RPI卡环受力分析与临床应用

本文讨论了常规设计的游离端义齿存在的问题,并对Kratochvil提出的RPI卡环,结合力学知识,提出了RPI卡环在游离端义齿应用中的优缺点,并通过典型病例介绍和对20名病例随访分析表明,用RPI卡环修复游离端牙齿缺失,可获得较好的临床效果。     

Patient compliance with Hawley retainers fitted with the SMART® sensor: A prospective clinical pilot study

Objective:To evaluate the compliance of patients while wearing maxillary Hawley retainers embedded with SMART microsensors.Methods:The sample population consisted of 22 patients who were divided into an experimental (group A) and a control group (group B). Group A was informed that they would be monitored through the use of SMART microsensors, while group B was not informed that they would be monitored. After the delivery of the retainers (T0), the patients were evaluated at T1 and T2, represented by 6- and 12-week follow-up visits, respectively. At T1, group B was informed of our ability to monitor their compliance. Both groups continued wearing their retainers during T1 to T2.Results:During T0–T1, Group A wore their retainers for an average of 16.3 hours (SD 4.39), while group B wore their appliances for an average of 10.6 hours (SD 5.36, t  =  2.426, P  =  .027). Although group B increased their retainer wear by 0.5 hours/day from T1 to T2, this increase was not statistically significant.Conclusions:Despite significant differences being noted between the two groups at T1, group B did not show significant mean changes in their wear time before and after becoming aware of the use of the SMART microsensor.     

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.     

冠外固位体义齿基牙牙周组织应力分布的三维有限元分析

目的研究下颌第一磨牙缺失、第二磨牙近中倾斜30°或45°时,用栓道附着体义齿或套筒冠义齿2种冠外固位体(extra-coronal retainer,ECR)义齿修复的基牙牙周组织应力分布。方法采用CT扫描技术和Mimics、Freeform、ANSYS软件,建立下颌第一磨牙缺失、第二磨牙近中倾斜30°或45°及ECR义齿修复后的三维有限元模型,模拟加载并计算分析基牙牙周组织应力的分布情况。结果下颌第二磨牙近中倾斜30°、45°模型,修复前第二前磨牙Von Mises应力分别是2.80 MPa、3.47 MPa,栓道附着体义齿修复后分别是19.26 MPa、25.18 MPa,套筒冠义齿修复后分别是19.47 MPa、24.48 MPa,ECR义齿修复后下颌第二前磨牙牙周组织应力明显增大;修复前第二磨牙Von Mises应力分别是20.45 MPa、20.50 MPa,栓道附着体义齿修复后分别是15.02 MPa、11.84 MPa,套筒冠义齿修复后分别是18.04 MPa、12.18 MPa,ECR义齿修复后下颌第二磨牙牙周组织应力明显减小。结论栓道附着体义齿和套筒冠义齿均能改善倾斜基牙牙周组织的应力分布,当下颌第二磨牙近中倾斜角度过大或下颌第二前磨牙牙周状况欠佳时,应该考虑增加近中端基牙数目。     

Universal Adhesive for Fixed Retainer Bonding: In Vitro Evaluation and Randomized Clinical Trial

This study aims to assess the efficacy of a universal adhesive (Scotchbond Universal, 3M ESPE) (SB) in total-etch mode, compared to a traditional orthodontic primer (Transbond XT Primer, 3M ESPE) (XT Primer), to perform bonding of orthodontic fixed retainers along with the Transbond XT Light Cure Adhesive Paste (3M ESPE). For the in vitro study, a round section wire (Ortosmail Krugg) was bonded using XT Primer for 20 bovine incisors (Group 1) and SB for other 20 (Group 2). Samples were debonded in a universal testing machine applying a tangential force to specimens (crosshead speed of 1 millimeter per minute). Shear bond strength (SBS) and adhesive remnant index (ARI) scores were calculated. For the in vivo study, 100 patients needing upper and lower canine-to-canine fixed retainers after orthodontic treatment were randomly assigned to two groups of 50 participants each, i.e., group 1 (retainer bonding with XT Primer) and group 2 (retainer bonding with SB). Over two years, examinations were carried out monthly, and detachments were registered by considering the teeth and arches affected. In vitro, no statistically significant differences in SBS and ARI scores were demonstrated between the two groups, both showing a mean bond strength of about 12 MPa and major frequency of ARI “2” (>50% remnant adhesive on the enamel). Conversely, a significantly lower failure rate over 2 years was assessed clinically for group 2 in both arches. Independently of the adhesive and arch, incisors reported a significantly higher failure rate than canines. Scotchbond Universal used in total-etch mode could be a valid alternative to the traditional orthodontic Transbond XT Primer.     

