7 Spreading infection
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.
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.
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’.
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.
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.
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.
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.
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.
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.
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.
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.
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.
There is usually no difficulty in distinguishing infective from other disorders. However, confusion can arise in the slower, lower-grade infection and the superficial infected tumour. Secondary malignancies are less common in the mouth than primaries, and by arising within bone may cause confusion.
Generally, infection develops over a few days, but responds to removal of the cause and/or drainage of pus. Malignancies develop over weeks to months and do not respond to treatments suited to infections. Induration is common in long-standing infection, and may persist for days to weeks after treatment, but should show signs of improvement with treatment. By the time tumours are evidently infected, they are usually obviously ulcerated, which would be rare for an infection of dental origin.
Lymph node involvement may also reveal differences between tumours and infection. Usually, dental infections cause lymphadenopathy in the upper part of the cervical chain and submandibular nodes. Infected lymph nodes are likely to be enlarged, firm or rubbery in consistency, tender, usually mobile, whil/>