Local features

Many signs of infection (Fig. 7.1) are those of inflammation (pain, swelling, redness, heat), but not all inflammation is in response to infection: all these signs can be seen in rheumatoid arthritis. In infection you may also find suppuration (pus formation), an obvious cause and a greater systemic response.

Fig. 7.1 An acute facial infection of dental origin.

The pain tends to be throbbing or aching or tenderness. Its severity depends upon the pressure of fluid within the tissue and changes with time.

Where swelling is largely due to oedema it is relatively soft. It tends to move within the tissues and accumulates at sites least constrained by fascia, as for instance, lips and eyelids (Fig. 7.2).

Fig. 7.2 A spreading infection or ‘cellulitis’ with marked oedema, particularly seen in the lips.

Some swelling is due to the cellular infiltrate of inflammation. This is more firm and is described as ‘indurated’ (hard). This induration is not due to fibrosis, but nevertheless may take days or weeks to resolve in infections in which it is a prominent part.

For swelling due to oedema or to cellular infiltrate it is difficult to define the precise margin of a swollen area: there is a gradual change at the edge towards normality.

Many infections form pus; this adds to the swelling. A collection of pus is called an abscess. When close to the surface it may cause a yellowish discolouration of the overlying mucosa but, when deeper, all that will be seen is the redness of inflammation. Swelling due to pus has a very different feel to it from that due to inflammatory exudates. It is described as ‘fluctuant’, but that encompasses several different sensations detected by the examining fingers (Fig. 7.3). Classically, fluctuance is determined by placing two fingers at the sides of a swelling and detecting fluid movement caused by a third finger on the centre. That is not easy inside the mouth, where it may be possible to detect fluid movement only by running one finger along the swelling. For deeply placed abscesses in the neck, the feeling is more like tense springiness.

Fig. 7.3 Eliciting ‘fluctuance’.

a. Classical use of three fingers, the outer of which detect fluid movement as the central one applies pressure.

b. Inside the mouth one finger may be run across the surface to detect fluid movement.

c. For a deeply placed neck abscess, fluctuance is felt more as ‘springiness’.

The redness (and local heat) of inflammation is due to increased blood flow. There is no local increase above body core temperature and thus for intraoral locations there may be no local ‘heat’.

Bacterial infections of dental origin have a characteristic natural history. The time scale is typically hours to days, from the first symptoms to the first request for medical or dental assistance. If infection is initially periapical there may be considerable pain, while exudate and pus are under pressure within bone, followed by a reduction in pain and rapidly increasing facial or neck swelling as the infection escapes bone and pressure reduces. At this stage the external swelling is largely due to oedema, and therefore soft. Over a period of 1–5 days pus may form centrally within this swelling: this localization is associated with developing pain, local tenderness and fluctuance. Oedema and pus may spread inwards towards the pharynx as readily as outwards towards the face.

When infection shows no significant localization of pus and has a greater tendency to spread it is called cellulitis. Where the predominant feature is pus formation it is called an abscess. However, almost all infections show elements of both and any infection starting as a cellulitis tends to localize over a period of days.

Spread of infection

Pus tends to move under influences such as pressure, gravity, local heat or muscle layers towards surfaces. When it reaches a surface (internal or external) it bursts out or discharges, but often with large abscesses it takes days to drain and spontaneous drainage is unreliable. Pus is an effective defence against spreading infection.

Most suppurative dental infections discharge into the mouth via a sinus, sometimes without obvious acute infection (Fig. 7.4), and usually onto the labiobuccal aspect of the alveolus. Apical infection from maxillary lateral incisors is more likely to drain palatally and from any tooth may point lingually, palatally or even onto the skin (Fig. 7.5). The commonest site of discharge onto skin is the point of the chin, arising from infection at the apex of a mandibular incisor. However, it is when, rarely, the infection tracks beyond the alveolus but does not readily escape onto a surface that the infections described in this chapter develop. The interlinked planes and spaces to which dental infections may spread have few absolute boundaries but can be summarized by considering the example of the third molar.

Fig. 7.4 An intraoral sinus (arrow).

Fig. 7.5 An extraoral sinus (beneath the mandible on the right side, related to apical infection on a lower molar).

The crown of the part-erupted mandibular third molar, particularly if distoangular, may be below the attachment of buccinator/superior constrictor, allowing infection to escape laterally to the buccal space (Fig. 7.6), posteriorly to the masticator space or posteromedially to the lateral pharyngeal space. The masticator space is the potential space surrounding the ascending ramus and the elevator muscles of the mandible. Infection (whether or not pus has formed) makes these muscles resistant to lengthening, resulting in limited mouth opening, called trismus. Trismus in odontogenic infection indicates involvement of masticatory muscles.

Fig. 7.6 Routes of spread of infection from a lower third molar.

