The effect of increased crown-to-implant ratio on single-tooth locking-taper implants.
OBJECTIVE
It has been proposed that increased crown heights lead to greater crestal stresses on dental implants, crestal bone loss, and other complications. The purpose of this study was to evaluate the effect of increased crown-to-implant ratio (C/IR) on single-tooth implants.


METHODS
A retrospective cohort study was conducted between July 2001 and August 2003. The cohort was composed of patients who had at least one single-tooth Bicon implant restored with a cementless restoration and attended recall examinations in 2004, 2005, and 2007, during which several clinical and radiographic variables were documented. Descriptive statistics and univariate and multivariate mixed-effects regression models, adjusted for multiple implants in the same patient, were used.


RESULTS
The cohort was composed of 81 subjects who received 326 Bicon implants. The mean duration of follow-up was 70.7 months. Mean change in the mesiodistal crestal bone levels was -0.33 mm. The mean C/IR was 1.6 (range, 0.79 to 4.95). Forty implant restorations (16%) had a C/IR ≥ 2. Implant restorations with increased C/IR were significantly more likely to have increased mesiodistal crown width, larger implant diameter, larger distance to mesial and distal adjacent structures, and deeper sulcular probings. Increased C/IR had a statistically significant effect in the loosening of maxillary anterior Integrated Abutment Crowns (Bicon) as well as a significant effect in the fracture of 2-mm-wide titanium abutment posts used to restore posterior areas. A C/IR up to 4.95 did not lead to an increased risk of crestal bone loss or to an increase in implant failures, crown failures, or crown fractures.


CONCLUSIONS
Larger C/IR was associated with a significant increase in prosthetic complications but had no significant effect on crestal bone levels on single-tooth locking-taper implants.
Urdaneta
Rainier A
RA
Implant Dentistry Centre, Boston, Massachusetts, USA. rainieru@yahoo.com
Rodriguez
Sujey
S
McNeil
D Cary
DC
Weed
Meghan
M
Chuang
Sung-Kiang
SK
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016301:Alveolar Bone Loss / Q000209:etiology; D001696:Biomechanical Phenomena; D001732:Bite Force; D015331:Cohort Studies; D003442:Crowns; D000044:Dental Abutments; D003724:Dental Arch / Q000473:pathology; D019250:Dental Implants, Single-Tooth; D003764:Dental Materials / Q000737:chemistry; D003766:Dental Occlusion; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008409:Mastication / Q000502:physiology; D008875:Middle Aged; D010514:Periodontal Pocket / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
D003764:Dental Materials; D014025:Titanium