Effect of the CAD/CAM Milling Protocol on the Fracture Behavior of Zirconia Monolithic Crowns.

Although advancements in CAD/CAM technology allow for more personalized treatments, it is not clear how modifications in the CAD/CAM milling process could affect the restoration surface conditions and their mechanical behavior. The objective of this study was to evaluate the effect of different CAD/CAM milling protocols on the topography and fracture behavior of zirconia monolithic crowns (3Y-PSZ) subjected to a chewing simulation. Monolithic 3Y-PSZ premolar crowns were milled using three protocols (n = 13) (slow (S), normal (N), and fast (F)). Crowns were cemented on a dentin analog abutment and subjected to mechanical aging (200 N, 2 Hz, 1,500,000 cycles, 37 °C water). Surviving crowns were subjected to compressive load test and analyzed using fractography. Fracture load data were analyzed with two-parameter Weibull analysis. The surface topography of the crowns was examined with a stereomicroscope and a 3D non-contact profiler. All crowns survived the chewing simulation. Crowns milled using the F protocol had the greatest characteristic fracture load, while crowns produced with the S protocol showed high Weibull modulus. Groups N and S had a more uniform surface and detailed occlusal anatomy than group F. The CAD/CAM milling protocol affected the topography and mechanical behavior of 3Y-PSZ monolithic crowns.

Effects of printing orientation and artificial ageing on martens hardness and indentation modulus of 3D printed restorative resin materials.

BACKGROUND: Three-dimensional (3D) printing is increasingly used to fabricate dental restorations due to its enhanced precision, consistency and time and cost-saving advantages. The properties of 3D-printed resin materials can be influenced by the chosen printing orientation which can impact the mechanical characteristics of the final products. PURPOSE: The objective of this study was to evaluate the influence of printing orientation and artificial ageing on the Martens hardness (HM) and indentation modulus (EIT) of 3D-printed definitive and temporary dental restorative resins. METHODS: Disk specimens (20 mm diameter × 2 mm height) were additively manufactured in three printing orientations (0°, 45°, 90°) using five 3D-printable resins: VarseoSmile Crownplus (VCP), Crowntec (CT), Nextdent C&B MFH (ND), Dima C&B temp (DT), and GC temp print (GC). The specimens were printed using a DLP 3D-printer (ASIGA MAX UV), while LavaTM Ultimate (LU) and Telio CAD (TC) served as milled control materials. Martens hardness (HM) and indentation modulus (EIT) were tested both before and after storage in distilled water and artificial saliva for 1, 30, and 90 days at 37 °C. RESULTS: 90° printed specimens exhibited higher HM than the other orientations at certain time points, but no significant differences were observed in HM and EIT between orientations for all 3D-printed materials after 90 days of ageing in both aging media. LU milled control material exhibited the highest HM and EIT among the tested materials, while TC, the other milled control, showed similar values to the 3D printed resins. CT and VCP (definitive resins) and ND displayed higher Martens parameters compared to DT and GC (temporary resins). The hardness of the 3D-printed materials was significantly impacted by artificial ageing compared to the controls, with ND having the least hardness reduction percentage amongst all 3D-printed materials. The hardness reduction percentage in distilled water and artificial saliva was similar for all materials except for TC, where higher reduction was noted in artificial saliva. SIGNIFICANCE: The used 3D printed resins cannot yet be considered viable alternatives to milled materials intended for definitive restorations but are preferable for use as temporary restorations.

Effect of bioceramic powder abrasion on different implant surfaces.

