Poster 1, Sprache: Deutsch
Introduction: Important parameters in osteoradionecrosis (ORN) are the direct damage of osteocyte cells and vascular fibrosis. Objectives: Microscopic visualization of early, sub-clinical radiation induced degenerations.
Materials and methods: Bone samples from the lower jaw: - sound bone samples, mostly from orthodontic surgery (n=10 patients); - samples with manifest ORN (n=12 patients). - 36 Gy pre-surgery, radio(chemo)therapy, samples obtained 2 -3 weeks post radiation (n=9); - 60 - 70 Gy irradiation, no evidence for ORN (12 months post-irradiation; n = 9 patients); All samples were inspected with confocal laser scanning microscopy (CLSM). For additional conventional light microscopy the intact DNA was fluorescent labeled with bisbenzimide. Comparing studies with the different microscopic techniques were carried out with thin sections (Donath sawing grinding technique) of the Technovit embedded samples.
Results: In conventional microscopy all irradiated bone samples showed areas with partial to total loss of vital osteocytes. This radiation damage was observed also after 36 Gy and short interval before surgery. CLSM images additionally showed micro-morphological modifications of the lamellar structure: early loss of lamellar contours (36 Gy), progressive loss of contours (60 - 70 Gy), up to totally irregular lamella (IORN).
Conclusion: The observed loss of vitality of the osteocytes confirms existing studies. Additional CLSM evidence for early radiation damages are the effects on the lamellar structure of the bone samples.
Poster 2, Sprache: Deutsch
Endodontal reactions due to caries lesions may cumulate with those of restorative procedures and cause unexpected endodontal complications. It was therefore the aim of this study to characterize semiquantitatively the endodontal reactions by a new complex coding system of pulpal pathosis. 79 teeth without marginal periodontitis and scheduled for extraction were investigated clinically as well as radiographically: Caries superficialis (9 teeth, group 1); Caries media (23 teeth, group 2); Caries profunda (43 teeth, group 3); no carious lesions (4 teeth, control group). The teeth were serially sectioned, stained with haematoxilin-eosin and according to J.Hopkins (bacterial stain). The sections were histologically investigated according to modified BRD criteria (J Dent Res 75:1230, 1996) including the parameters: (i) Bacterial invasion, (ii) Regenerative parameters, (iii) Degenerative parameters. Bacterial invasion into dentin tubules and degenerative changes did not occur in all types of carious lesions but was most pronounced in teeth exhibiting deep caries (BRD coding for bacterial invasion: group1/group2/group3/control: 0,13/1,05/2,34/0; BRD coding for irregular irritation dentin: group1/group2/group3/control: 0,67/0,82/2,00/0,50), whereas necrosis was exclusively found in group 3 teeth (BRD coding: 0,84). It is concluded that BRD criteria proposed for long term biocompatibility testing of restorative materials and techniques are also useful in the characterization of the histopathology of caries progression. Concerning the clinical caries diagnosis superficial caries induces typical degenerative but localized pathological reactions. Only deep carious lesions may cause severe reactions showing signs up to the desintegration of pulp tissue. For restorative procedures of deep carious lesions a limited reactibilty of the endodont has to be taken into consideration.
Poster 3, Sprache: Deutsch
The aim of this study was to determine a relationship between various tooth cleaning methods and the values measured with the DIAGNOdent-laser-diagnostic-system for caries detection. Forty filling-free crowns of extracted teeth stored in physiological saline solution were examined. The measurements at four points in every tooth were checked after 1.5 hours for reproducibility. After this the teeth were cleaned using four different methods. Immediately after the cleaning as well as after a further 1.5 hours the measurements were repeated. A cleaning according to all methods investigated did not cause changes of the measured values in points without any plaque or stain. If the tooth surface was changed in visible carious areas or if plaque and stain were removed, the measured values decreased. It could be shown that at apparent caries-free measuring points without any plaque or stain the measured values are not dependent on various tooth cleaning methods. Using the laser-diagnostic-system the teeth should be cleaned before use, to have always the same conditions especially when the system is used for a regular examination of apparent caries-free teeth.
Poster 4, Sprache: Deutsch
The aim of this study was to compare the completion and tightness of root canal fillings made with a calcium hydroxide root filling paste. Using seven different methods the paste was placed in ISO-standardized, simulated canal lumens in transparent plastic. The tightness of the root filling was assessed using digital radiographs and appropriate picture handling computer software. With a root filling spiral instrument, with a McSpadden Compactor and after injection of the material and vertical condensation a filling of the entire canal length could be achieved. Radiographs indicated that the greatest tightness was achieved using vertical condensation after initially injecting with a needle or applying with a root filling spiral instrument. It was concluded that calcium hydroxide root filling paste should be placed in root canals using an injection needle or a root filling spiral instrument, and that subsequent vertical condensation leads to complete filling of the apical region and additional compression of the material. These effects could also be expected with the application of other paste root filling materials (eg. chloropercha).
