Chipping remains a big challenge during the clinical application of glass ceramics in dentistry. The fabrication procedure used affects the mechanical properties of dental feldspathic porcelain and ...is associated with technical failures. This study aimed to compare the effect of the use of manufacturers’ liquids versus H2O on the flexural strength of glass ceramics. Specimens (n = 120, n = 15 per group) (25 × 4 × 1.2 mm) were obtained using four porcelain powders (Creation CC, IPS InLine, Noritake EX-3, and Vita VM 13). Four groups were produced using porcelain powder and modeling liquid, and four groups using distilled water. The specimens were fired, sintered, and polished. Flexural strength was measured using a universal testing machine. Statistical analyses were conducted using post hoc Tukey’s, two-way ANOVA, and Weibull analysis. Flexural strength values (mean ± SD) of the ceramic-manufacturer’s liquid mixture ranged between 67.2 ± 10.2 and 85.8 ± 12.8 MPA (NR < VT < IV < CR), while flexural strength values of the ceramic–water mixture were between 72.2 ± 6.9 and 95.2 ± 12 MPA (CR < NR < VT < IV). While the choice of the ceramic type significantly affected flexural strength, the use of water vs. manufacturers’ liquid showed in almost all cases no significance. To achieve better flexural strength results, InLine should be used with distilled water mixtures, while all ceramic powders except for Noritake can be used with the manufacturer’s liquid mixtures.
•Radiodensity values (HU) were significantly affected by the material classification where polycaprolactone presented significantly lower HU values followed by PMMA.•Among silicone materials, OPT ...demonstrated the lowest radiodensity and together with MEM, more dimensional stability.•Polycaprolactone, PMMA (except for TAB), the silicone materials (OPT and MEM) and resin composite tested were significantly more dimensionally stable compared to those of the other silicone materials (LAB, ADI, PRE, SIA) tested in this study.•For fabricating intraoral stents during radiotherapy of head and neck carcinomas, when reduced radiodensity values are required polycaprolactone, but for dimensional stability except for some silicones (LAB, ADI, PRE, SIA) other siliconematerials (OPT, MEM), PMMA and resin composite tested could be recommended. The amount of shrinkage in dimensional stability requires clinical observations as regards to fitting of the intraoral stent in case of prolonged sessions of radiotherapy.
Intraoral stents protect the healthy tissues from ionizing radiation during external beam radiotherapy reducing mucositis, hyposalivation and osteoradionecrosis.This study investigated the radiodensity and dimensional stability of polymeric materials for suitability in construction of intraoral stents and aimed to provide clinical guidelines.
Specimens were fabricated using 4 material types namely, resin composite (ProTemp-PRO), polymethylmethacrylate (PMMA) (Enamel Temp Plus-ETP, Palapress-PAL, TAB 2000-TAB), polycaprolactone (Orfit-ORF) and silicone (Adisil-ADI, Lab Putty-LAB, Memosil2-MEM, Optosil-OPT, President Plus-PRE, Siolaplast A-SIA).They were randomly assigned to measuretheir radiodensity inHounsfield Units(HU)(12x12x11mm3) (Nradiodensity = 66; n = 6)using a computer tomograph (CBCT,Toshiba Aquillon LB scanner)at baseline and after 6 weeks. The scanning protocol was applied with and without single energy metal artifact reduction (SEMAR) scans using a slice thickness of 1 and 5 mm.The same materials have been tested for their dimensional stability (µm3)at baseline, 1, 6, 12, 24 h, 3 and 6 weeks(14 × 4 × 2 mm3)(Ndimension = 55; n = 5 per material) using stereolithography (STL) files generated by a lab scanner (L2i, Imetric4D, Courgenay, Switzerland) and analyzed using a matchingsoftware(Geomagic ControlX 2020,3D Systems).Data were analyzed using a paired t-test (alpha = 0.05).
Radiodensity values (HU) were significantly affected by the material classification (p < 0.05).Polycaprolactone(43.6) presented significantly lower HU valuesfollowed by PMMA (91.3–414.9) than those of silicone materials (292.8–874.5). In terms of dimensional stability (µm3), PMMA materials (Δ:1.53–2.68) andresin composite (Δ:2.89)were significantly more dimensionally stable compared to those of silicone materials(Δ:13.64–6.63)andpolycaprolactone (Δ:-0.76) and (p < 0.05).
