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Purpose: This retrospective study investigated the survival rate of 174 clasp-retained removable partial dentures (CR-RPDs) made at the Department of Prosthodontics of the Regensburg University Medical Center over a 25-year period (1984 to 2009). Materials and Methods: The study analyzed the frequency of and time to the fracture of clasps, connectors, or denture bases; the occurrence of caries or periodontal lesions; the loss of abutment teeth; and the necessity of maintenance procedures such as relining or treatment of pressure areas. Results: The median follow-up time of 3 years was calculated using the inverse Kaplan-Meier method. The 5-year survival rate (time to renewal) of all CR-RPDs was 96.4%; the 10-year survival rate was 89.8%. Fractures most frequently occurred in clasps (n = 28, 16.1%) followed by major connectors (n = 9, 5.1%) and minor connectors (n = 6, 3.4%). The 5-year event-free rate for clasp fracture was 80.4%; the 10-year event-free rate was 76.9%. Caries lesions on abutment teeth were seen in 31.6% of patients, and 35.6% showed inflammation of the periodontal tissue surrounding the abutment teeth. The 5-year event-free rate for caries was 58.4%; the 10-year rate was 39.6%. A frequent complication was loss of abutment teeth (n = 15), but this complication was not age-dependent. After insertion of their prostheses, one-third of patients (n = 53, 30.5%) showed pressure areas of the mucosa. Significantly more (P < .001) pressure areas were caused by prostheses of the mandible (39.6%) than by those of the maxilla (12.5%). Conclusions: CR-RPDs showed a survival rate of approximately 90% after 10 years of oral service. The predominant complications during oral service were caries lesions, loss of abutment teeth, and fracture of clasps. [ABSTRACT FROM AUTHOR]

Purpose: The influence of resilient support of abutment teeth on the fracture resistance of all-ceramic three-unit fixed partial dentures (FPDs) was tested in this study. Materials and Methods: Three groups (n = 8) of glass-infiltrated, alumina-based, all-ceramic FPDs that were adhesively bonded to human molar teeth were investigated. In control group A, teeth that were rigidly inserted in polymethyl methacrylate (PMMA) resin were used for thermocycling and mechanical loading (TCML), as well as for fracture testing. In group B, TCML was conducted on teeth that had their roots covered with a polyether layer. After TCML, the polyether layer was removed entirely, and the teeth were rigidly fixed in PMMA for fracture testing. In group C, teeth roots remained covered with a polyether layer during TCML as well as during fracture testing. Using a resilient attachment, tooth mobility was determined in axial, buccal, and oral directions. Results: Mean tooth mobility was 76 ± 4 m in the axial direction, 278 ± 41 m in the buccal direction, and 128 ± 17 m in the oral direction. Group C showed the lowest mean fracture strength (polyether during both TCML and fracture testing) of 523 N. For group B (polyether during TCML but not during fracture testing), a fracture strength of 676 N was found, and for control group A (rigidly embedded teeth), it was 919 N. Conclusion: These results confirmed the influence of resilient attachments on the aging process and fracture strength testing of FPDs. Fracture resistance was significantly reduced when this particular interface was used in both TCML and fracture testing. Int J Prosthodont 2011;24:465-468. [ABSTRACT FROM AUTHOR]

PURPOSE: The aim of this study was to investigate the survival rates and technical failures of removable prostheses (RPs) supported by telescopic double crown (TDC)-retained abutment teeth luted with zinc-phosphate or glass-ionomer cement. MATERIALS AND METHODS: Clinical records of 577 patients (288 women, 289 men) who received 577 TDC-retained RPs supported by 1,807 abutments at the Department of Prosthodontics of the University Hospital Regensburg, Regensburg, Germany, between 1984 and 2007 were analyzed. The 577 prostheses included 200 attached to telescopic crowns with friction fit (FFs), 62 to conical crowns (CCs), and 315 to parallel-sided telescopic crowns with clearance fit (CFs). Survival probabilities were evaluated for the RPs, loss of cementation of the inner copings, secondary caries, and abutment teeth that required endodontic treatment using the Kaplan-Meier method. A Cox regression analysis determined the impact of covariates such as sex, denture location (maxilla/mandible), Eichner classification, number of abutment teeth, and the type of double crown system used. RESULTS: The 10-year survival probability was 98.8% +/- 0.09% for FFs, 92.9% +/- 0.41% for CCs, and 86.6% +/- 0.05% for CFs. During the observation period, loss of cementation was frequently observed (FFs: 32%, CCs: 53.2%, CFs: 21.3%). After 15 years, more than 75% of patients had experienced at least one 'loss of cementation' event. In this respect, zinc-oxide phosphate and glass-ionomer cements did not show any significant difference. CONCLUSION: The long-term successful outcome of the RP experience was not compromised, although numerous clinical visits were required for maintenance. The predominant maintenance procedure was the need for recementation of the inner copings. [ABSTRACT FROM AUTHOR]

