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The Effects of The Effects of Sterilization on Tensile Sterilization on Tensile Strength of Orthodontic Strength of Orthodontic

wires wires

Guided by: Guided by: Dr.(Mrs.) Dr.(Mrs.) P.V.Hazarey P.V.Hazarey Prof. And HeadProf. And Head

Presented by: Presented by: Madhvi BhardwajMadhvi BhardwajPostgraduate studentPostgraduate student

Sharad Pawar Dental CollegeSharad Pawar Dental CollegeDatta Meghe Institute of Medical Datta Meghe Institute of Medical

Sciences, Wardha Sciences, Wardha www.indiandentalacademy.com

Introduction Introduction

• As overhead costs rise, orthodontists are continually searching for ways to reduce costs.

• The newer orthodontic wires display an excellent combination of strength resiliency and low-load deflection rates.

• Beta-titanium (TMA) three times while NiTi usually two times more expensive than stainless steel wires.


• It is unlikely that orthodontist will discontinue their use due to their relatively high price.

• Hence, the challenge is to make more cost effective use of these wires.

• Sterilization and reuse of the more expensive orthodontic wires is one option.


• During finishing stage of treatment when lower grade wires may be reused in the same patient

• Also one can recycle and reuse the same wire in different patient


• When considering the reuse of orthodontic wires, it is important to:– Evaluate the effect of sterilization on

the physical properties of wires – Eliminate the risk of cross infection


AIM AND OBJECTIVESAIM AND OBJECTIVES

• To evaluate the effects of sterilization on the tensile strength of Nickel- Titanium, TMA and Stainless steel wires.

• To compare the effects of three different methods of sterilization methods on the tensile strength of Nickel- Titanium, TMA and Stainless steel wires.


Materials• Wires used: • 5 samples of each

– 0.016” (round) and 0.016”X0.022” (rectangular) TMA (Ortho organizer)

– 0.016” (round) and 0.016”X0.022” (rectangular) Nickel – Titanium (Libral Traders)

– 0.016” (round) and 0.016”X0.022” (rectangular) Stainless Steel wires (Libral Traders)


• Control group: The used wires were ultrasonically cleaned and air dried but was not processed through different sterilization procedures.


• Experimental group: The used wires were ultrasonically cleaned and air dried and was processed through different sterilization procedures.


• Equipments used for sterilizations:

HOT AIR OVEN STEAM AUTOCLAVE

BIOCLENZ SOLUTION (2% GLUTERALDEHYDE)www.indiandentalacademy.com

• Universal testing machine: – For measuring the ultimate tensile strengths of the

wires


Method• Part 1:

– The different types of sterilization methods used on three types of wires:

• Dry heat sterilization: Hot air oven was used at 320°to 340°F (160° to 171°C) for a period of 1 to 2 hours.

• Autoclaving: Used at 250 °F (121 °C) at 15 psi for 15 minutes or 270 °F (132 °C) at 30 psi.

• Cold sterilization: 2% Glutaraldehyde was used for a duration of 10 minutes and upto 10 hours of time.


• Part 2 :– Determining the effects of repeated sterilization

on tensile strengths of 0.016 ” and 0.016”X 0.022” TMA, Nickel -Titanium and Stainless steel wires.

• All wires were tested using a Universal Tensile Testing Machine (Model No. 1.3 D) with a load cell capacity of 2500 N having a least count of 50 N.


• The machine consisted of two movable fixtures so as to tightly grip the wire specimen in place when the test is being performed and the speed of the machine was kept at a constant rate of 1mm/min.


Table 1 Ultimate Tensile strength of stainless steel wire(0.016 round)

Sterilization cycles

Sterilization Method

Dry heat Autoclave Cold

0 1237 ± 85 1211 ± 85 1087 ± 48

1 1282 ± 57 1251 ± 84 1091 ± 38

5 1212 ± 95 1238 ± 180 1088 ± 47F- value*

p-level 8.06

NS2.95

NS2.01

NS

Comparison Between Cycles

(0-1) NS --- ---

(0-5) NS --- ---

(1-5) NS --- ---

Observation and Results


Sterilization Method Sterilization cycles Dry heat

Autoclave

Cold

0 1855.33 ± 26.39 1840.27 ± 5.53 1797.29 ± 17.36 1 1825.44 ± 30.97 1832.12 ± 5.40 1794.75 ± 19.82 5 1849.71 ± 20.42 1835.32 ±

19.15 1776.80 ± 19.62

F- value* p-level

1.82 0.20

NS,p>0.05

0.59 0.56

NS,p>0.05

1.73 0.21

NS,p>0.05

(0-1) 0.21

NS, p>0.05 0.54

NS, p>0.05 0.97

NS, p>0.05

(0-5) 0.93

NS,p>0.05 0.79

NS, p>0.05 0.24

NS, p>0.05 Comparison

Between Cycles

(1-5) 0.34

NS,p>0.05 0.90

NS, p>0.05 0.32

NS, p>0.05

Table 2 : Ultimate Tensile strength of stainless steel wire (0.016 x 0.022inch)


• Dry heat sterilization, Autoclaving and Cold sterilization did not affect the tensile strength of round and rectangular Stainless steel wires.


