Management of The Exposed Non-Vital Pulp in Permanent Dentition (Open & Closed Apex)
- Dr. Adnan Alakhras
- 9 hours ago
- 22 min read
Compete root formation occurs approximately two to three years after the eruption of tooth in the oral cavity (Tarpomanov et al., 2018). In case of a traumatic injury or carious exposure leading to pulp-necrosis during this period, this can potentially pose challenges in the treatment. This happens due to incomplete root formation, lack of apical constriction, thin dentinal walls and low crown to root ratio (Mente et al., 2013). Consequently, treating immature non-vital teeth with conventional root canal treatment(RCT) can pose difficulty in irrigation of the canals and obtaining root obturation seal (Mente et al., 2013).
Therefore, the primary goal before inducing RCT would be to create a calcified barrier in a tooth with no apical constriction or inducing further apical formation of the incomplete root in non-vital teeth (Harlamb, 2016).Thus, restoring the function of the tooth in the oral cavity and completing the treatment with a root canal treatment (RCT) (Harlamb, 2016).
Fully understanding the biological processes and determining an accurate diagnosis of the tooth are integral parts in the success of the proposed treatment plan.
Diagnosis
An integration between history, clinical and radiographical assessment along with diagnositic tests allow us to draw a proper diagnosis (Bender, 2000). Subjective symptoms that include spontaneous and severe pain can indicate irreversible pulpal damage (Bender, 2000), however, throbbing pain or no pain with severe pain on percussion or pulpation can indicate a necrotic pulp (Levin et al., 2009). In addition, occurrence of swelling or a sinus tract can imply for pulpal necrosis along with periapical involvement (Bender, 2000).
Radiographic assessment in the immature tooth can be useful but rather rendered difficult as the tooth with an open apex already present with a radiolocuency surrounding the developing apex (Levin et al., 2009). Therefore, it maybe helpful to compare the radiograph with the contra-lateral tooth for any periapical changes (Ghoddusi et al., 2012).
Part of the radiographic assessment integrated with clinical assessment is critical to determine the prognosis and restorability of the tooth, this can be related to the relation between the bone level and intended restoration and the crown-to-root ratio (Ghoddusi et al., 2012). It is also important to check if there is any root fractures in the tooth in case of truama as this can influence the restorability of the tooth (Walton, 2017).
American Association of Endodontists (AAE) recommends one occlusal and two periapical radiographs from mesial and distal in order to rule out the possible presence of a root fracture (Walton, 2017).
In regards of Pulp Tests, it was shown that it is not reliable to utilize pulp tests in immature permanent teeth with open apex as the nervus plexus in the subodontoblastic layer didn’t fully develop, hence, can lead to erratic response (Karayilmaz & Kirzioğlu, 2011). Other factors such as the anxiety and fear of the child can also lead to false positives. (Koch, 2017).
In case of truamatized tooth initial assessment with pulp tests is not accurate. (Gopikrishna et al., 2007).Teeth with recent truama can give false-negative response to EPT due to nerve rupture or disruption(Gopikrishna et al., 2007). Therefore, it was recommended to re-assess the pulpal status 6 weeks after the incidence of trauma(AAE, 2013).
Management Of The Non-Vital Pulp In The Permanent Dentition:
To fully understand the objectives and uses of different treatment options, first we have to know the requirements for a successful endodontic treatment. These involve first, canal debridement and disinfection, secondly, obtaining a proper apical seal at the correct canal length with a root canal filling, and lastly, obtaining a coronal seal that would prevent microleakage (Tronstad, 2003).
In case of a a tooth with a closed apex, these requirements can be achieved readily with conventional root canal treatment since we have completed root growth and an apical constriction. (Tronstad, 2003). However, to achieve this in a tooth with an open apex we need to undergo other procedures such as apexification, apical barrier placement or revascularization before we continue with the final treatment which is RCT.
In addition, extraction of the tooth involved is still an option but decision making in regards of this treatment differs for anterior and posterior teeth.
In the anterior teeth with non-vital pulp and open apex it is advocated that the tooth is retained and treated with apexification and the last option is to be extraction (Masaki et al., 2015). This lies behind aesthetics and the benefit of preserving the alveolar bone structure for future prosthetic treatment in the adult life (Masaki et al., 2015).
