A novel computer-aided method for direct measurements and visualization of gingival margin changes.

AIM: To introduce and validate a computer-aided method for direct measurements and visualization of gingival margin (GM) changes. MATERIALS AND METHODS: The method consists of five main steps: digital model acquisition, superimposition, computer-aided GM detection, distance calculation between the GM curves, and visualization. The precision of the method was evaluated with repeatability and reproducibility analysis (n = 78 teeth). The method's repeatability was evaluated by repeating the algorithm on the same digital models by two operators. The reproducibility was evaluated by repeating the algorithm on two consecutive digital models obtained with a scan-rescan process at the same time point on the same patient. For demonstration, the proposed method for direct measurements of GM changes was performed on patients who had undergone root coverage procedures and treatment of periodontal disease. RESULTS: Excellent repeatability was found for both intra- and inter-operator variability, that is, 0.00 mm, regarding computer-aided GM detection. The reproducibility of computer-aided GM detection evaluated on scan-rescan models was 0.10 mm. CONCLUSIONS: The presented method enables the evaluation of GM changes in a simple, precise, and comprehensive manner through non-invasive acquisition and superimposition of digital models.

Gingival shape analysis using surface curvature estimation of the intraoral scans.

BACKGROUND: Despite many advances in dentistry, no objective and quantitative method is available to evaluate gingival shape. The surface curvature of the optical scans represents an unexploited possibility. The present study aimed to test surface curvature estimation of intraoral scans for objective evaluation of gingival shape. METHODS: The method consists of four main steps, i.e., optical scanning, surface curvature estimation, region of interest (ROI) definition, and gingival shape analysis. Six different curvature measures and three different diameters were tested for surface curvature estimation on central (n = 78) and interdental ROI (n = 88) of patients with advanced periodontitis to quantify gingiva with a novel gingival shape parameter (GS). The reproducibility was evaluated by repeating the method on two consecutive intraoral scans obtained with a scan-rescan process of the same patient at the same time point (n = 8). RESULTS: Minimum and mean curvature measures computed at 2 mm diameter seem optimal GS to quantify shape at central and interdental ROI, respectively. The mean (and standard deviation) of the GS was 0.33 ± 0.07 and 0.19 ± 0.09 for central ROI using minimum, and interdental ROI using mean curvature measure, respectively, computed at a diameter of 2 mm. The method's reproducibility evaluated on scan-rescan models for the above-mentioned ROI and curvature measures was 0.02 and 0.01, respectively. CONCLUSIONS: Surface curvature estimation of the intraoral optical scans presents a precise and highly reproducible method for the objective gingival shape quantification enabling the detection of subtle changes. A careful selection of parameters for surface curvature estimation and curvature measures is required.

Assessment of reference areas for superimposition of serial 3D models of patients with advanced periodontitis for volumetric soft tissue evaluation.

AIM: This study aimed to determine the optimal reference area for superimposition of serial 3D dental models of patients with advanced periodontitis. MATERIALS AND METHODS: Ten pre- and post-periodontal treatment 3D models (median time lapse: 13.1 months) of patients with advanced periodontitis were acquired by intraoral scanning. Superimposition was performed with the iterative closest point algorithm using four reference areas: (A) all stable teeth, (B) all teeth, (C) third palatal rugae and (D) the whole model. The superimposition accuracy was evaluated at two stable evaluation regions using the mean absolute distance and evaluated with two-way ANOVA and post-hoc multivariate model. The intra- and inter-operator reproducibility was calculated by intraclass correlation coefficient (ICC). RESULTS: Superimposition accuracy evaluated at stable tooth evaluation region were 71 ± 29 µm, 73 ± 21 µm, 127 ± 52 µm and 113 ± 53 µm for areas A, B, C and D, respectively. All reference areas showed similarly high ICC values >0.990, except for reference area C showing ICC of 0.821 (intra-operator) and 0.767 (inter-operator) for tooth evaluation area. CONCLUSIONS: Area A and B provide the highest accuracy for superimposition of serial 3D dental models acquired by intraoral scanning of patients with advanced periodontitis.

The precision of gingival recession measurements is increased by an automated curvature analysis method.