PURPOSE: Bioceramic coatings have been shown to promote bone repair, which aids in the early integration of implants. This study aimed to evaluate the influence of air abrasion with a bioceramic abrasive on the surface characteristics of different implant materials and surfaces. The dissolution of the applied treatment from the surfaces over 3 weeks was also assessed. MATERIALS AND METHODS: Discs of three alloys used for dental implants were studied and compared: two types of commercially pure titanium (CpTi)/ (CpTi SLActive) and titanium-zirconia (TiZr). The tested surfaces were: CpTi control (CpC), sandblasted (SB), sandblasted and acid-etched (SBE), and CpTi SLActive®, (TiZr) Roxolid®. Three discs from each group underwent air abrasion with apatite bioceramic powders, 95% hydroxyapatite (HA)/5% calcium oxide (CaO), and 90% hydroxyapatite (HA)/10% calcium oxide (CaO). The treated discs were surface characterized by optical profilometry to obtain surface roughness, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) to compare element weight percentages of titanium, calcium, and phosphate. Dissolution was assessed using inductively coupled plasma optic emission spectrometry (ICP-OES). RESULTS: Bioceramic powders were deposited on all tested surfaces leading to changes in surface characteristics. The only statistically significant differences between the material groups for surface roughness were found with 95% HA/5% CaO powder in the Sp and Rp parameters (p = 0.03 and 0.04, respectively). There were no significant differences in the Ca and P wt% between all groups and powders 95% HA/5% CaO and 90% HA/10% CaO (p = 0.14, 0.18, and p = 0.15, 0.12, respectively). A non-uniform dispersion of the treatment on the surface layer was visible on all treated surfaces. The bioceramic powder continued to dissolute from the tested surfaces for 3 weeks. CONCLUSION: Bioceramic abrasion modifies implant surface characteristics, although the change in surface characteristics resulting from such treatment was not influenced by the implant material or surface treatment. Air abrasion with hydroxyapatite and calcium oxide bioceramics leaves powder deposits on the treated implant surfaces that could potentially influence the healing of implants affected by peri-implantitis.

Staining and bleaching susceptibility of zirconia-reinforced lithium silicate glass-ceramics with different thicknesses, translucencies, and fabrication methods.

STATEMENT OF PROBLEM: The influence of different thicknesses, translucencies, and fabrication methods on the spectrophotometric and topographical properties of zirconia-reinforced lithium silicate glass-ceramics (ZLSs) for dental restorations remains unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of thicknesses, translucencies, and fabrication methods on the color stability, translucency parameter, opalescence parameter, whiteness stability, transmitted irradiance, light transmittance, opacity, gloss, and roughness of ZLSs exposed to coffee staining and bleaching treatments. MATERIAL AND METHODS: Two pressable ZLSs (VITA AMBRIA, VA and Celtra Press, CP) and 2 machinable ZLSs (VITA Suprinity, VS and Celtra Duo, CD) were examined at high translucency (HT) and low translucency (LT) levels in 2 thicknesses (n=160). The specimens were evaluated at baseline, after coffee staining, and after bleaching. The color stability (ΔE2000), translucency parameter (TP), opalescence parameter (OP), whiteness index (WID), and whiteness stability (ΔWID) were measured with a spectrophotometer. Transmitted irradiance (It), light transmission (T), and opacity (O) were obtained from a light-polymerizing unit and a polymerization light collection device. Roughness stability (ΔSa%) was determined with an optical profilometer, and gloss stability (ΔGU%) was recorded with a gloss meter. Data of ΔCIE2000, ΔWID, ΔSa%, and ΔGU% were analyzed by 4-way ANOVA, and data of the TP, OP, WID, It, T, and O were analyzed by repeated 4-way ANOVA (α=.05). RESULTS: VS-HT exceeded the ΔCIE2000 acceptability threshold after coffee staining and bleaching protocols. Pressable ZLSs exhibited greater color stability than machinable ZLSs. The 1-mm-thick VA, CP, and CD materials exceeded the ΔWID perceptibility threshold after bleaching. The highest TP and OP was displayed by the 1-mm-thick CP after bleaching. ΔGU increased after water storage and decreased after coffee staining and bleaching. ΔSa% significantly increased after bleaching (P<.05). CONCLUSIONS: The color stability and other spectrophotometric properties of ZLSs depended on material thickness. The effects of ZLS fabrication methods and translucency levels on their measured properties were inconsistent. Subjecting 1-mm-thick ZLS materials to acidic media adversely impacted their stainability and surface texture.

Effect of repeated firing on the topographical, optical, and mechanical properties of fully crystallized lithium silicate-based ceramics.

