Complexos polieletrólitos de quitosana e xantana carregados com ativos naturais e sintéticos: estudo físico/químico e microbiológico para aplicação de drug delivery / Polyelectrolyte complexes of chitosan and xanthan loaded with natural and synthetic actives: physicochemical and microbiological study for drug delivery application

A eficácia dos implantes osseointegrados é amplamente reconhecida na literatura científica. Contudo, infiltrações bacterianas na junção implante-pilar podem desencadear inflamação nos tecidos circundantes, contribuindo para a evolução de condições mais sérias, como a peri-implantite. O objetivo desse estudo foi produzir complexos polieletrólitos (PECs) de quitosana (Q) e xantana (X) em forma de membranas, carregá-las com ativos naturais e sintéticos antimicrobianos, caracterizálas estruturalmente e avaliá-las frente a degradação enzimática, cinética de liberação e ações antimicrobianas com finalidade de aplicação para drug delivery. Membranas de QX a 1% (m/v) foram produzidas em três proporções, totalizando doze grupos experimentais: QX (1:1); QX (1:2), QX (2:1), QX-P (com própolis) (1:1); QX-P (1:2); QX-P (2:1); QX-C (com canela) (1:1); QX-C (1:2); QX-C (2:1) e CLX (com clorexidina 0,2%) (1:1); CLX (1:2); CLX (2:1). Para os estudos de caracterização foram feitas análises da espessura em estado seco; análises morfológicas superficial e transversal em Microscopia Eletrônica de Varredura (MEV); análise estrutural de espectroscopia de infravermelho por transformada de Fourier (FTIR); análise de degradação por perda de massa sob ação da enzima lisozima; e análise da cinética de liberação dos ativos em saliva artificial. Para os testes microbiológicos, análises de verificação de halo de inibição e ação antibiofilme foram feitas contra cepas de Staphylococcus aureus (S. aureus) e Escherichia coli (E. coli). Os resultados demonstraram que a espessura das membranas variou conforme a proporção, sendo que o grupo QX (1:2) apresentou a maior média de 1,022 mm ± 0,2, seguida respectivamente do QX (1:1) com 0,641 mm ± 0,1 e QX (2:1) com 0,249 mm ± 0,1. Nas imagens de MEV é possível observar uma maior presença de fibras, rugosidade e porosidade nos grupos QX (1:2) e QX (1:1) respectivamente, e, no QX (2:1) uma superfície mais lisa, uniforme e fina. No FTIR foram confirmados os picos característicos dos materiais isoladamente, além de observar as ligações iônicas que ocorreram para formação dos PECs. Na análise de degradação, os grupos com ativos naturais adicionados tiveram melhores taxas de sobrevida do que os grupos QX. No teste de liberação, os grupos QX-P tiveram uma cinética mais lenta que os QX-C, cuja liberação acumulada de 100% foi feita em 24 h. Já nos testes do halo inibitório, somente os grupos CLX tiveram ação sobre as duas cepas, e os QX-P tiveram sobre S. aureus. Nas análises antibiofilme, os grupos CLX apresentaram as maiores taxas de redução metabólica nas duas cepas (± 79%); os grupos QX-P apresentaram taxas de redução similares em ambas as cepas, porém com percentual um pouco maior para E. coli (60- 80%) e os grupos QX-C tiveram grande discrepância entre as duas cepas: de 35 a 70% para S. aureus e 14 a 19% para E. coli. Pode-se concluir que, frente as análises feitas, o comportamento do material foi afetado diretamente pelos ativos adicionados a matriz polimérica. As proporções de Q ou X afetaram somente a espessura final. Quanto a aplicação proposta de drug delivery, os dispositivos apresentaram grande potencial, principalmente os grupos CLX e QX-P. (AU)

The effectiveness of osseointegrated implants is widely recognized in scientific literature. However, bacterial infiltrations at the implant-abutment interface may trigger inflammation in surrounding tissues, contributing to the development of more serious conditions, such as peri-implantitis. The aim of this study was to produce chitosan (Q) and xanthan (X) polyelectrolyte complexes (PECs) in the form of membranes, load and evaluate them for enzymatic degradation, release kinetics, and antimicrobial actions for drug delivery applications. QX membranes at 1% (w/v) were produced in three proportions, totaling twelve experimental groups: QX (1:1), QX (1:2), QX (2:1), QX-P (with propolis) (1:1), QX-P (1:2), QX-P (2:1), QX-C (with cinnamon) (1:1), QX-C (1:2), QX-C (2:1), and CLX (with 0.2% chlorhexidine) (1:1), CLX (1:2), CLX (2:1). Characterization studies included analyses of dry state thickness, surface and crosssectional morphology using Scanning Electron Microscopy (SEM), structural analysis by Fourier Transform Infrared (FTIR) spectroscopy, mass loss degradation analysis under lysozyme action, and active release kinetics analysis in artificial saliva. Microbiological tests included verification analyses of inhibition halos and antibiofilm action against strains of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Results showed that membrane thickness varied according to proportion, with group QX (1:2) presenting the highest average of 1.022 mm ± 0.2, followed by QX (1:1) with 0.641 mm ± 0.1, and QX (2:1) with 0.249 mm ± 0.1. SEM images showed greater presence of fibers, roughness, and porosity in groups QX (1:2) and QX (1:1) respectively, while QX (2:1) exhibited a smoother, more uniform, and thinner surface. FTIR confirmed characteristic peaks of the materials individually, besides showing ionic bonds formed for PECs. Degradation analysis revealed that groups with added natural actives had better survival rates than QX groups. In release tests, QX-P groups exhibited slower kinetics than QX-C, with 100% cumulative release achieved in 24 h. inhibitory halo tests, only CLX groups exhibited action against both strains, while QX-P acted against S. aureus. Antibiofilm analyses showed CLX groups with the highest metabolic reduction rates in both strains (± 79%); QX-P groups showed similar reduction rates in both strains, slightly higher for E. coli (60-80%), and QX-C groups had a significant discrepancy between strains: 35-70% for S. aureus and 14-19% for E. coli. In conclusion, material behavior was directly affected by added actives to the polymeric matrix. Proportions of Q or X only affected final thickness. Regarding proposed drug delivery applications, the devices showed great potential, especially CLX and QX-P groups.(AU)

