Enhancement of human dental cyst PGI2 formation by platelet derived growth factor and its role in cyst growth and bone resorption.

Various prostaglandins, particularly PGE2 and PGI2, appear to play a major role in osteolytic processes. Radiochromatographic studies have demonstrated that 6-oxo-PGF1-alpha is a major product of exogenously added arachidonic acid in human dental cysts. As platelets may also act as inflammatory cells, platelet-derived growth factor might also have a PGI2-stimulating influence in such cysts. Eleven human dental cysts were examined by a radioimmunoassay and bioassay which can show PGI2 synthesis in human dental cysts without addition of PDGF. Incremental PDGF addition caused a highly significant increase in the rate of PGI2 synthesis. PGDF thus stimulates PGI2 synthesis in chronic inflammatory processes in vitro and may thereby elicit or accelerate osteolysis.

[Dental magnetic resonance tomography (dental MRI) as a method for imaging maxillo-mandibular tooth retention structures]. / Dentale Magnetresonanztomographie (Dental-MRT) als Verfahren zur Darstellung des maxillo-mandibulären Zahnhalteapparates.

PURPOSE: To establish a new method for dental imaging using magnetic resonance tomography named Dental-MRT and to demonstrate its usefulness in diagnosing dentogen pathologies of the mandible and maxilla. METHODS: Seven healthy volunteers, three patients with pulpitis, two patients with dentigerous cysts, two patients after tooth transplantation, and three patients with atrophic mandibles have been evaluated. Optimized axial T1- and T2-weighted gradient echo and spin echo sequences in 2D and 3D technique have been established to perform studies of the jaws. The acquired images were reconstructed with a standard dental software package on a work-station as panorama and cross-sectional views of the mandible or maxilla. RESULTS: The entire maxillo-mandibular bone, teeth, dental pulp, and the content of the mandibular canal were well depicted. Patients with pulpitis demonstrate bone marrow edema in the periapical region. Dentigerous cysts and their relation to the surrounding structures are clearly shown. After contrast media administration marked enhancement of the dental pulp can be demonstrated. CONCLUSION: Dental-MRT promises to provide a new tool for visualization and detection of dental diseases.

Examination of the damping behavior of IMZ implants.

The damping behavior of 392 IMZ implants with a diameter of 4 mm was examined by performing Periotest measurements during regular implant follow-up. The results were correlated with radiographically assessed peri-implant bone reduction. To guarantee statistical independence, only one randomly chosen implant per patient was considered in the examination. In 167 implants, the difference between the mean mandibular and maxillary Periotest values proved to be statistically significant. Age, sex, and radiographic length of the endosseous part of the abutment had no influence on the Periotest values. Assessment of the Periotest values can thus be considered an additional parameter for objective determination of IMZ implant success. However, exclusive use of the Periotest method without additional radiographic examinations does not seem to be justified.

Survival of 1,920 IMZ implants followed for up to 100 months.

A total of 1,920 IMZ implants, placed between March 1984 and December 1993, were evaluated retrospectively. The Kaplan-Meier cumulative survival rate of the implants was 89.9% after 60 months and 83.2% after 100 months. Life table analysis revealed a statistically significantly lower cumulative survival rate for maxillary implants (71.6% at 60 months and 37.9% at 100 months) than for mandibular implants (90.4% at 100 months). Implants placed in the anterior region of the maxilla failed significantly more often than those placed in the posterior region. This was not observed in the mandible. The age and sex of the patients, the status of the jaw (edentulous, partially edentulous), the time of implant placement in relation to tooth extraction, and the length and diameter of the implants had no statistically significant influence on the cumulative survival rate.

Sonographic imaging of the soft-tissue thickness of the edentulous maxilla.

For preimplantologic evaluation and diagnosis, there are various mechanical methods for measuring the thickness of the soft tissue and thus indirectly measuring the osseous bed of the implant. This study evaluated the use of real-time sonography for analyzing the soft-tissue thickness of the entire edentulous maxilla in an anatomic examination of human cadaver specimens. The data obtained were compared with findings from the usual needle measurement method. The ultrasound measurement method produced realistic data in all measurement points of all sectional planes selected.

Use of crestal bone for augmentation of extremely knife-edged alveolar ridges prior to implant placement: report of 3 cases.

