Coronectomy: Patients with comorbidities, carious teeth and associated cyst



Patients with comorbidities, carious teeth and associated cyst – Nine year’s experience

Dental News Magazine January Issue 2021

Dr Parmanand Dhanrajani – BDS, MDS, MSc, MSC, FRACDS, FDSRCS, FFDRCSI, Oral Surgeon

Dr Mark Smith – BDS, MQIHC, Technical Consultant – Dental, 403 George Street, Sydney, NSW 2000, Australia


Aim: The paper presents a retrospective study of patients who underwent coronectomy from 2012-2019. An earlier paper (Dhanrajani et al 1) described in detail the surgical procedure with modifications. The present paper is an evaluation of post-coronectomy pain, migration of roots and follow-up of patients with comorbidities and/or decayed teeth.

Material and Methods: A retrospective study involving lower third molar surgery performed by a single surgeon in an outpatient extraction clinic under local anaesthesia as well as in the day surgery under general anaesthesia was conducted from January 2012 to December 2019.

A total of 5,497 lower third molars were removed. In the cohort of 1,543 (28.06%) teeth removed in outpatient under local anaesthesia, 109 (1.98%) were coronectomies and of 3,954 (71.93%) removed under general anaesthesia, 305 (5.54%) were coronectomies.

This study also discusses the advantages of the modified procedure as well as intra-pulpal deposition of local anaesthetic to control post-surgical pain.

Results: The results demonstrate that:

• coronectomy is a safe and viable technique for the surgical management of wisdom teeth at high risk of neurosensory loss. 

• Intra pulpal deposition of local anaesthetic intraoperatively reduced the post coronectomy pain significantly. 

• The modification in surgical technique did help reduce the post-surgical complications such as wound dehiscence. 

• Migration of roots does occur but to quantify the amount is challenging. 

• Follow-up results with patients with comorbidities and decayed teeth are encouraging. 

Clinical Relevance 

This study presents the outcome and follow-up of post-coronectomy patients managed to date with particular emphasis on the clinical difficulties encountered routinely including:

• Use of intra-pulpal deposit of xylocaine with adrenaline following coronectomy helps reduces post-surgical pain significantly.

• Practical difficulties achieved during the procedure like primary closure leading to wound dehiscence.

• Outlines advantages of modified procedure to achieve optimal closure and reduce chances of wound dehiscence during healing phase.

• Follow-up on medically compromised patients and decayed teeth, previously considered as contraindicated in the literature. 


Coronectomy is recognised as a procedure performed in patients whose lower third molar roots are proximate to the inferior alveolar nerve and where surgical removal may result in neuropraxia 2, 3, 4, 5, 6.  

The acceptance of this procedure has been increasing by documented evidence of reduction in risk of IAN injuries and the number of patients is willing to consent for this alternative technique 7,8,9. The oral and maxillofacial community has welcomed this procedure as a means to lessen the burden of medico-legal issues and facilitate patient quality of life 10, 11, 12, 13.

In our first paper (Dhanrajani et al 1) we presented the outcomes of coronectomies performed from 2012-2016. A modification of the coronectomy procedure was described, indications and advantages for the modified technique were listed and extension of the indications to include patients with comorbidities and/or carious teeth as well as associated cysts were outlined. 

This paper extends the earlier study and reviews patients who were treated with coronectomy from 2012 to 2019.

It will address the following: 

1. Modified coronectomy

2. Complete removal of the tooth

3. Post coronectomy pain

4. Migration of roots

5. Dehiscence of the wound

6. Decayed teeth

7. Medically compromised patients

Materials & Methods

A total of 5,497 lower third molars were extracted by a single surgeon (PD) at the HCF Dental Centres, the Strathfield Private Hospital and the Holroyd Private Hospital, all located in metropolitan Sydney, Australia. Of 1,543 (28.06%) teeth removed under local anaesthesia, 109 (1.98%) were coronectomies and of 3,954 (71.93%) removed under general anaesthesia, 305 (5.54%) were coronectomies (Fig 1).

The initial study reported on a total of 3,654 lower third molars which were removed during the period of 2012-2016. Out of 855 (23.4%) teeth removed under local anaesthesia, coronectomy accounted for 42 (4.9%) of the total ; 2,799 (76.6%) were removed under general anaesthesia, of which 172 (6.1%) were coronectomies. 

During the period 2016-2019, a total of 1,843 lower third molars were removed. Of which 688 (37.33%) were under local anaesthetic and 1,155 (62.66%) were under general anaesthesia and 200 (10.85%) were coronectomies. Of 200, 133 (7.21%) were performed under general anaesthetic and 67 (3.63%) under local anaesthetic.

