Guided removal of a fractured fiber post and immediate restoration with a digitally prefabricated titanium post-and-core and zirconia crown: A clinical report

Augmented Reality Head-Mounted Device and Dynamic Navigation System for Postremoval in Maxillary Molars

INTRODUCTION

This study evaluates the feasibility of an augmented reality (AR) head-mounted device (HMD) displaying a dynamic navigation system (DNS) in the surgical site for fiber postremoval in maxillary molars and compares it to the DNS technique.

METHODS

Fifty maxillary first molars were divided into 2 groups: AR HMD + DNS (n = 25) and DNS (n = 25). The palatal canal was restored with RelyX fiber post (3M ESPE) luted with RelyX Unicem (3M ESPE). A core buildup was performed using Paracore (Coltene/Whaledent). Cone beam computed tomography (CBCT) scans were taken before and after postremoval. The drilling trajectory and depth were planned under X-guide software (X-Nav Technologies, Lansdale, PA). For the AR HMD + DNS group, the AR HMD (Microsoft HoloLens 2) displayed the DNS in the surgical site. The three dimensional (3D) deviations (Global coronal deviation [GCD] and global apical deviation [GAD]) and angular deflection (AD) were calculated. The number of mishaps and operating time were recorded.

RESULTS

Fiber post was removed from all samples (50/50). The AR HMD + DNS was more accurate than DNS, showing significantly lower GCD and GAD deviations and AD (P < .05). No mishap was detected. The AR HMD + DNS was as efficient in time as DNS (P > .05).

CONCLUSIONS

Within the limitations of this in vitro study, the AR HMD can safely display DNS in the surgical site for fiber post-removal in maxillary molars. AR HMD improved the DNS accuracy. Both AR HMD + DNS and DNS were time-efficient for fiber postremoval in maxillary molars.

Effect of reapplication on pull-out bond strength of fibre post to root dentin: An in vitro study

Purpose

Post removal may be necessary for many reasons and is inevitable after the re-application of a dental post. The present study investigated the bond strength between root dentin and a re-applied fibre-reinforced composite (FRC) post by a pull-out test.

Materials and methods

After root canal treatments of 30 extracted human maxillary canine teeth, post spaces were prepared (10 mm), and FRC posts (Hi-Rem Post; Overfibres, İmola, Italy) were luted with self-adhesive resin cement. The samples were than randomly divided into test and control groups (n = 15 in each). The FRC posts were removed in the test group, and new posts were cemented. The pull-out test (1 mm/minute speed) was used to measure the bond strength. Failure types were determined using a stereomicroscope. Mann-Whitney U, chi-square and Fisher-Freeman-Halton exact tests were used for statistical analysis.

Results

The bond strength values of the test (119.5 ± 36.86 N) and control (115.55 ± 55.44 N) groups did not differ significantly (p >.05). In terms of the percentage of failure types, there was a significant difference only in the test group between the mixed failure type and the other failure types (p <.05).

Conclusions

The re-application of FRC post did not seem to affect the bond strength. The distribution of failure types was similar between the control and test groups.

Removal of fiber posts using conventional versus guided endodontics: a comparative study of dentin loss and complications

OBJECTIVES

To compare the efficacy of fiber post removal using conventional (CONV) versus guided endodontics (GE) in terms of dentin loss, residual resin material, procedural errors, and working time in vitro.

MATERIAL AND METHODS

Ninety human central incisors were root-filled and scanned by micro-computed tomography (CT), then restored with fiber posts and composite. Twenty-four sets of teeth with up to four human maxillary central incisors were fabricated and divided into three groups: conventional post removal by a general dentist (CG) or endodontology specialist (CS) and guided endodontics (GE) by a general dentist, yielding 30 teeth per operator and group. After treatment, the prepared access cavities were volumetrically assessed by micro-CT. Statistical significance was evaluated by one-way analysis of variance followed by post hoc comparisons with Tukey's HSD test and Pearson's chi-squared test for independence.

RESULTS

Both CONV and GE resulted in dentin loss and residual resin material. CS resulted in more dentin loss and less residual resin material than CG and GE (p < .05). All groups had some deviations from the original root canal but no perforations. The shortest working time was observed in the GE group.

CONCLUSIONS

Compared to the conventional freehand technique, GE resulted in significantly less radicular dentin loss, a few deviations but no perforations.

CLINICAL RELEVANCE

Guided endodontics can improve the speed and safety of fiber post removal without root perforation.

Mechanical properties, biosafety, and shearing bonding strength of glass fiber-reinforced PEEK composites used as post-core materials

OBJECTIVE

To investigate the mechanical properties, biosafety, and shearing bonding strength of glass fibers-reinforced polyether-ether-ketone (PEEK-GF) for post-core materials.

