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Background The digital panoramic radiograph (orthopantomogram, OPG) is the standard radiographic technique for basic diagnostics in dental practice. A correctly taken image provides a good overview of teeth and jaw, whereas radiopaque foreign materials, e. g. metal, can obscure relevant findings. Methods A literature review on unexpected metallic foreign bodies in OPG was performed to determine the spectrum of metallic foreign bodies that may cause radiopaque areas on panoramic radiographs in routine clinical use. Results and Conclusion A total of 37 different unexpected metallic foreign bodies were found. They can be categorized as jewelry, clothing, personal protective equipment, medical devices, iatrogenic foreign bodies, and rare incidental findings. Radiopaque foreign materials in the OPG are often relatively easy to recognize as artifacts because of their location, and they are avoidable in most cases. If unclear, a three-dimensional radiograph was helpful for determining the location. Radiopaque areas caused by foreign bodies can lead to misinterpretation or partial or complete non-evaluability and should therefore be avoided. Key Points: Citation Format

The journal of evidence based dental practice 23(1S), 101794 (2023). doi:10.1016/j.jebdp.2022.101794 special issue: "Dental patient-reported outcomes 2022 Dental PROs / Edited by Fang Hua", Published by Elsevier, Amsterdam [u.a.]

Objectives This feasibility study aimed to investigate the reliability of multi-factorial age estimation based on MR data of the hand, wisdom teeth and the clavicles with reduced acquisition time. Methods The raw MR data of 34 volunteers—acquired on a 3T system and using acquisition times (TA) of 3:46 min (hand), 5:29 min (clavicles) and 10:46 min (teeth)—were retrospectively undersampled applying the commercially available CAIPIRINHA technique. Automatic and radiological age estimation methods were applied to the original image data as well as undersampled data to investigate the reliability of age estimates with decreasing acquisition time. Reliability was investigated determining standard deviation (SSD) and mean (MSD) of signed differences, intra-class correlation (ICC) and by performing Bland-Altman analysis. Results Automatic age estimation generally showed very high reliability (SSD TA of 4 min). Radiological age estimation provided highly reliable results for images of the hand (ICC ≥ 0.96) and the teeth (ICC ≥ 0.79) for short acquisition times (TA = 16 s for the hand, TA = 2:21 min for the teeth), imaging data of the clavicles allowed for moderate acceleration (TA = 1:25 min, ICC ≥ 0.71). Conclusions The results demonstrate that reliable multi-factorial age estimation based on MRI of the hand, wisdom teeth and the clavicles can be performed using images acquired with a total acquisition time of 4 min.

Objectives To compare oral health-related quality of life (OHRQoL) in patients with either molar replacement by partial removable dental prostheses (PRDP) or with restored shortened dental arches (SDA) over a period of 10 years. Methods In this multi-center RCT, a consecutive sample of 215 patients with bilateral molar loss in at least one jaw was initially recruited in 14 prosthodontic departments. Of those patients, 150 could be randomly allocated to the treatment groups (SDA: n = 71; PRDP: n = 79), received the allocated treatment, and were available for follow-up assessments. OHRQoL was assessed using the 49-item version of the Oral Health Impact Profile (OHIP) before treatment (baseline) and at follow-ups after treatment (4–8 weeks and 6, 12, 24, 36, 48, 60, 96, and 120 months). To investigate the course of OHRQoL over time, we longitudinally modelled treatment and time effects using mixed-effects models. Results OHRQoL substantially improved from baseline to first follow-up in both groups indicated by a mean decrease in OHIP scores of 20.0 points (95%-CI: 12.5–27.5). When compared to the SDA group, OHRQoL in the PRDP group was not significantly different (−0.6 OHIP points; 95%-CI: −7.1 to 5.9) during the study period when assuming a constant time effect. OHRQoL remained stable over the 10 years with a statistically insignificant time effect (p = 0.848). Conclusions For patients requesting prosthodontic treatment for their lost molars, treatments with SDA or PRDP improve clinically relevantly OHRQoL and maintain it over a period of 10 years with no option being superior to the other. Clinical significance Since there was no significant difference between the two treatment options over the observation period of 10 years, and since results have stayed stable over time, patients can be informed that both treatment concepts are equivalent concerning OHRQoL.

