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The Journal of Prosthetic Dentistry Nov 2023A 55-year-old man wearing maxillary and mandibular clasp-retained removable partial dentures (RPDs) sought improvement in retention, support, mastication efficiency, and...
A 55-year-old man wearing maxillary and mandibular clasp-retained removable partial dentures (RPDs) sought improvement in retention, support, mastication efficiency, and esthetics. Three prosthodontic treatment options were provided to the patient, who selected maxillary and mandibular conical crown-retained removable partial dentures (CCRPDs) without strategic implants. Oral health-related quality of life (OHRQoL) and satisfaction of the patient were evaluated before treatment and 2 weeks and 1 year after inserting the CCRPDs. The patient reported better retention, support, stability, mastication efficiency, esthetics, and an improved OHRQoL after CCRPD placement than before treatment. These improvements were maintained after 1 year.
PubMed: 37953210
DOI: 10.1016/j.prosdent.2023.09.041 -
The Journal of Prosthetic Dentistry Oct 2023The properties of commercially pure titanium are better than those of cobalt chromium alloys in various ways. However, casting pure titanium is challenging because of...
STATEMENT OF PROBLEM
The properties of commercially pure titanium are better than those of cobalt chromium alloys in various ways. However, casting pure titanium is challenging because of its high melting point and chemical reactivity. Because of excellent mechanical strength, a titanium alloy, Ti-6Al-4V, has been commonly adopted, but the aluminum and vanadium ions released may be cytotoxic.
PURPOSE
The purpose of the present study was to evaluate a new titanium alloy, Ti-7.5Mo, developed by the National Cheng Kung University for casting removable denture frameworks. The casting success rate, porosity, and guide plane or rest fit were compared among frameworks cast with Ti-7.5Mo alloy and pure titanium for 3 types of edentulism.
MATERIAL AND METHODS
Ti-7.5Mo alloy and pure titanium were used to cast frameworks for Kennedy Class I and II and completely edentulous conditions, with 5 frameworks for each condition. Wax patterns of the frameworks were designed and fabricated by using computer-aided design and computer-aided manufacture (CAD-CAM) technology to ensure their geometrical consistency. They were then invested with aluminum oxide-based material and cast. The castings were examined with microcomputed tomography (μCT) for porosity, and fit was evaluated from the thickness of a vinyl polyether silicone material at the guide plane or the rest by using an optical microscope. The casting was determined to be successful if the frameworks were complete. The porosity and fit were statistically evaluated by using 2-way ANOVA (α=.05).
RESULTS
Using pure titanium, the casting success rate was 80%, with only 64% of the major connectors in the deficient castings being complete. The μCT images showed that the percentage of casting defects in Ti-7.5Mo castings was one-third of the pure titanium castings. Furthermore, internal voids were detected in the clasps of the pure titanium castings, while the Ti-7.5Mo castings had few defects in the minor connectors and no radiographically detectable defects in the clasps. The fit analysis demonstrated smaller gaps over both guide planes and rests in the Ti-7.5Mo castings.
CONCLUSIONS
Ti-7.5Mo alloy had better castability than pure titanium. Based on the results, Ti-7.5Mo alloy is suitable for dental casting and may provide better performance.
PubMed: 34920871
DOI: 10.1016/j.prosdent.2021.10.014 -
The Journal of Prosthetic Dentistry Feb 2024Conventional removable partial dentures with metal clasps are still a common option for patients with distal-extension tooth loss. However, unilateral nonmetal clasp... (Randomized Controlled Trial)
Randomized Controlled Trial
Oral health-related quality of life of conventional removable partial dentures, unilateral nonmetal clasp dentures, and shortened dental arch with 2- or 3-tooth unilateral distal extension tooth loss in the mandible: A randomized, crossover, clinical trial.
STATEMENT OF PROBLEM
Conventional removable partial dentures with metal clasps are still a common option for patients with distal-extension tooth loss. However, unilateral nonmetal clasp dentures fabricated by using a thermoplastic denture base resin are increasingly being used. Furthermore, the shortened dental arch concept remains controversial, in spite of being advocated for many years. Nevertheless, these treatment options remain controversial, particularly in patients with the loss of a few distal teeth unilaterally.
