POST-IMPLANT NEUROLOGICAL COMPLICATIONS IN THE HORIZONTAL MANDIBULAR ARCH

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1 Maxillofacial Surgery POST-IMPLANT NEUROLOGICAL COMPLICATIONS IN THE HORIZONTAL MANDIBULAR ARCH O. Stamatin¹, Maria Voroneanu², Carmen Stelea³ 1. PhD Student, Dept of OMF Surgery, Faculty of Med Dent, Gr.T.Popa U.M.Ph. Iasi 2. Prof.,PhD Dept of OMF Surgery, Faculty of Med Dent, Gr.T.Popa U.M.Ph. Iasi 3. Lecturer, PhD, Dept of OMF Surgery, Faculty of Med Dent, Gr.T.Popa U.M.Ph. Iasi Abstract Objectives: Evaluation of alveolar bone and of bone morphology, the anatomical ratios of the inferior alveolar nerve, involving clinical and paraclinical examination of the edentulous crest in the implanting site, are essential aspects for pre-operative planning of implant therapy, associated to bone rehabilitation. Materials and method: The quality of bone regeneration, as well as the possible sensorial disorders were evaluated on recordings from patients having received implants after bone rehabilitation performed in the posterior area of the mandibular arch. Results: Two cases of post-therapeutical paresthesia, representing 2/37 (0.5%) of the total number of implants inserted in the posterior segment of the mandible, or 2/ 27 (0.7%) of the patients, were analyzed. Conclusions: The data obtained in the present study agree with the conclusions of previous investigations, demonstrating that panoramic radiography, together with Computer Tomography, should be viewed as a golden standard of implant therapy and bone rehabilitation, especially in partial and total edentulism, receiving implants in the posterior segment of the mandible. Keywords: tomographic diagnosis implant therapy tissular regeneration sensorial disorders INTRODUCTION qualitative and quantitative samplings. Localization of the mandibular canal tract in the implant site is especially important, for avoiding any sensorial modifications at the level of the lower lip, as a result of the inferior alveolar nerve alteration, which is one of the most severe complications of implant surgery at mandibular level. A 43.5% parasthetic ratio was registered 2 weeks after the insertion of a mandibular implant, following bone addition (3); a subsequent study reported a ratio of 8.5% of patients with sensorial modifications (1), while a retrospective questionnaire approaching sensorial modification recorded 37% of sensitivity modified 1 month after the reconstructing implant therapy (4). Various imagistic techniques, used prior to surgery, radiography (retrodentoalveolar and X- ray panoramics, tomography, cephalometry) and computer tomography (CT) included (fig.1), are proposed for establishing the quality of the mandibulary bone and the tract of the mandibular canal. OPT (ortopantomography) is frequently used for establishing the diagnosis in implantology (1). Even if the use of the transversal section of images was recommended (2, 5), CT examination is viewed as the golden standardul in treatments for planning implant therapy, following bone augmentation, because it implies a low radiation dose, offering the best Fig. 1. Imagistic analysis for avoiding lesions of the inferior alveolar nerve images/ galileos.jpg MATERIALS AND METHOD Prior to surgery, bone height was evaluated according to a panoramic radiographic standard International Journal of Medical Dentistry 197

