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Biomedical subjects

P Astrand

Publications and source records attributed to P Astrand.

At least 37 records · Page 2Linked to original sources
PubMed1990

Applicability of osseointegrated oral implants in the rehabilitation of partial edentulism: a prospective multicenter study on 558 fixtures.

Nine clinical centers using the Brånemark System participated in a prospective study of 159 partially edentulous patients between 18 and 70 years of age. Clinical parameters evaluated were plaque index, gingivitis, pocket depth, bleeding index, tooth mobility, and stomatognathic function. Initially, 558 fixtures were placed and 521 remained in the study following prosthesis placement (199 prostheses in 154 patients). Fixtures were lost or unaccounted for because of nonintegration prior to prosthesis fabrication (19), patient withdrawal (11), prosthodontic reasons (6), and failure during prosthetic procedures (1). Failure was primarily attributable to unfavorable bone quality, sex (more in males), and smaller fixture size. Complications and failure related to other patient characteristics are presented. After 1 year of a 5-year study, preliminary results suggest that a success rate equal to or better than that obtained with edentulous patients may be expected.

Adult↗
PubMed1990

Osseointegrated implants in edentulous jaws: a 2-year longitudinal study.

Osseointegrated implants in 50 edentulous jaws were studied during a 2-year observation period. The implant survival rate was 89% in the maxillae and 97% in the mandibles. The marginal bone loss averaged 1.7 mm in the maxillae and 1.1 mm in the mandibles. Most of this bone loss occurred during the first year. The bone loss was greater in jaws with a preoperatively minor resorption of the alveolar ridge than in those with moderate or advanced resorption. The bone loss was also greater at the medially positioned implants than at those more posterior.

Adult↗
PubMed1989

ATP as a sympathetic co-transmitter in rat vasomotor nerves--further evidence that individual release sites respond to nerve impulses by intermittent release of single quanta.

A combination of intra- and extracellular recording was used to study neurotransmitter release in sympathetic vasomotor fibres in rat femoral and mesenteric arteries. The results show that neurotransmission in these preparations is similar to that in the 'short' sympathetic nerves in guinea-pig vas deferens and the 'long' sympathetic nerves in rat tail artery in the following respects: (1) The intracellularly recorded excitatory junction potentials (EJPs) and the extracellularly recorded junction currents (EJCs) presumably are caused by ATP secreted as a sympathetic co-transmitter. (2) The stimulus-evoked and spontaneous EJCs share the same brief time-course, which is similar to that of spontaneous EJPs, but much briefer than that of stimulus-evoked EJPs. (3) 'Successful' nerve impulses appear to release single transmitter quanta. (4) The probability of activation of individual release sites is low (0.002-0.02). (5) The low release probability cannot be accounted for by failure of the nerve impulse to invade the terminals. Moreover, it is also shown that application of tetrodotoxin to the medium within the recording electrode effectively abolishes transmitter secretion in the area enclosed by the tip of the electrode, indicating that the effective length constant for a passively propagating nerve action potential is probably very small and that activation of the release mechanisms in 'long' sympathetic nerve fibres seems to require that the varicosities are actively invaded.

Adenosine Triphosphate↗
PubMed1989

On the secretory activity of single varicosities in the sympathetic nerves innervating the rat tail artery.

1. Nerve terminal impulses (NTIs) and spontaneous or stimulus-evoked excitatory junction currents (SEJCs or EJCs), reflecting secretion of transmitter quanta from release sites in the sympathetic nerves of rat tail artery, were recorded by extracellular electrodes. 2. The release of transmitter quanta from single varicosities was analysed on a pulse-by-pulse basis. 3. Since the SEJCs were tetrodotoxin-resistant, and hence probably caused by single quanta, they were employed to analyse the quantal content of EJCs. 4. In the majority of recordings, EJCs were large compared to SEJCs from the same attachment, and preceded by prominent NTIs. This type of activity appeared to reflect simultaneous activation of several nerve fibres and numerous varicosities. 5. By focal stimulation, it was usually possible to improve the resolution by examining spots in which a large proportion of the suprathreshold stimuli failed to cause EJCs. Here, averaged NTIs preceding large EJCs were indistinguishable from averaged NTIs not followed by EJCs. Thus, failure of invasion by the nerve impulse was not a cause of the frequent secretory failure. 6. In these attachments the amplitude distribution of nerve stimulus-evoked EJCs was similar to that of the SEJCs and many individual EJCs could be matched in amplitude and time course by SEJCs. Thus, transmitter secretion from these sympathetic nerve varicosities seems to be basically monoquantal. 7. Under conditions when all EJCs were smaller than or equal to the largest SEJCs some characteristic EJC profiles appeared only a few times in response to several hundred suprathreshold stimuli at low frequency (0.5-1 Hz). Using tentatively these EJCs as 'fingerprints' of single quanta from particular release sites, the probability for activation of individual release sites ranges from 0.002 to 0.02.

Action Potentials↗
PubMed1988

Intermediate bone grafting of alveolar clefts.

