Core Veneer Research Articles

Evaluation of Young Falcata Plus-Trees for Veneer and Plywood Production in the Philippines

Young (3-, 5-, and 7-yr-old) falcata [Falcataria moluccana (Miq.) Barneby & J W. Grimes] trees were evaluated for their suitability to be processed into veneer and plywood. Three sample trees per age level were harvested from industrial tree plantations in Agusan del Norte and Surigao del Sur, Mindanao, Philippines. A straight portion of each tree from the bottom up to 4.5 m long was cut and divided into three billets at 1.5 m each. These were assigned to be peeled into 0.85-, 2.20-, and 2.80-mm veneer thicknesses. Veneering was done in a spindleless lathe using established lathe settings for falcata billets. Veneer quality per thickness and age level was evaluated based on the frequency and depth of lathe checks (LC). Results showed that LC occurred more frequently in the 2.20-mm-thick veneer, but these were shallower than the 2.80- mm, which had less frequent but deeper LC. On the other hand, age was found to significantly affect the formation of deeper LC in the 3-year-old 0.85-mm thick veneer; thus, it should only be used as a core veneer. The bond strength quality test showed that, regardless of age, falcata plywood passed the glue bond requirement of PNS ISO 12466-2:2016.

Effect of Nanosilica Incorporation on Flexural Strength, Shear Bond Strength, and Color of Veneering Porcelain after Thermocycling

AIM: The focus of this research was to see how silica nanoparticles changed veneering porcelain over a zirconia core affected flexure strength, shear bond strength, and color. METHODS: A total number of 30 zirconia core veneer samples were constructed and classified according to silica nanoparticles modification of veneering porcelain into two groups: Group 1 (control group) veneering porcelain without any modification (n = 15) and Group 2 (modified group) veneering porcelain modified by silica nanoparticles (n = 15). Silica nanoparticles were added to the veneering porcelain powder at a rate of 5% by weight. Silica nanoparticles powder and veneering porcelain powder were manually crushed for about 10 min using a pestle and mortar then the mixed powder was combined with the porcelain moldings liquid to make a paste. After thermal cycling, each group was examined for flexural strength, shear bond strength, and color measurement (n = 5). Universal testing equipment was used to determine flexural and shear bond strength. The color shift was measured using a spectrophotometer. RESULTS: Flexural strength levels in the modified group (280.9 ± 29.85 Mpa) were substantially higher than in the control group (431.78 ± 22.73 Mpa). Shear bond strength values in the modified group (34.31 ± 5.6) were significantly higher than in the control group (26.97 ± 4.03). Color change was within the clinical acceptable range (1.71 ± 0.32). CONCLUSIONS: The addition of silica nanoparticles to veneering porcelain improved the flexural and shear bond strength, as well as, color change was within the clinical acceptable limits.

Effect of the thickness and translucency of the lithium disilicate veneer ceramic on the optical properties of bilayered zirconia

