Coronectomy-prevention from Injury of the Inferior Alveolar Nerve (N. Alveolaris Inferior)  

Velickovski Boris , Peeva-Petreska Marija , Veleska-Stevkovska Daniela , Kacarska Marina
Department of Oral Surgery – Faculty of Dentistry in Skopje, Ss Cyril and Methodius University, Republic of Macedonia
Author    Correspondence author
International Journal of Clinical Case Reports, 2015, Vol. 5, No. 14   doi: 10.5376/ijccr.2015.05.0014
Received: 30 Jan., 2015    Accepted: 03 Mar., 2015    Published: 04 Apr., 2015
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Boris et al., 2015, Coronectomy-prevenention from Injury of the Inferior Alveolar Nerve (N. Alveolaris Inferior), International Journal of Clinical Case Reports, Vol.5, No.14 1-5 (doi: 10.5376/ijccr.2015.05.0014)

Abstract

In order to reduce or minimize the present high risk of injury to the inferior alveolar nerve (IAN) determined by an X-ray, some alternative techniques are described for extraction of the lower third molars. Some of these techniques have been confirmed and as such established in surgical practice, while others are subject to future, additional analyzes within the differently designed clinical studies. Coronectomy(partial root removal, deliberate vital root retention, intentional partial odontectomy) is defined as a method of extracting the dental crown and retainig the root which is closely corelated with the IAN.The article presents a case where this type of intervention was performed on the third mandibular right molar with a female patient, 38 years of age, who was referring that the extraction of the third mandibular left molar led to her having unpleasant sensations (paresthesia) for a longer period of time. The indications and contraindications for coronectomy, the surgery phases and post-surgical follow up are explained in details. Today, in the era of medicine/surgery based on evidence, the coronectomy gained enhanced reputation as an effective method in reducing the risk of injury of the inferior alveolar nerve. The injury of the IAN during the extraction of mandibular third molars is clinical and medical-legal issue. For this reason, it is worth considering any therapeutic procedure that reduces this problem. The decision is adopted by the oral surgeon with patient’s consent.

Keywords
Coronectomy; Oral surgery; Inferior alveolar nerve; Third mandibular molars; Paresthesia

An injury of the inferior alveolar nerve (IAN) presents a rare but serious complication, which results in the emergence of certain neurologically sensitive aberrations (hypoesthesia, hyperesthesia, dysesthesia, and anesthesia) of temporary but of permanent nature, as well. Generally, it can be said that the prevalence of the temporary aberrations ranges between 0.41%- 8.1%, and the prolonged, i.e. permanent symptoms are rarer and range between 0.014%-3,6% (Valmaseda-Castellonet et al., 2001; Brian, 2004; Queral-Godoy et al., 2005). It is an interesting fact that when, risky” third molars (teeth whose roots are in a very close correlation with the IAN) are extracted, the prevalence of this complication is higher than 20%. When we talk about these injuries of the inferior alveolar nerve, it is concerning the fact that to certain percent with these cases a complete physiological and functional recovery of the nerve is not achieved and these patients are permanently affected by certain neurosensory aberrations (Cheung et al., 2009). Namely, the ongoing therapeutic modalities purposed for taking care of the neurosensory deficit (two surgical and two non-surgical) enable only limited improvement of the sensations, i.e. not always a complete rehabilitation is achieved of the developed situation (Leung et al., 2012). In order to reduce or minimize the present high risk of injury to the nerve, determined by an X-ray, some alternative techniques are described for extraction of the lower third molars. Some of these techniques have been confirmed and as such established in surgical practice, while others are subject to future, additional analyzes within the differently designed clinical studies.

