Frequently asked questions 3

How can you give 2 diagnoses for a single rooted tooth?

The diagnoses are both pulpal and periapical. Both diagnoses relate to the tooth and are merely a reflection of your interpretation of generally what is going on inside the pulp and outside in the apical tissues, based on imaging and clinical tests.

Can a single rooted tooth have a diagnosis of symptomatic irreversible pulpitis + symptomatic chronic apical Periodontitis?

The use of ‘chronic’ in apical diagnosis was removed some time ago. There is debate whether it should come back into use. So If I interpret this question to be- Can a symptomatic irreversible pulpitis also have symptomatic apical periodontitis. The answer is yes of course!

If the pulp is inflamed due to microorganisms their toxins can still leave via the apical foramina and cause inflammation, that would create a symptomatic apical periodontitis. Usually in these cases a lesion is difficult to see radiographically or very small. But of course anything is possible.

How do I diagnose phoenix abscess?

The term phoenix abscess is merely a name for an acute exacerbation of what was a chronic or low-grade periapical inflammation. In other words, the asymptomatic periapical inflammation (visible before treatment radiographically) has now become acute, and an abscess has formed. This causes pain and swelling, as well as pus creation (because without pus it’s not an abscess) and the usual signs of abscess.

Hello Dr.Ikram, what do you generally use to irrigate with when a pt has an open apex ie 47 on 13y/o with gross decay

Measure the working length correctly using an apex locator and back this up with a periapical radiograph, measure the syringe to 2mm short of the working length and irrigate the canals with sodium hypochlorite carefully. You should also use an activator to bring the irrigants apically. Bear in mid teeth with open apices usually have healthy stem cells that close the apex after removal of infection so you often do not need to go over the top with irrigating the apical part of the root canal in these open apex cases. Remove the infection in the canal and close their path of entry and the body will heal nicely.

When will you recommend electively extracting a heavily decayed 1st molar in a child to allow 7s to erupt into the space? instead of restoring the 6s?

Great question! From my ortho knowledge we first should establish whether the 3rd molars will be present.  Then if they are extraction of the first molar should occur when the bifurcation of the second molar forms and then the second molar generally erupts into the space left by the first molar!

May i know why premedication helps the IANB successful?

The use of non steroidal anti-inflammatory medications reduce the prostaglandins that are responsible for creating hypersensitivity in the pulp. This is how they improve success of inferior alveolar nerve blocks.

How do you diagnose hot pulp before starting the treatment, I had few cases where IANB is not effective and that is when I know I have hot pulp? what are the signs of hot pulp?

The patient will always tell you that they have severe temperature sensitivity and that they have changed their daily routine to deal with this sensitivity. Drinking iced water, warming tap water to brush teeth, pain when breathing cold morning air etc. Then you can be reasonably sure the pulp is inflamed. As always you need to do your tests to confirm an endodontic cause of this.

Any tips for anaesthetising hot pulp in upper molar?

These are usually easier. Preoperative ibuprofen, buccal and then palatal infiltration, intraligamentary anaesthetic and if needed inhalation sedation is always helpful.

Can pulpotomy be used on mature teeth?

Yes, but it has to offer an advantage over full root canal treatment. The healing potential of a root with a closed apex is not as good as one with an open apex. The success of root canal treatment to the apex is very high. I have used it in patients who are difficult to treat in the chair and only for teeth not requiring a crown after treatment.

I’m confused with the oxygen bubble technique you talked about. Could you elaborate over it more?

Sodium hypochlorite creates oxygen when it interacts with pulp tissue, and this can be seen as bubbles. These should guide you to the canal or at least reveal that it is present. To use this technique, you require good magnification and a light. Most likely an operating microscope.

What are your tips to manage heavily bleeding pulp after access?

Use of local anaesthetic with high adrenaline and just start preparing the canals! If you remove the tissue the bleeding will stop.

Sounds tricky to find mb2. Can we use ultrasonic tip?

The Start X2 tip is a good one for ultrasonic location of MB2 the disadvantage I find with ultrasonics is they scratch the pulpal floor, making the floor anatomy trickier to read, but they provide less damage and more visual access of calcified canals, so I do use these when the going gets tough!

How do you negotiate and instrument canals where they’re calcified in the apical 1/3?

I like using C pilot and the C+ files for these.

Can you go back over best bur for troughing to find and open canal orifices initially?

