12: Dental Drugs, Materials, Instruments and Equipment

CHAPTER 12 Dental Drugs, Materials, Instruments and Equipment

Chapter points

• This chapter covers the requirements of the NEBDN syllabus Section 12: Dental drugs, materials, instruments and equipment.

Introduction

The hazards associated with materials commonly used in dentistry are also discussed in Subchapter 1.1. Oral health products are discussed in Chapter 8.

The many different drugs and materials used in dentistry greatly benefit the patient. Some, however, can occasionally harm the patient, dental staff or the environment.

With all drugs and materials, ensure that the expiry date has not passed.

Dental drugs and products

Toothpastes, fluorides, anti-plaque and other mouthwashes, etc. are discussed in Chapter 8. Whitening agents, antiseptics and disinfectants (decontaminating agents), the other products used in oral healthcare, are discussed here. The most common drugs used in dentistry are anaesthetics, sedatives, analgesics and anti-microbial drugs.

Whitening Agents

Tooth-whitening products include strips, gels and varnishes containing hydrogen peroxide (H₂O₂) and are used for bleaching. H₂O₂ has been used for more than 70 years for oxygenating mouthwashes and to bleach teeth. The most common source of H₂O₂ used for whitening is carbamide peroxide which typically contains between 10% and 30% peroxide (15% is recommended), roughly equivalent to 3–10% hydrogen peroxide.

There are two methods of bleaching or whitening teeth:

External bleaching

External bleaching can be done in two ways:

• Laser bleaching uses laser light energy to accelerate the bleaching using high-concentration agents (30% peroxide) in gels in the dental office.

• At-home whitening is usually done with low-concentration oxidising agents in a whitening strip or a thin mouthguard. These hold a relatively low concentration of the bleaching agent next to the teeth for long periods of several hours a day and they are usually used for from five to 14 days. During this period, the oxidising agent penetrates enamel porosities and oxidises inter-prismatic enamel stain deposits (dentine is also bleached).

Enamel porosities: gaps in the mineral structure (hydroxyapatite) of enamel.

Inter-prismatic: The mineral deposits in enamel are laid out in bundles called enamel prisms. The spaces between these prisms are called inter-prismatic spaces.

The effects of bleaching can last for several months, but may vary depending on the patient’s lifestyle.

Some teeth may lose the bleached effect with time (rebound effect).

Bleaching is not recommended in:

• Children under the age of 16

• Pregnant or lactating women.

Problems with External Bleaching

• Temporary soft tissue irritation and increased tooth sensitivity, which disappear within one to three days of stopping or completing the whitening.

• Over-bleaching (‘over-white teeth’ or ‘hyperodonto-oxidation’).

• Chemical burns – this is a more serious problem and occurs if a high-concentration oxidising agent contacts unprotected tissues.

• Direct exposure of skin or eyes to hydrogen peroxide may cause irritation or burns, while ingestion may be irritating to the oesophagus and stomach.

Internal bleaching

Internal bleaching is performed on teeth that are discoloured due to internal staining. This usually happens in teeth that have become non-vital from trauma or caries (see Chapter 5). Internal bleaching involves drilling a hole to the pulp chamber, cleaning and filling the root canal, and sealing a hydrogen peroxide gel into the pulp chamber for some days, and replacing this as needed (so called ‘walking-bleach’ technique).

Antiseptics and Decontaminating Agents

Antiseptics and decontaminating agents should be used carefully as they can produce adverse reactions.

Adverse effects

Dermatitis: inflammation of the tissues of the skin.

Decontaminating agents such as hypochlorite, glutaraldehyde, hexachlorophene, benzalkonium chloride, formaldehyde, chlorhexidine, and alcohols can cause dermatitis. Furthermore:

• Hand-cleansing now usually involves the use of alcohol gels (see Chapter 1)

• Commercial alcohol-based agents, however, bind blood and protein to stainless steel and thus should not be used on surgical instruments

• Alcohols such as ethanol or isopropanol damage gloves so therefore, alcohol rubs/gels should not be used to decontaminate gloves

• Alcohol-impregnated wipes can be used for cleaning surfaces

• Alcohol-impregnated wipes are not effective in hand decontamination.

Metal instruments can be decontaminated using aldehydes, chlorhexidine or hypochlorite.

Hypochlorite may corrode metal.

Mouthwashes containing chlorhexidine occasionally cause stomatitis (sore mouth) or even rarely, severe allergies.

Local Anaesthetics

Local anaesthetics (LAs) most commonly used for dental procedures belong to a group of drugs called amides (for example lidocaine, prilocaine, articaine and mepivacaine). Most LA dental cartridges also contain a vasoconstrictor, either adrenaline or felypressin (see Chapter 13).

