M26.23 identifies an excessive horizontal overlap of the teeth — clinically termed overjet — where the upper incisors protrude too far horizontally beyond the lower incisors. This is the coding equivalent of what is colloquially called a 'horizontal overbite' or Angle Class II, Division 1 malocclusion.
Verified May 8, 2026 · 3 sources ↓
- Status
- Billable
- Chapter
- 13
- Related CPT
- 15
- Region
- Other
Documentation tips
What should appear in the chart to support M26.23.
Source · Editorial brief grounded in 3 cited references ↓
- Record the measured overjet in millimeters — payers and auditors need quantification to confirm 'excessive' meets clinical and coverage thresholds.
- Document whether the overlap is skeletal, dental, or combined in origin; skeletal contribution may require additional M26.0x/M26.1x codes.
- Specify Angle's classification if established (Class II Div 1 maps closely to M26.23); this supports medical necessity for surgical correction.
- Note any prior orthodontic treatment history and its outcome — this substantiates that non-surgical management was attempted or is insufficient.
- If orthodontic records (cephalometric analysis, study models) are referenced in the note, name them — they are the primary objective support for this diagnosis.
Related CPT procedures
Procedure codes commonly billed with M26.23. Linking the right diagnosis to the right procedure is what establishes medical necessity.
Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis
Common coding pitfalls
The recurring mistakes coders make with M26.23 and adjacent codes.
Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓
- Confusing horizontal overjet (M26.23) with vertical overbite or open bite (M26.22x block) — the direction of the discrepancy drives the code selection.
- Omitting the underlying skeletal jaw anomaly code (M26.0x–M26.1x) when the excessive overjet is driven by a documented maxillary or mandibular skeletal deformity.
- Using M26.211 (Angle Class I) or M26.212 (Angle Class II) alone when excessive horizontal overjet is also explicitly documented — both codes may be reported together when both conditions are present.
- Applying M26.23 to vertical overbite documented as 'deep bite' — deep bite without a horizontal component does not belong here.
Clinical context
Source · Editorial summary grounded in 3 cited references ↓
M26.23 falls under parent code M26.2 (Anomalies of dental arch relationship) within Chapter 13 of ICD-10-CM (Diseases of the Musculoskeletal System and Connective Tissue). Use it when the documented finding is specifically excessive horizontal overlap or overjet — meaning the maxillary incisors extend an abnormal horizontal distance anterior to the mandibular incisors. This is distinct from vertical open bite (M26.22x) or Angle's class malocclusion codes (M26.211–M26.219), although Class II Division 1 malocclusion and excessive overjet frequently co-occur.
In orthopedic and oral/maxillofacial surgery contexts, M26.23 is most relevant when a patient presents for surgical correction of dentofacial deformity — for example, maxillary setback or mandibular advancement procedures. It maps to MS-DRG groups 157–159 (Dental and Oral Diseases) and DRGs 011–013 for cases requiring tracheostomy. If the horizontal overlap is secondary to a skeletal jaw discrepancy (e.g., mandibular retrognathia), consider whether an additional M26.0x or M26.1x code is warranted to capture the underlying skeletal anomaly.
The ICD-10-CM tabular list explicitly includes 'excessive horizontal overjet' as an 'Applicable To' note under M26.23, confirming that overjet and overlap are coded identically here. Do not use this code for vertical overbite — that relationship is addressed elsewhere in the M26.2x block.
Inclusion & exclusion notes
Per the official ICD-10-CM Tabular List.
Source · CDC ICD-10-CM Official Tabular List · 2026
Includes
- Excessive horizontal overjet
Sibling codes
Other billable codes under M26.2 (laterality / anatomic variants).
Frequently asked questions
Source · Generated from the editorial pipeline, verified against 3 cited references ↓
01Is excessive horizontal overjet the same as excessive horizontal overlap for coding purposes?
02Can M26.23 be coded alongside Angle's Class II malocclusion (M26.212)?
03What MS-DRGs does M26.23 group to?
04Should I code the skeletal jaw discrepancy separately when it causes the overjet?
05Is M26.23 valid for orthodontic-only treatment encounters, or only surgical cases?
06Does M26.23 require a 7th character extension?
Sources & references
Editorial content was developed using the following public sources. Last verified May 8, 2026.
- 01CDC ICD-10-CM Tabular List 2026 (effective October 1, 2025)
- 02icd10data.comhttps://www.icd10data.com/ICD10CM/Codes/M00-M99/M26-M27/M26-/M26.23
- 03aapc.comhttps://www.aapc.com/codes/icd-10-codes/M26.23
Mira AI Scribe
Mira's AI scribe captures the measured overjet distance, Angle's classification, skeletal versus dental etiology, and any referenced cephalometric findings from the encounter note — ensuring M26.23 is supported by quantified, specific documentation rather than a generic 'malocclusion' entry that risks downcoding or payer scrutiny on medical necessity review.
See how Mira captures M26.23 documentation