An In Vitro Study of Retention and Marginal Adaptation of Endocrowns With Different Intracoronal Depths.

BACKGROUND: Marginal adaptation and retention of endocrowns are crucial for the success and survival of endocrowns. This study aimed to investigate the effect of different materials and intracoronal depth on the retention and marginal adaptation of CAD/CAM fabricated all-ceramic endocrowns. METHODS: Thirty-six mandibular premolar teeth with an average surface area of 64.49 mm2 were prepared to receive CAM/CAM fabricated endocrowns. Samples were divided randomly and equally into groups of lithium disilicate with 2 mm intracoronal depth (LD2), lithium disilicate with 4 mm intracoronal depth (LD4), polymer infiltrated ceramic network with 2 mm intracoronal depth (PICN2) and polymer infiltrated ceramic network with 4 mm intracoronal depth (PICN4). All endocrowns were cemented using ParaCore resin cement with 14N pressure and cured for 20 seconds. Fifty measurements of absolute marginal discrepancy (AMD) were done using a stereomicroscope after cementation. After 24 hours, all samples were subjected to thermocycling before the retention test. This involved using a universal testing machine with a crosshead speed of 0.5 mm/min and applying a load of 500N. The maximum force to detach the crown was recorded in newtons and the mode of failure was identified. RESULTS: Two-way ANOVA revealed that the AMD for PICN was statistically significantly better than lithium disilicate (p=0.01). No statistically significant difference was detected in the AMD between the two intracoronal depths (p=0.72). PICN and endocrowns with 4 mm intracoronal depth had statistically significant better retention (p<0.05). 72.22% of the sample suffered from cohesive failures and 10 LD endocrowns suffered adhesive failures. CONCLUSIONS: Within the limitations of this study, we found that different materials and intracoronal depths can indeed influence the retention of CAD/CAM fabricated endocrowns. Based on the controlled setting findings, PICN was found to have better retention and better marginal adaptation than similar lithium disilicate premolar endocrowns.

An In Vitro Evaluation of Periotest Implant Stability Measurements Taken on Implant Retained Crowns and Healing Abutments.

OBJECTIVE: To assess the reliability of implant stability measurements recorded with the Periotest device and to investigate the differences in values when these measurements were taken on implant retained crowns and healing abutments. MATERIALS AND METHODS: Fifty-six implants in eight synthetic bone blocks were used to carry out implant stability measurements using the Periotest device by two different operators. Each block constituted an example of bone of density D1, D2, D3, or D4, and two blocks of each density were used. The healing abutments placed were of a height to allow approximately 6 mm of the implant-abutment complex to be supracrestal and temporary crowns were made to match the dimensions of an average central incisor. Descriptive statistics were used to describe the perio test values (PTVs) at each of the different heights on the implant abutments and implant crowns. Means for each site were calculated and distribution of data assessed using the Kruskal Wallis test. The interclass correlation coefficient (ICC) was used to determine the relationship between the PTVs recorded on the implant abutments and implant crowns. RESULTS: The mean PTV (±standard devidation) recorded across all sites was 5.57 ± 11.643 on the implant abutments, and 12.27 ± 11.735 on the temporary crowns. Excellent/good inter-operator ICCs were recorded for the mid-abutment site in all bone blocks D1-D4 (ICC = 0.814, p < 0.001, ICC = 0.922, p < 0.001, ICC = 0.938, p < 0.001, ICC = 776, p < 0.001). For mid crown sites, ICC between operators was excellent/good only for recordings in D2 bone (ICC = 0.897, p < 0.001). CONCLUSIONS: Periotest device seems to be able to reliably measure implant stability across all types of bones when the implant stability is assessed at approximately 3 mm coronal to the implant platform for abutments and 4.5 mm for implant supported single crowns.

Influence of torque and bone type on stability quotient of two implant platforms: a clinical trial.

