Selecting implant techniquesNews
Posted by: The Probe 25th February 2020
For many patients dental implants are – aesthetically and functionally – the best means available to treat edentulism. Success rates of 90-95% after a decade are commonly reported. However, as with any surgical procedure, complications do remain a possibility. Host factors, the implant site, surgical method and the design of the implant, can all have a bearing on the success of treatment.[i]
Many complications can be avoided through careful case selection and preoperative planning. The general health and behaviours of the patient can be a risk factor, as is the case for smokers, diabetic patients and those with epilepsy, among others. There are also aspects of a patient’s medical history that may present an absolute contraindication to treatment, such as strong immunosuppression after an organ transplant.i These and other host factors can be easily screened for.
Localised anatomical factors can influence the success of procedures and increase the potential for complications. Numerous surgical techniques and implant systems have been developed in response to particular challenges that can arise from specific anatomical factors.
In many cases the primary limiting factor concerning dental implants is the quality and quantity of bone in the region. Once a permanent tooth is extracted or lost, bone resorption is a biological inevitability. Bone structure is adaptive and remodels in response to strain; the absence of a tooth reduces strain on the area beneath it, leading to reductions in the buccolingual and apicocoronal dimensions of the alveolar ridge.[ii] In addition to the normal bone remodelling process, periodontal disease and other conditions can result in inadequate bone tissue.
The insertion of a titanium implant results in increased stiffness in the mandible, making it more resistant to compressive force. Theoretically, this results in a reduction in the forces the underlying bone is subject to, and can therefore result in bone resorption continuing (if not to the extent that an empty socket causes). This can be compensated for by using implants with suitably designed retention elements, which confer the needed routine strain to maintain bone mass.ii
Where the bone is inadequate to properly support an implant, this needs to be compensated for. Methods for accomplishing this include bone augmentation using grafts and sinus lift procedures, using 3D customised implants or utilising zygomatic implants.
Among bone grafts, autografts are ideal where possible as they will not result in immunogenic complications. However, this requires additional surgery at the donor site (with the potential for morbidity there), and the amount of bone available may be quite limited. Where the patient is unsuitable for autogenous grafting, graft materials from other donors, animals, or synthetic sources are also available.[iii]
Zygomatic implants are longer than conventional dental implants, allowing the prosthesis to be anchored into the cheek bone, bypassing the need for a bone graft. However, this method can still result in complications, chiefly osseointegration failure and sinusitis.[iv]
Parts of the soft tissue will also resorb relatively quickly following extraction, including the interdental papillae. Insufficient soft tissue affects aesthetic outcomes, including the potential visibility of the implant screw. Inadequate bone will also affect how well an aesthetically pleasing gingival contour can achieved. Soft tissue augmentation can be used to restore the gingival line.[v]
The inferior alveolar nerve is a branch of the mandibular nerve that relays sensation from mandibular posterior teeth, the surrounding bone structure and the mucosa of the posterior tongue.[vi]
Many patients receiving implants already exhibit significant bone atrophy, preventing the use of long fixtures. In these instances, lateralisation of the inferior alveolar nerve (LIAN), can help provide the space required to support the prosthesis in a more ideal location and avoid injury of the nerve. LIAN requires the surgeon to expose the nerve, temporarily move it aside while the implants are placed, then permit it to fall back into position. Nerve transposition is also possible, which involves a corticotomy around the mental foramen in order to reposition it. If advanced alveolar resorption has already occurred, this procedure is contraindicated.[vii]
Biological variations in this region are not unknown, with some patients having bifid or trifid alveolar nerves. A second, or third mandibular foramen can be present, which can be observed preoperatively as a double or triple mandibular canal on a conventional panoramic radiograph. If not accounted for, these variations can lead to inadequate anaesthesia or damage to the nerve, leading to bleeding, paraesthesia or neuroma development. Where bifid or trifid mandibular canals are detected, further CBCT scanning to provide confirmation and a better view of the anatomy is advisable.[viii], [ix]
If you are dealing with a complex case or have a patient with failing implants that require complex surgical intervention, consider referring your patient to the Centre for Oral-Maxillofacial and Dental Implant Reconstruction. Led by Professor Cemal Ucer – Specialist Oral Surgeon – the practice offers a wide variety of advanced procedures, including nerve lateralisation and repositioning, allografts, and zygomatic dental implants. With a wealth of experience and state-of-the-art facilities your patient will be in the best of hands.
Inadequate bone continues to pose a challenge to providing dental implants. There are numerous techniques and technologies that can help many patients, however, successfully employing the optimal solution requires careful preoperative case-selection, knowledge and surgical skill.
[i] Raikar S., Talukdar P., Kumari S., Panda S., Oommen V., Prasad A. Factors affecting the survival rate of dental implants: a retrospective study. Journal of International Society of Preventative & Community Dentistry. 2017; 7(6): 351-355. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5774056/ October 25, 2019.
[ii] Hansson S., Halldin A. Alveolar ridge resorption after tooth extraction: a consequence of a fundamental principle of bone physiology. Journal of Dental Biomechanics. 2012; 3: 1758736012456543. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3425398/ October 25, 2019.
[iii] Raghavan R., Shajahan P., Raj J., Raju R., Monisha V., Jishnu S. Review on recent advancements of bone regeneration in dental implantology. International Journal of Applied Dental Sciences. 2018; 4(2): 161-163. http://www.oraljournal.com/archives/2018/4/2/C/4-2-29 October 25, 2019.
[iv] Molinero-Mourelle P., Baca-Gonzalez L., Gao B., Saez-Alcaide L., Helm A., Lopez-Quiles J. Surgical complications in zygomatic implants: a systematic review. Medicina Oral, Patología Oral y Cirugía Bucal. 2016; 21(6): 751-757. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5116118/ October 25, 2019.
[v] Brouwers J., Buis S., Haumann R., de Groot P., Laat B., Remijn J. Successful soft and hard tissue augmentation with platelet-rich fibrin in combination with bovine bone space maintainer in a delayed implant placement protocol in the esthetic zone: a case report. Clinical Case Reports. 2019; 7(6): 1185-1190. https://doi.org/10.1002/ccr3.2177 October 25, 2019.
[vi] Yoon T., Robinson D., Estrin N., Tagg D., Michaud R., Dinh T. Utilization of cone beam computed tomography to determine the prevalence and anatomical characteristic of bifurcated inferior alveolar nerves. General Dentistry. 2018; 66(4): 22-26. https://www.ncbi.nlm.nih.gov/pubmed/29964244 October 25, 2019.
[vii] Abayev B., Juodzbalys G. Inferior alveolar nerve lateralization and transposition for dental implant placement. Part I: a systematic review of surgical techniques. Journal of Oral & Maxillofacial Research. 2015; 6(1): e2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4414233/ October 25, 2019.
[viii] Mizbah K., Gerlach N., Maal T., Bergé S., Meijer G. The clinical relevance of bifid and trifid mandibular canals. Oral and Maxillofacial Surgery. 2012; 16(1): 147-151. https://link.springer.com/article/10.1007/s10006-011-0278-5 October 25, 2019.
[ix] Kumar V. Bifid mandibular canal: an aberrant anatomic variation. Journal of Dentomaxillofacial Science. 2017; 2(2): 133-134. https://jdmfs.org/index.php/jdmfs/article/view/531 October 25, 2019.
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