(a) When seen in horizontal section, infection may track laterally into the buccal space, posteriorly, either side of the mandible into the masticator space, further medially into the lateral pharyngeal space or lingually into the sublingual space.

(b) When seen in coronal section, routes to the buccal, submandibular and sublingual spaces are visible.

Apical infection from the lower wisdom tooth may escape laterally to the buccal space, producing swelling of the cheek above the lower border of the mandible. As the apex is below the attachment of mylohyoid, infection tracking medially enters the submandibular space, producing swelling in the neck, but sometimes upward bulging of the floor of the mouth too.

Infections involving the lateral pharyngeal or retropharyngeal spaces are of particular concern, because of the risk of respiratory obstruction and because they may track downwards directly into the mediastinum, resulting in life-threatening mediastinal infections.

Occasionally infection arising from a maxillary canine or premolar may spread upwards and backwards to involve the orbit. If there develops a thrombophlebitis of the ophthalmic veins or the deep facial vein, such infections may spread to the cavernous sinus.

Recognizing these clinical features should enable you to describe an infection in terms of its spread (i.e. the spaces involved) and its tendency to localization or further spread, then with the duration thus far and the level of systemic upset, make an estimate of the severity of the infection. For all infections of dental origin, there should also be an identifiable cause: a part-erupted third molar; a non-vital tooth with its apex beyond muscle attachments; a site of injection; a fracture; a foreign body.

Systemic features

A raised body core temperature is common in infections of all types. The normal temperature varies widely according to the metabolic rate and the time of day. The upper limit of the normal range is 37.0°C but this may actually be a raised temperature for some individuals, and a ‘normal’ temperature may be higher than this such as at the time of ovulation in women. Therefore take temperature only as a guide and watch for changes over time. Temperature may be measured sublingually, provided that the mouth will open satisfactorily and it is not too painful. Endaural (within the ear) measurement can also be accurate and convenient if the equipment is available. Alternatively, take the axillary temperature, allowing for it being about 1°C below core temperature.

A substantial abscess may cause temperature ‘spikes’ (Fig. 7.7) on a daily basis. A single temperature reading taken at a trough between such spikes will be misleading. The pulse and respiratory rates rise with or slightly ahead of the temperature.

Fig. 7.7 A spiking temperature (oral measurement) in a patient with a submandibular abscess of dental origin.

The malaise (feeling unwell) that is standard with infections such as influenza is often not a prominent feature of bacterial odontogenic infection. If the infection is severe, a greyish pallor of the face may be evident, but again this is relatively unusual and less than that with viral infections.

Regional lymph nodes are usually enlarged and tender, although if there is much neck swelling individual groups of nodes may not be distinguishable on palpation. Almost all cervicofacial infections drain to the jugulodigastric node in the upper part of the deep cervical chain, but mandibular infections tend to go first to the submandibular nodes (or anteriorly, to the submental nodes). Facial skin infections may drain to the facial node.

Alveolar abscess

This infection is largely confined to the mouth, with swelling centred around the alveolus near the cause. Usually within 2 days of appearance of first symptoms pus forms and becomes evident as a fluctuant swelling on the labiobuccal aspect of the alveolus. The degree of systemic disturbance is often slight.

Cellulitis

The overlying skin is swollen and oedematous (pitting occurs in some cases), with particular swelling of lips and eyelids. There is usually no true fluctuance (unlike the abscess, although most infections do form some localized fluid collection) and the development tends to be more open-ended, with a progressive spread to involve adjacent spaces, cross the midline and eventually down the neck. Often the systemic upset is more severe than with an abscess.

Cervicofacial space abscess

There is less oedema, and the infection seems more deeply placed than that of a cellulitis because there is less skin inflammation, but the clinical signs and the symptoms depend upon the spaces involved. Both masticator and lateral pharyngeal space infections are associated with severe trismus. In either case the abscess cavities may be inaccessible to the examining finger, preventing identification of fluctuance. Lateral pharyngeal abscesses and sublingual space infection may cause severe pain on swallowing. Sublingual space infection also causes raising of the floor of mouth and the tongue.

Microbiology

The identity and antibiotic sensitivity of the causative microorganisms is commonly determined from pus samples. To sample with a swab (Fig. 7.8), soak it in pus from the main abscess cavity and not from the skin or mucosal incision, to avoid contamination by surface organisms. In samples left open to the air, oxygen kills the anaerobes and drying kills most other bacteria; therefore swabs must be sent for culture within 1 hour, in an appropriate transport medium, to the microbiology laboratory. Aspirates of pus taken with a syringe and needle are more readily protected from the air and may be more reliable, but still require rapid attention. For a spreading infection, without pus, the organisms can often be grown from a blood sample. This procedure is best performed in hospital. On occasion organisms might be sought in tissue washings or biopsies.

