Influence of Different Undercut Depths of Clasp Fabricated by Selective Laser Melting on Retentive Force.

INTRODUCTION: The purpose of this study was to investigate the influence of undercut depths on abutment teeth regarding the retentive force of clasps fabricated through selective laser melting (SLM), and to compare them with conventional cast clasps. METHODS: Akers clasps made of cobalt chromium alloy were fabricated using the SLM method (SLM), and the retentive forces were compared with clasps made with the conventional cast method (Cast). Three undercut amounts (0.25 mm, 0.15 mm, and 0 mm) were applied on the abutment tooth. The specimens were subjected to 10,000 repetitive insertion/removal cycles. RESULTS: SLM-0.15 showed slightly lower initial retentive force than the Cast specimens, it remained within an acceptable range. During insertion/removal test, the SLM-0.15 specimen showed a significant difference between the initial retentive force and the retentive force after 5,000 cycles, indicating that SLM-0.15 was the least likely to change in retentive force within the parameters established in this study. The inner clasp surface on the SLM groups had higher surface roughness before testing compared to the Cast specimen. CONCLUSIONS: Akers clasps fabricated by SLM demonstrated optimal initial retentive forces with smaller undercuts than conventional Cast clasps, and the retentive forces changed less with repetitive insertion/removal.

Failure and complication rates of different materials, designs, and bonding techniques of ceramic cantilever resin-bonded fixed dental prostheses for restoring missing anterior teeth: A systematic review and meta-analysis.

OBJECTIVES: The objective of this review was to assess clinical trials that have examined the materials, design, and bonding of ceramic cantilevered resin-bonded fixed dental prostheses (RBFDPs) as a potential option for replacing missing anterior teeth. The evaluation primarily focuses on the rate of restoration failure and clinical complications. MATERIALS AND METHODS: A thorough search of databases including PubMed/MEDLINE, Scopus, and the Cochrane Library, was conducted. The most recent search was performed in October 2023. Clinical studies that compared ceramic cantilevered RBFDPs with double retainers or cantilevered RBFDPs using different ceramic materials or bonding systems were included. The outcome measures considered were restoration failure and complication rates. RESULTS: Twelve studies met the eligibility criteria. The pooled data showed a statistically significant decrease in complication events when using cantilever designs compared with double retainer designs (p < 0.05); however, there were no differences found between the two designs in terms of restoration failure. The complication and failure rate of cantilever RBFDPs did not show a statistically significant difference with or without ceramic primer application before luting with phosphate monomer-containing luting resin (p > 0.05). CONCLUSIONS: Ceramic cantilevered RBFDPs have lower complication rates compared with those with double retainers. The use of a ceramic primer prior to luting composite resin for ceramic cantilevered RBFDPs decreases the occurrence of complications and failures, although this effect was not statistically significant. Additional research is required to confirm these findings. Glass ceramic cantilever RBFDPs showed a decrease in success after 6 years, requiring ongoing monitoring, but both zirconia and glass-infiltrated alumina cantilever RBFDPs have demonstrated durability with excellent long-term success and survival rates for up to 10 and 15 years. CLINICAL SIGNIFICANCE: Cantilever ceramic RBFDPs in the anterior region are a less invasive and valuable treatment option, providing good esthetic results.

Influence of a mesial cantilever on stress, strain, and axial force in fixed partial dentures with a distally tilted implant in the atrophic posterior maxilla.

