Assessing peri-implant bone microarchitecture: conventional vs. osseodensification drilling - ex vivo analysis.

The aim was to evaluate primary implant stability and bone microarchitecture in two drilling situations, by comparing the conventional technique (CT) and osseodensification (OD) (Versah Burs - Jackson - Mississippi - USA). The implant insertion torque (IT), implant stability quotient (ISQ), and the peri-implant trabecular microstructure were assessed on bone fragments obtained from pig's tibia (n=12), divided between CT (n=6) and OD (n=6). After the drilling procedure, the implants were installed (3.5x8.5 mm, Epikut - SIN - São Paulo - Brazil). The IT and ISQ were measured using a digital torque wrench and resonance frequency analysis. Then, the bone fragments containing the implants were removed with a trephine and analyzed by Microtomography (µCT, 8.0 µm). The comparison between groups was performed using the unpaired t-test (α=0.05). The results revealed that OD promotes a higher insertion torque (CT: 7.67±2.44 Ncm; OD: 19.78±5.26 Ncm) (p=0.0005), although ISQ was not different (CT: 61.33±4.66; OD: 63.25±4.58) (p=0.48). There was a significant increase in peri-implant bone volume (CT: 23.17±3.39 mm3; OD: 32.01±5.75 mm3) (p=0.008), and trabecular parameters: separation (CT: 0.4357±0.03 mm; OD: 0.3865±0.04 mm) (p=0.0449), number (CT: 1.626±0.18 1/mm; OD: 1.946±0.13 1/mm) (p=0.007), and thickness (CT: 0.1130±0.009 mm; OD: 0.1328±0.015 mm) (p=0.02). Structure model index (SMI) data demonstrate no significant differences between groups (CT: 1.7±0.2; OD: 1.4±0.4) (p=0.12). In conclusion, OD increases the insertion torque values and promotes beneficial changes regarding bone microarchitecture compared with CT, revealing more peri-implant bone volume with consequent higher primary stability.

Assessing peri-implant bone microarchitecture: conventional vs. osseodensification drilling - ex vivo analysis

Abstract: The aim was to evaluate primary implant stability and bone microarchitecture in two drilling situations, by comparing the conventional technique (CT) and osseodensification (OD) (Versah Burs - Jackson - Mississippi - USA). The implant insertion torque (IT), implant stability quotient (ISQ), and the peri-implant trabecular microstructure were assessed on bone fragments obtained from pig's tibia (n=12), divided between CT (n=6) and OD (n=6). After the drilling procedure, the implants were installed (3.5x8.5 mm, Epikut - SIN - São Paulo - Brazil). The IT and ISQ were measured using a digital torque wrench and resonance frequency analysis. Then, the bone fragments containing the implants were removed with a trephine and analyzed by Microtomography (µCT, 8.0 µm). The comparison between groups was performed using the unpaired t-test (α=0.05). The results revealed that OD promotes a higher insertion torque (CT: 7.67±2.44 Ncm; OD: 19.78±5.26 Ncm) (p=0.0005), although ISQ was not different (CT: 61.33±4.66; OD: 63.25±4.58) (p=0.48). There was a significant increase in peri-implant bone volume (CT: 23.17±3.39 mm3; OD: 32.01±5.75 mm3) (p=0.008), and trabecular parameters: separation (CT: 0.4357±0.03 mm; OD: 0.3865±0.04 mm) (p=0.0449), number (CT: 1.626±0.18 1/mm; OD: 1.946±0.13 1/mm) (p=0.007), and thickness (CT: 0.1130±0.009 mm; OD: 0.1328±0.015 mm) (p=0.02). Structure model index (SMI) data demonstrate no significant differences between groups (CT: 1.7±0.2; OD: 1.4±0.4) (p=0.12). In conclusion, OD increases the insertion torque values and promotes beneficial changes regarding bone microarchitecture compared with CT, revealing more peri-implant bone volume with consequent higher primary stability.