The best burs I’ve found for location of MB2 are the Endo Tracer burs and the LN bur which is a short goose neck 0.5 mm round bur

When placing CaOH, should it be on dry canals or could be mixed with CHX or NaOCl?

I will withdraw the irrigant with a syringe and then place the calcium hydroxide. I don’t dry the canals prior to placement of the medicament. Just remove the irrigant by pulling back on the syringe.

Can I ask for tip in obturating the mb2? Generally, I find it trickier compared with the mb1 due to it sometimes joining with the mb1 canal or generally being tighter.

I place one cone in the MB1 and then another in the MB2. Before filling you should establish whether these canals join. Using the GP point and file technique. Then you know whether the cone in the MB2 needs to go to the reference point or it will hit the MB1 cone. Fill Mb1 and 2 both at the same time.

What is the name of those tips for CaOH placement?

Inject the calcium hydroxide using Navi tips and then activate it using the Endoactivator or Eddy sonic activation unit, to move the medicament apically.

CaOH is toxic to cells if in contact for a long time. - how long is considered long?

Calcium hydroxide needs significant time to dissociate into ions and exert the effects of its high PH. This makes it ideal for endo because if a small amount us pushed inadvertently outside the canal, then the body removes it before its able to exert a significant effect. However, inside the canal it can stay in place and exert its effect. The time it takes to have a significant effect is approximately 1 week. So, it takes a few days of it being in contact with cells to do this.

"Hi Dr. Omar! You absolutely Rock!!!

Thanks for your kind comment, but you are the real star for giving up your time to watch and learn for the betterment of your knowledge and for your patients! Teachers can only show their students the door, but the student opens it.

What is your file sequence with wave one gold after finding the orifice? Once you locate the orifice…what’s your sequence of hand files and wave one gold?

The sequence for wave one gold would be glide path preparation till size 10 K file and then either the Wave one gold glider or a size 15K depending on difficulty. Then use of the primary 25 07 file. If the first 0-5mm of the blades are filled with dentine on the last pass of the file, then no further work is required. However small is available for cases where primary does go to the apex and medium and large sizes for wide canals where the primary doesn’t debride the canal apically.

Can necrotic teeth present sensitivity to hot?

Good question. Our diagnoses are just snap shots of what we find clinically. Often the pulp is a mix of necrotic inflamed and even sometimes abscessed areas and we have multirooted teeth. So yes a pulp can have areas of necrosis and inflamed areas or canals which will make it sensitive to hot. Almost anything is possible when we are treating the human body!

How long does the irreversible pulpitis to pulpal necrosis transition last?

Another good question! There is no answer to this though. Some patients have pulpitis for many months and others just a few days before necrosis. It probably has something to do with a number of factors such as viability and age of the pulp (immature pulps survive better), size of the defect the bacteria are gaining access through and the type of bacteria involved.

Does term symptomatic apply only when the patient has pain? Do you think it should be applied to painless necrotic tooth with a radiographically visible radiolucency?

The term symptomatic means the patient has symptoms of the disorder. Symptomatic apical periodontitis means the patient feels discomfort related to apical periodontitis. So this is generally tenderness when touching the sulcus or percussing the tooth. A painless tooth with a necrotic pulp - which has a radiographically visible radiolucency would be described as- Asymptomatic apical periodontitis associated with a necrotic pulp.

Is the disinfection of the canal one of the most critical steps in RCT? at dental school I was taught it was optimal obturation but what I have read recently it says is thoroughly cleaning all the canals with hypochlorite is more crucial than to reach as close to the apex as possible. thank you.

Removal of the bacteria and their food/energy source (pulp tissue), then closing this ‘clean’ environment are the most important steps. Filling of the canals is a way to show the length of preparation and create a rudimentary apical and coronal seal, but removal of bacteria (and the pulp tissue) is what heals apical periodontitis.

I have a question about if the Ultracal XS pump comes out of the apical foramen of the tooth during placement (in teeth that are not yet apical), will it cause apical closure with deformed root? Does it create hypercementosis root appearance?

Are you worried about extrusion of CaOH medicament following placement at all?

I place the stopper 1-2mm short of the apex and don’t let the tip bind. Extrusion of calcium hydroxide has not been an issue using this technique.

Does NaOCl react with Gp solvents?

