Hanns Plenk

Gingivomorphometry - esthetic evaluation of the crown-mucogingival complex: a new method for collection and measurement of standardized and reproducible data in oral photography

OBJECTIVES A new method is introduced for the esthetic evaluation of the periimplant mucogingival complex through collection of standardized oral photographs and computer-assisted measurement of reproducible data. Using this method, different soft tissue and crown parameters in the dentogingival complex can be measured and the esthetic outcome monitored. MATERIAL AND METHODS A photographic device for standardized oral photography and a standard protocol for the esthetic evaluation of the crown-mucogingival complex is presented, comprising six soft tissue parameters: (1) mesial and (2) distal papilla areas, (3) mesial and (4) distal papilla heights, (5) soft tissue-crown perimeter, and (6) gingival recession. In order to demonstrate the reproducibility of standardized oral photographs and the accuracy of the measurement of the six parameters, the data obtained in each of two such standardized clinical photographs, taken at 10-14 days intervals, of the anterior maxillary region from 10 patients with no apparent dental disease were compared. For the statistical analysis of the reproducibility of these dependent data the 95% confidence interval and the coefficients of variation were calculated from measurement means and ranges of each of the above parameters, pooled from all 10 patients. RESULTS Statistical analysis revealed high reproducibility with no significant differences between the range of mean values of all six parameter measurements on the first and second standardized oral photograph of the same patient, respectively. CONCLUSION Gingivomorphometry on standardized oral photographs can be considered to be an accurate and reproducible method for the evaluation and measurement of different dentogingival and periimplant parameters.

Hydrogel-coated and platinum coils for intracranial aneurysm embolization compared in three experimental models using computerized angiographic and histologic morphometry

Angiographic and histologic results of hydrogel-coated (HydroCoil®) and platinum coil-treated canine sidewall, canine bifurcation, and rabbit elastase aneurysms (2–52 weeks follow-ups) were quantified by computer-assisted morphometry. Angiograms were analyzed using density determination to differentiate embolic mass and contrast medium filling. Aneurysm total and occluded areas, embolic material and red thrombus areas were determined from images of surface stained, plastic embedded ground sections. Long-term stable occlusion was observed in all three models with the use of hydrogel-coated coils. However, platinum coils were as effective only in the canine sidewall model. With the use of hydrogel-coated coils, a two-fold increase in the volumetric filling of the aneurysm sac resulted in improved outcomes.

Histomorphology of the Penis Bone (Baculum) in the Gray Long-Eared Bat Plecotus austriacus (Chiroptera, Vespertilionidae)

For the first time, the histomorphology of the penis bone of a bat (Plecotus austriacus) was examined in detail. From Plecotus austriacus, 14 whole penes and 11 isolated bacula were studied and compared to bacula of Plecotus auritus and Plecotus macrobullaris. The baculum was located on specimen microradiographs and in micro‐CT images in the tip of the penis. Using serial semithin sections and surface‐stained, undecalcified ground sections, the types of bone and other tissues constituting the baculum were examined by light microscopy. 3D reconstructions were generated from the serial semithin sections and from micro‐CT images. The shaft and the proximal branches of the Y‐shaped baculum form a tubular bone around a medullary cavity. Since the small diameter of this channel and the main lamellar bone around it resemble a Haversian canal, the baculum is equivalent to a single‐osteon bone. Several oblique nutrient canals enter this medullary cavity in the shaft and branches. All ends of the baculum consist predominantly of woven bone. The collagen fiber bundles of the tunica albuginea of both corpora cavernosa insert via fibrocartilage into the woven bone of the branches. Thus, the microscopic structures support the hypothesis that the baculum functions as a stiffening element in the erect penis. In this study, several microscopic imaging techniques were evaluated for displaying the microscopic structures of the baculum. Specimen microradiography, but especially micro‐CT proved to be suitable nondestructive methods for accurate and reproducible demonstration and comparison of the three‐dimensional structures of the baculum in different bat species. Anat Rec 293:1248–1258, 2010.

The role of materials biocompatibility for functional electrical stimulation applications.