Resumo O objetivo deste estudo foi avaliar a estabilidade de implante e a microarquitetura óssea em duas técnicas de fresagem, comparando a técnica convencional (CT) e a osseodensificação (OD) (Versah Burs - Jackson - Mississippi - EUA). O torque de inserção do implante (IT), quociente de estabilidade primária (ISQ) e a estrutura trabecular peri-implantar foram avaliados em fragmentos ósseos obtidos de tíbia de porco (n=12), divididos entre CT (n=6) e OD (n=6). Após o procedimento de fresagem, foram instalados implantes (3,5x8,5 mm, Epikut - SIN - São Paulo - Brasil). O IT e o ISQ foram aferidos por meio de um torquimetro digital e análise de frequência de ressonância. Em seguida, os fragmentos ósseos contendo os implantes foram removidos com trefina e analisados ​​por microtomografia computadorizada (µCT, 8,0 µm). A comparação entre os grupos foi realizada por meio do teste-t não-pareado (α=0.05). Os resultados revelaram que a OD promove maior torque de inserção (CT: 7,67 ± 2,44º Ncm; OD: 19,78 ± 5,26 Ncm) (p=0,0005), embora a estabilidade primária não tenha sido diferente (CT: 61.33 ± 4.66; OD:63.25 ± 4.58) (p=0,48). Houve um aumento significativo no volume ósseo peri-implantar (CT: 23,17±3,39 mm3; OD: 32,01±5,75 mm3) (p=0,0089) e parâmetros trabeculares: separação (CT: 0,4357 ± 0,03 mm; OD: 0,3865 ± 0,04 mm) (p=0,0449), número (CT: 1,626 ± 0,18 1/mm; OD: 1,946 ± 0,13 1/mm) (p=0,007) e espessura (CT: 0,1130 ± 0,009 mm; OD: 0,1328 ± 0,015 mm) (p=0,02) O índice de modelo estrutural (SMI) não demostrou diferença estatisticamente significativa (p=0.1228). Concluindo, OD apresenta maiores valores de torque de inserção e promove mudanças benéficas na microarquitetura óssea em comparação com a TC, revelando maior volume ósseo peri-implantar.

Microbiological analysis of bacterial sealing of internal conical implants with different taper angles.

The present study evaluated the effect of the taper angle of different internal conical connection implants and cyclic loading on the implant-abutment bacterial seal. A total of 96 implant-abutment sets were divided into eight groups. Four groups of different taper degrees with cyclic mechanical loading of 500,000 cycles per sample, with a 120-N load at 2 Hz before analysis [16DC (16-degree, cycled), 11.5DC (11.5-degree, cycled), 3DC (3- degree, cycled) and 4DC (4- degree, cycled)] were compared to four control groups without cyclic loading [16D (16-degree), 11.5D (11.5-degree), 3D (3-degree), and 4D (4-degree)]. Microbiological analysis was performed by immersing all samples in a suspension containing Escherichia coli and incubating them at 37°C. After 14 days, the presence of bacterial seals was evaluated. Fisher-Freeman-Halton exact tests and binomial tests were performed (5% significance level). The groups showed significant differences in bacterial seal, and mechanical load cycling improved the bacterial seal in the 3DC group. In all other groups, no significant differences in bacterial seal were found between cycled and uncycled samples. To conclude, the internal conical connection with a 3-degree taper angle showed better results than the other connection with different angles when subjected to load cycling. However, none of the angles tested were fully effective in sealing the implant-abutment interface.

Evaluation of the peri-implant tissues in the esthetic zone with prefabricated titanium or zirconia abutments: A randomized controlled clinical trial with a minimum follow-up of 7 years.

STATEMENT OF PROBLEM: Long-term clinical studies are lacking on the influence of the type of abutment, titanium or zirconia, on peri-implant tissues. PURPOSE: The purpose of this randomized clinical trial was to evaluate peri-implant tissues with titanium or zirconia abutments. MATERIAL AND METHODS: A total of 26 single-tooth implant-supported prostheses in 14 participants were analyzed. They received either a titanium abutment with a metal-ceramic crown (TAG) or a zirconia abutment with a ceramic crown (ZAG). Data were collected immediately, at 5 months, and at a minimum of 7 years after crown delivery. The success rate, plaque and bleeding indexes, bleeding on probing, white and pink esthetic scores, and the relationships of the gingival phenotype with the pink esthetic score were analyzed. Statistical analyses were conducted with the t test for paired and independent data (α=.05). RESULTS: The mean follow-up time was 95.2 ±2.6 months, showing an implant success rate of 96.7%. No statistically significant differences were found between TAG and ZAG among the time intervals evaluated for plaque or bleeding indexes (P>.05). A statistically significant difference was found for peri-implant probing depths in the mid-buccal sites between the groups at all the time intervals evaluated (TAG, P=.008; ZAG, P=.021): TAG showed an increase between 5 months (3.65 ±0.93 mm) and over 7 years (4.47 ±1.32 mm); and ZAG showed a reduction (5 months=5.22 ±1.71 mm; over 7 years=4.25 ±1.28 mm) in values. For the pink (PES) and white esthetic score (WES), ZAG (PES: immediately=6.33 ±1.41; 5 months=7.44 ±1.81; over 7 years=8.25 ±1.03; WES: immediately=7.67 ±1.50; over 7 years=8.38 ±0.74) showed higher mean values than TAG (PES: immediately=5.94 ±2.35; 5 months=6.53 ±2.15; over 7 years=7.44 ±1.81; WES: immediately=7.00 ±1.17; over 7 years=8.35 ±1.27) (P<.05). Statistically significant differences were found for gingival phenotype and for PES in TAG (P=.031), and the participants with thick phenotype showed higher PES in the 3 time intervals studied. CONCLUSIONS: Zirconia abutments exhibited better results than titanium abutments in terms of the peri-implant tissues. Moreover, in those with a thin phenotype, zirconia provided improved gingival esthetics.

