Biomedical subjects

R S Nanda

Publications and source records attributed to R S Nanda.

At least 19 recordsLinked to original sources

PubMed1996

Perceived orthodontist behaviors that predict patient satisfaction, orthodontist-patient relationship, and patient adherence in orthodontic treatment.

Orthodontist-patient relationships have significant effects on the success of orthodontic treatment. The purpose of this study was to evaluate the effects of patient-perceived orthodontist behaviors on (a) patient perceived orthodontist-patient relationship, (b) patient satisfaction, and (c) orthodontist-evaluated patient adherence or compliance in orthodontic treatment. The sample consisted of 199 orthodontic patients, 94 boys and 105 girls, ages 8 to 17 years, who were recruited at the beginning of orthodontic treatment by a member of the research team who was not involved in treating the patients. The patients were asked to complete standardized questionnaires in a room away from the orthodontic clinic, 8 to 12 months into treatment. At the same time, the orthodontic resident treating each patient completed a standard instrument that evaluated patient compliance. Orthodontist behavior items such as politeness, friendliness, communicativeness, and empathy were evaluated by the patients. Stepwise multiple regression analyses (p < 0.05) showed that eight behaviors predicted perception of the orthodontist-patient relationship (final model R2 = 0.7930 and 0.7333) as well as patient satisfaction (final model R2 = 0.7952) and two behaviors predicted patient compliance (final model R2 = 0.0986). Of the 24 orthodontist behaviors, 22 were significantly correlated (p < 0.0001) with favorable orthodontist-patient relationship and patient satisfaction. Of the 24 behaviors, 10 were significantly correlated (five at p < 0.01 and five at p < 0.05) with patient compliance. Patient-perceived orthodontist behaviors are related to and predict (1) patient perceived orthodontist-patient relationship, (2) patient satisfaction, and (3) orthodontist-evaluated patient adherence or compliance.

Adolescent↗

PubMed1996

Frictional resistances in stainless steel bracket-wire combinations with effects of vertical deflections.

This research evaluated the effects of different bracket-wire combinations and second-order deflections on kinetic friction. Thirteen different brackets, six with 0.018 x 0.025 inch slots and seven with 0.022 x 0.028-inch slots were evaluated with six different sizes and shapes of stainless steel orthodontic wire, i.e., 0.016, 0.016 x 0.022, 0.017 x 0.025, 0.018, 0.018 x 0.025 and 0.019 x 0.026 inch for four second order deflections of 0.00, 0.25, 0.50, and 0.75 mm. The wires were ligated into the brackets with elastomeric modules. Bracket movement was implemented by means of an Instron universal testing instrument (RMO, Denver, Colo.), and frictional forces were measured by a tension load cell and recorded on an X-Y recorder (Hewlett-Packard, Anaheim, Calif.). Second-order deflection was created by a specially designed and machined testing apparatus that allowed two alternate pairs of the four total brackets to be offset in increments of 0.25 mm. The kinetic frictional force increased for every bracket-wire combination tested as the second-order deflection increased. Friction also increased with an increase in wire size, whereas rectangular wires produced greater friction than round wires. Bracket designs that limited the force of ligation on the wire generated less friction at low second-order deflections (0.00 and 0.25 mm).

Dental Stress Analysis↗

PubMed1996

The effects of exogenous prostaglandin E2 on root resorption in rats.

