C. Ulm

Maxillary sinus septa: incidence, morphology and clinical implications

This study was carried out to examine the incidence, morphology and clinical implication of antral septa. Out of 265 maxillary sinuses, 65 sinuses in atrophic maxillae were examined clinically during sinus floor elevation and 200 sinuses examined radiographically (CT), the latter being further subdivided into non-atrophic/dentate and atrophic/edentulous maxillary segments. Eighteen (27.7%) out of 65 clinically-examined maxillae and 32 (16%) out of the 200 non-preselected CT-examined maxillary sinuses showed antral septa. CT-topogram subclassification revealed 21 septa (13.2%) in 159 non-atrophic and 11 septa (26.8%) in 41 atrophic maxillary segments (P < 0.01). Morphologically, CT examination yielded one complete septum (0.5%), 21 incomplete septa on the sinus floor and 10 incomplete septa on the anterior antral wall (5%). CT revealed a significantly greater dimension of antral septa in non-atrophic maxillary segments than in atrophic ones (P < 0.01). In atrophic maxillary sinuses, the incidence (27.7% vs 26.8%), morphology (all septa located on sinus floor) and height (8.1 +/- 2.5 mm vs 6.8 +/- 1.6 mm) did not differ between the clinical and the CT examinations. Detailed knowledge about location, morphology and height of antral septa is clinically relevant to reduce the rate of complications when maxillary sinus surgery, i.e. sinus floor elevation, is carried out.

The incidence, location, and height of maxillary sinus septa in the edentulous and dentate maxilla

PURPOSEnThis study evaluated the incidence, location, and height of antral septa and demonstrates their clinical implications.nnnMATERIALS AND METHODSnOne hundred ninety-four maxillary posterior regions, subdivided into four groups (group 1, 61 clinically examined atrophic ridges; group 2, 41 anatomically examined atrophic ridges; group 3, 42 radiographically [CT] examined atrophic ridges; and group 4, 50 CT examined dentate maxillary ridges), were examined for the incidence, location, and height of antral septa.nnnRESULTSnThe incidence of antral septa was significantly greater (P<.01) in atrophic edentulous regions (groups 1, 2, and 3) than in dentate regions (group 4). However, the septa were much lower (P<.01). In atrophic maxillae, about 70% of antral septa were located in the anterior (premolar) region.nnnCONCLUSIONSnAntral septa are more commonly found in edentulous atrophic maxillae than in dentate maxillae. The septae in edentulous atrophic maxillae are shorter than those found in dentate maxillae. When present, maxillary sinus septae are more common anteriorly than posteriorly. CT scanning is the preferred radiographic method for detecting the presence (or absence) of sinus septae. Panoramic radiography has less sensitivity and specificity than CT scanning for the detection of sinus septa.

The edentulous maxillary alveolar process in the region of the maxillary sinus- a study of physical dimension

From 47 anatomic specimens, vertical sections were cut in the molar region, and computer-assisted measurements of both height and width of the alveolar ridge were made to assess the available bone volume for endosseous implant placement. The mean ridge heights ranged between 9.30 and 3.23 mm, the highest and lowest values being 13.8 and 0.8 mm, respectively. The ridge widths generally proved to be sufficient for placement of endosseous implants. Small knife-edge ridges are rarely found in the posterior maxilla. Reduction of the cancellous portion of the posterior maxilla seems to be influenced by the duration of edentulousness, as well as by osteoporotic changes, without being directly related to ridge configuration and bone volume.

Reproducibility of three-dimensional CT-assisted model production in the maxillofacial area

In the mid-eighties, computerised tomography (CT) assisted three-dimensional imaging, and modelling of skull structures was introduced into preoperative diagnosis in maxillofacial surgery. This new method is already being used in the preoperative planning of corrections of post-traumatic defects and craniofacial deformities as well as in tumour surgery and implantology. The aim of the present study was to collect information on the reproducibility of a skull model milled from hardened polyurethane foam, and based on the CT data of a real skull. Thirty one measurements were carried out on the model and on the original skull, leading to the result that the model showed a mean inaccuracy of 1.5 mm. The deviations ranged between 0.0 and 3.6 mm. Generally, the model structures, however, tended to be larger than those of the original. As far as the total of all measurements is concerned, the model deviated from the original skull by 1.6%. A convincing aspect of the model, which cannot be obtained by any other method, is its plasticity and the possibility of 3-D orientation on a lifesize model. However, the study indicates that surgeons using this technique should consider the possible discrepancies between the model and the real skull when making preoperative assessments.

