An Integrated Framework for Data Quality Fusion in Embedded Sensor Systems.

The advancement of embedded sensor systems allowed the monitoring of complex processes based on connected devices. As more and more data are produced by these sensor systems, and as the data are used in increasingly vital areas of applications, it is of growing importance to also track the data quality of these systems. We propose a framework to fuse sensor data streams and associated data quality attributes into a single meaningful and interpretable value that represents the current underlying data quality. Based on the definition of data quality attributes and metrics to determine real-valued figures representing the quality of the attributes, the fusion algorithms are engineered. Methods based on maximum likelihood estimation (MLE) and fuzzy logic are used to perform data quality fusion by utilizing domain knowledge and sensor measurements. Two data sets are used to verify the proposed fusion framework. First, the methods are applied to a proprietary data set targeting sample rate inaccuracies of a micro-electro-mechanical system (MEMS) accelerometer and second, to the publicly available Intel Lab Data set. The algorithms are verified against their expected behavior based on data exploration and correlation analysis. We prove that both fusion approaches are capable of detecting data quality issues and providing an interpretable data quality indicator.

[Phacovitrectomy-Influence of the timing of intraocular lens implantation on the corneal endothelium]. / Phakovitrektomie ­ Einfluss des Zeitpunktes der Kunstlinsenimplantation auf das korneale Endothel.

BACKGROUND AND PURPOSE: In phacovitrectomy the cataract is usually operated on first including implantation of the intraocular lens (IOL) before beginning vitrectomy but the IOL can also be implanted following vitrectomy. This variation avoids optical impairments from corneal opacities and the lens rim, improves the visualization of the retina during surgery and might thereby reduce intraoperative complications, such as peripheral retinal tears or IOL subluxation. It might, however, increase stress on the corneal endothelium. The aim of this study was, therefore, to compare postoperative corneal endothelial cell loss for the standard procedure of phacovitrectomy and the surgical variation. METHODS: In this retrospective study 41 eyes were each assigned to group I (standard phacovitrectomy) or group II (variation of phacovitrectomy). The primary endpoint was the absolute and relative corneal endothelial cell loss appearing 5 ± 1 weeks postoperatively with reference to the preoperative number of endothelial cells. Secondary endpoints included visual acuity, intraocular pressure, coefficient of variation of endothelial cell area (CV), proportion of hexagonal endothelial cell forms (6A), pachymetry, intraoperative and postoperative complications. RESULTS: The absolute and relative endothelial cell loss in group I (-108 ± 146; -4.1 ± 5.7%) did not differ significantly from that in group II (-73 ± 122; -3.1 ± 5.3%, p = 0.299; p = 0.388). The secondary endpoints also showed no significant differences. CONCLUSION: The presented variation of phacovitrectomy expands the surgical options and does not show a significantly different postoperative corneal endothelial cell loss compared to the standard procedure.

A Smart Capacitive Sensor Skin with Embedded Data Quality Indication for Enhanced Safety in Human-Robot Interaction.

Smart sensors are an integral part of the Fourth Industrial Revolution and are widely used to add safety measures to human-robot interaction applications. With the advancement of machine learning methods in resource-constrained environments, smart sensor systems have become increasingly powerful. As more data-driven approaches are deployed on the sensors, it is of growing importance to monitor data quality at all times of system operation. We introduce a smart capacitive sensor system with an embedded data quality monitoring algorithm to enhance the safety of human-robot interaction scenarios. The smart capacitive skin sensor is capable of detecting the distance and angle of objects nearby by utilizing consumer-grade sensor electronics. To further acknowledge the safety aspect of the sensor, a dedicated layer to monitor data quality in real-time is added to the embedded software of the sensor. Two learning algorithms are used to implement the sensor functionality: (1) a fully connected neural network to infer the position and angle of objects nearby and (2) a one-class SVM to account for the data quality assessment based on out-of-distribution detection. We show that the sensor performs well under normal operating conditions within a range of 200 mm and also detects abnormal operating conditions in terms of poor data quality successfully. A mean absolute distance error of 11.6mm was achieved without data quality indication. The overall performance of the sensor system could be further improved to 7.5mm by monitoring the data quality, adding an additional layer of safety for human-robot interaction.

23G pars plana vitrectomy for vitreal floaters: prospective assessment of subjective self-reported visual impairment and surgery-related risks during the course of treatment.

