Compositional characteristics and hardness of acrylic and composite resin artificial teeth

In-vitro evaluation of wear characteristics, microhardness and color stability of dental restorative CAD/CAM materials

The aim of this study was to demonstrate the vertical and volumetric wear characteristics of CAD/CAM materials. The microhardness and color stability were evaluated. A polymer infiltrated ceramic network CAD/CAM block, resin nanoceramic CAD/CAM blocks, a resin composite, and enamel tissue were investigated. Samples were loaded in a chewing simulator. Other samples were aged and immersed in coffee. Color change was evaluated using the digital image analysis and a spectrophotometer. The data were analyzed using Kolmogorov-Smirnov, Kruskal Wallis, Mann Whitney U, Friedman, Spearman's rho tests (p<0.05). The lowest level of wear was obtained in enamel tissue group 0.20 (Q1:0.14; Q3:0.27μm). Resin composite group 2.48 (Q1:2.12; Q3:2.92) showed lower level of discoloration. No agreement was obtained between the digital image analysis and spectrophotometer data (Spearman's rho -0.314, p=0.014). Similar wear rate to the natural enamel tissue was obtained for Vita Enamic. Digital image analysis was considered a promising technique for monitoring the color change.

Feldspar-Modified Methacrylic Composite for Fabrication of Prosthetic Teeth

This study was aimed at investigating poly(methyl methacrylate) (PMMA), modified with a silanized feldspar filler at 10 wt.% and 30 wt.%, as a dental material system for the production of prosthetic teeth. Samples of this composite were subjected to a compressive strength test, three-layer methacrylic teeth were fabricated with the said materials, and their connection to a denture plate was examined. The biocompatibility of the materials was assessed via cytotoxicity tests on human gingival fibroblasts (HGFs) and Chinese hamster ovarian cells (CHO-K1). The addition of feldspar significantly improved the material's compressive strength, with neat PMMA reaching 107 MPa, and the addition of 30% feldspar raising it up to 159 MPa. As observed, composite teeth (cervical part made of neat PMMA, dentin with 10 wt.%, and enamel with 30 wt.% of feldspar) had good adhesion to the denture plate. Neither of the tested materials revealed any cytotoxic effects. In the case of hamster fibroblasts, increased cell viability was observed, with only morphological changes being noticed. Samples containing 10% or 30% of inorganic filler were determined to be safe for treated cells. The use of silanized feldspar to fabricate composite teeth increased their hardness, which is of significant clinical importance for the duration of use of non-retained dentures.

Fracture toughness of 3D printed denture teeth

BACKGROUND

Advances in digital dentistry lead to use of three-dimensional (3D) printed resin denture teeth. Fracture toughness of these teeth must be assessed.

OBJECTIVE

This study aimed to compare the chipping and indirect tensile fracture resistance of denture teeth fabricated by 3D printing technique with traditionally fabricated resin denture teeth.

METHOD

Four groups (Gr) were made (n= 50/group): Gr-1 3D printed denture teeth (denture teeth; Formlabs Inc., Somerville, MA, USA), Gr-2 SR-Orthosit-PE (Ivoclar Vivadent AG), Gr-3 Portrait IPN (Dentsply Sirona), Gr-4 Pala Premium 8 (Heraeus Kulzer GmbH). Stereolithography 3D printing was used to create the methacrylate-based photopolymerized resin teeth models and remaining group teeth were collected commercially. A 1 mm/min chipping and indirect tensile fracture speed tests were carried out till fracture occurred. The data so obtained were statistically analysed using one-way analysis of variance with Tukey's honestly significant difference multiple comparisons test (p< 0.05). At the end of the test, the fractured areas of the specimens were evaluated by the chief researcher to assess the fracture pattern of the teeth.

RESULTS

The indirect tensile fracture values of the 3D printed teeth were more than that of Pala Premium-8 and SR-Orthosit-PE but it was lower than that of Portrait IPN teeth. In chipping test, buccal chipping of the loaded cusp was seen in 3D printed resin without distortion and in indirect tensile test in 3D printed resin teeth, line of fracture emerges near the loading point propagates from the inner incline of both cusps and extends cervically, unlike in other groups where first deformation occurs then fracture.

CONCLUSION

Prosthetic teeth fabricated by the 3D printing technique using printable resin material provide adequate fracture resistance as denture teeth.

