Survival Analysis and Torque Loosening of Experimental Screw After Mechanical Performance for Micro Conical Abutment

ABSTRACT: The most common failure in implantology are due to mechanical instability. Torque loosening or fracture of the screws are the most frequent complications. Furthermore, the fractured screw retrieval is complicated and time-consuming. So, modifications in the design of implant systems are justifiable to offer a greater degree of biomechanical stability. Thus, the present study proposes to evaluate an experimental geometry for abutment screw regarding failure probability and torque loss. Twenty implant/abutments sets (e-fix, A.S. Technology - Titanium Fix) were divided into the following groups (n=10 in each group): (1) Conventional screw (Screw neck ø 1.5 mm) and (2) Experimental screw (screw neck constricted ø 1.2 mm). The abutments were tightened with a controlled torque meter device following the manufacturer's recommendations. Mechanical cycling was carried out with a load of 50 N.cm during 5 x 10 6 cycles with a frequency of 2 Hz at a temperature of 37°C (ISO 14801). A digital torque meter was used to measure the reverse torque values of the prosthetic screw and the micro abutment screw, before and after loading. Data were statistically analyzed by One-way Anova and Tukey test (95 %). The results of the mean values of torque loss of the micro abutment screw were 58.44 % for the control group and 55.31 % for the experimental group and the mean torque loss for the prosthetic screw was 53.3 % and 61.3 % of the conventional and experimental groups, respectively. The survival probability was 100 % for both screw groups. It was concluded that experimental screw showed a similar behavior to conventional screws, showing similar reliability after fatigue life testing.

RESUMEN: En implantología las fallas más habituales se deben a la inestabilidad mecánica. El aflojamiento del torque o la fractura de los tornillos son las complicaciones más frecuentes. Además, la recuperación del tornillo fracturado es complicada y requiere mucho tiempo. Por tanto, las modificaciones en el diseño de los sistemas de implantes están justificados para ofrecer un mayor grado de estabilidad biomecánica. Por lo tanto, el presente estudio propone evaluar una geometría experimental para tornillo de pilar en cuanto a probabilidad de falla y pérdida de torque. Se dividieron veinte conjuntos de implantes / pilares (e-fix, AS Technology - Titanium Fix) en los siguientes grupos (n = 10 en cada grupo): (1) Tornillo convencional (cuello de tornillo ø 1,5 mm) y (2) Tornillo experimental (cuello de rosca estrechado ø 1,2 mm). Los pilares se apretaron con un dispositivo medidor de torque controlado siguiendo las recomendaciones del fabricante. El ciclo mecánico se realizó con una carga de 50 N.cm durante 5 x 10 6 ciclos con una frecuencia de 2 Hz a una temperatura de 37° C (ISO 14801). Se utilizó un medidor de torque digital para medir los valores de torque inverso del tornillo protésico y el tornillo de micro pilar, antes y después de la carga. Los datos se analizaron estadísticamente mediante la prueba One-way Anova y Tukey (95%). Los resultados de los valores medios de pérdida de torque del micro tornillo de pilar fueron 58,44 % para el grupo de control y 55,31 % para el grupo experimental y la pérdida de torque media para el tornillo protésico fue 53,3 % y 61,3 % de los grupos convencional y experimental, respectivamente. La probabilidad de supervivencia fue del 100 % para ambos grupos de tornillos. Se concluyó que el tornillo experimental mostró un comportamiento similar a los tornillos convencionales, mostrando una fiabilidad similar después de la prueba de vida a fatiga.

Effects of heat treatment on the bonding strength of pure titanium processed via selective laser melting and porcelain / 口腔疾病防治

