7.2.2 Probable Aetiological Factors

7.2.3 Signs and Symptoms of NaOCl Complications

1. 1.

   Strong taste of chlorine.

    
2. 2.

   Burning sensation: When these extrusions involved the maxillary sinus, the first sign noticed is the irrigant flowing from the nostrils along with the taste of NaOCl in the throat. A burning sensation in the maxillary sinus rather than severe pain was usually present, with little or no bleeding from the canal and no evidence of immediate swelling [8].

    
3. 3.

   Severe pain.

    
4. 4.

   Tissue necrosis: Mucosal and bone necrosis as a result of the chemical burn caused by NaOCl, sometimes accompanied by a purulent discharge.

    
5. 5.

   Paraesthesia: Contact with NaOCl is highly toxic to vital tissues, including nerves. Consequently, neurologic signs such as sensory and/or motor defects after extrusion can be expected [5].

    
6. 6.

   Haematoma.

    
7. 7.

   Ulcer and haemorrhage (Fig. 7.2).

    
8. 8.

   Swelling: Occurs very commonly with sodium hypochlorite extrusion, it appears within a few minutes up to a few hours after the accident. Swelling is usually large and diffuse (similar to cellulitis), extending intra- and extra-orally well beyond the site of the affected tooth. It may sometimes result in difficulties opening the ipsilateral eye [11–13, 108].

    
9. 9.

   Ophthalmologic symptoms: It may present as eye pain, blurring of vision, diplopia or right corneal patchy colouration. These constellations of signs/symptoms have been described in the literature as emanating from a maxillary central incisor [12] and canine [13].

    

7.2.4 Management of NaOCl Extrusion

Despite careful consideration during RCT, if faced with a suspected NaOCl-related extrusion injury, a thorough clinical and radiological assessment is recommended to determine the degree and extent of the injury. This information should assist the clinician to instigate the appropriate management plan to minimize any detrimental effects and to improve the final outcome [14, 109].

Guidelines for the management of NaOCl extrusions [14]:

The guidelines presented have been developed through clinical experience in the management of such injuries in a secondary care environment, as well as through reviewing relevant literature. Researchers have proposed to categorize extrusion injuries as mild, moderate and severe according to a patient’s signs and symptoms. Each category has been subdivided into immediate, early and late management to optimize the care provided. Although the patients are initially categorized as mild, moderate or severe according to their degree of the injury, they can be recategorized if their signs and symptoms do change.

7.2.5 Treatment

7.3 Relative to the Time of Injury and Includes Immediate, Early and Late Treatment (Appendix 7.1)

7.3.1 Prevention

The best treatment of a NaOCl accident is to prevent it from happening. Patient safety is paramount when considering intracanal fluid dynamics, including irrigant delivery rate, agitation and exchange, and needle design; pressure gradient management, wall shear stress and cleaning efficacy; and, ultimately, treatment outcome. Different preventive measures have been recommended in the literature to minimize potential complications associated with the use of NaOCl [5, 15]. These include:

1. (a)

   Replacing NaOCl with another irrigant

    
2. (b)

   Using a lower concentration of NaOCl

    
3. (c)

   Placing the needle passively and avoiding wedging of the needle into the root canal

    
4. (d)

   Irrigation needle placed 1–3 mm short of working length.

    
5. (e)

   Using a side-vented needle for root canal irrigation (Fig. 7.3)

    
6. (f)

   Avoiding the use of excessive pressure during irrigation

    
7. (g)

   Plastic bib to protect patient’s clothing

    
8. (h)

   Provision of protective eyewear for patient, operator and dental assistant

    
9. (i)

   The use of a sealed rubber dam for isolation of the tooth under treatment

    

Sodium hypochlorite (NaOCl), the widely used irrigant in endodontics, has many complications following its inadvertent use. However, NaOCl accidents are rare in endodontic practice. Nevertheless, the patient should be notified of potential accidents and the evolution of the case, with appropriate follow-up and, whenever necessary, hospital care.

The extrusion of NaOCl during root canal therapy into the periradicular tissues is a rare occurrence; nevertheless, the consequence of which can be potentially serious and can cause significant morbidity to the patient. Prior to root canal treatment, the assessment of teeth is important to identify any factors which may predispose extrusion injuries, so that adequate preventive measures can be undertaken. As there is currently little in the way of protocols or guidelines to manage such injuries, the clear guidelines to manage hypochlorite extrusion injuries presented in Appendix 7.1 aim to assist practitioners in the assessment of patients following hypochlorite injuries, with the aim to grade the severity of these injuries into mild, moderate and severe. The presented guidelines also aim to help develop standards for future management of sodium hypochlorite extrusion injuries [14].