Microbiological analysis of bacterial sealing of internal conical implants with different taper angles

Abstract The present study evaluated the effect of the taper angle of different internal conical connection implants and cyclic loading on the implant-abutment bacterial seal. A total of 96 implant-abutment sets were divided into eight groups. Four groups of different taper degrees with cyclic mechanical loading of 500,000 cycles per sample, with a 120-N load at 2 Hz before analysis [16DC (16-degree, cycled), 11.5DC (11.5-degree, cycled), 3DC (3- degree, cycled) and 4DC (4- degree, cycled)] were compared to four control groups without cyclic loading [16D (16-degree), 11.5D (11.5-degree), 3D (3-degree), and 4D (4-degree)]. Microbiological analysis was performed by immersing all samples in a suspension containing Escherichia coli and incubating them at 37°C. After 14 days, the presence of bacterial seals was evaluated. Fisher-Freeman-Halton exact tests and binomial tests were performed (5% significance level). The groups showed significant differences in bacterial seal, and mechanical load cycling improved the bacterial seal in the 3DC group. In all other groups, no significant differences in bacterial seal were found between cycled and uncycled samples. To conclude, the internal conical connection with a 3-degree taper angle showed better results than the other connection with different angles when subjected to load cycling. However, none of the angles tested were fully effective in sealing the implant-abutment interface.

A Comparative Histomorphometric Analysis of Two Biomaterials for Maxillary Sinus Augmentation: A Randomized Clinical, Crossover, and Split-Mouth Study.

Introduction: Considering oral rehabilitation with dental implants, many studies have aimed at improving bone regeneration through the use of biomaterials. Objective: This study aimed at comparing bone neoformation in patients undergoing bilateral maxillary sinus surgery with two bovine biomaterials. Materials and Methods: This is a randomized, blinded, clinical crossover, and divided mouth study. Ten participants with an indication of maxillary sinus enlargement were selected and underwent surgical treatment with Bio-Oss® graft biomaterial (graft 1) on one side and Lumina-Porous® graft biomaterial (graft 2) on the other. The samples were collected after nine months and fixed and then decalcified in 10% ethylenediamine tetra-acetic acid (EDTA) solution for 30 days to process and make histological slides. Connective and bone tissue were further analyzed to identify the amount of newly formed bone. Results: The graft 1 group had a greater formation of vital mineralized tissue when compared to the graft 2 group (p = 0.01). For nonvital mineralized tissue and amount of connective tissue, there was no statistical difference (p = 0.21 and p = 0.09, respectively). The medullary spaces were larger in the graft 2 group. The group treated with graft 1 presented a higher percentage of osteoclasts and viable osteocytes compared to the graft 2 group (p = 0.014 and p = 0.027, respectively). Conclusion: Every day, new alternative biomaterials are offered as an option in oral rehabilitation. In this study, both treatments induced bone neoformation after 9 months; however, the group treated with Bio-Oss® showed a higher percentage of vital mineralized bone tissue.

Bone and gingival tissue thicknesses of maxillary anterior teeth with and without a metal post: a cone beam computed tomographic study.

The objective of this retrospective study was to evaluate buccal bone and gingival thickness measurements obtained from cone beam computed tomographic (CBCT) images of maxillary anterior teeth with and without metal posts. A convenience sample of 71 CBCT images of healthy maxillary anterior teeth and 61 CBCT images of maxillary anterior teeth with a metal post were selected from a database. Eight tomographic measurements (4 bone thicknesses and 4 gingival thicknesses) were performed in the parasagittal section of each tooth, perpendicular to the tooth axis. The Mann-Whitney U test was used to compare these thicknesses, and the Spearman correlation coefficient was calculated for correlation of age with sex. Statistically significant differences were observed for almost all measurements (P < 0.05); the CBCT images of teeth with metal posts displayed lower bone thickness values and higher gingival thickness values. No statistically significant correlations were observed between the thickness measurements and age. However, significantly higher bone thickness values were observed in men (P < 0.05). Cone beam computed tomographic images of teeth with metal posts showed differences in mean bone and gingival measurements compared to teeth without metal posts, suggesting a possible interference of metal artifacts.

Artifacts caused by titanium implants in CBCT images of the mandible: an experimental study.