Objective@# To evaluate the effect of heat treatment on the bonding strength of pure titanium formed by selective laser melting (SLM) and porcelain.@*Methods@#Ninety-six pure titanium specimens were laser machined to meet ISO 9693 standards. The specimens were divided into a heat treated group (A) and a nonheat treated group (B). According to the porcelain type, the specimens in groups A and B were divided into Super Ti22 (a), Titankeramik (b), and Triceram (c) groups. Then, according to sandblasting pressures of 0.25 MPa (1) and 0.45 MPa (2), they were further divided into Aa1, Aa2, Ab1, Ab2, Ac1, Ac2, Ba1, Ba2, Bb1, Bb2, Bc1, and Bc2 groups. The surface morphology and roughness of the sandblasted specimens were assessed using a laser scanning confocal microscope. After the porcelain was fused, the three-point bending titanium-porcelain bonding strength was tested. A stereomicroscope was used to characterize the titanium-porcelain interfaces and determine the mode of failure.@* Results@# The Vickers hardness of group A specimens (188.21 ± 11.94) was significantly lower than that of group B specimens (204.48 ± 6.32) HV (P<0.05). The roughness value in group A1 (2.90 ± 0.32) μm was significantly lower than that in group A2 (3.43 ± 0.43) μm (P<0.05). Specimens in group B1 (2.62 ± 0.08) μm were significantly smaller than those in group B2 (3.01 ± 0.06) μm (P<0.05). The bonding strength in group Aa1 was (33.75 ± 2.31) MPa, group Aa2 was (36.32 ± 1.44) MPa, group Ab1 was (39.82 ± 2.28) MPa, group Ab2 was (33.74 ± 1.53) MPa and group Ac2 was (38.63 ± 1.36) MPa, which was significantly higher than that in the corresponding groups Ba1 (29.65 ± 1.10) MPa, Ba2 (27.17 ± 2.24) MPa, Bb1 (27.29 ± 1.61) MPa, Bb2 (23.85 ± 0.97) MPa, and Bc2 (35.75 ± 1.93) MPa (P<0.05). With increasing sandblasting pressure, the bonding strength of the titanium ceramic in group Aa2 was significantly higher than in group Aa1, while that in group Ab2 was significantly lower than that in group Ab1 (P<0.05). In groups A, Bc1 and Bc2, the fracture model showed mixed failure, while in groups Ba1, Ba2, Bb1, and Bb2, the model showed interfacial failure.@* Conclusion @# The Vickers hardness of SLM titanium can be significantly reduced by heat treatment. SLM pure titanium after heat treatment is beneficial to combination of the three porcelain types and titanium. The titanium-porcelain bonding strength may be affected by sandblasting pressure.

Table-Top Lithium Disilicate Ceramic Restoration Thickness Effect on the Stress Distribution in Upper Premolars: 3D Finite Element Analysis

ABSTRACT: To evaluate the stresses generated in upper premolars rehabilitated with ceramic fragments (table-top) of lithium disilicate on the occlusal surface. An upper premolar was modeled following its anatomical references using computer aided design software (Rhinoceros version 5.0 SR8, USA). The dental tissues were individually designed containing enamel, dentin and periodontal ligament. The main anatomical points were used as parameters for model creation. Ceramic fragments were modeled varying their maximum thicknesses as: 0.5 mm, 1.0 mm and 1.5 mm. Solid geometries were exported to the analysis software (ANSYS 17.2, USA) in STEP format. The materials were considered isotropic, homogeneous and linear, and the values of the elastic modulus of the materials and structures were used to perform a static structural mechanical analysis. The set was submitted to 200 N load. The system fixation was defined on the basis of the three- dimensional model, and the results were obtained in MPa according to the failure criteria of the analyzed materials (tensile stress). Occlusal restoration was not detrimental to mechanical behavior. Stress distribution in the internal region of the restoration was similar between the groups. Thicker fragments presented a lower concentration of tensile stress, therefore suggesting better prognosis in attenuating tensile stresses in the tooth region. More conservative occlusal ceramic fragments presented worse prognosis. However, all evaluated thickness for table-tops support the occlusal rehabilitation of upper premolars when submitted to 200 N loading.

