How to Avoid Hitting the Mental Foramen Nerve?

Anon. asks:

I will be placing two dental implants in the first and second premolar sites in the mandible. The final restoration will be free standing porcelain fused to metal crowns on Atlantis abutments.

This is the first time that I will be placing implants in this area. I am very concerned about the extent and distribution of the mental foramen nerve, especially its anterior loop. According to the literature this may extend as far as 10mm anterior to the mental foramen. I do not have CBCT scans easily available. What do you recommend I do to avoid hitting the mental foramen nerve? How should I lay the flap? Is flapless surgery a possibility?

46 thoughts on “How to Avoid Hitting the Mental Foramen Nerve?

  1. Marcus says:

    At this point I still always expose the nerve with a flap. The patient may be transiently numb but at least I don’t end up drilling through the nerve. I don’t know what the proportion of the population has an anterior loop 10 mm but I suspect it’s real low.

  2. Dr. Bill Woods says:

    You are asking the wrong questions by even asking the one you have proposed, in my view. With This nerve being in close proximity to where you are attempting surgery, I would not even attempt to do it until you are certain where it is. Get a CT scan. If you do not have simplant, you can still look at the images in DICOM to get an idea.I think knowing where the nerve is is paramount. If you are very concerned, then get the CT. It will show you. What size implants are you planning? 1 or 2 stage? how far apart? Have you done a waxup of the final restorations? Do you have a surgical stent? What is the bone width, length to the canal, bone type? what is the soft tissue anatomy? You have to look at many things, but if you get the nerve, where are you? Be sure before going in surgically. You can reflect the flap and see the nerve easily, but its where the implants are going to be placed that counts. If you hit it, it doesnt matter if it was flapless or how you reflected it. Personally, I want all the info and then I want to see the bundle to avoid it during sx. My flaps are papilla sparing, wide, curvilinear with a cutback, and surely clear of the bundle area. Surgically, I want to be 2mm short of the canal for safty, and I cant be sure without knowing in advance. And I still take a pic after the pilot drill with an angulation pin. Measure twice, cut once. And get Anthony Sclar’s text. Hope that helps some. Bill

  3. JOHN ACKLEY says:

    CBCT is now the standard of care for implant placement, to not use one you are opening yourself up to significant problems. Proper planning makes all the difference. The question should be how and where can I get CBCT services for my placement needs.

  4. Dr. S says:

    Listen to Dr. Woods! He took the time out to give you very important and concise information regarding your case. Do not consider flapless surgery. Without CT imaging, your level of experience, and flapless surgery is a risk you dont need.

  5. Dr. Ben Eby says:

    When in doubt, forget flapless surgery. Flapless surgery is only for cases that are slam dunk and only in the hands of experienced surgeons. It is a wonderful concept, but easy to make a mistake, even in very experienced hands. Looking directly at the bone that will support your implant outweighs the advantage of flapless surgery, unless you are absoultly sure of what you are dealing with.

    Exposing the mental foramen and the bundle gives a lot of information you need. In my experience, the anterior loop can branch off the inferior alveolar nerve bundle up to 7 mm anterior to the mental foramen, but usually less. If you use a perio probe in the foramen, you can often tell about how far the mandibular nerve goes anteriorially to the foramen, before the mental nerve branches distally.

    If you are grafting the area, be very carefull of the multiple sensory branches the are very close to the periostium. Releasing the periostium to streach the mucosa for primary closure needs very close attention.

  6. JOnathan Abenaim says:

    I beleive the standard of care for placing implants in the mandible is a ct scan. The nerves are there and you need to make sure you are not going to hit them. Get a ct scan, Simplant, PLace the implant virtually and have no worries at time of surgery. Just place one right on top of the foramen, used one size drills and had no issue and no worries during surgery. As I say Do on to patients as you would do for yourself. Do you want transient paraesthsia or even the nerves of your patient getting it. get the CT scan or refer it out!
    Good luck
    Jonathan Abenaim

  7. Dr. Ben Eby says:

    If you require a CT scan for all your implant cases, maybe you should refer your implant surgery to a more experienced surgeon.