Prediction of abrasive wears behavior of dental composites using an artificial neural network

Resin composites are widely used as dental restorative materials since dental parts are subjected to prolonged wear and ultimately need to be replaced. The objective of this study is to analyze the potential of the feed-forward back propagation artificial neural network (ANN) in assessing the wear of dental composite materials when immersed in chewable tobacco solution, by utilizing the in-vitro test results of the pin-on-disc tribometer [ASTM G99-04]. In this study, four different dental composite material specimens are dipped in a chewable tobacco solution for a few days, and the specimens are removed from the solution for conducting the wear test. Three different training procedures are used to simulate ANN models for predicting the wear of dental composite specimens. The Bayesian regularization training algorithm outperforms the other algorithms significantly. The findings of the ANN modeling were prominently matching with the results of the experiments; therefore, parametric analysis was used based on the model's predicted values.

Composite 3D printing of biomimetic human teeth

Human teeth are mechanically robust through a complex structural composite organisation of materials and morphology. Efforts to replicate mechanical function in artificial teeth (typodont teeth), such as in dental training applications, attempt to replicate the structure and morphology of real teeth but lack tactile similarities during mechanical cutting of the teeth. In this study, biomimetic typodont teeth, with morphology derived from X-ray microtomography scans of extracted teeth, were 3D printed using an approach to develop novel composites. These composites with a range of glass, hydroxyapatite and porcelain reinforcements within a methacrylate-based photopolymer resin were compared to six commercial artificial typodont teeth. Mechanical performance of the extracted human teeth and 3D printed typodont teeth were evaluated using a haptic approach of measuring applied cutting forces. Results indicate 3D printed typodont teeth replicating enamel and dentine can be mechanically comparable to extracted human teeth despite the material compositions differing from the materials found in human teeth. A multiple parameter variable of material elastic modulus and hardness is shown to describe the haptic response when cutting through both human and biomimetic, highlighting a critical dependence between the ratio of material mechanical properties and not absolute material properties in determining tooth mechanical performance under the action of cutting forces.

Comparison of Microhardness of Artificial Teeth with Different Contents After Waiting in Various Liquids

Objectives: This study aimed to assess the long-term microhardness of different artificial teeth after waiting in liquids of various pH values. Materials and Methods: Four different artificial teeth [conventional PMMA(Ivostar) as control group), double cross-linked PMMA(DCL), micro-filled composite resin(VivodentPE), nanohybrid composite resin(PhonaresiII)] were used for the study. After the samples fixed on acrylic blocks were immersed in distilled water at 37˚C for 24 hours, initial microhardness (T0) measurements were performed. Randomly selected samples from each group were immersed in liquids with different pH values (artificial saliva, kefir, orange juice, cola). Measurements repeated on the 7th day on the same samples were recorded as T1, and measurements repeated on the 14th day were recorded as T2. The data obtained were evaluated in the SPSS 22.0 program. Friedman and Kruskall Wallis tests were used to compare of the groups. Results: While the highest initial microhardness averages were found in the Phonares II group, the lowest average belongs to the Ivostar group. Microhardness findings of all materials measured at different times were obtained in the order of T0>T1>T2. When the data of samples aged in different liquids are compared, significant differences are observed (p0.05) Conclusions: A decrease in microhardness of materials that are immersed in liquids with different pH values for a long time was observed, and the microhardness of the materials exposed to these solutions is adversely affected.

Characterization of various acrylate based artificial teeth for denture fabrication

Acrylic resins-based artificial teeth are frequently used for the fabrication of dentures has and contribute a very strong share in the global market. However, the scientific literature reporting the comparative analysis data of various artificial teeth is scarce. Focusing on that, the present study investigated various types of commercially available artificial teeth, composed of polymethyl methacrylate (PMMA). Artificial teeth are characterized for chemical analysis, morphological features, thermal analysis, and mechanical properties (surface hardness, compressive strength). Different types of artificial teeth showed distinct mechanical (compression strength, Vickers hardness) and thermal properties (thermal gravimetric analysis) which may be attributed to the difference in the content of PMMA and type and quantity of different fillers in their composition. Thermogravimetric analysis (TGA) results exhibited that vinyl end groups of PMMA degraded above 200 °C, whereas 340-400 °C maximum degradation temperature was measured by differential thermal analysis (DTA) for all samples. Crisma brand showed the highest compressive strength and young modulus (88.6 MPa and 1654 MPa) while the lowest value of Vickers hardness was demonstrated by Pigeon and Vital brands. Scanning electron microscope (SEM) photographs showed that Crisma, Pigeon, and Vital exhibited characteristics of a brittle fracture; however, Artis and Well bite brands contained elongated voids on their surfaces. According to the mechanical analysis and SEM data, Well bite teeth showed a significantly higher mechanical strength compared to other groups. However, no considerable difference was observed in Vickers hardness of all groups. Graphical abstract.