The objective of this study was to analyze the influence of insertion torque, bone type, and peri-implant bone loss on implant stability quotient (ISQ) of cylindrical external hexagon (EH) and Morse Taper (MT) implants. Forty-four single implants were placed in the edentulous areas of 20 patients who met the inclusion and exclusion criteria. Immediately after implant placement (t1) and after osseointegration (four and six months for mandible and maxilla, respectively) (t2), insertion torque, resonance frequency, and peri-implant bone loss were measured using probing depths and digital periapical radiography. A significant difference was noted in the ISQ values between t1 and t2 in type III bone for EH and MT implants. No significant difference in bone loss values was observed when comparing bone types for EH or MT in all evaluated sites. Based on marginal bone loss assessed using radiography, there was no significant difference between the MT and EH groups. A positive correlation between torque and ISQ t1 value was observed for MT (correlation: 0.439; p = 0.041) and EH (correlation: 0.461; p = 0.031) implants. For EH and MT implants, the greater the insertion torque, the greater was the ISQ value (moderately positive correlation). A weak negative correlation was found between bone type and ISQ t1 for MT implants. Contrarily, no correlation was observed between bone type and ISQ t1 for EH implants. In all cases, bone loss around the implants was clinically normal.

Influence of pretreating radicular dentin with different polyacrylic acids and isopropanol on the retention of posts.

STATEMENT OF PROBLEM: The optimal pretreatment of radicular dentin before cementing a post with glass ionomer cement is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the retention of prefabricated tapered titanium posts to endodontically treated teeth after applying different pretreatment protocols on the radicular dentin. MATERIAL AND METHODS: The coronal part of 32 single-rooted human teeth was removed 1-mm coronally to the cemento-enamel junction. All specimens received endodontic treatment, and the root canals were prepared with an instrument to a depth of 10 mm to receive a titanium post. The dentin walls of each specimen were roughened with a hand-held diamond cutting instrument. The specimens were randomly divided according to the surface treatments into 4 groups (n=8): KW: etched with 20% to 30% polyacrylic acid (PAA) (Ketac Conditioner) and rinsed with water; KWI: etched with 20% to 30% PAA, rinsed with water and 70% isopropanol; DW: etched with 30% to 50% PAA (Durelon Liquid) and rinsed with water; DWI: etched with 30% to 50% PAA, rinsed with water and 70% isopropanol. The prefabricated titanium posts were airborne-particle abraded and cemented with glass ionomer cement. The specimens were fixed in custom-made brass cylindrical holders with autopolymerizing acrylic resin with the holder parallel to the long axis of the post. All specimens were stored in water for 3 days at 37 °C. Retention was evaluated using a tensile test with a universal testing machine (Zwick Z010) at a crosshead speed of 2 mm/min. Data were statistically analyzed with a 1-way ANOVA, followed by the Tukey post hoc test for pairwise comparisons between groups (α=.05). RESULTS: Mean ±standard deviation retention values ranged from 201.8 ±55.5 N (KW) to 328.1 ±70.9 N (DWI). Groups DWI and KWI (316 ±58.3 N) showed statistically higher retention values than group KW (P<.05) but did not significantly differ from retention values obtained in group DW (P>.05). CONCLUSIONS: An additional final rinse with isopropanol after using PAA increased the retention of the post significantly for all groups. Although group DWI achieved the highest retention values, pretreatment of radicular dentin as in group KWI may also be considered.

Estudio in vitro del ajuste de supraestructuras pasivadas sobre implantes múltiples / In vitro study of the adjustment of passivated suprastructures on multiple implants

Objetivo: Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para co- nectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos: A partir de un modelo maes- tro que representa un maxilar desdentado con cuatro implan- tes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilla- das al modelo maestro. Su desajuste inicial se analizó utili- zando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un pro- cedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructu- ra metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significa- ción fue establecido en p<0,05. Resultados: El Grupo I tuvo un desajuste inicial de 97,30±13,81µm y el Grupo II de 98,53±11,24µm. Luego de la soldadura, el Grupo I registró 98,53±17,17µm, 1,23µm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61µm, 4,60µm por encima del original. Se analizaron mediante prue- ba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se ob- servaron diferencias no significativas, p=0,41 y p=0,38 res- pectivamente (AU)

Aim: Compare two conventional welding procedures us- ing a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods: From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master mod- el. Its initial mismatch was analyzed using a stereoscop- ic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statisti- cally. The level of significance was established at p<0.05. Results: Group I had an initial mismatch of 97.30 ±13.81µm, and Group II of 98.53±11.24µm. After welding, Group I registered 98.53±17.17µm, 1.23µm higher than the initial one. In Group II, 103.13±17.61µm was observed, 4.60µm above the original. They were analyzed using Stu- dent's t test; in both cases the result was p>0.05. When com- paring groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions: Under the conditions of this study, it was ob- served that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit (AU)

Techniques for locating the screw access hole in cement-retained implant-supported prostheses: A systematic review.

