Effect of different ceramic systems on antagonist dental structure by microtomographic analysis.

OBJECTIVES: This study aims to identify the two-dimensional and three-dimensional analyses and evaluate the loss of tooth structure in the tooth's different constituent elements and the ceramic antagonist's surface. METHODS: In this study, three groups (n = 10) represented by different ceramic systems (lithium disilicate [GDis], lithium silicate reinforced with zirconia [GSil], and monolithic zirconia [GZir]) were evaluated. Each group obtained ten ceramic blocks and submitted them to the sintering/crystallization process. To carry out the wear test, healthy mandibular premolars were used as the specimens and the ceramic blocks as antagonists. The premolars were submitted to two-dimensional and three-dimensional analyses using a computerized microtomography (µTC) before and after the wear test. The wear test was performed with 30 N and 300,000 cycles load, with occlusion, laterality, and disocclusion movements. RESULTS: The statistical analysis comparing the loss of two-dimensional tooth structure showed a statistically significant difference among all groups (p < 0.05). Statistical analysis comparing the percentage of loss of three-dimensional tooth structure showed a statistically significant difference between groups GDis and GSil and between groups GDis and GZir. However, when comparing GSil with GZir, no statistically significant difference was found. The qualitative analysis of the teeth showed that GDis showed considerable enamel loss and dentin exposure, GSil showed enamel wear with flattening the cusp without dentin exposure, and GZir showed minimal enamel wear without dentin exposure. In the qualitative analysis of ceramic antagonists, more significant wear of the ceramic material for GDis was observed, followed by the GSil and GZir groups, respectively. SIGNIFICANCE: The use of the lithium disilicate should be cautious, restricting it to areas with lower masticatory forces. Areas of higher masticatory forces showed a large amount of antagonist wear, with dentin involvement. This can lead to dentinal hypersensitivity, risk of compromising patients' occlusion, by harming group disocclusion guides, causing pain and temporomandibular disorders.

Effects of the Finishing Protocols and Oral Hygiene Procedures in the Microhardness and Surface Roughness of CAD/CAM Ceramics

ABSTRACT: The objective of this in vitro study was to evaluate the effects of finishing protocols and oral hygiene procedures on the surface and mechanical properties of CAD/CAM ceramics. Specimens (n = 96, (15x10x2mm) of the leucite glass-ceramic (LGC) and feldspathic ceramic (FP) received mechanical polishing or glazing. Surface roughness (Ra) and microhardness (VHN) were obtained with a profilometer and a hardness tester, respectively, before and after each oral hygiene procedure (TB: toothbrushing; PB: prophylaxis with paste and rubber cup; and BJ: prophylaxis with bicarbonate jet). ANOVA, paired t and Tukey's tests were applied (a=0.05). For both materials, only BJ affected Ra's values when mechanical polishing was performed. Moreover, no significant variations in VHN were observed only for LGC glazed with TB. Significant Ra and VHN changes in both materials were observed with BJ. Besides, BJ exhibited similar effects to TB on VHN, regardless of the material and finishing protocol used. Changes in mechanical and surface properties varied with the finishing protocol and the oral hygiene method. In general, prophylaxis with bicarbonate jet was the most harmful method for both materials and the type of finishing protocol did not have a protective effect against changes produced by oral hygiene methods.

RESUMEN: El objetivo de este estudio in vitro fue evaluar los efectos de los protocolos de acabado y los procedimientos de higiene oral sobre la superficie y las propiedades mecánicas de las cerámicas CAD/CAM. Los especímenes (n = 96, (15x10x2mm) de vitrocerámica de leucita (LGC) y cerámica feldespática (FP) recibieron pulido mecánico o glaseado. La rugosidad de la superficie (Ra) y la microdureza (VHN) se obtuvieron con un perfilómetro y un probador de dureza, respectivamente, antes y después de cada procedimiento de higiene oral (TB: cepillado dental; PB: profilaxis con pasta y vaso de hule; y BJ: profilaxis con chorro de bicarbonato). Se aplicaron ANOVA, t pareada y prueba de Tukey (a=0.05). Para ambos materiales, solo BJ afectó los valores de Ra cuando se realizó el pulido mecánico. Además, no se observaron variaciones significativas en VHN solo para LGC vidriado con TB. Se observaron cambios significativos de Ra y VHN en ambos materiales con BJ. Además, BJ exhibió efectos similares a TB en VHN, independientemente del material y protocolo de acabado utilizado Los cambios en las propiedades mecánicas y superficiales variaron con el protocolo de acabado y el método de higiene oral. En general, la profilaxis con chorro de bicarbonato fue el método más perjudicial, tanto los materiales como el tipo de protocolo de acabado no tuvieron un efecto protector frente a los cambios producidos por los métodos de higiene oral.

