Effect of Different Abutments and Connections in Deformation Crestal Bone.

STATEMENT OF PROBLEM: The use of Morse taper connections is increasing, but little is known about the biomechanical use of abutments and their use in fixed prostheses. PURPOSE: This study evaluated the transmission of load on the bone implant-supported dentures, varying the type of prosthetic connection and abutment. MATERIAL AND METHODS: Using 4 polyurethane models, 3 implants were inserted into each block, establishing the following groups: (a) external hexagon and Micro-Unit abutments; (b) external hexagon and UCLA abutment; (c) Morse taper and Micro-Unit abutments; and (d) Morse taper and UCLA abutments. The prosthetic structures were cast, and in a universal testing machine, load was applied midway between the implants, with cantilever intervals of 5, 10, 15, 20, and 25 mm. Data were analyzed by Mann-Whitney, Friedman, and Kruskal-Wallis tests (P < 0.05). RESULTS: Regarding the prosthetic connection, there was no difference in the use of hexagonal or Morse taper, but the use of Micro-Unit abutment showed lower deformation values than UCLA for the 2 connections. CONCLUSIONS: The use of intermediate abutments affects the distribution of masticatory loads: the greater the length of the cantilever, the greater the surface deformation of the bone around the distal implant.

Influence of surface treatment on the shear bond strength of ceramics fused to cobalt-chromium.

PURPOSE: To evaluate the influence of surface treatment on the shear bond strength between a Co-Cr alloy and two ceramics. MATERIALS AND METHODS: Forty-eight metal cylinders were made (thickness: 4 mm, height: 3.7 mm) according ISO TR 11405. The 48 metallic cylinders were divided into four groups (n = 12), according to the veneering ceramic (StarLight Ceram and Duceram Kiss) and surface treatments: air-particle abrasion with Al(2)O(3) or tungsten drill (W). Gr1: StarLight + Al(2)O(3); Gr2: StarLight + W; Gr3: Duceram + Al(2)O(3); and Gr4: Duceram + W. The specimens were aged using thermal cycling (3000x, 5 to 55 degrees C, dwell time: 30 seconds, transfer time: 2 seconds). The shear test was performed with a universal testing machine, using a load cell of 100 kg (speed: 0.5 mm/min) and a specific device. The bond strength data were analyzed using ANOVA and Tukey's test (5%), and the failure modes were analyzed using an optical microscope (30x). RESULTS: The means and standard deviations of the shear bond strengths were (MPa): G1 (57.97 +/- 11.34); G2 (40.62 +/- 12.96); G3 (47.09 +/- 13.19); and G4 (36.80 +/- 8.86). Ceramic (p= 0.03252) and surface treatment (p= 0.0002) significantly affected the mean bond strength values. CONCLUSIONS: Air-particle abrasion with Al(2)O(3) improved the shear bond strength between metal and ceramics used.

Development and validation of new methodologies for teaching preparations in fixed partial prosthesis.

CONTEXT: Students can have some issues in the comprehension and execution of coronal preparations in fixed partial prosthesis (FPP). Some issues pertain to the amount of reduction, the inclination, and the positioning, all of which are important for the execution of an ideal preparation while respecting the required biomechanical principles. OBJECTIVE: The present study's aim was to evaluate the main problems experienced by graduation students regarding coronal preparation in FPP and to suggest teaching skills to help students and professors. DESIGN: A total of 87 students, who were enrolled in the 3rd year of Dentistry at the FPP course - in the Institute of Science and Technology, São Paulo State University, between 2017 and 2018, participated in the study. Two methodologies were developed, applied, and validated: first, a mannequin with a scheme of colors to help students visualize the coronal preparation; second, a comparison of different didactic methods. RESULTS: Only 54.02% of the students answered the questionnaire, and the main problem identified by the respondents was the amount of reduction required (78.2%). In the second place, 50.9% of the students stated that they had problems with the inclination and angle of the preparation. The mannequin method with color schemes was approved by 91.5%. The favorite didactic method was a live demonstration (face to face), with 61.8%. In the second place, 47.3% of the students stated that live projection was also adequate. CONCLUSIONS: Both auxiliary didactic methods were approved by the students and they reported that it helped them to visualize the amount of reduction necessary and the sequence of the preparation. Hence, it was concluded that the mannequin with color schemes and the live projection were approved as auxiliary didactic resources for teaching FPP.

A 10-Year Follow-Up of Different Intra-Radicular Retainers in Teeth Restored with Zirconia Crowns.

PURPOSE: To evaluate the survival rate in restored teeth with three different types of retainers prior to the fixing of crowns with zirconia through this retrospective clinical study. It is unclear how the type of post and core rehabilitation, and type of resin cement affect the longevity of teeth restored with crowns. METHODS: In a private clinic, a total of 101 retainers installed by the same professional between June 2008 and January 2018, with an average time of 58.2 months (4.8 years), were analyzed regarding the following factors: survival, cement and failure type. Three types of retainers were used according to the indications found in the literature: filling with Z250 light-cured composite resin, 22 elements; fiberglass post with Z250 light-cured composite resin, 45 elements; and cast metallic core in silver-tin alloy, 34 elements. The retainers were cemented with chemically cured cement, U100, U200, or Panavia F. RESULTS: Data were subjected to Kaplan-Meier analysis (p=0.495). Although the study presented several limitations, no significant differences were observed in the success rates between the types of intra-radicular retainers and the type of cement. The success rates were as follows: metal core, 97.1%; fiberglass post, 95.6%; and filling, 100%. On average, failures occurred at 48.4 months. CONCLUSION: In view of the results, it is possible to conclude that the different retainers evaluated have similar survival rates.

