游离端义齿修复中太极扣附着体对基牙牙周的影响

目的研究单侧后牙游离缺失修复中太极扣附着体对基牙牙周健康的影响。方法选择肯氏Ⅱ类缺损患者20例,采用太极扣附着体修复。纵向观察修复前、修复后2周、修复后6个月第一、二、三基牙的牙周指数及牙槽骨吸收情况,并进行统计学分析。结果太极扣附着体修复后牙游离缺失后2周和修复后6个月内,义齿稳定,固位良好。第一、二、三基牙牙龈指数、菌斑指数、探诊深度在治疗前、修复后2周之间的差异,以及治疗前、修复后6个月之间的差异均无统计学意义;基牙X线根尖片未见根尖病变,未见明显牙周膜增宽、牙槽骨吸收或高度降低;修复前基牙的松动度在进行联冠修复后有所降低。结论太极扣附着体应用于游离端义齿修复对基牙牙周健康未见不利影响。     

Quality of written communication and master impressions for fabrication of removable partial prostheses in the Kingdom of Bahrain

The aim of this study was to examine the quality of written instructions and choice of impression trays and materials for removable partial dentures (RPDs) in the Kingdom of Bahrain. All six private dental laboratories in Bahrain were contacted and invited to participate in the study. Five laboratories participated, and submitted written instructions received by them for fabrication of both acrylic (A-RPDs) and cobalt-chromium (CC-RPDs) RPDs. These were examined for evidence of selected design variables. Types of impression trays and materials used were also recorded. One hundred and thirty-one written instructions were examined. Eleven percent (n = 14) were for CC-RPDs, 89% (n = 117) for A-RPDs. All treatments were provided on a private basis. Fifty-seven percent (n =1 8) of CC-RPD instructions requested the technician to design the prosthesis, 43% (n = 6) contained a diagram and 43% (n = 6) mentioned all design variables. Seventy-nine percent (n = 92) of A-RPDs requested the technician to design the denture, and only 1% (n = 1) mentioned all design variables. Alginate impression material was most commonly used for master impressions (83% of impressions (n = 109); 85% (n = 99) of A-RPDs, and 71% (n = 10) of CC-RPDs). Master casts were poured after a minimum of 24 h. Acrylic custom trays were used in 14% (n = 19) of cases (43% (n = 6) of CC-RPDs; 13% (n = 15) of A-RPDs). The quality of written instructions to dental laboratories for the fabrication of RPDs was found to be inadequate in Kingdom of Bahrain. There was widespread use of inappropriate impression trays and materials.     

A survey of chrome-cobalt RPD design in Ireland

PURPOSE: The aims of this study were to investigate the quality of written instructions given to dental laboratories for fabrication of chrome-cobalt removable partial dentures (RPD) in Ireland, and to examine the extent and nature of technical/laboratory support available for the fabrication of this prosthesis type. MATERIALS AND METHODS: All dental laboratories listed in the commercial telephone book were contacted and invited to participate in the study. Written instructions received by dental technicians for fabrication of chrome-cobalt RPDs were examined for evidence of four design variables: denture base configuration, retention, support, and connector design. The use of diagrams was also examined. RESULTS: Of 112 dental laboratories listed, 100 agreed to take part. Sixteen laboratories had the facilities to fabricate chrome-cobalt frameworks on their premises; 122 sets of written instructions were received. All four design variables were described in 10% (n = 12) of instructions, 7% (n = 9) contained reference to three variables, 13% (n = 16) contained reference to two variables, and 17% (n = 20) contained reference to one variable. No design features were prescribed in 53% (n = 65), and 5% (n = 6) requested the technician to design the prosthesis. Only 7% (n = 8) of instructions included a diagram. CONCLUSION: A high proportion of written instructions to dental laboratories regarding fabrication of chrome-cobalt RPDs contained no reference to the mentioned design variables.     

