Efficacy of the Nance appliance as an anchorage-reinforcement method.

INTRODUCTION: 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.

Evaluation of early healing events around mesenchymal stem cell-seeded collagen-glycosaminoglycan scaffold. An experimental study in Wistar rats.

PURPOSE: Tissue engineering using cell-seeded biodegradable scaffolds offers a new bone regenerative approach that might circumvent many of the limitations of current therapeutic modalities. The aim of this experiment was to study the early healing events around mesenchymal stem cell-seeded collagen-glycosaminoglycan scaffolds. METHODS: The 5-mm critical size defects were created in the calvarial bones of 41 Wistar rats. The defects were either left empty to serve as controls (n = 11), filled with cell-free scaffolds (n = 12), cell-seeded scaffolds that were maintained in standard culture medium (n = 9), or cell-seeded scaffolds that were maintained in osteoinductive factor-supplemented medium (n = 9). The animals were sacrificed at 7 days after surgery, and specimens were prepared for histological analysis. Early healing events such as host cell penetration, blood vessel in-growth, and scaffold integration were observed. The degree of inflammatory cell infiltrate was assessed. RESULTS: While defects in the control group healed with a thin fibrous tissue, the collagen-glycosaminoglycan scaffold in the test groups preserved the three-dimensional form of the defects. After 7 days in vivo, the scaffold maintained its integrity and appeared populated with host cells. The cell-seeded scaffold induced more inflammatory response compared to the cell-free scaffolds. New blood vessels and areas of early bone formation were also evident in the cell-seeded scaffolds. CONCLUSIONS: In conclusion, the findings show that mesenchymal stem cell-seeded collagen-glycosaminoglycan scaffolds have good tissue tolerance and exhibit an osteoinductive effect as indicated by early stage healing.

Re-osseointegration on rough implant surfaces previously coated with bacterial biofilm: an experimental study in the dog.

OBJECTIVE: The purpose of the study was to investigate whether osseointegration can occur on rough implant surfaces that previously had been coated with bacterial biofilm. MATERIALS AND METHODS: The premolars on both sides of the mandible in four beagle dogs were extracted. Following 3 months healing, three titanium implants Ti-Unite, Nobel Biocare were partially inserted in the left side of each mandible. Some threads protruded from the tissues into the oral cavity. Plaque accumulated on the exposed part of the implant. Following a 5-week healing period, the contaminated parts of each implant were treated using three different techniques: (1) swabbing with citric acid for 30 s followed by rinsing with physiological saline, (2) cleansing with a toothbrush and physiological saline for 1 min, and (3) swabbing with 10% hydrogen peroxide for 1 min followed by rinsing with physiological saline. The treated implants and one pristine implant (control) were installed to the full implant length on the contralateral sides of the mandibles. Following 11 weeks of healing, the dogs were sacrificed and biopsies were obtained. Ground sections were prepared for histomorphometric analysis. RESULTS: All treatment modalities were associated with direct bone-to-implant contact on the portion of implant surface previously exposed to the oral environment. CONCLUSIONS: The results demonstrate that rough surfaces, which were plaque contaminated and cleaned by different methods, can re-osseointegrate.