7.4 Air Emphysema

Emphysema is derived from a Greek word whick which means to ‘blow in’. This condition refers to trapped air and may occur when the root canal is dried with compressed air, which may be expressed through the apical constriction into the periapical tissues. Air emphysema is usually uncommon but may lead to subcutaneous emphysema, also known as tissue emphysema of the head, neck and thorax due to the introduction of air into the fascial planes of the connective tissue. Using compressed air in endodontics [16], periodontics [17], oral surgery [18] and operative procedures [19] can cause emphysema. It is a possible complication of both nonsurgical and surgical endodontic treatments [20]. When the condition is caused by surgery, it is called surgical emphysema [21]. Surgical emphysema may occur during root treatment, and reports in the literature [22] indicate that the complication occurs most commonly as a result of overzealous irrigation with hydrogen peroxide or drying root canals with compressed air blasts.

Sometimes, spread of larger amounts of air into deeper fascia may cause more serious complications, including accumulation of air in the retropharyngeal space, pneumomediastinum and pneumopericardium [23]. Its occurrence with a dental procedure was first reported more than 100 years ago when Turnbull extracted the premolar of a musician who blew his bugle immediately after extraction. Air enters into anatomical spaces through the root canal space [5]. But it can sometimes pass through the dentoalveolar membrane [24]. Following its introduction into the soft tissues, air remains in the subcutaneous connective tissue and does not spread to deep anatomic spaces in the majority of the cases [25].

However, emphysema can also involve deeper structures as the tissue planes commonly connect [26]. The potential avenues of travel for compressed air involve the superficial area, parotid area, submandibular, sublingual, tonsillar, masticatory and the parapharyngeal region [20].

The apices of the first, second and third molars directly communicate with the sublingual and submandibular spaces. These spaces, in turn, communicate with the parapharyngeal and retropharyngeal spaces, where accumulation of air may lead to airway compromise [27]. The retropharyngeal space (‘danger space’) is the main route of communication from the mouth to the mediastinum.

Secondarily, it can escape along the path of introduction, such as a patent root canal, and be released into the dental operatory air, causing no damage [28]. From Rickle’s [29] post-mortem study, it is obvious that one definite risk of air emphysema during endodontic treatment is introduction of air into the cardiovascular system. In large volume, this can cause heart failure [30].

Air emphysema during endodontic treatment may also be misdiagnosed as infection because of similar location and size of swelling. In fact, such accidents may develop into an infection from microbes forced into the spaces created by the air blast [30].

7.4.1 Hydrogen Peroxide as Endodontic Irrigant Causing Air Emphysema

Hydrogen peroxide (H₂O₂) has been widely used for irrigation of the root canal system, although it is less effective in killing microorganisms. Hydrogen peroxide is a colourless liquid and has been used in dentistry in concentrations varying from 1 to 30%. H₂O₂ degrades to form water and oxygen.

Hydrogen peroxide has been implicated, along with compressed air, in the aetiology of subcutaneous emphysema [31, 32]. It has been used as a canal irrigant and disinfectant during routine root canal therapy [33]. When hydrogen peroxide comes into contact with blood or tissue proteins, it very rapidly undergoes effervescence and liberates oxygen [34]. This gaseous expansion may drive debris or simply gas through the apical foramen or into the adjacent bone if an inadvertent perforation of the canal wall were present [20]. Kaufman et al. [31] presented a case of delayed onset of emphysema subsequent to hydrogen peroxide irrigation.

It is active against viruses, bacteria, bacterial spores and yeasts [35] via the production of hydroxyl free radicals which attack proteins and DNA [36].

It has been shown that sodium hypochlorite (NaOCl) combined with H₂O₂ is no more effective against E. faecalis than NaOCl alone [31]; however, chlorhexidine (CHX) combined with H₂O₂ was a better antimicrobial agent than either one on their own [37]. The current evidence does not support the use of H₂O₂ over other irrigants, and it has not been shown to reduce bacterial load in canals significantly [38]. There is the rare but potential danger of effervescence with H₂O₂, and seepage into the tissues may lead to air emphysema [39].

7.4.2 Signs and Symptoms

The typical symptoms of sudden, severe pain are accompanied by a rapid swelling and erythema in the region of the treated tooth [20]. The area will rapidly swell and examination of the swelling will reveal a mild tenderness [43] (Fig. 7.4). Crepitus [28] is evident along with oedema, erythema and lymphadenopathy [23]. Patient may experience mild fever and local discomfort. Radiographic findings such as dark area of air and bubble accumulation are visible on CT scan and MRI images [44].

If the air pocket breaks through into the neck region, there is a sudden swelling of the neck, the voice sounds brassy and the patient has difficulty breathing and swallowing (dyspnoea) [25]. If it breaks through into the mediastinum, a crunching noise is heard on auscultation.