2 O. Stamatin, Maria Voroneanu, Carmen Stelea (OPT), performed with the technique recommended by the producer. In the region of surgical interest, vertical linear section measurements were made, from the upper part of the alveolar crest up to the upper margin of the mandibular canal, by means of a scale-type implant model (with measurements calibrated according to the amplification factor) (fig. 2). Fig. 2. OPT with contrast markers for comparative sizing. The values for each site on which bone addition and, respectively, implant, had been performed, were recorded while, on the OPT, a 2 mm lower limit was taken, as a safety measure, for establishing the length of the necessary implant. Starting from such measurements, 8, 10 or 13 mm-long implants were introduced, according to ITI recommendations (2, 5). No implant longer than 14 mm was inserted, even when the available bone height permitted insertion of a 16 mm-long implant. When the superior limit of the duct was difficult to vizualize, the worst possible position of the duct was selected, which led to a reduced bone height, a short-sized implant being preferred. All implants were inserted by standardized procedures a surgical stage (2), preceeded by prophylaxy with antibiotics, initiated 1 h prior to the surgery 3 gr amoxycillin p.o. A total number of 37 implants were inserted, out of which 14 in the premolar region and 23 in the molar one. 18 (48.6%) implants were 10 mm long, 9 (24.3%) were 13 mm long, 7 (18.9%) 8 mm long and 3 inplants (0.8%) were 6 mm long. After surgery, the control procedure was standardized for all patients, alongwith continuing antibiotherapy 1 gr amoxycilline (macrolides for allergy to penicilline 1 gr). A panoramic radiography was taken immediately after the surgery, and analyzed for checking whether the image of the implant tip had not been superposed on the mandibulary canal. One week later, the follow-up visit included suture removal, monitorization hygiene and recording possible post-surgery complications, as well as evaluation of the nervous function at mentone level and of other subjective sensations, such as pain. Each patient was systematically examined to assess his/her neurosensorial disorders on the lower lip and/or chin, after surgery, and the general condition over this period of time. The impaired sensitivity in an injured area was recorded as hypoesthesis, while the absence of sensation as paresthesis. Considering that the value of neurosensorial testing of the inferior alveolary nerve (2 discrimination points, Semmes-Weinstein and pinprick tests) is limited (3), as due to some disagreements between the results of the objective and subjective results of the tests, no evaluations were made for the lips and chin when the patient had no complaints, being therefore examined and followed only for sensorial disorders of the inferior alveolar nerve in the patients subjected to treatment. RESULTS AND DISCUSSION Two cases of post-surgery paresthesis, representing 2/37 (0.5%) of the implants inserted in the posterior mandibular segment, i.e. 2/27 (0.7%) of the patients, were recorded. The former was a case was a totally edentulous 54 year-old woman. The accidental shifting of the surgery guide during the implant operation caused placing of the 10 mm-length implant too near the menton foramen, in the premolar site (position 44), which resulted in a minor pareshtesis at the border with the lower lip. The modified sensation lasted for 6 weeks, disappearing without any treatment. The latter case was that of a partially edentulous 44 year-old woman. In this case, no one noticed that the magnification factor was changed between the evaluation made with Orthopantomograph 10 and that with 198 volume 15 issue 2 April / June 2011 pp

3 POST-IMPLANT NEUROLOGICAL COMPLICATIONS IN THE HORIZONTAL MANDIBULAR ARCH Scanora, respectively, a 1.2 magnification scale being applied, instead of the 1.3 required by the Scanora program of 001 images (6). The panoramic post-surgery radiography showed that the 13 mm-long peak of the implant inserted in position 35 was superposed over the menton foramen. On lips and chin, the modified sensation of the enervated area disappeared spontaneously after 3 weeks. No permanent sensorial disorders of the inferior alveolar nerve occurred. DISCUSSION The panoramic radiography represents the technical image used for pre-surgery planning of the 37 implants inserted in the posterior mandibular area, following on-lay augmentation of the crest. Periapical retrodentoalveolar X-rays (fig. 3) were used only to put into evidence the details of some region (e.g., the residual root or some possible signs of periapical pathology), and not for establishing the available height of the bone, existing after regeneration. It is especially important to exactly determine the position of the mandibular duct for planning the length of the implants to be inserted on the posterior part of the mandible (7), even if size is considerably improved after augmentation: precision depends on the technique used for image taking and processing. Fig.3. Rx bony reconstruction with implant insertion. Panoramic radiographies have sufficient precision to measure size vertically, when a patient is correctly positioned (8). Some tendency of underestimating the distance from the alveolar crest to the upper border of the duct might occur on the panoramic radiography (7), which may be less harmful than an overestimation of the height of the available bone, causing sensorial disorders at the menton and labial levels. According to the above recommendations for mandibular-inserted implants (9), a safety margin of at least 2 mm is necessary between implants, the tract of the duct being strictly observed in all surgical studies. The vertical amplification factors, established with metal balls on OPT, were found as being highly constant (1: 1.27 ± 0.01) (10,5). The physician should be accustomed to the imagistic distortion, which depends on the technique used, and also he should know that, when measuring the same distance on an X-ray, various researchers may reach different results. When using different imagistic techniques, the ratios obtained are contradictory, as to the precision of the measurements made on crosssections. Linear tomography is significantly less precise than spiral tomography in providing information on the position of the mandibular canal (11). The average difference of the available mass of bone height over the alveolar canal noticed between hypocycloidal tomography and panoramic X-ray was of 2.4 mm (9, 12). A clinical study performed in 2004 showed that, in vertical plane, bone height after bone regeneration on a spiral tomography was about 1 mm larger than the mean bone height measured on a panoramic X-ray (10, 13), which may lead to dangerous situations, when the vertical bone height is measured exclusively on a spiral tomography. In the same study, the mandibular canal could be CT-evaluated in 11/77 (14%) of the implant sites, while the additional information on the cross-section obtained with spiral tomography did not influence the initial planning in most of the implant sites (96.1%). Frequently, the incapacity of identifying the inferior alveolar canal renders the linear tomography less valuable than the CT (8), as a study developed in 1995 showed that the distances measured on a CT were not more precise than those obtained with simple tomographic techniques (13). CT reliability and CT examination depend on the technique applied. (fig. 4.) International Journal of Medical Dentistry 199

