How long do dental implants last?
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There exists a series of clinical and radiological criteria for the identification of an implantation success.
Of course, the patient counts freedom from pain as a success, but pain is a very unreliable partner in medicine. For example, as a rule, malignant tumors are only painful shortly before the end. A general rule in medicine is that slow changes are rarely painful, while only acute changes are noticed as pain.
So what constitutes a successful implant? The doctor does not just evaluate pain, he has a series of negative criteria whose absence is a condition for success and at whose occurrence a failure must be admitted. A successful implant must be clinically fixed in the jaw, be free of any inflammation and pain, and not show any loss of bone.
In most implant systems, a loss of bone around the implant can be observed in the first two years. This is probably due to the implant superstructures, the so-called abutments.
However, since most implant systems do not have a conus, but a plug connection, the initial bone resorption is defined as “normal”. In this process, the decrease of the height of the bone around the implant should not be more than 0.2 mm after the second year following the implantation. The majority of the loss is registered in the first year, both in toothless jaws as well as in partially edentulous jaws, with a decrease of around 0.4 – 0.5 mm / year, while only 0.1 – 0.2 mm / year are measured in the second year and the years following that. Implants performed in combination with bone augmentations show a significantly higher resorption rate in the first year (1.1 mm), but approaching that of the area bone in the subsequent progress.
Conical connection between implant and abutment
Physicians use standardized analytical processes in order to assess the success rate of an implant system. A common procedure is the analysis of the retention period: Contrary to the frequently used ratio calculated between all failed implants and all placed implants (“Input-Output Statistics”), the analysis of the retention period results in a realistic representation of the failures. In this case, the probability of the loss of an implant is calculated based on its retention time. Since the effect relating to the retention period is missing in the simple “input-output statistics”, their failure rates are significantly lower. However, in the calculation of corrected failure rates, there is also a degree of uncertainty due to the fact that the individual implant, the patient, or the implant-supported construction can be subject of the success assessment as a “calculation unit”.
So when you read an implant statistic, it is important that the correct analysis method was used. At the present time, hundreds of thousands of implants of varying kinds are placed worldwide every year. Unfortunately, the evaluation of the life span and thus the success rate of implants in the various areas of application are conducted in very different ways! The multitude of possible approaches mentioned above, the definition of the inclusion and exclusion criteria of different studies, as well as the variable definition of what constitutes an implant success complicate the assessment of the results and the comparability of the surveys among them.
Nevertheless, scientifically substantiated long-term results have been documented for the most common implant systems that are anchored in the bone by now, while such data has not yet been presented for other systems such as, for example, implants underneath the periosteum or ceramic implants.
Depending on the implant system used, the success probability for implants in toothless lower jaws for bar-supported provisions in implant-related statistics after 8-10 years is given with 88-97% and in patient-related statistics after 5 or 8 years with 95 and 97%. For fixed, conditionally removable replacements, the success rate in implant-related statistics after 8 years is between 92 and 98% and in patient-related analyses 86%.
Thanks to such analyses, news findings are still being arrived at. Thus, for example, a perforation of the osseous sinus cavity floor during the placement of the implant in the upper jaw apparently does not influence the prognosis for the placed implants. Nevertheless, one should be careful not to injure the sinus cavity during the implantation. It is postulated that implants, which are projecting into the sinus cavity, can be more easily infected in a sinus cavity infection within the course of a simple infection. However, there are still very few studies regarding this point.
A lack of a stable anchoring after the healing phase of the implants or a loss due to functional stress express themselves clinically through a mobility of the implant and would necessitate a removal. Reasons for such a failure during the healing phase could be an improper action during bone preparation with a thermal injury to the bone, an infection of the implant bedding during the healing phase, premature mechanical stress, or structurally weak bone bedding.
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