Reactions to these LAs are very rare.

Oral Sedation Agents

For oral sedation, drugs called benzodiazepines (BZPs) are used. These include alprazolam, diazepam, oxazepam, temazepam and lorazepam. The most commonly used are diazepam and temazepam.

Most benzodiazepines take effect within one hour after they are taken. There is often little to choose between them in terms of anxiolytic effect and, in prolonged use, all (especially lorazepam) may produce dependence. All impair memory and judgement at least for a while. Alcohol and other drugs that depress central nervous system (CNS) function (e.g. antihistamines, anti-convulsants, tranquillizers) must be avoided as fatalities have occurred (Chapter 13).

Anxiolytic: a substance that helps reduce anxiety.

Intravenous Conscious Sedation Agents

Again, benzodiazepines (especially midazolam) are the main agents used in conscious sedation. Midazolam is commonly used for intravenous sedation and occasionally for intra-nasal administration.

Intra-nasal: through the nose.

Adverse effects of benzodiazepines include confusion, slurred speech, lack of co-ordination, dizziness, headache, and nausea. In children, benzodiazepines can cause unusual behavioural reactions.

Flumazenil is a specific benzodiazepine antagonist, which allows rapid reversal of conscious sedation with benzodiazepines.

Antagonist: a drug that counteracts or reduces the effects of another drug.

Inhalational Sedation Agents

For inhalational sedation, sometimes termed relative analgesia or RA, two medical gases, nitrous oxide (N₂O) and oxygen, are used. These gases are stored in specifically coloured cylinders (Tables 12.1 and 12.2). At least 20% and more usually 30% oxygen is given.

TABLE 12.1 Medical Gases Used in the UK

TABLE 12.2 Gases Used in Anaesthesia/Sedation Machines

Size of Cylinder	Capacity (litres)
Size of Cylinder	Oxygen	Nitrous Oxide
E	680	1800
J	6800	18 000

ISO: stands for International Organization for Standardization, the body that is responsible for setting standards for a range of products worldwide.

Gases used in sedation/anaesthesia are usually supplied under high pressure either in cylinders or as a piped gas supply. The cylinders are made from molybdenum steel, in which gases and vapours are stored under pressure. The shape and colour of the plastic disc around the neck indicates when the cylinder was last examined. The most commonly used types/sizes are:

• H – these are free-standing and attached to the anaesthesia/sedation machine by a flexible hose. These are most economical, but reduce the mobility of the machine. Gas-specific connectors are used that make it impossible to attach the wrong regulator or fitting to the cylinder.

• E – these are attached directly to the machine via a yoke. A gas-specific pin-index system is provided on cylinders: pins on the yoke of the machine mate with holes drilled in specific positions on the valve of the cylinder. This provides a mechanical means of preventing incorrect connection.

What is molybdenum steel and why is it used for these gas cylinders?

Nitrous oxide (N₂O) is contraindicated for patients with:

• Bowel obstruction

• Pneumothorax

• Middle ear disease

• Sinus disease.

It is also contraindicated:

• Following eye operations (the use of nitrous oxide during general anaesthesia in gas-filled eyes may have serious side-effects because of gas expansion and increased intra-ocular pressure).

• In the first two trimesters of pregnancy (because of the effect of nitrous oxide on DNA production and the experimental and epidemiological evidence that nitrous oxide causes undesirable reproductive outcomes).

• In immunosuppressed patients or in patients requiring multiple general anaesthetic inductions, since nitrous oxide affects white blood cell production and function.

Pneumothorax: abnormal collection of air in the space between the chest wall and the outer surface of the lung.

Intra-ocular pressure: the pressure exerted by the fluids within the eye.

Analgesics (Pain Killers)

Pain is probably the most important symptom suggestive of disease. However, the absence of pain does not mean a patient may not have disease. Different people respond differently to pain. The threshold for tolerance is lowered by tiredness, psychological factors, etc.

Why does Pain Occur?

Pain occurs when there is tissue damage that leads to the release of chemicals such as prostaglandins. These chemicals are produced via an enzymatic pathway involving a chemical called cyclo-oxygenase (COX). Certain drugs such as non-steroidal anti-inflammatory drugs (NSAIDs, for example aspirin) block COX and thus prostaglandin synthesis.

NSAIDs

• Produce a bleeding tendency

• Produce gastric irritation and sometimes ulceration

• Can cause deterioration of kidney function

• May worsen asthma and cause fluid retention as well as nausea, diarrhoea or tinnitus (buzzing in the ears)

• Interfere with the action of anti-hypertensive drugs and diuretics.

