In conclusion, the benefit of rough surfaces relative to minimally rough ones in this loaded animal model was confirmed histologically. The comparison of different surface treatment modalities revealed no significant differences between the modern moderately rough surfaces. Resonance frequency analysis seems to be influenced in a major part by the transducer used, thus prohibiting the comparison of different implant systems.

We can confirm the "classic" grouping of dental implants by type of surface treatment into the groups minimally rough, ablative, TPS coated, and HA coated as these treatments lead to different ascending Sas; however, the additional value of the ratio Sdr including both spatial and amplitude aspects of the surface could not be confirmed in this study. Functional parameters describing the topographic differences are still lacking.

Summary: Surface characteristics of enosseous titanium implants have been known to influence the quality of osseointegration. Parameters recommended for metrical analysis should be supplemented by a topographical description. In this study, R a values obtained by established tactile and optical profilometric methods are correlated with those obtained by stereo scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). As test specimens, standardised CVD diamond-coated titanium alloys with different microwave coating power ranging from 2000 to 3000 W were used. A non-CVDcoated corund grit-blasted specimen (NC) was used as reference. After coating with a CVD, power of 2000 W R a ranges from 4.33 to 5.69 µm depending on the method used. With increasing power of the coating process, the amplitude of the surface roughness is significantly increased to 4.53 to 6.89 µm. R a values of the same sample obtained by different methods are also significantly different (p=0.001). Compared with the established methods of tactile and optical profilometry, SEM and CLSM offer valid data on the surface roughness accompanied by a topographical imaging. In future studies, the underlying method should be specified to interpret roughness values correctly, as not every method is suitable for each specimen and values obtained by different methods vary extremely.

Microscopy of bony tissue usually requires special treatment for decalcification and processing of thin sections. Confocal laser scanning microscopy (CLSM) allows the nondestructive histotomography of organic hard tissue. The aim of this study was to visualize healthy human bone structures and to correlate identical areas in CLSM and conventional light microscopy. Each sample of healthy human lower jaw (n = 20) was divided into three parts: (1) fresh, untreated bony blocks studied by CLSM; (2) MMA-embedded thin sections (without decalcification), HE stained and studied by CLSM and conventional light microscopy (correlation of identical areas); (3) decalcificated, HE stained, histological sections studied by conventional light microscopy. In untreated bony blocks, microstructures such as osteocytes and lamellae were identified by CLSM. These structures could be correlated with conventional light microscopy. In CLSM, subcellular structures cannot yet be interpreted, whereas cytoplastic processes of osteocytes were seen with high contrast. With CLSM, nondestructive histology of cortical bone can be obtained. The risk of artifacts due to pretreatment is minimized, and subsurface visualization does not affect the interpretation.

Dear Sirs, Goracci et al. reported [1] about the terminal endings of odontoblast processes in extracted human teeth using scanning electron microscopy (SEM) and confocal scanning microscopy (CLSM). They showed that cylindrical structures are found in SEM only in the inner third of the dentin. In CLSM, they showed tubular structures up to the dentoenamel junction (DEJ). Thus, they concluded that these cylindrical structures must be the odontoblast processes and that the tubular structures extending to the DEJ represent the lamina limitans.Two main questions arise:1. How can it be assured that, during the extensive specimen preparation for SEM (fracture in liquid nitrogen, dehydratation in alcohol, critical point drying, low pressure atmosphere), no method-related retraction of the odontoblast processes occurs? In our studies [2], the subsurface areas of fresh unstained specimens without prior preparation were observed. This artefact minimised, subsurface microscopy of hard tissues is the main advantage and indication of the CLSM technique. No staining is necessary for it. Moreover, after drying and mechanical grinding, an ex vivo retraction or total loss of odontoblast processes is also observed in CLSM, as shown in Fig. 1. It is obvious that exclusively the odontoblast processes are seen as contrasting structures inside the dentin tubule, with no remaining structure in the periodontoblastic area. 2. How do the authors interpret the extension of tubular structures into the basal areas of the enamel (Fig. 2)