Wear Resistance of 3D Printed and Prefabricated Denture Teeth Opposing Zirconia

PURPOSE

To evaluate the wear resistance of a recently developed three-dimensional (3D) printed denture teeth resin compared to three commercially available prefabricated denture teeth.

MATERIALS AND METHODS

A total of 88 maxillary first molar denture teeth were evaluated: C (Classic; Dentsply Sirona, York, PA), DCL (SR Postaris DCL; Ivoclar Vivadent, Schaan, Liechtenstein), IPN (Portrait IPN; Dentsply Sirona, York, PA), and F (Denture Teeth A2 Resin 1 L; Formlabs, Somerville, MA). The 3D printed denture tooth specimens were fabricated from a methacrylate-based photopolymerizing resin using stereolithography (SLA). Denture teeth were subjected to a three-body wear test with a poly(methylmethacrylate) (PMMA) abrasive slurry. A Leinfelder-style four station wear apparatus with custom bullet-shaped milled zirconia styli was utilized with a load force of 36-40 N at 1.7 Hz for 200,000 cycles. Maximum depth of wear was measured using a lab grade scanner and analyzing software program. Data were analyzed using a one-way ANOVA followed by the Tukey's Multiple Comparisons post hoc test (α = 0.05).

RESULTS

A statistically significant difference in depth of wear was found between denture tooth materials (p < 0.001). The mean vertical depth of wear for the 3D printed denture teeth (0.016 ± 0.010 mm) was statistically significantly less than the prefabricated denture teeth. The highly cross-linked denture teeth, DCL (0.036 ± 0.011 mm) and IPN (0.035 ± 0.014 mm), exhibited statistically significantly less wear than the conventional acrylic denture teeth. The conventional acrylic denture teeth demonstrated the greatest wear (0.058 ± 0.014 mm). No significant difference in depth of wear was found between DCL and IPN (p > 0.001).

CONCLUSIONS

Denture tooth material significantly influences the depth of wear. The 3D printed denture teeth demonstrated superior wear resistance compared to the commercially available prefabricated denture teeth when opposed to zirconia. Denture teeth fabricated with SLA technology may have a promising future in prosthetic dentistry.

Shear bond strength between CAD/CAM denture base resin and denture artificial teeth when bonded with resin cement

PURPOSE

The bond strengths between resin denture teeth with various compositions and denture base resins including conventional and AD/CAM purposed materials were evaluated to find influence of each material.

MATERIALS AND METHODS

Cylindrical rods (6.0 mm diameter × 8.0 mm length) prepared from pre-polymerized CAD/CAM denture base resin blocks (PMMA Block-pink; Huge Dental Material, Vipi Block-Pink; Vipi Industria) were bonded to the basal surface of resin teeth from three different companies (VITA MFT®; VITA Zahnfabrik, Endura Posterio®; SHOFU Dental, Duracross Physio®; Nissin Dental Products Inc.) using resin cement (Super-Bond C&B; SUN MEDICAL). As a control group, rods from a conventional heat-polymerizing denture base resin (Vertex™ Rapid Simplified; Vertex-Dental B.V. Co.) were attached to the resin teeth using the conventional flasking and curing method. Furthermore, the effect of air abrasion was studied with the highly cross-linked resin teeth (VITA MFT®) groups. The shear bond strengths were measured, and then the fractured surfaces were examined to analyze the mode of failure.

RESULTS

The shear bond strengths of the conventional heat-polymerizing PMMA denture resin group and the CAD/CAM denture base resin groups were similar. Air abrasion to VITA MFT® did not improve shear bond strengths. Interfacial failure was the dominant cause of failure for all specimens.

CONCLUSION

Shear bond strengths of CAD/CAM denture base materials and resin denture teeth using resin cement are comparable to those of conventional methods.

