Lower jaw defects: causes, symptoms, diagnosis, treatment

Depending on the etiology, all defects of the lower jaw are divided into two main groups: gunshot and non-gunshot. The first group of defects is characteristic mainly of wartime.

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What causes mandibular defects?

In peacetime, non-gunshot defects of the lower jaw are usually observed. They arise as a result of resection or exarticulation of the jaw (due to a benign or malignant tumor), its lengthening during the correction of underdevelopment, after osteomyelitis or excessively extensive and wasteful sequestrectomy, after accidental trauma, etc.

The clinical picture of a defect of the lower jaw depends on its location and extent, the presence of cicatricial contractions between the fragments of the jaw, the presence of teeth on bone fragments and antagonist teeth on the upper jaw, the integrity of the skin in adjacent areas, etc. According to the classification developed by V. F. Rudko, the following types of defects of the lower jaw are distinguished:

1. midsection defects;
2. defects of the lateral parts of the body;
3. combined defects of the middle and lateral parts of the body;
4. branch and angle defects;
5. subtotal and total body defects;
6. absence of a branch or body part;
7. multiple defects.

B. L. Pavlov divides defects of the lower jaw into 3 classes and 8 subclasses:

• Class I - terminal defects (with one free bone fragment);
• Class II - defects along the jaw (with two free bone fragments);
• Class III - double (bilateral) jaw defects (with three free bone fragments).

In classes I and II, the author identifies three subclasses: with preservation of the chin section, with partial (up to the middle) loss of it, and with complete loss; and in class III, two subclasses: with preservation and without preservation of the chin section.

The above classifications do not take into account the presence of teeth on the jaw fragments, cicatricial contraction between the fragments, etc. Therefore, they cannot help the surgeon in choosing the method of forming a bed for the seedling, the method of intraoral fixation of fragments after surgery, etc. In this regard, the classifications proposed by orthopedic dentists, who attach great importance to the presence of teeth on the fragments of the lower jaw, differ favorably, since this solves the problem of fixing the jaw fragments and ensures rest for the transplant in the postoperative period.

According to the classification of K. S. Yadrova, gunshot defects are divided into three groups:

1. with unstable displacement of fragments (without a shortened scar or with a slight shortening);
2. with persistent displacement of fragments (with a shortened scar);
3. incorrectly healed fractures with loss of bone substance of the lower jaw (with shortening of the jaw).

Each of these groups is divided, in turn, into the following subgroups:

1. single defect of the anterior part of the body of the lower jaw;
2. single defect of the lateral part of the body of the lower jaw;
3. single defect of a branch or a branch with a part of the body of the lower jaw;
4. double defect of the lower jaw.

This classification, close to the classification of V. F. Rudko, also does not reflect the presence or absence of teeth on fragments of the jaw body.

It is simply impossible to compile a comprehensive classification of mandibular defects that would be compact and convenient for practical use. Therefore, the diagnosis should indicate only the main characterological features of the defect: its origin, localization and extent (in centimeters or with orientation to the teeth). As for the other features of the mandibular defect, which appear in various classifications and are undoubtedly of great importance, they should be indicated, but not in the diagnosis, but when describing the local status: cicatricial reduction of fragments to each other, cicatricial contracture of a short fragment (branch of the jaw), the presence of an incomplete osteomyelitic process, the number and stability of teeth on each fragment and on the upper jaw (dental formula, detailed in the text), the presence of a skin defect in the area of the body and branch of the jaw, cicatricial deformations of the tongue, vestibule and floor of the oral cavity. Jaw defects resulting from gunshot injuries are often combined with cicatricial contractions of the tongue and the floor of the mouth, which makes speech very difficult. The surgeon must thoroughly examine the condition of the soft tissues in the area of the lower jaw defect in order to determine in advance whether they are sufficient to create a full-fledged transplant bed.

The ends of the jaw fragments may be sharp or saw-shaped sclerotic spines (with a bridge thrown between them, as it were). These spines are covered with rough scars, which can be difficult to separate from the bone without damaging the oral mucosa. There is evidence that in the pseudoarthrosis of the lower jaw with a bone defect, a zone of newly formed bone beams is determined histologically, which are a continuation of the old beams of the spongy layer. The neoformation of these beams occurs metaplastically, and partly osteoblastically. This process is often insufficiently expressed, so the bone callus between even relatively closely located fragments stops developing, which ultimately leads to non-union of the fragments and the formation of the so-called "false" joint.

A defect of the lower jaw causes severe disturbances in chewing, swallowing and speech functions. With a defect of the chin section of the lower jaw, the patient suffers from constant retraction of the tongue, the inability to sleep on the back.

If the bone defect is combined with a defect in the surrounding tissues, constant salivation is observed.

If there is a defect in the chin section, both fragments are displaced inward and upward; if there is a defect in the lateral section of the body of the jaw, the short (edentulous) fragment is pulled up-forward and inward, and the long one is pulled down and inward. In this case, the chin is displaced to the affected side, and the angle of the lower jaw on this side falls inward.

Treatment of defects of the lower jaw

Treatment of defects of the lower jaw is, as a rule, a complex surgical task, the solution of which has been dealt with by outstanding surgeons and orthopedists from various countries for over 100 years.

Orthopedic replacement of defects

Orthopedic replacement of lower jaw defects was first used by Larrey in 1838, who made a silver prosthesis for the chin area. To this day, in cases where surgical treatment is postponed or seems impossible, orthopedists use various types of prostheses and splints fixed to the teeth or gums.