STATEMENT OF PROBLEM: Different techniques for retrieving cement-retained implant-supported prostheses have been described to minimize damage to the prostheses. Nevertheless, a classification of the described techniques remains ambiguous. PURPOSE: The purpose of this systematic review was to review and classify the described techniques for recording and locating the screw access hole in cement-retained implant-supported prostheses. MATERIAL AND METHODS: A bibliographic search was completed on MEDLINE/PubMed, Web of Science, Scopus, and Cochrane databases. A manual search was also conducted. The articles that described or evaluated techniques for recording and locating the screw access hole of cement-retained implant-supported prostheses were included. Two investigators independently assessed the quality assessment of the studies using the Revised Cochrane risk of bias tool for randomized trials. A third examiner was consulted to resolve the lack of consensus. RESULTS: A total of 30 articles were included. The different methods were classified according to whether the screw access hole location was registered before or after cementation. The precementation techniques were classified into 4 subgroups: identification marks, photographic records, digital files, and precementation screw access hole location guides. The postcementation techniques were subdivided into 2 subgroups: radiographic records and postcementation screw access hole location guides. CONCLUSIONS: Different techniques have been proposed to facilitate the location of the screw access hole in cement-retained implant-supported restorations. Although the evidence is scarce, studies seem to ascertain that some techniques, such as the use of drilling guides, orientation with cone beam computed tomography images, or holes made in the metal framework, can increase the retrievability of cement-retained implant-supported prostheses and decrease complications in the location of the screw access hole. The proposed classification summarizes precementation and postcementation techniques and provides a tool to decide the most suitable for each specific clinical situation.

Screwmentable implant-supported prostheses: A systematic review.

STATEMENT OF PROBLEM: Screwmentable prostheses were developed to combine the benefits of screw retention and cement retention. However, data are limited on the clinical performance of this type of prosthesis. PURPOSE: The purpose of this systematic review was to collect scientific evidence on screwmentable prostheses and evaluate their long-term clinical behavior. MATERIAL AND METHODS: An electronic search was conducted by 2 independent reviewers for articles published in scientific dental journals in English from 2004 to April 2020. The search strategy followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Inclusion criteria were scientific studies concerning the screwmentable type of prosthesis. RESULTS: The search provided 494 records. Of these, 24 studies fulfilled the inclusion criteria and were included in the review. The included articles presented significant heterogeneity concerning the manufacturing process and the materials used. One randomized clinical trial, 2 prospective clinical studies, 14 in vitro studies, 3 protocol descriptions, 1 case series, and 3 case reports were included. CONCLUSIONS: Based on the systematic search of the literature, it is concluded that the screwmentable prosthesis combines advantages of both cement-retained and screw-retained restorations, including passive fit, retrievability, excess cement control, tissue-friendly emergence profile, and improved esthetics. Nevertheless, data from well-designed clinical trials are limited, and further research is required to provide evidence on their long-term clinical behavior.

The effect of different cleansing methods for removing temporary cement on the tensile bond force of permanently cemented implant-supported metal copings: An in vitro study.

OBJECTIVES: Complete cleaning of temporary cement before permanent cementation of cement-retained implant-supported prosthesis (CISP) when recementing the crown is critical. This study evaluated the effect of different cleaning methods for removing traces of temporary cement on the final tensile bond force (TBF) of CISP recemented with resin cement. MATERIALS AND METHODS: Seventy computer-aided design/computer-aided manufacturing metal implant-supported copings were prepared and distributed into seven groups (N = 10). Copings of six groups (60 samples) were cemented with temporary cement with eugenol and subjected to 5000 thermocycling. After debonding by a universal testing machine, the internal surfaces of the copings were cleaned using one of the six following methods: 1-an ultrasonic water bath (UW), 2-sandblasting, then washing with water (SW), 3-sandblasting and an ultrasonic water bath (SUW), 4-an ultrasonic isopropyl alcohol bath (UA), 5-sandblasting, then washing with isopropyl alcohol (SA) or 6-sandblasting and an ultrasonic isopropyl alcohol bath (SUA). Then the subjects were subsequently cemented by dual-cure self-adhesive resin cement. In the seventh group (control, N = 10), the copings were cemented by dual-cure self-adhesive resin cement without the temporization phase. The TBF was tested using a universal testing machine with a cross-head speed of 1 mm/min. Two-way analysis of variance (ANOVA) and post-hoc Tamhane tests were used for statistical analysis at a significance level of α = .05. RESULTS: The maximum mean of TBF value was observed in SUA group (845 ± 203 N), and the minimum was observed in the temporary cement group (49 ± 20 N). All groups which were cleaned with isopropyl alcohol showed significantly higher TBF values compared with those cleaned with water. CONCLUSIONS: Cleaning of the inner surface of metal copings after debonding with sandblasting and isopropyl alcohol results in the highest value of TBF by eliminating the effect of remaining eugenol and removing traces of temporary cements.

