Load and Strain during Lateral Condensation and Vertical Root Fracture

By Lertchirakarn V, Palamara J, Messer H

Date: 01/1999
Journal: JOE

Purpose:

To compare load & strain in various teeth by hand (HS) & finger spreaders (FS).

Materials/Methods:

N: 60 total teeth. 10 each of maxillary central incisor, premolar and molar; and mandibular incisor, pre-molar and molar.

M&M: Teeth excised 2 mm coronal to CEJ, gauges placed (apical & middle 1/3 on Buccal), cleaning and shaping , each tooth obturated twice (hand and finger spreader, randomly assigned order), strain recorded during obturation. Measured force necessary to induce Vertical root fracture (VRF) with spreader.

Exclusion criteria: fracture, craze lines, gross caries, immature apex

Results:

  • Apical load & overall strain: HS; D11T > FS (statistically significant)
  • No significant difference in loads recorded b/w apical & middle 1/3 gauges
  • Differences in mean load fracture observed among different tooth types. Weakest tooth = mandibular incisors, then M root of mandibular molars.
  • Fracture site usually BL. ↑ variation in location with maxillary premolar and MB root of mx molars.
  • LC does not appear to be a direct cause of VRF unless excessive force used. Previous study states 4.9kg is safe. Pitts recommended “safe-limited load” is 70% min force required to cause fracture.
  • Many fractures take place in the apical third and are due to transmission of the force from the gutta percha and average time is over 20 months.

Clinical Significance:

In cases of mandibular incisors, overinstrumented root(s), thin dentinal walls, recommended obturation by finger spreaders to decrease risk of fracture.