Background A shortened dental arch (SDA) is an established treatment concept for patients with missing molars. However, little is known regarding long-term course of oral health-related quality of life (OHRQoL) in patients with SDA and the benefits from replacement of missing molars. Aim Purpose of this multi-center randomized clinical trial was to assess OHRQoL over a period of 15 years in patients with molar replacement by a removable partial denture (RPD) compared to patients with a restored SDA without molar replacement. Design Patients at least 35 years of age with all molars missing in one jaw and at least the canine and one premolar present on each side were included. Patients received either a precision attachment-retained, RPD for replacement of missing molars (N=79), or the dental arch ended with the second premolar (SDA) that had to be present or replaced by a cantilever fixed dental prosthesis (N=71). Follow-up examinations continued for 15 years. OHRQoL was assessed with the 49-item Oral Health Impact Profile (OHIP). OHIP summary and dimension scores were longitudinally modeled in the statistical analyses to assess course of OHRQoL over time applying an intention-to-treat approach. In addition, scores for the OHRQoL dimensions Oral Function, Orofacial Pain, Orofacial Appearance, and Psychosocial Impact were analyzed. Results After an initial improvement in OHRQoL indicated by a mean decrease of 20.0 OHIP points with an effect size of 0.61 in the entire study population, OHRQoL stayed relatively constant over the entire follow-up period. Assuming a constant time and treatment effects over the study period, OHRQoL did not differ statistically significant between the two treatments (0.4 OHIP points; 95%-CI: −7.1 to 6.2). OHRQoL after treatment did not change notably over 15 years and was statistically nonsignificant as well (p=0.872). Similar findings were observed in all four OHRQoL dimensions. Conclusions In patients, missing all molars in one jaw OHRQoL improved providing RPD or restoring SDA to a clinically relevant degree. Treatment-related improvement remained mostly stable over a period of at least 15 years. Therefore, patients can be informed that both treatment concepts are equivalent concerning long-term OHRQoL. Accordingly, patients’ preferences regarding treatment options should be granted priority in treatment decision making with the SDA treatment option being the default.

Journal of oral rehabilitation 48(6), 738-744 (2021). doi:10.1111/joor.13167, Published by Wiley-Blackwell, Oxford [u.a.]

Journal of prosthodontic research 64(4), 498-505 (2020). doi:10.1016/j.jpor.2020.01.005, Published by Elsevier, Amsterdam [u.a.]

The aim of this investigation was to create an automated cephalometric X‑ray analysis using a specialized artificial intelligence (AI) algorithm. We compared the accuracy of this analysis to the current gold standard (analyses performed by human experts) to evaluate precision and clinical application of such an approach in orthodontic routine. For training of the network, 12 experienced examiners identified 18 landmarks on a total of 1792 cephalometric X‑rays. To evaluate quality of the predictions of the AI, both AI and each examiner analyzed 12 commonly used orthodontic parameters on a basis of 50 cephalometric X‑rays that were not part of the training data for the AI. Median values of the 12 examiners for each parameter were defined as humans’ gold standard and compared to the AI’s predictions. There were almost no statistically significant differences between humans’ gold standard and the AI’s predictions. Differences between the two analyses do not seem to be clinically relevant. We created an AI algorithm able to analyze unknown cephalometric X‑rays at almost the same quality level as experienced human examiners (current gold standard). This study is one of the first to successfully enable implementation of AI into dentistry, in particular orthodontics, satisfying medical requirements.

Forensic age estimation has recently become an important topic due to a steady increase of cross border migration. Dental age assessment is one pillar of the forensic age estimation in living persons. Currently it is done by evaluating an orthopantomogram, which is generated using ionizing radiation. Nevertheless, the use of X-ray without medical indication is ethically questionable. Therefore, the aim of the study was to provide reference values for dental MRI to have an alternative radiation-free method for the assessment of dental age. In this cross-sectional study, 316 adolescent, male individuals were investigated. Two dentists evaluated the stage of mineralization and eruption of the third molars of the upper and lower jaws, according to the staging systems established by Demirjian and Olze. Following data analysis and the creation of reference tables, the likelihood ratios to be over specific age limits were calculated. In the mineralization evaluation mainly stages D-H were seen (range A-H); regarding eruption, all four stages (A-D) appeared. A significant difference between the teeth was only found for eruption stage A. However, the evaluation of participants who had all four third molars, showed partly different stages for the individual teeth as well for mineralization as for the eruption. Therefore, it seems to be important to include all available teeth in the age estimation. The likelihood ratios showed about 99% probability to be 18 years or older for stage H (mineralization), but only about 93% for stage D (eruption). In summary, it can be concluded that dental MRI holds promise as an alternative to conventional orthopantomogram based age assessment.

