Single and partial tooth replacement with fixed dental prostheses supported by dental implants: A systematic review of outcomes and outcome measures used in clinical trials in the last 10 years.

AIM: To evaluate outcome measures, methods of assessment, and analysis in clinical studies on fixed single- and multiple-unit implant restorations. MATERIALS AND METHODS: Three independent electronic database searches (MEDLINE, EMBASE, and Cochrane) were done to identify prospective and retrospective clinical studies published from January 2011 up to June 2021 with ≥20 patients and minimum 1-year follow-up period on technical and clinical outcomes of implant-supported single crowns (SCs) and partial fixed dental prostheses (P-FDPs). An entire data extraction was performed to identify primarily the most reported outcome measures and later to define the choice of assessment methods of those outcome measures. The outcomes were analysed descriptively, and the strength of association was evaluated using the Pearson chi-square test (p ≤ .05). RESULTS: In a total 531 studies, 368 on SCs (69.3%), 70 on P-FDPs (13.1%), and 93 on both restoration types (17.5%) were included; 56.3% of all studies did not clearly define a primary outcome. The most frequent primary outcome was marginal bone level (MBL) (55.2%) followed by implant survival (5.3%), professional aesthetic evaluation (3.4%), and technical complications (2.1%). Peri-implant indices were the most reported secondary outcome (55.1%), followed by implant survival (39.9%), MBL (36%), and implant success (26.4%). Prosthetic failure (seven studies [3.9%]) was one of the least reported outcome measures. CONCLUSIONS: Outcome measures and their assessment methods showed high heterogeneity among studies. Primary outcomes were not often defined clearly, and the most frequently selected primary outcome was marginal bone loss. Prosthetic outcomes, implant survival, and patient-related outcomes were only infrequently reported.

Clinical outcomes of full-arch immediate fixed prostheses supported by two axial and two tilted implants: A retrospective cohort study with 12-15 years of follow-up.

PURPOSE: To retrospectively assess clinical and radiographic outcomes of immediately loaded full-arch fixed prostheses supported by axial and tilted implants up to 15 years of function. MATERIALS AND METHODS: Patients with one completely edentulous arch received an immediate full-arch fixed prosthesis supported by two anterior axial and two posterior tilted implants. Definitive prosthesis consisting of a CAD-CAM titanium framework and acrylic teeth was delivered 6 months later. Patients were regularly followed to assess clinical parameters and marginal bone level (MBL) change. Multilevel regression analysis was performed to investigate factors affecting implant failure and MBL. RESULTS: Six hundred ninety-two implants were placed in 72 maxillae and 101 mandibles. Seven maxillary implants (5 axial and 2 tilted) in 6 patients and 12 mandibular implants (6 axial and 6 tilted) in 5 patients failed. 15-year cumulative implant survival was 97.51% and 96.91% in maxilla and mandible, respectively (p = .64). After 10 years, the difference in MBL between axial and tilted implants was not significant in the maxilla (p = .47, 65 patients), while it was in the mandible (p < .001, 80 patients). Significant higher bone loss was reported in the mandible at both 5- and 10-year follow-up (p < .001 and p = .004, respectively). Mixed-effect multilevel linear regression evidenced a correlation between arch and bone loss at 5- and 10-year follow-up, while no correlation was found with age, gender, smoking, diabetes, and history of periodontal disease. CONCLUSION: This long-term study suggests that the present technique can be considered a viable treatment modality for the immediate rehabilitation of both maxilla and mandible.

Single and partial tooth replacement with fixed dental prostheses supported by dental implants: A systematic review of outcomes and outcome measures used in clinical trials in the last 10 years.