RESUMEN: El objetivo fue evaluar las tensiones generadas en los premolares superiores rehabilitados con fragmentos cerámicos (tablero) de disilicato de litio en la superficie oclusal. Se modeló un premolar superior siguiendo sus referencias anatómicas utilizando un software de diseño asistido por computadora (Rhinoceros versión 5.0 SR8, EE. UU.). Los tejidos dentales se moldearon individualmente conteniendo esmalte, dentina y ligamento periodontal. Los principales puntos anatómicos se utilizaron como parámetros para la creación del modelo. Los fragmentos cerámicos se modelaron variando sus espesores máximos como: 0,5 mm, 1,0 mm y 1,5 mm. Las geometrías sólidas se exportaron al software de análisis (ANSYS 17.2, EE. UU.) En formato STEP. Los materiales se consideraron isotrópicos, homogéneos y lineales, y los valores del módulo elástico de los materiales y estructuras se utilizaron para realizar un análisis mecánico estructural estático. El conjunto se sometió a una carga de 200 N. La fijación del sistema se definió a partir del modelo tridimensional, y los resultados se obtuvieron en MPa según los criterios de falla de los materiales analizados (tensión de tracción). La restauración oclusal no perjudica el comportamiento mecánico. La distribución de la tensión en la región interna de la restauración es similar entre los grupos. Los fragmentos más gruesos presentaron una menor concentración de tensión de tracción, lo que sugiere un mejor pronóstico en la atenuación de las tensiones de tracción en la región dentaria. Los fragmentos cerámicos oclusales más conservadores presentaron peor pronóstico. Sin embargo, todos los espesores evaluados para tableros de mesa en disilicato de litio apoyan la rehabilitación oclusal de los premolares superiores cuando se someten a una carga de 200 N.

Infiltration by Streptococcus mutans in provisional crowns fixed by two types of cementing agents ­ pilot double-blind randomized clinical trial / Infiltração por Streptococcus mutans em coroas dentárias provisórias fixadas por dois tipos de agentes cimentantes ­ estudo clínico randomizado duplo-cego piloto

Objective: When provisional acrylic crowns are used for a long time, they become more susceptible to marginal leakage by cariogenic bacteria. The objectives of this pilot clinical study were to compare cement based on zinc oxide-eugenol and calcium hydroxide by contamination with Streptococcus mutans, and calculate the sample size for the continuation of this study. Methods: Individuals receiving provisional crowns and following inclusion/exclusion criteria, were randomly distributed into 2 groups: zinc oxide-eugenol (n=8); calcium hydroxide (n=9). The temporary crowns were made by a blind researcher and cemented by another. Patients were also blinded by the cement used inside their crowns. After 2 months, a cement sample from the crowns' peripheral inner face was collected, placed in a tube containing 1 mL of sterile saline, serially diluted, plated on Mitis Salivarius Bacitracin agar, and incubated for 48 hours. Colony-forming units (CFU/mL) were counted. A statistical power analysis was performed to calculate sample size (1-ß=80%) and the Mann Whitney test to compare both cements (α=0.05). Results: Both cements were contaminated with S. mutans, with an average of 166.6 x 102 CFU/mL for calcium hydroxide and 435.3 x 102 CFU/mL for zinc oxide-eugenol, with no significant difference (p=0.311). The sample size calculated for this study was 36 per group. Conclusion: This pilot study suggests that there is important contamination inside provisional crowns used for two months, independent of the cement. The continuation of this study is needed, with a bigger sample size, to enable a comparison between the cements.

Objetivo: Quando coroas dentais provisórias são utilizadas por um longo período, elas se tornam susceptíveis à infiltração marginal por bactérias cariogênicas. O objetivo deste estudo clínico piloto foi comparar os cimentos a base de óxido de zinco e eugenol e hidróxido de cálcio pela contaminação com Streptococcus mutans e calcular o tamanho amostral para continuação deste estudo. Métodos: Indivíduos recebendo coroas provisórias e seguindo critérios de inclusão/exclusão, foram distribuídos aleatoriamente em dois grupos: óxido de zinco e eugenol (n=8); hidróxido de cálcio (n=9). As coroas provisórias foram feitas por um pesquisador cego e cimentadas por outro. Os pacientes também foram cegos quanto ao cimento utilizado dentro de suas coroas. Depois de 2 meses, amostras de cimentos foram coletadas da face interna periférica das coroas, colocadas em um tubo contendo 1 mL de solução salina estéril, diluídas de forma seriada, plaqueadas em ágar Mitis Salivarius Bacitracina e incubadas por 48 horas. Unidades formadoras de colônias (UFC/mL) foram contadas. Um teste de poder estatístico foi realizado para calcular o tamanho amostral (1-ß=80%) e o teste de Mann Whitney para comparar os dois cimentos (α=0.05). Resultados: Os dois cimentos foram contaminados com S. mutans, com uma média de 166.6 x 102 UFC/mL para o hidróxido de cálcio e 435.3 x 102 UFC/mL para o óxido de zinco e eugenol, com nenhuma diferença significativa (p=0.311). O cálculo amostral para este estudo foi 36 indivíduos por grupo. Conclusão: Este estudo piloto sugere que existe importante contaminação dentro de coroas provisórias utilizadas por 2 meses, independente do cimento. A continuação deste estudo é necessária, com maior tamanho amostral, para possibilitar a comparação entre os cimentos.