PURPOSE
The purpose of this randomized, crossover, clinical trial was to investigate the oral health-related quality of life of participants who requested a new dental prosthesis (unilateral nonmetal clasp dentures or conventional removable partial dentures) at a private practice.
MATERIAL AND METHODS
A 3-period, randomized, crossover design was used in a within-subject, controlled, clinical trial. Twenty-four participants (mean age 59.0 years [7 men: 62.6 {45-85} years; 17 women: 57.5 {24-75} years]) were enrolled. All experimental procedures were approved by the Ethics Committee of Nagasaki University Hospital (#15022313) and registered in the International Standard Randomized Controlled Trial Number registry (ISRCTN49105064). All participants were fully dentate in the maxilla and had unilateral distal-extension loss of 2 or 3 teeth in the mandible. Participants were allocated to 1 of 6 groups and treated with prescribed options in accordance with their allocated sequences and used a dental prosthesis or nothing for 2-week periods. At the end of each intervention, the participants were asked to answer the Oral Health Impact Profile questionnaire. Differences in Oral Health Impact Profile scores among groups were estimated with a mixed-effects model (α=.05).
RESULTS
Total Oral Health Impact Profile scores were higher for unilateral nonmetal clasp dentures (P=.002) and shortened dental arch (P=.049) than for conventional removable partial dentures, with medium and small effects. The unilateral nonmetal clasp dentures had a similar effect compared with shortened dental arch (P>.05). unilateral nonmetal clasp dentures (P=.011) and shortened dental arch (P=.005) demonstrated medium effects in the oral function dimension compared with conventional removable partial dentures. Unilateral nonmetal clasp dentures exhibited large and medium effects in the orofacial appearance dimension compared with conventional removable partial dentures (P=.001) and shortened dental arch (P=.006). In the orofacial pain dimension, shortened dental arch showed effects similar to those of conventional removable partial dentures and unilateral nonmetal clasp dentures (P>.05), and no significant differences were observed in the psychosocial impact dimension (P>.05), but the unilateral nonmetal clasp denture score was lower than the conventional removable partial denture score, with a small effect. Men had significantly lower total Oral Health Impact Profile scores for shortened dental arch than women (P=.033).
CONCLUSIONS
Unilateral nonmetal clasp dentures and shortened dental arch were better than conventional removable partial dentures for the oral health-related quality of life of individuals with unilateral distal-extension tooth loss in the mandible, and sex had a significant effect on removable prosthetic planning.
Topics: Aged; Aged, 80 and over; Female; Humans; Male; Middle Aged; Cross-Over Studies; Dental Arch; Dental Clasps; Denture Design; Denture, Partial, Removable; Mandible; Quality of Life; Tooth Loss; Young Adult; Adult
PubMed: 35697550
DOI: 10.1016/j.prosdent.2021.07.014 -
Journal of Prosthodontic Research Feb 2024The processes and methods of treating and polishing additive-manufactured (AMed) cobalt-chromium (Co-Cr) alloy clasps were assessed in vitro to determine their...
PURPOSE
The processes and methods of treating and polishing additive-manufactured (AMed) cobalt-chromium (Co-Cr) alloy clasps were assessed in vitro to determine their suitability for constant clinical use and the reduction of dental technician work.
METHODS
AMed Aker clasps were fabricated by selective laser sintering of approximately 50 μm Co-Cr alloy powders. After the nodules and fins on the inner surface of the AMed clasps were removed and morphological correction was performed, a dental technician manually polished the clasps as a control. Four surface treatments, barrel finishing, shot peening, and wet and dry electropolishing, were performed to obtain smooth surfaces. In addition, hybrid manufacturing, which integrates repeated laser sintering and high-speed milling for one-process molding, was added to this study. After observing the treated surfaces using SEM and Hybrid Laser Microscope (HLM) the surface roughness, fitness accuracy, and retentive forces of the treated AMed clasps were measured, and their polishing efficiencies were compared.
RESULTS
Similar to manual polishing, dry electropolishing yielded the smoothest surfaces in all treatments. The fitness accuracy of all clasp regions and treatment methods ranged from 80 to 140 μm, without significant differences among the treatment methods. All treated clasps showed acceptable retentive forces for clinical use, and hybrid manufacturing and wet electropolishing showed significantly higher forces.
