Any situation that poses a risk to successful osseointegration and restoration of a dental implant at the level of the implant site and surrounding teeth must be considered.

Implant Stability

The primary stability of the implant is a critical factor for implant survival. Several methods and devices are used to measure implant stability, including subjective evaluation, resonance frequency analysis (RFA), and insertion torque. However, they are insufficient to assess the primary stability, or to provide any predictive value of implant outcome. From a clinical point of view, insertion torque value is routinely used. The surgeon should strive to achieve high insertion torque values whenever possible (35 Ncm).

Bone Density

Poor bone quality must be considered as a local risk factor. In the scientific literature, bone quality is often referred to as bone density. It is defined in terms of metabolism, cell turnover, mineralization, maturation, and vascularity; each of these factors plays a role in the osseointegration success of dental implants. Bone density is measured according to histological and morphometric analyses (Molly, 2006). The clinical evaluation of bone quality is questionable since no commercial instrument is currently available to measure bone density. Bone quality can only be evaluated by radiographic examination and confirmed during preparation of the surgical site.

Interproximal Space

The three-dimensional position of the dental implant shoulder is defined as the relationship to bone crest level of the teeth adjacent to the implant. This critical factor influences the position of the interdental papillae surrounding the implants.

Tooth–Implant

The risk of proximal bone resorption increases when the distance between the implant shoulder and the adjacent tooth is less than 1.5 mm. In esthetic areas, this lack of bone support may compromise papilla preservation. In narrow spaces, this risk can be prevented with the use of narrow implants. Decreased implant survival rate has been reported when the implant is placed too close to the tooth.

Implant-Implant

Similarly, a 3 mm horizontal distance between two dental implant shoulders is the minimum required to prevent soft and hard tissue loss.

Infected Sites

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