Guided bone regeneration around dental implants in the atrophic alveolar ridge using a bioresorbable barrier. An experimental study in the monkey

The aim of this study was to evaluate guided bone regeneration (GBR) around dental implants placed in atrophic alveolar ridges using an experimental, nonporous bioresorbable barrier. In 8 Rhesus monkeys, the maxillary canines and lateral incisors were extracted bilaterally and the remaining alveoli were reduced to create atrophic ridges. After a healing period of 3 months, soft tissue expansion was performed using a subperiosteal tissue expander. After 1 month of tissue expansion, and IMZ implant was placed in the atrophic ridge on each side in such a way that its coronal 4 mm to 5 mm remained circumferentially exposed above the bone level. The test implants were covered with a bioresorbable barrier made of poly (D,L-lactid-co-trimethylencarbonate) in a 70/30 ratio, whereas the control implants were covered with a nonresorbable expanded polytetrafluoroethylene (e-PTFE) barrier. The e-PTFE barriers were stabilized with titanium minipins while the bioresorbable barriers were analogously fixed using bioresorbable minipins made of poly (L-lactid-co-D,L-lactid) 70/30. Clinical healing progressed uneventfully in both groups and no soft tissue dehiscences occurred. Histometric and histomorphometric analyses were performed 5 months post surgery. Both test and control implants exhibited direct bone-to-implant contact to variable extents. The mean direct mineralized bone-to-implant contact length fraction was 32% of the total implant length in the test sites and 58% in the control sites. Control sites exhibited significantly greater bone fill compared to the experimental sites (P < 0.001). Histologic observations of test specimens demonstrated a moderate inflammatory reaction related to the degradation and resorption products of the barrier. In conclusion, the nonresorbable e-PTFE GBR barrier was found to be superior to the bioresorbable barriers tested in the present investigation.     

An experimental study of the effectiveness of brainstorming.

In the study of conditions favorable to creativity 2 different ways of conducting brainstorming groups were compared. 3 groups each composed of 7 university students were given instructions to uncritically invent names for 3 kinds of articles; 3 other groups of students each composed of 7 persons were given instructions to also invent names for the same articles only to do so critically. 150 different students rated the invented names of both groups for quality. "For each product, the noncritical condition produced a greater number or responses than the critical condition… . If it is the purpose of problem solving to produce a specific number of ideas of highest possible quality, these best ideas will tend to be of higher or equal quality when the noncritical method is used." From Psyc Abstracts 36:02:2HD45W. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental study of the double bind hypothesis.

The primary aim of the study was to assess whether persons highly conversant with the double bind concept could reliably identify such communication in letters, and, if so, whether its presence or absence was related to the fact of the letter having been written by the parent of a schizophrenic or nonschizophrenic person. The interjudge correlations of the double bind judges were very low, indicating that their judgments regarding presence or absence of double bind communication were not reliable. Other judges achieved statistically significant interjudge reliability and were able to differentiate between letters written by parents of patients and a comparison group. It was concluded from these results that a more critical appraisal of the double bind concept is indicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tooth mobility and resolution of experimental periodontitis. An experimental study in the dog

The aim of the present experiment was to study alterations in the mobility of teeth that occurred during resolution of experimentally induced periodontitis lesions in the dog. 5, 1-year-old, beagle dogs were used in the study. The left and right 4th, 3rd, and 2nd mandibular premolars (4P4, 3P3, 2P2) served as experimental teeth. Periodontal tissue breakdown was initiated by placing plaque-collecting cotton-floss ligatures around the neck of the experimental teeth. The ligatures were replaced to the level of the receding gingival margin 1 x every month. On Day 120, the ligatures were removed and debridement was performed. A groove, parallel to the long axis of the mesial root, was prepared in the mesio-buccal surface of the crowns of 2P and P2. Guided by the groove and with a probing force of 0.5 N, a probe was inserted into the buccal gingival pocket of the mesial root and was attached to the buccal surface. Biopsies including both the mesial and distal root of 2P and P2 and the surrounding hard and soft tissues were harvested. The biopsy procedure was repeated in a similar manner 15 days (i.e. Day 135) and 3 months (i.e. Day 225) after ligature removal in the 4th (4P4) and 3rd (3P3) premolar regions. After fixation, decalcification and sectioning, the biopsy material was exposed to histometric and morphometric measurements. Assessment of the mobility of the experimental teeth was performed on Days 120, 135 and 225 using the Periotest system.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mode of termination of retinotectal fibers in macaque monkey: an autoradiographic study