In case of having an anterior tooth which is non-restorable ‘Decoronation’ is also considered a viable treatment option (Malmgren, 2000).
In the posterior teeth extraction of the 1st permanent molar with non-vital pulp and open apex can be considered as a reliable and a cost-effective option.
This however depends on multiple factors such as the prognosis of the tooth, the age of the patient, the dental arch crowding and occlusal relationship (Profitt, 2013). The indications are patient at dental age of 8-9 years with a confirmed presence of 2nd premolar and 2nd permanent molar with the bifurcation area calcifying and class 1 occlusion (Profitt, 2013). If Lower 1st molar extraction is required, removal of upper 6 to avoid its overeruption is done and it’s called compensating extraction (Cobourne et al., 2014).On the other hand, if the upper 1st molar is to be extracted there is no need to do compensation (Cobourne et al., 2014).
It is important to note that the decision for this treatment must be confirmed after the consultation of the orthodontist.
Below we will discuss each treatment option excluding extraction when treating non-vital teeth with open apexes in order to draw a conclusion towards the most favorable treatment that can be performed in the pediatric dentistry practice.
Apexification
Apexification is a procedure that induce the formation of a calcified barrier at the root end of necrotic teeth with open apex (Dominguez et al., 2005). Utilizing this barrier can allow the proper placement of root canal filling while reducing the potential for extrusion in the periapical tissue (Dominguez et al., 2005). The rationale behind this treatment is that due to the increased vascularity and cellularity it is believed that root formation may still proceed after an apical infection subsides (Rafter, 2005).
Indications of apexification are restorable immature tooth with necrotic pulp, lack of clinical or radiographical signs of root fracture, presence of at least one to one root to crown ratio or more radiographically and lack of any significant systemic disease(El Meligy et al, 2006).
Calcium Hydroxide Apexification
Calcium hydroxide(CaOH) in apexification procedure was introduced in the 1960’s by Frank (Morse et al., 1990). Calcium hydroxide was the gold standard material in apexification because of its bacteriostatic properties, High Ph or alkalinity and release of hydroxide ions which acts as an antioxidant (Kim, 2014).
Mechanism of action of CaOH is controversial, the most accepted theory suggest that it reacts with the periapical tissue and produces a multilayered necrosis thereafter causing mineralization of the tissue (Rafter, 2005). Calcium ions were believed to be obtained from the bloodstream of the rich vascular supply periapically rather than the material itself (Rafter, 2005).
Clinical Procedure
Local anesthesia.
Good isolation of the tooth (using rubberdam is Ideal).
Access cavity and canal debridment of necrotic pulp tissue.
Determine the working length using an apex locator and confirm with a periapical radiograph, ideally it should be 1-2 mm shorter than the radiographic apex.
Flushing the canal using a proper irrigation system.
Only minor filling using hand files.
Irrigate the canal with saline and dry the canal with paper points
Mix CaOH powder with saline and this mixture is then positioned short of apex using plugger, using magnification can be helpful.
Access cavity is then filled with an adequate temporary filling (glass ionomer cement).
Radiograph is taken to ensure that the whole canal is filled with calcium hydroxide.
Patient is then recalled after 3 months for follow-up.
Lastly until calcific barrier detected the tooth is treated with RCT.
(Damle et al., 2012)
Canal irrigation
The ideal canal irrigant should be able to have a broad-spectrum antibacterial affect, ability to dissolve necrotic pulp tissue, dissolve smear layer or inorganic debris and systemically nontoxic in contact to vital tissue (Jaju, 2011).
Chlorhexidine is usually used in 2% concentration; some authors advocate its use over sodium hypochlorite due to its lack of cytotoxicity and excellent antimicrobial activity(Jaju, 2011) In addition, it is thought to have a synergistic effect with calcium hydroxide (Basrani et al., 2004). However, completely lacks tissue dissolving capability (Basrani et al., 2004).
Sodium Hypochlorite in endodontic treatment is reported from concentrations of (0.5-5.25%), it is the most commonly used irrigant in the literature(Jaju, 2011).
