Sterilization And Disinfection In Dentistry Notes

History Of Surgery Ancient Period

India: Ayurveda is the name of ancient Hindu medicine. The origin of Ayurveda has been traced to Vedic times, about 5000 BC. Dhanwanthari is called the father of Ayurvedic medicine.

• Application of bone prosthesis, concepts of wound healing, ligation of bleeders, and knowledge of instruments were known to the treating Vaidyas (doctors). Sushrutha is called the father of Indian surgery.
• His book Sushruta Samhita written in 1500 BC also describes various instruments and operations. Cutting off the nose and ears was a type of punishment in the olden days. Hence the reconstruction of these organs was required. The result is ancient Indian rhinoplasty. It was very popular.

Read And Learn More: Clinical Medicine And Surgery Notes

Egypt: Civilization which took place along the Nile Valley also had a good knowledge about wounds, case histories, and even trephination of skulls. All this information was written in the leaf of the papyrus plant which is still preserved. King Hammurabi laid the code of conduct for the treatment and for the surgeons. For wrong treatment, surgeons were punished by severing their hands.

China: A few books are available describing physical signs, examination of pulse, and acupuncture.

Greece And Rome: Hippocrates, known as the father of medicine and surgery was from the island of Cos. The description of amputation and treatment of ulcer and fistula is present in Corpus Hippocratic.

• The body of writing attributed to Hippocrates, the Hippocratic Corpus, is a collection of roughly 70 works that show no uniformity in teaching or in prose style. With a few exceptions, the dates of these works range between 450 and 350 BC.
• They are the oldest surviving complete medical books. Corpus contains concepts about acute diseases, epidemics, and regimens. Hippocratic oath is one of the parts of the corpus.
• Galen, a Greek physician, was the first to do anatomical dissection of cadavers. He had done a lot of experiments on animals and conducted cataract surgery.

History Of Surgery Medieval Period

• There was a decline in surgery in India and Europe during this time. Because of growing Buddhism and the message of nonviolence (ahimsa), many people considered surgery as ‘demoniacal’ or asuri medicine.
• However, during this period Arabs and Muslims entered the intellectual arena. Between the 7th and 15th centuries, they made considerable contributions to the field of surgery like building hospitals (for example. the first hospital in Baghdad), writing books, etc.
• In Spain, many hospitals came into existence in this period. Treatment of empyema, pericarditis, and hysterectomy was done for the first time.

History Of Surgery Modern Period

1514–1564: Andreas Vesalius, born in Brussels, professor of anatomy and surgery at Padua in Italy, published his first anatomy text called Fabrica. (This was possible because of the printing press.) He emphasized for the first time that anatomy can be learned only by dissecting the human body, not the animal body He was the first to put forth the concept of ‘hands-on’ education. Knowledge of anatomy strengthened surgery.

1510–1590: Ambroise Pare was trained as a barber surgeon. He served in the military of France as an army surgeon. He played a major role in updating old-fashioned surgery and concepts.

• He represented the severing of the final link between surgical thought and techniques of the ancient and pushed towards the modern era. He innovated the use of turpentine oil in gunshot wound dressings.
• He felt that individual vessels should be ligated rather than mass ligation for amputations. He always said, “I treated him. God cured him”.

1728–1793: John Hunter was a surgeon, anatomist, physiologist, pathologist, and experimentalist. He is described as the father of the modern science of surgery. He was considered to be one of the most influential surgeons of all time. He was Scottish.

1800: King George 3 chartered the Royal College of Surgeons of London.

1. First ligated a case of aneurysm and demonstrated that collaterals will develop and limb can be saved.
2. Gave the idea of tissue preservation
3. Introduced study of surgical pathology
4. The Adductor canal in the thigh is in his name— Hunter’s canal
5. Worked vigorously on venereal diseases like syphilis and gonorrhea.
6. Hunterian chancre in syphilis
7. Did transplantation of a spur in Cock’s comb
8. Great teacher
9. Collection of more than 13,000 specimens— Hunter’s collection is housed in England’s Royal College of Surgeons’ Museum. Unfortunately, the Nazi bombing attack on London in World War II destroyed most of Hunter’s assemblage.

1843: Queen Victoria chartered the Royal College of Surgeons of England.

1827–1912: Joseph Lister introduced the present-day concept of asepsis and antisepsis. He introduced for the first time carbolic acid as an antiseptic for destroying bacteria. Carbolic acid (phenol) has been in use as a means of deodorizing sewage.