Oral Health Status and Oral Health-Related Quality of Life (OHRQoL) in Patients with Removable or Fixed Partial Dentures in King Saud Bin Abdulaziz University for Health Sciences (KSAU-HS) Dental Clinics

Introduction: Many factors of tooth loss will compromise chewing and general health and quality of life. Saudi populations demonstrate a high prevalence of caries and a striking increase in dmft/DMFT. Usually, tooth loss is rehabilitated by different prosthetic options including implant, fixed partial denture and removable partial denture. Aim: To evaluate the relation of oral health-related quality of life with the type of prosthesis and oral health status among patients who have removable or fixed partial dentures in King Saud bin Abdulaziz University for health science, college of dentistry. Material and methods: Cross-sectional study would be conducted at the College of Dentistry, King Saud bin Abdulaziz University (KSAUHS) and Dental Centre, KAMC, NGHA. Convenient sampling was carried out by selecting 109 patients from those who visited the dental clinic. Oral health status was captured using the DMFT index. The collected data were entered and analyzed by adapting the SPSS computer software. Result: The type and quality of prosthesis and its effect on the OHRQoL on patients showed no significant relation (p=0.459), but the duration of wearing of prosthesis showed significant relation (p=0.046). Regarding DMF total of (n=109), 61 had low DMF, 48 had high DMF witch was statically significant (p=0.02). Conclusion: At the end of this study we conclude that there were no significant impacts on quality of life in relation to the type of prosthesis. On the other hand, we found a significant relation with OHRQoL in function domain, esthetic part and oral health status.

Restoration of bilateral distal extension removable partial denture using a fixed implant prosthesis in unilateral partial edentulous patient: A case report / 대한치과보철학회지

Traditional removable partial denture is a successful treatment for partial edentulous patients. When the abutment is formed with unilateral minority teeth, satisfaction with the use of removable partial denture may be lowered due to patient's discomfort and damage of the abutment. Recently, it has been reported that the unilateral posterior extension partial denture is used as a bilateral posterior extension partial denture using implant fixed prostheses as abutments. In this case, by using implant surveyed crown prostheses, bilateral posterior extension partial denture is fabricated in site that is predicted to have a poor prognosis. This resulted in improved support, maintenance, and stabilization of the removable partial denture, which were economically beneficial to patient and satisfied with use.

Retrospective study on survival, success rate and complication of implant-supported fixed prosthesis according to the materials in the posterior area / 대한치과보철학회지

PURPOSE: The purpose of this study was to retrospectively investigate the survival and success rate of implant-supported fixed prosthesis according to the materials in the posterior area. Other purposes were to observe the complications and evaluate the factors affecting failure. MATERIALS AND METHODS: Patients who had been restored implant prosthesis in the posterior area by the same prosthodontist in the department of prosthodontics, dental hospital, Chonbuk National University, in the period from January 2011 to June 2018 were selected for the study. The patient's sex, age, material, location, type of prosthesis and complications were examined using medical records. The Kaplan-Meier method was used to analyze the survival and success rate. The Log-rank test was conducted to compare the differences between the groups. Cox proportional hazards model was used to assess the association between potential risk factors and success rate. RESULTS: A total of 364 implants were observed in 245 patients, with an average follow-up of 17.1 months. A total of 5 implant prostheses failed and were removed, and the 3 and 5 year cumulative survival rate of all implant prostheses were 97.5 and 91.0, respectively. The 3 and 5 year cumulative success rate of all implant prostheses were 61.1% and 32.9%, respectively. Material, sex, age, location and type of prosthesis did not affect success rate (P>.05). Complications occurred in the order of proximal contact loss (53 cases), retention loss (17 cases), peri-implant mucositis (12 cases), infraocclusion (4 cases) and so on. CONCLUSION: Considering a high cumulative survival rate of implant-supported fixed prostheses, regardless of the materials, implant restored in posterior area can be considered as a reliable treatment to tooth replacement. However, regular inspections and, if necessary, repairs and adjustments are very important because of the frequent occurrence of complications

The use of implant surveyed fixed prosthesis for removable partial denture with a few unilateral remaining teeth: A case report / 대한치과보철학회지

