Biomaterials Group: | Biomechanics | Mechanical Physical Properties |
Biological Evaluation of Materials | Research Members | Collaboration | Equipment
Mercury Toxicity
Potential adverse effects arising from mercury exposure are important issues
of increasing concern to the dental profession and the public. At present,
there is a paucity of information regarding mercury concentrations in patients
with neurological disorders. In previous studies, we reported that the blood
and urine concentrations of mercury and selenium from patients with probable
Alzheimer's disease (AD) are not statistically different from controls.
However, blood and urine mercury concentrations are not reliable indicators
to predict body burden of mercury. Recently, we determined brain tissue
concentrations of mercury and selenium from deceased subjects with AD or
multiple sclerosis (MS), and compared these to normal controls without known
central nervous system disorders. Since brain mercury concentrations from
deceased subjects with either AD or MS were not significantly higher than
controls, the present study provides no scientific support for the hypothesis
that mercury plays a significant role in the pathogenesis of these neurodegenerative
disorders.
Dental Sealants
For about 30 years, plastic resins have been used in dentistry as restorative
materials to repair/seal teeth. Recently, a study indicated that a significant
amount of bisphenol A, a chemical building block of these resins, leached
into the saliva of patients one hour after placement of a bisphenol A diglycidylether
methacrylate (Bis-GMA)-based sealant. Bisphenol A, the precursor of many
monomers including Bis-GMA, and bisphenol A dimethacrylate have been shown
to exert estrogenic activity in tissue cultures of breast tumor cells. This
finding generated considerable public concern regarding the potential adverse
effects of dental sealants. We are designing studies to determine the quantities
and time-course of leachable bisphenol A, bisphenol A dimethacrylate and
bis-GMA from composite resin after placement in fields containing human
saliva and blood.
Nicotine
Nicotine is the most pharmacologically active ingredient in tobacco products.
A tobacco-related deficit in bone mass has been reported among both pre-
and post-menopausal women, implicating tobacco use as a risk factor in osteoporosis.
Although nicotine has been shown to depress osteoblast activity in a number
of in vitro and animal studies, limited information is available regarding
the effects of nicotine on bone development and remodelling. Furthermore,
fundamental questions about the effects of nicotine on serum levels of several
important endocrine hormones, which include 25-hydroxyvitamin D, 1,25-dihydroxyvitamin
D, parathyroid hormone and calcitonin, remain unanswered. With the dramatic
increase in smokeless tobacco use among children and youths, studies will
be conducted to determine the effects of nicotine in old and young female
rats to provide information on the role of nicotine in mature and rapidly
developing skeletal systems. Together, the results of these studies will
clarify the role of nicotine on bone. Furthermore, they will provide a basis
for understanding the potential health implications associated with the
use of tobacco products.
Cytotoxicity of Dental Materials
The biocompatibility of dental materials must be assured to prevent adverse
biological reactions. We have focused on the effects of two restorative
dental materials, namely, denture base resins and root canal sealing materials,
in an effort to determine their cytotoxicity. Recent studies have shown
that, in vitro, eluate from microwave-activated resin decreases gingival
fibroblast cell viability more than heat-activated resin eluate, but less
than eluate from the chemically-activated resin. The proposal for use of
glass ionomer cements as a root perforation material has drawn attention
to its biocompatibility with tissues of the periodontium. We determined
that eluate from two glass ionomer cements, one chemically-activated and
one both chemically and light-activated, were slightly less harmful to periodontal
ligament cells than eluate from dental amalgam. These research projects
exemplify our efforts to test the cytotoxicity of new dental materials and
materials intended for novel applications.
Caries Control Treatment
Rampant caries presents a challenging technical and socio-economic problem
to the dental profession. While full restoration of the dentition is the
ideal treatment, economic considerations and/or the lack of modern dental
operatories in under-served geographic areas can make this goal unrealistic.
Caries control involving the minimal use of dental instrumentation is the
first and primary treatment goal. The recent introduction of resin modified
glass ionomer dental cements (RGIC) may make this first rehabilitation step
possible.
A clinical trial of a caries control treatment (CCT) that involves the placement
of RGIC in teeth prepared without the use of rotary instrumentation is being
conducted at the UNMC College of Dentistry. The longitudinal study of CCT
restorations with an average age of 10.2 months has found that all restorations
are satisfactory in performance and no restorations have required replacement.
This treatment allows patients with complicated treatment needs to receive
care over an extended period of time, minimize the patient's financial burden
and facilitate treatment scheduling.
Orthodontic Bracket Cements
An increase in dental caries occurrence is common during orthodontic treatment.
The application of fluoride-releasing glass ionomer cements for the attachment
of orthodontic brackets is seen as a possible solution to this problem.
A clinical trial is being conducted to evaluate the use of these cements.
Patients receiving comprehensive orthodontic care at the UNMC College of
Dentistry are receiving brackets bonded either with a conventional resin
adhesive or with a new light-cured glass ionomer cement adhesive. The incidence
of bracket de-bonding and dental caries formation is being evaluated.
Last modified: July 16, 2008 12:08 PM