Eligibility of a novel BW + technology and comparison of sensitivity and specificity of different imaging methods for radiological caries detection.

OBJECTIVES: Bitewing radiography is considered to be of high diagnostic value in caries detection, but owing to projections, lesions may remain undetected. The novel bitewing plus (BW +) technology enables scrolling through radiographs in different directions and angles. The present study aimed at comparing BW + with other 2D and 3D imaging methods in terms of sensitivity, specificity, and user reliability. MATERIALS AND METHODS: Five human cadavers were used in this study. In three cadavers, natural teeth were transplanted post-mortem. BW + , two-dimensional (digital sensors, imaging plates, 2D and 3D bitewing radiographs) and 3D methods (high and low dose CBCT) were taken. Carious lesions were evaluated on 96 teeth at three positions (mesial, distal, and occlusal) and scored according to their level of demineralization by ten observers, resulting in 35,799 possible lesions across all observers and settings. For reference, µCT scans of all teeth were performed. RESULTS: Overall, radiographic evaluations showed a high rate of false-negative diagnoses, with around 70% of lesions remaining undetected, especially enamel lesions. BW + showed the highest sensitivity for dentinal caries and had comparatively high specificity overall. CONCLUSIONS: Within the limits of the study, BW + showed great potential for added diagnostic value, especially for dentinal caries. However, the tradeoff of diagnostic benefit and radiation exposure must be considered according to each patient's age and risk.

Is online-only learning as effective as blended learning? A longitudinal study comparing undergraduate students' performance in oral radiology.

INTRODUCTION: Blended learning seems to be an effective teaching concept in oral radiology. During the COVID-19 pandemic, blended learning shifted towards online-only learning. The aim of the present study was to compare the effectiveness of pandemic online-only and pre-pandemic blended learning in three consecutive oral radiology courses (C1, C2 and C3) and to examine whether additional video-based e-learning modules (VBLMs) had a positive impact on undergraduate students' performance during pandemic semesters. MATERIALS AND METHODS: Data from 205 undergraduate dental students participating either in a blended learning or an online-only learning concept were analysed. Pre-pandemic blended learning comprised face-to-face seminars and access to an oral radiology platform (ORP). Pandemic online-only learning comprised online seminars, access to the ORP and additional VBLMs (two VBLMs for C1, four VBLMs for C2 and six VBLMs for C3). Through standardised e-exams at the beginning and end of each semester, performance in final exams and knowledge gain were compared between the two groups. RESULTS: No significant differences in scores in final exams (p = .11) and knowledge gain (p = .18) were found when comparing the pre-pandemic and pandemic groups. On course level, however, students receiving a lower number of VBLMs performed significantly worse in final exams (C1: p < .01, C2: p = .02) and showed inferior knowledge gain (C2: p < .01) during the pandemic. CONCLUSIONS: Within the limitations of the study, the present investigation confirmed that pandemic online-only learning involving VBLMs might be as effective as pre-pandemic blended learning.

Is there any sustained effect of the coronavirus disease 2019 pandemic? - A controlled trial comparing pre- and post-pandemic oral radiology courses.

PURPOSE/OBJECTIVES: Due to the coronavirus disease 2019 (COVID-19) pandemic, undergraduate education shifted towards online-only formats from April 2020 until July 2021. Previous research indicated a negative effect on students' competence development, and it remains unclear whether blended learning concepts could provide compensation. Therefore, the present study aimed to compare pre- to post-pandemic students' performance in standardized baseline (BL) and final exams (FE), as well as the associated knowledge gain (KG) in three consecutive undergraduate blended learning-based oral radiology courses (C1-3). METHODS: Ninety-four students participated during two pre-pandemic semesters (October 17-July 18), and ninety-eight students during two post-pandemic semesters (October 21-July 22). Before the pandemic, conventional face-to-face lectures were combined with an oral radiology platform. Two years into the COVID-19 pandemic, additional video-based e-learning modules were adopted from the pandemic online-only curriculum. In each semester, skills and KG were assessed by conducting standardized BL and FE. Students' performance in BL, FE, and the associated KG during pre-pandemic semesters was compared to post-pandemic semesters. RESULTS: In post-pandemic courses, students showed significantly lower BL scores, whereas KG was significantly higher in post- compared to pre-pandemic semesters (27.42% vs. 10.64%, p < 0.001, respectively). FE scores in C1 significantly improved from pre- to post-pandemic semesters. CONCLUSIONS: Within the limitations of our study, the lower BL scores confirmed the negative effect of the pandemic on competence development. Blended learning concepts seem to compensate for this effect and enable students to return to pre-pandemic levels. Future studies are needed to assess the additional impact of video-based e-learning modules.