Aim: This study evaluates the effect of lithium disilicate veneer ceramics on the color difference (∆Eab and ∆E00), translucency parameters (TPab and TP00), and opalescence parameter (OP) of different thicknesses and translucencies. Methodology: Ten 0.5 mm thick zirconia core specimens were prepared, and sixty veneer ceramics in A2 shade were prepared from high-translucence (HT) and low-translucence (LT) lithium disilicate glass-ceramics (IPS e.max CAD) in three different thicknesses (0.5 mm, 0.7 mm, and 1 mm). The specimens were evaluated as bilayered structures, and group names were assigned based on the thickness of the core–veneer combinations (n = 10): E1 = (0.5 + 0.5), E2 = (0.5 + 0.7), and E3 = (0.5 + 1). A spectrophotometer (Vita EasyShade V) was used to measure the Commission Internationale de l'Elcairage (CIE) color coordinates L*, a*, and b*, and the ∆Eab, ∆E00, TPab, TP00, and OP values were calculated. A two-way analysis of variance (ANOVA) and Tukey HSD tests (α = 0.05) and Pearson correlation tests (α = 0.01) were applied for statistical analysis. Results: The optical properties (∆E76, ∆E00, TP76, TP00, and OP) of the bilayered zirconia-based ceramics were significantly affected by the thickness and translucency of the lithium disilicate veneer ceramics (p<0.001). However, the interaction between the thickness and translucency of the veneer ceramic was significant only for OP (p<0.05). For each thickness, the TP76 and TP00 values were significantly higher for the HT groups than for the LT groups. The HT groups demonstrated higher OP values than the LT groups, and there were strong correlations between ∆E76 and ∆E00 and TP76 and TP00. Furthermore, there were significant correlations between the TP76 and TP00 values and the OP parameter. Conclusion: The optical properties of the bilayered structures were significantly affected by the thickness and translucency of the veneer ceramics. Therefore, the thickness and translucency of the veneer ceramic must be taken into account to achieve a restoration with the desired shade and appearance. How to cite this article: Yılmaz Savaş T, Savaş A. Effect of the thickness and translucency of the lithium disilicate veneer ceramic on the optical properties of bilayered zirconia. Int Dent Res 2022;12(1):1-8. https://doi.org/10.5577/intdentres.2022.vol12.no1.1 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Physical and Mechanical Properties of Stems and Branches of Falcata [Falcataria moluccana (Miq.) Barneby & J.W. Grimes] Grown in Caraga, Philippines

The physical and mechanical properties of branch wood from falcata [Falcataria molucanna (Miq.) Barneby & J.W. Grimes] grown in Caraga Region, Philippines were determined to assess suitability for end-uses such as core veneer and as material for light construction and handles and boxes as the stem wood. Tests done to compare the properties with the stem wood showed significant differences in relative density (average values of 0.284 for the stem wood and 0.255 for the branch wood) and shrinkage properties in all directions. Axial position significantly influenced variation in moisture content (p = 0.0024) for stem and branch wood, as well as relative density (p = < 0.0001) plus percent tangential (p = < 0.0001) and radial (p = 0.0014) shrinkage. For the mechanical properties, the stem wood end hardness was significantly higher by 28.8% at green condition (p = 0.0003) and by 13.36% at 12% MC (p = 0.0133) than the branch wood. The compression perpendicular to the grain at 12% MC of the stem wood was also higher by 16.10% (p = 0.0166). However, for the other mechanical properties studied, the differences were not significant. The bottom portion of the stem and branch wood exhibited the highest mechanical properties, which can be attributed to the higher relative density at this portion (p = 0.0001). Based on the results that showed insignificant differences in most of the properties between the wood types of F. moluccana, the branch wood can possibly be used for similar applications as the stem wood such as for light construction, non-structural veneer, and plywood; for tool handles, boxes, and other household items; and for pulp and paper. The utilization of the branch wood of F. moluccana, therefore, can augment the raw materials supply for the local wood industry.

A REVIEW OF MECHANICAL BEHAVIOR OF DENTAL CERAMIC RESTORATIONS

Dental ceramics are well known for restoring the function and aesthetic of lost or damaged teeth. Understanding these materials’ mechanical and aesthetic properties can make a suitable choice for those materials. The longevity of dental ceramics depends on several factors, including manufacturing method, clinical process, and the oral cavity’s aqueous environment. Failure mechanisms in restorative ceramics are complex and a combination of several factors. Different microstructures in the crystalline phase will involve the propagation of cracks and eventually the fatigue of ceramic materials. Large grains reduce mechanical performance compared to small grain sizes. Aesthetic materials used for veneering are weaker than the core materials and fail when even subjected to small loads. The soft bonding in the core–veneer interface and possible residual stresses created during the veneering method are drawbacks of these systems. Studies on the mechanical behavior of these materials have grown significantly in recent years and provide helpful information about static and fatigue experimentation and the failure behavior of various materials used in dental crowns.

