Comparisons of analog and digital methods to produce an accurate trial restoration.

STATEMENT OF PROBLEM: A trial restoration is an important diagnostic tool that can be fabricated through analog or digital pathways. Digital workflows may have improved accuracy, but this is yet to be demonstrated conclusively. PURPOSE: The purpose of this in vitro study was to compare the dimensional accuracy of trial restorations produced by different analog (molded) and digital (milled and 3D printed) methods. Parameters studied included fabrication methods, Shore-A hardness of silicone putty indices, length of span, and labial tooth levels. MATERIAL AND METHODS: Digital additive trial restorations were designed on a single virtual cast from maxillary right to left lateral incisor teeth (4 teeth) and from maxillary right to left first premolar teeth (8 teeth). Both designs were identical on the 4 anterior teeth. Each digital trial restoration was 3-dimensionally (3D) printed to produce reference casts. The original cast was 3D printed to produce 44 replica casts. There were 8 experimental groups (4 analog and 4 digital) with 10 specimens each. For the analog groups, 20 silicone indices per reference cast were made: 10 from standard silicone putty (63 to 70 Shore-A hardness) and 10 from hard silicone putty (90 Shore-A hardness). The analog trial restorations were molded on replica casts with silicone indices and bis-acryl resin. The digital trial restorations were either milled or 3D printed and adapted onto replica casts. Each trial restoration was scanned and digitally superimposed onto respective scanned reference casts. Measurements were recorded at 3 levels: cervical, middle, and incisal. The independent samples Kruskal-Wallis, 2-sample Mann-Whitney, and Bonferroni tests were used to compare the distribution of accuracy among all groups (α=.05). RESULTS: The dimensional accuracy of the different trial restoration fabrication methods was comparable in terms of median values of trueness (how close the readings were to the reference), and no statistically significant difference was found among them (P>.05). When the dimensional accuracy in terms of precision (how close the readings were to each other) were analyzed, the hard putty groups demonstrated a statistically significant better outcome, whereas standard putty consistently showed the poorest result. The incisal level displayed the most significant deviation (P=.005) when all groups were compared. The incisal discrepancy values of the short-span standard putty trial restoration varied by as much as 0.84 mm in some specimens. CONCLUSIONS: Milled and 3D printed trial restoration fabrication techniques showed dimensional accuracy comparable with that of the analog groups. However, the choice of silicone putty was shown to affect the dimensional accuracy of an analog molded trial restoration. A high Shore-A hardness silicone putty produced the best precision and should be used when fabricating an analog molded trial restoration.

Effects of Novel Dental Composites on Streptococcus mutans Biofilms.

With the phase-out of amalgam and the increase in minimally invasive dentistry, there is a growing need for high-strength composite materials that can kill residual bacteria and promote tooth remineralization. This study quantifies how antibacterial polylysine (PLS) and re-mineralizing monocalcium phosphate monohydrate (MCPM) affect Streptococcus mutans biofilms and the strength of dental composites. For antibacterial studies, the MCPM-PLS filler percentages were 0-0, 8-4, 12-6, and 16-8 wt% of the composite filler phase. Composite discs were immersed in 0.1% sucrose-supplemented broth containing Streptococcus mutans (UA159) and incubated in an anaerobic chamber for 48 h. Surface biomass was determined by crystal violet (CV) staining. Growth medium pH was measured at 24 and 48 h. Biofilm bacterial viability (CFU), exo-polysaccharide (water-soluble glucan (WSG) and water-insoluble glucan (WIG)), and extracellular DNA (eDNA) were quantified. This was by serial dilution plate counting, phenol-sulfuric acid microassay, and fluorometry, respectively. The biaxial flexural strengths were determined after water immersion for 1 week, 1 month, and 1 year. The MCPM-PLS wt% were 8-4, 8-8, 16-4 and 16-8. The normalized biomass, WSG, and WIG showed a linear decline of 66%, 64%, and 55%, respectively, as the PLS level increased up to 8%. The surrounding media pH (4.6) was all similar. A decrease in bacterial numbers with the 12-6 formula and a significant reduction with 16-8 compared to the 0-0 formulation was observed. The eDNA concentrations in biofilms formed on 12-6 and 16-8 formulations were significantly less than the 0-0 control and 8-4 formulations. Doubling MCPM and PLS caused a 14 and 19% reduction in strength in 1 week, respectively. Average results were lower at 1 month and 1 year but affected less upon doubling MCPM and PLS levels. Moreover, a 4% PLS may help to reduce total biomass and glucan levels in biofilms on the above composites. Higher levels are required to reduce eDNA and provide bactericidal action, but these can decrease early strength.

Accuracy of Original vs. Non-Original Abutments Using Various Connection Geometries for Single Unit Restorations: A Systematic Review.