CONCLUSIONS
AMed Co-Cr clasps with all surface treatments could be clinically used if additional slight manual polishing was performed; however, each processing condition should be carefully selected.
PubMed: 38417870
DOI: 10.2186/jpr.JPR_D_23_00258 -
The Saudi Dental Journal Jun 2024This in vitro study aimed to evaluate the additive manufacturing (AM) of cobalt chromium Co-Cr and titanium Ti alloy clasps for clinical use. After scanning the Ni-Cr...
This in vitro study aimed to evaluate the additive manufacturing (AM) of cobalt chromium Co-Cr and titanium Ti alloy clasps for clinical use. After scanning the Ni-Cr die of the first molar, Akers' clasps were designed using computer-aided design/ computer-aided manufacturing (CAD/CAM). The clasps were manufactured from Co-Cr-W dental alloy and Ti-6Al-4V alloy powder using AM machines. Then, they were divided into two groups. The initial retentive force of the clasps was measured using a universal testing machine. Cyclic loading of the clasps was carried out by a specially designed insertion-removal testing apparatus in wet condition up to 5000 cycles. Retentive force was measured at 1000, 2000, 3000, 4000, and 5000 cycles. Moreover, the intaglio surface of each clasp was scanned using the scanner; and superimposition between the pre- and post-cycling clasp files was performed to evaluate deformation after cyclic loading. The fitting surfaces of retentive clasp tips were examined with a scanning electron microscope (SEM). Finally, it has been found that the initial retentive force for the Co-Cr group was 10.81 ± 0.37 N, and for the Ti group was 5.41 ± 0.18 N. Additionally, during the testing periods, both Co-Cr and Ti clasps continued to lose retentive force within the cycles of placement and removal. This effect was more prominent in the Co-Cr than in the Ti clasps. The distances between pre- and post-cycling in the retentive arm were -0.290 ± 0.11 mm and -0.004 ± 0.01 mm in Co-Cr and Ti alloys, respectively, and in the reciprocal arm were -0.072 ± 0.04 mm and -0.032 ± 0.04 mm in Co-Cr and Ti alloys, respectively. The retentive force required to remove the Ti clasps was found to be significantly lower than those required to dislodge the Co-Cr clasps. Co-Cr and Ti clasps lost significant amounts of retentive force from the initial use to the 3.5-year periods of simulated clinical use.
PubMed: 38883903
DOI: 10.1016/j.sdentj.2024.04.001 -
Journal of Dentistry Nov 2023To examine the effect of novel prefabricated auxiliary devices with different geometric features called Scan Body Clasp (SBC) at different levels on the accuracy of...
OBJECTIVES
To examine the effect of novel prefabricated auxiliary devices with different geometric features called Scan Body Clasp (SBC) at different levels on the accuracy of intraoral scanning of complete-arch with multiple implants.
METHODS
An edentulous maxilla 4-implant model and SBCs with different geometric features (flat or curved) were fabricated by a 3D printer (AccuFab-C1s, 3DShining, Hangzhou, China). Test scans were performed using an intraoral scanner (Aoralscan 3, 3DShining, Hangzhou, China) software version 1.0.0.3104 under different scenarios: group A (CO), without any SBCs; group B&C (LC&HC), with curved SBCs adjacent to and away from the mucosa; group D&E (LF&HF), with flat SBCs adjacent to and away from the mucosa. 20 scans were done for each group (CO, LC, HC, LF and HF). Reference Scans were obtained by digitizing the model in group A using a dental laboratory scanner (D2000, 3Shape, Copenhagen, Denmark). The related files were imported into inspection software for trueness and precision assessment. Statistical analysis was performed with One-way ANOVA, Independent-Sample T test for trueness values. Kruskal-Wallis test and Mann-Whitney test were used to assess the precision values. The level of significance was set at α=0.05.
RESULTS
Groups with SBCs demonstrated trueness enhancement, among which LF revealed the best trueness. Significant differences were also found between LF and HC (p < .01), LF and HF (p < .001), LC and HF (p < .01). LF and HF showed precision enhancement. The best precision was LF, which was found to be more precise than LC (p < .001) and HC (p < .001). HF was more precise than LC (p < .001) and HC (p < .001).
CONCLUSIONS
Attaching the scan bodies with SBCs at different levels significantly influenced the scanning accuracy. The SBCs near the mucosa result in superior trueness, while the flat morphology benefits the precision.
