Showing papers by "University of Gothenburg published in 1976"

On qualitative differences in learning—ii outcome as a function of the learner's conception of the task

Abstract: Summary. Two groups of 20 first-year students were asked to read three sections of a textbook. After the first two sections the groups received different types of question. One group received questions which demanded a thorough understanding of the meaning of the passage. The other group was given detailed factual questions. After the final section of reading a common set of questions of both types was asked. Besides providing further evidence of qualitative differences in learning, the experiment showed that students did adapt their way of learning to their conception of what was required of them.

The effect of systematic plaque control on bone regeneration in infrabony pockets.

Abstract: A clinical trial was undertaken to test the hypothesis that periodontitis can be cured and that bone regeneration occurs in infrabony pockets in patients maintained on an optimal standard of oral hygiene. The material comprised 24 patients with advanced periodontal disease. After an initial examination, the patients were randomly distributed into one test group and one control group. All the patients were given instruction and practice in a proper oral hygiene technique, and then subjected to periodontal surgery using the modified Widman flap procedure. Following treatment, during a 2-year period the patients of the test group were recalled once every second week for professional tooth cleaning. The control patients were recalled once every 12 months for prophylaxis. The results showed that all osseous defects of the patients of the test group were refilled with bone. The control patients, on the other hand, could not maintain a high standard of oral hygiene, and exhibited a progressive deterioration of the periodontal tissues during the postsurgical observation time.

The healing potential of the periodontal tissues following different techniques of periodontal surgery in plaque-free dentitions. A 2-year clinical study.

Abstract: A clinical trial was undertaken to study the healing capacity of the periodontal tissues following different modes of periodontal surgery in patients whose oral hygiene was professionally maintained at an optimal level. Fifty patients, distributed into five groups, participated in the study. Following an initial examination and presurgical treatment, the various patient groups were subjected to one of the following surgical procedures: 1) the apically repositioned flap operation including elimination of bony defects, 2) the apically repositioned flap operation including curettage of the bony defects but without removal of bone, 3) the “Widman flap” technique including elimination of bony defects, 4) the “Widman flap” technique including curettage of the bony defects but without removal of bone, 5) gingivectomy including curettage of the bony defects but without removal of bone. After surgery, all patients received oral hygiene instruction and professional cleaning of the teeth once every 2 weeks during a 2-year period. The results showed that periodontal disease can be cured and further destruction of the periodontal tissues avoided irrespective of the surgical technique utilized for pocket elimination. Different surgical techniques, however, promoted varying degrees of regeneration of the supporting tissues. The most favourable healing was obtained when resection of bone was avoided and when complete coverage of the alveolar bone was ensured.

Determination of monoamine and monoamine metabolites in the human brain: post mortem studies in a group of suicides and in a control group.

Abstract: Different nuclei and regions of the brain from patients who had committed suicide and from controls were analysed for their content of monoamine and monoamine metabolites. There was a post mortem breakdown of 5-hydroxyindoleacetic acid (5-HIAA) which could be correlated to the time elapsed between the occurrence of death and autopsy. Homovanillic acid (HVA) and the monoamines did not decrease post mortem during the time observed (6–148 hours). There was no significant correlation between age and chemical variables in this investigation. There were no significant group differences between suicides and controls concerning dopamine, noradrenaline, 5-hydroxytryptamine, and HVA, 5-HIAA levels were significantly lower in the suicide group in six out of eight parts of the brain investigated. It was, however, also demonstrated that there was a longer time elapse between the occurrence of death and autopsy in the suicide group. The suicides came on average 48 hours later to autopsy than the controls. As there was a post mortem decrease of 5-HIAA, this time variable had to be kept constant when group differences were analysed. When the influence of this time variable had to be kept constant when group differences were analysed. When the influence of this time variable was eliminated there were no longer any differences between suicides and controls. According to this investigation, there seem to be no differences in levels of monoamines and their metabolites between suicides and controls.

