Premolar extractions
Premolar extractions can be tricky because on conventional radiography it can sometimes be hard to determine the proper root structure to plan your extraction. This is because there can be one, two or even three roots superimposed on one another and you can't gain detail about the convergence or divergence of these roots. One tip to determine the number of roots is to carefully examine the PA radiograph and carefully count the number of root borders. This number divided by two will give you the likely number of roots present. If there are multiple roots and they appear quite short of the Xray there are a few possibilities. Your Xray angulation may have forshortened the tooth, the tooth may actually be short or there is a large buccal-lingual divergence of the teeth which has resulted in their occluso-apical dimension appearing short. You can attempt to take a tube shift xray from a different misal-distal angulation. This may give more information of the number and angulation of the roots.
During extraction, the tooth that mobilises quite easily but is very difficult to remove likely has a curved root. This is because the crestal bone has expanded quite easily and the tooth is rotation around a very highly positioned fulcrum but the curve of the roots is stopping complete delivery due to differential paths of elevation. In this case, you will either fracture the crown, root or bone in delivering the tooth. Very rarely in this situation will the tooth come out satisfactorily. You must then take a step up to a sectional or surgical extraction to ensure atraumatic delivery of the tooth. Have a feel with the forceps with gentle force to see which way the tooth wants to go. This direction will suggest that the opposite side root is the more curved one as it following the path of least resistance and the straighter root is acting as a vertical post against a vertical stop. Initially, section the tooth and deliver the straighter root first allowing you room to deliver the more curved root. If you must deliver the more curved root first, be sure to decoronate the other section to allow room for the root to be elevated. If you force the tooth with forceps you will almost inevitably fracture the straighter root at the point of fulcrum (furcation) as it is the root that has the most resistance to lateral movements.
During extraction, the tooth that mobilises quite easily but is very difficult to remove likely has a curved root. This is because the crestal bone has expanded quite easily and the tooth is rotation around a very highly positioned fulcrum but the curve of the roots is stopping complete delivery due to differential paths of elevation. In this case, you will either fracture the crown, root or bone in delivering the tooth. Very rarely in this situation will the tooth come out satisfactorily. You must then take a step up to a sectional or surgical extraction to ensure atraumatic delivery of the tooth. Have a feel with the forceps with gentle force to see which way the tooth wants to go. This direction will suggest that the opposite side root is the more curved one as it following the path of least resistance and the straighter root is acting as a vertical post against a vertical stop. Initially, section the tooth and deliver the straighter root first allowing you room to deliver the more curved root. If you must deliver the more curved root first, be sure to decoronate the other section to allow room for the root to be elevated. If you force the tooth with forceps you will almost inevitably fracture the straighter root at the point of fulcrum (furcation) as it is the root that has the most resistance to lateral movements.
Excellent breakdown. What are your strategies for upper canines? I've encountered rampant caries requiring full clearance and boy were those canines unyielding.
ReplyDeleteThanks for your comment. Definitely. Upper and lower canines are the longest teeth in the body and are buttressed by the canine eminences. They are difficult to extract as heavy forces on them in excursive function also toughens the bond around them reducing its expandability. On the other hand I find that the bone on the buccal plate mesial and distal to the tooth can be quite thin and these can be sites of common buccal plate fractures which is undesirable for future implant placement as well as affecting the bony contour for dentures down the line. Canines also tend to be quite heavily restored as we understand their importance in the occlusion and tend to try and save the teeth with RCT and large restorations.
DeleteI don't think there's an easy way to extract a canine. If you happen to have a CBCT you could check the thickness of the buccal plate, height of bone and shape of root structure to determine the risk of fracture. Sometimes there is a significant mesial or distal groove in the tooth structure that makes mobilisation difficult. I have also seen a handful of 2 rooted canines. Raising a flap will also give you improved visibility and access and if you are required to proceed to surgical extraction the flap is already done for you. I have been told by a more senior dentist that he raises full arch, full thickness flaps in clearances to improve his visibility. From his point of view, vision will allow him to see and smooth sharp bone edges, clean debris and gain full closure. A large flap will have good blood supply, a fast recovery and very low chance of morbidity.
From a personal point of view, my strategy is to luxate first to try to get mobility. In clearances canines are often the last to go as you can use them to elevate out the adjacent premolar and lateral incisor. In perio cases this is often true as the other teeth are mobile but the canine usually isn't due to its longer root. In caries cases I would tend to stay away from this due to the risk of crown fractures in heavily broken down or restored teeth. When i luxate the canine, I would carefully try to expand the buccal bone with slow controlled force. I would work my way around mesially, distally and palatally and see if I can gain some mobility. Jumping early to the forceps on a canine tooth can be dangerous. Excess force from forceps can extract the tooth but it may break the crown, root or bone. If I get some good mobility then I would move to forceps slowly at first with very slight buccal lingual pressure placing guard fingers on the buccal plate to feel for movement indicating a fracture. This is a bit of wishful thinking on my part because by the time you feel a buccal plate fracture it's probably best to just remove the buccal plate with the tooth. Usually once you get movement it's a straight forward extraction. Avoid rotational movements early on as the cross sectional shape of the root of the canine is quite elongated like a premolar. Once you get some mobility, as per normal, slip the forceps further apically to get a better application point and continue buccal palatal movements with slight rotation.
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If there is no movement after a few minutes of luxation. I would seriously consider raising a flap for improved visibility. The amount of remaining teeth requiring extraction will determine the extent of your flaps. Be sure not to cut relieving incisions that will prevent you from extending your flap if required. In my mind a controlled extraction with bone removal with a bur or expansion with piezotome will be less destructive than an uncontrolled extraction with the fracture of the buccal plate. You may consider gutterring mesially and distal to try and preserve the buccal bone but this doesn't always guarantee the buccal plate will survive without some sort of grafting as it is usually quite thin at the crest.
DeleteCertainly very high level practitioners who also place implants in these sites recommend sectioning even anterior teeth to preserve bone. Without raising a flap, they use long shank surgical stainless steel or tungsten carbide burs on high speed without air to section teeth mesiodistally as far as they can towards the apex. They then use luxators to fracture the tooth towards the space made by the section site. and continue their sectioning down. This is especially used in the socket shield technique where some buccal tooth structure is preserved to protect the crestal bone and soft tissue. It is a very difficult and technique sensitive method and I probably consider wouldn't try it myself.
In the end, I guess if you don't care about the bone height or shape after extraction you can go fairly crazy with the forces you apply during extraction. If you care about the condition of the bone I would consider controlling the extraction surgically. I find in full clearances, the access that is given to luxated 360 degrees around a tooth is sufficient to get mobility is most cases. You MUST take it slowly and allow the bone to expand sufficiently before jumping to forceps. A good rule of thumb I got from an omfs was to set your limits on how long you would try something during an extraction. Try something 3 times or for 5 minutes then move onto the next step. If there is no mobility after 5 minutes with a luxator then consider raising a flap. If you have tried forceps 3 times and the molar is stiff, consider sectioning or guttering bone etc. I think that applies well in this case. If the tooth is still despite your best efforts. Take a step back, take a deep breath and move onto the next thing. Panicking and pushing the tooth harder is often not the way to go.
Hope that helped!