Objective: This study investigated how patients' knowledge, attitude, and perceptions influence their oral hygiene practices as well as peri-implant health. Materials and Methods: Participants with single implant crowns placed in 2007-2011 completed a questionnaire that examined their knowledge, attitude, and perceptions on oral hygiene practices and peri-implant health before receiving a periodontal examination, prophylaxis, and oral hygiene education. Clinical parameters recorded were peri-implant probing depths and plaque index, width of keratinized mucosa, implant crown characteristics, reason for tooth loss, and diagnosis of peri-implant health.

First, a trained clinical research dental assistant interviewed the participants and showed them pictures of oral hygiene aids so that the participants could answer the survey questions accurately. Subsequently, a periodontal examination, dental prophylaxis, and oral hygiene education were performed. Participants with active diseases e.g. caries, periodontitis, or peri-implantitis were referred for further management. The following clinical parameters were recorded during the examination:

1. Probing depths at 6 sites around the implant (mesiobuccal, midbuccal, distobuccal, distolingual, midlingual and mesiolingual)

2. Plaque index (Silness & Loe 1964) at 4 sites around the implant (mesial, buccal, distal and lingual)

3. Amount of keratinized mucosa at the implant site

4. Characteristics of the implant crown:

   • Type of implant crown (screw- or cement-retained) and
   • Position of crown margins (supra-, equi- or sub-gingival)

5. Reason(s) for tooth loss

6. Diagnosis of peri-implant health

   • Normal
   • Mucositis, defined as 3 or more bleeding points per implant
   • Peri-implantitis, defined as implant thread exposure that was either clinically visible or detectable with a periodontal probe.

Inclusion Criteria:

• English speaking patient
• Aged 21 years old or above
• Received at least 1 implant-supported single crown from NUH in the year 2007-2011 (in functional loading for at least 5 years)

Exclusion Criteria:

• Implant is used to restore overdentures or multi-unit restorations such as splinted crowns, fixed partial dentures, and cantilevers.
• Pregnant/lactating women
• Parkinson's disease or any other debilitating diseases
• Physical or mental disabilities that may impair oral hygiene practices
• Poorly controlled diabetes
• Heavy smoker (10 or more cigarettes per day)
• Radiation therapy in head and neck region
• HIV, TB, hepatitis or other infectious diseases
• Drug and alcohol abuse

Study population is made up 50.6% male and 49.4% female, mainly Chinese (87.3%), Indian (5%), Malay (3.8%), Caucasian (1.3%), Eurasian (1.3%), and Japanese (1.3%), with a mean age of 58.6 years old.