PURPOSE: Quantifying the subjective impairment due to floaters based on an indication-specific questionnaire and setting its change between prior to and 3/12 months after elective vitrectomy in relation to surgical risks. METHODS: Single-arm longitudinal observational multicenter study. Sixty-four floater patients underwent 23G pars plana vitrectomy; simultaneous phacoemulsification was excluded. An overall self-rated impairment index (SRI) and sub-indices SRI were calculated on the basis of a modified Visual Quality of Life questionnaire (VQoL), which addresses general vision, glare, near-sight problems and mobility of floaters. SRI ranged from 0 to 100% (maximum impairment). Secondary endpoints included corrected visual acuity and complications. RESULTS: Data were collected prior to and 3 (n = 64) and 12 (n = 62) months after surgery. The median overall SRI improved (44, 12, 11%) with a statistically significant median reduction of 69% (95% confidence interval 50-89%) 3 months postop. The median sub-SRIs improved for glare (50, 17, 17%), near sight problems (50, 17, 8%), and mobility of floaters (43, 5, 0%). Sixteen eyes needed cataract surgery during follow-up (10 showed cataract already prior to vitrectomy). Eight complications were reported (6 intra-operative retinal holes, 2 post-operative retinal detachments). CONCLUSION: For the majority of floater patients, subjective impairment was profoundly reduced by vitrectomy. Benefits of surgery prevailed despite complications.

Retention of bonded titanium copings fixed to implant abutments.

STATEMENT OF PROBLEM: Conical abutments can be laser welded to the abutment base to compensate for differing implant axes. As laser welding requires expensive equipment, alternative methods for bonding the conical abutment part with the abutment base should be considered. PURPOSE: The purpose of this in vitro study was to evaluate the retention of Ti-6Al-7Nb copings bonded adhesively to Ti-6Al-7Nb abutments and to compare it with the stability achieved by laser welding. MATERIAL AND METHODS: A total of 104 two-part Ti-6Al-7Nb specimens were prepared and divided into 13 groups with 8 specimens each. In this 2-part study, 3 luting resins (Panavia F 2.0 [PF]; Multilink Automix [MA]; Superbond C&B [SB]) were used with or without metal priming (PR). The laser welding group (LW) served as the control. After storage for 1 or 150 days (150 days with thermal cycling [TC]), push-out retention and welded joint stability were tested. The data were analyzed with ANOVA and the Tukey HSD multiple comparison tests. RESULTS: The choice of resin, thermal cycling, and metal priming had a significant effect on resin push-out retention. LW provided the strongest retention, followed by PF, MA, and SB. For PF and SB, TC decreased retention. PR did not lead to higher retention but provided better bonding stability when TC was applied. CONCLUSIONS: The retention values suggest that considering the maximum mastication forces, resin bonding is an appropriate substitute for the laser welding method.

Wear, microleakage and plastic deformation of an implant-supported chair-side bar system.

PURPOSE: This in-vitro study was designed to evaluate retention forces, microleakage and plastic deformation of a prefabricated 2-implant bar attachment system (SFI-Bar, Cendres+Métaux, Switzerland). MATERIALS AND METHODS: Two SFI implant-adapters were torqued with 35 Ncm into two implant analogues. Before the tube bars were finally sealed, the inner cavity of the tube bar was filled with liquid red dye to evaluate microleakage. As tube bar sealing agents three different materials were used (AGC Cem (AGC, resin based), Cervitec Plus (CP; varnish) and Gapseal (GS; silicone based). Four groups with eight specimens each were tested (GS, GS+AGC, AGC, CP). For cyclic loading, the attachment system was assembled parallel to the female counterparts in a chewing simulator. The mean retention forces of the initial and final ten cycles were statistically evaluated (ANOVA, α≤.05). RESULTS: All groups showed a significant loss of retention forces. Their means differed between 30-39 N initially and 22-28 N after 50,000 loading cycles. No significant statistical differences could be found between the groups at the beginning (P=.224), at the end (P=.257) or between the loss of retention forces (P=.288). Microleakage occurred initially only in some groups but after 10,000 loading cycles all groups exhibited microleakage. CONCLUSION: Long-term retention forces of the SFI-Bar remained above 20 N which can be considered clinically sufficient. The sealing agents in this study are not suitable to prevent microleakage.

