Classification of dental arch defects

Causes and symptoms of partial tooth loss

Tooth loss leads to disruption of the dental arch continuity. This condition is divided into primary adentia (failure of permanent tooth germ development or developmental anomalies) and secondary adentia (a nosological form where teeth are lost during a lifetime).

The clinical picture depends on many factors: the number and role of lost teeth, bite type, periodontal condition, and the patient's general health. Symptoms develop in a specific chronological order:

• Primary (immediately after loss): appearance of the defect itself, division of the remaining teeth into functioning and non-functioning groups, speech problems.
• Secondary (over time): dental arch deformation, temporomandibular joint (TMJ) disorders, decompensated periodontal overload of the remaining teeth, development of musculoskeletal disorders, and increased tooth wear.

Kennedy classification

The Kennedy system (Kennedy) is the most common classification in Western countries. It was originally created for planning removable partial dentures. There are 4 main classes:

1. Class I: Bilateral distal-extension defects (missing posterior teeth on both sides).
2. Class II: Unilateral distal-extension defect.
3. Class III: Bounded defect in the lateral region on one side.
4. Class IV: Absence of teeth only in the anterior (front) region. Important feature: this class has no subclasses.

If Classes I, II, or III have additional missing teeth, the arch is assigned the corresponding subclass. When multiple different defects are present, the rule of the lower class applies: the dental arch is always classified under the lower-numbered class (e.g., a combination of Class IV and Class I will be considered Class I).

Disadvantages of the Kennedy classification: it is not suitable for the universal evaluation of all types of defects and does not reflect absolutely all possible combinations of them.

Other well-known classifications

Due to the huge number of tooth loss variations, creating a single ideal system is difficult, so alternative approaches exist:

• Eichner classification (1962): Based on the presence of antagonists in 4 support zones (premolars and molars). Group A — contacts are present in all zones; Group B — zones are partially lost; Group C — no antagonists at all. Convenient for assessing chewing function.
• E. Körber classification: Based on how the tissues of the denture foundation bear masticatory pressure. It identifies 5 groups: from pressure transmission exclusively to the periodontium (Group 1, bounded defects) to transmission predominantly to the mucosa (Groups 4–5, few remaining teeth).
• E.I. Gavrilov classification (1966): Divides defects into 7 types: unilateral and bilateral distal-extension, unilateral and bilateral bounded in the lateral regions, bounded in the anterior region, combined, and jaws with single-standing teeth.
• Classification by localization and size: Divides defects into two classes (distal-extension and bounded) with subclasses depending on the number of missing teeth, but it is considered inconvenient to use.

Restoration methods (prosthetic structures)

The dental arch can only be restored using prostheses.

Fixed prostheses (e.g., fixed bridges) are cemented permanently. They are indicated for the loss of incisors, canines, premolars, or a combination of premolars and the first molar. A mandatory condition is the use of reliable abutment teeth (intact or properly root-canally treated). Teeth with periapical inflammation must not be used. Fixed structures restore chewing and speech, prevent deformities, and prevent periodontal overload.

Removable prostheses (acrylic base and removable partial dentures) are indicated, for example, if the third molar is rudimentary and cannot withstand the load of a fixed prosthesis, or in the presence of general contraindications to tooth preparation (coronary heart disease, hypertensive crisis). Acrylic base dentures transmit pressure to the mucosa, which is not physiologically adapted to this, potentially causing inflammation.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Criteria for choosing between removable and fixed prostheses
• Features of using removable partial dentures in patients with somatic pathology
• Biomechanics of masticatory pressure transmission when using acrylic base dentures
• Pathophysiology of TMJ changes in secondary adentia
• Rigidity requirements for fixed dental bridges

Other topics in the section "Chapter 10. Methods of restoring dental arch defects (orthopedic design)"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.