Longevity of acrylic and cobalt-chromium removable partial dentures-A ten-year retrospective survival analysis of 1246 denture-wearing patients.

OBJECTIVES: to assess the survival rates of removable partial dentures (RPDs) and identify factors impacting their longevity. METHODS: electronic health records were retrieved of patients aged ≥18 who received RPDs between 2010 - 2021 with a follow-up of ≥ three months. Data extracted included demographics, medical history, dental charting, periodontal screening and recording scores, prostheses details and related interventions, including new dentures/denture remakes, and maintenance. Multivariate Mixed-Effect Cox regression was performed to identify potential RPD survival risk factors. Reduced model selection was reached using a backward step-down by comparing the performance of these multivariable models using the ANOVA test. RESULTS: 1893 RPDs from 1246 patients were included, with a median follow-up of 21.8 months (range from 3 to 131.3 months). Three hundred and twelve patients received a maxillary RPD, 460 received a mandibular RPD, and the remaining 474 patients received both maxillary and mandibular RPDs. Metal-based RPDs had a median survival of 73 months (95%CI: 70 - 82) versus 45 months (95% CI: 37-67) for acrylic ones. Multivariable mixed effects Cox model showed that the lifespans of RPDs were longer amongst patients receiving more maintenance care within three months [Hazards Ratio (HR)=0.89 (0.83, 0.96)] and after three months [HR=0.53 (0.46, 0.61)] of denture delivery, patients wearing both maxillary and mandibular RPDs [HR=0.67 (0.52, 0.87)], and patients receiving metal-based RPDs [HR=0.31 (0.23, 0.42)]. CONCLUSIONS: Metal-based dentures, dual arch restoration, and increased maintenance positively impact the survival of RPDs. CLINICAL SIGNIFICANCE: Adapting consent and warranty practices is advised to reflect RPD performance variations.

Material extrusion of thermoplastic acrylic for intraoral devices: Technical feasibility and evaluation.

With global demand for 3D printed medical devices on the rise, the search for safer, inexpensive, and sustainable methods is timely. Herein, we assessed the practicality of the material extrusion process for acrylic denture bases of which successful outcomes can be extended to implant surgical guides, orthodontic splints, impression trays, record bases and obturators for cleft palates or other maxillary defects. Representative materials comprising denture prototypes and test samples were designed and built with in-house polymethylmethacrylate filaments using varying print directions (PDs), layer heights (LHs) and reinforcements (RFs) with short glass fiber. The study undertook a comprehensive evaluation of the materials to determine their flexural, fracture, and thermal properties. Additional analyses for tensile and compressive properties, chemical composition, residual monomer, and surface roughness (Ra) were completed for parts with optimum parameters. Micrographic analysis of the acrylic composites revealed adequate fiber-matrix compatibility and predictably, their mechanical properties improved simultaneously with RFs and decreased LHs. Fiber reinforcement also improved the overall thermal conductivity of the materials. Ra, on the other hand, improved visibly with decreased RFs and LHs and the prototypes were effortlessly polished and characterized with veneering composites to mimic gingival tissues. In terms of chemical stability, the residual methyl methacrylate monomer contents are well below standards threshold for biological reactions. Notably, 5 vol% acrylic composites built with 0.05 mm LH in 0° on z-axis produced optimum properties that are superior to those of conventional acrylic, milled acrylic and 3D printed photopolymers. Finite element modeling successfully replicated the tensile properties of the prototypes. It may well be argued that the material extrusion process is cost-effective; however, the speed of manufacturing could be longer than that of established methods. Although the mean Ra is within an acceptable range, mandatory manual finishing and aesthetic pigmentation are required for long-term intraoral use. At a proof-of-concept level, it is evident that the material extrusion process can be applied to build inexpensive, safe, and robust thermoplastic acrylic devices. The broad outcomes of this novel study are equally worthy of academic reflection, and further translation to the clinic.

The Effect of Stacking on the Accuracy of 3D-Printed Full-Arch Dental Models.