  8. steve c says:

    CBCT is a must in this situation. A surgeon with years of experience including years of implant work may be able to safely flap to expose the foramen, probe the canal and then place a successful implant. Myself, even with those years of surgical and implant experience, I wouldn’t consider this case without tomography.

  9. Dr.R. Mosery says:

    With all due respect,the questions being asked frighten me.You should NOT attempt a simple case like this by yourself even with a cat scan.It’s obvious you need an experienced doctor doing a surgery like this,watching him,then you do one and he watches you and guides you.THEN and maybe then you’re ready to take this on.You need TRAINING before you go drilling holes in peoples heads (poking probes in the foramen?) or you’re going to ruin it for all of us.Sorry, but there’s no nice way to say this.

  10. Dr. Z says:

    Listen to Dr. Mosery. There is no reason to feel inferior by referring this type of case out. I am an endodontist and do periapical surgery in this area. I will always locate the nerve radiographically, then clinically before I make any osseous access. Surgery should never be a guessing game. Please send this case out.

  11. Bruce Knecht says:

    Make a surgical template. Have a pilot hole drilled into the center of the central groove. Cut the resin of the template site from the occlussal to 1/2 the clinicla height of the crown. Fill the pilot hole with gutta percha. Measure the length of the gutta percha and write it down. Take a digital panorex or ct. Calibrate the pano to the measured gutta percha. Then measure from the crestal bone to the foramen. Note this measurement and adjust the length of the implant. Know that the crestal bone may need osseous contouring before placement and if worried again place the template and re-pano and remeasure. Remember “Measure twice and cut once.”
    Then remove the gutta percha and drill your pilot hole and take a digital x-ray and make sure you are safe. Also feel the osteotomy with a hand held probe that has a small ball on the bottom. Push and sound the bottom and hopefully it is hard and not soft. Sound out that lateral walls of the osteotomy buccal and lingual to check for perforations. Do this at each width as you go to length. This should get you home.

  12. Dr. Bill Woods says:

    CBCT s the standard of care? It is certainly exciting and I will be glad to have one, but not yet. The standard of care is what is being practiced the most as acceptable parameters for diagnosing. An experienced clinician can do bone mapping, but I want a CT. I have simplant and I would certainly use a surgiguide from the reformat and feel safe doing so. But I dont believe that CBCT is yet the standard of care. Awesome, yes. Maybe one day they will be S.O.C. when they are the price of a pan machine.Bill

  13. Dr. Mehdi Jafari says:

    Observe the position of the inferior alveolar nerve and mental foramen on a panoramic radiograph and periapical films. It is desired to place an implant leaving a 2-mm safety zone above the nerve. If the nerve canal, after adjusting for radiographic distortion, is close to the anticipated osteotomy depth, a CT scan would be helpful in determining the exact position of the neurovascular structures. If an anterior loop is detected radiographically (panoramic or periapical film), corroborate its presence surgically. If there are doubts regarding the amount of bone available for an implant in the foraminal region, surgically locate the mental foramen and establish the safety zone in millimeters. Verify the presence of the anterior loop using a curved probe. The proximity of the nerve to the alveolar crest needs to be considered when designing initial incisions. Implants can be placed over the mental foramen, anterior to it, and posterior to the foramen up to the mesial half of the first molar using the length of the safety-zone measurement which was defined radiographically (adjust for radiographic distortions and severe crestal bone loss) or with surgical exposure of the mental foramen. Before placing an implant anterior to the mental foramen, which is longer than the safety-zone measurement, probe the mental foramen to determine whether there is an anterior loop. If the loop is present, place implants no longer than the safety-zone measurement. If there is no loop, clinicians can place an implant anterior to the foramen beyond the length of the safety zone. However, for safety, place an implant so that its distal aspect is ‡2 mm mesial to the mental foramen to allow for surgical error. (Greenstein G. and Tarnow D. J Periodontol 2006 ; 77:1933-1943).