Evaluation of Retention Forces of Implant-Supported Zirconia Copings on Titanium Abutments Coated with Metal Opaquers Using Different Cements.

PURPOSE: To evaluate the use of a new resin metal opaquer on the surface of titanium abutments, in combination with two luting agents, and its effect on the retentive strength of implant-supported zirconia copings. MATERIALS AND METHODS: Sixty customized titanium abutments were designed and fabricated with virtual design software and a milling machine. Thirty abutment specimens were coated with metal opaquers, and the others were not coated. Then, the titanium abutments were fitted into the implant analogs, and the abutment-implant analog complexes were embedded in acrylic resin blocks. Sixty CAD/CAM-fabricated zirconia copings were seated on the abutments and secured with glassionomer cement or self-adhesive resin cement. The specimens were stored in 100% humidity for 1 hour and artificial saliva for 23 hours at 37°C before thermocycling for 5,000 cycles of 5°C to 55°C with a 30-second dwell time. The retentive strength was measured using a pull-out test with a universal testing machine. The dislodgment forces were statistically analyzed via two-way analysis of variance (ANOVA). The failure modes were evaluated and categorized by examining the fracture surface. RESULTS: The metal opaquer material had a significant negative effect on retention of zirconia copings. The nonopaquer titanium abutments showed significantly (P < .05) higher retentive strength than the metal opaquer abutments. Comparing the cements, the retentive strength values of self-adhesive resin cement were significantly higher than those of glass-ionomer cement. The metal opaquer groups exhibited mostly mixed-type failures, a combination of adhesive failures and cohesive failures, whereas the nonopaquer groups showed mostly adhesive-type failures. CONCLUSION: The titanium abutments coated with the new metal opaquer material resulted in a reduction of retentive strength. Self-adhesive resin cements exhibited significantly higher retention than glass-ionomer cements.

The effects of provisional resin cements on the color and retentive strength of all-ceramic restorations cemented on customized zirconia abutments.

This study aimed to evaluate the effects of two types of provisional resin cements on the color and retentive strength of two different all-ceramic restorations cemented onto customized zirconia abutments. Forty-two crowns were made of monolithic zirconia and lithium disilicate ceramics (n = 21 per group) and cemented on customized zirconia abutments by using two provisional resin cements of TempBond Clear and Implantlink Semi, and TempBond serving as the control (n = 7 per cement subgroup). The specimens' color was measured before and after cementation and after thermocycling. The color difference was calculated by using CIEDE2000 formula (ΔE00). The tensile force was applied to assess the retentive strength. Kruskal-Wallis, Dunn's post-hoc, and Mann-Whitney non-parametric tests were used to compare ΔE00(1) and ΔE00(2) and two-way ANOVA followed by one-way ANOVA and Tukey's HSD post hoc test and T-test were used to compare retentive strength between subgroups. In the lithium disilicate group, ΔE00 of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi cements subgroup (P = 0.001). But, in the monolithic zirconia group, ΔE00 of the control subgroup (TempBond) was significantly higher than that of Implantlink Semi (P = 0.020) and TempBond Clear cements (P = 0.007). In the monolithic zirconia group, the control subgroup (TempBond) was significantly more retentive than TempBond Clear (P = 0.003) and Implantlink Semi cement (P = 0.001). However, in the lithium disilicate group, Implantlink Semi cement was significantly more retentive than TempBond Clear (P = 0.019) and TempBond (control) (P = 0.001). The final color of both restorations was significantly affected by the provisional resin cement type. The retentive strength was influenced by both the type of cement and ceramic.