Effect of clasp design on retention at different intervals using different abutment materials and in a simulated oral condition.

PURPOSE: The purpose of this study was to compare the retention of circlet (E) clasps and back-action clasps against three abutment surface materials during long-term simulation of attachment and detachment. MATERIAL AND METHODS: Forty-eight test models were constructed by placing premolars (natural abutments or metal dies) inside metal blocks to test different abutment retention surface materials (sound enamel, composite resin, and glass-ceramic; 16 each). The models were duplicated into investment models for construction of circlet (E) and back-action clasps. Removal and insertion cycling of clasps was carried out for 250, 500, 1000, 2000, 4000, 8000, and 16,000 cycles. The retention of each clasp was measured before cycling and after each interval. Data were analyzed using 1-way-ANOVA, 2-way-ANOVA, and Mann-Whitney U tests. RESULTS: No significant differences in retention of either clasp were found between the three abutment material surfaces; however, there was a significant decrease in retention force of the circlet (E) clasp between 1000 and 2000 cycles but not of the back-action clasp. CONCLUSIONS: (1) The back-action clasp maintains its retention force for a longer period than the circlet (E) clasp. (2) Composite resin contouring of teeth provided retention comparable to enamel and a ceramic material.

Linear and volumetric dimensional changes of injection-molded PMMA denture base resins.

OBJECTIVES: The aim of this study was to evaluate the linear and volumetric dimensional changes of six denture base resins processed by their corresponding injection-molding systems at 3 time intervals of water storage. MATERIALS AND METHODS: Two heat-curing (SR Ivocap Hi Impact and Lucitone 199) and four auto-curing (IvoBase Hybrid, IvoBase Hi Impact, PalaXpress, and Futura Gen) acrylic resins were used with their specific injection-molding technique to fabricate 6 specimens of each material. Linear and volumetric dimensional changes were determined by means of a digital caliper and an electronic hydrostatic balance, respectively, after water storage of 1, 30, or 90 days. Means and standard deviations of linear and volumetric dimensional changes were calculated in percentage (%). Statistical analysis was done using Student's and Welch's t tests with Bonferroni-Holm correction for multiple comparisons (α=0.05). RESULTS: Statistically significant differences in linear dimensional changes between resins were demonstrated at all three time intervals of water immersion (p≤0.05), with exception of the following comparisons which showed no significant difference: IvoBase Hi Impact/SR Ivocap Hi Impact and PalaXpress/Lucitone 199 after 1 day, Futura Gen/PalaXpress and PalaXpress/Lucitone 199 after 30 days, and IvoBase Hybrid/IvoBase Hi Impact after 90 days. Also, statistically significant differences in volumetric dimensional changes between resins were found at all three time intervals of water immersion (p≤0.05), with exception of the comparison between PalaXpress and Futura Gen. SIGNIFICANCE: Denture base resins (IvoBase Hybrid and IvoBase Hi Impact) processed by the new injection-molding system (IvoBase), revealed superior dimensional precision.

Effects of long-term simulated RPD clasp attachment/detachment on retention loss and wear for two clasp types and three abutment material surfaces.

PURPOSE: The purpose of this in vitro study was to measure the loss of retention and wear of two clasp types (E-circlet, back action) against three abutment materials (enamel, composite, CAD/CAM ceramic) after 16,000 simulated cycles of attachment-detachment. MATERIALS AND METHODS: Forty-eight models were constructed by placing either an upper first premolar or a metal die inside a metal rectangular block. Models were divided according to the abutment teeth into three groups. Group E consisted of 16 unrestored human premolars with sound enamel. Group R had 16 premolars recontoured buccally using composite resin. Group C had 16 metal dies (duplicated from a human premolar) covered by CAD/CAM all-ceramic crowns. On the models, E-circlet (E) and back-action (B) clasps were constructed to engage the model's teeth. Withdrawal and insertion cycling of clasps was carried out for 16,000 cycles by using a chewing simulator. The retention force of each clasp was measured after cycling. An acrylic replica was made for each abutment retention surface before and after cycling. Each replica was examined by SEM, and the wear areas were measured. The data were analyzed statistically using one-way ANOVA, two-way ANOVA, and Mann-Whitney tests. RESULTS: There was no significant retention loss after 16,000 cycles (p≥ 0.05) of both clasps (E, B) on the three abutment materials (E, R, C). The mean of wear areas in mm(2) were 1.83 ± 0.36, 0.85 ± 0.66, 2.37 ± 1.88, 1.7 ± 1.11, 0.6 ± 0.2, and 0.06 ± 0 for EE, BE, ER, BR, EC, and BC, respectively. There were significant differences among the wear areas of the abutment surface of the six subgroups (p≤ 0.05). CONCLUSION: The composite resin contoured surfaces showed more wear than the enamel and ceramic surfaces. E-clasps caused more wear on the abutment materials than back-action clasps.

