dramatically. The form, size and surface characteristics of the test piece, the presentation order, subject-related factors and the method of scoring all have their effect on the results. With regard to subject-related factors, ageing has a negative influence on stereognostic ability; gender is considered of no importance. Another influencing factor is dental status. A healthy natural dentition offers a very good oral stereognostic ability. Edentulous subjects usually show a decreased oral stereognostic ability, depending on the rehabilitation form. A number of questions have been addressed, especially with regard to the perception itself. Receptors mainly involved in oral stereognostic ability are located in various oral structures and form perception results from an association of more than one group of receptors. The following review tries to deal with these questions and attempts to provide clear guidelines for further research on oral stereognosis.

For certain surgical procedures (e.g. placement of implants), an accurate localisation of the mandibular canal is of utmost importance to avoid injuries to the neurovascular bundle. The aim of the present study was to evaluate, on human fresh cadavers (n = 6), the accuracy of conventional spiral tomography for the localisation of the mandibular canal. By means of the Cranex TOME multifunctional unit (Orion Corporation Soredex, Helsinki, Finland), tomographic slices were taken at 3 different locations in the left posterior mandible (distal to the mental foramen). The mandibles were then sectioned at these 3 sites with a microtome. With a digital sliding caliper, the following 3 measurements were performed both on the tomograms and the bone sections at the three sites: 1) distance from the crest to mandibular canal, 2) overall bone height and 3) bone width. Overestimations of the distance to the mandibular canal (8/18) ranged from 1.05 to 0.10 mm and underestimations from 0.30 to 1.36 mm. The same number of over- and underestimations occurred for the bone height (1.14 to 0.14 mm and 0.15 to 1.40 mm, respectively). The bone width scored more overestimations (10/18), ranging from 1.40 to 0.12 mm, while underestimations ranged from 0.25 to 1.35 mm. From the present results, it is concluded that spiral tomography using the Cranex TOME multifunctional X-ray unit provides accurate information and sufficient detail for preoperative planning of implant placement in the posterior mandible.

This work confirmed the superiority of autogenous bone when it comes to bone grafting. Nevertheless, some bone substitutes can improve bone formation when compared to the control. New bone substitutes with growth factors to improve their abilities to induce bone formation should be experimented.

When planning to place implants in the posterior region of the maxilla, the location of the maxillary sinus floor is influencing the available bone height and the implant length chosen. The aim of the present study was to evaluate in vitro the spiral tomographic technique that could be used for pre-operative implant planning. Tomographs were taken of 6 dry human skulls using the Cranex Tome multifunctional unit (Orion Corporation Soredex, Helsinki, Finland). Three sites were selected in the left posterior maxilla and marked with gutta percha meaning a total of 18 sites (6 x 3 = 18) for interpretation. Bone height and width were measured on the tomographs and after sectioning also on the skulls. The values obtained from the measurements on tomographs were divided by an enlargement factor of 1.5 (as defined by the manufacturer) and then compared with those from the real measurements on the skulls. Real measurements were on average 0.24 mm (SD 0.19) lower than the tomographic measurements (P < 0.05). From the present results it could be concluded that spiral tomography using the recently developed Cranex Tome reveals sufficient information and detail for pre-operative planning of a limited edentulous region.

One of the main advantages of digital imaging is the possibility of altering display options for improved image interpretation. The aim of the present study was to evaluate the subjective image quality of direct digital panoramic images and compare the results with those obtained from conventional images. Furthermore, the effect of various filter settings on image interpretation was assessed. Panoramic images were obtained with three different types of panoramic equipment (one direct digital and two conventional units) from three groups of 54 patients with a natural dentition in all quadrants. The first series of panoramic images consisted of 54 unprocessed digital images; conventional film images (n = 108) comprised the second and third series. A final series consisted of the digital images treated with three different filters ("smoothening," "sharpening," and "contrast enhancement"). All images were scored randomly by four experts in oral radiology on a 4-point rating scale. The results showed a statistically significant difference in scorings between the conventional and digital panoramic units. The main reason for poor image quality appeared to be a combination of blurring and overlapping in the panoramic image. The premolar region in the upper jaw was the region where most additional radiographs were needed.

For several radiological examinations, a clinician can select between conventional and spiral computed tomography. Using both techniques, this study aimed at evaluating the difference in absorbed doses when examining a single lateral jaw segment in a human cadaver head and Rando phantom. The present study involved the placement of thermoluminescent dosimeter (TLD) chips (GR-200) in the thyroid gland, and bilaterally, in the parotid and submandibular glands and the lenses of the eyes in both a human cadaver and a Rando phantom at corresponding locations. Consecutive conventional spiral tomographic examinations were carried out in both the left upper and lower premolar area, using a Cranex TOME multifunctional unit. Each examination consisted of 4 slices with a 2 mm slice thickness and exposure parameters of 57 kV, 56 seconds and 1.6-2.0 mA. Regarding spiral computed tomography (CT), a Somatom Plus S scanner (Siemens, Erlangen, Germany), with a slice thickness of 1 mm with settings at 120 kV and 165 mA, was used on both phantoms and separately in the upper and lower jaw. With conventional tomography, the findings of the present study showed that the parotid and submandibular glands on the side near the X-ray tube received the highest dose, both for the cadaver head (doses ranging from 0.5 to 1.3 mGy) and the phantom (doses ranging from 0.6 to 2.6 mGy). For CT of the upper jaw, the highest doses were delivered to the parotid glands with an average absorbed dose of 9.2 and 10.6 mGy for the cadaver head and phantom, respectively. The submandibular glands received the highest doses during CT examination of the lower jaw with an average of 7.8 and 12.9 mGy for the cadaver head and phantom, respectively. It appears from the present investigation that if small edentulous regions are examined, radiation doses during conventional tomography remain much lower than during CT imaging. However, when multiple tomographic cuts are required, a spiral CT examination can replace a series of conventional examinations, especially in cases such as the rehabilitation of an edentulous upper jaw or a more complex surgery.

A stereognostic ability test was performed in 60 patients. Forty patients were rehabilitated by means of osseointegrated implants. One group consisted of 20 patients with fixed prostheses on implants in both the upper and lower jaws. The other 20 patients had a maxillary denture while in the mandible an overdenture was retained by means of two implants connected by a bar. They were compared to a group of 20 subjects (controls) with a non-restored natural dentition. For the stereognostic ability test, subjects had to recognise ten different test pieces by manipulating them with two antagonistic incisor teeth, avoiding any contact with other oral structures. Both response time and percentage accuracy of recognition were evaluated. The present findings indicated that subjects with an overdenture on implants did not score significantly different from those with an implant-supported fixed prosthesis. In contrast, subjects with teeth had a significantly better stereognostic ability. The percentage of correct responses was 52% for overdentures, 56% for fixed prostheses on implants and 75% for natural dentitions. From these results, it could be concluded that the stereognostic ability is impaired in subjects rehabilitated with osseointegrated implants by about one-third to one-quarter compared to subjects with natural teeth.