Graham Roy Davis

Background: Pre-clinical training in endodontics relies heavily on typodont teeth to develop operative skills before patient care, but conventional polymer-based typodonts differ from human teeth in their cutting response, requiring greater force and producing an unrealistic cutting experience that often dissatisfies students. Methods: This study evaluated four alternative 3D-printed typodont materials—15 wt.% carbonated hydroxyapatite, 15 wt.% Puraflake^® (glass flake filler), 15 wt.% zinc oxide, and a urethane/triethylene glycol dimethacrylate resin composite—based on their cutting force, post-cut surface roughness, and perceived cutting feel relative to extracted enamel, assessed via a five-point Likert scale questionnaire completed by 46 (n = 46) fourth- and fifth-year dental students. Results: No statistically significant differences in cutting force were detected between the four printed materials and extracted enamel, a finding confirmed using formal two one-sided equivalence testing (TOST); larger confirmatory studies would allow this equivalence to be established with greater statistical precision. Perception scores differed significantly between materials, and fifth-year students rated the dental resin composite significantly more favourably than fourth-year students, with only the composite effect surviving stringent Bonferroni correction across all four material comparisons, underscoring the reliability of this specific finding. Post-cut surface roughness showed a strong, statistically robust monotonic association with perception scores at the individual-respondent level (Page’s L trend test, n = 46, p < 0.001), suggesting that surface behaviour during material removal may contribute to perceived haptic similarity. Conclusions: Matching cutting force alone does not guarantee perceptual equivalence. Among the materials tested, the dental resin composite most closely approximated extracted-enamel surface roughness, received the most favourable and consistent perception scores, and is recommended as the preferred material for pre-clinical typodont fabrication where accessible. These 3D-printed typodonts offer a standardised, openly documented alternative to commercial typodonts for pre-clinical training, with digital models and manufacturing workflows openly available via an institutional platform (TactiTooth).

Objectives: Examine the histomorphometric bone composition, following alveolar ridge preservation techniques and unassisted socket healing.Materials and Methods: Forty‐two patients (42) requiring a single rooted tooth extraction were randomly allocated into three groups (n = 14 per group): Group 1: Guided Bone Regeneration (GBR) using deproteinised bovine bone mineral (DBBM) and a porcine collagen membrane; Group 2: Socket Seal (SS) technique using DBBM and a porcine collagen matrix; Group 3: Unassisted socket healing (Control). Trephined bone biopsies were harvested following a 4‐month healing period. Forty‐two samples underwent Back‐Scattered Electrons ‐Scanning Electron Microscopy (BSE‐SEM) imaging, with 15 samples examined using Xray Micro‐Tomography (XMT) (n = 6 for each GBR/SS and n = 3 Control). Images were analysed to determine the percentage (%) of connective tissue, new bone formation, residual DBBM particles and direct bone to DBBM particle contact (osseointegration).Results: BSE‐SEM analysis demonstrated that new bone formation was higher in the Control (45.89% ± 11.48) compared to both GBR (22.12% ± 12.7/p < .004) and SS (27.62% ± 17.76/p < .005) groups. The connective tissue percentage in GBR (49.72% ± 9), SS (47.81% ± 12.57) and Control (47.81% ± 12.57) groups was similar. GBR (28.17% ± 16.64) and SS (24.37% ± 18.61) groups had similar levels of residual DBBM particles. XMT volumetric analysis indicated a lower level of bone and DBBM particles in all test groups, when matched to the BSE‐SEM area measurements. Osseointegration levels (DBBM graft and bone) were recorded at 35.66% (± 9.8) for GBR and 31.18% (± 19.38) for SS.Conclusion: GBR and SS ARP techniques presented with less bone formation when compared to unassisted healing. GBR had more direct contact/osseointegration between the DBBM particles and newly formed bone.

Objectives: Micro-computed tomography (micro-CT) is an invaluable tool in measuring residual voids after filling root canals as an indicator of the quality of root canal treatment. This study compares void volumes in root canals filled using the cold lateral condensation (CLC) continuous wave (CWC), or single cone (SC) techniques. METHODS: 99 maxillary premolars allocated according to internal anatomy into three matching groups. The root canals were shaped and cleaned and filled with Gutta‑percha and TubliSeal^® EWT sealer using cold lateral condensation (CLC), continuous wave condensation (CWC) or single cone (SC) technique. Void volumes were calculated using a novel software at 30 µm isotropic voxel size resolution. The total void volumes (TVVs) for each technique were statistically compared using Mann-Whitney non-parametric test. RESULTS: The mean percentage of the TVVs (%TVVs) found in SC (1.86±1.64%) group was statistically higher than that in CLC (0.75±0.45%) group, which in turn had statistically significantly more %TVVs than CWC (0.55±0.52%) group. CONCLUSION: The results of this study show that, in maxillary premolars, the SC obturation method resulted in significantly larger %TVVs than both CLC and CWC. The CWC technique resulted in significantly less %TVVs compared to CLC and SC methods.

