Examination of the effect of aging process on marginal fit and fractute strength of temporary crowns prepared from different materials.

Aim: The aim of this study is to investigate the effect of the aging process on the marginal fit and fracture resistance of temporary crowns prepared using different materials. Materials and method: The steel die to represent the maxillary first premolar used in this study was produced on a CNC turning machine to include an anatomical occlusal surface. A total of 160 epoxy resin dies were obtained by taking impressions with conventional impression methods on the metal die. Epoxy resin dies were randomly divided into four groups. Temporary crowns were prepared for each group from poly acrylic resin (Vita CADTemp®), bis-acryl composite resin (Protemp 4), poly methyl methacrylate (PMMA; Imident) and poly ethyl methacrylate (PEMA; Dentalon Plus) restorative materials. Half of the specimens (n = 20) in each group (n = 40) were randomly separated and the aging process was applied 5000 times in the device. Marginal gap measurements on epoxy resin dies were made using a stereomicroscope. The fracture strength test of the specimens was performed by using the Instron Universal Test Device. Jamovi 2.2.5 statistical program was used for statistical analysis. Results: When compared to temporary crowns prepared from all other materials, poly acrylic resin (Vita CADTemp ®) temporary crowns observed significantly lower marginal gap values (59,05 µm) regardless of the aging process, and a significantly higher fracture resistance (478,44 N) in the presence of aging process (p < .05 for each). While the highest marginal gap value was detected in PMMA (Imident) (120.36 µm) temporary crowns with aging process, the lowest marginal gap value was observed in poly acrylic resin (Vita CADTemp®) (59.05 µm) crowns without non-aging process. The marginal fit and fracture resistance of all temporary crowns were negatively affected by the aging process. Conclusion: Our findings revealed the superiority of poly acrylic resin (Vita CADTemp®) crowns to the temporary crowns prepared from all other materials in terms of the significantly lower marginal gap in the absence of aging process, and the significantly higher fracture resistance in the presence of aging process. Marginal fit and fracture resistance values for all materials were found to be within clinically acceptable limits.

Mechanical and Biocompatibility Properties of 3D-Printed Dental Resin Reinforced with Glass Silica and Zirconia Nanoparticles: In Vitro Study.

This study aimed to assess the mechanical and biocompatibility properties of dental resin reinforced with different nanoparticle additives. Temporary crown specimens were 3D-printed and grouped based on nanoparticle type and amount, including zirconia and glass silica. Flexural strength testing evaluated the material's ability to withstand mechanical stress using a three-point bending test. Biocompatibility was tested using MTT and dead/live cell assays to assess effects on cell viability and tissue integration. Fractured specimens were analysed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) for fracture surface examination and elemental composition determination. Results show that adding 5% glass fillers and 10-20% zirconia nanoparticles significantly improves the flexural strength and biocompatibility of the resin material. Specifically, the addition of 10%, 20% zirconia, and 5% glass silica by weight significantly increases the flexural strength of the 3D-printed resins. Biocompatibility testing reveals cell viabilities greater than 80% in all tested groups. Reinforced 3D-printed resin holds clinical potential for restorative dentistry, as zirconia and glass fillers have been shown to enhance mechanical and biocompatibility properties of dental resin, making it a promising option for dental restorations. The findings of this study may contribute to the development of more effective and durable dental materials.

The comparison of the accuracy of temporary crowns fabricated with several 3D printers and a milling machine.

PURPOSE: The purpose of this in vitro study was to compare the accuracy of various 3D printers and a milling machine. MATERIALS AND METHODS: The die model was designed using CAD (Autodesk Inventor 2018 sp3). The 30 µm cement space was given to the die and the ideal crown of the mandibular left first molar was designed using CAD (ExoCAD). The crowns were produced using the milling machine (Imes-icore 250i) and the 3D printers (Zenith U, Zenith D, W11) and they were divided into four groups. In all groups, the interior of each crown was scanned (Identica blue) and superimposed (Geomagic Control X) with the previously designed die. The difference between the die and the actual crown was measured at specific points. The Kruskal-Wallis test, the Mann-Whitney test, and Bonferroni's method were performed with a statistical analysis software (P < .008 in inter-group comparison P < .001 in intra-group comparison). RESULTS: In all groups, the center of the occlusal area and the anti-rotational dimple area showed significantly greater difference and the marginal area showed the smallest difference comparatively. The mean value of the difference in each area and the sum of the differences were higher in order of W11, Imes-icore 250i, Zenith D, and Zenith U. CONCLUSION: The digital light processing (DLP) method shows higher accuracy compared to the sereolithography (SLA) method using the same resin material.