The distribution of retinotectal projections was studied in 4 macaque monkeys by examining the tectum autoradiographically 3-21 days after eye injection with radioactive proline or a proline-fucose mixture. Contrary to previous reports the optic fibers project to all regions of the tectum including a relatively sparse but nevertheless very clear projection to the anterolateral one-third, where the fovea is represented. Here the terminals were distributed within the superficial grey layer of the tectum at a depth extending from about 50 mum to 125 mum and in a patchy fashion, with a tendency to aggregation in clumps 0.1-0.5 mm wide from one or other eye. Further posteromedially, corresponding to more peripheral retinal regions, the input from the contralateral eye became more continuous superficially, with tongues extending more deeply in the superficial grey, apparently enclosing clumps of ipsilateral terminals. These deeper ipsilateral clumps occupied a rather well defined layer extending in depth from about 100 mum to about 175 mum. Still further posteromedially, in the temporal crescent representation, only the continuously distributed label from the contralateral eye was found. Continuous label was also seen in the optic disc region on the ipsilateral side; on the corresponding area contralaterally, label was absent. Both ipsilaterally and contralaterally, the pattern of input was roughly symmetrical about the representation of the horizontal meridian, which ran from anterolateral to posteromedial. The regional aggregations of input from one or other eye were to some extent reflected physiologically in a regional variation in eye dominance, though this was perhaps less than might have been expected from the marked heterogeneity of the inputs.     

The mucosal attachment at different abutments. An experimental study in dogs

The present experiment was performed to examine if the material used in the abutment part of an implant system influenced the quality of the mucosal barrier that formed following implant installation. 5 beagle dogs were included in the study. The mandibular premolars and the 1st, 2nd and 3rd maxillary premolars were extracted. Three fixtures of the Br?nemark System were installed in each mandibular quadrant (a total of 6 fixtures per animal). Abutment connection was performed after 3 months of healing. In each dog the following types of abutments were used: 2 "control abutments" (c.p. titanium), 2 "ceramic abutments" (highly sintered Al2O3), 1 "gold abutment", and 1 "short titanium abutment". This "short titanium abutment" was provided with an outer structure made of dental porcelain fused to gold. Following abutment connection a plaque control program was initiated and maintained for 6 months. The animals were sacrificed and perfused with a fixative. The mandibles were removed and each implant region was dissected, demineralized in EDTA and embedded in EPON. Semithin sections representing the mesial, distal, buccal and lingual aspects of the peri-implant tissues were produced and subjected to histological examination. The findings from the analysis demonstrated that the material used in the abutment portion of the implant influenced the location and the quality of the attachment that occurred between the periimplant mucosa and the implant. Abutments made of c.p. titanium or ceramic allowed the formation of a mucosal attachment which included one epithelial and one connective tissue portion that were about 2 mm and 1-1.5 mm high, respectively. At sites where abutments made of gold alloy or dental porcelain were used, no proper attachment formed at the abutment level, but the soft tissue margin receded and bone resorption occurred. The abutment fixture junction was hereby occasionally exposed and the mucosal barrier became established to the fixture portion of the implant. It was suggested that the observed differences were the result of varying adhesive properties of the materials studied or by variations in their resistance to corrosion.     

