• The Journal of Advanced Prosthodontics
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• v.13 no.5
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• pp.304-315
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• 2021

PURPOSE. Esthetic expectations have increased the use of polyetheretherketone (PEEK) clasps as alternatives to Cr-Co in removable partial dentures (RPDs). The objective of this study was to evaluate the retentive force and dimensional change of clasps with different thickness and undercut made from PEEK by the thermo-mechanical fatigue. MATERIALS AND METHODS. PEEK clasps (N = 48) with thicknesses of 1 or 1.50 mm and 48 premolar monolithic zirconia crowns with undercuts of 0.25 mm or 0.50 mm were fabricated. Samples are divided into four groups (C1-C4) and were subjected to 7200 thermal aging cycles (at 5 - 55℃). The changes in the retentive force and dimensions of the clasps were measured by micro-stress testing and micro-CT devices from five measurement points (M1 - M5). One-way ANOVA, paired t-test, two-way repeated ANOVA, and post-hoc tests were used to analyze the data (P < .05). RESULTS. The retentive forces of C1, C2, C3, and C4 groups in initial and final test were found to be 4.389-3.388 N, 4.67 - 3.396 N, 5.161 - 4.096 N, 5.459 - 4.141 N, respectively. The effects of retentive force of all PEEK clasps groups were significant decreased. Thermo-mechanical cycles caused significant dimensional changes at points with M2, M4, and M5, and abraded the clasp corners and increased the distance between the ends of the clasp, resulting in reduced retentive forces (P^* = .016, P^* = .042, P < .001, respectively). CONCLUSION. Thermo-mechanical aging decreases the retentive forces in PEEK clasps. Increasing the thickness and undercut amount of clasps decreases the amount of dimensional change. The values measured after aging are within the clinically acceptable limits.

• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.235-248
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• 1994

There were many studies that distribute the partial edentulous states and examine the removable partial denture designs in the planning of removable partial denture treatment. This study was performed in the point of removable partial denture prescription to evaluate partial edentulism and its removable partial denture designs. The data was collected from the dental laboratory of each three dental colleges in Seoul and from two dental laboratories only for removable partial dentures as a prescription form. A total of 1411 cases with prescription form collected from dental laboratories were distributed for this study, then 788 cases were selected for this study. The case selection was done according to the contents of prescription form. The selected cases were divided into maxillary arch and mandibular and classified in terms of types of major connector and direct retainer, unbroken anterior teeth, Kennedy classification, the number of remaining teeth, and distribution of age and sex. The analyzed results were as follows : 1. The Kennedy classification I showed highest frequency both in maxilla and mandible. 2. The arch distribution of removable partial denture was 50.08% for maxilla and 49.92% for mandible. 3. The highest frequency in the distribution of direct retainer was the RPA clasp design. 4. The frequency of unbroken anterior 6 was 73.36% for maxilla and 82.30% for mandible. 5. The design of broad palatal strap and lingual bar revealed the highest prevalence in the major connector construction. 6. The mean number of remaining teeth per arch was 8.25 for maxilla and 8.37 for mandible. 7. The mean age of the patients supplied with removable partial denture was 52.25 years for men, 51.68 years for women, 52.11 years for maxilla, and 51.76 years for mandible and women showed more prevalence.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.3
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• pp.189-193
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• 2010

Purpose: This study was aimed to investigate the frequency of different classes of partial edentulism and the most frequently used design components of conventional removable partial dentures. Materials and methods: 63 patients who were treated with removable partial denture in Kyungpook National University hospital for 2003-2006 were selected. A total of 76 removable partial denture frameworks were investigated. Kennedy classification was used to identify the class of partial edentulism. Results: Results indicated that Kennedy class I removable partial dentures were the most frequently constructed. Most patients' cases were designed without modification areas. Conclusion: The most common type of direct retainer were the RPI clasp and RPA clasp in both maxilla and mandible. Lingual bar, linguoplate and anterior posterior palatal straps were the more frequently used mandibular and maxillary major connectors respectively. We did not have any case about Kennedy class IV patients.

• The Journal of Korean Academy of Prosthodontics
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• v.19 no.1
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• pp.7-16
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• 1981

The technology of precision attachments has developed at such a pace that from a very few T-shaped attachments and bar attachments from the years 1915 to 1935 since removable bridge utilizing a T-shaped intracoronal attachment was constructed by Dr. Herman E.S. Chayes in 1906. There are now more than 120 models of the most diversified designs, ready made or laboratory fashioned. In 1971, 126 attachments were listed and classified by Mensor in his E M Attachment Selector. This selector consists of five charts giving specifications as to type, vertical dimensions, application, type of resilience, size of movement, type of retention and type of material and alloy. Thus the E M Attachment Selector is a useful guide for dentists to choose the attachment for his patients. But dentists should apply the attachment in each patient's case according to an accurate diagnosis and treatment plan. This paper is a case report of removable partial dentures utilizing CSP, PD and Bar attachment on a patient who needed full mouth reconstruction. Patient has right first, second molar and left first molar on the upper arch and also left first molar, first premolar and right canine on the lower arch. (Fig. 5)All remaining teeth are relatively healthy in their supporting tissues. On upper arch, ring shape CSP attachment was designed on left first molar and modified ring shape CSP attachment was designed on right first and second molar as the direct retainer of the removable partial denture. Full palatal coverage was used as the major connector in this case. (Fig. 23) On lower arch, author first splinted with a fixed bridge between left first molar and second premolar and a splint bar between left second premolar and right canine. (Fig. 11) A lower removable partial denture in which was designed with an Aker clasp on the left first molar and a PD attachment on .the right canine was constructed. (Fig. 17) This denture could get additional support from anterior splint bar. After both removable partial dentures were delivered to the patient (Fig. 26), author evaluated function of the dentures and supporting structures of the abutment teeth by means of clinical and X-ray examinations for eighteen months. According to the examination data author came to the conclusion that the prognosis of this case was excellent.