As I mentioned sodium hypochlorite interacts with everything because the chlorine ion is in a positive state and its stable state is Cl-. So yes if you add anything to sodium hypochlorite it dissociates and the chlorine is used up interacting with what was added to it. What this means is that you should not mix sodium hypochlorite with any other irrigants when you want it to work on biofilms and pulp tissue. Because you just reduce the available chlorine and therefore its effectiveness by doing so.

What % NaOCl do you use?

Currently I’m using 4% sodium hypochlorite and Chlorcid surf 3% when I treat cases in a single visit.

How to remove all the calcium hydroxide from the canal during obturation?

I use files and irrigants to do this, the citric acid 20% is recommended for removing Ultracal.

When you’re irrigating the canals, how do you use EDTA and NaOCl? Do you need to use one before the other? You mentioned that the NaOCl degrades the EDTA. Thanks ????

It’s the sodium hypochlorite which interacts with everything and that includes EDTA. So EDTA is unaffected by sodium hypochlorite and still functions well. BUT the available chlorine is degraded when anything is added to sodium hypochlorite. Therefore, if the sodium hypochlorite is interacting with the pulp tissue and bacterial biofilm then this is what we want. But we don’t want anything in the canal that wil take away from thus interaction. So, I use sodium hypo the entire time and just at the end after all preparation use EDTA to remove the inorganic smear layer. Then sodium hypochlorite again just before finishing. Because we want to get sodium hypochlorite into areas covered by the inorganic smear layer once it is removed. The smear layer plugs lateral canals and covers microbes on the canal wall and offers them further protection. SO, after EDTA it is advisable to use sodium hypochlorite. After that you could go back with EDTA to finish off if you wish that would help remove sodium hypochlorite and open the tubules prior to filling the canal and restoring the access.

Hi. Can you please provide your thoughts on bioceramic as a sealants? if yes, do you recommend any? are there any risk if post are planned in future, like with the MTA?

I have used bioceramic sealers, mainly in situations where there is a long canal and a blunderbuss (cola bottle shaped) apex. So in situations where the canal is narrow and long but the apex is very wide from resorption. I wouldn’t recommend them routinely we have epoxy resin sealers which I use routinely. But in theory bioceramics should be good for resorption cases. The jury is still out on their effectiveness and there needs to be some moisture BUT not too much fro them to actually set. This is a major problem. How can we judge moisture? They wash out a lot before setting. As you mentioned there may be difficulties with post placement, but you would need to use a lot of sealer for this to occur. I don’t recommend using large amounts of bioceramic sealer and a single cone. Use enough to fill the defect you need to fill and use GP and the rest.

I am GDP using 1% NaOCL, can I move to using 4%? I am little concerned, any recommendation? Please

Increasing the percentage of sodium hypochlorite will improve tissue dissolving speed and biofilm dissolving speed. If you treat patients in multiple visits I see no advantage in increasing your percentage of sodium hypochlorite , unless you treat single visit cases or lots of retreatment cases with established biofilms. These are the kind of cases I treat every day and that’s why I use higher strength sodium hypochlorite. The same principles apply irrigate safely and if you are concerned about perforations don’t irrigate using sodium hypochlorite until you are sure that you are inside the canals.

For acute apical abscess do we need to irrgiate with saline only during emergency appointment?

You should use sodium hypochlorite. This dissolves flushes the canal, removes pus, biofilms and tissue and kills bacteria. Saline only flushes the debris out.

Hi Dr Omar, thank you for the great talk. Do you have any advice for root canal treatment on teeth covered by orthodontic wire? Thank you

If you cant isolate the tooth you will need to have the orthodontic arch wire removed.

Do warm hypochlorite has any advantage?

This improves tissue dissolving capacity, but mist be down inside the pulp chamber. Heating outside the mouth wont retain the temperature after the small volume enters the chamber.

Does Microscope is mandatory to achieve a great endo treatment? Can I use loup only? Since it's not available in my clinic and it's kinda difficult to refer my patients to Endodontist due to cost issue for them. Thank you.

Really a microscope changes your life and quality of treatment you can provide. It’s a bit like upgrading your car. At the start it takes a little while to get used to but once you get used to it, the reduction of eye strain, neck strain, back strain and STRESS is amazing. A good scope makes endo fun and fascinating. It is almost impossible to deliver good quality endodontics for teeth with those ‘extra’ canals. The second mesio-buccal canal in upper molars, the lingual canal in lower incisors, the second distal in lower molar teeth and those premolars with 3 canals, just to name a few, without a scope!