This study evaluated the amount and depth of root resorption associated with varying concentrations and frequencies of injectable, exogenous prostaglandin E2 (PGE2) in conjunction with orthodontic tooth movement in rats. The sample consisted of 155 maxillary right and left first molars from 88, 8-week old, male Sprague-Dawley rats. The animals were divided into three control groups and two experimental groups. The control animals were divided into one nonappliance and two appliance groups. The experimental animals were divided into 2- and 4-week experimental time periods that were further subdivided based on single and weekly injection intervals of PGE2 and four different injectable concentration levels, i.e., 0.1, 1.0, 5.0, and 10.0 micrograms. A fixed orthodontic appliance was ligated between the maxillary incisors and maxillary first molars with closed-coil nickel-titanium springs. The appliance had an initial activating force of 60 gm. Serial histologic sections of the mesial root of the maxillary first molar were made, and a quantitative histomorphometric analysis of root resorption on the mesial and distal surfaces was performed. This study demonstrated increased root surface resorption when using exogenous PGE2 injections to enhance orthodontic tooth movement over a 2-week period with increasing root resorption on the mesial surface as compared with the distal surface in PGE2 treated teeth. No differences in root resorption were found with either multiple injections or increasing concentration in the 4-week experimental group. Local injection of PGE2 appeared to have no effect on the number or depth of resorption lacunae in either the 2- or 4-week groups.

Analysis of Variance↗

PubMed1996

A study of force application, amount of retarding force, and bracket width in sliding mechanics.

We investigated the relationship of the retraction force to the location of force application, retarding force and bracket width during simulated sliding tooth movement along an arch wire. Point 1 for retraction was located at the center of the bracket, and points 2 and 3 were at 4.0 mm and 6.0 mm from the bracket slot, respectively. Weights of 100 gm, 200 gm, and 400 gm were suspended at 9.0 mm from the bracket slot as the point of simulated center of resistance. Stainless steel standard edgewise wide, medium, and narrow twin brackets were engaged with two elastomeric ligatures on a stainless steel wire (0.016 x 0.016 inch). The bracket was retracted at the rate of 0.1 mm per second for a distance of 2.0 mm. Measurements were repeated six times, and the results were compared with multiple ANOVA tests. For all brackets, with an increase of the retarding weight, the mean retraction force at points 1 and 2 increased but decreased at point 3. The mean retraction force at point 1 for the narrow twin bracket was significantly (p < 0.05) higher than that for the wide twin bracket at all retarding force levels. However, the mean retraction force at points 2 and 3 for the narrow twin bracket was significantly (p < 0.05) lower than for the wide twin bracket at all retarding force levels. These findings indicated that the point of force application, the resistance force of a tooth, and the width of the bracket are crucial in consideration of the tipping moments on the bracket.

Analysis of Variance↗

PubMed1996

A longitudinal cephalometric study of the soft tissue profile of short- and long-face syndromes from 7 to 17 years.

The longitudinal growth and development of the soft tissue drape for boys and girls with long and short vertical patterns was examined from age 7 to 17 years. The sample was taken from the Denver Growth Study and consisted of 32 subjects who were selected on the basis of their percentage of lower anterior vertical face height. All subjects were of northern European ancestry, and none had undergone orthodontic treatment. The sexual dimorphism was evident as anticipated for several soft tissue measurements. The boys showed continued growth through age 16 years in contrast to the girls who attained the adult size of the soft tissue integument around 14 years. A significant difference between vertical facial patterns was reported for all soft tissue variables with the exception of the soft tissue thickness at A point and the upper lip height. The boys and girls with long vertical patterns exhibited a thicker and longer soft tissue drape for the most variables when compared with those with short facial patterns. These soft tissue differences are believed to be compensatory mechanisms in long-face subjects, which may attempt to mask the vertical dysplasia, thereby producing a more normal facial profile. Individual growth assessments revealed that the perioral soft tissues follow a pattern similar to that of the mean group patterns. The subjects with long vertical facial patterns experienced their pubertal growth spurt earlier than the short-face subjects. This may have clinical implications in the timing of orthodontic intervention and treatment.

Adolescent↗

PubMed1996

Evaluation of an intraoral maxillary molar distalization technique.