AIM: To evaluate outcome measures, methods of assessment, and analysis in clinical studies on fixed single- and multiple-unit implant restorations. MATERIALS AND METHODS: Three independent electronic database searches (MEDLINE, EMBASE, and Cochrane) were done to identify prospective and retrospective clinical studies published from January 2011 up to June 2021 with ≥20 patients and minimum 1-year follow-up period on technical and clinical outcomes of implant-supported single crowns (SCs) and partial fixed dental prostheses (P-FDPs). An entire data extraction was performed to identify primarily the most reported outcome measures and later to define the choice of assessment methods of those outcome measures. The outcomes were analysed descriptively, and the strength of association was evaluated using the Pearson chi-square test (p ≤ .05). RESULTS: In a total 531 studies, 368 on SCs (69.3%), 70 on P-FDPs (13.1%), and 93 on both restoration types (17.5%) were included; 56.3% of all studies did not clearly define a primary outcome. The most frequent primary outcome was marginal bone level (MBL) (55.2%) followed by implant survival (5.3%), professional aesthetic evaluation (3.4%), and technical complications (2.1%). Peri-implant indices were the most reported secondary outcome (55.1%), followed by implant survival (39.9%), MBL (36%), and implant success (26.4%). Prosthetic failure (seven studies [3.9%]) was one of the least reported outcome measures. CONCLUSIONS: Outcome measures and their assessment methods showed high heterogeneity among studies. Primary outcomes were not often defined clearly, and the most frequently selected primary outcome was marginal bone loss. Prosthetic outcomes, implant survival, and patient-related outcomes were only infrequently reported.

Load-bearing capacity and wear characteristics of short fiber-reinforced composite and glass ceramic fixed partial dentures.

The aim of this study was to evaluate load-bearing capacity and wear performance of experimental short fiber-reinforced composite (SFRC) and conventional lithium-disilicate CAD/CAM fabricated fixed partial dentures (FPDs). Two groups (n = 12/group) of three-unit CAD/CAM fabricated posterior FPDs were made. The first group used experimental SFRC blocks, and the second group fabricated from lithium-disilicate (IPS e.max CAD). All FPDs were luted on a zirconia testing jig with dual-curing resin cement. Half of FPDs per group were quasi-statically loaded until fracture. The other half experienced cyclic fatigue aging (100.000 cycles, Fmax = 500 N) before loading quasi-statically until fracture. Fracture mode was examined using SEM. Wear test was performed using 15,000 loading cycles. Both material type and aging had a significant effect on the load-bearing capacity of FPDs. Experimental SFRC CAD without fatigue aging had significantly the highest load-bearing capacity (2096 ± 149N). Cyclic fatigue aging decreased the load-bearing capacity of the SFRC group (1709 ± 188N) but increased it for the lithium-disilicate group (1546 ± 155N). Wear depth values of SFRC CAD (29.3µm) were significantly lower compared to lithium-disilicate (54.2µm). Experimental SFRC CAD demonstrated the highest load-bearing capacity before and after cyclic fatigue aging, and superior wear behavior compared to the control material.

Potential Impact of Prosthetic Biomaterials on the Periodontium: A Comprehensive Review.

The success of a prosthetic treatment is closely related to the periodontal health of the individual. The aim of this article was to review and present the importance of prosthetic restorative materials on the condition of the periodontium, the changes that occur in the composition of the subgingival microbiota and the levels of inflammatory markers in gingival crevicular fluid. Articles on the influence of different prosthetic restorative materials on subgingival microbiota and proinflammatory cytokines were searched for using the keywords "prosthetic biomaterials", "fixed prosthesis", "periodontal health", "subgingival microbiota", "periodontal biomarkers" and "gingival crevicular fluid" in PubMed/Medline, Science Direct, Scopus and Google Scholar. The type of material used for prosthesis fabrication together with poor marginal and internal fit can result in changes in the composition of the subgingival microbiota, as well as increased accumulation and retention of dentobacterial plaque, thus favoring the development of periodontal disease and prosthetic treatment failure. Biological markers have helped to understand the inflammatory response of different prosthetic materials on periodontal tissues with the main purpose of improving their clinical application in patients who need them. Metal-free ceramic prostheses induce a lower inflammatory response regardless of the fabrication method; however, the use of CAD/CAM systems is recommended for their fabrication. In addition, it is presumed that metal-ceramic prostheses cause changes in the composition of the subgingival microbiota producing a more dysbiotic biofilm with a higher prevalence of periodontopathogenic bacteria, which may further favor periodontal deterioration.

Risk Factors Associated with Failure and Technical Complications of Implant-Supported Single Crowns: A Retrospective Study.

