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Ultrasound detection of submerged dental implants through soft tissue in a porcine model

Culjat, Martin O; Choi, Mijin; Singh, Rahul S; Grundfest, Warren S; Brown, Elliott R; White, Shane N
STATEMENT OF PROBLEM: Current methods of measuring soft tissue thickness over potential dental implant sites and locating submerged implants may be imprecise or invasive. PURPOSE: The purpose of this study was to develop and demonstrate proof of the concept of a customized ultrasound imaging system in locating and measuring the depth of implants submerged beneath soft tissue. MATERIAL AND METHODS: A complete ultrasound system, including a customized soft tissue-matched transducer, transceiver, and digital signal processing algorithms, was created for the specific application of detecting dental implants anchored in bone beneath soft tissue. The system was used to locate implants placed in cancellous bone and measure overlying soft tissue depth in a porcine model. Ten measurements were made on each porcine model by manually moving the transducer laterally over the soft tissue surface. Data were analyzed with descriptive statistics. RESULTS: The mean signal-to-noise ratio, SNR (standard deviation), from the bone surfaces, was 19.1 (4.6) dB, and the mean SNR from the implant surfaces was 36.6 (2.2) dB, resulting in a mean difference of 17.5 dB, or x56.2, in average signal power between the bone and implant surfaces. Consequently, implants were easily and accurately (+/-0.2 mm) located beneath at least 5 mm of soft tissue. Likewise, soft tissue depths over bone and implants were accurately measured and were within the corresponding caliper tissue measurement error (+/-0.5 mm). CONCLUSIONS: The specialized ultrasound imaging system located and measured the depth of implants placed in bone submerged beneath soft tissue in a porcine model
PMID: 18319093
ISSN: 0022-3913
CID: 153408

Effects of varied dimensions of surgical guides on implant angulations

Choi, Mijin; Romberg, Elaine; Driscoll, Carl F
STATEMENT OF PROBLEM: Fabrication of a proper surgical guide is critical for success of implant restorations. The effects of the dimensional factors of the surgical guide on implant placement have not been studied. PURPOSE: The purpose of this study was to determine the effect of varied dimensions (diameter, length, and distance between the underside of the surgical guide and the implant recipient site) of a surgical guide on the accuracy of implant angulation. MATERIAL AND METHODS: In this in vitro study, 240 implant recipient sites were randomly prepared using varied dimensions of a surgical guide. The varied dimensions of the surgical guide's channel and distance were: channel diameter (2, 3, 4, or 5 mm), channel length (6 or 9 mm), and distance between the underside of the surgical guide and the simulated implant recipient site (2 or 4 mm). From these varying dimensions and distances, 16 combinations of dimensions and distances were tested. For each combination, 15 simulated implant recipient site (SIRS) specimens were prepared. The deviated angulation (DA) from the midpoint of the top surface of the 1- x 1-inch simulated implant recipient site (each simulated implant recipient acrylic block contained 5 SIRS of 1 x 1 inch), in the right-to-left (DA(RL)) and front-to-back (DA(FB)) directions, were measured in degrees using a protractor. The data was analyzed using factorial analysis of variance and Tukey's HSD test (alpha=.05). RESULTS: The DA(RL) , in degrees, at a channel length of 9.0 mm (2.33 +/- 1.27) was significantly smaller than at a channel length of 6.0 mm (3.0 +/- 1.42, P =.0001). The DA(RL) , in degrees, at a distance of 4.0 mm (2.13 +/- 1.16) was significantly smaller than at a distance of 2.0 mm (3.16 +/- 1.39, P =.0001). Also, a significant interaction for DA(RL) was found between diameter and distance ( P <.05). For DA(FB) , the varying diameters ( P <.05), lengths ( P =.0001), and distances ( P =.0001) showed significant differences. The DA(FB) at a channel length of 9.0 mm (2.56 degrees +/- 1.51) was significantly smaller than that at 6.0 mm (3.82 degrees +/- 1.87). Significant interactions found for DA(FB) were: diameter by length ( P =.0001), diameter by distance (F=4.547, P =.004), and length by distance (F=11.512, P =.001). CONCLUSION: Within the limitations of this study, the results suggest channel length as the primary controlling factor in minimizing deviated angulations
PMID: 15523335
ISSN: 0022-3913
CID: 153404

Fabrication of a custom eyelid implant prosthesis: a clinical report

Choi, Mijin; Driscoll, Carl F
Patients with lagophthalmos are often treated with a stock gold weight that has been implanted in the upper eyelid. This relatively simple surgical technique does not, however, always produce the desired result. This article describes a technique for the fabrication of a custom eyelid implant prosthesis for patients who present with a non-functioning and unaesthetic eyelid implant
PMID: 15210005
ISSN: 1059-941x
CID: 153402

Redox regulation of calcineurin in T-lymphocytes

Reiter, T A; Abraham, R T; Choi, M; Rusnak, F
To explore whether the Ca(2+)/calmodulin-dependent protein phosphatase calcineurin is subject to redox regulation in vivo, we used a luciferase reporter gene construct whose expression was controlled by the transcription factor NF-AT (the nuclear factor of activated T-cells) to monitor intracellular calcineurin activity following redox state perturbations. The NF-AT reporter construct was transfected into Jurkat cells, and luciferase activity was assessed following treatment with phorbol ester and ionomycin in the presence of either hydrogen peroxide or dithiothreitol (DTT). While DTT had no effect, H(2)O(2) completely abrogated NF-AT transactivation in response to stimulation. The inhibitory effect was specific for NF-AT as comparable levels of H(2)O(2) had only minor effects on constitutive transcription factors while an analogous construct under AP-1 control showed a 5-fold stimulation in transactivation in the presence of H(2)O(2). The inhibitory effect of H(2)O(2) was observed up to approximately 3 h following mitogen stimulation, a time point where NF-AT activity begins to increase under normal conditions. Protein serine/threonine phosphatase activities from Jurkat lysate indicated that calcineurin activity was inhibited not only by H(2)O(2) but also by high concentrations of DTT. These results indicate that calcineurin activity is subject to redox regulation in vivo and are discussed in the context of redox reactions involving active site metal ions.
PMID: 10550693
ISSN: 0949-8257
CID: 1815382