Biomechanical behavior of implant retained prostheses in the posterior maxilla using different materials: a finite element study.

BACKGROUND: The aim of this study is to evaluate the biomechanical behavior of the mesial and distal off-axial extensions of implant-retained prostheses in the posterior maxilla with different prosthetic materials using finite element analysis (FEA). METHODS: Three dimensional (3D) finite element models with three implant configurations and prosthetic designs (fixed-fixed, mesial cantilever, and distal cantilever) were designed and modelled depending upon cone beam computed tomography (CBCT) images of an intact maxilla of an anonymous patient. Implant prostheses with two materials; Monolithic zirconia (Zr) and polyetherketoneketone (PEKK) were also modeled .The 3D modeling software Mimics Innovation Suite (Mimics 14.0 / 3-matic 7.01; Materialise, Leuven, Belgium) was used. All the models were imported into the FE package Marc/Mentat (ver. 2015; MSC Software, Los Angeles, Calif). Then, individual models were subjected to separate axial loads of 300 N. Von mises stress values were computed for the prostheses, implants, and bone under axial loading. RESULTS: The highest von Mises stresses in implant (111.6 MPa) and bone (100.0 MPa) were recorded in distal cantilever model with PEKK material, while the lowest values in implant (48.9 MPa) and bone (19.6 MPa) were displayed in fixed fixed model with zirconia material. The distal cantilever model with zirconia material yielded the most elevated levels of von Mises stresses within the prosthesis (105 MPa), while the least stresses in prosthesis (35.4 MPa) were recorded in fixed fixed models with PEKK material. CONCLUSIONS: In the light of this study, the combination of fixed fixed implant prosthesis without cantilever using a rigid zirconia material exhibits better biomechanical behavior and stress distribution around bone and implants. As a prosthetic material, low elastic modulus PEKK transmitted more stress to implants and surrounding bone especially with distal cantilever.

The effect of cyclic loading on the fracture resistance of 3D-printed and CAD/CAM milled zirconia crowns-an in vitro study.

OBJECTIVES: The aim of this study was to evaluate the effect of cyclic mechanical loading on the fracture resistance of 3D-printed zirconia crowns in comparison to milled zirconia crowns. MATERIALS AND METHODS: Monolithic zirconia crowns (n = 30) were manufactured using subtractive milling (group M) and 3D additive printing (group P). Nine samples of each group were fractured under one-time loading while the other 6 samples were subjected to cyclic loading for 1.2 million cycles before being subjected to one-time loading until fracture. Scanning electron microscope (SEM) fractographic analysis was carried out on fractured fragments of representative samples. RESULTS: The mean for fracture resistance of group M was 1890 N without cyclic loading and 1642 N after being subjected to cyclic loading, and they were significantly higher than that of group P (1658 N and 1224 N respectively). CONCLUSIONS: The fabrication technique and cyclic loading affect the fracture resistance of zirconia crowns. Although the fracture resistance values for the 3D-printed crowns were lower than those of the milled, still they are higher than the masticatory forces and thus could be considered being clinically acceptable. CLINICAL RELEVANCE: Concerning fracture resistance, 3D-printed crowns can withstand the masticatory forces for the long term without any cracks or failure.

Marginal gap and internal fit of 3D printed versus milled monolithic zirconia crowns.

BACKGROUND: This study aimed to evaluate and compare the marginal gap using two different methods and the internal fit of 3D printed and zirconia crowns. METHODS: 3Y-TZP zirconia crowns (n = 20) were manufactured using subtractive milling (group M) and 3D printed (group P). The marginal gap was measured at 60 points using vertical marginal gap technique (VMGT). On the other hand, the silicone replica technique (SRT) was used to evaluate the internal fit and was divided into 4 groups: marginal gap, cervical gap, axial gap, and occlusal gap where the thickness of light impression was measured at 16 references. The numerical data was tested for normality using Shapiro-Wilk's test. They were found to be normally distributed and were analyzed using an independent t-test. RESULTS: Using VMGT, group P had significantly higher mean marginal gap values of 80 ± 30 µm compared to group M = 60 ± 20 µm (p < 0.001). Also, with the SRT, the marginal gap of group P (100 ± 10 µm) had significantly higher values compared to group M (60 ± 10 µm). The internal fit showed significant difference between the tested groups except for Axial Gap. CONCLUSIONS: Although milled crowns showed better results. The 3D printed zirconia crowns offer clinically acceptable results in terms of marginal adaptation and internal fit. Both VMGT and SRT are reliable methods for the assessment of the marginal gap.

