60 Chapter 3.1 (nine implants). In all but five cases, two fixtures were placed on the indicated side, one acting as a ‘‘sleeper.’’ One implant was lost before the second-stage surgery; therefore, 175 implant systems were fitted with abutments and followed from this point. Patient demographics and systems implanted by each surgical technique are provided in Table 1 for direct comparison. 3.1 Second Stage Interval Analysis The mean healing period between stage one and stage two was 14.3 weeks (SD 3.25; range, 9–24). The longer healing periods were used for patients with very thin bone (<2 mm) or due to social factors such as medical or school commitments. 3.2 Implant Survival For the entire cohort, a median 12-month implant survival of 96.6% n = 169), implant failure rate of 2.8% (n = 5), and traumatic loss rate of 0.6% (n 1) were determined (Table 1). All but one implant loss occurred before the 6-month review, the exception being traumatic loss, which occurred between the 6 and 12 months reviews. Lost implant systems were replaced outside this study. All data from the patients up to the point of implant loss were included in the analysis. There was no statistically significant difference in the implant survival rate for the group of implants installed with minor soft tissue reduction (31 implants) compared with those that had no soft tissue reduction (145 implants) (failure rates of 3.2 and 3.8%, respectively). Most implants were 3 mm long (n 124, 70.5%) and considered the fixture of choice when the thickness of calvarial bone was less than or equal to 2 mm. These fixtures were placed with a low torque of 25 to 30 Nm2 and where possible positioned flush with the calvarial bone. Spontaneous implant loss occurred in four female patients and one male patient aged 4 to 15 years (median 7). One 3-mm implant failed before the second stage of surgery, two implants (3 and 4 mm) failed by the 3-month review, and the remaining two (3-mm) failed by 6 months. Two patients within this group had undergone single stage procedures performed by two different operating surgeons which were recorded at the 3 and 6 month review points.
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