Malocclusion is a dentofacial condition in which the upper (maxillary) and lower (mandibular) teeth do not meet in proper alignment when the jaws are closed, resulting in a disrupted occlusal relationship that may range from mild cosmetic irregularity to significant functional impairment of chewing, speech, and temporomandibular joint mechanics. It is distinguished from dental crowding (M26.31) and tooth displacement (M26.33), which are anomalies of individual tooth position rather than of the arch-to-arch relationship, and from temporomandibular joint disorder (M26.60-M26.69), which involves joint dysfunction that may coexist with but is not synonymous with malocclusion. The underlying mechanisms include skeletal discrepancies between jaw size or position (e.g., prognathism, retrognathism), dental crowding from arch-length tooth-size discrepancy, habits such as prolonged thumb-sucking or mouth breathing, tooth loss leading to drift, and developmental or hereditary factors affecting craniofacial growth. Malocclusion is classified clinically using Angle’s classification — Class I (M26.211; normal molar relationship with crowding or spacing problems), Class II (M26.212; upper teeth protrude over lower — “overbite”), and Class III (M26.213; lower teeth protrude past upper — “underbite”) — with additional subtypes for open bite (M26.220, M26.221), excessive overjet (M26.23), and reverse articulation (crossbite, M26.24). It is commonly confused with dental crowding (a tooth-position anomaly not involving arch relationship) and prognathism (a jaw-size/position anomaly that often underlies Class III malocclusion but is coded separately under M26.09 or M26.19).
Latin occludere (oh-KLOO-deh-reh), from ob- (against) + claudere (to shut, to close)
“to shut,” “to close,” “to block” — combining form denoting closing or contact between opposing surfaces
-sion
Latin -sio / -sionis (-see-OH-nis)
Noun-forming suffix — “act or process of,” “state resulting from”
The word entered English in the 1880s as malocclusion (noun), coined directly from Latin components within dental medicine by the orthodontist Edward Angle to describe deviations from his described “normal” occlusion standard. The base term occlusion (from Latin occlusio, “a shutting up”) had been in medical use since the 1640s, denoting the closing of a passage or the contact of opposing dental surfaces. The root occlu- connects Malocclusion to the broader occlu- root family: occlusion (the act of closing — dental contact relationship), occlusor (that which closes), and occlude (verb — to close off or block). The pejorative prefixmal- is among the most productive prefixes in medical and dental terminology, also appearing in malformation, malnutrition, malignant, malalignment, and maladaptive.
Bad bite(lay term; used in patient-facing documentation and informed consent — commonly encountered in orthodontic and general dentistry settings)
Faulty occlusion(clinical synonym; used in operative notes and insurance narratives when describing arch relationship abnormalities requiring correction)
Angle’s Class I Malocclusion|Class I Malocclusion(normal molar relationship with anterior crowding or spacing; coded M26.211; most common subtype)
Angle’s Class II Malocclusion|Class II Malocclusion(upper arch protrudes relative to lower — “overbite” / “buck teeth”; coded M26.212; associated with deep bite and retrognathia)
Angle’s Class III Malocclusion|Class III Malocclusion(lower arch protrudes past upper — “underbite”; coded M26.213; often associated with mandibular prognathism M26.03)
Open bite(failure of upper and lower teeth to contact — anterior M26.220 or posterior M26.221; often due to tongue thrust or digit-sucking habits)
Crossbite(reverse articulation in which upper teeth occlude inside lower teeth — coded M26.24; may be unilateral or bilateral, anterior or posterior)
Overjet(horizontal protrusion of upper teeth beyond lower — excessive overjet coded M26.23; distinct from overbite which is vertical)
Deep bite(excessive vertical overlap of upper over lower anterior teeth; often associated with Class II malocclusion; may be coded under M26.29 — other anomalies of dental arch relationship)
Crowding(insufficient arch space causing overlapping teeth — coded M26.31; a tooth position anomaly often coexisting with malocclusion but coded separately)
🔗 RELATED TERMS
Occlusion — the normal, correct contact relationship between maxillary and mandibular teeth when the jaws are closed; the functional opposite of malocclusion — proper occlusion distributes bite forces evenly across all teeth
Prognathism — abnormal forward projection of the jaw(s); mandibular prognathism is the primary skeletal driver of Class III malocclusion; coded under M26.03 (mandibular hyperplasia) or M26.09 (other jaw size anomalies)
Retrognathia — posterior positioning of the mandible or maxilla relative to the cranial base; drives Class II skeletal malocclusion; coded under M26.04 (mandibular hypoplasia) or anomalies of jaw-cranial base relationship (M26.19)