Effect of Different Immediate Implant Loading Protocols on Peri-implant Soft Tissue Health / Efeito de diferentes protocolos de implante com carga imediata no tecido mole peri-implantar

Objectives: This clinical study was conducted to evaluate the effect of immediate loading on peri-implant soft tissue health using three protocols: I) Immediate functional loading using polymer infiltrated ceramic (PIC) material (IFLV). II) Immediate functional loading using polymethyl methacrylate (PMMA) followed by delayed functional loading using PIC material (IFLP). III) Immediate non-functional loading using PMMA followed by delayed functional loading using PIC material (INFLP). Material & Methods: 30 Implants were placed in the upper premolar area and divided randomly according to the immediate loading protocol. In the control group (INFLP), CAD/CAM PMMA crowns were placed out of occlusion for 3 months, and then replaced by CAD/CAM VITA ENAMIC crowns in functional occlusion. For (IFLV) group, CAD/CAM VITA ENAMIC crowns were immediately loaded in functional occlusion; while in (IFLP) group, CAD/CAM PMMA crowns were placed in functional occlusion for 3 months, and then replaced by CAD/CAM VITA ENAMIC crowns. Modified pink esthetic score (MPES) and probing depth were used for evaluation of peri-implant soft tissue at base line and follow up periods. Results: INFLP showed higher MPES results compared to IFLV and IFLP. Moreover, the INFLP probing depth at 3 months showed higher results compared to the other groups. Conclusions: Immediate non-functional loading showed the best outcomes. However, peri-implant soft tissue health of the immediate functional loading using the PIC crown material was clinically acceptable (AU)

Objetivo: Este estudo clínico foi realizado para avaliar o efeito da carga imediata na saúde do tecido mole peri-implantar usando três protocolos: I) Carga imediata funcional usando material de cerâmica infiltrada com polímero (PIC) (IFLV). II) Carga imediata funcional usando polimetilmetacrilato(PMMA) seguida por carga funcional retardada usando material PIC (IFLP). III) Carga imediata não funcional usando PMMA seguida por carga funcional retardada usando material PIC (INFLP). Material e Métodos: 30 implantes foram colocados na área dos pré-molares superiores e divididos aleatoriamente de acordo com o protocolo de carga imediata. No grupo controle (INFLP), as coroas CAD / CAM PMMA foram colocadas sem oclusão por 3 meses, e então substituídas pelas coroas CAD / CAM VITA ENAMIC na oclusão funcional. Para o grupo (IFLV), as coroas CAD / CAM VITA ENAMIC foram carregadas imediatamente em oclusão funcional; enquanto no grupo (IFLP), as coroas CAD / CAM PMMA foram colocadas em oclusão funcional por 3 meses, e então substituídas por coroas CAD / CAM VITA ENAMIC. O escore da estética rosa modificado (PESM) e a profundidade de sondagem foram realizados para avaliação do tecido mole peri-implantar no início e nos períodos de acompanhamento. Resultados: INFLP apresentou resultados de PESM superiores em comparação com IFLV e IFLP. Além disso, a profundidade de sondagem INFLP em 3 meses apresentou resultados superiores em comparação com os outros grupos. Conclusões: A carga imediata não funcional apresentou os melhores resultados. No entanto, a integridade do tecido mole peri-implantar da carga imediata funcional usando o material da coroa PIC foi clinicamente aceitável. (AU)

Acute pneumoperitoneum following coitus.

Vaginal rupture leading to pneumoperitoneum is well documented to occur after hysterectomy or surgery. However, it is extremely rare in a young woman following conventional intercourse. We report one such case. A 16-year-old woman presented to the accident and emergency department with a clinical picture of an acute abdomen. Results of radiography showed gas under the diaphragm, suggesting the possibility of bowel perforation. A detailed sexual history pointed toward the possibility of vaginal trauma. Diagnosis was confirmed on examination under anesthesia, and the tear repaired. A concomitant laparoscopy ruled out any other intra-abdominal injury. This case reminds us that acute peritoneum can occur after sexual intercourse and also reiterates the importance of a detailed sexual history and vaginal examination in young women presenting with an acute abdomen.