Advantages of sodium hypochlorite are cost-effectiveness, antimicrobial effects and ability dissolve organic and inorganic tissue (Mohammadi, 2008). However, the main disadvantage is the cytotoxicity if extruded to the periapical tissue, where it can lead to Sodium hypochlorite accident which is common in teeth with open apex (Guivarc'h et al., 2017).
Chances of this accident can be reduced by using irrigation systems such as EndoVac, EndoVac is considered to be a negative pressure system(Siu & Baumgartner, 2010), this system uses suction to pull the irrigant down through the canal and then recycled up into the high-volume suction unit (Siu & Baumgartner, 2010). Instead of the conventional needle which applies a positive pressure and can cause extrusion of the irrigant (Mohammadi, 2008).
Replacement of CaOH
The proposed time for physiological barrier formation is 6 to 24 months (Feloppe et al., 2005). This can be evaluated by a radiograph which shows the size of the involved periapical lesion and the formation of a calcified barrier or clinically using a file gently or with gutta percha to check the diameter of the opex (Feloppe et al., 2005).
There is a controversy regarding the frequency of times that calcuim hydroxide must be replaced in the root canal. On one hand, it is suggested that after 3 months the radiographs are taken to assess the calcific tissue barrier and to evaluate if there was wash out of calcuim hydroxide, if no wash out was indicated or no signs and symptoms of reinfection the dressing is left intact (Rafter, 2005).
However on the other hand, some authors suggest the regular replacement every 3 months to facilitate a consistent clinical evaluation of the barrier formation and to avoid any chances for canal re-infection (Rafter, 2005).
Root Canal Filling
Generally, in immature teeth the apical orifice diameter is still larger than the coronal orifice (Tuna et al., 2011). In addition, the teeth present with weak and thin dentin structure. Therefore, excess lateral force must be avoided during placement of the root canal filling and the use of Lateral condensation technique is not advocated (Tuna et al., 2011). Rather softened Gutta percha filling technique is recommended for these teeth (Trope, 2010).
Coronal Filling
Since the tooth structure in immature non-vital teeth is inadequate the treatment with crown or post and core is not recommended. Therefore, the use of resin filling material such as composite is the material of choice (Katebzadeh et al., 1998). It can provide an adequate seal and good aesthetics (Chesterman et al., 2017). Additionally, it was also proposed to extend the resin material 3mm into the canal to strengthen the cervical portion of the root and reduce the chance of cervical root fracture (Chesterman et al., 2017).
Bottom-line
Although this technique has been studied extensively and was shown to be successful with rates up to 74-100% (Dominguez et al., 2005). However, it has some disadvantages that limits its use today. Main disadvantage is the length of the procedure where it takes 6-24 months to form the apical barrier(Guerrero et al., 2018). In addition, the patient needs to report every 3 months to evaluate, hence high cost of treatment (Guerrero et al., 2018). The need of compliance for at least 6 visits will also lead to some patients to fail to report back. Moreover, there is reports that there is high incidence of cervical root fracture due to weakened dentin by CaOH (Guerrero et al., 2018).
when teeth were examined histologically the CaOH induced barrier was revealed to be porous showing a “Swiss cheese” consistency (Ham et al., 2005).
Therefore, to overcome some of these limitations, artificial barrier technique was developed.
Artificial Barrier Technique
This technique is described as the compaction of biocompatible material at the apex of the tooth to form a physical barrier (Rudagi, 2012). Materials used in artificial barrier include MTA (mineral trioxide aggregate), calcium enriched cement, Neo-MTA and Biodentine (Rudagi, 2012). Usually, the material of choice in this procedure is MTA due to its high success rate and sufficient evidence in the literature for its use (Huang, 2009).
When compared to CaOH apexification this procedure has shown a higher success rate (Guerrero et al., 2018), owing to the multiple advantages of MTA apexification that include:
1. Less chance of cervical root fracture.
2. Need for one or two visits only.
3. MTA provides a more rigid seal than CaOH.
4. MTA can set in case of blood contamination.
5. MTA has a high pH similar to CaOH and is biocompatible.
(Rudagi, 2012).