For fabricating intraoral stents, when reducedradiodensity valuesarerequiredpolycaprolactone could be recommended as it fulfils the requirements for reduced radiodensity and dimensional stability. Among all silicone materials,OPT and MEMcan be recommended based on the low HU and dimensional stability.
STATEMENT OF PROBLEMInterim dental restorations can be fabricated from additively manufactured ingots. However, the flexural strength and surface roughness of restorations fabricated by using this ...technique are unknown. PURPOSEThe purpose of this in vitro study was to assess the influence of the manufacturing method (milling, additive manufacturing, or a combination of subtractive and additive methods) and accelerating aging on the flexural strength and surface roughness of interim dental materials. MATERIAL AND METHODSA bar design (25×2×2 mm) was used to fabricate the specimens by using 3 methods: milling (M group), additive manufacturing (AM group), and a combination of subtractive and additive methods (AM+M group). In the M group, an interim material (CopraTemp PMMA) was used to fabricate the milled (350i imes-icore) specimens. In the AM group, specimens were fabricated by using a printer (Form3B+) and an interim resin (Temporary CB) according to the manufacturer's protocol. In the AM+M group, specimens were milled from AM ingots (Temporary CB) and with the same milling machine as in the M group. Two subgroups were created based on the artificial aging (thermocycling): nonaged and aged (n=10). Flexural strength was calculated by using a universal testing machine, followed by determination of the Weibull distribution. Surface roughness was measured by using a digital microscope. The Shapiro-Wilk test revealed that the flexural strength and surface roughness (Ra) data were normally distributed (P>.05). Two-way ANOVA followed by post hoc multiple comparison Tukey tests were used to examine the data (α=.05). The Shapiro-Wilk test revealed that the surface roughness area data were not normally distributed (P<.05). Therefore, the Kruskal-Wallis followed by pairwise multiple comparisons tests were selected (α=.05). RESULTSManufacturing methods (P<.001) and artificial aging (P=.043) were significant factors in the flexural strength measured. The M group had the highest flexural strength mean values (180 MPa), while the AM group showed the lowest flexural strength mean values (77 MPa). Additionally, nonaged specimens (128 MPa) had significantly higher flexural strength values than aged specimens (117 MPa). Manufacturing method (P<.001) was a significant factor in the surface roughness measured. The M group had the highest linear surface roughness mean values (0.86 μm), while the AM group showed the lowest linear surface roughness mean values (0.49 μm). CONCLUSIONSManufacturing method and thermocycling influenced the flexural strength and surface roughness of the groups tested.
This study evaluated the bond strength of relining materials to different denture base materials polyamide and polymethylmethacrylate denture base materials after various surface conditioning ...methods. Denture base resin specimens (N = 128; n = 8 per group) (10 × 10 × 2.5 mm
3
) were fabricated out of injection-moulded thermoplastic polyamide resin (POL) (Deflex) and heat-polymerized polymethylmethacrylate (PMMA, Dura Dent) (HC). The specimens were randomly divided into 4 main groups according to different surface conditioning methods: (a) No conditioning, control (C), (b) grinding with green stone (G), (c) application of primer (V), (d) silica coating with Al
2
O
3
particles coated with SiO
2
(Rocatec) (R). Half of the specimens in each group received auto-polymerized hard relining resin (GC, GC Reline Hard) and the other half PMMA based relining resin (SC, Dura Dent). After thermocycling (×5000), the bonded specimens were tested under tensile forces (0.5 mm/min). Data (MPa) were analyzed using Mann-Whitney U and Kruskal-Wallis tests (alpha = 0.05). Bond strength of relining resins were significantly higher to PMMA than to POL, regardless of the conditioning method (p < 0.05). While R positively affected the bond strength results (p < 0.05) (4.99 ± 1.65-3.27 ± 1.31), application V or G did not show significant effect to POL-relining resin adhesion. After R conditioning, bond strength values were significantly higher in HC-GC group (7.48 ± 2.32) than POL-GC group (3.27 ± 1.31) (p < 0.05). Adhesion of auto-polymerized relining materials to thermoplastic polyamide or polymethylmethacrylate denture resins could be improved after surface conditioning with silica-coating.