PURPOSE: This study aimed to investigate whether the presence of a mesial cantilever influences the biomechanical behavior and screw loosening in fixed partial dentures (FPDs) with a distally tilted implant in the atrophic posterior maxilla and where to best place the distal implant. METHODS: Two configurations of implant-supported four-unit FPDs were modelled using finite element analysis. Five interabutment distances were considered. The stress and strain distributions in the implants, abutments, and prosthetic screws were verified under occlusal loading. The development of the axial force on the abutments and screws was also examined. Two-sample t-tests were used to identify differences (P < 0.05). RESULTS: The von Mises stress distributions of the components in the two configurations were similar, as were the maximum plastic strains of the distal prosthetic screws, distal implants, and 30° abutments. The difference in the maximum plastic strains of the straight abutments was statistically significant. The preload of the 30° abutment screws was significantly reduced after the initial loading. In the absence of a mesial cantilever, the axial force on the straight abutments increased. However, when a mesial cantilever was used, the preload of the straight abutments was maintained, and the axial force on the prosthetic screws fluctuated less. The axial force fluctuation of the abutments gradually decreased as the interabutment distance increased. CONCLUSIONS: Mesial cantilever usage had minimal effect on stress or strain distribution in FPD implants, abutments, or prostheses. However, it helped resist screw loosening. The distal screw access hole was preferably positioned close to the prosthetic end.

Efficacy of a Virtual 3D Simulation-Based Digital Training Module for Building Dental Technology Students' Long-Term Competency in Removable Partial Denture Design: Prospective Cohort Study.

Background: Removable partial denture (RPD) design is crucial to long-term success in dental treatment, but shortcomings in RPD design training and competency acquisition among dental students have persisted for decades. Digital production is increasing in prevalence in stomatology, and a digital RPD (D-RPD) module, under the framework of the certified Objective Manipulative Skill Examination of Dental Technicians (OMEDT) system reported in our previous work, may improve on existing RPD training models for students. Objective: We aimed to determine the efficacy of a virtual 3D simulation-based progressive digital training module for RPD design compared to traditional training. Methods: We developed a prospective cohort study including dental technology students at the Stomatology College of Chongqing Medical University. Cohort 1 received traditional RPD design training (7 wk). Cohort 2 received D-RPD module training based on text and 2D sketches (7 wk). Cohort 3 received D-RPD module pilot training based on text and 2D sketches (4 wk) and continued to receive training based on 3D virtual casts of real patients (3 wk). RPD design tests based on virtual casts were conducted at 1 month and 1 year after training. We collected RPD design scores and the time spent to perform each assessment. Results: We collected the RPD design scores and the time spent to perform each assessment at 1 month and 1 year after training. The study recruited 109 students, including 58 (53.2%) female and 51 male (56.8%) students. Cohort 1 scored the lowest and cohort 3 scored the highest in both tests (cohorts 1-3 at 1 mo: mean score 65.8, SD 21.5; mean score 81.9, SD 6.88; and mean score 85.3, SD 8.55, respectively; P<.001; cohorts 1-3 at 1 y: mean score 60.3, SD 16.7; mean score 75.5, SD 3.90; and mean score 90.9, SD 4.3, respectively; P<.001). The difference between cohorts in the time spent was not statistically significant at 1 month (cohorts 1-3: mean 2407.8, SD 1370.3 s; mean 1835.0, SD 1329.2 s; and mean 1790.3, SD 1195.5 s, respectively; P=.06) but was statistically significant at 1 year (cohorts 1-3: mean 2049.16, SD 1099.0 s; mean 1857.33, SD 587.39 s; and mean 2524.3, SD 566.37 s, respectively; P<.001). Intracohort comparisons indicated that the differences in scores at 1 month and 1 year were not statistically significant for cohort 1 (95% CI -2.1 to 13.0; P=.16), while cohort 3 obtained significantly higher scores 1 year later (95% CI 2.5-8.7; P=.001), and cohort 2 obtained significantly lower scores 1 year later (95% CI -8.8 to -3.9; P<.001). Conclusions: Cohort 3 obtained the highest score at both time points with retention of competency at 1 year, indicating that progressive D-RPD training including virtual 3D simulation facilitated improved competency in RPD design. The adoption of D-RPD training may benefit learning outcomes.

Effect of orthodontics combined with fibre-reinforced composite resin-bonded fixed partial denture on anterior dentition defects with minimal vertical intermaxillary space.

