Get to the root of the problem

15 March, 2013 / Infocus
 

As an experienced, specialist endodontist, surgery has continued to be a regular part of my clinical practice, offering high success rates for teeth that would otherwise be extracted. There are many referrals for surgery, however, that are not always appropriate and root canal retreatment may be the preferable option. This article will describe the indications for surgery and the techniques that are used to obtain an optimum result.

The aim of root canal treatment is to access, clean, disinfect and shape the root canal system. This should remove necrotic debris and reduce the number of microorganisms, allowing the canals to be sealed to prevent further reinfection.

Published success rates vary from 37 per cent to 91 per cent1, and can be described as no clinical signs or symptoms, and radiographically, bony healing of a previous periradicular radiolucency with a normal periodontal space around the root.

Persistent periradicular radiolucencies of endodontically treated teeth are caused by intra–radicular infection, extra-radicular infection, foreign body reactions, true radicular cysts, fibrous scar tissue and vertical root fractures. Root canal retreatment should always be considered before surgical intervention, which is not a substitute for incomplete debridement and inadequate endodontics.

Indications for surgical endodontics

  • Previous root canal treatment has failed and retreatment is not possible or will not correct the problem. In the case of a post-retained crown, an assessment should be made as to whether or not this can be safely dismantled. Most posts can be removed using ultrasonics providing an adhesive resin cement has not be used (Figures 1a, 1b, 2a, 2b).
  • Anatomical deviations that have prevented complete cleaning and obturation
  • Procedural errors such as ledges, blockages, perforations, file breakages and overfills
  • Exploratory surgery to aid with identification of vertical root fractures
  • Failure of previous surgery often completed using traditional techniques (Figures 3a, 3b).

Surgical endodontics is not indicated:

  • when root canal retreatment is possible
  • difficult anatomical factors such as proximity to neurovascular structures, thick cortical bone and difficult access
  • when assessment using cone beam CT shows a defect such as resorption or perforation is not accessible for surgical repair
  • inadequate periodontal support
  • non restorable tooth
  • complex medical history

The high success rates that are obtained require highly trained, experienced clinicians and the equipment, materials and techniques as described below.

Surgical microscope

The use of magnification, illumination and microsurgical instruments has changed the traditional ’blind’ procedure commonly referred to as an apicectomy into one that is visually dominated and, therefore, extremely accurate. The microscope is based on Galilean principles that focuses on infinity and, therefore, unlike loupes, allows treatment for long periods of time without causing eye fatigue2.

Magnification

The eyepiece, binoculars and magnification changer determine magnification. The eyepiece is available with 6.3, 10, 12.5, 16 and 20 magnification powers. The 12.5 is recommended for endodontic practice. Diopter settings from –5 to +5 allow adjustment for accommodation and refractive error of the clinician.

The binoculars are used to project an intermediate image into the focal plane of the eyepiece. They are set at the correct interpupillary distance for the operator and are available at different focal lengths. The longer the focal length, the greater is the magnification, but the narrower is the field of view. The focal length of the objective lens determines the distance between the lens and the surgical field. A typical working distance would be 25cm for a 250mm lens.

Binoculars are available with inclinable tubes of up to 180 degrees to accommodate virtually any head position. The magnification changer is located within the head of the microscope and is available in three or five step manual changers, manual zoom or power zoom changers. Before using the microscope, it must be made parafocal. Most surgical microscopes allow magnification from x3 to x30. With high magnification, the focal depth is shallow and this is used only for inspection of fine detail (fig 4).

Illumination

The light provided is two to three times more powerful than surgical headlamps. Most microscopes now use xenon bulbs that project a bright, warm light against bone and soft tissues. A beam splitter can be used to supply light to a camera or auxiliary observation tube.

Documentation

Photographs and videos can be recorded and used for patient information, and dental education.

Soft tissue management:

Local anaesthesia

This eliminates pain during surgery and also causes haemostasis, which is of equal important when using magnification3. Buckley suggested the use of 2 per cent lidocaine with 1:50,000 epinephrine4. This causes activation of alpha-receptors in the arteriolar muscles, submucosa and periodontium causing vasoconstriction.

