1. NMeanStd. DeviationStd. Error Mean BONE LOSS 4 MONTHS Int Con 19,0893,25863,05783 Ext Con 20,1628,24124,05394 NMeanStd. DeviationStd. Error Mean BONE LOSS 4 MONTHS MT 19,1152,21371,04663 NMT 20,1379,28983,06649 A split mouth clinical and radiographic comparison of four implants with different neck design in maxillary overdenture patients; A preliminary report. Glibert Maarten, DDS; De Bruyn Hugo, DDS, MsC, PhD Ghent University, Ghent, BELGIUM Materials and Methods: All studied implants are straight walled with an integrated platform shift and a moderately rough surface. (Deep Conical Connection; Southern Implants, Pretoria, South Africa) As shown in figure one 4 different implant neck designs are used; Type 1/ Internal connection with micro-threads Type 2/ Internal connection without micro-threads Type 3/ External connection with micro-threads Type 4/ External connection without micro-threads.(Figure 1) Patients in need of an implant supported maxillary overdenture were selected. Exclusion criteria were unregulated diabetes mellitus type 1 or 2, a general contra-indications for oral surgery and a limited vertical height. Smoker were not excluded. Each patient received 4 implants and the position of each implant type was randomized. During implant surgery a compact conical abutment (Figure 2;Southern Implants, Pretoria, South Africa) was placed and the provisional prosthesis was relieved to create space for the healing caps and a soft reliner (COE-soft, GC, Alsip, IL, USA) was applied to avoid direct contact and excessive pressure on the abutments. Each patient was seen every 2 – 3 weeks to replace this reliner. Crestal bone level was assessed using standardized peri-apical radiographs. Crestal bone level served as the main variable and crestal bone loss is calculated by comparing bone-to-implant contact level of 3 – 4 months with baseline (implant placement)(Figure 3). Background: Some clinical studies describe the effect of implant-abutment connection (internal versus external connection (1)) and implant neck design (Micro versus no micro- threads (2)) on initial crestal bone remodelling. However none of these studies uses implants with the same macro-design or surface which makes the comparison biased. This prospective split mouth study evaluates crestal bone levels of 4 implants with the same surface and macro-design but with a different implant neck. Results: Ten patients were included and received forty implants. After a follow-up of 3- 4 months one implant failed leading to a survival rate of 97,5%. The failed implant lacked primary stability ( 0.05) (Table 1, Figure 4). No difference in bone loss was found between Micro-threaded and Non-Micro-Threaded implants (0.12 mm (SD: 0.21) and 0.14 mm (SD: 0.29)) (Table 2, Figure 5) Conclusion: If excessive pressure of the provisional prosthesis is avoided a high survival and a limited crestal bone loss is found around the studied implants with no difference between micro – and non-micro-threaded implants. The preliminary results implies that the implant- abutment connection has an impact on initial crestal bone remodelling; yet a longer follow up period is needed to show if these differences have a significant influence on implant outcome. References: 1/ Pozzi A, Agliardi E, Tallarico M, Barlattani A. Clinical and radiological outcomes of two implants with different prosthetic interfaces and neck configurations: randomized, controlled, split-mouth clinical trial. Clin Implant Dent Relat Res. 2014;16(1):96- 106. 2/Lee DW, Choi YS, Park KH, Kim CS, Moon IS. Effect of microthread on the maintenance of marginal bone level: a 3-year prospective study. Clin Oral Implants Res. 2007;18(4):465-70. Figure 1: 4 implant neck designs used in this study Figure 2: 2 weeks post-surgery Figure 3: PA radiographs at baseline (left) and after 3-4 months (right) Figure 4: Boxplot of crestal bone loss around implants with an internal (1) and external (2) connection Figure 5: Boxplot of crestal bone loss around implants with (1) and without (2) micro-threads Table 1: Crestal bone loss around implants with an internal and external connection Table 2: Crestal bone loss around implants with and without micro-threads BONE LOSS 4 MONTHS Int Con vs Ext con MT vs NMT