October, 2011

An in-vitro study to assess the biohostability of Orthodontic arch wires to Hepatitis B virus

 

Dr. Joby Paulose, B.D.S, M.D.S (Orthodontics)
Senior Lecturer,Department of orthodontics and dentofacial orthopedics
Mar Baselious Dental College and hospitals
Kothamangalam,Ernakulam Dist
Kerala State – 686691
India

Dr Rhea Mini Jayan, B.D.S
Lecturer, Department of pedodontics
Mar Baselious Dental College and hospitals
Kothamangalam,Ernakulam Dist
Kerala State – 686691
India

 

ABSTRACT

Objective: The purpose of the study was to assess 1) whether surface roughness and composition affects the bio-hostability of archwires for HBV 2) To find out the effect of temperature and moisture on bio-hostability.

 

Materials and Methods: Four different types of archwires of similar dimensions but varying compositions were selected for the study. Arch wires were immersed in HBsAg positive serum. They were incubated at room temperature and 37⁰C in both dry and wet environments respectively.The bio-hostability of archwires to HBV was studied using ELISA. All the sets of samples were tested at 24 hourly for 192 hours.

 

Results: Positive results were observed in all test samples, irrespective of dry/wet environment as well as the inoculation temperature.

 

Conclusion: The study ascertains the bio-hostabilty of archwires and alarms the Orthodontist’s on the highly infectious nature of HBV infections.

 

Key words: Bio-hostabbility, Arch wires, HBsAg, ELISA

 

INTRODUCTION

The risk of occupationally acquiring infection is significant among orthodontic professionals because orthodontic treatment procedures involves the use of arch wires, ligature wires, band material and other sharp cutting instruments constantly in contact with saliva and blood. Any percutaneous injuries by these sharp materials can be the principal source of transfer of Hepatitis B virus. The quantum of blood required to transmit Hepatitis B virus is 0.0004ml⁷ while for HIV it is only 0.1ml⁶. Hepatitis B virus is perhaps the most common blood-borne infection in the world.

 

Hepatitis B

Hepatitis B virus was first described in 1965 by Blumberg¹. Type B is the most wide spread and most important type of viral hepatitis. It is important from a dental healthcare point of view to note that the risk of transmission of HBV following accidental exposure to a positive patient is 7-30%. In 1992, Capilouto et al showed that annual cumulative rate of infection among dentists from routine treatment is 57 times greater for HBV than HIV⁴. The risk of acquiring HBV as a result of percutaneous exposure through contaminated devices is 5% to 45%. As HBV has a greater incubation period, it remains undiagnosed for longer.

 

Bio-hostability of Orthodontic Archwire

Archwires are active components of fixed appliance therapy designed to bring about tooth movement with light continous forces. Among the other properties, “Biohostability” plays an important role in the transmission of the diseases. Kusy RP et al in 1997 defined Biohostability as the ease with which a material will culture bacteria viruses and spores⁹. Hence an ideal archwire should have poor Biohostability to prevent transmission of pathogenic micro-organisms. Hence a study was undertaken in vitro to determine the Biohostability of four commonly used archwires of same dimension, but different compositions and surface texture.

 

AIMS AND OBJECTIVES

1. Whether surface roughness and composition of archwires attributes to the biohostability for HBV.

2. To find out the effect of temperature and moisture on bio-hostability.

 

MATERIALS AND METHODS

Four different types of archwires of similar dimension but varying composition were selected for the study (Table: 1). The archwire samples were cut into pieces of 1-1.5cm length, sterilized in autoclave and grouped in to 4 sets (Table: II). Each set included 8 samples from each of the 4 types of archwires, comprising of 32 specimens.

 

Table I: Recommended dose of the hepatitis vaccine according to JA Cottone

Table II: Archwire samples used for the study

 

All the four sets of samples were immersed in high titer HBsAg Positive Serum. Set 1 and 2 samples were transferred immediately to sterile screw capped containing vials containing 300ul of normal human serum whereas set 3 and 4 to sterile screw capped vials(Fig: 1). To test the effect of temperature, archwires were incubated at room temperature and at 37^oC (M.C.Dalal, India).

