A Positive Correlation Between Occlusal Trauma and Peri-implant Bone Loss: Literature Support

To what extent does the crown-implant ratio affect the survival and complications of implant-supported reconstructions? A systematic review

OBJECTIVE

To evaluate the occurrence of biological and technical complications with respect to the crown-implant (C/I) ratio of implant-supported reconstructions.

MATERIAL AND METHODS

Electronic (MEDLINE) and hand searches were conducted for longitudinal prospective studies with a follow-up period of at least 4 years. One reviewer performed screening and data abstraction. The following complications were evaluated: implant survival, peri-implant crestal bone loss, implant fracture, and technical complications related to implant components and suprastructure.

RESULTS

The search provided 41 articles and abstracts, seven of which were selected for full-text analysis. Only two articles were finally included. A qualitative data analysis revealed that the survival rate of implant-supported reconstructions with a C/I ratio of more than 2 was 94.1%. In addition, peri-implant crestal bone loss seemed not to be influenced by the C/I ratio of the implant rehabilitation, except in one study, which noted greater crestal bone loss with lower (<1) compared with higher (>2) C/I ratios. Technical complications related to implant components and suprastructure according to different C/I ratios were not found in any of the studies.

CONCLUSIONS

Despite the diversity among studies with respect to data collection and study design, the current literature shows that the C/I ratios of implant-supported reconstructions do not influence peri-implant crestal bone loss.

Influence of implant connection type on the biomechanical environment of immediately placed implants - CT-based nonlinear, three-dimensional finite element analysis

PURPOSE

The purpose of the present study was to evaluate the biomechanical environment of immediately placed implants, before and after osseointegration, by comparing three different implant-abutment connection types.

MATERIALS AND METHODS

A computer tomography-based finite element model of an upper central incisor extraction socket was constructed containing implants with either external hex, internal hex, or Morse-taper connection. Frictional contact elements were used in the bone, implant, abutment, and abutment screw interfaces in the immediately placed simulations. In osseointegrated simulations, the repair of bone alveolar defect and a glued bone-to-implant interface were assumed. By analysis of variance, the influence was assessed of connection type, clinical situation, and loading magnitude on the peak equivalent strain in the bone, peak von Mises stress in the abutment screw, bone-to-implant relative displacement, and abutment gap.

RESULTS

The loading magnitudes had a significant contribution, regardless of the assessed variable. However, the critical clinical situation of an immediately placed implant itself was the main factor affecting the peak equivalent strain in the bone and bone-to-implant displacement. The largest influence of the connection type in this protocol was seen on the peak equivalent stress in the abutment screw. On the other hand, a higher influence of the various connection types on bone stress/strain could be noted in osseointegrated simulations.

CONCLUSIONS

The implant-abutment connection design did not significantly influence the biomechanical environment of immediately placed implants. Avoiding implant overloading and ensuring a sufficient initial intraosseous stability are the most relevant parameters for the promotion of a safe biomechanical environment in this protocol.

Implant success, survival, and failure: the International Congress of Oral Implantologists (ICOI) Pisa Consensus Conference

The primary function of a dental implant is to act as an abutment for a prosthetic device, similar to a natural tooth root and crown. Any success criteria, therefore, must include first and foremost support of a functional prosthesis. In addition, although clinical criteria for prosthetic success are beyond the scope of this article, patient satisfaction with the esthetic appearance of the implant restoration is necessary in clinical practice. The restoring dentist designs and fabricates a prosthesis similar to one supported by a tooth, and as such often evaluates and treats the dental implant similarly to a natural tooth. Yet, fundamental differences in the support system between these entities should be recognized. The purpose of this article is to use a few indices developed for natural teeth as an index that is specific for endosteal root-form implants. This article is also intended to update and upgrade what is purported to be implant success, implant survival, and implant failure. The Health Scale presented in this article was developed and accepted by the International Congress of Oral Implantologists Consensus Conference for Implant Success in Pisa, Italy, October 2007.

Impact of implant overloading on the peri-implant bone in inflamed and non-inflamed peri-implant mucosa

OBJECTIVE

To assess the impact of overloading on peri-implant bone level and the bone-to-implant contact (BIC) in the presence of healthy or inflamed peri-implant tissues.

MATERIALS AND METHODS

Four screw-shaped machined implants were placed bilaterally in the mandible of four beagle dogs and left submerged for 3 months. Prosthetic abutments were connected either in supra-occlusal contact with the opposite teeth (overloaded) or in infra-occlusal position (unloaded). In each dog, cotton floss ligatures were placed unilaterally around abutments to promote plaque accumulation; the contralateral side was brushed three times a week. There were four experimental sites, two implants in each: loaded uninflamed (LU), loaded inflamed (LI), unloaded uninflamed (UU), and unloaded inflamed (UI). Clinical and radiographic parameters were recorded at baseline and every 3 months throughout the observation period. At 12 months, the dogs were sacrificed and histomorphometric analysis was performed.

RESULTS

Implants with ligature-induced peri-implantitis presented high inflammatory indices throughout the observation period. Clinical parameters did not change from baseline for both LU and UU. Loading significantly increased the percentage of BIC (BIC%) (P<0.05) and slightly increased crestal bone resorption, but not apical to the implant neck. Both LI and UI groups showed significant peri-implant bone loss (P<0.01), mostly horizontal on the buccal aspect and angular on the lingual aspect, which exposed implant threads. Loading significantly (P<0.05) increased implant thread exposure due to buccal and lingual vertical bone resorption.

CONCLUSIONS

In the presence of uninflamed peri-implant mucosa, overloading of implants in the dog model increased BIC% and slightly reduced marginal bone level. However, resorption did not progress beyond the implant neck. Overloading aggravated the plaque-induced bone resorption when peri-implant inflammation was present.

Schwann cell graft: A method to promote sensory responses of osseointegrated implants

Osseointegrated dental implants have been widely used in clinics to restore the missing teeth of patients. Since there are no periodontal ligament and associated Ruffini endings in the peri-implant tissues, sensory thresholds of the implant are much higher than those of natural teeth, and its self-protective reflex is quit poor. Implant fracture or aggressive bone loss sometimes occurs because the patient cannot feel the overloads exerted on the implant. Until now, no available method has been issued to solve such a problem. Schwann cell is the glial cell of peripheral nerve system. It has been widely accepted to play indispensable roles during neural development and regeneration. Its mechanism includes forming Büngner's band, producing neurotrophic factors, synthesizing surface cell adhesion molecules, and elaborating basement membrane. Furthermore, Schwann cell is quite important for the periodontal Ruffini endings. Applying these functions of Schwann cells, we put forward a hypothesis that transplanting Schwann cells into the implant site can be a method to promote sensory responses of the dental implants.

Influence of forces on peri-implant bone

Occlusal forces affect an oral implant and the surrounding bone. According to bone physiology theories, bones carrying mechanical loads adapt their strength to the load applied on it by bone modeling/remodeling. This also applies to bone surrounding an oral implant. The response to an increased mechanical stress below a certain threshold will be a strengthening of the bone by increasing the bone density or apposition of bone. On the other hand, fatigue micro-damage resulting in bone resorption may be the result of mechanical stress beyond this threshold. In the present paper literature dealing with the relationship between forces on oral implants and the surrounding bone is reviewed. Randomized controlled as well as prospective cohorts studies were not found. Although the results are conflicting, animal experimental studies have shown that occlusal load might result in marginal bone loss around oral implants or complete loss of osseointegration. In clinical studies an association between the loading conditions and marginal bone loss around oral implants or complete loss of osseointegration has been stated, but a causative relationship has not been shown.