Long-term effects of various cleaning methods on polypropylene/ethylene copolymer retainer material

Objectives:To evaluate long-term light transmittance, surface roughness, and flexural modulus of polypropylene/ethylene copolymer retainer material after exposure to different cleaning methods.Materials and Methods:Standardized polypropylene/ethylene copolymer retainer specimens (n = 70, 50.8 mm × 12.7 mm × 1.0 mm) were subjected to seven chemical cleaning solutions: Invisalign cleaning crystals, Retainer Brite, Polident, Listerine mouthwash, 2.5% acetic acid, 0.6% NaClO, and 3% H₂O₂ for 6 months. The specimens were exposed to the different solutions twice a week for 15 minutes or according to manufacturer''s instructions, then stored in artificial saliva at 37°C. Another group of specimens (n = 10) were brushed with a standardized toothbrushing machine for 2 minutes twice a week. At baseline and 6 months, light transmittance, surface roughness, and flexural modulus of the specimens were quantified using spectrophotometry, profilometry and three-point bend testing, respectively. Qualitative analysis was performed using a scanning electron microscope (SEM). Statistical analyses were performed at a significance level of .05.Results:The results showed that light transmittance decreased significantly from baseline for all cleaning methods at 6 months. For an individual method, no significant differences were observed between specimens at baseline and 6 months in surface roughness and flexural modulus. No discernible differences in surface features were observed on SEM images.Conclusions:The results indicate that different cleaning methods affect the long-term light transmittance of the studied polypropylene/ethylene copolymer retainer material. However, for an individual cleaning method, no significant differences were shown for surface roughness or flexural modulus values at 6-months compared to baseline.     

Video versus lecture: effective alternatives for orthodontic auxiliary training.

Abstract

Many studies have compared the relative effectiveness of visually-aided lectures and videotapes, but methodological flaws have prevented definitive comparison of the techniques. This study assessed the relative effectiveness of the two approaches for orthodontic auxiliary training. This study was a prospective, randomised trial, conducted at the Eastman Dental Hospital and Institute. Two groups of 16 dental auxiliaries, selected at random, studied identification and positioning of orthodontic brackets: one group attended a lecture accompanied by slides and the other viewed a video. Subjects bonded brackets onto acrylic teeth and the results were assessed by computerised image analysis. The subjects completed a questionnaire on their attitudes to the respective teaching methods. Results were assessed for accuracy of bracket placement and variations in type of auxiliary. There was no significant difference between the teaching methods except for bracket positioning where video was slightly better (P < 0.05). There was no significant difference between the types of auxiliary. Generally, video teaching and lecturing were equally effective, with video achieving slightly better results. Both methods were effective at teaching bracket placement, and dental nurses and student hygienists proved equally adept at bracket positioning.     

微波消毒对正畸活动保持器尺寸稳定性和适合性的影响

目的研究微波消毒对正畸活动保持器尺寸稳定性和适合性的影响。方法选择不同材料制作3种正畸保持器试样（热凝Hawley保持器、自凝Hawley保持器和压膜保持器）,测量所有保持器微波消毒前后尺寸稳定性及适合性的变化。结果所有试样微波消毒后尺寸均未发生明显改变（均P＞0.05）;微波消毒使2种Hawley保持器的适合性下降（均P＜0.05）,但对压膜保持器无明显影响（均P＞0.05）。结论热凝Hawley保持器和压膜保持器可采用微波辐照进行消毒。     

正畸舌侧保持器和透明压膜保持器对牙周组织的影响

目的：研究正畸舌侧保持器和透明压膜保持器对下前牙舌侧牙周健康的影响。方法选择新疆医科大学第二附属医院固定矫治结束后患者30人（男14,女16）,随机分成2组,每组15人。A组戴用舌侧固定保持器,B组戴用透明压模保持器。于戴入后1周、1个月、3个月和6个月分别检查记录下前牙的舌侧菌斑指数（PI）、牙龈指数（GI）、牙石指数（CI）和硫化物水平（SUL）,并作统计学分析。结果保持器戴入6个月后与1周时比较,2组PI、CI和SUL指数均显著增加,差异有统计学意义（P<0.05）,但2组的GI差异无统计学意义（P>0.05）。CI在3个月时A组显著大于B组（P<0.05）;SUL在6个月时B组显著大于A组（P<0.05）。结论保持器使口腔自洁作用减弱,对牙周组织有一定的影响,且硫化物引起的口臭影响社交,6个月时应进行必要的刮治去除菌斑和牙石,维护牙周健康。     