The accuracy of the prediction models for surface roughness and micro hardness of denture teeth

The paper aimed to compare the performance of artificial neural network (ANN) model with the results of in vitro experiments. For these experiments, maxillary molars of four different denture teeth were subjected to tea, coffee, cola, cherry juice, distilled water. Vickers microhardness and surface roughness values were measured. Subsequently, ANN model for the prediction of microhardness and surface roughness of different denture teeth were examined. A back-propagation ANN has been used to develop a model relating to the amount of microhardness and surface roughness. The independent variables of the model are distilled water, tea, filtered coffee, cola, cherry juice, time and denture teeth. Microhardness and surface roughness were chosen as the dependent variables. According to the results, a neural network architecture having one input layer with ten neurons, two hidden layers with six neurons, one output layer with two neurons and an epoch size of 48 gives better prediction. Prediction models for dental materials could also be supportive for in vitro studies.

Analysis of behavior of the wear coefficient in different layers of acrylic resin teeth

STATEMENT OF PROBLEM

Analysis of the wear coefficient (k) of the superficial and deep layers of acrylic resin teeth can help predict denture durability, but little has been published on the wear coefficient of denture teeth.

PURPOSE

The purpose of this in vitro study was to determine the k value for the superficial and deep layers of the acrylic resin teeth of 6 different brands by using the fixed-ball microabrasive wear method.

MATERIAL AND METHODS

Six artificial tooth specimens of 4 commercial brands were tested: Artiplus IPN (Ar), Biotone IPN (Bi), Magister (Ma), Premium (Pr), Trilux (Tr), and SR Vivodent (Vi). Two specimens from each brand were created, one for the superficial layer and the other for the deep layer. The test was performed on fixed-ball microabrasive wear equipment set to operate at a constant normal force of 0.5 N and a rotation speed of 100 rpm. The test time periods were 5.00, 8.33, and 11.66 minutes. The characteristics of the wear craters were measured by using an optical microscope at a magnification of ×50 and Leica Microsystems software. Wear coefficient (k) values were deduced by using the Archard equation for abrasive wear, Q=k·N, and were analyzed by using 1-way analysis of variance, complemented by the Tukey HSD test (α=.05). A different analysis was used for each layer.

RESULTS

The analysis of variance of the wear coefficient revealed significant differences among the groups regarding the superficial layers (P=.009). The Tukey HSD test showed that the k values for the superficial layers of Artiplus specimens were significantly lower than those of the Vivodent and Magister specimens.

CONCLUSIONS

One brand (Ar) presented significantly lower wear coefficient value for the surface layer. No difference in wear coefficient values was found among the tooth brands for the deep layer.

3D Printing of Resin Material for Denture Artificial Teeth: Chipping and Indirect Tensile Fracture Resistance

3D printing of denture artificial teeth with resin materials is worthy of study in a novel way. This study evaluated chipping and indirect tensile fracture resistance of 3D printing resin material (Dentca 3D printing denture teeth resin) compared with conventionally prefabricated resin denture teeth (Premium-8, Surpass, SR-Orthosit-PE, and Preference). One hundred tooth specimens were prepared for testing. The 3D printed tooth specimens were printed at a 50 µm layer thickness with methacrylate-based photopolymerized resin by stereolithography 3D printing. Chipping and indirect tensile fracture tests were conducted at a speed of 1 mm/min until fracture. The indirect tensile fracture loads of the 3D printed resin teeth were higher than those of Premium-8, Surpass, and SR-Orthosit-PE, and lower than those of Preference teeth. Regarding chipping resistance, the 3D printed resin teeth were not different from Surpass and SR-Orthosit-PE, and were lower than Premium-8 and Preference teeth. The 3D printed resin teeth exhibited vertical fracture of the loaded cusp without deformation in chipping. The 3D printed resin teeth showed simultaneous fracture of two cusps in indirect tensile fracture, unlike other teeth. The results of this study suggest that 3D printing technology using resin materials provides adequate fracture resistance for denture artificial tooth use.

Management of dental trauma in a child with Xeroderma Pigmentosa

Xeroderma Pigmentosa is a rare dermatological autosomal recessive disorder that manifests itself early in life as severe sunburn usually after a short exposure to sunlight. The prime characteristic features include photosensitivity, hyperpigmentation and ichthyosis in sun exposed areas, and an increase in the risk of basocellular and squamous cell carcinomas and melanomas of the skin and eyes. The case report highlights the preventive treatment options along with all necessary precautions that should be taken to protect the patient from any iatrogenic inadvertent exposures that may be deleterious to his present state. The purpose of the report is also to discuss the important role of dental professionals when dealing with debilitating medical conditions.

