Biomedical subjects

Krister Nilner

Publications and source records attributed to Krister Nilner.

7 recordsLinked to original sources

PubMed2003

On the accuracy of some in vitro models for mechanical studies of maxillary removable partial dentures.

OBJECTIVES: Comparative in vitro/in vivo studies show wide differences in functional strain magnitudes and patterns of functional strain distribution in prosthetic devices. The aim of this study was to evaluate the accuracy of three in vitro models for biomechanical studies of prosthetic devices. METHODS: Strain gages were attached to the test RPDs of six subjects. In vitro maxillary models with simple (model A), intermediate (model B) and advanced (model C) features for the anatomical simulation of supporting structures were manufactured for each subject. The dentures were subjected to two separate series of standardized functional and laboratorial loading tests. The principal maximum strain value (epsilon (1)) obtained for each gage and experiment was used to calculate the intra-experiment variance and inter-experiment variance for the in vivo and in vitro experiments. The integrated strain gage difference value between the in vitro and in vivo data (Sigma(diff)) was calculated for every loading test and compared to the in vivo inter-experiment variance with ANOVA and Scheffés test. RESULTS: The bite forces recorded were similar for each subject and loading position and between the two loading sessions. The inter- and intra-experiment variance was found to be higher for in vivo loadings than for in vitro. Results showed that the (Sigma(diff)) values for model B and model C were significantly different from the in vivo strain inter-experiment variance (p<0.05). SIGNIFICANCE: This study showed that the anatomical simulation of in vitro models is insufficient to allow for accurate mechanical analyses of maxillary RPDs and that only simple verifications of the strain levels in prosthetic appliances can be attained in vitro.

Aged↗

PubMed2002

Analysis of a device for assessment of abutment and prosthesis screw loosening in oral implants.

Screw loosening is an irritating problem in implant dentistry. Loosened abutment screws and prosthesis screws are often found at yearly examinations. Loosened screws may cause costly complications, such as screw fractures and fracture of the framework, and methods to prevent them would be welcome. The purpose of this study is firstly to describe a mechanical protractor device designed to fit the electrical Torque Controller (Nobel Biocare, DEA 020, Gothenburg, Sweden) and measure the number of degrees necessary to retighten the abutment screw or the prosthesis screw to reach the target torque value. A second purpose is to analyse the precision and validity of the device. The results of the study indicate that the degree of preset loosening of abutment and prosthesis screws can be well reflected in the number of degrees necessary for retightening. It was also shown that it is possible to retighten the abutment and prosthesis screws with a precision of 1.7 degrees and 1.3 degrees, respectively. The study shows that the device has good precision and validity. By using this device, we hope to be able to evaluate various parameters for screw stability, such as the type of implant system, the number of fixtures, the type of abutments, the type of bridge material and the need for retightening of the abutment and prosthesis screws.

Algorithms↗

PubMed2002

Contact allergy to gold is correlated to dental gold.

Questionnaire studies have indicated that patients with dental gold will more frequently have contact allergy to gold. This study aimed at investigating the relationship between contact allergy to gold and the presence and amount of dental gold alloys. A total of 102 patients were referred for patch testing because of suspicion of contact allergy. Patch tests were performed with gold sodium thiosulphate 2% and 5%. The patients underwent an oral clinical and radiological examination. Contact allergy to gold was recorded in 30.4% of the patients, and of these 74.2% had dental gold (p=0.009). A significant correlation was found between the amount of gold surfaces and contact allergy to gold (p=0.008), but there was no statistical relationship to oral lesions. It is concluded that there is a positive relationship between contact allergy to gold and presence and amount of dental gold alloys.

Adult↗

PubMed2002

Gold concentration in blood in relation to the number of gold restorations and contact allergy to gold.

Previous studies have demonstrated an association between gold allergy and the presence of dental gold restorations. The aim of the present study was to investigate the relationship between the concentration of gold in blood (B-Au) and the number of tooth surfaces with gold alloys in subjects with and without contact allergy to gold. In 80 patients referred for patch testing because of eczematous disease, blood samples were taken and analyzed for B-Au using inductively coupled plasma mass spectrometry. The detection limit for the Au determination was 0.04 microg/L. In addition, a dentist made a clinical and radiological examination of the patients and registered the number of dental gold surfaces. Patients with dental gold restorations had a statistically significantly higher B-Au in Mann-Whitney U test (P = 0.025), (range < 0.04-1.07 microg/L) than patients without (range < 0.04-0.15 microg/L). Furthermore, a positive correlation was found between B-Au and the number of dental gold surfaces (P < 0.01). There was no statistically significant difference in B-Au between persons with and without contact allergy to gold. The study thus indicates that gold is released from dental restorations and taken tip into the circulation.

Acrylic Resins↗

PubMed2002

Dental care utilization: a study of 50- to 75-year-olds in southern Sweden.

This study investigates dental care utilization in an adult population in Southern Sweden in relation to dental and social conditions, attitudes to costs, and perceived need to obtain dental services. The study was based on responses to a questionnaire sent in 1998 to a random sample, 1974 persons, aged 56-75 years. The response rate was 66%. A significantly higher probability of dental care utilization less than once a year was found for men, for those with few remaining teeth, and for those with removable dentures. A higher probability of dental care utilization less than once a year was found for those who stated perceived need to obtain dental care with no possibility because of the cost and for those who stated that the cost had influenced their attendance for dental care. The results showed that there were differences for sex and dental conditions in dental care utilization and that dental care utilization was related to attitudes towards costs of dental care.

Aged↗

PubMed2002

Quality of fixed prosthodontics after twenty-two years.

After an observation period of 22 years, this study was conducted to clinically examine and interview patients who in 1984 and 1989 had participated in similar investigations regarding the quality, over time. of treatments with fixed partial dentures. The patients were examined by two standardized and experienced clinicians using thc California Dental Association quality rating system, their results indicating that after 22 years the overall survival rates were 46.5% and 41.1% for the originally placed crowns and pontics, respectively. However, a continuing decrease of the crown quality rating was noted during the more than 20-year-long observation period. Restorative treatments with common types of fixed partial dentures can therefore be regarded as both safe and reliable over long periods of time.

Aged↗

PubMed2002

Early functional loading using Brånemark dental implants.

The present review article discusses the one- and two-stage surgical protocol for dental implant placement as well as the critical amount of micromotion at the bone-implant interface to obtain proper osseointegration. The relevant literature supporting the hypothesis that "splinting of individual implants as soon as possible following installation via a rigid fixed device will most likely decrease the micromotion at the bone-implant interface thus facilitating proper bone healing (osseointegration)" is reported. As a consequence of this approach, the treatment period can be significantly reduced. Finally, the importance of an objective evaluation of the bone quality and initial implant stability is highlighted. The information thus obtained via tools already available will facilitate the decision as to whether to load implants immediately, early, or late, and the term "individual functional loading" is coined.

Dental Implantation, Endosseous↗