Preclinics of Conservative Dental Medicine · MU Sofia

47. Techniques for root canal filling – central cone and lateral compaction; indications, advantages, disadvantages.

Explains two cold gutta-percha root canal filling methods: the single central cone technique and cold lateral compaction. Walks through the step-by-step lateral compaction procedure with a diagram of the stages, then gives indications, advantages and disadvantages of each, followed by a comparison table, common mistakes such as short or overextended fillings and spreader-induced fracture, and key points.

Inside: 7 sections · 1 labelled picture · 1 table · 17 flashcards · 7 min

Topic 47 of 53 in the MU Sofia syllabus for Preclinics of Conservative Dental Medicine (Dental Medicine, Year 3). The free AceMed note covers it in 7 sections, about 896 words (7 min of reading), with 17 flashcards.

In this note

  1. Introduction
  2. Common principles
  3. Single (central) cone technique
  4. Cold lateral compaction
  5. Comparison
  6. Main mistakes
  7. Key points

Introduction

Obturation of the root canal (obturatio canalis radicis) seals the cleaned and shaped canal in three dimensions, so that remaining bacteria are entombed and no tissue fluid or oral bacteria can re-enter. This note covers the two cold gutta-percha techniques taught first: the single (central) cone technique and cold lateral compaction, the reference against which other techniques are judged.

Common principles

Both techniques use a gutta-percha core cemented with a sealer: gutta-percha gives the bulk, the sealer fills the gaps between cones and walls and the small irregularities. The canal must be shaped and cleaned to full length, dry and free of exudate, and the tooth without acute symptoms. Materials: topic 46; evaluation of the filling: topic 48.

The filling ends at the working length (WL) – the apical constriction, usually 0.5–1 mm short of the radiographic apex – and the sealer layer should be as thin as the technique allows.

Single (central) cone technique

One master cone whose size and taper match the last shaping instrument (e.g. a 25/.06 cone after a 25/.06 rotary file) is cemented at WL with sealer; nothing is compacted. The cone sits centrally and the sealer fills everything around it, so the result depends on how closely the canal matches the cone.

  1. Fit the matching cone: it reaches WL with tug-back; confirm with a radiograph.
  2. Dry the canal with paper points and coat the walls with sealer.
  3. Insert the sealer-coated cone slowly to WL, so that excess sealer escapes coronally.
  4. Sear off at the orifice, condense lightly, take the final radiograph.
  • Indications: narrow, round canals; canals shaped with matched-taper rotary or reciprocating files; today mostly with bioceramic (calcium silicate) sealers, which set in moisture and do not shrink, so a thicker layer is acceptable.
  • Advantages: quick and simple; no spreader wedging, so little fracture risk; little gutta-percha extruded; suits narrow curved canals a spreader cannot enter.
  • Disadvantages: the seal relies on the sealer – conventional sealers shrink and slowly dissolve, so thick layers leave voids and leak; poor in oval, ribbon-shaped or irregular canals, where a round cone leaves the extensions filled only with sealer or empty.

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