Pelvic strength after major amputation of the sacrum. An exerimental study.

Abstract: Major sacral resections up to the level of S 1 and even higher have been performed. This has raised the question of the degree to which such operations weaken the pelvic ring. Fifteen cadaver pelves, including the fifth lumbar vertebra, were loaded to failure, five unresected, five after resection of the sacrum between S 1 and S 2, and five after resection about 1 cm below the promontory. The weakening of the pelvic ring amounted to approximately 30 per cent with the former type of resection and 50 per cent with the latter. Taking into consideration the calculated normal load on L 5 in upright standing it seems safe from this study to allow patients to stand with full weight-bearing at an early stage postoperatively after submaximal resection of the sacrum.

Frequency of symptoms of mandibular dysfunction in young Swedish men.

Abstract: Summary The occurrence of symptoms of dysfunction of the masticatory system was studied in 253 Swedish men from the region of Stockholm with an average age of 19 years. Besides inquiry by questionnaire regarding subjective symptoms a clinical functional examination of the masticatory apparatus was performed. Fourteen per cent were aware of clicking of the temporomandibular joint and 12% of other symptoms of dysfunction such as difficulties in opening the mouth wide, locking and pain on performance of various movements of the mandible. In the clinical investigation, symptoms of dysfunction were noted in 28 % of those examined, mainly in the form of tenderness to palpation over the temporomandibular joints and of the masticatory musculature as well as difficult, painful and irregular movements of the mandible. Individuals with clinical symptoms of dysfunction of the masticatory system had a higher frequency of other joint and muscle symptoms, clicking of the temporomandibular joint and occlusal disturbances in the form of balancing side interferences, than those without clinical symptoms. Balancing side interferences were the only occlusal disturbance that was significantly correlated with the symptoms of dysfunction (pain on movement and tenderness to palpation).

The influence of trauma from occlusion on reduced but healthy periodontal tissues in dogs

Abstract: The experiments were performed in five dogs fed a soft diet which allowed dental plaque accumulation. Experimental periodontal breakdown was introduced on Day 0. After 180 days trauma from occlusion was produced in 4P and P4 i.e. the mandibular fourth premolars, in the manner described by Svanberg & Lindhe (1973). On day 280 the periodontal pockets around 4P and P4 were eliminated. A notch was prepared in the root at the level of the bottom of the surgically eradicated pocket. In addition, the occlusal trauma in the 4P region was deleted. From Day 280 to Day 370 the teeth of the animals were brushed twice a day. The animals were then sacrificed, radiographs of the premolar regions were taken, and tissue sections comprising 3P4P1M (and P3P4M1) were produced and subjected to microscopic analysis. The results indicate that jiggling type occlusal trauma and tooth hypermobility are not factors which detrimentally affect healing following periodontal surgery.

Postnatal development of the human temporomandibular joint. I. A histological study.

Abstract: Temporomandibular joints from 61 humans, aged 2 days to 27 years, were examined histologically. Four layers of the condyle were studied in detail. The outermost layer was richly vascularised in new-borns but by 3 years of age it had become avascular and contained few cells. In neonates the cartilage layer constituted a large part of the condyle but soon decreased in thickness and by 5-6 years of age it constituted only a thin zone of the top of the condyle. In the proliferative zone, mitoses occurred up to 13-15 years of age. This zone then decreased in thickness; the number of cells decreased, while the amount of intercellular substance increased. At birth, the temporal component was flat and was lined by vascularised connective tissue which became richer in collagen with increasing age. The cartilage layer was lacking in the fossa but was present on the tuberculum. A proliferative zone in this cartilage could be seen up to the age of 17-18 years and cartilage having only few cells was found in adults. Remodelling processes were seen in all components of the joints. The significance of the remodelling seen in the fossa and on the mandibular neck is discussed with relation to condylar and periosteal growth of the mandible.

Enzyme activities in skeletal muscles from patients with peripheral arterial insufficiency.