Figure 1: Pie chart showing number of patients treated under general and local anaesthetics.

Pre-operative assessment of patients included clinical examination and orthopantomograph (OPG). An assessment of the type and degree of impaction and the course of the inferior dental canal (IDC) in relation to the tooth was conducted for each patient.

Cone Beam CT scan (CBCT) was utilised for further assessment of the patient when any of the following radiologic findings of the IDC in association with the tooth was noted on OPG:

• Darkening of the mandibular third molar roots.

• Interruption of radiopaque lines of IDC.

• Diversion of the course of the canal by mandibular third molar roots.

• Narrowing of the canal as it passes over the root.

The option of coronectomy was offered to a patient when there was evidence of moderate to high risk of damage to the inferior alveolar nerve (IAN) if the tooth were to be removed completely. 

The features of moderate to high risk are:

• Tooth root perforation by the IDC fortunately a rare phenomenon;

• Lingual position of the IDC in relation to mandibular third molar roots;

• Narrowing and grooving of the mandibular third molar roots by the IDC;

• Loss of lingual cortex occurs frequently if the root is positioned between the missing lingual cortex and the IDC.

All patients were consented for coronectomy. They were also consented for complete removal of the tooth intraoperatively if the remaining portion of root was mobilised or coronectomy failed. Patients referred from their dentist with the option of coronectomy were provided with a detailed explanation, based on clinical and radiographic evaluation, of the risks and benefits of coronectomy versus complete removal. 

The patient group for whom coronectomy has been considered to be contraindicated are those with systemic comorbidities such as diabetes, are immunocompromised, having liver, kidney and joint or connective tissue involvement or on medication for osteoporosis such bisphosphonates and denosumab. Patients in this group have continued to be treated successfully. All the patients with comorbidities were consulted with their respective physician for their advice and opinion prior to the procedure.

Similarly, patients in whom the wisdom teeth are carious have continued to be treated successfully if the caries was limited to dentine with no pulpal involvement and did not extend to the roots of the tooth. Patients in whom  pathology was associated with lower third molars were also included in the study.

The procedure for all patients commenced as a standard coronectomy by sectioning the crown near the cemento-enamel junction (CEJ). At this stage of the procedure the wound was evaluated to assess whether primary closure was achievable while maintaining a collar of bone of 3-4 mm height around the roots. If this was not the case, then the procedure was modified.

In the modified technique the crown is sectioned at or below the furcation by further reduction of the height of the roots utilising a Tungsten Carbide bur (Densply HP Rd 8) to achieve a good skirt of alveolar bone around the roots and advancement of a buccal flap to achieve good postoperative bone and soft tissue healing. 2% Xylocaine with 1:80,000 adrenaline few drops were deposited intrapulpal before closure of the socket.

The lingual periosteum was not reflected to avoid lingual nerve injury. A 3/0 plain catgut suture (Ethicon, USA) was used in the majority of cases. All the patients were prescribed Amoxicillin 500 mg eight hourly for five days and for patients allergic to penicillin, Clindamycin 300mg 12 hourly for five days. They were also prescribed simple Paracetamol 500-1000mg every 4-6 hourly and/or Non-steroidal anti-inflammatory drug such as Ibuprofen 600mg every eight hourly post-operative for three days.

All patients were reviewed one week after surgery with an Orthopantomograph. Further follow-up was undertaken at six months, 12 months and yearly intervals.

Although a post-operative orthopantomograph was not mandatory it served to show the patient the outcome of the procedure as well as facilitating comparison of root migration during long-term follow-up.

Patients were contacted 24 hours post-operatively to assess pain and nerve function. Post-operative pain was measured subjectively by using the visual analogue scale (VAS) where 0 is equivalent to no pain and 10 to be excruciating pain.. Altered sensation was also assessed subjectively by using cotton wool and blunt probe.



The patients in the standard coronectomy group were comparatively younger (mean age 25 years) than those patients in the modified coronectomy group (mean age 41.55 years). 

The patient’s age is important in treatment planning. There was a similar count of male and female patients. (Fig 2)

Figure 2: Chart/Graph shows distribution of age and sex and distribution of standard and modified coronectomy.

The results achieved so far are elaborated as follows:

1. Post-operative Pain

Post-operative pain or discomfort is experienced to some extent by all patients after dentoalveolar surgery, but as the conservative management results in less tissue disturbance, postoperative pain should be reduced. This was supported by Renton et al. 2,11,15 but Hatano et al. 16 reported that the incidence of postoperative pain was greater in the coronectomy group.

