Histomorphologic and histomophometric evaluation of immediately and early loaded mini-implants for orthodontic anchorage.
BACKGROUND
The purpose of this study was to evaluate the bone response to statically loaded 2.5-mm diameter mini-implants of 6 and 10 mm lengths activated after various healing periods in a dog model.


METHODS
Seventy-eight machined-surface Ti-6Al-4V mini-implants were bilaterally placed in the mandibular premolar and molar regions of 6 beagle dogs. The left (experimental) and the right (control) hemi-arches received 6 and 7 mini-implants, respectively. Experimental mini-implants healing periods of 0 days (immediately activated), 1 week, and 3 weeks were followed by a 12-week load activation period (250 g between parallel implant pairs). Control (nonloaded) mini-implant groups were placed for 12 weeks, 3 weeks, and 1 week before the dogs were killed they provided data concerning the experimental groups' bone to mini-implant scenarios at load activation times. The mandibles were exposed by sharp dissection, and decalcified specimens were prepared for histomorphologic and histomorphometric (bone to mini-implant contact) assessment.


RESULTS
Survival rates were 100% and 77.78% for the control and the experimental groups, respectively. Survival rates were 88.89% for the 10-mm and 66.67% for the 6-mm experimental groups. All failed devices had tissue inflammation and were lost after spring placement. The control groups showed classic bone-healing events, and the experimental groups showed mature bone morphology after 12 weeks in vivo regardless of placement time before load activation. Bone to implant contact values were not significantly different between the experimental and the control groups that remained 12 weeks in vivo.


CONCLUSIONS
These results showed that low-intensity immediate or early orthodontic static loads did not affect mini-implant performance.
Freire
José Nilo O
JN
Department of Prosthodontics, New York University, New York, NY, USA.
Silva
Nelson R F A
NR
Gil
José N
JN
Magini
Ricardo S
RS
Coelho
Paulo G
PG
D000497:Alloys; D000704:Analysis of Variance; D000818:Animals; D003722:Dental Alloys; D003758:Dental Implantation, Endosseous / Q000009:adverse effects; D015921:Dental Implants / Q000009:adverse effects; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D004285:Dogs; D008297:Male; D008334:Mandible / Q000601:surgery; D008904:Miniaturization; D023421:Models, Animal; D052280:Orthodontic Anchorage Procedures / Q000009:adverse effects / Q000295:instrumentation*; D016348:Osseointegration; D010518:Periodontitis / Q000209:etiology; D013997:Time Factors; D014025:Titanium; D014945:Wound Healing
D000497:Alloys; D003722:Dental Alloys; D015921:Dental Implants; C031462:titanium alloy (TiAl6V4); D014025:Titanium