If you don’t have a scope, then be prepared to refer these cases. If you love endo, you should get a scope and there is huge variation in quality amongst these as well! If you are happy to refer these tricky cases, then loupes will be fine.

Thanks for the information.  My question is, sometimes I found that the canal seal was good in Xray and I try to maintain all aseptic preparation but after that patient feels pain ? Sometimes severe pain was observed, what will be the cause or what I missed ?

There are so many possibilities here- was the diagnosis correct? Is the tooth cracked into the periodontal tissues, is the restoration high, is there food impaction……the list of possibilities is immense. If you get a case where you think you’ve done well and there are still problems this means you should refer the patient for assessment to a colleague who can assist.

In which cases can you do single visit tx? Is that if pt has necrotic pulp?

There are many reasons why I would treat a patient in a single visit. Generally speaking, if I can do the treatment in a time that allows enough time for preparation and copious irrigation and there are little to symptoms, I will try and complete all the treatment the in one very long session. To do this you need the right tooth in the right patient. Not one or the other but both !

How often and what detrimental affects will occur if the Hypo percolated through apex ? Always my fear

This is called a hypochlorite accident and is a serious side effect of root canal treatment. It would commonly occur after a perforation rather than overzealous irrigation. Most dentists are cautious whilst irrigating. But if there is a perforation and they are unaware this can be a problem.

Can you recommend irrigant activator?

I am currently using the Eddy sonic activator or the EndoActivator. Both utilise polymer tips and they cannot damage the canal wall. They are very safe to use on patients and I’ve never had any complications using either of these. The EndoActivator is also very transportable as it runs off batteries that cant be bought in most stores. Its handy for my general anaesthetic surgery cases, due to its transportability. The Eddy is a higher frequency version and requires a separate air scaler, but I love it for those wide canals, where the file doesn’t touch the walls very much.

Do you activate NaOCl for 1 minute?

Yes, I recommend activation of sodium hypochlorite, it creates microstreaming and this aids in tissue and bacterial removal. I activate at least 1minute per canal.

Activate liquid EDTA (1 min)

Activation of EDTA has not been shown to be required but it cant hurt to try and get it into latreral canals and isthmuses.

When you say to heat the sodium hypochlorite, do you mean with a heat and touch system, ours is set at 200 degrees, is this too hot?

The general rule is a burst of less than 3 seconds using these units is ok. If the setting is 200 degrees this is ok for a short burst, in the same way that its ok when you use it to fill a canal.

Hi Dr Ikram. Thanks for all the excellent tips. I would like to ask; how long would you recommend heating sodium hypochlorite inside the canal using the downpack tip?

Just short bursts of heat with the tip less than 3 seconds at a time. I generally just do 1 second bursts to warm it.

What can be the cause of postoperative pain and swelling after finishing the treatment?

There is good evidence for use of ibuprofen 600mg and 500mg paracetamol taken together for a few days (less than 5 days). If pain goes longer than 5 days, patients need to know they can call you. Remember patients who have long standing pain following root treatment (longer than 5 days) often (assuming the diagnosis is correct) have either an acute exacerbation (phoenix abscess) or the restoration is high thus reducing the speed of post operative healing. Reducing the bite helps these patients heal faster.

Should we give calcium hydroxide at every time for multiple appointment RCT?

This is what I recommend, because it has good evidence for its use.

For calcified canals, other than crown down technique, are there any specific instruments that could help?

The more rigid files are better for opening calcified canals. The 19mm long XA orifice opener is a favourite of mine.

What is your irrigant of choice the draining sinus tract?

Sodium hypochlorite is always the first irrigant I use.

If the caries is from buccal extending to pulp (tooth 37), will you do caries removal, then restore the from buccal, then access from occlusal?

With a case like this if you can use the buccal cavity to access the canals this would be my preferred method. If not you should restore the buccal cavity and then access occlusally.

Any tips for anesthetizing tooth with a swelling where it is difficult for the local to reach the nerve?

These are tricky cases! Preoperative non-steroidal anti-inflammatories may help. You need to anaesthetise as much as possible before starting treatment. Use of a tungsten carbide bur also creates less vibration than a diamond bur and this may help get into the canals. Intrapulpal is another option once you reach the chamber.

Hi Dr Ikram, how do you access a calcified MB2?