Precision attachment-retained removable partial dentures. Part 3. General practitioner results up to 2 years

PURPOSE: The aim of this study was to analyze the techniques, production problems, and 2-year results of attachment-retained removable partial denture (RPD) treatment provided by general practitioners in Sweden. MATERIALS AND METHODS: At a major dental laboratory, consecutive cases involving new production of crowns, or of fixed partial dentures (FPDs) and RPDs retained with precision attachments, were studied. Parameters of the dentition, crown or FPD, type and brand of attachment, etc, as well as early satisfaction by dentist and patient, were recorded using specially designed forms at the dental laboratory and questionnaires for the dentists. After 2 years, questionnaires were again sent out to the dentists to record complications and patients' and dentists' opinions of the results. The sample gathered totaled 83 constructions. After 2 years, responses for 57 patients, all of whom had distal-extension RPDs, were received. Most drop-outs in the study were explicable. RESULTS: The most frequently cited reasons for using attachments were esthetics and need for crowning the teeth abutting the RPD. McCollum rigid slide attachment was the predominant brand used (43% of constructions). Dentists and patients were dissatisfied with 6% of the constructions. During the first 2 years, 22 of 57 constructions were complication-free. Seventeen had attachment complications and 9 had serious complications related to the abutment teeth or RPDs. A comparison between these 2 groups revealed that those with complications had every second abutment root-canal treated and a root post, while the group without complications had every fifth abutment root-canal treated. CONCLUSION: There were many technical and biotechnical complications and failures; the exact ratio, however, depended on the definition of "complications" and "failure." The 2-year results also deviated considerably from the dentists' opinions of the early results.     

3种游离端附着体义齿基牙位移的实验研究

目的:探讨3种附着体类型作为下颌单侧游离端义齿固位体对基牙的影响。方法:选用Snap附着体、Ceka附着体和Mini-SG附着体,制作单侧附着体义齿,在义齿侧上下牙列间放置食物片,咬合时用LB-72型高精度半导体激光位移测量仪,测量并计算出基牙在不同方向的位移量,并用随机方差分析法进行统计学分析。结果:3种附着体义齿基牙的近远中向、颊舌向、垂直向的位移、倾斜、扭转均有统计学差异(P<0.05)。Mini-SG附着体导致基牙近远中向的倾斜角度最大,Ceka附着体对基牙近远中向和根尖位移的影响最大,Snap附着体基牙的牙合方移动和逆时针旋转角度最小。结论:Snap附着体的弹性固位装置使应力在基牙和剩余牙槽嵴之间得到了最为均匀的分布,Ceka附着体的应力主要由基牙承担,Mini-SG附着体不能有效减少施于基牙上的有害的扭力。     

Incidence of various classes of removable partial dentures.

The purpose of a classification for removable partial dentures (RPDs) is to simplify identification and enhance its teaching. A classification also allows a longitudinal comparison of various classes of RPDs to determine whether the teaching of RPD design is consistent with the relative frequencies of RPD use. This study surveyed the types of removable partial dentures being fabricated in a regional dental laboratory and compared these findings with data from previous studies. Results indicate that mandibular RPDs are more common than maxillary RPDs and the class I mandibular RPD is the most common type of RPD for either dental arch. A palatal strap was the most frequently used maxillary major connector and a lingual bar was used three times more often than a lingual plate in the mandibular arch. Cast circumferential clasps were used twice as often as RPI clasp designs. The percentage of Kennedy class I RPDs was 40%, class II 33%, class III 18%, and class IV 9%. Comparisons with a previous study indicate the percentage of Kennedy class II has increased, whereas class I, class III and class IV RPDs have not changed significantly. Findings of the study indicate that the frequency of use of the various types of RPDs have changed in the past 30 years.     

Accuracy of CAD-CAM-fabricated removable partial dentures

Statement of problem

The conventional fabrication of removable partial dentures (RPDs) is a complex, error-prone, time-consuming, and expensive process. The use of computer-aided design and computer-aided manufacturing (CAD-CAM) techniques, especially rapid prototyping, promises a more effective method for fabricating RPD frameworks.

Removable partial denture design: a study of a selected population in Saudi Arabia

Determination of the incidence of various classes of removable partial dentures (RPDs) including their designs and their comparison with previous studies provide clinically useful information for dental training and continuing education. The purpose of this study is to determine the pattern of partial edentulism, the major connector, clasping, and design of 740 cobalt chromium RPD frameworks constructed for a selected population in Saudi Arabia. RPD framework design information and patient personal data were obtained from the work authorization form and the dental records respectively. The relationship among age, sex, nationality, and various Kennedy classes of the RPDs was determined by chi-square statistical analysis. Results indicate that Kennedy Class III removable partial dentures were the most frequently constructed. Although gender had no significant relationship, age and nationality had statistically significant relationship with the distribution of various Kennedy classes of removable partial dentures. Lingual bars and anterior posterior palatal straps were the most commonly used mandibular and maxillary major connectors. Lingual and palatal plates, however, were more frequently used than any major connectors for distal extension RPDs. Comparison with previous findings confirms the established variation in designing RPDs. The distribution of partially edentulousness revealed the influence of the general pattern of tooth loss, which could be modified by patient's demands and socio-economic status. Practitioners need to avail themselves fully of basic RPD design principles concerning the most commonly encountered classes of RPDs.     

