Influence of two different machined-collar heights on crestal bone loss.
OBJECTIVE
The purpose of this trial was to evaluate crestal bone level changes radiographically in a standardized fashion over a period of 12 months in humans for implants with a 0.7-mm machined collar (implant type A) versus type B implants with a 1.5-mm machined collar.


METHODS
Twenty-five patients with multiple missing teeth in posterior sectors were randomly assigned to one of the two groups: A (0.7-mm machined-collar implants) or B (1.5-mm machined-collar implants). Changes at crestal bone level were assessed by measuring the shoulder-crest distance (SCD) on the mesial and distal aspects of each implant on customized periapical radiographs, which were taken on the day of surgery and 3, 6, and 12 months after surgery.


RESULTS
Eighty-one implants were included in the study. Mean SCD was 0.54 ± 0.53 mm at baseline and 1.49 ± 0.40 mm after 12 months. For 0.7-mm-collar implants, mean SCD was 1.40 ± 0.39 mm, while it was 1.56 ± 0.40 mm for 1.5-mm-collar implants. Statistically significant differences were found only between the two types of implants for distal measurements at 3 and 12 months after placement.


CONCLUSIONS
Both 0.7- and 1.5-mm machined-collar implants can be used with predictable results, as changes in peri-implant crestal bone levels are similar for both implant types and do not seem to be significant from a clinical point of view. The SCD may well depend more on the location of the abutment-implant interface than on machined-collar height.
Mariano
M
Herrero-Climent
Manuel María
MM
Romero Ruiz
Carmen María
CM
Díaz-Castro
Pedro
P
Bullón
Jose Vincente
JV
Ríos-Santos
D016301:Alveolar Bone Loss / Q000145:classification / Q000000981:diagnostic imaging*; D015519:Bone Density / Q000502:physiology; D059605:Dental Implant-Abutment Design; D003758:Dental Implantation, Endosseous / Q000379:methods; D015921:Dental Implants; D017267:Dental Prosthesis Design; D017268:Dental Prosthesis Retention; D019094:Dental Prosthesis, Implant-Supported; D004311:Double-Blind Method; D005500:Follow-Up Studies; D006801:Humans; D007576:Jaw, Edentulous, Partially / Q000534:rehabilitation / Q000601:surgery; D016348:Osseointegration / Q000502:physiology; D016300:Radiography, Bitewing; D013499:Surface Properties
D015921:Dental Implants