CLINICAL SIGNIFICANCE
The results demonstrated the feasibility of the SBCs in enhancing intraoral complete-arch implant scanning accuracy. Among the configurations tested in the present study, low-level and flat surfaces of the artificial landmarks may be the potential pivotal elements to optimizing long-span scanning accuracy.
Topics: Humans; Imaging, Three-Dimensional; Dental Impression Technique; Models, Dental; Computer-Aided Design; Mouth, Edentulous
PubMed: 37714453
DOI: 10.1016/j.jdent.2023.104702 -
Journal of the Mechanical Behavior of... Jun 2024Polyetheretherketone (PEEK) is considered as an alternative to metal material for removable partial denture (RPD). However, the retentive force is not strong as a metal...
PURPOSE
Polyetheretherketone (PEEK) is considered as an alternative to metal material for removable partial denture (RPD). However, the retentive force is not strong as a metal RPD. This study investigated the retention and fatigue performance of PEEK clasps with different proportions of clasp arm engaging the undercut to verify a new strategy to improve their clinical performance.
METHODS
Three groups (n = 10/group) of PEEK clasps with their terminal 1/3, 2/3 and the whole of retentive arms engaging the undercut were fabricated along with a group (n = 10) of conventional cobalt-chrome (CoCr) clasps as control group. Retentive forces were measured by universal testing machine initially and at an interval of 1500 cycles for a total of 15,000 fatigue cycles. The fatigue cycles were conducted by repeated insertion and removal of the clasp using fatigue testing machine. Each clasp was scanned by Trios3 scanner before and after fatigue test to obtain digital models. The deformation of the clasp was evaluated by root mean square (RMS) through aligning the two models in Geomagic wrap (2021). Scanning electron microscopy (SEM) and finite element analysis were carried out to observe the abrasion and the von Mises stress of the clasp arm. Kruskal-Wallis H test was used to compare the retentive forces and the RMSs of the studied groups followed by Bonferroni multiple comparisons.
RESULTS
The whole of PEEK clasp arm engaging the undercut provided higher mean retentive forces (7.99 ± 2.02 N) than other PEEK clasp groups (P < 0.001) and was closer to CoCr clasps (11.88 ± 2.05 N). The RMSs of PEEK clasps were lower than CoCr clasps (P < 0.05) while the differences among PEEK clasps were of no statistical significance (P > 0.05). SEM showed that evidences of surface abrasion were observed on the section that engaged the undercut for all groups of clasps. The stress concentration mainly occurred on the initial part of the retentive arm. The maximum von Mises stress of each group was below the compressive strength of PEEK.
CONCLUSIONS
Proportions of PEEK clasp arm engaging the undercut positively influenced the retentive force and the fatigue resistance of PEEK clasps was superior than CoCr clasps. It is a feasible method to improve the retention of PEEK clasps by increasing the proportion of clasp arm engaging the undercut. Clinical trials are needed to further verify this innovation.
Topics: Denture Retention; Polyethylene Glycols; Polymers; Ketones; Chromium Alloys; Denture, Partial, Removable; Dental Stress Analysis; Dental Clasps; Benzophenones
PubMed: 38598917
DOI: 10.1016/j.jmbbm.2024.106539 -
Journal of Prosthodontic Research Oct 2023Although digital removable partial dentures have been previously described, there have been no reports on how to fabricate them in one piece. This study proposes a new...
PURPOSE
Although digital removable partial dentures have been previously described, there have been no reports on how to fabricate them in one piece. This study proposes a new method for fabricating patient-specific digital removable partial dentures using a custom plate.
METHODS
First, a gypsum model was scanned using a laboratory scanner and a removable partial denture was designed using computer-aided design (CAD) software based on standard tessellation language data. The metal clasp was fabricated from Ti-6Al-4V using a 3D printer. For custom plate fabrication, a resin plate frame was designed using computer-aided design (CAD) software and fabricated using a 3D printer. An artificial tooth and metal clasp were fixed on the base surface of the frame, an auto-polymerizing resin was poured into the frame for the denture base, and the artificial tooth and metal clasp were packed to form a custom plate. The plate was cut using a milling machine. Subsequently, the support attached to the denture was removed and polished for complete fabrication of the denture.
