Iowa Section of AADR - The University of Iowa College of Dentistry

23. The Effect of Maxillary Restriction on Mandibular Fossa Morphology
J. Kelly 1 , N.E. Holton 1 , S.D. Marshall 1 , R. Franciscus 1 , T.E. Southard 1
1 University of Iowa
Objectives: In previous analyses, we found that experimentally-induced maxillary restriction in a pig model
resulted in predictable changes in mandibular condylar morphology. In the present study we extend our analysis to
assess the potential effects of maxillary restriction on the morphology of the mandibular fossa.
Methods: Ten female domestic pig sibship cohorts, each consisting of three individuals, were allocated to one of
months. The sham group underwent surgery, receiving only screw implantation, and the control group underwent
no surgical procedure. Pigs were euthanized at six months of age. Mandibular fossa length and breadth were
assessed using the Mann-Whitney U-test. Additionally, we assessed variation in mandibular fossa size and shape
via geometric morphometric analysis of coordinate landmark data describing the fossa. To assess these data,
we used Procrustes analysis, which distills a form, represented by coordinate landmark data, into size and shape
information. Shape differences were quantitatively assessed using principal components (PC) of Procrustes scaled
coordinate landmarks.
Results:
differences in shape. The results of our principal components indicated that the experimental group, relative to
the control and sham groups, had a more superiorly positioned joint surface with lateral displacement relative to
(from our previous analysis) describing differences in mandibular condylar morphology (r=0.49; p=0.012).
Conclusions:
This suggests that altering maxillary growth may have important consequences on masticatory function and joint
biomechanics.
Supported by: University of Iowa, College of Dentistry, Iowa Dental Research Grant
24. Effect of Benzalkonium Chloride Adhesive System on Resin-Dentin Bond Durability
A. Murray 5 , M.A. Vargas 5 , S. Geraldeli 9 , F. Qian 8 , L. Chen 7
5 University of Iowa College of Dentistry, Iowa City, IA; 7 Research and Development, Bisco, Schaumburg, IL;
8 Department of Preventive and Community Dentistry, University of Iowa, Iowa City, IA,; 9 Restorative Dental
Sciences, University of Florida, Gainesville, FL
Objectives: The resin-dentin bond is degraded by endogenous dentinal proteinases activated by acidic compounds
contained in dental adhesive systems. Several compounds have been suggested to neutralize these proteinases,
including benzalkonium chloride (BAC). The objective is to evaluate the effect of incorporating various
concentrations of BAC on the short and intermediate bond strength of a one-step self-etch adhesive.
Methods: Forty-eight human molars stored in 0.5% chloramine solution were used within 3mo of extraction
and randomly assigned to 4 groups (n = 12). Flat dentin surfaces were prepared with a water-cooled, low-speed
diamond saw (Isomet1000, Buehler). A standardized smear layer was prepared using 600-grit wet sandpaper.
Three experimental one-step self-etching adhesives (Bisco Inc.) were formulated with 0.1%, 0.2% and 0.5% BAC
following manufacturer’s guidelines. A three increment build-up of approximately 5mm was made using resin
composite Estelite Sigma Quick (Tokuyama). Each increment was light cured (690-730 mW/cm 2 ) for 20sec with
sectioned to obtain six rectangular sticks from the central part of the bonded surface with a cross section area of
approximately 0.8mm. At random, two sticks from each group were subjected to tension at a crosshead speed of
1.0mm/min using a Zwick testing machine at 1wk and two sticks at 10wks.
Results: A two-way repeated measures ANOVA was used to evaluate differences among the groups by adhesive and
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