Efeito do desafio ácido nas propriedades superficiais das camadas externa e interna de dentes acrílicos reforçados

Resumo Introdução Os dentes acrílicos artificiais devem apresentar característica de resistência aos ácidos, a fim de assegurar a manutenção de suas propriedades, ao longo de sua vida útil. Entretanto, não há estudos disponíveis na literatura pertinente sobre as propriedades superficiais de dureza e rugosidade das diferentes camadas de resina acrílica que compõem os dentes artificiais submetidos a ensaios de erosão simulada. Objetivo Avaliar a dureza e rugosidade superficiais das camadas externa e interna de dentes artificiais acrílicos reforçados submetidos a desafio ácido. Metodologia Molares (SR Postaris e Trilux) seccionados transversalmente foram avaliados inicialmente quanto à dureza Vickers e rugosidade. Esses ensaios foram repetidos após metade das amostras de cada tipo de dente (n=10) ser imersa em água destilada (controle) e outra metade em vinagre durante 15 min/dia por 28 dias. Os resultados foram analisados por ANOVA 2-critérios e teste de Tukey (α=0,05). Resultado A dureza inicial da camada externa dos dois diferentes tipos de dente não sofreu alteração significativa pelo desafio ácido (p>0,05) e a imersão em vinagre não causou efeito deletério à dureza inicial da camada interna dos dois tipos de dentes avaliados (p>0,05). Após 28 dias, a rugosidade inicial de ambos os tipos de dentes estudados, para as duas camadas, não foi alterada com água ou vinagre (p>0,05). Conclusão Os dentes acrílicos reforçados foram resistentes ao desafio ácido uma vez que suas camadas interna e externa não apresentaram alteração significativa de dureza e rugosidade superficiais.

Evaluation of Surface Microhardness Following Chemical and Microwave Disinfection of Commercially Available Acrylic Resin Denture Teeth

INTRODUCTION

Denture disinfection is an indispensable procedure for preventing cross contamination and the maintenance of a healthy oral mucosa in patients rehabilitated with removable dental prosthesis. Nevertheless, they are known to cause changes in the physical and mechanical properties of denture base resins and acrylic resin denture teeth following immersion of a denture in a suitable chemical disinfectant solution or by undergoing microwave irradiation. One such mechanical property indicator for artificial tooth materials is hardness.

AIM

To assess the surface hardness of acrylic resin teeth of three different commercial brands (Ivoclar, Newace, Acryrock) following chemical (2% glutaraldehyde, 1% sodium hypochlorite) and microwave disinfections.

MATERIALS AND METHODS

Ten specimens of each of the three commercial brands were made for control and each simulated disinfection type and stored in distilled water at room temperature for 24 hours. After water storage, specimens were immersed in 2% glutaraldehyde and 1% sodium hypochlorite (one and three cycles) at room temperature for 10 minutes. Irradiation with microwave (one and three cycles) was done in domestic microwave for three minutes with the specimens immersed in 150 ml of distilled water. The specimens were stored in distilled water at room temperature for seven days after each disinfection cycle. Vickers hardness measurements were made using a hardness indenter under a load of 50 g force for 10 seconds. Data was subjected to repeated measure two-way ANOVA test and Tukey's test.

RESULTS

There were statistically significant differences for the variables disinfection, tooth, and cycle (p<0.05 for teeth & disinfectant interaction, p<0.05 cycle and disinfectant interaction). The mean surface hardness following one microwave disinfection cycle was lower than control, glutaraldehyde and sodium hypochlorite. Comparison among cycles revealed that microhardness was significantly decreased for three cycles of microwave disinfection.

CONCLUSION

It was concluded that there was no significant difference in microhardness when the teeth were subjected to chemical disinfection but three cycles of microwave disinfection produced decrease in the microhardness of different types of artificial teeth.

Surface properties of multilayered, acrylic resin artificial teeth after immersion in staining beverages

Objective

To evaluate the effect of staining beverages (coffee, orange juice, and red wine) on the Vickers hardness and surface roughness of the base (BL) and enamel (EL) layers of improved artificial teeth (Vivodent and Trilux).

Material and Methods

Specimens (n=8) were stored in distilled water at 37°C for 24 h and then submitted to the tests. Afterwards, specimens were immersed in one of the staining solutions or distilled water (control) at 37°C, and the tests were also performed after 15 and 30 days of immersion. Data were analyzed using 3-way ANOVA and Tukey’s test (α=0.05).