BACKGROUND: Prosthodontics are often performed to treat patients with malocclusion and dentition defects. However, single prosthodontics cannot properly correct the disharmony of teeth, dental arch and other parts affected by malocclusion, and some patients may have difficulty in recovering the occlusal function due to poor prosthodontics. OBJECTIVE: This study aims to investigate the effect of orthodontics combined with fibre-reinforced composite resin-bonded fixed partial denture (FRC-RBFPD) on anterior dentition defects with minimal vertical intermaxillary space. METHODS: Sixty-two patients with anterior dentition defects with minimal vertical mandibular space admitted to our hospital between March 2021 and May 2023 were enrolled in this study. The participants were divided into the observation group (31 cases) and the control group (31 cases), according to the treatment plan. The control group was treated with traditional therapy, and the observation group was treated with orthodontic combined FRC-RBFPD therapy. Periodontal conditions (periodontal pocket depth [PD], the plaque index [PLI], the sulcus bleeding index [SBI]), levels of inflammatory factors in gingival crevicular fluid (high mobility group box 1 [HMGB1]), myeloid cell triggering receptor-1 (TREM-1), monocyte chemoattractant protein-1 (MCP-1), pain (visual analogue scale [VAS]), the clinical response rate and the incidence of adverse reactions were collected and compared. RESULTS: After 1, 3, 5 and 9 months following treatment, the scores of the PD, PLI, SBI, HMGB1, VAS, TREM-1 and MCP-1 in the observation group were found to be lower than those in the control group (FPD treatment= 352.532, FPLI score treatment= 112.341, FSBI score treatment= 79.479, FVAS score treatment= 96.132, FHMGB1 treatment= 52.532, FTREM-1 score treatment= 64.593, FMCP-1 score treatment= 53.582, and they were all statistically significant P< 0.05). There was a statistically significant difference in the response rate between the two groups (97.77% vs. 80.65%, χ2= 4.026, P= 0.045). No statistically significant difference was observed in the incidence of adverse reactions between the two groups (6.45% vs. 16.13%, χ2= 1.449, P= 0.229). CONCLUSION: Orthodontics combined with FRC-RBFPD shows an ideal restorative effect on patients with anterior dentition defects and minimal vertical intermaxillary space.

Oral health-related quality of life and reasons for discontinuing partial removable dental prosthesis usage: a cross-sectional study with one to seven years of follow-up.

BACKGROUND: In partial edentulous individuals, a partial removable dental prosthesis (PRDP) is a common dental replacement option to improve oral function and quality of life. However, some patients discontinue using their denture over time. The aim of this study was to determine the prevalence and characteristics of partial edentulous patients who no longer wear their dentures, explore their reasons, and assess their oral health-related quality of life (OHRQoL). METHODOLOGY: This cross-sectional study, conducted at Chulalongkorn University Dental School from 2013 to 2019, involved patients who received PRDP treatment. They were contacted via phone calls and asked about their denture usage. Eligible participants were patients who had stopped or rarely used their PRDPs. Data on oral status, health insurance, and PRDP variables were collected from hospital records. Telephone interviews were conducted to collect the initial reasons for seeking PRDP treatment, reasons for discontinuation, desire for a new PRDP, and OHRQoL. The Oral Impacts on Daily Performances index was used to assess the OHRQoL. The score was dichotomized into the absence or presence of oral impacts. Chi-square tests and multivariable binary logistic regression were employed to determine the associations between oral impacts and various factors in the participants who discontinued PRDP usage. RESULTS: Among the 975 contacted participants, 175 (17.9%) discontinued using their PRDPs. Most of these individuals had at least 20 remaining natural teeth and/or 4 posterior occluding pairs. The primary initial reason for seeking PRDP treatment was often based on a dentist's suggestion. Although many participants reported no impact on OHRQoL and did not express the need for new PRDPs, those experiencing oral impacts were more likely to seek replacements. CONCLUSIONS: With up to 7 years follow-up duration, individuals with partial edentulism and sufficient remaining functional dentition without oral impacts were more inclined to discontinue PRDP usage. Those with maxillary anterior teeth loss were less likely to discontinue using their PRDP. The primary initial reason for seeking PRDP treatment was often a dentists' suggestion. However, the individuals reporting oral impacts expressed their needs for new denture replacements. This highlights the significance of incorporating patient needs and preferences in prosthodontic decision-making.

