Effect of surface treatment on cell responses to grades 4 and 5 titanium for orthodontic mini-implants.
BACKGROUND
Mini-implants are used to improve orthodontic anchorage, but optimal composition and surface characteristics have yet to be determined. We investigated the behavior of osteoblast-like cells on grade 4 commercially pure titanium and grade 5 titanium alloy with different surface treatments for mini-implants.


METHODS
MC3T3 cells were plated on machined, acid-etched, or acid-etched grade 4 titanium enriched with calcium phosphate, or machined, anodized, or anodized and calcium phosphate-enriched grade 5 titanium disks. Surface and cell morphologies were assessed by scanning electron microscopy. Cell viability was measured by chemiluminescence, cytoskeletal organization was investigated by immunofluorescence, and real-time polymerase chain reaction for osteoblast-specific genes was performed to measure cell differentiation.


RESULTS
Flattened shapes and strong stress fibers were observed on the machined surfaces; cells on the rough surfaces had a spindle shape, with lower cytoskeletal polarization. Cell proliferation was highest on smooth grade 4 titanium surfaces, whereas cells quickly reached a plateau on rough grade 4 titanium; no difference was observed after 72 hours in the grade 5 titanium groups. Calcium phosphate enrichment on grade 4 titanium significantly increased the messenger RNA levels for alkaline phosphatase and osteocalcin. Osteoblastic markers were higher on the grade 5 titanium machined surfaces than on the rough surfaces, and comparable with acid-etched grade 4 titanium.


CONCLUSIONS
Although the grade 4 titanium enriched with calcium phosphate had the highest level of differentiation in vitro, the grade 5 titanium machined surfaces supported cell proliferation and matrix synthesis, and induced high expression of early differentiation markers. Increased mechanical resistance of grade 5 titanium makes it a potential candidate for orthodontic mini-implants.
Section of Odontostomatologia, University of Parma, Parma, Italy. carlo.galli@unipr.it
Carlo
C
Galli
Marilina
M
Piemontese
Francesca
F
Ravanetti
Simone
S
Lumetti
Giovanni
G
Passeri
Mauro
M
Gandolfini
Guido M
GM
Macaluso
D016475:3T3 Cells; D000134:Acid Etching, Dental; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002130:Calcium Phosphates; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D020099:Coated Materials, Biocompatible / Q000494:pharmacology; D003722:Dental Alloys / Q000494:pharmacology; D015921:Dental Implants; D003799:Dental Stress Analysis; D008163:Luminescent Measurements; D051379:Mice; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000096:biosynthesis; D053244:Osteoprotegerin / Q000096:biosynthesis; D013499:Surface Properties; D014025:Titanium / Q000494:pharmacology
D002130:Calcium Phosphates; D020099:Coated Materials, Biocompatible; D003722:Dental Alloys; D015921:Dental Implants; D053244:Osteoprotegerin; D015675:Osteocalcin; D014025:Titanium; D000469:Alkaline Phosphatase