ABSTRACT

Objective:

To compare the initial failure rate (≤4 months) for extra-alveolar mandibular buccal shelf (MBS) miniscrews placed in movable mucosa (MM) or attached gingiva (AG).

Materials and Methods:

A total of 1680 consecutive stainless steel (SS) 2 × 12-mm MBS miniscrews were placed in 840 patients (405 males and 435 females; mean age, 16 ± 5 years). All screws were placed lateral to the alveolar process and buccal to the lower first and second molar roots. The screw heads were at least 5 mm superior to the soft tissue. Loads from 8 oz–14 oz (227 g–397 g, 231–405 cN) were used to retract the mandibular buccal segments for at least 4 months.

Results:

Overall, 121 miniscrews out of 1680 (7.2%) failed: 7.31% were in MM and 6.85% were in AG (statistically insignificant difference). Failures were unilateral in 89 patients and bilateral in 16. Left side (9.29%) failures was significantly greater (P < .001) compared with those on the right (5.12%). Average age for failure patients was 14 ± 3 years.

Conclusion:

MBS miniscrews were highly successful (approximately 93%), but there was no significant difference between placement in MM or AG. Failures were more common on the patient's left side and in younger adolescent patients. Having 16 patients with bilateral failures suggests that a small fraction of patients (1.9%) are predisposed to failure with this method.

ABSTRACT

Objective:

To provide a road map of buccal cortical bone thickness in interradicular locations where miniscrew implants are commonly placed.

Materials and Methods:

Cone-beam computed tomography images from 100 study quadrants (50 maxillary and 50 mandibular) were studied. Cortical bone thickness was measured at the most mesial point, the midpoint, and the most distal point in interradicular areas from the canine to the first molar in both arches at 4 mm and 6 mm from the alveolar ridge. Indicator variables of whether the cortical bone thickness was thinner than 1 mm and thicker than 1.5 mm were constructed and analyzed in a general linear mixed model.

Results:

Buccal cortical bone was significantly thinner at a point bisecting two teeth than the bone adjacent to the teeth (P < .0001). The site with the greatest percentage of measurements <1 mm (20%) was at the midpoint bisecting the mandibular canine and the first premolar. The site with the highest percentage of measurements >1.5 mm (50%) was in the mandible adjacent to the first molar (distal to the midpoint of the second premolar and first molar) at 6 mm from the alveolar crest.

Conclusion:

Cortical bone thickness is significantly thinner centrally between two teeth than in the areas adjacent to the roots.

ABSTRACT

Objective:

To evaluate the proliferation and morphology of human osteoblasts cultured on two brands of mini-implants after 24, 48, and 72 hours, in addition to the chemical composition found on their surface.

Materials and Methods:

Two brands of mini-implant (Morelli and Neodent) were evaluated; polystyrene was used as a control group (n = 3). Osteoblasts were cultured on the surface of sterilized mini-implants in a CO₂ incubator at different time periods (24, 48, and 72 hours). Osteoblast proliferation was quantified by scanning electron microscopy using up to 5000× magnification, and cell morphology was analyzed by a single observer. For the chemical analysis, spectroscopy X-ray fluorescence was used to identify and quantify chemical components on the surface of the mini-implants.

Results:

Two-way ANOVA showed no significant interaction between the factors studied (P = 0.686). A Tukey test revealed no significant difference in osteoblast proliferation between the mini-implants at all studied periods; however, a difference in cell proliferation was detected between the Neodent and the control group (P = .025). For all groups, time had a direct and positive effect on osteoblast proliferation (P < .001). The significant elements present in both brands of mini-implants were titanium, aluminum, vanadium, and iron.

Conclusions:

Osteoblast proliferation was present on the mini-implants studied, which increased over time; however, no significant difference between brands was observed. No difference was seen between the mini-implants evaluated in terms of chemical composition. Cell adhesion after 72 hours suggests that areas of bone remodeling can be achieved, thus initiating the process of mini-implant anchorage.

This listing of academic opportunities is provided as a free service to the profession and the community.

BRITISH COLUMBIA, CANADA

University of British Columbia

Division of Orthodontics

Apply: Rosamund Harrison, DMD Msc

rosha@dentistry.ubc.ca

Professor and Chair, Department of Oral Health Sciences

University of British Columbia, 2199 Wesbrook Mall

Vancouver, Canada V6T 1Z3

Rank and Salary: Commensurate with training and experience; Full time.

Require: Postgrad training & experience in orthodontics/be eligible for licensed specialist

FLORIDA

Nova Southeastern University

College of Dental Medicine

Ft Lauderdale, FL

Must apply at: www.nsujobs.com position #992943

Dr. Abraham Lifshitz, Professor & Chair

Orthodontic Dept,

Lip incompetence resolved by active vertical control in nonsurgical treatment of a protrusion case with vertical maxillary excess

Johnny JL Liaw,

Jae Hyun Park,

Fang Fang Tsai,

Betty MY Tsai, and

Wendy WT Liao