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The Effect of Crown-to-Implant Ratio on the Clinical Performance of Extra-Short Locking-Taper Implants

Mangano, Francesco DDS; Frezzato, Irene DDS; Frezzato, Alberto MD, DDS; Veronesi, Giovanni PhD; Mortellaro, Carmen MD, DDS; Mangano, Carlo MD, DDS

Journal of Craniofacial Surgery: May 2016 - Volume 27 - Issue 3 - p 675–681
doi: 10.1097/SCS.0000000000002562
Clinical Studies

Background: The aim of the present prospective 5-year study was to evaluate the influence of crown-to-implant ratio (C/I ratio) on the survival, peri-implant marginal bone loss, and complications of extra-short (6.5 mm) locking-taper implants placed in the posterior areas of the jaw.

Methods: Over a 2-year period, all patients presenting with partial edentulism associated with vertical defects of the posterior alveolar ridges and sufficient bone volume to place extra-short (6.5 mm length × 5 mm diameter) implants were considered for inclusion in this study.

Results: Fifty-one patients (22 men, 29 women; aged between 40 and 75 years) were included in this study. Sixty-eight extra-short, locking-taper implants were placed to support 49 single crowns and 9 fixed partial dentures. The C/I ratio was <2 for 51 implants and ≥2 for 17 implants. All patients underwent the 5-year clinical examination. Two implants failed. Failure proportion was 2% in the C/I<2 group, and 6% in the C/I≥2 group: this difference was not statistically significant (P = 0.4). After 1 year of loading, a mean marginal bone loss of 0.29 and 0.39 was reported in the C/I<2 group and the C/I≥2 group, respectively. After 5 years of loading, a mean marginal bone loss of 0.38 and 0.48 was reported in the C/I<2 and C/I≥2 groups, respectively. The linear regression model failed to find a correlation between the C/I ratio and marginal bone loss along time, with a 0.023 mm (95% CI: −0.002; 0.048) increase in 1-year bone resorption for every 0.1 increase in C/I ratio (P = 0.07). At 5-year, the association reduced to 0.019 mm (P = 0.18). Only a few complications were reported. There was no statistically significant difference in the prevalence of biological (P = 0.9) complications between the 2 groups. Prosthetic complications were more frequent with C/I≥2 (12.5%) than with C/I<2 (6%), but this difference was not statistically significant (P = 0.6).

Conclusions: Extra-short, locking-taper implants may be successfully used in the posterior areas of the jaw.

*Department of Surgical and Morphological Sciences, University of Varese, Varese

Private Practice, Rovigo

Department of Clinical and Experimental Medicine, University of Varese, Varese

§Department of Health Science, University of Eastern Piedmont, Novara

||Department of Medical, Oral and Biotechnological Sciences, University of Chieti, Chieti, Italy.

Address correspondence and reprint requests to Francesco Mangano, DDS, Piazza Trento 4, 22015 Gravedona (Como), Italy; E-mail:

Received 10 December, 2015

Accepted 9 February, 2016

The authors report no conflicts of interest.

© 2016 by Mutaz B. Habal, MD.