Tolerance Limits on Surface Errors of the Plates of Lummer-Gehrcke Interferometers

A power inverter circuits is normally designed to meet its design specifications when the applied input DC voltage is within specified tolerance limits. Thus, single input inverters are usually specified to work from a DC source having a fixed nominal voltage. This limits the usefulness of the inverter circuit when a DC source having the specified nominal voltage is not available. In this work, a modified square wave inverter system that is specified to work properly from batteries with nominal voltages of 6, 12, 18 and 24 V was designed. A model of the microcontroller-based circuit was developed with Proteus® software and its firmware was written in C language using the MicroC® development tool. A prototype of the circuit was constructed and then tested. The constructed circuit was found to work properly by producing a 50 Hz modified square waveform when it was powered from batteries having nominal voltages of 6 V, 12 V, 18 V and 24 V.

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Accuracy of intraoral scan images in full arch with orthodontic brackets: a retrospective in vivo study

Clinical Oral Investigations ◽

10.1007/s00784-021-03792-0 ◽

2021 ◽

Author(s):

Young-Kyun Kim ◽

So-Hyun Kim ◽

Tae-Hyun Choi ◽

Edwin H. Yen ◽

Bingshuang Zou ◽

...

Keyword(s):

Orthodontic Brackets ◽

Digital Impression ◽

Orthodontic Bracket ◽

Average Surface ◽

Mandibular Arch ◽

Surface Errors ◽

Digital Impressions ◽

Surface Deviations ◽

Orthodontic Patients

Abstract Objectives The purpose of this retrospective study was to evaluate the accuracy of intraoral scan (IOS) images in the maxillary and mandibular arches with orthodontic brackets. Material and methods From digital impressions of 140 patients who underwent orthodontic treatment, consecutive IOS images were selected based on standardized inclusion criteria: Two pre-orthodontic IOS images (IOS1 and IOS2) of permanent dentition with fully erupted second molars and IOS images obtained immediately after orthodontic bracket bonding (IOSb). Superimpositions were performed to evaluate the reproducibility of repeated IOS images. Accuracy of IOSb images was analyzed by comparing the average surface errors between IOS1c and IOS2c images, which were IOS images cut based on the same region of the interest as between IOS1 and IOSb images. Results A total of 84 IOS images was analyzed. The average surface errors between IOS1 and IOS2 images were 57 ± 8 μm and 59 ± 14 μm in the maxillary and mandibular arch, respectively, and their reliability was almost perfect. The average errors between IOSb and IOS1c images exhibited an increase, which measured 97 ± 28 μm in the maxillary arch and 95 ± 29 μm in the mandibular arch. These surface deviations between IOSb and IOS1c images were significantly larger in each region as well as entire dentition (P < 0.001) compared to those between IOS1c and IOS2c images. Conclusions The average surface errors of the scans with brackets showed increased values compared with those without brackets. This suggests that orthodontic brackets could affect the trueness of intraoral scan images. Clinical relevance It is necessary for clinicians to consider the effect of brackets on digital impression when using IOS images in orthodontic patients.

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