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Biomedical subjects

K A Selvig

Publications and source records attributed to K A Selvig.

At least 55 records · Page 3Linked to original sources
PubMed1991

Periodontal repair in dogs: healing in experimentally created chronic periodontal defects.

A need exists for well-defined animal models to objectively evaluate surgical principles and a possible role for biochemical wound conditioning and biomaterials in promoting periodontal regeneration. To test an existing model for its usefulness in quantitative evaluation of periodontal wound healing, large supraalveolar periodontal defects were surgically created around the mandibular premolars (P2, P3, P4) in left or right jaw quadrants in 5 beagle dogs. The defects were exposed to the oral environment for 6 months and were then subjected to reconstructive flap surgery (chronic defects). Healing in these defects was compared to healing following reconstructive surgery in similar contralateral defects which had not been exposed to plaque and calculus (acute defects). The animals were sacrificed after a 4-week healing period and tissue blocks including teeth and surrounding structures were processed for histometric analysis. Mean defect height (+/- s.d.) for chronic and acute defects amounted to 4.6 +/- 0.3 and 4.4 +/- 0.4 mm, respectively. Mean connective tissue repair to the root surface in chronic defects amounted to 62% (range 49% to 74%) of the defect height. Mean connective tissue repair in the acute defects exceeded 94% of the defect height in 4 of the dogs, but amounted to only 48% in 1 dog. Regeneration of alveolar bone and cementum was limited under both experimental conditions. Root resorption was frequently encountered, whereas ankylosis was seen in only few teeth. This study indicates that healing may vary not only as a result of controlled experimental variables, but also due to differences in biological response between dogs or to fortuitous traumatic factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Alveolar Bone Loss↗
PubMed1991

Caries-inhibitory effect of titanium tetrafluoride in rats.

The purpose of this study was to evaluate the caries-inhibitory effect of TiF4 as compared with equimolar solutions of neutral and acidified NaF. Sixty Sprague-Dawley rats were weaned 19 days after birth and given a cariogenic diet. They were randomly divided into four groups and given a 1-min topical treatment of the molar teeth on day 1 and day 17 of the experiment with the following solutions: group 1: 1% TiF4, pH 1.5; group 2: 1.3% NaF, pH 7.0; group 3: 1.3% NaF, pH 1.5; and group 4: control, distilled water. From day 2 the rats were inoculated with Streptococcus mutans twice weekly. On day 55 the rats were killed, and caries scored in accordance with Keyes. Total caries scored were (mean +/- SD): group 1, 12.7 +/- 9.5; group 2, 17.4 +/- 8.6; group 3, 14.3 +/- 9.7; and group 4, 29.5 +/- 9.0. There were significantly (p less than 0.05) reduced caries scores for total caries and for buccal + lingual and sulcal areas for all test groups as compared with the control group. Differences between control and test groups in proximal surfaces and between fluoride groups were non-significant. The results showed that the caries-inhibitory effect of TiF4 is at least as good as that of NaF in rats.

Animals↗
PubMed1991

Release of fluoride and metal ions from root surfaces after topical application of TiF4, SnF2, and NaF in vitro.

Aqueous solutions of TiF4 cause a rapid uptake and a long-lasting retention of fluoride when applied to dentin. The aim of this study was therefore to investigate the pattern of fluoride release after TiF4 application in vitro, compared with SnF2 and NaF application. TiF4, SnF2, and NaF were applied for 4 min and 1 min to standardized areas of six groups of root surface specimens immersed in distilled water. Untreated specimens were used as controls. The water was changed daily for 30 days, and F concentrations measured by an ion-selective electrode. All test groups showed a rapid decline in F concentration. In the 4-min group F concentration more than double the detection limit of the F electrode could be registered the first 28 days for TiF4, 11 days for SnF2, and 7 days for NaF. In the 1-min group periods of F registration were shorter. Analysis of Sn by atomic absorption spectrophotometry showed decreasing concentrations in the first 12-day samples in the 1-min and 4-min groups. Traces of Ti were found in the first few samples, but no pattern of release could be observed.