  14. JOnathan Abenaim says:

    It may not be the standard of care in your practice , but if I had an implant placed in my mouth I would want to know exactly where the nerve is and how wide the bone is and place the perfect implant. If you want to take a 2Dimensional Pan and be ok with that is fine. I learned from a clinician who is on this blog frequently and he not only take CT scans but he places his implants with something called a Robodent, Robotically guided implant surgery, perfect placement, perfect implant. Why not I dont understand the hesitation to take a CT scan. In my practice even if I know there is bone I will get a CT scan, place the implant with simplant and then decide on a surgiguide or not but I already know the type, width and length of implant that I will be placing. SO sorry to Y’all if I try to go above and beyond for my patients.

  15. JOnathan Abenaim says:

    And to post a comment like if you “need” a ct for every case I should refer it out. It is different to need than to WANT!

  16. Dr Shabbir/Tanzania says:

    Dr Mehdi
    he is the best listen to him ,i have put 6 implants in a radiated jaw and it was success its Mehdi who guided me right

  17. osurg says:

    The use of the term “standard of Care”
    concerns me.I am sure all of you know that this is an open website. I would not be suprised if several lawyer types monitor the site. By making such a broad and opinionated statement we are potentially causing a great deal of harm. There is no doubt in my mind that there are occasions when a scan can be of great help or even necessary. However, this is still something to be determined by the doctor. Just as we are allowed off label uses of medications. The ultimate decission to scan or not is not at this point legally the “standard of care”,and should be based on experience and ability.

  18. Jonathan Abenaim says:

    I agree that I should not have used the term standard of care. But my point is that in my mouth that is what i would want done. Maybe I am too picky but that is waht makes me comfortable knowing all the information before anything is done. Sorry, but that is the way that I run my practice.

  19. Dr. Bill Woods says:

    Osurg is correct. CBCT isnt the standard of care and attorneys are not aware of what just is the standard. There reaally isnt one yet and there are many ways to determine appropriate surgical care and execute that care. It is a fact that a CT has more information to offer with reduced margin of error. But, there are many many clinicians who have performed excellent surgically without CT over the years. Suffice it to say that ten years from now, things will be different all around. We will probably be looking at holograms together online and interacting with each other to preplan cases.

  20. Robert J. Miller says:

    The entire concept of “standard of care” has changed dramatically in the last few years. It used to be a procedure that the majority of clinicians performed in a geographical area. It has now morphed into what a “prudent” clinician would do in a case. While it is true that CBCT numbers do not allow it to be used by most implantologists, there are CT scanners on virtually every corner. The AVAILABILITY of 3D scans is what shapes a juries decision on what is now the de facto standard. CBCT simply gives a superior image at a much lower radiation dose. As an expert witness in dental malpractice cases in Florida, attornies are not only well prepared, they also read this website! I was contacted by a law firm, based on a previous blog I contributed to, for a review of a parathesia case. Don’t think for a moment that in a courtroom you will be able to convince them that a scan was not necessary. They will eat you for breakfast.
    With regard to the “anterior loop” quoted earlier, this is a pipedream. It does not exist. This is because it is NOT a loop but rather a continuation of the inferior alveolar branch known as the incisve nerve. It continues through the symphysis to anastamose contalaterally with the opposite side. We have reviewed hundreads of CBCT scans over the past three years and it exists in 100% of our patients! The dysesthesia cases after placement of implants anterior to the mental nerve are caused by damage to this branch and Wallerian degeneration. There is generally an absence of numbness to the lip, but altered sensation to the anterior teeth and a burning sensation as well. This also occurs when harvesting symphyseal block grafts if you get too far medially, as this branch tends to rest close to the lingual wall. CBCT scans will also help to locate the positions of the lingual and submental arteries to reduce the possibity of severe bleeding episodes. And it will also help locate, in the 80% of patients who exhibit them, the superior genial foramina. This is a secondary neurovascular bundle exiting at the cuspid positions innervating the chin. The use of our active navigation unit (RoboDent) allows us to bypass these critical structures and maintain control over critical implant placement. Whether you are using active or passive (CAD guide) navigation for surgery, it will dramatically reduce the possibility for morbidity in a case. This technology is available to very clinician; there is no longer an excuse to avoid using it. RJM

  21. Horneman says:

    I like the discussion about the CBCT and the jury, but what if your patient is complaining that she has side-effects from the radiation? It is still more then normal 2D pan. What will the jury decide if you not have followed the ALARA concept for X-rays. So I think not in all cases it is justified to make a CBCT.

