Comparison of major connectors for removable partial dentures

Twenty dentists compared three maxillary and two mandibular major connector designs during speaking, mastication, swallowing, and normal, nonfunctional rest. Most preferred the single palatal bar and the mandibular lingual bar.     

Patients' preference for acrylic resin major connector analogues formulated for titanium alloy removable partial dentures

PURPOSE: Aim of this study was to determine patients' preference to acrylic resin major connector analogues (MCA) that simulated strengthened major connector designs formulated for Ti-6Al-7Nb alloy. MATERIALS AND METHODS: Four MCA namely wide design (Wide), design with 2 strengthening ridges (2SR), design with 1 strengthening ridge (1SR), and thick design (Thick) were fabricated using light-polymerizing acrylic resin for 10 patients with Kennedy Class I or II partially edentulous maxillary arches. They were asked to wear each MCA in the mouth for 30 seconds in 6 pairs, and to report their preference for each pair. Using these data the 4 MCA were ranked in a descending preference order for each patient. A within-subject comparison of preferences was performed with the Friedman test and multiple comparisons with Wilcoxon Signed Ranks test. RESULTS: A statistically significant preference order was revealed: Wide, 1SR, 2SR, and Thick (P < 0.008). The wide design (P < 0.004) and the 1SR (P < 0.01) were significantly preferred to the thick design. However, individual data showed that the first preference varied depending upon the subject. CONCLUSION: Thinner designs tended to be preferred to the thicker design by the subjects, while none of the designs tested were consistently selected as the best design.     

纯钛支架义齿与钴铬合金支架义齿修复效果的比较

目的评估纯钛铸造支架义齿的临床应用效果。方法为168例肯氏Ⅰ、Ⅱ类牙列缺损的患者制作71例纯钛支架义齿和97例钴铬合金支架义齿,通过比较两组患者临床试戴情况、初戴义齿适应期的调改情况、义齿性口炎的发生情况以及满意度,评估纯钛铸造支架义齿的临床修复效果。结果纯钛支架义齿比钴铬合金支架义齿就位顺利、调改少、患者满意度高,并且义齿性口炎的发生率低。结论纯钛铸造支架义齿与传统的钴铬合金铸造支架义齿相比临床修复效果好。     

纯钛义齿支架表面抛光的临床研究

目的：探索纯钛义齿支架的表面抛光方法，确保义齿有良好稳定的抛光效果，且不影响义齿支架的精度。方法：为78例患者制作105件纯钛可摘义齿，分三组，每组35件，分别为未酸洗，酸洗，酸洗并组织面适量均匀打磨抛光，分别测定义齿戴入时的抛光亮度与义齿与口腔组织的贴合程度和半年后义齿的抛光度。结果：三组之间的义齿与组织的贴合度无显著性差异（P＞0．05），第二，三组义齿的表面抛光度明显好于未酸洗组即第一组（P＜0．001），组织面抛光的亮度第三组明显好于未抛光第二组（P＜0．001），结论：酸洗和组织面的均匀适量打磨抛光可提高纯钛可摘义齿的表面亮度而不影响其精度。     

钴-铬合金铸造可摘局部义齿折断临床分析

目的：分析临床Co-Cr合金铸造可摘局部义齿(RPD)折断原因，以提高义齿质量。方法：对289件Co-Cr合金铸造RPD进行回顾总结，并对其发生铸造缺陷、折断进行统计分析。结果：本文289件铸件中，肉眼检查有铸造缺陷者93件，占31．3％，其余196件行X线探测检查有缺陷者36件，占18．6％。义齿各部位出现铸造缺陷机率：卡环小连接体处较高，下颌高于上颌。戴牙2年后折断32件，其中原铸造有缺陷者28件，占87．5％。结论：①铸造缺陷是造成铸造RPD折断的主要原因。②应用X线探测仪进行铸造义齿检测，是提高修复质量的有效方法。     

Stiffness of different designs and cross-sections of maxillary and mandibular major connectors of removable partial dentures