• So, Lister tested the results of spraying instruments, surgical incisions, and dressings with a solution of it. Lister found that carbolic add solution swabbed on wounds markedly reduced the incidence of gangrene and subsequently published a series of articles on the Antiseptic Principle of the Practice of Surgery describing this procedure on 16 March 1867 in the journal The Lancet.
• He also sprayed carbolic acid in the operation theatres and around the operation table. He dipped his hands in phenol solution and corrosive sublimate. He developed sterile absorbable sutures so that they could be left deep inside the wound.
• Earlier after suturing at depth, these sutures were brought outside which will be removed at a later date. He said for the first time “Laudable pus in fact is not laudable but due to some organisms”. Thus, Listerism became popular and acceptable among German-speaking surgeons.
• The late 19th century saw developments in the direction of asepsis and antisepsis in the form of boiling, autoclaving, and wearing of sterile gowns, drapes, gloves, hats, masks caps, etc.
• He also made surgeons wear clean gloves and wash their hands before and after operations with 5% carbolic acid solutions. It should be noted that he first persuaded Charles Goodyear1 to manufacture rubber gloves for his nurse since the carbolic acid caused her to suffer from contact dermatitis.
• Instruments were also washed in the same solution and assistants sprayed the solution in the operating theatre. One of his conclusions was to stop using natural porous materials in manufacturing the handles of medical instruments.

1822–1895: Louis Pasteur was a French scientist. He discovered microbes and putrefaction. He reasoned that this could be the cause of pus. Pasteurization of milk was a landmark concept. This has largely decreased milk-borne diseases including tuberculosis.

1929: Landsteiner made a discovery of blood groups. This led to further development of blood banks and storage which helped surgery to grow further. Spenser Wells devised hemostat-artery forceps.

Antibiotics

Paul Ehrlich was a German who wanted to treat and cure syphilis; he developed “Salvarsan 606”.

Alexander Fleming accidentally discovered penicillin in 1928 and heralded a new era in chemotherapy.

Radiology

1895: Roentgen discovered X-rays.

1901: Walter Cannon discovered fluoroscopy when he was a medical student.

Surgery of Body Cavities

• The technique of suturing slowly developed and surgeons started resections and anastomosis of various structures (hollow tubes).
• Wilkie removed the first inflamed appendix (Wilkie’s syndrome).
• Bassini and Halsted contributed to hernia repair. Billroth, a great Viennese surgeon, operated on gastric cancer.
• Antoine Lambert is famous for his ‘in and out’ and ‘out and in’ inverting sutures for gastrojejunostomy.
• Charles McBurney of America described the famous incision for appendicectomy in 1889.
• Lord Moynihan of Leeds did a lot of work on gallbladder stones.

To conclude, the evolution of surgery has taken more than 2,000 years. What is practiced today is evidence-based medicine. Surgery has become safe today. The results of surgery are good in good hands. It means proper training and coaching of a surgeon.

Sterilisation And Disinfection

In spite of scientific advances in understanding the pathogenesis of various diseases and better understanding of pharmacotherapy, infection remains the ‘number one’ enemy for surgeons. So, every attempt should be made to minimize the infection rates in the ward, hospital, and in the operation theatre.

• Joseph Lister called infective agents disease dust and introduced carbolic acid spray as an antiseptic agent. Hence, Joseph Lister is called the father of modern surgery.
• This chapter deals with the fundamental principles of various methods of sterilization and disinfection and their usage in day-to-day clinical practice.

Sterilization is defined as a process by which an article, object, or surface is free of all microorganisms in the vegetative form and in the spore state. This includes viruses, bacteria, their spores, and fungi.

Disinfection means the destruction of all pathogenic organisms capable of giving rise to infection. Rarely does this process kill spores. Disinfection must never be used when sterilization is possible.

Antisepsis means the prevention of infection by inhibiting the growth of bacteria in wounds or tissues.

Agents Used In Sterilisation

Gives the classification of agents used in sterilization.

Sterilisation Classification

Agents used in Sterilisation Physical agents

1. Sunlight
2. Drying
3. Heat
   • Dry heat
   • Moist heat
4. Filtration
5. Radiation

Agents used in Sterilisation Chemical agents

1. Alcohol
2. Aldehyde
3. Dye
4. Halogens
5. Phenols and cresols
6. Gases
7. Surface-active agents
8. Metallic salts

Physical Agents

1. Sunlight

It is an example of a natural bactericidal agent which causes sterilization of tank water, rivers, etc. It is mainly because of ultraviolet rays in addition to heat rays.

