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Journal of Prosthodontic Research Jan 2024This study aimed to investigate the retentive force and deformation of double Akers' polyetherketoneketone (PEKK) clasps on removable partial dentures (RPDs) with...
PURPOSE
This study aimed to investigate the retentive force and deformation of double Akers' polyetherketoneketone (PEKK) clasps on removable partial dentures (RPDs) with varying designs and undercut depths.
METHODS
Thirty double Akers' PEKK clasps with two different widths and heights (Groups I and II) were fabricated using computer-aided design and computer-aided manufacturing (CAD/CAM). Each design was further subdivided (n = 5) into three undercut depths (0.25, 0.50, and 0.75 mm). The retentive force of the clasps was measured after 10 years of clinical use (15,000 insertion/removal cycles), and the deformation of the clasp tips was analyzed before and after cycling.
RESULTS
Clasps with 0.50-mm and 0.75-mm undercut depths exhibited greater initial retentive forces (3.15-3.51 N) compared to those in the 0.25-mm undercut group (2.40-2.80 N). Group I maintained consistent retentive forces over the cycles (P = 0.345), whereas Group II showed declining forces after the initial use (P < 0.003). In both groups, the 0.50-mm undercut exhibited a greater retentive force than the 0.25-mm (P < 0.001 and P < 0.004, respectively), with no significant differences between the 0.50-mm and 0.75-mm undercut depths. Despite a lower initial retentive force, the 0.25-mm undercut showed less deformation and clasp tip wear.
CONCLUSIONS
The PEKK clasps did not exhibit significantly reduced retentive forces or permanent deformations after 15,000 fatigue cycles. These results suggest that the PEKK polymer displays superior mechanical properties as an esthetic clasp material, and clasps with 0.50-mm and 0.75-mm undercut depths are recommended for long-term clinical use.
PubMed: 38220161
DOI: 10.2186/jpr.JPR_D_23_00080 -
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 -
IEEE Journal of Biomedical and Health... Oct 2023The ever-growing aging population has led to an increasing need for removable partial dentures (RPDs) since they are typically the least expensive treatment options for...
The ever-growing aging population has led to an increasing need for removable partial dentures (RPDs) since they are typically the least expensive treatment options for partial edentulism. However, the digital design of RPDs remains challenging for dental technicians due to the variety of partially edentulous scenarios and complex combinations of denture components. To accelerate the design of RPDs, we propose a U-shape network incorporated with Transformer blocks to automatically generate RPD clasps, one of the most frequently used RPD components. Unlike existing dental restoration design algorithms, we introduce the voxel-based truncated signed distance field (TSDF) as an intermediate representation, which reduces the sensitivity of the network to resolution and contributes to more smooth reconstruction. Besides, a selective insertion scheme is proposed for solving the memory issue caused by Transformer blocks and enables the algorithm to work well in scenarios with insufficient data. We further design two weighted loss functions to filter out the noisy signals generated from the zero-gradient areas in TSDF. Ablation and comparison studies demonstrate that our algorithm outperforms state-of-the-art reconstruction methods by a large margin and can serve as an intelligent auxiliary in denture design.
Topics: Humans; Aged; Denture, Partial, Removable; Denture Design; Jaw, Edentulous, Partially
PubMed: 37471183
DOI: 10.1109/JBHI.2023.3295387 -
Journal of Functional Biomaterials Aug 2023To evaluate fit and retention of cobalt-chromium removable partial denture (RPD) frameworks fabricated with selective laser melting (SLM).
PURPOSE
To evaluate fit and retention of cobalt-chromium removable partial denture (RPD) frameworks fabricated with selective laser melting (SLM).
METHODS
Three types of framework for clasp-retained RPDs were virtually designed and fabricated using SLM (n = 30). For comparison, 30 additional frameworks were produced using conventional lost-wax casting. A biomechanical model was created, incorporating extracted teeth mounted on flexible metal posts. Using this model, horizontal constraint forces resulting from a misfit were measured using strain gauges, while vertical forces were not recorded. The constraint force components and resultant forces were determined for all abutment teeth, and the maximum retention force during RPD removal from the model was also assessed. For statistical evaluation, the two fabrication methods were analyzed by calculating the means and standard deviations.