The influence of a hyperbaric environment and increased oxygen partial pressure on the corrosion of dental alloys.

OBJECTIVES: The purpose of this in-vitro study was to determine whether there is a correlation between a hyperbaric environment or increased oxygen partial pressure and the corrosion of dental alloys used for dental restorations in divers. METHOD AND MATERIALS: Samples of three commercially available dental alloys (palladium-based, reduced-gold-content and high-gold-content) were tested in the DIN EN ISO 1562 static immersion test and the amount of dissolved ions measured by atomic absorption spectrometry. The specimens were exposed to one of the following three conditions: normobaric and normoxic conditions (PO2 21 kPa); 608 kPa (6 bar, PO2 127 kPa) pressurised air in a pressure chamber or 506 kPa (5 bar, PO2 304 kPa) pressurised nitrox in a pressure chamber. RESULTS: None of the exposures suggested a correlation between increased ion solubility as a measure of corrosion and increased ambient pressure of the three alloys. The reduced-gold-content alloy released zinc ions at twice the weekly recommended dose. When the palladium-based alloy was exposed to a hyperbaric or hyperbaric/hyperoxic environment, ion solubility increased only slightly for gallium and silver. CONCLUSIONS: Within the limited sample size of the current study it can be concluded that hyperbaric and/or hyperoxic conditions do not seem to be a risk for increased corrosion for any of the three tested alloys.

Fracture strength of prefabricated all-ceramic posterior inlay-retained fixed dental prostheses.

OBJECTIVES: The purpose of this in vitro study was to compare the centric and eccentric quasi-static and fatigue fracture strength of industrially prefabricated resin-bonded three-unit inlay-retained fixed dental prostheses (IPIRFDPs). The IPIRFDPs consisted of industrial manufactured yttria-stabilized tetragonal zirconia (Y-TZP) frameworks with an industrially added microhybrid composite veneering. METHODS: Identical IPIRFDP-models consisted of a second premolar, a missing first molar and a second molar (CoCrMo alloy) integrated in a low melting alloy base. Roots were covered with a soft silicone layer to simulate an artificial parodontium. Premolars had an occlusal-distal inlay-preparation and molars a mesial-occlusal inlay-preparation. Forty-two IPIRFDPs with a connector size of 9 mm(2) and a framework connector size of 4.7 mm(2) were cemented adhesively to the IPIRFDP-models. Quasi-static fracture strength was tested with centric (n=12) and eccentric (n=6) loading in a universal testing machine at a cross-head speed of 1 mm/min. Fatigue fracture strength was tested at 1200 N with centric loading (n=12) and at 600/500 N with eccentric loading (n=6) at a frequency of 0.5 Hz. Statistical comparison of groups was performed with the Mann-Whitney U test. RESULTS: Quasi-static fracture strength differed significantly between centric (1749 N) and eccentric loading (880 N, p<0.001). Mean loading cycles until fracture were 4432 for centric loading at 1200 N compared to only 3 and 410 loading cycles for eccentric loading at 600 and 500 N, respectively. SIGNIFICANCE: Considering the maximum chewing forces in the molar region, it seems clinically possible to use prefabricated IPIRFDPs with Y-TZP as a core material with a framework connector size of 4.7 mm(2).

Load-bearing capacity of all-ceramic posterior inlay-retained fixed dental prostheses.

