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Biomedical subjects

R Nanda

Publications and source records attributed to R Nanda.

At least 91 records · Page 5Linked to original sources
PubMed1980

Biomechanical and clinical considerations of a modified protraction headgear.

The choice of treatment of children with developing skeletal Class III malocclusions has always posed a dilemma. Chin cups and various types of reverse headgears with elastics have been used in the past to minimize the growth and development discrepancy of the midface and the mandibular bones. In the present article, a critique of commonly used protraction devices is presented. A modified protraction headgear design and the biomechanical considerations of its clinical use are presented in this study. The clinical results show that a modified protraction headgear with a chin cup helps in the correction of moderately severe Class III malocclusions by the anterior displacement of the maxilla and maxillary dentition, and possibly restricting or changing the direction of the growth of the mandible. This headgear can also be used to correct axial inclinations and/or mesial displacement of posterior teeth.

Activator Appliances↗
PubMed1980

Biomechanical approaches to the study of alterations of facial morphology.

An analysis of past experimental and clinical studies on orthopedic changes of craniofacial bones is presented. The theoretical aspects and technical improvements necessary for relating biomechanical principles to attain the desired alterations in craniofacial morphology are discussed. A critical evaluation of the past measurements and histologic techniques is also presented. Suggestions are given for directions to future research methodology which can offer reliable results.

Animals↗
PubMed1979

Effect of metabolic alteration of periodontal fibers on orthodontic tooth movement. An experimental study.

In the present study orthodontic force was applied to the molars of rats treated with the lathyrogen beta-aminopropionitrile (BAPN). New bone formation was measured at two alveolar locations after 9 days of force application. Observation resulted in the following conclusions: 1. New alveolar bone formation in response to orthodontic force in BAPN-treated rats statistically exceeded corresponding bone formation in control animals when measured at two tension sites in the periodontal ligament. 2. BAPN administration produced disorganization of the collagenous fibers of the periodontium of experimental animals. Multiple eosinophilic cell-free areas were found distributed throughout the radicular portions of affected periodontal ligaments. Normal ligament function architecture was disrupted in treated animals. The areas of periodontium surrounding orthodontically treated teeth exhibited relatively normal organization under these conditions, while the periodontium of adjacent nonorthodontically treated teeth was markedly disorganized. Orthodontic stimulation of the periodontium of BAPN-treated rats may have disrupted the formation of eosinophilic cell-free areas characteristically seen in the periodontium of the experimental group. 3. The present results suggest that the typical histologic response to orthodontic force application can occur in the presence of a chemically and physically altered periodontium. The quantitative data collected infer that fiber tension on the alveolus may not be absolutely necessary to stimulate bone formation. Distortion of the alveolus related to force application may be a more important factor initiating bone response. However, the fibers of the periodontium may play a passive role in transferring orthodontic force to the alveolus.

Alveolar Process↗
PubMed1979

Fetal skeletal malformations associated with moderate zinc deficiency during pregnancy.

This study investigated the effects of moderate zinc deficiency on the development of rat fetal skeleton. Eighteen pregnant rats were fed zinc deficient diet (1.3 ppm) from days 3 to 15 of gestation. An additional 18 rats were pair fed the same diet supplemented with 100 ppm zinc and served as controls. The levels of zinc in plasma were determined on days 15 and 20 of gestation and in the amniotic fluid on day 20. The pregnant rats were killed on day 20 and fetuses were cleared and stained with alizarin red. The weight of zinc deficient fetuses was significantly less than that of controls. The uncleared, as well as stained zinc supplemented fetuses, showed no anomalies. The alizarin stained experimental fetuses showed severe anomalies of long bones, vertebrae, and ribs. The overall calcification of bones was also considerably less as compared to zinc supplemented controls. The zinc levels were significantly less in plasma (day 15) and amniotic fluid (day 20) of experimental dams. The results also indicated that although moderate zinc deficiency does not cause external craniofacial malformations, it severely affects the calcification and development of cranial bones.

Amniotic Fluid↗
PubMed1978

Craniofacial adaptations after total maxillary osteotomy in Macaca irus: a cephalometric and histologic study.

