The Impact of Peri-implant Soft Tissue Properties on Patient-reported and Clinically Assessed Outcomes: A Prospective Study

In the oral cavity, the soft tissue of the alveolar ridge can be classified as keratinized mucosa (KM) or alveolar mucosa (AM). Typically KM forms a cuff around an implant, while AM is farther away and covers the alveolar ridge, as well the lips, the inside of the cheeks, the floor of the mouth under the tongue. KM is pink in color and has a keratinized epithelium. AM is red and has a non-keratinized epithelium. Due to anatomical or surgical reasons KM on the buccal site might be missing. Therefore implants without KM have AM directly around their collar. The two groups in the research will be defined according to the presence or absence of KM. Group 1 will be implants with KM and Group 2 implants without KM. In Group 2 AM will be directly present around the implant.

Although specific situations recommend a minimal width of 2 mm of keratinized tissue around teeth to prevent gingival inflammation, the influence of keratinized tissue on peri-implant clinical and patient-reported outcomes still needs to be investigated. Many authors have stated that that the presence of peri-implant keratinized mucosa is a prerequisite for the maintenance of soft tissue health and have advocated for soft tissue augmentation procedures around implants. Nevertheless, since other authors failed to demonstrate a significant association between clinical inflammatory parameters and the quality of peri-implant mucosa, soft tissue augmentation procedures are not recommended, unless the patient reports pain and discomfort while brushing around an implant without KM or unless there are esthetic concerns. Those recommendations are however not evidence-based. To the best of our knowledge no prospective studies have been conducted to evaluate systematically discomfort during brushing at implant sites and patient soft tissue esthetic assessment, with special emphasis on the quality of peri-implant soft tissue.

Dental implants can be placed according to a one-stage or a two-stage protocol. For two-stage implant surgery, as is required for this study, there are the following steps (stages).

1. Implant placement surgery occurs. At this time, the implant is placed in the bone. A cover screw is placed on top of the implant and then covered with mucosa (gums).
2. After a period of a few months to allow for healing, the mucosa (gums) on top of the implant is opened making a small incision. The cover screw is removed. Then, an additional implant piece called a healing abutment is placed that penetrates through the gums. This healing abutment allows for soft tissues to heal around the implant abutment before an impression is made for the manufacture of the implant crown.

Additional steps are then required for placement of the implant crown (artificial tooth). For this study, the baseline visit will be at the time of step 2. The implant will already have been placed previously and the patient will be returning to the clinic for their scheduled second stage surgery.