Micro finite element analysis of continuously loaded mini-implants - A micro-CT study in the rat tail model.

Implant migration has been described as a minor displacement of orthodontic mini-implants (OMIs) when subjected to constant forces. Aim of this study was to evaluate the impact of local stresses on implant migration and bone remodelling around constantly loaded OMIs. Two mini-implants were placed in one caudal vertebra of 61 rats, connected by a nickel­titanium contraction spring, and loaded with different forces (0.0, 0.5, 1.0, 1.5 N). In vivo micro-CT scans were taken immediately and 1, 2 (n = 61), 4, 6 and 8 (n = 31) weeks post-op. Nine volumes of interest (VOIs) around each implant were defined. To analyse stress values, micro-finite element models were created. Bone remodelling was analysed by calculating the bone volume change between scans performed at consecutive time points. Statistical analysis was performed using a linear mixed model and likelihood-ratio-tests, followed by Tuckey post hoc tests when indicated. The highest stresses were observed in the proximal top VOI. In all VOIs, stress values tended to reach their maximum after two weeks and decreased thereafter. Bone remodelling analysis revealed initial bone loss within the first two weeks and bone gain up to week eight, which was noted especially in the highest loading group. The magnitude of local stresses influenced bone remodelling and it can be speculated that the stress related bone resorption favoured implant migration. After a first healing phase with a high degree of bone resorption, net bone gain representing consolidation was observed.

Autoclaving-induced dimensional changes of three-dimensional printed surgical guides: An in vitro study.

OBJECTIVES: Surgical guides are frequently used for dental implant placement. The aim of this study was to evaluate the impact of the 3D printing process itself and subsequent steam autoclaving on the dimensional stability of five different resin/printer combinations (RPCs). MATERIALS AND METHODS: Fifty identical surgical guides (10 per group) were produced consisting of five RPCs. Half of the guides (5 per group) were steam autoclaved with cycle 1 (121°C, 1 bar, 20.5 min) and the other half with cycle 2 (134°C, 2 bar, 5.5 min). All guides were scanned with a structured-light (SL) 3D scanner before (T0) and after (T1) autoclaving. Linear measurements along the x-, y-, and z-axes were performed at landmarks on the original STL file and on SL scans at T0 and T1, respectively. Wilcoxon signed-rank test, Kruskal-Wallis test, and linear mixed-effects models were performed, depending on the analysis. RESULTS: Three-dimensional printing was associated with significant dimensional alterations for all RPCs. Steam autoclaving using cycle 1 was associated with significant shrinkage in x- (1 RPC), y- (2 RPCs), and z-direction (2 RPCs), while cycle 2 was also associated with shrinkage in x- (2 RPCs), y- (1 RPC), and z-direction (1 RPC). One resin did not present any dimensional changes independently of the cycle. CONCLUSIONS: The majority of the guides presented minor but significant shrinkage due to 3D printing itself and both steam autoclaving cycles, the extent varied between different RPCs. Whether these changes compromise implant placement accuracy remains to be investigated.

Dual Stimuli-Responsive Orthodontic Aligners: An In Vitro Study.

Aligner therapy for orthodontic tooth movement is gaining importance in orthodontics. The aim of this contribution is to introduce a thermo- and water-responsive shape memory polymer (SMP), which could lay the foundation for a new type of aligner therapy. The thermal, thermo-mechanical, and shape memory properties of thermoplastic polyurethane were studied by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and various practical experiments. The glass transition temperature of the SMP relevant for later switching was determined to be 50 °C in the DSC, while the tan δ peak was detected at 60 °C in the DMA. A biological evaluation was carried out using mouse fibroblast cells, which showed that the SMP is not cytotoxic in vitro. On a digitally designed and additively manufactured dental model, four aligners were fabricated from an injection-molded foil using a thermoforming process. The aligners were then heated and placed on a second denture model which had a malocclusion. After cooling, the aligners were in a programmed shape. The movement of a loose, artificial tooth and thus the correction of the malocclusion could be realized by thermal triggering the shape memory effect, at which the aligner corrected a displacement with an arc length of approximately 3.5 mm. The developed maximum force was separately determined to be about 1 N. Moreover, shape recovery of another aligner was realized within 20 h in 37 °C water. In perspective, the present approach can help to reduce the number of orthodontic aligners in therapy and thus avoid excessive material waste.