Objective: To determine the fracture resistance of resin-bonded fixed partial dentures (RBFPDs) by examining the influence of framework design and abutment mobility. Method and Materials: RBFPD frameworks were made of zirconia (Cercon Base, Degudent) or a nonprecious alloy (reference; Dentitan, Elephant Dental) and veneered with ceramic (Cercon Ceram S, Degudent). The zirconia framework design varied between a 2-retainer RBFPD with 3 different levels of tooth mobility (groups 1 to 3) and a 1-retainer cantilever version with 2 different grades of tooth mobility (groups 4 and 5). To achieve different mobility (rigid, medium, movable), the roots of the teeth were covered with a polyether material of different thicknesses. All RBFPDs were adhesively luted on prepared human teeth (Panavia 21 Ex, Kuraray). The specimens were mechanically (1.2 3 106; 25 N) and thermally (6,000 3 5°C/55°C; 2 minutes per cycle) cycled and finally loaded to failure (universal testing machine 1445, Zwick) at a speed of 1 mm/min. Results: The fracture force of the reference RBFPD (541 N) was significantly higher than that of both cantilever RBFPDs (group 4 = 271 N, group 5 = 104 N) and one 2-retainer group with rigid abutments (group 3 = 150 N). With 2 movable abutments, the fracture force increased to 261 N (group 1) and with mixed movable/rigid teeth to 324 N (group 2). Zirconia RBFPDs showed improved survival with increased tooth mobility, but the framework design showed only a minor influence on loss rate and fracture resistance. Conclusions: Assuming chewing forces in anterior areas between 200 and 300 N, 1- and 2-retainer zirconia RBFPDs may be suitable as minimally invasive provisional alternatives to metal-supported RBFPDs. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The aim of this in vitro study was to examine the fracture strength of metal-free 3-unit adhesive fixed partial dentures (AFPDs) bonded to mandibular incisors. METHOD AND MATERIALS: Extracted human incisors were positioned in pairs in polymethyl methacrylate resin simulating a clinical anterior situation. Their lingual sides were prepared for adhesive retainers with surfaces and finishing lines in enamel. Eight 3-unit AFPDs were made on master casts per material system: Connect/belleGlass (Girrbach), StickNet (StickTech)/Sinfony (3M Espe), and Empress 2 (Ivoclar Vivadent). The dentures were bonded adhesively using the dual-curing system ED Primer/ Panavia F (Kuraray Europe) and aged by thermocycling (6,000 x 5 degrees C/55 degrees C H2O; 2 minutes each cycle) and mechanical loading (1.2 x 10(6) x 20 N with 1.66 Hz) in an artificial oral environment representing a wearing period of 5 years. The fracture strength was determined in a universal testing machine (UTM 1446, Zwick) at a speed of 1 mm/min, applying the load buccoincisally on the pontics. The different forms of failure were described optically. Medians (25th/75th percentiles) of the fracture results were calculated. Statistical analysis was performed using Mann-Whitney U and Kruskal-Wallis tests (P < or = .05). RESULTS: Five StickNet/Sinfony AFPDs and 7 Empress 2 restorations failed in the artificial oral environment. The remaining Empress 2 dentures showed the highest medians of fracture forces (339 [200/506] N) compared to Connect/belleGlass (257 [242/310] N) and StickNet/Sinfony (256 [204/347] N). Statistical comparisons showed no significant differences. CONCLUSION: Only Connect/belleGlass and Empress 2 showed sufficient resistance against mastication [ABSTRACT FROM AUTHOR]

