 Astra Tech
BioManagement Complex
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 Cresco
Cresco™ is the easy-to-use solution for screw-retained implant bridges, providing freedom and a perfect fit every time. Cresco is available in different framework materials for all major implant systems. The technique is carefully described and clinical result are presented in the following summaries.
 Evaluation of the marginal precision of one-piece complete arch titanium frameworks fabricated using five different methods for implant-supported restorations
Considerable differences of opinion exist in the literature as to whether a marginal discrepancy of fit between prosthesis and supporting abutments causes biological complications. However there is consensus that cast frameworks do not fit as precisely as milled structures and in addition the use of titanium is thought to be preferable to cast gold with respect to tissue response possibly due to the absence of galvanic reactions.
Purpose: To compare the marginal accuracy of fit of full arch splinted frameworks fabricated using 1) the lostwax casting technique(LWC) with burnout cylinders, 2) cast frameworks laserwelded to prefabricated titanium cylinders (LWP), 3) a Procera® milled framework (PMF, Nobel Biocare), 4) the Cresco'" Ti system (CTS, Astra Tech), and 5) the CAMStructSURE® precision milled bar system (CAM, Biomet 3i).
Materials and Methods: Patients who had received 5 to 9 ITI Straumann implants and were due to have a total of 15 full arch reconstructions with crossarch splinted titanium restorations were enrolled to the study and randomly assigned to one of the five groups LWC, LWP, PMF, CTS, and CAM. The methodology for each of the 5 techniques has been described elsewhere. Frameworks in the LWC and LWP groups were cemented restorations while the restorations fabricated in the other groups were all screwretained. All structures were designed to be metalceramic except for those in the CAM group which were due to be metalacrylic. To be most representative of normal working procedures the frameworks were all fabricated by technicians unaware of the intended study, thereby allowing for all possible laboratory errors. The fit of each framework was measured directly on the master working cast, prior to delivery to the patient using stereomicroscopy at lOOx magnification. Measurements were made at 4 sites on each abutment replica (91 implants, total 364 measurements) and means and standard deviations calculated. Statistical analysis using ANOVA was performed to determine the presence of any differences at the 95% confidence level.
Results: With respect to marginal integrity of fit the groups performed with decreasing accuracy and increasing gap width as follows: CTS (18 pm) > PMF (21 pm) > CAM (27 pm) > LWP (33 pm) > LWC (78 pm). There was a significant difference between the pooled groups, p < 0.01 although there was no significant difference between CTS, PMF, and CAM techniques. The lostwax casting technique (LWC) was significantly less accurate when compared to all other groups, p < 0.01 and the laser-welding technique to prefabricated copings (LWP) was significantly less accurate than the PFM technique, p < 0.05 and the most accurate technique using the Astra Tech Cresco TI system" (CTS), p < 0.01. In addition the LWC technique yielded the widest standard deviation while the CTS technique yielded the lowest deviation. In the former the largest gap was as much as 300 pm in width compared to the smallest gap measured which was only 10 pm with CTS.
Discussion and Conclusion: It has previously been demonstrated that that while the lost-wax casting technique has served the dental community well for many years, it does not offer the accuracy of fit achieved with milled structures, especially when employing titanium since this metal is more difficult to cast accurately. The introduction of laser-welding of frameworks to prefabricated copings was thought to provide significant improvements in precision and this has been verified in the current study. Numerous studies have presented the Procera® technology and results for accuracy of fit are close to those presented here. Like Procera the CAMStructSURE* precision milled bar system is based on the milling of a solid titanium block and it is not surprising that results are comparable. The Cresco Ti system differs from these in that this technology is aimed at eradicating marginal discrepancies intrinsic within a cast framework and as such it is appropriate to compare data with that of the LWC group which did not benefit from this technique. Results demonstrated a highly significant difference, p < 0.01, for accuracy of fit and indeed the CTS technique yielded a more accurate fit than either of the milling techniques. If a cemented restoration is needed, use of laser welding of cast framework to pre-fabricated copings, should be preferred. |
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