Comparación de las características anatómicas del conducto nasopalatino en pacientes dentados y desdentados mediante tomografía computarizada de haz cónico. Lima 2018-2020 / Comparison of the anatomic characteristics of the nasopalatine duct in toothed and edentulous patients by cone beam computed tomography. Lima 2018-2020

Objetivo : Comparar las características anatómicas del CNP en pacientes dentados y desdentados mediante Tomografía Computarizada de Haz Cónico (TCHC) del Servicio de Radiología Bucomaxilofacial realizadas en el Centro Dental Docente de la Universidad Peruana Cayetano Heredia. Material y métodos : Se evaluaron todas las TCHC adquiridas entre los años 2018 y 2020, que cumplan con ciertos criterios; donde se comparó las características anatómicas del CNP. Los datos fueron registrados en una base de datos, luego representados en tablas. Resultados : Se evaluaron 216 volúmenes tomográficos (VT), divididos en dos grupos: dentados y desdentados. La forma cilíndrica y la forma de canal único fueron las más encontradas en ambos grupos. La longitud y la distancia fueron mayores en pacientes dentados, no se encontró asociación con relación al diámetro; la inclinación fue mayor en pacientes desdentados, encontrándose asociación con relación a la inclinación entre los grupos comparados. Conclusiones : Se encontraron múltiples diferencias anatómicas del CNP entre los pacientes dentados y desdentados evaluados con TCHC con relación al sexo y la edad.

Objective : To compare the anatomical characteristics of the NPC in dentate and edentulous patients using Cone Beam Computed Tomography (CBCT) of the Bucomaxillofacial Radiology Service performed at the Centro Dental Docente of the Universidad Peruana Cayetano Heredia. Material and methods : All TCHC acquired between the years 2018 and 2020, which meet certain criteria, were evaluated; where the anatomicals characteristics of the CNP were compared. The data were recorded in a database, then represented in tables. Results : 216 tomographic volumes were evaluated, divided into two groups: dentate and edentulous. The single cylindrical shape and the single channel shape were the most found in both groups. The length and distance were greater in dentate patients, no association was found in relation to the diameter, the inclination was greater in edentulous patients, finding an association in relation to the inclination between the compared groups. Conclusions : Multiple anatomical differences of the CNP were found between the dentate and edentulous patients evaluated with TCHC in relation to sex and age.

The assessment of periimplant soft tissue condition with morse taper abutment connection: a rapid review

Aim: This study aims to evaluate the clinical assessment results of periimplant soft tissue with morse taper (internal abutment connection). Methods: The study was conducted using a rapid review by searching the articles from PubMed NCBI and Cochrane by using keywords. All articles were selected by the year, duplication, title, abstract, full-text, and finally, all selected articles were processed for final review. Following clinical parameters were included; Periimplant Probing Pocket Depth (PPD), Plaque Score (PS), modified Plaque Index (mPI), Mucosal Thickness (MTh), Gingival Height (GH), periimplant mucosal zenith, Pink Esthetic Score (PES), Bleeding On Probing (BOP), Sulcus Bleeding Index (SBI), and modified Gingival Index (mGI). Results: 9 selected articles were obtained from the initial literature searching count of 70 articles. The overall samples included 326 morse taper implants. Based on the evaluation, 3 out of 4 articles reported pocket depth < 4 mm, no bleeding was reported in 2 out of 4 articles. 4 out of 4 articles reported low plaque accumulation, low soft tissue recession was reported in 3 out of 3 articles, and 4 out of 4 articles reported acceptable PES values. Conclusion: The evaluations indicate that the morse taper (internal abutment connection) has favorable assessment results based on various clinical parameters

Analysis of the Mechanical Behavior and Effect of Cyclic Fatigue on the Implant-Abutment Interface / Análisis del comportamiento mecánico y efecto de la fatiga cíclica en la interface implante-pilar

ABSTRACT: Purpose: The seal of the interface formed at the implant-abutment connection is essential for the long-term success of the implant-supported restoration. The aim of this study was to analyze the mechanical behavior and the effect of cyclic fatigue before and after in the marginal fit of implant-abutment according to the manufacturing technique of the abutment. Materials and methods: Machined titanium abutments (DENTIS), cast abutments with Nickel-Chromium alloy (VeraBond II), and manufacturing custom milled Zirconia abutments (Zirkonzahn) were evaluated. The implant-abutment assemblies were subjected to cyclic loads of 133 N at a frequency of 19.1 Hz for 200,000 cycles. The microgap was measured using Scanning Electronic Microscope and the distribution of compressive stress by the three-dimensional Finite Element (FE) method. Results: The microgap measurement values of the machined abutments were 1.62μm and 1.92μm, cast abutments were 14.14 μm, and 28.44 μm, and the milled abutments were 14.18μm and 20.15μm before and after cyclic fatigue, respectively. Only the cast abutments and the machined abutments showed a statistically significant difference before and after cyclic fatigue (p≤0.05). The FE analysis showed that the critical areas of compressive stress were located at the implant-abutment connection, increasing in the cast abutments and decreasing in the milled and the machined abutments. Conclusion: Cyclic fatigue exerts an effect on the dimensions of the microgap at the implant-abutment interface before and after loading; this microgap depends of the type of abutment material and the manufacturing technique.

