Role of Occlusal Reduction in Post Endodontic Pain

Dental occlusion and occlusal forces play an essential role in maintaining the normal dentition in health and function. Occlusion in an individual keeps on changing over a period of time, starting from tooth eruption, restorations, tooth loss and implants. Whenever the occlusion changes due to any of these reasons, it might not adapt to oral anatomical structures and may become non harmonious, sometimes leading to pain or discomfort for the patient. The pain arising from traumatic occlusion is varied and complex. Different patients present it in a different way.

In endodontics the tooth is most commonly made out of the occlusion to alleviate post endodontic pain. The endodontic postoperative pain is one of the most common and frequent complication, with incidence of 3% to 57%. (1,2). It is crucial to treat this complication because the most important aspect of root canal treatment is pain control. The mechanism of action of pain is multifactorial and is complex in nature. Some studies have confirmed that tooth should be made out of occlusion in patients presenting with pre-operative signs like bite tenderness and percussion sensitivity but this is mostly effective for 12 hrs (3). The most common cause of post-endodontic pain is acute periapical inflammation (4). It develops as a sequela of diseases of pulpal origin, most commonly, irreversible pulpitis; but it can also develop postoperatively as a result of mechanical, chemical, and/or microbial insults (5). Trauma from occlusion is listed as one of the most common mechanical irritant which can further propagate the progression of disease (6).

Many treatment protocols have been used to alleviate post-operative pain. The treatment considerations for pain control in symptomatic apical periodontitis range from taking drugs, cryotherapy applications, low-level laser therapy, irrigating solutions, intracanal medicaments and reduction in the occlusion.

Occlusion reduction of the tooth undergoing root canal treatment, is the first step, which many endodontists do as a precautionary method to manage post-operative endodontic pain. It has been hypothesized that occlusal reduction could prevent further pressure on a tooth with inflamed periapical tissue and avoid further mechanical periapical tissue irritation and inflammation (7). The study concluded that occlusal reduction is beneficial in patients whose teeth exhibit pulp vitality, percussion sensitivity, preoperative pain, and/or the absence of a peri radicular radiolucency (7). The main reason behind occlusal reduction is that it relieves or decreases the force and pressure on a tooth with symptomatic apical periodontitis, reducing the impact of mechanical allodynia. This release of pressure and force reduces the periapical tissue irritation and inflammation. Occlusal adjustment also helps as it reduces mechanical stimulation of sensitized nociceptors, thus decreasing the level of pain (8).

Though majority of the endodontists take the tooth out of occlusion prior or post root canal treatment, the clinical studies on occlusion reduction and symptomatic apical periodontitis is very limited and varied with conflicting results. No study has been published that demonstrates the direct relation between the efficacy of the occlusion reduction and post endodontic pain. There are some studies which concluded that reduction of occlusion was not effective in post endodontic pain in teeth exhibiting irreversible pulpitis and mild tenderness to percussion (9). The study determining occlusion reduction using computer analysis also concluded that occlusion reduction was not effective in providing post endodontic pain relief (10). Till date there is no direct relation determined between effectiveness of occlusion reduction in patients undergoing root canal treatment (11).

I think that in order to determine whether occlusion reduction is beneficial or not, it can be assessed by proper and thorough diagnosis, which is largely based on patient presenting with symptoms. There are many instances and case reports where dental treatment has been done because patient complained of pain, but later it turns out to be pain due to occlusal reasons, combination of occlusion and pulpal disease. One of the cases presented in UBC graduate endodontics clinic was of a patient complaining of dull constant pain in lower first molar with porcelain fused to metal (PFM). The tooth was endodontically treated as there were signs of pulp necrosis. But even after the root canal treatment, the patient continued to have the same dull constant pain. Many diagnostic tests were performed but nothing was conclusive. In the end, it turned out to be a very heavy occlusal bite which was the main etiology behind the dull pain present on that particular tooth which had PFM. After selective grinding, patient started feeling better. Therefore, it is important to detect the predisposing factors that may contribute to persistent pre- or post-operative pain.

In my experience, occlusal reduction has effect on post endodontic pain especially in patients who present with severe bite or percussion sensitivity pre-operatively. In such cases the tooth undergoing root canal treatment should be completely made out of occlusion to further reduce the progression of disease. In patients exhibiting no clinical signs of symptomatic pulpitis, occlusion reduction has little benefit. There is also a necessity to understand the importance of stable occlusion and trauma from occlusion. If a patient has harmonious occlusion, then occlusal reduction is not necessary.

