Incidence and suggested surgical management of septa in sinus-lift procedures.

A variable number of septa, also referred to as Underwood's septa, divide the floor of the maxillary sinus into several recesses and may thus cause various complications during sinus-lift procedures. The incidence of Underwood's septa was evaluated by examining 41 edentulous maxillas. In 13 of these maxillas (31.7% of the cases), sinus floors with at least one septum were observed. Most of the septa were located in the region between the second premolar and the first molar. A possible cause of septal formation could be the variable phases of maxillary sinus pneumatization of the empty alveolar process following tooth extraction.

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.

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.

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.

Surgical criteria for endosseous implant placement: an overview.

This paper presents an overview of important criteria for successful endosseous implantation. It discusses implant-specific anatomy, preoperative planning, the influence of structure and quality of the available bone on implant prognosis, and the principles of mechanical implant site preparation. The presentation also considers the vitality of adjacent bone, implant surface integrity, local bone defect augmentation, implant selection, and immediate implantation. The learning objective of this article is to enhance the knowledge of surgical and implant site preparation protocol.

Praziquantel and liposomized glucan-treatment modulated liver fibrogenesis and mastocytosis in mice infected with Mesocestoides vogae (M. corti, Cestoda) tetrathyridia.

Beta-glucans are immunomodulators able to activate innate immunity and to potentiate acquired immune reactions. We investigated the impact of co-administration of liposomized beta-glucan on the larvicidal effect of the anthelmintic praziquantel (PZQ) in the livers and peritoneal cavities in mice infected with Mesocestoides vogae (M. corti). Also, within 2 weeks following therapy (up to day 29 p.i.) we examined collagen synthesis in the livers of mice by means of biochemical determination of hydroxyproline concentration, total mast cell counts and cell proliferative capacity using immunohistochemical and radiometrical methods. After co-administration of liposomized glucan (LG) and PZQ efficacy (%) was significantly higher than after treatment with either compound alone, particularly in the peritoneal cavity compared to the liver. In comparison with the control, more intense collagenesis was found in the B-liver parts (high intensity of infection) and lowering of collagen content in the A-parts (very weak infection). This effect was strongest after LG treatment and co-administration of PZQ abolished the pro-fibrotic effect of LG. In all groups, mast cell counts were higher in the B-liver parts than in the A-parts and the dynamics of mastocytosis was profoundly modulated following therapy. Whereas the effect of PZQ was only moderate, early and very strong onset was seen after LG treatment. Administration of PZQ suppressed LG induced-elevation of mast cells counts in both liver parts. Using DNA S-phase markers (BrdU and 3H-thymidine) the proliferative capacity was shown to be associated with several kinds of liver cells. Therapy significantly stimulated [3H]-thymidine incorporation (cell proliferation) only in the A-parts over that in control, the most after LG administration. In summary (i) the anthelmintic effect of PZQ could be enhanced after simultaneous administration of the immunomodulator beta-glucan entrapped in a liposomal carrier, (ii) intense mastocytosis seen after treatment with LG seems to have a direct role in the glucan's pro-fibrotic activity and can be abolished after co-administration of PZQ in a time-dependent manner, (iii) the pattern of cell proliferation indicates that in the case of PZQ treatment, the reparative processes of liver parenchyma are enhanced in an inverse correlation with the intensity of infection.

[Dental CT in the planning of surgical procedures. Its significance in the oro-maxillofacial region from the viewpoint of the dentist]. / Dental-CT zur Planung chirurgischer Eingriffe. Bedeutung im oro-maxillofazialen Bereich aus zahnärztlicher Sicht.

Dental computer assisted tomography (Dental CT) represents a valuable addition to the diagnostic spectrum for planning oral and maxillofacial surgery. High resolution CT and specially designed computer software allow representation of the jaws in different planes that are easy to match. They further allow the display of very small structures relevant to oral surgical interventions and reveal their spatial relationship in three dimensions. Thus communication between dentists and radiologists may be intensified and supported by usage of modern telecommunication systems. Dental CT is indicated, when clinical and conventional radiological techniques will not allow exact interpretation of the situation. It is modern oral implantology that primarily benefits from computer software enabling the assessment of surgical sites in the presurgical phase. Such planning was not yet possible using two dimensional radiographic techniques. The dental-implantological part expects from radiography sharply defined contours of the external bony contours and the mandibular canal, exactly defined relation between slices and planes, no distortion in the orthoradial planes, tools for reliable measurements of distances, angles and volumes, possibility to transmit pictures electronically or on hardcopy without loss of quality.

Ultrasonographic measurement of the soft-tissue of the upper jaw.

For preimplantation diagnoses, various mechanical methods for measuring the width of the soft tissue and thus measuring indirectly the osseous bed of the implant can be used. The ability to determine soft tissue thickness above the jaw by ultrasound was evaluated in 8 autopsy specimens. The data obtained were compared with findings from the needle measurement method which is usually employed in clinical practice. The ultrasound measurement method produced realistic data in all sectional planes chosen.

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.

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

PURPOSE: This study evaluated the incidence, location, and height of antral septa and demonstrates their clinical implications. MATERIALS AND METHODS: One 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. RESULTS: The 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. CONCLUSIONS: Antral 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.

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 men's mandibles tended to increase slightly, whereas those in the women's 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.

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.

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.

[Anatomy of the atrophic mandible. 1. The location of the mandibular canal in the atrophic mandible]. / Anatomische Untersuchungen an der atrophen Mandibula. Teil 1. Die Lage des Canalis mandibulae im atrophen Unterkiefer.