On the other hand, disadvantages of MTA include long setting time, tooth discoloration and poor handling properties with challenging mixing technique (Mooney & North, 2008).
The use of Neo-MTA and Biodentine vs. white MTA have shown to reduce tooth discoloration this is due to lack of bismuth oxide which is responsible for discoloration (Mooney & North, 2008). Other authors suggest the use of Biodentine in single visit apexification which is reported to provide a shorter setting time 10.1 minutes (Kaur et al., 2017). However, the literature suggest a high predictable results with single visit MTA apexification.This is because moisture provided by the tissue fluids of the periapical area in open apex teeth facilitates sufficient setting of the MTA. (Dominguez et al., 2005)
Clinical Procedure
Determine the working length using an apex locator and confirm with a periapical radiograph, ideally it should be 1-2 mm shorter than the radiographic apex.
Irrigation of the canals with sodium hypochlorite and 17% EDTA is advocated.
Calcium sulfate (or similar material) is pushed through the apex to provide a resorbable extra radicular barrier against which the MTA is packed.
MTA is placed into the apical 3 to 4 mm through the use of MTA carrier or with MAP system.
Cotton pallet wet with normal saline is then placed in the canal to allow the setting of MTA which takes 2 hours for initial setting and upto 6 hours for final setting.
A radiograph is taken to evaluate the MTA plug which shouldn’t exceed 5 mm.
(Damle et al., 2012)
Then the procedure can be completed in the same visit or done in two-visit, the rationale behind the two-visit MTA apexification is to allow the MTA to reach a final setting before root filling, in addition to allowing more time for disinfection of the canal and in case of extrusion of MTA, it will allow the chance for intervention (Matt et al., 2004).
In case of two-visit the canal is then filled with non-setting CaOH and sealed with a temporary restoration.
At the second visit, the calcuim hydroxide is flushed with Soduim hypochlorite and the canal is filled with Gutta percha and a proper final restoration.
(Damle et al., 2012)
Bottom-line
There is lack of evidence in the literature to support the use of Biodentine and neo-MTA over conventional MTA. The literature confirm that MTA provide adequate apical plug formation that allows immediate obturation and prevention of the extrusion of filling materials (Rafter, 2005)
Time frame for the barrier formation with MTA compared to CaOH is significantly lower (Sharma, 2016) and teeth restored in single visit MTA apexification reported lower rates of cervical root fracture (Simon et al, 2007). Therefore, to date MTA should be the ideal material of choice in artificial barrier technique and MTA Apexification is more favourable than CaOH apexification.
Regenerative Endodontics
Regenerative endodontics is a relatively new treatment approach for immature non-vital teeth, this method is designed to stimulate the continued apical development and root maturation (Mao et al., 2012). Proposed techniques and terminologies in this area is also known as ‘Revascularization’, which simply means re-establishing a vascular supply in the necrotic pulp canal space (Iwaya et al., 2001). On the other hand, the term ‘Regeneration’ is to replenish injured tissues, involving dentin and root structures, in addition to cells of the pulp-dentin complex (Huang, 2009). Lastly the term ‘Revitalization’, which include the regeneration of damaged tissues and re-establishment of the vitality of the necrotic tooth (Huang, 2009).
The main advantages of this technique in comparison to apexification include the ability to increase the thickness of the dentin walls, potential increase in length of the root by continued root formation which will improve the crown-root ratio (Mao et al., 2012) and finally the formation of the natural apical constriction which will facilitate the final treatment with RCT (Wigler et al., 2013). By providing these advantages over apexification, the chances of cervical root fracture can be reduced (Huang, 2009).
The reasoning behind regenerative endodontics is that new cell formation occur when provided with a sterile matrix tissue, which in turn re-establish the pulp vitality (Wigler et al., 2013). In order to do this, we have to have three basic components: the scaffold, the growth factors and stem cells (Wigler et al., 2013).
The scaffold is created by the blood clot of the induced bleeding in the canal space which provides the matrix (Deepak et al., 2011). In the blood clot (scaffold) the growth factors(GF) can induce the differentiation of undifferentiated cell types(Deepak et al., 2011). The GFs in the clot include platelet derived GF, tissue GF and vascular endothelial GF (Thomson & Kahler, 2010). The continuation of root development is contributed by the stem cells and progenitor cells(DPSC) from the pulp or/and periodontal tissue(SCAP) (Thomson & Kahler, 2010).
