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Biomedical subjects

O Malmgren

Publications and source records attributed to O Malmgren.

9 recordsLinked to original sources
PubMed1991

Rapid orthodontic extrusion of crown root and cervical root fractured teeth.

This study concerns the relapse tendency and extent of root resorption in 33 extruded non-vital crown root fractured or cervical root fractured teeth in 32 patients 10-20 years old. They constitute all orthodontically extruded teeth at the Orthodontic or Pedodontic Departments, Eastman Institutet, Stockholm (1982-1987). A simple extrusion mechanism exerted a force of 60-70 p along the root axis of the tooth. An extrusion of 2-3 mm was obtained in most patients; the most extreme effect was 6 mm. In 16 patients the extrusion was achieved within 3 weeks, in 12 it lasted for 4-6 weeks and in 5, 7-9 weeks. The treatment was more complicated in the lower jaw. After the extrusion, a fibrotomy was done and in most patients also a gingival recontouring to create an optimal relation between the gingiva and the margin of the restoration. Periodically identical radiographs were taken immediately before and after the extrusion, after 3 months and after 1 year. A minor relapse, about 0.5 mm, was observed in 3 patients. Limited root resorption was found in 6 teeth and severe in only 1. The resorptions did not progress in the following 2 years of observation.

Adolescent↗
PubMed1989

Class II correction in Herbst and Bass therapy.

The purpose of this study was to make a quantitative evaluation on lateral cephalograms of skeletal and dental changes contributing to Class II correction in Herbst and Bass appliance therapy. From two male patient samples treated with either the Herbst appliance (n = 72) or the Bass appliance (n = 32) 18 pairs of subjects were selected. The subjects within each pair had to be in the same growth period at the time of therapy and to exhibit a similar pretreatment sagittal (ANB angle) and vertical (ML/NSL angle) jaw base relationship. Lateral cephalograms in centric occlusion taken before treatment and after 6 months were analysed according to the method of Pancherz (1982a). After six months of treatment the Bass appliance seemed to have a greater influence on mandibular jaw base position than the Herbst appliance, although no statistical significant differences existed between the treatment groups. The correction in overjet and sagittal molar relationships was more complete in the Herbst than in the Bass patients. This was due to greater dental changes (distal movement of the maxillary molars, proclination of the mandibular incisors) taking place in the Herbst subjects.

Activator Appliances↗
PubMed1988

Changes after correction of maxillary retrusion by Le Fort I osteotomy. A comparison of 2 methods of skeletal fixation.

2 methods of skeletal fixation are compared in 24 patients with maxillary retrusion treated with Le Fort I osteotomy only: group I, intraosseous fixation only (10 patients); group II, enhanced fixation, intraosseous and suspension wires (14 patients). Follow-up checks on the patients were carried out using lateral cephalograms. The changes of the maxillary position in relation to the anterior cranial base were analyzed via a technique of superimposition in a computer system without using conventional landmarks. Vertical and horizontal changes and rotations were studied. The method error was small. In the vertical direction, there was a significant difference between the groups. In group I, the vertical relapse during the early postoperative period was 55%, while in group II, it was only 15%. The conclusion is that a rigid vertical fixation is needed.

Adolescent↗
PubMed1987

Treatment with an orthopedic appliance system in relation to treatment intensity and growth periods. A study of initial effects.

The study comprises an analysis of the effect of treatment with a modified activator combined with a high-pull headgear during a standardized observation period of the initial 6 months of treatment. All patients (24 girls and 32 boys, aged 8.5 to 15 years) had severe skeletal Class II malocclusion. In the first part of the study, the effect of treatment with the appliance both day and night is compared with the effect when it was worn only at night. Only a small and nonsignificant difference was found, but the patients tended to cooperate better if they were instructed to wear the appliance continuously. In the second part of the study, the effect of treatment is related to the somatic maturation of the patients. Longitudinal records of standing height were used to assess whether treatment had been performed before maximal pubertal growth (prepeak period), during maximal pubertal growth (peak period), or after maximal pubertal growth (postpeak period). The skeletal effect was significantly greater in boys treated during the peak period than in those treated during the prepeak period and a similar tendency, although not significant, was found among girls. The number of patients treated during the postpeak period was too small for statistical analysis.

Activator Appliances↗
PubMed1978

The effect of various pretreatment methods of the enamel in bonding procedures.

Thirty-eight pairs of premolars, extracted for orthodontic reasons, were tested for the effects of various pretreatment methods of the enamel in bonding procedures. Etched enamel surfaces and inner bracket surfaces facing the etched enamel were studied with the scanning electron microscope. The results were based on a pair-by-pair evaluation of 650 photographs. The degree of surface irregularities indicating the quality of microretentions was evaluated. A scale from 0 to 3 was used; 0 represented a smooth surface, and 3 represented optimum irregularities. Scores for bracket inner surfaces were always higher than those for corresponding etched enamel surfaces. Future SEM comparative investigations, therefore, ought to be based on replicas of etched enamel surfaces. One-minute etching with an acid gel had the same effect as etching with an acid liquid for the same time. Furthermore, mechanical pretreatment procedures, such as diamond grinding and aluminum oxide grinding, as opposed to pumicing did not improve the effect of the acid. Chemical pretreatment of the enamel with organic solvents such as 8 to 12 percent sodium hypochlorite did not improve the effect of the acid. Fluoride pretreatment with a fluoride varnish, Duraphat, did not have any negative effect on the etching results.

Acid Etching, Dental↗
PubMed1978

Computerized cephalometrics.

A method to analyse cephalometric radiographs with the help of a computer has been described. With the system a cephalometric radiograph can be analysed and the results compared to corresponding analyses of individuals with ideal occlusion. The results can also be visualized as schematic figures of the patients. The computer calculates means and standard deviations of groups of individuals and can visualize the results as mean figures. A program to train operators in pinpointing radiographic reference points has also been developed. A methodological study has shown that the errors of the computerized method are of little importance compared to the errors made in pinpointing radiographic reference points. A clinical test of the system has shown that inexperienced operators are able to use the system after about one hour's training. The method is about twenty minutes faster compared to an ordinary manual radiographic analysis. Some future aspects are also discussed.

Cephalometry↗