Features of Peri-implant Soft Tissue Early Healing Around Different Abutment Materials

Dental implants are anchored in jawbone through a direct bonding between bone and the implant. Success and survival of an implant do, however, not depend solely on osseointegration. A soft tissue, which surrounds the transmucosal part of a dental implant, separates the peri-implant bone from the oral cavity. This soft tissue collar is called "peri-implant mucosa". The soft tissue attachment to the implant surface serves as a biological seal that prevents the development of inflammatory peri-implant diseases (i.e. peri-implant mucositis and peri-implantitis) Thus, the soft tissue seal around implants ensures healthy conditions and stable osseointegration and therefore also the long-term survival of an implant. While the soft tissue seal around teeth develops during tooth eruption, the peri-implant mucosa forms after the the surgical wound created to insert the implant. The wound healing phase may occur following the closure of a mucoperiosteal flap around the neck portion of an implant placed in a so-called one-stage procedure or after a second surgical intervention for abutment connections to an already installed dental implant (two-stage procedure).

It seems that the soft tissue adhesion is influenced by the properties (abutment material and micro-topography) of the implant components that are placed in contact with the soft tissues. Abutment material was found to influence bleeding on probing (BoP) at peri-implant soft tissues, as well.

Since wound healing occurs in the presence of a biomaterial (i.e. a foreign body) at a critical region, positive or negative interferences of wound healing events with this biomaterial and adaptation of the soft tissue to this biomaterial have to be taken into consideration. Biocompatibility, soft tissue adhesion, plaque retention, mechanical behavior and esthetics are listed among the criteria of material abutment selection. Titanium remains the most reliable material given its mechanical resistance, biocompatibility, modification of surface increasing cell adhesion and plaque retention. However, in the case of increased esthetics demands, particularly for thin biotype, zirconia and ceramics aluminum abutments give better results with comparable technical and biological outcomes to titanium abutments.

Polyetheretherketone (PEEK) is a strong thermoplastic material produced from polyetheretherketone resin. Because of its high mechanical strength and durability, good electrical characteristics and outstanding resistance to hydrolysis, PEEK has been used extensively in aerospace, automotive, chemical, electronics, petroleum, and food and beverage industries. Recently, a medical-grade PEEK was developed. Medical-grade PEEK has the same physical properties as PEEK; however, PEEK-OPTIMA™ is also biocompatible, has high chemical resistance and resists several different sterilization methods. It is noteworthy to mention that PEEK has an elastic modulus similar to that of the bone preventing marginal bone loss in case of occlusal overload. Due to the aforementioned properties, PEEK has been used as abutment material.

Morphology of the abutment deserves considerations, as well. Some physiological soft-tissue recession can be seen in time around implant restorations when a divergent emergence profile (the most common) is chosen next to the soft tissue. Recently it has been shown how some gingival coronal migration can be seen with the use of tapered emergence profile abutments. In fact, by using these tapered abutments or an implant design with a tapered shape at the neck implant level (transmucosal level), not only soft tissue migration but also hard tissue migration could be achieved over time.