Tinnitus: the perception of a ringing-type sound in the ears when there is no sound.

Diuretic: a drug that increases urinary flow and so reduces the amount of fluids in the body when they are in excess.

Aspirin, however, has long been in use, and its efficacy and adverse effects are well recognised. This is however, not so of the newer NSAIDs. Nevertheless, aspirin is contraindicated in:

• Children under the age of 12 years (because it possibly causes Reye syndrome – a serious liver disease)

• Mothers who are breastfeeding (again, because it possibly causes Reye syndrome)

• Patients with gastric disease

• Patients with bleeding tendency.

Paracetamol is preferred in these situations.

Why is aspirin avoided in people with a bleeding tendency?

Paracetamol

• Paracetamol, also called acetaminophen, is the first choice analgesic for management of mild transient pain, especially in children and old people. It also reduces fever.

• It is not an NSAID but has similar analgesic properties to aspirin. However it is less irritant to the stomach than is aspirin.

• Paracetamol overdose – or repeated doses – lead to liver damage (hepatotoxicity). Paracetamol may be given in the short term to any patient with a healthy liver, but it should not be given to a heavy alcohol drinker or one who has stopped alcohol after chronic intake.

• Compound preparations (co-codamol) of paracetamol with codeine have no significant advantages; in fact codeine has no place in dental analgesia since it can be very constipating and may occasionally cause dependence.

Patient-controlled analgesia (PCA)

• PCA means using a special machine that allows the person in pain to control the amount of drug they are using for relief of the pain. PCA is increasingly used when pain is severe, for example cancer pain. Much stronger analgesics, such as morphine, are used in PCA.

Anti-Microbials

Anti-microbials is a term that includes anti-bacterial (antibiotics), anti-fungal and anti-viral drugs. Indications for the use of antibiotics include:

• Odontogenic infections in ill, toxic or susceptible patients (e.g. immunocompromised patients)

• Acute ulcerative gingivitis

• Severe jaw or neck infections

• Some instances of:

• Prophylaxis in surgery:

In major procedures (e.g. osteotomies or tumour resection)

In immunocompromised or debilitated patients, or following intravenous bisphosphonate therapy, or after radiotherapy to the jaws.

Bisphosphonate: a group of drugs that prevent loss of bone mass and, in some patients may cause death of part of the jaws (osteonecrosis).

Anti-microbials will not remove pus. Drainage is therefore essential if there is pus.

Anti-bacterial drugs

• The bacteria causing most odontogenic infectious are penicillin sensitive.

• Pus (as much as possible) should be sent for culture and sensitivities, but anti-microbials should be started immediately if they are indicated.

• Anaerobic bacteria are implicated in many odontogenic infections: they often respond to penicillins or metronidazole.

• Very high blood levels of the drug can be achieved with oral amoxicillin; also patients usually comply well with this treatment (see below).

• Another anti-microbial should be used if the patient is allergic, or has had penicillin within the previous month (resistant bacteria).

Culture and sensitivities: this involves inoculating a special nutrient medium with the sample of pus (or other sample) to allow the micro-organisms to grow. The micro-organisms are then identified and various drugs added to them to see which one will stop their growth or kill them.

Anti-fungals

Anti-fungals, for example miconazole, are used to treat oral or oropharyngeal fungal infections. However, before starting with anti-fungals the clinician will check why the patient is having the infection (see below). It is important to treat this underlying cause along with anti-fungal treatment.

Anti-virals

Most anti-virals, for example aciclovir, will be of maximum benefit if given early in the disease. They are indicated mainly for patients who have an immune defect.

Adverse effects of anti-microbials

• Anti-bacterials predispose to candidosis (see Chapter 5).

• Tetracyclines are contraindicated in pregnancy and children younger than 7–8 years. This is because they can cause tooth discoloration (see Chapter 5).

Anti-microbials and foods

Erythromycin, penicillins (some), rifampicin and tetracyclines (except doxycycline) should be taken at least 30 minutes before food. This is because their absorption is otherwise delayed. Metronidazole may cause headaches if taken with alcohol.

Anti-microbial and drug interactions

• Metronidazole, erythromycin, some anti-fungals such as miconazole, and occasionally amoxicillin, can enhance the action of warfarin, causing bleeding.

Haemostatic Agents

• Haemostatic agents act to stop bleeding. They act at differing sites in the complex pathways of blood coagulation and fibrinolysis.

• Most haemorrhage will cease with the use of topical haemostatic agents.

