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Biomedical subjects

H Rydén

Publications and source records attributed to H Rydén.

At least 19 recordsLinked to original sources
PubMed1992

The holodent system, a new technique for measurement and storage of dental casts.

A system for producing holograms and for three-dimensional measuring on holograms is described. The precision of the system was evaluated when three-dimensional measurements were made on (1) a holographic image superimposed on the corresponding object and (2) two superimposed holographic images of the same object. When a metal test object with sharp well-defined contours, easy to reorientate was used, the precision was 0.02 to 0.11 mm for x, y, and z coordinates (transverse, longitudinal, and vertical planes). When dental casts that have less distinct contours were used, precision was reduced to 0.03 to 0.43 mm. Precision was high for the x and y coordinates and satisfactory for the z coordinate. The system has a precision that is equal to that of previously reported methods and may be well-suited for studies of dental positional changes in longitudinal materials of study models. Holograms of dental casts may solve storage problems by replacing space consuming plaster models.

Dental Records↗
PubMed1992

Surface changes on dental materials. II. The influence of two different dentifrices on surface roughness measured by laser reflexion and profilometer techniques.

Surface changes on eight different dental materials were investigated, using laser reflexion technique and a profilometer. The tested materials were: Acrylic veneers Isosit, Isosit N, K+B+, Multiplus and K+Bpaste Gold Sjödings C Titanium pure non-rolled titanium Ceram a potential ceramic direct filling material The materials were subjected to brushing in a brushing machine, with a toothpaste-water slurry. Two different toothpastes were used separately; Clinomyn and Colgate. The new ceramic material showed no measurable wear by the brushing. All the other materials were affected to some extent. On titanium increasing values of light intensity were obtained thus indicating a smoother surface. Among the veneer materials K+Bpaste was the most wear resistant.

Acrylic Resins↗
PubMed1991

A comparative study of plaque removing efficiency using rotary electric and manual toothbrushes.

Plaque removing efficiency was compared between rotary electric and manual toothbrushes. The first part of the study included 19 dental hygiene students randomly assigned to a "rotary" or a "manual" brushing group. The subjects were instructed to brush their teeth three minutes twice a day for three weeks either with rotary electric or with manual brushes. Then for another period of three weeks brushing techniques were reversed. The results showed that the median plaque index for all sites and for buccal and lingual sites was significantly lower in the rotary brushing group (28% vs 39% and 3% vs 6%, p less than 0.05). During the second part of the study 10 of the students refrained from all oral hygiene procedures for four weeks in the anterior mandibular region, i.e. from 33 to 43. They were then randomly assigned to a "rotary" or a "manual" brushing group. Registrations of accumulated plaque were made from photographs at baseline and after 15, 30 and 60 seconds of brushing. ANOVA analysis of the plaque scores showed a significant difference in reduction of plaque in favour of the rotary electric brush (p less than 0.01). The results suggest that the rotary electric toothbrush removes plaque more efficiently than the conventional manual toothbrush.

Adult↗
PubMed1989

Surface changes on dental materials. The influence of two different dentifrices on surface roughness measured by laser reflexion and profilometer techniques.

Surface changes and wear resistance were investigated on eight different dental materials, using a laser reflexion technique and a profilometer. The tested materials were: (table; see text) The materials were subjected to brushing in a brushing machine, containing a toothpaste-water slurry. Two different toothpastes were used separately; Clinomyn and Colgate. The results showed that all the materials were to some extent affected by the brushing. Titanium was the most and SR Isosit N the least wear resistant material. Clinomyn and Colgate influenced the materials in different ways depending on their abrasive properties.

Acrylic Resins↗
PubMed1988

The effect of low-energy infra-red laser radiation on wound healing in rats.

The aim of this study was to evaluate the effect of low-energy infra-red laser treatment on wound healing in rats, both histologically as well as by gross observation. In the caudal area of the back of 14 rats, identical full thickness dermal wounds were punched out bilaterally. One wound in each rat was randomly selected for laser radiation. The contralateral wound was left untreated, serving as a control. All the laser-treated wounds and the untreated control wounds healed in the same way within the same period of time. No difference was observed concerning bleeding time, nor as to the formation and loss of crust. None of the wounds showed signs of infection during the observation period. Histological examination indicated no obvious morphological difference between the laser-treated and the untreated wounds. The present study did not confirm that the use of low-energy infra-red laser radiation could improve the wound healing process.

Animals↗
PubMed1985

Lustre changes on teeth. The use of laser light for reflexion measurements on the tooth surface--in vivo.

Lustre changes on teeth in vivo were studied with the use of equipment based on a helium-neon gas laser. Variations of the intensity of laser light reflected from the tooth surface were measured under different conditions of accumulation and removal of deposits, which were assumed to consist mainly of the pellicle. The possibility of using fluoride varnish as an artificial surface layer in this kind of investigation was also tested but rejected. Measurements were made after toothbrushing with water alone and with two toothpastes possessing different degrees of abrasivity. Teeth that had been left without toothbrushing for 24 hours showed statistically significant (p less than 0.05) lower light reflexion values than those recorded immediately after the teeth had been brushed with a toothpaste. During a period of seven months, persons brushing their teeth with water alone generated lower intensity values than did those brushing with the two toothpastes. The more abrasive paste yielded the highest intensity values, indicating a more polished or cleaner surface. The results suggest that the use of a toothpaste containing abrasives contributes to the cleaning effect of toothbrushing.

