Study was terminated due to the difficulty in identifying suitable participants.

In recent years, dental implants have gained popularity as the treatment choice for replacement of missing teeth. With this, one of the late biological complications that arise is peri-implantitis. Based on a consensus conference in 2008, peri-implantitis was found in 28% and ≥ 56% of subjects and in 12% and 43% of implant sites (Zitzmann & Berglundh 2008). Detection of peri-implantitis is currently based on clinical parameters like probing depths and radiographic findings of bone loss. There is however no study that assess the variability of clinical probing and radiographic reading in relation to the true outline of the peri-implantitis lesion. The present study will measure variability of clinical probing and radiographs in relation to the true outline of the peri-implantitis lesion, as well as assess the use of 2 different bone substitutes in regenerating the lesions with a barrier membrane.

Identification of peri-implant bony lesions by clinical parameters or radiographs alone may sufficiently reflect the topographical outline of a peri-implant bony lesion. To date, no comparative studies are available that identify the accuracy of clinical parameters or radiographs in outlining the extent and the severity of the lesion. If these parameters are of sufficient accuracy, surgical procedures to regenerate the lesion may be more predictable to plan.

The study population will be patients undergoing regular implant maintenance care in the National Dental Centre Singapore, Periodontics Unit, Department of Restorative Dentistry and yielding peri-implantitis (residual probing depths ≥6mm and bleeding on probing, bone loss of ≥2mm documented on periapical radiographs).

In the first part of the study, the variability of the clinical parameters and periapical radiographs will be assessed and compared to the actual bony lesions revealed after surgical access. This prospective cohort study will encompass 24 subjects. In the second part of the study, a randomised controlled clinical trial will be staged exploring the clinical outcomes of regenerative therapy of the peri-implant lesions applying 2 different bone substitutes with a barrier membrane for the principle of guided bone regeneration (GBR).

First part of study:

The null hypothesis is that of no difference in the mesial and distal radiographic readings as compared to the measurement obtained by clinical probing of the actual peri-implant lesions. The null hypothesis is also that of no difference between probing depth measurements and the actual lesions measured under open access.

Second part of study:

The null hypothesis is that of no difference in clinical outcomes with the use of a synthetic membrane (Guidor®) with a compound of biphasic calcium phosphate, 60 % hydroxyapatite and 40 % beta-tricalcium phosphate (Guidor easy-graft® CRYSTAL) (test) when compared to the same membrane and phase-pure beta-tricalcium phosphate (Guidor easy-graft® CLASSIC ) (control), in GBR of peri- implantitis lesions.

End Points - Efficacy For the subjects, the potential benefits may include improvement in the clinical outcomes.

End Points - Safety The risks involved include complications that may result with all surgeries, i.e., risk of infection, swelling, pain and bruising.

Inclusion Criteria:

1. Medically healthy adults (ASA classification I-II), at least 21 years of age.
2. Diagnosed with peri-implantitis (at least one site with PPD of ≥ 6 mm, a positive bleeding on probing (BOP) and radiographic bone loss of ≥ 2 mm).
3. Had non-surgical therapy performed previously
4. Ability to comply with 6-month study follow-up.

Exclusion Criteria:

1. Medically compromised subjects (ASA classification III-V).
2. Had not gone through non-surgical therapy
3. Known allergy or other severe adverse reactions to the synthetic membrane and bone substitutes.
4. Self declared pregnancy or intend to conceive.