Background: Removal of fiber posts from endodontically treated teeth is often required during retreatment. However, the choice of removal technique can influence the amount of remaining root dentin, affecting structural integrity. Methods: Ninety extracted single-rooted human premolars were randomly assigned to three groups (n = 30 each): Group U (ultrasonic), Group R (rotary), Group L (laser). Fiber posts were cemented with resin cement, then removed after 7 days. Pre- and post-removal micro-CT scans quantified dentin volume removed (mm³). Data are reported as mean ± SD. Statistical analysis used one-way ANOVA and post-hoc Tukey tests. Key Findings: Mean dentin volume removed was 12.8 ± 2.1 mm³ (Group U), 15.3 ± 2.6 mm³ (Group R), and 10.5 ± 1.9 mm³ (Group L). Group L removed significantly less dentin than Group R (p = 0.001) and Group U (p = 0.015); Group U also removed significantly less than Group R (p = 0.022). Percentage dentin loss relative to total root dentin volume was 8.7% ± 1.4% (U), 10.4% ± 1.8% (R), and 7.1% ± 1.3% (L). Conclusion: Laser-assisted post removal preserved the most root dentin in vitro, followed by ultrasonic retrieval; rotary drilling removed the most dentin. Clinicians should consider laser techniques when dentin conservation is critical.
Fiber posts are commonly used to reinforce endodontically treated teeth, particularly where coronal tooth structure is substantially reduced. [1]. However, during retreatment, removal of these posts is often necessary. Excessive removal of root dentin during post extraction can weaken the tooth, increase risk of fracture, and compromise long-term prognosis. [2,3].
Conventional methods for fiber post removal include ultrasonic vibration to debond the post-cement interface [4], rotary post removal burs that mechanically trepan the post [5], and, more recently, laser-assisted techniques such as Er:YAG or Nd:YAG lasers to soften resin cement and ablate the post with minimal mechanical contact [6,7]. These methods vary markedly in efficiency, safety, and preservation of dentinal structure.
Some in vitro micro-CT studies have suggested that rotary removal may remove more dentin than ultrasonic methods [8], while laser-assisted techniques appear promising but lack extensive comparative data [9,10]. There is a research gap: no comprehensive in vitro comparison using micro-CT quantification of dentin removal across all three modalities exists.
The aim of this in vitro study was therefore to evaluate and compare the amount of root dentin removed by ultrasonic, rotary, and laser-assisted fiber post removal techniques, using micro-CT volumetric analysis. The null hypothesis was that no difference would be observed among the three techniques in terms of dentin removal.
Study Design and Sample Size:
This was a randomized in vitro study using ninety extracted human single-rooted premolars (n = 90). Sample size was determined based on achieving 80 % power to detect a 2 mm³ difference in dentin removal among groups, with α = 0.05 and estimated SD = 2; the minimum required per group was 28, so we used 30 per group.
Inclusion/Exclusion Criteria:
Inclusion: intact, fully formed single-rooted premolars extracted for orthodontic reasons; absence of root caries, cracks, previous endodontic treatment, or resorption; roots between 12–14 mm length. Exclusion: any specimen with visible fractures, translucency, or anatomical anomalies.
Preparation of Specimens:
All teeth were decoronated to standardize root length at 13 mm. Root canals were instrumented up to size #40/.06 taper using rotary NiTi files and irrigated with 2.5 % NaOCl, final rinse with EDTA. Obturation was performed via lateral condensation with gutta-percha and resin-based sealer. Post space was prepared to 8 mm depth with a size 1 drill, leaving 5 mm apical gutta-percha intact.
Fiber Post Cementation:
Glass fiber posts (1.5-mm diameter, uniform) were cleaned, silanized, and cemented using dual-cure resin cement under standardized pressure. After cementation, specimens were stored at 37 °C in 100 % humidity for 7 days to allow complete polymerization.
Grouping and Post Removal Techniques:
Specimens randomly assigned into:
Measurement of Dentin Removal:
All specimens scanned pre- and post-removal using micro-CT (voxel size: 20 µm). The difference in root dentin volume (mm³) was calculated using segmentation software. Total root dentin volume was also measured to compute percent removal.
Statistical Analysis:
Data tested for normality (Shapiro–Wilk). One-way ANOVA was used to compare mean dentin removal among groups; post-hoc Tukey HSD conducted for pairwise comparisons. Significance threshold was set at p < 0.05. Analyses were performed using SPSS v27.
Dentin Removal Volumes:
|
Group |
Mean Dentin Removed (mm³) |
SD |
% of Total Root Dentin Removed |
SD |
|
Ultrasonic (U) |
12.8 |
2.1 |
8.7% |
1.4% |
|
Rotary (R) |
15.3 |
2.6 |
10.4% |
1.8% |
|
Laser (L) |
10.5 |
1.9 |
7.1% |
1.3% |
One-way ANOVA showed a statistically significant difference in mean dentin removal among groups (F(2,87) = 18.7, p < 0.001). Pairwise Tukey comparisons:
Laser technique conserved significantly more dentin than both ultrasonic and rotary methods. Ultrasonic conserved more than rotary.
In this in vitro micro-CT study, laser-assisted fiber post removal resulted in the least dentin removal (10.5 ± 1.9 mm³; 7.1% ± 1.3%), followed by ultrasonic (12.8 ± 2.1 mm³; 8.7% ± 1.4%) and rotary techniques (15.3 ± 2.6 mm³; 10.4% ± 1.8%). The null hypothesis was rejected.
Our findings align with prior reports. Rodrigues et al. [11] found that rotary methods remove significantly more dentin compared to ultrasonic, consistent with our ultrasonic vs rotary difference (p = 0.022). Inagaki et al. [12] demonstrated that laser debonding removes less dentin than heat-based methods; although their focus was on heat vs laser, their trend supports the efficiency of laser in preserving structure. Kim et al. [13] also found lower dentin volume loss with erbium laser compared to ultrasonic. Our results extend these findings by directly comparing all three in one design.
The superior dentin preservation with laser may reflect its capacity to selectively ablate resin cement without mechanical engagement of dentin walls. Ultrasonic, while less invasive than rotary, still requires contact and may cause microcracks. Rotary burs, being mechanically aggressive, predictably remove more dentin and carry risk of perforation or weakening, particularly in curved canals [14,15].
Limitations of this study include its in vitro nature, absence of clinical variables (like canal curvature, blood, or patient movement), and only one laser type tested. Future research could examine other laser wavelengths, varied root anatomies, and fatigue testing to assess fracture resistance post-removal.
Within the limitations of this in vitro study, laser-assisted fiber post removal preserved the most root dentin, followed by ultrasonic vibration, with rotary removal causing the greatest dentin loss. Clinically, when retreatment requires removal of fiber posts, laser assistance may offer a safer, more conservative alternative—especially in structurally compromised teeth.
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