Compressive Strength of Temporary Crowns Made from Default design in Two Types of Software.

Statement of the Problem: Various default values in each software can eventually lead to different crown thicknesses and affect their compressive strength. Purpose: This study aimed to compare the compressive strength of temporary crowns made with the milling machine, designed in Exocad and 3Shape Dental System software. Materials and Method: In this in vitro study, 90 temporary crowns were made and evaluated based on each software settings. For this purpose, a sound premolar was first scanned as a pre-operative model by 3Shape laboratory scanner. The standard tooth preparation and scanning were performed, and then the temporary crown files (designed by each software) were transferred to the Imesicore 350i milling machine. A total of 90 temporary crowns (45 based on the file of each software) were made using poly methyl methacrylate (PMMA) vita cad-temp block. The value of compressive force displayed on the monitor was recorded at the first crack and the ultimate failure of the crown. Results: The first crack and the ultimate strength of crowns designed with the Exocad software was 903.5±96N and 1490±139.3N and for crowns designed with 3Shape Dental System software was 1060.4±160.2N and 1691.1±73.9N, respectively. The amount of compressive strength of temporary crowns made with 3Shape Dental System was significantly higher than those made with Exocad software and this difference was statistically significant(p= 0.000). Conclusion: The compressive strength of temporary dental crowns made by both softwares is in a clinically acceptable range, but considering that the average compressive strength in the 3Shape Dental System group was slightly higher than of the other group, it is preferable to design and fabricate with 3Shape Dental System software to increase the compressive strength of these crowns.

The effect of different staining solutions on the color stability of temporary crown materials.

Background: The esthetic expectations of patients are increasing by the day. That is why it is important to minimize the color changes in the oral cavity in both the temporary and permanent restorations. Aim: This study was carried out to compare the time-dependent color changes of polished and unpolished temporary crown materials prepared by different methods in various solutions. Materials and Methods: Half of the two different temporary restoration materials prepared with a diameter of 10 mm and a thickness of 2 mm were polished, and half were not polished. The ΔE* values of the samples kept in various solutions were recorded. Data were statistically evaluated by using variance analysis (ANOVA) and a Tukey HSD multiple comparison test. Results: It was determined that the material type, the solution, the interaction between the material types and the surface treatment, and the interaction between the surface treatment and the solution were statistically significant for color change (p < 0.001). Conclusion: The most significant color change in the inter-material evaluation was observed in chemically polymerized polymethyl methacrylate. In the evaluation between beverages, the highest color change was found in sugared coffee, and the lesser color change was observed in polished samples.

Soft-tissues stabilization after immediate implant; platform switch with supraperiosteal augmentation.

The architecture around an oral implant pushes the clinicians for an equalization of biological and physiological requirements. An esthetic implant-supported restoration needs plethora of knowledge and expertise. Surgeon skills can be of use for correct tridimensional position of implant in the extraction socket, shaped abutment contours, and anatomical final crown. An immediate implant placement for a fresh socket requires existing oral parameters judgment and evidence-based treatment plan. They are hard- and soft-tissue relationship, gingival biotype, and the tooth position. In this article, we describe a case of immediate implant placement, provisional crown, bovine bone contraction, soft-tissue collapse, and its management.

Laboratory Study of Color Stability of Different Types of Materials for Temporary Constructions.

INTRODUCTION: A temporary construction serves as a preliminary representation of the type and appearance of a future permanent one that is tailored to the patient's requirements. Like any prosthetic construction, it should meet the functional requirements, preserve or improve chewing and speech function. No matter how well maintained a prophylactic and functional prosthetic structure is, it will not be evaluated by the patient unless it retains and restores the existing shape, size and color of the natural teeth. AIM: To determine instrumentally to what extent different colorants change the color of temporary constructions. MATERIALS AND METHODS: Two materials for temporary restoration were tested - Protemp II and Protemp IV, of which a total of 100 test specimens, were fabricated. Under the equal storage conditions of room temperature and no direct access to sunlight, they were exposed to five 100-ml staining solutions: Coca-Cola, coffee (espresso), berry tea, orange juice and red wine in five separate containers. Measurements of color changes in the three areas of the tooth were performed using two spectrophotometric devices - Vita EasyShade and SpectroShade, at different time intervals - immediately before placement in the staining solution, at 1, 4, 7, and 14 days. RESULTS: The results were analysed using the SPSS Statistical Processing Program (SPSS Inc., IBM SPSS Statistics) version 21.0. They were converted to a text file with the converter of the same program. In hypothesis testing, a standard value of p ≤ 0.05 was chosen for the level of significance that rejects the null hypothesis. CONCLUSION: Based on this study, the strong colouring effect of coffee and red wine on these restorations was demonstrated. We can conclude that Protemp IV material showed better color stability compared to Protemp II.

