'Thermo-mechanical behavior of alternative material combinations for full-arch implant-supported hybrid prostheses with short cantilevers'.

OBJECTIVES: To compare the fracture resistance (FR) of three combinations of materials for full-arch maxillary implant-supported hybrid prostheses (HPs) with short cantilevers (≤ 10 mm). METHODS: Maxillary HPs were fabricated and classified as follows (n = 5 each): Group-1 (CC-A, control): acrylic-resin-veneered Co-Cr frameworks; Group-2 (CF-A): acrylic-resin-veneered carbon-fiber mesostructures; and Group-3 (CF-R): composite-resin-veneered carbon-fiber frames. Specimens were thermal-cycled (5,000 cycles; 5 °C-55 °C; dwell time: 30 s). Vertical loads were applied until failure, first at the 10-mm-long cantilever (LC), and, afterwards, at the anterior region (AR), using a universal testing machine (crosshead speed: 0.05 mm/s). The fracture pattern was assessed by stereomicroscope and SEM. The one-way ANOVA, the Bonferroni, and the independent samples t tests, were run (α= 0.05). RESULTS: At LC, CF-A, and CC-A samples exhibited the highest FR values (p< 0.001), showing no differences to each other. At AR, CC-A specimens recorded the highest FR, followed by CF-A samples (p< 0.001). CF-R HPs displayed the lowest FR at both locations (p< 0.001). The only group with differences between the tested sites was the CC-A, the AR being more resistant (p< 0.001). Most CC-A and CF-A HPs failed cohesively. CF-R prostheses mainly failed adhesively. CONCLUSIONS: Maxillary HPs with short cantilevers (≤ 10 mm) made of Co-Cr or carbon-fiber veneered with acrylic resin demonstrated an adequate mechanical resistance (> 900 N). CLINICAL SIGNIFICANCE: For maxillary HPs with cantilevers up to 10 mm, acrylic-veneered carbon- fiber mesostructures may be recommended, whereas coating carbon-fiber frames with composite resin seems not suitable.

'Role of the modulating factors on the self-perceived OHRQoL of fully dentate subjects and wearers of screw-retained and cement-retained implant-supported FPDs: A cross-sectional study'.

OBJECTIVES: This research aimed to compare the oral health-related quality of life (OHRQoL) between fully dentate subjects and edentulous patients wearing implant-supported fixed partial dentures (i-FPDs). The clinical conditions of both types of restorations were evaluated. METHODS: Participants were assigned to: Group-1 (SR, n = 50): screw-retained i-FPD wearers; Group-2 (CR, n = 50): cement-retained i-FPD wearers; and Group-3 (ND, n = 50): dentate subjects with a healthy natural dentition (controls). Patients answered the OHIP-14sp and QoLIP-10 questionnaires. Data related to sociodemographics, prosthesis features, peri­implant status, complications, and subjective evaluations, were compiled. Potential modulators of the OHRQoL and the i-FPDs' clinical conditions were assessed using non-parametric tests (α= 0.05). RESULTS: ND individuals were the least satisfied (OHIP-14sp; p< 0.001). Both prosthodontic groups reported similar levels of wellbeing, excluding the speaking difficulties, which were lower for SR wearers as shown by both scales (p = 0.001). The most discontented patients (OHIP-14sp) were: women (p = 0.022), under 65 years (p = 0.03), without partner (p< 0.001) and having a crown (p = 0.033). The level of education/schooling also affected the OHIP-14sp scores (p< 0.001). Implant mobility and peri­implantitis were more frequent among CR wearers (p-values= 0.008 and 0.05, respectively). CONCLUSIONS: The OHRQoL of both prosthodontic groups was comparably higher than that of the dentate subjects, who were the most nonconformist. The self-perceived satisfaction was mainly modulated by sociodemographic factors. CLINICAL SIGNIFICANCE: Overall, the retention system did not impact the OHRQoL, prosthetic problems, and subjective evaluations of i-FPD wearers. However, the cementation may increase the risk of peri­implant diseases.

Fracture resistance of cantilevered full-arch implant-supported hybrid prostheses with carbon fiber frameworks after thermal cycling.

OBJECTIVES: This in vitro study aimed to find the best combination of mesostructure and veneering materials for full-arch implant-supported hybrid prostheses (HPs) in terms of the fracture resistance (FR) of their cantilevers. METHODS: Three groups (n = 5 each) of maxillary HPs were fabricated: Group-1 (CC-A, control): Co-Cr frameworks coated with acrylic resin; Group-2 (CF-A): carbon fiber veneered with acrylic resin; and Group-3 (CF-R): carbon fiber coated with composite resin. All specimens were submitted to 5,000 thermal cycles (5 °C - 55 °C, dwell time: 30 s), and subjected to a single cantilever bending test in a universal testing machine (crosshead speed: 0.5 mm/min) until failure. The fracture pattern was assessed using stereo microscope and SEM. The one-way ANOVA and Bonferroni tests were run (α= 0.05). RESULTS: The FR yielded significant differences among the three groups (p< 0.001). CC-A samples reached the highest FR values (p ≤ 0.001), whereas both CF-A and CF-R HPs exhibited the comparably (p = 0.107) lowest FR. CC-A specimens failed cohesively (100%): mostly without chipping (80%). CF-A mesostructures were always broken at the connections of the distal implants. CF-R prostheses often failed adhesively (80%). CONCLUSIONS: The HPs made of Co-Cr veneered with acrylic demonstrated the best mechanical behavior, being the only group whose 13-mm long cantilevers exceeded the clinically acceptable FR of 900 N. The HPs constructed with carbon fiber frameworks showed, additionally, more unfavorable fracture patterns. CLINICAL SIGNIFICANCE: For HPs with cantilevers up to 13 mm, Co-Cr mesostructures coated with acrylic may represent the optimum combination of materials.