两种附着体式覆盖义齿的制作及临床使用

介绍了根帽式附着体和杆式附着体用于增加覆盖义齿固位的制作方法，经两年多的临床应用表明：使用这两种附着体能显著地改善义齿的固位，提高患者的咀嚼功能，并且制作简单、成本低，便于在我国推广和应用。     

基牙数目对附着体式义齿基牙位移的影响

目的：探讨基牙数目对下颌单侧游离端MK-1附着体式义齿基牙位移的影响。方法：选用单基牙、双基牙和三基牙支持的MK-1附着体制作下颌单侧游离端MK-1附着体式义齿,在义齿侧上下牙列间放置食物片,咬合时用LB-72型高精度半导体激光位移测量仪,测量并计算出基牙在不同方向的位移量,并用随机方差分析法进行统计学分析。结果：单基牙组的近远中向、颊舌向、垂直向的位移、倾斜、扭转均大于双基牙组,差别有统计学意义（P〈0.05）。双基牙组的近远中向的位移大于三基牙组,差别有统计学意义（P〈0.05）,其余差别没有统计学意义（P〉0.05）。结论：单侧游离端MK-1附着体式义齿不宜设计单基牙,宜设计双基牙,如双基牙条件不理想时,可增加第三基牙。     

A Technique for Retrofitting a Metal Ceramic Crown to an Attachment‐Retained Removable Partial Denture: A Clinical Report

In dental applications, precision attachments have been used to retain removable partial dentures (RPDs) for several decades. Various types of extracoronal attachments are commonly used in combination with fixed partial dentures and RPDs to achieve retention and stability. Fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention are common reasons for a failed attachment‐retained RPD. Another complication of metal ceramic crowns with precision attachment is decementation of the crowns. When fixed components of the attachment‐retained RPD fail, the traditional treatment approach requires remaking both the fixed and removable components of the attachment‐retained RPD. This technique describes retrofitting of a metal ceramic crown to a resilient attachment‐retained RPD.     

A technique for fabrication of an extracoronal attachment-retained removable partial denture to fit an existing fixed partial denture

Precision attachments have been used for many years to retain removable partial dentures (RPDs). Common reasons for a failed attachment-retained RPD are fracture of the framework, fracture of the roots or teeth, and irretrievable decrease of retention. When an RPD framework major connector has been fractured, it should be remade. This article describes a technique to remake a fractured mandibular RPD using cast round profile attachment analogs without the need for replacement of the fixed partial denture.     

无基托可摘局部义齿的临床应用

作者选择了４１例牙列缺损患者，为其设计并制作成无基托的可摘局部义齿，对其中的２９例作了追踪观察，效果良好。本文就无基托的ＲＰＤＳ的适应证，设计原则及患者的修复效果等方面进行了讨论。     

An evaluation of the effects of two distal extension removable partial denture designs on tooth stabilization and periodontal health

A 30-month follow-up study was conducted on 36 patients to evaluate the effects of the lingual plate as a major connector in distally extended removable partial dentures (RPDs) on tooth stabilization. At the same time, the study evaluated the effects of lingual plate-type RPDs and lingual bar-type RPDs on periodontal health. The most striking finding of the study was that, with the exception of gingival recession (GR), periodontal conditions improved with both types of RPDs. At the end of 30 months, there were significant differences in plaque index, GR and tooth mobility (TM) values between treatment groups (P < 0.05). Plaque accumulation was greater in the lingual plate treatment group; however, this did not result in periodontal breakdown. There were no statistically significant differences between treatment groups with respect to pocket depth, gingival index or attachment loss (P > 0.05). Moreover, patients treated with lingual plate-type RPDs demonstrated less TM when compared with patients treated with lingual bar-type RPDs at the end of 30 months follow-up. Overall study findings established that with adequate checks on oral and denture hygiene at regular intervals, patients with RPDs may even experience improved periodontal health. Moreover, the clinical interpretation of decreased TM observed in patients treated with lingual plate-type RPDs may be questionable as the plaque accumulation was greater in the lingual plate treatment group inspite of periodic recalls.     