Linear dimensional accuracy of stereolithographic surgical guide after chemistry and physics sterilization.

OBJECTIVES: The purpose of this study was to evaluate the dimensional stability of prototyped surgical guides after autoclave and 2% glutaraldehyde sterilization processes. MATERIAL AND METHODS: Twenty prototyped surgical guides were prepared and submitted to two sterilization processes (n = 10): Physics - sterilization by autoclave (saturated water vapor under pressure, temperature of 126 to 130 °C, pressure of 1,7 at 1.9 kgf/cm2, 16 min); Chemistry - sterilization by 2% glutaraldehyde for 10 h. Six pre-established points were measured in the prototyped surgical guides, before and after sterilization, using a digital caliper rule. The comparisons were made using orthogonal contrasts using the linear model of mixed effects (random and fixed). RESULTS: there are no significant differences between autoclave and glutaraldehyde 2% (p>0.05) there are significant differences after autoclave sterilization (p<0.05) and there are not significant differences after 2% glutaraldehyde sterilization (p>0.05). CONCLUSION: autoclave promoted dimensional alteration of the prototyped surgical guides, and the chemical sterilization by glutaraldehyde 2% did not cause dimensional alteration of the prototype surgical guides, being a favorable choice for sterilization. CLINICAL SIGNIFICANCE: the sterilization of surgical guides can be performed through the chemical process with 2% glutaraldehyde without changing the linear precision of the prototype surgical guides.

Impact of Conservative Endodontic Cavities on Root Canal Preparation and Biomechanical Behavior of Upper Premolars Restored with Different Materials.

INTRODUCTION: The purpose of this study was to evaluate the impact of conservative endodontic cavities (CECs) on root canal preparation, restoration, and biomechanical behavior of teeth prepared using different shaping systems and restorative materials. METHODS: Ninety upper premolars with a bifurcated root were matched based on morphology and randomly assigned to a control group (n = 10) or 1 of the following experimental groups (n = 40): traditional endodontic cavity and CEC. Teeth were subdivided according to instrumentation (n = 10) as follows: ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), Reciproc (VDW GmbH, Munich, Germany), Reciproc Blue (VDW GmbH), and Hyflex EDM (Coltene/Whaledent, Altstätten, Switzerland). After canal obturation, teeth were restored using temporary material, conventional composite, regular bulk fill composite, or bulk fill flow combined with conventional composite. Before and after preparation and after obturation, the teeth were scanned using micro-computed tomographic imaging. Canal transportation (CT), the percentage of untouched canal surfaces (UCSs), voids in restoration (VRs), and residual filling material in the pulp chamber were evaluated. Finite element analysis, fracture resistance, and the failure pattern were recorded. The data were analyzed using analysis of variance and the Tukey and chi-square tests. RESULTS: CECs had greater CT, percentage of filling material, and VRs compared with traditional endodontic cavities (P < .0001). The highest CT and UCSs were observed in CEC with ProTaper Universal. Bulk fill flow combined with conventional composite showed a lower percentage of VRs compared with other restorative materials (P < .05). Finite element analysis, fracture resistance, and failure pattern revealed similar behaviors in all groups (P > .05) . CONCLUSIONS: CECs had a negative impact on root canal centralization, UCSs, cleaning of the pulp chamber, and percentage of VRs. Controlled memory instruments were the most adequate for the root canal preparation of CECs. The endodontic cavity did not influence the biomechanical behavior of restored teeth.

Mechanical behavior of endocrowns fabricated with different CAD-CAM ceramic systems.

