1 The median is the middle value of the data set. 2  The lower quartile (Q 1) is the median of the lower half of the data set. 3  The upper quartile (Q 3) is the median of the upper half of the data set. 4  The interquartile range (IQR) is the spread of the middle 50% of the data values.
Removable Essix retainers typically cost between $100-$250 for one or $200-$500 for two. They are made from a vacuum sealed clear plastic that is less noticeable but more likely to break or warp, meaning that you could be paying the price more than once for this style of retainer.
1 On average, a retainer can cost anywhere from $500 to $2,100 for both the top and bottom. 2  For those that have dental insurance, many policies will cover a portion of the procedure depending on what the deductible, co-pay, etc.3  For example, a patient in Houston, Texas had bonded retainers ordered for a total of $1,400. If braces are not needed, an orthodontist can fit a retainer to fix problems such as an overbite. 2  On average, a retainer can cost anywhere from $500 to $2,100 for both the top and bottom.