Results

Vivodent teeth exhibited a continuous decrease (p<0.0005) in hardness of both layers for up to 30 days of immersion in all solutions. For Trilux teeth, similar results were found for the EL (p<0.004), and the BL showed a decrease in hardness after 15 days of immersion (p<0.01). At the end of 30 days, this reduction was not observed for coffee and water (p>0.15), but red wine and orange juice continuously reduced hardness values (p<0.0004). Red wine caused the most significant hardness changes, followed by orange juice, coffee, and water (p<0.006). No significant differences in roughness were observed for both layers of the teeth during the immersion period, despite the beverage (p>0.06).

Conclusions

Hardness of the two brands of acrylic teeth was reduced by all staining beverages, mainly for red wine. Roughness of both layers of the teeth was not affected by long-term immersion in the beverages.

Two Body Wear of Newly Introduced Nanocomposite Teeth and Cross Linked Four Layered Acrylic Teeth: a Comparitive In Vitro Study

STATEMENT OF PROBLEM

Wear of complete denture teeth results in compromise in denture esthetics and functions. To counteract this problem, artificial teeth with increased wear resistance had been introduced in the market such as nanocomposite teeth.

PURPOSE

The purpose of this study was to compare the amount of wear between nanocomposite teeth and acrylic teeth.

MATERIALS AND METHODS

Fifteen specimens were chosen from each group namely the nanocomposite teeth (SR_-PHONARES) and the acrylic teeth (ACRY PLUS). Maxillary premolar was only chosen for testing and the samples were customized according to the specifications of the pin on disc machine. Pin on disc machine is a two body tribometer which quantifies the amount of wear under a specific load and time. Test samples were mounted on to the receptacle of the pin on disc machine and tested under a load of 0.3 kg for 1,000 cycles of rotation against a 600 grit emery paper. The amount of wear is displayed from the digital reading obtained from the pin on disc machine.

RESULTS

After statistical analysis, it was found that, the amount of wear is more in four layered acrylic teeth. The p value obtained is 0.002 (<0.005) thus implies that the difference in wear between nanocomposite teeth and acrylic teeth is statistically significant.

CONCLUSION

Though the nanocomposite teeth has less amount of wear than the four layered acrylic teeth, the difference is very less and adds only to a little clinical significance but the cost of the nanocomposite is four times that of the acrylic teeth. Further clinical studies must be performed to confirm our results.

Hardness and surface roughness of enamel and base layers of resin denture teeth after long-term repeated chemical disinfection

AIM

To evaluate the effect of successive cycles of disinfection in different denture cleansers on the surface roughness and the Vickers hardness of two layers of acrylic resin (base-BL and enamel-EL) of two commercial cross-linked artificial teeth.

MATERIALS AND METHODS

The occlusal surfaces of 60 acrylic resin denture posterior teeth (Trilux-TLX and SR Orthosit PE-SRO) embedded in autopolymerizing acrylic resin were ground fat with 1200-grit silicon carbide paper. Specimens were stored in distilled water at 37°C and then submitted to the microhardness (VHN) and roughness (μm) tests. Specimens were stored in distilled water at 37°C for 90 days and submitted to 720 disinfection cycles in sodium hypochlorite at 0.5%, 30% vinegar solution or distilled water (control). Afterward, micro-hardness and roughness tests were again performed. Data were analyzed using two-way ANOVA and Tukey's test (α=0.05).

RESULTS

Hypochlorite immersion decreased the hardness of BL and EL of SRO teeth, with an average reduction of 10.11% (p<0.008). TLX teeth demonstrated a hardness reduction of 28.96% of both layers for all solutions including water (p<0.0000). The roughness of both teeth was not affected by denture cleansers (p>0.37).

CONCLUSION

Hypochlorite promoted deleterious effects on the hardness of both layers of the artificial teeth tested. Immersion in vinegar and water also resulted in reduction of hardness of TLX teeth.

CLINICAL SIGNIFICANCE

The surface hardness of the different layers of cross-linked artificial teeth can be altered by daily disinfection in denture cleansers commonly indicated for removable dentures.

Nanotechnology and its application in dentistry

Nanotechnology influences almost every facet of everyday life from security to medicine. The concept of nanotechnology is that when one goes down to the bottom of things, one can discover unlimited possibilities and potential of the basic particle. In nanotechnology, analysis can be made to the level of manipulating atoms, molecules and chemical bonds between them. The growing interest in the dental applications of nanotechnology is leading to the emergence of a new field called nanodentistry. An electronic database search that included PubMed, MedLine, and Cochrane library was conducted. Key words used in the search are nanotechnology dentistry and applications. Language limitation was set as articles reviewed were only those written and published in English language. We did not search the gray literature. Initially, 52 articles were retrieved from the database, and articles considered were those published from 2008 to 2013. Eight articles that met the selection criteria were eventually selected and reviewed.