2. Drying

Drying in the air has ill effects on the growth of bacteria. In fact, 80% of the weight of bacteria is due to water. However, it does not affect spores and it is an unreliable method.

3. Heat

Heat is the most commonly employed and most reliable method of sterilization

• Most reliable
• A rapid method of sterilization
• No harmful residue

Agents used in Sterilisation Two types

• Dry heat
• Moist heat

Dry heat: This method of heat kills the organisms by protein denaturation and oxidative damage. Types

1. Red heat: Inoculating loops or wires, tips of forceps, and needles are held in the flame of a Bunsen burner till they become red hot.
2. Flaming: Glass slides, scalpels, and mouths of culture tubes are passed through Bunsen flame a few times.
3. Incineration: This is used to destroy soiled dressings, bedding, bandages, etc.
4. A hot air oven is the most widely used method of sterilization by dry heat.
   • The temperature required is 160° C for one hour or 180° C for 20 minutes.
   • Glassware, forceps, scissors, scalpels glass syringes can be sterilized. Materials like oils, greases, dry powder, etc. can also be sterilized by this method.

Hot Air Oven

• Glass syringes, test tubes, pipettes
• Metal forceps, scissors, scalpels
• Oil, jelly, powder
• Swab sticks

Sterilisation Control-Indicators

1. Spores of nontoxigenic strain of Claustridium tetani
2. Browne’s tube
3. Thermocouples.

Moist heat: This method of heat kills organisms by coagulation and denaturation of their proteins.

In cases of spores, steam condenses on it, increases its water content, and causes hydrolysis and breakdown of the bacterial protein.

Sterilisation Control-Indicators Types

1. At temperatures below 100° C
   • Pasteurization: Temperature of 63° C for 30 minutes (holder method) or 72° C for 15 to 20 seconds (flash method), followed by cooling quickly to 13° C or lower. Mycobacteria, brucellae, and salmonellae are destroyed by this method but spores are not destroyed.
   • Inspissation: Serum or egg media (Lowenstein-Jensen’s media) are sterilized in the inspissator at 80–85° C for half an hour on three consecutive days.
   • Vaccine bath: Vaccines of nonsporing bacteria are sterilized in special vaccine baths at 60° C for one hour.
2. At 100° C
   • Boiling (temperature 100° C): Vegetative bacteria are killed at 100° C but sporing bacteria require considerable time for boiling. Hence, boiling is not recommended for sterilizing instruments.
   • Tyndallisation: Steam at 100° C for 20 minutes on three consecutive days. It is used for sterilization of egg, serum, or sugar-containing media.
   • Autoclaving or steam under pressure (temperature above 100° C): This is the most popular method.

Principle: Water boils when its vapor pressure equals that of the surrounding atmosphere. When the pressure inside a dosed vessel increases, the temperature at which water boils also increases. When steam comes into contact with a cooler surface, it condenses to water and gives up its latent heat to that surface. Condensed water ensures moist conditions for killing the microbes present. All the air must be removed from the autoclave chamber before autoclaving.

Steam Above 100° C—Advantages

• Greater lethal action of moist heat
• Quick action
• Penetrates porous materials such as linen, paper and cloth wrappers, cotton wool stoppers

Temperature employed: Sterilisation is carried out between 108° C and 147° C. Commonly, a temperature of 121° C at 15 lb pressure for 15 minutes is used.

Thus dressings, instruments, laboratory-ware, and media can be sterilised with autoclaving. However, it is not suitable for bottled fluids.

Sterilization control: Spores of Bacillus stearothumophilus are used as test organisms.

• Chemical indicators: Browne’s tubes
• Thermocouples
• Autoclave tapes.

4. Filtration

It is used to get rid of microorganisms from heat-labile liquids and substances such as sugars and urea, which are used for the preparation of media. Hence it is useful for antibiotic solutions, sera, and carbohydrate solutions used in the preparation of culture medium. Different types of filters include earthenware filters, asbestos filters, sintered glass filters, membrane filters, etc.

5. Radiation

1. Nonionising radiation: Low energy type, for example
   • Infrared radiation: Used for mass sterilization of syringes.
   • Ultraviolet radiation: This can be used to disinfect hospital wards, operation theatres, viral laboratories, etc.
2. Ionizing radiation: X-rays and gamma rays are examples. They have high penetration power and are highly lethal to all cells including bacteria. Gamma radiation is used to sterilize plastic tubes, catheters, syringes, culture plates, etc. This method is also known as cold sterilization, as there is no appreciable increase in the temperature.