A technique is presented for interforaminal lateral augmentation of mandibles with adequate bone height, but extremely knife-edged mandibular alveolar ridges (Class IV of Cawood and Howell's classification of residual ridges), in which the crestal portion of the knife-edged ridge is used as grafting material. Following an osteotomy and rotation of the grafts by 180 degrees, the grafts were fixed to the residual ridge below the osteotomy line by means of miniscrews. All grafts showed only mild resorption after a healing period of 3 months, and it was possible to place 4 implants in the now sufficiently wide host region.

Five-year results of maxillary intramobile Zylinder implants.

We retrospectively analysed the time-dependent function of 501 Intramobile Zylinder (IMZ) implants inserted between August 1983 and December 1994 to restore partially and fully edentulous maxillae. To ensure the independence of implants when calculating level of significance, we chose one implant per patient at random. This was done 500 times to obtain a representative result. The simplified success rate was 473/501 (92%) whereas the time-related survival probability was 76% after 60 months. In 31% (156/500) of the life-table calculations, implants placed in completely edentulous maxillae showed a significantly lower probability of survival than did those placed in partially edentulous patients (P mean: 0.17; SD: 0.19). Implants, that had been placed in the anterior and premolar regions of edentulous maxillae, had a survival probability of 60%, after 60 months. The survival probability of implants placed in the molar region was 100%, over the same observation period. The patient's age, sex, and the time of placement of the implant after tooth extraction had no significant influence on the implant's prognosis. The prognosis of implants inserted for partial edentulism meets the criteria proposed for a viable implant system. Our findings indicate that in complete edentulous maxillae, implants should be placed in the posterior rather than in the anterior region, even though this necessitates augmentation procedures such as sinus lift.

Brånemark single tooth implants: a preliminary report of 76 implants.

Seventy-six Brånemark single-tooth implants were inserted over a 6-year period. Two implants (2.63%) were removed during the follow-up period. All other implants received esthetic and functional single tooth crowns placed on a single tooth abutment or a CeraOne abutment. The most common complication observed was abutment screw loosening, which occurred with 12 crowns. However, it was possible to clearly reduce the occurrence of screw loosening by applying a defined torque. Peri-implant parameters were investigated on 56 implants that were in place for more than 1 year. Acceptable implant function was demonstrated with preestablished clinical parameters and radiographs. Despite the submucosal edge of the crown, peri-implant mucositis was not a major problem. The favorable clinical and esthetic results found in the study encourage an increased application of implants for single tooth restorations.

[Bone resorption at the entry of osseointegrated implants--a biomechanical phenomenon. Finite element study]. / Die Knochenresorption an der Eintrittstelle osseointegrierter Implantate--ein biomechanisches Phänomen. Eine Finite-Element-Studie.

Using finite element analysis, osseointegrated implants exposed to physiologic stresses were examined for the occurrence of stress concentrations at the site of implant entry into bone and factors affecting such stress concentrations were looked for. Qualitative and quantitative alterations of stresses around endosseous implants were computed for different implant sizes, implant materials and cortical thicknesses. The following factors were found to be important for reducing peak stresses in cortical bone: Cylindrical implants are preferable to conical implant shapes. Large implant diameters provide for more favorable stress distributions. Implant materials should have a modulus of elasticity of at least 110,000 N/mm2. Slipping between implants and cortical bone is desirable.

The relationship of smoking on peri-implant tissue: a retrospective study.

The term "peri-implantitis" is used to describe the formation of deep mucosal pockets around dental implants, inflammation of the peri-implant mucosa, and increased resorption of peri-implant bone. It has been speculated that when left untreated, peri-implantitis can result in implant failure. This retrospective study examines a possible correlation between smoking and the appearance of peri-implantitis. The clinical and radiographic observations of 366 implants in 107 patients who smoke were compared with those of a group of 1000 implants in 314 nonsmoking patients. Despite the retrospective nature of this study, a comparison between the two groups was possible. The mean follow-up period, mean patient age, implant locations, and percentages of fixed partial dentures and overdentures were consistent in both groups. There was no significant difference in the mean maxillary and mandibular hygienic indices between the group of smokers and that of nonsmokers. However, the group of smokers showed a higher score in the bleeding index, the mean peri-implant pocket depth, the degree of peri-implant mucosal inflammation, and radiographically discernible bone resorption mesial and distal to the implant. In the maxilla of the smoking group, these observations were significantly higher than both the mandibular observations for smokers and the maxillary observations of the group of nonsmokers (p < 0.01). No differences between the two groups were observed in the mandible. Aside from the systemic effects of tobacco smoking on the human organism, local cofactors seem to be responsible for the higher incidence of peri-implantitis in smokers and have a particularly negative effect on the maxilla. These findings confirm that smokers treated with dental implants have a greater risk of development of peri-implantitis.