STATEMENT OF PROBLEM: The influence of different firing protocols on the topographical, optical, and mechanical properties of fully crystallized computer-aided design and computer-aided manufacturing (CAD-CAM) lithium silicate-based glass-ceramics (LSCs) for dental restorations remains unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of different firing regimens on the surface roughness, gloss, Martens hardness, indentation modulus, biaxial flexural strength, and crystalline structure of fully crystallized CAD-CAM LSCs and the effect of their interposition on the irradiance of a light-polymerization unit. MATERIAL AND METHODS: Three fully crystallized CAD-CAM LSC blocks were evaluated (N=150): lithium disilicate (Initial LiSi Blocks; LS), zirconia-reinforced silicate (Celtra Duo; CD), and lithium aluminum disilicate (CEREC Tessera; CT). Specimens were allocated to 5 subgroups according to their firing protocol. LSC roughness (Sa) was measured with an optical profilometer, and gloss (GU) was detected with a gloss meter. Martens hardness (HM) and indentation modulus (EIT) data were obtained from a hardness testing machine. The irradiance of a light-polymerization unit and transmittance of LSCs were measured with an instrument (Managing Accurate Resin Curing-Light Collector; BlueLight analytics, Inc) subsequent to ceramic interposition. Crystalline phases were analyzed by X-ray diffraction, and biaxial flexural strength (σ) was determined by the ball-on-3-ball method in a universal testing machine followed by Weibull analysis to calculate characteristic strength (σ0) and Weibull modulus (m). Two-way ANOVA and Tukey HSD post hoc tests (α=.05) were used to analyze the data. RESULTS: Statistically significant differences were found among different treatment groups based on Sa, GU, HM, and EIT values (P<.001). Delivered irradiance was significantly reduced following CT (P<.01) and glazed LSC (P<.005) interposition. CD displayed highest biaxial flexural strength and reliability after 1 firing cycle (σ=568.2 MPa, m=16.8) CONCLUSIONS: The type of material and firing regimens had a significant effect on the topographical, optical, and mechanical properties of fully crystallized CAD-CAM LSCs. Glazing significantly reduced delivered irradiance, Martens hardness, and biaxial flexural strength.

Synthesis and characterisation of microcapsules for self-healing dental resin composites.

AIM: The purpose of this study was to i) synthesise TEGDMA-DHEPT microcapsules in a laboratory setting; ii) characterise the resultant microcapsules for quality measures. MATERIALS & METHODS: Microcapsules were prepared by in situ polymerization of PUF shells. Microcapsules characterisation include size analysis, optical and SEM microscopy to measure the diameter and analyse the morphology of PUF microcapsules. FT-IR spectrometer evaluated microcapsules and benzyl peroxide catalyst polymerization independently. RESULT: Average diameter of TEGDMA-DHEPT microcapsules was 120 ± 45 µm (n: 100). SEM imaging of the capsular shell revealed a smooth outer surface with deposits of PUF nanoparticles that facilitate resin matrix retention to the microcapsules upon composite fracture. FT-IR spectra showed that microcapsules crushed with BPO catalyst had degree of conversion reached to 60.3%. CONCLUSION: TEGDMA-DHEPT microcapsules were synthesised according to the selected parameters. The synthesised microcapsules have a self-healing potential when embedded into dental resin composite as will be demonstrated in our future work.

The effect of water storage on nanoindentation creep of various CAD-CAM composite blocks.

BACKGROUND: To study the effect of water storage (3 months) on the creep deformation of various CAD-CAM composite structures at the nanoscale and compare it to that at the macroscale. METHODS: Seven CAD-CAM blocks were investigated: five resin-composite blocks (RCB), one polymer-infiltrated ceramic network (PICN) block, and one ceramic-filled polyetheretherketone (PEEK) block. Specimens of each material (n = 6) were separated into two groups (n = 3) according to their storage conditions (24 h dry storage at 23˚C and 3 months storage in 37˚C distilled water). Nano-indentation creep measurements were undertaken (creep depth measured in µm) using a nanoindenter (Nanovea) equipped with Berkovich three-sided pyramidal diamond tip. The machine was set for the chosen parameters: a load of 20 gf, a pause of 20 s, and the material type. Thirty indentations on 3 samples were made for each material for each test. Data were analysed using two-way ANOVA followed by one-way ANOVA and Bonferroni post hoc tests and independent t-test (< 0.05) for comparisons between the materials. RESULTS: The nanoindentation creep depth after 24 h storage ranged from 0.09 to 0.33 µm and increased after 3 months storage in distilled water to between 0.28 and 3.46 µm. There was a statistically significant difference in nanoindentation creep behaviour between the two storage conditions for each investigated material (independent t-test) and between all materials (Bonferroni post hoc). There was a non-significant negative correlation between nanoindentation creep (µm) and filler weight% at 24 h dry storage but a significant correlation at 3 months of water storage. A further non-significant positive correlation between nanoindentation creep (µm) and bulk compressive creep (%) was found. CONCLUSION: The PICN material showed superior dimensional stability in terms of nanoindentation creep depth in both storage conditions. Other composite blocks showed comparable performance at 24 h dry condition, but an increased nanoindentation creep upon water storage.

