Materials for Therapeutic Liners

Principles of apical periodontitis treatment

The disease develops following pulp necrosis (due to lack of or inadequate treatment of pulpitis), when breakdown products, toxins, and microorganisms spread beyond the root apex. The management of periodontitis requires a comprehensive approach aimed at:

• Eradication of pathogenic microflora in both main root canals and microcanals, including apical delta ramifications.
• Neutralization of biogenic amines.
• Resolution of the inflammatory focus.
• Initiation of reparative processes in the periodontium and adjacent alveolar bone.

The pulpo-periodontal tissue is located between the anatomical and physiological apical foramina. Cells in this zone (cementoblasts and odontoblasts) have a pronounced regenerative capacity: they produce secondary cementum and dentin, forming a biological barrier (plug) that prevents further egress of infection.

Single-visit treatment protocol

The standard endodontic protocol for apical periodontitis involves a strict sequence of steps:

1. Cavity preparation.
2. Access cavity deroofing to ensure straight-line access.
3. Removal of necrotic coronal pulp tissue (using an excavator).
4. Initial antiseptic irrigation of the pulp chamber.
5. Stepwise removal of necrotic debris from the root canal.
6. Thorough mechanical instrumentation and chemical debridement of the canal.
7. Root canal obturation.
8. Placement of the definitive restoration.

Working length determination

Before intracanal instrumentation, it is critical to determine the working length—the distance from the apical constriction (physiological foramen) to a stable coronal reference point (incisal edge of incisors, cusp tip of a molar or canine). In clinical practice, radiographic length is always 0.5–1.5 mm greater than the actual working length.

Four primary methods are available:

• Average anatomic tables: provides only an approximate reference, as individual anatomic variations can reach 3–5 mm.
• Anatomic (proportional): based on the crown-to-root ratio (1:2). It is unreliable and carries a risk of instrument overextension beyond the apex.
• Radiographic: performed with an endodontic instrument inserted into the canal and fitted with a rubber stop. Requires an X-ray unit (consisting of a pantograph arm and a collimator).
• Electronic (apex locator): performed using an electronic apex locator. The device closes a circuit via a passive lip clip and an active electrode attached to the endodontic instrument. The APEX indicator confirms reaching the apical constriction, while OVER warns of overinstrumentation.

Medication and Irrigating of Root Canals

Chemical debridement is performed continuously and concurrently with mechanical instrumentation. The main objective is to eradicate bacteria from the dentinal tubules and remove organic debris, dentin chips, and the smear layer. An ideal irrigant must be bactericidal, chemically stable, non-cytotoxic to periapical tissues, and effective even in the presence of organic matter.

Classification of non-specific antiseptic agents:

1. Oxygen-releasing agents: 3% hydrogen peroxide solution.
2. Halogen-releasing agents:
3. Chlorine compounds: chloramine (1–2%), chlorhexidine (0.2%), and sodium hypochlorite (3–5%). The latter has the unique capacity to dissolve necrotic tissue and eradicate viruses, fungi, and bacteria.
4. Iodine compounds: 1% Iodinol solution (exerts fungicidal action and promotes periapical repair).
5. Nitrofuran derivatives: 0.5% furacilin (nitrofural) solution with pronounced anti-exudative properties.
6. Quaternary ammonium compounds: 0.1% decamine solution, active against bacterial spores and yeasts.

Mechanical instrumentation and pulpectomy

Mechanical instrumentation aims to remove the pulp, infected predentin, and shape the root canal adequately. Pulpectomy (complete extirpation of the pulp) is performed in patent root canals under constant antiseptic irrigation.

The barbed broach is inserted strictly without apical pressure. Upon rotation by 90–180°, the pulp is torn off in a single strand, leaving a lacerated wound at the periodontal junction. When a reamer is used, the tissue is severed, producing an incised wound. In the presence of necrotic pulp tissue and apical periodontitis, necrotic debris is removed sequentially (at 1/3, then 2/3, and finally the full working length), cleaning the instrument in an antiseptic solution between steps to avoid pushing infected material into the periapical tissues. The traditional shaping technique involves scouting the canal with a K-reamer, followed by filing with a K-file and H-file of matching size.

Class and exam questions

What else to study on this topic

• Types of endodontic equipment (X-ray systems and apex locators)
• Interpreting apex locator readings (APEX and OVER indicators)
• Crown-down mechanical canal preparation techniques
• Microbiological profile of infected dentinal tubules

Other topics in "Chapter 7. Endodontics"

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