This local anesthetic is not licensed for use in the UK and, therefore, 4 per cent articaine with 10,000 epinephrine can be used as an alternative with an additional infiltration of 2 per cent lidocaine with 80,0000 epinephrine above the tooth requiring surgery. Articaine, because of its thiophene ring and additional ester ring, has been shown to have a greater ability to diffuse into the tissues.

Flap design

A sound knowledge of the anatomy of the gingival tissues is important prior to deciding on the type of incision and flap design. Healing by primary intention can be achieved by using complete and sharp incision of the tissues, by avoiding trauma to the reflected tissues and by preventing drying of the surgical site5.

Recommendations for flap design:

  • The flap should provide adequate access to the surgical site, and allow sufficient blood supply to the mobilised and non-mobilised tissues.
  • The flap should not cross a bony defect and the relieving incisions should be placed over concave bone surfaces and should end at the mesial or distal line angles and curve so that the incision meets the free gingival margin at 90 degrees to the gingival contour. The other end should not enter the mucolabial fold.
  • The base should be as wide as the free edge and relieving incisions should be vertical following the direction of the vessels.
  • The periosteum should be raised with the flap.

Flap designs include semilunar, submarginal mucoperiosteal and papilla-based. Semilunar is of historical interest and has no place in modern surgical practice. Since first being described by Velvart in 2002, the papilla-based incision has now become the flap design of choice6.

It consists of two vertical relieving incisions, connected by the papilla base incision and intrasulcular incision in the cervical area of the tooth. The papilla incision is performed using a microblade such as a CK1 (fig 5).
This comprises a shallow first incision at the base of the papilla and a second incision directed towards the crestal bone (fig 6).

Elevation and retraction
A sharp, small elevator is placed at the junction of the horizontal and vertical incisions with the concavity towards the bone, (fig 7). The periosteum should be completely reflected to prevent bleeding, diminish pain and inflammation and aid with healing. Many retractors are either too narrow or convex at the tip. This can contribute to trauma of the flap or soft tissues. The Kim-Percora or the Rubinstein retractors will give better anchorage.

Hard tissue management:

Osteotomy
On many occasions, following flap retraction, a bony defect will be present in the cortical bone that will allow access to the root apex either without bone removal or with minimal extension of the borders of the defect. The osteotomy involves removal of cortical and cancellous bone to gain direct access to the apical and also the lateral aspect of the root when required.

When removing bone, the generation of heat should be avoided by using a surgical round bur and copious irrigation of the area using saline. The bur should be used with a light brushing action. The use of magnification allows the clinician to easily differentiate the difference between bone and root surface, (fig 8).

Root end resection

This is considered critical to the overall success of surgery. The majority of unfilled lateral canals are located within the apical 3mm of the root and, therefore, 3–4mm of the root end should be exposed by the osteotomy6. This is resected 90 degrees to the long axis of the root using an Impact Air surgical handpiece 45 degrees and a Lindemann bur, (fig 9). High magnification can be used in conjunction with staining using methylene blue to ensure the root end has been completely resected and removed.

Surgical curettage
This should remove the soft tissue, granulomatous lesion, consisting of lymphocytes, plasma cells, macrophages, foreign bodies and epithelium. The source of periradicular periodontitis is not located in the soft tissue lesion, but within the root canal system, therefore there is debate over whether or not all of this tissue has to be removed. Certainly this should be attempted and carried out as quickly as possible to prevent unnecessary dehydration of the tissues. Haemostasis is directly related to removal of the soft tissue and a clean, bony crypt will be easier to manage when placing the root end filling. The soft tissue lesion is undermined using small curettes and dissected away from the crypt. The resected tissue should be sent for histopatholgical examination.

Root end preparation

The root end is inspected at high magnification for the presence of cracks and, in the case of multirooted teeth, the presence of an isthmus. Ultrasonic tips are used to remove root canal filling material from the apical 3mm of the remaining
root (fig 10). The cavity is inspected using a micromirror (fig 11) and the softened, apical gutta-percha vertically compacted using a microplugger (fig 12).

Root end filling

Prior to placing the filling, the bony crypt is lined with a cotton wool pellet impregnated with epinephrine (fig 13), which will maintain a dry field.

While materials such as amalgam, Intermediate Restorative Material, super ethoxybenzoic acid, glass ionomer and composites have been used, these materials do not satisfy the requirements of an ideal root end filling material.

