Non-contact temperature control and stereo digital image correlation for high-temperature testing of miniature tubular specimens.

Component failures very often occur due to high temperature and multiaxial stress states arising at critical component locations. To imitate such loading conditions, a multiaxial miniature testing system (MMTS) with axial, torsional, and internal pressurization capabilities for high-temperature testing of miniature tubular specimens has been developed. Among many challenges of developing the MMTS, uniform heating, temperature measurement and control, and surface strain measurement on a miniature tubular specimen at high temperatures have significant difficulties. This paper addresses two significant challenges: first, the development of a non-contact temperature control system using infrared thermography to uniformly heat a miniature specimen of 1 mm outer diameter (OD), and second, the development of a stereo digital image correlation (stereo-DIC) setup for strain measurement on the miniature specimen subjected to high temperature. The developed control system maintains the test temperature through a closed feedback loop and employs a fail-safe mechanism to protect the MMTS load frame components against unanticipated temperature rises. The thermocouple wire-size effect on the measured temperature was examined for three different wire sizes: 0.05, 0.25, and 0.5 mm for accurate emissivity determination required for infrared thermography. Emissivities of the specimen surface at different high temperatures were experimentally determined. Inherent error analysis of the developed high-temperature stereo-DIC setup showed acceptable strain measurement uncertainty. The effectiveness of the developed non-contact temperature control system and high-temperature stereo-DIC setup has been verified by performing tensile testing of a 1 mm OD specimen at 500 °C.

Decontamination procedures for tungsten carbide debonding burs: a cross-sectional survey of hospital-based orthodontic departments.

OBJECTIVE: To determine the current pattern of use and handling of tungsten carbide debonding burs (TCDBs) within UK hospital-based orthodontic departments. DESIGN: Cross-sectional survey. SUBJECTS AND METHODS: Questionnaires were sent to 217 departments within the UK and an overall response rate of 93% was achieved. RESULTS: Most hospital departments (68%) currently use TCDBs designed for a slow handpiece. Just over half (55%) discard their TCDBs after single-use, but only 24% adequately decontaminate new burs prior to initial use. Almost all those that reuse TCDBs decontaminate them in a sterilizer and carry out combinatorial presterilization cleaning. The most common methods are manual cleaning followed by an ultrasonic bath (26%) or washer-disinfector (15%); or alternatively, soaking of burs followed by manual cleaning (13%). For those departments that use only a single method, manual cleaning (29%) or a washer-disinfector (10%) are most common. In terms of sterilizing TCDBs, 58% used a vacuum phase autoclave and 13% a downward displacement. CONCLUSIONS: There is wide variation in the handling of TCDBs in UK hospital-based orthodontic departments. Decontamination of new TCDBs prior to initial use is carried out by less than a third of departments. Despite their classification as reusable devices, just over half discard TCDBs after single use. However, among those that do reuse TCDBs, almost all decontaminate them correctly.

Decontamination of viable Streptococcus mutans from orthodontic tungsten carbide debonding burs. An in vitro microbiological study.

OBJECTIVES: To investigate the effectiveness of currently recommended decontamination procedures on tungsten carbide debonding burs (TCDBs). DESIGN: In vitro microbiological study. SETTING: St George's Hospital NHS Trust, UK. MATERIALS AND METHODS: A total of 240 extracted tooth surfaces were bonded with orthodontic brackets, debonded to leave residual composite and artificially contaminated with Streptococcus mutans. INTERVENTION: Sterilized TCDBs in a slow handpiece were used to remove this composite before random allocation into one of six different decontamination groups of 40 burs each. These included a control group that was not decontaminated and a further five that underwent different methods of presterilization cleaning within the decontamination process (none, manual, ultrasonic, washer disinfector and enzyme soak) followed by sterilization in a vacuum phase autoclave at 134 degrees C for 3 min. MAIN OUTCOME MEASURES: The burs were placed in brain heart infusion (BHI) broths, incubated for 48 h. Following this the broths were inspected for turbidity and microbiological analysis was carried out to detect viable bacterial growth. Data were analysed using the Kruskal-Wallis test for single ordered data. RESULTS: S. mutans was recovered from 39 out of 40 burs in the control group and no burs from the decontamination groups, which was statistically significant (P = 0.001). No differences were found between decontamination groups (P = 0.271). However, skin flora contamination was noted in 17 broths. CONCLUSIONS: The five methods of decontaminating TCDBs investigated in this study were effective in removing viable S. mutans. Other investigations are required to determine if TCDBs can be successfully cleaned of blood and protein residue prior reuse.

A novel gripper for multiaxial mechanical testing of microtubes at elevated temperatures.

The success of a microtube hydroforming (µTHF) process heavily depends on the material properties of microtubes, which can reveal the material response under multiaxial stress and influence the formability of hydroformed products. However, these material properties are not well understood because of the limited availability of material testing apparatus that would permit control of axial force and internal pressure simultaneously to mimic realistic µTHF loading. The main purpose of this study is to develop a set of grippers that can transfer required testing loads under fully coupled combinations of axial force and internal pressure. The grippers are designed so that they may be kept at the safe working temperature even when tests are carried out at higher temperatures. The grippers are also designed to fit in a load frame that is integrated in a scanning electron microscope for in situ material testing. The capabilities of the grippers are demonstrated by performing uniaxial and multiaxial material tests on SS304 microtubes with 1 mm outside diameter and 0.15 mm nominal tube wall thickness. The finite element simulations and experimental results show that the designed grippers can firmly hold the specimen and thus enable tensile, compression, torsion, and microtube bulge material tests to be accurately performed.

The effects of orthognathic surgery on speech: a review.

PURPOSE: To assess the effects of orthognathic surgery on speech in non-cleft individuals. MATERIALS AND METHODS: A literature survey was undertaken using the Medline (Entrez Pubmed) and EMBASE databases (1966 to 2006). Key orthodontic, orthognathic, and speech journals were also hand searched. No language limitations were imposed. Randomized controlled trials, prospective and retrospective longitudinal trials (with and without controls), and case series were considered for inclusion. RESULTS: Eighteen studies were identified as fulfilling the inclusion criteria. Controls were used in one fifth of the trials; 13 articles reported preoperative articulation errors. In 8 of the trials, speech articulation either improved or was corrected for the majority of individuals assessed. In the studies assessed, the type of surgery or degree of movement did not appear to affect speech. CONCLUSION: There is no clear evidence directly relating malocclusions to speech discrepancies. Furthermore, it is difficult to draw any firm conclusions with respect to the effect of orthognathic surgery on speech. Further investigation is required.