Measurement of Lingual Cortical Plate Thickness and Lingual Position of Lower Third Molar Roots Using Cone Beam Computed Tomography

Quantitative and Qualitative Correlation of Mandibular Lingual Bone with Risk Factors for Third Molar Using Cone Beam Computed Tomography

Background

Lingual plate thickness, density, and proximity to the tooth are linked as risk factors for various complications associated with third molar extraction. The present study aimed to assess the lingual plate thickness, and density in the mandibular third molar region using cone beam computed tomography and to estimate its correlation with type and level of impaction, number of roots, age, and gender as the risk factors.

Methods

This was a retrospective study on CBCT images of 648 mandibular third molars. The lingual plate thickness at three different root levels - cervical, mid-root, and apex along with the position of the tooth, number of roots, density of lingual plate, age, and gender were evaluated. The measurements were done on Invivo 5-Anatomage software. Statistical comparison of the categorical variables was done by Chi-square test, and Fisher's exact test, and univariate and multivariate analysis were done using binomial logistic regression.

Results

Lingual plate thickness of the third molars at the cervical, mid root, and apex were 1.28 mm, 1.42 mm and .01 mm (mean). A significantly higher proportion of subjects with thin lingual plates at mid-root (p-value=0.01) and apex (p-value=0.05) were in the 21-30 age group. Lingual bone density was significantly associated with the thickness of the lingual plate at the mid-root. A significantly higher proportion of thinner lingual plates at the mid-root level were associated with mesioangularly placed third molars (p-value=0.002).

Conclusion

Our study presented that lingual plate thickness has a strong association with age, angulation, and the number of roots. Knowledge about these risk factors is imperative during the management of third molar impactions.

Bilateral isolated mylohyoid groove fracture progressing as submandibular abscess: an usual fracture pattern of mandible

The mylohyoid ridges or lines are pairs of anatomical bony structures located on the internal or lingual surface of mandible. They are the origin for the mylohyoid muscle. These bony structures are distinct in the mandibular molar region, well protected and gradually become undiscernible towards anterior mandible. Bilateral, isolated fracture of the mylohyoid ridges without concomitant mandibular fracture is rare and, to the best of the authors knowledge, was never previously described. This case report describes an isolated bilateral mylohyoid groove fracture, where one side of a necrotic bone fragment at the fracture site progress to became a nidus of infection, which later caused submandibular space abscess requiring emergency surgical intervention. Diagnosis, possible theory to explain the occurrence of isolated mylohyoid groove fracture and management of these condition are explained in this report.

Risk factors for lingual plate fracture during mandibular third molar extraction

OBJECTIVE

The aim of this study was to predict the risk of lingual plate fracture during mandibular third molar (M3) extraction.

MATERIALS AND METHODS

Cone beam computed tomography (CBCT) data from 264 mandibular M3s (erupted and impacted) from 264 patients (104 males and 160 females; age range, 17-75 years) were retrospectively analyzed. Lingual plate thicknesses at the levels of the mid-root and root apex of the M3s were measured and defined as "thicker" (bone thicker than 1 mm), "thinner" (bone thinner than 1 mm), or "perforated" (bone perforated by the M3 root). These measurements were correlated with potential risk factors for thinner and perforated lingual plates: tooth position of the mandibular M3, morphology of the lingual plate, and patient characteristics (age and sex).

RESULTS

The mean thickness of the lingual plate was 1.49 ± 1.38 mm at the mid-root of the M3s, and 2.35 ± 2.03 mm at the root apex. Multivariate regression analyses revealed that mesioangularly and horizontally impacted M3s were significantly associated with thinner and perforated lingual plates at the mid-root (P < 0.001), whereas the M3s in infra-occlusion positions (in infra-occlusion when compared with the adjacent second molar) had thinner lingual bone at the root apex (P = 0.022 and P = 0.027, depending on the level of impaction). Female patients were less likely to have lingual plate perforation (P = 0.036).