RESUMEN: Propósito: El sellado de la interface de la conexión implante-pilar es esencial para el éxito a largo plazo de la restauración implantosoportada. El objetivo de este estudio fue analizar el comportamiento mecánico y el efecto de la fatiga cíclica antes y después en el sellado de la conexión implante-pilar de acuerdo a la ténica de fabricación del pilar. Materiales y Métodos: Pilares mecanizados de titanio (DENTIS), pilares calcinables colados con aleación Niquel-Cromo (VeraBond II) y pilares fresados de Zirconia (Zirkonzahn) fueron evaluados. Los implantes y pilares atornillados se sometieron a una carga de 133 N a una frecuencia de 19.1 Hz durante 200 000 ciclos. El microgap fue medido con el Microscopio Electrónico de Barrido y la distribución del esfuerzo de compresión por el método tridimensional de Elemento Finito (EF). Los valores del microgap de los pilares mecanizados fueron de 1.62μm y 1.92μm, en los pilares calcinables fue de 14.14μm y 20.15μm, y los pilares fresados fue de 14.18μm y 28.44 μm antes y después de la fatiga cíclica, respectivamente. Los pilares calcinables y lo mecanizados mostraron diferencia estadísticamente significativa antes y después de la fatiga cíclica (p≤0.05). El análisis por EF mostró que las áreas críticas del esfuerzo de compresión estaban localizadas en la conexión implante-pilar, aumentando en los pilares calcinables y disminuyendo en los pilares fresados y en los mecanizados. Conclusión: La fatiga cíclica ejerce un efecto sobre las dimensiones del microgap en la interface implante-pilar antes y después de la carga cíclica; este microgap depende del tipo de material y de la técnica de fabricación del pilar.

Intermediarios protésicos en implantología oral. Revisión de la literatura / Prosthetic intermediaries in oral implantology: Literature review

Los intermediarios protésicos en implantología oral son los aditamentos que permiten la conexión entre el implante y la prótesis propiamente dicha. Aunque dicha rehabilitación posee una alta tasa de éxito, la selección del pilar protésico representa una fase importante en el tratamiento implantológico. Actualmente, existe una gran variedad de pilares intermediarios, que corresponden a las diversas técnicas y materiales. Los intermediarios protésicos se podrían clasificar según el tipo de conexión, su retención a la prótesis, su relación axial con el cuerpo del implante, su material de fabricación, su tipo de fabricación o si son para rehabilitación unitaria o múltiple. Esta situación puede generarle dudas al rehabilitador al momento de elegir los aditamentos implantológicos idóneos para cada caso en particular, lo que genera un escenario de dilema al seleccionar el aditamento protésico que permita lograr una rehabilitación satisfactoria: funcional, estética y que preserve los principios biológicos. En efecto, la implantología oral ha revolucionado la odontología y seguirá ampliando el abanico de posibilidades; por ello, es importante clasificar las opciones protésicas disponibles. La presente revisión de la literatura tiene como objetivo evidenciar las diferentes alternativas y opciones de pilares intermediarios más utilizados en prótesis sobre implantes. (AU)

Prosthetic intermediaries in oral implantology are attachments that allow connection between the implant and the prosthesis itself. Although this rehabilitation has a high success rate; the selection of the prosthetic abutment represents is important in implant treatment. Currently, there is a great variety of intermediate abutments, corresponding to various techniques and materials. Prosthetic intermediaries can be classified according to the type of connection, their retention to the prosthesis, their axial relationship with the implant body, the manufacturing material and type of manufacture, or whether rehabilitation is single or multiple. This scenario can lead to doubts as to the selection of the ideal implant attachment in each case in order to achieve satisfactory rehabilitation, as well as functional and aesthetic requirements and the preservation of biological principles. Indeed, oral implantology has revolutionized dentistry and will continue to expand the range of possibilities; therefore, it is important to classify the prosthetic options available. The present literature review aims to demonstrate the different alternatives and options available for the intermediate abutments most used in implant prostheses. (AU)

Internal and marginal fit and fracture strength of narrow diameter dental implant-abutment assembly

Abstract The aim of this study was to assess the internal and vertical marginal fit of metallic copings to abutments and the fracture strength of different narrow diameter dental implant/abutments, either submitted to thermomechanical cycling or not. Sixty-four implant/abutments (n=16) were divided into 4 groups according to diameter and abutment type: G3.5-UAC (morse taper implant Ø3.5mm + universal abutment with beveled chamfer finish); G2.9-UAS (morse taper implant Ø2.9mm + universal abutment with shoulder finish); G2.8-AA (morse taper friction implant Ø2.8mm + anatomical abutment) and G2.5-HP (one-piece implant Ø2.5mm with indexed hexagonal platform). Each group was divided into two subgroups (n=8): submitted and not submitted to thermomechanical cycling (TMC). To assess internal and vertical marginal fit of metallic copings, the assemblies were scanned using microtomography (micro-CT) (n=5). The samples were subjected to the compressive strength test on a universal test machine. Group G3.5-UAC showed the highest marginal misfit regardless of TMC (p<0.05). All other groups were similar after TMC. Group G2.8-AA showed the lowest internal misfit both with and without TMC (p<0.05). Group G2.8-AA showed the highest fracture strength, similar only to G2.5-HP without TMC and G3.5-UAC with TMC. The type of abutment affects the internal and marginal fit of metallic copings and the anatomical abutment led to the best internal and marginal coping fit. The narrow diameter dental implant/abutments differ in terms of fracture strength, the strongest assembly was that composed by implant of type V grade titanium without internal threads (friction implant).