The purpose of this study was to determine the effects of the pendulum appliance on distalization of maxillary molars and the reciprocal effects on the anchor premolars and maxillary incisors. Initial and follow-up cephalometric radiographs were obtained on 41 subjects (26 girls and 15 boys) who were treated with the pendulum appliance for bilateral distalization of the maxillary first molar teeth, for correction of the Class II molar relationship or for gaining space in the maxillary arch. Dental casts were available on 31 patients. Dental, skeletal, and soft tissue changes were determined. The mean maxillary first molar distalization was 3.37 mm, with a distal tipping of 8.36 degrees. The mean reciprocal mesial movement of the first premolar was 2.55 mm, with a mesial tipping of 1.29 degrees. The maxillary first molar position intruded 0.1 mm, whereas the first premolar extruded 1.7 mm. The transverse width between the mesiobuccal cusps of the first molars increased 1.40 mm. The maxillary second molars were also distalized 2.27 mm, tipped distally 11.99 degrees, and moved buccally 2.33 mm. The effect of distalization on the maxillary third molars was extremely variable. The eruption of maxillary second molars had minimal effect on distalization of first molars. The lower anterior face height increased by 2.79 mm. This increase was greater in patients with higher Frankfort-mandibular plane angle measurements. The pendulum appliance is an effective and reliable method for distalizing maxillary molars, provided the anchor unit is adequately reinforced. Its major advantages are minimal dependence on patient compliance, ease of fabrication, one-time activation, adjustment of the springs if necessary to correct minor transverse and vertical molar positions, and patient-acceptance.

Adolescent↗

PubMed1996

Class II, Division 1 malocclusion treated with molar distalization therapy.

A case report of an 11-year-old black girl with a Class II, Division 1 malocclusion is presented. There was associated lip incompetence and excessive display of gingiva on smiling. Nonextraction treatment was undertaken with distalization of maxillary molars to correct the Class II relationship. [This case was presented at the annual session of the American Association of Orthodontists held in Orlando, 1994. This was part of the University of Oklahoma, Department of Orthodontics participation in the display of patients treated by graduate students sponsored by the College of Diplomates, American Board of Orthodontics.]

Cephalometry↗

PubMed1996

Tomographic assessment of temporomandibular joints in patients with malocclusion.

There is a paucity of information on the morphological assessment of the temporomandibular joint in relation to varying skeletal and dental relationships. The purpose of this study was to evaluate the morphologic relationship of the condyle and fossa in patients with different malocclusions and skeletal relationships. Pretreatment records of 232 orthodontic patients, 95 males and 137 females, of Caucasian descent and ranging in age from 9 years 4 months to 42 years 6 months, were examined. Records included dental casts, lateral cephalometric radiographs, hand-wrist radiographs, and corrected tomograms of right and left TM joints. Nonconcentricity and mild asymmetry of the condyle-fossa relationship were commonly observed. The left condyle was found to be more anteriorly positioned than the right, with the mean percentage of joint space being 6.93% on the left side and -1.24% on the right. Skeletal and dental Class III patients demonstrated significantly more anteriorly positioned condyles (P < 0.05). There were no significant differences in condylar position between Class I and Class II groups based on ANB or Angle's classification. Further, no significant difference in condylar position was observed between groups based on overbite or crossbite.

Adolescent↗

PubMed1996

Three-dimensional facial analysis using a video imaging system.

The purpose of this article was twofold: (1) to provide an estimate of error in the digitization of various soft tissue landmarks using a video imaging system, and (2) to evaluate the relationships of various soft tissue measurements in balanced young adult faces. A video imaging system was used to digitize frontal and lateral soft tissue landmarks on 25 male and 25 female Caucasian young adults with Class I occlusion and esthetically pleasing and balanced soft-tissue profiles. Twenty subjects were redigitized and only two measurements showed a statistically significant error. Large variabilities were found for several measurements. Males, in general, had greater soft tissue thickness, facial depth and width, and lip length than females. The measurements were found to compare favorably with previous reports. Imaging systems were seen to have the advantage of providing reliable measurements in all three dimensions without the potential hazards of ionizing radiation.

