Mikro-CT-Untersuchung zur Effektivität drei verschiedener Methoden für die Entfernung von Glasfaserstiften und die Beurteilung dadurch induzierter Rissbildung im Dentin
by Insa Riggers
Date of Examination:2025-09-15
Date of issue:2025-08-29
Advisor:Prof. Dr. Tina Rödig
Referee:PD Dr. Wolfram Hahn
Referee:Prof. Dr. Dieter Kube
Persistent Address:
http://dx.doi.org/10.53846/goediss-11475
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Abstract
English
The aim of this in vitro study was to evaluate the effectiveness of three different methods for removing glass fiber posts and the resulting crack formation in dentin using micro-computed tomography. Effectiveness was measured by the working time, the loss of dentine, the induction of dentinal cracks, residual post and luting material, and procedural errors. The study was conducted on forty-five extracted human maxillary anterior teeth with straight roots . Specimens were coronally shortened to a root length of 15 mm and divided into three groups (n = 15) based on canal volume (mm³) and canal surface area (mm³). All experimental steps were performed under a dental operating microscope at 10x magnification. Following a standardized preparation protocol, the root canals were shaped with NiTi instruments (Reciproc 50) and obturated in the apical 4 mm using warm vertical compaction. After a drying period of 2 hours, the samples were scanned preoperatively using micro-CT at 80 kV and 125 µA with a resolution of 5 µm. The preoperative scans served as the control group. After scanning, glass fiber posts (X-Post) were cut to a standardized length of 10 mm and adhesively luted into the root canals using a dual-cure resin cement. The posts were then removed using three different methods: Long-shaft round bur (EndoTracer #08), sonic-activated diamond tip (SonicFlex Endo tip #68), and DT Post Removal Kit. Working time was recorded with a stopwatch. After another drying time of 2 hours, a postoperative micro-CT scan was performed. The raw data from the scans were reconstructed, superimposed, and quantified using software programs. Results were then statistically analyzed and compared. Crack evaluation was performed using a scoring system that recorded both the course/origin and the number of newly formed cracks. Removal with the SonicFlex tip resulted in the most dentin removal on average, with significant differences compared to the round bur and the DT Post Removal Kit. None of the three revision techniques could completely remove all post and luting material from the root canal, but the SonicFlex tip left the least residual material. Removal with the round bur took significantly the longest. Within the study, there were neither perforations nor instrument fractures. However, in all three test groups, deviations of the removal instrument from the tooth axis were observed (round bur: 2, SonicFlex tip: 1, DT Post Removal Kit: 2). These resulted in increased dentin removal and ledge formation. Each removal technique induced microcracks, with the DT Post Removal Kit causing the highest average number of microcracks and the SonicFlex tip the fewest. No correlation was found between dentin removal and crack formation. Within the limitations of this study, all methods investigated for the removal of glass fiber posts induced microcracks, led to dentin loss, and left post and composite residues in the root canal. These results demonstrate that post removal, regardless of the technique used, carries a risk of iatrogenic defects. In light of current literature, the clinical relevance of studies on crack formation in dentin using extracted teeth should be further questioned in the future.
Keywords: Fiber post removal; Micro-computed tomography; Effectiveness; Dentinal microcracks; Dentin-loss