  22. Dr. Mehdi Jafari says:

    When we talk about the anterior loop, we mean ‘‘an extension of the inferior alveolar nerve, anterior to the mental foramen’’. Some investigators have also referred to it as the anterior loop of the mental nerve, or described it as the mental neurovascular bundle traversing inferiorly and anteriorly to the mental foramen, which then doubles or loops back to exit the mental foramen. Detection and measurement of the anterior loop was attempted using a variety of diagnostic methods e.g. panoramic films of markers in dried skulls and cadaver mandibles, periapical films of cadaver jaws, and CT scans of patients and surgical cadaver dissections. Clinicians in doubt concerning the position of the mental foramen or who are considering placing an implant in the foraminal region at a depth where there is unease about not having a 2-mm clearance coronal to a location where an anterior loop exists should obtain a CT scan prior to implant placement to avoid injury of the inferior alveolar or mental nerve, however, the mental foramen’s location can be surgically verified. Evidence indicates that an anterior loop is present. It has been detected radiographically and by cadaver dissection; however, its size is debatable. In general, radiographic studies indicated that the anterior loop may be as long as 7.5 mm. Those who are still unwilling to accept the scientific facts can be referred to the following literature:
    1) Solar P et al. A classification of the intraosseous paths of the mental nerve. Int J
    Oral Maxillofac. Implants 1994; 9:339-344
    2) Mardinger O. et al. Anterior loop of the mental canal: An anatomical-radiologic study. Implant Dent 2000; 9:120-125.
    3) Jacobs R et al. Appearance, location, course, and morphology of the mandibular incisive canal: An assessment on spiral CT scan. Dentomaxillofac. Radiol. 2002; 31:322-327.
    4) Kieser J et al. Patterns of emergence of the human mental nerve. Arch Oral Biol 2002; 47:743-747.
    5) Kuzmanovic DV et al. Anterior loop of the mental nerve: A morphological and radiographic study. Clin Oral Implants Res 2003; 14:464-471
    6) Jacobs R, et al. Appearance of the mandibular incisive canal on panoramic radiographs. Surg Radiol. Anat. 2004; 26:329-333.

  23. Robert J. Miller says:

    In a CBCT scan using a 6″ field of view, the x-ray exposure is essentially the same as for a panorex (Mah, Danforth; USC). The voxel size is optomized so that intricate osseous anatomy can be visualized and assessed down to .1mm. The x-ray exposure increases as the field of view goes up and you loose fine detail. For implantology, generally a 6″ field is all you need.

    Anyone can go onto pubmed and find literature that supports a particular thesis. The point of research is to critically evaluate the literature and point out the deficiencies, if they exist, in each study. The quoted papers are studies using a CT scan. Higher radiation scanners tend to obliterate fine medullary structures making identification of critical anatomy very difficult. And, because the axial slices are at 1mm, additional information is lost through extrapolation. Anyone who has done a rapid prototyped biomodel using CT will attest to its’ “stepped” architecture. After evaluating hundreds of CBCT scans, there is ZERO evidence radiographically of a loop extending anteriorly and then coursing back to exit at the mental foramen. I truly believe that, after doing some cadaver studies, they are confusing marrow spaces that appear to be nerve pathways that then may course posteriorly. But the litmus test is a canal with clearly demarcated cortical architecture. The other studies that you quote clearly support the existence of the incisive canal and this can be seen clearly on 100% of the scans we have taken.

  24. Marcus says:

    I guess I’m confused as to how a radiographic image allows you to see the course of the nerve itself… Unless I’m wrong, the best way to see soft tissue structures is with MRI. I know that using absorbance differential the CBCT software can reconstruct soft tissue but, I haven’t seen pictures of actual nerve versus osseous canal.

  25. Dr. J says:

    The best way to avoid the nerve in this case by the scenario you described and your apprehension is to let an experienced surgeon perform the procedure. If you have completed a residency, you should know what to do and how to do it in the area. I would punt in your case.

