A novel approach for gingiva thickness measurements around lower anterior teeth by means of dental magnetic resonance imaging

Abstract

Objective: This diagnostic accuracy study aims to present the first measurements of gingiva thickness around lower anterior teeth using dental magnetic resonance imaging (MRI) and to compare these measurements with two established methods: (1) gingival phenotype assessment via periodontal probing, and (2) the superimposition of cone-beam computed tomography (CBCT) scans with intraoral scans of teeth and gums.

Materials and methods: Ten patients with substantial orthodontic treatment need and anterior mandibular crowding were consecutively included in this clinical case series. After periodontal probing, each patient underwent a CBCT scan, an intraoral scan of the mandible, and an MRI investigation using a novel mandibula 15-channel dental coil.

Results: The mean gingiva thickness was 0.72 mm measured on MRI and 0.97 mm measured on CBCT, with a mean difference between the measurement methods of 0.17 ± 0.27 mm (p < 0.001). Measurement agreement between the index tests (MRI and CBCT) and the clinical reference standard (probing) yielded an overall percent agreement of 64.94% and 47.02% for MRI and CBCT, respectively. Teeth with thin phenotypes were associated with lower soft tissue dimensions in both free (MRI: 0.56 mm vs. CBCT: 0.79 mm) and supracrestal gingiva (MRI: 0.75 mm vs. CBCT: 1.03 mm) when compared to those with thick phenotypes. However, only the measurements obtained from MRI scans showed statistically significant differences between the two phenotypes.

Conclusion: Dental MRI successfully visualizes delicate structures like the gingiva in the anterior mandible and achieves a high correlation with superimposed CBCT scans, with clinically acceptable deviations.

Clinical relevance: The present study helps to establish dental MRI as a radiation-free alternative to conventional radiographic methods.

Keywords: Gingival phenotype; Gingival thickness; Lower incisors; MRI; Orthodontic treatment.

Fig. 1

Example of a patient right before image acquisition. The dental mandibular coil is not yet fully adjusted around the patient’s head

Fig. 2

Example of analyzed image datasets: a horizontal plane of MRI; b horizontal plane of superimposed CBCT/intraoral scan of the same patient

Fig. 3

Representative example of the superimposition of an intraoral scan (blue color) with the CBCT dataset in Materialize Mimics after the creation of a 3D reconstruction from the DICOM data

Fig. 4

Representative examples of the three measurement methods: a periodontal probing of the gingival sulcus to assess probe transparency, b sagittal section through the axis of the lower left incisor with supracrestal measurement of the gingival thickness, c sagittal section through axis of the lower left incisor with supracrestal measurement of the gingival thickness

Fig. 5

Agreement between MRI and CBCT measurements (Bland–Altman plot)