STATEMENT OF PROBLEM: The mechanical behavior of ceramic endocrowns is unclear. PURPOSE: The purpose of this in vitro and 3-dimensional finite element analysis (3D-FEA) study was to evaluate the mechanical behavior of endodontically treated teeth restored with ceramic endocrowns made by using different computer-aided design and computer-aided manufacturing (CAD-CAM) systems. MATERIAL AND METHODS: Sixty mandibular human molars were endodontically treated, prepared for endocrowns, and divided into 4 groups (n=15) according to the following various ceramic systems: leucite-based glass-ceramic (LC group), lithium disilicate-based glass-ceramic (LD group), glass-ceramic based on zirconia-reinforced lithium silicate (LSZ group), and monolithic zirconia (ZR group). After adhesive bonding, the specimens were subjected to thermomechanical loading and then to fracture resistance testing in a universal testing machine. The failure mode of the specimens was qualitatively evaluated. Three-dimensional FEA was performed to evaluate the stress distribution in each group. Data were analyzed by using a 1-way ANOVA and the Tukey HSD test (α=.05). RESULTS: Statistically significant differences among the groups were observed (P<.05). The outcomes of the LC, LD, and LSZ groups were similar (1178 N, 1935 N, and 1859 N) but different from those of the ZR group (6333 N). The LC and LD groups had a higher ratio of restorable failures, while LSZ and ZR had more nonrestorable failures. Fractographic analysis indicated a regular failure pattern in the ZR group and irregular failure patterns in the other groups. Three-dimensional FEA revealed similar values and stress pattern distributions among the groups. CONCLUSIONS: The mechanical performance of monolithic zirconia was better than that of the other ceramic endocrowns considered in this research; however, monolithic zirconia presented a higher rate of catastrophic tooth structure failure.

Influence of different ceramic materials and surface treatments on the adhesion of Prevotella intermedia.

Ceramics are used in oral rehabilitation; however, these materials are prone to formation of biofilms that may cause periodontal diseases. This study aimed to evaluate the influence of distinct surface treatments on ceramic surface roughness and biofilm formation of oral bacteria (Prevotella intermedia). Eighty-four specimens of the following four ceramic systems were produced: LC - leucite-based glass ceramic, LD - lithium disilicate-based glass ceramic, LSZ - glass ceramic based on zirconia-reinforced lithium silicate, and ZR - monolithic zirconia. These were submitted to three different surface treatment protocols: C - control, G - glazing, and GDB - grinding with diamond bur (n = 7). The surface characteristics were assessed using a confocal laser microscope (Ra) and a scanning electron microscope (SEM). Thereafter, the groups were contaminated with a bacterial strain of P. intermedia ATCC 25611. The biofilms formed were quantified by counting the colony forming units (CFUs) and analyzed with scanning electron microscope (SEM) and confocal laser scanning microscope (CLSM). Data were analyzed by using a 2-way ANOVA and the Tukey test (ɑ = 0.05). Results showed that greater roughness was associated with GDB (p < 0.05). The same was also true for the ceramic material ZR (p < 0.05). There was a statistical significant difference in the CFU counts between the materials (p < 0.05) that revealed a greater amount of bacterial adhesion in the LC and ZR groups (p > 0.05). Thus, it was suggested that the surface roughness of the ceramic materials favored bacterial adhesion; and thus, finishing of ceramic surfaces with GDB should be avoided.

Effect of restorative treatment with endocrown and ferrule on the mechanical behavior of anterior endodontically treated teeth: An in vitro analysis.

This study evaluated the effect of endocrown and ferrule restorative treatment on the mechanical behavior of anterior endodontically treated teeth. Human canines were treated endodontically and distributed in five groups (n = 10): sound teeth (S), crown associated with glass fiber post (GFP) and ferrule (GFPf+) and that without ferrule (GFPf-), and endocrown with ferrule (Ef+) and that without ferrule (Ef-). The crowns were obtained in lithium disilicate-based glass ceramic and cemented with resin. Thermomechanical loading (TL) was performed with progressive load of 80, 120, 160, 200, 240, 280, and 320 N with 20,000 cycles each, 140,000 cycles in total, frequency of 5 Hz, and temperature variation of 5°C-55 °C, followed by fracture resistance testing with load cell of 1000 Kgf and crosshead speed of 0.5 mm/min in a universal testing machine. Failure mode has been evaluated. Data were compared by Kaplan-Meier survival analysis (p < 0.05) for TL and one-way ANOVA and Tukey's test (p < 0.05) for fracture resistance. TL showed higher number of fractures for groups without ferrule (GFPf- = 7, GFPf+ = 3, Ef- = 10, and Ef+ = 2) and lower mean fracture load probability (GFPf+ = 300 N, GFPf- = 280 N, Ef+ = 320 N, Ef- = 188 N) than those with ferrule. Regarding fracture, teeth rehabilitated with GFP were more resistant to endocrowns with ferrule (p < 0.05). A higher percentage of type III failures after fatigue and type II failures after fracture were found. In conclusion, rehabilitation using GFP with ferrule is more favorable for anterior teeth, but the use of endocrown with ferrule proved feasible.

Internal and Marginal Fit and Fracture Strength of Narrow Diameter Dental Implant-Abutment Assembly.

