Efficacy of the Nance appliance as an anchorage-reinforcement method.
BACKGROUND
The Nance appliance is widely considered to be an efficient method of anchorage reinforcement; however, much of the perceived advantage is based on clinical judgment. The aim of this study was to assess the amounts of anchorage loss and desired tooth movement associated with the Nance appliance.


METHODS
The mandibular arches of 7 beagle dogs were used. The first and third premolars were extracted. Reference miniscrews were placed at the first premolar sites as stable references to measure the amounts of anchorage loss and desired tooth movement. Four beagles were fitted with custom-made Nance appliances on the fourth premolars and orthodontic bands on the second premolars (Nance group). Three beagles were fitted with orthodontic bands on the second and fourth premolars with no anchorage reinforcement (control group). The second premolars were retracted over 15 weeks in both groups. The amounts of second premolar movement (desired tooth movement) and fourth premolar movement (anchorage loss) were recorded at 5, 10, and 15 weeks. The percentages of desired tooth movement and anchorage loss to the total space closure were calculated.


RESULTS
The mean desired tooth movement was significantly more in the Nance group than in the control group at 10 weeks (P <0.05) but was not significantly different at 5 and 15 weeks. The mean percentages of anchorage loss to the total space closure at 15 weeks were 45.7% in the control group and 28.8% in the Nance group. The Nance group had 16.9% less anchorage loss and 16.6% more desired tooth movement than did the control group at 15 weeks (P <0.05). Most of the anchorage loss (80%) in the Nance group occurred during the first 10 weeks.


CONCLUSIONS
The Nance appliance did not provide absolute anchorage, but there was significantly less anchorage loss with it than in the control group. The majority of anchorage loss occurred during the first 10 weeks in the Nance group.
Consultant and lecturer, Division of Public & Child Dental Health, Dublin Dental University Hospital, Trinity College, Dublin, Ireland. Electronic address: drealawadhi@gmail.com.
Ebrahim A
EA
Al-Awadhi
Consultant and senior lecturer, Division of Public & Child Dental Health, Dublin Dental University Hospital, Trinity College, Dublin, Ireland.
Therese M
TM
Garvey
Specialist periodontist, Division of Restorative Dentistry & Periodontology, Dublin Dental University Hospital, Trinity College, Dublin, Ireland.
Mohamed
M
Alhag
Professor emeritus, Division of Restorative Dentistry & Periodontology, Dublin Dental University Hospital, Trinity College, Dublin, Ireland.
Noel M
NM
Claffey
Professor, Division of Restorative Dentistry & Periodontology, Dublin Dental School and Hospital, Trinity College, Dublin, Ireland.
Brian
B
O'Connell
D000818:Animals; D001641:Bicuspid / Q000473:pathology; D001863:Bone Screws; D003722:Dental Alloys / Q000737:chemistry; D004285:Dogs; D008904:Miniaturization; D023421:Models, Animal; D009532:Nickel / Q000737:chemistry; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation*; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D019516:Orthodontic Space Closure / Q000295:instrumentation; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000737:chemistry; D013997:Time Factors; D014025:Titanium / Q000737:chemistry; D014087:Tooth Movement Techniques / Q000295:instrumentation*
D003722:Dental Alloys; C040654:titanium nickelide; D013193:Stainless Steel; D009532:Nickel; D014025:Titanium