Scientific evidence regarding conditioning of different ceramic and hybrid materials and their bonding on titanium abutments is lacking. Titanium disks (Tritan) (N=450, n=15) were randomly cemented ...onto five different ceramic and hybrid materials, namely 1. Zenostar T, 2. Lava Ultimate, 3. IPS e.max CAD, 4. Vita Enamic multicolor and 5. G-ceram using three different cements, Panavia 21, TheraCem and Multilink hybrid abutment. Half of all specimens were thermocycled (5000 cycles, 5-55°C), while the other half were kept dry. Macro shear bond testing was conducted using a universal testing machine. Failure types were classified using a digital microscope. Data was statistically analyzed with three-way ANOVA and Tukey HSD post hoc tests. Both the ceramic (P⟨0.0001) and cement type(P⟨0.0001) significantly affected the shear bond strength(MPa), while thermocycling did not (P⟩0.05). The incidence of cohesive (50.34%) and adhesive failures (49.66%) were not significantly different. As for implant superstructures, when ceramics are bonded to titanium bases, the ceramic and cement type both have an impact on the bond strengths along with the conditioning and bonding protocols for each substrate. An equal affinity of the cements tested to the ceramic, hybrid materials and to titanium can be assumed. Combination of zirconia and TheraCem can be recommended for clinical use.
This in vitro study aimed to investigate the changes in mechanical properties in dentin of third molars after radiation therapy using variable doses and frequencies.
Rectangular cross sectioned ...dentin hemisections (N = 60, n = 15 per group; >7 × 4 × 1.2 mm) were prepared using extracted third molars. After cleansing and storage in artificial saliva, random distribution was performed to 2 irradiation settings, namely AB or CD (A, 30 single doses of irradiation 2 Gy each for 6 weeks; B, control group of A; C, 3 single doses of irradiation 9 Gy each; and D, control group of C). Various parameters (fracture strength/maximal force, flexural strength, and elasticity modulus) were assessed using a universal Testing Machine (ZwickRoell). The effect of irradiation on dentin morphology was evaluated by histology, scanning electron microscopy, and immunohistochemistry. Statistical analysis was performed using 2-way analysis of variance and paired and unpaired t tests at a significance level of 5%.
Significance could be found considering the maximal force applied to failure when the irradiated groups were compared with their control groups (A/B, P < .0001; C/D, P = .008). Flexural strength was significantly higher in the irradiated group A compared with control group B (P < .001) and for the irradiated groups A and C (P = .022) compared with each other. Cumulative radiation with low irradiation doses (30 single doses; 2 Gy) and single irradiation with high doses (3 single doses; 9 Gy) make the tooth substance more prone to fracture, lowering the maximal force. The flexural strength decreases when cumulative irradiation is applied, but not after single irradiation. The elasticity modulus showed no alteration after irradiation treatment.
Irradiation therapy affects the prospective adhesion of dentin and the bond strength of future restorations, potentially leading to an increased risk of tooth fracture and retention loss in dental reconstructions.
The effect of a surface pre-reacted glass ionomer (S-PRG)-containing sealant on the demineralization inhibition and remineralization of intact enamel adjacent to the sealant material was ...investigated. BeautiSealant (BTS, S-PRG sealant, Shofu), Teeth Mate F-12.0 (TMF, fluoride-releasing sealant, Kuraray Noritake Dental), and an experimental silica-filler sealant were investigated. After pH cycling for 10 days, the enamel surface adjacent to the sealant material was observed using confocal laser microscopy and scanning electron microscopy. The polymerized sealant disks were immersed in a demineralized solution (pH: 4.3) to measure pH change. The enamel specimens with polymerized sealant disks were additionally immersed in demineralized solution, followed by energy-dispersive X-ray spectroscopy. The demineralized area of BTS was significantly smaller than that of TMF and SS (p < 0.05). The surfaces adjacent to the sealant of TMF and SS were demineralized, while the surface of BTS was comparatively intact. An increase in pH values were observed in the BTS and TMF groups. Enamel surfaces presented an inhibition of demineralization for BTS and TMF, but not for SS. Fluoride uptake from the polymerized sealant was greater for BTS than for TMF. The S-PRG-containing sealant showed a buffering ability, demineralization inhibition, promotion of remineralization, and it can be advised for clinical applications.