Efficacy of a Novel Computerized Aid in Designing Removable Partial Dentures.

BACKGROUND:  The development of computerized aids for dental education offers potential benefits in teaching complex procedures, such as the design of removable partial dentures (RPDs). This study aimed to assess the efficacy of a novel computerized tool in enhancing the ability of both dental students and practicing dentists to design RPDs, as well as to evaluate its utility as an interactive educational instrument. METHODS:  A cohort comprising a total of 75 individuals (25 practicing dentists and 50 undergraduate dental students) was enlisted. Participants were introduced to an online interactive application tailored for the design of RPDs. They were tasked with resolving clinical scenarios that necessitated the formulation of an RPD. Throughout the exercise, users were provided with hints addressing errors made during the process, fostering self-directed learning for improved RPD design. Post-interaction, the perceptions of both dentists and students regarding the tool were gauged through a comprehensive questionnaire. RESULTS:  The deployment of the online interactive application demonstrated significant promise in the effective design of RPDs, facilitated by self-directed learning. It also appeared to enhance the proficiency of practicing dentists in formulating partial dentures. CONCLUSION:  The computerized aid evaluated in this study provided an effective platform for both dental education and practice. It not only supported self-directed learning in the design of RPDs but also improved the efficiency of professional dentists in their clinical design work.

A dual composite resin injection molding technique with 3D-printed flexible indices for biomimetic replacement of a missing mandibular lateral incisor.

PATIENTS: This case report presents a minimally invasive approach to replace a missing mandibular lateral incisor using a dual-injection molding technique with flowable composite resins. Integrated with a comprehensive digital workflow, this method achieves a structurally and esthetically biomimetic, bi-layered prosthetic solution. A 34-year-old woman with congenital absence of a mandibular lateral incisor was successfully rehabilitated using a direct composite resin-bonded fixed partial denture (RBFPD). DISCUSSION: Two specialized three-dimensional (3D)-printed flexible indices stabilized by a custom-designed 3D-printed rigid holder were employed to ensure the meticulous injection molding of flowable composite resins formulated to emulate the inherent chromatic gradations between dentin and enamel. The inherent flexibility of the indices, combined with the holder, facilitated accurate and seamless adaptation to the complex morphological features of the dental arch, thereby mitigating the challenges commonly associated with rigid 3D-printed resin indices. CONCLUSIONS: The bilayered direct composite RBFPD using 3D printed flexible indices prepared with a full digital workflow has several advantages over other dental prosthetic solutions, including noninvasiveness, cost-effectiveness, biomimetic esthetics, repairability, and shortened treatment times. Although the initial results are promising, further longitudinal studies with larger patient cohorts are required to confirm the long-term efficacy of this approach.

Digital planning and surveying for a rotational path removable partial denture: a case report.

Digital technology has been applied to the planning and manufacture of removable partial dentures (RPDs), reducing the complexity of RPD treatment as well as the number and duration of clinical and laboratory steps. However, there is a lack of information regarding digital planning and surveying for rotational path RPDs. This article presents a case report of a digital diagnostic wax-up and survey for a rotational path RPD performed with prosthetic design software. The virtual diagnostic closure tool made it possible during the case study stage to visualize the edentulous spaces and simulate the preparations necessary for the restoration of occlusal and esthetic harmony. The virtual survey determined the dual-axis path of insertion and removal for the rotational path RPD based on the 4 major influencing factors: guiding planes, retentive undercuts, interferences, and esthetics. In this case, digital planning and surveying for a rotational path RPD were an effective means of esthetic and biomechanical analysis and allowed for minimal preparation of the abutment teeth.

Prosthetically driven robot-assisted implant surgery: turning a major failure into a simple case.