Maxillary space closure using a digital manufactured Mesialslider in a single appointment workflow.

New digital technologies, many involving three-dimensional printing, bring benefits for clinical applications. This article reports on the clinical procedure and fabrication of a skeletally anchored mesialization appliance (Mesialslider) using computer-aided design/computer-aided manufacturing (CAD/CAM) for space closure of a congenitally missing lateral incisor in a 12-year-old female patient. The insertion of the mini-implants and appliance was performed in a single appointment. Bodily movement of the molars was achieved using the Mesialslider. Anchorage loss, such as deviation of the anterior midline or palatal tilting of the anterior teeth, was completely avoided. CAD/CAM facilitates safe and precise insertion of mini-implants. Further, mini-implants can improve patient comfort by reducing the number of office visits and eliminating the need for orthodontic bands and physical impressions.

Procedure using CAD/CAM-manufactured insertion guides for purely mini-implant-borne rapid maxillary expanders.

With traditional rapid palatal expansion (RPE), orthopaedic forces are transmitted to the skeletal structures via the anchor teeth potentially leading to several unwanted dental side effects. To prevent these issues, tooth-bone-borne or purely bone-borne expanders were introduced using mini-implants in the palate. In this paper, the digitally planned Quadexpander is described which permits palatal expansion with only skeletal anchorage. The use of virtual insertion planning allows for insertion in areas of ideal bone, while avoiding roots and vital structures as well as the possibility of insertion into sites which would otherwise not be considered usable. A second advantage of digital planning is that mini-implants and the expander can be inserted in just one appointment.

Standardized assessment of bone micromorphometry around teeth following orthodontic tooth movement : A µCT split-mouth study in mice.

PURPOSE: Volumetric quantitative analyses of bone micromorphometry changes following orthodontic tooth movements are hardly standardizable. The present study aimed at validating and applying a novel microcomputed tomography (CT)-based approach that enables the segmentation of teeth and definition of a standardized volume of interest (VOI) around the roots to assess local bone micromorphometry. METHODS: The jaws of 3 untreated and 14 orthodontically treated mice (protraction of the upper right molar for 11 days with 0.5 N; untreated left upper molar) were scanned with a micro-CT. The first molars and the alveolar bone were segmented, and a standardized VOI was defined around the teeth. The bone volume per total volume (BV/TV) was assessed within the VOI, and BV/TV values were compared between contralateral sites in both untreated (method validation) and treated animals (method application). RESULTS: The intraclass correlation coefficient of 0.99 revealed high reliability of the method. In the untreated animals, Bland-Altman analysis confirmed comparable BV/TV fractions (mean difference: -1.93, critical difference: 1.91, Wilcoxon: p = 0.03). In the orthodontically treated animals, BV/TV values were significantly lower at the test compared to the control site (test: 33.23% ± 5.74%, control: 41.33% ± 4.91%, Wilcoxon: p < 0.001). CONCLUSION: Within the limits of the study, the novel approach demonstrated the applicability to evaluate bone micromorphometry around teeth subjected to orthodontic treatment.

Friction behavior of the wire material Gummetal®.

OBJECTIVES: Gummetal® (Maruemu Works, Osaka, Japan), a new orthodontic wire material successfully used in clinical applications since 2006, is biocompatible and exhibits exceptionally high elasticity, nonlinear elastic behavior, plasticity and strength. Systematic comparisons of friction behavior are lacking; thus, the friction of Gummetal® in the binding modus was compared to commonly used low friction wires. MATERIALS AND METHODS: In vivo tests were run with Gummetal®, CoCr (cobalt-chromium Elgiloy®, Rocky Mountain Orthodontics, Denver, CO, USA), ß­Ti (ß-Titanium TMA®, Ormco, Orange, CA, USA), NiTi (nickel-titanium, NiTi-SE, Dentalline, Birkenfeld, Germany), and stainless steel (SS; Ref. 251-925, 3M Unitek, Monrovia, CA, USA) [dimensions: 0.014 inch (0.35 mm), 0.016 inch (0.40 mm), 0.016â€¯× 0.022 inch (0.40â€¯× 0.56 mm), and 0.019â€¯× 0.025 inch (0.48â€¯× 0.64 mm)-ß-Ti not available in the dimension 0.014 inch]. These were combined with Discovery® (Dentaurum, Ispringen, Germany), Micro Sprint® (Forestadent, Pforzheim, Germany), Clarity™ (3M Unitek), and Inspire Ice™ (Ormco) and slots in the dimension 0.022 inch (0.56 mm) and, except for the 0.019â€¯× 0.025 inch wires, in the dimension 0.018 inch (0.46 mm). They were ligated with a 0.010 inch (0.25 mm) steel ligature (Smile Dental, Ratingen, Germany). Brackets were angulated by applying a moment of force of 10 Nmm against the wire, which was pulled through the slot at 0.2 mm/s. RESULTS: In 660 tests using 132 bracket-wire combinations, friction loss for Gummetal® was comparable to and, in a few combinations with Micro Sprint®, significantly lower (p < 0.05) than SS and CoCr. The friction for Gummetal® was significantly lower (p < 0.05) than NiTi, and ß­Ti. In some bracket-wire combinations, lower friction was found with round wires compared to rectangular wires, except for the combination with Inspire Ice™, which was higher but not significant. Slot size did not have a significant effect on friction in most combinations. CONCLUSION: The low friction associated with Gummetal® wires during arch-guided tooth movement will be a valuable addition to the armamentarium of orthodontists.

