J Periodontal Implant Sci.  2020 Feb;50(1):28-37. 10.5051/jpis.2020.50.1.28.

Radiomorphometric analysis of edentulous posterior mandibular ridges in the first molar region: a cone-beam computed tomography study

• Magat G

• KMID: 2470828
• DOI: http://doi.org/10.5051/jpis.2020.50.1.28

Abstract

PURPOSE
The aim of our study was to determine the prevalence and degree of lingual concavities in the first molar region of the mandible to reduce the risk of perforating the lingual cortical bone during dental implant insertion.
METHODS
A total of 163 suitable cross-sectional cone-beam computed tomography images of edentulous mandibular first molar regions were evaluated. The mandibular morphology was classified as a U-configuration (undercut), a P-configuration (parallel), or a C-configuration (convex), depending on the shape of the alveolar ridge. The characteristics of lingual concavities, including their depth, angle, vertical location, and additional parameters, were measured.
RESULTS
Lingual undercuts had a prevalence of 32.5% in the first molar region. The mean concavity angle was 63.34°±8.26°, and the mean linear concavity depth (LCD) was 3.03±0.99 mm. The mean vertical distances of point P from the alveolar crest (Vc) and from the inferior mandibular border were 9.39±3.39 and 16.25±2.44, respectively. Men displayed a larger vertical height from the alveolar crest to 2 mm coronal to the inferior alveolar nerve (Vcb) and a wider LCD than women (P<0.05). Negative correlations were found between age and buccolingual width at 2 mm apical to the alveolar crest, between age and Vcb, between age and Vc, and between age and LCD (P<0.05).
CONCLUSION
The prevalence of lingual concavities was 32.5% in this study. Age and gender had statistically significant effects on the lingual morphology. The risk of lingual perforation was higher in young men than in the other groups analyzed.

Keyword

Alveolar ridge; Cone-beam computed tomography; Dental implants; Edentulous jaw; Mandible

MeSH Terms

Alveolar Process
Cone-Beam Computed Tomography*
Dental Implants
Female
Humans
Jaw, Edentulous
Male
Mandible
Mandibular Nerve
Molar*
Prevalence
Dental Implants

Figure

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  Figure 1 Selection of a cross-sectional slice taken from a sagittal image.

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  Figure 2 Schematic illustration of measurements taken from a cross-sectional slice [11]. Wc: buccolingual widths at 2 mm apical to the alveolar crest, Wb: buccolingual widths at the level of line A, Vcb: vertical distance from the alveolar ridge to line A, LCD: linear concavity depth, Vc: vertical distances between point P and the alveolar crest, Vb: vertical distances between point P and the inferior mandibular border.

• 

  Figure 3 Cross-sectional views of the first molar region, showing the 3 types. C: convex, P: parallel, U: undercut.

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  Figure 4 Distribution of ridge types according to gender (%).

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  Figure 5 Measurements according to sex. Vcb: vertical distance from the alveolar ridge to line A, Wc: buccolingual widths at 2 mm apical to the alveolar crest, Wb: buccolingual widths at the level of line A, LCD: linear concavity depth, Vc: vertical distances between point P and the alveolar crest, Vb: vertical distances between point P and the inferior mandibular border.

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