Imaging of the focal spot size in X-ray generators can be achieved by means of a pinhole in a highly attenuating material, such as gold. For microfocus generators with spot sizes of only around 10 microns or less, the material must be very thin to avoid an impractical aspect ratio. With a 90 kV source, only 11% attenuation is attained with 5 µm gold. For a pinhole that is smaller than the focal spot, the signal-to-noise ratio (SNR) may be less than 1. To image the focal spot of a medical X-ray generator, a coded aperture has been used previously to reduce the exposure time required, however the same technique does not appear to have been used to increase the SNR when the attenuation is very low. Such a method is used here, using a no-two-holes-touching variation of a modified uniformly redundant array (MURA). In a prototype sample, with only 5 µm gold having 2.75 µm holes, the focal spot of a microfocus X-ray generator used in a micro-CT system could be clearly visualised and quantified. Directionality of the aberrations made focussing of the X-ray spot more intuitive and reduced the time required to obtain an optimal, quantifiable focus.

Imaging of the focal spot size in X-ray generators can be achieved by means of a pinhole in a highly attenuating material, such as gold. For microfocus generators with spot sizes of only around 10 microns or less, the material must be very thin to avoid an impractical aspect ratio. With a 90 kV source, only 11% attenuation is attained with 5 µm gold. For a pinhole that is smaller than the focal spot, the signal-to-noise ratio (SNR) may be less than 1. To image the focal spot of a medical X-ray generator, a coded aperture has been used previously to reduce the exposure time required, however the same technique does not appear to have been used to increase the SNR when the attenuation is very low. Such a method is used here, using a no-two-holes-touching variation of a modified uniformly redundant array (MURA). In a prototype sample, with only 5 µm gold having 2.75 µm holes, the focal spot of a microfocus X-ray generator used in a micro-CT system could be clearly visualised and quantified. Directionality of the aberrations made focussing of the X-ray spot more intuitive and reduced the time required to obtain an optimal, quantifiable focus.

The aim of this paper is to systematically analyse the effect of calcium silicate-based sealers in comparison to resin-based sealers on clinical and radiographic outcomes of non-surgical endodontic treatment in permanent teeth. Methods: The study was conducted according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement. The literature search was performed using PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, DOAJ and OpenGrey with no language restrictions. Two reviewers critically assessed the studies for eligibility. Grading of Recommendations, Assessment, Development and Evaluations (GRADE) was carried out to assess the evidence. Meta-analysis of the pooled data with subgroups was carried out using the RevMan software (p < 0.05). Results: Results from the included studies showed that there were no significant differences between the groups in the 24 h post-obturation pain levels (mean difference (MD), −0.19, 95% CI = −0.43–0.06, p = 0.14, I² = 0%), but at 48 h (MD, −0.35, 95% CI = −0.64–0.05, p = 0.02, I² = 0%), a significant difference was observed in favour of calcium silicate sealers. Furthermore, there were no significant differences between the two sealers due to risk of onset or intensity of postoperative pain, need for analgesic and extrusion of the sealer. The heterogeneity assessed using Q test between the included studies was 97% (I²). Conclusions: Within the limitations of this review, the paper shows that calcium silicate-based sealers exhibited optimal performance with similar results to resin-based sealers in terms of average level of post-obturation pain, risk of onset and pain intensity at 24 and 48 h. The observations from the included studies are informative in the clinical evaluation of calcium silicate-based sealers and provide evidence for the conduction of well-designed, controlled randomised clinical trials for a period of at least four years in the future.

Introduction: The aim of this systematic review is to analyse the effect of physico-chemical properties of calcium silicate-based sealers in comparison to epoxy resin sealers in permanent teeth using a single-cone obturation technique. Methods: The study was conducted according to the guidelines of Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement. Literature search was performed using the PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, DOAJ, Open Gray with no language restrictions until October 2020. Two reviewers assessed the studies for eligibility. Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) was carried out to assess the evidence. Meta-analysis of the pooled data with subgroups was performed using the RevMan software (p < 0.05). Results: Results from the 28 included studies showed that the mean difference in adaptation to root canal walls (marginal adaptation, interfacial gaps and void volume) for both sealers were non-significant. However, void volume values showed a significant mean difference (p < 0.00001) favouring the calcium silicate-based sealers. The pooled meta-analysis reported statistically significant differences for apical microleakage (p = 0.0007) whilst there were non-significant mean differences for fracture resistance (p = 0.09) and push-out bond strength (p = 0.63). The heterogeneity among the included studies was 97% (I²). Conclusions: Within the limitations of this review, calcium silicate-based sealers demonstrated a similar or superior performance in comparison to resin-based sealers in terms of the physico-chemical properties.

Computational flattening algorithms have been successfully applied to X-ray microtomography scans of damaged historical documents, but have so far been limited to scrolls, books, and documents with one or two folds. The challenge tackled here is to reconstruct the intricate folds, tucks, and slits of unopened letters secured shut with “letterlocking,” a practice—systematized in this paper—which underpinned global communications security for centuries before modern envelopes. We present a fully automatic computational approach for reconstructing and virtually unfolding volumetric scans of a locked letter with complex internal folding, producing legible images of the letter’s contents and crease pattern while preserving letterlocking evidence. We demonstrate our method on four letterpackets from Renaissance Europe, reading the contents of one unopened letter for the first time. Using the results of virtual unfolding, we situate our findings within a novel letterlocking categorization chart based on our study of 250,000 historical letters.