80 Chapter 3.2 In this study the procedure was performed using one of three techniques: Method 1: Linear incision for implant placement followed by a linear incision with no skin reduction for second stage. Method 2: A ‘U’ shaped incision for implant placement followed by a 4 mm skin punch with no skin reduction for second stage. Method 3: ’S’ shaped skin incision for stage one with no skin reduction followed by a 4 mm skin punch with slight skin reduction for second stage. Single stage procedures were performed in an identical fashion. Calvarial bone depth was measured indirectly by the subjective comparison to the bur and its guide. These devices are measured pre-operatively and as there is no variation in operating drill systems this remains uniform across all surgeons. No objective measuring device is used however the burr and guide provide the three important depths of assessment. The cutting end (ball) is 1 mm in depth, the guide cover is 2 mm and to the shaft of the burr 3+mm. These comparisons were used and recorded. 2.4 Implant and abutment The implant was the Ponto BHX implant (diameter, 4.5 mm; length 3 or 4 mm) (Oticon Medical AB Askim, Sweden). Ponto BHX with pre-mounted abutments of lengths 6, 9 and 12 mm were used for single stage surgeries. Abutment lengths of 6, 9, and 12 mm were used at the second stage Surgeries for all other children. 2.5 Follow up and review The second stage surgery for abutment placement occurred following a minimum of a threemonth osseointegration period. Following abutment placement clinical review was arranged at week 1 and 2, then at a 3, 6, 9 and 12 month points. Complications, revision rates, skin reactions according to Holger Classification, loss of abutment, implant failures and abutment level ISQ (Osstell ISAM. Osstell AB, Goteborg, Sweden) were documented at each review. Holgers ≥2 were considered as adverse skin reactions. Fixture and abutment level ISQ were recorded at each surgical stage and subsequently only abutment level ISQ was obtained. Two recordings were taken in perpendicular directions (ISQ H and ISQ L). 2.6 Statistical analysis All data was analysed using Stata 16 version 16.1 (StataCorp LLC, Texas USA). Categorical data were presented as n (%) and numeric data as mean (SD) and range or mean (95% CI). To assess the effect of time from surgery on the ISQ, a mixed effect model was applied, and comparisons were done using the data from the time of surgery as the baseline. The results were presented as coefficients or means with the appropriate confidence interval and p levels significance set at p = 0.01.
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