 

 

 

 

 

 

 

 

 

 

 

 

Wire samples from Set 3 and 4 were then transferred to vials containing normal human serum and was vortexed for 1 or2 minutes intermittently for 15 minutes to transfer the materials sticking on archwire to human serum. Samples were then tested for the presence of HBsAg at an interval of 24 Hrs for 192 Hrs using ELISA kit (Abott Auszyme Macro Elisa kit) (Fig: 2a & 2b). Control tubes containing normal human serum (negative control) and HBsAg positive plasma (positive control) were set up in each batch.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Principle of ELISA

Immunoassay procedure used beads coated with monoclonal HBsAg, when incubated with the sample. HBsAg is bound to the HBsAb. O-phenylenediamine (OPD) solution containing H₂O₂ added to bead produces a yellow-orange colour in proportion to the amount of HBsAg bound to the bead. The absorbance of controls and specimens is determined using a spectrophotometer(Fig: 3) with wavelength set at 492nm.Specimens giving absorbance value equal to or greater than the absorbance value of the negative control mean plus a factor are considered reactive for HBsAg.

 

 

 

 

 

 

 

 

 

 

 

 

 

RESULTS

The absence or presence of HBsAg is determined by relating the absorbance of the unknown sample to the cut-off value (which is the absorbance of negative control mean plus the factor 0.025). Specimens with absorbance values greater than or equal to the cut off value established with the negative control is to be considered reactive for HBsAg and the results are tabulated in tables III and IV. All the samples revealed positive results on ELISA testing. Results were not in influenced by the surface roughness and composition of arch wires. Both dry and wet samples showed positive results. (Table V) Varying inoculation temperature did not alter the results.

 

Table III: four sets of specimens required for the study

 

Table IV: Results of tests conducted in the samples of four different archwires in dry environment. (Optical density value >2.000)

TIMING	DRY SAMPLE TESTING
	Std SS	Braided SS	NiTi	TMA
	RT & 37o	RT & 37o	RT & 37o	RT & 37o
24 hrs	+ ive	+ ive	+ ive	+ ive
48 hrs	+ ive	+ ive	+ ive	+ ive
72 hrs	+ ive	+ ive	+ ive	+ ive
96 hrs	+ ive	+ ive	+ ive	+ ive
120 hrs	+ ive	+ ive	+ ive	+ ive
144 hrs	+ ive	+ ive	+ ive	+ ive
168 hrs	+ ive	+ ive	+ ive	+ ive
192 hrs	+ ive	+ ive	+ ive	+ ive

Table V: Results of tests conducted in the samples of four different archwires in wet environment. (Optical density value >2.000)

TIMING	WET SAMPLE TESTING
	Std SS	Braided SS	NiTi	TMA
	RT & 37o	RT & 37o	RT & 37o	RT & 37o
24 hrs	+ ive	+ ive	+ ive	+ ive
48 hrs	+ ive	+ ive	+ ive	+ ive
72 hrs	+ ive	+ ive	+ ive	+ ive
96 hrs	+ ive	+ ive	+ ive	+ ive
120 hrs	+ ive	+ ive	+ ive	+ ive
144 hrs	+ ive	+ ive	+ ive	+ ive
168 hrs	+ ive	+ ive	+ ive	+ ive
192 hrs	+ ive	+ ive	+ ive	+ ive

DISCUSSION

The observations points out to the highly infectious nature of Hepatitis B Virus. Biohostability of archwires is irrespective of the composition and surface characteristics of orthodontic archwires. All the samples (dry & wet) irrespective of incubation temperature were reactive for HBsAg (Optical density value >2.000) even after 192 Hrs irrespective of the surface roughness and composition of the wire.