Background and Objectives: Implant-supported single crowns have become a routine approach for the replacement of missing single teeth, being considered as one of the most common ways of rehabilitation when adjacent teeth are healthy. The present retrospective study aimed to investigate the risk factors possibly associated with failure and technical complications of implant-supported single crowns and their supporting implants. Materials and Methods: Patients treated at one faculty (2009-2019) were considered for inclusion. Complications investigated included ceramic fracture/chipping, crown loss of retention/mobility, crown failure/fracture, loosening/loss/fracture of prosthetic screw, and implant failure/fracture. Any condition/situation that led to the removal/replacement of crowns (implant failure not included) was considered prosthesis failure. Univariate/multivariate Cox regression models were used to evaluate the associations between clinical covariates and failure. Results: 278 patients (358 crowns) were included. Mean ± SD follow-up was 56.5 ± 29.7 months. Seven implants (after a mean of 76.5 ± 43.7 months) and twenty crowns (21.3 ± 23.5 months) failed. The cumulative survival rate (CSR) for crowns was 93.5% after 5, remaining at 92.2% between 6 and 11 years. The most common reasons for crown failure were porcelain large fracture (n = 6), crown repeatedly loose (n = 6), and porcelain chipping (n = 5). Men and probable bruxism were identified in the Cox regression model as being associated with crown failure. The most common observed technical complications were mobility of the crown and chipping of the ceramic material, with the latter being observed even in crowns manufactured of monolithic zirconia. Cases with at least one technical complication (not considering loss of screw hole sealing) were more common among probable bruxers than in non-bruxers (p = 0.002). Cases of ceramic chipping were more common among bruxers than in non-bruxers (p = 0.014, log-rank test). Conclusions: Probable bruxism and patient's sex (men) were factors associated with a higher risk of failure of implant-supported single crowns.

A multicentric study to evaluate the treatment outcome and complications after oral rehabilitation with implant-supported hybrid prostheses.

Background: As a newer modality of rehabilitation of completely edentulous patients, there is no conclusive evidence on which of the variants of hybrid prosthesis, namely acrylic teeth on a metal substructure or porcelain fused to metal teeth over on a metal substructure, is better in terms of treatment outcome, reduced mechanical complications, and better patient compliance. Methods: Sixteen completely edentulous patients, both male and female, were selected from the OPD of the study centers during the study period. Group A: Eight patients rehabilitated by maxillary and mandibular hybrid prosthesis using a substructure of metal covered by acrylic teeth, which was screwed on the implants. Group B: Eight patients rehabilitated by maxillary and mandibular hybrid prosthesis using a substructure of metal covered by porcelain fused to metal teeth, which was screwed on implants. The patients were recalled at 3 months, 6 months, and 1 year following rehabilitation, and necessary clinical and radiological observations were made to evaluate the overall health and complications. Oral health-related quality of life was measured using the Oral Health Impact Profile (OHIP)-EDENT questionnaire before treatment and after rehabilitation. The same methodology, clinical procedures, and evaluation criteria were followed in all the study centers. The data obtained were then compiled and analyzed. Results: None of the patients in group A or B showed any signs of need to remake. There was no statistically significant difference in proportions of cases showing signs of loosening of components, soft tissue overgrowth, breakage of acrylic, chipping of porcelain, and wear of teeth in both the groups. The amount of screw loosening, wear of prosthetic superstructure, and bone loss around implants were less (even though not statistically significant) in group A. Both the groups showed satisfactory esthetics. OHIP- EDENT evaluation gave completely satisfactory report after rehabilitation in both groups. Conclusion: Both the types of complete rehabilitation, hybrid prosthesis of acrylic teeth on a metal substructure and hybrid prosthesis of porcelain fused to metal teeth on a metal substructure were successful and comparably reliable.

Evaluation of marginal/internal fit of fixed dental prostheses after digital, conventional, and combination impression techniques: A systematic review.

Advances of digital technology are rapidly adopted in dental practice. This systematic review aimed to collect evidence on the accuracy of fit of different types of fixed dental prostheses (FDPs) fabricated through digital, conventional, or combination impression techniques. Data collection was based on the guidelines of the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Two databases (PubMed, Scopus) were searched for articles in English published between 2010 and 2021 resulting in 480 articles. Of those, 35 studies fulfilled the inclusion criteria. These articles referred to three groups of materials/techniques including all-ceramic (zirconia; lithium disilicate) and porcelain-fused-to-metal (PFM) restorations. Results showed clinically acceptable marginal fit (< 120 µm) for all materials and impression techniques. Α fully digital workflow appears more promising for the construction of short-span zirconia FDPs. Nevertheless, most articles evaluated marginal/internal fit of single crowns or short-span FDPs in vitro, while clinical data are limited for long-span FDPs. The necessity for gingival retraction remains a major drawback of all impression techniques, increasing procedural time and patient discomfort. Besides, factors related to the fabrication process, including milling and 3D printing of working models significantly influence the outcome. Overall, there still some way to go before digital technology can be incorporated in complex treatment plans in prosthodontics.