CONCLUSIONS

Mesioangulation, infra-occlusion, and male sex were risk factors for lingual plate fracture.

CLINICAL RELEVANCE

When the risk of lingual plate fracture is high, a sufficiently large flap, osteotomy, and tooth section by bur or piezosurgery are recommended to create a good operative field and avoid excessive pressure on the lingual plate.

The assesment of relationship between the angulation of impacted mandibular third molar teeth and the thickness of lingual bone: A prospective clinical study

Background

Our purpose was to investigate the relationship between the angulation of mandibular third molars and the thickness of the lingual bone, which can affect the risk of lingual nerve damage during lower third molars surgical extraction.

Material and Methods

This study consisted of 104 patients (42 males and 62 females), aged between 18-42 years (24.67 ± 6.11 years). Cone Beam Computed Tomography (CBCT) images were taken for preoperative assessment. The teeth were divided into four groups according to their positions: mesioangular, distoangular, vertical and horizontal. Lingual bone thickness around impacted teeth were measured at three points: cementoenamel junction (CEJ) of the mandibular second molar, mid-root of the impacted third molar, and apex of the impacted third molar root. Two predisposing factors of lingual nerve damage were recorded: lingual bone perforated by the impacted tooth and lingual bone thinner than 1 mm. Additionally, buccolingual angulations of the teeth in each group were measured. Impacted mandibular third molars were removed in usual way. One week after surgery, the patients were evaluated regarding lingual nerve paresthesia.

Results

None of the 104 patients experienced paresthesia, including the ones who had teeth with close proximity with lingual nerve. The mean thickness of bone was 1.21±0.63 mm at CEJ of the second molar; 1.25±1.02 mm at the mid-root; and 1.06±1.31 mm at the apex. Horizontally impacted teeth had thinner lingual bone at mid-root level (p=0.016). Buccolingual angulated teeth were more often associated with perforated lingual bone (p=0.002). Buccolingual and mesial/distal angulation had negative correlation with lingual bone thickness (p<0.05).

Conclusions

As the buccolingual and mesiodistal angulations increase, lingual bone thickness decreases. Horizontally impacted teeth seemed to compromise the integrity of the lingual bone more than impacted teeth in other positions. During the surgery, thin or perforated lingual bone may result in displacement of the impacted tooth lingually.

Key words:Lingual bone, impacted third molar, cone beam computed tomography, angulation, paresthesia.

Risk Factor in Endodontic Treatment: Topographic Evaluation of Mandibular Posterior Teeth and Lingual Cortical Plate Using Cone Beam Computed Tomography (CT)

BACKGROUND Topographic relationships of mandibular posterior teeth with mandibular cortical plate are extremely important both in terms of infection spread and endodontic and surgical procedures to be performed. The aim of this study was to determine the relationship between root apex of the mandibular posterior teeth and lingual plate of the mandible. MATERIAL AND METHODS CBCT data of 138 patients were retrospectively analyzed. The topographic relationship between root apex and lingual plate was classified as non-contact, contact, or perforation. Morphology of the mandibular lingual plate was classified into the 4 types (convex, parallel, undercut, slanted) and recorded for each tooth region. The prevalence of each group was calculated. RESULTS In 6.2% of all mandibular posterior teeth, the lingual plate was perforated by at least 1 root of the corresponding tooth. The teeth with the highest perforation rate were the third molar tooth (31.6%) and the second molar tooth (14.7%). The most common mandibular lingual plate morphology type was "undercut type" (61.3%) in the molar teeth region, while "parallel type" (55.7%) was most common in the premolar teeth region. CONCLUSIONS In conclusion, a high percentage of mandibular second and third molars root apex have topographically close relationships to the lingual plate of the mandible. Hence, endodontic consultants must be aware by this anatomical relationship and be aware of possible complications during endodontic and surgical procedures using radiographical modalities.