STATEMENT OF PROBLEM: Major connectors of removable partial dentures must distribute forces bilaterally without damaging the supporting tissues. PURPOSE: This study investigated which design and cross-sectional shape of major connectors most favorably influence rigidity and flexibility. METHODS AND MATERIAL: Five designs for maxillary removable partial denture major connectors and 5 lingual bar major connectors of different cross-sectional forms were cast in chrome cobalt alloy on a master cast. Points M and P, which represented the position of the first premolar and second molar teeth, were positioned 20 mm apart on the casting. Vertical and horizontal forces were applied to each point while the opposite side was gripped in an Instron testing machine. A force-deflection curve was obtained for each loading point. Mean stiffness values were obtained for loading in compression and torsion. RESULTS: Values for torsional loading simulating vertical forces were lower when compared with values obtained for compression loading that simulated horizontal occlusal forces. Differences in stiffness were greater in mandibular major connectors loaded at M and P. The half pear-shaped cross section was the stiffest. CONCLUSIONS: In the maxillary arch, the most rigid major connector was the anteroposterior palatal bar combination placed on different horizontal and vertical planes. The most flexible was the U-shaped design. In the mandibular arch, the most important factor in achieving rigidity was the cross-sectional shape of the major connector. The half pear-shaped cross section proved to be the most rigid.     

纯钛铸造支架可摘局部义齿的临床应用对比研究

目的：对比研究纯钛铸造支架、钴铬合金支架、塑料基托可摘局部义齿修复的临床疗效。方法：选择90件肯氏I类设计修复义齿,分别用三种义齿修复方法,戴用后半年～2年进行临床观察。结果：钝钛铸造支架叮摘局部义齿质量轻,佩戴舒适,咀嚼功能良好。结论：纯钛铸造支架可摘局部义齿可获得良好的临床效果。     

Discoloration of a titanium alloy removable partial denture: A clinical report

With recent advances in dental technology, titanium is currently used for fabrication of crowns, fixed partial dentures, implant frameworks, and removable partial denture frameworks. The use of titanium-aluminum-vanadium (Ti-6Al-4V) alloy assumes that it imparts similar anti-corrosion characteristics to the commercially pure titanium. This clinical report describes a patient who experienced discoloration of a Ti-6Al-4V alloy removable partial denture.     

Comparative study of circumferential clasp retention force for titanium and cobalt-chromium removable partial dentures

STATEMENT OF PROBLEM: The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies to support its use. PURPOSE: The objective of this study was to compare circumferential RPD clasps made of commercially pure titanium and identical clasps made of 2 different cobalt (Co)-chromium (Cr) alloys by testing insertion/removal and radiographically inspecting the casts for defects. MATERIAL AND METHODS: On refractory casts that represent a partially edentulous mandibular right hemi-arch segment, 36 frameworks were cast from commercially pure titanium (n = 12) and 2 Co-Cr alloys (n = 12 each) with identical prefabricated patterns and the manufacturer-designated investment and casting technique. Each group was divided into 2 subgroups, corresponding to .25-mm and .50-mm undercuts, respectively. No polishing procedures were performed to ensure uniformity. Only nodules and burs were carefully removed with tungsten burs under magnification when necessary. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. The data were subjected to analysis of variance and the Tukey complementary test (P<.01) to compare the retentive forces of RPDs made with the different materials. The Student t test (P<.01) was used to compare the retentive forces of RPDs fabricated with the same alloy with different undercuts. RESULTS: A total of 20% of the titanium specimens demonstrated porosity, showing casting difficulties, and any defect detected on the clasps determined the sample replacement. For Co-Cr alloys, casting difficulties were not found. The data were subjected to analysis of variance and the Tukey complementary test to compare materials for the same undercut. For the .25-mm undercut, no significant difference was found between Magnum and Rematitan alloys; they were both different from the Remanium alloy (P<.01). For the.50-mm undercut, no significant difference was found between Co-Cr alloys; they were both different from Rematitan alloy (P<.01). The Student t test used to compare the same alloys with different undercuts showed no significant difference between Remanium with .25-mm and .50-mm undercuts. For Magnum and Rematitan alloys, there was a significant difference between different undercuts (P=.01). CONCLUSION: Within the limitations of this simulation study, the results suggest that commercially pure titanium clasps maintained retention over a simulated 5-year period, with lower retention force than identical Co-Cr clasps.     