The aim of this study was to assess the internal and vertical marginal fit of metallic copings to abutments and the fracture strength of different narrow diameter dental implant/abutments, either submitted to thermomechanical cycling or not. Sixty-four implant/abutments (n=16) were divided into 4 groups according to diameter and abutment type: G3.5-UAC (morse taper implant Ø3.5mm + universal abutment with beveled chamfer finish); G2.9-UAS (morse taper implant Ø2.9mm + universal abutment with shoulder finish); G2.8-AA (morse taper friction implant Ø2.8mm + anatomical abutment) and G2.5-HP (one-piece implant Ø2.5mm with indexed hexagonal platform). Each group was divided into two subgroups (n=8): submitted and not submitted to thermomechanical cycling (TMC). To assess internal and vertical marginal fit of metallic copings, the assemblies were scanned using microtomography (micro-CT) (n=5). The samples were subjected to the compressive strength test on a universal test machine. Group G3.5-UAC showed the highest marginal misfit regardless of TMC (p<0.05). All other groups were similar after TMC. Group G2.8-AA showed the lowest internal misfit both with and without TMC (p<0.05). Group G2.8-AA showed the highest fracture strength, similar only to G2.5-HP without TMC and G3.5-UAC with TMC. The type of abutment affects the internal and marginal fit of metallic copings and the anatomical abutment led to the best internal and marginal coping fit. The narrow diameter dental implant/abutments differ in terms of fracture strength, the strongest assembly was that composed by implant of type V grade titanium without internal threads (friction implant).

Internal and marginal fit and fracture strength of narrow diameter dental implant-abutment assembly

Abstract The aim of this study was to assess the internal and vertical marginal fit of metallic copings to abutments and the fracture strength of different narrow diameter dental implant/abutments, either submitted to thermomechanical cycling or not. Sixty-four implant/abutments (n=16) were divided into 4 groups according to diameter and abutment type: G3.5-UAC (morse taper implant Ø3.5mm + universal abutment with beveled chamfer finish); G2.9-UAS (morse taper implant Ø2.9mm + universal abutment with shoulder finish); G2.8-AA (morse taper friction implant Ø2.8mm + anatomical abutment) and G2.5-HP (one-piece implant Ø2.5mm with indexed hexagonal platform). Each group was divided into two subgroups (n=8): submitted and not submitted to thermomechanical cycling (TMC). To assess internal and vertical marginal fit of metallic copings, the assemblies were scanned using microtomography (micro-CT) (n=5). The samples were subjected to the compressive strength test on a universal test machine. Group G3.5-UAC showed the highest marginal misfit regardless of TMC (p<0.05). All other groups were similar after TMC. Group G2.8-AA showed the lowest internal misfit both with and without TMC (p<0.05). Group G2.8-AA showed the highest fracture strength, similar only to G2.5-HP without TMC and G3.5-UAC with TMC. The type of abutment affects the internal and marginal fit of metallic copings and the anatomical abutment led to the best internal and marginal coping fit. The narrow diameter dental implant/abutments differ in terms of fracture strength, the strongest assembly was that composed by implant of type V grade titanium without internal threads (friction implant).

Resumo O objetivo deste estudo foi avaliar a adaptação marginal e interna de cópings metálicos em pilares sobre implantes, e a resistência a fratura de diferentes conjuntos de implantes/pilares de diâmetro reduzido, submetidos à ciclagem termomecânica ou não. Sessenta e quatro implantes/pilares (n=16) foram divididos em 04 grupos de acordo com o tipo de pilar e diâmetro do implante: G3.5-UAC (implante cone morse Ø3.5mm + munhão universal com término em chanfro); G2.9-UAS (implante cone morse Ø2.9mm + munhão universal com término em ombro); G2.8-AA (implante cone morse friccional Ø2.8mm + munhão anatômico); e G2.5-HP (implante de corpo único de Ø2.5mm com plataforma hexagonal indexada). Cada grupo foi dividio em dois subgrupos (n=8): submetidos ou não à ciclagem termomecânica (TMC). As amostras foram escaneadas por microtomografia (micro-CT) para avaliar a adaptação interna e marginal vertical dos copings metálicos. As amostras foram submetidas à resistência à compressão em uma maquina de ensaios universal. O grupo G3.5-UAC apresentou os maiores valores de desadaptação marginal independentemente da TMC (p<0,05). Todos os outros grupos foram similares entre si após TMC. O grupo G2.8-AA demonstrou o menor desajuste interno independentemente de TMC (p<0,05). O grupo G2.8-AA demonstrou a maior resistência à fratura, similar apenas ao grupo G2.5-HP sem TMC e G3.5-UAC com TMC. O tipo de pilar influencia a adaptação interna e marginal vertical de copings metálicos. O grupo do pilar anatômico (sem entalhes na superfície) levou à melhor adaptação, enquanto o grupo com plataforma expandida hexagonal e os grupos com munhão universal (com entalhes na superfície) proporcionaram os maiores desajustes (especialmente com termino em chanfro). Os implantes/pilares de diâmetro reduzido diferem em termos de resistencia à fratura, sendo que o conjunto mais resistente foi aquele composto por titânio tipo V e sem roscas internas (implante friccional).

