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The aim of the present study was to evaluate the long-term effect of implants installed in different dental areas in adolescents. The sample consisted of 18 subjects with missing teeth (congenital absence or trauma). The patients were of different chronological ages (between 13 and 17 years) and of different skeletal maturation. In all subjects, the existing permanent teeth were fully erupted. In 15 patients, 29 single implants (using the Brånemark technique) were installed to replace premolars, canines, and upper incisors. In three patients with extensive aplasia, 18 implants were placed in various regions. The patients were followed during a 10-year period, the first four years annually and then every second year. Photographs, study casts, peri-apical radiographs, lateral cephalograms, and body height measurements were recorded at each control. The results show that dental implants are a good treatment option for replacing missing teeth in adolescents, provided that the subject's dental and skeletal development is complete. However, different problems are related to the premolar and the incisor regions, which have to be considered in the total treatment planning. Disadvantages may be related to the upper incisor region, especially for lateral incisors, due to slight continuous eruption of adjacent teeth and craniofacial changes post-adolescence. Periodontal problems may arise, with marginal bone loss around the adjacent teeth and bone loss buccally to the implants. The shorter the distance between the implant and the adjacent teeth, the larger the reduction of marginal bone level. Before placement of the implant sufficient space must be gained in the implant area, and the adjacent teeth uprighted and paralleled, even in the apical area, using non-intrusive movements. In the premolar area, excess space is needed, not only in the mesio-distal, but above all in the bucco-lingual direction. Thus, an infraoccluded lower deciduous molar should be extracted shortly before placement of the implant to avoid reduction of the bucco-lingual bone volume. Oral rehabilitation with implant-supported prosthetic constructions seems to be a good alternative in adolescents with extensive aplasia, provided that craniofacial growth has ceased or is almost complete.

Purpose: A mechanism-based model is applied to analyse adaptive changes in the pharmacodynamics of benzodiazepines upon chronic treatment in rats., Methods: The pharmacodynamics of midazolam was studied in rats which received a constant rate infusion of the drug for 14 days, resulting in a steady-state concentration of 102 +/- 8 ng x ml(-1). Vehicle treated rats were used as controls. Concentration-EEG effect data were analysed on basis of the operational model of agonism. The results were compared to data obtained in vitro in a brain synaptoneurosomal preparation., Results: The relationship between midazolam concentration and EEG effect was non-linear. In midazolam pre-treated rats the maximum EEG effect was reduced by 51 +/- 23 microV from the original value of 109 +/-15 microV in vehicle treated group. Analysis of this change on basis of the operational model of agonism showed that it can be explained by a change in the parameter tissue maximum (Em) rather than efficacy (tau). In the in vitro studies no changes in density, affinity or functionality of the benzodiazepine receptor were observed., Conclusions: It is concluded that the observed changes in the concentration-EEG effect relationship of midazolam upon chronic treatment are unrelated to changes in benzodiazepine receptor function.

The aim of the study was to find out if implant-supported crowns in the upper incisor region run the risk of coming into an infraoccluded position later in life. Ten adolescents with 15 implant-supported crowns were included in the study. The age of the patients at the implant surgery ranged between 14 and 19 years. They were followed up during an 8-year period. No implant loss was observed. A good or acceptable aesthetic appearance at the last observation was found in most subjects. In some of them a change in the vertical position of the implant-supported crown, resulting in infraocclusion, could be registered, especially in subjects with no incisor contact. Throughout the follow-up period, only minor loss of marginal bone support was observed at the implants. At the teeth adjacent to the implant, a reduction of the marginal bone level was observed in some patients. Of importance to consider in single implant therapy is that a fixed chronological age is no guidance for implant placement, due to a slight continuous eruption of the adjacent teeth post adolescence. An orthodontic treatment should be performed not only in order to gain space in the implant area, but also to attain good incisor stability to reduce the risk of infraocclusion of the implant-supported crown. Furthermore, 3 cases will exemplify that infraocclusion also may occur in patients who had received single implants at adult ages.

In 15 adolescents (age 13.2 to 19.4 years) in the late dental stage implants (n = 27) were chosen to replace missing teeth due to congenital absence or trauma. The patients were followed for at least 3 years. No fixture losses occurred. Only minor loss of bone support at the fixture was observed, while adjacent tooth surfaces showed some loss. Infra-occlusion of the implant restorations was noticed in patients with residual craniofacial growth. Thus, the dental and skeletal maturation, and not the chronological age, must be taken into account to avoid infra-occlusion. Furthermore it is important to gain enough space for the fixture in the mesio-distal direction in order to avoid the risk of marginal bone loss at teeth adjacent to the implants.

In this investigation, the tissue reactions towards titanium implants inserted in growing jaws of pigs were studied by means of histology. At the age of 12 weeks, 5 test pigs each received 4 Brånemark System titanium implants (fixtures). The fixtures were inserted immediately after extraction of the mesial root of the second deciduous premolar (P2) and the deciduous canine (C) on one side of the mandible and the mesial root of the first deciduous premolar (P1) on the other side. The fourth implant was placed after extraction of the deciduous lateral incisor (L) on one side in the upper jaw. Furthermore, 1 pig in which no extractions or fixture installations were performed served as a control. All pigs were followed for 165 days with clinical, radiographic and biometric examinations, the results of which have been previously presented. In this study, 10-microns-thick ground sections were produced for histology after the jaws had been fixed by immersion in formalin and further processed and embedded in plastic resin. Six of the fixtures originally inserted were lost during the experimental period, and the remaining implants were found to be involved with mineralized bone to varying degrees. Regarding the fixture-to-teeth relationship, it was found that, in the premolar region of the lower jaw, the teeth were positioned superior to and buccally angulated in relation to the fixtures. In the upper jaw, the implants were positioned below the adjacent teeth but centrally in the alveolar process. Tooth germs adjacent to the fixture had a displaced eruption path, buccally or lingually to the fixture. If the bud developed in close contact with the fixture, a changed morphology of the germ could be observed.