Análisis in vitro de la resistencia a la fractura de estructuras de fibra de carbono termocicladas / In vitro resistance to fracture testing of carbon fiber structures after thermal cycling

Objetivos: Comparar la resistencia a la fractura de estructuras de fibra de carbono con estructuras de cobalto-cromo, unidas a resina y tras termociclado. Materiales y métodos: se confeccionaron cinco probetas de fibra de carbono y cinco de cromo-cobalto y se unieron a resina acrílica. Ambas probetas se sometieron a 5000 ciclos de termociclado, permaneciendo durante 30 segundos en saliva artificial entre 5º y 55º C de temperatura entre cada ciclo. Posteriormente se realizó un ensayo por carga en tres puntos hasta producirse fractura de las probetas. Resultados: Dos de las cinco probetas de fibra de carbono presentaron separación de los materiales tras el termociclado. El grupo de fibra de carbono obtuvo valores más bajos en la resistencia a la fractura (305,6 N), mientras que el grupo de cromo-cobalto alcanzó los 664,8 N de media (p=0,008). Conclusiones: Dentro de los límites del estudio, la resistencia a la fractura de las probetas de fibra de carbono fue significativamente menor que la de las probetas de cromo-cobalto. Es necesario mejorar las estructuras para poder indicar este material como alternativa al cromo-cobalto en prótesis híbridas implantosoportadas (AU)

Objective: To compare the resistance to fracture of carbon fiber and acrylic resin structures and with cobalt-chromium alloy and acrilic resin structures after thermal cycling. Material and methods: Five carbon fiber reinforced acrylic resin and five cobalt-chromium alloy embebed in acrylic resin specimens were fabricated. All specimens were thermal cycled from 5º to 55ºC for 5000 cycles with a 30-s dwell time. A three point loading test until fracture of specimens was performed. Results: In two of five specimens separation of carbon fiber from acrylic resin was observed after thermal cycling. The carbon fiber reinforced group presented lower resistance values (305,6 N) while cobalt-chromium group reached an average of 664,8 N (p=0.008). Conclusions: Within the limitations of this study, the resistance to fracture of carbon fiber specimens were significantly lower than cobalt-chormium group. More studies and improvment of carbon fiber reinforced resins are necessary in order to be used as alternative material for implant-supported hybrid prosthesis (AU)

Selección de pilares en implanto-prótesis / Abutment selection on implant-supported prostheses

Introducción: hoy día las casas comerciales ofrecen muchas posibilidades a la hora de seleccionar los pilares para nuestras prótesis implantosoportadas, lo que hace a veces difícil su selección. Con este trabajo queremos mostrar los criterios para escogerlos según el tipo de prótesis, su localización, la dirección de los implantes y las alternativas existentes. Materiales y Método: se ha empleado una revisión bibliográfica y experiencias propias de nuestra actividad para señalar los pilares indicados y sus posibles alternativas. Resultados: para la rehabilitación fija maxilar superior preferimos pilares cónicos tallables para prótesis cementada. Si los implantes no están paralelos usaremos pilares cónicos para atornillar para confeccionar una prótesis híbrida. En la mandíbula indicamos pilares cónicos para atornillar. En las sobredentaduras seleccionamos pilares cónicos para atornillar una barra de retención como primera opción. En los casos parciales preferimos pilares cónicos para cementar, así como en los unitarios. Si la dirección es desfavorable usaremos pilares metálicos o cerámicos tallables. Señalamos en el artículo las razones y alternativas en cada situación. (AU)

Tratamientos prostodóncicos en pacientes geriátricos / Prosthodontic treatment for geriatric patients

La experiencia clínica nos demuestra que un porcentaje de nuestra poblacion geriátrica requiere tratamiento protéslco. Para tener ura referencia más precisa de cual es la situación actual y hacia donde se encaminan las necesidades prostodónticas de los pacientes geriátricos realizamos una revisión bibliográfica de las Iinvestigaciones realizadas a nivel nacional y en otros países. Y nos encontramos con que la información disponible no es todo lo completa que nos gustaría Como consecuencia de la mejora en la salud bucal de la poblacion se está produciendo una reducción en la pérdida de piezas dentarias, sin embargo el porcentaje de pacientes desdentados totales es alto y además una parte importante de ellos no está tratado en absoluto o lo está Insuficientemente Previsiblemente la población geriátrica será más sana, mejor educada, más exigente, con más recursos económicos, etc, esto ocasionará que sus demandas de tratamiento se amplíen hacia la cirugía preprotesica, los implantes y prótesis fija y decaerá el énfasis en el tratamiento con prótesis completas convencionales (AU)