Restorative Possibilities Using Zirconia Ceramics for Single Crowns.

Two clinical cases are presented to explore technical differences and discusses the advantages and disadvantages of using veneered or monolithic zirconia to manufacture posterior single crowns. The first case describes the clinical steps in manufacturing a monolithic crown on a mandibular left second premolar using high translucency zirconia. It shows the use of a conservative tooth preparation based on the superior mechanical properties that this material presents as well as the final optical characteristics achieved by shading and staining. In the second case, a conventional bilayer restorative treatment was made using zirconia framework followed by veneering with feldspar ceramic on a mandibular left first molar. Recent literature indicates that each of these restorative alternatives presents specific advantages and disadvantages. Factors such as mechanical performance, fracture, esthetic characteristics, clinical success, complication rates, adhesion and antagonist wear performance are discussed comparing the two restorative assemblies. The data highlight that monolithic crowns prevent a major problem reported on bilayer restorations: the chipping of veneering ceramic. Monolithic crowns also allow minimally invasive tooth preparations, thus increasing tooth remnant preservation. However, data that support esthetic performance similarity between monolithic and bilayer assemblies are lacking, thus the predictability of use is restricted for the posterior region, as cases demanding high esthetic appeal continue to fundamentally use bilayer restorations. Failures were not found, and patient satisfaction was reported in both techniques after the 12-month follow up.

Different fabrication techniques of implant-supported prostheses: microhardness and fracture strength

Aim: This study evaluated the mechanical behavior of implant-supported crowns obtained by different fabrication technique after thermomechanical cycling. Methods: Thirty-two external hexagon dental implants were divided into four groups (n=10): CC ­ conventional casting with torch; EI ­ electromagnetic induction casting; PL ­ plasma casting; and CAD-CAM ­ milling through computer-aided design and computer-aided manufacturing. Vickers microhardness of the specimens were made before and after the thermomechanical cycling, and then subjected to fracture load. Fracture pattern was evaluated. Results: No significant difference was observed comparing the microhardness before and after thermomechanical cycling. CAD-CAM group presented significant lower microhardness than the other groups. No significant statistical difference was showed on fracture load between the groups. The CAD-CAM and PL presented lower number of failure by plastic deformation. Conclusion: The manufacturing techniques affected the mechanical behavior and the failure pattern of implant-supported crowns tested

Effect of Intracoronal Depth of Teeth Restored with Endocrowns on Fracture Resistance: In Vitro and 3-dimensional Finite Element Analysis.

INTRODUCTION: Endodontically treated teeth have an increased risk of biomechanical failure because of significant loss of tooth structure. The biomechanical behavior of endodontically treated teeth restored was evaluated using different extensions of endocrowns inside the pulp chamber by in vitro and 3-dimensional finite element analysis (FEA). METHODS: Thirty mandibular human molars were endodontically treated. Standardized endocrown preparations were performed, and the teeth were randomly divided into 3 groups (n = 10) according to different endocrown extensions inside the pulp chamber: G-5 mm, a 5-mm extension; G-3 mm, a 3-mm extension; and G-1 mm, a 1-mm extension. After adhesive cementation, all specimens were subjected to thermocycling and dynamic loading. The survival specimens were subjected to fracture resistance testing at a crosshead speed of 1 mm/min in a universal testing machine. All fractured specimens were subjected to fractography. Data were analyzed by 1-way analysis of variance and the Tukey post hoc test (P < .05). Stress distribution patterns in each group were analyzed using FEA. Qualitative analyses were performed according to the von Mises criterion. RESULTS: After dynamic loading, a survival rate of 100% was observed in all groups. For static loading, statistically significant differences among the groups were observed (P < .05) (G-5 mm = 2008.61 N, G-3 mm = 1795.41 N, and G-1 mm = 1268.12 N). Fractography showed a higher frequency of compression curls for G-5 mm and G-3 mm than for G-1 mm. FEA explained the results of fracture strength testing and fractography. CONCLUSIONS: Greater extension of endocrowns inside the pulp chamber provided better mechanical performance.

