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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 -
Clinical Oral Investigations Dec 2022To investigate how different types of dental prosthesis perform in patients with head and neck tumors.
OBJECTIVES
To investigate how different types of dental prosthesis perform in patients with head and neck tumors.
MATERIALS AND METHODS
In this retrospective clinical cohort study, the impact of different patient-related factors was analyzed as influencing factors on the survival probability of dental prosthesis using Kaplan-Meier estimate. For analysis, the dental prosthesis was divided into groups: group 1 (fixed dental prosthesis), group 2 (removable dental prosthesis), group 3 (implant-supported dental prosthesis), and group 4 (prostheses anchored using wrought wire clasps and obturators). The incidental aftercare measures were also evaluated.
RESULTS
Two hundred seventy-nine restorations were observed (mean observation: 2.7 ± 3.0 years, max.14.8 years) out of which 49 (17.6%) had to be replaced during the observation. After 5 years, 100% of group 1 restorations, 79.9% of group 2 restorations, 91.4% of group 3 restorations, and 30% of group 4 restorations were still functional. Four hundred eighty-eight dental implants were observed, of which 77 (15.8%) failed.
CONCLUSIONS
Groups 1, 2, and 3 restorations showed good survival times after 5 years in function, whereas group 4 presented the worst survival times. Group 2 restorations showed the highest amount of necessary aftercare measures.
CLINICAL RELEVANCE
The current investigation shows that groups 1, 2, and 3 restorations should be preferred in the prosthetic treatment planning of patients with head and neck tumors. A treatment with group 4 restorations should only be considered if no other prosthetic treatment is possible or as temporary treatment.
Topics: Humans; Dental Prosthesis, Implant-Supported; Dental Restoration Failure; Dental Implants; Retrospective Studies; Cohort Studies; Head and Neck Neoplasms; Dental Prosthesis Design
PubMed: 35976496
DOI: 10.1007/s00784-022-04673-w -
Beijing Da Xue Xue Bao. Yi Xue Ban =... Feb 2022To compare the retentions of different designs of cobalt-chromium (Co-Cr), pure titanium (CP Ti), and titanium alloy (Ti-6Al-4V) removable partial denture (RPD)...
OBJECTIVE
To compare the retentions of different designs of cobalt-chromium (Co-Cr), pure titanium (CP Ti), and titanium alloy (Ti-6Al-4V) removable partial denture (RPD) circumferential clasps manufactured by selective laser melting (SLM) and to analyze the stress distribution of these clasps during the removal from abutment teeth.
METHODS
Clasps with clasp arm size A (1.9 mm width/1.1 mm thickness at the body and 0.8-taper) or B (1.2 times A) and 0.25 mm or 0.50 mm undercut engagement were modeled on a prepared first premolar die, named as designs A1, A2, A3, and A4, respectively. The density and elastic modulus of SLM-built Co-Cr, CP Ti, and Ti-6Al-4V were measured and given to different groups of clasps. The density, elastic modulus, and Poisson ' s ratio of enamel were given to the die. The control group was the cast Co-Cr clasp with design A1, to which the density and elastic modulus of cast Co-Cr alloy were given. The Poisson's ratio of all metals was 0.33. The initial 5 N dislodging force was applied, and the maximum displacement of the clasp along the insertion path was computed. The load was reapplied with an increment of 5 N than in the last simulation until the clasp was completely dislodged. The retentive force range of different groups of clasps was obtained. The retentive forces of the SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with equivalent computed retentive force range to the control group were validated through the insertion/removal experiment. The von Mises stress distributions of these three groups of SLM-built clasps under 15 N loads were analyzed.
RESULTS
SLM-built Co-Cr, CP Ti, and Ti-6Al-4V clasps with designs B1 or B2, and Co-Cr clasps with design A2 had higher retentive forces than those of the control group. SLM-built CP Ti and Ti-6Al-4V clasps with design A1 had lower retentive forces than those of the control group. SLM-built Co-Cr clasp with design A1 and SLM-built CP Ti and Ti-6Al-4V clasps with design A2 had equivalent retentive forces to those of the control group. The insertion/removal experiment showed that the measured retentive forces of these three groups of SLM-built clasps were (21.57±5.41) N, (19.75±4.47) N, and (19.32±2.04) N, respectively. No statistically significant measured retentive force difference was found among these three groups of SLM-built clasps (>0.05). The maximum von Mises stress of these three groups of SLM-built clasps exceeded their responding yield strength except for the Ti-6Al-4V one.
CONCLUSION
SLM-built Co-Cr circumferential clasps had higher retention than CP Ti and Ti-6Al-4V ones with the same clasp arm size and undercut engagement. The retention of SLM-built circumferential clasps could be adjusted by changing the undercut engagement and clasp arm size. If SLM-built circumferential clasps are used in clinical practice, the Ti-6Al-4V clasp with clasp arm size A and 0.50 mm undercut engagement is recommended considering the long-term use of RPD in the patient's mouth.