Effect of surface treatments on optical, topographical and mechanical properties of CAD/CAM reinforced lithium silicate glass ceramics.

OBJECTIVES: To investigate the effect of different surface treatments on optical, topographical and mechanical properties of CAD/CAM lithium silicate-based glass ceramics (LSC's) and their combined effect on the output of a light curing unit (LCU). METHODS: Four CAD/CAM LSC's were investigated: Lithium Disilicate (Emax CAD; EC), Zirconia-reinforced silicates (Vita Suprinity; VS and Celtra Duo;CD) and Lithium Aluminum Disilicate (CEREC Tessera; CT). Ceramic specimens (n = 240) were divided into six subgroups according to their surface treatment: (a) Control, (b) Hydrofluoric acid (HF) 5%, (c) HF 5% + Neutralizing agent (N), (d) HF 9%, (e) HF 9% +N and (f) Self-etching ceramic primer (SEP). Irradiance, power and radiant exposure of a LCU were measured with MARC-LC following ceramic specimen interposition. Direct light transmission (T%) and absorbance (Abs%) of the specimens were measured with UV-Vis spectrophotometry. Roughness (Sa, Sq) and wettability (θ°) were measured with optical profilometry and sessile drop profile analysis, respectively. Biaxial flexural strength (σ) of the ceramic specimens was measured by the ball-on-three-balls method and ceramic specimens were examined microscopically. Statistical analyses was performed by two-way ANOVA followed by post hoc multiple comparisons (α = 0.05). RESULTS: Acid neutralization decreased T% and increased Abs% in all LSC's and highest T% was exhibited with VS. Neutralized EC, VS and CD displayed higher Sa in HF9, while neutralized CT displayed higher Sa in HF5. Self-etch primer significantly reduced θ° (p < 0.001). σ was observed in the followed ascending order: HF9 +N < HF9 < HF5 +N < HF5 < SEP < Control for all LSC's. SIGNIFICANCE: Optical, topographical and mechanical properties of the CAD/CAM ceramic blocks were strongly dependent on the type of surface treatment. Results of neutralization post-etching indicate promising potential for future investigations.

The impact of surgical guide design and bone quality on heat generation during pilot implant site preparation: an in vitro study.

BACKGROUND: Surgical guides restrict the flow of cooling agent to osteotomy site, which will lead to a temperature rise that provokes tissue injury. Few studies compared differences in the temperature changes between non-limiting 'conventional' and limiting 'guided' surgical guides during implant site preparation. The objective of this study was to investigate the difference in temperature changes during bone drilling for implant placement using non-limiting and limiting surgical guides at cortical and cancellous bone levels. METHODS: Forty-four bovine rib samples were used for implant bed preparation in this study with a minimum thickness of 11 mm was chosen for the ribs. The bone was stored in a freezer at 10 °C until it was used. On the day of the study, the bone was defrosted and soaked in water at 21 °C for three hours before embarking on drilling to make sure each sample was at the same temperature when tested. Forty-four bone specimens were prepared and randomly allocated to receive either a limiting or a non-limiting surgical guides (22 for each group). The osteotomy site was prepared by one operator following the manufacturer's instructions, using limiting and non-limiting surgical guides. Temperature changes were recorded during implant bed preparation using thermocouples that fit into 7 mm-horizontal channels at two different depths (Coronally) and (Apically) at 1 mm distance from the osteotomy site. The data were tested for homogeneity of variances using Levene's test, then data were analyzed using an Independent sample t-test and the significance level was set at P ≤ 0.05. RESULTS: The mean temperature rise for all samples was 0.55 °C. The mean temperature rises for the limiting and non-limiting surgical guides were 0.80 °C and 0.33 °C respectively. There was a statistically significant difference in temperature rise between the limiting and non-limiting surgical guides (P = 0.008). In relation to position of temperature recording (coronal vs. apical), there was no significant difference (P > 0.05). No significant difference was noted between the two groups at cancellous bone level (P = 0.68), but the difference was significant at cortical bone level (P = 0.036). CONCLUSION: Limiting surgical guides showed higher readings than non-limiting. However, for both techniques, temperature rise was not significant clinically and within a safe range.

Pattern, frequency and causes of tooth extraction among adult Syrian refugees.