PURPOSE: To ascertain whether the compatibility of non-original abutments (NOAs) with dental implants is influenced by the type of implant connection, i.e.- internal or external, and whether certain combinations of componentry may be as compatible as the original components. METHODS: A structured literature search was conducted using 3 electronic databases (MEDLINE® , The Cochrane Library, and Web of Science Core Collection) for studies reporting on the use of non-original abutments published between 1995 and 2020. This was supplemented with hand searching in relevant journals and references, as well as searching grey literature. Relevant studies were selected according to specific inclusion criteria. Data was collected for the following parameters: precision of fit, microleakage, micromorphological differences, micromotion, rotational misfit, screw loosening, maximum load capacity, fracture resistance, tensile strength, compressive strength and invivo implant and prosthesis outcomes. RESULTS: The electronic search and hand search yielded titles and abstracts of 5617 studies following de-duplication; based on the eligibility criteria, 40 studies were finally selected. Overall, original abutments showed better precision of fit, ability to resist microleakage, prevention of rotational misfit and micromotion, and fatigue strength compared with non-original abutments. Some non-original abutments on external connections were comparable with original abutments in terms of precision of fit and resistance to screw loosening and may be associated with less catastrophic failures than those on internal connections. CONCLUSION: Original abutments present more predictable outcomes than non-original abutments with regards to the parameters investigated. However, it seems that external connections can provide some level of compatibility in terms of precision of fit and may also exhibit less catastrophic failures than NOAs on internal connections. This may be due to the increased rotational freedom external connections provide. There is a lack of information regarding the influence of connection geometry on many aspects of compatibility and therefore the current clinical recommendation should be to use original abutments. More laboratory studies comparing non-original abutments on different implant connections are required. In addition, there is a need for long-term in vivo studies providing data on the clinical performance of non-original abutments.

Biomarkers associated with periodontitis and peri-implantitis: a systematic review.

PURPOSE: The pathology of peri-implantitis is still not fully understood and there have been recent challenges to the consensus on its aetiology and pathology, especially in comparison with periodontitis. The assessment of biomarkers allows a comparison of the pathology of these diseases. The aim of this systematic review was to answer the research question: "Is there a difference in the biomarkers associated with peri-implantitis compared with periodontitis in adult humans?" METHODS: Electronic databases were searched and screened, and a manual search was also undertaken. The inclusion criteria were adults with peri-implantitis who had been compared to adults with periodontitis with the outcome of biomarkers assessed via biopsies or crevicular fluid samples in primary or secondary care settings, as recorded in case-control, case series and retrospective, prospective and cross-sectional observational studies. Two reviewers independently screened titles and abstracts and assessed full text articles for eligibility and inclusion. Both reviewers independently extracted data and assessed risk of bias. Differences in biomarker levels were the primary outcome and a narrative review was undertaken due to the heterogeneity of studies. RESULTS: In total, 2,374 articles were identified in the search, of which 111 full-text articles were assessed for eligibility and 13 were included in the qualitative synthesis. Five of the 13 included studies were deemed to be at high risk of bias, with the others having moderate risk. All studies were cross-sectional and performed at university hospitals. Nine of the 13 included studies found significant differences in the levels of biomarkers or their ratios between peri-implantitis and periodontitis. Four of the studies found no significant differences. CONCLUSIONS: Within the limitations of the included studies, it appears that there may be a difference in biomarker levels and ratios between peri-implantitis and periodontitis, suggesting that these disease processes are somewhat distinct.

Comparison of Corrosion Products From Implant and Various Gold-Based Abutment Couplings: The Effect of Gold Plating.

This study compared titanium (Ti), palladium (Pd), platinum (Pt), and gold (Au) ion release following induced accelerated tribocorrosion from three Au alloy abutment groups coupled with Ti implants over time; investigated contacting surface structural changes; and explored the effect of Au plating. Three abutment groups, G (n = 8, GoldAdapt, Nobel Biocare), N (n = 8, cast UCLA, Biomet3i), and P (n = 8, cast UCLA, Biomet3i, Au plated), coupled with implants (Nobel Biocare), immersed in 1% lactic acid, were cyclically loaded. Ions released (ppb) at T1, T2, and T3, simulating 3, 5, and 12 months of function, respectively, were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and compared. Surface degradation and fretted particle composition after T3 were evaluated with scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). ICP-MS data were nonparametric, expressed as medians and interquartile ranges. SEM/EDX showed pitting, crevice corrosion, and fretted particles on the components. Released ion concentrations in all groups across time significantly decreased for Pd (P < .001, median range: 1.70-0.09), Pt (P = .021, 0.55-0.00), and Au (P < .001, 1.01-0.00) and increased for Ti (P = .018, 2.49-5.84). Total Ti release was greater than other ions combined for G (P = .012, 9.86-2.30) and N (P < .001, 13.59-5.70) but not for P (P = .141, 8.21-3.53). Total Ti release did not differ between groups (P = .36) but was less variable across group P. On average, total ion release was 13.77 ppb (interquartile range 8.91-26.03 ppb) across the 12-month simulation. Tribocorrosion of Ti implants coupled with Au abutments in a simulated environment was evidenced by fretted particles, pitting, and crevice corrosion of the coupling surfaces and release of ions. More Ti was released compared with Pd, Pt, and Au and continued to increase with time. Abutment composition influenced ion release. Au-plated abutments appeared to subdue variation in and minimize high-concentration spikes of titanium.

