SURFACE PROTECTION PROCEDURES

• Surfaces that are likely to be contaminated by the dental surgeon handling it or by the spill or spatter of oral contaminants should be disinfected .Surfaces touched by the dental surgeon are called TOUCH SURFACES.

• E.g. unit handles, various controls, light cure unit, micromotor, ultrasonic handpiece, 3 way syringe etc. these instruments need to be treated with disinfectants or covered with a protective barrier.

• The surfaces which are contaminated by contact with soiled instruments are called

TRANSFER SURFACES.

• E.g. instrument trays, tube and hand piece holders.

• SPLITTER SURFACE is any surface which is not a touch or transfer or instrument surface and is within few feet of the oral cavity e.g. the dental chair surface. These surfaces are not cross contamination surfaces.

• Prevention of contact by touching and elimination of spill and spatter is ideal for preventing infection from surfaces. Since it is not possible, two main methods of protection of surfaces are used which are disinfection and barriers

• Disinfection involves cleaning of surfaces after every patient and application of disinfectant chemical material. These chemicals include—alcohol, iodophore, synthetic phenols, gluteraldehyde, chlorine etc.

• Dental patient chair: All chair functions should be controlled from a foot switch to avoid possible contamination by use of hand operate switches. Greatest potential for cross contamination is from chair mounted controls. Covering switches with clear plastics, which is replaced between patient sessions, will allow visualization and use without contamination of switches.

• Task seat or chair: Dentist should not touch seat covering with contaminated hands. Cleaning and disinfecting of porous seat covering may be accomplished with soap and water.

• Spittoons: Spittoons should be flushed with water, scrubbed and disinfected. Assembly around spittoons can be protected by barriers and removed when contaminated.

• Cabinetry: The amount of cabinetry should be minimized and they should be made from material that will with stand repeat cleaning and disinfection.

PROCEDURE FOR CLEANING OF DENTAL UNIT WATERLINE

• All water lines should be flushed for 3-5 minutes if the system has been idle for several hours.

• After each patient running high speed hand pieces for a minimum of 20-30 seconds to discharge water and air should be done to flush out patient material that have entered during use.

• Routine disinfection of water lines is possible by using a disinfection solution in water lines while unit is idle.

• Anti-retraction valves to prevent backflow of patient material into water line should be regularly tested for proper functioning

• Suck about 1 litre of 1% sodium hypochlorite through thesuction line at the end of the day, leave it for overnight. Next day before starting the work rinse with water and use.

SURFACE DISINFECTION

• Materials like sodium hypochlorite 5.25% (1:10 dilution), iodophors like Biocide & combination synthetics (Phenolics, Multicide & Omni II Vitaphine) have the disadvantage of leaving surfaces wet for 10 minutes, which is inconvenient in a busy dental practice.

• Glutaraldehyde products that are intended to be used as surface disinfectants contain only 0.25% (w/v)glutaraldehyde. However, they should be used with care, as repeated contact may damage the skin.

• Surfasept S.A is a commercially available disinfection solution which is aldehyde free, contains Isopropyl alcohol, chlorhexidine digluconate and flavoured excipient. It must be sprayed onto the area which must be completely and uniformly moistened then wiped.[9]

• Surface disinfection can be done by scrubbing the surface with the iodophor-soaked gauze pads and allowed to dry. Then 70% isopropyl alcohol should be used to remove the residue.

INSTRUMENT DISINFECTION

Least critical instruments such as Ligature tier and distal-end cutter, tying pliers, arch forming pliers, torquing keys, boons gauge, elastomeric rings etc. should be disinfected

Quaternary ammonium compounds are cationic surface acting agents. Commonly used ones are Cetrimide and Benzylkonium chloride. Disadvantages with these compounds are that they get inactivated by soap, reduced activity in presence of metal ions common in natural water, reduced effectiveness in presence of organic matter, lack of activity against tuberculous bacteria and are not sporicidal

8% solution of formaldehyde in alcohol and 2% solution of activated glutaraldehyde were considered to be two disinfectant of choice. But apart from toxicity issues, aldehyde based solution cause corrosion and rusting of stainless steel instruments which comprise majority of dental and orthodontic instruments.