AIMS OR OBJECTIVES: The Syrian crisis has resulted in a significant impact on refugee oral health status, but the scientific literature lacks information characterizing the pattern of tooth extraction in refugees. MATERIALS AND METHODS: The current study analyzed the pattern of tooth extraction and the associated sociodemographic factors among 626 (53.4% females, 46.6% males) Syrian refugees who were treated in dental clinics in the Zaatari camp. All adult Syrian refugees attending the dental unit at Zaatari camp were eligible to participate. Clinical and sociodemographic data were collected from the study sample using a validated semi-structured survey over a period of 4 months. Descriptive statistics were generated and Chi-square test, independent sample t-test, ANOVA test and Bonferroni Post Hoc test were used to examine associations between the different variables. RESULTS: More than one third of the attendees (33.9%) were young adults (18-29 years), and nearly two thirds (69.8%) had no or very basic education. The mean number of teeth that needed extraction was (1.46 ± 0.84) and was significantly higher in males, smokers, older patients, and those with no or basic education. The most common cause for tooth extraction was dental caries (54.8%), followed by tooth fracture/un-restorability (38.5%), and periodontitis (3.4%); while the least common reason was tooth extraction for orthodontic treatment (0.20%). CONCLUSIONS: Dental caries and its sequelae were the leading cause of tooth extraction in this refugee population. Molar teeth were found to be the most frequently extracted and lower anteriors were the least. Older age, smoking, patients with lower educational level, poor oral hygiene and male gender all predispose to a higher incidence of tooth extractions.

The Effect of Simulated Chewing on the Surface Roughness of Direct and Indirect Resin-Composites Opposed by Zirconia: An In Vitro Study.

Purpose: To assess the surface roughness of two different light-cured resin-composites when opposed by monolithic zirconia after simulated mastication. Materials and Methods: Materials included a direct restorative nanohybrid (n = 10) and an indirect microhybrid (n = 10) resin-composite (Tetric EvoCeram and Sinfony, respectively). The antagonist material was 3 mol% yttria-stabilized tetragonal zirconia polycrystalline ceramic. Each material was subjected to in vitro chewing against zirconia using a chewing simulator for 250,000 cycles. A 3D profilometer was used to assess the surface roughness parameters of each resin-composite before and after the simulated chewing. Independent t-test and paired sample t-test were performed to compare roughness values for both materials and to compare baseline and after chewing simulation values (p = 0.05). Results: Sinfony showed significantly greater roughness values compared to Tetric EvoCeram (p ≤ 0.025) before and after simulated chewing, except for Sa and Sv parameters after simulated chewing where the difference between the two materials was insignificant (p = 0.06 and 0.89, respectively). Surface roughness increased for both materials after simulated chewing compared to baseline values, but the difference was insignificant (p ≥ 0.065). However, Sa (p = 0.04) and Sv (p = 0.012) for Tetric EvoCeram were significantly higher after compared to before chewing simulation. Conclusion: Tetric EvoCeram had a smoother surface than Sinfony before and after simulated chewing. Surface roughness for both materials was higher after simulated chewing compared to baseline values which represent surface damage that was significant for Tetric EvoCeram while Sinfony showed better resistance.

Sociodemographic Factors and Implant Consideration by Patients Attending Removable Prosthodontics Clinics.

Objective: This study is aimed at investigating the treatment options offered to and chosen by patients attending a student prosthodontics clinic and to investigate the effect of the sociodemographic background of participants on implant consideration. Material and Methods. A cross-sectional descriptive study was conducted on 200 participants including their socioeconomic background, treatment options presented, treatment preferences, and implant consideration. Bivariate tests (unpaired t-test, chi-square, and Mann-Whitney test) and Spearman correlation were used for comparison of different socioeconomic groups according to treatment preferences (implant consideration versus conventional removable prosthesis). Results: Treatment options presented by dental students include 63.5% complete denture, 32% implants/removable dentures, and partial denture 4.5%. Conventional removable prostheses were mostly chosen due to low income. Implants were only considered by 26% of participants. Age and implant consideration had a significant negative correlation. No significant difference in gender and residency area on implant consideration was found. The chi-square test showed a significant difference between implant consideration and conventional removable prostheses in the various occupation groups. Conclusions: Low income is the main factor prohibiting patients from considering dental implants. Age and educational level may play a considerable role in considering dental implants. There should be more emphasis on dental students' treatment planning education to include and explain dental implants as a treatment option for their patients in the prosthodontics clinic.

Quantitative nano-mechanical mapping AFM-based method for elastic modulus and surface roughness measurements of model polymer infiltrated ceramics.