Abstract: The enzyme pattern in gastrocnemius muscle tissue was studied in 3 9 patients with peripheral arterial insufficiency. Phosphofructokinase and glucose-6-phosphate-dehydroge-nase were significantly increased in the skeletal muscles from these patients. The most pronounced changes were found in 3-OH-acyl-CoA-dehydrogenase, citrate synthase, and in cytochrome-c-oxidase. These enzyme activities were increased by 60, 40 and 25 per cent respectively. In patients with claudication as the only symptom, the metabolic capacity was generally increased in skeletal muscles affected by the low blood flow. With increasing severity of arterial insufficiency, all enzyme activities decreased and glycolytic enzymes were affected first. 3-OH-acyl-CoA-dehydrogenase, citrate synthase and cytochrome-c-oxidase activities were still comparatively high in patients with gangrenous foot ulcers, indicating some maintenance of the muscle viability even in situations with very low blood flow.

Effect of toothbrushing with chlorhexidine gel on salivary microflora, oral hygiene, and caries.

Abstract: – The effect of daily toothbrushing with 0.5 % chlorhexidine-containing gel for 12 months was evaluated in a double-blind study in 37 dental students. The active gel did not markedly influence plaque formation, gingival conditions, or caries as compared with placebo gel treatment. Salivary bacterial counts were performed on subgroups of six subjects using chlorhexidine gel and on six using placebo gel. No differences in the effect of treatment on the microorganisms studied in the two subgroups could be detected except for S. sanguis. The percentage of this species decreased in the placebo group and increased in the chlorhexidine group. The difference became significant after 2 weeks. A tendency to a greater reduction of S. mutans noted in the chlorhexidine group was most marked in individuals who had high initial counts of this species. The proportion of S. sanguis, which could grow on chlorhexidine-containing mitis salivarius medium, increased and after 12 months of chlorhexidine treatment averaged 34 % of cultivable S. sanguis compared with 0.002 % prior to treatment. The number of less sensitive S. sanguis decreased in the 12 months following termination of treatment. There was no observed tendency for the selection or proliferation of other streptococci, gram-negative rods, yeasts, or staphylococci.

The effect of various plaque control measures on gingivitis and caries in schoolchildren.

Abstract: The aims of the present study were (1) to analyze the separate effects on plaque, caries, and gingivitis of several measures (oral hygiene instruction, professional tooth cleaning with mechanical instruments, topical application of sodium monofluorophosphate - MFP) which have been incorporated in a prophylactic treatment program, described by AXELSSON & LINDHE1, and (2) to prevent caries and gingivitis by applying the combined treatment but replacing the professional mechanical tooth cleaning with chemical cleaning using a chlorhexidine-containing gel. 164 children, 13-14 years old, divided into four groups, participated in a 2-year trial. All participants were recalled once every 2nd week for preventive treatment provided by dental nurses. During the 1st year Group 3 and 4 received prophylactic treatment identical to that described by AXELSSON & LINDHE1. During the 2nd year the professional tooth cleaning was omitted but oral hygiene instruction was given every 2nd week. During the 1st year Groups 1 and 2 were treated with 0.5% chlorhexidine but during the 2nd year they were subjected to professional tooth cleaning with mechanical instruments. Throughout the trial Groups 1 and 3 rinsed once every 2nd week with a 2% MFP solution. The results showed that by oral hygiene instruction and frequently repeated professional tooth cleanings it was possible to substantially reduce the frequency of gingivitis and prevent caries. When this treatment was used, mouthrinsings with 2% MFP had no additional effect on caries. The substitution of the mechanical cleaning procedure with topical application of a 0.5% chlorhexidine gel failed to (1) remove supragingival plaque accumulations, (2) reduce the frequency of gingivitis, and (3) retard the rate of caries development. The data also revealed that interdental cleaning with mechanical instruments was of decisive importance in the prevention of approximal surface caries.