This case report presents a challenging case of catastrophic failure of a fixed partial denture involving fracture of the prosthesis as well as supporting implants and teeth. The use of robotics facilitated efficient and successful restoration of the patient's dentition. After extraction of 2 fractured teeth and 1 fractured implant, 2 new implants were placed with haptic guidance from robotics, which allowed for stable osteotomies and high initial implant stability quotients. Due to the patient's tremors and heavy occlusal forces, restoration was delayed to allow the surgical site to heal, and the patient received a provisional partial denture. With subsequent placement of the final restoration, the treatment was fully completed in 4.5 months and required only a single surgical procedure. The use of haptic robotics in this case allowed for accurate planning, spacing, and placement of screw-retained implants with an optimal arch, leading to the best long-term outcome for the patient.

A Systematic Review of Patient Satisfaction With Removable Partial Dentures (RPDs).

Removable partial dentures (RPDs) offer a broad range of aesthetics and restorative functions for partially edentulous patients. This systematic review examines patients' satisfaction rates and the factors that influence RPD satisfaction. This systematic review was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and the Cochrane Handbook for Systematic Reviews. A systematic literature search was done on PubMed, Scopus, and Google Scholar using preset inclusion criteria. A total of 923 non-duplicate articles were screened, and 35 were included in this review. Among the included studies, RPDs generally exhibited high satisfaction rates, with reported rates ranging between 50% and 81%. Several factors influenced satisfaction. Age played a major role, with older adults expressing higher satisfaction. Gender differences were also noted, especially in appearance satisfaction where women were more satisfied with RPDs than men. Prior experience with RPDs correlated positively with overall satisfaction. The number and location of missing teeth, as well as the type of RPD (metal vs. flexible), significantly influenced satisfaction levels. Flexible dentures were more satisfactory than metal RPDs. Attachments, such as magnetic attachments and implants, increased satisfaction. Patient complaints, encompassing pain, aesthetics, and cleanliness, were identified as common sources of dissatisfaction. The results underscore the significance of customizing RPD treatment to individual needs, considering factors that influence RPD satisfaction. Recognizing the importance of influential factors such as age, gender RPD experience, etc., for clinicians seeking to optimize patient outcomes in RPD therapy is crucial.

A New Scale for Rating Oral Health-Related Quality of Life in Denture Wearers.

PURPOSE: When carrying out prosthetic rehabilitation of edentulous and partially edentulous patients, great attention is paid to the personal attitude of the patients, their satisfaction with oral health and psychosocial interaction due to tooth loss, as well as the treatment of the resulting disorders. This attention has led to the development of various instruments for examining the quality of life related to oral health. The aim of this study was to develop and validate a reliable instrument in the Serbian language suitable for measuring oral health-related quality of life in patients who have been rehabilitated with complete or partial dentures. Мaterials and Methods: The study was unicentric and cross-sectional, and assessed the reliability and validity of a newly developed instrument for measuring the oral health-related quality of life in denture wearers (OHRQoL-DW). It was conducted on a sample of 200 adults from Serbia, wearers of various types of dentures, with a mean age 66.9 ± 10.3 years and male/female ratio of 86/114 (43%/57%). RESULTS: The definitive version of the OHRQoL-DW scale with 28 items showed very good reliability, with Cronbach's alpha = 0.938. Good temporal stability of the questionnaire was demonstrated, and satisfactory results were obtained for divergent and convergent validity tests. Exploratory factorial analysis revealed four domains of oral health-related quality of life in denture wearers: physical, psychosocial, environmental and aesthetic. CONCLUSIONS: The OHRQoL-DW scale is a reliable and valid generic instrument for measuring the oral health-related quality of life in patients wearing dentures, which is one of the most important outcomes of oral health in prosthetic treatment.

Anomaly detection of retention loss in fixed partial dentures using resonance frequency analysis and machine learning: An in vitro study.