  26. Robert J. Miller says:

    CBCT in the 12 bit version, and even more so in the 16 bit version (TerraRecon), allows you to see soft tissue (both nerves and blood vessels). This was previously only possible with an MRI. By changing the threshold values, you can differentially image any combination of soft/hard tissue. Fortunately, within osseous architecture, neurovascular bundles are housed withing cortical canals easily discernable using CBCT technology. You do not need to see the soft tissue to measure distances from these structures. With regard to “experienced surgeons”, I have seen OMFS’ perforate the IAN by trying to extrapolate distances using a panorex. Active or passive navigation is certainly desireable where nonviolable structures are present.

  27. Dr. Mehdi Jafari says:

    The terminal mandibular canal is at an average of 4.5 mm under the mental foramen, advances 5.0 mm anteriorly, loops, and ends at the foramen. The maximum location of the mandibular canal is 8.4 mm below the mental foramen. The direction of the mandibular canal at the mental foramen is 39.4° lateral, 67.2° superior, and 80.2° posterior. Some investigations regarding the inferior alveolar nerve have proven the existence of the mental loop by dissection and/or noninvasive images (radiology, tomograph, etc) of the mandible (Klinge B, Petersson A, Maly P. Location of the mandibular canal: comparison of macroscopic findings, conventional radiography, and computed tomography. Int J Oral Maxillofac Implants 1989; 4:327-332). It has also been reported that the mandibular canal curved in the posterior segment of the body, descended anteriorly, and ascended to reach the mental foramen (Rajchel J, Ellis E, Fonseca RJ. the anatomical location of the mandibular canal; its relationship to sagittal ramus osteotomy. Int J Adult Orthodon Orthognath Surg 1986;1:37-47).The distal portion of the inferior alveolar nerve runs inferior-medially near the mental foramen, passes it anteriorly, and acutely turns superior-medially to reach the foramen. It is certainly possible to injure the inferior alveolar nerve as the osteotomy is performed near the mental foramen. There is considerable variation among researchers about extent of the anterior loop of the mental neurovascular bundle. The reported length of the anterior loop ranged as little as 0.5 mm in some patients [Rosenquist, B. (1996) is there an anterior loop of the inferior alveolar nerve? International Journal of Periodontics and Restorative Dentistry 16: 41–45] and as much as 10 mm in others [Rothman, S.L.G. (1998) Dental applications of computerized tomography: surgical planning for implant placement. In: Rothman, S.L.G., ed. Computerized tomography of the mandible, 1st edition, 43–47].
    Several methods and techniques for identifying the extent of the anterior loop of the mental neurovascular bundle have been proposed using panoramic radiographs, computed tomography, and determination of the anterior loop during surgery using a curved explorer [Misch, C.E. (1999) Contemporary implant dentistry. In: Misch, C.E., ed. Root form surgery in the edentulous mandible: stage I implant insertion, 2nd edition, 349–350]. [Bavitz, B.J., Harn, D.S., Hansen, A.C. & Lang, M. (1993) an anatomical study of mental neurovascular bundle–implant relationship. International Journal of Oral and Maxillofacial Implants 8: 563–567]
    Investigated the path of the mental nerve in human cadaveric samples and reported that the maximum length of the anterior loop based on anatomical measurements was 1 mm. However, the average radiographic loop was 2.5 mm for a dentate group and 0.6 mm for an edentulous group. [Mardinger, O., Chaushu, G., Arensburg, B., Taicher, S. & Kaffe, I. (2000) anterior loop of the mental canal: an anatomical–radiologic study. Implant Dentistry 9: 120–123] reported the presence of the anterior loop in 28% of dissected specimens (range 0.4–2.19 mm), and concluded that the periapical radiographs of the anterior loop of the mental nerve in cadaveric mandibles do not disclose the true ramification of the inferior alveolar nerve to the mental and incisive nerve. Anterior mental loop is not a pipedream and a safe guideline of 4 mm, from the most anterior point of the mental foramen, is recommended for implant placement.

  28. JOHN ACKLEY says:

    For those of you who disagree with the term “standard of care” maybe we should use the term standard of excellence. Of course that could be hard to explain as don’t all of our patients deserve excellence? Keep in mind we don’t need to have our own CBCT in order to have a scan done for a patient. There are plenty of places to have this done if you desire it. If there is no access in your area maybe that is a void that your office could fill. Think big picture and think what you would want done on yourself and then create the accessability for your patient base. The world will be a better place.