Dental crowding — insufficient arch length relative to tooth size resulting in overlapping teeth; coded M26.31; a tooth-position anomaly that commonly coexists with malocclusion
Temporomandibular joint disorder (TMD/TMJ) — dysfunction of the temporomandibular joint; may be caused or worsened by chronic malocclusion; coded under M26.601-M26.69; treated with splints, physical therapy, or surgery
Crossbite — a form of reverse articulation (M26.24) where upper teeth occlude lingual to lower teeth; may be skeletal or dental in origin
Open bite — a malocclusion subtype in which opposing teeth fail to contact; anterior form coded M26.220, posterior form M26.221; associated with speech articulation disorders
Orthognathic surgery — corrective jaw surgery to reposition the maxilla, mandible, or both to correct skeletal malocclusion; CPT codes include 21141-21160 for Le Fort osteotomies and 21193-21196 for mandibular osteotomies
Orthodontic treatment — non-surgical correction of malocclusion using braces, aligners, or appliances; reported with CDT codes or unlisted CPT 41899 on medical claims
Cephalometric radiograph — lateral skull X-ray used to assess skeletal jaw relationships and plan orthodontic or orthognathic treatment; CPT 70350
Sleep-disordered breathing — Class II malocclusion with retrognathia and Class III open bite patterns are associated with obstructive sleep apnea (G47.33); orthognathic surgery to advance the mandible is a recognized OSA treatment
CODING CORNER
🏥 ICD-10-CM CODES
Angle’s Classification — Malocclusion by Arch Relationship (M26.21x)
Code
Description
M26.211
Malocclusion, Angle’s class I — normal molar relationship, arch-length deficiency; most common class
M26.212
Malocclusion, Angle’s class II — maxillary protrusion / mandibular retrusion; “overbite” or “overjet” pattern
M26.213
Malocclusion, Angle’s class III — mandibular protrusion / maxillary retrusion; “underbite” pattern
M26.4
Malocclusion, unspecified — use only when class cannot be determined from documentation
Open Occlusal Relationship (M26.22x)
Code
Description
M26.220
Open anterior occlusal relationship — anterior open bite; upper and lower front teeth do not contact
M26.221
Open posterior occlusal relationship — posterior open bite; back teeth do not contact
Reconstruction of mandibular rami and/or body, sagittal split; with internal rigid fixation
21206
Osteotomy, maxillary, segmental (e.g., Wassmund or Schuchard type) — correction of segmental arch discrepancy
21210
Graft, bone; nasal, maxillary or malar areas — bone graft for skeletal correction supporting orthognathic procedures
20610
Arthrocentesis, aspiration and/or injection, major joint (TMJ) — used for TMJ lavage and corticosteroid injection in malocclusion-related arthralgia
21240
Arthroplasty, temporomandibular joint, with or without autograft — surgical TMJ reconstruction
21243
Arthroplasty, temporomandibular joint, with prosthetic joint replacement — total TMJ prosthesis
41899
Unlisted procedure, dentoalveolar structures — used on medical claims for orthodontic procedures (e.g., braces, aligners) when billed to medical insurance for medically necessary malocclusion
⚠️ Coding Note:MalocclusionICD-10-CM codes require specificity to Angle’s class whenever documented — do not default to M26.4 (unspecified) when the provider has documented Class I, II, or III in the chart; this is a common undercoding pattern on both outpatient and inpatient profee claims. When malocclusion is the indication for orthognathic surgery, the skeletal jaw-size anomaly code (e.g., M26.03 mandibular hyperplasia for Class III, M26.04 mandibular hypoplasia for Class II) should be sequenced as the primary diagnosis alongside the appropriate malocclusion class code — these codes are not mutually exclusive. For TMJ arthralgia coexisting with malocclusion, both the joint disorder (M26.601-M26.623) and the malocclusion code should be reported; laterality is required for all M26.6x codes — query if the operative or clinic note fails to specify right, left, or bilateral. On inpatient profee claims, orthognathic procedures such as sagittal split osteotomy (21195, 21196) and LeFort osteotomies (21141-21155) are frequently billed without the underlying skeletal anomaly diagnosis, resulting in medical necessity denials — always pair the procedure with both the skeletal etiology and the functional malocclusion code. Modifier -22 (increased procedural services) may be appended to orthognathic surgery CPT codes when the procedure is significantly more complex than typical due to prior surgery, severe asymmetry, or multi-piece osteotomy — documentation must support the increased time and complexity. For Medicare patients requiring dental procedures medically linked to a covered procedure (e.g., pre-transplant or pre-radiation oral clearance), append modifier -KX per CMS guidance effective July 1, 2025.
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