This study investigated the impact of preparation design and material types on fracture strength in maxillary premolars endocrowns after thermodynamic aging.
Eighty two-rooted maxillary premolar ...crowns underwent endodontic treatment (N = 80, n = 10). The teeth were categorized into ten groups (4-mm deep with no intracanal extension lithium disilicate glass ceramic & multilayer zirconia endocrowns (LE0 & ZE0); 4-mm deep with 4-mm intracanal extension in one canal (LE1 & ZE1); 4-mm deep with 2-mm intracanal extensions in both canals (LE2 & ZE2); flat overlays with no endocore (LO & ZO); glass fiber reinforced post & core and crown (LC & ZC)). After cementation, all specimens were subjected to 1500 thermocycles and 1,200,000 chewing cycles with an axial occlusal load of 49 N. A static loading test was performed at a non-axial 45° loading using a universal testing machine and failure modes (Type I: restoration debonding; Type II: restoration fracture; Type III: restoration/tooth complex fracture above bone level; Type IV: restoration/tooth complex fracture below bone level) were evaluated using a stereoscope. Data were ananalzed using 2-way ANOVA and Tukey's tests (alpha = 0.05).
The endocrowns manufactured from multilayered zirconia and pressed lithium disilicate glass ceramic exhibited a fracture load ranging between 1334 ± 332 N and 756 ± 150 N, with ZC presenting the highest and LE2 the lowest values. The differences were not statistically significant (p > 0.05).
All endocrowns tested in this study performed similar considering the different designs and materials tested. The distribution of fracture modes did not differ significantly depending on the design of the restoration and the type of material used.
Implant-supported prosthetic treatment options are reliable for elderly edentulous patients with systemic health problems. These patients often need cost- and time-efficient solutions to avoid ...complications. However, it is a challenge for clinicians to treat these patients without surgical interventions, placement of additional implants, or the need to renew existing prostheses.
A 75-year-old medically compromised caucasian male patient using multiple medications was referred for prosthetic rehabilitation of his edentulous maxilla after several implant failures. Because the patient's health was compromised, further surgical interventions were ruled out and the treatment was centered on the use of the remaining implants by placing a fixed attachment system and altering the existing prosthesis. The stepwise management of the patient's situation through the use of a new attachment system and adjustment of existing prosthesis is described in the present case report.
Although implant therapy is not always contraindicated for medically compromised patients, it is preferable not to perform extensive surgeries to avoid complications. This clinical report describes an alternative, safe option based on a novel fixed attachment system to salvage an existing maxillary implant-supported fixed complete dental prosthesis of a patient with systemic health problems.
Porcelains and glass-ceramics have been used to produce CAD-milled veneers and crowns for zirconia copings and implant-abutments. This study evaluated the bondstrength of a ...polymer-infiltrated-ceramic-network to zirconia using two adhesive cement systems: Panavia 21 and Multilink Automix. Lithium disilicate and feldspathic porcelain were also tested as reference CAD-On materials. Long beams (3x6x40 mm³) of zirconia and short beams (3x6x15 mm³) of the CAD-On materials were prepared. Zirconia and each CAD-On material were bonded in a crossbeam arrangement and subjected to a modified tensile bond-strength test. Half of the samples in each group (n=10) were tested 5 days after bonding (baseline) and the remaining (n=10) underwent aging (50,000 thermocycles at 5°C and 55°C) prior to bond-strength testing. The effects of material, cement, and aging on the tensile bond-strength were tested using a three-way ANOVA. The reference lithium disilicate/Multilink system showed no significant differences in bond strength compared to polymer-infiltrated-ceramic-network and porcelain. The long-term retention of polymer-infiltrated-ceramic-network was not statistically different compared to the baseline values and the two reference materials. With comparable bond strength between all materials, polymer-infiltrated-ceramic-network is the favorable choice for CAD-On to zirconia copings and implant-abutments due to its superior resistance to fatigue fracture relative to porcelain.
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