RESULTS
The average horizontal constraint forces showed similar values for both fabrication methods (SLM: 3.5 ± 1.0 N, casting: 3.4 ± 1.6 N). The overall scatter of data for cast RPDs was greater compared to those fabricated using SLM, indicating a better reproducibility of the SLM process. With regard to retention, the intended retention force of 5-10 N per abutment tooth was not attained in one of the cast groups, while it was consistently achieved in all SLM groups.
CONCLUSIONS
This in vitro study found that SLM is a promising option for the manufacture of cobalt-chromium RPD frameworks in terms of fit and retention.
PubMed: 37623661
DOI: 10.3390/jfb14080416 -
Cureus Dec 2023Maxillectomy defects can lead to oroantral communication, causing difficulties with chewing, swallowing, speech, and facial appearance. Prosthodontists play a crucial...
Maxillectomy defects can lead to oroantral communication, causing difficulties with chewing, swallowing, speech, and facial appearance. Prosthodontists play a crucial role in rehabilitating such defects using obturators. This case report presents the fabrication of a definitive obturator with a cast metal framework for a patient who had an acquired maxillary defect and previously experienced issues with an ill-fitting obturator. In this clinical report, the patient's canine teeth on both sides and the premolars and molars on the left side were used for rest placement. Retention was achieved by utilizing the remaining teeth, employing two embrasure Aker clasps on the left molars and premolars and a C-wrought wire clasp on the right canine. A complete palate was designed as the major connector to ensure optimal load distribution to the surrounding tissues. Additionally, an indirect retainer was planned for the right canine. This definitive prosthesis rehabilitated the patient, improving masticatory efficiency, enhancing speech clarity, and improving quality of life.
PubMed: 38222126
DOI: 10.7759/cureus.50578 -
Clinical Oral Investigations Apr 2024The primary objective of the present retrospective clinical study was to determine the survival time of obturators while analyzing possible influencing factors.
OBJECTIVES
The primary objective of the present retrospective clinical study was to determine the survival time of obturators while analyzing possible influencing factors.
MATERIALS AND METHODS
This retrospective clinical cohort study analyzed the influence of various clinical factors on the survival probability of obturators and their follow-up outcomes using Kaplan‒Meier analysis.
RESULTS
A total of 76 patients with 115 obturators were included in the study (47 men and 29 women, mean age 58.1 ± 18.1 years). The mean observation time was 3.0 ± 4.5 years (maximum 26.3 years). A total of 40.9% (47) of all obturators observed had to be replaced. The survival rate after 5 years was 79.5% for telescopic-crown-retained tooth-supported obturators, 86.9% for telescopic-crown-retained implant-supported obturators, 58.8% for removable full denture obturators, 22.1% for clasp-retained obturators and 0.0% for splints. The type of attachment, attendance at a regular follow-up and defect cause significantly influenced the survival of the obturators (p < .05).
CONCLUSIONS
The findings obtained in this study support the recommendation of using implant-supported obturators. Telescopic-crown attachments, either tooth- or implant-supported, seem to be favorable in terms of survival time. Attendance at a strict follow-up program seems to have a major influence on the longevity of the obturators.
CLINICAL RELEVANCE
The use of implant-supported obturators to cover permanent oral and maxillofacial defects is highly recommended. Additionally, the use of telescopic-crown attachments seems to be favorable in terms of survival time. Clasp-retained obturators and surgical splints should be used primarily for temporary restorations due to their shorter survival times.
Topics: Humans; Middle Aged; Retrospective Studies; Male; Female; Dental Restoration Failure; Dental Prosthesis, Implant-Supported; Aged
PubMed: 38684542
DOI: 10.1007/s00784-024-05681-8 -
Medicine Apr 2024This paper demonstrates a digital manufacturing technique of a removable orthodontic appliance from an intraoral scan. An intraoral scan was made for the maxillary and...
This paper demonstrates a digital manufacturing technique of a removable orthodontic appliance from an intraoral scan. An intraoral scan was made for the maxillary and mandibular arches. 3Shape Orthodontics Appliance Designer produced the virtual Hawley retainer, consisting of alloy components (Adam Clasps and Fitted Labial bow) and a base plate. The base plate design was modified to adapt to inserting the alloy components, which were combined using cold-cured acrylic. The finished Hawley retainer was assessed intraorally. The described technique emphasizes the design specifications of digitally designed and manufactured removable orthodontic appliances. A combination of additive and subtractive techniques was successfully employed to manufacture the alloy components and base plate. This novel method provides an alternative approach to manufacturing removable appliances with computer-aided design (CAD)/computer-aided manufacturing (CAM) technologies. The described process offers a precursor to digital manufacturing of other developed designs of dental appliances.