Five Macaca irus monkeys were used in this study to determine cephalometric and histologic changes after total maxillary impactions. In the three experimental animals, the maxilla was impacted 5 to 7 mm. and lateral cephalograms were taken over a 150-day period. By superimposing on craniofacial implants, osseous and dental changes were measured. Excellent skeletal stability was demonstrated during the postoperative period. Histologically, there was normal osseous healing of the osteotomized maxillas. Accompanying the counterclockwise rotation (overclosure) of the mandible, there was extensive change in the temporomandibular joint. In the experimental monkeys, the fibrous articular covering of the temporal fossa was thin and irregular. The condylar cartilage appeared atrophic and showed considerable aging; also, the articular disc was much thicker in the experimental animals. The study showed the superiorly repositioned total maxillary osteotomy to be a stable procedure after 150 days of postoperative observation. However, further studies are needed to investigate the neuromuscular and adaptive response of temporomandibular articulation and mandibular rest position after maxillary surgical procedures.

Animals↗
PubMed1977

Effect of intraamniotic administration of vitamin A on rat fetuses.

The present study examines the effect of intraamniotic (i/a) administration of vitamin A to rat fetuses. Vitamin A aquasol in concentrations of 50 I.U., 100 I.U., and 300 I.U., was mixed in 5 microliter of saline. On day 13 of gestation, each of the tree experimental subgroups were injected i/a with varying doses of vitamin A. The four control subgroups consisted of: (1) i/a injection of 5 microliter of saline only, (2) amniotic puncture only, (3) laparotomy or (4) i/a injection of sorethytan oleate. The fetuses were recovered on day 18 of gestation, and were weighed and examined for gross malformations. The viable fetuses from the experimental groups showed various malformations such as cleft palate, micrognathia and limb defects. The percentage of resorbed fetuses was significantly high. The control fetuses showed a moderate number of resorptions; however the percentage of malformations was small. The results show that the i/a method can be used effectively to study the direct teratogenic effect of vitamin A on the fetuses.

Abnormalities, Drug-Induced↗
PubMed1977

Salivary phenytoin radioimmunoassay. A simple method of the assessment of non-protein bound drug concentrations.

A simple, specific and rapid radioimmunoassay (RIA) method for the assessment of non-protein bound ('free') phenytoin (DPH) concentrations in mixed saliva is described. Epileptic patients on maintenance phenytoin therapy have mixed saliva phenytoin concentrations similar to 'free' drug levels measured directly in serum or cerebrospinal fluid (CSF), Salivary phenytoin levels are approximately 10% of the total serum level in treated epileptic patients and in normal subjects after ingestion of a single oral dose. The half time of disappearance of phenytoin after 100 or 300 mg doses is 12.2 +/- 3.0 (SD) h in serum and 12.3 +/- 3.2 (SD) h in saliva. This method of assessing the biologically active fraction of the drug may be particularly valuable in situations where serum protein binding is abnormal or in drug interactions. It is also non-invasive and requires small sample volumes (20mul) and may therefore be valuable in paediatric practice and in pharmacokinetic studies in which multiple venepunctures would otherwise be required.

Adult↗
PubMed1977

The effects of feeding a zinc-deficient diet on taste acuity and tongue epithelium in rats.

Taste preferences, fluid intake and histology of tongue epithelium were studied in rats fed a zinc-deficient diet and in pair-fed controls. The results of two-bottle preference tests demonstrated that zinc-deficient rats exhibited significantly increased preferences for 1.5 X 10(-1) M HCL and 1.28 X 10(-6) M quinine sulfate as well as a significant increase in relative fluid volume intake. Histologic examination of the tongue epithelium of the zinc-deficient rats showed a hypercellular prickle cell layer and a marked parakeratosis. The fungiform papillae of the zinc-deficient rats exhibited acanthosis and mild parakeratosis. However, the pore region of the taste buds did not seem to be covered by the parakeratotic epithelium. The results suggest that the impaired taste observed in zinc-deficient rats may not be related to blockage of tastants from the pore region.

Animals↗
PubMed1975

Differential cell proliferation of embryonic rat palatal processes as determined by incorporation of tritiated thymidine.

The differential cellular proliferation of the palatal processes in the Wistar albino rat was studied utilizing tritiated thymidine labeling. 3HTdr was given to pregnant rats at 14, 15, 16, and 17 days of gestation. The animals were killed one hour after injection. The fetuses were removed and the heads were embedded, sectioned, and an autoradiographic technique utilized. The autoradiograms were examined microscopically and labeling indices for various areas and regions of the palatal processes were calculated. The findings revealed that the pattern of cellular activity of mesenchymal and epithelial cells changes in different areas and regions of the palatal processes with different stages of secondary palate development.

Animals↗