Impact of adding palatal rugae to complete dentures on patient satisfaction and oral health-related quality of life: A randomized crossover clinical trial.

STATEMENT OF PROBLEM: The addition of palatal rugae to complete dentures has been suggested to improve the satisfaction of patients with different oral functions. However, clinical studies to support these claims are lacking. PURPOSE: The purpose of this randomized, single-blind, 2-period crossover trial was to assess the satisfaction of edentulous patients and their oral health impact profile when provided with complete dentures with palatal rugae compared with a polished palate. MATERIAL AND METHODS: Edentulous patients aged 45 to 80 years, with no relevant medical conditions, seeking complete dentures at a university hospital between May and July 2019 were recruited. Each participant received new complete dentures. After a 1-week adaptation period, the participants were randomly allocated to 2 sequences through a computer-generated sequence. In the first sequence, palatal rugae were added to the complete dentures, and after 2 months, the palatal rugae were removed and the dentures used for another 2 months. In the second sequence, the opposite sequence was followed: polished palate first and palatal rugae second. After each period, a blinded dentist asked participants to rate their general satisfaction on a 100-mm visual analog scale (primary outcome) and to rate their satisfaction regarding eating, taste perception, speaking, phonetics, and ease of cleaning. Participants were also asked to fill the 20-item oral health impact profile for edentulous patients (OHIP-EDENT). The paired sample t test and the Wilcoxon test were used (α=.05). RESULTS: Fifty participants were randomized, of whom 6 dropped out. No significant differences were found between ratings for the 2 palatal contours in terms of general satisfaction 2.32 (95% confidence interval: -3.65 to 8.29, P=.438), eating 1.70 (95% confidence interval: -4.05 to 7.46, P=.554), taste perception 0.57 (95% confidence interval -5.04 to 6.17, P=.839), phonetics 1.48 (95% confidence interval -4.46 to 7.41, P=.618), or speaking 3.68 (95% confidence interval: -1.92 to 9.28, P=.192). However, satisfaction with ease of cleaning dentures with palatal rugae was significantly less 12.16 (95% confidence interval: 6.81 to 17.50, P<.001). The differences in the OHIP-EDENT total scores were not significantly different -1.75 (95% confidence interval: -3.7 to 0.23, P=.082). Differences in each item ratings were also found to be not significantly different (P>.05), except for the frequency of mealtime interruption (P=.041), which was reported to increase when rugae had been provided. CONCLUSIONS: Complete dentures with palatal rugae were not perceived to improve patient satisfaction or oral health-related quality of life. However, they were perceived to be more difficult to clean and to increase frequency of interruptions during eating.

Adhesion of Methicillin-Resistant Staphylococcus aureus and Candida albicans to Parylene-C-Coated Polymethyl Methacrylate.

PURPOSE: To determine whether coating polymethyl methacrylate (PMMA) discs with Parylene-C would reduce Staphylococcus aureus and Candida albicans biofilm formation. MATERIALS AND METHODS: MRSA and Candida albicans single and dual biofilms were grown for 48 hours in artificial saliva on parylene-C-coated or uncoated PMMA, and the viable biofilm colony-forming units were counted. RESULTS: There was no significant difference in the count of viable methicillin-resistant Staphylococcus aureus or Candida albicans recovered from single- or dual-species biofilms between coated and uncoated PMMA discs. CONCLUSION: Parylene-C does not prevent biofilm formation on PMMA.

Polymerization kinetics stability, volumetric changes, apatite precipitation, strontium release and fatigue of novel bone composites for vertebroplasty.

