After 24 months, success rates of the two-piece ceramic implants showed no significant difference compared to control two-piece titanium implants. The bonded zirconia implant abutment connection appears to be capable with clinical application over the observed period. However, further control measurements need to confirm the presented data.
Clinical and radiographic parameters demonstrated a 95% integration of immediately loaded zirconia single-piece implants. A long-term randomized-controlled clinical trial was initiated to confirm evidence of this protocol.
Objectives
To prospectively evaluate, as part of an ongoing randomized pilot trial, the clinical outcomes of two‐piece zirconia implants in comparison with titanium implants 80 months after delivery of all‐ceramic (lithium disilicate) single‐tooth restorations.
Material and methods
The original sample included 31 (16 zirconia and 15 titanium) implants in 22 healthy patients. In addition to evaluating implant survival and success, a number of clinical or radiographic parameters were statistically analyzed: plaque index (PI), bleeding on probing (BOP), pink esthetic score (PES), and marginal bone loss (MBL). Both implant groups were compared using a Mann–Whitney U test.
Results
Three implants (2 zirconia and 1 titanium) had been lost, so that 28 implants (14 zirconia and 14 titanium) in 21 patients could be evaluated after a mean of 80.9 (SD: 5.5) months. All surviving implants had remained stable, in the absence of any fixture or abutment fractures and without any chipping, fracture, or debonding of crowns. The zirconia implants were associated with PI values of 11.07% (SD: 8.11) and the titanium implants with 15.20% (SD: 15.58), the respective figures for the other parameters being 16.43% (SD: 6.16) or 12.60% (SD: 7.66) for BOP; 11.11 (SD: 1.27) or 11.56 (SD: 1.01) for PES; and 1.38 mm (SD: 0.81) or 1.17 mm (SD: 0.73) for MBL.
Conclusions
No significant differences were found between the clinical outcomes of two‐piece zirconia and titanium implants based on the aforementioned parameters after 80 months of clinical service. Our results should be interpreted with the limited sample size in mind.
We study dynamic antiplane cracks in the time domain by the boundary integral equation method (BIEM) based on the integral equation for di� cement discontinuity (or crack opening displacement, COD) as a function of stress on the crack. This displacement discontinuity formulation present; the advantage, with respect to methods developed by Das and others in seismology, that it has to be solved only inside the crack. This BIEM is, however, difficult to implement numerically because of the hypersingularity of the kernel of the integral equation. Hence it is rewritten into a weakly singular form using a regularization technique proposed by Bonnet. The first step, following a method due to Sladek and Sladek, consists in converting the hypersingular integral equation for the displ&cement discontinuity into an integral equation for the displacement discontinuity and its tangential derivatives (dislocation density distribution); the latter involves a C9uchy type singular kernel. The second step is based on the observation that the hypersingularity is related to the static component of the kernel; the static singularity is then isolated and can be expressed in terms of weakly singular integrals using a result due to Bonnet. Alth
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