Studi Rendemen Finir dan Besarnya Limbah Pada Pengupasan Finir dengan Mesin Rotary Lathe Tipe Spindleless

In general, the log-block peeling yield on a rotary lathe machine ranges from 70 - 80% of the log volume in the form of veneer, and the remaining 20-30% is waste. This variation depends on the quality and type (species) of the log of the raw material. The veneer peeling usually consist of the face and back veneer (continuous veneer) ranging from 50% to 70% and core veneer as poly piece veneer ranging from 20 to 30%. Under certain conditions, the waste can reach up to 50% including losses due to rounding, shrinkage of the veneer, cracks, spurs, and pith (log-core).
 From the description above and several other observations, the research was carried out regarding this matter. There is a way to reduce the amount of waste in log peeling using rotary machines and at the same time increasing the recovery peeling. Thus, it will reduce production costs and increase profits for the company.
 One of the contributors to a large amount of veneer peeling waste is the use of rotary lathe veneer peeling machines with large spindles which are still widely used in veneer and plywood factories (plymill), especially in Indonesia. So far, on average half of raw logs turn into waste, and 25 percent is contributed by a rotary lathe machine. Meanwhile, on the other hand, the need for plywood products will continue to increase day by day. This is because plywood is one of the most environmentally friendly building materials and comes from renewable natural resources. Along with the development of the plywood industry, the increase of raw material needs is inevitable. So, waste products will also continue to increase too.
 In this regard, there must be fundamental changes in this industry, including the use of rotary lathe without spindles as the substitute from the conventional machine. In relevance to this situation, this research was directed with the aim of knowing the yield and amount of veneer peeled by a spindle-less rotary lathe machine and at the same time to find out the waste it produces. So, this information can later become a consideration for stakeholders to replace the old rotary lathe with a type spindle-less without a doubt.
 The results show that veneer peeling using a spindle-less rotary lathe machine increases the yield of the veneer and reduce the amount of waste. Most of the peeling results are in the form of a veneer consisting of 58.83% continuous/endless veneer for the face/back, and 22.83% of poly piece core (odd veneer) from the core veneer. The total veneer yield is 81.67%. The remaining were 1.32%, 0.93%, and 16.08% for log-core waste, cut edge finish, and round-up veneer, respectively. The spindle-less rotary lathe machine has provided increased yields and significantly reduced the amount of waste.
 
 Keywords : Waste, rotary lathe, spindle-less, veneer.

Performance properties of plywood composites reinforced with carbon fibers

In this study, carbon fibers were added as a reinforcement layer between wood veneers bonded with melamine-urea–formaldehyde (MUF) resin to improve properties of standard wood laminated composite. Two different fiber orientations were tested, being parallel and perpendicular to the veneers. In addition, two different locations were evaluated. Internal, surrounding the core veneer, and external, below the surface veneer. Flexural properties, water absorption, density, cutting force, and tensile shear strength were tested and evaluated. Results showed that reinforcing plywood panels with carbon fibers increased both MOR and MOE. The cutting force showed better results for composite panels with CF in a perpendicular orientation. Moreover, the water uptake and thickness swelling after 24 h showed better results for fibers in the core layer, either parallel or perpendicular.

Investigating face veneer check development in decorative plywood panels: the impact of four common manufacturing factors

An optical method based on digital image correlation was used to investigate the impact of four decorative plywood manufacturing factors (core type, veneer type, adhesive type and lathe check orientation) on face veneer checking. The four core types were: combination core, medium density fibreboard, particleboard, and veneer core. The four veneer types were: peeled 0.604 mm, peeled 0.706 mm, sliced 0.508 mm, and sliced 0.564 mm. Both loose-side out and tight-side out lathe check orientations were used. The adhesive systems were urea–formaldehyde, polyvinyl acetate, and soy-protein based. 96 treatment combinations with 8 replicates were tested. All specimens were exposed to harsh but realistic drying conditions (approximately 30°C and 26% relative humidity) for 4 h during inspection. Checks were detected on 428 out of a total of 765 specimens (56%). The estimated mean check densities (area of checking per unit area) indicated some unfavourable factor combinations. All factors had some degree of interaction with one another and check development could not be attributed to a single factor examined in this study. The data were fit to a generalized linear mixed model based on Tweedie’s compound Poisson distribution. Confidence intervals were calculated via bootstrapping. The check density estimates produced by this model can be used to cautiously guide manufacturers as they decide on panel components. The broader use of the model is to highlight the complexity of the problem and guide future research in this area.