This study evaluated the quantity of metal artifacts produced by dental implants placed in different mandibular regions using various cone beam computed tomography (CBCT) protocols. Titanium implants were placed in 4 regions (incisor, canine, premolar, and molar) of an artificial mandible and subjected to CBCT examinations with the mandibular model placed in different positions within the field of view (FOV) and imaged with different FOV and voxel sizes. An axial section of the cervical region of each implant was selected for artifact quantification. The artifacts were measured by normalizing the actual standard deviation (ASD) of the voxel values. Kruskal-Wallis and Student-Newman-Keuls tests were used to compare the tooth regions and the different positions of the mandible. The Wilcoxon test was used to compare changes in FOV and voxel size. The intraobserver agreement was calculated using the intraclass correlation coefficient. The significance level was 5%. The incisor region showed significantly more artifacts than other regions (P = 0.0315). No statistically significant difference was found when the position of the mandible varied within the FOV (P = 0.7418). Smaller FOV and smaller voxels produced more artifacts (P < 0.0001). The quantity of metal artifacts was affected by FOV and voxel size as well as by anatomical region. Variation of the mandible location within the FOV did not affect the artifacts as defined by the normalized ASD of the voxel values.

Rehabilitation of Atrophic Maxilla With Immediate Loading of Extrasinus Zygomatic Implant.

ABSTRACT: The aim of this case series was to evaluate the long-term success rate of immediate occlusal loading of extrasinus zygomatic dental implants after a 3-year follow-up. The sample consisted of 31 patients (mean age of 64 years) with atrophic maxillae rehabilitated with 1 to 4 extrasinus zygomatic implants, placed unilaterally or bilaterally. All the patients received complete implant-supported dental prostheses with immediate loading by associating zygomatic implants with conventional implants. None of the procedures were associated with bone grafts. During the 3-year period of follow-up in the present study, all the patients attended clinical sessions and underwent radiographic exams every 6 months. In total 55 zygomatic and 69 conventional implants were placed, where 1 zygomatic and 2 conventional implants were lost, representing success rates of 98.18% and 97.20%, respectively. None of the studied patients had signs of sinusitis or changes in the maxillary sinuses. All the patients showed occlusal contact on natural antagonist teeth or implant-supported dental prostheses. Therefore, it was concluded that the use of exteriorized zygomatic implants with immediate loading represented a feasible option with high success rates for the treatment of atrophic maxilla.

Implant site preparation-related bone microdamage: An alternative ex vivo analysis of drilling speed protocols / Microdanos ósseos gerados na preparação do sítio de instalação de implantes: uma alternativa para análise ex vivo de diferentes protocolos de velocidade de perfuração

ABSTRACT Objective: The aim of this study was to evaluate bone microdamage in sites prepared for implant placement by using an ex vivo model with three drilling rotation speeds. Methods: Bovine bone ribs were used for the creation of 18 osteotomy sites at different rotation speeds: 1200 rpm, 800 rpm, and 400 rpm. Specimens were stained with xylenol orange and prepared for histological analysis by using fluorescence and polarized light microscopies. Bone microdamage was evaluated by number and based on total bone area, as follows: microfracture density (Fr.D = n/mm2), microcrack morphology (diffuse or linear), and density (Cr.D = n/mm2), and presence of bone chips. To complement the analysis, linear microcracks were assessed by using confocal microscopy for three-dimensional visualization. Results: Bone microdamage on the osteotomy sites included microcracks, diffuse damages, microfracture, and bone chip formation. There was an association between bone microdamage and cancellous bone (p 0.0016), as well as a positive correlation between Fr.D and Cr.D (p 0.05, r 0.54). BM occurrence was not different between the three rotation speeds. In 3D, the height of the microcrack depth was 60.81 µm. Conclusion: Bone microdamage occurs during osteotomy, and the ex vivo model used was effective for the assessment of these biomechanical parameters. In addition, microdamage was not influenced by the drilling rotation speed in this experimental condition.