The effect of progesterone and of insulin administration on regional adipose tissue cellularity in the rat.

Abstract: Female rats were given progesterone in a high and a low dose or insulin by injection. Both hormones caused hyperinsulinemia and an elevated body weight, explainable by increased fat tissue weight, which in turn was due to an increased fat cell size. There was a regional specificity of these effects for both procedures. It was therefore concluded that adipose tissue does not react as a homogenous tissue to different stimuli. Although not definitely conclusive because of difference in the degree of hyperinsulinemia the results also indicate that the effects of insulin are primarily exerted on the small fat cells of the subcutaneous region while progesterone increased the size of the larger parametrial fat cells.

Morphology and life cycle of Ophryotrocha diadema, a new polychaete species from California

Abstract: A new Ophryotrocha species is described from the harbour of Los Angeles. It has a maximum size of 4.6 mmand a maximum of 25 segments. The maxillary plates are of the Pvtype. The new species is a simultaneous hermaphrodite with segments 1 and 2 sterile, 3 and 4 male, and the remaining ones female. The chromosome number is 2n = 8. The larvae develop inside the transparent membrane of a fusiform egg case until the 4-setiger stage. They have no pygidial stylus. The reproductive rate is age dependent reaching a maximum during the fourth week of reproduction. There are two homozygotes and one heterozygote for a colour gene, all with different reproductive patterns.

Effects of major resection of the sacrum. Clinical studies on urogenital and anorectal function and a biomechanical study on pelvic strength.

Abstract: (1976). Effects of Major Resection of the Sacrum Oinical Studies on Urogenital and Anorectal Function and a Biomechanical Study on Pelvic Strength. Acta Orthopaedica Scandinavica: Vol. 47, No. sup162, pp. 1-38.

Surface potential and adherence of oral streptococci to solid surfaces

Abstract: Strains of oral streptococci belonging to the same species but with different zeta-potential adhere with different strengths or become desorbed at different rates. However, strains of various species but with approximately the same zeta-potential also adhere differently. The adherence was found to be affected by the presence of polyvalent of counter ions in the microorganisms studied.

Molecular model for 5-S RNA. A small-angle x-ray scattering study of native, denatured and aggregated 5-S RNA from Escherichia coli ribosomes.

Abstract: A tertiary structural model is suggested for Escherichia coli 5-S RNA that consists of one large and two small double helices arranged in the form of the letter Y. This model is consistent with the small-angle X-ray scattering data of native 5-S RNA, measured in the angular range 20 less than or equal to 140 mrad. The radium of gyration is 3.61 +- 0.1 Nm. Denatured 5-S RNA yields a much lower radius of gyration, 2.7 nm, which might indicate that during denaturation one minor double-helical arm of the Y-shaped structure partially collapses into single-stranded areas. At high concentrations (60 mg/ml) of 5-S RNA, the X-ray scattering data indicate that 5-S RNA is aggregated.