Marginal and internal fit of provisional crowns fabricated using 3D printing technology.

BACKGROUND: Clinicians routinely provide provisional crowns following teeth preparation. Three-dimensional (3D) printing technology could be used over conventional methods for better fit as lack of adequate fit would result in plaque accumulation, micro-leakage, teeth sensitivity, caries and periodontal diseases. OBJECTIVE: The aim of the study was to evaluate the marginal and internal fit of provisional crowns fabricated using 3D printing technology and to compare it with that of compression molding and milling methods. METHODS: Ninety study models were fabricated by duplicating metal master models of the maxillary first premolar molar with three different finish line chamfer, rounded shoulder and rounded shoulder with bevel. On each study model, provisional crowns were fabricated using compression molding (Mo. group, n= 30 - by over impression technique), milling (Mi. group, n= 30 - by 5-axis dental milling machine), and 3D printing method (3D-P. group, n= 30 - by 3D printer). Marginal and internal fit of the samples were evaluated by measuring gap using a scanning electron microscope with a magnification of 27 ×, at 7 zones A-G on different finish line models. The data were statistically analysed using one-way analysis of variance (ANOVA) at the 0.05 significance level. The p-values were calculated using Dunnett's test. RESULTS: The marginal gap was minimal for the 3D-P. group for each finish line with lowest for rounded shoulder with bevel at zone A 30.6 ± 5.3 and at zone G 32.8 ± 5.4. In axial area, i.e. zones B and F, the minimum gap was noticed for the Mo. group and in Occlusal area (cusp and fossa), for zones C-E maximum gap was determined in Mi. group followed by Mo. and 3D-P. groups. CONCLUSIONS: 3D printed provisional crowns have better marginal and internal fit compared to milled and molded provisional crowns.

Management of the delicate phase of the temporary crown: an in vitro study.

The fundamental moment of prosthetic rehabilitation is the "temporary". Although the meaning of the term diminishes its importance, the provisional has fundamental biological, aesthetic and functional functions. The oral cavity must maintain an adequate level of oral hygiene to carry out this delicate phase in the best possible way; a result achieved only with the collaboration of the prosthetic dentist with the hygienist and the patient, as if they were a biological system in motion. The different methods of hygiene are effective in maintaining a good level of oral health; but they could, if too aggressive, affect the prosthetic restoration. Our objective in vitro is to understand, after applying a known bacterial load, which hygiene method is the most effective in removing bacterial biofilm but at the same time is less aggressive towards resinous material.

Real-time pulp temperature change at different tooth sites during fabrication of temporary resin crowns.

AIM: To record the pulp temperature at different tooth sites during fabrication of two different temporary crown systems. METHODOLOGY: Two temporary crown systems were investigated; a conventional direct fabricated and a preformed thermoplastic resin system. Extracted caries-free human teeth (incisor, premolar and molar) were prepared for full coverage ceramic restoration with roots sectioned below the cemento-enamel junction. Thermocouple wires were secured at the surface of crown material, the cut dentine and inside the pulp cavity. Provisional crowns (n = 10/group) from each system were formed prior to placement in a water bath of 37 °C to simulate pulpal temperature. Temperatures were recorded using a K-type thermocouple data logger to collect the mean and peak temperature during crown fabrication. Statistical analysis was carried out on all tested groups and heat flow was calculated. RESULTS: For direct fabricated crowns, the mean rise in pulpal temperature recorded was 0.1 °C with the mean temperature range of 37.3 °C-37.8 °C. For the preformed thermoplastic crowns, the mean rise in pulpal temperature recorded was 37.3 °C-45.1 °C. The increase in temperature was significantly higher (6.5 °C for the incisor group, 7.5 °C for the premolar group, and 6.7 °C for the molar group). For both crown systems, the temperature difference between the three different sites; pulp, crown and tooth surface showed a statistical difference (P < 0.01). CONCLUSIONS: The direct fabrication system showed minimal temperature changes within the teeth, while the preformed thermoplastic fabrication system showed larger temperature change in the teeth.