As implant can be covered by National Health Insurance Service (NHIS), it was increased the interest in the removable partial denture (RPD) with the surveyed fixed prosthesis supported by implant fixture. To achieve predictable result, it needs the prudent implant planning by basic principles of RPD and patient's residual ridge. This 67 years old age male had a few unilateral remaining teeth, and hoped the treatment covered by NHIS. As using CAD software, the position of implant is planned with regarding to occlusal table of provisional denture, basic principles of RPD, and resorbed residual ridge. The definitive prostheses can ensure the stability and retention of removable prosthesis. When planning implant fixed prostheses, the digital technique was utilized to consider basic principle of RPD and resorbed residual ridge. As a result, it provided satisfactory prostheses.

Full mouth rehabilitation of patient with severe dental caries with implant fixed prosthesis fabricated with milling and 3D printing method: A case report / 대한치과보철학회지

Passive fit of prosthesis is an essential property of implant supported prosthesis for long term success and minimization of complications. And the property is determined mostly by fabrication procedure. There were limitations of extensive implant prosthesis because conventional casting method generate contraction error of long span prosthesis. However, Computer-aided design/Computer-aided manufacturing (CAD/CAM) technology of 3D printing and milling metal framework can overcome those limitations. This case is a full mouth rehabilitation using extensive implant fixed prosthesis. Removable interim prosthesis was made for esthetic, functional evaluation and a guide for implant insertion. After the insertion, implant fixed interim prosthesis was delivered. After additional evaluation and adjustment, final prosthesis was designed with CAD, the fabricated with CAM. Milling technique was used for anterior screw type implant superstructure and 3D printing technique was used for the anterior and posterior implant copings. Fit of the final restoration was favorable. The practitioner and patient were both esthetically and functionally satisfied with the final result.

Biomechanical effect of inclined implants in fixed prosthesis: strain and stress analysis / Efeito biomecânico de implantes inclinados em prótese fixa: analise das tensões e deformações

Introduction: Implant inclinations can be corrected using mini abutments at different angulations. Objective: To analyze the influence of external hexagon implants in different inclinations (3 levels) on the microstrain distribution generated around three implants. Method: A geometric bone model was created through Rhinoceros CAD software (version 5.0 SR8, Mcneel North America, Seattle, WA, USA). Three implants (4.1 × 13 mm) were modeled and inserted inside the substrate at three different inclinations: 0º, 17º and 30º. Next, all groups received mini conical abutments, fixation screws and a simplified prosthesis. The final geometry was exported in STEP format to analysis software and all materials were considered homogeneous, isotropic and linearly elastic. An axial load (300N) was applied on the center of the prosthesis. An in vitro study was conducted with same conditions and groups for validating the tridimentional model. Result: Stress was concentrated on the external area of the implants, in contact with the cortical bone and external hexagon. For the bone simulator, the strain increased in the peri-implant region according to the increase in the implant's inclination. The difference between groups was significant (p = 0.000). The 30º group presented higher stress and strain concentration. Conclusion: The microstrain and stress increase around implants directly proportional to the increase of the installation angle.

Introdução: A inclinação dos implantes pode ser corrigida através de mini-pilares de diferentes angulações. Objetivo: Analisar a influência de implantes com hexágono externo em diferentes inclinações (3 níveis) na distribuição de microdeformações geradas em torno de três implantes. Método: Um modelo geométrico de osso foi criado através do software CAD Rhinoceros (versão 5.0 SR8, Mcneel North America, Seattle, WA, EUA). Três implantes (4,1 × 13 mm) foram modelados e inseridos no interior do substrato em três diferentes inclinações: 0º, 17º e 30º. Em seguida, todos os grupos receberam mini-pilares cônicos, parafusos de fixação e prótese simplificada. A geometria final foi exportada em formato STEP para software de análise e todos os materiais foram considerados homogêneos, isotrópicos e linearmente elásticos. Uma carga axial (300N) foi aplicada no centro da prótese. Um estudo in vitro foi conduzido com as mesmas condições e grupos para validar o modelo tridimensional. Resultado: A concentração de tensão ocorreu na área externa dos implantes, em contato com o osso cortical e o hexágono externo. Para o simulador ósseo, a deformação aumentou na região peri-implantar de acordo com o aumento da inclinação do implante. A diferença entre os grupos foi significativa (p = 0.000). O grupo de 30º apresentou maior concentração de tensão e deformação. Conclusão: O aumento da microdeformação e das tensões ao redor dos implantes aumenta diretamente proporcional ao aumento do ângulo de instalação.