Resumo O objetivo deste estudo foi avaliar a adaptação marginal e interna de cópings metálicos em pilares sobre implantes, e a resistência a fratura de diferentes conjuntos de implantes/pilares de diâmetro reduzido, submetidos à ciclagem termomecânica ou não. Sessenta e quatro implantes/pilares (n=16) foram divididos em 04 grupos de acordo com o tipo de pilar e diâmetro do implante: G3.5-UAC (implante cone morse Ø3.5mm + munhão universal com término em chanfro); G2.9-UAS (implante cone morse Ø2.9mm + munhão universal com término em ombro); G2.8-AA (implante cone morse friccional Ø2.8mm + munhão anatômico); e G2.5-HP (implante de corpo único de Ø2.5mm com plataforma hexagonal indexada). Cada grupo foi dividio em dois subgrupos (n=8): submetidos ou não à ciclagem termomecânica (TMC). As amostras foram escaneadas por microtomografia (micro-CT) para avaliar a adaptação interna e marginal vertical dos copings metálicos. As amostras foram submetidas à resistência à compressão em uma maquina de ensaios universal. O grupo G3.5-UAC apresentou os maiores valores de desadaptação marginal independentemente da TMC (p<0,05). Todos os outros grupos foram similares entre si após TMC. O grupo G2.8-AA demonstrou o menor desajuste interno independentemente de TMC (p<0,05). O grupo G2.8-AA demonstrou a maior resistência à fratura, similar apenas ao grupo G2.5-HP sem TMC e G3.5-UAC com TMC. O tipo de pilar influencia a adaptação interna e marginal vertical de copings metálicos. O grupo do pilar anatômico (sem entalhes na superfície) levou à melhor adaptação, enquanto o grupo com plataforma expandida hexagonal e os grupos com munhão universal (com entalhes na superfície) proporcionaram os maiores desajustes (especialmente com termino em chanfro). Os implantes/pilares de diâmetro reduzido diferem em termos de resistencia à fratura, sendo que o conjunto mais resistente foi aquele composto por titânio tipo V e sem roscas internas (implante friccional).

Three-dimensional misfit between Ti-Base abutments and implants evaluated by replica technique

Abstract An important factor affecting the biomechanical behavior of implant-supported reconstructions is the implant-abutment misfit. Objective: This study evaluated the misfit between Ti-Base abutments and implants by means of polyvinyl siloxane replica technique using microcomputed tomography (μCT). Methodology: Volumetric and linear (central and marginal) gaps of four Ti-base abutments (n=10/group): (i) Odontofix LTDA (OD), (ii) Singular Implants (SING), (iii) EFF Dental Components (EFF), and (iv) Control Group (S.I.N implants) compatible with an implant system (Strong SW, S.I.N Implants) were measured using μCT reconstructed polyvinyl siloxane replicas. Results: The results showed significantly lower volume gap for Control S.I.N (0.67±0.29 mm3) and SING (0.69±0.28 mm3) Ti-base abutments relative to OD (1.42±0.28 mm3) and EFF groups (1.04±0.28 mm3) (p<0.033), without significant difference between them (p=0.936). While gap values were homogenous in the central region, EFF presented a significantly higher marginal gap. Accordingly, the Control S.I.N and Singular Ti-base abutments showed improved volumetric and marginal fit relative to Odontofix and EFF. Conclusion: The method of manufacturing abutments influenced the misfit at the implant-abutment interface.

Failure probability, stress distribution and fracture analysis of experimental screw for micro conical abutment

Abstract The aim of this study was to evaluate the failure probability of two types of abutment screws after compressive load and to analyze the stress distribution with finite element method. Sixty (60) single-tooth implant restorations were assembled on titanium implants (e-fix, A.S. Technology - Titanium Fix). The groups were divided into Conventional screw (Screw neck 1.5 ø mm) and Experimental screw (Screw neck constricted with 1.2 ø mm). Specimens were subjected to single load to failure with compressive test according ISO 14801. The fractured specimens were subjected to stereomicroscopy for measurement of remaining screws inside the implant and characterization of fracture origin. Representative specimens were analyzed by scanning electronic microscopy. For finite element method (FEM), an identical 3D model of the two in vitro test groups were used with similar conditions (30º, 100 N load). The stress in the abutment screw was analyzed by von-Mises criteria. The results of strength means were 4132.5 ± 76 MPa and 4528.2 ± 127.2 for conventional and experimental groups, respectively. During microscopy, the mean (mm) of the remaining screw piece inside the implants were 0.97 ± 0.23 and 1.32 ± 0.12 for conventional and experimental groups, respectively. In FEM, the conventional group showed stress concentered in an unfavorable region (peak of 39.23 MPa), while the experimental group showed more stress areas but less concentration than the conventional group (36.6 MPa). In using the tested experimental geometry, the abutment screw can have its strength improved, and the origin of failure can be more favorable to clinical resolution.