There is no obvious explanation for increased pain in our experience. This can be attributed to initial pulpitis due to exposure of the nerve endings in pulp after sectioning of the tooth. There was no difference in incidence of pain between carious and non-carious teeth. Some authors have recommended pre-operative antibiotics in order to prevent transient bacteraemia leading to pain 16,17,18. Kim et al 2014 17 and Senciman el al 18 recommended vital pulp therapy option to treat the remaining root left following coronectomy to avoid complications such as pain migration. Unfortunately, these were isolated cases which had no support in literature.

Injecting 2% Xylocaine with adrenaline 1:80,000 intra pulpally following completion of the procedure before closure of the area was instrumental in controlling post-operative pain following coronectomy. Our study in 2017 reported a higher incidence of pain on the VAS scale of 7-8 or even 9 in some patients. Since 2016, all the patients who underwent coronectomies were supplemented by few drops of 2% Xylocaine with adrenaline intrapulpally. 

This appears to have contributed to improved pain control post-operatively. The VAS scale showed pain ranged from 3-5 in most of the patients (Fig 3). The reduction in VAS score is significant (p <0.02).

2. Migration of roots

Present study showed migration of roots following coronectomy on follow-ups. Migration was more often seen in younger patients as compared to patients over forty years of age. This was our clinical finding as the OPG machines were difficult to standardise to measure root migration accurately. Although all the patients reports are done by a single surgeon, but the source of the patients came from different centres and orthopantomograms were taken by different individuals.

None of the patients in this study required re-operation due to migration of roots.

Figure 3: Graph showing VAS scale score.

3. Complete removal of teeth

2016-2018 period had revealed significant increase of complete removal of teeth who were consented for coronectomies with no post-op paraesthesia (Fig 4). 

This finding was more seen in patients with a. conical roots and b. young patients where root was not fully mature, and roots were loose following coronectomies cuts.

Figure 4: Graph showing complete removal of teeth consented for coronectomy.

4. Dehiscence of wound 

A second complication seen was wound dehiscence. Criteria for wound dehiscence used was gap in the socket causing food trap and not due to post-operative infection. In present study over all wound dehiscence incidences was seen in 49 patients (12%). The gap/dehiscence was very minimal especially in the disto-lingual aspect of second lower molars, and none required second surgery which eventually healed with mouthwash and local irrigation using a monojet tip syringe (Covidien, Sydney, NSW, Australia). None of the patients with wound dehiscence were prescribed antibiotics.

This can be attributed to better surgical planning, meticulous tissue handling, and modified coronectomy technique used (Fig 5). 

5. Nerve Paraesthesia/anaesthesia

There was one incidence of nerve paraesthesia or anaesthesia reported in patients having coronectomies done during 2012-2018. It was associated to nerve to mylohoid. Patient reported to have paraesthesia around the chin which lasted over 6 months. 

Figure 5: Pie chart showing incidence of gap/dehiscence of wound.

6. Modified Coronectomy

Modified coronectomy was carried out in situations where it was felt that the post-surgical anatomy would not allow a passive primary closure of the socket. This has been advantageous in achieving good post-operative outcomes. The surgical area heals well primarily without getting dehiscence or gap there by avoiding food trap and subsequent infection. This has also helped in favourable periodontal health around lower second molars.

7. Medically compromised patients

Patients with the following co-morbidities were included in this study since last nine years: mainly osteoporosis, diabetes, immune-compromised 

Of those patients on osteoporosis medication, 9 (2.17%) had standard coronectomy (6 were on bisphosphonate and 3 were taking denosumab) and 5 (1.20%) had the modified procedure and were on denosumab. 

Figure 6: Table showing comorbidities included in study.

Patients with diabetes mellitus total (42/13.54%); 31 had a standard coronectomy and 11 had the modified technique. Nineteen patients were type I diabetic, controlled with insulin and 23 were type II controlled by oral hypoglycaemic drugs. HbA1c level was in the range 4.9% to 6.3%.

Of the patients on immunosuppressant medication (14/4.51%) 8 had standard and 6 had modified coronectomy procedures. Most of immune suppressed had liver, kidney and joint involvement. (Fig 6)

8. Carious teeth

A total of 68 (16.42%) patients with coronal caries (i.e. not involving the pulp) underwent coronectomy. Of these 30 (7.72%) had a standard coronectomy and 38 (9.17%) had modified coronectomy (Fig 7). Nineteen cases in this study were associated with cystic lesions, out of these four were odontogenic keratocyst and remaining were follicular/dentigerous cyst.

Figure 7: Pie chart showing patients included with carious teeth and associated cysts.

