Discrepancy Index Instructions
Occlusion is determined by placing the backs (bases) of the pre treatment dental casts on a flat surface after they have been pushed together in occlusion. All measurements must be made from this position.
Overjet is a measurement between two antagonistic anterior teeth (lateral and/or central incisors) comprising the greatest overjet and is measured from the facial surface of the most lingual tooth (Mx or Mn) to the middle of the incisal edge of the more facially positioned tooth (Mx or Mn). For overjet of 0 – 0.9 mm (edge-to-edge), 1 pt is scored; for overjet of 1 to 3 mm, no pts are scored; for 3.1 – 5 mm, 2 pts are scored; for 5.1 – 7 mm, 3 pts are scored; for 7.1 – 9 mm, 4 pts are scored; and if over 9 mm, 5 pts are scored. In addition, if there are teeth with negative overjet (canine to canine teeth in anterior crossbite), they are recorded as 1 pt per mm per anterior (canine to canine) tooth in crossbite.
For overbites of up to 3 mm, no pts are scored. If the overbite is between 3.1 to 5 mm, 2 pts are scored; if between 5.1 to 7 mm, 3 pts are scored. If the lower incisors are impinging on the palatal tissues and/or 100% overbite, then 5 pts are scored.
ANTERIOR OPEN BITE:
For each anterior tooth in an edge to edge relationship (0 mm) score 1 pt per tooth. Then add for each anterior tooth in open bite (>1 mm) any fractional remainder to the next full mm 1 pt per mm per tooth in an open bite. No points are scored for any tooth that is blocked out of the arch due to space deficiency or not fully erupted.
LATERAL OPEN BITE:
For each maxillary tooth (from the 1st premolar to 3rd molar) in an open bite relationship with the lower arch, 2 pts are scored per mm of open bite for each tooth. No pts are scored for any tooth that is blocked-out of the arch or simply not fully erupted.
When scoring, measure the most crowded arch circumference (only one arch) between the first molars. From 0 to 1 mm, 0 pts are scored; from 1.1 to 3 mm, one pt is scored; from 3.1 – 5 mm, 2 pts are scored; from 5.1 – 7 mm, 4 pts are scored. If the crowding is greater than 7 mm, 7 pts are scored.
When scoring occlusion, the Angle classification is used. If the mesiobuccal cusp of the maxillary first molar occludes with the buccal groove of the mandibular first molar or anywhere between the buccal groove and the mesiobuccal or distobuccal cusps, no pts are scored. If the mesiobuccal cusp of the maxillary first molar occludes with the mesiobuccal (Class II end-to-end) or distobuccal (Class III end-to-end) cusps of the mandibular first molar, then 2 pts per side are scored. If the relationship is a full Class II or III, then 4 pts per side are scored. If the relationship is greater or beyond Class II or III, then 1 additional pt per mm is scored. Each side should be scored individually and included in the point accumulation for this category.
LINGUAL POSTERIOR CROSSBITE:
For each maxillary posterior tooth where the maxillary buccal cusp is lingual to the buccal cusp tip of the opposing mandibular tooth (from the first premolar to the third molar), 1 pt is scored.
BUCCAL POSTERIOR CROSSBITE:
For each maxillary posterior tooth (from the first premolar to the third molar) in complete buccal crossbite, 2 pts are scored.
CEPHALOMETRICS: Construction of Mandibular Plane
- If the ANB angle is (6° or greater) OR (-2° or less) , then 4 pts are scored. An additional pt is scored for each degree above 6° or below -2°.
- If the SN-MP angle is between 27° and 37° , zero pts are scored.
- If the SN-MP angle is 38° or greater, then 2 pts are scored for each degree above 37°.
- If the SN-MP angle is 26° or less, then 1 pt is scored for each degree below 27°.
- If the Lower Incisor to MP angle is 99° or greater, then 1 pt is scored for each degree above 98°.
OTHER: (List number of occurrences and points on DI form.)
- Supernumerary teeth – 1 pt for each extra tooth
- Ankylosis of permanent teeth – 2 pts per tooth
- Anomalous morphology of tooth size & shape (e.g. natural and/or iatrogenic) - 2 pts per tooth
- Impaction (except third molars) of teeth – 2 pts per tooth
- Missing teeth (except third molars) – 1 pt per tooth; congenitally missing teeth – 2 pts per tooth
- Midline discrepancy – 2 pts for 3 mm or more
- Spacing – 2 pts per arch for generalized spacing of 4 teeth or more; 2 pts for Mx central diastema of 2mm or more
- Tooth transposition – 2 pts for each event
- Skeletal asymmetry (treated nonsurgically) – 3 pts (appropriate diagnostic information
- Additional treatment complexities – 2 pts each