The aim of this in vitro study was to determine the accuracy of digital subtraction radiography (DSR) to detect small changes in calcium mass in alveolar hone adjacent to tooth roots. In each of 4 dried porcine mandible segments, one interproximal and one buccal "defect" region was defined adjacent to a premolar root. A series of cortical and cancellous bone slices with a 50 µm-stepwise increasing thickness (0-5000 µm) were attached to the mandible segments covering the respective "defect" region. Standardized radiographs were quantitatively assessed for density changes using DSR. After dissolving each bone slice in hydrochloric acid, its calcium concentration was photometrically determined. For each bone slice, the mean calcium mass covering a single pixel of the subtraction image was calculated. The Wilcoxon signed-rank test and the Mann-Whitney U-test were used for statistical analysis (α=0.05). A strong linear correlation (r²=0.86-1.00; p≤0.001) was found between the thickness of the bone slices and their calcium mass. Cortical bone showed a 3.5 times higher mean calcium mass/pixel than cancellous bone. Furthermore, a strong linear correlation (r² = 0.63-1.00; p ≤0.001) was found between the mean calcium mass per image pixel and the radiographic density changes. Neither the bone type nor the "defect" localization had a significant influence on radiographic density changes caused by changes in calcium mass. A change in mean calcium mass per image pixel of 0.1-0.15 mg was necessary to be detected by DSR. In conclusion, this study revealed a high accuracy of DSR to detect small changes in calcium mass in alveolar cortical and cancellous bone. [ABSTRACT FROM AUTHOR]

This in vitro study evaluated the fracture strength and marginal adaptation of fiber-reinforced composite (FRC) three-unit posterior fixed partial dentures (FPD). Two groups were compared: polyethylene-fiber-reinforced composites (PFRC; Connect/belle Glass) and glass-fiber-reinforced composites (GFRC; Fiberkor/Conquest Sculpture). Sixteen FPDs were fabricated per group and cemented on abutment teeth with composite cement. The FPDs were then subjected to thermocycling and mechanical loading (TCML) before loading to failure using a universal testing machine. The fractured FPDs were examined radiologically. Marginal adaptation was examined under SEM before and after TCML. A dye-penetration test was also conducted on eight FPDs of each group that were not subjected to the fracture test. There was no statistically significant difference between the median fracture strength of PFRC and GFRC (830 N and 884 N, respectively). Radiographs of all fractured FPDs showed that the composite veneering material was sheared off from the framework, but there was no damage to the framework itself. The marginal quality of the GFRC system was slightly better than the PFRC system. The authors cautioned that although the fracture strength and marginal adaptation are satisfactory, the in vitro results may not be transferred to clinical conditions. [ABSTRACT FROM AUTHOR]

Objectives: The literature demonstrates that conventional luting of metal-based restorations using zinc phosphate cements is clinically successful over 20 years. This study compared the clinical outcomes of metal-based fixed partial dentures luted conventionally with zinc phosphate and self-adhesive resin cement. Methods: Forty-nine patients (mean age 54 ± 13 years) received 49 metal-based fixed partial dentures randomly luted using zinc phosphate (Richter & Hoffmann, Berlin, Germany) or self-adhesive resin cement (RelyX Unicem Aplicap, 3M ESPE, Germany) at the University Medical Center Regensburg. The core build-up material was highly viscous glass ionomer; the finishing line was in dentin. The study included 42 posterior, 5 anterior crowns and two onlays. Forty-seven restorations were made of precious alloys, 2 of non-precious alloys. The restorations were clinically examined every year. The clinical performance was checked for plaque (0DS5; PI, Quigley-Hein), bleeding (0DS4; PBI; Mühlemann) and attachment scores. The examination included pulp vitality and percussion tests. Statistics: Means of scores, standard deviation, cumulative survival and complication rates were calculated using life tables. Results: The mean observation time was 3.16 ± 0.6 years (min: 2.0; max: 4.5 years). During that time no restoration was lost, no recementation became necessary. One endodontic treatment was performed in the self-adhesive composite group after 2.9 years. At study end bleeding (1.44 RelyX Unicem vs. 1.25 zinc phosphate) and plaque (1.64 RelyX Unicem vs. 1.0 zinc phosphate) scores showed no statistically significant difference. Significance: The self-adhesive resin cement performed clinically as well and can be used as easily as zinc phosphate cement to retain metal-based restorations over a 38-month observation period. [ABSTRACT FROM AUTHOR]

We present an experimental X-ray photoelectron circular dichroism (PECD) study of liquid fenchone at the C 1s edge. A novel setup to enable PECD measurements on a liquid microjet [Malerz et al. , Rev. Sci. Instrum. , 2022, 93 , 015101] was used. For the C 1s line assigned to fenchone's carbonyl carbon, a non-vanishing asymmetry is found in the intensity of photoelectron spectra acquired under a fixed angle in the backward-scattering plane. This experiment paves the way towards an innovative probe of the chirality of organic/biological molecules in aqueous solution.