Resumo O objetivo deste estudo foi avaliar a probabilidade de falha de dois tipos de parafusos para pilar protético após a compressão e analisar a distribuição da tensão com o método dos elementos finitos. Sessenta (60) restaurações unitárias foram montadas em implantes de titânio (e-fix, A.S. Technology - Titanium Fix). Os grupos foram divididos em parafusos convencionais (parafuso de pescoço 1,5 ø mm) e parafuso experimental (parafuso de pescoço estreitado com 1,2 ø mm). As amostras foram sujeitas ao teste de compressão de acordo com ISO 14801. Os espécimes fraturados foram submetidos a estereomicroscopia para a mensuração dos parafusos restantes dentro do implante e caracterização da origem da fratura. Os espécimes representativos foram analisados ​​por microscopia eletrônica de varredura. Para o método de elementos finitos (FEM), utilizou-se um modelo 3D idêntico dos dois grupos de teste in vitro com condições semelhantes (30º, 100 N). A tensão no parafuso do pilar foi analisada pelo critério de von-Mises. Os resultados de resistência a compressão foram 4132,5 ± 76 MPa e 4528,2 ± 127,2 para grupos convencionais e experimentais, respectivamente. Durante a microscopia, a média do remanescente do parafuso restante dentro dos implantes foi de 0,97 ± 0,23 e 1,32 ± 0,12 mm para os grupos convencionais e experimentais, respectivamente. Em FEM, o grupo convencional mostrou tensão concentrada em uma região desfavorável (pico de 39,23 MPa), enquanto o grupo experimental apresentou mais áreas de tensão, porém menor concentração do que o grupo convencional (36,6 MPa). Ao usar a geometria experimental testada, o parafuso do pilar pode ter sua resistência melhorada e a origem da falha pode ser mais favorável à resolução clínica.

Does the implant-abutment interface interfere on marginal bone loss? A systematic review and meta-analysis

Abstract The objective of this systematic review was to compare the conical internal connection (IC) with the external hexagonal connection (EH) on the occurrence of marginal bone loss (ΔMBL). Different databases were used to carry out the selection of the elected studies. The studies were judged according to the risk of bias as "high", "low" and "unclear" risk. For the meta-analysis we included only studies that could extract the data of ΔMBL, survival rate (SR) and probing depth (PD). No statistically significant differences were found for ΔMBL data at one, three- and five-year survival rates between implant connections (p <0.05), however statistically significant differences were found for PD between EH and IC implants (1-year follow-up) -0.53 [95%CI -0.82 to -0.24, p = 0.0004]. This present systematic review demonstrated that there are no significant differences between IC and EH implants for both ΔMBL and SR at 1, 3 e 5 years after functional loading, although better PD values were observed for implants pertaining to the IC connections. Considering the high heterogeneity, more well-delineated, randomized clinical trials should be conducted.

Morse taper performance: A finite element analysis study

OBJECTIVES: To evaluate and compare the magnitude and distribution of stresses generated on implants, abutments and first molar metal-ceramic crowns using finite element analysis. METHODS: Preliminary three-dimensional models were created using the computer-aided design software SolidWorks. Stress and strain values were observed for two distinct virtual models: model 1 - Morse taper and solid abutment; model 2 - Morse taper and abutment with screw. A load (250 N) was applied to a single point of the occlusal surface at 15° to the implant long axis. Von Mises stresses were recorded for both groups at four main points: 1) abutment-retaining screws; 2) abutment neck; 3) cervical bone area; 4) implant neck. RESULTS AND CONCLUSION: Model 1 showed a higher stress value (1477.5 MPa) at the abutment-retaining screw area than the stresses found in model 2 (1091.1 MPa for the same area). The cervical bone strain values did not exceed 105 µm for either model.

Bone level measurements around platform switched and platform matched implants: a comparative study

Background: The overall success of dental implants depends on the crestal bone support around the implants. During the initial years, the bone loss around the implants determines the success rate of treatment. Platform switching (PLS) preserves the crestal bone loss, and this approach must be applied clinically. Aim: The purpose of this study was to determine the changes in vertical and horizontal marginal bone levels in platform-switched and platform-matched dental implants. Materials and Methods: One fifty patients received one fifty dental implants in the present study over a 1-year period. Measurement was performed between the implant shoulder and the most apical and horizontal marginal defect by periapical radiographs to examine the changes of peri-implant alveolar bone before and 12 months after prosthodontic restoration delivery. Results: These marginal bone measurements showed a bone gain of 1.56 ± 2.4 mm in the vertical gap and 1.49 ± 2.24 mm in the horizontal gap of the platform matching, while in the PLS, a bone gain of 2.67 ± 2.0 mm in the vertical gap (P < 0.05) and 2.89 ± 1.67 mm in the horizontal gap was found. Only a statistically significant difference was found comparing bone gains in the vertical gap between the two groups (P < 0.05). Conclusion: PLS helps preserve crestal bone around the implants, and this concept should be followed when clinical situations in implant placement permit

Effect of initial placement level and wall thickness on maintenance of the marginal bone level in implants with a conical implant-abutment interface: a 5-year retrospective study

PURPOSE: Implant wall thickness and the height of the implant-abutment interface are known as factors that affect the distribution of stress on the marginal bone around the implant. The goal of this study was to evaluate the long-term effects of supracrestal implant placement and implant wall thickness on maintenance of the marginal bone level. METHODS: In this retrospective study, 101 patients with a single implant were divided into the following 4 groups according to the thickness of the implant wall and the initial implant placement level immediately after surgery: 0.75 mm wall thickness, epicrestal position; 0.95 mm wall thickness, epicrestal position; 0.75 mm wall thickness, supracrestal position; 0.95 mm wall thickness, supracrestal position. The marginal bone level change was assessed 1 day after implant placement, immediately after functional loading, and 1 to 5 years after prosthesis delivery. To compare the marginal bone level change, repeated-measures analysis of variance was used to evaluate the statistical significance of differences within groups and between groups over time. Pearson correlation coefficients were also calculated to analyze the correlation between implant placement level and bone loss. RESULTS: Statistically significant differences in bone loss among the 4 groups (P<0.01) and within each group over time (P<0.01) were observed. There was no significant difference between the groups with a wall thickness of 0.75 mm and 0.95 mm. In a multiple comparison, the groups with a supracrestal placement level showed greater bone loss than the epicrestal placement groups. In addition, a significant correlation between implant placement level and marginal bone loss was observed. CONCLUSIONS: The degree of bone resorption was significantly higher for implants with a supracrestal placement compared to those with an epicrestal placement.