Bending properties of strengthened Ti-6Al-7Nb alloy major connectors compared to Co-Cr alloy major connectors

STATEMENT OF PROBLEM: Although Ti-6Al-7Nb alloy has several excellent mechanical properties, its poor rigidity has limited its clinical use as a material for the fabrication of a removable partial denture (RPD) major connector. PURPOSE: The purpose of this study was to develop and evaluate strengthening designs of Ti-6Al-7Nb RPD major connectors in an effort to increase rigidity. MATERIAL AND METHODS: Four strengthening designs of Ti-6Al-7Nb alloy major connectors were developed using finite element analysis modeling: wide, thick, thick at the middle, and thick at the anterior and posterior borders. The designs had similar rigidity values to a conventional Co-Cr alloy major connector, as measured by the maximum deformation when a simulated load was applied. Next, 30 Kennedy Class II maxillary RPD specimens, using 6 different major connector designs (n = 5), were fabricated. These 6 designs included Ti-6Al-7Nb alloy RPDs with 4 different strengthening designs, a Ti-6Al-7Nb alloy RPD without strengthening designs, and a conventional Co-Cr alloy RPD as a control. The rigidity of the RPDs was evaluated by measuring strains on the major connector and force on the intaglio surface of a denture base under a 30 N loading condition. The data obtained from the 6 different RPD designs were compared using a repeated measures analysis of variance and the Bonferroni correction (alpha=.05). RESULTS: The strains on the major connectors and the force on the denture bases measured from the Ti-6Al-7Nb RPD without strengthening designs were significantly larger than those of the standard Co-Cr alloy RPD. The strains measured from the 4 strengthening designs were not significantly larger than those of the Co-Cr alloy RPD. CONCLUSION: The results suggest that the strengthening designs tested may improve the rigidity of the Ti-6Al-7Nb alloy major connectors and, hence, may promote clinical application for RPDs.     

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.     

Laboratory considerations in rotational path removable partial dentures

Clinical indications and contraindications have been well covered in the literature for rotational path removable partial dentures (RPDs). However, only minimal coverage has been devoted to problems encountered that may prevent the proper fabrication of these restorations by dental technicians. The purpose of this article is to illustrate 2 problems that dental technicians occasionally encounter that make the fabrication of rotational path RPDs difficult or impossible. Design modifications by the clinician can eliminate 2 problems faced by technicians fabricating rotational path RPDs.     

Quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures in general dental practice in England,Ireland and Wales in 2009

Summary The aim of this study was to investigate the quality of communication and master impressions for the fabrication of cobalt chromium removable partial dentures (RPDs) in general dental practice in England, Ireland and Wales in 2009. Two hundred and ten questionnaires were distributed to 21 laboratories throughout England, Ireland and Wales. Information was collected regarding the quality of written communication and selection of master impression techniques for cobalt chromium partial dentures in general dental practice. One hundred and forty‐four questionnaires were returned (response rate = 68%). Alginate was the most popular impression material being used in 58% of cases (n = 84), while plastic stock trays were the most popular impression tray, being used in 31% of cases (n = 44). Twenty‐four per cent (n = 35) of impressions were not adequately disinfected. Opposing casts were provided in 81% of cases (n = 116). Written instructions were described as being ‘clear’ in 31% of cases (n = 44). In 54% of cases (n = 76), the technician was asked to design the RPD. Based on the findings of this study, written communication for cobalt chromium RPDs by general dental practitioners is inadequate. This finding is in breach of relevant contemporary legal and ethical guidance. There are also concerns in relation to the fabrication process for this form of prosthesis, particularly, in relation to consideration of occlusal schemes.     

An 8-year follow-up of removable partial denture treatment performed by the Public Dental Health Service in a Swedish county

The aim of the present study was to evaluate clasp-retained removable partial dentures (RPDs) made in the Public Dental Health Service (PDHS) in Orebro County in 1989. Records from all 25 PDHS clinics concerning RPDs from 1989 were collected after eight years and available information was registered. The entire material consisted of 447 RPDs (both attachment-retained and clasp-retained RPDs) in 387 patients. Of the 316 clasp-retained RPDs that were traceable, 208 were followed from 1989 to 1997. In most instances, information on diagnoses, alternative treatments and design of the RPDs was lacking. One hundred and thirty-two (42%) of the 316 clasp-retained RPDs were judged to still be in use in 1997 while 75 were not in use. The main reason for ceased use was dislike by the patient. There were 108 clasp-retained RPDs that were not possible to follow from 1989 to 1997 because there were no notes regarding follow-ups in the records. The most common technical complications noted in the records during the observation period were clasp fractures and loosened artificial teeth.