PURPOSE: The aim was to determine effects of diluent monomer and monocalcium phosphate monohydrate (MCPM) on polymerization kinetics and volumetric stability, apatite precipitation, strontium release and fatigue of novel dual-paste composites for vertebroplasty. MATERIALS AND METHODS: Polypropylene (PPGDMA) or triethylene (TEGDMA) glycol dimethacrylates (25 wt%) diluents were combined with urethane dimethacrylate (70 wt%) and hydroxyethyl methacrylate (5 wt%). 70 wt% filler containing glass particles, glass fibers (20 wt%) and polylysine (5 wt%) was added. Benzoyl peroxide and MCPM (10 or 20 wt%) or N-tolyglycine glycidyl methacrylate and tristrontium phosphate (15 wt%) were included to give initiator or activator pastes. Commercial PMMA (Simplex) and bone composite (Cortoss) were used for comparison. ATR-FTIR was used to determine thermal activated polymerization kinetics of initiator pastes at 50-80°C. Paste stability, following storage at 4-37°C, was assessed visually or through mixed paste polymerization kinetics at 25°C. Polymerization shrinkage and heat generation were calculated from final monomer conversions. Subsequent expansion and surface apatite precipitation in simulated body fluid (SBF) were assessed gravimetrically and via SEM. Strontium release into water was assessed using ICP-MS. Biaxial flexural strength (BFS) and fatigue properties were determined at 37°C after 4 weeks in SBF. RESULTS: Polymerization profiles all exhibited an inhibition time before polymerization as predicted by free radical polymerization mechanisms. Initiator paste inhibition times and maximum reaction rates were described well by Arrhenius plots. Plot extrapolation, however, underestimated lower temperature paste stability. Replacement of TEGDMA by PPGDMA, enhanced paste stability, final monomer conversion, water-sorption induced expansion and strontium release but reduced polymerization shrinkage and heat generation. Increasing MCPM level enhanced volume expansion, surface apatite precipitation and strontium release. Although the experimental composite flexural strengths were lower compared to those of commercially available Simplex, the extrapolated low load fatigue lives of all materials were comparable. CONCLUSIONS: Increased inhibition times at high temperature give longer predicted shelf-life whilst stability of mixed paste inhibition times is important for consistent clinical application. Increased volumetric stability, strontium release and apatite formation should encourage bone integration. Replacing TEGDMA by PPGDMA and increasing MCPM could therefore increase suitability of the above novel bone composites for vertebroplasty. Long fatigue lives of the composites may also ensure long-term durability of the materials.

Prosthodontic Complications of Metal-Ceramic and All-Ceramic, Complete-Arch Fixed Implant Prostheses with Minimum 5 Years Mean Follow-Up Period. A Systematic Review and Meta-Analysis.

PURPOSE: The purpose of this systematic review and meta-analysis was to review and analyze the prosthodontic complications, survival, and success of metal-ceramic (MC) and all-ceramic (AC) complete-arch fixed implant dental prostheses (CFIDPs) with a minimum mean follow-up period of 5 years. METHODS: A structured literature search was conducted using 3 electronic databases (MEDLINE, the Cochrane Library, Web of Science) for clinical studies reporting on prosthodontic complications of metal-ceramic and/or all-ceramic CFIDPs published between 2000 and 2016. This was complemented with hand searching in relevant journals, references, as well as searching in grey literature. Risk of bias analysis for randomized controlled trials was done following the recommendations from the Cochrane Collaboration. Quality appraisal for nonrandomized studies was executed according to the Newcastle-Ottawa scale (NOS). The final selection included only studies with a minimum mean follow-up time of 5 years. RESULTS: The electronic databases search yielded 1804 relevant titles and abstracts; 11 studies were finally selected (9 for MC and 2 for AC CFIDPs). Risk of bias in most selected studies was low. Heterogeneity across studies of MC CFIDPs was within acceptable range but not among AC CFIDP studies, so no meta-analysis was performed for the latter. Regarding MC CFIDPs, most studies recorded 100% survival rate (survival range: 92.4-100%, success range: 47-96.7%), with veneer fracture being the most-common complication. Five- and 10-year cumulative complication rates for MC CFIDP veneer fractures were 22.1% and 39.3%, respectively, but with variable confidence intervals. The 2 studies included for AC CFIDPs reported 100% survival rates but differed in success rates, with the one using predominantly monolithic zirconia restorations reporting 90.9%, and the one using bi-layered zirconia reporting 60.4%, with complications attributed to veneer fracture. CONCLUSIONS: MC and AC CFIDPs presented with veneer fractures as primary complication. This may require significant maintenance. Other complications were negligible after a mean follow-up period of at least 5 years. More long-term studies, especially on all-ceramic CFIDPs are needed.

Comparison of Accuracy Between a Conventional and Two Digital Intraoral Impression Techniques.