A clinical and physiological evaluation of prosthodontic treatment by removable partial dentures with free-end saddles--a 3.5-year follow-up study

The aim of this study was to evaluate the longitudinal clinical and physiological changes in jaw elevator muscle activity of partially edentulous patients, for approximately 3.5 years after treatment by removable partial dentures with free-end saddles. Seven patients (4 males and 3 females, aged 38-68 years) who visited a university dental hospital, and were found to have no signs and symptoms of TMJ disorders, participated in the follow-up study. The functional impression method with wax was used in the treatment process of these patients. At the follow-up times of 0.5, 1, 2, 3, and 3.5 years after denture deriverly, EMG activities using bipolar surface electrodes were recorded from masseter and anterior temporal muscle on both sides during maximal voluntary clenching and tapping, and at the same time the maximal bite force was also recorded using the Dental Prescale System. The integrated EMG, the correlation coefficient between muscle activities of both sides, bite force, and the location of the occlusal load center, were analyzed using repeated measured ANOVA. A comparison between each measuring session was carried out using Bonferroni's method. Results were as follows: i) The muscle function of partially edentulous patients was clearly activated by wearing a removable partial denture, and the activation was kept at the same level until 3.5 years after denture deriverly. ii) The activation of jaw elevator muscles by wearing a denture was greater in masseter muscle than in anterior temporal muscle. This finding reflected the effect of the recovered occlusal contact. iii) The occlusal load center of the recovered dentition by a removable partial denture shifted antero-posteriorly close to the end abutment teeth.     

Retention force of T-bar clasps for titanium and cobalt-chromium removable partial dentures

The objective of this study was to evaluate the retention force of T-bar clasps made from commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) alloy by the insertion/removal test simulating 5 years use. Thirty-six frameworks were cast from CP Ti (n=18) and Co-Cr alloy (n=18) with identical prefabricated patterns on refractory casts from a distal extension mandibular hemi-arch segment. The castings were made on a vacuum-pressure machine, under vacuum and argon atmosphere. Each group was subdivided in three, corresponding to 0.25 mm, 0.50 mm and 0.75 mm undercuts, respectively. No polishing procedures were performed to ensure uniformity. The specimens were subjected to an insertion/removal test and data was analyzed statistically to compare CP Ti and Co-Cr alloy in the same undercut (Student's t-test for independent samples) and each material in different undercuts (one-way ANOVA) (p=0.05). Comparisons between materials revealed significant differences (p=0.017) only for the 0.50-mm undercut. No significant differences (p>0.05) were found when comparing the same material for the undercuts. It may be concluded that for different undercuts, both Co-Cr alloy and CP Ti had no significant differences for T-bar clasps; CP Ti showed the lowest retention force values when compared to Co-Cr alloy in each undercut, but with significant difference only for the 0.50-mm undercut; and both materials maintained the retentive capacity during the simulation test.     

Comparison of deformation by stereophotogrammetry of various kinds of major connectors in maxillary Kennedy Class I removable partial dentures

PURPOSE: Major connectors must be rigid to perform their functions with maximum efficacy. This study investigated the deformation of four major connectors for maxillary Kennedy Class I removable partial dentures. MATERIALS AND METHODS: The designs were palatal plate, U-shaped plate, palatal strap, and anteroposterior bar. The deformation properties of major connectors were comparatively analyzed by two methods. In the photogrammetric part, a stereometric camera, Avipan-100 glass films, and an analytic apparatus were used. A computerized hydraulic machine was programmed to load the eight test dentures at 4-Hz frequency under a vertical load of 100 kg and a maximum of 300,000 cycles. The fluorescence penetrant liquid inspection test was used to detect the surface microcracks. RESULTS: The anteroposterior bar showed the least deformation. The other connectors, ranked in increasing order for the amount of deformation, were the U-shaped plate, the palatal strap, and the palatal plate. There were no microcracks in the U-shaped plate and the anteroposterior bar designs. CONCLUSION: Anteroposterior bar major connectors showed the least deformation among the maxillary major connector types tested. Microscopic cracks were seen in major connectors showing the highest degree of deformation and located at the depth of the hard palate.     

两种支架义齿合金材料临床应用的效果评价

目的:评估维他灵(Vitallium)2000铸造支架义齿临床应用的效果。方法:150例行可摘局部义齿修复的患者随机分为两组,实验组75例采用Vitallium 2000铸造支架义齿修复,对照组75例采用传统钴铬合金铸造支架修复,通过比较两组患者的满意度,评估Vitallium 2000铸造支架义齿的临床修复效果。结果:Vitallium 2000支架义齿与钴铬合金支架相比起来,患者在美观性、舒适度、语言功能方面的满意度较高(P<0.05)。结论:与传统的钴铬合金铸造支架义齿相比,Vitallium 2000铸造支架义齿临床修复效果较好。