Adult↗
PubMed1985

The laser reflection method. Computerized analysis of speckle pattern.

The laser reflection method of remote measurements permits registration of small tooth movements. Its precision was investigated by studying the errors associated with patient repositioning in the apparatus using the computer controlled image scanner OSIRIS. Fifty repositionings of healthy subjects were evaluated. The results show that the mean error of repositioning is 2.8 micron laterally and 9.2 micron sagittally. This agrees with earlier manual-visual measurements but the higher precision due to computer evaluation of the speckle patterns gives much more reliable estimate of the repositioning error. The study confirms the fact that the laser reflection method permits accurate measurements of tooth movements.

Adult↗
PubMed1984

Dentifrice abrasivity. The use of laser light and supplemental techniques for characterizing toothpastes containing different abrasives. An in vitro study.

The abrasivity characteristics of six commercially available toothpastes containing different abrasives were investigated by using laser light reflexion and radiotracer methods. Surface profile and laser diffusometer measurements were also included in the study. Significant and, in some cases, substantial variations of abrasivity were observed. A certain correlation between the results of the different methods was found and used for purposes of ranking the toothpastes. The investigation indicated a necessity to use a combination of quantitative and surface descriptive methods in order that a complete picture of the abrasive properties of a dentifrice might be obtained. The importance of including other than biological materials in the test was also emphasized.

Dentifrices↗
PubMed1982

Tooth position measurements on dental casts using holographic images.

A new accurate method for comparing tooth positions on dental casts at different stages is described. Holograms of casts were prepared with a helium-neon gas laser. For evaluation of tooth movements, a cast and hologram representing different time points were superimposed by means of an adjustable x-y stage. Occlusal surface detail was used as a reference for the superimposition. Positional changes of the upper incisors were detected as discrepancies between the cast and the hologram image.

Adult↗
PubMed1982

Movements of healthy and periodontally involved teeth measured with laser reflection technique.

The laser reflection method of remote measurement was used to register small tooth movements of upper central incisors from a group of subjects with healthy teeth and another group with periodontally involved teeth. The mobility of the healthy maxillary incisors over a period of 24 hours was well within normal limits. Among orthodontically treated and periodontally involved maxillary incisors relapse was larger sagittally than laterally and largest buccally. This tendency was greatest during the first 5 hours and almost reached its maximum after 1 day. These movements were within the limits of mobility but were not always correlated with mobility or the loss of marginal bone. Furthermore, the relapse was not correlated with the magnitude of orthodontic correction. In this respect, the mean buccal relapse was low, however, individual variations were large. The extent of relapse may be related to the varying intensity of parafunctional habits.

Adult↗
PubMed1982

Radiography in advanced periodontal disease. Determination of alveolar bone height over a 2-year interval.

An investigation was performed on 10 patients with advanced periodontal disease. A 3-step periodontal-orthodontic--occlusal therapy was performed followed by programmed plaque-control and professional tooth-cleaning. A longitudinal radiographic study was performed over a period of two years using an Eggen filmholder in combination with individual interocclusal acrylic indices. Measurements of tooth length and alveolar bone height were made using compasses and a transverse scale. An additional registration of bone height was made with a calibrated magnifier. In order to evaluate the precision of registrations a photogrammetric study was carried out using a stereo-comparator. The precision of tooth length and bone height measurements varied between 0.12-0.36 mm. No significant loss of alveolar bone was found during the two year study.

Adult↗
PubMed1981

Lustre changes on teeth. The use of laser beams for comparative studies in vivo.

An instrument for studies of lustre changes on teeth in vivo was constructed and evaluated. The equipment was based on a helium-neon gas laser, a coordinate screen and a photocell. The intensity of light reflected from incisors of ten test subjects was measured before and after brushing with different dentifrices. The investigation showed that the instrument was useful for measuring intensity differences of laser light reflected from teeth. The intensity was found to vary within wide limits from teeth of different persons. During a test period of 70 days only few lustre changes caused by dentifrices were registered.

Adult↗
PubMed1979

A laser instrument for measuring tooth movements.

An improved apparatus has been constructed which is based upon the laser reflexion method and is used in a highly accurate direct technique of measuring tooth movement without contact. The possibility of making clinical investigations of tooth movements with the equipment has been investigated by testing its various components. The most critical part of the system is the repositioning of the patient, which has been done with an accuracy of +/- 20 micron. The reflected pattern used during 3 months of experiments was the same. The instrument can be used for measurements down to 50 micron.

Adult↗
PubMed1979

Effect of flouride varnish (Duraphat) treatment every six months compared with weekly mouthrinses with 0.2 per cent NaF solution on dental caries.

Recent studies have shown a high fluorine uptake in the enamel and a considerable caries reduction following the application of varnished containing fluoride. As the application is easy to carry out it may in certain situations serve as an alternative to other topical fluoride school programmes. The aim of the present study, therefore, was to compare the caries increment in schoolchildren exposed to a fluoride varnish (Duraphat) every six months and in children receiving the conventional weekly fluoride mouthrinsing programme with 0.2 per cent sodium fluoride over a two-year period. Two hundred 14-year-old children, divided into one test and one control group took part in the study. They were clinically and radiographically examined every year. Preexperimental data revealed no differences between the groups. During the experimental period the children in the fluoride varnish group developed a statistically significant lower number of new carious lesions compared with those in the mouthrinsing group. The difference in caries increment was about 30 per cent. Further clinical studies to compare the effects of various topical fluoride programmes are recommended.

Adolescent↗