Hence, an alternative solution is 5% Bibforte solution (ALPRO MEDICAL GMBH, Germany) which is aldehyde free, non- toxic and non-corrosive disinfectant. 100g BIB forte contains2.2 g dodecyldipropylenetriamine, 1.7 g trialkylethoxyammoniumpropionate, tensides and auxillaries. It is bactericidal (incl. TBC, MRSA), yeasticidal and virus inactivating. 5% solution is made by adding 50 ml of Bibforte solution to 950 ml of water and instruments are immersed in 5% solution for 30 minutes for effective disinfection. In emergency situation, 10%Bibforte solution with 5 minutes immersion of instruments can used for early and effective disinfection (as recommended by manufacurer) [10].

STERILIZATION

Sterilization can be accomplished in one of several ways. Some of the most common ways that are followed in orthodontic practice include steam autoclave sterilization, dry heat sterilization, chemical vapour sterilization and ethylene oxide sterilization

Instrument Processing

The overall process consists of

• Holding ( presoaking )

• Precleaning

• Corrosion control, drying, lubrication

• Packaging

• Sterilization

• Sterilization monitoring

• Handling processed instruments

Presoaking: Placing instruments in presoak solution until time is available for full cleaning prevents drying, begins to dissolve organic debris and in some instances begin microbial kill. Presoak solution consists of detergents, enzymes, or detergents containing disinfectants. Used solution should be discarded atleast once a day.

Cleaning: Blood, saliva and materials on instrument can insulate underlying microorganisms from sterilizing agents. Cleaning reduces this bioburden. Cleaning solutions with antimicrobial activity can eliminate build up of contaminants as the cleaning solution is being repeatedly used.

Hand cleaning: is an effective method if performed properly. Heavy utility gloves and protective eyewear should be worn during hand cleansing of instruments. Instruments should beimmersed in the detergent solution and then scrubbed with soft brush.

Mechanical/Ultrasonic cleaning:

Coupling of powerful ultrasonic vibrations with cold disinfection increases the effectiveness of the process. In a densely packed pile of instruments, there is only a thin layer of disinfectant around each instrument; vibration assures penetration of a properly concentrated solution into every area of every instrument [13]. Cleaning solution specifically recommended for use in ultrasonic cleanser should be used in proper dilution. The instruments are kept in the ultrasonic cleanser basket and submerged in the cleaning solution.

Ultrasonic Cleaner: The cleaner should be covered and operated for 6-10 minutes or until no visible debris remains. If instrument cassettes are used cleaning time is increased to 15 minutes. After cleaning instruments are thoroughly rinsed. Cleaned instruments must be considered contaminated and handled with gloved hands.

CORROSION CONTROL AND LUBRICATION

To reduce corrosion

• Clean and remove debris from the instruments and rinse with distilled water.

• Avoid tap water which contains dissolved alkali and metallic ions.

• Water must be deionized and of good quality.

• Keep the pH of steam above 6.4; otherwise pitting will occur.

• Chrome plated instruments and stainless steel instruments should be sterilized separately because the electrolyte action can carry carbon particles from the exposed metal of a chromium plated instrument and get deposited on stainless steel.

• It is better to keep the instruments in wrapping. Detergents with chloride bases should be avoided because chloride residue unites with steam to form HCl.

• Detergents with pH of more than 8.5 may disrupt chromium oxide layer.

Packaging: Cleaned instruments should be packed prior to sterilization to protect them from recontamination after sterilization. The instruments should be packed in an appropriate wrapping material before sterilization. A wrapping material designed for a particular type of sterilizer should be used with the sterilizer. E.g. A single layer cloth wrap for steam sterilization, self sealingpolyfilm paper pouches for chemical vapour sterilization, paper wrap for dry heat sterilization. Wrapping material should be self sealing or heat sealed or double folded and sealed with appropriate tape.