RESUMO Objetivo: O objetivo desse estudo foi avaliar os microdanos ósseos em locais preparados para a instalação de implantes utilizando um modelo ex vivo acessando três velocidades de rotação de perfuração. Métodos: Fragmentos ósseos de costela bovina foram utilizados para a criação de 18 sítios de osteotomia em diferentes velocidades de rotação: 1200 rpm, 800 rpm e 400 rpm. As amostras foram coradas com Alaranjado de Xilenol e preparadas para análise microscópica em fluorescência e luz polarizada. Os microdanos ósseos foram avaliados em número e calibrados com base na área total óssea: densidade de microfraturas (Fr.D = n/mm2), morfologia (difusa ou linear) e densidade de microtrincas (Cr.D = n / mm2) e presença de espículas ósseas. Para complementar a análise, microtrincas lineares foram avaliadas por meio de microscopia confocal para visualização tridimensional. Resultados: Os microdanos ósseos incluíram microtrincas, danos difusos, microfraturas e formação de espículas. Houve uma associação entre MO e localização em osso esponjoso (p=0,0016), bem como uma correlação positiva entre Fr.D e Cr.D (p=0,05, r = 0,54). A ocorrência de microdanos ósseos não foi diferente entre as três velocidades de rotação utilizadas. Em 3D, a profundidade maior da microfissura atingiu 60,81 µm. Conclusão: Microdanos ósseos ocorrem durante a osteotomia e podem ser acessados em um modelo ex vivo na condução de experimentos em biomecânica. Sugere-se que a presença de microdanos não é influenciada pela velocidade de rotação durante a perfuração.

Biomechanical behavior of implants with prosthetic connection of the morse (Cone) type, with different angulations at the implant-abutment interface in multiple dental prostheses: a finite element study / Comportamento biomecânico de implantes com conexão protética tipo morse (cônica), com diferentes angulações na interface implante-pilar em próteses múltiplas: estudo de elementos finitos

ABSTRACT Objective: Evaluate the biomechanical behavior of the influence of different internal angles of conical prosthetic connections in fixed partial prostheses of three elements, through the tridimensional finite element method. Methods: Two different models of segment of the posterior portion of the mandible, with two implants with conical connections at angulations of 11.5 and 16 degrees. Afterwards, and occlusal load of 180N was used, and divided into 2 points of application on the premolar, and 400N divided into 5 points of application on the molar. Data were acquired as the tensile, compressive and shear stresses on cortical and medullary bone, and von Mises stresses on implants and prosthetic components of two implants in both in three-unit fixed partial prosthesis. In the quantitative analysis, both in cortical and medullary bone, the tension peaks in tensile, compression, and shear forces were higher for the CM16 group. Results: When analyzing qualitatively, the cortical and medullary bones presented a greater stress around the implant platform with a higher incidence in the implant in the molar region. In the von Misses analysis in both groups, the tensions were concentrated in the cervical region of the implants, in the first threads, in the premolar and molar regions. Regarding prosthetic pillars, the stress concentration was located in the region of contact with the implant. Conclusion: The increased angulation of conicity of the internal conical connections represents a determinant factor to increase in stress concentration in the implants, prosthetic components and adjacent structures, such as the cortical and medullary bone.

RESUMO Objetivo: Avaliar a influência das diferentes angulações internas de conexões protéticas cônicas em próteses parciais fixas de três elementos, em relação a distribuição de tensões no osso cortical e medular adjacente, também como nos implantes e componentes protéticos através do método dos elementos finitos. Métodos: Foram analisados de forma quantitativa e qualitativa, através do método de elementos finitos, as tensões de tração, compressão e cisalhamento no osso cortical e medular, e tensões de von Misses nos implantes e componentes protéticos de dois implantes, um com conexão cônica de 11.5 graus e o outro de 16 graus. Ambos em prótese múltipla de três elementos. Resultados: Na análise quantitativa, tanto no osso cortical quanto no medular, os picos de tensão nas forças de tração, compressão, e de cisalhamento foram maiores para o grupo CM16, se comparado ao CM11,5, exceto a força de cisalhamento do osso cortical, que obteve valores muito próximos em ambos os grupos. Ao se analisar qualitativamente, os ossos corticais e medulares apresentaram um maior stress ao redor da plataforma dos implantes com incidência maior no implante na região do molar. Na análise von Misses em ambos os grupos, as tensões concentraram-se na região cervical dos implantes, nas primeiras roscas, nas regiões de pré-molar e molar. No que diz respeito aos pilares protéticos, a concentração de tensões foi localizada na região de contato com o implante. Conclusão: Podemos concluir que conforme o ângulo da interface implante-pilar aumenta, ocorre uma incidência maior de tensões em todas as áreas envolvidas nesse estudo.

Biomechanical behavior of atrophic maxillary restorations using the all-on-four concept and long trans-sinus implants: A finite element analysis.