The objective of this study was to assess the effect of stacking on the dimensional and full-arch accuracy of 3D-printed models, utilising a standardised assessment methodology. A previously validated methodology involving a standard tessellation language image (STL) reference model, comprising seven spheres on a horseshoe base resembling a dental arch, was used. Six 3D-designed STL models were prepared, optimised, and stacked horizontally using 3D Sprint software. The stacking file was transferred to the NextDent 5100 printer to build the physical models. To assess accuracy, a coordinate measuring machine (CMM) measured the diameter of the spheres n=210, and twenty-one vectors extended between the centres of each of the seven spheres (n = 630). When compared to the reference model, significant differences were observed for dimensional (p = 0.006) and full-arch accuracy (p = 0.006) for all stacked models. Additionally, significant differences were observed between the stacked models for the dimensional accuracy between the posterior (p = 0.015), left posterior (p = 0.005) and anteroposterior (p = 0.002). The maximum contraction was observed in the fourth stacked model, which demonstrated the highest median deviation and least precision within the full-arch (MD = 666 µm, IQR = 55 µm), left posterior (MD = 136 µm, IQR = 12 µm), posterior (MD = 177 µm, IQR = 14 µm) and anteroposterior (MD = 179 µm, IQR = 16 µm) arch segments. In general, the anterior and left posterior arch segments recorded the highest contractions with a median deviation of 34 µm and 29 µm, and precision of 32 µm and 22 µm, respectively. Statistically significant differences were observed between the stacked models in terms of dimensional accuracy that were within clinically acceptable thresholds. The greatest contraction was noted in the fourth model, displaying the least full-arch accuracy compared to the other models. Stacked, additively manufactured, full arch models are a viable alternative for diagnostic, orthodontic, and single-unit prosthodontic applications. In contrast, caution should be exercised when utilising stacked models for full arch high accuracy prosthodontic applications. Further research is needed to assess the impact of additional variables including different printers and resins.

Tooth wear and socioeconomic status in childhood and adulthood: Findings from a systematic review and meta-analysis of observational studies.

OBJECTIVES: To evaluate the association and level of evidence between socioeconomic status (SES) and tooth wear (TW) in children, adolescents, and adults. DATA: Eligibility criteria comprised population-based observational studies assessing the association between SES and TW in permanent dentition of adolescents and adults. Interventional and descriptive studies or those without an internal comparison between exposed and nonexposed groups were excluded. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were applied where applicable. Risk of bias (RoB) was assessed using the Newcastle-Ottawa scale. Meta-analyses were conducted to estimate the pooled effect measures. Q-statistic, I2statistic, subgroup and sensitivity analyses assessed study heterogeneity. SOURCES: PubMed/Medline, Embase, Scopus, Web of Science, LILACS, SciELO, Cochrane Library, and Google Scholar databases were searched for articles published in English between 1st January 1980 and 31st March 2021. RESULTS: Sixty-five studies were included, involving 63,893 participants in over 30 countries. A positive association was found between TW and education (OR=1.25 [0.96; 1.62]), family income (OR=1.18 [0.91; 1.53]), and private school (OR= 1.24 [0.90; 1.72]) among adolescents. Higher educated adults had a lower risk for TW (OR=0.70 [0.52; 0.93]). Most included studies had a moderate RoB. Limitations relating to population representation and assessment methodologies were identified in the included studies. CONCLUSIONS: SES was associated with TW with its direction depending on the individuals' age. The overall quality of evidence was moderate. CLINICAL SIGNIFICANC: SES should be included as part of the routine screening and risk assessment for tooth wear.

Operators matter - An assessment of the expectations, perceptions, and performance of dentists, postgraduate students, and dental prosthetist students using intraoral scanning.

OBJECTIVE: to assess the expectations, perceptions and performance of different operators with varying backgrounds and training in the use of full-arch intraoral scanning (IOS). METHODS AND MATERIALS: Dentists (DENT), postgraduate dental students (DPG), and student prosthetists (PROS) were invited to join an IOS training workshop. Participants completed a satisfactory scan of a mannikin-mounted typodont with the total scanning time (TST) recorded. They also completed anonymised pre and post-training questionnaires covering their background, and IOS expectations and experience. Statistical analysis was performed using the Mann-Whitney U, Kruskal Wallis, and chi-square tests. Open-ended questions were analysed manually and using Leximancer. RESULTS: Twenty-seven participants were recruited: 10 DENT; 10 PROS; and 7 DPG. Positive expectations of IOS was reported by 93 % of participants. Combined TST was 285 ± 83 s, with the PROS TST significantly longer (p < 0.05, 337 ± 79 s). Further training need was reported by 60 % of PROS and 50 % of DENT versus 14 % of DPG. Positive IOS experience was reported by 96 % of participants, 74 % perceived it to be accurate, and 63 % found it easy to use. Eighty-five percent of all participants stated that cost would influence their decision of adopting IOS in their practice. CONCLUSION: Expectations and perceptions of IOS were overwhelmingly positive, irrespective of operator background and experience. Scanning performance and training needs depended on the operator's background. Cost of IOS remains a barrier to acquiring the technology. CLINICAL SIGNIFICANCE: IOS training must be customised to accommodate the needs of different operators. The cost of IOS needs revision to improve its accessibility.

Monitoring Alveolar Ridge Remodelling Post-Extraction Using Sequential Intraoral Scanning over a Period of Four Months.

