Korean J Orthod.  2017 Jan;47(1):39-49. 10.4041/kjod.2017.47.1.39.

Cone-beam computed tomography for the assessment of root–crown ratios of the maxillary and mandibular incisors in a Korean population

• Choi SH
• Kim JS
• Kim CS
• Yu HS
• Hwang CJ

• KMID: 2392195
• DOI: http://doi.org/10.4041/kjod.2017.47.1.39

Abstract

OBJECTIVE
This retrospective, cross-sectional study aimed to establish reference data for normal crown and root lengths and the root-crown ratios (R/C ratios) for the mature maxillary and mandibular incisors in a Korean population by using cone-beam computed tomography (CBCT).
METHODS
We included 672 Korean patients (141 men and 531 women; mean age, 27.2 ± 7.7 years) who underwent CBCT examinations during various dental treatments. Crown and root lengths and the R/C ratios of the maxillary and mandibular incisors were measured using CBCT data, which were analyzed to detect significant differences between demographic factors as well as sagittal and vertical skeletal or occlusal relationships.
RESULTS
Teeth of the same type in each half-arch were symmetrical. The mean R/C ratios varied from 1.1 to 1.2 for the maxillary incisors and from 1.3 to 1.4 for the mandibular incisors. Crown and root lengths were greater in men than in women, regardless of tooth type. Root lengths and R/C ratios for the mandibular incisors were significantly greater in patients with skeletal Class II malocclusion or an excessive overjet than in the other patients. The R/C ratios for the mandibular incisors were lower in patients with an open bite than in those with a normal or deep bite. Moreover, the R/C ratios for the mandibular incisors increased with age.
CONCLUSIONS
The data obtained in our study can serve as reference values for crown and root lengths and the R/C ratios for the maxillary and mandibular incisors in the Korean population.

Keyword

Tooth crown; Tooth root; Incisor; Cone-beam computed tomography; Population

MeSH Terms

Cone-Beam Computed Tomography*
Cross-Sectional Studies
Crowns
Demography
Female
Humans
Incisor*
Male
Malocclusion
Open Bite
Overbite
Reference Values
Retrospective Studies
Tooth
Tooth Crown
Tooth Root

Figure

• 

  Figure 1 Measurements of crown and root lengths on sagittal cone-beam computed tomography images acquired for a Korean population. Measurements for the eight maxillary and mandibular incisors are made along the tooth axes by using a reference line from the labial and palatal cementoenamel junction to the incisal tip and root apex.

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