Laser and scanning electron microscopy evaluation of residual microislands of calculus.

BACKGROUND: Recent studies suggest a role for microscopic crystalline particles of residual dental calculus in the pathogenesis of periodontitis. The purpose of this ex vivo study was to compare the effectiveness of scaling and root planing (SRP) alone versus SRP combined with 24% ethylenediamine-tetra acetic acid (EDTA) gel in removing calculus from extracted teeth and to determine the optimal length of time for application of the EDTA. METHODS: Specimens consisted of 32 extracted teeth with heavy root calculus. A 4-mm diameter site was prepared on the root surface of each tooth which then underwent SRP. EDTA was applied to four timed groups: 30 s; 60 s; 120 s; and 180 s. Photomicrographs were taken at 40× magnification using white light (WL) and laser fluorescence (LF). Photomicrographs were analyzed using ImageJ. Specimens were also evaluated with scanning electron microscopy (SEM). RESULTS: The mean area of residual calculus after SRP was 45%-53% (45.6% ± 19.6% WL, 53.8% ± 19.7% LF). Burnishing with EDTA for one minute following SRP reduced calculus to only 14%-18% (13.9% ± 12.5% LF, 18.2% ± 11.1% WL). Use of EDTA for greater than 1 min showed no further calculus removal. SEM revealed the surface of remaining calculus was altered by burnishing with EDTA. CONCLUSION: SRP alone or SRP + 24% EDTA gel failed to remove all calculus. SRP alone removed >60% of calculus from root surfaces. Adjunctive use of 24% EDTA gel burnished on the root surface removed most of the calculus residual after SRP. Calculus remaining after EDTA burnishing exhibited a significantly altered morphologic appearance.

Effect of EDTA Gel on Residual Subgingival Calculus and Biofilm: An In Vitro Pilot Study.

BACKGROUND: Residual calculus, following scaling and root planing (SRP), is associated with persistent inflammation and the progression of periodontitis. This study examined the effects of a 24% neutral ethylenediaminetetraacetic acid (EDTA) gel on subgingival calculus and biofilms. METHODS: Eleven single-rooted teeth extracted because of severe periodontal disease were randomly assigned to the following treatment groups: (1) three teeth served as untreated controls; (2) three teeth were treated by scaling and root planing (SRP) only; and (3) three teeth were treated by SRP + EDTA. The remaining two teeth, one SRP only and the other SRP + EDTA were designated for energy-dispersive X-ray spectroscopy (EDS) analysis. EDTA gel was placed on the SRP surface for 2 min and then burnished with a sterile cotton pellet. RESULTS: SRP + EDTA treated specimens exhibited severely damaged biofilm and the disruption of the extracellular polymeric matrix. EDS scans of the smear layer and calculus featured reductions in the Weight % and Atomic % for N, F, Na, and S and increases in Mg, P, and Ca. CONCLUSIONS: A 25% neutral EDTA gel was applied after SRP severely disrupted the residual biofilm and altered the character of dental calculus and the smear layer as shown by reductions in the Weight % and Atomic % for N, F, Na, and S and increases in Mg, P, and Ca.

SEM Evaluation of the Effects of Laser-Mediated Implant Surface Decontamination: An In Situ Human Pilot Study.

Successful treatment of peri-implantitis requires decontamination of implant surfaces exposed to biofilms and byproducts of tissue inflammation. In this regard, dental lasers may provide a clinical benefit. While the inherent characteristics of specific laser wavelengths may damage titanium implant surfaces, in vitro and animal studies have shown that damage to the target surface can be avoided with the selection of appropriate laser parameters. In this in situ human study, five hopeless implants were irradiated, each by one of the following lasers: Nd:YAG (1,064 nm), Er,Cr:YSGG (2,780 nm), Er:YAG (2,940 nm), CO2 (9,300 nm), and CO2 (10,600 nm) at their recommended settings. All implants were then removed and examined under scanning electron microscopy for the presence of residual bacteria and to assess the extent of damage to the implant surface. An additional implant (implant no. six) was irradiated and evaluated by the Limulus Amebocyte Lysate test for the presence of residual lipopolysaccharide endotoxin. The results showed that while there were localized areas of heat-related damage to an implant surface following laser irradiation, residual bacteria were rarely noted. Additionally, the Limulus Amebocyte Lysate test indicated a nearly complete removal of endotoxin. With the use of appropriate settings, all current dental lasers can be utilized for implant surface decontamination in a human.

Efficacy of Removal of Residual Dental Cement by Laser, Ultrasonic Scalers, and Titanium Curette: An In Vitro Study.