Decadron in the treatment of cerebral abscess. An experimental study

Forty rabbits were inoculated with Streptococcus pyogenes or Staphylococcus aureus to produce cerebral abscesses. One-third of the rabbits received no treatment and served as controls. One-third received dexamethasone (Decadron) plus an appropriate antibiotic. One-third received only the appropriate antibiotic in the same dosage. The animals were sacrificed 10 days after inoculation and the brains examined. In the control group, an abscess at the stage of granulation tissue encapsulation containing the inoculated organisms was found. The surrounding brain showed a marked inflammatory response. In the Decadron plus antibiotic group, necrotic lesions were found containing the inoculated organisms and surrounded by relatively normal brain. In the group treated with antibiotic alone, healed glial scars were found in relatively normal brain. Our findings are discussed with reference to the medical literature regarding the influence of glucocorticoids on the inflammatory response and the efficacy of antibiotics when this response is suppressed.     

Physiopathology of experimental Parkinsonism in the monkey

Postural or Parkinson-like tremor, which results from the impairment of mechanisms which are predominantly lateralized in the brain, is most likely related to the combined impairment of the dopaminergic nigrostriatal pathway and the corresponding rubro-olivo-cerebello-rubral loop (without excluding the possiblity that other nervous mechanisms interconnected with these structures may represent an alternative disturbance). The integrity of the internal division of the pallidum and the ventrolateral area of the thalamus and their efferent fibers as well as the motor cortex and certain of its cortico-subcortico-spinal pathways (Figures 1 and 2) is apparently an essential feature for the elaboration of the rhythmic bursts associated with the appearance of postural tremor. The integrity of the spinal sensory roots and the rubro-tegmentospinal tract is not a prerequisite for the expression of postural tremor, a condition which seems essential for the production of rigidity. The latter facts suggest that the disturbances which subserve these two types of motor impairment, often concomitantly present in Parkinsonism, partially involve the impairment of different mechanisms although the loss of the DA fibers originating in the substantia nigra and ending in the neostriatum (Figure 1) appears to represent a disturbance common to both types of disorders. Bradykinesia which may be associated with an impairment of catecholamine metabolism (and more especially the neostriatal DA mechanisms) on both sides of the brain may also result from bilateral lesions of the pallidum or of its outflow corresponding, in the main, to the pallidothalamic fibers ending in the ventrolateral thalamus. The latter types of lesion most likely exclude the influence of the monoaminergic, cholinergic and gabaminergic activities normally originating in the striopallidal system and influencing the activity transmitted to other CNS mechanisms. Severe akinesia, however, apparently depends on more profound and generalized disturbances of brain monoamine metabolism with or without the involvement of other ill-defined mechanisms. At any rate the impairment of the brain DA mechanisms (and especially those of the neostriatum) seems to represent a major feature in the production of the Parkinsonian type of akinesia. Further work is needed to establish the relative importance of the loss of catecholaminergic mechanisms other than those of the neostriatum in the production of akinesia.     

Percutaneous reinsertion of the nucleus pulposus. An experimental study

STUDY DESIGN: An analysis of the histologic changes in intervertebral discs after percutaneous reinsertion of the nucleus pulposus in rats. OBJECTIVE: To devise a way to delay further disc degeneration resulting from spinal deformity and the adverse effects of various treatments. SUMMARY OF BACKGROUND DATA: The role of the nucleus pulposus of the intervertebral disc described by many investigators has not been fully clarified. METHODS: Disc herniation was induced in the tails of 112 Wistar rats, using a fixation device between the 5th and 8th coccygeal vertebrae. After percutaneous nucleotomy at coccygeal vertebrae 5-6 and 6-7, fresh nucleus pulposus, cryopreserved nucleus pulposus, or an artificial substitute was inserted into the intervertebral disc at coccygeal vertebrae 5-6. Two, 4, or 8 weeks after reinsertion, disc sections from each coccygeal level were studied histopathologically. RESULTS: In the groups with reinsertion of fresh or cryopreserved nucleus pulposus, degenerative changes of the disc with the reinserted nucleus at coccygeal vertebrae 5-6 were milder than those of the disc without reinsertion at coccygeal vertebrae 6-7. However, no apparent benefit from reinsertion was observed in the group with artificial substitutes. CONCLUSIONS: Early reinsertion of the nucleus pulposus (fresh or cryopreserved) delays degeneration of such disc materials as the anulus fibrosus, endplate, and remaining nucleus pulposus.     