Mechanical properties and superficial characterization of a milled CAD-CAM glass fiber post.

Computer-aided design and computer-aided manufacturing (CAD-CAM) technology may be used to produce custom intraradicular posts, but studies are lacking. The purpose of this in vitro study was to evaluate the flexural properties (strength and modulus), failure mode, superficial morphology, and roughness of two CAD-CAM glass fiber posts (milled at different angulations) compared with a commercially available prefabricated glass fiber post. Three groups were tested (n = 10): PF (control group)- prefabricated glass fiber post; C-Cd-diagonally milled post; and C-Cv-vertically milled post. A 3-dimensional virtual image was obtained from a prefabricated post, which guided the posterior milling of posts from a glass fiber disk (Trilor Blanks; Bioloren). Surface roughness and morphology were evaluated using confocal laser microscopy. Flexural strength and modulus were evaluated with the 3-point bend test. Data were submitted to one-way analysis of variance followed by the Student-Newman-Keuls post hoc test (α = 0.05). The fractured surfaces were evaluated with scanning electron microscopy. The superficial roughness was highest for PF and similar for the experimental groups. Morphological analysis shows different sizes and directions of the glass fibers along the post. The flexural strength was highest for PF (900.1 ±â€¯30.4 > C-Cd - 357.2 ±â€¯30.7 > C-Cv 101.8 ±â€¯4.3 MPa) as was the flexural modulus (PF 19.3 ±â€¯2.0 GPa > C-Cv 10.1 ±â€¯1.9 GPa > C-Cd 7.8 ±â€¯1.3 GPa). A CAD-CAM milled post seems a promising development, but processing requires optimizing, as the prefabricated post still shows better mechanical properties and superficial characteristics.

Evaluation of Stress Distribution in Endodontically Weakened Teeth Restored with Different Crown Materials: 3D-FEA Analysis.

This study evaluated the stress distribution in endodontically treated teeth, weakened (W) or not weakened (NW), restored with different materials of prosthetic crown using 3D-FEA. Models of a maxillary canine were constructed based on micro-CT images and divided into the groups: G1 (control) - sound tooth; G2 to G7 - endodontically treated teeth restored with glass fiber post (GFP); which G2 to G4 simulated NW root and G5 to G7 simulated W root. For crown material the teeth were restored with: G2 and G5: metallic coping and ceramic veneering, G3 and G6: zirconia coping and ceramic veneering, G4 and G7: alumina coping and ceramic veneering. Load of 180 N was applied at the incisal third of lingual surface at 45º. Models were supported by the periodontal ligament (x=y=z=0). The von Mises stress (VMS) values were calculated. The W teeth presented higher VMS at coping when compared to NW teeth and group G1 showed lower VMS value. For crown material, for both W or NW teeth, increasing VMS was found at metallic, zirconia and alumina coping, respectively. Metallic coping showed a better performance despite its unfavorable esthetics, suggesting as an appropriate material for prosthetic restoration of endodontically treated teeth.

Evaluation of Stress Distribution in Endodontically Weakened Teeth Restored with Different Crown Materials: 3D-FEA Analysis

Abstract This study evaluated the stress distribution in endodontically treated teeth, weakened (W) or not weakened (NW), restored with different materials of prosthetic crown using 3D-FEA. Models of a maxillary canine were constructed based on micro-CT images and divided into the groups: G1 (control) - sound tooth; G2 to G7 - endodontically treated teeth restored with glass fiber post (GFP); which G2 to G4 simulated NW root and G5 to G7 simulated W root. For crown material the teeth were restored with: G2 and G5: metallic coping and ceramic veneering, G3 and G6: zirconia coping and ceramic veneering, G4 and G7: alumina coping and ceramic veneering. Load of 180 N was applied at the incisal third of lingual surface at 45º. Models were supported by the periodontal ligament (x=y=z=0). The von Mises stress (VMS) values were calculated. The W teeth presented higher VMS at coping when compared to NW teeth and group G1 showed lower VMS value. For crown material, for both W or NW teeth, increasing VMS was found at metallic, zirconia and alumina coping, respectively. Metallic coping showed a better performance despite its unfavorable esthetics, suggesting as an appropriate material for prosthetic restoration of endodontically treated teeth.