The purpose of this in vitro study was to compare the quasi-static load-bearing capacity of all-ceramic resin-bonded three-unit inlay-retained fixed dental prostheses (IRFDPs) made from computer-aided design/computer-aided manufacturing (CAD/CAM)-manufactured yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) frameworks with two different connector dimensions, with and without fatigue loading. Twelve IRFDPs each were made with connector dimensions 3 x 3 mm(2) (width x height) (control group) and 3 x 2 mm(2) (test group). Inlay-retained fixed dental prostheses were adhesively cemented on identical metal-models using composite resin cement. Subgroups of six specimens each were fatigued with maximal 1,200,000 loading cycles in a chewing simulator with a weight load of 25 kg and a load frequency of 1.5 Hz. The load-bearing capacity was tested in a universal testing machine for IRFDPs without fatigue loading and for IRFDPs that had not already fractured during fatigue loading. During fatigue testing one IRFDP (17%) of the test group failed. Under both loading conditions, IRFDPs of the control group exhibited statistically significantly higher load-bearing capacities than the test group. Fatigue loading reduced the load-bearing capacity in both groups. Considering the maximum chewing forces in the molar region, it seems possible to use zirconia ceramic as a core material for IRFDPs with a minimum connector dimension of 9 mm(2). A further reduction of the connector dimensions to 6 mm(2) results in a significant reduction of the load-bearing capacity.

Analysis of retention and wear of ball attachments.

OBJECTIVE: To evaluate the retention and the wear of different prefabricated precision ball attachments consecutively during long-term use. METHOD AND MATERIALS: Six commercially available ball attachment systems were selected. The balls were attached to stylized implants fixed in metal casts. The matrices were fixed in a stylized unilaterally removable partial denture (RPD). Using a chewing simulator with 8 units, 50,000 joining and separating cycles of the matrices were performed. After each joining movement, an eccentric load of 100 N was applied to the RPD at a distance of 12 mm from the ball attachment. The retention forces were measured at intervals. RESULTS: Initially, median retentive forces varied between 8.2 N and 14.0 N. During the test, patterns in retention changes were identified. At the end of the test, one group with a matrix using precious alloy lamellae and a titanium ball showed significantly higher median retention forces (10.4 N) than the other ball attachments (1.0 N to 3.7 N). Also, the wear of the ball attachments varied considerably. CONCLUSION: Within the limitations of this study, the material combination of a precious gold alloy matrix and a titanium ball seems to be favorable for long-term retention.

In vitro evaluation of a mechanical testing chewing simulator.

OBJECTIVES: In this in vitro study, the force-profile of a commonly used chewing simulator (Williytec, Munich, Germany) utilizing fixed weights for loading was evaluated. METHODS: Using piezoelectric force sensors the maximum and mean values of the applied forces were recorded in three different load configurations in order to determine the repetition accuracy in one test chamber. The variation in resulting forces of the eight test loading-chambers when using three different loads and descending speeds was explored. RESULTS: The simulator showed high load repetition accuracy between the different cycle rates. Significant differences (up to 38.2+/-0.4N) were observed between the different specimen chambers. In addition, the recorded loads were generally both higher (up to 137.5+/-0.4N) and lower than the nominal loads defined by the static weights. The extent of load variation at contact was highly dependent on the descending cross-speed and selected weight. Finally there were also ringing in the load profiles attributed to vibrations of the mechanical setup. SIGNIFICANCE: Studies using weight-controlled chewing simulators should consider these effects when reporting results. In addition, calibrations should be performed to check uniformity of tests conditions for each test chamber.

Implant-abutment interface design affects fatigue and fracture strength of implants.

OBJECTIVES: Failures of implant-abutment connections are relatively frequent clinical problems. The aim of this study was to evaluate the influence of long-term dynamic loading on the fracture strength of different implant-abutment connections. MATERIAL AND METHODS: Six implant systems were tested: two systems with external connections (Brånemark, Compress) and four systems with internal connections (Frialit-2, Replace-Select, Camlog, Screw-Vent). Fracture strength was tested in two subgroups for each system: one subgroup with (dyn) and the other without prior dynamic loading (contr). Each subgroup consisted of eight specimens with standard implant-abutment combinations for single molar crowns. Dynamic loading was performed in a two-axis chewing simulator with 1,200,000 load cycles at 120 N. RESULTS: Median fracture strengths in Newton (N) and 25th and 75th percentiles [in brackets] were: Brånemark: dyn=729 [0;802]/contr=782 [771;811], Frialit-2: dyn=0 [0;611]/contr=887 [798;941], Replace-Select: dyn=1439 [1403;1465]/contr=1542 [1466;1623], Camlog: dyn=1482 [1394;1544]/contr=1467 [1394;1598], Screw-Vent: dyn=0 [0;526]/contr=780 [762;847] and Compress: dyn=818[0;917]/contr=1008 [983;1028]. In some dyn subgroups, failures of the implant-abutment connection occurred already during dynamic loading: three specimens of the Brånemark and Compress groups and six specimens of the Screw-Vent and the Frialit-2 groups failed during dynamic loading. Statistically significant differences (P< or =0.05) in fracture strength could be found between groups with different connection designs. CONCLUSION: Implant systems with long internal tube-in-tube connections and cam-slot fixation showed advantages with regard to longevity and fracture strength compared with systems with shorter internal or external connection designs.

