The Use of Intensity Techniques for Noise Source Identification in Small Machinery

Intensity techniques are now widely used for two purposes: sound power determination and source identification. The work described in this presentation illustrates an application of the latter type. As part of a noise control program for a small domestic appliance, a narrow‐band intensity measurement system was developed based on a face‐to‐face microphone probe, a two‐channel FFT analyzer, and a personal computer. The probe was used to measure the nearfield normal intensity on planes parallel to the device\u27s major surfaces. Graphical display of these data allowed the radiated sound field to be visualized at any desired frequency. Further, it was possible to distinguish between various types of component sources by examining the field in detail. For example, airborne sound that is generated within the device and radiates to the exterior through apertures or “leaks” was plainly visible. Radiation from the exterior surface of the device resulting from direct vibrational excitation of the surface and from structure‐borne vibration could also be identified. Knowledge of this type was used to advantage to guide the noise control treatment program. Nearfield surveys conducted after these modifications yielded a particularly vivid indication of the effects and benefits of the individual modifications

Post-Retained Single Crowns versus Fixed Dental Prostheses: A 7-Year Prospective Clinical Study

Biomechanical integrity of endodontically treated teeth (ETT) is often compromised. Degree of hard tissue loss and type of final prosthetic restoration should be carefully considered when making a treatment plan. The objective of this prospective clinical trial was to assess the influence of the type of prosthetic restoration as well as the degree of hard tissue loss on 7-y clinical performance of ETT restored with fiber posts. Two groups (n = 60) were defined depending on the type of prosthetic restoration needed: 1) single unit porcelain-fused-to-metal (PFM) crowns (SCs) and 2) 3- to 4-unit PFM fixed dental prostheses (FDPs), with 1 healthy and 1 endodontically treated and fiber post-restored abutment. Within each group, samples were divided into 2 subgroups (n = 30) according to the amount of residual coronal tissues after abutment buildup and final preparation: A) >50% of coronal residual structure or B) equal to or <50% of coronal residual structure. The clinical outcome was assessed based on clinical and intraoral radiographic examinations at the recalls after 6, 12, 24, 36, 48, and 84 mo. Data were analyzed by Kaplan-Meier log-rank test and Cox regression analysis (P < 0.05). The overall 7-y survival rate of ETT restored with fiber post and either SCs or FDPs was 69.2%. The highest 84-mo survival rate was recorded in group 1A (90%), whereas teeth in group 2B exhibited the lowest performance (56.7% survival rate). The log-rank test detected statistically significant differences in survival rates among the groups (P = 0.048). Cox regression analysis revealed that the amount of residual coronal structure (P = 0.041; hazard ratio [HR], 2.026; 95% confidence interval [CI] for HR, 1.031–3.982) and the interaction between the type of prosthetic restoration and the amount of residual coronal structure (P = 0.024; HR, 1.372; 95% CI for HR, 1.042–1.806) were statistically significant factors for survival (ClinicalTrials.gov NCT01532947)

Six-month color change and water sorption of 9 new-generation flowable composites in 6 staining solutions

Abstract Color match and water sorption are two factors that affect restorative materials. Discoloration is essential in the lifespan of restorations. The aim of this study was to evaluate color change and water sorption of nine flowable composites at multiple time points over 6 months. 60 samples of each composite were divided into two groups (Color Change and Water Sorption/Solubility). Each Color Change group was divided into six subgroups, which were immersed in distilled water (DW), coffee (CF), Coca-Cola (CC), red wine (RW), tea (TE) and orange juice (OJ). The color was measured at the baseline, 1, 2, 3 and 4 weeks, and 3 and 6 months and color change values (&#916;E) were calculated. Each Water Sorption [WS]/Solubility [WL] group was tested according to ISO 4049:2009. The data were evaluated using two-way ANOVA, Fisher&#8217;s post-hoc test and Pearson&#8217;s correlation test. The composite with the lowest &#916;E differed for each solution: Filtek&#8482; Bulk Fill in DW (&#8710;E = 0.73 (0.17&#8211;1.759)); Vertise Flow in CF (&#8710;E = 14.75 (7.91&#8211;27.41)), in TE (&#8710;E = 7.27 (2.81&#8211;24.81)) and OJ (&#8710;E = 3.17 (0.87&#8211;9.92)); Tetric EvoFlow® in CC (&#8710;E = 1.27 (0.45&#8211;4.02)); and Filtek&#8482; Supreme XTE in RW (&#8710;E = 8.88 (5.23&#8211;19.59)). RW caused the most discoloration (&#8710;E = 23.62 (4.93&#8211;51.36)). Vertise Flow showed the highest water sorption (WS = 69.10 ± 7.19). The Pearson test showed statistically significant positive correlations between water sorption and solubility and between water sorption and &#8710;E; the positive solubility-&#8710;E correlation was not statistically significant. The findings suggest that water sorption is one factor associated with the ability of composites to discolor; however, discoloration is a multifactorial problem