BACKGROUND: The extent of gingival recession represents one of the most important measures determining outcome of periodontal plastic surgery. The accurate measurements are, thus, critical for optimal treatment planning and outcome evaluation. Present study aimed to introduce automated curvature-based digital gingival recession measurements, evaluate the agreement and reliability of manual measurements, and identify sources of manual variability. METHODS: Measurement of gingival recessions was performed manually by three examiners and automatically using curvature analysis on representative cross-sections (n = 60). Cemento-enamel junction (CEJ) and gingival margin (GM) measurement points selection was the only variable. Agreement and reliability of measurements were analysed using intra- and inter-examiner correlations and Bland-Altman plots. Measurement point selection variability was evaluated with manual point distance deviation from an automatic point. The effect of curvature on manual point selection was evaluated with scatter plots. RESULTS: Bland-Altman plots revealed a high variability of examiner's recession measurements indicated by high 95% limits of agreement range of approximately 1 mm and several outliers beyond the limits of agreement. CEJ point selection was the main source of examiner's variability due to smaller curvature values than GM, i.e., median values of - 0.98 mm- 1 and - 4.39 mm- 1, respectively, indicating straighter profile for CEJ point. Scatter plots revealed inverse relationship between curvature and examiner deviation for CEJ point, indicating a threshold curvature value around 1 mm- 1. CONCLUSIONS: Automated curvature-based approach increases the precision of recession measurements by reproducible measurement point selection. Proposed approach allows evaluation of teeth with indistinguishable CEJ that could be not be included in the previous studies.

3D computer-aided treatment planning in periodontology: A novel approach for evaluation and visualization of soft tissue thickness.

OBJECTIVE: Current approaches for soft tissue thickness evaluation and visualization still represent a challenge for full extent evaluation and visualization. The aim of this clinical technique article is to introduce a novel approach for comprehensive visualization and precise evaluation of oral soft tissue thickness utilizing a fusion of optical 3D and cone-beam computed tomography (CBCT) images. CLINICAL CONSIDERATIONS: 3D models of the maxilla were obtained by CBCT imaging and intraoral scanning. The CBCT images were reconstructed to standard tessellation language (STL) file format models by segmentation of teeth and bone using implants planning software. 3D soft tissues and teeth models were obtained by intraoral scanning and were exported in STL file format as well. 3D multimodal models were then superimposed using best-fit matching on teeth. Soft tissue thickness was then visualized and evaluated with a 3D color-coded thickness map of gingival and palatal areas created by surface comparison of both 3D models. Additionally, threshold color-coding was used to increase comprehensibility. Palatal areas were further visualized and evaluated for the optimal donor site. CONCLUSIONS: A novel approach for 3D evaluation and visualization of masticatory mucosa thickness presents all available 3D data in a comprehensible, "clinician-friendly" manner, using threshold regions and clinically relevant views. CLINICAL SIGNIFICANCE: Proposed approach could provide comprehensive presurgical treatment planning in periodontal plastic surgery and implantology without additional invasive procedures for the patient, resulting in more predictable treatment, improved outcomes, and reduced risk for complications.

Presentation of gaps around endodontic access cavity restoration by phase contrast-enhanced micro-CT.

OBJECTIVE: To evaluate the feasibility of synchrotron-based phase-contrast (PC) µCT for visualization of the gaps and differentiation between the gaps, restorative, and endodontic materials at the tooth-restoration interface. MATERIALS AND METHODS: Standardized access cavities were prepared in human maxillary molars and subjected to materials, simulating endodontic treatment: (1) saline irrigation; (2) NaOCl and 17% EDTA irrigation; (3) same as group 2, followed by application of Ca(OH)2; and (4) same as group 2, followed by application of root canal sealer. The access cavities were cleaned and restored using an etch-and-rinse adhesive and a composite material in multilayering technique. The samples were thermocycled (1000 cycles, 5-55 °C). Synchrotron-based µCT imaging was performed obtaining absorption and PC µCT images before and after the immersion of the samples into 50% AgNO3. PC µCT images were compared to absorption µCT and conventional optical microscopy images. RESULTS: PC µCT of unstained samples enabled the best visualization of gaps and differentiation of restorative and endodontic materials, contaminating the cavity surface. PC µCT revealed that AgNO3 staining leads to an overestimation of gap size due to anterograde and retrograde AgNO3 infiltration into dentinal tubules and underestimation of large gaps due to lack of AgNO3 penetration. CONCLUSION: Synchrotron PC µCT imaging enables better visualization of gap and differentiation of materials at the tooth-restoration interface. µCT imaging with AgNO3 staining has shown certain over- and underestimations. Future research should be aimed at incorporating PC µCT imaging of unstained samples for the validation of results obtained with other methods. CLINICAL SIGNIFICANCE: Contamination of cavity walls with an endodontic sealer or Ca(OH)2 leads to increased gap formation at the tooth-restoration interface.