Importance of interim restorations in the molar region.

Interim restoration protects abutment teeth and periodontal tissues until prosthetic treatment ends with the fabrication of a definitive prosthesis, restores and maintains the functions and morphology of the stomatognathic system, and preserves the occlusal contact relationship. Temporary prostheses are used for a short time, to confirm the diagnosis and treatment plan. However, because interim restorations are used only briefly, their importance in ensuring the success of definitive prostheses is often overlooked. This review includes a comprehensive literature review of interim restoration of molars and summarizes the current clinical understanding and status of this functionally important area. Peer-reviewed publications were identified by searching PubMed in November 2018. An interim restoration, even when used briefly, can help dentists evaluate many aspects of the treatment plan and contribute to accurate prognosis of prosthetic treatment.

Effect of different surface treatment methods on the shear bond strength of orthodontic brackets to temporary crowns.

INTRODUCTION: The number of adult patients seeking orthodontic treatment has been consistently increasing. Since the placing of the final restoration must be postponed until the completion of the orthodontic treatment, provisional restoration is recommended for the duration of the orthodontic treatment. These surfaces have special chemical properties, which necessitate the orthodontists to prepare the bonding area with special measures. METHODS: Polycarbonate and polymethylmethacrylate (PMMA) crowns (n=80) were randomly subdivided into 4 groups. Conditioning methods were grinding, sandblasting, CO2 laser and methyl methacrylate application. Samples underwent SBS testing. A scanning electron microscope (SEM) analysis was carried out. The data was analysed with ANOVA, Student t-test and Post-hoc test. Adhesive remnant index (ARI) was analysed with Chi2 test. RESULTS: In all surface treatments, the mean Shear Bond Strength (SBS) of PMMA was significantly higher than that of polycarbonate (P<0.001). In the polycarbonate groups, there was a significant difference between the mean SBS of the four treatment methods (P<0.001). However, there were no significant differences in PMMA group (P=0.076). In both crown materials, the mode of the failure was adhesive type, regardless of the conditioning method (P>0.05). CONCLUSIONS: PMMAs rendered higher bond strength than polycarbonates. In PMMA, all the surface treatment methods resulted in acceptable bond strength. However, if bonding the brackets to polycarbonate crown is needed, other conditioning methods are preferred over CO2 laser.

Comparison of color stability, mechanical and chemical properties according to temporary crown resin type / 대한치과재료학회지

Objective of this study was to compare the color stability, mechanical and chemical properties of three different types of temporary crown resins. Commercially available powder-liquid (Group PL), light-cured (Group LC) and auto-mix syringe (Group AM) types' temporary crown resins were used as experimental groups for each of the evaluation. All the test groups were evaluated after 1 day and 7 days of immersion in various staining solutions. The colors of all groups before and after storage in the staining solutions were measured by a spectrophotometer based on CIE Lab system, and the color differences (ΔE(*)) thereby calculated. Micro hardness test was performed before water storage and aging after 7 days at 37 ℃. In addition, flexural strength, water sorption and solubility tests were performed according to international standard, ISO 10477. All experimental groups showed significant color change in staining solutions when compared to those stored in the control solution (distilled water) (p PL > LC (p<0.05). Water sorption and solubility increased in the following order: AM < PL < LC (p<0.05). The results of this study would provide useful information when choosing temporary crown resin types in various clinical situations.