Administration, Topical↗
PubMed1991

Root surface reactions to TiF4 and SnF2 solutions in vitro. An ultrastructural study.

Previous studies have indicated that TiF4 and SnF2 differ in their demineralizing effect when applied topically to root surfaces at the same acidity. The aim of this study was to examine in more detail the outermost layer of root surface specimens by transmission electron microscopy (TEM) after short-term exposure to these acidic fluoride solutions. Root surface specimens were exposed for 1 min and 4 min to equimolar (1.1 M F) solutions of a) TiF4, native pH 1.0; b) SnF2, acidified to pH 1.0; and c) SnF2, native pH 2.5. The specimens were then rinsed in saline and processed for TEM. Exposure to TiF4 resulted in a partly demineralized zone 8-10 microns deep after 1 min and 5-27 microns deep after 4 min of application. A 0.1-micron-thick, electron-dense coating was present in all TiF4-treated specimens. Acidified SnF2 resulted in a completely demineralized zone, 4-7 microns deep, when applied for 1 min and 4 min, whereas SnF2 at native pH produced a 0.5- to 1.0-micron-wide partially demineralized zone. Unevenly distributed crystalline deposits were a frequent finding on SnF2-treated surfaces. The results indicate that solutions of TiF4 and SnF2 at native pH will cause only slight demineralization when applied topically to root surfaces.

Crystallography↗
PubMed1991

[Periodontal regeneration--finally a reality?].

Regeneration of lost tooth support has been the illusive goal of periodontal surgery for more than 100 years. Important progress was made in the nineteen-seventies when it was found that (1) periodontally involved root surfaces can be detoxified by mechanical and chemical means, (2) demineralized bone and dentin matrices have an osteoinductive potential, and (3) application of citric acid or tetracycline to the root surface during reconstructive surgery enhances attachment of granulation tissue and new collagen fibers. While experimental studies in animals have reported 100% connective tissue regeneration, clinical results have been less spectacular. More recently, improvements have included the introduction of membrane materials to guide tissue regeneration. Currently, resorbable membrane materials, osteinductive graft materials, and a variety of biologic response modifiers are being examined for their potential as adjuncts to periodontal regenerative procedures.

Animals↗
PubMed1990

Scanning electron microscopic observations of cell populations and bacterial contamination of membranes used for guided periodontal tissue regeneration in humans.

Fourteen intrabony periodontal defects and six furcation defects (Class II) were treated by a flap procedure which included the use of a polytetrafluoroethylene membrane to allow guided tissue regeneration. After 4 to 6 weeks of healing, the membranes were retrieved and examined by scanning electron microscopy for the presence of adherent cells and other tissue elements. The cervical open pore-structured collar of the membrane, which in most cases had become partially exposed to the oral cavity, had a deposit of bacterial plaque. Bacterial Bacterial colonies and a scatter of single cells in some instances extended into the mid-third of the membrane. Fibroblast-like cells and, in some specimens, blood vessels and fibrous structures were seen in the mid-third and deep parts of the membrane. Generally, however, the occlusive portion of the membrane was characterized by a sparseness of adherent tissue elements. There did not seem to be a systematic difference in the nature and distribution of the adherent structures on the inner and outer surfaces of the membrane. The findings suggest that, in addition to preventing flap tissues from contacting the root surface, an important function of the membrane is to protect the integrity of the underlying blood clot by diverting mechanical stress acting on the flap during early stages of healing.

Bacteria↗
PubMed1990

Effect of stannous fluoride and tetracycline on repair after delayed replantation of root-planed teeth in dogs.