A minimally invasive second-stage procedure for single-tooth implants.

The natural look of dental restorations has become a universally claimed treatment objective, especially when single-tooth gaps are restored with implants. A harmonious gingival margin is crucial to achieve this goal. This article presents a new procedure for exposure of single-tooth implants that yields a favorable esthetic result in the visible maxillary regions because of the simple type of incision used. The procedure consists of two incisions: the first incision makes it possible to find out the implant position and the second incision shapes the mucous membrane according to local supply. The second incision also prevents the soft tissue from tearing after careful stretching and subsequent pressing of the supraimplant mucosa. There is minimal soft tissue traumatization, and as a result, healing time can be reduced to 1 week and an appealing esthetic result can be reached.

Experimental study of the damping behaviour of IMZ implants.

Measurements of the damping behaviour of dental implants with the Periotest device are considered to be an objective means to assess the mobility of implants. The effects of the position of an implant in the maxilla or mandible, the period of time passing between the measurements and implant placement and the height at which the Periotest measurements are performed on the damping behaviour of implants have been discussed controversially. This experimental study examined the influence of the use of different measuring devices, the measuring height and the embedding depth on the damping behaviour of IMZ implants. The implants were embedded in resin at different depths and damping measurements were carried out at different measuring heights. It was found that the values rose with an increasing measuring height and a decreasing embedding depth. Analysis of variance was used to assess the influence of the embedding depth and revealed that the embedding depth had a significant impact on the measuring values at each measuring height, above 6 mm. Moreover, it was found that the higher the measuring height, the higher the measured values and the greater the differences between the values obtained at the individual depths. The different measuring devices had no influence on the measuring results (P = 0.79). The results of this study suggest that a longitudinal follow-up of the peri-implant residual bone height around individual implants is possible. Single measuring values by themselves do not allow any conclusions about the prognosis of an implant. The assessment of the peri-implant bone height through Periotest measurements is conceivable only when a table of damping values taking into account the physical length of the implant, the embedding depth and the measuring height for the examined implant system is available. In cylindrical implants, the head of the available prefabricated measuring post can be recommended as a constant measuring point for further studies, especially when the results are to be compared with those obtained by other study groups.

Bovine hydroxyapatite for maxillary sinus augmentation: analysis of interfacial bond strength of dental implants using pull-out tests.

This study examines the effect of sinus lift surgery using bovine hydroxyapatite on the bone anchorage of titanium plasma flame-spray-coated cylindrical implants. A total of 54 implants were placed in the lateral bony antral walls of 27 mountain sheep. Host site augmentation was done simultaneously using bovine hydroxyapatite and autogenous cancellous bone from the iliac crest in 18 sinuses each. The bone walls of the remaining 18 sinuses received no augmentation. Pull-out tests were carried out at 12, 16, and 26 weeks, revealing a significant influence of the implants' residence time on pull-out strength (P = 0.004). The implants of the non-augmented group and those of the group augmented using cancellous bone showed a linear increase in pull-out strength to 169.8 N and 523.7 N, respectively, until the 26th week. The implants of the group augmented with bovine hydroxyapatite exhibited the highest initial pull-out strength (325.1 N) that further increased to 521.8 N until the 26th week. All in all, this group showed a significantly greater pull-out strength tan did the negative control group (P = 0.03).

Elimination of bacteria on different implant surfaces through photosensitization and soft laser. An in vitro study.

Microbiologic examinations of implants have shown that certain microorganisms described as periodontal pathogens may have an influence on the development and the progression of peri-implant disease. This experimental study aimed to examine the bactericidal effect of irradiation with a soft laser on bacteria associated with peri-implantitis following exposure to a photosensitizing substance. Platelets made of commercially pure titanium, either with a machined surface or with a hydroxyapatite or plasma-flame-sprayed surface or with a corundum-blasted and etched surface, were incubated with a pure suspension of Actinobacillus actinomycetemcomitans or Porphyromonas gingivalis or Prevotella intermedia. The surfaces were then treated with a toluidine blue solution and irradiated with a diode soft laser with a wave length of 905 nm for 1 min. None of the smears obtained from the thus treated surfaces showed bacterial growth, whereas the smears obtained from surfaces that had been subjected to only one type of treatment showed unchanged growth of every target organism tested (P < 0.0006). Electron microscopic inspection of the thus treated platelets revealed that combined dye/laser treatment resulted in the destruction of bacterial cells. The present in vitro results indicate that lethal photosensitization may be of use for treatment of peri-implantitis.

