Effective pain management strategies in endodontic therapy

Diagnosis

Arriving at an accurate diagnosis is the first step in managing oro-facial pain. It serves a vital purpose in helping us to identify the aetiology of presenting symptoms, communicate between colleagues and determine the appropriate treatment options. This can be challenging and is the pivotal moment in determining if pain will be effectively controlled. Therefore, the importance of accuracy can be appreciated as an incorrect diagnosis can lead to incorrect treatment. For example, if a lateral periodontal abscess is misdiagnosed as an apical abscess, endodontic treatment would be indicated when in fact a far more conservative approach is required. Furthermore, the presenting symptoms would still persist until the correct treatment was provided.

For endodontic purposes, we are specifically concerned with arriving at a pulpal and apical diagnosis.⁷ Therefore, it would be useful to adopt a simple and practical classification system where diagnostic terms represent clinical findings. A good example of this is the classification set out by Abbott and Yu which depicts the progressive nature of pulpal and apical pathology.⁸ Furthermore, each histo-pathological diagnostic term is defined by clinical findings and the appropriate management strategy is clearly outlined.

When patients arrive in pain, the following information should be methodically acquired through systematic history-taking, thorough clinical examination and appropriate special investigations:

When the necessary information is collected, we can begin to form our definitive diagnosis followed by a treatment plan. It is important to appreciate the dynamic nature of the pathology in these tissues and occasions will occur where clinical findings contradict each other. If we are unable to arrive confidently at a diagnosis we should seek a second opinion or refer to an experienced practitioner.

Predictive models of pain

Is it possible to identify individuals that are more likely to experience pain throughout treatment? The evidence may suggest, as several pre-operative risk factors have demonstrated, a consistent link with post-operative discomfort. After Hargreaves carried out a literature review containing approximately 12,000 patients, it was determined that hyperalgesia and tenderness to mechanical stimulation were shown to be the most significant predictors of postoperative pain.⁹ Interestingly, other findings that showed a weaker correlation were the presence of apical pathology, a necrotic pulp and carrying out endodontic therapy in two stages.⁹ Several studies have also pointed to a more detailed relationship, concluding that particular presenting symptoms had an effect on the intensity and duration of the pain felt after treatment (Table 1).

Pulpotomy or pulpectomy

These procedures are effective clinical methods for directly treating the pathological causes of the patient's symptoms. A pulpotomy is the removal of diseased coronal pulp tissue whilst maintaining vitality of healthy radicular tissue. A pulpectomy is the complete removal of both coronal and radicular pulpal tissue.

Occlusal reduction

Having once been considered common practice amongst endodontically compromised teeth, the true benefit of occlusal reduction has been open for debate. Rosenberg et al discovered that teeth exhibiting pulp vitality, sensitivity to percussion, pre-operative pain and/or no periapical radiolucency on presentation, were statistically proven to gain the greatest chance of pain relief with occlusal reduction (Figure 2).¹³ It was concluded that any one of these signs/symptoms was enough to warrant occlusal reduction. Although there was an extensive exclusion criterion, a large sample size and the statistical significance, the findings cannot be ignored.

Recently, Rosenberg's findings have been challenged. Parirokh et al concluded that ‘Occlusal surface reduction did not provide any further reduction in post-operative pain for teeth with irreversible pulpitis and mild tenderness to percussion compared with no occlusal reduction'.¹⁴ Although results were statistically significant, no power calculation was used to determine the sample size, which was small, and there was also an uneven dropout rate between groups.

Our biological understanding of the surrounding periodontium may provide help. Irritation to the periodontal tissues (ie over instrumentation, infection) releases inflammatory cytokines that sensitize peripheral nociceptive nerve fibres at the periphery of the periodontal ligament and pulp. Therefore, any subsequent mechanical stimulation (ie occlusal loading) will stimulate both proprioceptive and sensitized nociceptive fibres, resulting in pain.¹⁵ Therefore, theoretically the anatomy does suggest a link.

Although there is contrasting research, compromised teeth presenting with the profile outlined by Rosenberg may benefit from occlusal reduction.

Local anaesthetics

An essential form of pain management is the ability to achieve profound pulpal anaesthesia for appropriate durations of time. The membrane stabilizing theory of local anaesthetics is well understood, however, we know that achieving anaesthesia is not just dependent on the anaesthetic but also the patient.¹⁶ There are those who have slower onsets and others that do not respond even after 60 minutes, despite the growing number of techniques and solutions available.¹⁷ The following section highlights practices that could help achieve appropriate anaesthesia in even the most difficult scenarios.

