PubMed Health⌕ Search

Biomedical subjects

K A Selvig

Publications and source records attributed to K A Selvig.

At least 73 records · Page 4Linked to original sources
PubMed1985

Location and ultrastructure of the first cementum formed in rabbit incisors.

The morphology of the continuously erupting rabbit incisor differs characteristically from that of the rodent incisor and is incompletely known. In this study, permanent incisors from fetal New Zealand white rabbits aged 26-30 days in utero were processed for transmission electron microscopy. Examination of longitudinal and cross-sections revealed that disintegration of the epithelial sheath on root analog surfaces was followed by cementogenesis. The first layer of cementum matrix was seen on the mesial aspect and consisted of a finely granular ground substance and a few embedded collagen fibrils which extended to the cementodentinal junction. Within the period 27-30 days in utero, acellular cementum was formed on all root-analog surfaces and, in addition, formed a fine coating over the enamel. Although the initially formed cementum layer contained fewer collagen fibrils than subsequent layers, a layer of so-called intermediate cementum was not observed.

Animals↗
PubMed1984

Surface coatings on dental cementum incident to periodontal disease. (II). Scanning electron microscopic confirmation of a mineralized cuticle.

Root surfaces, exposed by periodontal disease, were studied after treatment with sodium hypochlorite. Observations of the anorganic specimens demonstrated that substantial changes occur in root surfaces incident to periodontal disease. A mineralized surface coating was seen in all areas of the involved root surface, although local regions occurred where the coating was apparently unmineralized. These findings generally confirmed the results of a previous study where the same specimens were studied without hypochlorite treatment. It is concluded that the coating is probably identical to the dental cuticle, and stems from adsorption of components of the gingival inflammatory exudate to the root surface. The coating may also be the carrier matrix for exogenous cytotoxic substances, previously thought to be located in the cementum. The findings may have implications for the way of treating periodontitis-involved root surfaces.

Calcinosis↗
PubMed1984

Inhibition of bacterial growth by tetracycline-impregnated enamel and dentin.

Tetracyclines can react with enamel and dentin to form relatively insoluble fluorescent compounds. The purpose of this study was to evaluate the possible antimicrobial effect of these reaction products on various microorganisms associated with human dental plaque and periodontal disease. Slabs of native dentin and enamel as well as demineralized dentin were immersed in aqueous solutions of tetracycline HCl, oxytetracycline HCl and doxycycline HCl for periods of 1 h or 24 h. Unimpregnated enamel and dentin slabs sterilized by gamma irradiation and specimens impregnated with phenoxymethylpenicillin calcium were used as controls. Test and control specimens were placed on agar plates seeded with B. cereus, C. ochraceus, S. sanguis, F. nucleatum, B. melaninogenicus or A. viscosus and were subsequently incubated aerobically or anaerobically at 37 degrees C. With the exception of enamel impregnated for 1 h in a 0.01 mg/ml tetracycline solution, all test specimens caused growth inhibition zones, varying in size according to concentration of the drug, immersion period and bacterial species. The results indicate that tetracyclines react with enamel and dentin to form slightly soluble compounds with a pronounced antibacterial effect. In comparison, the antimicrobial effect of dentin treated with penicillin was small.

Bacteria↗
PubMed1984

The effect of citric acid on repair after delayed tooth replantation in dogs.

An experimental study of maxillary incisors in dogs was carried out to test the hypothesis that demineralization of denuded root surfaces by citric acid to expose collagen matrix fibrils might improve the rate of periodontal regeneration after replantation of traumatically avulsed and dried teeth, provided that the root surface is not traumatized during replantation or postoperatively. Experimental teeth (group 4) were allowed to dry in air for 45 min. A mid-portion of the root was then root-planed extensively, treated with citric acid for 3 min, rinsed with saline, and replanted. The apical region and a cervical collar were not instrumented, ensuring precise reseating and stability of the tooth during the postoperative period. Control teeth were either replanted immediately (group 1), bench-dried for 45 min and replanted (group 2), or bench-dried and the entire root surface root-planed and acid-treated before replantation (group 3). Histological examination of block specimens after 21 days of healing showed complete periodontal regeneration in group 1 and, by contrast, a high rate of ankylosis, inflammatory resorption, and surface resorption in group 2. Root planing and acid treatment of bench-dried teeth (group 3) did not improve the healing response, whereas the mid-root region of teeth in group 4 showed an absence of inflammatory resorption and less ankylosis than groups 2 and 3. These preliminary observations indicate that the frequency of adverse healing results after delayed replantation can be reduced by removing nonvital soft tissue remnants, demineralizing the root surface, and preventing mechanical trauma to the root surface in the postoperative period.

Animals↗
PubMed1983

Surface coatings on dental cementum incident to periodontal disease. I. A scanning electron microscopic study.

