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Biomedical subjects

R S Nanda

Publications and source records attributed to R S Nanda.

At least 19 recordsLinked to original sources
PubMed1992

Prediction of cooperation in orthodontic treatment.

A prospective study of patient cooperation with orthodontic treatment was conducted on 100 adolescent patients. Patient, parent, and orthodontist questionnaires were used at three stages of orthodontic treatment. The first was used at the initiation of treatment and the latter two at 6-month intervals. Psychosocial measures from investigators reported in orthodontic patient cooperation literature were screened for use in the present study. These measures included attitudes toward treatment, social desirability, need for approval, and need for achievement. None of the variables selected for this investigation adequately predicted cooperation of a patient in orthodontic treatment. The stepwise regression procedures indicated that inclusion of all variables accounted for 40% of the variability. Variables assessing the orthodontist's perception of orthodontist-patient relationship had the strongest association with patient compliance.

Adolescent↗
PubMed1992

Force degradation of closed coil springs: an in vitro evaluation.

This in vitro study was designed to determine the force degradation of closed coil springs made of stainless steel (SS), cobalt-chromium-nickel (Co-Cr-Ni) and nickel-titanium (Niti) alloys, when they were extended to generate an initial force value in the range of 150 to 160 gm. The specimens were divided into two groups. Group I included SS, Co-Cr-Ni, and two nickel-titanium spring types (Niti 1 and Niti 2), 0.010 x 0.030 inch with an initial length of 12 mm. Group II was comprised of SS, Co-Cr-Ni, and Niti 3 0.010 x 0.036-inch springs, with an initial length of 6 mm. A universal testing machine was used to measure force. A pilot study determined the extension required for each spring type, so that the initial force was in the range of 150 to 160 gm. Initial force was recorded, and then the springs were extended to the respective distances at 4 hours, 24 hours, 3 days, 7 days, 14 days, 21 days, and 28 days resulting in a total of eight time periods. Between the time intervals, all springs were extended to the same initial extension on specially designed racks and stored in a salivary substitute at 37 degrees C. Means and standard deviations of force values, percent force loss, and mean extension were statistically analyzed. All springs showed a force loss over time. Of the total, the major force loss for most springs was found to occur in the first 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

An evaluation of the nasolabial angle and the relative inclinations of the nose and upper lip.

The purpose of this study was to develop a consistent and reproducible method of constructing a nasolabial angle that would also permit an evaluation of the relative inclination of the lower border of the nose and the upper lip, as well as their relationship to each other. Comparison of repeated individual measurements of soft tissue profile landmarks on 15 subjects, as completed by four orthodontists, revealed that the proposed method of constructing the nasolabial angle was consistent and reproducible by the same orthodontist and among different orthodontists. Normative data for the three nasolabial parameters were produced from a sample of 104 young white adults determined by the authors to have well-balanced faces. Mean and standard deviation values from this pooled sample demonstrated a lower border of the nose to Frankfort horizontal plane angle at 18 degrees +/- 7 degrees, upper lip to Frankfort horizontal plane angle 98 degrees +/- 5 degrees, and nasolabial angle 114 degrees +/- 10 degrees. No statistically significant difference was demonstrated between the values for men and women in this study, but the women did have a slightly larger nasolabial angle. A linear comparison of the three nasolabial parameters with six skeletal measurements revealed no significant relationship between the soft tissue profile of the nasolabial region and the underlying skeletal relationships.

Adult↗
PubMed1992

Analysis of soft tissue facial profile in white males.

Three of the integumental variables, namely, the total facial convexity, upper lip to esthetic plane, and lower lip length, showed significant measurement errors in the preadolescent boys. Large standard deviations were also found for several variables in both age groups. This suggests that a range of values, rather than means, should be used in clinical cephalometric evaluations. A table of means, standard deviations, and ranges for the variables evaluated is provided. The nasolabial and the mentolabial angles did not differ significantly between the younger and the older age groups. The total soft tissue facial convexity was noted to have a marginally significant difference between the adults and children. Other variables were significantly different between the two age groups, and indicated that the adults had a relatively straighter facial profile than the children. In addition, the upper and lower lips were more retrusive relative to the esthetic plane in adults. Sagittal proportions relating nasal depth/nose to most protrusive lip/chin to most protrusive lip were found to have a ratio of 2.1:1.0:1.2 in children and 1.8:1.0:0.3 in adults.

Adult↗
PubMed1992

Considerations of dentofacial growth in long-term retention and stability: is active retention needed?