Consensos referidos a conceptos rehabilitadores en la enseñanza de la odontología. Parte I: conceptos generales y diseño de la prótesis parcial removible / Consensus referring rehabilitative concepts in the teaching of dentistry. Part I: general concepts and design of removable partial prosthesis

En este artículo se desarrolla el consenso alcanzado entre profesores, referido a los conceptos generales, componentes y la secuencia del diseño de la prótesis parcial removible, durante la formación del odontó-logo en el ámbito de la Facultad de Odontología de la Universidad de Buenos Aires (AU)

This article develops the consensus between professors on the general concepts, components, and the sequence of the design of the partial removable prosthesis during the training of the dentist in the field of the Faculty of Dentistry of the University of Buenos Aires (AU)

Confección de prótesis de carga inmediata mediante barras articuladas: componentes, modo de uso y longitud de la barra en función de la localización / Fabrication of immediately loaded prostheses using articulated bars: components, method of use and bar length depending on the location

En la implantología actual, la confección de prótesis de carga inmediata se ha convertido en un procedi-miento de rutina. Contar con elementos pre-formados con un correcto ajuste al implante o transepitelial so-bre el que se trabaja, minimiza el tiempo de trabajo sin renunciar a la eficiencia. En el presente trabajo se muestran elementos preformados articulados para la realización de prótesis de carga inmediata y su forma de uso, así como un análisis biomecánico de las estructuras para conocer su repercusión en las distintas fuerzas recibidas durante la masticación. Resultados: Al aplicar la carga en la zona central de la barra (paralela a los implantes), la tensión máxima recibida en la zona correspondiente al extremo de la barra sufre variaciones importantes, desde 128 Mpa en la longitud de 13 mm hasta un máximo de 391 Mpa (megapascales) en la longitud de 5 mm, siendo la ten-sión máxima, media para todas las medidas, de 242 Mpa (+/-96,76). En el ensayo de las diferentes medi-das de la barra se observa también una tensión cre-ciente para longitudes de barra a partir de 7 mm, al aplicar la tensión en la zona media de la estructura, por lo que longitudes entre 5 y 7 mm pueden consi-derarse prácticamente con la misma distribución de tensiones hacia los extremos y en la zona de unión. En conclusión, las barras articuladas son un elemento de confección de prótesis provisionales de carga in-mediata de gran utilidad, que pueden confeccionarse de forma rápida y generan un comportamiento bio-mecánico predecible (AU)

In current implantology, the fabrication of immediately loaded prostheses has become a routine procedure. Being able to have pre-formed elements with a correct fit to the implant or transepithelial on which we are working minimizes working time without sacrificing efficiency. Material and methods: We show articulated preformed elements for immediate loading prostheses and how they are used, as well as a biomechanical analysis of the structures to determine their repercussion on the different forces received during mastication. Results: When the load is applied in the central area of the bar (parallel to the implants) the maximum stress received in the area corresponding to the end of the bar undergoes significant variations, from 128 Mpa in the 13 mm length to a maximum of 391 Mpa in the 5 mm length, the average maximum stress for all the measurements being 242 Mpa (+/-96.76). In the test of the different bar sizes we can also observe an increasing stress for bar lengths from 7 mm onwards when applying the stress in the middle zone of the structure, so that lengths between 5 and 7 mm can be considered to have practically the same stress distribution towards the ends and in the joint zone. Conclusions: Hinged bars are a very useful fabrication element for immediately loaded provisional prostheses, which can be fabricated quickly and generate a predictable biomechanical behavior (AU)

Coronas cementadas comparado con coronas atornilladas para pacientes con restauraciones fijas implantosoportadas / Cement-retained versus screw-retained crowns in patients with implant rehabilitation