Effect of Er:YAG laser pretreatment on bond strength of a composite core build-up material to fiber posts.

The study evaluated the micro push-out bond strength of resin material (Multicore Flow) to two types of fiber posts (FP), namely fiber-reinforced composite (FRC) Postec and Radix Fiber posts using Er:YAG laser pretreatment. FP were divided into four groups, two being control groups. Before the core build-up procedure, representative specimens from each group were chosen to determine the surface roughness (Ra) at three different areas using a contact profilometer, while after the procedure, 1.5-mm-thick discs were sectioned and the micro push-out method was used to assess the bond strength of the core build-up material to the fiber post in each group. Two-way analysis of variance was used for statistical analysis with the level of significance set at p < 0.05. Scanning electron microscopy was used to analyze the post surfaces after Er:YAG laser pretreatment and to classify the failure mode after loading. The type of pretreatment (p < 0.001) and an interaction between the pretreatment and type of post (p < 0.001) had a significant effect on the bond strength, while the type of post did not (p = 0.965). The mean bond strength in the Er:YAG laser pretreatment group was significantly lower compared to the FRC Postec posts control group (p < 0.001), while there was no significant difference between the Radix Fiber posts groups (p = 0.680). Mean Ra values from the Er:YAG laser pretreatment groups were significantly higher compared to control groups (p < 0.001). Er:YAG laser pretreatment at tested parameters negatively affected the bond strength of Multicore to FP and cannot be recommended as a standard procedure.

Radiopacity of dental restorative materials.

OBJECTIVES: Radiopacity of dental materials enables clinician to radiographically diagnose secondary caries and marginal defects which are usually located on the proximal gingival margin. The aim of this study was to measure the radiopacity of 33 conventional resin composites, 16 flowable resin composites, and 7 glass ionomer cements and to compare the results with the radiopacity values declared by the manufacturers. MATERIALS AND METHODS: From each restorative material, six 2-mm-thick disk-shaped specimens were fabricated and eight 2-mm-thick sections of teeth were made and used as reference. The material samples and tooth sections were digitally radiographed together with the aluminum stepwedge. Gray values were obtained from the radiographic images and radiopacity values were calculated and statistically analyzed. Post hoc Tukey's honestly significant difference test was used to calculate significant differences in radiopacity values between materials and reference dentin and enamel values. RESULTS: The radiopacity values of all 56 restorative materials were above the dentin reference radiopacity value; however, 4 out of 33 conventional composites and 3 out of 16 flowable resin composites had significantly lower radiopacity than enamel (p < 0.05). There were up to 1.53 mm eq Al differences between the measured and the manufacturers' declared radiopacity values of some materials. CONCLUSIONS: Majority of the materials exceed enamel radiopacity and would not hamper radiographic diagnosis of secondary caries. However, manufacturers' data are not always reliable. CLINICAL RELEVANCE: Materials with radiopacity lower than enamel might be misinterpreted as secondary enamel caries on radiographic images, especially when applied as initial increment on the proximal gingival margin.

Retentive design of a small surgical guide for implant surgery: An in-vitro study.