PURPOSE: To compare the accuracy (ie, precision and trueness) of full-arch impressions fabricated using either a conventional polyvinyl siloxane (PVS) material or one of two intraoral optical scanners. MATERIALS AND METHODS: Full-arch impressions of a reference model were obtained using addition silicone impression material (Aquasil Ultra; Dentsply Caulk) and two optical scanners (Trios, 3Shape, and CEREC Omnicam, Sirona). Surface matching software (Geomagic Control, 3D Systems) was used to superimpose the scans within groups to determine the mean deviations in precision and trueness (µm) between the scans, which were calculated for each group and compared statistically using one-way analysis of variance with post hoc Bonferroni (trueness) and Games-Howell (precision) tests (IBM SPSS ver 24, IBM UK). Qualitative analysis was also carried out from three-dimensional maps of differences between scans. RESULTS: Means and standard deviations (SD) of deviations in precision for conventional, Trios, and Omnicam groups were 21.7 (± 5.4), 49.9 (± 18.3), and 36.5 (± 11.12) µm, respectively. Means and SDs for deviations in trueness were 24.3 (± 5.7), 87.1 (± 7.9), and 80.3 (± 12.1) µm, respectively. The conventional impression showed statistically significantly improved mean precision (P < .006) and mean trueness (P < .001) compared to both digital impression procedures. There were no statistically significant differences in precision (P = .153) or trueness (P = .757) between the digital impressions. The qualitative analysis revealed local deviations along the palatal surfaces of the molars and incisal edges of the anterior teeth of < 100 µm. CONCLUSION: Conventional full-arch PVS impressions exhibited improved mean accuracy compared to two direct optical scanners. No significant differences were found between the two digital impression methods.

Monomer conversion, dimensional stability, strength, modulus, surface apatite precipitation and wear of novel, reactive calcium phosphate and polylysine-containing dental composites.

PURPOSE: The aim was to assess monomer conversion, dimensional stability, flexural strength / modulus, surface apatite precipitation and wear of mono / tri calcium phosphate (CaP) and polylysine (PLS)-containing dental composites. These were formulated using a new, high molecular weight, fluid monomer phase that requires no polymerisation activator. MATERIALS AND METHODS: Urethane and Polypropylene Glycol Dimethacrylates were combined with low levels of an adhesion promoting monomer and a light activated initiator. This liquid was mixed with a hybrid glass containing either 10 wt% CaP and 1 wt% PLS (F1) or 20 wt% CaP and 2 wt% PLS (F2). Powder to liquid mass ratio was 5:1. Commercial controls included Gradia Direct Posterior (GD) and Filtek Z250 (FZ). Monomer conversion and polymerisation shrinkage were calculated using Fourier Transform Infrared (FTIR). Subsequent volume increases in water over 7 weeks were determined using gravimetric studies. Biaxial flexural strength (BFS) / modulus (BFM) reduction and surface apatite precipitation upon 1 and 4 weeks immersion in water versus simulated body fluid (SBF) were assessed using a mechanical testing frame and scanning electron microscope (SEM). Mass / volume loss and surface roughness (Ra) following 7 weeks water immersion and subsequent accelerated tooth-brush abrasion were examined using gravimetric studies and profilometer. RESULTS: F1 and F2 exhibited much higher monomer conversion (72%) than FZ (54%) and low calculated polymerization shrinkage (2.2 vol%). Final hygroscopic expansions decreased in the order; F2 (3.5 vol%) > F1 (1.8 vol%) ~ Z250 (1.6 vol%) > Gradia (1.0 vol%). BFS and BFM were unaffected by storage medium type. Average BFS / BFM upon 4 weeks immersion reduced from 144 MPa / 8 GPa to 107 MPa / 5 GPa for F1 and 105 MPa / 6 GPa to 82 MPa / 4 GPa for F2. Much of this change was observed in the first week of immersion when water sorption rate was high. Surface apatite layers were incomplete at 1 week, but around 2 and 15 micron thick for F1 and F2 respectively following 4 weeks in SBF. Mass and volume loss following wear were equal. Average results for F1 (0.5%), F2 (0.7%), and FZ (0.5%) were comparable but lower than that of GD (1%). Ra, however, decreased in the order; F1 (15 µm) > F2 (11 µm) > GD (9 µm) > FZ (5 µm). CONCLUSIONS: High monomer conversion in combination with large monomer size and lack of amine activator should improve cytocompatibility of the new composites. High monomer molecular weight and powder content enables low polymerisation shrinkage despite high conversion. Increasing active filler provides enhanced swelling to balance shrinkage, which, in combination with greater surface apatite precipitation, may help seal gaps and reduce bacterial microleakage. High monomer conversion also ensures competitive mechanical / wear characteristics despite enhanced water sorption. Furthermore, increased active filler could help reduce surface roughness upon wear.

The effect of metal ions released from different dental implant-abutment couples on osteoblast function and secretion of bone resorbing mediators.

