Rajiv gandhi university of health sciences, bangalore, karnataka



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RAJIV GANDHI UNIVERSITY OF HEALTH SCIENCES,

BANGALORE, KARNATAKA
ANNEXURE II
PROFORMA FOR REGISTRATION OF SUBJECTS

FOR DISSERTATION



1.

NAME OF THE CANDIDATE

AND ADDRESS

(in block letters)

Dr. sonu p. raju.

pOST GRADUATE STUDENT,

Department of ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS,

BAPUJI DENTAL COLLEGE AND HOSPITAL, DAVANGERE - 577 004.


2.


NAME OF THE INSTITUTION

BAPUJI DENTAL COLLEGE AND HOSPITAL, DAVANGERE-577004




3.


COURSE OF STUDY AND SUBJECT

MASTER OF DENTAL SURGERY IN



ORTHODONTICS AND DENTOFACIAL ORTHOPEDICS


4.


DATE OF ADMISSION TO COURSE

18th APRIL 2011.




5.


TITLE OF THE TOPIC

FORCE-DEFLECTION PROPERTIES OF SIX DIFFERENT INITIAL ALIGNING ORTHODONTIC ARCHWIRES USING



THREE-POINT BENDING TEST- AN

IN-VITRO STUDY”.



6.

7.


BRIEF RESUME OF THE INTENDED WORK :
6.1 Need for the study :

The initial stage of orthodontic treatment involves leveling and aligning of teeth. To accomplish this, an appliance should deliver optimum forces, which are light and continuous that decay over a period of time. The force required to align the teeth is not the activation force but the deactivation force (unloading force) of the appliance. This deactivation force of various wires used in the initial stages may not be the same. Therefore, force-deflection graph generated during activation and deactivation of these wires might vary. Knowledge of these wires in terms of deactivation behavior is important for the clinician for optimal wire selection.


The type of arch wires most frequently recommended in conventional practice during the initial stages of orthodontic treatment are multistranded stainless steel arch wires and martensitic NiTi wires. Advancements in technology introduced newer archwires like superelastic NiTi and thermoactivated NiTi. However, availability of so many archwires has led to the confusion in the clinicians’ mind to choose an optimum wire during initial aligning.
Therefore, this study aims to compare and measure the force deflection properties of six different aligning archwires used during the initial stages of orthodontic treatment.
Research Hypothesis:

There exists a difference in the force deflection properties between the six types of initial aligning orthodontic archwires- co-axial(6 stranded) wire, preformed stainless steel wire, stainless steel spool, conventional NiTi wire, superelastic NiTi wire and heat activated NiTi archwires.


Null Hypothesis:

There exists no difference in the force deflection properties between the six types of initial aligning orthodontic archwires- co-axial (6 stranded) wire, preformed stainless steel wire, stainless steel spool, conventional NiTi wire, superelastic NiTi wire and heat activated NiTi archwires.



6.2 Review of literature :

An in-vitro study was done to measure and compare the force-deflection behavior of selected initial orthodontic archwires. The purpose of the study was to test the null hypothesis that there would be no differences in the deactivation force among the groups- superelastic NiTi, thermoactivated NiTi, multistranded stainless steel or conventional stainless steel. The study concluded that there was significant difference in the deactivation forces among the groups. The multistranded stainless steel group had the lowest mean deactivation force compared to NiTi groups. The findings suggested that both the nickel-titanium and multistranded steel archwires tested have properties that favor their use during initial stage of orthodontic treatment.1

An in-vitro study was done to measure and compare the forces produced by 10 orthodontic archwires in a simulated clinical situation using a typodont and with the wires mounted on a jig for a simple three point loading. The hypothesis was that, there exists no difference in the unloading forces produced by initial arch wires when used in a clinical simulated condition. The study concluded that, there exists a difference in the unloading forces produced when used in a clinical simulated condition as well as when tested as simple beams. The forces recorded at each deflection during the simple beam test were much less compared to forces recorded at each deflection of an archwire in a clinical simulated condition. The study also concluded that multistranded archwires were as effective as more expensive Nitinol equivalents, especially at small deflections.2

A study was done to measure and compare the deactivation force-deflection behavior of selected multistranded stainless steel archwires. The study tested 20 wire designs: triple stranded twisted wires, 5- and 6-stranded coaxial wires of round cross-section, and 8- and 9-stranded braided wires of rectangular cross-section. The study concluded that multistranded wires of different cross-sections, weave, and strand number showed a narrow range of force magnitude at 1-mm and 0.5-mm deflection and wide ranges was observed at 3-mm and 2- mm deflections. The rectangular braided weave designs, with few exceptions, provided the higher levels of force delivery at 3-mm, 2-mm, and 1-mm deflections whereas the coaxial weaves produced lower force levels at same deflections. 3