It is extremely important to pay attention to the person's growth pattern, and a distinction must be made in the selection of retention devices on the basis of the nature and the extent of dentofacial dysplasia (growth pattern). The nature and duration of retention should depend on the maturation status of the patient and on anticipated future growth. Retention guidance is necessary for adjustment of the dentition to late growth changes and maturation of neuromuscular balance. "Active retention" is a concept we accept as readily as the orthopedic surgeon does for his scoliosis patients. There is some merit in the philosophy of those clinicians who advocate permanent retention guidance. Without always being aware of the biomechanics of growth change, they are in fact carrying the patient through the active stages of growth with their retention appliances. Finally, one may philosophize that nothing about the human morphology is stationary. Aging is a well-documented process of change. Lifetime dentitional adjustment and changing dental relationships are known to all, even in otherwise healthy persons. Then why do we expect long-term stability in every case? The answer to the question of long-term stability is long-term retention--dynamic, not static.

Adolescent↗
PubMed1992

Fracture strengths of ceramic brackets subjected to mesial-distal archwire tipping forces.

This study tested the strength of ceramic orthodontic brackets subjected to mesial-distal tipping forces on five types of preadjusted, maxillary right central incisor ceramic twin brackets for both 0.018" and 0.022" slot sizes. Description of each bracket was by manufacturer's abbreviation-crystallinity-slot bracket, eg., AL-P-18, meaning Allure-polycrystalline-0.018" slot bracket. Thirty brackets of each type were used for a total of 300 brackets, each bonded to a porcelain denture tooth. A special apparatus was designed to hold the denture tooth, the wire, and the bracket in a standard position while an Instron machine applied a tipping force to the full size rectangular archwire at a distance of 7.0 mm lateral to the center of the bracket. The tipping force was applied until the bracket fractured. The fracture force, fracture angle, and fracture location were recorded. High fracture force values tended to accompany large fracture angles while low fracture force values tended to be associated with small fracture angles. The clinical significance was that the stronger ceramic brackets can be expected to withstand larger amounts of archwire tipping adjustments prior to bracket fracture. With the literature indicating the optimum force for tipping of maxillary incisors to be from 50 to 125 g, all the brackets are sufficiently strong to consistently withstand the suggested magnitude of archwire tipping forces. However, if excessive tipping forces were required by the clinician, ceramic brackets would be prone to fracture.

Ceramics↗
PubMed1992

Blood flow changes in gingival tissues due to the displacement of teeth.

Changes in human gingival blood flow were measured using a Laser doppler flowmeter. The change of blood flow was correlated to the degree of force applied and there were variations in measurement of decreased blood flow among the subjects. The variation was attributed to the degree of tooth displacement and the size of the interdental space. This study examined the effect of tooth displacement on the gingival blood flow, as well as age and sex differences. Blood flow in gingival tissue was measured using a laser doppler flowmeter, and displacement of the maxillary incisors was measured using an eddy current sensor. The correlation coefficient of the decreased blood flow to the tooth displacement was 0.809, and it was higher than that to the degree of applied force (r = -0.625). The regression coefficient of decreased blood flow to the displacement of teeth was significantly correlated to the interdental space. The regression coefficient of decreased blood flow to the percentage of tooth displacement was independent of the interdental space. However, the regression coefficient of decreased blood flow to the percentage of tooth displacement was significantly higher in young subjects than in adults.

Adult↗
PubMed1992

Stability of transient, semirigid pin fixation of sagittal split mandibular osteotomies.

Cephalometric records of 16 patients who underwent mandibular lengthening, stabilized with noncompressive pin fixation, were examined retrospectively. Digitization and computer analyses of the cephalometric changes for various time intervals were performed. All linear changes were stable for 13 of the 16 patients over the follow-up period of 2 years. No significant correlation was found between postoperative horizontal relapse and amount of advancement. A high degree of postfixation stability was obtained with very short fixation periods. While further study of this pin fixation technique is indicated, these preliminary results are favorable.

Adolescent↗
PubMed1991

Fracture resistance of ceramic brackets during arch wire torsion.

The purpose of this study was to determine the fracture resistance of commercially available ceramic brackets during arch wire torsion. Lingual root torque was applied at the distal side of upper central incisor brackets with 0.022-inch slots by means of a 0.0215 x 0.028-inch arch wire. A specially designed apparatus was used to test six types of ceramic bracket in sample groups of 30. The amount of torque and degrees of torsional rotation at fracture were measured. The ceramic brackets could be separated into three statistically different groups with mean torques at fracture ranging from 3,706 to 6,177 gm-mm. The mean torsional rotation at fracture ranged from 9.5 degrees to 17.8 degrees. The single-crystal alumina bracket had the most intragroup variation. Eight to ten degrees of torsional rotation of the arch wire produced sufficient orthodontic force to achieve the torque. The fracture resistance of the ceramic brackets appears to be adequate for clinical use. The Starfire, Allure III, and Transcend brackets had the highest fracture resistance values.