OBJECTIVES: Instability of the surgical guide is an overlooked factor that can result in a difference between the planned and the actual positions of an implant. Our aim was to compare the stability of the retentive surgical guide (RSG) with a conventional surgical guide (CSG) in an in-vitro experiment. METHODS: A platform to evaluate the stability of the surgical guide was designed using 3D-modelling software (Meshmixer 3.5, Autodesk). Imaging data from 15 patients with a single missing tooth were used to plan the virtual implant. Two surgical guides were designed (Blue Sky Plan 4.8, Blue Sky Bio) and 3D printed (Form2, Dental SG resin, Formlabs) for each case: the CSG with the default, predetermined software settings, and the RSG, designed on a dental model with a 0.1-mm undercut and altered production parameters (reduced guide-to-teeth offset of 0.07 mm, reduced guide thickness of 2.3 mm and a retentive clasp in a marginal area). The dental models were reproducibly secured on the testing platform using a digital force gauge, and the surgical guides were positioned. An increasing force of 0.1 N, 1 N, 2.5 N, and 5 N was sequentially applied from the buccal and the oral directions to the surgical guide via a drill handle. For each force, either the magnitude of the guide's displacement was captured with an intra-oral scanner (CEREC Omnicam AC, Dentsply Sirona; software version: SW 4.5.2) or the dislodgement of the guide was recorded. Scans were imported for analysis (GOM Inspect 2018, GOM GmbH), and library files of the surgical guides and implants were superimposed as a joined complex. The deviation of the implant's position was calculated from the displacement of the guide's position RESULTS: Three-way repeated measures using ANOVA revealed a more significant guide displacement and virtually projected implant deviation in the CSG group than the RSG group and with increasing force in all the deviation parameters. Both groups showed greater resistance to the displacement with the force applied from the oral direction than the buccal direction. The application of the force in the buccal direction resulted in guide dislodgements of 13% and 0% for the CSG and RSG, respectively. In the oral direction, the dislodgement rates were 33% and 7% for the CSG and RSG, respectively. CONCLUSIONS: Within the limitations of this study, the retentive design increased the stability of the surgical guide and, consequently, the accuracy of the virtually projected implants in comparison to the conventional surgical guide designed using the default settings. Clinical trials are needed to confirm its advantages in clinical use. CLINICAL SIGNIFICANCE: With a simple modification to the design, the surgical guide retention provided greater stability, with smaller deviations under loading; this resulted in improved implant precision parameters without requiring additional materials or software. Further studies are needed to assess the clinical feasibility of this surgical guide with improved retention and function.

Image resolution and exposure time of digital radiographs affects fractal dimension of periapical bone.

OBJECTIVES: The aim of this study was to evaluate the effect of exposure time and image resolution on fractal dimension (FD) of periapical bone on images obtained using a storage phosphor plate (SPP) system. MATERIALS AND METHODS: Periapical images of premolar and molar teeth on both sides of ten dry human mandibles were obtained with Digora Optime (Soredex Corp., Helsinki, Finland) SPP system. The SPPs were exposed with three exposure times (0.05, 0.12, and 0.30 s) and scanned immediately after exposure with high and super resolutions. FD was calculated using public domain software (ImageJ with FracLac plug-in) on two non-overlapping region of interest (ROIs) on premolar and molar periapical bone areas of each radiograph using differential box-counting method. The ROIs on corresponding images were of the same size and position. FDs were compared using two-way ANOVA and Tukey-Kramer multiple comparison tests (p = 0.05). RESULTS: Images obtained with super resolution scans gave significantly higher FD values compared to high-resolution scanning for all exposures (p < 0.0001). FD values were decreasing with increase in exposure time for both resolutions (p < 0.0001). The highest FD was found for images with super resolution and shortest exposure time, which exhibited the highest noise. CONCLUSIONS: FD analysis seems not so robust method as it was believed previously. It shows significant changes with image resolution and exposure time. CLINICAL RELEVANCE: Exposure time and scanning resolution of SPPs should be carefully chosen when evaluating the change in FD of alveolar bone for various bone disorders.

Virus transmission by ultrasonic scaler and its prevention by antiviral agent: An in vitro study.