·           Coronectomy - intentional partial odontectomy (Ecuyer and Debien, 1984)
·           Extraction in stages (Landi et al., 2010)
·           Pericoronalosteotomy (Tolstunov et al., 2011)
·           Orthodontically supported extraction (Checchi et al., 1996)
·           Modified and grafted coronectomy (Leizerovitz and Leizerovitz, 2013)
Coronectomy (partial root removal, deliberate vital root retention, intentional partial odontectomy) is defined as a method of extracting the dental crown and retainig the root which is closely corelated with the IAN (Hatano et al., 2009). The main indication for application of this method is the extraction of mandibular third molars (erupted, partially impacted, impacted), in terms of the present high risk for injury of the IAN. This risk is due to the close relation of the tooth root and the IAN, which is normally determined by an X-ray. In addition, certain radiographic indicators are used by which is predicted the increased risk of injury of the IAN.
Those radiographic signs are:
a)          Deviation of a canal
b)         Narrowing of a canal
c)          Periapical radiolucent area
d)         Narrowing of the root
e)          Darkening of the root
f)          Deflection of the root and
g)         Discontinuity of the lamina dura from the canal
However, by using a panoramic dental x-ray, the exact correlation between the dental roots and the IAN cannot be detected, as it is a two-dimensional imagery technique. Today, the cone beam computerized tomography scanning, as a highly sophisticated tri-dimensional imagery method, is a standard in the evolution of the correlation of the IAN roots and the nerve, in order to determine an adequate therapheutic option (Tantanapornkul et al., 2007).
Whether the coronectomy is successfully rendered depends on two factors:
a)          adequate selection of patients
b)         adequate surgical technique
Coronectomy is contraindicated in the following situations (Pogrel, 2009):
1.     Acute infection in the oral cavity or around the tooth which is subjected to coronectomy.
2.     Chronic infection of the tooth (extensive dental caries, periodontal disease).
3.     Mobility of the tooth, whose roots can act like a mobile foreign body which can become core for infections or migration.
4.     Teeth which are horizontally placed, along the position of the mandibular canal. During the dental surgery there is a presence of high risk from nerve injury. This technique has to be used with vertical, mesioangular and distoangular impacted teeth, where by surgical operation the tooth cannot be threatened.
Basic Principles
Numerous variations are described in terms of coronectomy technique yet certain basic principles must be taken into account (Pogrel, 2009): -Tooth subjected to coronectomy should not be mobile;
-   The tooth should be vital or adequately endodontically treated;
-   The anatomical crown and sufficient part of the coronal third of the root should be removed, i.e. the retained root fragment should be at least 2-3 mm below the crestal part of the alveolar ridge inducing stimulation of bone tissue formation that overlaps the retained root fragment;
-   The exposed pulp of the tooth and the root does not need further treatment. The osteocementum usually extends and overlaps the root fragments (Whitaker and Shankle, 1974);
-   The root fragment left, in situ should not be mobile.
Case presentation
At the Clinic for Oral Surgery this type of intervention was performed on the third mandibular right molar with a female patient, 38 years of age, who was referring that the extraction of the lower third mandibular left molar led to her having unpleasant sensations (paresthesia) for a longer period of time. After the radiographic evaluation for a possible collision of the roots of the third mandibular right molar with the mandibular canal, it was decided that coronectomy should be performed (Figure 1).


Figure 1 Panoramic image


The pre-surgery preparations included:
a. Pre and post-surgical rinse of the oral cavity with chlorhexidine (Renton, 2012)
 
b. Antibiotic prophylaxis
Certain experts suggest pre-surgical antibiotic prophylaxis, by which a presence of antibiotic is enabled in the pulp chamber in the moment of the tooth separation. (Pogreletal., 2004; Dolanmaz, 2009).
The surgery phases included:
1. Formation and elevation of the triangular mucoperiosteal flap (no lingual approach is needed).
2. With a round borer a buccal, occlusal and distal osteotomy was made i.e. the crown was revealed and an enamel-cement border was exposed. In this way an adequate access for cutting through the enamel- cement border in pulp was provided (Figure 2).


Figure 2 Surgical exposition of the crown


3.
A lingual retractor must be placed throughout the procedure, because the lingual cortical lamina may be perforated by careless handling and additionally the lingual nerve may be at risk of injury. The vertical distance of the nerve from the distal lingual crest bone in a third molar region is 2,28-8,32mm, and the horizontal distance is 0,58-3,45mm. Using a fissure bur the crown of the tooth was separated directly under the enamel-cement border (Figure 3). Once the crown was completely cut, it was removed with a suitable tool and thus the possibility of mobilizing the retained root fragment was minimized. During the performance of this phase a continuous irrigation with saline is required and if noticed mobility of the root fragment, it should be removed.