Adult↗

PubMed1996

Fracture strength of ceramic brackets during arch wire torsion.

This study evaluated the fracture strengths of eight new vintage ceramic brackets with application of torsional forces. Palatal root torque was applied at the distal side of right maxillary central incisor brackets with 0.022-inch slots by means of a 0.0215 x 0.027-inch rounded edge stainless steel arch wire. A specially designed apparatus that attached to an Instron machine was used to test the ceramic brackets. The amount of torque, degrees of torsion at failure, and fracture locations were measured. The monocrystalline bracket did not break when the torquing test was applied; the portion of the wire outside the slot of the bracket twisted on itself. The mean torquing forces at failure ranged from 5755.2 gm-mm to 9316.5 gm-mm and could be separated into three statistically different groups. The mean torsional rotation at fracture ranged from 32.7 degrees to 68.1 degrees for the polycrystalline brackets. The results suggested that all the brackets studied were sufficiently strong to withstand the commonly accepted magnitudes of arch wire torquing forces. The present investigation showed higher angulation values for all the brackets than those reported by Holt who used the same apparatus with older style brackets.

Analysis of Variance↗

PubMed1995

Ceramic bracket design: an analysis using the finite element method.

This investigation was designed to generate finite element models for selected ceramic brackets and graphically display the stress distribution in the brackets when subjected to arch wire torsion and tipping forces. Six commercially available ceramic brackets, one monocrystalline and five polycrystalline alumina, of twin bracket design for the permanent maxillary left central incisor were studied. Three-dimensional computer models of the brackets were constructed and loading forces, similar to those applied by a full-size (0.0215 x 0.028 inch) stainless steel arch wire in torsion and tipping necessary to fracture ceramic brackets, were applied to the models. Stress levels were recorded at relevant points common among the various brackets. High stress levels were observed at areas of abrupt change in geometry and shape. The design of the wire slot and wings for the Contour bracket (Class One Orthodontic Products, Lubbock, Texas) and of the outer edges of the wire slot for the Allure bracket (GAC, Central Islip, N.Y.) were found to be good in terms of even stress distribution. The brackets with an isthmus connecting the wings seemed to resist stresses better than the one bracket that did not have this feature. The design of the isthmus for the Transcend (Unitek/3M, Monrovia, Calif.) and Lumina (Ormco, Glendora, Calif.) brackets were found to be acceptable as well. The Starfire bracket ("A" Company, San Diego, Calif.) showed high stresses and irregular stress distribution, because it had sharp angles, no rounded corners, and no isthmus. The finite element method proved to be a useful tool in the stress analysis of ceramic orthodontic brackets subjected to various forces.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Oxide↗

PubMed1995

Bond strengths and remnant adhesive resin on debonding for orthodontic bonding techniques.

Bond strengths and remnant adhesive resin on the tooth surface after debonding for three bonding techniques used to attach foil mesh orthodontic brackets to 315 freshly extracted bovine incisor teeth were compared in an in vitro study. Each method of bonding used 105 teeth in groups of 15, bonded with seven different (bis-GMA type) two-paste chemically cured resins. The direct method comprised bonding the attachments directly to the incisors with the composite resin. The indirect-1 method comprised securing attachments to die-stone models of the teeth with a water soluble glue, making silicone positioners to transfer the brackets from the models to the teeth, and bonding to the teeth with the use of the two-paste composite resin system. The indirect-2 method comprised bonding the attachments to die-stone models of the teeth with composite resin, making silicone positioners to transfer the brackets from the models to the teeth, and bonding to the teeth with the use of unfilled sealant resin. Significant differences in bond strength existed among the groups evaluated. The direct technique had statistically significant (p < 0.05) higher bond strength as compared with the indirect-1 and indirect-2 techniques in four of the seven groups evaluated. The indirect-1 and indirect-2 techniques were not significantly different (p < 0.05) in bond strength in six of seven groups tested. The indirect-2 technique had significantly lower adhesive remnant index scores (ARI) compared with the direct and indirect-1 techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗

PubMed1995

The effects of exogenous prostaglandins on orthodontic tooth movement in rats.