Evaluation of vertical accuracy of interocclusal recording materials.

OBJECTIVE: To evaluate 4 interocclusal recording materials for their ability to reproduce accurately interocclusal relationships after a storage time of 1 or 48 hours. METHOD AND MATERIALS: A custom-made metal apparatus was used to simulate the maxilla and mandible. The vertical discrepancies were measured by a precision dial gauge. Eight inter-occlusal records were made in each of the following groups: (G1) Futar D (polyvinyl siloxane; Kettenbach), (G2) Ramitec (polyether; 3M ESPE), (G3) LuxaBite (composite resin based on bisacryl; DMG), (G4) Aluwax (aluminum wax; Aluwax Dental Products), (G5) LuxaBite corrected with LuxaBite, and (G6) LuxaBite corrected with Aluwax. The vertical discrepancies were measured after storage of the records for 1 and 48 hours at room temperature and repositioning of the records in the metal apparatus. Data were statistically analyzed using 1-way analysis of variance followed by the Games-Howell test (P < or = .05). RESULTS: After storage times of 1 and 48 hours, respectively, the mean vertical discrepancies (microm) for G1 (23/33) and G2 (25/30) were statistically significantly lower than for G3 (431/745) and G4 (110/151) (P < .05) but higher than for G5 (8/16) and G6 (7/17). There was no statistically significant difference between G1 and G2 or between G5 and G6 for either measurement. CONCLUSION: These vertical discrepancies increased after a storage time of 48 hours. However, correction of the LuxaBite records with LuxaBite or Aluwax showed significantly lower vertical discrepancies than all other materials. Clinically, the vertical discrepancies the corrected records caused could be insignificant.

Marginal and internal fit of metal-ceramic crowns fabricated with a new laser melting technology.

OBJECTIVES: The purpose of this in vivo investigation was to evaluate the marginal and internal fit of metal-ceramic crowns fabricated with a new laser melting procedure (BEGO Medical, Bremen, Germany), and to investigate the influence of ceramic firing on the marginal and internal accuracy of these crowns. METHODS: After tooth preparation, impression taking using polyvinylsiloxane and model casting, each preparation was contact less scanned by strip-light-projection. The finishing line and the virtual construction of the metal coping were defined by means of a computer. Using CAD/CAM software the metal copings were produced by BEGO Medical (Germany). A base metal alloy (Wirobond C) and a precious alloy (BioPontoStar, both: BEGO Medical) were used in this study with 14 restorations each. The internal and marginal accuracy of the specimens were examined using a silicone indicator paste (Fit Checker, GC, Japan). After setting, the silicone films were embedded in acrylic resin and sectioned four times. Each slice was photographed digitally at 60x magnification for marginal and at 15x magnification for occlusal adaptation, respectively. Using a light microscope the thickness of the silicone layer was measured at 10 reference points, a total of 3360 measurements. This procedure was repeated after the ceramic firing in the dental laboratory and after intraoral adjustment clinically. RESULTS: No statistically significant differences between the two alloys were found at any time. The mean marginal discrepancies ranged from 74 to 99 microm for both alloys. The internal gaps ranged from 250 to 350 microm. Ceramic firing increased the marginal discrepancies while the internal gaps decreased especially at occlusal surface. However, only in one case a slight statistically significance could be determined (p=0.046). SIGNIFICANCE: The results of this in vivo study show that crowns produced with laser melting technology exhibit a marginal and internal accuracy that is comparable to conventional production procedures.

Selective surgical treatment of patients with rectal carcinoma and unresectable synchronous metastases based on response to preoperative chemotherapy.