Figure 3 Surgery of the crown


4.
After the removal of the crown, by using the fissure bur the retained root fragment is reduced, so that the root fragment is at least 3 mm below the crestal bone ridge, from the buccal and the lingual. In this, it is important that the pulp chamber is not frequently touched, so that the vitality of the tooth is maintained.
5. The operational area was closed primarily (Figure 4).


Figure 4 Placement of sutures


In
the period that followed it was necessary to make radiographic evaluation of the patient, in order to assess whether the coronectomy was adequately performed, and the subsequent monitoring of the process of creating the bone over the retained root fragment and the expected subsequent migration of the same.
Possible complications after coronectomy
Coronectomy, like any other operating procedure, carries with it a risk of early (immediate) and late (long-term) complications. In the literature we can find many differently designed studies, which are based on different research samples and in different observational postoperative period these complications have been analyzed:
1.With regard to the incidence of clinical manifestation of intraoperative and postoperative complications it is not found a significant difference between corticotomy and standard operating extraction,
2. Coronectomy significantly reduces the risk of injury of the inferior alveolar nerve (main benefit).
The further fate of the retained roots is decided by the following:
- The state of pulpal tissue (vital/non-vital)
- Root migration
- Root eruption
- Root mobility
Condition of pulpal tissue
Following the corticotomy, the retained pulpal tissue retains its vitality. Published studies have studied root and surrounding bone, en block" and they indicate that the retained pulp preserves its vitality (Cook et al., 1977).
Root migration
The most common long-time consequence after the coronectomy is a migration of the roots, which is unpredictable and occurs in the coming months and years. This root migration is noted in each published study, and its incidence ranges from 14% - 81%, depending on the length of postoperative observational period. By the subsequent migration, which is occlusally directed i.e. to the crown, the root distances from the mandibular canal, and if there is a need for reoperation (in the next stage), the risk of nerve injury is minimized. A paper (Leung and Cgeung, 2012) presents data that shows that almost all roots migrate during the first year. This migration gradually declines and during the second year it completely stops. The average value of the root migration in a three-year-observation period is 2,8 mm. After the termination of the root migration, there is no reactivation of the same. The first two years of postoperative period are crucial in terms of migration. Namely, during the first 24 months of intensive root migration can result in the eruption of the root in the oral cavity, and the second after this period (first 24 months) the root migration is completely absent. Root migration is greater among women. These key findings provide a better understanding of the behavior of the retained roots, after the performed coronectomy.
Root Eruption
Root eruption is directly related to the intensity of the root migration. Regarding the need for reoperation due to subsequent eruption of roots in the oral cavity, published data are different:
- Reoperation 5.5% - 6% (Brian, 2004)
- Reoperation 3% (Leung and Cgeung, 2012)
Root Mobility
Occurrence of root mobility during the intervention suggests that it is not carried out correctly and mobile roots should be removed. This mobility of the roots is due to the incomplete separation of the crown, which is fractured to be removed.
The incidence of this complication ranges within the range of 3% - 9% (Knutsson et al., 1989).
Conclusion
Today, in the era of medicine/surgery based on evidence the coronectomy gained enhanced reputation as an effective method in reducing the risk of injury of the inferior alveolar nerve. This actually represents a major benefit which this alternative procedure brings. In 2010 in Washington was held Third Molar Multidisciplinary Conference, (October 19, 2010) where coronectomy is introduced as a standard procedure for the extraction of third molars with a high risk of injury of the IAN. Also, in 2012 the coronectomy is listed on the standard procedures by the American Association of Oral and Maxillofacial Surgeons. The injury of the IAN during the extraction of mandibular third molars is clinical and medical-legal issue. For this reason, it is worth considering any therapeutic procedure that reduces this problem. Because of the expected root migration, monitoring the patient is highly necessary over a period of time (24 months) and if needed, a reoperation is performed i.e. removal of the retained migrated roots. This reoperation is also with a low risk of injury of the IAN. The patient should be offered the both options, with all the advantages and disadvantages. The decision is adopted by the oral surgeon with patient’s consent.