The long-term effects of varying concentrations and frequencies of injectable, exogenous prostaglandin E2 (PGE2) on the rate of tooth movement and the amount of root resorption were evaluated. There were 132 male Sprague-Dawley rats 8 weeks old that initially weighed 225 to 250 gm. Five animals were in a pilot study, while seven were baseline controls and eight were appliance controls. The remaining 112 animals were divided into two experimental time periods of 2 and 4 weeks. Then, each experimental time period was divided into four subgroups of 14 animals based on concentration levels of PGE2 injections, i.e., 0.1, 1.0, 5.0 and 10.0 micrograms. Half of these animals in the dosage subgroup received a single injection at appliance placement and the other half received weekly injections. A fixed orthodontic appliance consisting of closed-coil nickel-titanium springs were ligated between the maxillary incisors and maxillary first molars. The initial activating force was 60 gm. The results showed that injections of exogenous PGE2 over an extended period of time in rats did enhance the amount of orthodontic tooth movement. However, there was no statistically significant difference in tooth movement between the single and multiple injection groups or among the four concentration levels of PGE2 used in either the 2- or 4-week time periods. The amount of root resorption as seen from scanning electron micrographs did increase with the use of prostaglandin injections, specifically with increased numbers of injections and with increased concentrations of PGE2.

Anesthetics, Local↗

PubMed1995

Interlayer formation and its effect on debonding polycrystalline alumina orthodontic brackets.

During the debonding of ceramic orthodontic brackets, there is a risk of causing fractures, cracks, or flaking of enamel or of the bracket itself. Preliminary work on the resin-enamel interface under bonded brackets with the indirect (modified Thomas) or the thermal-cured indirect bonding techniques revealed an interlayer of unfilled resin formed between the filled resin and the enamel surface. The direct bonding technique, on the other hand, showed no such layer. This study was designed to determine the effect of the interlayer on conventional debonding techniques for polycrystalline ceramic orthodontic brackets. Variables examined were bracket failure or fracture (BF), amount of remnant adhesive (ARI), and enamel damage. Brackets were bonded to 90 fresh bovine teeth. These were divided into three groups of 30 each, based on three methods of bonding, i.e., direct, indirect (modified Thomas), and an indirect technique that used a thermal-cured resin. Each bonding group was further divided into three groups of 10 each, based on the type of debonding technique used, i.e., lift off, delamination, and twisting. Brackets bonded by the indirect (modified Thomas, BF mean = 0.27, ARI mean = 0.93) and the indirect technique that used a thermal-cured resin (BF mean = 0.03, ARI mean = 0.43) resulted in an overall significantly lower failure (p < 0.01) and ARI score on debonding (p < 0.0001) compared with those bonded by the direct technique (BF mean = 1.03, ARI mean = 1.97). Specimens evaluated under the stereomicroscope revealed that the brackets bonded with the indirect techniques debonded at the filled-unfilled resin interface or within the interlayer of unfilled resin.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Oxide↗

PubMed1995

Skeletal and dental changes associated with the treatment of deep bite malocclusion.

A retrospective study of 132 treated orthodontic cases presenting at least 70% overbite was conducted using dental casts and lateral cephalometric radiographs from before and after treatment. These were 61 Class I, 27 Class II, Division 1, and 44 Class II, Division 2 malocclusion patients. Six different treatment modalities for the correction of the deep bite were compared. On the basis of the analysis of cephalometric measurements, no statistically significant differences were observed between the various treatment mechanics in the correction of the deep bite. Only in the Class II, Division 2 sample, total anterior face height increased significantly (p < 0.01) with all treatment modalities. The data were then grouped according to Angle classification regardless of the type of mechanics used. Within each Angle class, the changes from before to after treatment were statistically significant for almost all of the cephalometric measurements. These significant changes were due to both anticipated growth and orthodontic treatment. The treatment of overbite primarily affected the proclination of incisors and the extrusion of molars. Within each Angle classification, the patients were also separated according to whether the permanent teeth had been extracted. The nonextraction group was compared with the extraction group for the changes in each cephalometric measurement. It was found that the extraction of teeth did have a significant effect on the changes observed with treatment in all the Angle classes but was more pronounced in the Class I sample. The proclination of incisors was less and the mesial movement of molars was more in patients who were treated with the extraction of premolar teeth than those who were treated with the nonextraction procedures.