Influence of veneer pore defects on fracture behavior of bilayered lithium disilicate glass-ceramic crowns

ObjectiveTo identify the conditions under which fabrication pore defects within veneering porcelain in bilayered lithium disilicate glass-ceramic (LDG) crowns will influence and jeopardize the mechanical integrity of the structure. MethodsThirty standardized molar crowns (IPS e.max Press) were fabricated and microCT scanned to 3D-analyze the size, morphology and distribution of pores in veneering porcelain, followed by in vitro fracture test and SEM fractographic observation. Finite element analysis (FEA) of the microCT reconstructed models was used to evaluate the stress state. ResultsThe volumes of pores in samples ranged from 3241μm3 to 1.29×109μm3 with the equivalent radius between 10μm to 680μm. Deviation of sphericity of pores ranged from 0.10 to 0.81 and the average of 99.97% pores was near 0.63. For the smaller pores their distribution tended to be uniform, while the larger pores were irregular with elongated ellipsoidal form and located at or near the veneer–core interface. During wedge loading blunt contact fracture testing 21 crowns failed from the fissure on the occlusal surface, of which 16 failed from surface or near surface pores, 2 from the midpoint of the oblique ridge, and 7 from larger interfacial pores. FEA analysis indicated that defects were detrimental to veneer integrity only in regions of tensile stress and where the pore radius associated with crack initiation ranged from 30 to 50μm. Pore morphology appeared to have only a minor effect on fracture. SignificanceWithin the limitation of the microCT resolution and FEA, it suggests that pores radius large than 30–50μm and located in the tensile stress area like grooves and fissures on the occlusal surface or near surface as well as cervical margins of veneering porcelain will jeopardize the bilayered structure and mechanical integrity of LDG.

An In Vitro Study to Investigate the Effect of Various Surface Treatments on the Core–Veneer Shear Bond Strength of Zirconia Restorations: A Scanning Electron Microscope Study

AbstractVeneering ceramic to the core is considered to be the weakest part of all-ceramic restorations. Zirconium dioxide, owing to its favorable properties such as high strength, chemical stability, and superior aesthetics, is the material of choice for fabrication of a core. The adhesion between the core and veneering porcelain is based on the same manner in which the connection occurs in metal–ceramic structures. However, the standard procedures for connecting zirconia to hard dental tissues and veneering materials do not achieve the required strength of bonding.The aim of this study was to investigate different surface treatments of the zirconium dioxide ceramic core for achieving highest adhesive bonding values to veneering porcelain. The study was primarily designed to investigate the bonding strength of the veneering porcelain to zirconia with in vitro macro shear bond strength test. The samples of zirconia were divided into four groups of 10 specimens, each according to the treatment of zirconium surface, and the results showed the highest bonding values for samples that were treated with the sandblasted group.

Tensile shear strength of natural wood decorative plywood from lesser known Sungkai (Peronema canescens) tree