Mandibular incisors were extracted and allowed to dry in air for 45 min. They were then root-planed extensively, leaving a cervical collar and the apical region uninstrumented, to prevent direct contact between root surface and alveolar bone after replantation while, at the same time, enabling precise and stable reseating of the tooth. Control teeth were replanted either without further treatment or after treatment with citric acid for 3 min. Experimental teeth were treated before replantation with 1% SnF2 for 5 min, 1% tetracycline HCl for 5 min, or 1% SnF2 followed by 1% tetracycline. Histometric analysis of healing in the root-planed areas showed minimal amounts of inflammatory resorption and ankylosis after 21 days in experimental teeth as compared with the control teeth. A persisting inflammatory reaction in the periodontal ligament without root resorption was, however, frequently seen. The observations confirm that the frequency of adverse healing reactions after delayed replantation of teeth from which nonvital soft tissue remnants have been removed can be reduced by demineralizing the root surface and preventing mechanical trauma to the root surface in the postoperative period. Root surface treatment with SnF2 followed by tetracycline resulted in complete absence of inflammatory resorption and ankylosis in this short-term experiment.

Animals↗
PubMed1990

Effect of TiF4 solutions on bacterial growth in vitro and on tooth surfaces.

The purpose of this study was to assess the antimicrobial effect of TiF4 as compared with equimolar solutions of NaF, APF, and SnF2 and to evaluate the effect, if any, on bacterial growth on topically treated tooth surfaces. In an in vitro study, paper discs impregnated with 20 microliters of equimolar solutions of SnF2, NaF, APF, and TiF4 were placed on blood agar plates seeded with Streptococcus mutans and Bacteroides gingivalis. Sterile saline was used as control. Similar growth inhibition zones were found for all fluorides. In the second part of the study six volunteers carried intraoral appliances containing enamel and root surface specimens treated with 1% TiF4 and untreated specimens for 18 h. Scanning electron microscopic examination of the experimental tooth surfaces showed great variation in bacterial growth between subjects, but no systematic difference between fluoride-treated and untreated specimens. Bacteria from test and control specimens were grown under aerobic and anaerobic conditions on blood agar and on mitis salivarius agar. Colony-forming unit counts showed great interindividual variations, but no differences could be observed between treated and untreated enamel or root surfaces. Thus, the hypothesis that the presence of a Ti-rich coating may influence bacterial colonization on TiF4-treated tooth surfaces could not be substantiated.

Bacteria↗
PubMed1989

Effect of tetracycline and SnF2 on root resorption in replanted incisors in dogs.

The present study was made to assess the effect of applying SnF2, tetracycline, or both, to root surfaces of extracted teeth prior to replantation. In five young adult beagles, a total of 18 mandibular incisors were extracted, bench dried for 45 min, and reimplanted in their respective sockets either after no further treatment or following treatment with 1% doxycycline HCl for 5 min, 1% SnF2 for 5 min, or 1% SnF2 followed by 1% doxycycline HCl. After 4 wk of healing, the relative frequency of root resorption (surface resorption, inflammatory resorption and replacement resorption) was approximately 27% of the root surface in bench-dried as well as in doxycycline-treated specimens. By contrast, SnF2-treated and SnF2 + doxycycline-treated teeth showed less than 1% resorption. In the latter two specimen groups an inflammatory reaction in the periodontal ligament without resorption occurred with a frequency of 38.3% and 11.1%, respectively. The results indicate that application of SnF2 to the root surface prior to replantation effectively reduces resorptive processes during the first postoperative weeks. By subsequently treating the root surface with tetracycline, the adverse effect of SnF2 on periodontal connective tissue repair may be reduced.

Animals↗
PubMed1989

Effects of TiF4 solutions on root surfaces in vitro after different application periods.

