Composite Restoration Wear Analysis
Amalgam based restoration has long been abandoned although still practiced its popularity has waned due to the possibility of mercury content on amalgam. A widely and more popular method of restoration is to use of resin based composites, prevalent in posterior teeth restoration. Resin based restoration is more popular to amalgam based restoration, again being mercury free and esthetically it is more appealing to patients where a resin based composite blends well with the teeth. Occlusal wear is one of the common causes of posterior failure. Although unavoidable, researchers have developed new and improved version of resin based composites thus improving wear resistance. From fillers to resin compositions of the material, new developments have been discovered to prolong resin based restoration. Filler types such as barium silicate, quartz and ytterbium fluoride have improved the wear resistance.
There have been several commonly practiced methods in evaluating intraoral wear of resin based composites; a method developed by Leinfelder which uses six calibrated clinical cast models showing progressive wear in 100 micrometer increments. Note that such measurement is made possible with use of a tool maker microscope. Another method is the Moffa-Lugassy or M-L wherein a scale consisting of 18 standard cast models all different at 25 micrometer increments, which shows the early stages of wear. The cast on an M-L method are cylindrical in shape rather than modeled from an actual tooth.
When determining occlusal wear measuring devices are needed to come up with a more objective examination. A tool maker microscope is one such tool. Also known as a measuring microscope usually incorporated with a compound microscope lenses or with a special lens for greater magnification. A tool maker microscope stage is equipped with a linear scale used to measure the stage motion which has the ability to measure positional differences. There are tool maker microscopes that are attached to a computer with the ability to capture video; it can record images for later studies or comparison. With the linear scales built unto the stage where the focusing mechanism of the microscope is directed. Using a computer attached to the tool maker microscope an object on stage is automatically measured, recording the distance every time a movement occurs.
Other mechanical devices used for measuring occlusal wear are; stereo microscope, laboratory scale, customized profilometers. Although used extensively in laboratories the result where inadequate producing inaccurate replicas and presenting repositioning problems and device restrictions.
A new technology which uses digital mapping scanning the tooth surface produces a more precise mechanical method for indirectly analyzing restoration wear. Providing a more quantitative and qualitative data which shows precise information on how much a composite wear has occurred and showing which areas of the restoration the wear has occur.
What are the advantages of digital mapping? The human eye has a limited optical ability compared with the digital mapping which has a higher resolution. Also the digital mapping has the advantage of elimination subjectivity compared to clinical studies of resin based composite wear. And has the advantage of covering the total surface area when measuring composite restoration. Read more on this topic