 

Assuming that biohostability could be attributed to the surface charecteristics of archwires, four orthodontic archwires with different surface charecteristics and composition were selected for this study. Scanning electron microscopy and laser spectroscopy studies on surface texture of archwires have shown that among the four wire alloy types that are commonly used in orthodontics, stainless steel appeared smoothest, followed by cobalt chromium and B titanium and nickel titanium. So stainless steel (standard, regular and braided regular), NiTi rectangular and TMA rectangulat wires were selected for the   study.

 

It has been the reported that Hepatitis B virus can be viable for 7 days even after drying⁵. So the present study was designed for 8 days. Polymerised chain reaction identifies the viral gene particles and hence is reported to be an ideal method of detecting Hepatitis B virus. Elisa was preferred in the study considering the cost factor and sample size. More over ELISA detects HBsAg which can be equated to the viability of the virus.

 

 

SUMMARY

HBsAg was detected in all samples under even at

1.      Incubation temperature – Both at 37⁰C and Room Temperature

2.      Dry / Wet environment

3.      Irrespective of surface roughness and composition of the wire

 

 

 

 

INFECTION CONTROL PROTOCOL IN AN ORTHODONTIC OFFICE

Preventive Measures

A systematic medical and dental history of every patient in an environment that permits the disclosure of sensitive personal information is imperative, to rule out any pre-existing infection. If possible, immunization records should be gleaned from the patient. It may not be possible to identify asymptomatic carriers; hence universal precautions must be adopted.

 

Use of physical barriers like gloves, mask, protective eye wear and aprons. Gloves should be discarded immediately after use. Aerosol generated during the debonding procedure has been shown to be routinely laden with oral bacteria. Hence the possibility of transmission of HBV during debonding procedure should be considered.

 

Above all, self protection from perctaneous injuries from orthodontic arch wires has to be kept in mind while treating each and every patient.

 

Immunization of the orthodontist as well as the patient: Both active and passive immunization is available for hepatitis B. Hyper Immune Hepatitis B globulin prepared from human volunteers with high titer of anti HBs administered IM in a dose of 300-500 i.u. constitutes passive immunization. Active immunization was first introduced in 1982. Currently it is manufactured by genetic engineering, by cloning of S gene of HBV in Baker’s yeast. It is administered intra-muscularly in the deltoid region at a dosage of 3 injections which are administered in the following sequence. The first immunization (which is considered as 0 month), is followed by the second administration after 1 month and then a booster dose after 6 months. The recommended dose of the hepatitis vaccine according to JA Cottone6 is well explained in Table I. Antibody titre is must be frequently monitored and booster dose to be taken if necessary.

 

Sterilization and disinfection procedures to be followed

a.         Use of autoclavable or disposable impression trays.

b.        Use of disposable mixing rubber bowls and spatulas

c.         Alginate impressions and removable orthodontic appliances to be cleaned with chemical disinfectants such as 2% glutaraldehyde, 1% sodium hypochlorite and sodium dichloroisocyanurate³. Immersion not more than 10 minutes is recommended as alterations in the surface characteristics are observed with prolonged immersions.

d.        Disposable coverings should be used in conjunction with Light Cure tips, Air Rotor handpiece and 3 ways syringe.

e.         Use of autoclavable cheek retractors and mirrors.

f.          Current sterilization protocols for orthodontic pliers are with effectiveness against organisms as well as longevity of instruments in mind.

1.    Ultrasonic cycle for 5 to 12 minutes depending on the capacity of the unit.

2.    Rinsing with distilled water.

3.    Remove excess moisture through drying with compressed air (Oil-free).

4.    Lubrication of plier joints and cutting surfaces with silicone based lubricants.

5.    Sterilization protocol using a Dry heat sterilizer at 190⁰ for 6 to 12 minutes with the placement of pliers in

an open storage.

