Occlusion, simply defined, is how teeth meet when the lower and upper jaw come together. Proper occlusion is necessary for eating, aesthetics, and disease prevention. However, many factors can cause malocclusion including trauma and genetics.
Before we cover the Occlusal Analysis, let’s review a few definitions from our Dentist’s guide to Erosion, Attrition, Abrasion, and Abfraction. If you’ve already read this article, feel free to skip ahead.
What is erosion, attrition, abrasion and abfraction?
Erosion is the wearing away of the tooth surface by an acid, which dissolves the enamel and dentine. Dental attrition is the wearing of the incisal or occlusal surfaces of teeth as a result of functional or parafunctional tooth-to-tooth contact. Some causes of dental attrition include chewing, Bruxism, porcelain crowns, an inadequate lubrication from saliva.
Related Reading: How to Perform a Salivary Gland and Salivary Flow Exam
Dental abrasion is tooth wear originating from friction or mechanical forces from a foreign object, and it predominantly impacts premolars and canines. Abfraction is tooth wear from flexural forces, but it has not been supported by dental research.
Dental Midline Assessment
The first step is performing a dental midline assessment. To do this, dentists should check and record the dental midline and cross check the maxillary midline with the patient’s facial midline to see that they are similar.
To diagram a midline discrepancy, such as a mandible 2 mm to the left, use a cross set of lines with a dotted vertical line and a solid horizontal line. Next, draw a solid line 2 mm to the left of the vertical dotted line and write 2 mm next to it.
Dentists can perform a fremitus test by placing the index fingertip on a single maxillary anterior tooth and asking the patient to tap their back teeth together slow and hard. While the patient taps their back teeth, feel for vibration or deflection of the anterior tooth.
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Erosion, Attrition, Abrasion, and Abfraction Exam
To perform an erosion, attrition, abrasion, and abfraction exam, dry the teeth with air and/or cotton and inspect teeth carefully under direct or reflected light. Next, document the severity of erosion with pictures and use these models to compare erosion over time.
Attrition can be scored as follows, starting from lowest to greatest amount of wear:
- 0 = no wear at all
- 1 = small enamel wear (physiologic)
- 2 = large enamel wear (accelerated but no dentin exposed)
- 3 = large enamel & dentin exposed (less than 1/3 of crown)
- 4 = greater than 1/3 of crown lost
Tooth wear from abrasion typically looks like a wedge or V-shaped indentation of the tooth at the gum margin, and it appears worn, shiny and is often discolored at the cervical margin.
Although it has not been supported by research, when teeth flex under pressure (abfraction) they touch each other creating tension on one side (v-shaped depressions) and compression (C-shaped depressions) on the other side of the tooth.
To perform an assessment of the patient’s class of occlusion, with the teeth in intercuspal position, retract the cheek on one side and then evaluate the position of the maxillary molar and canine relative to its mandibular counterpart.
To examine the posterior teeth for Intercuspal Contact Position, use paper forceps with the mylar strip positioned at the end of the holder. Place the mylar in between the patient’s teeth and ask them to close and hold their teeth together. Next, tug the paper slightly to test if it is retained between the teeth or not.
To perform an overbite/overjet assessment, hold the mm ruler horizontally with the teeth closed, and position the end of the ruler against the lower incisors just under the incisal edge of the maxillary incisors.
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