Can changes in implant macrogeometry accelerate the osseointegration process?: An in vivo experimental biomechanical and histological evaluations

Abstract

Objectives: The propose was to compare this new implant macrogeometry with a control implant with a conventional macrogeometry.

Materials and methods: Eighty-six conical implants were divided in two groups (n = 43 per group): group control (group CON) that were used conical implants with a conventional macrogeometry and, group test (group TEST) that were used implants with the new macrogeometry. The new implant macrogeometry show several circular healing cambers between the threads, distributed in the implant body. Three implants of each group were used to scanning electronic microscopy (SEM) analysis and, other eighty samples (n = 40 per group) were inserted the tibia of ten rabbit (n = 2 per tibia), determined by randomization. The animals were sacrificed (n = 5 per time) at 3-weeks (Time 1) and at 4-weeks after the implantations (Time 2). The biomechanical evaluation proposed was the measurement of the implant stability quotient (ISQ) and the removal torque values (RTv). The microscopical analysis was a histomorphometric measurement of the bone to implant contact (%BIC) and the SEM evaluation of the bone adhered on the removed implants.

Results: The results showed that the implants of the group TEST produced a significant enhancement in the osseointegration in comparison with the group CON. The ISQ and RTv tests showed superior values for the group TEST in the both measured times (3- and 4-weeks), with significant differences (p < 0.05). More residual bone in quantity and quality was observed in the samples of the group TEST on the surface of the removed implants. Moreover, the %BIC demonstrated an important increasing for the group TEST in both times, with statistical differences (in Time 1 p = 0.0103 and in Time 2 p < 0.0003).

Conclusions: Then, we can conclude that the alterations in the implant macrogeometry promote several benefits on the osseointegration process.

Fig 1. Schematic image of the implant models evaluated: The conventional implant macrogeometry (Group CON) and the new implant macrogeometry (Group TEST).

Fig 2. Representative image of the position predeterminate to install the implants (between the red lines), avoiding the most proximal position where bone tissue is less dense.

Fig 3. Schematic illustration of the implant stability quotient (ISQ) measurement in 2 directions: (A) disto-proximal and (B) antero-posterior.

Fig 4. Schematic image to demonstrate the areas analyzed separately in the descriptive histologic analysis: The cortical portion corresponding to the yellow square and the medullar portion corresponding to the green square.

Fig 5. Representative images showing the area of 2 mm² (1 mm from the implant towards the bone and 2 mm on the long axis of the implant) used for measure the parameters of new bone formed (●), osteoid matrix (*) and medullary spaces (#).

(a) cortical portion and (b) medullary portion.

Fig 6. Sequence of SEM images of the two implant macrogeometries used.

(a-c) implant of the CON group and (d-f) implant of the new macrogeometry of the TEST group.

Fig 7. Line graph presenting the ISQ progression on the three times: T1 = immediately after the installation; T2 = 3 weeks; T3 = 4 weeks.

*statistically significative (P < 0.05).

Fig 8. Bar graph showing the RTv values, standard deviation and statistical comparison on the two times of both groups.

Fig 9

In (a) an image of low magnification of the implant showing the deposition of a thin layer of bone tissue over the entire surface. In (b) an image with more increase showing the bone tissue is deposited on the implant surface. In (c) an image with great increase showing the deposition of bone tissue on the surface, but with spaces between the lumps of bone tissue.

Fig 10

In (a) an image of low magnification of the implant showing the deposition of bone tissue over the entire surface and the presence of larger lumps of bone tissue in several areas of the implant body. In (b) an image with more increase showing the bone tissue is deposited on the implant surface and the big quantity of bone tissue. In (c) an image with great increase showing the deposition of bone tissue on the implant with signs of consistent and even layer on the surface.

Fig 11

In (a) an image of low magnification of the implant showing the bone tissue deposition over the entire surface. In (b) an image with more increase showing the presence of bone tissue deposited on the implant surface with a uniform and consistent thick layer. In (c) an image with great increase showing that the bone tissue deposition with a more consistent layer.

Fig 12

In (a) an image of low magnification of the implant showing great quantity of bone tissue deposition over the entire surface. In (b) an image with more increase showing the presence of bone tissue deposited on the implant surface with a thick layer. In (c) an image with great increase showing that the bone tissue deposition.

Fig 13. Representative images of the CON group.

(a) cortical portion with 3-weeks, (b) medullar portion with 3-weeks, (c) cortical portion with 4-weeks, (d) medullar portion with 4-weeks. Images obtained by light microscopy. New bone formed (●), osteoid matrix (*), medullary spaces (#), implant (Imp) and native bone (Nat).

Fig 14. Representative images of the TEST group.

(a) cortical portion with 3-weeks, (b) medullar portion with 3-weeks, (c) cortical portion with 4-weeks, (d) medullar portion with 4-weeks. Images obtained by light microscopy. New bone formed (●), osteoid matrix (*), medullary spaces (#), implant (Imp) and native bone (Nat).

Fig 15. Bar graphs of the morphological parameters analysis of new bone formation (Nb), osteoid matrix (Ost) and medullary spaces (Ms) for both groups and in the two portions analyzed (cortical and medullary) at 3 weeks after the implantations.

*statistically significative (P < 0.05).

Fig 16. Bar graphs of the morphological parameters analysis of new bone formation (Nb), osteoid matrix (Ost) and medullary spaces (Ms) for both groups and in the two portions analyzed (cortical and medullary) at 4 weeks after the implantations.

*statistically significative (P < 0.05).