The potential applications of computer-aided design/computer-aided manufacturing (CAD/CAM) and intraoral scanning exceed the delivery of standard prosthodontic interventions. The aim of this study was to clinically present a developed assessment technique, that relies on the use of sequential intraoral scanning, three-dimensional superimposition, and 2D and 3D deviation analyses based on a standardised protocol, as an auxiliary tool in monitoring dimensional changes of residual ridge post-extraction with a follow-up period of four months.

Biomechanical and biological evaluations of novel BPA-free fibre-reinforced composites for biomedical applications.

This aim was to assess the biomechanical and biocompatibility properties of novel glass fibre-reinforced composites (FRCs) with a fluorinated urethane dimethacrylate (FUDMA) resin. Three ratios of FUDMA/TEGDMA (30/70 wt%, 50/50 wt%, 70/30 wt%) and two ratios of control FRCs with bis-GMA/TEGDMA (50/50 wt% and 70/30 wt%) containing long silanized E-glass fibres were prepared. Despite 70 wt% bis-GMA-FRC showed a significantly higher flexural strength (p < 0.05), 50 wt% FUDMA- and bis-GMA-FRCs were not differ from each other. The greatest surface hardness and weight increase after water storage were found in 70 wt% and 30 wt% FUDMA-FRCs, respectively. No significant difference was found in water sorption and solubility among all groups. Average surface roughness was 1.80 ±â€¯0.05 µm, while 70 wt% FUDMA-FRC exhibited the greatest contact angle (p > 0.05). Viabilities and ALP activities of MC3TC-E1 cells in all FUDMA-FRCs were higher than bis-GMA-FRCs after 5 days. To conclude, the novel FUDMA-FRCs are potential substitutes that exhibited superior cytocompatibility properties but comparable biomechanical properties to bis-GMA-FRCs.

Performance and perception of dental students using three intraoral CAD/CAM scanners for full-arch scanning.

PURPOSE: To assess the average full-arch scanning time, perception and likelihood of future adoption of technology by final-year dental students using three different Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) intraoral scanning systems. METHODS: Final-year undergraduate Dental Students (FDS), with no prior experience of intraoral scanning, full-arch scanned (IOS) a mannequin head-mounted model under supervision. Three scanning systems were used, TRIOS Colour (TRIOS); True Definition (TDef); and CEREC AC OmniCam (CEREC). Thereafter, FDS completed a questionnaire to assess their perception of IOS. Data were analysed by Generalized Estimating Equations, Fisher's exact tests and logistic regression. RESULTS: Forty-nine FDS participated. Average full arch IOS time varied significantly (p<0.001) among the TRIOS, CEREC, and TDef, at 4min (n=48), 4min 42s (n=33), and 7min 32s (n=41) respectively. IOS using the TRIOS was significantly (p<0.001) the quickest, while TDef was the slowest (p<0.001). Seventy-one percent of FDS had positive overall IOS experience. FDS who reported intraoral scanning was timesaving compared with conventional impressions were more likely to adopt the technology after graduation (odds ratio (OR)=11.91, 95% confidence interval (CI)=2.56-55.45, p=0.002). CONCLUSIONS: Intraoral scanning performance of novice users varied significantly and was dependent on the scanning system used. The questionnaire showed that the overall IOS experience was positive amongst FDS. The perception of time-saving, when using IOS versus conventional impression methods, determined the likelihood of future adoption of the technology.

We're Going Digital: The Current State of CAD/CAM Dentistry in Prosthodontics.

This paper reviews the current state of computer-aided design and manufacturing (CAD/CAM) in dentistry, with a special focus on restorative dental applications. The potential, advantages, and limitations of the technology will be discussed, comparing the digital workflow to conventional techniques, based on contemporary clinical evidence. The technology does seem to offer a more streamlined and efficient means of treatment planning and delivery of care through reduced chairside time, with reported improved patient satisfaction. Nonetheless, the accuracy and treatment outcomes of CAD/CAM treatment modalities are inconsistent and do not support a superior performance to existing conventional techniques, rather a comparable one.

Longevity of fiber-reinforced composite fixed partial dentures (FRC FPD)-Systematic review.

