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Biomedical subjects

R P Happonen

Publications and source records attributed to R P Happonen.

At least 37 records · Page 2Linked to original sources
PubMed1995

Glass-ceramic-coated titanium hip endoprosthesis. Experimental study in rabbits.

Titanium alloy hip endoprostheses coated with a bioactive glass ceramic (BGC) were followed in rabbits. All test endoprostheses remained stable, and image analysis showed an average of 78% bonding of the BGC-coated implants to bone at 52 weeks. The uncoated Ti-alloy controls demonstrated an average of 37% bone coverage after 52 weeks. By scanning electron microscopy the thickness of the BGC reaction layer was found to stabilize at 60 microns after bioactive bone bonding. The results indicate that the BGC coating must be thicker than the reaction layer to prevent detachment from the core metal.

Alloys↗
PubMed1995

Cytomegalovirus (CMV) and Helicobacter pylori (HP) found in oral mucosal ulcers.

The possible involvement of Cytomegalovirus (CMV) and Helicobacter pylori (HP) in oral mucosal ulcers is suggested by their role in the development of ulceration at other mucosal sites of the gastrointestinal tract. A series of 29 incisional biopsies from 29 consecutive and apparently immunocompetent patients attending the clinic for oral ulceration were examined by routine histopathology as well as by in situ hybridisation (ISH) with biotinylated CMV and HP DNA probes. In 14/29 biopsies, Giemsa staining disclosed spiral bacteria. Six (20.7%) of these 14 Giemsa-positive samples showed HP DNA on ISH and 3 ulcers (10.3%) contained CMV DNA. In none of the specimens were CMV and HP detected simultaneously. Two of the ulcers containing CMV DNA were found on the labial mucosa and one on the posterior palatal mucosa, whereas all HP DNA-positive ulcers were located on the buccal mucosa. The results indicate that CMV and HP DNA can be found in separate oral mucosal ulcers in apparently immunocompetent adults.

Adolescent↗
PubMed1995

Lack of effect of hormonal treatment and smoking on cytokeratin expression in buccal mucosa.

Differences in cytokeratin expression of clinically normal buccal mucosa were studied in 50 healthy women by indirect immunofluorescence staining with monoclonal antibodies. The subjects were divided into four groups: control group (N = 18), smokers (N = 8), oral contraceptive users (N = 8) and smokers receiving oral contraceptives (N = 16). Our findings indicate that cytokeratin expression in noncornified stratified epithelium is not influenced by smoking or oestradiol/progesterone treatment. Only cytokeratin No. 19 showed variable patterns of expression but the differences could not be ascribed to smoking or contraceptives. Cytokeratin No. 19 gave a positive reaction in the basal and suprabasal layers in 34 subjects (68%). In 9 (18%) specimens, the staining was positive in the basal cells and showed a positive heterogeneous cytoplasmic reaction in the suprabasal cells. Interestingly, cytokeratin No. 7 was recognized in all epithelial cells except the basal cells. Our results suggest that changes in the serum oestradiol levels do not affect the cytokeratin pattern in buccal mucosa.

Adult↗
PubMed1995

Bone formation in rabbit cancellous bone defects filled with bioactive glass granules.

We examined new bone formation after filling cancellous bone defects with bioactive glass (BG) in granular form. Cylindrical defects in the trochanter area of 18 rabbit femora were filled with BG granules (diameter 600-830 microns) and compared with similar defects filled with morcellized autogenous bone. New bone formation and surface reaction of BG particles were evaluated by light microscopy, histomorphometry, and scanning electron microscopy. The chemical profile at the bone- material interface was studied by energy dispersive x-ray analysis (EDXA). In the BG group, 41, 32, and 38 percent of the defects were filled with new bone after 3, 6, and 12 weeks, respectively. The corresponding figures for the autogenous bone group were 36, 29, and 34 percent. The thickness of the reaction layer on the glass surface increased from 82 to 163 microns during the observation periods. An intimate contact without intervening soft tissue between new bone lamellae and BG granules was a constant finding. EDXA showed a chemical continuum between the granules and the new bone. No adverse reactions related to BG were observed. BG is a promising material for filling cancellous bone defects.

Animals↗
PubMed1994

In vivo reactions of Ca,P particle containing surface reactive glasses.

