Evaluation of the effect of different minimally invasive access cavity preparations on discoloration in maxillary and mandibular first molars: An in vitro spectrophotometric study

Purpose: This study evaluated the effect of different minimally invasive access cavity designs on the discoloration of maxillary and mandibular first molars using spectrophotometric analysis.
Methods: Eighty first molars (maxillary n=40; mandibular n=40), free of caries and restorations, were randomly allocated—stratified by arch—to eight groups (n=10 per group) according to access cavity design (traditional, conservative, ultraconservative, truss; four groups per arch). Using a dental operating microscope, access cavities were prepared, working lengths determined, and canals instrumented with Reciproc R25. Irrigation activation was performed with a #20 Irrisafe ultrasonic tip, followed by single-cone obturation with R25 gutta-percha and A2 composite restorations. Color measurements were recorded using a Vita Easyshade V spectrophotometer at baseline, immediately after treatment, and at 1, 7, 30, and 60 d. L*a*b values were converted to Commission International de I’Eclairage (CIELAB) ΔE values. Data were analyzed with appropriate statistical tests.
Results: Clinically perceptible discoloration (ΔE≥3.3) was observed in all groups at various time points. In the maxillary molars, traditional access cavities showed significantly greater discoloration at one month compared at baseline (p<0.05). No significant differences were found among the other groups (p>0.05).
Conclusion: Traditional access cavities in maxillary molars produced greater discoloration than minimally invasive access cavities. Minimally invasive access cavity designs may help maintain tooth color by preserving dentin and reducing restorative material volume.

Keywords: Conservative access cavity, minimally invasive endodontics, tooth discoloration, traditional access cavity; truss access cavity; ultraconservative access cavity.