Clinical Evaluation of a Chairside Amalgam Separator to Meet Environmental Protection Agency Dental Wastewater Regulatory Compliance.

OBJECTIVES: The aim of this study was to evaluate the performance of a commercially available chairside amalgam separator (CAS) in a clinical setting in which a relatively high number of amalgam restorations are placed. Performance parameters investigated included service life, amalgam collected, mercury concentrations in effluent, and solids retention efficiency. METHODS AND MATERIALS: CASs were tested per International Organization of Standardization (ISO) 11143:2008 prior to installation in a military dental treatment facility and after removal from service (n=4) in order to confirm compliance with the recently enacted United States Environmental Protection Agency (EPA) Effluent Limitations Guidelines and Standards for the Dental Category. During the units' time in service, biweekly effluent grab samples were collected from the high-volume evacuation system of each chair (n=6) and analyzed for total mercury concentration by inductively coupled plasma mass spectrometry (ICP-MS). The mean total accumulated solids at the end of service life (n=6) was determined for potential design optimization. The service life expectancy in a military dental treatment facility was determined in terms of calendar and workdays. Procedural data were collected to determine the daily mean number of amalgam surfaces placed during the service life of each chairside amalgam separator (n=9). RESULTS: The CAS evaluated met minimum EPA compliance requirements when used in a military dental treatment facility. The solids removal efficiency at the end of service life was 99.82% ± 0.14% (n=4). The mean service life (n=8) was 131.6 ± 45.1 calendar days (67.1±37.6 workdays). Effluent mercury concentrations ranged from 0.05 to 11.93 mg/L. Total solids accumulated in each CAS (n=6) at the end of service life was 195.4 ± 63.4 g. The mean number of amalgam surfaces placed per workday during the service life span of each CAS was 8.4 ± 1.4.

Effect of Tooth-structure Thickness on Light Attenuation and Depth of Cure.

Newer bulk-fill composites claim a greater depth of cure than conventional resin-based composites. To facilitate complete curing, the manufacturer of SonicFill (Kerr) recommends curing from the occlusal, as well as the buccal and lingual, surfaces of the tooth. The purpose of this study was to quantify the degree of curing light attenuation as it passes through natural tooth structure, and how this attenuation affects the depth of cure of different posterior resin composites. Ten noncarious extracted mandibular third molars were sectioned to produce 5-mm-thick pieces of buccal tooth structure. Sanding 0.5-mm increments from the flattened surface produced 4.5-, 4.0-, 3.5-, 3.0-, 2.5-, 2.0-, and finally 1.5-mm-thick sections. A Bluephase G2 (Ivoclar) curing light with an 8-mm-diameter light guide set on high for 20 seconds was used for measurement of irradiance as it passed through different thicknesses of tooth structure and air. The average irradiance (mW/cm(2)) was measured with a MARC-RC Resin Calibrator with a 4-mm-diameter sensor (BlueLight Analytics). To measure depth of cure of a conventional hybrid composite (Herculite Ultra; Kerr) vs a bulk-fill hybrid composite (SonicFill) through varying thicknesses of tooth structure, composites were cured in a 4-mm-diameter × 10.25-mm-long split mold according to International Organization for Standardization 4049. A mean and standard deviation was determined per group. Data were analyzed with a one-way analysis of variance (ANOVA)/Tukey test and two-way ANOVA/Tukey test (α=0.05). One-way ANOVA/Tukey found a significant decrease in irradiance based on thickness of tooth structure or distance through air (p<0.001). Two-way ANOVA/Tukey found a significant decrease in depth of cure based on thickness of tooth structure (p<0.001) and on composite type (p<0.001) with no significant interaction (p=0.623). SonicFill had a significantly greater depth of cure than Herculite Ultra.

A serum factor that recalcifies demineralized bone is conserved in bony fish and sharks but is not found in invertebrates.

We investigated the evolutionary origin of a serum activity that induces calcification within a type I collagen matrix, an activity previously described in rat and bovine serum. Serum was obtained from vertebrates with calcified tissues (bony fish and shark), vertebrates without calcified tissues (lamprey and hagfish), and three invertebrates (marine worm, crab, and sea urchin). Serum from the bony fish and shark proved to contain a potent nucleator of collagen calcification; like the previously described calcifying activity in rat serum, the fish and shark activities are both able to recalcify a demineralized rat tibia when tested in Dulbecco's modified Eagle medium containing as little as 1.5% of the respective serum and have an apparent molecular weight of 50-150 kDa. No calcifying activity could be detected in any of several experimental tests of invertebrate or hagfish serum. Weak calcifying activity could be detected in lamprey serum, but calcification was restricted to the growth plate of the decalcified tibia, with no detectable calcification in the type I collagen of the midshaft. These studies reveal a correlation between the evolutionary timing of the appearance of calcified tissues in vertebrates and the appearance of the serum activity that initiates calcification within collagen and, therefore, support the hypothesis that this serum activity may play a role in normal calcification of bone.

Mineralization of decalcified bone occurs under cell culture conditions and requires bovine serum but not cells.

The purpose of this study was to develop an in vitro model system for bone matrix mineralization in the absence of cells. For this model, we utilized EDTA-decalcified new-born rat tibias with the cartilaginous ends intact, allowing us to visually determine the specificity of mineralization within the bone. Our results show that supplementation of DMEM culture medium with 10mM beta-glycerophosphate and 15% fetal bovine serum (FBS) results in non-physiological mineral percipitation in the tibia because of the generation of supraphysiological (5mM) levels of inorganic phosphate in the medium. The same medium supplemented only with inorganic phosphate to a final concentration of 2mM failed to mineralize a decalcified tibia matrix. However, additional supplementation of this medium with as little as 5% FBS resulted in mineralization of those regions of the type I collagen where mineral was found prior to decalcification, with no evidence for mineralization in the cartilage at the bone ends or in the periosteum. Analysis of the mineral by Fourier-transform infrared spectroscopy and powder X-ray diffraction shows that tibias that have been decalcified and then remineralized contain an apatitic mineral that is strikingly similar to the mineral in normal bone. Tendon, a type I collagen matrix not normally mineralized in vivo, also mineralizes when incubated in DMEM containing 2mM Pi and as little as 1.5% FBS, but not when incubated in DMEM without serum. These data indicate that serum contains a nucleator of type I collagen matrix mineralization, and that mineralization of type I collagen under cell culture conditions requires serum but not living cells.