A 3-Dimensional Finite Element Analysis of Resected Mandibular Bone to Determine the Most Stable Implant Positions for a Fixed Prosthesis.

This study was conducted to determine the most secure implant positioning on the marginally resected mandible to support a fixed complete denture through finite element analysis. Three or 4 implants were placed at near, middle, or far positions from the resected margin in a simulation model with a symmetrical marginal defect in the mandibular symphysis. The height of the residual bone was 5, 10, or 15 mm. The 4 possible implant patterns for 3 or 4 implants were defined as (1) asymmetrically isolated position 1 to position 2, (2) asymmetrically isolated position 1 to position 3, (3) asymmetrically isolated with greater-length position 1 to position 2, and (4) 2 implants symmetrically positioned on each side of the defect. The von Mises stress in the resected and peri-implant bone with respect to the occlusal force was calculated. Initially, because the peri-implant bone stress around the isolated implant at the near position was greater than at the middle and far positions regardless of the residual bone height, the near position was excluded. Second, the von Mises stress in the resected bone region was >10 MPa when the isolated implant was at the far position, and it increased inversely depending on the bone height. However, the stress was <10 MPa when the isolated implant was placed at the middle position regardless of the bone height, and it was significantly lower compared with the far position and equivalent to the symmetrically positioned implants. Furthermore, the use of a greater-length implant reduced peri-implant bone stress, which was even lower than that of the symmetrically positioned implants. These results suggest that the asymmetrically positioned 3-implant-supported fixed denture, using a greater-length isolated implant, placed neither too close to nor too far from the resected margin, can be an effective alternative to the symmetrically positioned 4-implant-supported fixed denture.

ZYGOMATIC IMPLANTS MAY IMPROVE QUALITY OF LIFE AND SATISFACTION IN PATIENTS WITH ATROPHIED MAXILLA.

ARTICLE TITLE AND BIBLIOGRAPHIC INFORMATION: Alberto J, Mariano S, Guerrero-s Y, Pato-mourelo J. Evaluation of Quality of Life And Satisfaction in Patients with Fixed Prostheses on Zygomatic Implants Compared with the All-on-Four Concept: A Prospective Randomized Clinical Study. Int J Environ Res Public Heal. 2021; 18(3426). SOURCE OF FUNDING: The Department of Oral Surgery, University of Murcia, Murcia, Spain. TYPE OF STUDY/DESIGN: Prospective randomized clinical trial.

The Relationship between Dental Findings and Tongue Pressure: A Survey of 745 Community-Dwelling Adults and Elderly Persons in Japan.

INTRODUCTION: Reduced tongue pressure is one of the causes of dysphagia. The purpose of this study was to investigate the relationship between dental findings and tongue pressure, and whether prosthetic treatment prevents reduced tongue pressure. METHODS: This was a cross-sectional study. Participants were 745 community-dwelling adults and elderly persons in the Goto Islands in Nagasaki, who underwent a health checkup for residents in 2015 and 2016. Data were collected on gender; age; grip strength; hemoglobin; Creatinine (Cr); glycated hemoglobin (HbA1c); history of stroke; smoking, drinking, exercise, and walking habits; number of teeth; wearing of removable dentures; functional units of natural teeth (n-FTUs), fixed prostheses (nif-FTUs), and removable dentures (t-FTUs); and tongue pressure. The associations between each variable and tongue pressure were examined using multiple regression analysis. Next, those with 3 or fewer n-FTUs were selected, and differences in tongue pressure were compared between those with 3 or fewer nif-FTUs and those with 4 or more nif-FTUs, using a propensity score matching method. RESULTS: Male gender, weak grip strength, low HbA1c, no drinking, and a low number of teeth were independent factors significantly associated with lower tongue pressure. Among participants with 3 or fewer n-FTUs, the 43 with 4 or more nif-FTUs showed significantly higher tongue pressure than the 43 with 3 or fewer nif-FTUs after propensity score matching, although the number of t-FTUs was not associated with tongue pressure. DISCUSSION/CONCLUSION: Tooth loss was significantly associated with lower tongue pressure. It was suggested that fixed prosthesis treatment might prevent the reduction of tongue pressure, but removable dentures did not have such an effect.

Zygomatic implant penetration to the central portion of orbit: a case report.

