Contact Digital Profiling
The three-dimensional profiling system uses DC servo-motors and a null-point contact stylus to provide rapid profiling of the surface of a structure. The surface is stored as a digitized image on a computer disk. This system was developed by Dr. Ralph DeLong, Dr. William H. Douglas, and Mr. Jon Anderson in conjunction with MTS Systems Inc., Minneapolis, MN. It provides an accurate method for the measurement of changes in surface contour, and it can be used to measure either laboratory or clinically produced surface changes.
The Steinbichler Comet 100 digitizing system consists of two rotational stages that automatically position the object for scanning from different views, a white light non-contact scanning system, and a control unit. Data is gathered from the optical digitizer to create 3-dimensional models in the form of a "point cloud." This data is then transferred to the software program, the Virtual Dental Patient, thus creating an accurate 3D digital dental record.
In order to quantify the changes in contour measured by the profiler, it was necessary to develop software that would present the digitized data as a three-dimensional surface. Dr. Ralph DeLong developed the software program AnSur© (Regents, University of Minnesota), which provides full three-dimensional fitting of two surfaces with the necessary graphics to locate and analyze changes that occur between the two surfaces, in terms of volume (mm³) and depth (µm).
Computer generated graphic image of the occlusal (chewing) surface of a tooth showing wear on the enamel tissue.
Officially called A Digital Environment for Learning Oral Anatomy - a Student Oriented Approach, this teaching aid takes Oral Anatomy from traditional teaching methods into a highly efficient digital environment, using a software program to allow students to rotate or manipulate 3-D models of individual, anatomically correct teeth. This project was initiated by Ms. Maria R. Pintado in response to the Oral Anatomy students' frustrations with visualizing three-dimensional teeth when working from two-dimensional drawings. Ms. Pintado has been digitizing natural teeth and incorporating them into a software program that is an outcome of the Virtual Dental Patient. All deciduous and permanent human teeth are completed. Once the final software additions and modifications are finalized, the software will be copied on CD/DVD disks for use by the students.
Digital Image Correlation
A new method – image correlation method – has been developed to measure the polymerization shrinkage of dental composites. The method provides an optical, non-contact technique whereby free shrinkage of dental composites can be achieved during measurement. Also, instead of an overall average shrinkage value, this method can provide a full-field shrinkage strain measurement over the surface of the specimen, including the depth of cure.
The setup of the experiment includes a CCD camera, an illumination light, curing light and the specimen. The surface of the specimen facing the camera is spray-painted to produce patterns for ease of tracking the deformation.
During polymerization, a series of images of the specimen are taken using the CCD camera. Then, the deformation of the specimen could be analyzed using specialist software to determine the shrinkage strain distribution on the specimen surface.
The picture below shows the shrinkage strain distribution within a composite specimen. The curing light was applied from the left. Red indicates more shrinkage.