An experimental study of cross-cultural norm conflict.

"An experimental study was conducted in which normative conflict of foreign students was examined. From a treatment of norms as force-fields, predictions were made about the resolution of intergroup norm conflict under two conditions of situational potency of membership. It was hypothesized that the resolution of intergroup norm conflict favors the norm of the group whose situational potency is increased. The results obtained did not show the clarity necessary for a definitive validation of the hypotheses. The major analyses led to acceptable levels of significance in only half of the tests made; nevertheless, all the results presented a consistent pattern in harmony with the theoretical formulation." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversibility of medialization laryngoplasty. An experimental study

Medialization laryngoplasty has become a routine procedure for cases of unilateral vocal fold paralysis. In certain clinical situations, it may become desirable to reverse the procedure and remove the implant. This process was studied experimentally in eight dogs in a chronic model of induced canine phonation. A silicone polymer implant was inserted to medialize one normal vocal fold for a period of 1 month, after which it was removed. Motion of the cricoarytenoid (CA) joint and induced phonation were studied weekly while the implant was in place, and for another month following implant removal. Significant abnormalities were found even with this relatively short period of implantation. With the implant in place, impairment of CA joint mobility was found in seven of the eight dogs, precluding phonation. A dense fibrous capsule rapidly developed around the implant, making its removal technically difficult. Following implant removal, a gradual return to normal function was found in only three of the eight dogs. One of the animals had evidence of neural injury, while four had intact neural function but impaired mobility or fixation of the CA joint. Medialization laryngoplasty should not be considered a reversible procedure. The clinical implications of these findings are discussed.     

Regeneration of the spinal ventral roots. An experimental study in cats

From a clinical standpoint recovery of spinal nerve roots is less likely than that of peripheral nerves, despite their identical structures. This may be due to several factors including the length of gap to be bridged, changes in the proximal stump or neuroma, and chromatolysis. In this paper we discuss the roles of some of these factors in relation to the neuronal depopulation in the spinal cord anterior horn area following section of the anterior root. The lack of growth or the successful growth of the axon through the gap in the root influences the degree of depopulation in the anterior horn area.     

The Missouri Mathematics Effectiveness Project: An experimental study in fourth-grade classrooms.

Investigated the effectiveness of an experimental mathematics teaching program. The treatment program was primarily based on a naturalistic study of 40 relatively effective 4th-grade mathematics teachers. Students were tested before and after with a standardized test and a content test (posttest only), which had been designed to approximate the actual instructional content that students had received during the treatment. Observational measures revealed that teachers generally implemented the treatment, and analyses of product data showed that students of treatment teachers generally outperformed those of control teachers on both the standardized and content tests. Since strong efforts were made to control for Hawthorne effects, it seems reasonable to conclude that teachers and/or teaching methods can exert a significant difference on student progress in mathematics. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental study of internalization fantasies in schizophrenic men.

Explored the types of internalization fantasies involving the constructs (or concepts or fantasies) of mother that are ameliorative in schizophrenia, using 120 18–65 yr old male schizophrenics (nonorganic). Four groups of 30 Ss received a subliminal experimental stimulus designed to activate a different fantasy of internalization as well as a subliminal neutral control message. The experimental messages were "Mommy and I are one," "Mommy and I are the same," "Mommy is inside me," and "Mommy and I are alike"; the control message was "People are walking." Assessments of pathological thinking and behavior were made before and after the presentation of each stimulus. Only the stimulus "Mommy and I are one" was effective in reducing pathology. Findings lend strong support to the contention that fantasies of oneness identification with the "good" mother are ameliorative for schizophrenics. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental study of the thematic structure of primal-scene imagery.