OBJECTIVES: The aim of this in vitro investigation was to assess and compare surface characteristics and nanomechanics of model polymer infiltrated ceramic network (PICN) materials compared to CAD/CAM resin composite blocks. MATERIAL AND METHODS: Four model PICN materials sintered at different temperatures (Exp.125, Exp.130, Exp.135 and Exp.155) were investigated along with three CAD/CAM resin composites; Lava Ultimate (LU), Cerasmart (CS) and Grandio Bloc (GB), and one commercial PICN block - Vita Enamic (VE). Forty samples were prepared with dimensions of 14 × 12 × 2 mm for resin ceramic and VE blocks and 15 × 2 mm discs for model PICN materials. All samples were scanned using atomic force microscopy (AFM) (n = 3) at multiple locations and two different scan sizes (20 ×20 µm and 3 ×3 µm). Surface optical gloss (n = 5) at 60° was also determined for all the groups. Data were analysed using one-way ANOVA, and Tukey's post hoc test (α = 0.05). RESULTS: Resin composite blocks showed smoother surfaces compared to the PICN materials. The average surface roughness values (Ra) ranged from 7.75 nm to 31.21 nm and the gloss value ranged from 56.43 GU to 91.81 GU. The highest surface roughness value was found for Exp.125 (31.21 nm) while LU showed the lowest roughness value (7.75 nm) (the difference being statistically significant: p = 0.001). Variation was noticed in terms of nanomechanical mapping within and between the groups. Images generated from the elastic modulus map values clearly indicated that all PICN materials had more than one phase and very different components. CONCLUSIONS: CAD/CAM resin composite blocks exhibited higher gloss and lower roughness values compared to PICN materials. However, both the commercial and model PICN materials showed more stiffness than resin composite with the presence of at least two different phases. Sintering temperature appears to have a significant effect on material topography and nanomechanical properties. The model PICN sintered at 1550 °C showed a comparable range of elastic modulus values to those of enamel.

Properties of A Model Self-Healing Microcapsule-Based Dental Composite Reinforced with Silica Nanoparticles.

AIM: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO2 nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. MATERIALS AND METHODS: Microcapsules were prepared by in-situ polymerisation of PUF shells, as explained in our previous work. The model SHDC included bisphenol A glycidyl dimethacrylate (Bis-GMA:TEGDMA) (1:1), 1 wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), 0.5 wt% benzoyl peroxide (BPO) catalyst, 20 wt% silanised silica dioxide (SiO2) (15 nm) and (0, 2.5, 5, 7.5, 10 wt%) of microcapsules (120 ± 45 µm). Light transmission, hardness, degree of conversion (DC), flexural strength and elastic modulus of the SHDC model were measured. RESULTS: The degree of conversion of the SHDC ranged from 73 to 76% 24 h after polymerisation. Hardness measurements ranged from 22 to 26 VHN (p > 0.05); however, the flexural strength was adversely affected from 80 to 55 MPa with increasing microcapsules of up to 10 wt% in the composites (p < 0.05). CONCLUSION: Only flexural strength decreased drastically ~30% with increasing microcapsules (>10 wt%) in the composites. All other measured properties were not significantly affected. Accordingly, we recommend a stronger composite material that could be created by increasing the filler content distribution in order to achieve a hybrid self-healing composite with enhanced mechanical properties.

Pattern, frequency and causes of dental extraction among children/adolescents Syrian refugees: an observational study.

BACKGROUND: The Syrian conflict has had a massive impact on the dental health of refugees. Dental extraction is a good indicator of socioeconomic position and degree of oral hygiene, however there is a scarcity of evidence in the scientific literature that characterizes the reasons for extraction in refugees. AIMS AND METHODS: The current study looked at the extraction causes and related sociodemographic variables of 322 Syrian refugees (46.3% females, 53.7% males) who were treated in a dental clinic in Zaatari camp (Jordan), from September to December 2019. All child Syrian refugees (aged 4-16) visiting the facility were eligible to participate. A validated semi-structured survey was used to collect clinical and sociodemographic data from the research sample. Chi-square test, Independent sample t-test, and ANOVA test were used to examine associations between the different variables. The significance level was set at P < 0.05. RESULTS: The total number of teeth extracted was 397: 25 (6.3%) permanent teeth, 371 (93.5%) primary teeth, and one mesiodens (0.2%). Overall, lower teeth were most commonly extracted (56.9%). The most common teeth that required extraction were the lower primary molars, with lower left primary second molars being the most commonly extracted (15.9%). As the level of parental education increased, the mean number of extracted teeth decreased (P = 0.035), additionally, as the frequency of toothbrushing increased extractions due to caries decreased significantly (P = 0.027). CONCLUSIONS: Dental caries and pulpal diseases were discovered to be the most prevalent causes for primary and permanent tooth extraction, with no difference between males and females. The lower left primary molar was the most commonly afflicted tooth.