Reação alérgica a resina acrílica em paciente com coroa provisória: relato de caso / Allergic reaction to acrylic resin in a patient with a provisional crown: case report

As resinas acrílicas são amplamente utilizadas na odontologia, especialmente em ortodontia e prótese. Este artigo relata o caso de um paciente de 33 anos de idade, do gênero masculino que relatava desconforto e dores na região de pré-molar superior esquerdo após a colocação de um provisório, com presença de uma lesão eritomatosa. Após biópsia incisional constatouse a processo inflamatório crônico inespecífico. A causa apresentada para tal patologia foi o provisório confeccionado com resina acrílica autopolimerizável à base de metil-metacrilato. (AU)

Acrylic resins are widely used in dentistry, especially in orthodontics and prosthetics. Patients: this article reports the case of a leukodermic 33-year-old male who reported discomfort and pain due to an erythematous lesion in the upper first left premolar (24) after the placement of an acrylic resin temporary restoration. Discussion: The signs and symptoms presented by the patient and his report of visiting the rural countryside generated concern regarding the possible diagnosis, which led to a more invasive biopsy to differentiate allergic inflammation from a paracoccidioidomycosis. Biopsy revealed a chronic inflammatory process. Conclusion: the pathology was caused by contact with methyl methacrylate-based provisional acrylic resin. After cementation of the final crown, the inflammatory signs and symptoms disappeared .(AU)

Efeito da ciclagem térmica sobre a resistência de união entre titânio comercialmente puro e um cerômero / Effect of thermocliccling on the bond strenght between a pure commecially titanium and ceromer

Objetivo: Verificar, por ensaio mecânico de cisalhamento, oefeito da termociclagem na resistência de união entre o titâniocomercialmente puro (Ticp) e um material para revestimentoestético (Resilab Wilcos/Brasil). Método: Vinte cilindrosmetálicos, com 5mm de comprimento e 4mm de diâmetro cada,foram obtidos por meio de usinagem de barras de titânio. Asbases metálicas foram então jateadas com óxido de alumínio(250 μm), com pressão de 20 bar durante 20 segundos a umadistância de 3cm. Em seguida, foi aplicado sobre as basesmetálicas o sistema adesivo Resibond (Wilcos/Brasil), seguidoda resina Resilab opaca e de revestimento estético. Asamostras foram armazenadas em água destilada por 24 horas,a 37C e em seguida divididos aleatoriamente em dois grupos(n=10): o G1 (controle) e o G2 (experimental), sendo estesubmetido a 500 ciclos térmicos (5º/55ºC±1, tempo de imersãode: 30 s). Os dois grupos foram submetidos ao ensaio decisalhamento em máquina de ensaio universal (modelo DL-1000 Equip. e Sist. Ltda., São José dos Pinhais - PR - Brasil)com célula de carga de 500 Kgf e velocidade de 0,5 mm/min. Osvalores numéricos (MPa) foram submetidos ao teste estatísticode Mann-Whitney (p=0,038). Resultados: Após análise dosdados, observou-se que o grupo G1 (7,83-18,72) diferiuestatisticamente de G2 (5,51-15,34). Conclusão: Baseado nosresultados é lícito concluir que houve uma diminuiçãosignificante na resistência adesiva após termociclagem.

Resistência ao cisalhamento de duas técnicas de reparo para metalocerâmicas / Shear resistance of two repair techniques for metalloceramics

O objetivo deste estudo foi medir e comparar as forças de uniãoentre uma liga de NiCr e uma resina, usando um adesivodentinário e um cimento resinoso como alternativas parareparar coroas metalocerâmicas. Vinte quatro bases em NiCr(Wironia, Bego) foram confeccionadas, jateadas por 20segundos com óxido de alumínio (250μm com uma pressão de2 bar), lavadas por 5 segundos e secas com jato de ar. As basesforam divididas aleatoriamente em 2 grupos (G1, G2) de 12espécimes cada. O grupo G1 foi tratado com 3M Single BondAdhesive System, e G2 com Panavia F metal primer, Panavia FED primer, e uma fina camada do cimento Panavia F (J.Morita).A resina W3D (Wilcos) foi aplicada nas superfícies de metal epolimerizada. O teste de cisalhamento foi realizado em umamáquina de ensaio universal (modelo DL-1000, EMIC -Equipamentos e Sistemas Ltda., São José dos Pinhais - PR -Brasil) com célula de carga de 50kg e velocidade de0.5mm/min. Após os testes mecânicos, os dados obtidos emMpa foram submetidos ao Mann-Whitney Test (p=0.006), o qualrevelou que os grupos G1 e G2 diferiram estatisticamente entresi, possibilitando concluir que 3M Single Bond Adhesive Systemdemonstrou valores de união significativamente maiores que o Panavia F