Aluminum Oxide↗
PubMed1991

The effects of extraction and nonextraction treatment on the mandibular position.

Decisions on extraction of teeth as an aid in orthodontic treatment depend on dental and skeletal discrepancies concerning sagittal and vertical relationships. The purpose of this study was to assess the effects of extraction and nonextraction procedures on the posterior rotation of the mandible and the position of gnathion. Forty-eight nonextraction patients and seventy-three extraction patients treated in the orthodontic department were selected. The patients were from 11 to 15 years old, with a mean age of 12 years 2 months. The lateral cephalometric radiographs taken before and after treatment were traced and measured. Eleven variables reflecting the mandibular rotation were selected on the basis of factor analysis. Before treatment, total arch circumferential discrepancy and the 11 selected measurements showed significant differences between the extraction and nonextraction groups. In the extraction group, the lower anterior facial height was larger, ramus height was smaller, and the difference between vertical position of both maxillary and mandibular first molars and posterior facial height was greater than in the nonextraction group. Consequently, the mandible showed posterior rotation and was in retruded position in the extraction group. In the nonextraction group, the type of force application had no significant effect on the changes in skeletal and dental measurements. In the extraction group, however, the type of force application had a significant effect (p less than 0.05) on the changes in total anterior facial height, the horizontal distance of the maxillary first molar to a perpendicular line to the S-N plane passing through point S, the vertical distance of the maxillary molar to the S-N plane, the vertical distance of the maxillary and mandibular first molars to the S-N plane, the difference between the vertical position of the first molars and posterior facial height, and the difference between the vertical position of the first molar and vertical height of the ramus. In the group in which high-pull face-bow headgear was used, the extraction/nonextraction procedures had a significant effect (p less than 0.05) on the changes in angle ANB, total anterior facial height, anterior lower facial height, and the difference between anterior and posterior facial height.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1991

Mandibular arch perimeter changes with lip bumper treatment.

The effects of lip bumper treatment on the mandibular arch were observed in 32 patients with late transitional and early permanent dentitions. Dental cast measurements were made for arch perimeter, arch length, and arch width. Cephalometric radiographs were used to determine labial tipping of the incisors and distal movement of the molars. Arch circumference increased in all patients, ranging from 0.7 mm to 8.8 mm, with an average of 4.1 mm. The mean increase in arch length was 1.2 mm and was largely attributed to anterior tipping of the mandibular incisors. Change in arch length was the most predictive variable for the increase in arch circumference. Passive changes in arch width were recorded, with a mean increase of 2.0 mm in the intercanine distance and 2.5 mm in the first premolar distance. Arch width increments contributed to the increase in arch circumference, but the increases in arch width were not found to be predictive of the change in arch circumference. Changes in either arch circumference or arch length were not related to the duration of treatment, age and sex of the patient, or the eruption status of the permanent second molars.

Activator Appliances↗
PubMed1991

Effect of orthodontic forces on blood flow in human gingiva.

The relationship of gingival blood flow to the magnitude and duration of applied force was studied in humans using Laser Doppler flowmetry. The sample consisted of five adult volunteers with interdental space between their maxillary central incisors. The labial surface of each central incisor was bonded with a buccal tube and a spring force was applied to close the space. The forces applied were 50 g, 80 g, 120 g, and 250 g. Each force was applied for 30 seconds, 60 seconds, 90 seconds, 5 minutes, and 10 minutes. The blood flow signals were recorded continuously using a pen recorder. Measurements indicated that blood flow was negatively correlated to the amount of force applied. The duration of reactive hyperemia was positively correlated to the duration of force. Laser Doppler flowmetry measures blood flow in superficial periodontal tissues. Yet, the relationship of blood flow changes to the magnitude and duration of orthodontic force suggests that measurements of gingival blood flow may provide a means of estimating physiologic orthodontic forces.

Adult↗
PubMed1991

[The profile and tegmental growth].

This work is about perceptions of "professionals" in projection of part of nose, lips and chin relations in well-balanced facial profile achievement and change in facial profile during the growth between 7 and 18 years. It's the first part of our research.

Adolescent↗
PubMed1990

Assessment of the stability of mandibular setback procedures with rigid fixation.

