<a href="https://www.webmd.com/webmd/consumer_assets/controlled_content/healthwise/multimedia/anatomy_of_the_mouth_multimedia_tp12512.xml" data-metrics-link="" data-crosslink-type="article">Mouth</a>&nbsp;guards are coverings worn over&nbsp;teeth&nbsp;and often used to protect&nbsp;<a href="https://www.webmd.com/oral-health/rm-quiz-what-do-you-know-about-your-teeth" data-metrics-link="" data-crosslink-type="tools">teeth</a> from injury from teeth grinding and during sports. <b>Stock&nbsp;mouth protectors are</b> preformed and come ready to wear. They are inexpensive and can be bought at most sporting goods stores and department stores. However, little can be done to adjust their fit, they are bulky, make breathing and talking difficult, and they provide little or no protection. Dentists do not recommend their use.

<b>Boil and bite mouth protectors</b>&nbsp;also can be bought at many sporting goods stores and may offer a better fit than stock mouth protectors. The "boil and bite" mouth guard is made from thermoplastic material. It is placed in hot water to soften, then placed in the mouth and shaped around the teeth using finger and&nbsp;tongue&nbsp;pressure.?
<blockquote>“ Generally, mouth guards cover your upper teeth only, but in some instances (such as if you wear braces or another fixed dental appliance on your lower jaw), your dentist will make a mouth guard for the lower teeth as well.&nbsp;”</blockquote>
<b>Custom-fitted mouth protectors</b>&nbsp;are individually designed and made in a dental office or a professional laboratory based on your dentist's instructions. First, your dentist will make an impression of your teeth and a mouth guard is then molded over the model using a special material.

Source: www.webmd.com