Comparison of physical properties of the various 3D printing temporary crown and bridge resin / 대한치과재료학회지

Conventional dental resins for crown and bridge fulfill ISO 10477 and ISO 10993 before clinical application. Although 3D printing or rapid prototyping (RP) for the fabrication of temporary crown and bridge have been proposed, a little studies were reported for 3D printing resin for temporary crown and bridge. The purpose of this study was to evaluate the physical properties (such as water sorption and solubility, color stability and flexural strength) of the various 3D printing temporary crown and bridge resin following the ISO 10477:2018 and estimate the effect of chemical composition of resin on the physical properties. Four resins approved by KFDA and 4 experimental resins developed by different manufacturer were tested in this study. Samples were prepared with DLP typed 3D Printer (G-Printer) and post-cured using UV-light Cure Unit (Cure M). Proper 3D printing and post-curing conditions were selected for different 3D printing resins. Each test was performed according to the ISO 10477 and results were statistically analyzed using Tukey-multiple comparison test (p=0.05). Only group-B did not satisfied the ISO requirement ( 60 MPa). Resin components may affect the flexural strength, then user should check the components of 3D printing resin. Deficient degree of polymerization may lead to large water sorption, water solubility and color changes. Further study should be done comparison between specimens printed with specific 3D printer recommended by manufacturer and specimens used in this study.

3D printed versus conventionally cured provisional crown and bridge dental materials.

OBJECTIVES: To optimize the 3D printing of a dental material for provisional crown and bridge restorations using a low-cost stereolithography 3D printer; and compare its mechanical properties against conventionally cured provisional dental materials. METHODS: Samples were 3D printed (25×2×2mm) using a commercial printable resin (NextDent C&B Vertex Dental) in a FormLabs1+ stereolithography 3D printer. The printing accuracy of printed bars was determined by comparing the width, length and thickness of samples for different printer settings (printing orientation and resin color) versus the set dimensions of CAD designs. The degree of conversion of the resin was measured with FTIR, and both the elastic modulus and peak stress of 3D printed bars was determined using a 3-point being test for different printing layer thicknesses. The results were compared to those for two conventionally cured provisional materials (Integrity®, Dentsply; and Jet®, Lang Dental Inc.). RESULTS: Samples printed at 90° orientation and in a white resin color setting was chosen as the most optimal combination of printing parameters, due to the comparatively higher printing accuracy (up to 22% error), reproducibility and material usage. There was no direct correlation between printing layer thickness and elastic modulus or peak stress. 3D printed samples had comparable modulus to Jet®, but significantly lower than Integrity®. Peak stress for 3D printed samples was comparable to Integrity®, and significantly higher than Jet®. The degree of conversion of 3D printed samples also appeared higher than that of Integrity® or Jet®. SIGNIFICANCE: Our results suggest that a 3D printable provisional restorative material allows for sufficient mechanical properties for intraoral use, despite the limited 3D printing accuracy of the printing system of choice.

Clinical application of light solidified calcium hydroxide as temporary crown adhesive / 口腔疾病防治

Objective @# To investigate the feasibility of using UV curable calcium hydroxide as temporary crown binder. @*Methods @#242 patients with temporary crown were selected and randomly divided into three groups according the order of registration week each month, and respectively underwent temporary crown cement with TempoCemNE (n = 78), Provicol (n = 80) and Calcimol LC (n = 84) for each tooth. The retention effect and the status of the gum and the pulp were observed at one week after operation.@*Results @# There was no significant difference between the three groups in the retention effect and the status of the gum and the pulp (χ12 = 5.553, P1 = 0.062 > 0.05; χ22 = 4.783, P2 = 0.091 > 0.05; χ32 = 3.290, P3 = 0.193 > 0.05). There was a good effect of temporary crown cement in three groups of TempoCemNE, Provicol and Calcimol LC.@*Conclusion @#Calcimol LC can be used as a new type of temporary crown cement with good bonding performance and the protection to gums and pulp, and simple operation.

A study to investigate and compare the physicomechanical properties of experimental and commercial temporary crown and bridge materials.