The systematic review pointed out that traumatic occlusion can affect the dental pulp, the periodontal ligament tissue and the supporting alveolar bone (8). Hence, it is important to have a thorough examination on the occlusion of tooth being treated. Its restorability concerns should be judged in the best anatomical position so that it is harmonious to other supporting structures, TMJ and rest of the dentition (12). Due to the lack of awareness and understanding of the effects of traumatic occlusion in pulp- and peri-radicular diseases, it is frequently neglected during the diagnosis and treatment planning of the patients with endodontic problems.

Some of the important things I personally would like to do clinically are:

1. Thorough diagnosis and checking the occlusion for any signs of interference or localised high points especially on the tooth or teeth being endodontically treated
2. Determining the good restorability or referring to prosthodontists
3. Ensure patient comfort by taking the tooth out of occlusion, as emergency pain relief, if patient has severe pain on biting or percussion sensitivity
4. Referring patients to prosthodontist for determining occlusal scheme or restorability especially if tooth/teeth have been made out of occlusion, for stabilization of occlusion and optimization of force distribution especially on the tooth being endodontically treated.

In conclusion, occlusal reduction prior to root canal treatment has been advocated to avoid post-operative pain in teeth with pre-operative pain and/or pain on percussion or used as a relief strategy in cases of emergency if painful symptoms develop following treatment (13). However, randomized clinical trials in this subject are few with conflicting results. This creates confusion on whether or not to perform occlusal reduction.

References:

1.  Sathorn C, Parashos P, Messer H. The prevalence of postoperative pain and flare-up in single- and multiple-visit endodontic treatment: a systematic review. Int Endod J. 2007 Oct 23;0(0):071025011828001

2.  Clem WH. Posttreatment Endodontic Pain. J Am Dent Assoc. 1970 Nov 1;81(5):1166–70.

3.  Emara RS, Abou El Nasr HM, El Boghdadi RM. Evaluation of postoperative pain intensity following occlusal reduction in teeth associated with symptomatic irreversible pulpitis and symptomatic apical periodontitis: a randomized clinical study. Int Endod J. 2019 Mar;52(3):288–96.

4.  Yu CY. Role Of Occlusion In Endodontic Management: Report Of Two Cases. Aust Endod J. 2004 Dec;30(3):110–5.

5.  Siqueira JF, Rôças IN, Favieri A, Machado AG, Gahyva SM, Oliveira JCM, et al. Incidence of postoperative pain after intracanal procedures based on an antimicrobial strategy. J Endod. 2002 Jun;28(6):457–60.

6.  Levin LG. Pulpal irritants. Endod Top. 2003;5(1):2–11.

7.  Rosenberg PA, Babick PJ, Schertzer L, Leung A. The effect of occlusal reduction on pain after endodontic instrumentation. J Endod. 1998 Jul;24(7):492–6.

8.  Clark GT, Tsukiyama Y, Baba K, Watanabe T. Sixty-eight years of experimental occlusal interference studies: What have we learned? J Prosthet Dent. 1999 Dec 1;82(6):704–13.

9.  Parirokh M, Rekabi AR, Ashouri R, Nakhaee N, Abbott PV, Gorjestani H. Effect of Occlusal Reduction on Postoperative Pain in Teeth with Irreversible Pulpitis and Mild Tenderness to Percussion. J Endod. 2013 Jan;39(1):1–5.

10.  Arslan H, Seckin F, Kurklu D, Karatas E, Yanikoglu N, Capar ID. The effect of various occlusal reduction levels on postoperative pain in teeth with symptomatic apical periodontitis using computerized analysis: a prospective, randomized, double-blind study. Clin Oral Investig. 2017 Apr;21(3):857–63.

11.  Jostes JL, Holland GR. The effect of occlusal reduction after canal preparation on patient comfort. J Endod. 1984 Jan 1;10(1):34–7.

12.  Neff P. Trauma from occlusion. Restorative concerns. Dent Clin North Am. 1995 Apr;39(2):335–54.

13.  Gatewood RS, Himel VT, Dorn SO. Treatment of the endodontic emergency: A decade later. J Endod. 1990 Jun 1;16(6):284–91.