4 O. Stamatin, Maria Voroneanu, Carmen Stelea should be also considered. The reported doses (at the level of the salivary glands included) are the following: 9 ìsv for panoramic radiography, (14) 9 ìsv for linear tomographic cross-sections, ìsv for a conventional cross-section through spiral tomography (15) and ìsv, respectively, for CT examination(16). CONCLUSIONS Fig. 4. Planning of surgery on sections (CT). Mandible positioning during scanning distorts image recomposition, more numerous precise measurements being obtained directly with a CT (10). Prior to surgery, the CT (fig.5) and clinical examination may help to the selection of the maximum length or of the height of an implant, which will be 1 mm higher, when inserted on the mandible, after bone restoration (11). With other authors (12), an error in measuring the distance from the alveolar crest to the mandibular canal is of 1 mm (± 1 mm), in 93.7% of the direct measurements by CT, and in 89.6% of those performed by the multiplanar reconstruction method. Fig. 5. CT 120 days after implanting therapy. Apart from imagistic precision, the technique used to assess and plan the radiation dose The results of the present study demonstrate the reduced post-implant incidence of the damage caused by the inferior alveolar nerve in the case in which an implant is surgically-positioned in a bone basis restored in the posterior segment of the mandible, a treatment that may be optimized by means of clinical and paraclinical safety measurements. References 1. Bartling, R., Freeman, K. & Kraut, R.A. (1999) The incidence of altered sensation of the mental nerve after mandibular implant placement. Journal of Oral and Maxillofacial Surgery 57: Dula, K., Mini, R., van der Stelt, P.F. & Buser, D. (2001a) The radiographic assessment of implant patients: decision-making criteria. International Journal of Oral Maxillofacial Implants 16: Kiyak, H.A., Beach, B.H., Worthington, P., Taylor, T., Bolender, C. & Evans, J. (1990) Psychological impact of osseointegrated dental implants. International Journal of Oral and Maxillofacial Implants 5: Ellies, L.G. (1992) Altered sensation following mandibular implant surgery: a retrospective study. Journal of Prosthetic Dentistry 68: Buser, D. & von Arx, T. (2000) Surgical procedures in partially edentulous patients with ITI implants. Clinical Oral Implants Research 11 (Suppl. 1): de Beukelaer, J.G., Smeele, L.E. & van Ginkel, F.C. (1998) Is short-term neurosensory testing after removal of mandibular third molars efficacious? Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology 85: Dula, K., Mini, R., van der Stelt, P.F., Sanderink, G.C., Schneeberger, P. & Buser, D. (2001b) Comparative dose measurements by spiral tomography for preimplant diagnosis: the Scanora machine versus the Cranex Tome radiography unit. Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology 91: volume 15 issue 2 April / June 2011 pp

5 POST-IMPLANT NEUROLOGICAL COMPLICATIONS IN THE HORIZONTAL MANDIBULAR ARCH 8. Todd, A.D., Gher, M.E., Quintero, G. & Richardson, A.C. (1993) Interpretation of linear and computed tomograms in the assessment of implant recipient sites. Journal of Periodontology 64: Kim, K.D., Jeong, H.G., Choi, S.H., Hwang, E.H. & Park, C.S. (2003) Effect of mandibular positioning on preimplant site measurement of the mandible in reformatted CT. International Journal of Periodontics and Restorative Dentistry 23: Frei, C., Buser, D. & Dula, K. (2004) Study on the necessity for cross-section imaging of the posterior mandible for treatment planning of standard cases in implant dentistry. Clinical Oral Implants Research 15: Jovanovic, S.A., Spiekermann, H. & Richter, E.J. (1992) Bone regeneration around titanium dental implants in dehisced defect sites; a clinical study. Internãtional Journal of Oral & Maxillofacial Implants 7: Hanazawa, T., Sano, T., Seki, K. & Okano, T. (2004) Radiologic measurements of the mandible: a comparison between CT-reformatted and conventional tomographic images. Clinical Oral Implants Research 15: Harris, D., Buser, D., Dula, K., Grondahl, K., Haris, D., Jacobs, R., Lekholm, U., Nakielny, R., van Steenberghe, D. & van der Stelt, P. (2002) E.A.O. guidelines fo the use of diagnostic imaging in implant dentistry. A consensus workshop organized by the European Association for Osseointegration in Trinity College Dublin. Clinical Oral Implants Research 13: Lindh, C., Petersson, A. & Klinge, B. (1995) Measurements of distances related to the mandibular canal in radiographs. Clinical Oral Implants Research 6: Lang, N.P., Hammerle, C.H., Bragger, U., Lehman, B. & Nyman, S.R. (1994) Guided tissue regeneration in jawbone defects prior to implant placement. Clinical Oral Implants Research 5: International Journal of Medical Dentistry 201