Root surfaces of extracted human teeth with advanced periodontal disease were studied by the apically migrated junctional epithelium, the topography characteristic of uninvolved cementum was frequently masked by a surface coating. The thickness of the coating increased in a coronal direction where it often blended with calculus. The observations indicate that this surface coating may originate from the inflammatory exudate and corresponds to the dental cuticle. The findings also indicate that the coating may be mineralized and may contain exogenous substances. These observations illustrate a need for further study and reexamination of the rationale for removal of tooth substance during scaling and root planing.

Dental Cementum↗
PubMed1983

Formation of the periodontal attachment in developing rabbit permanent incisors.

Permanent incisors from fetal New Zealand white rabbits aged 25-30 days in utero and from 1-20 days postnatally were processed for light microscopy. Examination of longitudinal and cross-sections revealed that cementum deposition and fiber attachment first occurred at 27 days in utero. A tooth-to-bone course of principal fibers confined to lateral aspects of the teeth was observed in 29-day fetal incisors, whereas lingually the periodontal ligament remained undeveloped as late as 5 days postnatally. In 20-day postnatal incisors, the development of the functional periodontal ligament was complete as evidenced by the fiber arrangement on all aspects of the root-analogue tooth surface. This study shows that 25-26-day fetal rabbit permanent incisors represent the end of the follicular phase, whereas 27-day fetal to 20-day postnatal teeth demonstrate distinct histologic characteristics of initial, incomplete and complete periodontal fiber attachment.

Animals↗
PubMed1982

Presence of enamel on the lingual surface of rabbit permanent incisors.

Permanent incisors from fetal New Zealand white rabbits aged 25-30 d in utero were processed for light microscopy. Examination of transverse and longitudinal sections of demineralized specimens revealed the development of a complete enamel covering of the incisal tip and an enamel extension on the linguoincisal surface of unerupted teeth, as evidenced by the presence and distribution of ameloblasts, enamel matrix and enamel space. Formation of lingual enamel appeared to be completed within a few days before eruption of the incisor. The transition from the enamel-covered to enamel-free areas coincided with a gradual disintegration of the orderly ameloblast layer. The findings indicate that, histologically, the linguoincisal part of the rabbit permanent incisor is characterized by amelogenesis.

Amelogenesis↗
PubMed1981

In vivo recalcification of dentin demineralized by citric acid.

Acid-treatment of root surfaces as adjunct to periodontal reconstructive surgery may have deleterious effects on that part which remains in a supragingival location after healing. The present experiment aimed to examine whether recalcification of such root surfaces may occur. Cylindrical blocks of root dentin were prepared for 10 premolars, treated with citric acid and mounted in acrylic specimen holders which were worn in the mouth continuously for 14 d by two test subjects. The specimens were then sectioned and microradiographs produced. The citric acid had produced a completely demineralized surface zone in the root dentin and the subjacent hard tissue showed a zone of partially reduced mineral content. Following exposure to the oral cavity, the demineralized surface layer appeared unchanged in width. The subjacent zone, however, had been reduced in width in all instances when compared with control specimens from the same teeth.

Citrates↗
PubMed1981

Absence of enamel matrix on root-analogue surfaces of rabbit permanent incisors.

Permanent incisors from fetal New Zealand white rabbits aged 27-29 in utero from offspring of New Zealand white rabbits until the 4th d after parturition were processed for scanning electron microscopy. Macroscopic examination and measurements on standardized scanning electron micrographs revealed that the lingual surface of unerupted teeth was covered with developing enamel extending about 2.1 mm from the incisal end as evidenced by the presence of typical Tomes' pits. Such structures were not observed more apically where the lingual tooth surface appeared to be covered by cementum. The permanent incisors erupted into the oral cavity at birth and attrition was initiated within a few hours after parturition, leading to an inverse correlation between attritional loss of tooth substance and extension of lingual enamel. The findings indicate that the enamel-covered, linguoincisal part of the rabbit permanent incisors is not a root-analogue surface. The results are discussed in the light of recent studies on rabbits and rodents.

Animals↗
PubMed1979

Clinical improvement of gingival conditions following ultrasonic versus hand instrumentation of periodontal pockets.

A study utilizing a split-mouth design in 18 subjects and with four operators was performed in order to compare the effect of hand and ultrasonic instrumentation of periodontal pockets. Contralateral pairs of teeth with pockets of comparable depth were treated by either hand or ultrasonic instruments. Instrumentation was repeated after 4 weeks. Pocket depth, bleeding on probing and gingival fluid measurements were used for evaluation. A gradual reduction of pocket depth and number of bleeding points took place throughout the 8-week experimental period. Clinically significant differences were not observed comparing the effect of hand instruments to ultrasonics for any of the operators. The amounts of gingival fluid were similar for both methods of instrumentation at the final examination. Thus, the present study failed to demonstrate any significant differences between the effect of ultrasonic root debridement and hand instrumentation in the treatment of 4-6 mm deep periodontal pockets.

Adult↗