BACKGROUND: It is well recognized that dental procedures represent a potential way of infection transmission. With the COVID-19 pandemic, the focus of dental procedure associated transmission has rapidly changed from bacteria to viruses. The aim was to develop an experimental setup for testing the spread of viruses by ultrasonic scaler (USS) generated dental spray and evaluate its mitigation by antiviral coolants. METHODS: In a virus transmission tunnel, the dental spray was generated by USS with saline coolant and suspension of Equine Arteritis Virus (EAV) delivered to the USS tip. Virus transmission by settled droplets was evaluated with adherent RK13 cell lines culture monolayer. The suspended droplets were collected by a cyclone aero-sampler. Antiviral activity of 0.25% NaOCl and electrolyzed oxidizing water (EOW) was tested using a suspension test. Antiviral agents' transmission prevention ability was evaluated by using them as a coolant. RESULTS: In the suspension test with 0.25% NaOCl or EOW, the TCID50/mL was below the detection limit after 5 seconds. With saline coolant, the EAV-induced cytopathic effect on RK13 cells was found up to the distance of 45 cm, with the number of infected cells decreasing with distance. By aero-sampler, viral particles were detected in concentration ≤4.2 TCID50/mL. With both antiviral agents used as coolants, no EAV-associated RK-13 cell infection was found. CONCLUSION: We managed to predictably demonstrate EAV spread by droplets because of USS action. More importantly, we managed to mitigate the spread by a simple substitution of the USS coolant with NaOCl or EOW.

Methods and parameters for digital evaluation of gingival recession: A critical review.

OBJECTIVES: The aim of the present review was to find, compare, and critically discuss digital methods for quantitative evaluation of gingival recessions dimensions. DATA: Collection of articles and classification related to digital evaluation of gingival recessions. SOURCES: A search of PubMed, Web of Science, Scopus, and reference lists of articles was conducted up to April 2021. STUDY SELECTION: Twenty-two articles used digital evaluation of gingival recessions dimensions. The methods in the included articles were extracted, compared, and categorized. RESULTS: Digital measurements were performed on 2D intraoral photographs, 3D models, or cross-sections obtained from 3D models. Baseline measurement were performed for diagnostic and treatment planning and categorised into distance and area measurements. Follow-up evaluation of treatment was based either on repeating the "baseline" measurements and calculating differences or measuring differences directly on composite images, composed from two superimposed images obtained at two time-points. Direct measurements were categorised into distance, area, and volume measurements. CONCLUSIONS: Digital evaluation predominantly means just digitalization of the established evaluation methods; therefore, increasing measurements accuracy and maintaining comparability with past studies. At present, a large variability of digital evaluation workflow among the included studies renders the comparison among different studies difficult if not impossible. The potential of digital evaluation seems not to have been fully exploited as only a few novel measurements and parameters introduced, i.e., volumetric evaluation of soft tissue dynamics. For reproducible and comparable studies in the future, the research should be aimed at evaluation, optimization and standardization of all phases of the digital evaluation. CLINICAL SIGNIFICANCE: Digital evaluation, based on 3D image superimposition is a promising approach as it increases measurements accuracy, maintains compatibility with past studies and simultaneously introduces novel evaluation possibilities.

Evaluation of gingival recessions with conventional versus digital methods.

OBJECTIVES: The present study aimed to compare the conventional clinical and a digital method for evaluating differences in gingival recession (ΔREC) in patients with advanced periodontitis treated with the non-surgical treatment protocol. METHODS: Agreement between the methods was evaluated on a sample of ten patients with periodontitis (stage III/IV, grade B/C) with acquired clinical measurements and digital models from baseline (T0) and 12-months after non-surgical treatment of periodontitis (T1). The evaluation was performed on maxillary teeth from right to left second premolar resulting in overall 99 teeth. Clinical evaluation was performed by subtracting the distance measurements between gingival margin and cemento-enamel junction, obtained at T0 and T1 by a calibrated examiner (intra-examiner agreement >90%). The digital evaluation was performed directly by measuring the distance between the gingival margins on superimposed T0 and T1 digital models. Using Bland-Altman and statistical analysis, all six measurements sites around each included tooth (n=594) acquired with both methods were compared. RESULTS: Median ΔREC (5th and 95th percentile) acquired with a conventional clinical and digital method was 0.0mm (-2.0 - 1.0) and -0.4mm (-1.6 - 0.8), respectively (p<0.0001). The complete agreement between rounded digital and clinical ΔREC values was only 38%, revealing high disagreement also confirmed by Bland-Altman analysis with 95% limits of agreement ranging from -2.6 to 1.8mm. Absolute differences between the methods higher than 0.5 and 1 mm, was found in 61% and 38% of measurement sites, respectively. CONCLUSIONS: The conventional clinical method for ΔREC evaluation exhibits lower sensitivity and accuracy than the digital method. CLINICAL SIGNIFICANCE: The quality of both clinical and research data in periodontology and implantology can be considerably improved by the digital method while still preserving the compatibility with the conventional clinical method.