RESUMEN: Introducción: Los implantes dentales se han transformado en una opción de tratamiento de suma relevancia para pacientes parcial o totalmente desdentados. El éxito del tratamiento puede verse afectado por la elección del tipo de retención de estos (cementada o atornillada). A pesar que ambas presentan ventajas, aún no existe consenso sobre el mejor tipo de retención para restauraciones fijas implantosoportadas. Métodos: Realizamos una búsqueda en Epistemonikos, la mayor base de datos de revisiones sistemáticas en salud, la cual es mantenida mediante el cribado de múltiples fuentes de información, incluyendo MEDLINE, EMBASE, Cochrane, entre otras. Extrajimos los datos desde las revisiones identificadas, analizamos los datos de los estudios primarios, realizamos un metanálisis y preparamos una tabla de resumen de los resultados utilizando el método GRADE. Resultados y conclusiones: Identificamos 14 revisiones sistemáticas que en conjunto incluyeron 43 estudios primarios, de los cuales cinco corresponden a ensayos aleatorizados. De estos, solamente dos ensayos responden a la pregunta de interés de manera directa. Concluimos que las coronas atornilladas podrían aumentar levemente el riesgo de pérdida de implante a largo plazo, podrían resultar en nula o poca diferencia en el riesgo de pérdida de implante a mediano plazo, reabsorción ósea y periimplantitis, pero la certeza de evidencia ha sido evaluada como baja. Por otro lado, no es posible establecer con claridad si las coronas cementadas disminuyen el riesgo de complicaciones estéticas y protésicas, ya que la certeza de la evidencia existente ha sido evaluada como muy baja.

ABSTRACT: Introduction: Dental implants have become a highly relevant treatment option for partially or totally edentulous patients. Implant retention systems (cemented or screwed) can influence the treatment success. Although both have advantages, there is still no consensus on the best type of retention for implant-supported fixed restorations. Methods: We searched in Epistemonikos, the largest database of systematic reviews in health, which is maintained by screening multiple information sources, including MEDLINE, EMBASE, Cochrane, among others. We extracted data from the systematic reviews, reanalyzed data of primary studies, conducted a meta-analysis and generated a summary of findings table using the GRADE approach. Results and conclusions: We identified 14 systematic reviews including 43 primary studies overall, of which five were randomized trials. Of these, only two trials answer the question of interest. We concluded that screw-retained crowns may increase long-term implant loss, may make little or no difference in the risk of medium-term implant loss, bone resorption, and peri-implantitis, but the certainty of the evidence has been assessed as low. On the other hand, it is not possible to clearly establish whether cemented crowns reduce the risk of cosmetic and prosthetic complications, since the certainty of the evidence has been assessed as very low.

Retention of luting agents used for implant-supported restorations: A comparative In-Vitro study.

AIMS: The aim of this study was to compare the retention of different luting agents used with implant-supported restorations. MATERIALS AND METHODS: A total of 90 custom metal frameworks and copings were prepared and divided into six different luting agent groups (n = 15/group): polycarboxylate cement (PC), resin-modified glass-ionomer cement (RMGIC), two self-adhesive resin cements (SARC), copper-ion zinc-phosphate cement (CZPC), and non-eugenol temporary resin cement (TRC). After sandblasting with 50 µm Al2O3, the copings were cemented on frameworks and stored in artificial saliva for 48 h at 37°C and thermocycled between 5-55°C for 37,500 cycles. Samples were subjected to tensile testing by a universal testing machine, and data were statistically analyzed. RESULTS: The differences between the retention values of types of cement were significant (P < 0.05). The maximum retention value was calculated for CZPC (755,12 ± 55 MPa) while the lowest value was for TRC (311,7 ± 61 Mpa). CONCLUSION: Neither of the tested cement had superiority over another to ensuring retention. The types of cement presented were meant to be a discretionary guide for the clinician in deciding the amount of the desired retention between castings and abutments.

Prótesis sobre implantes: ¿atornillada o cementada? / Implant supported prosthesis: screw retained or bonded?

El objetivo de este artículo es revisar la evidencia científica existente acerca de los tipos de retención protética fija sobre implantes: atornillada, cementada y cemento-atornillada. Fueron evaluadas sus ventajas y desventajas a fin de facilitar al clínico la elección del sistema de retención en el tratamiento rehabilitador con implantes. Si bien la evidencia científica no es concluyente, la prótesis atornillada presentaría más complicaciones técnicas, y las cementadas, más complicaciones biológicas. Por ello, las prótesis cemento-atornilladas podrían ser en la actualidad una opción de elección, por su versatilidad en la rehabilitación implanto-soportada, combinando las ventajas de cada tipo de retención (AU)

The objective of this article is to review the existing scientific evidence about the different types of retention of fixed prosthetic on implants: screwed, cemented and cement-screwed. The advantages and disadvantages of them were evaluated in order to facilitate the clinician's choice of the retention system in the rehabilitation treatment with implants. Although the scientific evidence is inconclusive, the screwed prosthesis would present more technical complications, while the cemented, more biological complications. Therefore, cement-screwed prostheses could be an option of choice, due to their versatility when rehabilitating an implant, combining the advantages of each type of retention (AU)

[Comparison of flow conditions of adhesives and retention force of restorations among four cement-retained methods of implant-supported fixed prostheses].

