Disk opener scrapers that scrape dirt off the outside of disk openers on planters come in a variety of designs. Each has advantages and disadvantages, depending on soil conditions in your area. For example:
-old-school spring-steel scrapers are adjusted by either bending the scraper closer or farther from the disk opener, or by adding or subtracting washers to the mounting bolts. These are the most economical scrapers on the market, but also the shortest -ived.
-rotary scrapers are small wheels about 3 inches in diameter that turn against the disk openers. Plastic rotary scrapers have good longevity, depending on the abrasiveness of soils. In fact, the plastic wheel usually outlasts the "button" at the center of the wheel that holds them to their mounting arm. Steel rotary scrapers last a long, long time, but make an incredible amount of squealing noise as they turn against the disk openers. I guess you can turn up the radio if it's too annoying. A weakness of both plastic and metal rotary scrapers is that if the planter gets dragged through serious mud, the wheels plug, stop turning, and the mounting arms get bent or ripped out of place.
-Carbide scrapers have a carbide bit attached to the mounting arm. They are expensive, but they last a long, long time and handle muddy conditions about as good as any scraper. Some farmers in sandy soils report that carbide scrapers actually wear into the disk openers and shorten disk opener longevity.
-running without scrapers is an option for some farmers. I've got customers who haven't used scrapers in 20 years, and they get along fine. Other farmers have tried running without scrapers, but can't make a complete round in their type of soil without problems. If you're curious about saving the cost of scrapers, try removing the scrapers from a couple outside rows and see how those rows perform. The outside rows are the ones that always get dragged through mud holes or wet spots, and moist soil will tell you quickly if you need scrapers or not.