Full mouth rehabilitation of fully edentulous patient with implant-supported fixed prosthesis preceding bone graft: A case report / 대한치과보철학회지

Prosthetic treatment using implants in fully edentulous patients includes implant-supported fixed prosthesis, implant hybrid prosthesis, implant retained- or supported-overdenture and implant supported fixed prosthesis has advantages such as psychological stability, pronunciation. If an implant supported fixed prosthesis is planned, the implants should be placed in consideration of pronunciation, esthetics, and oral hygiene. For this, clinical and radiological diagnosis is indispensable. When placing the prosthetic driven implant at the site determined from the diagnosis, a sufficient amount of alveolar bone and soft tissue support are required. If these requirements found to be insufficient, a wide range of bone grafting should be performed in advance. In this case, a fully edentulous patient with severe alveolar bone resorption due to periodontal disease was treated with a full mouth rehabilitation using implant-supported fixed prosthesis preceding maxillary sinus graft and alveolar bone augmentation. We report this patient were satisfied with esthetic and function.

Full mouth rehabilitation of the patient with crossed occlusion using implant fixed prosthesis: A case report / 대한치과보철학회지

Crossed occlusion can be treated either by overdenture and telescopic denture or by placing an implant at the edentulous area to reestablish the support on the occlusion. If alveolar bony support is sufficient and an the environment where an implant is inserted is favorable to restoring the masticatory and aesthetic function of a patient, the implant-supported fixed prosthesis can provide more definitive occlusal support and more aid for other oral functions. In this case report, a patient with a severe residual alveolar bone resorption following the extraction of teeth and who had a crossed occlusion was treated with sinus bone graft and alveolar bone augmentation in order to place the implants at prosthetically position. The definitive restoration was made to reflect the patient's occlusal and aesthetic function using the CAD/CAM double scanning method. Finally, the treatment had the masticatory and aesthetic function adequately restored, which is reported here.

Zirconia ceramic fixed dental prosthesis with all-on-4 concept implants for irradiated maxilla: A case report / 대한치과보철학회지

The implant-supported fixed dental prosthesis in irradiated maxilla needs meticulous treatment planning due to low bone healing capacity. All-on-4 concept implantation can reduce the number of implants to be placed avoiding bone grafting procedure. Conventionally, prefabricated angled abutments for tilted implants have been used. However, in this case, it was replaced with computer-aided design and computer-aided manufacturing (CAD/CAM) abutment. This case report described all-on-4 concept implantation and fabrication of CAD/CAM zirconia fixed dental prostheses using CAD/CAM titanium abutments.

Esthetic restoration in continuous maxillary anterior area using immediate implant placement: A case report / 대한치과보철학회지

In the case of an extraction in the maxillary anterior region, immediate placement of implant-supported fixed prosthesis can be considered as a treatment option. Fewer surgical operations, reduced treatment time, and optimal availability of existing bone are obvious advantages of the method; however, when applied in the continuous maxillary anterior region, inter-implant distance must be carefully considered, as well as accurate diagnosis and treatment planning for predictable outcome. In this case report, immediate placement of two implants in the continuous maxillary anterior along with bone graft following the extraction of root rests, and the restoration of provisional and implant-supported fixed prosthesis on a 63-year-old patient had resulted in both esthetically and functionally satisfactory clinical outcomes.

The selection criteria of temporary or permanent luting agents in implant-supported prostheses: in vitro study

PURPOSE: The use of temporary or permanent cements in fixed implant-supported prostheses is under discussion. The objective was to compare the retentiveness of one temporary and two permanent cements after cyclic compressive loading. MATERIALS AND METHODS: The working model was five solid abutments screwed to five implant analogs. Thirty Cr-Ni alloy copings were randomized and cemented to the abutments with one temporary (resin urethane-based) or two permanent (resin-modified glass ionomer, resin-composite) cements. The retention strength was measured twice: once after the copings were cemented and again after a compressive cyclic loading of 100 N at 0.72 Hz (100,000 cycles). RESULTS: Before loading, the retention strength of resin composite was 75% higher than the resin-modified glass ionomer and 2.5 times higher than resin urethane-based cement. After loading, the retentiveness of the three cements decreased in a non-uniform manner. The greatest percentage of retention loss was shown by the temporary cement and the lowest by the permanent resin composite. However, the two permanent cements consistently show high retention values. CONCLUSION: The higher the initial retention of each cement, the lower the percentage of retention loss after compressive cyclic loading. After loading, the resin urethane-based cement was the most favourable cement for retrieving the crowns and resin composite was the most favourable cement to keep them in place.

