# Root canal conicity of primary maxillary molars and its relationship with different rotational systems

## TL;DR

This study measured the root canal taper in primary maxillary molars and evaluated how well different rotary systems fit the anatomy.

## Contribution

The study provides new empirical data on root canal conicity in primary molars and evaluates the compatibility of rotary systems.

## Key findings

- The 2M showed higher tapers in the buccal-palatal direction compared to the 1M.
- Endogal® and ProTaper Universal® systems best matched the root canal dimensions and tapers.
- Taper variations were observed across different root canals and tooth types.

## Abstract

To determine the root canal taper of primary maxillary molars and the degree of compatibility of various rsotary systems concerning root anatomy.

This in vitro study collected donated first and second primary molars (1 M and 2 M) with mesio-buccal (MB), disto-buccal (DB) and palatal (P) roots canal without physiological resorption, type I according to Vertucci, and root length greater than 4 mm. The teeth were mounted in silicone blocks and scanned with tomographic equipment from which images were reconstructed and analysed with the 3D-Slicer® programme, allowing for the measurement of the diameters of the root canals and the calculation of their tapers. The tapers were compared with the characteristics of the rotary systems: Endogal®, Protaper universal®, Mtwo® and Protaper Next®. MANOVA and interclass correlation coefficient (ICC) tests were used for statistical analysis.

After the analysis of 130 root canals, a mean increase in taper in the buccal-palatal (BP) direction was observed in the 2 M (MB:16.7%; DB:16.23%; P:8.86%) and the 1 M (MB: 9.75%; DB: 11.30%; P: 2.26%). In the mesiodistal (MD) direction, the 1 M exhibited an average taper of MB:6.95%, DB:4.67%, P:12.74% and in the 2 M, an average taper of 4.67% for the MB canal; 6.60%; 20.14% for DB and P canals, respectively.

The rotary files that presented the best adaptation to the diameter and taper of the root canal were Endogal® and ProTaper Universal® systems.