Abstract
Aim To evaluate the influence of primary insertion torque (IT) values of narrow dental implants on the peri-implant health, implant stability, immunoinflammatory responses, bone loss, and success and survival rates. Methods Thirty-one edentulous patients received two narrow implants (2.9x10mm, Facility NeoPoros) to retain mandibular overdentures. The implants were categorized in four groups according to their IT: (G1) IT > 10 Ncm; (G2) IT ≥ 10Ncm and ≤ 30 Ncm; (G3) IT >30Ncm and < 45Ncm; (G4) IT ≥ 45Ncm, and all implants were loaded after 3 months of healing. The following clinical outcomes were evaluated 1, 3, 6, and 12 months after implant insertion: (i) peri-implant tissue health (PH), gingival index (GI), plaque index (PI), calculus presence (CP), probing depth (PD), and bleeding on probing (BOP); (ii) implant stability quotient (ISQ) by resonance frequency analysis; and (iii) IL-1β and TNF-α concentration in the peri-implant crevicular fluid. The marginal bone level (MBL) and changes (MBC) were evaluated. The Chi2 test, Kruskal-Wallis test, mixed-effects regression analysis, and the Kendall rank correlation coefficient were used for statistical analysis (α = 5%). Results G1 presented the highest PD at all evaluated periods. G2 presented higher PI at month 6 and 12. G4 showed increased GI at month 3 and 12 and more CP at month 1 (p=.003). G2 and G4 had higher ISQ values over the study period, while those from G1 and G3 presented lower ISQ values. The IL-1β concentration increased until month 12 and was independent of IT and bone type; G4 had a higher IL-1β concentration in month 3 than the other groups (p=.015). The TNF-α release was negatively correlated with IT, and TNF-α release was highest in G1 at month 12. The MBL immediately after surgery and the MBC at month 12 were similar between the groups, and G4 presented a positive MBC at month 12. The survival and success rates were 75% for G1, 81.3% for G2, 64.3% for G3, and 95% for G4. Conclusion The IT did not influence the clinical outcomes and the peri-implant immunoinflammatory responses and was weakly correlated with the narrow dental implants primary stability. The observed success rates suggest that the ideal IT for atrophic fully edentulous patients may deviate from the standardized IT of 32 Ncm.
Highlights
Oral rehabilitation with dental implants aims to establish functional, aesthetic, and phonetic success, with reduced morbidity and pain, aiming at reduced healing and rehabilitation periods with acceptable cost-effectiveness [1]
Bone density dictates the mechanical properties of the bone bed, which may suffer changes during healing depending on the surgical protocol, since the more porous, more elastic, and well vascularized trabecular bone favors the formation of a dense cortical bone near the surface of the implant, guaranteeing the achievement of biological stability and successful osseointegration [3,4,5]
The Group 4 (G4) group with the highest IT had a mean probing depth (PD) that was 30% lower than the other groups. This is consistent with the findings reported by Marconcini et al (2018), which showed that higher insertion torque (≥ 50 Ncm) in mandible led to greater bone resorption and mucosal recession than that registered for implants placed with a regular IT (< 50 Ncm)
Summary
Oral rehabilitation with dental implants aims to establish functional, aesthetic, and phonetic success, with reduced morbidity and pain, aiming at reduced healing and rehabilitation periods with acceptable cost-effectiveness [1]. One of the prerequisites for successful osseointegration of the implants is to achieve adequate primary stability after insertion of BioMed Research International the implants to prevent early failures [2]. Many of these failures are biomechanically induced and associated with risk factors such as low primary stability, low bone density, short or narrow implants, and occlusal overloading [3]. Bone density dictates the mechanical properties of the bone bed, which may suffer changes during healing depending on the surgical protocol, since the more porous, more elastic, and well vascularized trabecular bone favors the formation of a dense cortical bone near the surface of the implant, guaranteeing the achievement of biological stability and successful osseointegration [3,4,5]. The literature indicates that the optimal IT to achieve successful osseointegration is 30 Ncm, which is sufficient to allow both conventional and immediate occlusal loading of the implants while avoiding occlusal overload failures [6, 11]
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