The need for forensic age estimations in living adolescents is high mainly due to migration, particularly from countries where birth dates are not reliably documented. To date, the gold standard of dental age estimation is the evaluation of the mineralization and eruption stages of the third molars using an orthopantomogram (OPG). However, the use of ionizing radiation without medical indication is ethically controversial and not permitted in many countries. Thus, the aim of this study was to investigate if dental MRI can be used for the assessment of dental age with equally good results as when using an OPG. 27 healthy volunteers (19 ♀, 8 ♂, age range 13.6-23.1 years, median 18.9 years) underwent an MRI scan of the jaw after a clinically indicated OPG. Mineralization and eruption stages of the molars were independently analyzed on OPGs and MRI by two blinded dentists according to the staging system established by Demirjian and Olze, respectively. The results of OPG and MRI were compared and inter-rater agreement was determined. The developmental stages of the 262 evaluated molars could be clearly differentiated in MRI. For both, mineralization and eruption, there was a good correlation between MRI and OPG. Overall MRI tended to yield slightly lower stages than the OPG. Inter-rater agreement was moderate for mineralization and good regarding eruption. Although a validation of these results using modality-specific reference values is needed, dental MRI seems to be suitable for a use in dental age estimation.

In vivo measurement of the mobility of teeth under physiological loading has been subject of research for years. Comparing the deflection under load of dental implants with teeth provides valuable input for designing restorations spanning both teeth and implants. Physiological force rise time of about 50-100 ms and displacement of 10-100 μm requires high spatial and temporal resolution of the measurement set-up. Using an optical system attached to the teeth/implants to be measured and a light source attached to a point of reference, displacement of teeth and implants under axial and lateral loading was measured on a series of volunteers. Axial displacement of teeth shows strong time dependence consistent with (hydraulic) damping not observed for lateral loads. Displacement under lateral loading was found to be about one order of magnitude higher than under axial load. For dental implants elastic deflection was observed in axial and lateral direction without measurable influence of the load rise time. For purely axial loading, dental implants and teeth show similar deflection under physiological force rise time but for lateral loading the considerably difference between teeth and implant may put some restrictions on the construction of tooth-implant-bridges, especially for teeth in the anterior region.

The MRI-based contrast-enhanced method of tooth surface digitization provides an alternative possibility for making a dental impression. It has recently been demonstrated that tooth surface digitization with an accuracy sufficient for production of dental restorations is possible using a clinical whole-body MRI scanner. However, for an in vivo application of the technique, the required high nominal resolution and signal-to- noise ratio have to be achieved within reasonable measurement times. Existing radio fre- quency (RF) volume and surface coils have not been able to fulfill this requirement. The objective of this work was to develop a dedicated RF receiver coil for contrast-enhanced dental MRI which provides a high sensitivity in the region of the whole dental arch and allows for application of the contrast media into the mouth of the patient. To achieve this goal, an intraoral dental coil design with a built-in contrast medium applicator was devel- oped and implemented. The coil was shown to enable high-resolution contrast-enhanced dental MRI in vivo. This was demonstrated on four teeth prepared for dental restorations. The average accuracy obtained for all four teeth was below 100 lm. For two of the teeth, copings were modeled based on MRI data and produced from zirconium oxide using computer-aided design and manufacturing (CAD/CAM) technology. 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part B (Magn Reson Engineering) 33B: 244-251, 2008

The precision of localizing the mandibular canal prior to surgical intervention depends on the achievable resolution, whereas identification of the nerve depends on the image contrast. In our study, we developed new protocols based on gradient and spin echo sequences. The results from both sequences were quantitatively compared for their agreement to identify the most suitable approach.By limiting the field of view to one side of the mandible, three-dimensional acquisitions with TThe quantitative comparison of the segmentation resulted in an average surface distance of 0.26 ± 0.05 mm between both sequences and an interobserver difference of 0.26 ± 0.08 mm for gradient and 0.29 ± 0.07 mm for spin echo data. By repeated evaluation, a difference of 0.15 ± 0.02 mm for gradient and 0.18 ± 0.03 mm for spin echo data was observed, indicating a slightly higher variability for spin echo images.Both sequences can be used to achieve high-resolution images with good contrast and can be used for precise localization of the mandibular canal. Despite a slightly increased difference for the spin echo data, the advantage of an easy and robust setup remains.

