Orthodontics Reviewer: Diagnosis, Study Models, and Cephalometric Analysis

Vocabulary flashcards covering orthodontic diagnosis, diagnostic aids, case history, physical/extraoral/intraoral examination, study model analysis, mixed dentition analyses, Bolton and Pont analyses, and cephalometric landmarks and parameters.

Main purpose of orthodontic diagnosis

To identify the orthodontic problem and its etiology before treatment, and to develop a comprehensive, concise database of pertinent information.

Essential diagnostic aids

Case history, clinical examination, study models, certain radiographs, and facial photographs.

Ectomorphic body type

A Sheldon body type characterized as tall and thin.

Mesomorphic body type

A Sheldon body type characterized as muscular, with broad shoulders and a narrow waist.

Endomorphic body type

A Sheldon body type characterized as rounder and softer, with a broader waist and hips.

Mesocephalic head shape

An average head shape associated with normal arches.

Dolicocephalic head shape

A long and narrow head shape associated with narrow arches.

Brachycephalic head shape

A broad and short head shape associated with broad arches.

Mesoprosopic facial form

An average or normal facial form.

Euryprosopic facial form

A broad and short facial form.

Leptoprosopic facial form

A long and narrow facial form.

Convex facial profile

A facial profile associated with a prognathic maxilla or a retrognathic mandible.

Concave facial profile

A facial profile associated with Class III malocclusion.

Anterior facial divergence

A facial condition where the lower face inclines forward.

Posterior facial divergence

A facial condition where the lower face inclines backward.

Competent lips

Lips that make contact at rest without effort.

Incompetent lips

Lips that are short and require muscle contraction to achieve contact.

Potentially competent lips

Lips of normal length whose contact is blocked by protruding maxillary incisors.

Everted lips

Lips composed of hypertrophied or redundant tissue with weak tone.

Nasolabial angle

An angle where a value greater than $110^\circ$ suggests maxillary anterior retroclination, and a value less than $90^\circ$ indicates maxillary proclination.

Microglossia

Abnormally small tongue size that may cause narrow or collapsed arches.

Macroglossia

Abnormally large tongue size that may cause anterior flaring and spacing, as well as lateral tooth indentations.

Blanch test

A clinical test used to assess abnormal labial frenum attachment.

Arch perimeter analysis

Analysis performed on the maxillary cast to determine arch length and total tooth material using a wire from the mesial of one first permanent molar to the opposite first permanent molar.

Carey's analysis

A space analysis similar to arch perimeter analysis, but performed specifically on the mandibular cast.

Space available

The actual space present in the arch for teeth, measured along the arch from the mesial of one first permanent molar to the mesial of the opposite first permanent molar.

Space required

The total space needed to accommodate teeth in an arch, determined by adding the mesiodistal tooth widths.

Moyers analysis

A mixed dentition analysis that predicts the combined mesiodistal width of unerupted 3, 4, and 5 using the sum of the four mandibular permanent incisors and a probability table (commonly at the $75\%$ probability level).

Tanaka-Johnston analysis

A non-radiographic method introduced in 1974 that predicts unerupted 3, 4, and 5 using the four mandibular permanent incisors without radiographs or probability tables.

Bolton overall ratio

A ratio evaluating overall tooth-size discrepancy with an ideal value of $91.3\%$; values below $91.3\%$ indicate relative maxillary tooth-material excess, while values above indicate relative mandibular excess.

Bolton anterior ratio

A ratio evaluating anterior tooth-size discrepancy with an ideal value of $77.2\%$; values below $77.2\%$ indicate relative maxillary anterior excess, while values above indicate relative mandibular anterior excess.

Pont's analysis

An analysis reported in 1909 using the four maxillary incisors to determine whether an arch is narrow or wide, the need for lateral expansion, and possible expansion in premolar and molar regions.

Nasion (Na)

The most superior point on the curve of the frontonasal suture at the bridge of the nose.

Anterior Nasal Spine (ANS)

The most anterior point of the maxilla at the level of the palate.

Posterior Nasal Spine (PNS)

The most posterior point of the bony hard palate in the sagittal plane.

