*1.3. Problem Description*

An NCCL is a fairly common tooth lesion. The disease causes increased tooth sensitivity and violation of dentition aesthetics. NCCLs are located near the cervical area. The tooth perceives the worst loads from the antagonist's. Further development of the defect is possible. With the disease progression, movement of the gingival margin in the apical direction is possible, which leads to developing the gingival recession.

An NCCL and its development cause a change in the tissues surrounding the lesion [40]. According to research, a local detachment of enamel from dentin was found in 30% of clinical cases. The separation causes a gap. The gap leads to the breaking off of the enamel area and the development of the defect in the future [25]. According to existing data, enamel changes are of a different nature. Focal enamel demineralization occurs in the areas around the defect [25]. Demineralization is aggravated when exposed to an acidic environment [41]. Various lesions are fixed in the enamel. The nature of the damage depends on the defect form and the main cause of its development. The damage can take the form of microscopic furrows, cracks, and craters [42,43]. Microdamages can lead to enamel chipping and defect expansion in the future [25,44]. The directions of the cracks do not have a definite dependence. Cracks propagate deep into the pulp chamber in the direction of the lesion, also in different directions from the defect [41,44]. Dentin changes occur in the NCCL zone and depend on the shape and depth of the defect [44,45]. Replacement dentin appears with deep damage and prevents the expansion of the cavity with gradual development NCCLs [25,46].

At the moment, the most widespread are direct restorations. However, they have a number of disadvantages:


The necessity to create new technologies and methods for NCCL restoration has arisen. The new prosthetic inlays with an additional expansion of the wedge cavity are one of the solutions. The proposed method involves a significant amount of tissue preparation, both to expand the defect and to create zones of additional retention. It is important to note that mainly tooth tissues with accumulated macro- and micro-damages are removed.

Deformation of the tooth before and after restoration by a new method is considered in the work. Modeling is performed in the ANSYS Mechanical APDL application package (ANSYS Inc., Canonsburg, PA, USA). The tooth geometry is modeled as a first approximation and is more rounded. Crown geometry can be changed. In the first approximation, the crown geometry is not symmetrical and has different heights, i.e., an attempt is endeavored to bring the geometry of the crown closer to the individual case.