Topics: Humans; Printing, Three-Dimensional; Computer-Aided Design; Orthodontic Appliance Design; Polymers; Benzophenones; Polyethylene Terephthalates; Ketones; Alloys; Orthodontic Appliances, Removable
PubMed: 38669369
DOI: 10.1097/MD.0000000000038004 -
Journal of Prosthodontic Research Apr 2024This study aims to develop a numerical prediction method for the average and standard deviation values of the largely varied fatigue life of additively manufactured...
PURPOSE
This study aims to develop a numerical prediction method for the average and standard deviation values of the largely varied fatigue life of additively manufactured commercially pure titanium (CPTi grade 2) clasps. Accordingly, the proposed method is validated by applying it to clasps of different shapes.
METHODS
The Smith-Watson-Topper (SWT) equation and finite element analysis (FEA) were used to predict the average fatigue life. The variability was expressed by a 95% reliability range envelope based on the experimentally determined standard deviation.
RESULTS
When predicting the average fatigue life, the previously determined fatigue parameters implemented in the SWT equation were found to be useful after conducting fatigue tests using a displacement-controlled fatigue testing machine. The standard deviation with respect to stroke and fatigue life was determined for each clasp type to predict variability. The proposed prediction method effectively covered the experimental data. Subsequently, the prediction method was applied to clasps of different shapes and validated through fatigue tests using 22 specimens. Finally, the fracture surface was observed using scanning electron microscopy (SEM). Many manufacturing process-induced defects were observed; however, only the surface defects where the maximum tensile stress occurred were crucial.
CONCLUSIONS
It was confirmed that the fatigue life of additively manufactured pure titanium parts is predictable before the manufacturing process considering its variability by performing only static elasto-plastic FEA. This outcome contributes to the quality assurance of patient-specific clasps without any experimental investigation, reducing total costs and response time.
Topics: Humans; Chromium Alloys; Titanium; Reproducibility of Results; Dental Clasps; Denture, Partial, Removable; Materials Testing
PubMed: 37612075
DOI: 10.2186/jpr.JPR_D_23_00074 -
Biomedicines Aug 2023Conventional partially removable skeletal dentures are one of the most common therapeutic solutions offered to edentulous patients worldwide. The present study aims to...
Conventional partially removable skeletal dentures are one of the most common therapeutic solutions offered to edentulous patients worldwide. The present study aims to compare the skeleton of removable dentures realized via classical techniques to that realized via modern techniques, represented by the laser sintering technique, with the comparative aspects being realized through the evaluation of atomic force microscopy (AFM). A total of 20 metal frameworks made of Co-Cr were sectioned, representing the infrastructure of partially removable skeletal dentures, developed using the classical technique versus the laser sintering technique. The infrastructures of partially removable skeletal dentures were designed for both the maxilla and the mandible, with the design of each type of denture being identical, and were developed using both techniques. The roughness values are different depending on the technological method used; for the conventional casting technique, we have higher roughness for the component elements of the partially removable skeletal denture that have more stretch, e.g., the major connector, and for the 3D laser sintering technique, lower roughness is obtained for the component elements that have a lower stretch, e.g., the clasp arms, the minor connector, or the junction between the saddles and the major connector. The clinical implications of the presence of roughness at the level of the active arms or at the level of the connector saddle junction are represented by the risk of fracture, which confers real discomfort to the patient.
PubMed: 37760838
DOI: 10.3390/biomedicines11092397 -
The Journal of Prosthetic Dentistry Jul 2023Juvenile trabecular ossifying fibroma (JTOF) is a benign fibro-osseous lesion that usually occurs in the maxilla or mandible. Individuals with JTOF of the maxilla will...
Juvenile trabecular ossifying fibroma (JTOF) is a benign fibro-osseous lesion that usually occurs in the maxilla or mandible. Individuals with JTOF of the maxilla will most commonly require a resection that can result in a significant palatal defect. Appearance and articulatory, masticatory, and deglutitory functions can be restored with a clasp-retained obturator. Providing a prosthetic obturator with adequate retention in situations where the teeth cannot accommodate clasps because of insufficient eruption can be challenging. This article describes a technique that has been developed for such instances-in this situation, a 4-year-old child who had undergone a maxillary resection because of a JTOF.
PubMed: 37451901
DOI: 10.1016/j.prosdent.2023.05.029