Point A (Subspinale)

The deepest, most posterior point between ANS and prosthion, located approximately $2\,\text{mm}$ anterior to the maxillary central-incisor apices.

Prosthion (SPr)

The most anterior point of the maxillary alveolar process near the CEJ of the maxillary central incisors; also called supradentale.

Infradentale (Id)

The most anterior superior point of the mandibular alveolar process near the CEJ of the mandibular central incisors (inferior prosthion).

Point B (Supramentale)

The most posterior point of bony mandibular curvature below infradentale and above pogonion, usually near the apical third of mandibular incisor roots.

Pogonion (Pog)

The most anterior point on the contour of the chin.

Gnathion (Gn)

The most anterior point on the lateral shadow of the chin, located between Pogonion and Menton.

Menton (Me)

The lowest point on the symphyseal outline of the chin.

Basion (Ba)

The most inferior-posterior sagittal point on the anterior rim of the foramen magnum, representing the tip of the posterior cranial base.

Sella (S)

The center of the hypophyseal fossa (sella turcica).

Orbitale (Or)

The lowest point of the bony orbit.

Gonion (Go)

The most posterior-inferior point at the angle of the mandible.

Condylion (Co)

The most posterior-superior point on the mandibular condyle.

Articulare (Ar)

The intersection of radiographic shadows involving the cranial base and posterior condylar-neck surfaces.

Pterygomaxillary Fissure (PTM)

A teardrop-shaped radiolucency whose anterior shadow relates to the posterior maxillary tuberosities.

Porion (Po)

The top of the external auditory meatus (mechanical porion may use the top of the ear-rod shadow).

SN plane

Cephalometric plane connecting Sella to Nasion, representing the anteroposterior extent of the anterior cranial base.

Frankfort Horizontal (FH) plane

Cephalometric reference plane connecting Orbitale to Porion, used for assessing horizontal growth.

Mandibular plane

Cephalometric line connecting Menton to Gonion, used for assessing growth patterns.

Palatal plane

Cephalometric plane connecting ANS to PNS, used for growth-pattern assessment.

E-plane

The esthetic plane between the most anterior soft-tissue points of the nose and chin.

Down's Facial angle

Parameter with a normal range of $82^\circ\text{--}95^\circ$ that assesses the AP position of the mandible to the upper face; increased values indicate skeletal Class III, while decreased values indicate skeletal Class II.

Down's Angle of convexity

Parameter with a normal range of $-8.5^\circ\text{ to }10^\circ$; increased values indicate a prominent maxillary base relative to the mandible, while decreased values indicate a prognathic profile.

Down's A-B plane angle

Parameter with a normal range of $-9^\circ\text{ to }0^\circ$ that assesses maxillomandibular relationship to the facial plane; increased values indicate Class III, while decreased values indicate Class II.

Down's Mandibular plane angle

Parameter with a normal range of $17^\circ\text{--}28^\circ$; increased values indicate vertical growth, while decreased values indicate horizontal growth.

Down's Y-axis

Parameter with a normal range of $53^\circ\text{--}66^\circ$ that helps diagnose growth pattern; increased values indicate vertical growth, while decreased values indicate horizontal growth.

Steiner SNA angle

Cephalometric angle with a normal value of approximately $82^\circ$; increased values indicate maxillary prognathism and decreased values indicate maxillary retrognathism.

Steiner SNB angle

Cephalometric angle with a normal value of approximately $80^\circ$; increased values indicate mandibular prognathism and decreased values indicate mandibular retrognathism.

Steiner ANB angle

Cephalometric angle with a normal value of approximately $2^\circ$; increased values indicate a Class II skeletal tendency, while decreased values indicate a Class III tendency.

Steiner S line

A reference line for lip analysis where lips behind the line are considered too flat, and lips anterior to the line are considered too prominent.

Tweed triangle

A cephalometric diagnostic triangle consisting of FMA, IMPA, and FMIA.

Wit's appraisal

An appraisal assessing jaw disharmony by projecting points A and B perpendicularly to the occlusal plane (normal: AO about $1\,\text{mm}$ anterior to BO; Class II: BO well behind AO; Class III: BO ahead of AO).