Resumo Este estudo avaliou a distribuição de tensão em dentes tratados endodonticamente, fragilizados (F) ou não fragilizados (NF), restaurados com diferentes materiais para a coroa protética utilizando 3D-FEA. Modelos de um canino maxilar foram construídos baseados em imagens de micro-CT e divididos em grupos: G1 (controle) - dente hígido; G2 a G7 - dentes tratados endodonticamente com pino de fibra de vidro (PFV), sendo que G2 a G4 simularam raízes NF e G5 a G7 simularam raízes F. Para o material das coroas os dentes foram restaurados com: G2 e G5: coping metálico e revestimento cerâmico, G3 e G6: coping de zirconia e revestimento cerâmico, G4 e G7: coping de alumina e revestimento cerâmico. Carregamento de 180 N foi aplicado na superfície lingual em seu terço incisal com 45 graus de inclinação. Os modelos foram suportados pelo ligamento periodontal (x=y=z=0). Os valores da tensão de von Mises (VMS) foram calculados. Os dentes F apresentaram maiores valores VMS para o coping quando comparados aos dentes NF, sendo que o G1 apresentou menores valores VMS. Para o material das coroas, ambos F ou NF aumentaram VMS no coping metálico, zirconia e alumina, respectivamente. Copings metálicos apresentaram melhor comportamento mecânico apesar de não favorecerem a estética, o que sugere ser um material apropriado para a restauração de dentes tratados endodonticamente.

Biomechanical behavior of titanium and zirconia frameworks for implant-supported full-arch fixed dental prosthesis.

BACKGROUND: The biomechanical behavior of implant-supported titanium and zirconia full-arch fixed dental prosthesis (FAFDP) frameworks require further investigation. PURPOSE: Strains transferred by implant-supported titanium (Ti) and zirconia (Zr) FAFDP frameworks were analyzed. MATERIALS AND METHODS: Maxillary 14-unit FAFDPs supported by 6 implants and 12-unit FAFDPs supported by 4 implants were tested. One-piece frameworks were fabricated by computer-aided design/computer-aided manufacturing. Four groups were divided (n = 3): G1, Ti-6 implants; G2, Zr-6 implants; G3, Ti-4 implants; G4, Zr-4 implants. A 250 N single-point load was applied on the second premolar. A three-dimensional digital image correlation system recorded framework and maxilla model surface deformation. RESULTS: The following strains (µS) averaged over the length of the second premolar were calculated: frameworks, G1 (321.82 ± 111.29), G2 (638.87 ± 108.64), G3 (377.77 ± 28.64), G4 (434.18 ± 132.21); model surface, G1 (473.99 ± 48.69), G2 (653.93 ± 45.26), G3 (1082.50 ± 71.14), G4 (1218.26 ± 230.37). Zirconia frameworks supported by 6 implants (G2) presented higher surface strains (P < .05). FAFDPs with titanium frameworks transferred significantly lower strains to the supporting maxilla when 6 implants were used (G1) (P < .05). Both framework materials transferred similar strains when supported by 4 implants (G3 and G4) (P > .05). CONCLUSIONS: Zirconia frameworks supported by 6 implants showed higher strains. FAFDPs supported by 6 implants transferred less strains to the supporting maxilla, irrespective of framework material.

Reabilitação oral ­ parte 1: prótese total implantossuportada na mandíbula associada a próteses cerâmicas na maxila / Oral rehabilitation ­ part 1: mandibular implant-supported denture associated to maxillary ceramic dental prostheses

A presente coluna teve como objetivo apresentar um relato de caso clínico de reabilitação oral envolvendo diferentes possibilidades em prótese dentária: uma prótese total fixa implantossuportada (PTF) na mandíbula; e restaurações cerâmicas com infraestruturas de dissilicato de lítio sobre os dentes remanescentes e infraestruturas de zircônia sobre os implantes. O tratamento foi desenvolvido em quatro etapas: i) restabelecimento da dimensão vertical de oclusão (DVO); ii) PTF na mandíbula; iii) reabilitação temporária superior; e iv) próteses cerâmicas superiores. A coluna foi dividida em duas partes: 1) etapas i, ii e iii; e 2) etapa iv. Após o acompanhamento clínico de quatro anos da PTF na mandíbula e seis meses das próteses cerâmicas superiores, a reabilitação apresentou-se satisfatória do ponto de vista estético e funcional.