PURPOSE: This study aimed to determine the usefulness of machine learning techniques, specifically supervised and unsupervised learning, for assessing the cementation condition between a fixed partial denture (FPD) and its abutment using a resonance frequency analysis (RFA) system. METHODS: An in vitro mandibular model was used with a single crown and three-unit bridge made of a high-gold alloy. Two cementation conditions for the single crown and its abutment were set: cemented and uncemented. Four cementation conditions were set for the bridge and abutments: both crowns were firmly cemented, only the premolar crown was cemented, only the molar crown was cemented, and both crowns were uncemented. For RFA under cementation conditions, 16 impulsive forces were directly applied to the buccal side of the tested tooth at a frequency of 4 Hz using a Periotest device. Frequency responses were measured using a 3D accelerometer mounted on the occlusal surface of the tested tooth. Both supervised and unsupervised learning methods were used to analyze the datasets. RESULTS: Using supervised learning, the fully cemented condition had the highest feature importance scores at approximately 3000 Hz; the partially cemented condition had the highest scores between 1000 and 2000 Hz; and the highest scores for the uncemented condition were observed between 0 and 500 Hz. Using unsupervised learning, the uncemented and partially cemented conditions exhibited the highest anomaly scores. CONCLUSIONS: Machine learning combined with RFA exhibits good potential to assess the cementation condition of an FPD and hence facilitate the early diagnosis of FPD retention loss.

Radiographic evaluation of marginal bone levels around implants supporting splinted fixed bridges: A retrospective study on 412 implants.

OBJECTIVES: The effect of the implant position within the prosthesis on bone remodeling is scarcely documented so far. Thus, the aim of the present study was to investigate whether central implants may suffer higher peri-implant marginal bone levels (MBL) compared to laterals in case of fixed splinted bridges supported by ≥ three implants. MATERIALS AND METHODS: Partially edentulous subjects rehabilitated with at least one fixed bridge supported by ≥ three dental implants were enrolled. MBL was assessed radiographically by means of intraoral radiographs acquired with phosphor plates and imported in a dedicated software. MBL was calculated as the distance between the implant platform level and the most coronal visible bone-to-implant contact. A three-level linear mixed effects model was used for investigating the fixed effect of patient-, prosthesis-, and implant-level variables on the MBL. RESULTS: Overall, 90 patients rehabilitated with 130 splinted fixed bridges supported by 412 implants were included. The median follow-up was 136 months. The mean peri-implant MBL resulted statistically significantly higher at central implants if compared to lateral implants (p < .01). The estimated MBL averages for central and external implants were 1.68 and 1.18 mm, respectively. The prosthesis-level variables suggested that a cement-retained bridge was prone to a significant 0.82 mm higher MBL than a screw-retained one. Implant surface showed an association with MBL changes, although less pronounced than implant retention. CONCLUSIONS: In case of ≥3 adjacent implants supporting splinted bridges, central implants were more predisposed to MBL compared to laterals. At the prosthesis level, implants supporting cement-retained bridges were statistically more susceptible to MBL compared to screw-retained ones. Surface characteristics can also influence MBL stability at the implant level.

Evaluation and assessment of the wettabilty and water contact angle of modified poly methyl methacrylate denture base materials against PEEK in cast partial denture framework: an in vitro study.

INTRODUCTION: The prevalence of adults with partially dental arches is expected to be more than imagined and patients requiring replacement of missing teeth are slowly increasing in number too. Removable partial dentures are known to provide for substantial replacement for the missing teeth with also added advantages when compared to fixed or implant prosthesis, mainly in elderly patients. Denture base material performance and durability are greatly influenced by wettability and water contact angle. In the case of dentures; adequate moisture distribution is necessary to ensure excellent wettability which has an influence on comfort and oral health. The purpose of conducting this study was to find out whether the advancements made using PEEK (Polyether ether ketone) would prove to be more beneficial than the current upgrades in the current material spectrum. MATERIALS AND METHODS: This study was performed under in vitro conditions. All the fabrication and processing was done only by one operator. The materials used were divided into three groups each comprising 20 samples. Group A was modified polymethylmethacrylate (Bredent Polyan), Group B was polyoxymethylene acetal resin (Biodentaplast) and Group C was PEEK. An Ossila Goniometer was used to measure the contact angle. The three types of liquids used for the testing included distilled water, natural saliva and mouth wetting solution (Wet Mouth Liquid, ICPA India). Human saliva was collected from an individual with no medical conditions and normal salivary secretion. RESULTS: The data was analyzed using One-way ANOVA test and a pairwise comparison using the Post Hoc Tukey's Honest Significant Difference. Table 1 consists of the mean water contact angles of the denture base materials and mean contact angles of various denture base materials. In saliva, mouth wetting solution and distilled water, the highest mean and least mean contact angle was seen in Polyan and Biodentaplast respectively. A signicant difference was seen between PEEK and Polyan and Biodentaplast and Polyan on further comparison. CONCLUSION: From the resources and the materials at our disposal, it could be concluded that Polyan, Biodentaplast and PEEK and could be used as viable options in cast partial denture framework.