There are several techniques, my favoured one is to use a stainless-steel bur like the LN bur and create debris to show the orifice and then open using an orifice opening file.

For the case of emergency case in vital pulp which need to do RCT, do you recommend to do the treatment in single session or multiple session?

I prefer to treat vital inflamed /elective cases in a single visit, but this depends on the complexity and patient being treated.

What is your protocol if there is a residual pulp tissue in the apical 1/3 that just doesn’t respond to intrapulpal anasthetic?

Preoperative non steroidal anti-inflammatories then good anaesthesia and if needed intrapulpal injection and then if needed inhalation sedation. Prepare the apex well and make sure that pulp tissue is removed

When performing root canal therapy on a tooth with an associated sinus tract, do you need to do anything differently than if there was no sinus tract?

I do this procedure in the same way whether there is a sinus tract. I just prefer to see this sinus tract before I complete the root treatment, at the next visit.

What about Odontopaste for medicament?

I have not used a steroid/antibiotic paste in many years.

Ideally how long to wait between different visits of RCT to ensure the intracanal medcation has been adequately effective?

The recommended time between visits for root canal treatment with calcium hydroxide is between 1 to 3 weeks. Riccucci et al 2011 showed best success less than 3weesks.  But remember the seal of the temporary restoration is everything. If you can seal the access, you can leave it a long time if you need to. If its tricky to obtain this seal temporarily I suggest 1 week which is the shortest time.

When would you consider pre-op ABs? 

For patients who require antibiotic cover. The regulations are different in every country.

At what point would you decide a cracked tooth is not savage or would you always try RCT and only exo if that fails?

If the tooth has a crack onto the pulpal floor or the crack involves the periodontal tissues then I usually recommend extraction.

What would you give to a patient who cant take ibuprofen due to gut issues or gastric ulcer?

Patients can take paracetamol if they cant take ibuprofen.

Do you dress weeping canal with caoh on the first visit? or do you leave canal empty and recall pt 1 or 2 days later again?

I dress the canals with calcium hydroxide in these cases and monitor.

Could u please elaborate more on citric acid usage for endodontic?

Citric acid is used to replace EDTA. It removes the smear layer and cleans the access cavity due to its acidity.

Is there a way to try and retrieve the broken instrument from the canal? and ways to avoid instrument separation please?

Use new files for patients, learn to use the preparation system by attending hands on courses and practicing using it on extracted teeth. Always prepare a good reproducible glide path to reduce cyclic and torsional forces on the files.

How to remove 2 years old GP from canals for re-endo?

There are many solvents that can be used , some dental companies sell these, chloroform is the most well known one.

Hi sorry can you repeat how times a day for ibuprofen 600/800mg?

The maximum dose of ibuprofen is 2400mg in 24 hours. So, if you do the maths, that is 600mg a maximum of 4 times in 24 hours, If you are giving 800mg that can only be taken 3 times in 24 hours.

Is it an issue if the sealer goes out to the periapical area?

Sealer is cytotoxic therefore we hope not to extrude this. It has the potential to damage cells, and this is most important around nerves, such as the inferior dental nerve and the mental nerves. If we extrude a small amount it rarely causes problems but it can be catastrophic in the wrong situation. We should always aim to use enough sealer to coat the walls and avoid extruding too much.

In which cases should antibiotics be prescribed?

I only consider antibiotyic prescription if the patient has systemic signs of infection OR if they are immunocompromised (diabetic etc). Local disease around the tooth should be treated locally- with incison drainage and opening of the canals. Systemic disease should be treated BOTH locally and systemically.

Thank you for your presentation! Would you advise that AB be prescribed for phoenix abscesses?

Not if you can establish drainage successfully. There is generally no reason to prescribe systemic antibiotics unless the patient is immunocompromised or shows systemic signs of infection.

Can you use EDTA instead of citric acid for cleaning pulp chamber? Also what are your thoughts on using alcohol to clean the access after obturation? Thank you :)

did you say you use citric acid instead of EDTA?

Citric acid can be used as an alternative to EDTA

What are your thoughts of buffering LA to help anesthetise a hot pulp?

This has been shown to be a helpful adjunct in studies!

Is EDTA effective in negotiating calcified canals?

The irrigant is helpful but I don’t use viscous chelation gels at all.

How do we delineate between acute apical periodontitis vs Acute apical abscess?