Reduction of the compact and cancellous bone substances of the edentulous mandible caused by resorption

Examination of various bone sections of edentulous atrophic mandibles showed that the body of the mandible loses up to 60% of its original bone substance during progressive atrophy. Most of the bone loss occurs in a relatively early stage of the atrophic process. The greatest extent of bone reduction can be observed in the area of the second premolar and the first molar. In the interforaminal region, which is situated mesial from them, resorption, in most cases, is not as progressive as in the premolar/molar area. The compact and cancellous bone substances are most often equally affected by resorption. Moreover, it could be observed that the cancellous bone substance of extremely atrophic mandibles particularly in the interforaminal region, is marked by a significant increase in density. This might be interpreted as a restructuring process to compensate for bone losses and to secure the stability of the atrophic body of the mandible.

Location of the mandibular canal within the atrophic mandible

In 43 edentulous, lower jaw halves, sections were carried out in the area between the mental foramen and the third molar. The relative changes in the location and course of the mandibular canal which are caused by atrophy were analysed. For this purpose, the mandibles were classified according to so-called residual ridge orders which describe the different stages of alveolar ridge resorption. The following findings were obtained: The distance between the mandibular canal and the lingual and buccal external border does not change in any stage of the atrophic process, i.e. it remains conspicuously constant. However, the distance between the mandibular canal and the cranial and caudal borders of the body of the mandible partly changes to a statistically highly-significant extent, the distance between the canal and the atrophic alveolar ridge being affected more strongly than that between the canal and the base of the mandible. These changes were most clearly pronounced in the area of the first molar.

Sex-related changes in the bone mineral content of atrophic mandibles

In 25 edentulous anatomical mandible specimens (15 female, age range 69–90 years; 10 male, age range 68–88 years), the bone mineral content (BMC) was measured by dual-photon absorptiometry (DPA) and analyzed in a standardized area of the mandibular body. The results of our BMC examinations showed that there was a significant difference (P=0.05) between the two sexes. Another notable fact was that, with advancing age, the values measured in the male mandibles tended to increase slightly but in a statistically significant way. Those of the female mandibles tended to decrease with age. A possible explanation for this observation may be derived from the fact that a reduction of the mandibular height leads to a reduction of the moment of resistance. As functional adaptation in order to preserve the stability of the atrophic body of the mandible, the amount of inner cortical bone of the male mandibles increases, leading to a reduction of the cancellous portion. In the mandibles of women, postmenopausal osteoporosis seems to prevent an analogous compensation mechanism.

Magnetic resonance in lesions of the parotid gland

In a prospective study the relevance of magnetic resonance (MR) for the diagnoses of tumors of the parotid gland has been evaluated. Due to the excellent soft tissue contrast and also the possibility of imaging in various planes and sections and to the high resolution achieved by surface coils, it was possible to visualize the lesions and the surrounding anatomy in great detail. MR combines the advantages of ultrasound and computed tomography and is indicated if a tumor cannot be defined sharply by using ultrasound or CT.

Sex-related differences in the bone mineral density of atrophic mandibles.

The bone mineral content in a standardized site was measured in 25 edentulous mandibles with dual-photon absorptiometry. The results of the bone mineral content examinations demonstrated a significant difference between the sexes. With advancing age of the subjects, the values measured in the mens mandibles tended to increase slightly, whereas those in the womens mandibles tended to decrease. As a functional adaptation to preserve the stability of the male atrophic mandible, the amount of inner cortical bone is increased. Explanations for this observation are discussed. That the mandibles of men and women change differently with increasing age should be considered in routine examinations, because osteoporosis may be regarded as a cofactor of residual ridge resorption in women.

Sonographic measurement versus mapping for determination of residual ridge width

To achieve long-term success of dental implants, evaluation of the dimensions of the resorbing alveolar process must be accurate because an implant should be surrounded by at least 1 mm of bone. Estimating the thickness of bone is more difficult because the mucosal contour can mask the actual dimension of the residual ridge. With ultrasound, it is possible to analyze and visualize the diameter of maxillary or mandibular residual ridges. Data obtained from ultrasound measurement of residual ridges were compared with the data from ridge mapping with the Wilson bone caliper and the Spoerlein caliper. The ultrasound measurement produced nearly the same data at all measurement points as ridge mapping. Ultrasound also provides exact information about the location of the mental foramen and the maxillary sinus. By using all three methods the initial stage of implant treatment can be planned.