Mineral trioxide aggregate (MTA) (ProRoot), developed in 1995, is now considered the material of choice (fig 14). The powder consists of fine hydrophilic particles that, when mixed with water, forms a colloidal gel that solidifies in approximately three hours. The sealing ability, antibacterial effect and bio-compatibily have all been tested. MTA has also been shown to encourage cementogenesis around the resected root end7 8 9 10.

The material is placed in a carrier (fig 15) and deposited at the root end, where it is packed into the cavity using micropluggers. The cavity should be slightly over1filled and the excess removed using a damp cotton pellet. The material can then be smoothed using a mircoburnisher and the pellet removed.

Treatment of bony defects by Guided Tissue Regeneration (GTR)

Healing of a wound can either be by repair or regeneration. Repair will not fully restore normal architecture or function, while regeneration uses barrier membranes and bone-grafting materials to encourage the growth of surrounding tissues while excluding unwanted cell types.

Wound healing after endodontic surgery involves hemostasis, coagulation, inflammation, proliferation, regeneration or repair and remodelling or maturation. Granulation tissue formed during the proliferation stage is essential and regeneration requires progenitor or stem cells, growth factors and local factors such as adhesion and protein molecules.

Bone replacement grafts can be:

  • Osteogenic –living bone cells present in the graft material
  • Osteoinductive – encourages undifferentiated cells to become osteoblasts
  • Osteoconductive –guides the reparative growth of natural bone.

Grafts can be categorised as follows:

1. Autogenous
These are the gold standard and are taken from a remote site from the same host. They are osteogenic, osteoinductive and osteoconductive.

2. Allografts

These are genetically dissimilar members of the same species and are normally freeze dried bone. This type of graft is osteoinductive and osteoconductive.

3. Xenografts

Tissue is taken from one species and placed into another. This can be either bovine or porcine. The material is processed to remove the organic constituents and is osteoconductive, e.g. Bio–Oss.

4. Alloplasts

A synthetic or inert foreign body that is implanted into host tissue. This type of graft is osteoconductive and examples are hydroxyapatite, beta–tricalcium phosphate, calcium sulphate, non-ceramic polymer and bioactive glass.

Membranes are used to exclude epithelial cells and connective tissue fibroblasts to allow regenerative cells to repopulate the area and are thought to have some benefit in the treatment of buccal dehiscences. The barrier prevents migration of junctional epitheium and is therefore directed at the periodontal tissues rather than periradicular regeneration.

Bio–Gide is an example of a collagen membrane of porcine origin. It consists of two layers. The superior layer, which faces the tissues is cell occlusive and prevents invasion of connective tissue cells into the membrane-protected space. The porous layer faces the bony defect and promotes cell integration.

A ‘through and through’ lesion occurs when both the buccal and palatal cortical bone have been damaged as a result of apical periodontits or apical surgery. It is most likely that this type defect will heal by connective tissue scar formation. There is no conclusive evidence that placing a membrane barrier in large through and through defects has a better long–term outcome.

A systematic review of GTR by Tsesis et al. in 2011 11 concluded that, although there were slightly better outcomes, these were not statistically significant and only beneficial in large periapical lesions and ’through and through lesions’. Pecora et al. 2001 12 demonstrated that the addition of calcium sulphate in the treatment of a ’through and through’lesion improved the clinical outcome by acting as a scaffold to induce new bone formation.

Suturing and wound closure
Healing should occur by primary intention with no pain or inflammation. The reflected tissue flap should be kept moist during the surgical procedure to prevent shrinkage that will make repositioning difficult and may require additional incisions of the apical periosteum.

The flap should be gently handled and repositioned passively in the correct position. Polypropylene (Prolene) or Polytetrafluoroethylene (Tevdek) sutures are recommended as these cause minimal inflammation and promote rapid healing (fig 16).
Microsurgical needle holders are used and a surgeon’s knot, double overhand, then single underhand in the opposite direction, will prevent slippage (fig 17).

The flap should be compressed with damp gauze to reduce the coagulum to a thin fibrin layer between the repositioned flap and the cortical bone. Sutures are normally removed after three days to prevent epithelisation of the suture tract.

Clinical outcomes

Over 70 studies have been published reporting on the outcome of apical surgery. Many of these used poorly standardised materials and methods and, since their publication, new techniques have evolved with the introduction of magnification and illumination that make these success rates less relevant to todays practice.