Effect of chemical and microwave disinfection on the surface microhardness of acrylic resin denture teeth

PURPOSE

The purpose of this study was to evaluate the effect of simulated disinfections (2% glutaraldehyde, 1% sodium hypochlorite, and microwave energy) on the surface hardness of Trilux, Biocler, Biotone, New Ace, and Magister commercial artificial teeth.

MATERIALS AND METHODS

Specimens (n = 10) were made with the teeth included individually in circular blocks of acrylic resin, leaving the labial surface exposed. Cycles of simulated chemical disinfection were accomplished with the specimens immersed in the solutions at room temperature for 10 minutes, followed by tap water washing for 30 seconds and storage in distilled water at room temperature for 7 days until the next disinfection. Simulated disinfection by microwave energy was carried out in a domestic oven with 1300 W at a potency of 50% for 3 minutes with the specimens individually immersed in 150 ml of distilled water. Control (no disinfection) and the experimental groups (first and third disinfection cycles) were submitted to Knoop hardness measurements with indentations at the center of the labial tooth surface. Data were submitted to repeated measure two-way ANOVA and Tukey's test (α = 0.05).

RESULTS

Biocler, Magister, and Trilux showed lower surface microhardness when submitted to microwave. Lower microhardness for Biotone was promoted by hypochlorite, while no significant difference was shown for New Ace. The third disinfection cycle significantly decreased the tooth surface hardness only for microwave.

CONCLUSIONS

Different disinfection methods promoted different effects on the microhardness of different types of artificial teeth. Surface microhardness of the teeth was less affected by the simulated chemical disinfections when compared to microwaved specimens.

Factors affecting wear of composite resin denture teeth--24-month results from a clinical study

The objectives of this study were to measure the occlusal wear of composite resin denture teeth in patients wearing a complete denture and to evaluate factors affecting wear. Fifty participants provided with complete dentures in at least one jaw were included. Gypsum casts were made from preliminary vinyl polysiloxane impressions 4 weeks after insertion, then after 6 (t(1)), 12 (t(2)), and 24 months (t(3)). Three-hundred and three posterior denture teeth were evaluated after 24 months. Wear was measured indirectly, from the casts, by means of a three-dimensional laser scanner device. Sequential images of the occlusal surfaces were digitized and superimposed (occlusal matching). Statistical analysis was performed by the use of mixed regression models, with the patient being a random effect. Mean wear (median, interquartile range; micrometer) of the entire occlusal surface was 8 (19) at t(1), 18 (34) at t(2), and 40 (61) at t(3). Maximum vertical loss (median, interquartile range; micrometer) was 92 (112) at t(1), 146 (148) at t(2), and 226 (184) at t(3). The dental status of the opposing jaw and the nature of the opposing material significantly affected the wear of denture teeth at t (3). Gender, daily wearing time, jaw, and type of tooth had no significant effects on the extent of wear. Clinically relevant vertical loss of composite resin denture teeth occurs after 24 months. Considering the limitations of this study, wear of denture teeth was affected by dental status and opposing material. The results suggest that wear of composite resin denture teeth exceeds that of enamel.

Three-body wear of resin denture teeth with and without nanofillers

STATEMENT OF PROBLEM

The wear behavior of newly developed denture teeth with nanofillers may be different from teeth with other chemical formulations.

PURPOSE

The purpose of this study was to examine the 3-body wear resistance of 11 different commercially available resin denture teeth.

MATERIAL AND METHODS

The materials tested were conventional (SR Orthotyp PE, Orthognath) and cross-linked acrylic resin teeth without inorganic fillers (Premium 8, SR Postaris DCL, Trubyte Portrait, Artiplus), composite resin teeth with inorganic fillers (SR Orthosit PE, Vitapan), and composite resin teeth (experimental materials) with inorganic nanofillers (NC Veracia Posterior, e-Ha, Mondial). Human enamel and a ceramic denture tooth (Lumin Vacuum) were used as reference materials. The 3-body wear test was performed in a wear machine developed by the Academic Center for Dentistry Amsterdam (ACTA), with millet suspension acting as an abrasive medium (n=10, test load: 15 N, slip rate: 20%, number of cycles: 100,000). Wear was determined with the aid of a profilometer. Data were analyzed with the Kruskal-Wallis test and Mann-Whitney U test using the closed testing approach (significance level for familywise error rate, alpha=.05).