Teeth diagnosed with irreversible pulpitis should be approached with caution, especially the mandibular molar. These teeth have undeniably posed anaesthetic challenges to the dentist and are referred to by some as the ‘HOT TOOTH’ (Figure 3).¹⁸ Reports found objective sensibility tests were less reliable and operative pain was still experienced after consecutive negative readings.¹⁹ A single Inferior Dental Block (IDB) in a hot mandibular molar may not always achieve adequate pulpal anaesthesia and supplemental techniques may be needed for a greater chance of success.¹⁸

Upon failing to achieve pulpal anaesthesia in an irreversibly inflamed mandibular molar, dentists may find themselves questioning their technique, wondering if different anaesthetic preparations will help or if simply greater volumes are needed. However, repeated clinical trials fail to highlight superiority of various anaesthetic preparations (including articaine-4%) over lidocaine-2% epinephrine-1:100000 when applied to nerve blocks.^{20,21,22,23,24,25} Similarly, increasing volumes of anaesthetic or epinephrine concentration has no impact and giving a repeat injection following a failed IDB will only cause further discomfort.²⁶ Although technical inaccuracy can account for a percentage of failures, when Hannan et al used ultrasound to guide the needle to a precise location during an IDB, there was no statistical improvement in rate of pulpal anaesthesia achieved.²⁷ In addition, numerous clinical trials have failed to provide evidence to support the superiority of Gow-Gates or Vazirani-Akinosi techniques over conventional IDB techniques.^28,29,30 Therefore, accuracy cannot be the primary reason for failure and accessory nerve supply from the mylohyoid nerve does not seem to be a significant barrier either.³¹

Prior to treatment, an accurate history should be taken as those previously experiencing difficulty in getting numb have reduced chances of success.³² During administration, slower injections (60 seconds) are less painful and have proven to be more successful than rapid IDBs in healthy mandibular molars.³³ Following this, efforts to test pulpal anaesthesia objectively (ie thermal/electrical stimuli) should be made. It is common practice to probe the gingiva with sharp instruments, ask if the lip feels numb or even to start treatment and wait for a response to assess the degree of anaesthesia. However, these subjective methods are inaccurate representations of assessing pulpal anaesthesia.^23,24,25 It is suggested that true pulpal anaesthesia occurs in teeth exhibiting two consecutive negative readings at strengths of 80, on an analytic pulp tester, within 15 minutes and sustaining these readings for 60 minutes. Although this may seem impractical, it is the standard used in numerous studies.^23,24,25

Failure to position the needle accurately will result in failure of subjective signs (ie lip numbness) prompting a second attempt. However, when subjective signs are present and the pulp remains unaffected, supplemental techniques have been shown to be helpful. The most common of these is the Intra-Ligamentary (IL) injection.³⁴ Figures show that the technique aids achieving pulpal anaesthesia by ~75% initially and ~95% upon reinjection, with a modest rate of ~55% in patients presenting with irreversible pulpitis.^21,35 Achieving back pressure is essential to success and, without it, anaesthesia would be unlikely to occur.³⁵ Reports of buccal infiltrations with articaine-4% epinephrine-1:100000 alongside IDBs have been demonstrated to be more clinically significant.^36,37 However, it too suffers the same fate when it comes to the hot tooth, with reports of only 58% achieving pulpal anaesthesia.³⁵

The uncommon but gold standard Intra-Osseous (IO) technique provides immediate pain relief which can last for up to 60 minutes. Numerous clinical trials have demonstrated promising results even with patients presenting with hot teeth.^38,39,40 Reisman confirmed profound pulpal anaesthesia in 80% of initial IO injections and 96% after reinjection in irreversibly inflamed teeth following a failed IDB.³⁸ One must be mindful of the transient increase in heart rate, especially with medically compromised patients, however, mepivacaine-3% IO injections have proven to overcome such matters.⁴¹

Finally, 5–10% of mandibular posterior teeth diagnosed with irreversible pulpitis will be unresponsive to even repeat supplemental injections.^42,43 This indicates administration of intra-pulpal anaesthesia via a conventional needle. Although initially uncomfortable, the instant pain relief for a short duration allows the operator a small window to debride the pulp chamber, offering some pain relief.

Analgesics

A temporary method of pain management is the use of analgesics. With an extensive range available, it can be confusing to prescribe the correct regimen that is both effective and bares little consequences to an ageing population. The following discusses some common analgesics and flexible regimens that can be used for endodontic related pain.

Opioids/opioid combinations

Opioids block only the perception of pain by inhibiting opiate receptors in the CNS and they have no anti-inflammatory effects.⁴⁵ At 60 mg, codeine's significant analgesic effect can be experienced, all be it less than that of paracetamol (600 mg) and aspirin (650 mg).⁴⁸ Due to this weak effect, it is often used in combination with non-narcotic analgesics. Codeine (8–30 mg) alongside paracetamol (500 mg) has been reported to provide greater analgesia than paracetamol alone, but less than that of Ibuprofen.⁴⁸ There is little evidence that discusses codeine's effective analgesic dose alongside paracetamol, but suggestions of at least 25–30 mg have been put forward, implying that 8–10/500 preparations are not ideal.⁵³ The CNS depressant side-effects of codeine should be taken into account when prescribing.

Drugs should only be prescribed as temporary forms of pain relief for approximately 24–48 hours, whilst the aetiology is managed. Ibuprofen is the drug of choice and, where contra-indicated, paracetamol-codeine preparations can be used as part of a flexible regimen (Table 3).⁴ Furthermore, they can be taken together to provide continuous pain relief (Figure 4).^51,54 Antibiotics have no measurable impact in managing or preventing post-operative pain and so should only be prescribed in accordance with guidelines.^54,55,56

Table 3. Flexible regimen that provides effective analgesia whilst reducing risks of drug-related side-effects.

Pre-emptive pharmacological strategies