Research Thrusts

Driven to Discover

Present Research Thrusts and Interests

As an interdisciplinary research group, the MDRCBB has made strides in evaluating dental materials, restorative dentistry design, and improvement of biomaterials through bio-functionalization and mechanical testing. New research and new collaboration with visiting researchers, and industrial partners contribute to the ever growing list of endeavors. Some of the present research thrusts and interest include a new generation of Artificial Resynthesis Technology (ART), restorative dentistry evaluation using finite element analysis, and virtual dental anatomy simulation.

Shape Optimization of Dental Restorations

This is an interdisciplinary project involving engineers and dental scientists. Excessively high stresses at the interface between tissues and restorations are thought to be one of the main causes of restoration failure, such as deterioration at the restoration margins and bone resorption around dental implants. We propose to use engineering tools in the form of finite element simulation, shape optimization and acoustic emission to improve designs of dental restorations, and to perform clinically relevant, in-vitro mechanical tests to validate the approach. The aim is to provide the much needed experimental evidence to demonstrate that numerical simulation and structural optimization could play an important role in dental treatment planning.

Stresses at the tooth-composite interface with (a) conventional and (b) optimized cavity design.

Demineralization and Remineralization

The formation of dental caries is a dynamic process with intermittent episodes of mineral loss (demineralization) and redeposition (remineralization). Tooth minerals are dissolved by organic acids produced from carbohydrate metabolism of bacteria in tooth surface biofilm (dental plaque). When the secretion of saliva raises the pH, dissolved ions precipitate back to the demineralized area. Contemporary concept for dental caries treatment emphasizes mineral redeposition to reverse the caries process rather than treating caries lesions as damaged tissues subject to total eradication.

The initial stage of tooth decay (dental caries) and its reverse process of remineralization is simulated in vitro using a chemical model. The extent of the caries is measured with microhardness testing and quantitative micro-radiography. This quantitative technology enables us to follow the progression of caries and develop new strategies that can be used in the prevention and treatment of tooth decay. This effort is led by Dr. Daranee Tantbirojn Versluis, who has introduced a number of innovations in artificial caries assessment of new materials. The demineralization and remineralization (demin/remin) process is a major growth area for the MDRCBB.

hardnesscaries graph

lesion DVwhite spot

Nanocomposites and tissue engineering

MDRCBB has a major research effort in the development of Calcium Hydroxy Apatite/ Collagen nanocomposites as bone and dental hard tissue replacements. This research effort was headed by Dr. Ching-Chang Ko (now of the University of North Carolina) and Dr. Myung C. Chang. This work uses biomimetic processes to produce nanocomposites, which may offer novel properties and remineralization potential, as well as serve as scaffolding for the deposition of natural tissues in situ. The technology uses gated filters and pH controlled feedback pumps to create a benign biological environment favorable to the precipitation of highly calcified structures.

Implant Technology

Biofunctional surfaces to induce rapid bone integration of dental and maxillofacial implants

Commercially pure titanium (cp Ti) dental implants have been widely and successfully used with high rates of clinical success. However, there is still a lack of reliable synthetic materials to be used either a) when immediate loading of the implant is desired or b) when bone presents compromised conditions due to trauma, infection, systemic disease and/or lack of significant bone volume.

We are developing biomimetic strategies of surface modification to obtain metallic implants with osteostimulative capabilities. These surface modifications will provide implants with a rapid rate of new bone growth and with osseocoalescence, i.e. direct chemical contact with the surrounding tissues. Different chemical and biochemical surface treatments have already been successfully developed. The resulting biomimetically-modified implants can be reliably used in those more demanding clinical situations.

biofunctional surfaces

Above: Confocal laser microscopy images of surfaces (in grey) that have been treated to induce rapid extracellular matrix deposition (fibrils of fibronectin in green) by osteoblasts-like cells.

Biofunctional Surfaces

Rough and Bioactive surfaces

Cp Ti surfaces treated to obtain a combination of an optimal random surface topography (in the micro and nanolevels) with a chemical modification of the naturally-formed titania layer have been proved bioactive. These rough and bioactive surfaces can nucleate and grow a homogeneous hydroxyapatite layer both in vitro and in vivo. They stimulate the osteoblasts differentiation and trigger a rapid bone formation that mechanically fixes implants under immediate-loading conditions.

Above: Enviromental Scanning Electron Microscopy (ESEM) images showing rough and bioactive surfaces that induce nucleation and growth of hydroxyaptite (X-Ray diffraction pattern shown) in vitro. ESEM image of an osteoblast on a rough and bioactive surface, which significantly induces osteoblast differentiation (ALP results shown). Histomorphometric results and histology showing a rapid integration of rough and bioactive surfaces under immediate-loading conditions. SEM image showing the apatite layer formed in vivo on these surfaces.

Biofunctionalized surfaces

A simple process using silane chemistry has been proved specific, rapid, and reliable to covalently immobilize biomolecules on metallic surfaces. This methodology can be used to develop biofunctionalized implant surfaces with different or combined bioactivities. The biofunctional molecules can be proteins, growth factors, and synthetic peptides specifically designed to be attached to the surface and/or to self-assemble in order to form coatings with tailored properties. The bioactive properties of the molecules designed and used can be mineral growing and nucleation, osteoblast differentiation (bone regeneration), fibroblasts differentiation (biological sealing), antibiotic, biodegradable, drug delivering, etc.

Above: Schematics of the process used to biofunctionalize metallic surfaces. Different surface characterization (XPS, FT-IR, fluorescent labeling) results that prove specificity and reliability of the process. Osteoblasts-like cells on a cp Ti surface biofunctionalized with a RGD-containing recombinant elastin-like polymer.