Bilateral parotid glands aplasia: a case report and literature review.

OBJECTIVES: Bilateral parotid gland aplasia is a rare congenital anomaly that almost consistently leads to xerostomia and caries. It is often associated with other congenital craniofacial abnormalities. The objective was to describe a case with asymptomatic bilateral parotid gland aplasia and to review previously reported cases. METHODS: Panoramic radiograph, computed tomography and magnetic resonance imaging were obtained and an in-depth assessment of patient's dental status and sequence analysis of FGF10, FGFR2 and FGFR3 genes were performed. Previous reports of bilateral parotid gland aplasia were assessed. RESULTS: In a 64-year-old woman with extensive basal cell carcinoma of nasal skin an incidental bilateral parotid gland aplasia was noted during radiotherapy treatment planning. Dental status revealed surprisingly numerous (n = 15) teeth without active caries lesions. No other craniofacial abnormalities were identified. To rule out most probable syndromes associated with parotid gland aplasia, sequence analysis of FGF10, FGFR2 and FGFR3 genes was performed showing no pathogenic variants. With a literature review, we identified 148 cases of salivary gland aplasia in which median age at diagnosis was 21 years and one third were asymptomatic. In only 10 of these cases, the patients presented with bilateral aplasia of parotid glands without other craniofacial abnormalities. CONCLUSIONS: Absence of salivary glands can have a debilitating effect on oral health and is often accompanied by other craniofacial abnormalities. However, relatively frequent asymptomatic course suggests that this rare malformation is probably underdiagnosed. Therefore, we propose systematic reporting of salivary gland aplasia to assess its true prevalence in general population.

An Intron c.103-3T>C Variant of the AMELX Gene Causes Combined Hypomineralized and Hypoplastic Type of Amelogenesis Imperfecta: Case Series and Review of the Literature

Amelogenesis imperfecta (AI) is a heterogeneous group of genetic disorders of dental enamel. X-linked AI results from disease-causing variants in the AMELX gene. In this paper, we characterise the genetic aetiology and enamel histology of female AI patients from two unrelated families with similar clinical and radiographic findings. All three probands were carefully selected from 40 patients with AI. In probands from both families, scanning electron microscopy confirmed hypoplastic and hypomineralised enamel. A neonatal line separated prenatally and postnatally formed enamel of distinctly different mineralisation qualities. In both families, whole exome analysis revealed the intron variant NM_182680.1: c.103-3T>C, located three nucleotides before exon 4 of the AMELX gene. In family I, an additional variant, c.2363G>A, was found in exon 5 of the FAM83H gene. This report illustrates a variant in the AMELX gene that was not previously reported to be causative for AI as well as an additional variant in the FAM83H gene with probably limited clinical significance.

Biofilm in Endodontics: In Vitro Cultivation Possibilities, Sonic-, Ultrasonic- and Laser-Assisted Removal Techniques and Evaluation of the Cleaning Efficacy.

Incomplete and inadequate removal of endodontic biofilm during root canal treatment often leads to the clinical failure. Over the past decade, biofilm eradication techniques, such as sonication of irrigant solutions, ultrasonic and laser devices have been investigated in laboratory settings. This review aimed to give an overview of endodontic biofilm cultivation methods described in papers which investigated sonic-, ultrasonic- and Er:Yag laser-assisted biofilm removal techniques. Furthermore, the effectiveness of these removal techniques was discussed, as well as methods used for the evaluation of the cleaning efficacy. In general, laser assisted agitation, as well as ultrasonic and sonic activation of the irrigants provide a more efficient biofilm removal compared to conventional irrigation conducted by syringe/needle. The choice of irrigant is an important factor for reducing the bacterial contamination inside the root canal, with water and saline being the least effective. Due to heterogeneity in methods among the reviewed studies, it is difficult to compare sonic-, ultrasonic- and Er:Yag laser-assisted techniques among each other and give recommendations for the most efficient method in biofilm removal. Future studies should standardize the methodology regarding biofilm cultivation and cleaning methods, root canals with complex morphology should be introduced in research, with the aim of simulating the clinical scenario more closely.