Objective: To compare the effect on the flow conditions of adhesives and the retention force of restorations among different cement-retained methods of implant-supported fixed prostheses. Methods: Four common cement-retained methods were selected, including the occlusal hole for screw access (OH), the lingual hole for adhesives overflow (LH), the resin replica for titanium abutment (RR), and the traditional cement-retained method (the control group). The adhesive used in this study was resin-modified glass ionomer cement. The two-dimensional analysis models of computational fluid dynamics (CFD) were established. The flow conditions of adhesives in the adhesion process was analyzed by the CFD analysis. The internal filling ratio and the amount of neck overflow of adhesives below the edge of the prosthesis were calculated. Ten zirconia prostheses in each group were processed and cemented. The retention force was examined by mechanical tensile experiments in vitro. Results: The CFD analysis showed the internal filling ratio of adhesives from high to low was the LH group, the OH group, the RR group and the control group. The amount of neck overflow of adhesives below the edge of the prosthesis from less to more was the RR group, the OH group, the LH group and the control group. The retention force was (240.7±33.9) N in the control group, (278.2±59.1) N in the OH group, (292.9±47.9) N in the LH group, and (262.8±59.4) N in the RR group. There was a statistically significant difference in the retention force between the LH group and the control group (P=0.029). There was no significant difference among the other groups (P>0.05). Conclusions: The modified cement-retained methods can effectively reduce the amount of neck overflow of adhesives, and improve the filling condition of adhesive in the adhesive clearance to ensure the retention force of the prostheses. Clinically, the appropriate modified cement-retained method should be selected according to the three-dimensional position of the implant and the position of prosthetic margin.

A Simplified Technique to Control Excess Cement Material Underneath Cement-Retained Implant Restorations: Technical Note.

Subgingival presence of remaining excess cement may lead to implant complications and failures. This is a technical report and advice on how to cement implant-supported restorations using a simple and universal method applying liquid petroleum jelly to the peri-implant sulcus after cementation. This simple and user-friendly method eliminates excess cement and should be used in the daily practice.

Effect of the Unfilled Space Size of the Abutment Screw Access Hole on the Extruded Excess Cement and Retention of Single Implant Zirconia Crowns.

PURPOSE: To evaluate in vitro the effect of the size of the unfilled space of the abutment screw access hole on the amount of extruded excess cement and the retention of zirconia copings. MATERIALS AND METHODS: Twelve dental implant replicas were attached to the corresponding abutments and embedded in acrylic resin blocks. A total of 36 CAD/CAM zirconia copings were fabricated by one technician using the standard technique. Abutments were divided into group I: the entire screw access channel was completely filled (nonspaced); group II: 1-mm-spaced; and group III: 2-mm-spaced. The copings were air-abraded and temporarily cemented under constant load of 60 N for 10 minutes. The excess cement was calculated as the difference between the post-cementation and post-excess-removal weights using a digital scale. Retention test was performed by a universal testing machine at a 0.5 mm/min crosshead speed. The ultimate force and tensile strength required for separation were recorded. One-way ANOVA and Tukey's test were used for statistical analysis at p ˂ 0.05. RESULTS: The average amount of extruded cement in groups 1, 2, and 3 was 33.48 ± 1.55, 23.05 ± 5.48, and 15.58 ± 5.98 mg, respectively. Multiple comparisons showed significant differences in the amount of extruded excess cement between the three groups (p ˂ 0.001). The maximum load at decementation in groups 1, 2, and 3 was 98.8, 87.5, and 88.6 N, respectively. Groups 1, 2, and 3 separated at 6.90 ± 1.2, 6.12 ± 0.7, and 6.21 ± 0.9 MPa, respectively, with no significant differences between them. CONCLUSIONS: The amount of extruded excess cement was reduced by more than half when a 2-mm space of the screw access hole was left unfilled in comparison to the nonspaced counterpart. The retention of zirconia copings was not affected by the reported technique.