Background. Maxillary bone atrophy with a considerable amount of pneumatization and anterior expansion of the maxillary sinus might be a situation limiting oral rehabilitation with osseointegrated implants. Therefore, the present study aimed to biomechanically evaluate two rehabilitation techniques for maxillary bone atrophy: all-on-four and long trans-sinus implants. Methods. Two three-dimensional models consisting of atrophic maxilla with four implants were simulated. In the M1 model, two axially inserted anterior implants and two tilted implants, 15 mm in length, placed tangential to the maxillary sinus's anterior wall were used. In the M2 model, two axially inserted anterior implants and two trans-sinus tilted implants, 24 mm in length, were used. For the finite element analysis (FEA), an axial load of 100 N was applied on the entire extension of the prosthesis, simulating a rehabilitation with immediate loading. The peri-implant bone and the infrastructure were analyzed according to the Mohr-Coulomb and Rankine criteria, respectively. Results. The results were similar when the stresses on peri-implant bone were compared: 0.139 and 0.149 for models 1 and 2, respectively. The tension values were lower in the model with trans-sinus implants (27.99 MPa). Conclusion. It was concluded that the two techniques exhibited similar biomechanical behavior, suggesting that the use of long trans-sinus implants could be a new option for atrophic maxilla rehabilitation.

Clinical, Tomographic, and Histologic Evaluation of an Autogenous Bone Graft Harvested from the Maxillary Tuberosity for Guided Bone Regeneration: Case Report with a 4-Year Follow-up.

This report presents a case in which autogenous bone grafts were harvested from the maxillary tuberosity for guided bone regeneration and dental implant placement, with long-term follow-ups and assessment at the clinical, tomographic, and histologic levels. Particulate and block autogenous bone grafts were covered with a resorbable collagen membrane. Advanced bone remodeling and good bone quality, enabling dental implant placement, were observed after a short healing time (3 months). The differences in buccal bone plate thickness in the grafted area between the period immediately after implant placement and 4 years thereafter ranged from +0.879 mm to -0.001 mm. The implants osseointegrated uneventfully, and alveolar bone regeneration remained stable with a satisfactory result after 4 years.

Immediate three-dimensional changes in the oropharynx after different mandibular advancements in counterclockwise rotation orthognathic planning.

BACKGROUND: A retrospective cohort study was performed to evaluate the immediate effect on the oropharynx dimensions from different mandibular advancements in patients undergone counterclockwise rotation (CCW) of the maxillomandibular complex. MATERIAL AND METHODS: 138 CBCT images of patients, who had undergone orthognathic surgery, were identified from Dolphin Imaging archive according to pre- (T0) and post-operative (T1) times. Each pre-operative CBCT image was selected considering retrognathic mandible. Superimpositions of CBCT images were performed to measure mandibular advancement at B point in millimeters (mm) and divided into three groups: G1 (< 5 mm), G2 (between 5 and 10 mm) and G3 (> 10 mm). For evaluating oropharynx dimension at T0 and T1 for each group, medial sagittal area (MSA), volume, and minimum cross-sectional axial area (CSA) were measured on Dolphin Imaging. Pearson correlation verified reliability of method. Paired t-test were applied to compare values of measurements between T0 and T1 (p ≤ 0.05). RESULTS: 88 CBCT images were included. Method was reliable (r ≥ 0.93). According to MSA, volume and CSA values from G1, there was no significant difference between T0 and T1. CSA values presented significant difference comparing T0 and T1 in G2 (p ≤ 0.05). In subjects of G3, measurements increased in T1 significantly affecting oropharynx dimension. CONCLUSIONS: MSA, volume and CSA values showed a significant increase affecting upper airway in advancements higher than 10 mm. Mandibular advancement range showed different effects in the airway space and should be considered to achieve favorable post-operative results in the oropharynx dimensions. Key words:Retrognathia, orthognathic surgery, three-dimensional imaging, oropharynx, airway.

Influence of Surface Treatment of Lithium Disilicate on Roughness and Bond Strength.

PURPOSE: To evaluate the effect of different concentrations of hydrofluoric acid (HF) on the surface roughness of a ceramic reinforced by lithium disilicate and on the bond strength formed between the ceramic and self-adhesive resin cement. MATERIALS AND METHODS: A total of 100 disks of IPS e.max Press ceramic (Ivoclar Vivadent) reinforced by lithium disilicate were prepared as follows: group 1 remained untreated (control group); in groups 5-20, 5-40, and 5-60, the surfaces were etched with 5% HF for 20, 40, and 60 seconds, respectively; in groups 10-20, 10-40, and 10-60, the surfaces were etched with 10% HF for 20, 40, and 60 seconds, respectively; and in groups 10-20P, 10-40P, and 10-60P, the surfaces were etched with 10% HF for 20, 40, and 60 seconds, respectively, followed by treatment with 37% phosphoric acid for 5 seconds. Surface roughness and bond strength were analyzed with confocal microscopy and microshear testing, respectively. The values obtained were statistically analyzed using paired t test and two-way ANOVA followed by Tukey post hoc test at a 5% significance level. RESULTS: Surface roughness was influenced by the concentration and exposure time of acid applied (P < .05) and by the combination of these two factors (P < .05). Treatment with 10% HF for 40 seconds (group 10-40) achieved the highest roughness value. In contrast, bond strength was affected only by the acid exposure time (P < .05). CONCLUSION: Conditioning of lithium disilicate ceramics can change the surface morphology, thereby affecting bond strength with resin cement.