OBJECTIVES: The etiology of the reduced marginal bone loss observed around platform-switched implant-abutment connections is not clear but could be related to the release of variable amounts of corrosion products. The present study evaluated the effect of different concentrations of metal ions released from different implant abutment couples on osteoblastic cell viability, apoptosis and expression of genes related to bone resorption. METHODS: Osteoblastic cells were exposed to five conditions of culture media prepared containing metal ions (titanium, aluminum, vanadium, cobalt, chromium and molybdenum) in different concentrations representing the amounts released from platform-matched and platform-switched implant-abutment couples as a result of an earlier accelerated corrosion experiment. Cell viability was evaluated over 21days using the Alamar Blue assay. Induction of apoptosis was measured after 24h of exposure using flow cytometry. Expression of interleukin-6, interleukin-8, cyclooxygenase-2, caspase-8, osteoprotegerin and receptor activator of nuclear factor kappa-B ligand (RANKL) by osteoblastic cells were analysed after exposure for 1, 3 and 21days using real-time quantitative polymerase chain reaction assay RESULTS: Metal ions in concentrations representing the platform-matched groups led to a reduction in cell viability (P<0.01) up to 7days of exposure. Stimulated cells showed higher rates of early apoptosis (P<0.01) compared to non-treated cells. Metal ions up-regulated the expression of interleukin-6, interleukin-8, cyclooxygenase-2 and RANKL in a dose dependent manner after 1day of exposure (P<0.05). The up-regulation was more pronounced in the groups containing the corrosion products of platform-matched implant-abutment couples. CONCLUSION: Osteoblastic cell viability, apoptosis, and regulation of bone resorbing mediators were significantly altered in the presence of metal ions. The change in cytokine levels expressed was directly proportional to the metal ion concentration. CLINICAL SIGNIFICANCE: The observed biological responses to decreased amounts of metal ions released from platform-switched implant-abutment couples compared to platform-matched couples may partly explain the positive radiographic findings in respect to crestal bone level when utilising the "platform-switching" concept, which highlights the possible role of corrosion products in the mediation of crestal bone loss around dental implants.

Success and Survival of Various Types of All-Ceramic Single Crowns: A Critical Review and Analysis of Studies with a Mean Follow-Up of 5 Years or Longer.

PURPOSE: The aim of this critical review was to assess the survival and success rates of all-ceramic single crowns manufactured using different ceramic materials with a mean follow-up time of 5 years or longer. MATERIALS AND METHODS: An electronic search of studies published between 1980 and 2014 complemented by manual searching was conducted in Medline and Scopus. The terms ceramic, crown, survival, success, longevity, and complications were selected as keywords. Predetermined inclusion and exclusion criteria guided the search. Data were extracted and assessed by two independent reviewers. The results were statistically analyzed according to the type of material, and survival/success rate was calculated by assuming a Poisson-distributed number of events. RESULTS: The initial search yielded 972 articles. After subsequent filtering, 14 studies were selected. The inter-reviewer agreement was rated as good (κ = 0.65) and very high agreement (κ = 0.93) during the identification and screening phases, respectively. No studies on densely sintered zirconia or feldspathic crowns satisfied the minimum follow-up time. Only one study of each of the following materials satisfied the inclusion criteria: lithium disilicate, leucite reinforced, pressed Al2O3, and sintered Al2O3. Meta-analysis of the included studies on other materials resulted in the following estimated survival and success rates: for densely sintered alumina crowns, 93.8% and 92.75%, respectively; for fluoromica reinforced, 87.7% and 87.7%, respectively; and for glass-infiltrated alumina core, 94.4% and 92%, respectively. Crown fracture was considered the most frequent complication. CONCLUSION: Based on the present critical review, there was no evidence to support the superior application of a single ceramic system or material. Further long-term prospective studies are required.

The effect of different chemical intra-oral prostheses cleansers on the surface properties of Parylene-coated PMMA.

The purpose of this study was to investigate the effect of different chemical intra-oral prosthesis cleansers on the surface properties of Parylene-C coated and non-coated polymethyl methacrylate (PMMA). A total of 120 PMMA samples were prepared. Half of the samples were coated with 10 µm of Parylene-C. Samples were exposed to either air (control) or one of two types of denture cleansers, an alkaline peroxide cleanser (Steradent) or a neutral peroxide cleanser with enzyme (Poligrip). Surface roughness (Ra) and surface free energy (SFE) values were measured and compared between groups. Scanning electron microscopy was used for visual analysis. The samples coated with Parylene exhibited significantly lower mean Ra values compared to the non-coated samples (p<0.001). Immersion in Steradent increased the roughness of non-coated PMMA, but its effect was minimized on the coated surfaces. SFE increased for the samples exposed to air and Poligrip, but decreased for the samples exposed to Steradent.

The Effect of Different Water Temperatures on Retention Loss and Material Degradation of Locator Attachments.