METHODS

PEEK-GF composites with different glass fiber contents were prepared by extrusion injection and named PEEK-GF30, PEEK-GF40, and PEEK-GF50. Mechanical properties including flexural modulus, flexural strength, Vickers hardness, and compression strength were tested. The cross-sectional morphology was examined using scanning electron microscopy (SEM). Cytotoxicity was studied in vitro with Cell-counting kit-8 (CCK-8). Cell morphology was observed under a microscope. Cell growth on the composites' surfaces was analyzed with DAPI staining. The shearing bonding strength (SBS) of PEEK-GF50 was assessed after applying different pretreatments. Failure modes were evaluated by microscopy. SEM and contact-angle measurements were performed on the surfaces. Statistical analysis was conducted using one-way ANOVA (P < 0.05).

RESULTS

The mechanical properties of PEEK-GF composites improved with increased GF content. The PEEK-GF50 group exhibited flexural modulus (17.4 ± 0.5 GPa) close to that of dentin (18.6 GPa) and showed the highest flexural strength (350.0 ± 2.9 MPa), Vickers hardness (47.6 ± 4.5 HV), and compressive strength (264.0 ± 18.0 MPa). The SEM analysis demonstrated that the PEEK matrix combined well with glass fibers. The CCK-8 results confirmed the biosafety of all groups. DAPI staining indicated that cells were growing well on the composites' surface. The sample that was pretreated with sandblasting and plasma showed the highest SBS (16.0 ± 1.7 MPa).

SIGNIFICANCE

The PEEK-GF composites demonstrated excellent mechanical properties, biosafety, and SBS, and have great potential to serve as post-core materials.

Accuracy of Reduction Depths of Tooth Preparation for Porcelain Laminate Veneers Assisted by Different Tooth Preparation Guides: An In Vitro Study

PURPOSE

To evaluate the accuracy (trueness and precision) of reduction depths of guided veneer preparation assisted by four tooth preparation guides.

MATERIALS AND METHODS

Fifty resin artificial teeth were randomly divided into five groups (n = 10): a freehand group (F), silicone guide group (S), thermoplastic guide group (T), 3D printed uniform guide group (D), and 3D printed auto-stop guide group (A). A preparation for a window veneer on the maxillary right central incisor was performed by two surgeons who used tooth preparation guides for assistance. The maxillary right central incisors were scanned before and after the preparation. The reduction depths were measured in the cervical, middle, and incisal thirds of the prepared surface, and depth maps were created using Geomagic Control X software. The accuracy of the reduction depths at each third was evaluated using both trueness and precision values. The trueness of the reduction depths was determined by calculating the mean absolute differences (MADs) compared to the planning depth, and precision was determined by the standard deviation (SD). The collected data were statistically analyzed using one-way ANOVA and the least significant difference test (α = 0.05).

RESULTS

The MAD ± SD values of the reduction depths in the cervical-third region in groups F, S, T, D, and A were 0.19 ± 0.04, 0.12 ± 0.03, 0.09 ± 0.02, 0.07 ± 0.02, and 0.05 ± 0.01 mm, respectively. In the middle-third region, the MAD ± SD values of groups F-A were 0.19 ± 0.05, 0.13 ± 0.02, 0.09 ± 0.01, 0.06 ± 0.01, and 0.05 ± 0.01 mm. In the incisal-third region, the MAD ± SD values were 0.27 ± 0.05, 0.16 ± 0.04, 0.11 ± 0.03, 0.07 ± 0.01, and 0.05 ± 0.01 mm, respectively. Significant differences in trueness and precision values were found across different groups (F = 45.378, p = 0.000), where group F showed higher MADs than the other 4 groups (p = 0.000), and the highest MADs were detected in group S among the 4 groups in all regions (p = 0.000). Group T showed significantly higher MADs than groups D (P = 0.008) and A (p = 0.001), except in the cervical-third region, where no significant difference was observed between groups T and D (p = 0.077). There was no significant difference between groups D and A (p = 0.148). The deviation map showed significant differences among groups (F = 15.963, p = 0.000), group T presented less deviation than group F (p = 0.000) and group S (p = 0.027) and showed more deviation than group A (p = 0.007).

CONCLUSION

Tooth preparation guides provided more accuracy for veneer preparation than freehand preparation. Among the 4 guides, the 3D printed auto-stop guide presented the lowest absolute difference (0.05 mm) and the silicone guide showed the highest absolute difference of preparation (0.12-0.16 mm).