The purpose of this study was to investigate the achievable precision of localization of boundaries between extended uniform objects in MRI and to study the effect of zero-filling on reaching it.A theoretical model of an object boundary in the presence of noise was introduced, and the error of localization was derived. The effect of zero-filling on reaching the achievable precision was assessed by computer simulations and experimentally on an extracted tooth in a signal-giving medium.With the help of the theoretical model, the achievable precision of localization of boundaries between two uniform extended objects was shown to surpass the nominal resolution by a factor equal to the contrast-to-noise ratio. In the simulations and phantom experiments, zero-filling followed by image segmentation allowed for approaching the theoretical value. As an application example, an MRI-based dental impression was performed in vivo, and a bridge was produced and permanently fixed to the volunteer's teeth.This work demonstrates that in an MRI experiment, the achievable precision of localization of object boundaries is not limited to the nominal resolution and can surpass it by an order of magnitude. Zero-filling is a simple and effective method of reaching it.

The purpose of the study was to assess the feasibility of MRI of three-dimensional visualization and quantification of carious lesions, as well as measurement of the distance between the lesion and dental pulp in vivo.High-resolution 3D MRI was performed to measure seven carious lesions in vivo using gelatinous gadolinium-based oral contrast medium in combination with an intraoral radio frequency receiver coil on a clinical 1.5 T MRI scanner. Extension of the carious lesion in three spatial dimensions and the minimum distance between the lesion and dental pulp were quantified. When possible, the result was compared to an X-ray projection and an impression of the lesion taken using a plastic impression material before and after dental treatment.Carious lesions, including pit and fissure, approximal lesions, and occult dentin caries, could be visualized due to the MRI signal rise in the porous affected dentin. The minimum distance between the carious lesion and dental pulp could be determined in all cases.The results presented demonstrate the feasibility of high-resolution dental MRI to three-dimensionally visualize and quantify carious lesions, including approximal and occult caries lesions, and measure the minimum distance to the dental pulp.

Recent development of applications of magnetic resonance imaging (MRI) in dentistry demonstrate the potential of the technique in orthodontics and orofacial surgery, as well as in prosthodontics where a digital dental impression is acquired using oral contrast medium. The obtained negative impression of the tooth surface can be directly used for production of dental restorations by means of CAD/CAM technology. This paper deals with a further application of MRI in dentistry and investigates the potential of MRI in caries diagnosis.

Human teeth with substantial coronal defects are subject to reconstruction by means of post-and-core restorations. Typically, such a restoration comprises a slightly cylindrical post onto which an abutment of varying shape, depending on the designated restoration, is attached. As clinical results are not satisfactory to date, a new post-and-core design which makes use of positive locking (rather than relying on chemical bonding agents for retention in the residual root) was proposed. Using proprietary burs, an inversely conical hole is machined into the root, into which the prefabricated post-and-core restoration is inserted. This part can be spread at the bottom to match the cavity's undercut form, resulting in a positive lock which can only be separated by destruction of root, restoration or both. Another key feature of this system is a ring/groove geometry which is able to absorb the wedging forces created by said spreading and the stress of loading of the restoration which arises from mascatory forces. To assess the properties, especially in terms of the stress imposed on the remaining tooth at highest possible loading, both finite element simulations and in vitro failure tests were performed and the findings compared. The results suggest that the parameters of the finite element simulations are in good agreement with reality. As calculated and measured force levels immediately before failure of the restoration are high, the introduced new geometry has significant advantages over the classical restoration.

To assess the usefulness of different post and core materials and systems, in vitro testing of fracture strength and fatigue resistance is a useful tool. However, the literature does not present coherent results as to which system can withstand the highest loads. With a geometrical model, the effects of load angulation and contact point location on the generated forces were calculated. To validate the mathematical model, a set of measurements was performed with a set-up that made it possible to measure the critical forces on a post and core restoration. A high level of correlation between the predictions of the model and the measurements was found. It was shown that the resulting forces are strongly dependent on the precise design of the test set-up and results from different geometries cannot be compared directly. Very strong sensitivity to small misalignment was found, all of which serves to explain the large differences in the literature.

