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Biomedical subjects

A Ridell

Publications and source records attributed to A Ridell.

At least 19 recordsLinked to original sources
PubMed1999

Amphiphilic association of ibuprofen and two nonionic cellulose derivatives in aqueous solution.

The aqueous interaction of the sodium salt of ibuprofen with the cellulose ethers ethyl hydroxyethyl cellulose, EHEC, and hydroxypropyl methyl cellulose, HPMC, has been investigated in the concentration range 0-500 mM ibuprofen and 0.1-1% (w/w) polymer, by cloud point, capillary viscometry, equilibrium dialysis, and fluorescence probe techniques. Ibuprofen forms micelles in pure water, with the critical micelle concentration, cmc, at 180 mM. A combination of time-resolved and static fluorescence quenching shows that micelle-like ibuprofen aggregates are formed in the solution. The average aggregation number of pure ibuprofen micelles in water is about 40. In the presence of EHEC or HPMC the aggregation numbers decrease. The interaction of ibuprofen with cellulose ethers is similar to the normally accepted model for polymer-surfactant interaction, although more complex. Ibuprofen adsorbs to the polymer in the form of mixed polymer-drug micelles, noncooperatively up to cmc and cooperatively when cmc is passed. The interaction starts below 50 mM ibuprofen as monitored by the fluorescent probes pyrene and 1,3-di(1-pyrenyl)propane, P3P, with a maximum in microviscosity below cmc, corresponding to polymer-dense mixed micelles. The study illustrates the importance of a precise apprehension of the aggregation behavior as a background for transport studies in drug-polymer systems.

Adsorption↗
PubMed1988

Combined Le Fort I osteotomy and oblique sliding osteotomy of the mandibular rami. A follow-up.

Bimaxillary surgery involving mandibular set-back and maxillary advancement has been performed on eight patients with severe prognathic mandibles and in two patients with pronounced retropositioning of the maxilla. The combined surgical approach turned out to give a very satisfying result both from the functional and aesthetic points of view. Whereas a certain skeletal horizontal relapse occurred in the mandible and a vertical one in the maxilla, the occlusal stability was maintained in all but one case. A good postoperative occlusion obviously retains the teeth in position. The soft tissue adaptation and final configuration postoperatively takes a long time, and should if possible be subjected to more sophisticated analysis before surgery. The bimaxillary approach with step-wise surgery, using an intermediate wafer is, in our opinion, a good solution to marked malpositions and in many cases preferable to single jaw surgery.

Adult↗
PubMed1987

Accuracy of cephalometric prediction in orthognathic surgery.

The reliability of predicting the results of orthodontic surgical treatment was analysed. The sample consisted of 30 patients treated with one of the following six types of surgery: mandibular anterior alveolar surgery; maxillary anterior alveolar surgery; mandibular setback surgery; mandibular advancement surgery; Le Fort I surgery; and a combination of Le Fort I and mandibular setback surgery. Comparisons of tracings of the initial cephalometric radiographs, the prediction tracing and the six-month follow-up film showed great variation in the results both within and between the surgical subgroups. Generally, it was easier to predict the treatment results of alveolar segmental osteotomies, especially in the mandible, than of operations in which the whole mandible was repositioned. The results from Le Fort I surgery with or without a concomitant mandibular setback showed the greatest difference between the predicted and the actual outcome. The postoperative vertical dimension appeared to be particularly hard to predict. Explanations for these discrepancies are offered and possibilities for improvements suggested. It is concluded that prediction tracings are still of value despite the poor accuracy in some cases.

Adolescent↗
PubMed1987

Transposition of the mental nerve in orthognathic surgery.

Transposition of the mental nerve in association with orthognathic surgery was performed 25 times in 16 patients. Indications for transposition generally were use of the premolar region for surgical correction of anterior open bite or dentoalveolar prognathism. In one case, reduction of the mandibular base was the surgical indication. Postoperative hypesthesia occurred in 16 mental nerves but sensibility gradually returned to normal in almost all the patients at between six and 18 months. Partial nerve damage occurred accidentally in three cases with reduced sensibility at follow-up.

Adult↗
PubMed1987

Delayed healing of fractures of the mandibular body.

