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Biomedical subjects

P J van Mullem

Publications and source records attributed to P J van Mullem.

At least 19 recordsLinked to original sources
PubMed1991

The cumulative effect of disinfection, storage, histological fixation and demineralization on number and staining ability of gram-positive bacteria.

It has previously been shown experimentally using S. faecalis that the relative number of blue-staining Gram-positive bacteria was reduced by demineralizing agents as well as by disinfection (Wijnbergen & van Mullem 1987, van Mullem & Wijnbergen 1989). In this study the cumulative effect of disinfection, experimental period, fixation and demineralization was investigated. The use of additives to the fixative and the demineralizing agents to limit the loss of blue-staining bacteria was also studied. The numbers of bacteria were determined using a haemocytometer, and the percentage of blue-staining organisms were ascertained from smears. When compared with the start of the experiment, the sequence of disinfection with chlorhexidine, storage in PBS, fixation with neutral formaldehyde and demineralization with formic acid or EDTA appeared to reduce the relative numbers of Gram-positive staining bacteria. For storage periods of 0 and 4 days the reduction factors were 100 and 600, respectively, using formic acid. These factors were 50 and 95, respectively, using EDTA. Addition of cetyl pyridinium chloride to the fixative and the demineralizing agents, and addition of neutral formaldehyde to the demineralizing agents lowered these reduction factors to 80 and 200, respectively, for formic acid, and 40 and 85, respectively, for EDTA. If the results are extrapolated to animal experiments where disinfection, experimental period, fixation and demineralization form part of the experimental framework, even the lowest reduction in the number of blue-staining bacteria could lead to false interpretation of tissue sections.

Bacteriological Techniques↗
PubMed1991

Healing of the guinea pig incisor after partial pulp removal.

A histological and microradiographical study was made of eruption and healing of guinea pig lower incisors after endodontic treatment compared with intact incisors. One incisor per animal was cut perpendicularly at the level of the gingiva. One third to one half of the pulp was removed. The experimental periods were 0, 4, 7, 16, 21 and 31 days. Unstained, HE or Brown and Brenn stained sections were studied microscopically. Some teeth were sectioned undecalcified and studied microradiographically. In intact incisors the dentin matrix deposition and mineralization were described. In the dentin, incisally to the pulp proper, narrow canals, the walls of which consisted of mineralized material, were found opening at the occlusal surface. Histologically, in the treated teeth, a beginning of cell-rich fibrodentin deposition at the original dentin wall was present at Day 4. At Day 7 a substantial walling off of the pulp is achieved by cell-rich and some cell-poor fibrodentin. After 16 days large amounts of cell-rich and cell-poor fibrodentin were covered by some tertiary dentin. After 31 days the amount of tertiary dentin was larger than after 16 days and also covered the incisal part of the root canal walls. Further apically some vasodentin and newly formed normal, secondary, dentin was observed. In course of this period the cells of the cell-rich and cell-poor fibrodentin first showed necrobiosis, then necrosis. The cell-rich fibrodentin appeared not fully mineralized. All blood vessels and strands of soft tissue which ran in canals in the fibrodentin came to a dead end. Thus the root canal was fully obturated. Although the teeth appeared (nearly) normal to the naked eye and radiographically after 31 days, histologically they were not. Large amounts of fibrodentin still being present incisally which showed the dual potential of the guinea pig pulp to produce both fibrodentin and orthodentin.

Animals↗
PubMed1990

Implantation of porous acrylic cement in soft tissues: an animal and human biopsy histological study.

Long-term (8 and 24 month) reactions of the (hypo) dermis of the guinea pig to solid and porous (50 vol%) acrylic implants and four human biopsies from porous subcutaneous acrylic implants were studied light microscopically. The solid implants were encapsulated by dense connective tissue. Mobility was evidenced by the loss of 4 out of 36 after 2 yr and was considered the explanation for the occurrence of ectopic cartilage and mineralized material at some solid implants' surfaces after 2 yr. A dense capsule was not evident with the porous implants, instead vascularized collagenous connective tissues penetrated into and filled the pores, thus anchoring the implant to the body. None of these implants, was lost. Notwithstanding the presence of some multinucleated giant cells, scattered inflammatory cells and loosely packed inflammatory foci with both implant materials, the materials were considered well-tolerated by the body. The histology of the human biopsy did not differ significantly from the porous animal implants.

Acrylic Resins↗
PubMed1989

Effect of disinfection on number and stainability of gram-positive bacteria.

Evidence provided by the Brown and Brenn stain for the presence of bacteria in fixed tissue sections depends on the ability to demonstrate them by staining. Previously, in a model experiment, it has been shown that demineralizing agents reduce the number of blue-staining Gram-positive bacteria (Wijnbergen & Van Mullem 1987). In the present study the influence of a structure-destroying disinfectant, a structure-preserving disinfectant or heat disinfection on number and stainability was investigated using S. faecalis suspensions. Numbers were determined using a haemocytometer, and percentages of blue-staining organisms were ascertained from smears. Immediately after disinfection the relative number of Gram-positive staining bacteria was reduced by a factor of three for chlorhexidine, almost two for alcoformol, and was slightly reduced by heat. After 4 days of storage the reduction factors were 90, 4, and 2, respectively. After 14 days of storage the reduction factors were infinite, 30 and 5, respectively. These results were explained on the basis of the rate of cell wall destruction evoked by the respective agents.

Chlorhexidine↗
PubMed1988

Bone and soft connective tissue response to porous acrylic implants. A histokinetic study.