The purpose of this column was to present a clinical case report of oral rehabilitation involving different possibilities in dental prosthesis: a fixed implant-supported denture (FD) on the jaw; and ceramic restorations with lithium disilicate frameworks on the remaining teeth and zirconia frameworks on the implants. The treatment was developed in four steps: i) reestablishment of the vertical occlusion dimension (OVD); ii) FD on the jaw; (iii) maxil-lary temporary rehabilitation; and iv) ceramic prostheses on the maxillary. The column was divided into two parts: 1) steps i, ii and iii; and 2) step iv. After the four-year of FD clinical follow-up and six months of the superior ceramic prostheses, the rehabilitation was considered aesthetic and functional satisfactory.

Influence of Cyclic Fatigue in Water on Screw Torque Loss of Long-Span One-Piece Implant-Supported Zirconia Frameworks.

PURPOSE: It is still unclear whether four, six, or more implants should be used when restoring fully edentulous maxillae. This research evaluated the in vitro screw torque loss of zirconia frameworks supported by six implants and cantilevered zirconia frameworks supported by four implants. MATERIALS AND METHODS: Computer aided design/computer-assisted machining was used to fabricate 10 one-piece frameworks. Standardized pressable porcelain crowns were fabricated and luted to the frameworks. Specimens were divided into two groups (n = 5): AO4, cantilevered 12-unit full-arch fixed dental prosthesis supported by four implants; AO6, 14-unit supported by six implants. An opposing mandibular dental arch was fabricated with bis-acrylic composite resin. Specimens were submitted to 200 N underwater cyclic load at 2-Hz frequency for 1 × 106 cycles in a controlled 37°C temperature. A digital torque gauge assessed the initial and postload screw removal torque. Linear mixed-effects model was used for statistical analysis (α = 0.05). RESULTS: Significant screw torque loss was found for AO6 after cyclic loading (before: 36.20%/after: 52.82%; p < 0.05). Group AO6 (36.20%) presented lower preload loss before the cyclic loadings compared with AO4 (60.10%) (p < 0.05). CONCLUSIONS: Cyclic loading and lower implant-to-replaced-units ratio do not seem to compromise screw stability compared with higher implant-to-replaced-units ratio; however, a steep drop in preload was found before cyclic loading for both groups.

Use of Feldspathic Porcelain Veneers to Improve Smile Harmony: A 3-Year Follow-up Report.

This case report describes an esthetic treatment to improve the shape and alignment of the anterior teeth, reestablishing smile harmony, using feldspathic porcelain veneers. Results of clinical follow up after 36 months are also presented. The advantages, disadvantages and limitations of the technique are detailed with reference to the relevant literature. This suggests that the success of treatment depends on adequate conditions of bonding between the veneers and the tooth complex, which involves parameters such as the strength and durability of the bond interface. Therefore, the clinical success of feldspathic porcelain veneers depends on the accurate selection of cases and correct execution of clinical and laboratory procedures. The rehabilitation involved from first right premolar to the left with feldspathic porcelain veneers made on refractory dies. After the 3-year follow up, excellent clinical results and patient satisfaction were achieved.

Fracture Strength of Weakened Anterior Teeth Associated to Different Reconstructive Techniques.

This study evaluated the fracture strength of endodontically treated teeth submitted to reconstructive techniques through dynamic and static tests. Forty human anterior teeth were divided into 4 groups (n=10): GNW (non-weakened) - root restored with glass fiber post (GFP), GW - weakened root restored with GFP, GDA - weakened root restored with direct anatomic GFP, and GIA - weakened root restored with indirect anatomic GFP. The teeth were endodontically treated considering that experimental groups (GW, GDA and GIA) simulated weakened roots for restoration with GFP using different techniques. The GFP was luted with resin cement and the coronal portion was restored with composite resin and metallic crowns. All samples were submitted to chewing simulation at 60 cycles/min in a total of 300,000 cycles. The survival samples were further exposed to compressive loading at a crosshead speed of 1.0 mm/min in a universal testing machine. The load was applied at 135° to the long axis of the tooth until failure. Data were analyzed by ANOVA (a=0.05). After chewing simulation were observed: GNW: 100% of survival roots; GW: 70% of survival roots, and GDA and GIA: 80% of survival roots. The mean fracture strength values (N) were 280.6 (GNW), 239.0 (GW), 221.3 (GDA), and 234.1 (GIA) without significant difference among the groups (p=0.7476). The results suggested similar fracture strength in both weakened and non-weakened teeth regardless the reconstructive technique of root internal wall. Higher incidence of catastrophic fracture was observed in weakened teeth without restoration of the root internal wall.