Expert consensus on biomechanical research of dental implant / 华西口腔医学杂志

Current biomechanical research of dental implants focuses on the mechanical damage and enhancement mechanism of the implant-abutment interface as well as how to obtain better mechanical strength and longer fatigue life of dental implants. The mechanical properties of implants can be comprehensively evaluated by strain gauge analysis, photo elastic stress analysis, digital image correlation, finite element analysis, implant bone bonding strength test, and measurement of mechanical properties. Finite element analysis is the most common method for evaluating stress distribution in dental implants, and static pressure and fatigue tests are commonly used in mechanical strength test. This article reviews biomechanical research methods and evaluation indices of dental implants. Results provide methodology guidelines in the field of biomechanics by introducing principles, ranges of application, advantages, and limitations, thereby benefitting researchers in selecting suitable methods. The influencing factors of the experimental results are presented and discussed to provide implant design ideas for researchers.

Long-term Retrospective Clinical Study Comparing Submerged Type with External Hex Connection and Non-submerged Type with Internal Morse Taper Connection Implants

PURPOSE: This study was aimed to compare the survival and success rates, and long-term crestal bone loss according to the use of 2 connection types of dental implants (submerged-USII and non-submerged-SSII; Osstem Implant®) by analyzing the change in alveolar bone height after 1 year under load and during final follow-up period. MATERIALS AND METHODS: Between December 2004 and August 2008, patients with two types of Osstem implants (USII and SSII) were retrieved retrospectively. A total of 92 patients with 284 implants (USII=60, SSII=224) was finally selected. Their mean follow-up period was 7.5 years. The mesial and distal alveolar crestal bone changes were measured using radiographic images and the average was calculated at 1 year after loading and during final follow-up period. RESULT: Among the 284 implants, 4 USII and 7 SSII implants were removed, indicating 93.3% and 96.9% survival rates. Of the survived implants, mean crestal bone loss 1 year after loading was 0.39 mm for USII and 0.19 mm for SSII (P=0.018). During the final follow-up, mean crestal bone loss was 0.63 mm and 0.35 mm for USII and SSII, respectively, without statistical significance (P=0.092). According to the criteria for the success and failure of the implant by Albreksson and colleagues, final success rate was estimated as 86.7% for USII and 91.5% for SSII, respectively. CONCLUSION: At 1 year after loading, the average crestal bone loss was significantly different between USII and SSII; however, both types met the criteria for implant success. During the final follow-up, both groups showed insignificant bone resorption patterns and did not show any pathological clinical symptoms. Therefore, both implants exhibited high long-term stability.

Influence of implant-abutment connection structure on peri-implant bone level in a second molar: A 1-year randomized controlled trial

PURPOSE: This study aimed to evaluate the effect of two different implant-abutment connection structures with identical implant design on peri-implant bone level. MATERIALS AND METHODS: This clinical study was a patient-blind randomized controlled trial following the CONSORT 2010 checklists. This trial was conducted in 24 patients recruited between March 2013 and July 2015. Implants with internal friction connection were compared to those with external hex connection. One implant for each patient was installed, replacing the second molar. Implant-supported crowns were delivered at four months after implant insertion. Standardized periapical radiographs were taken at prosthesis delivery (baseline), and one year after delivery. On the radiographs, distance from implant shoulder to first bone-to-implant contact (DIB) and peri-implant area were measured, which were the primary and secondary outcome, respectively. RESULTS: Eleven external and eleven internal implants were analyzed. Mean changes of DIB from baseline to 1-year postloading were 0.59 (0.95) mm for the external and 0.01 (0.68) mm for the internal connection. Although no significant differences were found between the two groups, medium effect size was found in DIB between the connections (Cohen's d = 0.67). CONCLUSION: Considering the effect size in DIB, this study suggested the possibility of the internal friction connection structure for more effective preservation of marginal bone.

Influencia de parámetros de diseño sobre el comportamiento biomecánico de un implante dental corto / Influence of design parameters on the biomechanical behavior of a short dental implant

