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Influence of minimally invasive endodontic access cavities on root canal shaping and filling ability, pulp chamber cleaning and fracture resistance of extracted human mandibular incisors.

AIM
To evaluate the influence of the location and design of endodontic access cavities on root canal shaping and filling ability, pulp chamber cleaning and fracture resistance of extracted human mandibular incisors.


METHODOLOGY
After pre-selection using periapical radiographs, forty extracted intact human mandibular incisors were scanned in a micro-computed tomographic device. The teeth were matched based on similar anatomical features of the canals and assigned to four experimental groups (n=10) according to the endodontic access cavity and root canal preparation protocol: traditional/TRUShape (T/TRU); traditional/MTwo (T/MT); minimally invasive/TRUShape (MI/TRU); and minimally invasive/MTwo (MI/MT). The samples were scanned after root canal instrumentation and filling procedures. The parameters evaluated were: volume and area of the root canal, non-instrumented canal areas, canal transportation and centering ratio, accumulated hard tissue debris, voids in root canal fillings and root canal filling materials remnants in the pulp chamber. After root canal filling and cavity restoration procedures, the samples were submitted to the fracture resistance test. Data were statistically analysed using Shapiro-Wilk, one-way ANOVA and Bonferroni tests with a significance level of 5% (α=0.05).


RESULTS
There was no difference regarding all parameters evaluated before and after root canal preparation (volume and area of the root canal, non-instrumented canal areas, canal transportation and centering ratio, and accumulated hard tissue debris) among the groups (P>0.05). MI/TRU and MI/MT groups were associated with significantly more voids in root canal fillings when compared to the T/TRU and T/MT groups (P<0.05). Percentage of root canal filling material remnants in the pulp chamber after cleaning procedures and mean fracture resistance values were not ssignificantly different among the four experimental groups (P>0.05).


CONCLUSIONS
The location and design of the endodontic access cavity did not impact on the root canal preparation and resistance to fracture of extracted mandibular incisors, regardless of the instrument used. Minimally invasive access cavities were associated with significantly more voids in root canal fillings.