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

Abstract

(1) Background: Primary stability—one fundamental criterion for the success of dental implants—is influenced by implant geometry even if the effect of apical shape modifications on implant primary stability has not yet been examined. Therefore, the aim of the ex vivo study was to compare primary stability of implants differing in apically located screw threads (J-line) or a flat tip (K-line) only. (2) Methods: 28 implants of each group of the same diameter (4.3 mm) were randomly inserted into porcine bone blocks. The first group (9, 11 and 13 mm) was inserted into “hard”, the second (11 mm) into “soft” bone, here using a normal and an undersized drilling protocol. Insertion torque (Ncm), Periotest® value, resonance frequency (implant stability coefficient, ISQ) and push-out force (N) were measured. (3) Results: In “hard” bone, primary stability increased with increasing length in both groups but it was significantly higher in J-line (p < 0.03). An undersized preparation of the implant bed in “soft” bone resulted in a significant increase in primary stability in both groups. Here, J-line also showed a significantly increased primary stability when compared to equally prepared K-line (insertion torque: 37 Ncm vs. 26 Ncm; Periotest®: −6.5 vs. −4.3; push-out force: 365 N vs. 329 N; p < 0.05 each). (4) Conclusions: Primary stability is significantly higher with increasing implant length and apically located screw threads as well as with undersized drilling protocols. When preparing the implant site and subsequently selecting the implant system, modifying factors such as implant geometry (also at the tip) should be taken into account.

Preclinical study probing primary stability of dental implants in synthetic and natural bones

“…18,19 A group of researchers found out that the design of apically located threads and the type of healing chamber also affects the primary stability to an extent. 20 In a general consensus, conical implants exhibit better primary stability in comparison with cylindrical implants. [21][22][23] The physical interlocking with bone is determined by friction and biomechanical response of the bone at the bone-implant interface.…”

“…At the same time, there are some opposing views that lower IT too could result in good clinical outcomes 18,19 . A group of researchers found out that the design of apically located threads and the type of healing chamber also affects the primary stability to an extent 20 …”

Risk factors associated with loss of variable‐thread tapered implants: A retrospective observational study of 1–5 years

“…Aside from local bone condition (Rues et al, 2021) and specific sizes of dental implants (length, diameter), the macro‐morphology design plays an indispensable role in the primary stability, especially the thread structures (Menini et al, 2020; Valente et al, 2015). Currently, the main thread parameters include shape, pitch, depth, width, face angle, and helix angle (Abuhussein et al, 2010), and some scholars believe that the neck/apical geometry also belongs to this category (Calvo‐Guirado et al, 2018; Staedt et al, 2021). Most previous research has pointed out that appropriate pitch, relatively deeper threads, and tapered apical design might be beneficial to immediate mechanical embedment with alveolar bone (Ao et al, 2010; Pirmoradian et al, 2020; Romanos et al, 2019).…”

Osseointegration of a New, Ultrahydrophilic and Nanostructured Dental Implant Surface: A Comparative In Vivo Study

“…In general, patients' expectations have been rising and they are increasingly looking for comfort in terms of immediate implant placement and loading as well as shorter healing times [13][14][15][16]. Also, patients with conditions and/or diseases influencing bone turnover wish to be regenerated by implant-supported restorations [17].…”

“…In those compromised patients, implant survival and success rates might be reduced, with complication rates increased [3,[18][19][20]. Therefore, future challenges are immediate implant placement and loading in patients with non-degenerative conditions and implant placement in compromised patients [16,21]. This could be achieved through improvement of the implants' osseointegration, which is considered as a structural and functional connection between bone and implant [22].…”