9.  Re-operation

There was one case in this study where the root was to be removed due to recurrent infection. She was fit and well and came from 4th decade age group. This was bucco-horizontal impaction. It is very difficult to predict which patient might require re-operation.


Follow-up varied in this study from 4 months to three years. The majority of the cases were treated in the period 2015 to 2018. The mean follow-up period was 16 months (Fig 8).

Figure 8: Graph showing period of follow-ups.


Coronectomy has been proposed as a valid treatment option to reduce the risk of IAN injury in selected cases5, 6, 7, 11, 12. It is becoming the standard of care to assess its applicability during the development of the treatment plan and to explain the advantages and disadvantages during consultation19, 20, 21, 22. The technique was brought to the attention of the profession by the first publication by Pogrel et al in 20047 and has gained popularity internationally since then; however, it still remains controversial in its applications such as inclusion of patients with comorbidities and carious teeth.

To date there have been randomised control trials of coronectomies by Leung et al. 200910, Renton 200511, Hatano et al. 200916 and Pogrel et al. 20047. All these studies have recommended coronectomy as an acceptable procedure to reduce the risk of nerve injury in symptomatic mandibular third molar removal.

Studies on root migration have been reported in literature varies from 4 to 7 mm from 12 months to 24 months and this ceases by 24 months. (Leung et al 20123 , Dolanmaz19  and Knutsson20). The present study was not able to standardize the OPG and patients in study were referred from different centres as well as the x-rays were done by referring dentist. Our clinical observation supports the view of migration of roots. Migration is seen most commonly during 

• first year of follow-up and

• more often in younger patients 

With the increased acceptance of coronectomy the question must be asked as to whether the procedure is being over-utilised for fear of medicolegal repercussions. In answer to this question the profession must remain mindful of the debilitating effect of neuropraxia of the IAN particularly where this results in neurogenic pain.21,22.23

For this reason, discussion of coronectomy with patients is always worthwhile where the risk of IAN injury is likely; it is clear that the severity of post-operative complications with coronectomy will be less than the neurogenic pain associated with neuropraxia.21,22,23,24

There was one patient in the present study were the root required to be removed and second procedure was done. This was during the first 6 months of follow-up. The patient had recurrent pain and infection in the area of surgery and OPG showed root had migrated with widening of periodontal space. Pogrel (2015) 13 in a review of 742 patients, who underwent coronectomy, reported that six had subsequent infection which required removal of roots and 31% showed root migration. This led him to the conclusion that coronectomy should be considered in patients older than 25 years, where there appears to be intimate relationship between the roots of a retained lower third molar and IDN, in circumstances where it is not contraindicated. It can be used on younger patients with high risk of IDN damage23,24,25,26

The present study suggests that there may be a role for coronectomy in young individuals at high risk of IAN damage. If the nerve damage does occur, it is more likely to recover and less likely to result in permanent damage. There was no permanent nerve damage or long term paraesthesia in extraction group of patients in this study. One patient had paraesthesia of left chin for over four months in the coronectomy.  

Successful management and inclusion of carious teeth and patients with comorbidities is acknowledging wider support since we initially reported in 20181. It was encouraging to see recent study by Patel et al 202021, offering coronectomy of mandibular third molars with caries or resorption at the risk of inferior alveolar nerve injury. The days are not for when we will see studies offering coronectomies to patients with comorbidities.

Our experiences suggest coronectomies can be successfully carried out in patients with decayed teeth and in patients with co-morbid systemic diseases such as diabetes mellitus, on steroids, other immunosuppressants and/or bisphosphonates and denosamub. 

Present study has shown significant reduction of post-operative pain by injecting few drops of local anaesthetics intra-pulpal. Although this is purely our finding which is encouraging and yet to be acknowledged in the future to compare. This study suggests a trial would be necessary to demonstrate the link between using intra-pulpal local anaesthetics and reduce pain experience.

In our study the incidence of wound dehiscence was considerably less. This can be attributed to better surgical planning, meticulous tissue handling, and modified coronectomy technique used. Patients were followed regularly by clinical reviews or calling them by phone. All the patient had contact details of surgeon in case of any emergencies or advices. 

The flowchart (Fig 9) provides guidance in the decision-making process for selection of coronectomy. 

Figure 9: Flow chart of decision making for coronectomies.


Coronectomy has demonstrated its effectiveness and safety in the the management of cases where the roots of a mandibular third molar are proximate to the inferior alveolar nerve. The outcomes of the present study demonstrate that it is effective in patients with decayed teeth third molars and in those who are medically compromised.


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You can find this article in Dental News Magazine January Issue 2021

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