Premature Wear of Dental Implants

Change in the dominant side of mastication as an important factor for adjusting the prophylaxis strategy for implant-supported fixed dentures with limited lateral defects

Researchers from RUDN University have discovered that the cause of premature wear of dental implants is the change in the usual side of chewing.

It was concluded that this not only makes it difficult to get used to the prosthesis, but also leads to pathological changes in the bone tissue of the jaw. This discovery will help dentists plan the recovery of patients after placing implants. The results were published in the  European Journal of Dentistry .

Every year, up to 2 million dental implants are placed in the world, on top of which fixed prostheses are placed. This is an effective way to restore a missing or deformed tooth without affecting the patient’s quality of life. Modern implants are usually made of titanium, are strong and take root quickly in the jaw. The only problem is premature wear in 4-5% of cases, which is caused by microdamage due to incorrect calculation of the load on the implant before the operation.

Consequently, the union of the metal with the bone breaks down, bacteria enter the implant, giving rise to the inflammatory process. Dentists from RUDN University have suggested that loads on the implant appear due to changing the usual side of chewing in the first months after surgery.

Most people do not chew food symmetrically on both sides of the jaw. Up to 75% of movements are carried out on the usual chewing side. When there is a diseased tooth, the patient can change the usual side of chewing. It takes 3 to 4 months to get used to a denture. During this time, the type of chewing and the load on the teeth change.

Therefore, the patient can get used to chewing on the wrong side of the jaw, just before the operation, when the load on the implant has already been calculated. However, until now it had not been investigated how a radical change in chewing habits could affect the condition of dental implants.

RUDN University dentists monitored the recovery of 64 patients after placing dental implants. The study included only adults, who needed prosthetics strictly on one side of the jaw.

Surgery on both sides at the same time would not allow us to compare the effect of changing the usual chewing side. Before the operation and after it (twice in a year), specialists took x-rays of the teeth, measured the strength of the chewing muscles and, in some cases, performed tomography of the jaws. Treatment results were evaluated using questionnaires.

40 patients (62.5%) changed their usual chewing side after the operation. Dentists at RUDN University have suggested that this happens very frequently, since after placing prostheses, people return to the type of chewing that was usual before losing a tooth.

The dentists compared this group of patients with those who maintained the same chewing side and discovered that changing sides caused more problems in bone formation. X-rays of 4 patients in the group who changed the chewing side showed the first signs of lesions in the tissue around the implant.

• Among patients whose chewing side did not change, only one case was found.
   
• In the first six months after the operation, patients who changed their chewing side rated their adaptation to the prostheses on average 22% worse than patients who did not make the change.

"Changing the usual side of chewing is an important factor in the patient’s adaptation to dental implants.

And as our research shows, it can also be the cause of pathological processes, which can lead to the loss of an implant.

Dentists should be aware of the incidence of such changes, consider them when developing plans for the postoperative rehabilitation of their patients and during periodic check-ups," said Igor Voronov, Doctor of Medical Sciences, Professor of the Department of Dental Orthopedics at RUDN University. .

Discussion

Analyzing the results obtained, we start from the notion that the indicators of the two methods of investigation of the masticatory function used reflect quite well the specificity of the adaptation to dentures and complement each other when used together.

Using the finite element method, Alvarez-Arenal et al concluded that, in terms of loads along the axis of the implant and the abutment, it is not recommended that repeated forces exceed 150 N, while for lateral and rotational loads even Forces of 40 N can be negative.

Furthermore, the condition in the oral cavity that we observe before prostheses is related in many aspects to dynamic changes in interocclusal relationships, which, by definition, are not normal at the time of obtaining the occlusogram.

In their recent large review, Graves et al indicate that there is debate about how much of a role occlusion plays in posterior implant stability and the incidence of peri-implantitis. They conceive that these discussions are probably determined by the extreme diversity of implants and their design. All other things being equal, the closer to physiological norms the occlusal surfaces are formed, the lower the risk of developing late complications of dental implantation.

The emergence of so-called solid freeform manufacturing technologies or rapid prototyping technologies gave the opportunity to manufacture specially designed products directly from a computer model with specific shapes and porosity.

In this case, the occlusal relief of the restored tooth is selected from the database and customized for a particular patient. At the same time, there are limitations due to the lack of long-term studies or clinical trials, especially in relation to the prediction of the life cycle of such prostheses.

Anyway, Diment et al show in a large meta-analysis that of 350 evidence-based clinical trials comparing the results of 3D printing for clinical purposes using routine technologies, 58.3% of the studies were conducted in the field of oral and maxillofacial surgery, which included dentistry and orthopedic surgery of the jaw, face and skull, and those covering the musculoskeletal system (23.7%) made up the second group.

It was concluded that the 3D printed devices outperformed their conventional comparators. At the same time, it is clear that more rigorous, long-term evaluations are needed to determine whether 3D printed devices are clinically relevant before they become part of standard clinical practice.

Studies of 804 patients from Osaka Dental University, divided into pre- and post-implant groups and subgroups based on the number of remaining dental supports according to the Eichner classification, showed that subjective evaluation of treatment expectations and results is very variable and multifaceted. . The participants were evaluated using the general questionnaire: the General Oral Health Assessment Index and the oral health-related quality of life questionnaire.

While before the start of treatment, the total score on the questionnaire depended significantly on the volume of upcoming prostheses, after the end of treatment, there was practically no dependence. The authors once again emphasize that when evaluating the results of orthopedic treatment in dentistry, much depends on the subjective expectations of the patient. 

The treatment satisfaction questionnaire was specifically developed to assess the importance of age, sex, readiness to improve oral hygiene, specific treatment duration, and implantation volume. In total, 182 patients underwent the survey, and the duration of prosthesis use averaged 2.5 to 5.0 years. A significant relationship was found between the comfort indicator and prior information to the patient about the nature and characteristics of the upcoming treatment, between the general experience of treatment with dentists and the conscious decision to choose dental implantation as a method of said treatment.

The results obtained emphasize the need to transmit logical and truthful information to patients when considering the next treatment using dental implants.

The most informed patient will have realistic expectations, which will ultimately be realized with a high degree of satisfaction.

Our study has shown that adaptation to fixed dentures is accompanied by a period of relatively high and unusual loads on the mounted dentures due to increased functional activity of the masticatory muscles. As a result, within a 3- to 6-month adaptation period to non-fixed dentures supported by intraosseous implants, almost two-thirds of patients returned to the usual functionally dominant side of chewing.

This process, as the results of our study showed, is accompanied by a temporary decrease in satisfaction with the results of the treatment, both from the point of view of the dentist and the patient. This, in particular, is associated with a period of relatively high and unusual loads on mounted dentures due to increased functional activity of the masticatory muscles. Uncontrolled loads on implant-supported intraosseous dentures can cause microtrauma, penetration of infections into the osseointegration zone and contribute to its violation due to the development of secondary complications up to the loss of implants.