Adolescent↗

PubMed1995

Lateral cephalometric analysis of skeletal patterns in patients with and without internal derangement of the temporomandibular joint.

Twenty-three female volunteers with normal temporomandibular joints (TMJ) were compared with 24 female patients with documented TMJ internal derangements. Magnetic resonance imaging and lateral cephalometric radiographs were used to investigate the relationship between TMJ disk displacement and skeletal facial form. Results indicated that the patients with internal derangements have significantly smaller mandibles and maxillae. However, these sagittal measurements of jaw length were not associated with disproportionate changes in other cephalometric variables. In general, no district relationship was found between the morphologic features of the face and the internal derangements of the temporomandibular joint.

Adolescent↗

PubMed1995

Relative kinetic frictional forces between sintered stainless steel brackets and orthodontic wires.

The level of kinetic frictional forces generated during in vitro translation at the bracket-wire interface were measured for two sintered stainless steel brackets as a function of two slot sizes, four wire alloys, and five to eight wire sizes. The two types of sintered stainless steel brackets were tested in both 0.018-inch and 0.022-inch slots. Wires of four different alloy types, stainless steel (SS), cobalt chromium (Co-Cr), nickel-titanium (Ni-Ti), and beta-titanium (beta-Ti), were tested. There were five wire sizes for the 0.018-inch slot and eight wire sizes for the 0.022-inch slot. 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 time dependent frictional forces were measured by a load cell and plotted on an X-Y recorder. For most wire sizes, lower frictional forces were generated with the SS of Co-Cr wires than with the beta-Ti or Ni-Ti wires. Increase in wire size generally resulted in increased bracket-wire friction. There were no significant differences between manufacturer for the sintered stainless steel brackets. The levels of frictional force in 0.018-inch brackets ranged from a low of 46 gm with 0.016-inch Co-Cr wire to a high of 157 gm with 0.016 x 0.025-inch beta-Ti wire. In comparing the data from a previous study by Kapila et al. 1990 performed at OUHSC with the same apparatus, the friction of sintered stainless steel brackets was approximately 40% to 45% less than the friction of the conventional stainless steel brackets.

Analysis of Variance↗

PubMed1995

Longitudinal growth changes in the sagittal relationship of maxilla and mandible.

This is a longitudinal study of the growth pattern in sagittal linear measurements at points A, B, and pogonion relative to the pterygoid vertical plane in a Class I sample. Serial cephalometric radiographs were traced and digitized at ages 6, 12, 18, and 24 years. The results indicated that between the ages of 6 and 24 years there was a total growth increment of 6.07, 7.53, and 11.17 mm at points A, B, and pogonion, respectively, in the female Class I sample and 9.49, 11.65, and 16.21 mm at points A, B, and pogonion, respectively, in the male sample. Although the actual change in length of these measurements was larger in the male subjects than in the female subjects, in terms of percentage of growth increment in each of these three measurements from age 6 to 24 years, the anterior movement at point B relative to point A, and at pogonion relative to points B and A was approximately the same for both male and female subjects. When each of the subjects in both male and female samples was rank-ordered according to the size at age 6 years, considerable individual variation was noticeable for most persons within the group. The individual variation in growth pattern in each of the different measurements continues to raise questions about growth prediction and its application in visual treatment objectives.

Adolescent↗