Influence of Implant Thread Morphology on Primary Stability: A Prospective Clinical Study

Abstract

Objectives. The purpose of this study was to evaluate the primary stability of two implants with the same macro- and micromorphology but different thread design and analyze their clinical outcomes over a one-year period. Materials and Methods. 14 patients needing a partial rehabilitation with a delayed loading approach (DEL group: 9 patients) or a full-arch rehabilitation treated with immediately loaded fixed prostheses supported by 4 implants following the Columbus Bridge Protocol (CBP) (IL group: 5 patients) were included. In each patient, at least one SY (implant with standard threads) and one SL implant (implant with an augmented depth of the threads) were randomly inserted. Primary outcome measures were the number of threads exposed at a torque of 30 Ncm and 50 Ncm and final insertion torque. Secondary outcome measures were implant and prosthetic failure, peri-implant bone resorption, and periodontal parameters: bleeding on probing (BoP), plaque index (PI), and probing depth (PD) evaluated at 3, 6, and 12 months of healing. Results. Nineteen SY and 19 SL implants were inserted in 14 patients. Twenty implants (10 SL and 10 SY) were inserted in the IL group, while 18 (9 SL and 9 SY) were inserted in the DEL group and followed-up for 12 months. No patients dropped out. No implants and prostheses failed. No biological complications were identified. No significant differences were found between SY and SL implants comparing the number of exposed threads when inserting the implant with a torque insertion of 30 N (T student test p=.142 and U test p=.164). At 50 N, no threads were visible in either groups. Final torque insertion values were higher for SL (mean: 48.42 Ncm) compared to SY implants (mean: 43.42 Ncm) without a statistically significant difference. All the implants showed good clinical outcomes at the 1-year-in-function visit. Conclusions. After 12 months of function, both implant types provided good clinical outcomes without statistically significant differences between the two groups. A difference in insertion torque (even if not statistically significant) was found with higher insertion torque values for SL implants with a larger thread depth.

Effect of Implant Surface Roughness and Macro- and Micro-Structural Composition on Wear and Metal Particles Released

“…Implant A showed double threads for increasing the contact area with the bone and reducing the cortical occlusal stress. This macro-morphology appeared to be more favorable in terms of surface changes during the implant placement than the single-threaded ones, even if it was able to ensure a faster implant insertion [32][33][34][35].…”

Does the Modification of the Apical Geometry of a Dental Implant Affect Its Primary Stability? A Comparative Ex Vivo Study

“…It is known that not only the depth but also the shape of the screw threads can influence the primary stability of a dental implant and the peri-implant bone resorption. Thus, it has been shown that occlusal loads after implant placement are mainly concentrated in the bone section adjacent to the first screw winding, indicating that the implant width and the configuration of the windings could lead to a reduction of the loads [ 14 , 15 , 20 ]. For example, a more square shape of the threads allowed an increase of the bone–implant contact as well as a distribution of the loads on a larger bone surface with a better distribution, especially of lateral forces.…”

“…For example, a more square shape of the threads allowed an increase of the bone–implant contact as well as a distribution of the loads on a larger bone surface with a better distribution, especially of lateral forces. A V-shape of the threads in the most apical part of the implant determines a greater aggressiveness of the implant, especially in bone of lower density, achieving a greater mechanical stability of the implant and a greater resistance to vertical forces [ 14 , 20 , 46 ]. Not only do the observed effects of apically located screw threads on the primary stability of the implant correspond to the current literature, but also fit the mathematical calculations for improving the pressure distribution around the implant by increasing the surface area [ 14 , 16 , 47 ].…”

“…In contrast, Makary et al provided evidence that the use of implants with deep screw threads could be beneficial in implant rehabilitations in soft bone (D3 and D4) only [ 17 ]. Altogether, an ideal implant design should allow a balance between compressive and tensile forces while minimizing the generation of shear forces [ 18 , 19 , 20 ].…”

Does the fixture thread depth affect the accuracy of implant placement during fully guided immediate implant placement?: A human cadaver study

“…Deeper threads can provide an additional advantage in the tapered fixture design since the engagement of more threads in the bone may provide greater stability when there is lack of bone or the quality of bone is poor (Lee et al, 2015), such as for an extraction socket during immediate implant placement. However, the larger discrepancy between the drill and fixture diameters associated with deeper threads may negatively affect the placement accuracy, especially in the presence of a peri‐implant dehiscence or at an extraction socket (Menini et al, 2020). However, no previous study has verified this hypothesis.…”