Social Behaviour and Communication in the Great Skua

Abstract: [Social behaviour in Great Skuas was observed in a breeding colony at Noss, Shetland, 28 April-2 June 1972, with emphasis on displays and communication. The display repertoire consists of a number of "basic" elements, which occur in different combinations. Motivation of displays was examined with temporal sequence analysis. Association between displays and overt patterns was studied in ten-second time units over a range of ± 100 seconds time lag. Upright postures, Bend, Wing-raising and Long Call showed positive associations mainly with attack and escape. "Squeaking Ceremony" was associated mainly with nest-building patterns, Neck Low with "courtshp feeding", and Staccato Call with copulation. Most agonistic displays were of short duration, whereas "Squeaking" and Staccato Call were performed during longer periods. Signal function of agonistic displays was studied in dyadic interactions, examining occurrence and sequential order of patterns in both individuals. One aspect of the message of a display, probability of subsequent action, was estimated by recording the frequency of attack, stay put and escape following it. The probability of accurately predicting communicator action usually increased if the preceding display was considered. The best predictability was obtained for displays mainly indicating escape, whereas attack was least predictable. Some displays gave similar information about subsequent actions. Closer examination revealed differences in use, depending on position of the rival. There may also be undetected differences in subsequent motor patterns. Long Call and Wing-raising, which are conspicuous at long distance, were most frequently used towards aerial intruders, Upright postures towards nearby intruders on the ground. Besides conveying different messages, different agonistic displays may thus be used for communication with recipients at different positions and distances. The effect of displays on other individuals was studied by recording their responses to different patterns. Results from the analysis of subsequent actions by the same individual permitted some predictions, which were used to test the hypothesis that displays influence the behaviour of recipients. For example, displays indicating high attack probability should more often be followed by escape in recipients than should escape indicators. These predictions in general were confirmed. However, overt patterns and territorial status also had an influence on the recipient's response. To assess the relative importance of one particular factor, cases where the two other factors did not vary were compared. Overt movements had a strong influence and territorial status also played a role. Other factors besides displays therefore are important in the communication process, and need consideration. When allowance was made for the influence of territorial status and mode of approach, a significant association was obtained between the probability of communicator attack subsequent to various displays, and the responses in recipients of these displays. Recipients hence use information about subsequent communicator action provided by displays for adapting their responses, which shows that displays function as signals., Social behaviour in Great Skuas was observed in a breeding colony at Noss, Shetland, 28 April-2 June 1972, with emphasis on displays and communication. The display repertoire consists of a number of "basic" elements, which occur in different combinations. Motivation of displays was examined with temporal sequence analysis. Association between displays and overt patterns was studied in ten-second time units over a range of ± 100 seconds time lag. Upright postures, Bend, Wing-raising and Long Call showed positive associations mainly with attack and escape. "Squeaking Ceremony" was associated mainly with nest-building patterns, Neck Low with "courtshp feeding", and Staccato Call with copulation. Most agonistic displays were of short duration, whereas "Squeaking" and Staccato Call were performed during longer periods. Signal function of agonistic displays was studied in dyadic interactions, examining occurrence and sequential order of patterns in both individuals. One aspect of the message of a display, probability of subsequent action, was estimated by recording the frequency of attack, stay put and escape following it. The probability of accurately predicting communicator action usually increased if the preceding display was considered. The best predictability was obtained for displays mainly indicating escape, whereas attack was least predictable. Some displays gave similar information about subsequent actions. Closer examination revealed differences in use, depending on position of the rival. There may also be undetected differences in subsequent motor patterns. Long Call and Wing-raising, which are conspicuous at long distance, were most frequently used towards aerial intruders, Upright postures towards nearby intruders on the ground. Besides conveying different messages, different agonistic displays may thus be used for communication with recipients at different positions and distances. The effect of displays on other individuals was studied by recording their responses to different patterns. Results from the analysis of subsequent actions by the same individual permitted some predictions, which were used to test the hypothesis that displays influence the behaviour of recipients. For example, displays indicating high attack probability should more often be followed by escape in recipients than should escape indicators. These predictions in general were confirmed. However, overt patterns and territorial status also had an influence on the recipient's response. To assess the relative importance of one particular factor, cases where the two other factors did not vary were compared. Overt movements had a strong influence and territorial status also played a role. Other factors besides displays therefore are important in the communication process, and need consideration. When allowance was made for the influence of territorial status and mode of approach, a significant association was obtained between the probability of communicator attack subsequent to various displays, and the responses in recipients of these displays. Recipients hence use information about subsequent communicator action provided by displays for adapting their responses, which shows that displays function as signals.]

Human adipose tissue in culture. IV. Evidence for the formation of a hormone antagonist by catecholamines.