Tongue cancer. Sonographic assessment of tumor stage.

In an effort to improve preoperative evaluation of tumors of the tongue, a prospective study on the value of ultrasound (US) for the staging of 50 surgically proven cancers of the tongue and floor of mouth was performed. Sonography was correlated with clinical staging and surgical outcome. Real-time high-frequency transducers and an echo-free silicone interface were used. The dorsal and middle thirds of the tongue were scanned from a submental access and the tip of the tongue directly. US accurately defined tumor sizes and locations in all cases. US staged cancers correctly in all cases but one. In contrast, clinical staging was correct in only 66% of cases. Surgically relevant details, such as crossing of the midline of the tongue or infiltration of the lateral pharyngeal wall, were detected with US. The major limitations of US include the nonvisualization of the epiglottis and retropharyngeal space as well as bone infiltration.

[Ionomeric vitreous cement for retrograde root filling]. / Glasionomerzement als retrogrades Wurzelfüllmaterial.

In an in vitro study the sealing properties of materials commonly used for retrograde filling of apicectomized teeth were investigated in extracted teeth and compared with those of ionomeric vitreous cement. Materials tested included: --Heat-sealed guttapercha; --Guttapercha + phosphate cement; --Amalgam; --Standardized ceramic pins (Ulm system); and --Ionomeric vitreous cement. Sealing was established by methylene blue perfusion. Seals produced by heat-sealed guttapercha, guttapercha + phosphate cement and non-gamma-2 amalgam were found to be inferior to those obtained with ionomeric vitreous cement and standardized aluminium oxide ceramic pins.

[The use of sonography in the diagnosis of pathological changes in the mouth floor and tongue region]. / Zum Einsatz der Sonographie in der Diagnostik pathologischer Veränderungen im Mundboden-Zungenbereich.

The application of real-time sonography in the area of the tongue and floor of the mouth is described. Its value is examined by a sonographic-surgical correlation of 40 examinations. In 38 cases, the sonographic findings correlated well with the clinical picture, as well as with the intraoperative and pathologic findings. Ultrasound seems to be a practicable imaging method, especially with malignant infiltration of the tongue.

[Prognostic factors in the treatment of inoperable orofacial tumors with simultaneous radiotherapy and intra-arterial chemotherapy]. / Prognostische Faktoren bei der Behandlung inoperabler orofazialer Malignome mit simultaner Radio- und intraarterieller Chemotherapie.

Between January 1973 and April 1982 66 evaluable patients with advanced inoperable orofacial tumours underwent intraarterial Bleomycin and Methotrexate with simultaneous radiotherapy in a prospective study. 32 patients had no previous treatment, 34 patients had initial surgery, radiotherapy and/or chemotherapy. 15 mg Bleomycin were administered through a catheter into the arteria externa carotis daily in the morning. 25 mg Methotrexate were given in the same way at night followed by 3 mg Calcium-Leucovorin i.m. every 8 hours. The cumulative dose was 300 mg Bleomycin and 500 mg Methotrexate. Four hours after the administration of Bleomycin the target volume was irradiated (single fraction 2 Gy, total dose 60 to 65 Gy). The overall response rate was 65% containing 17% complete and 48% partial remission. Destruction of the bone appeared to be the most important index at the start of the therapy. Further prognostic determinants as previous treatment, localisation of the primary tumours (maxilla and mandibula respectively oral cavity and oropharynx) and local regional lymphnode stage missed statistically significance in the survival time, may be due to a possible radiosensitizing effect of the simultaneous chemotherapy. Complete remission turned out to be the most important prognostic factor after the end of treatment. Patients responding with complete remission show a median disease free survival of 56+ months and a median survival time of 82 months. Acute reactions were reversible. Only in 14% of the patients the treatment could not be finished. Better results could be obtained by electron-affinic radiosensitizers and high LET radiation.