Fig. 7.8 A swab used for transport to microbiology.

For most minor infections of dental origin, culture of microorganisms adds little because, by the time sensitivity results are known (2–3 days), the local treatment and antibiotics have substantially resolved the infection. This is not a safe approach with extensive infections, which have a low, but real, incidence of serious outcomes.

Response to infection

Reduced resistance should be considered in those with severe infection. The normal response to acute bacterial infection includes a considerable increase in circulating blood white cells, particularly the neutrophil polymorphs. (An increase in lymphocytes is associated with viral infections.) A full blood count will also demonstrate anaemia (if present), or a reduced white cell count. A blood film will identify abnormalities of red or white cell morphology. If the infective nature of the condition is doubted, C-reactive protein (CRP) may be a helpful guide to the severity of inflammation. Urinalysis or a fasting blood sugar estimation may detect previously undiagnosed diabetes, but remember that severe infection itself tends to raise the blood sugar level. Also consider the recent use of corticosteroids, alcohol or drug abuse or HIV infection.

Anaesthesia

The author prefers to use local anaesthetic injected close to the abscess or, if this is not practicable, general anaesthesia. Some prefer to relieve pain with a topical spray of ethyl chloride (to lower the mucosal temperature below 4°C); however, this provides little pain relief. Topical local anaesthetics work to a depth of several millimetres and can be satisfactory for very superficial abscesses.

Drains

Larger and deeper abscesses tend to seal off shortly after drainage, leaving pus inside or still forming: something must be done to hold the cavity open. In the mouth a corrugated rubber or tubular plastic drain (Fig. 7.10)—or, in desperation, the finger of a sterile rubber glove—may be used. These must be sutured in for at least 24 hours. For palatal abscesses, it is more convenient and successful to excise an ellipse of mucosa from the centre of the abscess so that when the mucosa is pushed flat by the tongue the wound cannot seal.

Fig. 7.10 Corrugated rubber and tubular plastic drains.

Larger abscesses

Cervicofacial space abscesses require a more vigorous approach to drainage, and even the buccal space abscesses, which can theoretically be incised intraorally, are better approached from outside the mouth. Usually this will be under general anaesthesia on an inpatient basis.

The incision should be placed in a neck crease to leave the least evident scar (Fig. 7.11). To approach a submandibular abscess, make the incision at least two fingers’ breadth below the angle of the mandible to avoid the marginal mandibular branch of the facial nerve. The nerve may also be displaced downwards by the swelling of tissue above, and in inflamed tissue its identification is near impossible.

Fig. 7.11 Landmarks for drainage of a submandibular abscess. The marginal mandibular branch of the facial nerve dips below the lower border of the mandible. The incision line should be at least two fingers’ breadth below the lower border.

As pus tends to track downwards under gravity, it is usual to make the incision at the lowest (most dependent) part of the expected cavity. For buccal space abscesses the incision may also be placed in the neck to hide it in a skin crease.

Once the skin incision is made, the abscess is approached by blunt dissection using scissors or a curved haemostat. This involves pushing the end of the instrument into the wound with the tips together, then forcibly opening the instrument to develop a plane of dissection. This is repeated until the abscess cavity is reached. Blunt dissection minimizes the risk of injury to nerves and vessels. A sample of pus should be taken by aspiration at this time, reducing the likelihood of skin contamination.

When the cavity is entered, the access should be enlarged to enable the little finger to be inserted to explore the cavity and gently disrupt any fibrous septae between locules of pus. Some operators irrigate the cavity with saline at this stage to reduce residual contamination.

A drain should be cut that will extend from the deepest part of the cavity beyond the skin edge. This is sutured in place with a material which can be found easily for removal (such as black silk), but the wound is not closed. A non-adherent dressing is placed over the wound and an absorbent dressing placed over that. Some surgeons prefer to seal a stoma bag over the wound to collect the pus. The drain is usually removed after 24–72 hours, depending upon the size of the abscess and its tendency to continue draining. Some surgeons will shorten the drain daily, to allow the deeper part of the wound to fill with inflammatory tissue first. The wound often continues to discharge for a week or more after the drain is removed and the dressings need to be changed daily (or sooner if soaked) until the wound dries.

Choice of antibiotics

The initial choice of antimicrobial drug is empirical. Most infections of dental origin are caused by a mixture of organisms and both aerobes and anaerobes can often be cultured. In mixed infections, eliminating one organism can be effective in treating the infection, because of synergism between the organisms.

Factors that determine the choice of antimicrobial drug include:

A common first choice is metronidazole (note: this is active only against anaerobes). For mild infection it may be given orally at a dose of 200–400 mg three times a day for 5–7 days. Metronidazole should be taken with or after meals as it is irritant to the stomach. It produces an unpleasant reaction with alcohol and patients should therefore be advised to avoid alcohol while they are taking the drug. Compliance is likely to be poor in patients who drink a lot of alcohol.

