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。     

压膜保持器与改良HawleyⅡ型保持器联合应用对正畸保持效果的临床研究

目的：通过比较正畸矫治完成后两种保持方式在保持效果、牙周健康两方面的异同,评价联合应用压膜保持器与改良HawleyⅡ型保持器的临床效果。方法选择航天中心医院口腔科正畸固定矫治结束后病例80例,随机分为两组,每组40例。联合组日间戴用压膜保持器,夜间戴用改良HawleyⅡ型保持器;压膜组全天均戴用压膜保持器。两组患者在拆除固定矫治器当天及戴用保持器12个月取记存模型对比研究,评价保持效果;在戴用保持器1个月、3个月、6个月和12个月分别检查记录牙周指数,评价牙周健康状况,比较两种保持方式效果的异同。结果反映保持效果的各指标在保持器戴用12个月后,两组间未见到统计学差异(P>0.05);反映牙周健康状况的指标中牙龈指数和菌斑指数在保持器戴用3个月、6个月及12个月,牙石指数在保持器戴用12个月时联合组低于压膜组,差异具有统计学意义(P<0.05)。结论压膜保持器与改良HawleyⅡ型保持器联合应用与单独应用压膜保持器均可达到良好的保持效果;在牙周健康方面,联合组对牙周健康的影响较压膜组小,但两组均出现了一定程度的牙龈炎症。     

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.     

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。     

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。     

Prevalence of partial edentulism and RPD design in patients treated at College of Dentistry,Imam Abdulrahman Bin Faisal University,Saudi Arabia

This study aimed to investigate the prevalence of partial edentulism, RPD type, design, and components and their frequency of use by patients at the prosthodontic clinics of the College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam, Saudi Arabia. The prepared surveys, laboratory authorization forms, and images of the RPD metal frameworks on casts were used for data collection. Two calibrated investigators studied the digital photographs to identify the Kennedy classification, type of RPD, major connector, clasp assembly, and other details. Data was collected and analyzed statistically. The results showed that the most common class of partial edentulism was Kennedy class I, whereas class IV was the least (p < 0.001). Sixty two percent of fabricated RPDs had metal frameworks, whereas 37.2% were frameless. RPI was the most frequently used clasp assembly (38.9%), a significant finding in Kennedy class I(p < 0.01). The maxillary anteroposterior palatal strap and mandibular lingual plate were the most commonly used major connectors, at 41.2% and 60.8%, respectively. Conclusions: Simple RPD design that accomplishes the treatment objectives as well as proper communication with a well-trained dental technician would promote the success of RPDs.     

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.