Four Ca,P particle containing surface reactive glass composites and two glasses (in the SiO2-CaO-P2O5-Na2O-Al2O3-B2O3 system) were implanted in the diaphyseal area of goat femora up to 24 weeks. Scanning electron microscopic, energy dispersive x-ray, and histological analysis were performed to evaluate the material-tissue interactions. A new type of integration mechanism was observed. Instead of the bone growing to the material surface, a gel-like silica formation appeared between the cortex bone and the material surface. In time the gel-like formation was replaced by a Ca,P layer. The results provided indirect evidence that pure silica gel formed in the tissues could also achieve an apatite layer formation and bone bonding on its surface.

Animals↗
PubMed1994

Effect of glass bioactivity on new bone development induced by demineralized bone matrix in a rat extraskeletal site.

The effects of two kinds of bioactive glass and two kinds of phosphate-free glass on new bone development induced by demineralized bone matrix (DBM) were studied in the rat abdominal muscle pouch model. After 8 weeks' implantation histomorphometric analysis revealed that the amount of new bone in DBM combined with bioactive glass was comparable to DBM without bioactive glass. DBM grafts combined with phosphate-free glass showed significantly less new bone formation. Scanning electron microscopic examination confirmed that new bone bonded to the surface of bioactive glass. The release of ions from the glass seemed to slow down after new bone had bonded to it. Exclusion of phosphate from a bioactive glass resulted in loss of ability to develop the Ca,P-rich surface layer needed for bone bonding.

Animals↗
PubMed1994

Odontogenic myxoma--a radiographic study of 21 tumours.

Radiological features of 21 odontogenic myxomas found in 14 women and 7 men were analysed. Ten of the tumors were unilocular and 11 were multilocular. Unilocular lesions were mostly located in the anterior and multilocular in the posterior areas of the jaws. Intralesional trabeculation was seen in all multilocular but only in 3 unilocular lesions. Because radiological appearance of myxoma may be essentially similar with many other lesions of the jaws careful radiological examination is mandatory for planning of proper treatment.

Adolescent↗
PubMed1994

Distribution of tenascin in oral premalignant lesions and squamous cell carcinoma.

The distribution of the extracellular matrix (ECM) protein tenascin (Tn) was studied in oral premalignant lesions and squamous cell carcinoma by using the monoclonal antibody (Mab) 143DB7. In normal buccal and palatal mucosa, in ventral tongue, in floor of mouth and in gingiva, immunoreaction for Tn was seen to be distributed as a continuous thin, delicate line merely in the basement membrane region. Hyperkeratosis without dysplasia showed a distinct zone of enhanced Tn immunoreactivity immediately beneath the epithelium. In dysplasias of various degree, enhancement of the stromal Tn content could be observed, being most conspicuous in carcinoma in situ lesions. In most invasive carcinoma cases the Tn immunoreactivity was intense, extending deeply into the underlying stroma. In such lesions Tn-reaction often covered the total stroma. Notably, the strongest immunoreaction was seen at the advancing edges of the tumor. The triggering factor for stromal Tn enhancement seems to be of epithelial origin. The enhanced expression of Tn suggests that Tn plays a role in organizing and remodelling the stroma to support active epithelial proliferation and migration. However, it also seems that inflammation is associated with Tn expressions.

Antibodies, Monoclonal↗
PubMed1993

Detection of cancer recurrence in irradiated mandible using positron emission tomography.

Positron emission tomography (PET) is a promising method for pretherapeutic assessment of spread of squamous cell carcinomas (SCC) in the head and neck. A 41-year-old man with a history of operated and irradiated SCC of the tongue presented 4 years later with symptoms and signs of mandibular osteoradionecrosis. No changes related to malignancy could be seen in panoramic radiographs or computed tomography scanning with contrast enhancement. Since a biopsy of the involved region was positive for SCC, a PET study with [18F]fluorodeoxyglucose (FDG) was performed. In dynamic PET images, intensive uptake of FDG was seen in a small area close to the right mental foramen. A hemimandibulectomy with reconstruction using a free vascularized graft from iliac crest was performed. In the resected specimen, histological examination showed a 1.2-mm focus of SCC in the soft tissue and bone around the mental foramen. These findings indicate that FDG-PET might be useful for presurgical evaluation of cancer recurrence in a previously irradiated mandible, especially if PET can accurately differentiate viable tumor tissue from radiation-induced fibrosis and inflammation.

Adult↗
PubMed1993

Different healing patterns of experimental osteotomies treated by intramedullary nailing.