CONCLUSIONS
Our novel removable partial denture fabrication method is more efficient than the conventional method. The obtained removable partial dentures demonstrated satisfactory accuracy.
PubMed: 36725080
DOI: 10.2186/jpr.JPR_D_22_00100 -
BMC Oral Health Sep 2023Digital technologies have recently been introduced into the fabrication of removable partial dentures (RPDs). However, it is still unclear whether the digitally... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Digital technologies have recently been introduced into the fabrication of removable partial dentures (RPDs). However, it is still unclear whether the digitally fabricated RPDs fit better than conventionally cast ones in the rest region. The aim of this study was to evaluate the fit accuracy in the rest region of RPDs fabricated by digital technologies and compare it to those made by conventional lost-wax (CLW) technique.
METHODS
A comprehensive search was conducted in Cochrane Library, PubMed, EMbase, Web of Science and SpringerLink. Studies published up to August 2022 were collected. Two authors analyzed the studies independently and assessed the risk of bias on the modified methodological index for non-randomized studies (MINORS) scale. The mean values of gap distance between rests and corresponding rest seats of each study were extracted as outcome. A random-effects model at a significance level of P < 0.05 was used in the global comparison and subgroup analysis was carried out.
RESULTS
Overall, 11 articles out of 1214 complied with the inclusion criteria and were selected, including 2 randomized controlled trials (RCTs), 1 non-randomized clinical trial and 8 in vitro studies. Quantitative data from Meta-analysis revealed that fit accuracy in the rest region of RPDs fabricated with CLW showed no statistically significant difference with digital techniques (SMD = 0.33, 95%CI (-0.18, 0.83), P = 0.21). Subgroup analysis revealed a significantly better fit accuracy of CLW-fabricated RPDs in the rest region than either additive manufacturing (AM) groups or indirect groups (P = 0.03, P = 0.00), in which wax or resin patterns are milled or printed before conventional casting. While milled RPDs fit significantly better than cast ones in the rest region (P = 0.00). With digital relief and heat treatment, hybrid manufactured (HM) clasps obtained better fit accuracy in the rest region (P < 0.05). In addition, finishing and polishing procedure had no significant influence in the fit accuracy in all groups (P = 0.83).
CONCLUSIONS
RPDs fabricated by digital technologies exhibit comparable fit accuracy in rest region with those made by CLW. Digital technologies may be a promising alternative to CLW for the fabrication of RPDs and additional studies are recommended to provide stronger evidence.
TRIAL REGISTRATION
CRD42020201313.
Topics: Humans; Denture, Partial, Removable; Digital Technology; Research Design; Rest; Dental Casting Technique
PubMed: 37715159
DOI: 10.1186/s12903-023-03348-6 -
The Journal of Prosthetic Dentistry Feb 2024The retentive force and deformation of milled polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) removable partial denture (RPD) frameworks are not well...
STATEMENT OF PROBLEM
The retentive force and deformation of milled polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) removable partial denture (RPD) frameworks are not well understood.
PURPOSE
The purpose of this in vitro study was to assess the retentive force and deformation of PEEK and PEKK Akers clasps with different designs and undercut depths.
MATERIAL AND METHODS
A master model containing the first and second molar abutments was used to design Akers clasps of different cross-sectional dimensions, undercut depths (0.5 and 0.75 mm), and materials. The components of the removable partial denture framework also included an occlusal rest and were manufactured using a milling machine (n=5). The fatigue resistance of the Akers clasps was measured before and after deformation regarding the retentive forces.
RESULTS
The PEEK2-U50 clasp had the largest retentive force with no significant difference among all groups before and after the insertion and removal cycle. In addition, the increased cross-sectional dimensions of the design resulted in significant differences in retentive forces between the PEEK1 and PEEK2 groups and between the PEEK and PEKK materials.
CONCLUSIONS
Increasing the clasp's cross-sectional dimensions significantly impacted retentive forces, especially between different PEEK groups and between PEEK and PEKK materials.
Topics: Chromium Alloys; Denture, Partial, Removable; Cross-Sectional Studies; Denture Retention; Polyethylene Glycols; Ketones; Dental Clasps; Benzophenones; Polymers
PubMed: 38057199
DOI: 10.1016/j.prosdent.2023.09.042