The broad-spectrum penicillin amoxicillin covers a range of organisms wider than that of the basic penicillin, penicillin V, but is still well tolerated orally (and with less tendency to cause diarrhoea than oral ampicillin). It is given at a dose of 500 mg three times daily.

The cephalosporins, such as cefradine (250–500 mg four times daily), also have a wider range of activity against oral organisms than penicillin V, and there is some evidence that they may be more effective clinically than either amoxicillin or metronidazole. However, the differences appear to be small and, although cephradine is not an expensive drug it does cost more than penicillin V and metronidazole.

Where it is necessary to ensure a high and consistent blood level of an antibiotic, it is usual now to administer the drug intravenously. This implies hospital admission.

Because the initial choice is empirical, there is a tendency to use two antibiotics in combination when an infection is severe and there is a risk of serious outcome. Again there are arguments for and against a variety of combinations of drugs. The author’s choice for intravenous use is metronidazole 500 mg 12-hourly and ampicillin 500 mg 6-hourly.

Alternative drugs are needed in cases of adverse reaction or if the organisms isolated are not sensitive to the first-choice drugs. Consideration may be given to macrolide antibiotics such as erythromycin (for oral use) or clarithromycin (parenteral), tetracyclines, lincosamides and occasionally the aminoglycosides. Reference may be made to texts on microbiology and therapeutics, and consultant microbiologists will advise in cases of difficulty.

Failure to control an infection with antibiotics may be due to:

Supportive care

The role of supportive care is more difficult to prove. There is little evidence that bed rest affects the outcome of dental infections. However, it is unlikely that taking vigorous exercise is beneficial.

Fluid intake, on the other hand, is of great importance. A patient with a painful mouth and face, especially if it is painful to swallow, often eats nothing and drinks too little, resulting in dehydration over a period of days. Fluid requirements are increased if the temperature is raised, so rehydration is essential. The average adult requires about 2.5 L of fluid per day, but if pyrexial that may rise to 3 or 3.5 L. If adequate fluid cannot be taken by mouth, it must be given intravenously, which implies hospital admission.

Patients with dental infections rarely become dangerously pyrexial (temperature exceeding 40°C), but if they do it is necessary to reduce the temperature with aspirin or paracetamol, or by sponging with tepid water and circulating air over the body.

Clinical features

The clinical features are thus those of infection in general, plus tenderness of more teeth than would be expected, possibly mobility of teeth, loss of function of the inferior alveolar nerve and numbness of the lower lip. Because of periosteal inflammation and stripping there is a firm or woody expansion of the affected bone area, with no clearly defined junction between the swelling and normal bone. The overlying skin may be mobile, provided there is little acute infection. If the infection is not rapidly resolved, bone resorption becomes evident on radiographs (Fig. 7.14a), necrotic bone may separate as a sequestrum, and new bone may form on the inner aspect of the stripped periosteum and may become visible on tangential radiographs (Fig. 7.14b). Eventually the weakened mandible may fracture.

Fig. 7.14 (a) Typical radiological appearance of osteomyelitis. Patchy bone resorption is highlighted by arrows. (b) A thin layer of subperiosteal bone (arrows) has formed at the lower border of the mandible in a patient with osteomyelitis.

Time scale is important in the diagnosis of osteomyelitis. It often takes weeks from the first symptoms till a clear diagnosis is made, even though the condition is obviously infective early on.

Predisposing factors

Factors predisposing to osteomyelitis include those which make any infection more likely (e.g. use of corticosteroids or alcohol dependency) and anything which tends to open up the marrow space widely (fracture or surgical removal of a tooth), or increased density of bone, such as in Paget’s disease or osteopetrosis.

Treatment

The investigation and management of osteomyelitis are best performed within a hospital setting.

Treatment relies upon antibiotics, maintained for 6–8 weeks. The initial choice of antibiotic is usually empirical. Penicillin V is safe and well tolerated, with a reasonable spectrum of activity against oral microorganisms and appears to be effective in this condition. The tetracyclines are bound in bone by chelation of calcium, but are inactive in that form; they have, however, been very successfully used in osteomyelitis. The lincosamides achieve high bone concentrations, but there is a small risk of pseudomem-branous colitis on long-term use. The cephalosporins and penicillins also have their advocates. The initial choice may not be that critical, but the causative organism should be identified and antibiotic treatment modified accordingly.

Any controllable predisposing factor (such as anaemia) should be dealt with early in the management of osteomyelitis.

Surgery is necessary if a substantial sequestrum forms. Occasionally, in resistant cases, it is necessary to remove the lateral cortical plate of bone to allow access for granulation tissue to the remaining bone. Pathological fractures require immobilization and often bone grafting once the infection is settled.