BACKGROUND: Zygomatic implants have been proposed in literature for atrophic maxillary fixed oral rehabilitations. The aim of the present research was to evaluate, by a clinical and tomography assessment, a surgical complication of a zygomatic implant penetration to the orbit. CASE PRESENTATION: A 56 year-old female patient was visited for pain and swelling in the left orbit after a zygomatic implant protocol. The orbit invasion of the zygomatic implant screw was confirmed by the CBCT scan. The patient was treated for surgical implant removal and the peri- and post-operative symptoms were assessed. No neurological complications were reported at the follow-up. The ocular motility and the visual acuity were well maintained. No purulent secretion or inflammatory evidence were reported in the post-operative healing phases. CONCLUSION: The penetration of the orbit during a zygomatic implant positioning is a surgical complication that could compromise the sight and movements of the eye. In the present case report, a zygomatic implant removal resulted in an uneventful healing phase with recovery of the eye functions.

Can Implant-Retained Fixed Prostheses Trigger Bone Response in the Posterior Region of Edentulous Mandibles? A 32-Month Cone-Beam Computerized Tomography Study Analyzing Bone Height and Density.

Research has shown that the presence of implants can revert bone resorption and thus contribute to a greater preservation of the residual bone ridge, especially in edentulous mandibles. Bone remodeling has yet to be extensively studied in the context of prosthetic options for edentulous arches. This study aims to evaluate the long-term behavior of bone tissue in the posterior region of edentulous mandibles rehabilitated with implant-retained fixed prostheses using cone-beam computerized tomography (CBCT). Selected individuals were rehabilitated with 5 external hexagon platform implants and an implant-retained fixed prosthesis. The CBCT scans were performed immediately after surgery and after 8, 22, and 32 months (T0, T8, T22, and T32, respectively). Implants were installed between the mental foramen. Subsequently, bone crest height and density were measured in the posterior region of the mandible on the images in 3 distinct areas at 5, 10, and 15 mm from the center of the distal implant axis. Analysis of variance and the Bonferroni post hoc test were used for multiple analyses. The results indicate a statistically significant difference in bone height between T0 and all subsequent times; the bone height at T32 was 8.85% higher than at T0 (P = .05). There was a difference in bone height between all analyzed regions. The bone growth difference between the 5-mm and 15-mm positions was 28.42% after 32 months (P = .00). A significant increase of 5.76% in bone density was observed between T0 and T22 (P = .03). Within the limitations of this study (sample size, follow-up duration), it was demonstrated that the use of implant-retained fixed prostheses in the mandible resulted in qualitative and quantitative bone growth (bone preservation) in the posterior region of the mandible. Further research is needed to identify the validity of our findings for other populations and to determine the duration of the bone-remodeling process in rehabilitated edentulous mandibles.

Morphometry and displacement analysis of the upper lips following maxillary full-arch implant-supported fixed prostheses: a 3D morphometric study.

BACKGROUND: With the emergence of three-dimensional (3D) integration technology, analysis of soft tissue displacement and morphological changes after maxillary full-arch implant-supported fixed prostheses can be performed. The aim of this study was to verify the feasibility of the 3D integration method for constructing the relative position of the prostheses and facial soft tissue, evaluate the displacement and morphological variation of the upper lips after maxillary full-arch implant-supported fixed prostheses. METHODS: Twenty-five maxillary edentulous patients were recruited in this study. At the time of final prosthesis delivery, the 3D prostheses data and three 3D facial profiles were integrated. After method validation, the 3D position changes of seven soft tissue landmarks were used to reflect the 25 upper lips. The variation of four morphological distances were analyzed to reflect the morphological alteration of the upper lips. Two pairs of dentofacial landmarks were used to analyze the sagittal relative position of the prostheses and soft tissue. The included patients were also grouped to determine the impact of sex, upper lip thickness, and length on lip support changes. RESULTS: The average distance of the two matched relative reliable forehead regions was only 0.32 mm. The sagittal shifts of labrale superius (LS), stomion (STO), crista philtri left (CPHL) and crista philtri right (CPHR) were 3.44 ± 1.39 mm, 2.52 ± 1.38 mm, 3.04 ± 1.18 mm, and 3.12 ± 1.21 mm, respectively. With the exception of the decrease in the length of subnasale (SN)-LS, the length of cheilion right (CHR)-cheilion left (CHL), CPHR-CPHL, and LS-STO significantly increased. The two pairs of dentofacial landmarks had strong positive movement correlations along the sagittal direction. Patients with thinner and longer lips showed more lip support than those with thicker and shorter lips by a clinically insignificant amount. CONCLUSIONS: The integration method of 3D facial and dental data showed high repeatability in constructing the dentofacial relative position. The linear equations reflecting dentofacial relative position could aid clinicians in evaluating the restoration effect and estimate the upper lip variation.