Sungkai (Peronema canescens) small logs has been harvested from a private sungkai plantation (Sabahpuri Nursery Sdn Bhd) in Telipok, Sabah. The logs were then rotary peeled to 0.6mm thick and made into 4’ x 4’, 3 plies Urea Formaldehyde (UF) plywood with Acacia Hybrid wood used as the core veneer (1.2 mm thick) at a local plywood facility; Cymao Plywood Sdn Bhd in Sandakan. Remaining dried veneer were brought back to University Malaysia Sabah for further study. Laboratory scale 3 plies plywood (Sungkai-Acacia, Sungkai-Seraya) were made using the same source of UF resin and veneer, and used for comparison studies. Commercial 3 plies Nyatoh plywood were also used as control samples. The samples were then tested according to Japanese Agricultural Standard for Plywood 2003 (amended: 2008) Tensile Shear Strength of Type II Natural Wood Decorative Plywood. All of the samples pass the Tensile Shear Strength (TSS) minimum standard of 0.7 N/mm2 in untreated condition or even after hot and cold water immersion treatment. The untreated mill samples of Sungkai-Acacia plywood perform the best with mean TSS = 1.74 N/mm2, SE = 0.05 while Nyatoh shows the lowest mean tensile shear strength with 1.06 N/mm2, SE = 0.07. Further statistical analysis shows there was no significance difference between Sungkai mixed plywood group samples. However, Sungkai mixed plywood samples shows a significant difference (p < 0.05) with superior strength when compared to commercial Nyatoh plywood samples. If these criteria met the final requirement for the end use of the veneer, then the potential of Sungkai as an alternative or supplemental raw material is something worth given due consideration.

RENDEMEN KAYU KARET RAKYAT DAN SENGON PADA PRODUKSI VENEER CORE PLYWOOD

Suplai bahan baku industri plywood pada saat ini terbatas karena kondisi hutan alam yang tidak memungkinkan lagi untuk memenuhinya. Salah satu upaya yang ditempuh untuk memenuhi kebutuhan bahan baku adalah mencari sumber bahan baku yang berasal dari hutan tanaman, hutan rakyat ataupun perkebunan diantaranya tanaman Karet rakyat dan Sengon yang dimanfaatkan sebagai bahan baku veneer core. Perbedaan jenis bahan baku veneer core akan menghasilkan perbedaan rendemen. Penelitian ini bertujuan untuk membandingkan rendemen kayu karet rakyat dan sengon dalam pembuatan veneer core di industri plywood PT. Ewan Superwood yang terletak di Propinsi Riau dan menentukan faktor-faktor yang mempengaruhi rendemen . Populasi penelitian ini adalah kayu karet rakyat dan sengon dengan mengambil sampel sebanyak 60 batang yang terdiri dari 30 batang kayu karet rakyat dan 30 batang kayu sengon yang diambil secara acak. Rata -rata nilai rendemen veneer core yang berasal dari Kayu Karet Rakyat adalah 66,63 %. Rata -rata nilai rendemen veneer core yang berasal dari Kayu Sengon adala h 74,65 %. Faktor yang mempengaruhi rendemen veneer core pada kayu karet adalah Kondisi bahan baku ,diameter, keselindrisan dan cacat kayu yang disebabkan oleh bekas sadapan. Sedangkan pada kayu sengon dipengaruhi oleh adanya empelur yang rapuh.&#x0D; Kata kunci : Rendemen, plywood, vener core, kayu karet, kayu sengon

Three-dimensional characterization and distribution of fabrication defects in bilayered lithium disilicate glass-ceramic molar crowns

ObjectiveTo investigate and characterize the distribution of fabrication defects in bilayered lithium disilicate glass-ceramic (LDG) crowns using micro-CT and 3D reconstruction. MethodsTen standardized molar crowns (IPS e.max Press; Ivoclar Vivadent) were fabricated by heat-pressing on a core and subsequent manual veneering. All crowns were scanned by micro-CT and 3D reconstructed. Volume, position and sphericity of each defect was measured in every crown. Each crown was divided into four regions—central fossa (CF), occlusal fossa (OF), cusp (C) and axial wall (AW). Porosity and number density of each region were calculated. Statistical analyses were performed using Welch two sample t-test, Friedman one-way rank sum test and Nemenyi post-hoc test. The defect volume distribution type was determined based on Akaike information criterion (AIC). ResultsThe core ceramic contained fewer defects (p<0.001) than the veneer layer. The size of smaller defects, which were 95% of the total, obeyed a logarithmic normal distribution. Region CF showed higher porosity (p<0.001) than the other regions. Defect number density of region CF was higher than region C (p<0.001) and region AW (p=0.029), but no difference was found between region CF and OF (p>0.05). Four of ten specimens contained the largest pores in region CF, while for the remaining six specimens the largest pore was in region OF. SignificanceLDG core ceramic contained fewer defects than the veneer ceramic. LDG strength estimated from pore size was comparable to literature values. Large defects were more likely to appear at the core–veneer interface of occlusal fossa, while small defects also distributed in every region of the crowns but tended to aggregate in the central fossa region. Size distribution of small defects in veneer obeyed a logarithmic normal distribution.