The ingrowth kinetics of soft and hard tissues near pre-polymerized and in-situ-polymerized large pore, in-situ-polymerized small pore and solid acrylic implants were investigated. Empty cavities served as controls. Aqueous sodium carboxymethyl cellulose (CMC) gel was dispersed in bone cement to create interconnected porosity. After periods of insertion from 2 days up to 26 weeks in frontal and parietal bones in pigs, tissue blocks containing implants were embedded in JB4 and studied by light microscopy. After the disappearance of the CMC-gel, at first only cells invaded the large pore implants but necrotized when at some distance from the implant surface. Later, when blood vessels grew into the pores, accompanying vital fibrous connective tissue was observed. Finally, all pores were filled with connective tissue. Surrounding bone was first resorbed, starting at day 7, creating a soft tissue interface. A zone of bone deposition, starting deep in the remaining bone at day 2, moved towards the implant, thereby bridging the soft tissue interface. At 6 weeks bone grew into the pores, thus anchoring the implant. Continuing deposition of bone around the implant provided a so-called lamina dura effect with all implants. Qualitatively similar tissue kinetics were observed around solid and pre-polymerized large pore implants, evidently in the case of solid implants without tissue ingrowth. Into the small pore implants only superficial soft or hard tissue ingrowth was seen because of the too small interconnections.

Animals↗
PubMed1988

Porous acrylic cement: evaluation of a novel implant material.

The preparation and some properties of in situ curing porous acrylic cement, a modification of the traditional bone cement, are described. Through numerous animal experiments, the behavior of the porous cement in a biological environment has been studied. The histological evaluation reveals that hard and soft tissues readily grow into the pores of the cement, thus anchoring the implant to the host tissues. Some inflammatory foci, decreasing in number with residence time, together with varying numbers of multinucleated giant cells were found occasionally in the tissues in and around implants. When implanted in soft tissues, the porous cement behaved favorably with respect to solid acrylic implants because of the immobility of the implants and the absence of ectopic hard tissue formation. The biocompatibility of porous acrylic cement is judged to justify clinical trials in plastic and reconstructive surgery.

Animals↗
PubMed1988

Craniofacial contouring and porous acrylic cement.

Porous acrylic cement permitting ingrowth of soft and hard tissue was developed in the mid-1970s. After several years of animal experimentation, a clinical trial started in 1978. Twenty-nine selected patients had craniofacial contouring with in situ curing porous acrylic cement. It is an easy one-stage procedure with a good fixation of the prosthesis. The result is a definite good contour reconstruction. It offers the craniofacial surgeon a useful alternative in selected cases when autogenous bone grafting or an intracranial approach is not indicated or not sought by the patient.

Carboxymethylcellulose Sodium↗
PubMed1985

Ultrastructural study of epithelial cell attachment to implant materials.

Attachment of gingival tissues to the protruding post of an endosseous dental implant is of great importance for the prognosis of its clinical success. Little is known about the requirements an implant material must meet to secure a durable permucosal seal. The objective of this study, therefore, was to gain insight into the morphology of epithelial cell-implant interfaces for a number of well-known or potential implant materials. Guinea pig epithelial cells were cultured on gold, titanium, carbon, hydroxylapatite, carbonate apatite, and modified polystyrene substrates. The metallic and carbon substrates were obtained by vapor-phase deposition of thin films on polystyrene carriers. This technique allowed for the preparation of ultra-thin sections for transmission electron microscopy containing substrate as well as the cells adhering to it. The cultures on apatite were decalcified prior to sectioning. The results revealed tht as attachment structures, focal contacts, extracellular matrix contacts, and hemidesmosome-like contracts could be distinguished. Hemidesmosome-like contacts were only observed on apatite and polystyrene and not on the metallic or carbon surfaces. The results of this study suggest the existence of some, as yet unknown, property of the substrate that determines the nature and the structure of the contact site with epithelial cells.

Animals↗
PubMed1984

Bacteria-tight sealing of exposed dog pulps.

Penetration of bacteria past filling materials can interfere with the vitality of exposed pulps. In the present study, seventy-three dog's teeth were filled--after exposure--with Cavit -W and then sealed either with a chemically or a UV polymerizing bonding. After 14 days a failure rate of 28% was demonstrated using the chemically polymerizing Concise and of 4.5% using the UV polymerizing Uvio -Bond. After 42 days the latter bonding revealed a success rate of 100%. To achieve a bacteria-tight seal of deep cavities for middle long term animal experimentation, Uvio -Bond can be used--after etching--to cover the filling material and the surrounding enamel.

Acid Etching, Dental↗
PubMed1983

Histological investigation of the effect of a controlled-released anti-inflammatory drug on exposed inflamed dog pulps.

The effect of controlled release of the antipholgistic benzydamine hydrochloride (Tantum), from two carriers, Cavit W and Durelon, on inflammatory and necrotic tissue changes was investigated on intentionally inflamed pulps of dogs. Statistical tests to detect differences in biocompatibility between Cavit and Durelon, both without drug, led to the conclusion of a similar biocompatibility as determined after 2 and 7 days. Benzydamine hydrochloride appeared to reduce necrosis during the period from 2-7 days slightly with Cavit as carrier and substantially with Durelon as carrier. However, in the latter case necrosis was enhanced after 2 days. During the same period inflammatory reaction was decreased at 10% level of significance by Durelon containing benzydamine hydrochloride. It was decreased significantly after 2 days with Cavit as carrier. Controlled release of benzydamine hydrochloride from Cavit or Durelon which was placed on an exposed inflamed pulp was effective in reducing inflammatory reaction and necrosis.

Animals↗