Radiographic evaluation of a cross-shaped incision technique for thick-gingiva and thin-gingiva patients treated with implant-supported fixed prosthesis.

BACKGROUND: To evaluate a cross-shaped incision technique for thick-gingiva and thin-gingiva patients treated with implant-supported fixed prosthesis. METHODS: Total 55 patients receiving cross-shaped incision were assigned into thick-gingiva group (29 cases) and thin-gingiva group (26 cases). Follow-up was performed at 3 and 12-month after final restoration. RESULTS: Mesial and distal papilla height was significantly greater in thick-gingiva group than thin-gingiva group at 3 and 12 months, while periodontal depth and crestal marginal bone level around implant had no significant difference between the two groups during follow-up. No case of recession of buccal marginal gingiva was observed in thick-gingiva group. However, the recession of marginal gingiva of buccal aspect of the crown was found in 5 patients (19.2%) with thin-gingiva. CONCLUSIONS: The cross-shaped incision may be applied to reconstruct gingival papillae and avoid the gingival recession in patients with thick-gingiva phenotype. Trial registration This study was registered at ClinicalTrials.gov (registration number NCT04706078, date 12 January 2021, Retrospectively registered).

Comparison of stresses in monoblock tilted implants and conventional angled multiunit abutment-implant connection systems in the all-on-four procedure.

BACKGROUND: The All-on-four dental implant method is an implantology method designed to provide a comfortable prosthetic treatment option by avoiding advanced surgical procedures. This research aims to compare and evaluate the stress and tension values in conventional angled multiunit abutment-implant connection systems and monoblock dental implants used in the all-on-four procedure with finite element analysis. METHODS: Two master models were created by placing four implants connected to multiunit abutments (group A) in the interforaminal region of a completely edentulous mandible and four monoblock implants (group B) in the same region of another completely edentulous mandible. Group A implants were classified according to their diameter as follows: 3.5 mm (M1A), 4.0 mm (M2A), and 4.5 mm (M3A). Similarly, group B implants were classified as M1B, M2B, and M3B. In the six models rehabilitated with acrylic fixed prostheses, a 100 N force was applied to the anterior implant region, and a 250 N force was applied to the posterior cantilever in both axial and 30° oblique directions. Von Mises stresses were analyzed in the bone and implant regions of all models. RESULTS: M1A and M1B, M2A and M2B, and M3A and M3B were compared with each other under axial and oblique forces. The maximum Von Mises stresses in the bone around implants and the prosthesis screws, and the maximum and minimum principal stresses in the cortical and trabecular bone in group A models were significantly higher than those in group B models. CONCLUSIONS: In monoblock implant systems under axial and oblique forces, higher stress is accumulated in the bone, prosthesis screw and implant compared to multiunit abutment-implant connection systems.

Biomechanical Properties and Biocompatibility of Implant-Supported Full Arch Fixed Prosthesis Substructural Materials.

OBJECTIVES: The purpose of this study was to investigate the fracture resistance, biocompatibility, hardness, and transverse strength of non-precious metal alloy (chromium-cobalt; Cr-Co), titanium (Ti), zirconia (Zr), polymethylmethacrylate (PMMA), and polyetheretherketone (PEEK) when employed as substructure materials according to the implant supported full arch fixed prosthesis treatment concept. MATERIALS AND METHODS: In total, 150 Cr-Co, Ti, Zr, PMMA, and PEEK samples (n = 30 per material) measuring 25 × 2 × 2 mm in size were produced. Of the samples, 50 (n = 10 for each material, all having dimensions of 6 × 3 mm) were subjected to biocompatibility tests. The Vickers hardness test and three-point bending test were performed; fracture resistance measurements were taken and the biocompatibility of the samples was evaluated by the XTT assay. RESULTS: Vickers hardness was highest for Zr (p < 0.05). PEEK and PMMA had the lowest (and similar) fracture resistance values (p < 0.05). Cell proliferation on the surfaces of the materials was similar between PEEK and Zr (p > 0.05), which were the most biocompatible materials. CONCLUSIONS: Within the limitations of this study, the most favorable materials in terms of biocompatibility were found as PEEK and Zr. When biomechanical properties are evaluated, the most durable materials can be specified as Cr-Co and Zr. Also, further studies are needed to improve material stability.

