HIGH IMPACT LOADING APPLIED DURING PUBERTY INTENSIFIES BONE (RE)MODELLING IN GROWING RATS


Bohao Ning1,2, Catherine Laporte1,3, Tanvir Mustafy1,2, Isabelle Villemure1,2
1CHU Sainte-Justine 2Polytechnique Montréal 3École de technologie supérieure

Objective

Investigate the effects of high impact axial tibial loading applied during puberty on bone (re)modelling in growing rats.

 

Material and Methods

Male Sprague-Dawley rats of 28 days old were randomly divided into two groups (n=6/group): sham and high impact, the later mimics jumping exercise (1250 με on tibia). An in vivo axial tibial cyclic compression (2 Hz) was applied 5 days/week on the impact group rats during their pubertal stage (until 84 days old). Sham group rats received the same experimental conditions without any load. A micro-CT scanner provided weekly scan of the right tibia at a voxel resolution of 18 μm [1]. Reconstructed images were registered on the cortical area using a custom-developed algorithm between consecutive scanning time points [2]. Cortical bone (re)modelling parameters including bone formation (BFR/BV) and resorption (BRR/BV) rates (%/day), mineral apposition (MAR) and resorption (MRR) rates (μm/day), mineralizing (MS/BS) and eroded (ES/BS) surfaces were further calculated at 37% proximal sites [3]. Statistical significance was analyzed using one-tailed paired t-tests (p<0.01 and p<0.05).

 

Results

High impact group showed significantly higher BFR/BV and MAR compared to the shams for all stages, except for 56 days old. Rats from the impact group also resulted in significantly higher BRR/BV and MRR compared to the sham rats for all ages, except for 49 days old. As for MS/BS, significant decrease was observed at 42, 56 and 70 days old while ES/BS showed significantly greater values at all stages except for 49 and 63 days old.

 

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Conclusions

High impact loading intensifies bone (re)modelling, both in terms of apposition and resorption volumes, surfaces and thicknesses, at most pubertal time points. Whether this effect is biomechanically and morphologically positive or not on skeleton growth remains to be investigated. Similar analysis could be conducted with lower intensity of loading, to provide more insights about different loading levels on pubertal growth.

 

References

1.         Mustafy, T., et al., High Impact Exercise Improves Bone Microstructure and Strength in Growing Rats. Scientific Reports, 2019. 9(1): p. 1-14.

2.         Johnson, H.J., M.M. McCormick, and L. Ibanez, The ITK Software Guide Book 2: Design and Functionality-Volume 2. 2015: Kitware, Inc.

3.         de Bakker, C.M.J., et al., μCT-based, in vivo dynamic bone histomorphometry allows 3D evaluation of the early responses of bone resorption and formation to PTH and alendronate combination therapy.Bone, 2015. 73: p. 198-207.

 

Acknowledgments

The authors acknowledge helpful contributions of laboratory team members, especially Irène Londoño. Funding was provided by NSERC programs.

 

 

Peri-Implant Healing Around Different Machined-Collar Designs After 25 Years


Marwa Benkarim1, Hugo Ciaburro1, Robert Durand1, Geneviève Guertin1, Pierre Rompré1, Aldo J.Camarda1
1Université de Montréal

Objectives: The goal of this research was to study the long-term effects of different implant machined-collar designs on peri-implant healing.

 

Method and Materials: Twenty-two subjects (age 69.8±0.79 years, mean±SE 11 women) who received five mandibular implants to support fixed or removable prostheses were enrolled in this prospective study. Acid-etched internal-hex Screw-Vent® implants with a 3.6mm-long machined collar were compared to external-hex machined Brånemark® and acid-etched Swede-Vent® implants with an identical 1.2mm machined collar. Each subject received one of the three implants alternately at five sites between mental foramen, allowing within-subject comparison. With implant platforms placed at the crest, and following calibration, mesial and distal peri-implant crestal bone levels were measured at baseline and after 23-to-26-years of function with standardized peri-apical radiographs. Keratinized gingiva height (mm); probing depth (mm); and presence or absence of plaque, bleeding and purulent exudate after probing were also evaluated after calibration. Descriptive and mixed models for repeated measures analyses were used, with level of significance set at P<.05 and Bonferroni correction for pairwise comparisons.

 

Results: Screw-Vent® implants had significantly greater mean bone loss (-1.70±0.21mm) compared with Brånemark® (-0.59±0.21mm; P<0.001) and Swede-Vent® (-0.95±0.21mm; P=0.003) implants. Brånemark® implants exhibited less bone loss than Swede-Vent® microtextured implants, but this difference was not statistically significant (P=0.368). There was a significant difference for mean keratinized gingiva height between Screw-Vent® (0.74mm±0.10) and Swede-Vent® (0.51mm±0.08, P=0.011), but no significant differences between groups for plaque (P=0.780), probing depth (P=0.419), bleeding (P=0.067) and exudate (P=0.999). Implant survival rate was 100%.

 

Conclusion: Within the confines of this study, all implant types exhibited minimal peri-implant bone loss (<2mm) after a mean of 24.5 years of function. The internal-connection implant design with the longer, narrower machined collar that did not require countersinking had significantly more bone loss compared to both external-connection implants with the 1.2mm-long machined collar. Further long-term controlled studies are warranted to confirm these findings.

ClinicalTrials.gov Identifier No. : NCT03862482. Certificat No. : CERC-19-015-P.