In vitro study of optimal removable partial denture clasp design made from novel high-performance polyetherketoneketone.

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.

Implant-assisted removable partial dentures: Part I. a scoping review of clinical applications.

PURPOSE: This scoping review aimed to systematically map research regarding implant-assisted removable partial dentures (IARPDs), and identify existing gaps in knowledge. STUDY SELECTION: Two reviewers independently conducted a search of the MEDLINE-PubMed and Scopus databases according to the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) extension for Scoping Review and included articles published in English up to August 31, 2022, including human studies, reviews, and in vitro studies. Expert opinions, animal studies, and clinical studies involving complete overdentures were excluded, and ten aspects for establishing the treatment strategy for IARPDs were examined. RESULTS: One hundred and twelve articles were chosen. There were two treatment modalities: IARPDs retained by implant- and tooth-supported surveyed single crowns (SCs) or fixed partial dentures (FPDs). In IARPDs retained by tooth-supported surveyed SCs or FPDs, the survival rate of dental implants for IARPDs was relatively higher with a wide range of marginal bone loss and many complications, but with improved functional performance, oral health-related quality of life, and patient satisfaction. There were limited data on survival or success rates and designs of IARPDs, attachment selections, length and diameter, inclination, placement sites, and loading protocols of implants, regardless of prosthetic types. There was limited information on maxillary IARPDs except for survival rates of implants. CONCLUSIONS: Although IARPDs could become a useful treatment strategy, there is limited scientific consensus with gaps in knowledge about their use. Additional well-designed clinical and in vitro studies are necessary to scientifically establish IARPDs as definitive prostheses in implant dentistry.

Implant-assisted removable partial dentures: Part II. a systematic review of the effects of implant position on the biomechanical behavior.

PURPOSE: This systematic review aimed to evaluate the effects of implant placement sites on the biomechanical behavior of implant-assisted removable partial dentures (IARPDs) using finite element analysis (FEA). STUDY SELECTION: Two reviewers independently conducted manual searches of the PubMed, Scopus, and ProQuest databases for articles investigating implant location in IARPDs using FEA, according to the 2020 Systematic Reviews and Meta-analyses statement. Studies published in English up to August 1, 2022, were included in the analysis based on the critical question. RESULTS: Seven articles meeting the inclusion criteria were systematically reviewed. Six studies investigated mandibular Kennedy Class I and one study investigated mandibular Kennedy Class II. Implant placement reduced the displacement and stress distribution of the IARPD components, including dental implants and abutment teeth, regardless of the Kennedy Class type and dental implant placement site. Most of the included studies showed that, based on the biomechanical behavior, the molar region, rather than the premolar region, is the preferred implant placement site. None of the selected studies investigated the maxillary Kennedy Class I and II. CONCLUSIONS: Based on the FEA regarding mandibular IARPDs, we concluded that implant placement in both the premolar and molar regions improves the biomechanical behaviors of IARPD components, regardless of the Kennedy Class. Implant placement in the molar region results in more suitable biomechanical behaviors compared with implant placement in the premolar region in Kennedy Class I. No conclusion was reached for Kennedy Class II due to the lack of relevant studies.