The postsurgical changes associated with sagittal ramus osteotomy and mandibular setback stabilized with rigid fixation were evaluated. Lateral cephalometric radiographs of 25 individuals (11 males and 14 females) with a mean age of 23.4 years were evaluated presurgery, immediate postsurgery, and after a follow-up period of 7 to 42 months. The mean amount of surgical setback was 5.1 +/- 3.0 mm and the mean amount of postsurgical anterior movement was 0.51 +/- 1.04 mm, representing a 10% relapse of the original surgical correction. The postsurgical relapse of the mandible was not found to be related to the amount of surgical movement. Sixteen of the 18 cases that demonstrated anterior relapse moved forward between 0.5 and 1.5 mm. The amount of relapse was consistent and statistically significant (P less than .05), but small enough that it was not considered to be clinically significant. The findings of this study indicate that mandibular setback with a sagittal ramus osteotomy and its stabilization with rigid fixation appears to be a stable clinical procedure.

Adult↗
PubMed1990

Evaluation of friction between edgewise stainless steel brackets and orthodontic wires of four alloys.

This investigation was designed to determine the effects of wire size and alloy on frictional force generated between bracket and wire during in vitro translatory displacement of bracket relative to wire. Stainless steel (SS), cobalt-chromium (Co-Cr), nickel-titanium (NiTi), and beta-titanium (beta-Ti) wires of several sizes were tested in narrow single (0.050-inch), medium twin (0.130-inch) and wide twin (0.180-inch) stainless steel brackets in both 0.018- and 0.022-inch slots. The wires were ligated into the brackets with elastomeric ligatures. Bracket movement along the wire was implemented by means of a mechanical testing instrument, and frictional forces were measured by a compression cell and recorded on an X-Y recorder. beta-Ti and NiTi wires generated greater amounts of frictional forces than SS or Co-Cr wires did for most wire sizes. Increase in wire size generally resulted in increased bracket-wire friction. The wire size-alloy interaction on the magnitude of bracket-wire friction was statistically significant (p less than 0.005). With most wire sizes and alloys, narrow single brackets were associated with lower amounts of friction than wider brackets were. The levels of frictional forces in 0.018-inch brackets ranged from 49 gm with 0.016-inch SS wires in narrow single brackets to 336 gm with 0.017 x 0.025-inch beta-Ti wires in wide twin brackets. Similarly for 0.022-inch brackets, frictional forces ranged from 40 gm with 0.018-inch SS wires in narrow single brackets to 222 gm with 0.019 x 0.025-inch NiTi wires in wide twin brackets.

Analysis of Variance↗
PubMed1990

Evaluation of friction between ceramic brackets and orthodontic wires of four alloys.

The purpose of this investigation was to determine the frictional resistance offered by ceramic brackets used in combination with wires of different alloys and sizes during in vitro translatory displacement of brackets. Findings with ceramic brackets were also compared with outcomes of treatment with stainless steel brackets. Stainless steel, cobalt-chromium, beta-titanium, and nickel-titanium wires of different cross-sectional sizes were tested in medium-twin monocrystalline ceramic brackets with both 0.018-inch and 0.022-inch slot sizes. The wires were ligated into the brackets with elastomeric modules. Brackets were moved along the wire by means of an Instron universal testing machine, and frictional force was measured by a compression cell and recorded graphically on an xy recorder. Wire friction in the ceramic brackets increased as wire size increased, and rectangular wires produced greater friction than round wires. Beta-titanium and nickel-titanium wires were associated with higher frictional forces than stainless steel or cobalt-chromium wires. These findings follow the same general trends as those found with stainless steel brackets; however, wires in ceramic brackets generated significantly stronger frictional force than did wires in stainless steel brackets.

Analysis of Variance↗
PubMed1990

An evaluation of the shape-memory phenomenon of nickel-titanium orthodontic wires.

This investigation was undertaken to quantitatively analyze the shape-memory phenomenon of wires made of seven commercially available nickel-titanium alloys. The shape memory was determined by calculation of the percent shape recovery that occurred when the wire of each alloy was first plastically deformed below its TTR and then heated to a temperature above its TTR. The findings indicate that: 1. The mean percent recovery ranged from 89% to 94% for Ni-Ti, nitinol, Orthonol, Titanol, Sentinol Light, and Sentinol Medium alloys. The Sentinol Heavy alloy showed a mean recovery of 41.3%, which was significantly less than that of the other alloys. 2. It appears that Sentinol Heavy wire showed relatively less percent recovery because its TTR was close to room temperature. This resulted in minimal plastic deformation, because the alloy recovered its original length almost immediately, and this also indicates the importance of a proper TTR. It was concluded that the TTR should be reasonably higher than the oral temperature for clinical application of the shape-memory phenomenon of nickel-titanium alloys. 3. The heat-recovery temperature was kept to 300 degrees F in this study for maximum possible recovery. Although the results indicate that the recovery was around 90% for most alloys tested, future studies are required to determine the shape recovery at or just above oral temperature.

Dental Alloys↗