Denture occlusal rims, or bite rims, do more than just record the patient’s bite. They help your technician choose tooth size and shape, determine the correct position of the incisal edge of the teeth and establish esthetic gingival contours of your full denture.
Bite rims are designed with the wax directly over the patient’s bony ridge. This is the most stable position for denture teeth to be set for function and wear. The bite rims also record the patient’s occlusal vertical dimension or the VDO. This is the vertical distance between the upper and lower jaws when natural teeth or denture teeth are in correct occlusion. An appropriate VDO will appear as an ordinary positioning of the patient's nose, lips and chin. An excessive VDO will appear as though the patient has something stuffed into their mouth and the patient may not be able to close his or her lips around the bite rims. A deficient VDO will appear as though the patient's mouth has collapsed, the chin will appear too close to the nose, and the lip corners will be drawn down.
Sometimes it is necessary for your technician to block out any undercuts on the master model while fabricating the base plate to avoid breaking it during bite rim fabrication. This could make the baseplate feel a little loose in the mouth. It may be necessary to use a small amount of denture adhesive for your try in appointments. Once the denture is processed, the fit will be correct.
Before trying bite rims, measure your patient’s VDO. With the patient wearing their old dentures, mark a dot on the patient’s nose and a dot on their chin. Record the distance between the two dots. If the patient has worn down their old teeth or if they are edentulous, you will need to estimate the VDO and determine the correct position based off how the wax rims look and feel inside the mouth. You can add or remove wax from the rims as necessary until the exact measurement you recorded is reached.
Next, you will want to check the amount of lip support the wax rims give. Look at your patient’s side profile. The edge of the wax rim should fall in-line with the incisal edge of the upper anteriors. Have the patient talk with the bite rims in place; determine if the edge is in a comfortable place for speaking and smiling. This is especially important if your patient has a natural class II or class III bite that you may want to try to correct. If necessary, add wax or remove wax from the rim to achieve the correct incisal edge.
Check the occlusal plane by ensuring that the edge of the upper wax rim is straight across and not slanted to one side or the other. When smiling, the incisal edge should show in equal amounts across the lip line. If corrections are needed, mark the correct occlusal plane by scoring a line in the wax or by drawing it with a sharpie. Mark the midline by marking a line on the wax at the exact middle of the patient’s face. Also mark the approximate positions of the canine teeth. This should be about even with the corner of the patient’s lips at rest. Mark the height of the patient’s lips when they are smiling as this will determine the correct height of the teeth selected. When all your measurements have been recorded, add the impression material to the bottom wax rim and help guide the patient into centric relation.
If your patient has a current denture and they are happy with the general appearance and size of the teeth, send a study model copy for reference. It is also helpful to send a study model when describing what your patient does not like about their current denture. If you are making a first denture, pictures of the patient’s face will help your technician choose the correct tooth size and shape. Record any specific desires or expectations your patient may have. Lastly, do not forget to record the desired shade.
By giving your technician as much information as possible at this preliminary stage, they will fabricate a new denture your patient will love with fewer appointments.
Please be reminded that should you wish to discuss a case in more detail, our experienced technical team is here to assist you.