Fractal analysis of periapical bone from lossy compressed radiographs: a comparison of two lossy compression methods.

The aim of the study was to evaluate the effect of two lossy image compression methods on fractal dimension (FD) calculation. Ten periapical images of the posterior teeth with no restorations or previous root canal therapy were obtained using storage phosphor plates and were saved in TIF format. Then, all images were compressed with lossy JPEG and JPEG2000 compression methods at five compression levels, i.e., 90, 70, 50, 30, and 10. Compressed file sizes from all images and compression ratios were calculated. On each image, two regions of interest (ROIs) containing healthy trabecular bone in the posterior periapical area were selected. The FD of each ROI on the original and compressed images was calculated using differential box counting method. Both image compression and analysis were performed by a public domain software. Altogether, the FD of 220 ROIs was calculated. FDs were compared using ANOVA and Dunnett tests. The FD decreased gradually with compression level. A statistically significant decrease of the FD values was found for JPEG 10, JPEG2000 10, and JPEG2000 30 compression levels (p < 0.05). At comparable file sizes, the JPEG induced a smaller FD difference. In conclusion, lossy compressed images with appropriate compression level may be used for FD calculation.

A Critical Review of Methods for Quantitative Evaluation of Root Canal Transportation.

INTRODUCTION: A comparison between root canal transportation studies is nearly impossible because of nonstandardized transportation evaluation methods. The aim of the present review was to search, compare, and critically discuss transportation evaluation methods. METHODS: A search of PubMed, Web of Science, Scopus, ScienceDirect, and reference lists of articles was conducted up to March 2020 using appropriate key words to identify transportation evaluation methods. The methods in the included articles were extracted, compared, and categorized. RESULTS: Seventy-four articles using original methods were selected. All studies share 3 main steps: image acquisition, image measurements, and calculation of parameters. Images were acquired by photography, radiography, and computed tomographic imaging. Two types of measurements were used: the amount of removed material and the canal center point distance. The parameters were calculated and reported as distance or ratio. Relationships between the different transportation parameters were found and confirmed with mathematical simulation. CONCLUSIONS: Although methods were proposed as being novel, similarities between them were found, enabling the classification of the methods and identifying correlations. The canal center point distance is the most suitable for the description of canal transportation because it is comprehensible and it relates to the mathematical concept of translation. Removed material-based measurements are double the value of the canal center point distance. Ratio parameters are not suitable for reporting transportation.

Urgent dental care on a national level during the COVID-19 epidemic.

OBJECTIVE: This paper aims to report and discuss the organization and statistics of dental care during the COVID-19 epidemics on the national level in Slovenia, providing helpful information to health policy planners worldwide. MATERIAL AND METHODS: During an eight-week lockdown, Emergency Dental Centers (EDCs) were established and coordinated on the national level to treat patients' urgent dental conditions. Telemedicine was used on the first level of triage to reduce contacts between healthcare workers and patients. Weekly coordination between EDCs was supported by real-time data acquisition on the number of patient visits, prescribed medicine, the number and type of dental procedures, and the usage of personal protective equipment (PPE). RESULTS: In EDCs, 27,468 patients were serviced, on average 235 patients per day/million people. The care was provided by 4798 man days of dental health care workers. Except for the first week, treatment and triage visits showed a slight increase. The number of incisions was nearly constant, while the number of extractions increased. A nearly threefold increase was found for emergency endodontic treatments (EET). The number of antibiotic prescriptions demonstrated an increasing trend. Analgesic prescriptions showed a decreasing trend from the beginning of lockdown. CONCLUSIONS: The reorganization and centralization of dental care proved to be an efficient model in Slovenia for the provision of urgent dental care, and the management of the healthcare workforce and PPE. Data from this study may provide helpful information for planning the needs and corresponding resources for the next waves of epidemics of COVID-19.