Optimization of Press time and Properties of Laminated Veneer Lumber Panels by Means of a Punching Technique

The impact of veneer punching pattern and density (343, 356, and 1424 hole·m-2) was tested relative to selected physic-mechanical properties of 5-ply laminated veneer lumber (LVL) panels fabricated from poplar wood (Populus deltoides) under different press time (5, 6, and 7 min). Samples were made with urea-formaldehyde resin using hot press technology at a uniform pressure of 10.8 N·mm-2 and temperature of 120 °C. The results indicated that punching the inner veneers (except the core veneer) of LVL significantly improved the average values of shear strength, modulus of elasticity, and bending strength (both parallel and perpendicular to the grain). In contrast to control samples, the veneer punching technique showed an overall negative impact on the water resistance of LVL (after either 2 or 24 h of immersion in water). Nevertheless, specimens with punching densities of 1424 hole·m-2 pressed for a maximum of 5 min were more dimensionally stable than the control samples. The physic-mechanical properties of LVL were significantly affected by presstime as well. Considering the data obtained, the presstime of LVL could be reduced to nearly 16.7%, or 1 min, by using a punching density of 1424 hole·m-2 without any significant negative change in the major physic-mechanical properties.

Evaluation of shear bond strength of a novel nano-zirconia and veneering ceramics

The core–veneer bond strength of zirconia is believed to be influenced by various factors, including zirconia types. To date, studies on bond strength between veneering porcelain and zirconia core fabricated by slip-cast technique are few. The aim of this study was to investigate and compare the shear bond strength (SBS) of three core materials with two veneering porcelains. Sixty cylindrical discs (11mm in diameter and 3mm in thickness) were fabricated and divided into Experimental zirconia (Zir), Cercon® (Cer) and metal (Met) core group. Ceramkiss® (Ck) and InLine® (IL) veneering porcelains were fired to each core at a thickness of 3mm. Before veneering, all core materials were sandblasted with 100µm Al2O3, and a layer of opaque liner was applied in the first firing. The bonded samples were subjected to shear bond test following storage in distilled water (37°C) for 24h. Scanning electron micrograph (SEM) was used to identify the mode of bonding failure. The results were analyzed with One-way ANOVA and Independent t-test with Tukey post-hoc test. Interaction effect analysis was performed using two-way ANOVA. Met-IL showed the highest mean SBS value (28.9±3.8MPa), whereas Cer-IL group obtained the lowest value (2.8±0.7MPa). The mean SBS values of Zir-Ck and Zir-IL were found to be 23.1±2.4MPa and 4.1±0.9MPa respectively. When veneered with the same veneering porcelain, both experimental zirconia and Cercon® were comparable, whereas significant differences were observed between metal and zirconia groups. All core materials exhibited significant differences in terms of shear bond strength when veneered with different veneering ceramics. Cohesive failure occurred in the high SBS group, whereas mixed cohesive-adhesive failures were seen in the other groups. The core–veneer SBS is material dependent. The types of core and veneering materials significantly affected the SBS. Slip casted experimental zirconia and commercial zirconia demonstrated similar bonding capabilities with the existing veneering porcelain designed for zirconia core.