 

g.         Decontamination of tried in preformed molar bands is similar to that of orthodontic pliers with dry heat sterilization at 190⁰ for 6 minutes ^{2, 8}.

h.         Use of disposable archwire markers should be used, especially ink based.

i.           Elastomeric chains are not suited for chemical disinfection as it may alter their physical characteristics. Use of proper methods of dispensing elastomeric chains using cassettes is advised. It’s better to cut a little extra than required and discard the rest.

j.          Recycling of orthodontic brackets and archwires should be avoided and If necessary should be done only after autoclaving.

 

Management of Acute Exposure

a.         Immediately clean the wound with thoroughly with soap and water.

b.        Obtain the patient’s and exposure recipient’s permission for blood testing.

c.         Testing should be carried out for HBsAg.

d.        The exposure recipient’s blood tested for hepatitis antibody titre if he has received a hepatitis B vaccination. In HBsAb negative patient HBIG should be administered within 48 hrs of exposure (0.6ml/kg i.m.) and Hepatitis B passive vaccination as per recommendation.

 

CONCLUSION

The clinical significance of this study is the alarming risk of orthodontist’s to acquire infections from blood borne pathogens and the biohostable nature of orthodontic archwires. However biohostability of Hepatitis B virus cannot be attributed only to the archwires but also to various other components like band materials and brackets must be considered.

 

It is the responsibility of the Orthodontist to implement effective and efficient infection control policies in his office that would help prevent the outbreak of infections and cross-contamination, thereby, safeguarding not only his own health and of the orthodontic assistants but also of the ancillary staff, and even the community. Careful attention should be exercised in all aspects of infection control, thus, making the Orthodontic office a safe vista for designing a beautiful smile.

 

 

ADDRESS FOR CORRESPONDENCE

 

 

Dr. Joby Paulose, B.D.S, M.D.S (Orthodontics),

Orthodontics department,

Mar Baselious Dental College,

Kothamangalam,

Ernakulam Dist,

Kerala State – 686691

India

 

Ph: 9446323720

Email: drjobypaulose@gmail.com

drjobypaulose@hotmail.com

 

 

Dr Rhea Mini Jayan, B.D.S,

Mar Baselious Dental College,

Kothamangalam,

Ernakulam Dist,

Kerala State – 686691

India

Ph: 9946200589

Email: rheajayan@yahoo.com

 

REFERENCES

 

1.      Baruch S. Blumberg; Harvey J. Alter A “New” Antigen in Leukemia Sera JAMA 1965; 191: 541 – 546.

2.      Benson PE, Douglas CWI. Decontamination of orthodontic bandsfollowing size determination and cleaning. Journal of orthodontics 2007;34(1):18-24

3.      Blair FM, WAssell RW. A survey of the methods of disinfection of dental impressions used in dental hospitals in the United Kingdom. Br Dent J 1996; 180(10):369-75.

4.      Capilouto E I, M C Weinstein, D Hemenway, and D Cotton What is the dentist’s occupational risk of becoming infected with hepatitis B or the human immunodeficiency virus? Am J Public Health 1992; 82: 587-589.

5.       Cleveland JL, SA Lockwood, BF Gooch, MH Mendelson, ME Chamberland, DV Valauri, SL Roistacher, JM Solomon, and DW Marianos  Percutaneous injuries in dentistry An observational study J Am Dent Assoc 1995; 126(6): 745-751.

6.      Cottone JA, Terezhalmy GT, Molinari JA, eds. Practical Infection Control in Dentistry, 2nd ed. Baltimore: Williams & Wilkins, 1996: 149–160.

7.      Nirmal Kumar, Saigal S. Hepatitis B: Currrent status in dentistry. JIOS 1998; 34:109-12.

8.      Dowsing PE, Benson PE. Molar band re-use and decontamination: A survey of speacialists journal of orthodontics 2006; 33(1): 30-37.

9.      Robert P.Kusy A review of contemporary archwires: Their properties and charecteristics. The Angle orthodontist 1997; 67(3): 197-207.