  29. JOHN ACKLEY says:

    Maybe we should use the term standard of excellence. Of course that could be hard to explain as don’t all of our patients deserve excellence? Keep in mind we don’t need to have our own CBCT in order to have a scan done for a patient. There are plenty of places to have this done if you desire it. If there is no access in your area maybe that is a void that your office could fill. Think big picture and think what you would want done on yourself and then create the accessability for your patient base. The world will be a better place.

  30. JOHN ACKLEY says:

    Maybe we should use the term standard of excellence. Keep in mind we don’t need to have our own CBCT in order to have a scan done for a patient. There are plenty of places to have this done if you desire it. If there is no access in your area maybe that is a void that your office could fill. Think big picture and think what you would want done on yourself and then create the accessability for your patient base. The world will be a better place.

  31. Robert J. Miller says:

    Dr. Jafari, I certainly do respect your defense of the thesis of the anterior loop at the mental foramen. But I live in an evidence based world. The literature is replete with the detritus of assumptions that have been discarded over time. I believe that the concept of the anterior loop is one of them. If you repeat a misconception often enough, it not only becomes truth, but people start to quote that evidence. This perpetuates the problem. I have submitted my paper, “Maxillofacial Anatomy:The Mandibular Symphysis” for publication. Using large voxel 12 and 16-bit CBCT scanners, I have included tomographic slices showing the course of the IAN to and from the mental foramen, the incisive canal, submental/lingual ateries, and superior genial foramena. Cortical canals can be clearly seen throughout the course of all of these structures. Why would the cortical neurovascular canal suddenly disappear in an “anterior loop” exiting at the mental foramen when all other structures exist(including, posteriorly, the long buccal nerve)? I believe that what they are probing or measuring is the bifurcation of the mental and incisive branches of the IAN. After a 22 year involvement in the discipline of Oral Implantology, I have learned to be critical of all assumptions about our discipline, including the literature. We have all been wrong in the past about some material/methodology. But that should not blind us to advancing this discipline. It is still about patient care and performing minimally invasive procedures. Active or passive navigation will help us to avoid damaging important anatomy, while fulfilling the goals of procedure based dentistry.

  32. GC says:

    dear colleagues, there is no doubt reading this blog that much has still to be said about this “holy loop” that divides opinions and schools…
    however, the recent french literature provides us excellent and clinical guidelines for determining the location of the foramen,its shape and correlation to absence or existence of an anterior loop before exiting the bone.Type “GAUDY and atlas anatomie implantaire ” and you”ll get a unique textbook'(in french, sorry…) about REAL anatomy related to our procedures. -this is not an ad , I think some clinicians are sometimes going too far : for example ,would you go for a CT -let’s say your patient is your mother-in-law- if bone probing gives you 10mm at crest level and the panoramic view shows more than 20mm above a visible image of the nerve?on the other end, why not refer and get some clinical course in anatomy before your first delicate case above the foramen?
    In between, the best attitude to my opinion would be to handle each case with empathy and good sense,knowing clinical limitations,implant systems limitations and learning to refuse some cases or refer to “acrobatic” surgeons.

