Features of cone-beam computed tomography (CBCT) of the distal parts of the mandible and the possibility of dental implants installation ‘‘bypassing’’ the inferior alveolar nerve: a review of the literature and the results of our own experience

Abstract

Summary. In cases of atrophy of the distal mandible, the possibility of dental implantation is often limited by the lack of the required height of the alveolar ridge due to the proximity of the mandibular canal, which requires the use of short or ultra-short implants or vertical augmentation using autologous, allogeneic, xenogeneic materials. The invention of single-stage cone-shaped implants of various lengths and diameters has led to the idea of bypassing the inferior alveolar nerve, minimizing or avoiding the need for additional surgery to increase bone volume.

The aim of the study – to clarify the features of the morphology of the edentulous distal mandibular aspects on the basis of analysis of professional literature and computed tomography of patients, to propose a technique for installation of dental implants ‘‘bypassing’’ the inferior alveolar nerve.

Materials and Methods. From the database of the Center of Medical 3D Diagnostics, 30 computed tomographies of the mandible of patients (women – 12, men – 18 aged 36–68 years) who applied for the study during 2018–2020 were selected and analyzed. In the clinic of the Department of Surgical Dentistry and Maxillofacial Surgery of Danylo Halytskyi LNMU 16 patients (men – 7, women – 9) aged 45–66 years with uni-bilateral free-end defects or complete mandibular adentia were examined and treated. All patients in the distal mandible were fitted with single-stage dental implants (Ihde Dental AG, Switzerland) "bypassing" the inferior alveolar nerve with their immediate loading by prosthetic structure within 3–4 days after implantation.

Results and Discussion. As a result of studying 30 computed tomographies of the mandible of patients with unilateral and bilateral free-end defects of the mandible, we found that the average distance from the mandibular canal to the vestibular cortical plate is (5.12±1.04) mm, to the lingual cortical plate – (2.95±0.89) mm, to the top of the alveolar crest – (6.18±1.9) mm (p<0.001), which is consistent with the reports of other researchers. Treatment was performed in 16 patients with unilateral, bilateral free-end defects or complete mandibular adentia using single-stage cone-shaped KOS® and TPG® Uno dental implants (Ihde Dental AG, Switzerland) "bypassing" the inferior alveolar nerve on the lingual or vestibular side (depending on the location of the mandibular canal). A total of 42 implants were installed in the distal mandible (at the level of premolars and molars), of which 34 implants bypassed the inferior alveolar nerve on the lingual side and 8 on the vestibular side. 4–5 days after surgery all implants were loaded with temporary metal-acrylic prosthetic construction. On the control computed tomography of patients performed 1–4 days after implantation, in none of the cases no complications were found in the form of direct mechanical damage to the walls of the mandibular canal or cortical plates with surgical tools or the body of the implant itself.

Conclusions. The results of our own experience, which are fully consistent with the reports of other researchers, suggest that the installation of dental implants in the distal mandible "bypassing" the inferior alveolar nerve creates a serious alternative to traditional methods of vertical augmentation, allows to rehabilitate the functional state of the maxillomandibular system due to the implementation of the protocol of immediate loading. At the same time, the procedure of implant placement "bypassing" the inferior alveolar nerve on the lingual or vestibular side requires in-depth knowledge of the anatomy of the maxillofacial area and careful planning with the involvement of CBCT.