[Confocal laser scanning microscopy (CLSM) for validation of non-destructive histotomography of healthy bone tissue]. / Konfokale Laser-Scanning Mikroskopie (CLSM) Validierung der zerstörungsfreien Histotomographie gesunden Knochengewebes.

OBJECTIVES: Fixation (formalin), decalcification (sections) or mechanical treatment (grinding) all bear the risk of artifacts occurring during hard-tissue histology. Because studies on the etiology of pathological changes mostly focus on subclinical lesions, artifacts can simulate early changes or even be superimposed on existing changes. The objective of this study was to determine how artifacts can be reduced. MATERIAL AND METHODS: In confocal laser scanning microscopy (CLSM) a focused laser beam scans the surface of the specimens and penetrates into the tissue. The intensity of the remitted light is recorded. The confocal effect is due to an extremely small aperture (pin-hole), excluding light from out-of-focus planes of the sample. By stepwise movement of the object table, a tomographic series of tomographic images is obtained. Sound cortical bone samples of the lower jaw (n = 20) were studied by light microscopy and by CLSM, visualizing identical areas of a ground sectioned sample after H&E staining. Additionally, embedded and fresh blocks of tissue of the same bone sample were studied histotomographically in the CLSM. RESULTS: (1) Light microscopic micromorphology of cortical bone can be visualized adequately in the CLSM; (2) many structures that can be visualized by light microscopy only after special staining (e.g., osteozyte processes) can be visualized by the CLSM using sample blocks without pretreatment. CONCLUSION: (1) Nondestructive subsurface histotomography by CLSM totally excludes mechanical artifacts; (2) physicochemical artifacts can be handled more easily because fresh samples can be studied; (3) pseudo-three-dimensional imaging allows histological interpretation of the tissue that is equivalent to macroscopic tomographic techniques (CT, MRT).

Histotomography of the odontoblast processes at the dentine-enamel junction of permanent healthy human teeth in the confocal laser scanning microscope.

The translucency of teeth allows the non-destructive subsurface visualisation of their microstructure by confocal laser scanning microscopy (CLSM) at a level of about 150 microns below the surface. The dentine-enamel junction (DEJ) is accessible only directly adjacent to the cervix of the tooth. Therefore teeth have to be sectioned for studying marginal areas of the dental hard tissue. The potential of the technique for (pseudo) three-dimensional visualisation allows the study of an array of individual confocal images, the interpretation of which is similar to that of macroscopic tomographs (CT-scan, MRI). Additionally, the extended focus mode yields the overlay of individual confocal images in the form of a two-dimensional projection. This mode of operation proved to be particularly suited for the visualisation of odontoblast processes in their whole extension. The three-dimensional junction between enamel and dentine, the branches of the odontoblast processes and their interactions with the DEJ is demonstrable by CLSM without staining or other procedures of sample preparation. The direct microscopic comparison between samples, either fresh or kept in a humid chamber, and Technovit-embedded sample blocks gives evidence that the risk of artefacts by sample storage or by the embedding procedure is minimal. The tomographs limited to subsurface areas of the tissue also exclude mechanical surface artefacts due to grinding or cutting.

Treatment of injuries to the inferior alveolar nerve after endodontic procedures.

Overextension of filling material into the mandibular canal after root treatment in the lower jaw is a rare but serious complication. Mechanical compression, chemical neurotoxicity and local infection may cause irreversible nerve damage. A report on 11 patients with neurological complaints of the inferior alveolar nerve after endodontic treatment is summarised. The neurological findings are dominated by hypaesthesia and dysaesthesia. Half of the patients reported pain. Hyperaesthesia is found much more rarely. Nearly all the patients had a combination of one or more symptoms. Initial X-rays showed root filling material in the area of the mandibular canal. Nine cases were treated with apicectomy and decompression of the nerve; in two cases, extraction of the tooth was necessary. Only one patient reported persistent pain after surgery. If neurological complaints appear after root filling in the lower jaw, a nerve injury due to root filling material should be ruled out. In cases of overfilling, immediate apicectomy and decompression of the nerve with conservation of the tooth is often the treatment of choice; the tooth may be preserved and the best chance of avoiding permanent nerve damage is provided.