Neurosensory Function and Implant Survival Rate Following Implant Placement With or Without an Interposed Bone Graft Between the Implant and Nerve: Prospective Clinical Trial.

PURPOSE: This prospective clinical study evaluated the influence of an interposed bone graft with inferior alveolar nerve lateralization in terms of rates of sensory disturbance, mean sensation recovery time, and survival rates for placement of osseointegrated implants. MATERIALS AND METHODS: Patients with an atrophic posterior mandible were enrolled in this study and randomized into two groups: bone graft group (a bone graft was placed between the implant and inferior alveolar nerve after lateralization) and control group (implants were placed in direct contact with the inferior alveolar nerve after lateralization). Neurosensory disturbances were evaluated via questionnaire 1 week after surgery and at the end of each month during the first year after surgery. RESULTS: Eighty-two implants were placed, with a survival rate of 97.56%. Two implants were removed due to mandibular fracture. All patients reported initial sensory disturbances arising from the surgical procedure. In the control group, the mean time for recovery from sensory disturbance was 3.95 ± 2.33 months, compared with 4.11 ± 4.68 months in the bone graft group (P = .587). CONCLUSION: The interposition of a bone graft between implants and the inferior alveolar nerve after lateralization did not prevent sensory disturbances and did not influence the sensation recovery time or implant survival rates.

Marginal Bone Remodeling Around Dental Implants with Hexagon External Connection After 10 Years: A Case Series with 10 to 19 Years of Function.

Peri-implant bone remodeling occurs in all osseointegrated implants and can be defined as an adaptive process of bone around the implant in response to functional loading. This retrospective study evaluated the marginal bone remodeling around dental implants with external hexagonal connections in function for more than 10 years. The sample consisted of 17 implants placed in the posterior region of the mandible to replace one or several teeth. For all cases, the initial periapical radiograph was assessed together with a subsequent follow-up periapical radiograph. Image analysis was performed using ImageJ software to establish the initial bone measurements and subsequent bone loss. The data were statistically analyzed using paired t test at a significance level of 5%. There was significant bone remodeling when the baseline and follow-up were compared (P < .001). The mean values of peri-implant bone remodeling on the mesial aspect were 0.90 ± 0.63 mm vertically and 1.17 ± 0.60 mm horizontally. The distal aspect of the implants showed 1.01 ± 0.82 mm and 1.06 ± 0.75 mm of marginal bone remodeling vertically and horizontally, respectively. Within the limitations of this study, marginal bone remodeling was visible, and bone levels around the external hexagon implants remain stable after 10 years of function.

Fatigue Behavior of Different CAD/CAM Materials for Monolithic, Implant-Supported Molar Crowns.

PURPOSE: To evaluate the fracture resistance after the thermal and mechanical fatigue of feldspathic, lithium disilicate, and resin-modified CAD/CAM monolithic crowns cemented onto a universal post abutment. MATERIALS AND METHODS: A right second mandibular molar was designed in CAD/CAM software, and 30 crowns were machined using three different materials (n = 10): feldspathic ceramic, finished only with a glaze cycle (G1); lithium disilicate, sintered and finished with a glaze cycle (G2); and resin, modified by nanoceramic and finished with rubber (G3). All crowns were cemented under a constant 50 N load, the excess cement was removed, and the crowns were light-cured for 30 seconds. After being immersed in deionized water for 7 days, the crowns were submitted to thermal cycling, which consisted of varying the temperature from 2 to 50°C for 350,000 cycles, and mechanical cycling in a fatigue simulator, where a 250 N load was applied for 1,000,000 cycles at 2 Hz. The resistance of each crown was verified in a compression-to-failure test at 1 mm/min in a universal test machine. The groups were compared using one-way ANOVA with a Bonferroni post hoc test and Weibull statistics. RESULTS: The resin-modified group was the least resistant group (1755 ± 124 N), followed by the feldspathic (2147 ± 412 N) and lithium disilicate groups (2804 ± 303 N). The Weibull statistics demonstrated that lithium disilicate is the most reliable material and has the lowest fracture probability. CONCLUSIONS: It was possible to conclude that all of the tested CAD/CAM materials can be used as monolithic, implant-supported molar crowns.