Describes an experimental method in which the affective reactions evoked by primal-scene imagination were quantitatively assessed and systematically compared with those reactions evoked by the imagination of other scenes that usually elicit various theoretically related themes. 50 college-age persons, 25 males and 25 females, imagined a scene of their parents engaging in sexual relations, as well as other scenes emphasizing incestuous sexuality, loss and aloneness, or cognitive-confusion themes, and rated their reactions to each. Commonalities in reactions to the primal scene and the other scenes indicated that incest and aloneness themes underlie reactions to primal-scene imagery for this population. Data are consistent with observations from the clinical situation. It is expected that the scene-comparison method, which is a new research technique, will have further application for studies of unconscious processes and mental imagery. (11 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental study of reinforcement and participant satisfaction.

The Es attempted to condition each S to accept a "relayer role" (see 35: 743). The relayer in a 5-man circle net collects information from the participant on one side and then passes that information plus his own to the participant on the other side. He has no opportunity to solve the problem himself. Ss were encouraged to perform the "relayer role" and were told that the group had succeeded only when they performed this role. For the questionnaire administered at the end of Trial 4, all of the satisfaction questions except task interest were interrelated in an essentially unidimensional or single-factored fashion and were significantly corelated with the number of rewards on Trials 1-4. At the end of 10 trials, however, these same items had separated into 2 independent factors. 1 factor repreesnted an evaluation of group performance and was correlated with rewards on Trials 1-10. The 2nd factor represented an evaluation of personal performance and was not related to rewards on Trials 1-10. This latter finding is not surprising in light of the fact that the Ss never did solve the problem themselves and many did not seem to understand who was solving it. The Ss with an understanding of the reward contingencies were more "satisfied" than those who did not believe their productivity was instrumental to reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The distribution of neurotrophin receptor TrkC-like immunoreactive fibers and varicosities in the rhesus monkey brain

The distribution of immunoreactivity for the neurotrophin receptor tyrosine kinase TrkC was examined in the brain of the adult rhesus monkey. TrkC-like immunoreactivity was widespread and consisted primarily of varicose fibers. The most dense populations of fibers were in the basal forebrain (in the cholinergic cell groups Ch1, Ch2 and Ch4), in the raphé complex throughout its rostrocaudal extent, and in the locus coeruleus. Other fibers were present in the thalamus, hypothalamus, central gray matter of the midbrain, dorsal midline of the brainstem and the cerebral cortex. The only neuronal cell bodies with consistent labeling were located in the lateral hypothalamus. Purkinje cells in the cerebellum showed variable labeling. Specific labeling of varicosities and cell bodies was abolished by omission of the primary antiserum or by preabsorption with the TrkC peptide antigen. We conclude that TrkC-like immunoreactivity can be detected in a wide variety of subcortical locations in the adult rhesus monkey. Labeling was particularly prominent in the vicinity of the major cholinergic, serotonergic and adrenergic nuclei, known from other studies to be vulnerable in the ageing brain. This suggests that the ligand for TrkC, neurotrophin-3, may persist as a survival factor for critical neurons into adulthood.     

Guided bone regeneration in long bone. An experimental study

To assess the satisfaction with the department and hospital services provided by a medium-size community hospital during a 2 month period (April-May 1995), 118 randomly chosen patients were asked to complete a questionnaire designed to reflect their opinions during hospitalization. The principal points of the survey concerned the general perception regarding the services in the department and the hospital, the admission and discharge procedures, the quality of food and sanitary conditions, an evaluation of the physicians' and nurses' skill and attitude, as well as their compliance to patients' needs. Overall satisfaction with the medical care was very high, the physicians' attitude and nurses' compliance being the two most important determinants. The role of this type of questionnaire as an instrument for improving health services is emphasized.