Improving the compatibility of an Y-TZP/porcelain system using a new composite interlayer composition

The aim of this study was to evaluate the effects of different cooling procedures and a new composite interlayer composition on the flexural strength, and veneer delamination resistance, of an all-ceramic veneered translucent Y-TZP core. One hundred twenty bar-shaped specimens of a translucent Y-TZP ceramic were prepared and divided into three groups: (1) no composite interlayer; (2) a glass interlayer (silica-based glass); (3) a mixed composite interlayer of glass and porcelain veneer material. A veneering porcelain (with and without a composite interlayer) was applied on the specimen surface and sintered. Each core–veneer group was cooled using a rapid or a slow cooling rate. All specimens were tested in four-point bending. Data were statistically analyzed using two-way ANOVA, followed by Post-Hoc tests with Bonferroni correction (α=0.05) and Weibull analysis. The group with no interlayer using the rapid cooling technique exhibited the highest flexural strength. However, with low reliability and the greatest delaminated area of porcelain under tension. A glass interlayer between porcelain veneer and zirconia core presents as a good alternative for maintaining flexural strength and porcelain veneer delamination resistance in zirconia based restorations.

Evaluation of Mechanical Properties of Plywood Treated with a new Wood Preservative (CEB) Chemical

The objective of this study was to explore the physical and mechanical properties of the plywood made with phenolic glue and rubber wood as core veneer with CEB as a wood preservative. The studied properties were glue shear strength in dry, wet mycological, modulus of elasticity, modulus of rupture and tensile strength in parallel to grain direction as per IS:1734 part-4, 11 and 9 (1983) respectively. Results of the above mentioned tests were compared with the prescribed values given in IS 710-2010 and results revealed that samples conformed the prescribed values.

Fatigue strength of bilayered ceramics under cyclic loading as a function of core veneer thickness ratios

Statement of problemMinimal evidence is available concerning the appropriate thickness of each layer in bilayered ceramic systems. PurposeThe purpose of this in vitro study was to examine the effect of core-veneer thickness ratios on the fatigue strength of a bonded bilayered ceramic system. Material and methodsSpecimens of Ivoclar Porcelain System (IPS) e.max lithium disilicate were fabricated with core/veneer thicknesses of 0.5/1.0 mm, 0.75/0.75 mm, 1.0/0.5 mm, and 1.5/0.0 mm. All specimens were cemented to bases of a dentin-like material. Each specimen was cyclically loaded by a 2-mm–diameter G10 piston in water. Loads ranging from 10 N to the target load were applied at a frequency of 20 Hertz for 500 000 cycles. If cracked, the next specimen was cycled at a lower load; if not cracked, at a higher load (step size of 25 N). ResultsMean and standard deviations of fatigue loads for the different core thicknesses were 0.5-mm core 610.94 N ±130.11; 0.75-mm core 600.0 N ±132.80; 1.0-mm core 537.50 N ±41.67; a Nd 1.5-mm core 501.14 N ±70.12. All veneered groups were significantly stronger than the full thickness group (ANOVA, P<.001; 95% post hoc). Cone cracking was observed only in the 2 thinner core groups (χ2 test, P<.05), possibly indicating residual stresses. ConclusionsResults indicate that the addition of veneering porcelain to lithium disilicate cores increases the fatigue strength of the biceramic system.

Flatwise compressive properties of oil palm core sandwich panel subjected to static compressive load

Sandwich panel consisting of oil palm wood core and rubberwood veneer faces were produced. Effects of three different oil palm core density ranges (200–250, 300–350 and 400–450 kg/m3) and two different oil palm core grain orientations (oriented in vertical and horizontal direction of the flat plane) on flatwise properties of the panels under uniform compressive (load displacement curve, maximum stress and Young’s modulus) and localized point loads (load displacement curve and load at limit) were explored. The result revealed that the feature of load displacement curve under compression and indentation test was strongly influenced by oil palm core grain orientation. The maximum stress, Young’s modulus and load at limit values were very dependent on grain orientation and density of oil palm wood core. The panels with core grain oriented in vertical direction of the flat plane and higher core density showed greater maximum stress, Young’s modulus and load at limit than those of core grain oriented in horizontal direction of the flat plane and lower core density. From this result, it was suggested that the panel with oil palm core grain oriented in vertical direction of the flat plane would have a greater performance to be used to carry uniform compressive and localized point loads.

Design of the Stools by Using Lightweight Corrugated Veneer Core Panel

Design of the Stools by Using Lightweight Corrugated Veneer Core Panel