PURPOSE: To examine the changes in Locator attachments after exposure to different water temperatures and cyclic loading. MATERIALS AND METHODS: Four groups of pink Locator attachments (3.0 lb. light retention replacement patrix attachments; 10 per group) were soaked for the equivalent of 5 years of use in distilled water at the following temperatures: 20°C, 37°C, 60°C. One group was kept dry to test the effect of water. A universal testing machine was used to measure the retention force of each treated attachment during 5500 insertion and removal cycles, simulating approximately 5 years of use. The results were compared using Kruskal-Wallis one-way ANOVA by ranks. Surface changes of tested attachments were examined using scanning electron microscopy (SEM). RESULTS: The exposure to 60°C water significantly increased the percentage of retention loss in Locator attachments (p < 0.05) compared to the 20°C water group and significantly reduced the final retention force compared to the other groups (p < 0.05). SEM examinations revealed severe cracking and material degradation in Locator attachments after exposure to 60°C water and cyclic loading, which were not evident in other groups. Cracking was observed after exposure to 60˚C water before cyclic loading. CONCLUSIONS: Exposure to 60°C water, potentially similar to denture cleansing procedures, could cause cracking in Locator attachments. Cracking is associated with hydrolytic degradation of nylon at 60°C. The change in structure could result in a significant loss of retention.

Dental Composites with Calcium / Strontium Phosphates and Polylysine.

PURPOSE: This study developed light cured dental composites with added monocalcium phosphate monohydrate (MCPM), tristrontium phosphate (TSrP) and antimicrobial polylysine (PLS). The aim was to produce composites that have enhanced water sorption induced expansion, can promote apatite precipitation and release polylysine. MATERIALS AND METHODS: Experimental composite formulations consisted of light activated dimethacrylate monomers combined with 80 wt% powder. The powder phase contained a dental glass with and without PLS (2.5 wt%) and/or reactive phosphate fillers (15 wt% TSrP and 10 wt% MCPM). The commercial composite, Z250, was used as a control. Monomer conversion and calculated polymerization shrinkage were assessed using FTIR. Subsequent mass or volume changes in water versus simulated body fluid (SBF) were quantified using gravimetric studies. These were used, along with Raman and SEM, to assess apatite precipitation on the composite surface. PLS release was determined using UV spectroscopy. Furthermore, biaxial flexural strengths after 24 hours of SBF immersion were obtained. RESULTS: Monomer conversion of the composites decreased upon the addition of phosphate fillers (from 76 to 64%) but was always higher than that of Z250 (54%). Phosphate addition increased water sorption induced expansion from 2 to 4% helping to balance the calculated polymerization shrinkage of ~ 3.4%. Phosphate addition promoted apatite precipitation from SBF. Polylysine increased the apatite layer thickness from ~ 10 to 20 µm after 4 weeks. The novel composites showed a burst release of PLS (3.7%) followed by diffusion-controlled release irrespective of phosphate addition. PLS and phosphates decreased strength from 154 MPa on average by 17% and 18%, respectively. All formulations, however, had greater strength than the ISO 4049 requirement of > 80 MPa. CONCLUSION: The addition of MCPM with TSrP promoted hygroscopic expansion, and apatite formation. These properties are expected to help compensate polymerization shrinkage and help remineralize demineralized dentin. Polylysine can be released from the composites at early time. This may kill residual bacteria.

The effect of platform switching on the levels of metal ion release from different implant-abutment couples.

The improved peri-implant bone response demonstrated by platform switching may be the result of reduced amounts of metal ions released to the surrounding tissues. The aim of this study was to compare the levels of metal ions released from platform-matched and platform-switched implant-abutment couples as a result of accelerated corrosion. Thirty-six titanium alloy (Ti-6Al-4V) and cobalt-chrome alloy abutments were coupled with titanium cylinders forming either platform-switched or platform-matched groups (n=6). In addition, 18 unconnected samples served as controls. The specimens were subjected to accelerated corrosion by static immersion in 1% lactic acid for 1 week. The amount of metal ions ion of each test tube was measured using inductively coupled plasma mass spectrometry. Scanning electron microscope (SEM) images and energy dispersive spectroscopy X-ray analyses were performed pre- and post-immersion to assess corrosion at the interface. The platform-matched groups demonstrated higher ion release for vanadium, aluminium, cobalt, chrome, and molybdenum compared with the platform-switched groups (P<0.05). Titanium was the highest element to be released regardless of abutment size or connection (P<0.05). SEM images showed pitting corrosion prominent on the outer borders of the implant and abutment platform surfaces. In conclusion, implant-abutment couples underwent an active corrosion process resulting in metal ions release into the surrounding environment. The highest amount of metal ions released was recorded for the platform-matched groups, suggesting that platform-switching concept has a positive effect in reducing the levels of metal ion release from the implant-abutment couples.