Micro-angiogenic patterns around orthodontic implants migrating in bone: A micro-CT study in the rat tail model.

AIM: Recent studies revealed that implants can migrate in bone when subjected to continuous loading. Since this process is suspected to be accompanied by bone remodelling, which requires blood vessel formation, the present work aimed at assessing the micro-angiogenic patterns around migrating implants. MATERIALS AND METHODS: In 16 rats, two customized implants were placed in a single tail vertebra and connected with contraction springs (forces: 0 N, 0.5 N, 1.0 N, 1.5 N). After 2 or 8 weeks of loading, the animals were scanned by micro-CT before and after vasculature perfusion with a silicone rubber. Vessels were segmented by subtraction of the two micro-CT scans. Vessel thickness (V.Th), vessel volume per total volume (VV/TV), and vascular spacing (V.Sp) were assessed in a peri-implant volume of interest (VOI) around each implant. RESULTS: At 2 weeks of loading, force magnitude was significantly associated with VV/TV and V.Th values (χ2  = 10.942, p < .001 and χ2  = 6.028, p = .010, respectively). No significant differences were observed after 8 weeks of loading. CONCLUSIONS: Within the limitations of an animal study, peri-implant vessel thickness and density were associated with force magnitude in the early loading phase, whereas effects diminished after 8 weeks of loading.

Bone remodelling patterns around orthodontic mini-implants migrating in bone: an experimental study in rat vertebrae.

BACKGROUND: Orthodontic implant migration has been clinically observed in presence of continuous loading forces. Recent studies indicate that osteocytes play a crucial role in this phenomenon. OBJECTIVES: Aim of this study was to investigate local osteocytic gene expression, protein expression, and bone micro-structure in peri-implant regions of pressure and tension. MATERIAL AND METHODS: The present work reports a complementary analysis to a previous micro-computed tomography study. Two customized mini-implants were placed in one caudal rat vertebra and connected by a nickel-titanium contraction spring generating different forces (i.e. 0, 0.5, 1.0, and 1.5 N). Either at 2 or 8 weeks, the vertebrae were harvested and utilized for 1. osteocytic gene expression using laser capture micro-dissection on frozen sections coupled with qPCR, 2. haematoxylin-eosin staining for qualitative and quantitative analyses, 3. immunofluorescence staining and analysis, and 4. bone-to-implant contact on undecalcified samples. RESULTS: At the two time points for all the performed analyses no significant differences were observed with respect to the applied force magnitudes and cell harvesting localization. However, descriptive histological analysis revealed remarkable bone remodelling at 2 weeks of loading. At 8 weeks the implants were osseointegrated and, especially in 1.0 and 1.5 N groups, newly formed bone presented a characteristic load bearing architecture with trabecula oriented in the direction of the loading. CONCLUSIONS: The present study confirmed that stress-induced bone remodelling is the biological mechanism of orthodontic implant migration. Bone apposition was found at 'tension' and 'pressure' sites thus limiting implant migration over time.

The Effects of Three Chlorhexidine-Based Mouthwashes on Human Osteoblast-Like SaOS-2 Cells. An In Vitro Study.