The biocompatibility of all metallic, polymeric, or ceramic materials used for functional electrical stimulation is governed by the inevitable inflammatory tissue response, but possibly also by immunological reactions to the bulk material or released constituents. Besides chemical, physical, and corrosion properties of the conductive electrode materials, increased surface area and roughness of the electrode can influence tissue contact and signal delivery, and can also affect electrode-tissue impedance due to increased connective tissue encapsulation. The polymeric materials used for electrode insulation and those for leads and stimulator packaging seem more or less compatible in an aggressive biological environment. For the long-term performance of electrodes and leads, the relative motion in the various implant bed situations also has to be considered.

Correlative 3D‐imaging of Pipistrellus penis micromorphology: Validating quantitative microCT images with undecalcified serial ground section histomorphology

Detailed knowledge of histomorphology is a prerequisite for the understanding of function, variation, and development. In bats, as in other mammals, penis and baculum morphology are important in species discrimination and phylogenetic studies. In this study, nondestructive 3D‐microtomographic (microCT, µCT) images of bacula and iodine‐stained penes of Pipistrellus pipistrellus were correlated with light microscopic images from undecalcified surface‐stained ground sections of three of these penes of P. pipistrellus (1 juvenile). The results were then compared with µCT‐images of bacula of P. pygmaeus, P. hanaki, and P. nathusii. The Y‐shaped baculum in all studied Pipistrellus species has a proximal base with two club‐shaped branches, a long slender shaft, and a forked distal tip. The branches contain a medullary cavity of variable size, which tapers into a central canal of variable length in the proximal baculum shaft. Both are surrounded by a lamellar and a woven bone layer and contain fatty marrow and blood vessels. The distal shaft consists of woven bone only, without a vascular canal. The proximal ends of the branches are connected with the tunica albuginea of the corpora cavernosa via entheses. In the penis shaft, the corpus spongiosum‐surrounded urethra lies in a ventral grove of the corpora cavernosa, and continues in the glans under the baculum. The glans penis predominantly comprises an enlarged corpus spongiosum, which surrounds urethra and baculum. In the 12 studied juvenile and subadult P. pipistrellus specimens the proximal branches of the baculum were shorter and without marrow cavity, while shaft and distal tip appeared already fully developed. The present combination with light microscopic images from one species enabled a more reliable interpretation of histomorphological structures in the µCT‐images from all four Pipistrellus species. J. Morphol. 276:695–706, 2015.

Effects of intraoperatively applied glucocorticoid-hydrogels on residual hearing and foreign-body reaction in a guinea pig model of cochlear implantation

Abstract Conclusion: The intraoperative application of glucocorticoid-loaded hydrogels seems to cause a reduction in neutrophil infiltration. No beneficial effect on hearing thresholds was detected. Objectives: To evaluate the application of dexamethasone- and triamcinolone acetonide-loaded hydrogels for effects on hearing preservation and foreign body reaction in a guinea pig model for cochlear implantation (CI). Methods: A total of 48 guinea pigs (n = 12 per group) were implanted with a single channel electrode and intraoperatively treated with 50 μl of a 20% w/v poloxamer 407 hydrogel loaded with 6% dexamethasone or 30% triamcinolone acetonide, a control hydrogel, or physiological saline. Click- and tone burst-evoked compound action potential thresholds were determined preoperatively and directly postoperatively as well as on days 3, 7, 14, 21, and 28. At the end of the experiment, temporal bones were prepared for histological evaluation by a grinding/polishing technique with the electrode in situ. Three ears per treatment group were serially sectioned and evaluated for histological alterations. Results: The intratympanic application of glucocorticoid-loaded hydrogels did not improve the preservation of residual hearing in this cochlear implant model. The foreign body reaction to the electrode appeared reduced in the glucocorticoid-treated animals. No correlation was found between the histologically described trauma to the inner ear and the resulting hearing threshold shifts.