Effect of different initial finishes and Parylene coating thickness on the surface properties of coated PMMA.

STATEMENT OF THE PROBLEM: The colonization of microorganisms on acrylic resin dentures may result in denture-induced stomatitis. No efficient coating has yet been proposed to address this issue. PURPOSE: The purpose of this in vitro study was to assess the effect of various initial surface finishes and different Parylene coating thicknesses on the surface roughness (Ra) and surface free energy (SFE) of Parylene coated polymethyl methacrylate (PMMA). MATERIAL AND METHODS: One hundred and sixty PMMA specimens were produced and divided into 8 groups as follows: group A: uncoated, 1000 grit finish; group Ap1: 10 µm Parylene coated, 1000 grit finish; group B: uncoated, 1200 grit finish; group Bp: 10 µm Parylene coated, 1200 grit finish; group C: uncoated, 2400 grit finish; group Cp: 10 µm Parylene coated, 2400 grit finish; group Ap2: 20 µm Parylene coated, 1000 grit finish; group Ap3: 30 µm Parylene coated, 1000 grit finish. The Ra of all specimens was measured with a noncontact profilometer. To calculate the SFE, the Owens-Wendt approach was applied after measuring the contact angles with a goniometer. The topography of the specimens was observed by scanning electron microscope. RESULTS: Groups Ap1 and Bp presented significantly lower Ra values compared with their respective uncoated groups A and B (P<.001). No statistical difference was found between the Ra values of groups C and Cp, between A and Ap3, and between Ap2 and Ap3. The SFE values of the coated groups were significantly higher than the SFE values of the uncoated groups with the same initial finish (P<.001). CONCLUSIONS: Coating with a 10-µm layer of Parylene C resulted in lower Ra values for the rougher groups and increased SFE values. Increasing the coating thickness resulted in an increase of the Ra.

An Assessment of the Risk of Bias in Randomized Controlled Trial Reports Published in Prosthodontic and Implant Dentistry Journals.

PURPOSE: The objective of this study was to assess the risk of bias of randomized controlled trials (RCTs) published in prosthodontic and implant dentistry journals. MATERIALS AND METHODS: The last 30 issues of 9 journals in the field of prosthodontic and implant dentistry (Clinical Implant Dentistry and Related Research, Clinical Oral Implants Research, Implant Dentistry, International Journal of Oral & Maxillofacial Implants, International Journal of Periodontics and Restorative Dentistry, International Journal of Prosthodontics, Journal of Dentistry, Journal of Oral Rehabilitation, and Journal of Prosthetic Dentistry) were hand-searched for RCTs. Risk of bias was assessed using the Cochrane Collaboration's risk of bias tool and analyzed descriptively. RESULTS: From the 3,667 articles screened, a total of 147 RCTs were identified and included. The number of published RCTs increased with time. The overall distribution of a high risk of bias assessment varied across the domains of the Cochrane risk of bias tool: 8% for random sequence generation, 18% for allocation concealment, 41% for masking, 47% for blinding of outcome assessment, 7% for incomplete outcome data, 12% for selective reporting, and 41% for other biases. CONCLUSION: The distribution of high risk of bias for RCTs published in the selected prosthodontic and implant dentistry journals varied among journals and ranged from 8% to 47%, which can be considered as substantial.

Publication of statistically significant research findings in prosthodontics & implant dentistry in the context of other dental specialties.

OBJECTIVES: To assess the hypothesis that there is excessive reporting of statistically significant studies published in prosthodontic and implantology journals, which could indicate selective publication. METHODS: The last 30 issues of 9 journals in prosthodontics and implant dentistry were hand-searched for articles with statistical analyses. The percentages of significant and non-significant results were tabulated by parameter of interest. Univariable/multivariable logistic regression analyses were applied to identify possible predictors of reporting statistically significance findings. The results of this study were compared with similar studies in dentistry with random-effects meta-analyses. RESULTS: From the 2323 included studies 71% of them reported statistically significant results, with the significant results ranging from 47% to 86%. Multivariable modeling identified that geographical area and involvement of statistician were predictors of statistically significant results. Compared to interventional studies, the odds that in vitro and observational studies would report statistically significant results was increased by 1.20 times (OR: 2.20, 95% CI: 1.66-2.92) and 0.35 times (OR: 1.35, 95% CI: 1.05-1.73), respectively. The probability of statistically significant results from randomized controlled trials was significantly lower compared to various study designs (difference: 30%, 95% CI: 11-49%). Likewise the probability of statistically significant results in prosthodontics and implant dentistry was lower compared to other dental specialties, but this result did not reach statistical significant (P>0.05). CONCLUSIONS: The majority of studies identified in the fields of prosthodontics and implant dentistry presented statistically significant results. The same trend existed in publications of other specialties in dentistry.