不同类型保持器对固定矫治后再矿化的影响

目的:观察不同类型保持器对固定矫治后牙釉质再矿化的影响,以及氟保护剂的再矿化作用。方法:将30名固定矫治结束后釉质脱矿患者随机分为2组(n=15),传统保持器组(A组,117个牙)和压膜保持器组(B组,116个牙)每组再分为3个亚组,分别进行不同再矿化处理。1组:生理盐水;2组:1 mg/m L氟保护剂;3组:350 g/L磷酸凝胶酸蚀+1 mg/m L氟保护剂。每月复诊处理1次并观察半年,用ZWCAD2010软件测量数据并进行统计学分析。结果:拆除固定矫治器时A、B组内以及相应各亚组间釉质脱矿面积差异无统计学意义(P>0.05)。再矿化处理后釉质脱矿面积改变量:A1组0.05);B1组0.05);A1>B1、A2>B2、A3>B3,均P<0.05。结论:用传统保持器更有利于再矿化;给予氟保护剂能够促进再矿化。     

The effect of retainer thickness on posterior resin-banded prostheses: a finite element study

According to its design concept, a resin-bonded prosthesis, compared with the conventional fixed partial denture, is a weak and unstable structure. Therefore, a resin-bonded prosthesis induces a higher failure rate, especially in the posterior region. Recently, adhesion agents have been profoundly improved. However, the design guidelines of posterior resin-bonded prostheses (RBP) have seldom been evaluated from a biomechanical perspective. The objective of this study was to investigate the biomechanical effects of the retainer thickness on posterior RBP using the finite element method. A solid model of a posterior mandibular resin-bonded prosthesis, which employed the second molar and second premolar as the abutment teeth, was constructed and meshed with various retainer thickness (ranging from 0.2 to 1.0 mm). Horizontal and vertical loadings of 200 N were applied respectively at the central fossa of the pontic to examine the stress level at the interface between the retainer and abutment teeth. All exterior nodes in the root, below the cementoenamel junction were fixed as the boundary condition. The results showed that horizontal loading would induce higher interfacial stresses than the vertical loading which indicated that the horizontal component of the occlusal force plays a more important role in evaluating the debonding phenomenon. Further, the peak interfacial stresses increased as the retainer thickness decreased and, based on the fitted relation between retainer thickness and interfacial stresses, a 0.4 mm retainer thickness was suggested as the minimum required to prevent severe interfacial stresses increasing.     

改良式压膜保持器与Hawley保持器在下颌后缩患者保持疗效的比较研究

目的 对比改良式透明压膜保持器与Hawley保持器在恒牙早期下颌后缩患者保持治疗中的临床疗效.方法 选择以下颌后缩为主的恒牙早期安氏Ⅱ类错[牙合]患者30例,下颌后缩均已纠正,咬合关系稳定,已达到正常[牙合]标准,进入保持阶段治疗.患者随机分为两组,每组15例,治疗组分别配戴改良式透明压膜保持器,对照组配戴Hawley保持器进行保持.在配戴前后分别拍摄X线头颅侧位定位片,计算头影测量各指标的均值与标准差,采用配对t检验对两组配戴前后的测量结果进行分析.结果 保持治疗12个月后,X线头影测量显示30例患者上下颌骨均有少量生长,但对照组上颌骨前方生长显著,下颌骨前方生长减弱,前牙覆[牙合]覆盖增大且有复发趋势.实验组头影测量显示软硬组织生理性变化,下颌骨前方生长较上颌骨显著,前牙覆[牙合]覆盖关系保持稳定并有减小趋势.结论 改良式透明压膜保持器较Hawley保持器有效地促进下颌骨的生长发育,协调上下颌骨的位置关系,保持[牙合]关系的稳定及有效改善侧貌外形.