Introducción: Los implantes dentales deben transmitir esfuerzos al tejido óseo y generar deformaciones que favorezcan el equilibrio entre los procesos de formación y reabsorción ósea. Debido al alto número de pacientes que presentan maxilares con dimensiones reducidas, es necesario estudiar el comportamiento biomecánico de implantes dentales cortos. Objetivos: Evaluar el efecto de los parámetros de diseño: diámetro máximo, longitud de la interfaz hueso-implante y altura del filete de la rosca sobre el comportamiento biomecánico de un nuevo diseño de implante dental corto. Métodos: Los modelos tridimensionales del implante dental corto fueron creados usando el software Autodesk Inventor Profesional versión 2011 (Autodesk Inc, California, USA) y analizados con el software de elementos finitos Autodesk® Algor® Simulation (Autodesk Inc, California, USA). Resultados: Los niveles máximos de esfuerzos equivalentes de von Mises se obtuvieron, en el hueso cortical peri-implantar. Las cargas aplicadas al implante generaron, en el hueso trabecular peri-implantar, los mayores esfuerzos equivalentes de von Mises en la región apical y los menores valores en la región próxima al hueso cortical. Además, los mayores valores de deformación se obtuvieron en el hueso trabecular para todos los modelos estudiados. Conclusiones: En general, los resultados de las simulaciones mostraron que la mayoría de los modelos estudiados generan esfuerzos y deformaciones en el hueso cortical peri-implantar en niveles que estimulan el crecimiento y la remodelación ósea. No obstante, en algunas de las variantes simuladas se observaron niveles de esfuerzos y deformaciones, en zonas del hueso trabecular peri-implantar, que pueden provocar pérdida ósea en los maxilares. Las variables diámetro del implante y altura del filete de la rosca exhibieron la mayor influencia sobre los esfuerzos y deformaciones máximas generados en el tejido óseo(AU)

Introduction: Dental implants should transmit stresses to the bone tissue and generate strain levels that favor the balance between the bone formation and bone resorption processes. Due to the high number of patients with reduced jawbone dimensions, it is essential to study the biomechanical behavior of short dental implants. Objective: Evaluate the effect of the design parameters: Maximum diameter, Length of the bone-implant interface and Thread depth on the biomechanical behavior of a new design of short dental implant. Methods: The 3D models of the short dental implant were created using Autodesk Inventor Professional software (Autodesk Inc, California, USA) and analyzed by finite elements with Autodesk® Algor® Simulation software (Autodesk Inc, California, USA). Results: The maximum von Mises equivalent stress was obtained in peri-implant cortical bone. The loads applied to the implant generated in peri-implant cancellous bone, the highest von Mises equivalent stress in the lower end of the apical region and the lowest stress values in the region next to the cortical bone. In addition, the highest strain values were obtained in cancellous bone for all models under study. Conclusions: In general, the simulation results showed that most of the models under study generate stresses and strains in peri-implant cortical bone at levels that stimulate bone growth and bone remodeling. However, for some models, it was observed levels of stress and strain in peri-implant cancellous bone that could provoke the bone onset. The variables Implant diameter and Thread depth exhibited the greatest influence on the maximum stresses and strains obtained in the bone tissue(AU)

Evaluación biomecánica de una prótesis fija con conector no rígido, soportada por diente-implante con conexión hexágono interno y cono morse mediante el método de elementos finitos / Biomechanical evaluation of a fixed partial denture with a non-rigid connector supported by tooth implant with internal hexagon and Morse taper connection by means of finite element method

Objetivo: Comparar la máxima tensión en dos diseños que incluyen una prótesis fija soportada por diente e implante (PFDI) y conector no rígido (CNR) con dos tipos de conexiones de implante ­hexá- gono interno (HI) y cono Morse (CM)­ cuando son sometidos a una carga vertical de 300 N mediante el método de elementos finitos (MEF). Materiales y métodos: Se evaluaron 3 diseños con el MEF. Diseño 1: PFDI soportada por un segundo premolar y un implante en la posición 47 con conectores rígidos (CR), mediante un implante de conexión hexá- gono interno. Diseño 2: PFDI soportada por un segundo premolar y un implante en la posición 37, con CNR cerca al rete- nedor que va sobre el pilar, mediante un implante de conexión HI. Diseño 3: PFDI soportada por un segundo premolar y un implante en la posición de la pieza 37 con CNR, cerca al retenedor que va sobre el pilar, mediante un implante de cone- xión CM. Se aplicó una carga vertical de 300 N en los 3 diseños. También se consideró la fuerza de gravedad (9,8 N). Posteriormente, se evaluó la máxima tensión de Von Mises en los tres diseños. Resultados: En los diseños 1, 2 y 3, la máxima tensión de Von Mises en el hueso que rodea el implante fue de 2,43 MPa, 0,15 MPa y < 0,01 MPa, respectiva- mente. Conclusiones: La conexión CM es la más adecuada para los tipos de puentes que usan un CNR. (AU)

Objective: To compare the maximum equivalent von Mises yield in two models, including a tooth implant supported prosthesis (TISP) with nonrigid connector (NRC) with two types of implant connection [internal hexagon (IH) and Morse taper connection (MC)] when subjected to a vertical load of 300N using the finite element method (FEM). Materials and methods: Three models were evaluated using the FEM. Model 1: supported by a second premolar and one implant placed in position 47 with rigid connectors (RCs) using an IH connection implant. Model 2: TISP supported by a second premolar and an implant in position 37 with a NRC close to the retainer over the implant abutment, using an IH connection implant. Model 3: TISP supported by a second premolar and an implant in position 37 with NRC close to the retainer over the implant abutment, using a MC implant. A vertical load of 300N was applied to the three models. Force of gravity was also considered (9.8N). The maximum equivalent von Mises yield was then evaluated in each model. Results: The maximum equivalent von Mises yields in the bone surrounding the implant in models 1, 2 and 3 were as follows: 2.43 MPa, 0.15 MPa and <0.01 MPa, respectively. Conclusions: The MC is the most appropriate implant for these types of fixed partial NRC dentures. (AU)

Evaluación de la colonización bacteriana de la interfase implante-pilar en implantes de conexión interna: estudio piloto / Evaluation of bacterial colonization of the implant-abutment interface in implants with internal connection: pilot study