Chemical Agents

• Chemical agents act by protein coagulation and disruption of cell membranes. They are mainly used for disinfection rather than sterilization.
• Disinfectants are antimicrobial agents used to kill potentially infectious agents present in inanimate objects, for example. surfaces, water, etc.
• Chemical disinfectants that can be safely applied to skin or mucous membranes and are used to prevent infection by inhibiting the growth of bacteria are called antiseptics.

1. Alcohols

Ethyl alcohol (ethanol) and isopropyl alcohol are commonly used. They rapidly kill bacteria, including tubercle bacilli, but they have no action on spores and viruses. They are used in a concentration of 60–70% in water as skin antiseptics before a surgical incision.

• Isopropyl alcohol is better than ethanol because it is a fat solvent, more bactericidal, and less volatile. Hence, it is used to disinfect clinical thermometers.
• Methyl alcohol is effective against fungal spores. However, it is toxic and inflammable and hence, not used.

2. Aldehydes

They are bactericidal and sporicidal.

1. Formaldehyde (HCHO): This is used to preserve anatomical specimens. It is an irritant, water-soluble gas.
   • Formaldehyde gas is used to fumigate wards, sick rooms, etc.
2. Glutaraldehyde: It is effective against tubercle bacilli, fungi, and viruses. It is less irritant than formaldehyde.
   • This is used to sterilize cystoscopes, bronchoscopes, endotracheal tubes, and metal instruments, which are heat-sensitive.
   • A 2% buffered solution is used.
   • It has no deleterious effect on the cement or the lenses of instruments.
   • Commercially available as ‘Cidex’.

3. Dyes

• They are aniline dyes and acridines which are used as skin and wound antiseptics. Acriflavine and proflavine are examples of acridine dyes.
• They act against gram-positive and gram-negative organisms. They are little if at all, affected by the presence of pus.
• Whenever a cavity has to be packed or a tie-over dressing to be applied following skin grafting, gauze soaked in acriflavine can be used.

Aniline Dyes

• Brilliant green, malachite green, crystal violet
• More active against gram-positive organisms
• Pus inhibits their activity

4. Halogens

Iodine is a bactericidal agent with moderate activity on spores. It is also active against tubercle bacillus. Iodine is used almost exclusively as a skin disinfectant (antiseptic).

• Mixtures of iodine with surface-active agents that act as a carrier for iodine are known as iodophores. Betadine is an example of this. This is also active against fungi, trichomonas.
• When chlorine or hypochlorites are added to water, the chlorine reacts with water to form hypochlorous acid. It is a strong oxidizing agent and an effective disinfectant.
• Chlorine and hypochlorite solution (EUSOL) also are other examples.

5. Phenols and cresols

These are obtained by distillation of coal between temperatures of 170° C and 270° C. They cause cell membrane damage.

• Phenol (carbolic acid) was introduced first by Lister, the father of antiseptic surgery. It is a powerful microbicidal substance. It is bactericidal at a concentration of 1%.
• Lysol, cresols, and Chlorhexidine are also phenols. Chlorhexidine (hibitane) is nontoxic, skin antiseptic, active against gram-positive and gram-negative organisms, and moderately active against mycobacteria.

6. Gases (vapor-phase disinfectants)

1. Ethylene oxide: It is a highly inflammable colorless gas. Hence, it is mixed with inert gases such as carbon dioxide or nitrogen so that its explosive tendency is eliminated. It is highly lethal to all kinds of microbes including spores and tubercle bacilli.
   • It is used for sterilizing heart-lung equipment, books, clothing, glass, plastic, etc. Thus routinely used catheters such as Foley’s catheters, Ryle’s tube, etc. are sterilised by ethylene oxide gas.
2. Formaldehyde gas: Used for fumigation of operation theatres and rooms, often after doing septic cases.
3. Betapropiolactone: It is also used for fumigating purposes. It is also active against viruses.

7. Surface-active agents

Substances that alter energy relationships at interfaces leading to a reduction of surface or interfacial tension are known as surface-active agents or surfactants. They are used as wetting agents, detergents, etc.