Topical application of aqueous solutions of TiF4 to root surfaces has been shown to result in a rapid uptake of fluoride. The purpose of this study was to assess whether the application period and/or the ionic strength of the TiF4 solution can be reduced without a corresponding reduction in the fluoride uptake. Root halves from human teeth were exposed to (a) 1% TiF4 for 10 sec and 1, 2, and 4 min, and (b) 3.4% TiF4 for the same application periods. Root surface areas protected by nail polish served as controls. Transverse ground sections through the treated root surface areas were then prepared and analyzed for F by electron microprobe analysis. Most treated specimens showed F concentrations in the 0.60-1.94% range, whereas control surfaces contained less than 0.30%. Similar F concentrations were found in the surfaces treated with the two solutions. Reducing the application period resulted in a shallower penetration of F into the hard tissue but only a slight reduction of the F concentration in the surface layer. High concentrations of Ti were found on the surface of all treated specimens. This shows that both the application period and the ionic strength of TiF4 solutions can be considerably reduced and still enable a high uptake of fluoride. The results indicate that TiF4 may be an efficacious agent for F application to root surfaces under clinical conditions.

Administration, Topical↗
PubMed1989

In vivo uptake and retention of fluoride after a brief application of TiF4 to dentin.

The purpose of this study was to examine the long-term retention of F and Ti in dentin after a brief application of 1% TiF4. Six facets of exposed dentin in each of four beagle dogs were treated for 10 sec or 1 min with a 1% solution of TiF4. Four control facets in a fifth dog were left untreated and extracted after 12 weeks. The TiF4-treated teeth were harvested after 4, 8, and 22 weeks and analyzed for F and Ti with an electron microprobe. The F concentrations in dentin surfaces of specimens retained in the mouth for 4, 8, and 22 weeks were after the 10-sec treatment 0.48% +/- 0.24, 0.51% +/- 0.20, and 0.56% +/- 0.20, respectively, and after the 1-min treatment 0.64% +/- 0.20, 0.66% +/- 0.18, and 0.71% +/- 0.19. High concentrations of Ti were found at the specimen surfaces in all groups. None of the control specimens showed F or Ti contents above the detection limits for the method used. The results showed that a very brief application of 1% TiF4 deposited high concentrations of F and Ti which were retained for at least 22 weeks.

Administration, Topical↗
PubMed1988

Collagen linkage in periodontal connective tissue reattachment. An ultrastructural study in beagle dogs.

Early stages of connective tissue reattachment to surgically denuded cementum and root dentin following citric acid application were studied in fenestration wounds. Block specimens were obtained after seven, 14, and 21 days. Continuity between newly deposited collagen fibrils in the granulation tissue and unmasked dental matrix collagen had been established within seven days by interdigitation of fibrils in an up to 0.5 micron-wide zone at the cementum or dentin surface. Splicing of collagen at the fibrillar level by direct attachment to the severed end of matrix fibrils or by juxtapositioning of new and old fibrils was seen in rare instances only. At 14 and 21 days, distinct bundles of collagen fibrils inserted deeply into the orifice of dentinal tubules. Arrested and reversed surface resorption was encountered at all time points. At these sites as well, new collagen fibrils interdigitated with denuded matrix collagen, while some resorbed surfaces were characterized by absence of collagen continuity. The results lend continued support to the concept of reattachment based on interdigitation of collagen fibrils. However, since attachment is established even in the absence of this feature, a significant role for specific attachment substances not shown can also be postulated.

Animals↗
PubMed1988

Long-term retention of TiF4 and SnF2 after topical application to dentin in dogs.

As part of an evaluation of the potential of topical application of TiF4 in the prevention or arrest of root caries, the longevity of the titanium-rich glaze and the long-term retention of titanium and fluoride in exposed dentin surfaces were examined in dogs. For comparison, the effect of fluoride in combination with another cation, tin, was studied as well. Facets of exposed dentin were prepared in two beagles and treated for 1 or 4 min with either a TiF4 or an SnF2 solution (1.1 M F, native pH). After 3, 7, or 21 wk, the experimental surfaces were analyzed for fluoride, titanium, tin, and calcium using an electron microprobe. Dentin surfaces treated with TiF4 for 1 min showed fluoride concentrations ranging from less than 0.15% to 1.03%, while those treated for 4 min with SnF2 showed values from 0.22% to 1.28%. The calcium analyses revealed partial surface demineralization in one half of the SnF2-treated specimens, while this was a rare finding in the TiF4 group. The findings show that a brief application of TiF4 to exposed dentin results in approximately the same increase in fluoride content as a 4-min application of SnF2, with, however, less surface demineralization. In addition, the presence of a surface glaze may impart an added benefit to the use of TiF4 as a topical agent in the prevention of root caries.