Indications
In the literature some of the indications that were proposed for this treatment are patients with necrotic tooth and open apex as a result of trauma or caries, usually in the age range of 8-15 years old (Namour et al, 2014). In addition to patients that are not allergic to antibiotics or medicaments used in regenerative endodontics (Mao et al., 2012). The apex diameter is considered controversial, it was believed before that the apex should be more than 1.1 mm in diameter (Andreasen et al., 1990), however, more recently the studies suggest that the apex diameter doesn’t affect the success of revascularization (Laureys et al., 2013).
Clinical Procedure
The revascularization procedure is usually done in two stages:
The first stage :
Local anesthesia and rubber dam isolation.
Establish access cavity.
Determine the working length 1 mm short of the apex radiographically.
The canal is then irrigated with 20ml of 1.5% NaOCl (Primary disinfection).
The canal is flushed with saline and then dried with paper points gently.
No instrumentation is done in the canal to avoid the risk of damaging the stem cells in the dentinal walls and apical region.
Application of intracanal medicament (Secondary disinfection). Options for intracanal medicaments include calcuim hydroxide paste or triple antibiotic paste (TAP).
A glass-ionomer temporary restoration material is placed to prevent coronal leakage.
Follow up appointment after 1-4 weeks.
(Moodley et al., 2017)
If the signs of infection persist, the first step is repeated, if they continue to present with re-infection after multiple repetition of the procedure, apexification should be considered (Mao et al., 2012).
Primary disinfection
It is proposed that using NaOCl at lower concentration and higher volume can provide adequate antiseptic affect, reduce the chance of toxicity to the periapical tissue, and preserve the remaining vital tissues and stem cells (Namour et al, 2014). It is also recommended to use safe-ended needle or Negative pressure irrigation system to prevent extrusion and possible accident (Wigler et al., 2013). Another material that is recommended for irrgation in revascularization procedure is 17% Ethylenediaminetetraacetic acid(EDTA) (Namour et al., 2014). EDTA is a chelating agent which can remove the smear layer (Mohammadi et al., 2013), This effect can also improve the delivery of GFs from the surface of dentin, Hence, will enhance cell differentiation and proliferation (Namour et al., 2014).
Secondary disinfection
Triple antibiotic paste(TAP) comprises of Metronidazole, Minocycline and Ciprofloxacin, these antibiotics are mixed in ratios of 1:1:1 at a dose of 1mg/ml (Nagata et al., 2014). This combination is usually mixed with saline into a paste form and then injected in the canal up to the CEJ (Nagata et al., 2014). The use of TAP as an intracanal medication has shown to be affective against the bacteria in the canals and was reported to have low cytotoxicity to the vital tissue and stem cells (Windley et al., 2005). The rationale for using a combination of three antibiotics is to reduce the formation of resistant bacteria and include the broad-spectrum effect of the antibiotics which is affective against aerobic and anaerobic bacteria in the canal (Taneja et al., 2012). However, there was some disadvantages reported using TAP such as difficulty upon removal in the next visit and discoloration of the crown associated with Minocycline (Windley et al., 2005).
Therefore, to manage the undesirable discoloration it is suggested that the TAP to be placed below the cementoenamel junction (Arslan et al., 2014). Other options can be modified (mTAP) where minocycline is replaced by cefaclor or double antibiotic paste (DAP) which excludes the use of minocycline responsible for the tooth discoloration (Taneja et al., 2012).
Calcium hydroxide is considered the first choice of root canal dressing materials in endodontics due to its high antimicrobial activity and low toxicity to vital tissues (Kim, 2014). It was recommended to be used when allergy to antibiotics in TAP is reported (Kim, 2014). Although, drawback of using CaOH in revascularization is that it can induce the formation of calcific tissue in the canal space which can prevent pulp tissue regeneration in the space (Nagata et al., 2014). Therefore, it was recommended to be used in the coronal third of the canal over the TAP to maximize its benefits and reduce its risks (Nagata et al., 2014).