RESULTS

None of the acrylic and composite resin materials tested in this study demonstrated the 3-body wear resistance of ceramic teeth or human enamel. Teeth with inorganic fillers demonstrated significantly lower wear values than conventional or cross-linked acrylic resin teeth without fillers. Composite resin teeth with traditional fillers showed significantly lower wear than composite resin teeth with nanofillers.

CONCLUSIONS

Denture teeth with and without inorganic fillers differed significantly with regard to the degree of wear generated in the ACTA wear simulator. The incorporation of nanofillers did not improve the wear resistance compared to teeth with traditional fillers.

Abrasion wear resistance of different artificial teeth opposed to metal and composite antagonists

One of the most important properties of artificial teeth is the abrasion wear resistance, which is determinant in the maintenance of the rehabilitation's occlusal pattern.

Influence of incorporation of fluoroalkyl methacrylates on roughness and flexural strength of a denture base acrylic resin

Fluorinated denture base acrylic resins can present more stable physical properties when compared with conventional polymers. This study evaluated the incorporation of a fluoroalkyl methacrylate (FMA) mixture in a denture base material and its effect on roughness and flexural strength. A swelling behavior assessment of acrylic resin specimens (n=3, per substance) after 12 h of FMA or methyl methacrylate (MMA) immersion was conducted to determine the solvent properties. Rectangular specimens (n=30) were allocated to three groups, according to the concentration of FMA substituted into the monomer component of a heat-polymerized acrylic resin (Lucitone 550), as follows: 0% (control), 10% and 20% (v/v). Acrylic resin mixed with concentrations of 25% or more did not reach the dough stage and was not viable. The surface roughness and flexural strength of the specimens were tested. Variables were analyzed by ANOVA and Tukey's test (α=0.05). Immersion in FMA produced negligible swelling, and MMA produced obvious swelling and dissolution of the specimens. Surface roughness at concentrations of 0%, 10% and 20% were: 0.25 ± 0.04, 0.24 ± 0.04, 0.22 ± 0.03 μm (F=1.78; p=0.189, not significant). Significant differences were found for flexural strength (F=15.92; p<0.001) and modulus of elasticity (F=7.67; p=0.002), with the following results: 96 ± 6, 82 ± 5, 84 ± 6 MPa, and 2,717 ± 79, 2,558 ± 128, 2574 ± 87 MPa, respectively. The solvent properties of FMA against acrylic resin are weak, which would explain why concentrations over 20% were not viable. Surface changes were not detected after the incorporation of FMA in the denture base acrylic resin tested. The addition of FMA into denture base resin may lower the flexural strength and modulus of elasticity, regardless of the tested concentration.

Effect of filler type and polishing on the discoloration of composite resin artificial teeth

In this study, the effects of filler type and polishing on the discoloration of composite resin artificial teeth were examined. Four types of experimental resins were prepared: one was a matrix resin, while the others were composite resins containing three different types of fillers (nano-sized silica filler with or without silanization, and prepolymerized filler). Specimens were immersed in distilled water, coffee, red wine, or curry. Color change after immersion was measured using a colorimeter. Color difference values (delta E) and changes in translucency parameter (delta TP) were statistically analyzed using three-way ANOVA and Tukey's comparison. On the influence of the polishing factor, statistically significant differences were neither observed in delta E nor delta TP between polished and non-polished tooth surfaces. On the contrary, the influences of filler type and discoloration medium, and their interaction thereof, were significant. With unsilanized filler, the delta E value of composite resin artificial teeth was significantly increased.

Effect of ultraviolet light irradiation on bonding of experimental composite resin artificial teeth

The purpose of the present study was to evaluate how ultraviolet light (UV) irradiation using an ordinary UV sterilizer would affect the bonding of experimental composite resins to an autopolymerizing acrylic resin. To this end, three composite resins and one unfilled resin--of which the compositions were similar to commercial composite resin artificial teeth--were prepared as repair composites. Their shear bond strengths after UV irradiation for one to 60 minutes were significantly greater than those before UV irradiation regardless of composite resin type. Failure mode after UV irradiation for one to 60 minutes was mainly cohesive failure of the composite resins, but that before UV irradiation and after 24 hours' irradiation was mainly adhesive failure. These results thus suggested that a short period of UV irradiation on composite resin teeth would improve the bonding efficacy of composite resin artificial teeth to autopolymerizing resin.