Topics: Chromium Alloys; Dental Clasps; Denture Retention; Denture, Partial, Removable; Finite Element Analysis; Humans; Lasers; Titanium
PubMed: 35165476
DOI: 10.19723/j.issn.1671-167X.2022.01.017 -
International Journal of Implant... Oct 2020Implant-supported removable partial dentures (ISRPDs) are an effective treatment for partially edentulous patients. ISRPDs improve patients' satisfaction and oral...
BACKGROUND
Implant-supported removable partial dentures (ISRPDs) are an effective treatment for partially edentulous patients. ISRPDs improve patients' satisfaction and oral function to a greater extent than RPDs by improving denture stability and enhancing support. However, the effect of a type of direct retainer on displacement of the abutment teeth and dentures in ISRPDs remains unclear. Therefore, we made a resin mandibular model of unilateral mandibular distal-extension partial edentulism for mechanical simulation and compared the dynamic behavior of the abutment teeth and the denture base among different tooth-borne retainers with various rigidities for RPDs and ISRPDs.
METHODS
A resin mandibular model for mechanical simulation that had unilateral mandibular distal-extension edentulism and was missing the first molar, second molar, first premolar, and second premolar, and a denture fabricated from the patient's computed tomography images were used. Three types of direct retainers with different connecting rigidities were evaluated. The vertical displacement of the denture base and buccal and lingual sides and the mesial displacement of the abutment teeth were measured.
RESULTS
Regardless of the rigidity of the direct retainers and loading positions, the displacement of the denture bases in the ISRPDs was significantly smaller than that in the RPDs (P < 0.001). There was no significant difference in vertical displacement of the denture bases among direct retainers with various connecting rigidities in the ISRPDs. Conversely, horizontal displacement of the abutment teeth in both the RPDs and ISRPDs tended to be larger with the cone crown telescope, which has high rigidity, than with the cast cingulum rest and wire clasp, which have much lower rigidities.
CONCLUSION
Our results suggested that cast cingulum rest and wire clasps as direct retainers are appropriate ISRPDs to minimize denture movement and suppress displacement of the remaining teeth in patients with unilateral mandibular distal-extension partial edentulism.
PubMed: 33089410
DOI: 10.1186/s40729-020-00260-4 -
European Journal of Dentistry Feb 2022The aim of the study was patients' satisfaction evaluation and radiographic evaluation of the terminal abutments of attachment-retained maxillary obturators with...
OBJECTIVE
The aim of the study was patients' satisfaction evaluation and radiographic evaluation of the terminal abutments of attachment-retained maxillary obturators with metal framework versus milled polyetheretherketone (PEEK) framework in the management of maxillectomy cases.
MATERIALS AND METHODS
Eighteen participants were randomly divided into three parallel groups ( = 6). Participants of the PEEK group received attachment-retained obturators with milled PEEK framework, the metal group received an attachment-retained obturator with a metallic framework, and the conventional group received conventional clasp-retained obturators with a metallic framework (Control group). The evaluation included was radiographic evaluation and patients' satisfaction in this study included two scales-"The Obturator Functioning Scale" and "The European Organization for Research and Treatment of Cancer Head and Neck 35" using one-way ANOVA test.
RESULTS
Both PEEK and metal groups showed a statistically significant lower mean bone loss ( <0.050) compared with the conventional group during all follow-up periods. There is no statistically significant difference between the PEEK and metal groups during all follow-up periods. Regarding patient satisfaction, both the PEEK and metal groups showed a statistically significant decrease score ( <0.050) compared with the conventional group in various aspects of patients' satisfaction scales as satisfaction with the look and difficulty of talking to the public, and noticeable clasps. In comparison, the PEEK group showed a statistically significant decrease score ( <0.050) than the metal group with respect to satisfaction with the look along all follow-up periods.
CONCLUSIONS
PEEK attachment-retained maxillary definitive obturators could be considered a promising treatment modality for patients with acquired maxillary defects with regard to esthetics and satisfaction.
PubMed: 34814222
DOI: 10.1055/s-0041-1731839 -
Clinical, Cosmetic and Investigational... 2021This clinical report describes a technique for fabricating a retrofit zirconia crown and clasp for an existing removable partial denture (RPD) using computer-aided...