The design of a post and core restoration is a trade-off between a series of requirements to achieve stability of the post itself, the surrounding root dentine and the joint between tooth and post, while maintaining a sufficient apical seal of the remaining root canal filling. Post and core restoration systems come in a variety of different designs and dimensions, where each has its specific strength and weakness. With the exception of threaded versions, posts normally rely on either chemical and/or frictional locking between the post and the remaining root. Failure due to fatigue of the joint or root fracture due to overloading of the dentine is a frequent failure mode, especially for posts anchoring removable prostheses. Perforation of the root in an attempt to maximize the post length is a main cause for failure, too. A new design is proposed which uses a short but large diameter post. The risk of decementation is reduced by positive locking. A cavity with an undercut is prepared into the root, into which the post is fitted. Once joined, the post cannot be separated from the tooth without destruction of either the root or the post. The principle of the new design uses preparation tools and a post which is spread at the bottom. A cylindrically prepared hole is re-shaped to a defined inverse taper with the wider diameter at the bottom of the hole. A cylindrical post is inserted and spread at the bottom to a matching shape after placement. A first in vitro test of the stability showed that the positive locking provides at least as good extraction resistance as conventional post without the critical reliance on the luting/bonding agent.

Human teeth with substantial coronal defects are subject to reconstruction by means of post and core restorations. Typically, such a restoration comprises a slightly cylindrical post onto which an abutment of varying shape, depending on the designated restoration, is attached. As clinical results are not satisfactory to date, we proposed a new proprietary post and core design which makes use of positive locking. As this prefabricated system is not customised to an individual root's cross-sectional geometry (usually oval), a varying amount of radicular dentin is left in periphery of the core's outer edge. The aim of this study was to assess the implications of this fact, i.e., whether the root has to endure higher overall stress levels which ultimately may lead to failure of one of the components involved. A series of finite element simulations were performed to evaluate stress and strain on the system, in which the proposed post and core was embedded into a virtual dentin cylinder of different diameters, ranging from flush mounting of the restoration to a dentin excess of 4 mm, and subsequently loaded with forces with two angles of attack (90 degrees and 130 degrees ). The results show that flush mounting yields an agreeable stress and strain distribution within the radicular dentin, but overall stress levels drop significantly with an excess of 0.5 mm of surrounding dentin. More than 1 mm excess was not found to have profound positive effects.

Objectives: The objective of this study was to examine the kinematics of structures of the temporomandibular joint (TMJ) under physiological load while masticating. Methods: Radial MRI was chosen as a fast imaging method to dynamically capture the motions of the joint’s anatomy. The technique included a golden ratio-based increment angle and a sliding window reconstruction. The measurements were performed on 22 subjects with and without deformation/displacement of the intra-articular disc while they were biting on a cooled caramel toffee. Results: The reconstructed dynamic images provided sufficient information about the size and localization of the disc as well as the change of the intra-articular distance with and without loading. Conclusions: The feasibility of the golden ratio-based radial MRI technique to dynamically capture the anatomy of the TMJ under physical load was demonstrated in this initial study.

To investigate the potential influence of standard dental materials on dental MRI (dMRI) by estimating the magnetic susceptibility with the help of the MRI-based geometric distortion method and to classify the materials from the standpoint of dMRI.A series of standard dental materials was studied on a 1.5 T MRI system using spin echo and gradient echo pulse sequences and their magnetic susceptibility was estimated using the geometric method. Measurements on samples of dental materials were supported by in vivo examples obtained in dedicated dMRI procedures.The tested materials showed a range of distortion degrees. The following materials were classified as fully compatible materials that can be present even in the tooth of interest: the resin-based sealer AH Plus(®) (Dentsply, Maillefer, Germany), glass ionomer cement, gutta-percha, zirconium dioxide and composites from one of the tested manufacturers. Interestingly, composites provided by the other manufacturer caused relatively strong distortions and were therefore classified as compatible I, along with amalgam, gold alloy, gold-ceramic crowns, titanium alloy and NiTi orthodontic wires. Materials, the magnetic susceptibility of which differed from that of water by more than 200 ppm, were classified as non-compatible materials that should not be present in the patient's mouth for any dMRI applications. They included stainless steel orthodontic appliances and CoCr.A classification of the materials that complies with the standard grouping of materials according to their magnetic susceptibility was proposed and adopted for the purposes of dMRI. The proposed classification can serve as a guideline in future dMRI research.