Clinical application of lithium disilicate glass ceramic cantilever resin-bonded fixed partial denture in the restoration of single anterior tooth loss / 口腔疾病防治

Objective@#To investigate the clinical effect of lithium disilicate glass ceramic cantilever resin-bonded fixed partial dentures (CRBFPDs) on single anterior tooth loss to provide a reference for the selection of restoration methods for single anterior tooth loss.@*Methods@#This study was reviewed and approved by the Ethics Committee, and informed consent was obtained from the patients. Forty-two patients with less than two anterior teeth with monomaxillary loss were included in this study. After 6 months, 1 year, 2 years, and 3 years, the aesthetic and functional effects of the restorations and the periodontal health status were evaluated, and the visual analog scale (VAS) was used to assess patient satisfaction.@*Results@#During the observation period, the connector fractured in one case within 3 months. One case had debonded within 2 years. The aesthetic restoration effect of all lithium disilicate glass ceramic CRBFPDs was categorized as Class A. The periodontal health was good, there was no clinical absorption in the soft and hard tissues of the abutment or subbridge, periodontal status according to the evaluation indices was classified as class A, and the total satisfaction rate of the patient was 100%.@*Conclusion@#For single anterior tooth loss patients, lithium disilicate glass ceramic cantilever resin-bonded fixed partial denture can achieve the restoration effect of less invasion, better adhesion, aesthetics, comfort and good biocompatibility. With high patient satisfaction, it can be considered an ideal restoration method for replacing a single anterior tooth.

Evaluation and Assessment of the Colour Stability of Modified Polymethyl Methacrylate Denture Base Materials and Polyether Ether Ketone in a Cast Partial Denture Framework: An In-Vitro Study.

Background One of the frequent aesthetic issues patients confront is the loss of colour and lifeless appearance of the dentures of the base materials of their dentures after regular use. This leads to a lack of motivation to use the denture regularly. Due to the drawbacks of conventional PMMA, polyether ether ketone (PEEK) and newer polymethyl methacrylate (PMMA)-based materials have now started being used in cast partial denture frameworks due to their superior physical and biological properties. The lack of long-lasting colour is one of the main reasons for the repeat of dental prostheses. Hence, the need for the study is to help clinicians decide which would be the most suitable denture base material to be used based on colour stability. Aim To assess and compare the colour stability of PEEK, polyan, and biodentaplast denture base materials (DBMs) upon staining with distilled water, tea, coffee, and turmeric solutions after one day, seven days, and 30 days. Methods A total of 20 cuboidal specimens were constructed and immersed in distilled water, tea, coffee, and turmeric (five specimens of each material in each solution, a total of 60 specimens): Group 1: PEEK, Group 2: polyan, Group 3: biodentaplast. All specimens were subjected to colour measurements before exposure to beverage solutions, after 24 hours, on the seventh day and 30th day with a colour reflectance spectrophotometer with computer software. A one-way ANOVA test followed by post hoc Tukey's honestly significant difference (HSD) was performed for comparison of colour stability between the DBMs, revealing a significant difference between PEEK and polyan and PEEK and biodentaplast. Polyan showed the highest delta E values, followed by biodentaplast and PEEK. A two-way ANOVA test, followed by Tukey's HSD post hoc, was done to compare the staining ability of various staining solutions. Turmeric had the highest delta E values, followed by coffee, tea, and distilled water. Data were assessed using Statistical Product and Service Solutions (SPSS, version 23) (IBM SPSS Statistics for Windows, Armonk, NY) software. Results The highest mean delta E value at T1 was seen in biodentaplast immersed in turmeric (12.3900+/-0.442), and the least value at T1 was obtained for PEEK immersed in distilled water (0.4460+/-0.036). The highest mean delta E value at T2 was seen in polyan immersed in turmeric (13.0160+/-0.28962), and the least value at T2 was obtained for PEEK immersed in distilled water (0.5860+/-0.051). At T3, the highest mean delta E value was seen in polyan immersed in turmeric (16.8600+/-0.49845), and the least value at T3 was obtained for PEEK immersed in distilled water (0.700+/-0.037). Conclusion PEEK had the highest colour stability when compared with polyan and biodentaplast.