The healing of 52 diaphyseal osteotomies in rabbit tibiae was followed up histologically from 3 to 24 weeks after rigid intramedullary nailing. The histological evaluation was made from longitudinal sections through the osteotomy area. Particular attention was paid to the fracture healing pattern. A bulky periosteal response was visible in every specimen. At 24 weeks, the external callus was always well remodeled. The osteotomy line rapidly filled with bone from 6 weeks onwards. At 24 weeks, the site of osteotomy was detectable only on the basis of slight irregularity in the cortex. The secondary gap healing seen in 19 specimens was the most common type of bone union from 6 weeks onwards. In 13 specimens, the exact type of osteonal healing was not definable, since a solid union with good cortical reconstruction was always the final outcome. Altogether, four nonunions were detected throughout the study, none of these, however, in the specimens at 24 weeks. Considerable endosteal resorption was detected at 24 weeks, at which time at least one third of the original cortex had disappeared in all specimens. The rigid nail seems to ensure a relatively uneventful healing of the experimental osteotomies. Vast endosteal resorption and some nonunions make the use of medullary reaming in this connection doubtful.

Animals↗
PubMed1993

Immunohistochemical demonstration of androgen receptors in human salivary glands.

Androgen receptors were demonstrated in human salivary glands by immunohistochemistry using polyclonal antibodies. Fresh, clinically healthy salivary gland samples (two from minor, seven from parotid and eight from submandibular glands) of both sexes were used. Frozen tissue sections were incubated with the antibody against human androgen receptor and visualized by an indirect immunoperoxidase technique. Androgen receptors could be detected in all salivary tissues studied. Positive staining was confined to nuclei of almost all acinar cells as well as to the majority of nuclei in ductal cells. Very few of the nuclei of connective tissue and endothelial cells stained positively. The presence of androgen receptors in human salivary glands suggests possible direct effects of androgens on these tissues.

Adult↗
PubMed1993

Transforming growth factor beta 2 in epithelial differentiation of developing teeth and odontogenic tumors.

Dysregulation of TGF beta 2, a modulator of cell growth and differentiation, can result in uncontrolled growth and tumor formation. Our comparative studies on the expression of TGF beta 2 mRNA and protein indicate that TGF beta 2 may primarily be a regulator of epithelial differentiation during tooth development (between 13 and 20 gestational wk) and tumorigenesis of odontogenic neoplasms. A paracrine mode of action for TGF beta 2 in early human tooth germ (cap/early bell stage) is suggested by location of mRNA in the mesenchyme surrounding the tooth germ, whereas protein is found in the epithelial dental lamina and enamel organ. During the late bell stage, TGF beta 2 gene expression shifted from the mesenchyme to the odontogenic epithelium and was colocalized with protein, suggesting an autocrine role for the terminal differentiation of ameloblasts. In odontogenic tumors of epithelial origin (ameloblastomas) and epithelial-ectomesencymal origin (ameloblastic fibromas), TGF beta 2 mRNA was mostly located in the mesenchymal tumor component and protein in the epithelial tumor component. Odontogenic ectomesenchymal tumors (myxomas) were not associated with TGF beta 2 mRNA and protein expression. The results imply that TGF beta 2 may play an important role in epithelial-mesenchymal interactions in human tooth morphogenesis and development of odontogenic tumors.

Adolescent↗
PubMed1993

Bioactive glass versus hydroxylapatite in reconstruction of osteochondral defects in the rabbit.

We studied osseointegration of a bioactive glass (BG) and hydroxylapatite (HA) in rabbit femur epiphyseal and metaphyseal regions. 17 BG and 24 HA cones implanted in defects through arthrotomy were analyzed. The holes for implants were drilled through distal femur joint surfaces. The cartilage wound repaired generally by fibrous tissue. Histomorphometry showed that 61, 78, and 79 percent of BG surface was covered by bone at 3, 6, and 12 weeks, respectively. The corresponding figures for HA were 47, 67, and 78 percent. Chemical bonding between bone and implants of both types was confirmed by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDXA). Formation of a calcium phosphate-rich layer on the surface BG implant was demonstrated by EDXA. Our results indicate that the osseointegration rate of bioactive glass does not differ from that of hydroxylapatite.

Animals↗
PubMed1993

Effect of bovine bone morphogenetic protein and bioactive glass on demineralized bone matrix grafts in the rat muscular pouch.