Abstract: . Explants of human adipose tissue were cultured for several days with noradrenaline (NA). After the culture period the explants were carefully washed, preincubated and then incubated for 2 h by a technique analogous to those generally used to study adipose tissue metabolism. The results show that explants cultured with NA were considerably less responsive to the acute lipolytic effect of catecholamines than explants not previously exposed to NA. The diminished responsiveness could not be reversed by the addition of phentolamine or by preincubating the explants with a prostaglandin antagonist and it was dependent upon the concentration of noradrenaline used in the culture medium as well as upon the period of time that the explants were exposed to the hormone. The cyclic AMP (cAMP) levels did not increase in response to NA in these explants. Addition of theophylline or dibutyryl cAMP elicited a lipolytic response. However, the phosphodiesterase levels were not increased in the explants cultured with noradrenaline. When freshly excised tissue specimens were incubated in the culture medium which had previously contained NA the acute lipolytic effect of catecholamines was blunted. The results indicate that an antagonist is formed during the incubation with NA which inhibits the responsiveness to catecholamines. The effect of the antagonist seems to be exerted at a step prior to the formation of cAMP.

The effects of adrenal corticosteroids on regional adipocyte size in man.

Abstract: In order to determine the effects of adrenal corticosteroids on regional adipose tissue cellularity groups of age-matched women subjected to long-term treatment with adrenal corticosteroids due to bronchial asthma or rheumatoids due to bronchial asthma or rheumatoid arthritis were compared with control of women A small group of women suffering from Cushing's syndrome was also examined Body composition, adipose cellularity in four major subcutaneous regions and metabolic variables were determined The Cushing's syndrome patients weighed more than the other groups and seemed to have more fat cells while the patients with rheumatoid arthritis showed decreases in body cell mass, body fat and average fat cell size These differences necessitated a body fat matching between patients and controls before analysis of regional depot fat differences Body fat, average fat cell size and total fat cell number were similar in patients and controls The Cushing's syndrome group was too small to allow this matching All three groups exposed to increased levels of adrenal corticosteroids showed smaller fat cells in the gluteal region in comparison with controls, but no differences in fat cell size in the femoral, epigastrial or hypogastrial regions This change also corresponded to a diminution of the thickness of subcutaneous plus skin layer in the gluteal region, measured with an ultrasonic technique All the groups of patients had elevated fasting plasma insulin The possibility was considered that the observed regional redistribution of fat is characteristic for adrenal corticosteroids

Facial morphology and activity of temporal and lip muscles during swallowing and chewing.

Abstract: The correlations between facial and bite morphology and the activity in the temporal muscle and in the musculature of the lip during swallowing and chewing were studied in 50 girls, aged 9-13 years. The activity was recorded electromyographically by determining the maximal mean voltage amplitude and morphologically by analysis of profile roentgenograms and dental casts. The activity in the lower lip during the swallowing was not correlated with any of the variables of the facial morphology with the exception of the width of the upper dental arch. On the other hand, the activity of the upper lip during swallowing, as in the anterior and posterior portions of the temporal muscle, was correlated with a number of variables used for measuring facial form. The activity was low in girls with a facial shape with anterior inclination of the maxilla and mandible, small face height, and pronounced prognathism. The activity in the upper lip during chewing varied, as in the lower lip, independently of facial form, while the activity of the temporal muscle during chewing showed the same relation to facial form as during swallowing. The number of chewing cycles required for trituration of the test media (apples and peanuts) was negatively correlated with the number of teeth and with age. This was interpreted as adaptation in such a way that the number of cycles decreased with development of the dentition.

Postnatal development of the human temporomandibular joint. II. A microradiographic study.

Abstract: Temporomandibular joint specimens from 22 subjects aged 1 month to 23 years were examined microradiographically. There occurred considerable interindividual variations in mineralization of the joints but nevertheless, systematic changes in mineralization were demonstrated during the periods of development and growth. A continuous compact bony layer formed early in the fossa and tubercle while the outer mineralized layer of the condyle consisted of calcified cartilage. A continuous bony layer around the periphery of the condyle was not fully developed before about 20 years of age. Growth of the articular tubercle was characterized by a spongy appearance of the bony layer over the tuberculum up to the end of puberty. No corresponding growth changes could be seen in the fossa. No mineralized parts could be seen in the disk or the fibrous layers of the articular surfaces.

