Investigation of the accuracy of dynamic condylar position: A model study

OBJECTIVES

To evaluate dynamic condylar positions by integrating mandibular movement recording data and cone-beam computed tomography (CBCT) and to investigate its accuracy via dynamic model experiments.

METHODS

A polyvinyl chloride skull model was utilized. A robot arm was used to operate the mandible to perform mouth opening, closing, protrusion, and lateral movements. A recording device, worn on the skull, was used to record the dynamic process and an optical position tracking (OPT) system was used to simultaneously trace the movements. A self-developed software module was used to evaluate the dynamic condylar position by integrating the dynamic tracing data and a virtual skull model derived from CBCT images. Errors were defined as differences between the dynamic coordinates of six landmarks around the condylar area derived from the software module (test) and OPT system (gold standard).

RESULTS

The condylar position errors were 0.76 ± 0.31, 0.55 ± 0.15, and 0.68 ± 0.23 mm for mouth opening, bilateral, and protrusion movements, respectively. Furthermore, the errors for small, moderate, and large mouth opening movements were 0.62 ± 0.19, 0.69 ± 0.29, and 0.94 ± 0.31 mm, respectively. The errors for all movements, except for large mouth opening, were significantly less than 1 mm (P < 0.05). The error was not different from 1 mm in the large mouth opening movement (P > 0.05).

CONCLUSIONS

Our developed method of achieving dynamic condylar position by integrating mandibular movement recording data and CBCT images is clinically reliable.

CLINICAL SIGNIFICANCE

This study proved the reliability of evaluating dynamic condylar position using a commercial dynamic recording instrument and CBCT images.

Towards quantifying atmospheric dispersion of pesticide spray drift in Yuma County Arizona

While pesticide vapor and particles from agricultural spray drift have been reported to pose a risk to public health, limited baseline ambient measurements exist to warrant an accurate assessment of their impacts at community-to-county-wide scale. Here, we present an initial modeling investigation of the transport and deposition of applied pesticides in an agricultural county in Arizona (Yuma County), to provide initial estimates on the corresponding enhancements in ambient levels of these spray drifts downwind of application sites. With a 50 × 50 km domain, we use the dispersion model CALPUFF with meteorology from the Weather Research and Forecasting (WRF) to investigate the spatiotemporal distribution of pesticide abundance due to spray drift from a representative sample of nine application sites. Data records for nine application days in September and October 2011, which are the peak months of pesticide application, were retroactively simulated for 48-h for all nine application sites using an active ingredient lambda-cyhalothrin, which is a commonly-used pesticide in the county. Twenty-one WRF/CALPUFF simulations were conducted with varying emissions, chemical lifetime, deposition rate, application height, and meteorology inputs, allowing for an ensemble-based analysis on the possible ranges in modeled abundance. Our results show that dispersion of vapors released at time of application heavily depends on prevailing meteorology, particularly wind speed and direction. Dispersion is limited to thin plumes that are easily transported out of the domain. The ensemble-mean vapor concentrations of the 48-h average (> 90 percentile domain-wide) range from 0.2 nanograms (ng)/m3 to 200 ng/m3, and the peak can be as high as 1000 ng/m3 near the application sites. Pesticide particles are mainly deposited within 1-2 km from the application sites at an average rate of 106 ng/km2/h but vary with particle mean diameter and standard deviation. While these findings are generally consistent with reported ambient levels in the literature, the associated ensemble-spread on these estimates are in the same order of magnitude as their ensemble-mean. At the two nearby communities downwind of these sites, we find that peak vapor concentrations are less than 50 ng/m3 with exposure times of less than an hour, as approximately 99.4% of the vapors are advected out and 99.5% of the particles deposit within the domain. Results of this study indicate pesticide spray drift from a sample of application sites and representative days in Fall may have a limited impact on neighboring communities. However, we strongly suggest that field measurements should be collected for model validation and more rigorous investigation of the actual scale of these impacts when the bulk of pesticide applications across the county, variation in active pesticide ingredients, and potential resuspension of deposited particles are considered.

Comparison of the accuracy of dental implant placement using static and dynamic computer-assisted systems: an in vitro study

OBJECTIVES

The study aimed to compare the accuracy of implant placement between static and dynamic computer-assisted systems (CAS) in a partially edentulous mandible model.

MATERIALS & METHODS

A total of 80 implants was placed in mandible models. The implants were placed using either static or dynamic computer-assisted system. Deviations of implant hex, apex and angulation were measured between preoperative planning and postoperative CBCT in planning software.

RESULTS

The mean deviations of implant hex, apex and angulation in static CAS group were 1.15 ± 0.34 mm, 1.37 ± 0.38 mm and 2.60 ± 1.11 degree, while in dynamic CAS group were 0.40 ± 0.41 mm, 0.34 ± 0.33 mm and 0.97 ± 1.21 degree, respectively. Implant placement with dynamic CAS showed less deviations of shoulder, apex and angulation than with static CAS significantly.

CONCLUSIONS

The implant accuracy using CAS system could be influenced by the guiding technique.

Formation and reduction of 5-hydroxymethylfurfural at frying temperature in model system as a function of amino acid and sugar composition

5-Hydroxymethylfurfural (HMF) is formed during heat treatment of carbohydrate-containing foods, especially in a deep-fat frying process. This study aimed to investigate the effect of amino acids on the formation and reduction of HMF from glucose, fructose and sucrose at frying temperature in model systems containing binary mixtures of an amino acid and a sugar in equal concentrations (0.3M). The results revealed that the formation of HMF from sugars accelerated in the presence of acidic amino acids (i.e. glutamic and aspartic acids). Conversely, the presence of basic amino acids (i.e. lysine, arginine and histidine) led to reduced concentrations of HMF to non-detectable levels in model systems. The results showed that both pH and heating time significantly affected the formation of HMF from fructose in the presence of glutamic acid. In this regard, a higher amount of HMF was formed at lower pH.