OBJECTIVES: to assess FRC FPDs longevity through systematically reviewing contemporary clinical evidence. Population investigated comprised patients requiring replacement of a single missing anterior/posterior tooth. Intervention was FRC FPDs. No control/comparison selected. Outcome was longevity of FRC FPDs. The focus question was: 'What is the longevity of FRC FPDs used to replace one anterior or posterior tooth in patients?' DATA: Randomised, non-randomised, controlled, prospective and retrospective clinical studies were included. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses were applied. The Overall Strength of Clinical Recommendation (OSCR) was assessed using the Strength of Recommendation Taxonomy system. Survival of FPDs was assessed using the Kaplan-Meier method. Analysis of FPD-survival according to location and occurrence of different failures was performed using Logrank and Chi-square testing. SOURCES: PubMed, MEDLINE, and Web of Science databases were searched between January 2007 and December 2015. STUDY SELECTION: Nine studies were included, involving placement of 592 FRC FPDs in 463 patients. Follow-up periods ranged between 2 months and 8 years. Kaplan-Meier overall survival probability was 94.5% (95%C.I: 92.5%-96.5%) at 4.8 years. There was no significant difference in survival probability of anterior versus posterior FRC FPDs (P=0.278). Veneering material fracture/delamination occurred significantly more than other types of failures (Ps<0.05). A meta-analysis could not be performed. OSCR was moderate. CONCLUSIONS: FRC FPDs demonstrated high overall survival with predictable performance outcomes. However, long-term performance remains unclear. CLINICAL SIGNIFICANCE: FRC FPDs are viable medium-term management alternatives for replacing single anterior or posterior teeth in patients.

Clinical Monitoring of Tooth Wear Progression in Patients over a Period of One Year Using CAD/CAM.

PURPOSE: The aim of this study was to clinically monitor the progression of tooth wear over a period of 1 year in a cohort of referred tooth wear patients through the use of a computer-aided design/computer-assisted manufacture (CAD/CAM) scanner and a standardized scanning/assessment methodology. MATERIALS AND METHODS: Polyether impressions were made of 11 participants (130 teeth) at baseline and at 1 year. Impressions were poured in type IV dental stone and the anterior teeth were 3D scanned. A surface-matching software was used to compare 1-year and baseline scans and identify any dimensional differences. RESULTS: Parafunctional habits were reported by all patients. All participants exhibited tooth wear ≥ 140 µm in depth and extending to ≥ 280 µm in at least one tooth. Maxillary central incisors were the most commonly and severely affected teeth. CONCLUSION: The ability of the developed CAD/CAM scanning methodology in clinical monitoring of tooth wear was demonstrated. Further research is needed to assess its practicality in large-scale epidemiologic tooth wear studies.

Management of Tooth Wear: A Holistic, Dental, Medical, and Mental Healthcare Approach.

Tooth wear is a condition that affects a substantial cohort of dental patients. It has a measurable impact on patients' satisfaction, and overall quality of life. Recently, with growing evidence, our understanding of the aetiology, progression, and management of tooth wear has evolved. The paper argues that pathological tooth wear should not be solely considered as a dental condition, but rather a dental manifestation of other mental and medical disorders. As such, successful management of tooth wear, and its underlying aetiology, requires a holistic, multidisciplinary management approach, involving dental, medical, and mental healthcare providers.

A Proposed Methodology to Assess the Accuracy of 3D Scanners and Casts and Monitor Tooth Wear Progression in Patients.

PURPOSE: The aim of this study was to detail and assess the capability of a novel methodology to 3D-quantify tooth wear progression in a patient over a period of 12 months. MATERIALS AND METHODS: A calibrated stainless steel model was used to identify the accuracy of the scanning system by assessing the accuracy and precision of the contact scanner and the dimensional accuracy and stability of casts fabricated from three different types of impression materials. Thereafter, the overall accuracy of the 3D scanning system (scanner and casts) was ascertained. Clinically, polyether impressions were made of the patient's dentition at the initial examination and at the 12-month review, then poured in type IV dental stone to assess the tooth wear. The anterior teeth on the resultant casts were scanned, and images were analyzed using 3D matching software to detect dimensional variations between the patient's impressions. RESULTS: The accuracy of the 3D scanning system was established to be 33 µm. 3D clinical analysis demonstrated localized wear on the incisal and palatal surfaces of the patient's maxillary central incisors. The identified wear extended to a depth of 500 µm with a distribution of 4% to 7% of affected tooth surfaces. CONCLUSION: The newly developed 3D scanning methodology was found to be capable of assessing and accounting for the various factors affecting tooth wear scanning. Initial clinical evaluation of the methodology demonstrates successful monitoring of tooth wear progression. However, further clinical assessment is needed.

The psychology of tooth wear.

AIM: To review the main psychological and mental conditions that are manifested dentally in the form of tooth wear. These conditions include depression, eating disorders, and alcohol and drug use disorders. The paper will also review the comorbidity of these conditions and the relevance of other medical conditions and lifestyle factors, such as gastroesophageal reflux disorder, smoking and diet, in the expression of tooth wear. CONCLUSION: A holistic, multidisciplinary, healthcare approach is required in management of tooth wear patients with underlying mental health disorders. Dentists and Dental Care Professionals can have an important role in identifying these mental disorders through the observed tooth wear. They can also play a key role in monitoring patients' response and compliance to medical treatment through the monitoring of tooth wear progression and expression.