  33. Dr. Mehdi Jafari says:

    Several clinical applications for CBCT such as diagnosis of impacted teeth, assessment of airway, and TMJ morphology have been identified. For diagnostic purposes, the lack of precision in landmark identification does not preclude a proper diagnosis. In research, however, the ability to reliably identify landmarks in the maxillofacial region before and after a specific treatment is of significant importance since the research results will have an impact on the effectiveness of treatment modality. Future research in medical and CBCT will need to focus on identifying and testing landmarks that have high reliability and represent the pertinent anatomy of interests to a clinician. It is interesting to note that the accuracy result obtained with cone beam CT in the study by Lascala et al. [analysis of the accuracy of linear measurements obtained by cone beam computed tomography (CBCT-NewTom), Dentomaxillofac Radiol 33 (2004), pp. 291–294] was quite different from the study results using spiral CT [Cavalcanti et al. Craniofacial measurements based on 3D-CT volume rendering: implications for clinical applications, Dentomaxillofac Radiol 33 (2004), pp. 170–176]. Spiral CT has been in use since late 1970, and researchers and clinicians have gained the experience and knowledge of working with spiral CT using different parameters while software for manipulating spiral CT images are in constant refinement. Unlike spiral CT, CBCT is a relatively new imaging technique for the maxillofacial region, where the most effective scanning protocol is still being researched. A study by Marmulla et al. [geometric accuracy of the NewTom 9000 Cone Beam CT, Dentomaxillofac Radiol 34 (2005), pp. 28–31] using CBCT on a 12 × 12 × 12-cm phantom geometric cube has shown an absolute measurement error of 0.13 mm and a standard deviation of 0.09 mm. This would suggest that the potential for improved measurement accuracy exists when CBCT is compared with medical CT. Further research regarding accuracy of the NewTom 3G and other CBCT units will be required. Software tools for accurate landmark identification and quantitative measurements and software to facilitate segmentation of anatomical areas of interests in individual slice sections for volumetric measures must be developed and refined.(doi:10.1016/j.tripleo.2006.07.015). I hope that we are all practicing within the limits of an evidence based world. Good night and good luck.

  34. LC says:

    Could anybody specify the specificity and sensitivity of current CBCTs for hard tissue, nerve and blood vessels respectively?

    A web site would be great.

    This might help us to understand the discussions about the loop.

  35. Kumar Dr. says:

    I have placed two implants 4.3*10 in lower left first & second molar area 15 days back. Patient still have severe pain, although patient was very apprehensive. Post-op IOPA & OPG shows both implants are very much close to IAN. I have placed 58 implants till date but no patient have pain after maximum 3-4 days. I have no facility of CBCT near by. How can i access this pain is due to IAN intervention and can anybody suggest what should i do in this situation?

  36. berto says:


    Severe pain probabily means severe problems, if i were you, i would remove those implants at once.Even thougt the IOPA & OPG don’t show direct contact with IAN, simetimes the pressure can couse some IAN damage.

  37. Ihde says:

    This answer may come from the opposite corner of this discussion:
    A german court ruling from 1994 reads as follows: if bone is missing, either extensive exploration such as 3d-visualization is necessary before implant placement, or implants with lower risk of nerve injuries , – basal implants (BOI) – should be used.

  38. Man of Steel DDS says:

    I feel compelled to make some comment here. First I’ll bet those guys telling you to “refer it out”are probably oral surgeons or periodontists trying to protect their own turf and monopolize the implant surgery end. And all this stuff about ” Standard of care”…. Osurg is right some shyster lawyer is going to eat that stuff up and use it against some dentist OS or perio to make a case against him. In these situations where other DDS’S rip each other apart, even indirectly does nothing but breed ill will and ultimately benefits the Lawyers pockets! In my experience the perio guys are the worst about this!!!! IMO this web site should be closed to anyone without a DDS, DMD and State license!!!

  39. Man of Steel DDS says:

    Also to ANON, you might make a splint with the gutta percha or 5mm steel balls and re take your pano. Some pano’s have up to 20% distortion and this will give you some idea of how much you have. Try to stay 2mm min from the IAN and mental foramen. Lay a full flap measure down to the foramen to know where you are and expose the mental nerve, so you know where it is at. You can explore the foramen with an explorer for an anterior loop. If the explorer or probe tip goes mesially by more than 2-3 mm you have an ant loop an can get some idea how anterior it is. Those CT scans can be done at a medical imaging center for le$$, and some Orthodontists are using ICAT’s in lieu of cephs and pano’s and believe me they’ll be more than happy to scan a patient for you about $350. here. They’ll get their $200k machine paid on an they’ll not steal your patient for themselves like some OS or Perio will. Lastly get the educational background it’s costly in both money and time. Some program like MISCH’S in Detroit or Med College of Georgia both have ICOI and AAID fellowship programs. I’ve went through Misch’s program (Very good!), taken a pot load of manufacturer sponsored courses mostly from Arun Garg U of Miami. Just attended one in Nashville on bone grafting.. very interesting! Also have a Certificate in Prosthodontics and FICOI, so I’m a professional at playing “Cat and Mouse” With all that I can surely tell you that NO ONE has a monopoly on learning…

  40. Dr. Chace Pratt says:

    Congrats Man of Steel you succeeded in sounding more foolish then the ones calling for people to refer. Pat yourself on the back.