As for the explantation of foreign materials between the fragments of the lower jaw in the historical aspect, it begins with rubber prostheses and wire spacers, used more for immobilization than for filling the defect. Subsequently, other alloplastic explants were used for this purpose: metal (including gold) plates, acrylic preparations, such as AKR-7, polyvinyl and polyethylene sponges, prostheses made of vitalium, polyacrylate, chrome-cobalt-molybdenum alloy, tantalum and other metals.

Such explants can be located between the fragments of the lower jaw only temporarily, since they are not capable of growing together with bone fragments. In addition, complications often arise in the form of perforations and fistulas on the mucous membrane or skin, which is why the explants have to be removed. Therefore, alloplastic materials are used only for temporary replacement of defects of the lower jaw in order to preserve the bed for subsequent bone grafting (when it cannot be performed simultaneously with the resection of the lower jaw) and to prevent significant postoperative deformation in the area of the resected section of the jaw.

In the development of bone grafting of mandible defects, a number of periods can be distinguished during which surgeons sought methods that would relieve the patient from bone autotransplantation required to replace the jaw defect, i.e. from additional trauma at the "donor site" - the chest, iliac crest, etc. These include xeno- and alloplasty methods, as well as the most gentle methods of autoosteoplasty of the mandible. We will list the main ones.

Xenoplastic replacement of defects

Xenoplastic replacement of lower jaw defects frees the patient from an additional operation - borrowing bone material from a rib, etc. This type of plastic surgery began to be used at the beginning of the 19th century, but its widespread use had to be abandoned due to the biological incompatibility of xenoplastic material.

To overcome this obstacle, some authors propose pre-treating the xenobone with ethylenediamine, after which all organic components of the bone dissolve and the remaining part consists only of crystalline and amorphous inorganic salts.

Alloplasty

Alloplasty of the lower jaw has been used for a long time; for example, Lexer performed two such operations in 1908. But all of them ended, as a rule, in complete failure not only because of tissue incompatibility, but also because of the great difficulties of performing an immediate bone transplant from one person to another. Therefore, surgeons began to resort to using various methods of chemical treatment and preservation of fragments of the lower jaw of a human corpse ("os purum" - "pure bone" and "os novum" - "new bone").

The experimental and clinical use of "pure bone" by E. S. Malevich (1959) using a modified method by A. A. Kravchenko led the author to the conclusion that only under the condition of subperiosteal resection of the lower jaw (due to a benign tumor), without opening the corneal cavity, can the replacement of the resulting bone defect with "pure bone" be successful. The necessity of the above conditions, as well as the complexity (multi-stage nature) and duration of the preparation of "pure bone" transplants, predetermined that this method did not find wide application.

Each of the existing methods of preservation has its own advantages and disadvantages. Preserved bone fragments are used for certain indications.

The replacement of large (more than 25 cm) mandibular defects using cold-preserved bone and cartilage allografts has proven to be unpromising, according to some authors. As the results of experimental and clinical studies have shown, cold-preserved allografts cannot be used for secondary bone grafting if the defect to be replaced is 2 cm or more. At the same time, other authors consider it advisable to use bone and cartilage tissue preserved at low and ultra-low temperatures for reconstructive surgeries on the face, since this produces good clinical and cosmetic results.

A special place among the methods of alloplasty of the lower jaw in recent years is occupied by the use of lyophilized allografts, especially those taken from the lower jaw of a corpse. This material can be stored for a long time at room temperature, its transportation is simple, the body's reaction to the transplantation of such a transplant is less pronounced, etc.

The essence of the lyophilization method is the sublimation of water from previously frozen tissue in vacuum conditions. Dehydration of the tissue is carried out by maintaining the equilibrium of the concentration of water vapor in the tissues and the surrounding space. With such drying of the tissue, there is no denaturation of proteins, enzymes and other unstable substances. The residual moisture of the dried material largely depends on the method of lyophilization and equipment and significantly affects the quality of the transplant, and therefore, the outcome of the transplant.

At the same time, recently there have been searches for other ways to solve the problem of “donation” of hard plastic material for restorative and reconstructive operations in craniofacial areas; for example, V. A. Belchenko et al. (1996) demonstrated the successful use of perforated titanium plates as endoprostheses for extensive post-traumatic defects of bone tissue of the cranial and facial skull.

A. I. Nerobeev et al. (1997) believe that titanium implants can be an alternative to bone grafting in elderly and senile patients, while in young patients they should be considered as a temporary means of preserving the function of the remaining (after resection) part of the lower jaw until the wound heals and as the formation of a transplant bed for subsequent bone grafting. Titanium mesh endoprostheses, made to the shape of the jaw, allow for immediate bone grafting by placing the autogenous bone in the groove of the titanium implant.

E. U. Makhamov, Sh. Yu. Abdullayev (1996), having compared the results of replacing defects of the lower jaw with auto-, allografts and glass-ceramic implants, indicate the advantage of using the latter.

Along with this, in recent years there has been active development of new implantation materials based on hydroxyapatite (V.K. Leontiev, 1996; V.M. Bezrukov, A.S. Grigoryan, 1996), which may possibly be an alternative to auto- and allogenic bone.

The success of using various forms of hydroxyapatite and materials based on them will depend on the rate of development of differentiated indications for their use in experiments and clinical practice; for example, A. S. Grigoryan et al. (1996) demonstrated in animal experiments the high potential of using a new composition with structured collagen, powder and hydroxyapatite granulate (KP-2) in maxillofacial surgery.

Hydroxylapatite, the average composition of which is usually presented as Ca ₁₀ (PO ₄ ) ₆ (OH) ₂, has already found application for replacing defects in hard tissues, hard organs or their parts (joints, bones, implants), as a component of composite biological materials or an osteogenesis stimulator (V.K. Leontiev, 1996). However, “in recent years, a number of controversial issues have accumulated, including those related to some negative experience with the use of this material.