Several decontamination methods for removing biofilm from implant surfaces during surgical peri-implantitis treatment have been reported, including the intraoperative usage of chlorhexidine (CHX)-based antiseptics. There is a lack of information on possible adverse effects on bone healing. The study aimed to examine the impact of three CHX-based mouthwashes on osteoblast-like cells (SaOS-2) in vitro. Cells were cultured for three days in 96-well binding plates. Each well was randomly treated for either 30, 60 or 120 s with 0.05% CHX combined with 0.05% cetylpyridinium chloride (CPC), 0.1% CHX, 0.2% CHX or sterile saline (NaCl) as control. Cell viability, cytotoxicity and apoptosis were assessed at day 0, 3 and 6. Cell viability resulted in being higher in the control group at all time points. At day 0, the CHX 0.2 group showed significantly higher cytotoxicity values compared to CHX 0.1 (30 s), CHX + CPC (30 s, 60 s and 120 s) and control (60 s and 120 s), while no significant differences were identified between CHX + CPC and both CHX 0.1 and NaCl groups. All test mouthwashes were found to induce apoptosis to a lower extent compared to control. Results indicate that 0.2% CHX presented the highest cytotoxic effect. Therefore, its intraoperative use should be carefully considered.

Efficacy of 0.05% Chlorhexidine and 0.05% Cetylpyridinium Chloride Mouthwash to Eliminate Living Bacteria on In Situ Collected Biofilms: An In Vitro Study.

Chlorhexidine (CHX) mouthwashes are frequently used as an adjunctive measure for the treatment of periodontitis and peri-implantitis, as well as in patients on maintenance therapy. However, their prolonged use is associated with several side effects. This study aimed at evaluating if a mouthwash with a reduced concentration of CHX combined with cetylpyridnium chloride (CPC) was as effective as a conventional CHX mouthwash in the reduction in living cells in oral biofilms attached to hydroxyapatite (HA) and micro-rough titanium (Ti) surfaces. Four healthy volunteers wore a customized acrylic appliance containing HA and Ti discs for in situ plaque accumulation. Biofilms were grown on the discs for 24 or 48 h and then randomly exposed for 60 s to: 0.05% CHX + 0.05% CPC, 0.1% CHX (positive control) or sterile saline (negative control). Viability assay and live-dead staining were performed to quantify bacterial viability and to distinguish live and dead cells, respectively. At both time points, contrary to saline, CHX, both alone and in combination with CPC, exhibited high antibacterial properties and induced a significant reduction in biofilm viability. This study demonstrates the potential of mouthwashes containing a low concentration of CHX combined with CPC as effective antibacterial agents for long-term applications with reduced undesired side effects.

Treatment of maxillary transversal deficiency by using a mini-implant-borne rapid maxillary expander and aligners in combination.

Bone-borne rapid maxillary expansion distraction devices are used to achieve a more skeletal expansion and to avoid dental side effects of conventional expanders such as tipping of anchorage teeth. In this article, we report the use of a prefabricated expander fixed on 2 mini-implants in the anterior palate. This allows for the insertion of the mini-implants and the expander to occur without the need for an impression or any laboratory procedures. Especially when aligners are going to be used, the use of a mini-implant-borne expander seems to be reasonable because the expander can be left in place as a skeletal retainer during the aligner finishing.

Automated tooth segmentation as an innovative tool to assess 3D-tooth movement and root resorption in rodents.

BACKGROUND: Orthodontic root resorptions are frequently investigated in small animals, and micro-computed tomography (µCT) enables volumetric comparison. Despite, due to overlapping histograms from dentine and bone, accurate quantification of root resorption is challenging. The present study aims at (i) validating a novel automated approach for tooth segmentation (ATS), (ii) to indicate that matching of contralateral teeth is eligible to assess orthodontic tooth movement (OTM) and root resorption (RR), (iii) and to apply the novel approach in an animal trial performing orthodontic tooth movement. METHODS: The oral apparatus of three female mice were scanned with a µCT. The first molars of each jaw and animal were segmented using ATS (test) and manually (control), and contralateral volumes were compared. Agreement in root volumes and time efficiency were assessed for method validation. In another n = 14 animals, the left first upper molar was protracted for 11 days at 0.5 N, whereas the contralateral molar served as control. Following ATS, OTM and RR were estimated. RESULTS: ATS was significantly more time efficient compared to the manual approach (81% faster, P < 0.01), accurate (volume differences: - 0.01 ± 0.04 mm3), and contralateral roots had comparable volumes. Protracted molars had significantly lower root volumes (P = 0.03), whereas the amount of OTM failed to reveal linear association with RR (P > 0.05). CONCLUSIONS: Within the limits of the study, it was demonstrated that the combination of ATS and registration of contralateral jaws enables measurements of OTS and associated RR in µCT scans.