Schlagwörter: Zahnerhaltung, Kalziumhydroxid, Hypocal, ISO, Wurzelkanal, Wurzelfüllspirale, Lentulo, McSpadden-Compactor, Wattepellet, Injektion, Injektionskanüle, vertikale Kondensation, K-Feile, Papierspitze
Poster 5, Sprache: Deutsch
The recommended bond strength for polymer-based crown and bridge veneering materials without macromechanical retention is at least 5 MPa (ISO 10477, amendment 1, 04-98). The purpose of this study was to evaluate the shear bond strength of veneering composite resins to the gold alloy using different bonding systems. Two commercial bonding systems [Kevloc (Kulzer), Rocatector Delta (ESPE)] were evaluated. Bonding was attempted with the opaque resin provided by each system. Dentacolor, Artglass (Kulzer) and Sinfony (ESPE) were used as veenering composite resins. Samples with mechanical retention acted as a control group. Nine specimens were tested from each combination. Shear bond tests were performed after aging the disk samples (Au-Pt) by 5000 thermocycles (5 - 55 oC) and one week water storage at 37 oC. Data were analyzed by ANOVA at a significance level of 0.05. Shear bond strengths, exceeding 8 MPa, were achieved for all the bonding systems with corresponding veneering composite resins (control groups: 10 - 15 MPa). Mean shear bond strengths of the Kevloc system in combination with different composites (10 - 13 MPa) showed no significant differences to the Rocatector/Sinfony combination (10 MPa). Bond strength of nearly all combinations of products of different manufacturers (Dentacolor/Artglass/Rocatector and Sinfony/Kevloc) were close (with the exception of Sinfony/Kevloc) to the recommended clinical threshold value of 5 MPa for the resin/alloy bond (ISO). Strong, durable bonds can be achieved between the chemically conditioned (Kevloc, Rocatector Delta) gold alloy and the corresponding veneering composite resins, thus enhancing the usefulness of chemical bonds for resin-veneered crowns.
Poster 6, Sprache: Englisch
Introduction: Radiogenic effects on enamel as an early stage for radiation induced caries are still discussed in controversy. The drawback of existing studies on direct radiogenic enamel degradation is the lacking comparability of the results.
Objective: The aim of this study is to provide evidence for direct effects of radiation on enamel in contrast to the well-known damage post-radiationem induced in the oral environment.
Material and Methods:
1: totally impacted, surgically extracted teeth (n = 10)
2: teeth irradiated in vitro (500 - 2500 Gy) (n = 20)
3: irradiated in situ (experimental enoral; 60 Gy) (n = 20)
4: radiotherapy (extraction after 18 days; 36 Gy) (n = 20)
5: radiotherapy (extraction after 2.5 years; 60 Gy) (n = 20)
Demineralization: lactic acid gel (pH = 5.0) up to 270 min CLSM-histology: prospective after 0, 90, 180, 270 min etch. Interpretation of micro-morphological and micro-morphometric criteria (extension of the demineralized area)
Conclusions: Enamel after radiotherapy and in vitro irradiated enamel is more vulnerable to acid attack than sound enamel.
Schlagwörter: radiotherapy, radiation caries, enamel, demineralization, in vitro
Poster 7, Sprache: Englisch
Introduction: Micro-morphological and physicochemical studies on mechanisms of the rapid caries progress after radiotherapy are focused mainly on enamel. Discrimination between defects induced during the irradiation and damage due to subsequent radio-xerostomia is not possible to date. As a consequence, the specific aetiology of radiotherapy induced caries is far from being understood.
Objectives: Only few investigations deal with effects of radiotherapy on the dentoenamel junction. This experiment was to study the micro-morphology of the dentoenamel junction and to discriminate between: effects due to the irradiation alone defects induced by radio-xerostomia. The concept of the study was the CLSM visualization of the dentoenamel junction: of sound extracted teeth irradiated extraorally in a Co-60 source of teeth extracted from patients in different phases of radiotherapy.
Materials and Methods: Sound, totally impacted and surgically removed teeth, as standards (n = 50) teeth with 33 ± 10 Gy in vivo, no visible defects; (n = 61, 11 patients) teeth with 63 ± 6 Gy in vivo, macroscopically visible defects (n = 147, 24 patients) 500 - 2500 Gy in vitro irradiated teeth, doses 0.1, 1 and 10 Gy/min (n = 30) CLSM is a non-destructive technique for tomographic visualisation of microscopic areas of tooth structures, with the potential of nearly artefact free imaging.
Discussion and Conclusions: Radiotherapy induced caries seems to originate from radiation induced defects in the dentoenamel junction.
Schlagwörter: radiotherapy, radiation, caries, dentoenamel junction
Poster 8, Sprache: Deutsch
The preparation of cavities with oscillating instruments facilitates optimal formation of an exact bevel for composite fillings especially in smaller defects. The aim of the examination was to determine whether side effects of the sonoabrasive SonicSys®-System causes zones of debris or cracks in enamel and dentin. As standard of comparison conventional rotating instruments should serve. 11 freshly extracted, caries-free teeth were fixed in a plaster-block between 2 phantom-teeth. Mesial and distal small cavities were prepared with a diamond bur (ISO 830 010). The margin of one cavity was finished conventionally with a flame shaped bur, (ISO 8830 009) in an angle of 45°; the other cavity was smoothed with the SonicSys®-approx-instrument. The 22 cavities were filled accordingly to the manufacturers advices with the composite system Syntac®/Tetric®. Afterwards the teeth were fixed in formalin and embedded in a light-curing plastic medium. For the histological examination undecalified cuts of 10 µm thickness were prepared from the se samples. The comparative light-microscopic evaluation of the samples showed no differences in dependence on the chosen finishing instruments in reference to the margin quality and the adjoining tissue-layers. Zones of debris and cracks were not verifiable in dentin and enamel. In reference on the sealing quality no differences were to be proven between the two examined systems. In this study oscillating vibrations of the SonicSys®-Systems did not cause verifiable side effects in the area of the cavity walls. We are not expecting an impairment of the quality of the restoration.