The effect of mesio-distal chamber dimension on access preparation in mandibular incisors

By Nielson CJ, Shahmohammadi K

Date: 01/2005
Journal: JOE


to investigate the mesio-distal narrowing of the chamber with age and to suggest when the triangular access preparation should go to oval.

  • N= 30 extracted permanent mandibular incisors
  • Inclusion criteria: non carious permanent mandibular incisors from patients aged (40-78y). Exclusion criteria: carious incisors


  • 30 non-carious permanent mandibular incisors from patients aged 40-78y were included.
  • The teeth were mounted in acrylic with adjacent millimeter rulers on each side.
  • Roots were removed and the crowns were sectioned in 0.5 mm increments in an apical to coronal direction starting from CEJ and moving coronally until the chamber no longer existed
  • The chambers mesio-distal dimensions were measured for all increments for all the teeth by a measuring microscope.
  • The chamber widest mesio-distal dimension of each tooth was recorded. these dimensions were compared in relation to age.

Most highlighted Results:

  • All the teeth except 4 had the widest mesio-distal dimension less than 1 mm.
  • The mean value was (0.628 ±0.39 mm).
  • The chamber widest mesio-distal dimension decreased with age, the correlation coefficient (r= -0.6)

Clinical Significance:

In patients older than 40y, the recommended access for mandibular incisors is limited to an oval preparation of less than 2mm in MD width.

Strengths:  using multiple small horizontal increments of the crown to measure the chamber widest MD dimension could increase the accuracy of the results.

weakness: other factors that may affect the size of the pulp (e.g. trauma of occlusion, severe attrition) were not controlled or considered in the exclusion criteria. Pts under age of 40 were not included.