TYPES OF STERILIZATION

HOT AIR OVEN: Dry heat denatures protein of microorganisms rendering it nonviable. It operates at a temperature of 160oC for 1-2 hours. Smaller dental units are convection ones without forced air circulation. Larger units have large capacities and are either convection or forced air circulation unit. Sterilization time begins only after the proper temperature of 160°C is reached and then this temperature must be maintained.Common misuse is opening the door to keep forgotten things without starting the cycle again.

RAPID HEAT STERILIZER:Uses controlled internal air flow system at 375°F. Sterilization claims of 6 minutes are made with unwrapped instruments and 12 minutes for wrapped instruments.

AUTOCLAVE: Moist heat denatures and coagulates protein of microorganisms. The sterilization is due to latent heat of vaporization present in moist heat. When steam condenses on contact with cooler surfaces, it becomes water and gives latent heat to that surface. This principle is used in autoclave.Temperature required is 121°C for 20 minutes at 15 pounds pressure. For practical considerations high pressure vacuum models are operated at a temperature of136°C for 5 minutes at 30 pounds pressure.

Generally all pliers stood well to combination of routine clinical use and steam autoclaving. However, the SS pliers appeared to perform the best.

UNSATURATED CHEMICAL VAPOUR STERILIZATION:

Uses specialsolution containing 0.23%formaldehyde (active ingredient) and 72.38% ethanol plus acetone, ketone, water and other alcohols. It’s a suitable method for orthodontic instruments.

Operates at 270oF(132o C) with 25 pounds pressure for 20 minutes.

ETHYLENE OXIDE STERILIZATION:

Ethylene oxide at normal temperature is a gas with very high penetrating ability. It acts by alkylating the amino, carboxyl, sulphhydril groups in protein molecules. It reacts with RNA and DNA. Used to sterilize heat sensitive instruments.

SPECIAL CONSIDERATIONS FOR ORTHODONTIC ARMAMENTARIUM

ORTHODONTIC PLIERS:

High quality stainless steel pliers can be sterilized by steam, dry heat, chemical vapour and ethylene oxide gas .For low quality pliers steam autoclave is not preferred for it may damage the material. For pliers with plastic parts ethylene oxide sterilization is the only effective method. Effects of Three Types of Sterilization on Orthodontic Pliers were studiedby Mazzochi et al. [15]. The study showed that clinical and metallurgic modifications of common orthodontic pliers after 500 cycles of sterilization in autoclave, chemiclave, or dry-heat units are negligible. Vendrell and Hayden compared the wear of orthodontic ligature-cutting pliers after multiple cycles of cutting stainless steel ligature wire and sterilizing with dry heat or steam autoclave. Fifty ligature-cutting pliers with stainless steel inserts were randomly divided into 2 equal groups to be sterilized in either dry heat or steam autoclave. Each plier was subjected to a series of ligature wire cuts followed by the assigned sterilization method. The amount of wear at the tip of each plier in both groups was measured with a stereomicroscope system and digital photomicrography. Orthodontic ligature-cutting pliers with stainless steel inserts showed no significant difference in mean wear whether sterilized with steam autoclave or dry heat. Steam autoclave sterilization can be used with no significant deleterious effects on pliers with stainless steel inserts.

ORTHODONTIC WIRES:

Smith et al18 evaluated the effect of clinical use and various sterilization/disinfection protocols on three types of nickel-titanium, and one type each of β-titanium and stainless steel arch wire. The sterilization/disinfection procedures included disinfection alone or in concert with steam autoclave, dry heat, or cold solution sterilization. Load/deflection and tensile tests showed no clinically significant difference between as-received and used-then-disinfected/sterilized wires. Although sterilization of stain less steel wire is not of much use as most of them have bends and do not fit in another patients mouth but this is very useful in case of NITI wires as they do not have bends and can be reused. These results suggest that nickel-titanium arch wires can be recycled at least once. Mayhew and Kusy [19] studied the effects of sterilization on the mechanical properties and the surface topography of 0.017 ×0.025-inch Nitinol and Titanal arch wires. Three approved heat sterilization methods were used namely, dry heat applied at 180° C (355° F) for 60 minutes, formaldehyde alcohol vapor pressure of 20 to 25 psi for 30 minutes at 132° C (270° F) and steam autoclave at 121° C (250°F) and 15 to 20 psi pressure for 20 minutes. They concluded that neither the heat sterilization nor multiple cycling procedures had a deleterious effect on the elastic moduli, surface topography, or tensile properties of Nitinol or Titanal arch wires.The bending moduli and the tensile strengths were approximately 10% greater for Nitinol than for Titanal. Kapila, Haugen and Watanabe [20] determined the effects of in vivo recycling interposed by dry heat sterilization (together referred to as clinical recycling, CR) on the load-deflection characteristics of nickel-titanium alloy wires (Nitinol and NiTi). The results indicated that both dry heat sterilization (DHS) alone, as well as clinical recycling (CR), produced significant changes in the loading and unloading characteristics of Nitinol and NiTi wires.

LIGATURES

Metal and elastomeric ligatures are potential agents in the transmission of infectious diseases. Cross-contamination in handling elastomeric ligatures is a serious concern in the orthodontic office, since cold sterilization can damage the elastomeric material. Mulick [21] recommended single-use dispensing of elastomeric materials to eliminate contact of canesor sticks with contaminated hands. Schneeweiss [22] described a method of cutting elastomeric modules into smaller sections and covering them with clear tubing, which could then be cold sterilized. During arch wire placement, the operator contacts only the outside tubing while removing ligatures. The used section of ligatures is cut off and discarded after ligation

ORTHODONTIC BANDS

Preformed bands are first checked on the patient cast, if in case they don't fit intraorally then these tried bands are cleaned in ultrasonic cleaner and disinfected with disinfectant solution for recommended time as per manufacturer before placing it back in the box .

ELASTICS AND ELASTOMETRIC CHAINS:

5% Bibforte. Elastomeric Rings, Chains etc are sterilized by immersing in 5% Bibforte Solution for 30 Minutes. Vapoclave(ethylene oxide) is preferred for E-chain and ligature wires.Retrieved Arch wires, ligatures other sharps are treated with 5% Bibforte solution and dispatched to the central processing unit in plastic boxes

ORTHODONTIC BRACKETS AND BUTTONS:

Reuse is not advised as it may impair the performance and increase the risk of patient injury. Effects of recycling on metallic direct-bond orthodontic brackets was studied by Buchman. The methods of three recycling companies (Esmadent, Ortho-Cycle, and Ortho-Bonding) as well as the author's flame method were examined for their effects on bracket base torque, slot width, and mechanical properties. While it appeared that the amount of dimensional changes in the brackets after recycling is of little clinical signifficance, the changes in the metallurgic microstructure suggest susceptibility to metallic intergranular corrosion .

RUBBER ITEMS AND SALIVA EJECTORS:

Best method is to discard them after each use. Ethylene oxide sterilization is ineffective for rubber material and they may be damaged by dry or moist heat sterilization.

HAND PIECES:

• Steam, dry heat, chemical vapour and ethylene oxide sterilization are acceptable for hand pieces.

• Run the handpiece over a sink for 20 seconds allowing water to flush through the hand piece thoroughly. Remove the bur.

• Scrub the hand piece thoroughly with detergent and water, to remove any debris. Rinse and dry the hand piece.

• Lubricate the hand piece with a good quality oil recommended by the hand piece manufacture

• Expel excess oil by running the hand piece for 2 seconds, after replacing the bur or hanging the hand piece in a hand piece rack.

• Remove the bur, if replaced. Clean the fiber-optic, bundle ends with alcohol Place the hand piece in a clear view sterilisation pouch, together with a chemical indicator strip

• Sterilise in an autoclave or chemiclave, according to themanufacturer's instructions. Do not leave the handpiece in the steriliser after sterilisation cycle is complete.

