Sleeve material, height, and drill surface changes in guided endodontics: Vicker's hardness and scanning electron...

Area of Science:

• Dentistry
• Biomaterials Engineering
• Mechanical Engineering

Background:

• Guided endodontic access utilizes CBCT-derived templates and guide sleeves for precise canal location, offering conservative and efficient treatment.
• Sleeve materials (zirconia, CoCr, titanium, resin) vary in hardness and durability, impacting drill wear and heat generation during endodontic procedures.
• Existing research lacks characterization of sleeve material and height effects on endodontic drill wear, a critical factor for tool longevity.

Purpose of the Study:

• To evaluate the effect of different guide sleeve materials and heights on endodontic drill wear.
• To assess drill surface changes, including thermal damage and abrasion, using Scanning Electron Microscopy (SEM).
• To determine the Vickers Hardness (HV) of various sleeve materials before and after simulated guided endodontic access drilling.

Main Methods:

• In vitro testing of 30 guide sleeves (3, 5, 7 mm heights; resin, Y-TZP, Co-Cr, Ti-6Al-4V materials) with a 1.5 mm carbide bur.
• Vickers Hardness Test (HV0.2) performed pre- and post-drilling; ANOVA used to analyze material and height effects (p<0.05).
• SEM imaging (1000x) of drill tips and flutes to assess wear (Grades 0-2); thermal discoloration (burn marks) noted.

Main Results:

• Zirconia sleeves exhibited the highest hardness (~1392 HV), while resin sleeves had the lowest (~7 HV); material type significantly affected hardness (p<0.001), but height did not (p>0.8).
• Significant drill wear (Grade 2) was observed in 60% of cases, with thermal damage (burn marks) present in five drills.
• Resin, zirconia, and CoCr sleeves, particularly longer ones, were associated with increased drill abrasion and Grade 2 wear, while short sleeves showed Grade 1 wear.

Conclusions:

• Sleeve material is the primary determinant of hardness, with zirconia being the hardest and potentially most wear-resistant.
• Considerable drill wear and thermal damage occurred with static sleeves, irrespective of material hardness.
• Optimized irrigation and intermittent drilling may be necessary to mitigate thermal and mechanical damage, especially with rigid guide sleeves, to ensure successful guided endodontic procedures.