Table 3 Ultimate Tensile strength of Nickel -

Titanium wire ( 0.016 round)




0 1226 ± 11 1226 ± 11 1226 ± 11

1 1382 ± 60 1366 ± 54 1222 ± 15

5 1364 ± 31 1382 ± 29 1234 ± 14F- value*

p-level 32.2 S,p<.01

28.6 S,p<.01

1.06 NS

Comparison Between

Cycles

(0-1) P<.01 P<.01 ---

(0-5) P<.01 P<.01 ---

(1-5) NS NS ---



Sterilization cycles Dry heat

Autoclave

Cold

0 1748.92 ± 20.64 1746.45 ± 23.42 1748.92 ± 20.64 1 1836.36 ± 21.68 1826.71 ± 21.47 1768.31 ± 0.27 5 1758.79 ± 17.02 1844.98 ± 21.68 1748.26 ± 1.75

F- value* p-level

28.99 0.00

S,p<0.05

27.83 0. 00

S,p<0.05

4.53 0.30 NS

(0-1) 0.00

S, p<0.05 0.00

S, p<0.05 0.06

NS, p>0.05

(0-5) 0.71

NS,p>0.05 0.00

S, p<0.05 0.99


Between Cycles

(1-5) 0.00

S,p<0.05 0.42

NS, p>0.05 0.05

NS, p>0.05

Table 4 : Ultimate Tensile strength of Nickel Titanium( 0.016 x 0.022 inch)


• Dry heat sterilization significantly increased the tensile strength of both round and rectangular Nickel -Titanium wires after one cycle.

• Autoclaving increased the tensile strength of rectangular and round Nickel -Titanium wires.

• Cold sterilization did not affect the tensile strength of both round and rectangular Nickel -Titanium wires.


Table 5 Ultimate Tensile strength of TMA wire (0.016 round)




0 1087 ± 48 1087 ± 48 1087 ± 48

1 1282 ± 57 1251 ± 84 1091 ± 38

5 1212 ± 95 1238 ± 180 1088 ± 47

F- value* p-level

8.06 S,0.01

2.95

S,0.02

0.01

NS,0.2

Comparison Between

Cycles

(0-1) S --- ---

(0-5) S S ---

(1-5) NS NS ---


Sterilization Method Sterilization cycles

Dry heat

Autoclave

Cold

0 1673.53 ± 20.64 1866.02 ± 16.83 1773.53 ± 20.64 1 1840.89 ± 22.70 1823.73 ± 21.26 1766.03 ± 4.87 5 1672.03 ± 33.65 1878.45 ± 21.89 1792.68 ± 22.11

F- value* p-level

68.12 0.00

S,p<0.05

10.15 0.003

S,p<0.05

3.01 0.08

NS,p>0.05

(0-1) 0.00

S, p<0.05 0.01

S, p<0.05 0.78

NS, p>0.05

(0-5) 0.90

NS,p>0.05 0.60

NS, p>0.05 0.24


Between Cycles

(1-5) 0.00

S,p<0.05 0.003

S, p<0.05 0.08

NS, p>0.05

Table 6 : Ultimate Tensile strength of TMA (0.016 x 0.022 inch)


• Dry heat sterilization significantly increased the tensile strength of both round and rectangular Beta-Titanium wires after one cycle.

• Autoclaving also increased the tensile strength of in case of round and rectangular Beta-Titanium wires

• Cold sterilization did not affect the tensile strength of both round and rectangular Beta-Titanium wires.


Statistical analysis showed that with the comparison between the cycles no significant differences were found in the tensile strength of wires between zero cycle and five cycles of sterilization but increases after one cycle of sterilization.


Discussion

• The purpose of present study was to examine the effect of repeated cycles of different methods of sterilizations on tensile strength of round and rectangular (0.016” and 0.016”X 0.022” ) Beta – Titanium, Nickel – Titanium, and Stainless steel wires.


• Tensile strength was chosen as the parameters as it has a direct impact on the clinical use of wire.

• If a wire’s tensile strength decreases it is more prone to breakage, which may cause a problem for both the patient and the orthodontist


• It can be concluded that sterilization of Beta – Titanium and Nickel – Titanium wires with dry heat or autoclave produces an increase in their tensile strength.

• The decrease in tensile strength of stainless steel wires produced by autoclave or dry heat sterilization may not present a clinical problem since only few Orthodontists reuse these wires.


Conclusion

• Whether or not recycling is a practical method of reducing orthodontic overhead cost

• The results of this study suggest that Orthodontists who choose to recycled Nickel – Titanium, TMA or Stainless steel arch wires do not need to be concerned about reducing the wire’s ultimate tensile strength by sterilization procedures.

• Instead, tensile strength increases in case of Nickel-Titanium and TMA wires



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