Implant supported fixed prosthesis for complete edentulous maxilla with severe alveolar ridge resorption: A case report / 대한치과보철학회지

Implant fixed prosthesis for the complete edentulous maxilla provides significant benefits in the aspects of functions and esthetics compared with the conventional denture. Implant supported fixed prosthesis are totally supported by implant, and thus stabilizes the prosthesis to the maximum degree as possible. Also, the improved retention and stability of fixed prosthesis enhance patients' psychological and psychosocial health. This clinical presentation describes a maxillary full arch implant-supported fixed prosthesis in complete maxillary edentulous patient who showed vertical and horizontal alveolar bone resorption in the anterior ridge. To rehabilitate the esthetics and proper lip support, the zirconia framework was fabricated and the pink porcelain was veneered to reproduce the natural gingival tissue. After 9 months of follow up, the restorations were maintained without complications and the patient was satisfied with the restoration both functionally and esthetically.

Prótesis fija con sistema tubo-barra en odontopediatría: reporte de un caso clínico de 12 meses de seguimiento / Fixed prosthesis with tube-bar system in pediatric dentistry: a case report over 12 months of follow-up

Introducción: La pérdida prematura de incisivos primarios puede producir alteraciones estéticas, funcionales y psicológicas. La rehabilitación protésica permite reemplazar los dientes faltantes y evitar las secuelas que ello puede acarrear. Objetivo Describir la técnica y evolución clínica de una prótesis fija anterior tipo Denari durante 12 meses de seguimiento. Descripción del caso Paciente de sexo femenino de 3 años de edad que acude en busca de atención profesional posterior a la avulsión de los incisivos centrales superiores. Con la finalidad de devolver la estética del sector anterosuperior, recuperar la función oral e interferir con el hábito de interposición lingual se decidió realizar una terapia basada en prótesis parcial fija tipo Denari. Durante el año de seguimiento la prótesis fue muy bien tolerada por la paciente y sin alteración de los tejidos blandos adyacentes, destacando un aumento en el espacio interincisal, lo que demuestra el crecimiento transversal. Conclusión La prótesis dental en niños es una tarea exigente, marcada por la necesidad de adaptación a los cambios continuos que conllevan los procesos de crecimiento y maduración de complejo maxilofacial. En este contexto es que la prótesis tipo Denari con sistema tubo-barra es una excelente y estética alternativa en pacientes de corta edad en donde la prótesis va a permanecer en la boca por un largo período de tiempo, sin interferir en el crecimiento, desarrollo y función del sistema estomatognático.

Introduction: Premature loss of primary incisors may result in aesthetic, functional and psychologic problems. Prosthetic restoration allows replacing missing teeth, avoiding the unwanted consequences that their absence may carry. Objective The aim of this clinical case is to describe the technique and clinical evolution of a Denari fixed anterior prosthesis over 12 months of follow-up. Case description 3 year-old female patient sought professional attention after the avulsion of the upper central incisors. In order to restore the natural appearance of the anterior superior area, recover oral function and intervene in the habit of tongue interposition, the treatment decided upon was a partially fixed Denari prosthesis. During the follow-up year the prosthesis was very well tolerated by the patient and without altering any adjacent soft tissues. We highlight an increase in the interincisal space, which demonstrates transversal growth. Conclusion A dental prosthesis in a child is a demanding task marked by the need to adapt to the continuous changes brought about by maxillofacial growth and maturation. It is in this context that the Denari prosthesis with its tube-bar system is an excellent and esthetic alternative in young patients where the prosthesis is going to remain in place for a prolonged period without interfering in the growth, development and function of the stomatognatic system.