We present a unique experimental design that enables the measurement of photoelectron circular dichroism (PECD) from chiral molecules in aqueous solution. The effect is revealed from the intensity difference of photoelectron emission into a backward-scattering angle relative to the photon propagation direction when ionizing with circularly polarized light of different helicity. This leads to asymmetries (normalized intensity differences) that depend on the handedness of the chiral sample and exceed the ones in conventional dichroic mechanisms by orders of magnitude. The asymmetry is largest for photon energies within several electron volts above the ionization threshold. A primary aim is to explore the effect of hydration on PECD. The modular and flexible design of our experimental setup EASI (Electronic structure from Aqueous Solutions and Interfaces) also allows for detection of more common photoelectron angular distributions, requiring distinctively different detection geometries and typically using linearly polarized light. A microjet is used for liquid-sample delivery. We describe EASI's technical features and present two selected experimental results, one based on synchrotron-light measurements and the other performed in the laboratory, using monochromatized He-II α radiation. The former demonstrates the principal effectiveness of PECD detection, illustrated for prototypic gas-phase fenchone. We also discuss the first data from liquid fenchone. In the second example, we present valence photoelectron spectra from liquid water and NaI aqueous solution, here obtained from a planar-surface microjet (flatjet). This new development features a more favorable symmetry for angle-dependent photoelectron measurements.

Purpose: We recently described the validation of deep learning-based auto-segmented contour (DC) models for organs at risk (OAR) and clinical target volumes (CTV). In this study, we evaluate the performance of implemented DC models in the clinical radiotherapy (RT) planning workflow and report on user experience., Methods and Materials: DC models were implemented at two cancer centers and used to generate OAR and CTVs for all patients undergoing RT for a central nervous system (CNS), head and neck (H&N), or prostate cancer. Radiation Therapists/Dosimetrists and Radiation Oncologists completed post-contouring surveys rating the degree of edits required for DCs (1 = minimal, 5 = significant) and overall DC satisfaction (1 = poor, 5 = high). Unedited DCs were compared to the edited treatment approved contours using Dice similarity coefficient (DSC) and 95% Hausdorff distance (HD)., Results: Between September 19, 2019 and March 6, 2020, DCs were generated on approximately 551 eligible cases. 203 surveys were collected on 27 CNS, 54 H&N, and 93 prostate RT plans, resulting in an overall survey compliance rate of 32%. The majority of OAR DCs required minimal edits subjectively (mean editing score ≤ 2) and objectively (mean DSC and 95% HD was ≥ 0.90 and ≤ 2.0 mm). Mean OAR satisfaction score was 4.1 for CNS, 4.4 for H&N, and 4.6 for prostate structures. Overall CTV satisfaction score (n = 25), which encompassed the prostate, seminal vesicles, and neck lymph node volumes, was 4.1., Conclusions: Previously validated OAR DC models for CNS, H&N, and prostate RT planning required minimal subjective and objective edits and resulted in a positive user experience, although low survey compliance was a concern. CTV DC model evaluation was even more limited, but high user satisfaction suggests that they may have served as appropriate starting points for patient specific edits.

