Effect on osseointegration of two implant macro-designs:A histomorphometric analysis of bicortically installed implants in different topographic sites of rabbit's tibiae

Abstract

Background: To evaluate the effect of two different implant macro-designs on the sequential osseointegration at bicortically installed implants in the rabbit tibia. A further aim is to compare the osseointegration at different topographic zones.

Material and methods: 27 New Zealand rabbits were implemented. Two implants, one for each macro-design (Ticare Inhex® or Ticare Quattro®, Mozo-Grau, Valladolid, Spain), were randomly implanted in the diaphysis or metaphysis of each tibia. The flaps were sutured to allow a submerged healing. The animals were sacrificed after 2, 4 or 8 weeks. Ground sections were prepared and analyzed.

Results: No statistically significant differences were found between the two groups for newly formed bone in contact with the implant surface, being about 16%, 19% and 33% in both groups, after 2, 4, and 8 weeks of healing. Bone apposition was slightly higher in the diaphysis, reaching values of 36.4% in the diaphysis, and 29.3% in the metaphysis at 8 weeks of healing. It was observed that the implant position showed a statistical significance regarding BIC values at 4 and 8 weeks (p<0.05). Multivariate analysis fails to detect statistical significant differences for the interaction between implant designs and topographic site. Ticare Quattro® design had a slight better BIC values at diaphysis sites across healing stages, but without reaching a statistical significance.

Conclusions: The both implant macro-designs provided similar degrees of osseointegration. Bone morphometry and density may affect bone apposition onto the implant surface. The apposition rates were slightly better in diaphysis compared to metaphysis.

Figure 1

(a) Image of different implant macro-designs tested. Inhex® (Left) and Quattro® (Right) (Ticare implants, Mozo-Grau, Valladolid, Spain). Ticare Inhex®: the implant body had a little conicity and a large area of micro-threads at the coronal portion, and higher number of triangular threads per unit length and with little thread depth compared to Quattro® model. Moreover, the implant had a double self-tapping at the apical portion. Ticare Quattro®: the implant body had a marked conicity. Fewer micro-threads at the coronal portion and a lower number of macro-threads were present compared to Inhex implants. The threads were squared in the middle part of the implant and become triangular and deeper at the apex. Aggressive self-tapping at the apex. (b) The flaps were raised, and the bone was exposed below the anterior tibial tuberosity (blue arrow), that provides a visual reference point to identify the two experimental sites, one in metaphysis “M” and one in the diaphysis “D”. Thereafter, two implants macro-designs were bicortically installed in each tibia (c).

Figure 2

Ground sections illustrating the healing of implants installed in the diaphysis (a-c) and metaphysis (d-f) areas after 2, 4 and 8 weeks. Toluidine blue (1.6x).

Figure 3

(a) Graphics reporting the amount of new bone and old bone for Inhex® (I) and Quattro® (Q) implant designs (New I; New Q) and (Old I; Old Q) at different time intervals respectively. (b) Differences of new bone (New D; New M) and old bone (Old D; Old M) at diaphysis (D) or metaphysis (M) sites. (c) BIC values for both macro-designs according implantation site (diaphysis or metaphysis), to visually appreciate the interaction (Design*Position).