In Vitro Evaluation of Cell Compatibility of Dental Cements Used with Titanium Implant Components.

PURPOSE: To evaluate the biocompatibility of five dental cement compositions after directly exposing human gingival fibroblast (HGF) and MC3T3-E1 preosteoblast cells to cement alone and cement applied on commercially pure titanium (cpTi) specimens. MATERIALS AND METHODS: Nanostructurally integrated bioceramic (NIB), resin (R), resin-modified glass ionomer (RMGIC), zinc oxide eugenol (ZOE), and zinc phosphate (ZP) compositions were prepared according to the respective manufacturer's instructions. Samples were prepared in cylindrical Teflon molds or applied over the entire surface of polished cpTi discs. All samples were cured for 0.5, 1, 12, or 24 hours post-mixing. Direct contact testing was conducted according to ISO 10993 by seeding 6-well plates at 350,000 cells/well. Plates were incubated at 37°C in a humidified atmosphere with 5% CO2 for 24 hours before individually plating samples and cpTi control discs. Plates were then incubated for an additional 24 hours. Microtetrazolium (MTT) cell viability assays were used to measure sample cytotoxicity. RESULTS: For samples that cured for 24 hours prior to direct contact exposure, only NIB and ZP cements when cemented on cpTi demonstrated cell viability percentages above the minimum biocompatibility requirement (≥70%) for both the investigative cell lines. R, RMGIC, and ZOE cements exhibited moderate to severe cytotoxic effects on both cell lines in direct contact and when cemented on cpTi specimens. For HGF cells, ZOE cemented-cpTi specimens exhibited significantly decreased cytotoxicity, whereas RMGIC cemented-cpTi specimens exhibited significantly increased cytotoxicity. CONCLUSIONS: Despite previous studies that showed enhanced cpTi corrosion activity for fluoride-containing compositions (NIB and ZP), there was no significant difference in cytotoxicity between cement alone and cemented-cpTi. In general, the MC3T3-E1 preosteoblast cells were more sensitive than HGF cells to cement composition. Ultimately, cement composition played a significant role in maintaining host cell compatibility. Results of this work help illustrate the impact of different cement formulations on host cell health and emphasize the need for understanding material properties when selecting certain formulations of dental cements, which can ultimately influence the survival of dental implant systems.

The Effect of Milling Metal Versus Milling Wax on Implant Framework Retention and Adaptation.

PURPOSE: The metal framework of implant-supported restorations can be made using different methods. For a successful outcome, the acceptability of each method depends on the retention and fit of the restoration. The aim of this study was to evaluate and compare the retention and adaptation of copings fabricated using two methods: casting wax patterns made by computer-aided design/computer-aided manufacturing (CAD/CAM) technology, and milling sintered chromium-cobalt (Cr-Co) blocks. MATERIALS AND METHODS: Twenty-four abutment analogs (height, 5.5 mm) were divided into two groups according to the framework fabrication method. In one group, wax patterns were prepared using a CAM milling machine, and they were cast with a Ni-Cr-Ti metal alloy. In the second group, the copings were milled from Cr-Co blocks using a CAD/CAM milling machine. All copings were equal in contour, thickness, and internal relief and were seated on the abutment analogs after the necessary adjustments. The vertical marginal discrepancy was investigated using a silicone replica method and stereomicroscope with 75× magnification. After copings were cemented onto the abutment analogs using zinc phosphate, a tensile resistance test was performed using a universal testing machine. Mann-Whitney U and Student's t-test were used for statistical analyses at a significance level of 0.05. RESULTS: An independent sample t-test revealed a significant difference between the two groups for retention (p = 0.010), and the milled wax group showed higher tensile resistance compared with the milled metal group. There was also a significant difference between the two groups in marginal discrepancy (p < 0.001), with a larger marginal gap in the milled metal group compared with the milled wax group. The milled metal copings required more adjustments to fit on the abutment analogs compared with the wax milled copings (p < 0.001). CONCLUSIONS: The CAD/CAM technique for wax milling resulted in more retentive copings with better marginal and internal adaptations compared with milling the metal blocks.