The purpose of this study was to conduct an in vitro evaluation of the efficacy of six dental lasers, two ultrasonic scalers, and a titanium curette in the removal of dental cement from the surface of an implant. The study used a total of 39 dental implants, representing three different surface textures. The implants were divided into 13 groups with one of each of the three surface textures in a group. A standardized amount of modified resin dental cement was applied to the implant surface. Each test instrument was used as a monotherapy. Additionally, three of the lasers were used as part of a dual therapy in conjunction with the piezo ultrasonic scaler. Laser irradiation was limited to 2 minutes. Following treatment, implants were graded visually and by scanning electron microscopy (SEM) for the presence of unremoved cement and concomitant damage, if any, to the implant surface. The results showed that no treatment removed all residual cement from any of the three implant surfaces, although specific protocols appeared more effective than others. Implant surface damage was frequently observed, both visually and by SEM, and appeared to result from laser irradiation and the use of ultrasonic scaling instruments.

Characterization of elemental distribution across human dentin-enamel junction by scanning electron microscopy with energy-dispersive X-ray spectroscopy.

The human dentin-enamel junction (DEJ) is a natural junction that unites two dissimilar mineralized tissues in the human tooth: enamel and dentin. DEJ plays a critical role in maintaining structural and functional integrity of the tooth. However, its structure, chemical composition and function remain unclear and controversial. Systematic investigation of elemental distribution across human DEJ is still lacking in the literature. This study aimed to investigate the elemental distributions of Ca, P, O, C, N, Na, and Mg across the DEJ of human teeth using scanning electron microscope with energy dispersive spectroscopy of X-ray. The results revealed abrupt changes in the distributions of six elements (C, N, Ca, P, Na, and Mg) across the DEJ. Specifically, the four mineral elements showed similar level of change in distribution, with Ca, P, Na decreasing while Mg increasing by 21%-25% from enamel to dentin side of the DEJ. The two organic elements C and N showed much larger changes in distribution, with C increasing by ~150% and N increasing by ~270% from enamel to dentin side of the DEJ. The slope of the distribution curves across the DEJ was estimated to be ~2 µm in width and coincided with the phase intermixing of the micro-scallop structure of the DEJ.

Biological templated synthesis of water-soluble conductive polymeric nanowires.

One-dimensional (1D) conductive nanowire is one of the most important components for the development of nanosized electronic devices, sensors, and energy storage units. Great progresses have been made to prepare the 1D-conducting polymeric nanofibers by the low concentration process or the synthesis with hard or soft templates. However, it still remains as a great challenge to prepare polymeric nanofibers with narrow dispersity, high aspect ratio, and good processibility. With the rod-like tobacco mosaic virus as the template, 1D-conducting polyaniline and polypyrrole nanowires can be readily prepared via a hierarchical assembly process. This synthesis discloses a unique way to produce composite fibrillar materials with controlled morphology and great processibility, which can promote many potential applications including electronics, optics, sensing, and biomedical engineering.

Microbial diversity in ultra-high-pressure rocks and fluids from the Chinese Continental Scientific Drilling Project in China.

Microbial communities in ultra-high-pressure (UHP) rocks and drilling fluids from the Chinese Continental Scientific Drilling Project were characterized. The rocks had a porosity of 1 to 3.5% and a permeability of approximately 0.5 mDarcy. Abundant fluid and gas inclusions were present in the minerals. The rocks contained significant amounts of Fe2O3, FeO, P2O5, and nitrate (3 to 16 ppm). Acridine orange direct counting and phospholipid fatty acid analysis indicated that the total counts in the rocks and the fluids were 5.2 x 10(3) to 2.4 x 10(4) cells/g and 3.5 x 10(8) to 4.2 x 10(9) cells/g, respectively. Enrichment assays resulted in successful growth of thermophilic and alkaliphilic bacteria from the fluids, and some of these bacteria reduced Fe(III) to magnetite. 16S rRNA gene analyses indicated that the rocks were dominated by sequences similar to sequences of Proteobacteria and that most organisms were related to nitrate reducers from a saline, alkaline, cold habitat; however, some phylotypes were either members of a novel lineage or closely related to uncultured clones. The bacterial communities in the fluids were more diverse and included Proteobacteria, Bacteroidetes, gram-positive bacteria, Planctomycetes, and Candidatus taxa. The archaeal diversity was lower, and most sequences were not related to any known cultivated species. Some archaeal sequences were 90 to 95% similar to sequences recovered from ocean sediments or other subsurface environments. Some archaeal sequences from the drilling fluids were >93% similar to sequences of Sulfolobus solfataricus, and the thermophilic nature was consistent with the in situ temperature. We inferred that the microbes in the UHP rocks reside in fluid and gas inclusions, whereas those in the drilling fluids may be derived from subsurface fluids.