Evaluation of the quality of fixed prosthesis impressions in private laboratories in a sample from Yemen.

BACKGROUND: Fixed prosthodontics require an accurate impression for the teeth and the area to be restored for the laboratory to fabricate the desired restoration without mistakes. This study evaluated the quality of impressions received by private laboratories for the fabrication of fixed prosthesis by describing the frequency of clinically detectable errors and by analyzing association between the various factors involved. METHODS: 165 impressions were collected from four dental laboratories. Jaw involved, type of tray, size of tray, number of prepared units, type of impression materials, techniques and viscosity in case of elastomeric impressions and type of prosthesis requested were recorded. Data referring to errors and visible defects including errors in finish line, in preparation area, in silicone impression technique and blood in impression were also documented. Factors affecting errors present were also assessed. Association between dentist gender and experience years and impression errors was assessed. Chi square and Fisher exact tests used to examine the association between categorical variables and outcomes. RESULTS: The total of error considering not immediately pouring as an error. Alginate was the most impression used. of impressions evaluated (50.9%), 97% were have at least one visible error; 92.1% had errors in finish line, 53.9% had errors in preparation area and (72.8%) of elastomeric impressions were have at least one error in technique. Blood in impression was detected in 52.1% of impressions. Significant association was found between material type and errors in finishing line and preparation area. Significant relationships were found between gender and errors in silicone impression technique (p < 0.05). CONCLUSION: Within the limitations of this study, high frequency of detectable errors was found in fixed prosthesis impressions received by private dental laboratories. This high frequency is of serious concern, as this will result in poor fitted fixed prosthesis provided to patients.

Retention of luting agents used for implant-supported restorations: A comparative In-Vitro study.

AIMS: The aim of this study was to compare the retention of different luting agents used with implant-supported restorations. MATERIALS AND METHODS: A total of 90 custom metal frameworks and copings were prepared and divided into six different luting agent groups (n = 15/group): polycarboxylate cement (PC), resin-modified glass-ionomer cement (RMGIC), two self-adhesive resin cements (SARC), copper-ion zinc-phosphate cement (CZPC), and non-eugenol temporary resin cement (TRC). After sandblasting with 50 µm Al2O3, the copings were cemented on frameworks and stored in artificial saliva for 48 h at 37°C and thermocycled between 5-55°C for 37,500 cycles. Samples were subjected to tensile testing by a universal testing machine, and data were statistically analyzed. RESULTS: The differences between the retention values of types of cement were significant (P < 0.05). The maximum retention value was calculated for CZPC (755,12 ± 55 MPa) while the lowest value was for TRC (311,7 ± 61 Mpa). CONCLUSION: Neither of the tested cement had superiority over another to ensuring retention. The types of cement presented were meant to be a discretionary guide for the clinician in deciding the amount of the desired retention between castings and abutments.

Evaluation of flexural strength of Zirconia using three different connector designs: An in vitro study.

AIM: The aim of this study is to evaluate the flexural strength of zirconia using three different connector designs under vertical and oblique loads. SETTING AND DESIGN: Invitro - analytical study. MATERIALS AND METHODS: For simulating zirconia fixed partial prosthesis, a specimen with three octagonal cylinders connected with each other was designed. Each face of the octagon was 3.75 mm ± 0.1 mm, and the total width was 9 mm ± 0.1 mm with a standard connector area of 10 mm2 at cross-section. Three different connector designs, i.e., round, oval, and triangular were milled. Universal testing machine was used to test flexural strength with vertical and oblique forces. STATISTICAL ANALYSIS USED: Intergroup comparison of flexural strength was made using Descriptive statistics (1) one-way ANOVA, Bonferroni's post hoc test (2) Kruskal-Wallis test. The confidence interval was set at 95%, P < 0.05 was considered statistically significant for both the tests. RESULTS: The highest flexural strength was observed in the triangle connector with vertical forces and lowest with oblique forces. CONCLUSIONS: Triangle connector design proved to be better than round and oval connectors on the application of vertical loads. Round connector design proved to be better than triangle and oval connector on application of oblique loads.