Even in these days of rapid development of medical science, when approaches and therapies are constantly improving, new materials and technologies are being developed, many medical and social issues still need to be addressed [1, 2]. These include oncological diseases [3], which is due to a number of reasons; high rates of morbidity and mortality, high incidence of the advanced stage of the disease, delayed seeking for medical help, and high disability rates, which is especially true for mouth malignancy [4, 5]. Currently, the treatment of maxilla malignancies is based on the multidisciplinary approach, uniting oncologists, ENT doctors, plastic and maxillofacial surgeons, dentists, defectologists, and speech therapists [6, 7]. Treatment of maxilla neoplasms is often associated with extensive tissue defects. Medical rehabilitation depends on the presence of oronasal and/or oroantral communication (fistula), the severity of scarring, the condition of the mucosa around the defect and the mouth in general, and the degree of functional impairment [8, 9]. All the above predispose to severe functional disorders of breathing, chewing, swallowing, salivation, and speech [10]. Due to the small sample of patients, lack of dental oncology specialists, and underfunding for research of state-of-the-art digital dentistry, there is a lack of data on the medical rehabilitation of such patients and their adaptation ability after major surgery [11, 12].

The Department of Orthopedic Dentistry and Orthodontics of the South Ural State Medical University purchased the equipment with the funds of the President of the Russian Federation, the Russian Foundation for Basic Research (RFBR), and university grants, which allowed to conduct research with the most state-of-the-art diagnostic equipment. Over many years we have studied the prosthetics of patients with palatal defects and monitored the process of adaptation to replacement dentures during different postoperative periods, and we have accumulated extensive clinical and scientific experience [13, 14]. However, adaptation studies focused on temporomandibular joint function analysis have not been conducted previously due to the high cost of diagnostic equipment and lack of adequately skilled physicians [15, 16].

The objective of the study was to assess the adaptation of patients to obturator dentures across the adaptation periods using objective (digital) test methods, electronic axiography, cone-beam computed tomography, digital facial scan, and intraoral dental scanning.

Materials and methods

Within the scientific strategy of the Department of Orthopedic Dentistry and Orthodontics of the South Ural State Medical University, 17 patients with postoperative defects of the hard palate participated in the study conducted by the department. All defects were unilateral and formed due to combined treatment of maxilla malignancies. All patients received standard medical rehabilitation, including the making of resection, shaping, and replacement (obturation) dental prostheses. Adaptation assessment was performed after making of a permanent removable obturator denture. Adaptation analysis included cone-beam computed tomography using a CT scanner (Planmeca); intra-oral dental scanning using Cerec Omnicam (Sirona); electron axiography using Prosystom device (Proart) (Fig. 1, 2). In addition, all patients had a clinical examination for temporomandibular joint disorders by the Hamburg test.

Fig. 1. Superimposition of computer tomography data, digital models of the dental arches and facial 3D-scan.

a — frontal view; b — lateral view.

Fig. 2. 3D-reformate of a patient’s face.

a — with obturator; b — without obturator.

Fourteen patients with postoperative defects have been using removable dentures for one to two years, and three patients for seven years. All patients report good adaptability to denture construction, normalization of chewing, breathing, and swallowing.

During the electronic axiography, certain technology features were revealed. The axiographic analysis complex implies intra-oral scanning of the dental arches; however, in patients with voluminous and heavy constructions, a denture dropping is common. Therefore it is crucial to fix it in maximum contact with the denture bed, both when taking the electronic impression of the maxilla and making the correction with the bite fork. When fixating the data with a central marker to determine the head position, the removable denture is similarly stabilized. In addition, cone-beam CT involves the removal of metal-based removable dentures due to possible artifacts on the CT scan. However, there is an uncontrolled decreased occlusal vertical dimension when the construct is removed; and there are no reference points to combine electronic models and tomography data. We concluded that in order to adapt the technique to this category of patients, as well as to patients with secondary edentulism replaced by plastic teeth that are not radiopaque, a composite material 2 mm in diameter should be fixed in the projection of teeth 1.6, 2.6, 1.1 and 2.1 on the vestibular side to correlate data obtained by these two diagnostic methods.

We studied the symmetry of movements of both heads of the temporomandibular joint during mouth opening, mandible protrusion, movement of the mandible during mouth opening, and mandible moving forward, to the right, and to the left.

Results and discussion

Restriction of the mouth opening and mandible movement to the intact side was revealed in 15 (88.2%) out of 17 patients. In subjects with restricted mouth opening, the mean value was 19.48±6.18 mm. The minimum mouth opening was recorded in a patient with the longest denture use of 7 years (10.50 mm). The mean value of mandibular advancement was 6.38±1.71 mm; the mean value of mandible deviation to the intact side in laterotrusion was 7.84±3.24 mm; the mean value of condyle movement on the balancing side was 5.42±2.69 mm; the mean value of the mandible deviation towards the bone defect in laterotrusion was 10.30±3.54 mm; the mean value of condyle movement on the balancing side was 8.36±2.65 mm.

No restriction of mouth opening was detected in 2 patients out of 17, with a mean opening value of 41.40±1.41 mm; the mean value of mandibular advancement was 6.38±1.71 mm.

Thus, patients with unilateral postoperative defects of the maxilla due to combined treatment of malignant neoplasm have restriction of the mouth opening and mandible movements of varying severity, which manifested by difficulty in dental care, biting food, daily oral care, and dentures care. All the above often lead to reduced quality of life. Some patients report normal opening immediately after surgery, but gradual restriction occurs during medical rehabilitation. Despite the small sample size, all cases of restricted mouth opening (88.2% of cases) have reduced condyle mobility on the intact side. This is most likely due to the gradual development of postoperative extra-articular contraction.

The entire medical rehabilitation period, from the surgery to the placement of a permanent replacement denture and beyond, can be divided into three stages:

Stage 1, the first two weeks after surgery. A resection plate is used during this stage. It addresses the key issues of normalizing basic nutritional and respiratory functions. However, this stage is characterized by pain, edema, and postoperative extra-articular contraction. It is very challenging and not quite physiologically appropriate to do function restoration at the first stage.

Stage 2 lasts up to six months; during this stage, a shaping prosthesis is used. The objective of this stage is to restore chewing function, speech, and the formation of the postoperative defect margins. It is reasonable to conduct a set of medical rehabilitation measures immediately after the insertion of the formative prosthesis to prevent muscle and cicatricial contractions, the restriction on mouth opening, and lateral displacement of the mandible.

Stage 3, placement of a permanent replacement prosthesis. With the proper approach and adequate medical rehabilitation, the risk of contractions and dislocations during this period is significantly reduced. That is why it is possible to restore the normal function of the temporomandibular joint and the entire maxillofacial region.

It is necessary to implement preventive measures continuously to prevent mouth opening restrictions and long-term complications. Performing medical rehabilitation only at the third stage will not be as effective due to already formed scarring.

Conclusion

All patients with unilateral postoperative defects of the maxilla due to combined treatment of the malignant neoplasms are recommended to have medical rehabilitation with simulators and myogymnastic exercises to prevent extra-articular contractions and preserve the mandible mobility, mouth opening, and the full range of movements during the long-term period.

Follow-up using axiography in different rehabilitation periods allows us to expand our understanding of the pathogenesis of changes in the temporomandibular joint in patients with unilateral maxilla resection.

The use of the facial scan module allows the creation of a 3D model to assess soft tissue aesthetic changes with and without the obturator. It is possible to combine the two models and translate them into numerical values to assess improvement in facial symmetry.

The reported study was funded by RFBR according to the research project No. 20-315-90058.

The authors declare no conflicts of interest.