The Effect of Crown-to-Implant Ratio on the Clinical Performance of Extra-Short Locking-Taper Implants.
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.
Francesco
F
Mangano
Irene
I
Frezzato
Alberto
A
Frezzato
Giovanni
G
Veronesi
Carmen
C
Mortellaro
Carlo
C
Mangano
D000328:Adult; D000368:Aged; D017267:Dental Prosthesis Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology*; D011446:Prospective Studies; D013223:Statistics as Topic