401 mandibular body fractures occurring during a 5-year period were analysed retrospectively. Out of these, 38 fractures (9.5%) were not consolidated by 50 days and made up the delayed healing group (DHG). A control group (CG) of another 38 fractures was constituted using the first mandibular body fracture consecutively following one in the DHG. The mean time until consolidation of the fractures was 116 days in the DHG and 35 days in the CG. The 2 groups were statistically analysed and mutually compared using a great number of variables including patient-, fracture site-, treatment- and end-result characteristics. It was concluded that a few days delay between trauma and treatment did not necessarily lead to a delayed healing. Uncooperative alcoholics with psycho-social handicaps, and general as well as local periodontitis, were found to be especially liable to consolidate their fractures at a slower rate than the average patient. The DHG more often required changes of unstable dental fixation, prolonged maxillo-mandibular fixation time and treatment for late infections at the fracture site. The patients in this group lost more teeth than those in the CG but above all required considerably extended therapeutic efforts. It is suggested that patients with the above-mentioned characteristics should be given special attention and care.

Adult↗
PubMed1980

Bone plate fixation of mandibular fractures.

Bone plate fixation has been applied in 11 out of 1400 patients with fractures of the jaws treated between 1970 and 1978. Most of the case were edentulous patients with dislocated fractures or nonunion fractures due to infection or inadequate immobilization of the fragments in the mandible. A relatively high incidence of complications was noted, depending mostly on the nature of the fracture and in some cases on an extensively resorbed mandible. Bone plate fixation doses have its field of application, although the need for its application in routine treatment of uncomplicated mandibular fractures in dentulous patients is rather limited.

Adult↗
PubMed1979

Prognosis of teeth involved in the line of mandibular fractures.

The management of teeth positioned in the line of mandibular jaw fractures was studied by a follow-up examination of 132 patients with mandibular fractures involving 185 teeth. The observation period varied from 1 to 3 years. The clinical and radiographic findings revealed complete recovery in 59% of the involved teeth. The degree of periodontal and pulpal complications were closely related to the displacement between the fragments and to the type of fracture. Six different fracture types were classified with regard to the extent of involvement of the tooth supporting tissue; 23% of the teeth which initially responded negatively to electric stimulation showed positive sensibility at the time of reexamination. Thus, a long time observation period is advisable with regard to the final outcome of the pulp damage. Conservative treatment of teeth involved in the line of mandibular fractures has a favorable prognosis especially if optimal reduction of the jaw fragments is achieved.

Dental Pulp Diseases↗
PubMed1979

Surgical correction of mandibular prognathism by the oblique sliding osteotomy. A clinical and radiological follow-up study of 112 consecutive cases.

The oblique sliding osteotomy has been used for surgical correction of mandibular prognathism, sometimes in combination with open bite, in 112 patients treated from 1969 to 1978. The method has proved to be connected with few surgical complications and minimal relapse tendency. No correlation was found between the degree of posterior positioning or closure of open bite at the operation and relapse tendency. Consequently no limitations in the field of application concerning the degree of mandibular protrusion or open bite have been found in this study.

Adolescent↗
PubMed1977

Periapical condition of anterior teeth after surgical correction of mandibular prognathism. A radiographic study.

Extrusion and root resorption of the mandibular anterior teeth have been reported after surgical correction of mandibular prognathism by horizontal osteotomy of the rami. The aim of the present study was to find out whether oblique sliding osteotomy also has such side effects. Intraoral radiographs of the maxillary and mandibular anterior teeth of 61 patients were studied. Enlargement of the periodontal space and signs of root resorption were estimated postoperatively and at a later review 1 1/2-5 years after the operation. Enlargement of periodontal space occurred postoperatively in 16.2% of the maxillary incisors and 52.2% of the mandibular incisors. The enlargements were mostly reversible and at the final review only 1.1 and 8.5% of the maxillary and mandibular incisors, respectively, showed such enlargements. Root resorption was rarely found in radiographs from the postoperative control. At the final review, however, there were signs of root resorption of 1.6 and 20.8% of the maxillary and mandibular incisors, respectively. It appears warranted to conclude that the anterior teeth, especially the mandibular incisors, are exposed to strong forces also after oblique sliding osteotomy of the mandibular rami.

Adolescent↗