7.4.3 Management

7.4.4 Prevention

A well-fitted rubber dam should be used [25]. Perforations may cause seepage of the irrigant into the tissues. Therefore, care must be taken to avoid that. Avoid wedging the irrigating needle into the root canal [46] by using a side-vented irrigation needle (Fig. 7.5). During irrigation, a low and constant pressure should be used and the clinician must ensure that excess irrigant leaves the root canal coronally via the access cavity. However, it has been shown that contact between the periapical tissues and the irrigant cannot be avoided completely.

It is not recommended to use compressed air to dry the root canal system. Use a handpiece that exhausts the spent air out at the back of the handpiece rather than into the operating field. This can be achieved by using remote exhaust handpieces or electric motor-driven handpieces [41].

Use paper points to dry the canal [20], or a vacuum system, and avoid the use of hydrogen peroxide while irrigating canals [23]. Ultrasonic or sonic instruments should be used for root-end cavity preparations. Early recognition may be of extreme importance to prevent possible secondary infections and cardiopulmonary complications [47].

Air emphysema is usually an uncommon complication occurring during a routine endodontic treatment but occurring most commonly due to iatrogenic error by the clinician. Thus, concentration at all times could avoid emergency dental situations like this. The irrigating and local anaesthetic needles should be colour-coded to avoid confusion and mishaps.

7.5 Sodium Hypochlorite Mix with Chlorohexidine

Bacteria in the root canal system provokes and causes periapical inflammatory lesions [48]. The main aim of root canal treatment is to eliminate bacteria from the infected root canal and to prevent reinfection. Biomechanical cleaning and shaping of the root canal greatly decreases the number of bacteria [49]. Nevertheless, because of the anatomical complexity of the root canal system, organic/inorganic residues and bacteria cannot be completely removed and often persist [50]. Various irrigants have been used during the canal preparation to minimize the residual debris, necrotic tissue and bacteria, as well as to remove smear layer formed by the mechanical preparation of the dentin [49, 51, 52].

7.5.1 Concern with Sodium Hypochlorite (NaOCl)

As mentioned before, due to its broad-spectrum antimicrobial action and tissue-dissolving properties, sodium hypochlorite (NaOCl) at various concentrations is the most common endodontic irrigant used [53–55].

Despite its germicidal abilities, NaOCl in high concentration is cytotoxic and can cause necrosis of periapical tissues [54, 56, 57]. NaOCl is not a substantive microbial agent [58]. These troubles have led clinicians and researchers to explore alternative irrigants.

7.5.2 Concern with Chlorhexidine Gluconate (CHX)

Chlorhexidine gluconate (CHX) is a broad-spectrum antimicrobial agent that has been advocated as an effective medication in endodontic treatment [59, 60, 110]. When used as an endodontic irrigant, CHX has an antimicrobial efficacy comparable to that of NaOCl but lacks the cytotoxic effects [59, 61]. CHX has also been shown to have antimicrobial substantivity in root dentin [61–63, 110].

A drawback of CHX is that it lacks the ability to dissolve organic matter. For this reason, CHX is often used in conjunction with NaOCl [54].

7.5.3 NaOCl and CHX Interaction

A combination of NaOCl and CHX has been advocated to enhance their antimicrobial properties. Kuruvilla [54] suggested that the antimicrobial effect of 2.5% NaOCl and 0.2% CHX used in combination was better than that of either component. Zehnder [2] proposed an irrigation regimen in which NaOCl is used throughout instrumentation followed by EDTA, while CHX would be used as a final irrigant. If hypochlorite is still present in the canal, a precipitate was observed when the medications interacted [2, 64] (Fig. 7.6). This precipitate contains the cytotoxin para-chloroaniline (PCA) which can coat the canal surface and significantly occludes the dentinal tubules in the coronal and middle thirds of the canal [65, 66]. The obliteration of dentinal tubules was not found to be significant at the apical third. This might be due to the fact that the apical third is more difficult to irrigate [65].

7.5.4 PCA Toxicity

It is known that PCA and its degradation product are toxic and carcinogenic, so potential leaching of PCA into the surrounding tissues is a concern [65]. Short-term exposure of humans to PCA results in cyanosis, which is a manifestation of methaemoglobin formation [67]. In 1991, it was reported that PCA to be carcinogenic in rats due to increased sarcomas in the spleen. Furthermore in male mice, there was an increase in hepatocellular carcinomas and haemangiosarcomas of the spleen [67].

7.6 Prevention

The interaction between NaOCl and CHX can be minimized or prevented using saline or distilled water as intermediate flushes [68]. Also using EDTA alone would be convenient; however, EDTA also produces a precipitate in the presence of CHX [65].

A sequence of irrigation to avoid any interaction between all these chemicals can be seen in Table 7.3.

Table 7.3

Endodontic irrigation timeline

NaOCl	17% EDTA	NaOCl rinse	Rinse out	2% CHX
During endodontic instrumentation	2 min		Saline or water

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