80 Chapter 5 Outcome measures The study’s primary outcome measures were implant and overdenture survival. Secondary outcome measures were marginal bone level change (MBLC), clinical outcome measures (presence of plaque and calculus, mucosal health, bleeding on probing and pocket depth change (PDC)), masticatory performance, patient related outcome measures (PROMs) and complications. Implant and overdenture survival, MBLC and clinical outcome measures were evaluated after 1 month (T1) and 12 months (T12) after placement of the prosthesis. Complications were recorded throughout the entire follow-up period. Masticatory performance and PROMs were evaluated prior to treatment (T0) and at T12. Implant and overdenture survival Implant survival was defined as the percentage of initially placed implants still present and immobile at T12. Implant mobility was assessed by performing a percussion test. Overdenture survival was defined as the percentage of overdentures still present at the follow-up evaluation. Marginal bone level change Intra-oral radiographs were made at T1 and T12 to assess the MBLC. The radiographs were standardised with the paralleling extension-cone technique by using a corresponding system (RINN, Dentsply, Elgin, IL, USA). The solitary attachments were digitally cropped from the digital radiographs, aiding in blinded assessment. By using computer software (Biomedical Engineering, UMCG, the Netherlands) the marginal bone level change was then assessed, utilising the implant diameter (3.5 mm) for measurement calibration and using the neck of the implant as a horizontal reference line. Measurements were done by one examiner (HJAM) at the mesial and distal side of the implant and from the neck of the implant to the crestal bone, perpendicular to the reference line. This measurement method was evaluated by Telleman et al.13 with a Cronbach’s alpha of 0.867 which is similar to an almost perfect agreement. MBLC was defined as the difference in bone height between the measurements made at T1 and T12. Clinical outcome measures Measurements were done by one examiner (PO). • Probing depth (PD) was measured the mesial, vestibular, distal and oral site of each implant using a manual periodontal probe. The distance between the marginal border of the mucosa and the tip of the periodontal probe was noted as probing depth. PDC was calculated by subtracting the measurements of T1 from T12. • The presence of plaque was assessed by using the index described by Loë and Silness14, ranging from 0 to 3, corresponding with no plaque detection (0); plaque accumulation after probing (1); visible plaque detection (2); and an abundance of visible plaque (3). • The presence of calculus was scored 0 or 1, corresponding with the absence (0) or presence of calculus (1), respectively. • The health of the peri-implant mucosa was assessed by using the modified Löe and Silness index14, ranging from 0 to 3, corresponding with normal mucosa (0); mild inflammation with
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