Avaliação biomecânica da angulação dos implantes posteriores nas reabilitações totais implantossuportadas em mandíbula através de método de elementos finitos / Biomechanical evaluation of hindraft implant anglulation in total implant-su-pported mandible rehabilitations through finite element method

Introdução: Como uma opção de tratamento ao edentulismo mandibular foi desenvolvido o conceito All-on-4®, uma técnica de ancoragem com a instalação de quatro implantes distribuídos na região anterior da mandíbula edêntula para uma reabilitação total implantossuportada. Objetivo: Neste estudo, analisamos pelo método de elementos finitos o comportamento biomecânico dos implantes e tecidos ósseos. Material e métodos: Foram utilizados 3 modelos tridimensionais computadorizados, cada um com 4 implantes hexágono externo 3,75x13mm na região interforames mentuais, os implantes anteriores mantidos na posição axial e a variação ocorreu nos implantes posteriores: grupo 1, implantes posteriores retos; grupo 2, implantes posteriores com inclinação em 17° e grupo 3, com implantes posteriores inclinados em 30°. Uma carga axial de 150N foi aplicada nos molares e de 100N nos pré-molares bilateralmente. Resultados: Após análises evidenciou-se que nos grupos 17° (13,68Mpa, 34,76Mpa e 14,36Mpa para as tensões de tração, compressão e cisalhamento respectivamente) e 30° (14,26Mpa, 23,14Mpa e 10,31Mpa para as tensões de tração, compressão e cisalhamento respectivamente) apresentaram menores picos de tensão no osso. O mesmo padrão de distribuição de tensões foi observado para os implantes, com redução quando inclinamos os implantes distais. Conclusão: Os resultados mostraram que a angulação dos implantes favoreceu a distribuição das tensões no osso e implantes, interferindo positivamente na performance biomecânica das reabilitações totais implantossuportadas em mandíbulas edêntulas, considerando que no grupo dos implantes retos os valores das tensões foram maiores.

Introduction: As a treatment option for mandibular edentulism, the All-on-4® concept was developed, an anchoring technique with the installation of four implants distributed in the anterior region of the edentulous mandible for total implant-supported rehabilitation. Objective: In this study, we analyzed by the finite element method the biomechanical behavior of implants and bone tissues. Material and methods: Three computerized three-dimensional models were used, each with 4 external hexagon 3.75x13mm implants in the mental interforam region, the anterior implants kept in the axial position and the variation occurred in the posterior implants: group 1, straight posterior implants; group 2, posterior implants inclined at 17° and group 3, posterior implants inclined at 30°. An axial load of 150 N was applied to the molars and 100 N to the premolars bilaterally. Results: After analysis, it was found that in the 17° (13.68Mpa, 34.76Mpa and 14.36Mpa groups for tensile, compressive and shear stresses respectively) and 30 ° (14.26Mpa, 23.14Mpa and 10.31Mpa for tensile, compressive and shear stresses respectively) presented lower stress peaks in the bone. The same pattern of stress distribution was observed for the implants, with reduction when the distal implants were tilted. Conclusion: The results showed that the angulation of the implants favored the distribution of stresses in the bone and implants, positively interfering in the biomechanical performance of the total implant-supported rehabilitations in edentulous jaws, considering that in the group of straight implants the stress values were higher.

Effect of cavity-cleaning agents on shear bond strength between self-etching adhesives and dentin

Aim: The effect of cavity-cleaning agents on shear bonding strength between self-etching adhesives and dentin was evaluated. Methods: Twenty-five healthy human third molars were worn to obtain flat middle dentin. The samples were randomly divided into five groups according to the cleaning agent used: group CB not treated with any cavity disinfectants and served as control. Following groups, dentin surfaces were treated with 2% chlorhexidine (CHX group); 3% hydrogen peroxide (HP group); calcium hydroxide water (CH group); and 70% ethyl ethanol (E group). The dentin surfaces were cleaned by friction for 20 s and dentine bonding agent, Clearfil SE Bond, was applied. Cylinders (5.0 mm  1.2 mm, n = 19) of fluid composite resin were placed on the dentin surface, and the teeth were stored in deionized water at 37°C for 24 h. Subsequently, the samples were subjected to the shear bonding test, and the obtained values were subjected to one-way ANOVA and Tukey's test (α = 0.05). The failure pattern was analyzed descriptively by examining the specimens with a stereoscope at a magnification of 4, and failure was classified into adhesive, cohesive or mixed type. Results: Shear bonding was significantly lower in group HP (6.17 ± 5.69 MPa). The groups CB, CHX, CH and E were statiscally similar, 22.15 ± 6.54MPa; 18.40 ± 7.26MPa; 18.07 ± 5.98MPa ; 16.43 ± 6.19MPa respectively. The failure modes observed were only adhesive and mixed. Conclusion: The use of 2% chlorhexidine, calcium hydroxide water, and 70% ethyl ethanol did not negatively affect bond strength. Only 3% hydrogen peroxide is contraindicated as a cavity cleaner in adhesive restorative procedures when self-etching system is used