    I am a General dentist and I have tons of associates that are Periodontist and OMFS. I work well with them all. I refer cases to them, they refer cases to me and so on. Sometimes it best to spread the liability around.

    I dont look down on someone who makes a comment like refer. In this modern era I find we dont refer enough.

    I am a firm believer that everyone is capable of being involved in Implant cases. General Dentist to Oral and Periodontal Surgeons can all surgically and restore implants.

    Who knows maybe Implants will become a specialty of its own, as there is certainly alot of aspects to learn in implant therapy. Until that time I practice whats in the best interest of my patients.

    In my practice I place the implants that I am comfortable placing. I stick with the easy ones, non grafted, straight foward single unit cases. The rest I refer to a more experienced surgeon.

    I do this because it is in the best interest of the patient and why push my comfort level. I do very well in my practice and dont need to worry about squeezing every little drop and forget what is in the best interest of my patients. Even if I didnt do well I still put the patient first. ITs not wrong to refer and its not wrong to ask for a referral. Whats wrong is not know when to refer. There is always someone more experienced then you.

    After all isnt it the patients well being that we should be concerned about.

    We live in a time when there is a major shortage of dentists, there is plenty of work to go around, put your patient first and good things will follow.

  41. Toofdoc says:


    There have been many very good comments. It is obvious you are concerned about your patients or you would not have asked the questions. The bottom line answer is your surgical comfort and experience.

    I also agree with Dr Chace Pratt, “REFER” is NOT a “four letter word.” If this surgery is too far outside you comfort zone refer it and get more education. Then you can do the surgery next time.

    Good luck and keep on learning for your benefit and that of your patients.

    Yours in Dentistry,


  42. Dr SS says:

    Refering is fine
    The whole point of this blog is to find out how our specialists are treating these cases
    It seems to me that they (the specialists)are with their elevated liability status are taking CT orother 3 D views
    Seems sensible to me
    I would expect no less of a specialist

    I live and work in a developing country
    No access to 3d technology unless you fly 3 hours and 2 nights in a hotel and return with a ct from the US

    I do however place many implants and have no specialist to refer to

    Clinically i palpate the foramen by drawing the lower lip down vertically and use an amalgam burnisher to feel the invagination (LA in place!)

    Actually quite easy to find
    Measure 6mm anterior and drop a pilot drill
    X ray after EVERY pilot drill

    To date (14 years of implants) I have had 3 very minimal mental parasthesias all full recovery
    Implants were not removed and no further procedure done
    I hear all of you and respect all of your oppinions
    It is my intention to purchase an in Office Illuma CT next year and perhaps things will be clearer ..will my clinical success be better..perhaps not

    We cannot forsake our clinical instincts and tactile skills for technology ..with or without access to the technology

    most intresting commentary I eagerly await your comments

  43. prof.Dr.Dr.Hossam Barghash says:

    i think before talking about risk we have to talk about the cause. first do we realy need CT or further investigation or not depend on how far is the foramen according to my planning if I have enough bone on the panoramic x ray & i,m toatly away from the foramen then asking the patient for further investigation for me like asking for telescope to see somthing in front of you.
    another point is when you plane for the implant make the drilling direction towared lingual side (not too much)
    also by clinical examination you can see the mucosal fold where the nerve travel to the lip.
    other points which are important, you should be carfull while designing your flap,dissection& reflection. also take care when you suturing the flap you still can hit the nerve.
    flapless technique is not recommended

  44. Dr Yogesh says:

    I have a case of edentulous mandible requiring full arch fixed prosthesis. the CT scan image shows the inferior alveolar nerve canal extending beyond the mental foramen almost upto the midline or the symphysis area as a single canal. is it the anterior loop or the incisive branch. How do i confirm preoperatively . what precautions should i take to avoid damage to the mental nerve nerve intraoperatively. i dont have the facility of CBCT at hand.


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Posted in Clinical Questions, Flapless Surgery, Hot Posts, Techniques and Procedures.
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