‘Acute’ and ‘chronic’ were removed from the diagnostic terminology some time ago. So these two terms mean essentially mean similar things. Acute apical periodontitis formerly meant swelling, redness, and pain - essentially acute signs. The only small difference is that an abscess must contain pus. Because without pus it can’t be an ‘abscess’.

What will be the treatment steps in case of endodontic flare up?

The same as with an acute abscess. Drainage via the canal and or incision. Reduction of occlusion. No antibiotics are required unless the patient is immunocompromised or exhibits signs of systemic infection- such as fever, malaise, lymphadenopathy.

Citric acid before/after obturation?

Citric acid can be used as a replacement for EDTA and to clean the pulp chamber after.

Do you ever use the EPT (electronic pulp test?). How do you go about interpreting results from the cold test and/or EPT?

An electric pulp tester has been shown to be a useful test for use along with cold testing. It is more open to false positives because the electrical signals can stimulate other teeth and the periodontal ligament.

How do you accurately assess vitality of a tooth?

The most accurate way to assess vitality or presence of a blood supply, is laser doppler flowmetry, because it assesses movement of red blood cells. This machine is not readily available so, all routinely used tests are aimed at stimulating A delta fibres in the pulp and then assuming this means vitality (or blood supply) is present. Testing with cold is the most reliable test but the test must be done with very cold CO2 snow or Endofrost. The cold draws the dentinal tubule fluid outwards, and this causes firing of the A delta fibres, felt by the patient as a sharp pain. The electric pulp tester is helpful also, as it stimulates the A delta fibres by electrical signal. The major flaw of the electric pulp tester is that false positives are relatively common.

Don’t forget radiographs and CBCT also are helpful tools for assessing vitality. If we can see root closure or development in teeth with immature apices, this indicates vitality!

In case of apical periodontitis can we use Oradexon?

I have not prescribed this medication before.

Do you use the endo prep or paste with hand files if so why or why not?

I don’t use this because I prefer use of irrigants which do not attract debris to the blades of the file.

Is it okay to wash the canals with normal saline after sodium hypochlorite irrigation?

I don’t see any harm in doing this

Can we use cotton pellets instead of Cavit before placing the temporary filling?

I don’t use cotton pellets. They can create a path for leakage with their fibres, undermine the temporary restoration and make a poor restorative material.

If I place a temporary restoration the base is either IRM for its strength and antimicrobial properties or grey Cavit which is easily removed. Usually, I place a glass ionomer over these bases.

hi what would you do for patients who experience sever pain and swelling post operatively ? any methods to reduce post op pain

why do you use IRM and a GIC. Why not just the GIC? Also would the use of IRM affect the final bonding for the final composite

IRM is easier to remove from the pulpal floor, rather than GIC and easier to visualise also. You can use ethanol on the pulpal floor to remove the eugenol after filling the canals. This is not a problem, if you do this.

Are there any roles of prescribing antibiotics post pulpectomy or shaping and cleaning?

If the infection in the canals has been treated there is no reason to prescribe antibiotics systemically. This is a clinical decision though dependent on the patient.

What are your thoughts on sealer puffs?

Sealer puffs should not be something we try to create, so are an undesirable side effect of treatment. Most of the time they are of little consequence, but they can injure nerves if they are close to the apex.

How can I manage postoperative pain that happens after biomechanical preparation?

Anti-inflammatories are important and reduction of the occlusion.

How do we manage a sinus tract which drains through the chin, extra-orally (abscess was on tooth 32)? antibiotics? refer to a plastic surgeon?

Treat the source of the infection such as the tooth and review. Often the dental treatment will help resolve this and then a plastic surgeon can be required to improve the aesthetics.

So following up with an apical periodontal abscess, is there any case where you would leave the canal open for draining or you will still seal? Thank you.

I dont recommend leaving the tooth open to drain.

What techniques do you use to reduce the risk of extrusion of GP?

Work out the apical size of the root before filling, you can do this by using hadn files pressed down the canal or paper points to check for bleeding on the tip. Good radiographs and an apex locator also help.

What is your opinion on doing root canal with normal saline for necrotic tooth?

Saline isn’t antimicrobial or a tissue solvent so it neither dissolves bacterial biofilms nor their energy source (pulp tissue). Sodium hypochlorite accomplishes both of these important features.

Do you always check apical patency before  obturating? Is there risk of damaging apical tissues?

Passing a small file such as a size 10 k file through the apex by 0.5mm is unlikely to damage the apical tissues.