The Effects of Estrogens on Regional Adipose Tissue Cellularity in the Rat

Abstract: The effects of high and low dose estrogen administration on adipose tissue cellularity and metabolism were investigated and compared with the effect of total starvation in female rats. Total starvation in female rats resulted in local fat cell size decrease which was, in different adipose tissue regions, directly proportional to the primary fat cell size. Thus, the largest fat cell size decrease was observed in the parametrial depot of adipose tissue, with primarily the smallest adipocytes. High doses of estrogen (Estradurin-120 mug/kg/month) resulted in a body and adipose tissue weight decrease after 10 weeks treatment. Contrary to the starvation effect the greatest fat cell size decrease was observed in the subcutaneous depot with primarily the smallest adipocytes. Lower estrogen dose (60 mug/kg/month) resulted, after 4 weeks treatment, in weight increase of adipose tissue. Fat cell size increased most in the parametrial depot-an adipose tissue region with primarily the biggest adipocytes. This is in contrast to the situation after insulin treatment and overfeeding which produce the largest size increase in the region with the smallest fat cells, and can be interpreted as evidence for regional specificity of the estrogen effect on fat cells.

Carnitine concentration in relation to enzyme activities and substrate utilization in human skeletal muscles.

Abstract: The relationships between the carnitine concentration and enzyme activities representative of different metabolic pathways, glycogenolysis, glycolysis, beta-oxidation of fatty acids, citric acid cycle, and respiratory chain were studied in skeletal muscle tissue from 18 volunteering subjects. In addition, the in vitro incorporation rates of glucose-carbon and palmitate-carbon into different metabolites, and the concentration of glycogen, triglycerides, and phospholipids were determined in the same tissue specimen. The carnitine concentration correlated positively and statistically significantly with the activities of 3-OH-acyl-CoA dehydrogenase and citrate synthase, with the incorporation rate of palmitate-carbon into CO2, and the incorporation rate of glucose-carbon into lactate in the muscle tissue. The results indicate a coupling between the concentration of carnitine and the capacity for long-chained fatty acid oxidation in human skeletal muscles.

Effect of a fluoride‐containing chlorhexidine gel on bacteria in human plaque

Abstract: — The effect on the plaque flora of a fluoride-containing chlorhexidine gel in mouthpieces was studied in seven subjects. Use of the gel during a 3-month period resulted in a change in the pattern of sensitivity to chlorhexidine in the plaque flora as displayed by determination of the minimal inhibitory amount (MIA) of the drug in agar diffusion assays. Three months after the use of gel was discontinued, the MIA value for plaque bacteria had returned to its original level. The relative proportions of S. mutans and S. sanguis in plaque changed during the chlorhexidine period. Thus S. mutans could not be detected in plaque samples after 3-month use of the gel, and the frequency of S. sanguis was altered.

A method for studying adherence of oral streptococci to solid surfaces.

Abstract: The adherence of different streptococci to test pieces of glass, human enamel and whale dentin carried in the mouth or immersed in saliva or bacterial suspensions was studied by examining the number and frequency of microorganisms which were selectively desorbed by a standardized washing technique. The results obtained from in vivo and in vitro experiments were similar in principle. The proportion of streptococci obtained in the first washing resembled that found in the saliva, but with more vigorous washing the proportion of S. sanguis increased while that of S. salivarius decreased. This illustrates that different microorganisms can attach to solid surfaces with different strengths. The applicability of the method was tested by treating dentin surfaces with fluoride solutions and by incorporating sucrose in the test solution. The fluoride treatment reduced while the sucrose addition increased the number of streptococci which could be removed from the surfaces.