Purpose: Deep learning-based auto-segmented contour (DC) models require high quality data for their development, and previous studies have typically used prospectively produced contours, which can be resource intensive and time consuming to obtain. The aim of this study was to investigate the feasibility of using retrospective peer-reviewed radiotherapy planning contours in the training and evaluation of DC models for lung stereotactic ablative radiotherapy (SABR)., Methods: Using commercial deep learning-based auto-segmentation software, DC models for lung SABR organs at risk (OAR) and gross tumor volume (GTV) were trained using a deep convolutional neural network and a median of 105 contours per structure model obtained from 160 publicly available CT scans and 50 peer-reviewed SABR planning 4D-CT scans from center A. DCs were generated for 50 additional planning CT scans from center A and 50 from center B, and compared with the clinical contours (CC) using the Dice Similarity Coefficient (DSC) and 95% Hausdorff distance (HD)., Results: Comparing DCs to CCs, the mean DSC and 95% HD were 0.93 and 2.85mm for aorta, 0.81 and 3.32mm for esophagus, 0.95 and 5.09mm for heart, 0.98 and 2.99mm for bilateral lung, 0.52 and 7.08mm for bilateral brachial plexus, 0.82 and 4.23mm for proximal bronchial tree, 0.90 and 1.62mm for spinal cord, 0.91 and 2.27mm for trachea, and 0.71 and 5.23mm for GTV. DC to CC comparisons of center A and center B were similar for all OAR structures., Conclusions: The DCs developed with retrospective peer-reviewed treatment contours approximated CCs for the majority of OARs, including on an external dataset. DCs for structures with more variability tended to be less accurate and likely require using a larger number of training cases or novel training approaches to improve performance. Developing DC models from existing radiotherapy planning contours appears feasible and warrants further clinical workflow testing., Competing Interests: The commercial auto-segmentation software used was provided without cost through a research agreement with Limbus AI Inc. No financial support was provided for this study. JAG, JG, and CK are directors of Limbus AI Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Wong, Huang, Giambattista, Teke, Kolbeck, Giambattista and Atrchian.)

Background: Radiotherapy aggravates implant-based prosthetic rehabilitation in patients with head and neck cancer., Purpose: To evaluate the impact of radiation dose at implant and parotid gland site for prosthetic rehabilitation., Material and Methods: The retrospective study includes 121 irradiated head and neck cancer patients with 751 inserted implants. Radiation doses on implant bed and parotid gland site were recorded by 3-dimensional modulated radiation plans. Implant success was clinically and radiographically evaluated according to modified Albrektsson criteria and compared to treatment- and patient-specific data., Results: Implant overall survival after 5 years was 92.4% with an implant success rate of 74.9%. Main reasons for implant failure were marginal bone resorption (20.9%), implant not in situ or unloaded (9.6%) and peri-implantitis (7.5%). A mean radiation dose of 62.6 Gy was applied with a mean parotid dose of 35 Gy. Modulating radiation techniques went along with lower grades of xerostomia (p < 0.001). At implant site mean doses of 57.5, 42.0, and 32.3 Gy were recorded for oral, oropharyngeal, and hypopharyngeal/laryngeal carcinoma, respectively. Implant success inversely correlated to radiation dose at implant site. Strong predictors for implant failure in uni- and multivariate analysis were implant-specific dose >50 Gy (HR 7.9), parotid dose >30 Gy (HR 2.3), bone (HR 14.5) and soft tissue (HR 4.5) transplants, bad oral hygiene (HR 3.8), nonmodulated radiation treatment planning (HR 14.5), and nontelescopic prosthetics (HR 5.2)., Conclusion: Radiotherapy impedes implant success in a dose-dependent manner at implant site. Modern radiation techniques effectively reduce xerostomia favoring implant-based prosthetic rehabilitation. Implantation in bone grafts is more critical and telescopic-retained overdentures should be preferred., (© 2021 The Authors. Clinical Implant Dentistry and Related Research Published by Wiley Periodicals LLC.)

Objectives: Definition of implant success is unclear in prosthetic implant-based rehabilitation of head neck cancer patients., Materials and Methods: Fifty-two patients with 309 inserted implants were included in this prospective observational study. Implant survival (in situ and loaded) and implant success (modified Albrektsson criteria) at 2-year follow-up were evaluated under the influence of patient- and implant-specific variables., Results: Thirty-nine patients with 234 implants finished the study. Overall implant survival after 2 years was 92.3% (216/234) with an osseointegration rate of 94% (220/234). Implant success was 78.6% (184/234). Main reasons for failure were "bone resorption > 1.7mm" (n = 27, 11.5%) and "implant not in situ or not loaded" (n = 18, 7.7%). Smoking (OR 3.1, p = 0.034), bone grafts (OR 2.4, p = 0.021) and radiation dose > 60 Gy (OR 3.8, p = 0.025) revealed as significant predictors for implant failure., Conclusion: Implant survival differs significantly from implant success in head and neck cancer patients. Implant success is mainly determined by radiographic peri-implant bone resorption., Clinical Relevance: Dealing with head and neck cancer patients a higher amount of peri-implant bone resorption must be taken into account and warrants for intensified implant monitoring.