In-vitro and in-vivo measurement of the animal's middle ear acoustical response by partially implantable fiber-optic sensing system

The main obstacle in realization of a totally implantable hearing aid is a lack of reliable implantable microphone. In this paper we have described a potentially miniature fiber-optic vibrometer based on a modified Michelson interferometer, designed to serve as a middle-ear microphone for totally implantable cochlear- or middle-ear hearing aids. A model of the sensing system was used for in-vitro and in-vivo investigation of acoustical response of sheeps middle-ear ossicles. Surgical and implantation procedure of introducing the sensing optical fiber into the middle-ear and its aiming at the incus was investigated and described here in detail. The frequency responses of the incus was measured while a cadaver and living sheep was exposed to the sinusoidal acoustical excitation of 40-90dB SPL, in the frequency range from 100Hz to 10kHz. The amplitude of the incus vibration was found to be in the range between 10pm to 100nm, strongly depending on the frequency, with a lot of resonant peaks, corresponding mainly to the natural outer ear canal gain. The noise floor in the experiments was about 2pm/Hz1/2, but recently we have decreased it to < 0.5pm/Hz1/2, which corresponds to a minimal detectable sound level of 31-35dB(A) SPL for humans. The histological examination of temporal bones of cadaver animals and the intensity of in-vivo optical signal demonstrated that the aiming of the sensing fiber to the target has been preserved for five months after the implantation.

The diagnostic value of surface-stained ground sections for pathohistological evaluation of coil-embolized aneurysms

It is my privilege, being one of the pioneers using plasticembedded ground sections for the light microscopic evalua-tion of coil-embolized aneurysms, to oppose with a commenttothepaperpublished2009inActa Neurochirurgica [5]. LeoDe Ridder, Ghent University, Belgium, had criticized thattwo-dimensional (ground) sections, only stained on theirsurfaces, are not representative for microscopic evaluation ofa three-dimensional, coil-filled aneurysm.Plastic-embedded ground sections are now regarded thegold standard for hard tissue implant evaluation. Metallic,ceramic, and also polymeric implant materials can be cuttogether with undecalcified bone or teeth [6]. It was only alogical consequence to section also soft tissue implants,with the advantage of preserving, for example, the metalliccoils in situ when evaluating aneurysms. To my knowledge,first reports of using ground sections for the evaluation ofpostmortem retrieved human aneurysms [1, 7]andofexperimental aneurysms in rabbits [2]appearedin1999.Incontrast to conventional paraffin-embedded microtome sec-tions,wherethemetalliccoilsdamagetheknifeandfallout,orhave to be removed before sectioning as again advertised [4],in ground sections, the coil–tissue interfaces are preservedfor evaluating also the biocompatibility aspects of thevarious coil devices. At least for me, surface-stained groundsections can now also be regarded the gold standard forpathohistological aneurysm evaluation.Furthermore, it has to be pointed out that all conven-tional 5- to 10-µm-thick microtome sections of aneurysmsare also two-dimensional slices of a three-dimensionalstructure. Only consecutive serial microtome sections,which are technically not feasible because of artifacts andtoo elaborate, could represent the three-dimensional bodyof a coiled aneurysm. Depending on size, at least two ormore consecutive 100-µm-thick ground sections are madefrom aneurysms in my and other laboratories, eachrepresenting an initial specimen thickness of about0.5 mm. Thus, a considerable volume of the aneurysm,still containing all the loops of the coils in cross ortangential sections, is available for microscopic evaluation.Since surface stains penetrate only a few microns into thefinally 60- to 100-µm-thick ground sections of the resin-embedded tissues, solely this surface-stained layer isfocused under the light microscope, providing resolutionof cellular detail equally good to much thinner microtomesections. Our group has shown by computer-assistedmorphometry that the coil density measured in groundsections of experimental [8] and retrieved human aneur-ysms [9] corresponded well with the calculated coildensities in respective angiograms. Combined applicationof computer-assisted morphometry on angiograms andground sections allowed even for a comparison of differentcoil types in different aneurysm models from independentexperimental studies [3].Therefore, the weakness of the above cited study [5]israther the subjective estimation of angiographic aneurysmocclusion, serving as sole basis for performance ranking ofthese second-generation and bare platinum embolic devices.Apparently, only not-blinded scoring according to theRaymond scale was performed by one observer, and alsomore objective histomorphometry was not used. It is only aminor further complaint that neither the origin of thehistological specimens nor of the pathohistological evalu-ation was even acknowledged by the authors.