New bone formation induced by allogeneic demineralized bone matrix (DBM) and bone morphogenetic protein (BMP) combined with bioactive glass (BG) was studied in a rat abdominal muscle pouch model. At four weeks the amount of new bone was not influenced by DBM combined with BMP and/or bioactive glass. The mean proportional areas of new bone varied among different DBM test groups from 8.6% to 13.4%. New bone was induced in inactivated DBM samples containing BG, while no bone formation was seen in DBM samples without BG. The results indicate that bioactive glass favours bone induction in inactivated allogeneic bone matrix.

Animals↗
PubMed1993

EGF receptor and its ligands, EGF and TGF-alpha, in developing and neoplastic human odontogenic tissues.

Epidermal growth factor (EGF) and transforming growth factor-alpha (TGF-alpha) regulate cell proliferation and functional maturation through the EGF receptor (EGF-R). Their roles in human tooth development and odontogenic tumorigenesis have not been explored. We studied the expression of EGF, TGF-alpha and EGF-R in human fetal teeth (cap stage to early hard tissue formation) and various odontogenic tumors. EGF-R mRNA and immunoreactive cells were mostly located in odontogenic epithelium. EGF-R expression was subject to temporospatial variation at different stages of tooth development. EGF and TGF-alpha mRNAs were detected in fetal teeth only by the reverse transcription polymerase chain reaction (RT-PCR). However, EGF and TGF-alpha immunoreactive cells were demonstrated in epithelial elements of tooth germ, suggesting that the peptides partially originate from non-odontogenic sources. In odontogenic tumors, EGF-R mRNA and immunoreactivity were confined to neoplastic epithelium. Transcripts for TGF-alpha but not for EGF were detected in tumors of odontogenic epithelial, epithelial-ectomesenchymal and ectomesenchymal origins. It is concluded that regulation of EGF-R expression is developmentally regulated in human odontogenesis. Furthermore, the odontogenic epithelium is the main target tissue for both EGF and TGF-alpha during tooth development. TGF-alpha and its receptor may also be involved in odontogenic tumorigenesis.

Adolescent↗
PubMed1992

Stereographic assessment of mandibular canal in relation to the roots of impacted lower third molar using multiprojection narrow beam radiography.

The position of the mandibular canal in relation to the superimposed roots of 173 impacted lower 3rd molars was evaluated radiologically. A multiprojection narrow beam radiography (MNBR) technique recently developed for oral radiography was applied in this study. This method enables stereoscopic examination of the area of interest. The mandibular canal was located bucally to the roots of 105 (61%) teeth, lingually to the roots of 57 (33%) teeth, and between the roots of 6 (3%) teeth. The relationship of canal to roots of 5 (3%) teeth was not possible to determine. Disagreement between radiological assessment and clinical observation was found in 4 (5%) of 80 operated teeth. The canal was visible at operation in 23 (29%) cases, which was predicted at stereographic examination in 21 (91%) cases. The MNBR stereographic technique is a useful method with high sensitivity (0.83) for evaluating the bucco-lingual relationship of the mandibular canal to the roots of a 3rd molar.

Adult↗
PubMed1992

Isolation, characterization and immunolocalization of a 53-kDal dentin sialoprotein (DSP).

We isolated a sialic-rich protein from rat dentin extracts and have named it dentin sialoprotein, DSP (formerly called 95K glycoprotein). DSP is rich in aspartic acid, glutamic acid, glycine and serine, but contains no cysteine or phosphate. The 30% carbohydrate content includes about 9% sialic acid and indicates that several N-glycosides and O-glycosides are present. Sedimentation equilibrium analysis gave a M(r) of 52,570. Based on this molecular weight we calculated that DSP contains about 350-amino acids and 75 monosaccharides. With automated Edman degradation the sequence of the first 8-amino acids was shown to be: Ile-Pro-Val-Pro-Gln-Leu-Val-Pro. The initial 3 residues of this sequence are identical to the first 3 in human osteopontin (OPN) and are closely similar to the Leu-Pro-Val sequences of OPN from other species, as well as at the beginning of bone acidic glycoprotein-75 (BAG-75). On Western immunoblots, purified polyclonal antibodies reacted only with DSP in dentin extracts and with none of the proteins from bone. Similarly, immunolocalization experiments showed the presence of DSP in dentin but not in enamel or alveolar bone. Along with immunohistochemical localization data reported elsewhere, these observations suggest that DSP may be an important marker for cells in the odontoblast lineage.

Amino Acid Sequence↗