Following surgical endodontics, teeth should be reviewed after one year. The definitions of treatment outcomes can be described as follows:

Successful (healed)

Complete healing, radiographic and clinical normalcy. Included in this category is scar formation.

Incomplete healing (healing in progress)

A persistent radiolucency in the absence of clinical signs or symptoms. The presence of clinical signs or symptoms and incomplete bony healing.

Uncertain healing (persistent disease)

Presence of signs or symptoms combined with a reduced or persistent radiolucency.

A review by the Cochrane collaboration in 2008, entitled Surgical versus non-surgical endodontic re-treatment for periradicular lesions, included three studies 13. The paper concluded that the initial advantage of surgery appears to disappear if the follow-up is prolonged for four years. It also quite rightly stated the fact that surgery can isolate but not completely eliminate endodontic bacteria from the root canal system.

A systematic review carried out by Torabinejad et al. in 2009 compared outcomes of nonsurgical retreatment and endodontic surgery14. Success rates for surgery was higher at two to four years (77.8 per cent), compared with retreatment (70.9 per cent). At four to six years this was reversed, with surgery 7.8 per cent and retreatment 83 per cent. This paper concluded that retreatment offers a more favorable long-term outcome.

Tsesis et al. 2009 published a meta-analysis of the literature looking at the outcome of surgical endodontic treatment performed by a modern technique15. Eleven ıarticles were included and concluded that surgery was successful in 19.4 per cent of cases.

Conclusions

Surgical endodontics will continue to be a part of specialist endodontic practice. The results are predictably high when using the techniques described in this paper.

Dentists should therefore consider this treatment for their patients in cases where a coronal approach to retreatment is not possible.

The Royal College of Surgeons of England has recently published Guidelines for Surgical Endodontics that the reader may also find useful. see it online at bit.ly/RCSsurgicalendo


References

1. Friedman S Treatment outcome and prognosis of endodontic therapy. In: Ørstavik D, Pitt Ford TR eds. Essential Endodontology 2nd edn. Oxford: Blackwell Science; 2008. 441-447.

2. Rubinstein R. Magnification and illumination in apical surgery. Endod Topics 2005; 11: 56-77.

3. Witherspoon DE, Gutmann JL. Haemostasis in periradicular surgery. Int Endod J 1996; 29: 135-149.

4. Buckley JA et al. Efficacy of epinephrine concentration in local anaesthesia during periodontal surgery. J Periodontol 1984; 55: 653-657.

5. Velvart P. Papilla base incision: a new approach to recession-free healing of the interdental papilla after endodontic surgery. Int Endod J 2002; 35: 453-460.

6. Stropko JJ et al. Root-end management: resection, cavity preparation, and material placement. Endod Topics 2005; 11: 131-151.

7. Andelin WE et al. Microleakage of resected MTA. J Endod 2002; 28: 573-574.

8. Torabinejad M, Chivian N. Clinical applications of mineral trioxide aggregate. J Endod. 1999; 25: 197-203.

9. Koh ET et al. Cellular response to MTA. J Endod 1998; 24: 543-547.

10. Apaydin ES et al. Hard-tissue healing after application of fresh or set MTA as root-end filling material. J Endod 2004; 30: 21-24.

11. Tsesis I et al. Effect of guided tissue regeneration on the outcome of surgical endodontic treatment: a systematic review and meta-analysis. J Endod 2011; 37: 1039-1045.

12. Pecora G et al. The use of calcium sulphate in the surgical treatment of a ‘through and through’ periradicular lesion. Int Endod J. 2001; 34: 189-197.

13. Del Fabbro M et al. Surgical versus non-surgical endodontic re-treatment for periradicular lesions. Cochrane collaboration 2008.

14. Torabinejad M et al. Outcomes of nonsurgical retreatment and endodontic surgery: a systematic review. J Endod 2009; 35: 930-937.

15. Tsesis I et al. Outcome of surgical endodontic treatment performed by a modern technique: a meta-analysis of literature. J Endod 2009; 35: 1505-1511.


About the author

Carol Tait BDS Hons, MSc, MFDS RCS Ed, MRD RCS Eng, is a specialist endodontist at Edinburgh Dental Specialists and senior clinical teacher in endodontics at Dundee Dental School.

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