BACKGROUND: The time schedule for chemotherapy and primary tumor resection in patients with rectal carcinoma (RC) and unresectable synchronous metastases (USM) is not well defined. We evaluated whether response to chemotherapy is an appropriate criterion for deciding to perform surgery. METHODS: We treated 22 patients with RC and USM who received chemotherapy and were regularly evaluated. After documentation of a partial remission (PR) or stable disease (SD), patients were offered resection of the primary tumor. Results were compared with those of a historical control group of 42 patients who underwent immediate surgery. RESULTS: Seven patients had a PR, four showed SD, and 11 progressed under chemotherapy. Seven patients underwent resection of the primary tumor (no perioperative mortality). The median survival for all 22 patients was 20.2 months. Patients with primary tumor resection survived 27.2 months, whereas patients without resection survived only 12.4 months (p = 0.017). The median survival in the control group was 13.5 months (perioperative mortality, 9.5%). CONCLUSION: Chemotherapy and response-dependent resection of the primary tumor results in the same survival time as that attained with immediate surgery. Patients who face a poor prognosis due to progressive disease are thereby spared the risks of major rectal surgery.

Two-body wear of resin and ceramic denture teeth in comparison to human enamel.

OBJECTIVES: To evaluate the two-body wear resistance of different artificial denture teeth when opposed to steatite ceramic balls in a dual-axis chewing simulator. METHODS: Artificial denture teeth including the ceramic tooth Bonartic CT, the composite resin tooth Condyloform II NFC, the acrylic resin teeth Bonartic TCR, Orthognath, Polystar Selection, SR Orthotyp DCL, and Vitapan Cuspiform, and human maxillary premolars were tested in a chewing simulator. Wear resistance was analyzed measuring vertical substance loss and volume loss using profilometry and an optical macroscope after various chewing cycles (49N, up to 1,200,000 cycles). Data were statistically analyzed using one-way analysis of variance (ANOVA) followed by the Fisher test (LSD) at p< or =0.05. RESULTS: After 1,200,000 chewing cycles the mean vertical substance loss and volume loss for the composite resin teeth (117microm and 0.144mm3) were significantly lower than for all acrylic resin teeth (149-166microm and 0.220-0.292mm3) (p< or =0.05), but higher than for ceramic teeth (36microm and 0.029mm3) and for enamel (56microm and 0.033mm3) (p< or =0.05). No significant differences were found among the acrylic resin teeth for both parameters (p>0.05). SIGNIFICANCE: The composite resin showed improved in vitro two-body wear resistance compared to modern acrylic resin denture teeth; however, it showed less wear resistance than ceramic teeth and human enamel. Ceramic teeth should be preferred over natural teeth when occlusal stability is considered a high priority.

Fracture strength of all-ceramic posterior inlay-retained fixed partial dentures.

OBJECTIVES: The purpose of this in vitro study was to compare the quasi-static (QSFS) and fatigue fracture strength of all-ceramic resin-bonded three unit inlay-retained fixed partial dentures (IRFPDs) made from a heat-pressed lithium-disilicate based glass-ceramic (LDGC) and a CAD/CAM-manufactured yttrium-oxide partially stabilized zirconia framework (YPSZ). METHODS: Identical IRFPD-models of the maxilla were used. They consisted of a second premolar, a missing first molar and a second molar (Co-Cr-Mo alloy) integrated in a low melting alloy base. Roots were covered with a soft silicone-layer to simulate an artificial parodontium. Premolars had an occlusal-distal inlay-preparation and molars a mesial-occlusal inlay-preparation. Thirty-two IRFPDs were made from each ceramic using two different connector dimensions: 3mmx3mm (LDGC_9, YPSZ_9); 4mmx4mm (LDGC_16, YPSZ_16). All IRFPDs were cemented adhesively to the IRFPD-models, using composite resin cement. QSFS was tested in a universal-testing-machine (UTM) for six specimens. The other specimens were fatigued either with cyclic loading at 250N (n=4) in a chewing simulator or at 600N (n=6) using the UTM, and group YPSZ additionally at 1500N. RESULTS: The medians of QSFS (N) were 960 (LDGC_9), 1316 (LDGC_16), 3180 (YPSZ_9) and 3120 (YPSZ_16). For both QSFS and cyclic loading significant differences were found between LDGC_9 and LDGC_16 (p0.05). Differences between LDGC and YPSZ were significant for both connector sizes (p