Introducción: la interfase implante-pilar da lugar a la formación de un espacio, cuyo tamaño varía de acuerdo a variables como las tolerancias de maquinado, los micro- movimientos, el tipo de fabricación de los aditamentos protésicos y el material de los mismos. Este espacio, en cercanía a los tejidos peri-implantares, es una oportunidad para la movilización de microorganismos de forma bidireccional, desencadenando eventualmente respuesta tisular. Objetivo: comparar la filtración de Echerichia coli (E. coli) en la interfase de implantes de conexión interna con pilares prefabricados y personalizados. Materiales y métodos: nueve implantes (Osseotite® Tapered Certain®, 3i Biomet) fueron divididos en tres grupos basados en el tipo de pilar utilizado. Grupo 1 pilares prefabricados Provide®, grupo 2 pilares personalizados Encode® Titanio, grupo 3 pilares personalizados Encode® Zirconia. Los pilares fueron conectados a los implantes y fueron ciclados según la norma ISO 14801:2007 (250.000 ciclos) en un dispositivo de carga dinámica. Fueron sumergidos en caldo infusión cerebro corazón (BHI) inoculado con E. coli. Se tomaron muestras y se midió la turbidez del medio. Se realizó test ANOVA para comparar el tamaño de la interfase implante-pilar. Resultados: se encontró que todas las muestras filtraron en diferentes proporciones. Conclusiones: todas las muestras mostraron filtración de E. coli.

Background: the implant-abutment interface leads to the formation of a space whose size varies according to different variables such as machining tolerances, micro-movements, the type of fabrication of prosthetic devices and the fabrication material. This space in close proximity to the peri-implant tissues is an opportunity for the colonization of microorganism bidirectionally, eventually triggering tissue response. Objective: to compare the filtration of Echerichia coli (E. coli) in the interface of implants of internal connection with prefabricated and customized abutments. Materials ands methods: nine implants (Osseotite® Tapered Certain®, 3i Biomet) were divided into three groups based on the type of abutment used. Group 1 prefabricated abutment Provide®, Group 2 customized abutment Encode® Titanium, Group 3 customized abutment Encode® Zirconia. The implants were connected to the abutments and cycled according to ISO 14801:2007 norm (250,000 cycles) in a dynamic loading device. They were immersed in brain heart infusion (BHI) medium inoculated with E. coli. Samples were taken and the turbidity of the medium was measured. An ANOVA test was performed to compare the size of the implant-abutment interface. Results: All samples were found to be colonized in different proportions. Conclusions: All samples showed E. coli colonization.

Comparison of marginal bone loss between internal- and external-connection dental implants in posterior areas without periodontal or peri-implant disease

PURPOSE: The purpose of this retrospective study with 4–12 years of follow-up was to compare the marginal bone loss (MBL) between external-connection (EC) and internal-connection (IC) dental implants in posterior areas without periodontal or peri-implant disease on the adjacent teeth or implants. Additional factors influencing MBL were also evaluated. METHODS: This retrospective study was performed using dental records and radiographic data obtained from patients who had undergone dental implant treatment in the posterior area from March 2006 to March 2007. All the implants that were included had follow-up periods of more than 4 years after loading and satisfied the implant success criteria, without any peri-implant or periodontal disease on the adjacent implants or teeth. They were divided into 2 groups: EC and IC. Subgroup comparisons were conducted according to splinting and the use of cement in the restorations. A statistical analysis was performed using the Mann-Whitney U test for comparisons between 2 groups and the Kruskal-Wallis test for comparisons among more than 2 groups. RESULTS: A total of 355 implants in 170 patients (206 EC and 149 IC) fulfilled the inclusion criteria and were analyzed in this study. The mean MBL was 0.47 mm and 0.15 mm in the EC and IC implants, respectively, which was a statistically significant difference (P < 0.001). Comparisons according to splinting (MBL of single implants: 0.34 mm, MBL of splinted implants: 0.31 mm, P=0.676) and cement use (MBL of cemented implants: 0.27 mm, MBL of non-cemented implants: 0.35 mm, P=0.178) showed no statistically significant differences in MBL, regardless of the implant connection type. CONCLUSIONS: IC implants showed a more favorable bone response regarding MBL in posterior areas without peri-implantitis or periodontal disease.

Digital evaluation of axial displacement by implant-abutment connection type: An in vitro study

PURPOSE: To measure axial displacement of different implant-abutment connection types and materials during screw tightening at the recommended torque by using a contact scanner for two-dimensional (2D) and three-dimensional (3D) analyses. MATERIALS AND METHODS: Twenty models of missing mandibular left second premolars were 3D-printed and implant fixtures were placed at the same position by using a surgical guide. External and internal fixtures were used. Three implant-abutment internal connection (INT) types and one implant-abutment external connection (EXT) type were prepared. Two of the INT types used titanium abutment and zirconia abutment; the other INT type was a customized abutment, fabricated by using a computer-controlled milling machine. The EXT type used titanium abutment. Screws were tightened at 10 N·cm, simulating hand tightening, and then at the manufacturers' recommended torque (30 N·cm) 10 min later. Abutments and adjacent teeth were subsequently scanned with a contact scanner for 2D and 3D analyses using a 3D inspection software. RESULTS: Significant differences were observed in axial displacement according to the type of implant-abutment connection (P < .001). Vertical displacement of abutments was greater than overall displacement, and significant differences in vertical and overall displacement were observed among the four connection types (P < .05). CONCLUSION: Displacement according to connection type and material should be considered in choosing an implant abutment. When adjusting a prosthesis, tightening the screw at the manufacturers' recommended torque is advisable, rather than the level of hand tightening.