CAD fabrication of the mandible All-on-4 implant photoelastic model / 实用口腔医学杂志

Objective:To explore the method of the establishment of edentulous mandible All-on-4 implant photoelastic model with various distally tilted implants by computer-aided design(CAD).Methods:The edentulous mandible specimen was scanned by CT. Three-dimensional models of the mandible consisting of implant location were reconstructed and edited with Mimics and Geomagic Stu-dio software.Each of the four models had four implant sockets in the interforaminal area.In the first model,the bilateral distal im-plants were placed vertically.In the other models,the posterior implants were respectively inclined by 1 5°,30°and 45°distally.The four models were manufactured by RP and then the All-on-4 photoelastic models were made by traditional ways.Results:The ob-tained ethoxyline resin models featured bright surface,homogeneous structure,faintly yellowish,high optical sensibility,precision im-plants location and with no natural stress.The model offered a good experimental basis for the stress measurement.Conclusion:The method of fabricating ethoxyline resin models by CAD is reproducible,which simplifies the operating process.

Expansão cirúrgica da maxila para reabilitação com próteses fixas sobre implantes do tipo protocolo / Surgical expansion of maxillary alveolar ridge for rehabilitation with implant-supported fixed prosthesis. Clinical case report

A instalação de implantes em áreas com perda óssea horizontal pode resultar em uma relação prótese-implante desfavorável, o que compromete o resultado estético, funcional e a higienização pelo paciente, prejudicando o prognóstico do tratamento. Desta forma, previamente ou durante a instalação de implantes, a reconstrução óssea para aumento da largura do rebordo alveolar é frequentemente realizada através de técnicas cirúrgicas, como enxertos ósseos ou biomateriais, utilizados isoladamente ou associados a membranas ou a fatores de crescimento. Contudo, mediante as limitações destes procedimentos, a técnica de divisão e expansão do rebordo alveolar (técnica de split crest) tem sido utilizada. O presente caso clínico teve o objetivo de demonstrar as vantagens e a importância desta técnica, com instalação imediata de implantes para o aumento da espessura óssea, possibilitando a confecção de próteses fixas do tipo protocolo que garantam aos pacientes condições de higienização, fonética, mastigação e estética satisfatórias.

Implant placement in an area with horizontal bone loss can be associated with an unfavourable prosthesis/implant ratio, which can compromise the aesthetic outcome, masticatory function and adequate oral hygiene, impairing clinical outcomes. Therefore, before or during implant placement, horizontal bone augmentation can be required and performed using surgical techniques, such as onlay bone grafting, associated or not with membranes and/or growth factors. However, due to limitations of such procedures, a technique for surgical expansion of the alveolar ridge (split crest technique) has been performed. The objective of this paper is to present a clinical case, demonstrating the advantages and importance of this technique to increase bone thickness, with immediate implant placement, and by means of a complete fixed implant-support prosthesis, which permits adequate oral hygiene, phonation, masticatory function, and aesthetic results.

Does matching relation exist between the length and the tilting angle of terminal implants in the all-on-four protocol? stress distributions by 3D finite element analysis

PURPOSE: To explore whether there is matching relation between the length and the tilting angle of terminal implants in the All-on-Four protocol by studying the effects of different implant configurations on stress distributions of implant, bone, and framework. MATERIALS AND METHODS: Four implants were employed to support a full-arch fixed prosthesis and five three-dimensional finite element models were established with CT images, based on the length (S and L) and distal tilt angle (0degrees, 30degrees and 45degrees) of terminal implants for an edentulous mandible, which named: Tilt0-S, Tilt30-S, Tilt30-L, Tilt45-S and Tilt45-L. An oblique 240 N was loaded at second molar. The von Mises Stresses were analyzed. The implants were consecutively named #1 to #4 from the loading point. RESULTS: 1) Tilt0-S had the greatest stress on the implants, with the other groups exhibiting variable reductions; the four implants of Tilt45-L demonstrated the greatest reduction in stress. 2) Tilt0-S had the greatest stress at bone around #1 implant neck, and Tilt45-L exhibited the least stress, which was a 36.3% reduction compared to Tilt0-S. 3) The greatest stress in the framework was found on the cantilevers distal to #1 implant. Tilt45-S exhibited the least stress. CONCLUSION: Matching different length and tilting angle of the terminal implants led to variable stress reductions on implants, bone and the superstructure. By optimizing implant configuration, the reduction of stress on implants and surrounding bone could be maximized. Under the present condition, Tilt45-L was the preferred configuration. Further clinical testings are required.