• Blood and blood products such as blood-clotting factors are required if there is serious bleeding. In the past, these were typically derived from human or animal material. This carried a potential risk of transmission of infections (e.g. HIV, hepatitis B virus infection, prion disease – see Chapter 5). Nowadays, drugs called recombinant factors are widely available, which avoid these risks and the religious objections to certain treatment (e.g. among Jehovah’s Witnesses).

• Occasionally drugs such as desmopressin (which promotes release of some blood-clotting factors), tranexamic acid (anti-fibrinolytic agent), aprotinin (inhibitor of proteolytic enzymes plasmin and kallikrein) or etamsylate (corrects abnormal adhesion of platelets) are needed.

Topical Haemostatic Agents

• Haemostatic agents are often of animal source (Table 12.3) and, unless they are of synthetic origin, may thus be contraindicated in some patients on cultural/religious grounds.

• Floseal and fibrin sealants are the most effective.

• Gelfoam swells, so a lot of the effect is a mechanical effect.

• Surgicel has a relative anti-microbial effect compared with other haemostatic agents.

• Avitene has the worst foreign body reaction of all of these particular agents.

TABLE 12.3 Some Topical Haemostatic Agents

Agent	Main Constituent	Origin
Avitene	Collagen	Bovine
Colla-Cote	Collagen	Bovine
Floseal	Thrombin	Bovine
Gelfoam	Gelatin	Bovine
Helistat	Collagen	Bovine
Instat	Collagen	Bovine
Thrombinar	Thrombin	Bovine
Thrombogen	Thrombin	Bovine
Thrombostat	Thrombin	Bovine
Beriplast	Fibrin	Various
Cyclokapron	Tranexamic acid	Synthetic
Surgicel	Cellulose	Synthetic

Floseal, Avitene and fibrin sealants are expensive. Gelfoam, Surgicel and collagen sponges are relatively inexpensive.

Drug safety

Adverse Drug Reactions

Almost any drug may produce unwanted or unexpected adverse reactions, some of which are life-threatening – such as anaphylaxis (Chapter 2). These reactions are often predictable. However, some are rarely predictable unless the person has previously reacted adversely.

Patients should be warned if serious adverse reactions are predictable and likely to occur (e.g. weight gain, hypertension and diabetes with systemic corticosteroids). They should also be provided with the appropriate warning card to carry.

The real number of adverse drug reactions that occur is not known, and many adverse reactions are probably not, at present, recognised as drug related.

Adverse drug reactions should be reported using the ‘Yellow card’ system.

Using Controlled Drugs

• Some prescription medicines contain drugs that are controlled under the Misuse of Drugs legislation. These medicines are called controlled medicines or controlled drugs. A clinician can prescribe privately any Schedule II or III controlled drug on an FP10PCD form as long as the drug meets the dental needs of the patient. The forms are available from primary care trusts (PCTs).

• NHS and private controlled drug (Schedule II, III or IV) prescriptions are valid for 28 days. Invoices for controlled drugs must be kept for a minimum of two years. All Schedule II, III, and IV (part 1) controlled drugs must be denatured or rendered irretrievable before they are disposed.

• Patients, or their representatives collecting Schedule II and III controlled drugs must sign for them when collecting from the pharmacy.

• Midazolam and temazepam are UK Schedule III controlled drugs. Midazolam does not need to be kept in a controlled drug cabinet and records do not have to be kept in a controlled drug register.

• If temazepam (Schedule III) is held in a dental practice it must be stored in a controlled drug cabinet but no record in the controlled drug register is required.

Schedule: under the Controlled Substances Act (CSA), all controlled drugs are classified into five groups called schedules. Schedule I drugs are recreational drugs not meant for medical use (e.g. heroin); schedule II drugs also have a potential for misuse but are used as medicines also (e.g. cocaine and morphine); schedule III, IV and V are drugs with decreasing potential for misuse but which are useful medicines.

Visit the website of the Medicines and Healthcare products Regulatory Agency (MHRA; http://www.mhra.gov.uk), the medicines safety watchdog, to read more about Yellow cards.

The webpage ‘Controlled drugs guidance for GP practices’ (http://www.gp-training.net/protocol/therapeutics/cd.htm) gives useful information about what should be included in a controlled drugs register and how they should be stored.

Drugs, Products and Cultural Issues

Cultural issues may affect the use of and prescription of certain drugs and dental healthcare products. However, remember that some religions, though at first sight apparently objecting to some constituents of drugs, do not prohibit their use if the product is designed to enhance health. Alcohol and some animal products are the sources of most concern. Some cultures are characterised by the use of certain drugs, for example Rastafarians often use cannabis.

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