J Dent Rehabil Appl Sci.  2018 Dec;34(4):280-289. 10.14368/jdras.2018.34.4.280.

Influence of crown-to-implant ratio of short vs long implants on implant stability and marginal bone loss in the mandibular single molar implant

  • 1Department of Prosthodontics and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea. limdds@snu.ac.kr
  • 2Dental Life Science Research Institute and Clinical Translational Research Center for Dental Science, Seoul National University Dental Hospital, Seoul, Republic of Korea.


The purpose of this randomized clinical trial is to determine whether implant length and the crown-to-implant (C/I) ratio influence implant stability and peri-implant marginal bone loss (MBL).
46 patients with single tooth missing in the posterior molar region of the mandible were included in this study. 19 implants (CMI IS-III active® long implant) of 5.0 mm diameter and 10 mm length were installed for the control group, while 27 implants (CMI IS-III active® short implant) of 5.5 mm diameter and 6.6, 7.3 or 8.5 mm length were placed for the experimental group. Each implant was inserted and immediately loaded using the digitally pre-fabricated surgical template and provisional restoration. The CAD-CAM monolithic zirconia crown was fabricated at 3 months after the surgery as a definitive restoration. The ISQ value and the MBL was measured at 48 weeks after the surgery. The correlation between the C/I ratio, MBL, and secondary implant stability was analyzed.
Successful results in terms of ISQ and MBL were achieved with both groups. There was no significant difference between the groups in terms of ISQ values and MBL at 48 weeks after the surgery (P > 0.05). No significant correlation was found between the C/I ratio and secondary stability as well as the C/I ratio and the MBL (P > 0.05).
The influence of C/I ratio in both groups was not shown on the stability nor the marginal bone loss in implants supporting single crown of the mandible. Short implant could be a preferable alternative option in the reduced bone height mandible under the limited condition despite its higher C/I ratio.


dental implants; short dental implants; immediate loading; primary stability; marginal bone loss; crown to implant ratio
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