During the five year period 1980 to 1985 bone grafting was performed in 37 cleft patients before the eruption of the canine tooth (group IBG) and in 30 patients after the eruption of the canine tooth (group SGB). The initial healing was more favourable in the IBG group. In 72.5% of the clefts oro-nasal fistulae were present preoperatively. In all cases the fistulae were successfully closed. In the IBG group with orthodontic closure of the gap in the dental arch the interdental bone height in the grafted area was more than 75% of normal bone height in all clefts. In group SBG this situation was found in only 66% of the bone-grafted areas. There seems to be a clear relation between the age or the developmental stage of the canine tooth on the one hand and the possibility of orthodontic closure of the gap in the dental arch and good interdental bone height on the other hand. This also leads to the suggestion that if bone grafting to the alveolar cleft is required the operation should be performed before the eruption of the canine tooth on the cleft side.

Adolescent↗
PubMed1988

Time course of transmitter action at the sympathetic neuroeffector junction in rodent vascular and non-vascular smooth muscle.

1. Transmitter release from sympathetic postganglionic nerve terminals innervating the guinea-pig and mouse vas deferens and the rat tail artery has been studied in vitro by focal extracellular recording with particular emphasis on the time course of transmitter action underlying the intracellular potential changes. 2. In the absence of stimulation, spontaneous excitatory junction currents (SEJCs) were recorded with amplitudes up to 500 microV and durations between 40 and 100 ms. SEJCs were unaffected by the competitive alpha-adrenoceptor antagonist prazosin but blocked by alpha, beta-methylene ATP which desensitizes P2-purinoceptors. 3. During trains of supramaximal stimuli at 0.1-4 Hz stimulus locked excitatory junction currents (EJCs) were evoked intermittently from the population of varicosities located under the suction electrode. 4. SEJCs were similar in amplitude and time course to EJCs evoked by low-frequency stimulation in the same attachment in all three tissues. 5. SEJCs recorded using either a conventional AC amplifier or a patch clamp amplifier had the same time course. 6. These studies show that the time course of the current underlying the excitatory junction potential is brief and essentially the same in three different tissues. The prolonged time course of the excitatory junction potential in different tissues can be accounted for by the passive membrane properties.

Action Potentials↗
PubMed1987

Extraoral or intraoral approach in the oblique sliding osteotomy of the mandibular rami? Clinical experience and results.

The clinical results of oblique sliding (subcondylar) osteotomy of the mandibular rami performed by the extraoral or intraoral approach were compared. The patient material comprised 40 patients with mandibular prognathism. Twenty patients were operated upon using the extraoral approach and 20 patients were operated on using the intraoral approach. All patients had intermaxillary fixation for 7 weeks. The patients in both groups were followed up for 18 months. The experience of the operations was that the intraoral approach gave a shorter operation time than the extraoral approach. The extraoral approach, however, gave better visibility in the operation field and greater possibilities of manipulating the proximal fragment into an optimal position. In the follow-up evaluation, there were no significant differences between the two surgical techniques with regard to dental relapse, post-operative occlusion and mandibular function.

Adolescent↗
PubMed1986

Neuropeptide Y--a cotransmitter with noradrenaline and adenosine 5'-triphosphate in the sympathetic nerves of the mouse vas deferens? A biochemical, physiological and electropharmacological study.

UNLABELLED: A combination of biochemical, physiological and electropharmacological methods was employed to examine the occurrence of neuropeptide Y and the pre- and postjunctional effects of this peptide on sympathetic neuromuscular transmission in the mouse vas deferens. This tissue had a high content of neuropeptide Y-like immunoreactive material, suggesting a dense innervation by neuropeptide Y-containing nerve fibres. Addition of neuropeptide Y at concentrations from 5 X 10(-9) to 5 X 10(-7) M induced both pre- and postjunctional effects in vitro. Neuropeptide Y per se induced a rise in the resting tension, and "instantly" potentiated the contractile effects of exogenous noradrenaline and of the stable adenosine 5'-triphosphate (ATP) analogue, alpha,beta-methylene ATP. Neuropeptide Y reduced the secretion of [3H]noradrenaline evoked by electrical nerve stimulation, and selectively depressed the stimulus-evoked, but not the spontaneously occurring excitatory junction potentials in smooth muscle cells. Further, neuropeptide Y reduced the amplitudes of the twitch contractions evoked by electrical field stimulation with short stimulus trains at 10 Hz, and also (although to a smaller extent) the delayed contractile response to longer trains of nerve stimuli. The pre- and postjunctional effects of neuropeptide Y were not changed by alpha- or beta-adrenoceptor blocking agents, or by tachyphylaxis to the effects of ATP, or by the calcium channel blocker nifedipine. IN CONCLUSION: sympathetic neuromuscular transmission in the mouse vas deferens may be mediated not only by noradrenaline and ATP, but also by neuropeptide Y.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1986

Skeletal remodelling in the temporomandibular joint after oblique sliding osteotomy of the mandibular rami.