Long-term hydrolytic stability of CAD/CAM composite blocks.

This study aimed to assess water sorption and solubility of CAD/CAM composite blocks compared to CAD/CAM ceramic after 8 months storage in water and artificial saliva. Eight CAD/CAM blocks were investigated: Five resin-composite blocks (RCBs), one polymer-infiltrated ceramic network (PICN) block, one ceramic-filled polyetheretherketone (PEEK) block, and one feldspathic ceramic block. One hundred and twelve specimens were prepared comprising 14 specimens of each of the eight materials. From each group of specimens, seven randomly selected specimens were immersed in 10 mL of water, while the other seven specimens were immersed in artificial saliva. All specimens were stored at 37°C and weighed at various time intervals. The data were analysed via repeat measures ANOVA, one-way ANOVA and Tukey's post hoc test (α = 0.05 for all tests). Sorption values (mean [SD]) in water were within the range -1.21 (0.4) to 39.3 (2.1) µg/mm3 and in artificial saliva between -0.7 (0.2) and 41.6 (1.3) µg/mm3 . Solubility values in water were between -0.43 (0.08) and 0.34 (0.18) µg/mm3 and in artificial saliva between -0.53 (0.07) µg/mm3 and 0.33 (0.2) µg/mm3 . CAD/CAM composite blocks were hydrolytically stable under long-term storage (according to ISO 4949:2009), although not as stable as ceramic. Water sorption of CAD/CAM composite blocks was dependent on the resin-matrix and was influenced by the filler weight %.

Hot Isostatically Pressed Nano 3 mol% Yttria Partially Stabilised Zirconia: Effect on Mechanical Properties.

Objective: To investigate the flexural strength of hot isostatically pressed nano 3 mol% yttria partially stabilised zirconia and conventionally sintered micro 3 mole% yttria partially stabilised zirconia. Methods: A total of 40 bar-shaped (2 mm × 4 mm × 16 mm) specimens were prepared from hot isostatically pressed nano 3 mol% yttria partially stabilised zirconia (CeramaZirc Nano HIP, Precision Ceramics) and conventionally sintered micro 3 mole% yttria partially stabilised zirconia (CeramaZirc, Precision Ceramics). Two groups were prepared for each material (n = 10), with one serving as 'control' and the other being cyclically loaded using a chewing simulator (7 kg; 250 k cycles): SEM imaging was also undertaken on selected specimens. Flexural strength until fracture was recorded (ISO 6872). Paired and unpaired t-tests were chosen to compare mean outcomes between the four groups (p < 0.05). Results: Significant statistical difference was only found between the means of control specimens. CeramaZirc Nano HIP had the highest mean value (1048.9 MPa), whilst the lowest was seen for CeramaZirc after loading (770 MPa). Values for both materials were higher without loading than after loading. Values after cyclical loading showed large SD values (276.2−331.8) in comparison to 'control' (66.5−100.3). SEM imaging after cyclical loading revealed a smoother and less destructed surface of CeramaZirc Nano HIP compared to CeramaZirc. Significance: HIP nano zirconia exhibited inferior strength, surface polishability and behaviour to loading. Therefore, further investigation on the behaviour of such materials should be conducted before recommending for clinical use.

Oral Hygiene Awareness, Practices and Attitudes among Syrian Refugees in Zaatari Camp and Their Impact on Oral Health Status.