References
Brian C. O' Riordan, 2004, Coronectomy ( intentional partial odontectomy of lower third molars), Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology and Endodontology, 98(3): 274-280
Checchi L., Bonetti G.A., and Pelliccioni G.A., 1996, Removing of high-risk impacted mandibular third molars, a surgical orthodontic approach, J. Am. Dent. Assoc., 127: 1214
http://dx.doi.org/10.14219/jada.archive.1996.0413
Cheung L.K., Leung Y.Y., Chow L.K., et al, 2009, Incidence of neurosensory deficits and recovery after lower third molar surgery: A prospective clinical study of 4338 cases, Int. J. Oral Maxillofac. Surg., 108: 821
Cook R.T., et al., 1977, Periodontal osseous defects associated with vitally submerged roots, J. Periodontol., 48: 249-260
http://dx.doi.org/10.1902/jop.1977.48.5.249
Dolanmaz D., et al.,2009, A preferable technique for protecting the inferior alveolar nerve: coronectomy, J. Oral Maxillofac. Surg., 67:1234-1248
http://dx.doi.org/10.1016/j.joms.2008.12.031
Ecuyer J., and Debien J., 1984, Surgical deductions, Actualites Odonto-Stomatologiques, 32(148): 695-702
Hatano Y., et al., 2009, Clinical evaluations of coronectomy (intentional partial odontectomy) for mandibular third molars using dental computed tomography: A case control study, J. Oral Maxillofac. Surg., 67: 1806-1814
http://dx.doi.org/10.1016/j.joms.2009.04.018
Knutsson K., Lysell L., and Rohlin M., 1989, Postoperative status after partial removal of the mandibular third molar, Sweed Dent J., 13: 15-22
Landi L., Manicone P.F., Piccinelli S., Raia A., and Raia R., 2010, A novel surgical approach to impacted mandibular third molars to reduce the risk of paresthesia: a case series, Journal of Oral and Maxillofacial Surgery, 68(5): 969-974
http://dx.doi.org/10.1016/j.joms.2009.09.097
Leizerovitz M., and Leizerovitz O., 2013, Modified and Grafted Coronectomy: A New Technique and a Case Report with Two-Year Follow ap, Case Reports in Dentristy
Leung Y.Y., Fung P.P., and Cheug L.K., 2012, Treatment modalities of neurosensory deficit after lower third molar surgery: a systematic review, Journal of Oral and Maxillofacial Surgey, 70(4): 768-778
http://dx.doi.org/10.1016/j.joms.2011.08.032
Leung Y.Y., and Cgeung L.K., 2012, Coronectomy of the lower third molar is safe within the first 3 years, J. Oral Maxillofac. Surg., 70: 1515-1522
http://dx.doi.org/10.1016/j.joms.2011.12.029
Pogrel M.A., 2009, Coronectomy to prevent damage to the inferior alveolar nerve, Alpha Omegan, 102(2): 62-67
http://dx.doi.org/10.1016/j.aodf.2009.04.011
Queral-Godoy E., Valmaseda-Castellon E., Berini-Aytes L., and Gay-Escoda C., 2005, Incidence and evolution of inferior alveolar nerve lesions following lower third molar extraction, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod., 99: 259
http://dx.doi.org/10.1016/j.tripleo.2004.06.001
Renton T., 2012, Notes on coronectomy, British Dental Journal, 212: 323-326
http://dx.doi.org/10.1038/sj.bdj.2012.265
Tantanapornkul W., et al., 2007, A comparative study of cone-beam computed tomography and conventional panoramic radiography in assessing the topographic relationship between the mandibular canal and impacted third molars, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod., 103: 253-259
http://dx.doi.org/10.1016/j.tripleo.2006.06.060
Tolstunov L., Javid B., Keyes I., and Nattestad A., 2011, Pericoronal ostectomy: an alternative surgical technique for management of mandibular third molars in close proximity to the inferior alveolar nerve, Journal of Oral and Maxillofacial Surgery, 69(7): 1858-1866
http://dx.doi.org/10.1016/j.joms.2011.03.002
Valmaseda-Castellon E., Berini-Ayte L., and Gay-Escoda C., 2001, Inferior alveolar nerve damage after lower third molar surgical extraction: A prospective study of 1117 surgical extractions, Oral Surg. Oral Med. Oral Pathol. Oral Radiol. Endod., 92: 377
http://dx.doi.org/10.1067/moe.2001.118284

Whitaker D.D., and Shankle R.J., 1974, A study of the histologic reaction of submerged root segments, Oral Surg. Oral Med. Oral Pathol., 37: 919-935
http://dx.doi.org/10.1016/0030-4220(74)90445-9

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