改良式压膜保持器戴用期间的牙周健康维护及其效果评价

目的对改良式压膜保持器戴用期间的牙周健康状况与Hawley’s保持器戴用期间牙周健康状况进行比较和效果评价。方法将80例结束固定正畸治疗的患者,随机分为改良式压膜保持器组和Hawley’s保持器组,每组40例,分别于拆除固定矫治装置全口洁牙后（作为基线数据）和戴保持器后1、3、6、12个月进行牙周指数[牙周袋探诊深度（PD）、菌斑指数（PLI）、牙龈指数（GI）]的检测;同时还教会患者自身有效的口腔卫生自我检查与自我维护的方法。结果（1）无论压膜保持器组或Hawley’s保持器组,除各阶段的PLI与基线数据间差异有统计学意义（P〈0.05）外,各阶段的PD、GI差异无统计学意义（P〉0.05）;（2）两组间PD在3个月后差异有统计学意义（P〈0.05）,GI则在12个月后差异有统计学意义（P〈0.05）。结论（1）只要保持器设计制作合理,牙周预防保健措施到位,压膜保持器戴用期间对牙周健康的影响并不明显;（2）无论压膜保持器或Hawley’s保持器,戴用期间都必须采取各种措施预防牙体牙周病变。     

Microplate cell-retaining methodology for high-content analysis of individual non-adherent unanchored cells in a population

A high throughput Microtiter plate Cell Retainer (MCR) has been developed to enable, for the first time, high-content, time-dependent analysis of the same single non-adherent and non-anchored cells in a large cell population, while bio-manipulating the cells. The identity of each cell in the investigated population is secured, even during bio-manipulation, by cell retention in a specially designed concave microlens, acting as a picoliter well (PW). The MCR technique combines micro-optical features and microtiter plate methodology. The array of PWs serves as the bottom of a microtiter plate, fitted with a unique flow damper element. The latter enables rapid fluid exchange without dislodging the cells from their original PWs, thus maintaining the cells' identity. Loading cell suspensions and reagents into the MCR is performed by simple pouring, followed by gravitational sedimentation and settling of cells into the PWs. Cell viability and cell division within the MCR were shown to be similar to those obtained under similar conditions in a standard microtiter plate. The efficiency of single cell occupancy in the MCR exceeded 90%. No cell dislodging was observed when comparing images before and after bio-manipulations (rinsing, staining, etc.). The MCR permits the performance of kinetic measurements on an individual cell basis. Data acquisition is governed by software, controlling microscope performance, stage position and image acquisition and analysis. The PW's unique micro-optical features enable rapid, simultaneous signal analysis of each individual cell, bypassing lengthy image analysis. Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s10544-006-9143-y.     