OBJECTIVES: To develop two experimental temporary crown and bridge materials with improved physicomechanical properties. METHODS: Commercial materials: Trim (TR, monomethacrylate, Bosworth) and Quicktemp2 (QT, dimethacrylate, Schottlander). EXPERIMENTAL MATERIALS: isobutyl methacrylate/poly(ethyl methacrylate) (IBMA/PEM) and n-butyl methacrylate/PEM (nBMA/PEM), both monomethacrylates. For water absorption/desorption studies rectangular samples (40 mm × 10 mm × 1 mm) of each material were prepared, immersed in deionized water (DW, control) and artificial saliva (AS), and weighed at regular time intervals. %solubility and diffusion coefficients (D) for uptake/loss processes were calculated and compared with theoretical predictions. Polymerization exotherm (cylindrical samples 10 mm × 18 mm) and flexural moduli were measured (three point bending; rectangular samples 80 mm × 10 mm × 4 mm, dry and after 9 days storage in DW). The data were compared statistically. RESULTS: QT and nBMA/PEM had lower %equilibrium uptakes/loss in DW (0.68%/0.884% and 0.64%/0.895% respectively). QT had the lowest water absorption/desorption D (P<0.05) compared to the three monomethacrylates, in DW and AS. %solubility for all systems showed no differences in DW (P>0.05), but a difference for QT in AS (P<0.05). QT reached its maximum temperature rapidly (∼2 min; 3 monomethacrylates ∼7-13 min). The commercial materials exhibited high peak temperatures (∼51°C, P<0.05; experimental materials ∼43°C). QT had a higher flexural modulus (∼4 GPa; 3 monomethacrylates ∼0.7-1 GPa) for dry and wet samples. The moduli for commercial materials reduced significantly after immersion in DW; there was no difference between the dry and wet experimental materials samples (P>0.05). SIGNIFICANCE: The experimental materials merit further studies since they presented with lower setting exotherms, and contained no phthalate plasticizer, thus being less of a risk to patients.

Color Stability of Self-Cured Temporary Crown Resin according to Different Surface Treatments / 치위생과학회지

In this study, the surface treatment of a self-cured temporary crown was polished using a denture bur, silicone bur, or pumice. The color stability of the temporary crown resin specimen was evaluated by immersing it in coffee, and cola, wine, beer, red pepper paste, or soybean paste. Two-hundred eighty-five identical resin specimens with six types of staining solution and three types of surface treatment were placed in a shaking incubator at 37℃. The degree of discoloration was observed using a time-lapse recording of days 1, 5, and 7. L*, a*, and b* were measured using a spectrophotometer, which shows the quantitative value of discoloration, and statistically processed after calculating ΔE*. The results show that as time passed, all the specimens showed a color change (p<0.001). The amount of color change was the greatest in in crowns with denture bur polishing on the day 1, 5, and 7. As the precipitation time increased, the ΔE* value was also increased. Of the specimens immersed on day 1, the greatest color change in crowns polished with denture bur was observed in those immersed in red pepper paste, while the smallest color change was observed in those immersed in cola. On days 5 and 7, the greatest color change in crowns polished with denture bur was observed in those immersed in red wine. Crowns polished with silicone bur and immersed in soybean paste exhibited the smallest color change. Based on the results, compared to pumice polishing, silicone bur polishing results in better color stability, saves time and money, and is recommended for patients with temporary crowns.

In vitro study of fracture strength of provisional crown materials.

PURPOSE: The purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns. MATERIALS AND METHODS: A master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at 37℃ for 24 hours, and then they were thermocycled (TC, 5000×, 5-55℃) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (α=.05). RESULTS: Fmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01). CONCLUSION: Composite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CAD-CAM technique offers more advantages than the direct technique.

In vitro study of fracture strength of provisional crown materials

PURPOSE: The purpose of this report was to evaluate the effect of the fabrication method and material type on the fracture strength of provisional crowns. MATERIALS AND METHODS: A master model with one crown (maxillary left second premolar) was manufactured from Cr-Co alloy. The master model was scanned, and the data set was transferred to a CAD/CAM unit (Yenamak D50, Yenadent Ltd, Istanbul, Turkey) for the Cercon Base group. For the other groups, temporary crowns were produced by direct fabrication methods (Imident, Temdent, Structur Premium, Takilon, Systemp c&b II, and Acrytemp). The specimens were subjected to water storage at 37degrees C for 24 hours, and then they were thermocycled (TC, 5000x, 5-55degrees C) (n=10). The maximum force at fracture (Fmax) was measured in a universal test machine at 1 mm/min. Data was analyzed by non-parametric statistics (alpha=.05). RESULTS: Fmax values varied between 711.09-1392.1 N. In the PMMA groups, Takilon showed the lowest values (711.09 N), and Cercon Base showed the highest values (959.59 N). In the composite groups, Structur Premium showed the highest values (1392.1 N), and Acrytemp showed the lowest values (910.05 N). The composite groups showed significantly higher values than the PMMA groups (P=.01). CONCLUSION: Composite-based materials showed significantly higher fracture strengths than PMMA-based materials. The CAD-CAM technique offers more advantages than the direct technique.