Skeletal remodelling of the temporomandibular joints took place in 80% of cases after oblique sliding osteotomies of the rami. The new bone formation was found in both the condylar and temporal parts of the joint. It was mostly located on the posterior surface of the condyle and in the roof of the temporal part of the joint. No differences in skeletal remodelling were found between wiring and nonwiring cases.

Adolescent↗
PubMed1985

Relative pre- and postjunctional roles of noradrenaline and adenosine 5'-triphosphate as neurotransmitters of the sympathetic nerves of guinea-pig and mouse vas deferens.

Experiments were designed to examine the relative roles of noradrenaline and adenosine 5'-triphosphate (ATP) as mediators of the contractile responses of the guinea-pig and the mouse vas deferens to electrical nerve stimulation. To study possible prejunctional actions of the agents used, in some experiments their effects on the secretion of [3H]noradrenaline were determined. The contractile responses were recorded with force displacement transducers. Pharmacological techniques were employed to examine the pre- and/or postjunctional effects mediated by noradrenaline and ATP, respectively. Noradrenaline-mediated components were "removed" by depleting the neuronal stores of noradrenaline (by pretreatment with reserpine), or by addition of adrenoceptor-blocking agents. ATP-mediated components were "removed" by desensitizing ATP receptors (with the stable analogue alpha, beta-methylene ATP). The results permit three major conclusions: (1) In both species noradrenaline and ATP "auto-inhibit" mechanisms responsible for transmitter secretion; the prejunctional effects of ATP are less marked in the mouse vas deferens, and in both species much weaker than those mediated by noradrenaline, acting via alpha 2-adrenoceptors. (2) In these species, both noradrenaline and ATP participate in the generation of both phases of the contractile responses to nerve stimulation. The relative roles of each vary with the frequency and train length of stimulation, and also with the species. The main transmitter of "phase I" contractions in guinea-pig vas deferens is ATP, and in the mouse vas deferens, noradrenaline. "Phase II" contractions are triggered mainly by noradrenaline, in both species. Sympathetic neuroeffector transmission in these tissues can be accounted for almost entirely in terms of dynamic interplay between pre- and postjunctional actions of noradrenaline and ATP. (3) The results are compatible with the hypothesis that ATP is a co-transmitter with noradrenaline in these sympathetic nerves.

Adenosine Triphosphate↗
PubMed1984

Discrete events measure single quanta of adenosine 5'-triphosphate secreted from sympathetic nerves of guinea-pig and mouse vas deferens.

Intracellularly recorded excitatory junction potentials in smooth muscle cells, and the first time differentials of their rising phases ("discrete events") were used to analyse transmitter secretion from the postganglionic sympathetic nerves of guinea-pig and mouse vas deferens. The aim was to determine whether the transmitter causing these responses is noradrenaline or adenosine 5'-triphosphate (ATP). Depletion of the noradrenaline stores following treatment with reserpine reduced the frequency of occurrence, but not the amplitude, of spontaneous junction potentials and discrete events. Nerve stimulation could still evoke "fast" junction potentials and discrete events, normal in appearance, but "slow" junction potentials were reduced in amplitude and had shorter times to peak. In contrast, desensitization of ATP receptors by alpha, beta-methylene ATP abolished spontaneous and stimulus-induced "fast" (but not "slow") junction potentials and discrete events, reversibly. It is concluded that it is not noradrenaline, but ATP or some related compound which causes spontaneous and "fast" stimulus-induced junction potentials, and discrete events. The present and earlier data show that discrete events reflect the secretion of individual quanta of ATP (or quanta of "ATP + noradrenaline", if both are secreted in parallel from the same vesicle) from postganglionic sympathetic nerve terminals in guinea-pig and mouse vas deferens.

Adenosine Triphosphate↗
PubMed1984

Intraoral or extraoral approach in oblique sliding osteotomy of the mandibular ramus. A cephalometric study.

Positional changes of the mandible after oblique sliding osteotomy of the mandibular rami were investigated by means of cephalometric analysis. The patient material comprised 40 patients. Twenty patients were operated upon using an extraoral approach and 20 were operated on using an intraoral approach. The patients were followed up with lateral cephalograms for 18 months after operation. In both groups, a posterior rotation of the mandible took place during the fixation period. This rotation gave a further retro-displacement of gnathion and a shortening of posterior facial height. The incidence of patients with considerable posterior rotation of the mandible was higher in the intraoral than in the extraoral group. The difference between the means of the changes in the mandibular plane angle (dEO = 4.9 degrees, dIO = 6.3 degrees) of the groups was, however, not statistically significant. Nor was there any significant difference in relapse between the two groups after release of the fixation.

Adolescent↗
PubMed1983

Intraosseous wiring in ramus osteotomy.

The value of intraosseous wiring of the fragments after oblique osteotomy of the mandibular rami was studied. A wired group (14 patients) and a nonwired group (15 patients) were compared cephalometrically. There were only small differences between the groups but there was a tendency toward a smaller postoperative posterior rotation of the mandible in the wired group. It was concluded that in routine cases of mandibular prognathism wiring is not necessary.

Adolescent↗