The Essential Work of Fracture of Thermoplastic Orthodontic Retainer Materials

Objective:To investigate whether oral cleansing agents affect the essential work of fracture (EWF) and plastic work of fracture (PWF) for two types of orthodontic thermoplastic retainer materials.Materials and Methods:Polyethylene-terephthalate-glycol (PETG; Tru-Tain Splint) and polypropylene/ethylene-propylene rubber (PP-EPR) blend (Essix-C+) sheets were compared. For each material, six sets of 25 sheets were thermoformed into double-edge-notched-tension specimens; subsets of five specimens were formed with internotch distances (L) equal to 6, 8, 10, 12, or 14 mm, respectively. Sets were stored (160 hours, 25°C) in air (DRY), distilled water (DW), Original Listerine (LIS), mint Crest ProHealth (CPH), 3% hydrogen peroxide (HP), or Polident solution (POL). Specimens were fractured in tension at 2.54 mm/min. Areas under load-elongation curves were measured to determine total work of fracture (W_f). Linear regressions (W_f vs L [n  =  25]) yielded intercepts (EWF) and slopes (PWF). Ninety-five percent confidence intervals were used to evaluate differences in EWF and PWF estimates.Results:PP-EPR blends showed higher EWFs after storage in HP vs storage in DW. PP-EPR blend showed higher EWFs after storage in CPH vs PETG. After HP storage, PP-EPR exhibited lower PWFs than with any other storage conditions. PP-EPR exhibited higher PWFs than PETG after storage in DRY, DW, and LIS.Conclusions:Compared with DW, none of the cleansers decreased the energy to initiate fracture. With one exception, no cleanser decreased the energy to continue plastic fracture extension. In PP-EPR blend, increased resistance to fracture initiation was observed with CPH and HP, yet, surprisingly, HP decreased resistance to plastic fracture growth.     

Surgical Correction of Retracted Nostril Rim with Auricular Composite Grafts and Anchoring Suspention

Among concerned nasal appearances, a deformity with supero-lateral displacement of the nostril rim, called retracted nostril rim or elevated nostril rim is commonly seen and is considered one of the most difficult types of cases to treat aesthetically. A new surgical method for treating retracted nostril rim was performed in 10 patients, using the combination of auricular composite graft, internal fixation with a retainer, and external continuing suspension with anchoring sutures. The procedure was successful in maintaining the grafted cartilage in the ideal position and in avoiding recurrence of retraction or elevation of the constructed alar rim. The presented method merits consideration as a standard operative approach for correction of retracted nostril rim.     

应用正畸保持器片牙弓夹板治疗颌骨骨折的疗效评价

目的:探讨应用正畸保持器片牙弓夹板治疗颌骨骨折的临床效果。方法:对12例颌骨骨折患者应用正畸保持器片牙弓夹板固定合并颌间弹性牵引治疗,恢复咬合关系后第2周,停止颌间牵引,第4周拆除牙弓夹板,术后1、2、6个月时复查咬合关系,X线检查骨折愈合情况。结果:所有患者咬合关系恢复理想,X线检查显示骨折断端对位良好,骨折愈合良好,患者无不适感。结论:正畸保持器片牙弓夹板具有骨折对位准确、固位稳固、骨折愈合快、美观卫生、配戴舒适、费用低廉、操作简便等优点,适用于单发性、多发性、移位不明显的颌骨骨折。     

Long-term effects of seven cleaning methods on light transmittance,surface roughness,and flexural modulus of polyurethane retainer material

Objectives: To evaluate the long-term effects of seven different cleaning methods on light transmittance, surface roughness, and flexural modulus of a polyurethane retainer material.Materials and Methods: Polyurethane retainer specimens (Vivera®, Align Technology Inc) (70 specimens, n = 10 per method, 50.8 mm × 12.7 mm × 1.0 mm) were exposed to seven cleaning methods twice a week for 6 months. Before treatment and after 6 months, light transmittance, surface roughness, and flexural modulus of the specimens were quantified. Qualitative assessment of randomly selected specimens from each solution was performed at baseline and after 6 months using a scanning electron microscope. Statistical analyses were performed at the .05 significance level.Results: Of the three test variables, light transmittance through the specimens was the only one that changed significantly from baseline to 6 months for all cleaning solutions, with all of them causing a decrease. However, except for 0.6% sodium hypochlorite showing a change in surface roughness values and 2.5% vinegar and toothbrushing showing an increase in flexural modulus, none of the other four cleaning methods resulted in significant changes in surface roughness or flexural modulus values for the polyurethane specimens between baseline and after 6 months.Conclusions: Of the seven cleaning methods, Invisalign® cleaning crystals, Polident®, and Listerine® showed the least amount of change in light transmittance values for the polyurethane specimens over 6 months, and they had no effect on surface roughness and flexural modulus values.