PURPOSE: To characterise the oral hygiene habits, attitudes, and oral health practices in relation to sociodemographic factors among refugees in Jordan and to investigate their impact on the oral health status of these refugees. MATERIALS AND METHODS: This cross-sectional study consisted of two parts. First, a face-to-face interview was conducted using a structured questionnaire including demographic and oral health-related questions. Second, clinical oral examination was performed using WHO criteria, DMFT and oral health indices (OHI-S). The participants were adults, aged 18 and older. All patients attending dental clinics and accompanying personnel in the waiting areas at Zaatari camp during the study period were invited to participate, with a sample size of 547 refugees (males = 212, females = 335). RESULTS: 547 adult refugees participated. 75.3% reported toothbrushing less than twice daily, while flossing was uncommon (9.5%). Toothbrushing habits were significantly associated with gender and smoking status. Untreated carious lesions had a high incidence (94.1%); the mean number of decayed teeth was 5.4 and was statistically significantly higher in males and smokers. The mean number of missing teeth was 3.2 and was significantly associated with males, age, smoking, and presence of chronic disease. Participants who reported conditions that had persisted 1 year or more and required ongoing medical attention or limited activities of daily living or both (e.g. diabetes mellitus, hypertension, heart diseases, thyroid disease, chronic renal disease, rheumatoid arthritis, anemia, peptic ulcer, or asthma) were recorded as having chronic disease. The mean number of filled teeth was 3.2 and was statistically significantly associated with age and presence of chronic disease. The mean DMFT was 11.8 and was statistically significantly higher in males, older people, smokers, and those with chronic disease. The OHI-S was 2.2. The most common complaint was pain (92.2%), and only 1.1% visited a dentist for a check-up. CONCLUSION: The prevalence of caries was extremely high, with poor oral hygiene practices among refugees, justifying the urgent need to develop and implement targeted oral health promotion, preventive programs and curative strategies and to enable collaboration of the oral healthcare providers and funding agencies to design the most appropriate interventions for this disadvantaged population. In addition, this information can be used as a basis upon which preventive programs can be assessed for efficacy.

Relationship between dental caries, oral hygiene and malocclusion among Syrian refugee children and adolescents: a cross-sectional study.

BACKGROUND: Little is known about the oral disease burden in refugee children and associated risk factors. This cross-sectional study aimed to explore the oral hygiene status and prevalence of caries, and to investigate their association with malocclusion characteristics in a child refugee population. METHODS: 606 Syrian refugee children and adolescents aged 7-19 years, registered as refugees in Jordan and residing in Zaatari camp, were recruited to the study. Oral hygiene and caries status were recorded using DMFT (mean of decayed, missing, and filled permanent teeth) and OHI-S (Simplified Oral Hygiene Index) according to WHO criteria. Oral health results were then cross tabulated with previously reported malocclusion traits for the same study sample (crowding, spacing, contact point deflection and IOTN) to detect any associations. Statistical analysis was conducted using chi-square test, independent sample t-test, one-way ANOVA, Welch test and Post Hoc testing (Gabriel and Games-Howell). RESULTS: Overall DMFT and OHI-S were 4.32 and 1.33 respectively with no difference between males and females. Around 40% of the sample showed ≥ 5 DMFT score. 96.1% of the sample either do not brush or brush occasionally: females showed better oral hygiene practices (P = 0.002). No significant differences in DMFT scores were noted for gender or age, other than the 7-9.9 year old group having significantly higher mean DMFT scores than all other age groups (P < 0.01);the mean of OHI-S was not significantly different between different age groups (P = 0.927). Subjects with malocclusion, specifically crowding, contact point deflection and IOTN grades 3, 4 and 5 had higher scores in both arches for OHI-S and DMFT than subjects without malocclusion traits, although this was not statistically significant for DMFT scores. Overall, patients with generalized spacing had a significantly lower OHI-S score than those without spacing (P = 0.021). Significant correlations were found between parameters of intra-arch and inter-arch relationships and oral health indices (DMFT and OHI-S). CONCLUSION: Malocclusion may increase the risk of caries and periodontal disease; the magnitude of this risk is amplified in populations with poor oral health and limited access to oral healthcare services, highlighting the need for preventive and curative oral health programs.

Knowledge and awareness of dental implants among Syrian refugees: a cross sectional study in Zaatari camp.

BACKGROUND: The popularity of implant dentistry is increasing dramatically, but the success of implant treatment depends on a patient's knowledge and expectations. METHODS: This study aimed to assess dental implant knowledge among refugees as a treatment option (n = 565), using face-to-face interviews. The frequency distribution of the responses in general and according to age, gender and education was calculated. RESULTS: 81.8% of the interviewees had missing teeth, however, only 26.2% replaced them. 16.6% of participants had never/hardly heard about implants. Females who never heard of implants were more than males (P < 0.001). 51.3% of participants described dental implants as a screw, and only 35.4% knew implants were placed in jawbones. 6.2% of respondents reported that implants required more care than a natural teeth, with 47.6% believing that diseases affect implant success. Friends were the main source of information (61.4%). Highly educated participants showed higher knowledge about implants. CONCLUSIONS: The surveyed sample revealed limited knowledge about dental implants with high cost being a major obstacle, warranting more strategies to increase awareness and to make implants more affordable for this population.