Animals↗
PubMed1987

Topical application of tetracycline in regenerative periodontal surgery in beagles.

This study was designed to test the effect of tetracycline on healing subsequent to periodontal surgery. Aqueous solutions of tetracyclines are highly acidic and may therefore represent a suitable substitute for citric acid. Furthermore, tetracyclines react with dental hard tissues to from long-lasting antimicrobial compounds, and they have a retarding effect on pellicle and plaque formation and an antienzymatic effect. The alveolar bone around mandibular premolars was surgically reduced up to 6 mm from the cementoenamel junction in two beagles. The denuded root surfaces were exposed to the oral environment during 3 months without plaque control. Regenerative surgery was then carried out, using root surface conditioning with 1% tetracycline and coronally repositioned flaps. Six months later, histologic evaluation showed connective tissue attachment extending to the cementoenamel junction in most of the specimens. Superficial root resorption was prevalent in the cervical region, below which a collar of replacement resorption partly surrounded the roots in a characteristic manner. Morphometric analysis showed that attachment gain was similar to that obtained with citric acid in a preceding series of seven dogs. These preliminary results indicate that connective tissue attachment gain after topical use of tetracycline is similar to that obtained with citric acid. In addition, the antibacterial capacity and biological effects of tetracycline warrant further study of its possible clinical use in periodontal reconstructive surgery.

Administration, Topical↗
PubMed1985

Ultrastructure of lingual enamel epithelium in rabbit permanent incisors.

The recent observation that the lingual surface of the permanent rabbit incisor, in contrast to the rodent incisor, is covered with enamel near the initially formed tip, initiated a histologic study of the enamel epithelium in this region. Tooth buds from fetal New Zealand white rabbits aged 27 and 30 days in utero were processed for transmission electron microscopy. Examination of longitudinal and cross-sections revealed a transition of secretory ameloblasts to postsecretory ameloblasts on the facial aspect of the enamel organ. Incisally, the facial ameloblast layer was continuous with postsecretory ameloblasts on the lingual aspect. More apically on the lingual surface, a gradual transition between postsecretory and reduced ameloblasts occurred. This study shows that by day 27 in utero, the ameloblasts on the lingual aspect of the tooth are in the postsecretory and degenerative stages and that, by day 30, the enamel epithelium lingually has been replaced by cementum on the prismatic enamel and by connective tissue.

Ameloblasts↗
PubMed1985

Tetracycline-impregnated enamel and dentin: duration of antimicrobial capacity.

The present study was done in order to examine the durability of the tetracycline-induced antimicrobial capacity, and also to assess the reproducibility of the bacterial growth-inhibitory assay used. Standardized enamel and dentin specimens were impregnated in aqueous solutions of tetracycline HCl, oxytetracycline HCl or doxycycline HCl, rinsed in water, and stored dry for 200 days. Another series of specimens was impregnated in solutions of doxycycline HCl and then rinsed in tap water for varying periods up to 35 days. In addition, drug-impregnated specimens were used for reproducibility tests without storage or prolonged rinsing. Impregnated specimens were tested for antimicrobial capacity on agar plates seeded with S. sanguis. After 24 h aerobic incubation in 10% CO2 atmosphere, the plates were inspected and the diameter of the bacterial growth inhibition zones measured. The drug-impregnated enamel and dentin specimens consistently demonstrated growth-inhibitory capacity. The results of the reproducibility tests showed moderate intrasample and day-to-day variation. Two hundred days of dry storage or 35 days soaking in water reduced, but did not eliminate, the bacterial growth-inhibitory capacity of the impregnated dental specimens. The results show that a short-term exposure of dental hard tissues to tetracyclines may result in a long-lasting antibacterial capacity.

Bacteria↗