This clinical report describes a technique for fabricating a retrofit zirconia crown and clasp for an existing removable partial denture (RPD) using computer-aided design and computer-aided manufacturing (CAD/CAM). A 58-year-old patient developed acute pulpitis of a tooth, and the RPD clasp was broken on the tooth. A pre-preparation scan was captured using an intraoral scanner. The existing RPD was placed in the mouth, and scans of the post-preparation, antagonist arch, and interocclusal record were made. A zirconia crown was designed by superimposing the pre-preparation scan and the post-preparation scan of the abutment tooth. The design data were transferred to a 5-axis milling machine, and the crown was milled from zirconia. The crown was luted using resin cement. An intraoral scan of the crown with RPD was taken, and the RPD was removed to re-scan the proximal guide plane of the crown. The I-bar clasp was designed, and the casting pattern was built using a 3D printer. The pattern was used to cast the clasp. The clasp was set using autopolymerizing acrylic resin to the RPD. The main advantages of this efficient process are that patients can use their RPDs during fabrication of the crown of the abutment tooth. The limitations of using this technique include the cost of the intraoral scanner and the education for the dental clinicians and technicians. In this clinical report, CAD/CAM technology prevented human error, required no adjustment, and uninterrupted use of the RPD for fabricating a retrofit zirconia crown and clasp for an existing RPD.
PubMed: 34675685
DOI: 10.2147/CCIDE.S332944 -
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 -
PloS One 2021Flipped classroom may overcome weaknesses of live demonstration in teaching orthodontic wire-bending. This study aims to compare the effectiveness between flipped...
Flipped classroom may overcome weaknesses of live demonstration in teaching orthodontic wire-bending. This study aims to compare the effectiveness between flipped classroom and live demonstration in transferring skills for fabricating Adams clasp. Forty third-year undergraduate dental students were assigned to two groups. The students in group LD (n = 20) attended a live demonstration while students in group FC (n = 20) attended a flipped classroom. Both groups were taught on skills to fabricate Adams clasp in a standardised way. Each student from both groups were asked to submit an Adams clasp for a blinded quality assessment by two trained and calibrated assessors using a 18-item rubric, followed by validated students' satisfaction questionnaires to evaluate their perceived satisfaction on the teaching method received. A crossover study was then conducted three weeks later where LD attended a flipped classroom while FC attended a live demonstration. Students' satisfaction questionnaires were again collected from each student for blinded analysis. Mean scores for the quality of Adams clasp were 9.775 and 9.125 for LD and FC, respectively. No significant difference was detected between the two groups. Statistically significant association was found for one statement on the questionnaire, "I found the classroom arrangements conducive for the wire-bending activity" (p = 0.010). No significant differences were found between the two groups for other statements (p > 0.05). In conclusion, within the limitations of the study, flipped classroom is equally effective as conventional live demonstration in transferring orthodontic wire-bending skills for fabrication of Adams clasp. However, students perceived the classroom arrangements during the flipped classroom significantly more conducive for teaching orthodontic wire-bending.
Topics: Cross-Over Studies; Female; Humans; Male; Orthodontic Wires; Problem-Based Learning; Surveys and Questionnaires
PubMed: 34243187
DOI: 10.1371/journal.pone.0254478 -
BMC Medical Education Jun 2021Wire-bending skills is commonly taught through live demonstrations (LD) though flipped classroom (FC) method has gained popularity. Continuous formative assessment...
BACKGROUND
Wire-bending skills is commonly taught through live demonstrations (LD) though flipped classroom (FC) method has gained popularity. Continuous formative assessment promotes personalised learning via closely monitored progress, with the identification of students' strengths and weaknesses. This study aims to evaluate the effects of LD and FC teaching methods, supplemented with continuous formative assessment, on dental students' learning of wire-bending skills for six types of removable orthodontic appliance components. A deeper understanding of the relative effectiveness between LD and FC teaching methods can help identify the most appropriate method to achieve student learning objectives, which is especially important given the current Covid-19 pandemic.
METHODS
Forty third-year undergraduate dental students were randomly assigned into FC (n = 20) or LD (n = 20) cohort. Each student attended six teaching sessions, each to teach students' competency in fabricating one type of wire component, for a total competency in fabricating six wire components over the course of six teaching sessions. Either LD or FC teaching methods were used. After each session, wire assignments had to be submitted. Wire assignments were then evaluated using a blinded wire-bending assessment protocol. As part of their formative assessment, the assessment results were distributed to students, lecturers, and technicians before the next session. After the first session (T0) and at the end of all six sessions (T1), students completed a self-reported questionnaire.
RESULTS
The mean wire-bending scores for FC were significantly higher than LD for two of the six assignments, namely the Adams clasp (p < 0.01) and Z-spring (p = 0.03). Scores for both LD and FC increased significantly over time, which may be attributed to formative assessment. There was no statistically significant correlation between wire-bending scores and video usage. Students were satisfied with both teaching methods, according to T0 and T1 questionnaires.
CONCLUSIONS
Both LD and FC are equally effective in transferring practical orthodontic wire-bending skills and well-received by students. Continuous formative assessment may have enhanced students' learning of orthodontic wire-bending skills. Further studies with control group are recommended to investigate the effect of formative assessment on teaching practical dental skills.
Topics: COVID-19; Educational Measurement; Humans; Orthodontic Wires; Pandemics; Problem-Based Learning; SARS-CoV-2; Students, Dental; Teaching
PubMed: 34098931
DOI: 10.1186/s12909-021-02717-5