43 atrophic left hemimandibles were divided by 6 saw cuts made between the mental foramen and the third molar to analyze the location of the mandibular canal. Mandibles were classified by the severity of alveolar absorption using Atwood's classification and changes in the distances of the mandibular canal from the superior and inferior borders of the mandibular body were correlated wit the degree of atrophy. Measurements were obtained with a digitizer and a computer and results were analyzed statistically. The following statistically significant observations were made: The distance of the mandibular canal to the external lingua and buccal cortical layers did not change with increasing atrophy, but remained remarkably constant. By contrast, highly significant changes in the distance of the mandibular body were found to be present. These were more pronounced at the superior than at the inferior border. The changes seen were consistently most severe at the level of the first molar. Prior to surgical interventions involving an atrophic mandible the location of the mandibular canal should invariably be identified by imaging techniques such as orthopantomography, telemetric X-rays, tomographies, CT and MRI, if indicated, in order to avoid injuries of the inferior alveloar nerve and preclude forensic consequences.

Evidence that cyclosporine inhibits periodontal prostaglandin I2 synthesis.

Cyclosporine (CsA) is a selective immunosuppressant widely used in clinical therapy. Like phenytoin and nifedipine, the drug is associated with gingival overgrowth. This study considers the interaction of CsA and prostaglandin I2 (PGI2), in particular the action of the drug on gingival tissue in vitro and in vivo. The PGI2-synthesis of rat, rabbit and human gingival tissue was examined by bioassay. In vivo CsA-therapy reduces gingival PGI2-synthesis. The results furthermore show a dose-dependent inhibition of PGI2-synthesis by CsA (1-100 micrograms/ml) in vitro. PGI2-synthesis from in vivo CsA-pretreated probes was further dose-dependently diminished by in vitro addition of CsA. As PGI2 exerts an antiproliferative activity via cAMP-elevation, the drug-induced inhibition of PGI2 production is claimed to be responsible for gingival hyperplasia in CsA-treated patients.

Characteristics of the cancellous bone of edentulous mandibles.

Trabecular bone volume and trabecular connectivity (trabecular bone pattern factor) of edentulous mandibles were examined using undecalcified bone sections from the region of the 1st premolar to investigate atrophy-related changes in mandibular cancellous bone. The mean trabecular bone volume was 21.8% in female mandibles and 36.6% in male mandibles. The mean trabecular bone pattern factor was -0.22 mm-1 for female mandibles and -2.29 mm-1 for male mandibles. The difference between the sexes was statistically conspicuous for both parameters, but did not attain statistical significance. A notable fact was the extreme range of variation in both trabecular bone volume and trabecular connectedness. A difference of 65% between the highest and the lowest trabecular bone volumes measured in the present study (min, 7.6%; max, 73.6%, both male) reflects the possible variation in trabecular density of edentulous mandibles.

Localization of the mandibular neurovascular bundle using dental magnetic resonance imaging.

OBJECTIVE: To assess the reliability of a commercially available 3D-MPR MRI program for the jaws for imaging the mandibular neurovascular bundle. METHODS: A gradient echo sequence (TR: 49 ms/TE: 6.3 ms/flip angle: 25 degrees/excitations: 3) with a spectral fat suppression pre-impulse and a voxel size of 0.9 x 0.9 x 0.8 mm was designed. Cross-sectional and panoramic reconstruction of the whole mandible were performed from the axial scans using Easy Vision (Philips, Best, The Netherlands) software package. The ability of differentiate the mandibular neurovascular bundle was assessed in 11 patients. RESULTS: The mandibular neurovascular bundle was clearly visualized in all cases. CONCLUSION: Dental MRI is a possible alternative to plain films or CT for patients requiring surgery near the mandibular canal.

Blood supply to the maxillary sinus relevant to sinus floor elevation procedures.

The maxillary blood supply is essential for preserving the vitality of the affected maxillary region, integration of the grafting material, and wound healing such as following sinus floor elevation. Although it is well established that edentulous maxillae demonstrate a decreasing vascularity as bone resorption progresses, the vascular conditions relevant to sinus floor elevation procedures have not been investigated yet. This study deals with maxillary arteries relevant to sinus floor elevation surgery and examines the vascularization of the lateral maxilla after tooth loss. The vessels of the lateral maxilla of 18 maxillary specimens (10 male, 8 female, mean age 67 years) were prepared anatomically and the local main arteries, the number of macroscopically discernible branches and anastomoses, their calibers, and the distance between the caudal main branches and the alveolar ridge recorded. The lateral maxilla is supplied by branches of the posterior superior alveolar artery (PSAA) and the infraorbital artery (IOA) that form an anastomosis in the bony lateral antral wall, which also supplies the Schneiderian membrane. This intraosseous anastomosis was found in all of the specimens. Eight of 18 also showed an extraosseous anastomosis between PSAA and IOA, vestibular to the antral wall, giving off an average of 3 branches cranially and 5 branches caudally. The two anastomoses form a double arterial arcade to supply the lateral antral wall and, partly, the alveolar process. The PSAA had a mean caliber of 1.6 mm and exhibited an average of 2 endosseous and 1 extraosseous branches. The IOA had a mean diameter of 1.6 mm and showed an average of 1 endosseous and 3 extraosseous branches. The mean distance between the intraosseous anastomosis and the alveolar ridge was 19 mm in 2 defined measuring sites. Its mean length was 44.6 mm. The epiperiosteal vestibular anastomosis was situated further cranially at a mean distance of 23 to 26 mm from the alveolar ridge and had a mean length of 46 mm. The rather large caliber of the vessels supplying the lateral antral wall seems to be crucial to the fact that the periosteal blood supply is maintained even in severe maxillary atrophy and after complete disappearance of the centro-medullary vessels.