• Remove the hand piece from the bag, insert the bur, and use.

ROTARY INSTRUMENTS

Burs become very contaminated and are classed as critical items; they must be sterilised after use. Diamond and carbide burs may be safely autoclaved with minimal damage but carbon-steel burs are damaged by autoclaving. Carbon-steel burs may be sterilised by using a chemical vapoursteriliser. A glass bead steriliser at 218ºC for 10 seconds may be used to sterilise grossly contaminated carbon-steel burs during the same dental procedure.

VISIBLE-LIGHT CURING UNITS

It has been shown that light curing devices are a potential source of transmission of infectious diseases, due to contamination of the light curing tip, which directly contacts oral structures, and the handle, which becomes contaminated with blood and saliva from the operator's or assistant's gloved hands. Some new designs of unit feature removable, autoclavable light curing tips. However, the handles still present a problem, since they cannot be sterilised. Units should be cleaned and disinfected with a phenolic disinfectant after use. Plastic units should be disinfected using an iodophor. Glutaraldehyde disinfectants have been found to damage the glass rods in a fiber-optic light tip, with a subsequent reduction in light output; the use of this disinfectant should be avoided.

Procedure

• Thoroughly wipe and clean the whole unit.

• If the fiber optic light tip can be sterilised, detach it and sterilise as recommended by the manufacturer.

• Wrap the handle and light curing tip (if not autoclavable) in a wrap, soaked with an iodophor disinfectant. The wrap should remain in place for at least 10 minutes or until the unit is next used.

• Remove 
  the 
  wrap 
  and 
  wipe 
  the 
  unit 
  with 
  distilled water to remove residual disinfectant.

• Some practitioners cover the top light curing tip with Clingfilm, which is removed after use

• Disposable protective coverings could be used on the handles, providing they do not interfere with the unit's cooling mechanism.

STONES:

For diamond stones dry heat , chemical vapour and ethylene oxide gas sterilization are preferred. For polishing stones chemical vapour and ethylene oxide sterilization are preferred. Polishing buff is disinfected by immersing it in CIDEX (2% glutaraldehyde) solution or alternatively in 5% Bibforte for 30 minutes.

IMPRESSION TRAYS:

For aluminum trays dry heat is not preferred. For chrome plated trays all methods of sterilization can be employed. For plastic or acrylic trays, ethylene oxide or gluteraldehyde sterilization is preferred.Stainless steel hand instruments can be sterilized by autoclave, dry heat, chemical vapour and ethylene oxide sterilization. Ultrasonic tip can be autoclaved but for ultrasonic cord preferred methods are vapoclave and gluteraldehyde. Tongue blade, lip and cheek retractors can be sterilized by steam or dry heat. Welder points sterilized preferably by vapoclav(ethylene oxide).

ORTHODONTIC MARKING PENCILS.

Conventional orthodontic marking pencils cannot be autoclaved. Gas sterilization, as used in this study, is effective in killing bacteria, but is also costly and difficult, making it impractical for orthodontic offices. One article has suggested alcohol-containing permanent markers as a safe and effective alternative to pencils, but this report also noted that the pens become increasingly ineffective in eliminating bacteria the longer they are used. Because alcohols are intermediate disinfectants that do not kill spores or certain viruses, the permanent markers may be unreliable infection-control devices. Soaking or spraying the tips of marking pencils with disinfectants could be more effective than wiping, but this method is unlikely to gain acceptance from practitioners. The only sure way to avoid potential cross-contamination is to use the inexpensive disposable markers available from orthodontic supply companies [24].

Orthodontic adhesives. Composites used as orthodontic direct bonding adhesives have a polymeric matrix that can host and nurture a variety of aerobic and anaerobic microorganisms acting alone or in combination. Their accumulation can lead to the weakening of the bond and possibly the attacking of the tooth. A number of microorganisms have been identified as present on the removed direct bonding brackets. Results of rendering the adhesive microbe-resistant by adding a bactericide have shown to be encouraging [25].

Standard Operative Procedure For Dental Chair