• The most commonly used preparations are cationic surface-active agents. They are bactericidal. They have no action on spores, tubercle bacilli, etc. Commercially available preparation includes cetrimide (cetavalon). They are most active in alkaline pH. Pseudomonas aeruginosa is particularly resistant to these compounds.
• Soaps are also active against gram-positive and negative organisms.

8. Metallic salts

The salts of silver, copper, and mercury are used as disinfectants. Mercurochrome is less toxic and is used as a mild antiseptic. Clinically it is used in the treatment of skin grafted ulcers after the graft has taken up well.

Quick Revision Of Sterilisation Of Commonly Used Instruments In The Operation Theatre

• Surgeon’s knife (scalpel): Glutaraldehyde
• Forceps, retractors, etc.: Hot air oven
• Foley’s catheter: Gas sterilization (ethylene oxide)
• Glass syringes: Hot air oven
• Operation theatre: Formaldehyde gas
• Clinical thermometer: Isopropyl alcohol

Testing Of Disinfectants

1. Rideaol Walker test: Phenol is taken as a standard disinfectant. Suspension of typhoid bacilli is subjected to the action of varying concentrations of phenol and the disinfectant to be tested and compared with phenol.

2. Chick Martin test Disinfectant acts in the presence of organic matter.

Procedure Of A Patient Undergoing Surgery

Admission

A patient who requires a surgical procedure that needs to be done under general or regional anesthesia is admitted 1–2 days before the procedure. Admission is necessary to assess his fitness before surgery and provide him with adequate preoperative care, and appropriate medication to optimally control his other medical conditions such as diabetes, asthma, cardiac conditions, etc.

In The Ward

• The patient is also seen and examined by duty doctors (maybe a postgraduate or teaching faculty) and a complete case record is written (case sheet). Generally in a medical college, it is written by interns.
• The patient is also given proper medication if required, for example. treatment of hypertension diabetes or asthma, etc. If a patient has serious comorbid medical conditions, he will be seen by cardiologists and anesthesiologists so that preoperative optimization is done to decrease the risks of surgery, for example.
• The patient had a myocardial infarction 1 year back and he has come for laparoscopic gallbladder removal (lap cholecystectomy). Such moderate to high-risk patients are seen well in advance by the concerned department may be as outpatient or as an inpatient so as to decrease the risks involved in surgery.

Premedication

A patient who is undergoing surgery will have a lot of anxiety, apprehension, worries, etc. Hence, drugs are administered the previous night which will help in a smooth transfer of the patient to the operation theater (OT).

In The Operation Theatre

1. The patient will be anesthetized by anesthesiologists.
2. Surgeons and nursing staff will scrub (hand wash) for a minimum of 3 minutes. Scrub solutions include Chlorhexidine solution, povidone iodine, etc. This simple method of washing before surgery will decrease the contamination of the surgical site by bacteria on the surgeon’s skin.
3. The surgical site is cleaned with povidone-iodine and spirit.
4. The entire body is covered with sterile drapes except the surgical site for incision.
5. A surgical procedure is carried out.
6. The patient is shifted to the postoperative ward for monitoring hemodynamic parameters for a few hours to days depending upon the severity of the situation. A few examples are given below.
   • A patient who undergoes a lymph node biopsy or hernia surgery can be discharged on the same day evening—daycare surgery.
   • In laparoscopic surgery, for example. lap cholecystectomy, the patient can be discharged within 1–2 days.
   • Open heart surgeries need to be monitored for 3–5 days in the postoperative ward.
7. Once hemodynamic stability is achieved as in major surgical procedures, he is shifted to the ward.

In The Ward

• Till discharge, the wound is examined for any wound infection, or a careful search is carried out for any postoperative complications, for example. the patient developed a fever on the 2nd postoperative day following a partial glossectomy done for carcinoma tongue.
• The most probable reason is respiratory infection which may be atelectasis (collapse) or pneumonia. Another example: The patient has developed pain in the leg and edema of the leg on the 4th postoperative day. It may be deep venous thrombosis. Many such examples can be given.

Discharge

• When a patient recovers completely with or without complications, when the surgeon feels he is fit for discharge, he is discharged with advice tailored to the patient depending upon the type of surgery, occupation of the patient, etc.
• For example, in a day care surgery like a hernia the patient may be discharged on the same day but he would be advised not to do heavy work for a month or so.
• A patient who develops deep vein thrombosis needs to take anticoagulants for at least 6 months in the postoperative period.

Follow Up

Generally, the patient is asked to come for a follow-up once, twice, or more depending upon the case. You will understand this better after you study various diseases.