An in-vitro study was done to compare the force deflection properties of 8 superelastic NiTi archwires of different manufacturers { CopperNiTi 35°C (Ormco), CopperNiTi 27°C (Ormco), Elastinol 35 (Masel), Elastinol 27 (Masel), Nickel-Titanium (Morelli), Nitinol heat-activated (3M/Unitek), Neosentalloy F200 (GAC), Rematitan Lite (Dentaurum)}, under controlled moment and temperature (37°C). Force-deflection diagrams of each archwire were determined from a passive position to an activation of 2mm and then during deactivation. Forces on deactivation at a deflection of 1 mm were compared. The study concluded that superelastic wires- Nickel-Titanium and Elastinol 35 tested had lowest deactivation forces, whereas Rematitan lite wire had the highest deactivation force.4
An in vitro study was done to investigate load-deflection characteristics of three commercially available thermoactivated NiTi archwires using conventional nickel–titanium archwire as a control. Wires were subjected to 2 mm and 4 mm of deflection in a water bath at temperatures of 20°, 30°, and 40°C and forces were measured in three-point bend and phantom head situations. The study concluded that irrespective of the test set up and wire type; wire size had a significant effect on the forces produced. An increase in size from 0.4 mm round to 0.4 × 0.56 mm rectangular wire approximately doubled the force values for a given deflection. The effect of wire deflection on the force values varied according to the test system, forces being much higher in the phantom head tests than in the beam tests. In the beam tests, an increase in wire deflection from 2 to 4 mm had no significant effect on the forces exerted, but in the phantom head tests the forces produced by each wire at 4 mm deflection were four to five times greater than those at 2 mm deflection. Each of the thermally active wires produced less force than that of the non-thermally active wire. However, there was a large variation between the three types of thermally active wires. The forces exerted by thermoelastic wires in beam tests increased significantly with each 10°C temperature rise. In phantom head tests, however, although a temperature rise from 20° to 30°C increased forces significantly, further increases between 30° and 40°C were not significant.5

6.3 Objectives of the study :

  1. To compare the force deflection properties of six types of arch wires used in initial stages of orthodontic treatment.

  2. To measure the deactivation force of each type of wire in controlled condition.



MATERIALS AND METHODS
7.1. Source of the data:

Six different orthodontic archwires commercially obtained from various manufacturers will be examined:

Wire dimensions ( in inches) Manufacturer

Co-axial wire (6- stranded) 0.0175" Libral

Conventional NiTi 0.014" Libral

Heat-activated NiTi 0.014" 3M-Unitek

Superelastic NiTi 0.014" Libral

Preformed Stainless Steel 0.014" Libral

Stainless Steel Spool 0.014" Jaypee Company
7.2. Method of collection of data:
Sample Size Determination:

For the proposed study, the probability of type 1 error (α) is fixed at 5% and probability of type 2 error (β) at 20%. Hence, the power of the study will be 80%.

The sample size for this study has been determined scientifically. Data required for determining the sample size was imported from a previously published article1. Sample size determination was done using Cohen’s d power table. The following formulae was used to calculate Cohen’s d,

Cohen’s d =

=

= 0.9


So, for the power of the study 80% the sample size of minimum of 21 wires in each group should be included in the study, as derived from the Cohen’s d power table.

Based on the above calculations, the study will include 150 specimens - 25 round wires of each of the six types: co-axial wire (6-stranded), conventional NiTi, heat-activated NiTi, superelastic NiTi, preformed stainless steel, and stainless steel spool will be tested. Wires used in the study will be preformed and custom made archwires of 0.014-inch or 0.0175-inch diameter and round cross section.


Method of the study:

The study will be conducted on maxillary phantom head jaw, in which each typodont tooth will be secured by a screw at the root apex. The teeth are well aligned and in good contact, except for the maxillary right central incisor which is removed. The teeth will be bonded with 0.018" slot PEA brackets and first molars bonded with buccal tubes. Each archwire will be placed in the bracket slots of orthodontic brackets and secured with stainless steel ligature wires. This archwire will be tested using a three point bending test, carried out under controlled temperature of 37°C, on a mechanical testing machine. The archwire will be deflected at a point midway between the brackets on each side of the missing tooth, at a crosshead speed of 0.3 mm/min, with a 100N load cell. The load deflection test will be conducted separately at two deflection distances i.e., at 2 mm and 4 mm. The load exerted by each wire will be measured during the subsequent unloading process. The archwires will be unloaded (deactivated) at the same crosshead speed until the load becomes zero.

Deflections of each of the six types of archwires will be repeated 25 times with a new wire on the testing machine.

Statistical Analysis :

Based on the normalcy of the distribution of the data, results obtained will be statistically analyzed and compared using analysis of variance (ANOVA) / Kruskal Wallis ANOVA and followed up with Tukey post-hoc test / Mann Whitney test for pair wise comparisons.


7.3 Does the study require any investigations or interventions to be conducted on patients or other humans or animals? If so, please describe briefly.

No.



7.4 Has ethical clearance been obtained from your institution in case of 7.3?

Not applicable.





8.

LIST OF REFERENCES :


  1. Quintao CC, Cal-Neto JP, Menezes LM, Elias CN.Force-deflection properties of initial orthodontic archwires. World J Orthod 2009; 10: 29-32.



  1. Rock WP, Wilson HJ. Forces exerted by orthodontic aligning archwires. Br J Orthod 1988; 15: 255-259.




  1. Gurgel JA, Kerr S, Powers JM, LeCrone V. Force deflection properties of super elastic nickel-titanium archwires. Am J Orthod Dentofacial Orthop 2001; 120: 378-82.




  1. Taneja P, Duncanson MG Jr, Khajotia SS, Nanda RS.Deactivation force deflection behavior of multistranded stainless steel wires. Am J Orthod Dentofacial Orthop 2003; 124: 61-8.




  1. Parvizi F, Rock WP. The load deflection characteristics of thermally activated orthodontic archwires. Eur J Orthod. 2003; 25: 417-421.






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