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Biomedical subjects

H S Siirilä

Publications and source records attributed to H S Siirilä.

At least 19 recordsLinked to original sources
PubMed1994

Collagenase, gelatinase and elastase activities in sulcular fluid of osseointegrated implants and natural teeth.

Proteinases play a key rôle in the physiological degradation and remodelling of the periodontal tissues. The rôle of these enzymes in tissue remodelling remodelling in connection with the insertion of dental endosseous implants has not been elucidated. Therefore, the aim of the present study was to identify the eventual presence of collagenase, gelatinase and elastase activities in periimplant sulcus fluid (PISF) of osseointegrated implants. Gelatinolytic activity in the samples was studied with gelatin-zymograms. Collagenase activity and its susceptibility to tetracycline-inhibition were monitored with SDS-polyacrylamide gel electrophoresis and laser densitometry, and elastase activity with synthetic substrate. Low activities of elastase and collagenase were detected in both PISF of osseointegrated implant patients and gingival crevicular fluid (GCF) of the control patients whereas significantly higher activities were detected in GCF of adult periodontitis patients. Also the profiles of gelatinases were similar in PISF of osseointegrated implant patients and GCF of the controls, but differed from the profile of active gelatinases present in GCF of adult periodontitis patients. The similar activities/characteristics of these proteinases in both periimplant sulcus fluid of healthy dental implants and GCF of healthy natural teeth suggest that they comprise the major proteinases for both periodontal and periimplant tissue remodelling or destruction.

Adult↗
PubMed1992

Reparative bone growth in an extremely atrophied edentulous mandible stimulated by an osseointegrated implant-supported fixed prosthesis: a case report.

This case report demonstrates that severe disuse atrophy of an edentulous mandible can be changed to reparative bone growth through restoration of function and masticatory ability using an osseointegrated implant-supported fixed prosthesis. In 8 years, bone height in the retroforaminal area nearly doubled and a new bony layer remodeled the cranial roof of the mandibular canal.

Adult↗
PubMed1991

The effect of oral topical fluorides on the surface of commercially pure titanium.

This study investigated the risk of corrosion of titanium abutments by the accidental or unauthorized use of preventive fluorides in the mouth. Polished test pieces of commercially pure ASTM grade 1 titanium were immersed in topically used fluorides (toothpaste, gel, and varnish). They were brushed in vitro with toothpaste and gel, corresponding to the time and effect of brushing with toothpaste twice a day for 6 years and with gel once a week for 12 years. Results indicate that an aminofluoride toothpaste with low ionizable fluoride content (0.125%) used in brushing natural teeth does not cause deterioration of the titanium abutments in the same mouth if the titanium is grade 1 purity. Carefully controlled use of fluoride gel (F 1.25%) and varnish (F 2.25%) is likewise not dangerous. The mechanical abrasion caused by toothbrush bristles appears to be the main deteriorating factor for the titanium surface.

Corrosion↗
PubMed1988

Technique for converting an existing complete denture to a tissue-integrated prosthesis.

A technique for modification of an existing complete denture into a tissue-integrated prosthesis is described. An acceptable conventional denture is clinically attached to titanium abutments in the maxillomandibular position that has proved to function well during a trial period. The framework is fabricated to fit the reduced denture base (Fig. 16). The advantages of this technique include (1) the appearance of the tissue-integrated prosthesis is known in advance; (2) the technique is simple and requires only four visits to complete; (3) the framework fit is predictable; (4) there is minimum insertion and removal; (5) the base has a natural look and the lips have support; and (6) minimum phonetic problems are encountered.

Dental Abutments↗
PubMed1980

Effect of instruction and motivation on dental knowledge and behavior among wearers of partial dentures.

Patients receiving partial dentures were divided into three groups. One "maximum" group was taught and motivated, both individually and as a group, as thoroughly as possible. The second "medium" group was given instruction sheets describing the essential facts related to the cleaning and maintenance of teeth and dentures., but no individual instruction and motivation were provided. In the third "minimum" group the obtaining of information was left entirely to the initiative of the patients themselves. By the end of the period of treatment, the patients' knowledge was in proportion to the amount of teaching they had received. As regards dental health behavior, the groups did not differ significantly from one another, although there were some indications that increased knowledge and motivation had promoted positive oral hygiene habits. A year after the completion of treatment the positive behavior habits were markedly fewer in all groups, and no longer bore any relation to the amount or type of instruction or motivation given.

Adult↗
PubMed1977

Enamel bonding plastic materials in modifying the form of abutment teeth for the better functioning of partial prostheses.

The potential uses of enamel bonding sealants and composite filling materials in increasing the retentive form of abutment teeth and covering the preparations for the occlusal supports of partial prostheses were studied in laboratory conditions. The materials tested were Nuva and Concise sealants and composite resins. Extracted permanent human molars, premolars and canines were inserted into acrylic blocks, two teeth in each block. An unretentive clasp framework was made on every test block. A retention prominence was built up separately of sealants and of composite materials occlusally to the tip of each clasp arm. The bond strength and wear resistance of the materials was tested in a device designed for this study. The bond of the prominences was very good, only two out of 114 prominences loosened. The retention gained with prominences was, on average, 18 N measured by the force needed for removal. The decrease in the total retention of the four clasp arms was measured by the force needed to remove the clasp framework. The total retention of the prominences made of Nuva and Concise sealants after 5000 removals was 53 and 50% of the original, when long, flexible clasp arms were used. The corresponding figures for composite resins were 56 and 59%. Short rigid clasp arms caused a distinctly faster abrasion. The prominences made of sealants, in particular, were abraded rapidly, one-fifth of retention being left after 3000 removals.

Composite Resins↗
PubMed1977

The effect of muscle function in discriminating thickness differences interocclusally and the duration of the perceptive memory.

The thresholds in discriminating the thickness differences interocclusally were measured with three different mouth openings on subjects having natural dentitions. Also the duration of the perceptive memory was studied. The results showed that the functional activation or fatiguing of masticatory muscles and the degree of mouth opening affect size discrimination interocclusally. The ability to perceive thickness differences between the incisors was more accurate after 1 hour's chewing than normally. The trend was significant with 0.5 mm and 10 mm mouth openings (2 P less than 0.01) and highly significant with an 20 mm mouth opening (2 P less than 0.001). With a 20 mm mouth opening (2 P less than 0.01) and 10 mm mouth opening (2 P less than 0.05) size discrimination was less accurate after two hours' fatiguing chewing than after one hour's conventional chewing. After 30 seconds' forceful isometric contraction and with 20 mm mouth opening discrimination was more accurate than normally (2 P less than 0.01). The trend was the same with a 10 mm mouth opening, but no difference could be observed when the mouth opening was 0.5 mm. The memory tests showed that with a 0.5 mm mouth opening thickness differences of 0.3-0.5 mm were most commonly correctly perceived twenty-four hours later, but when the mouth openings were 10 and 20 mm an interval of only 1 min between the reference and test piece trial impaired the performance.

Fatigue↗