The second stage:
Local anesthesia with no vasoconstrictor, vasoconstrictor is not used in order to not disrupt the bleeding in the canal. (Moodley et al., 2017)
Rubberdam placement, disinfection of the tooth with 10% iodine and removal of temporary restoration.
20ml of 17% EDTA is gently flushed in the canal and then it is dried with paper points.
A K file is used to go 2 mm over the apical foramen to induce bleeding in the canal, the favourable outcome would be filling the entire canal with blood up to the CEJ.
Using a moist cotton pallet, the bleeding is then stopped coronally to allow a 3-4 mm space.
Placement of 3-4 mm MTA carefully over the blood clot.
Followed by final filling such as RMGIC (Vitremer, 3M ESPE) or composite resin.
The follow up ranges from 6 months to 5 years.
(Moodley et al., 2017)
Discussion of the clinical procedure
In step number 4 of the second stage the rationale behind inducing bleeding is to introduce stem cells of the mesenchyme from periapical tissue to the pulp space and by creating a scaffold by the blood clot which can allow new cells to grow (Deepak et al., 2011). This scaffold also contains growth factors & nutrients that are necessary for the differentiation and proliferation of stem cells to fibroblasts, odontoblasts, osteoblasts and cementoblasts (Deepak et al., 2011).
In the literature there was different types of scaffolds used in regenerative endodontics which include biological/natural scaffolds such as platelet rich plasma and collagen or artificial scaffolds such as polymers, hydorogel and bioceramics (Gathani & Raghavendra, 2016). There is limited evidence in the literature regarding the success of different types of scaffolds. However, the ideal properties of a scaffold in the regenerative endodontic treatment are, biodegradability and biocompatibility, high porosity and adequate mechanical strength which can allow seeding and diffusion of cells and lastly the scaffold should allow effective transport of nutrients. (Murray et al., 2007; Gathani & Raghavendra, 2016)
In step number 6 of the second stage the MTA is used due to its good sealing property, ability to set in moisture and its biocompatibility (Kaur et al., 2017). However, it has a long setting time, have negative effect on the stem cells and leads to tooth discoloration due to bismuth oxide (Marconyak et al., 2016). Therefore, a suitable alternative to MTA would be NeoMTA and Biodentine which contain titanium oxide rather than bismuth, leading to a reduced crown discoloration and toxicity to stem cells (Kaur et al., 2017). Nevertheless, more studies must be done to determine the success and support their use of in revascularization (Mente et al., 2013).
Success criteria of regenerative endodontics
The criteria for the success of revascularization is evaluated primarily by eliminating the signs and symptoms of non-vital pulp with evidence of periapical tissue repair (AAE, 2014). Secondly by the formation and increase in the dentin root thickness and length of the root. Lastly, vitality testing that determine a positive response indicating a vital pulp tissue (AAE, 2014).
Although some case-reports in the literature suggested that teeth after revascularization produced positive vitality tests and suggested that the tooth could possibly be revitalized.The evidence to the type of tissue present in the canal is currently controversial.
Wang X et al (2010) investigated the type of tissue generated in the pulp space of immature dog teeth with apical periodontitis after revascularization. Histological exam of the generated tissue in the canal space of immature dog teeth with necrotic pulp after regenerative endodontics were shown to be cementum and bone-like tissue that is called intracanal cementum(IC) and intra canal bone(IB) which causes the increased thickness in the root walls(Wang X et al., 2010). In addition, the soft tissue in the pulp space was PDL-like tissue rather than an actual pulp parenchymal. This tissue doesn’t function like a vital pulp but rather a granulation tissue growth. (Wang X et al., 2010).
Therefore, even after completion of the revascularization in my opinion RCT should be implemented for the success of the treatment.
Conclusion
Revascularization procedure is challenging, lengthy and has a high cost of treatment.
Although there is evidence for short term success, but the evidence is mostly case-reports and case-series thus, it is insufficient to support its use.
More controlled clinical trials are needed to generalize the results in the clinical practice. Therefore, for the treatment of immature non-vital teeth MTA apexification is the ideal treatment choice to date.
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