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.

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 Modified Technique for Induced Gingival Growth Around Compromised Teeth Prior to Implant Placement: A Report of Two Cases.

Regenerative and reconstructive periodontal plastic surgery are important options for treating marginal tissue recession and can be indicated for root coverage or periodontal procedures prior to implant placement. Among the available procedures, periodontal flaps with subepithelial connective tissue graft (CTG) is the most common treatment option to achieve proper tissue manipulation. The present study proposes a modification of a previous technique for inducing spontaneous gingival growth around teeth that will be extracted prior to implant placement, through successive reduction of the buccal root surface. This successive reduction of root surfaces is performed with diamond burs, and such reductions create space for the gingival tissue to grow coronally by reducing root convexity and, consequently, stimulating the healing process with the formation of granulation tissue that will then differentiate into keratinized tissue. The presented technique is suggested to improve the esthetic outcomes for cases involving tooth extraction, implant placement in the extraction socket, and immediate loading with interim restoration and CTG.

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.

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.

Comparative Clinical Study Using Short and Conventional Implants in Bilateral Jaw Posteriors.

The aim of this study was to clinically and radiographically compare extra short and standards implants. Forty-two implants were installed in 10 selected patients. They received prosthetic loading only after the conventional waiting time for osseointegration and the prostheses were made ferulized. Radiographic shots were performed to evaluate vertical and horizontal bone losses at times T1 (prosthetic installation), T2 (6 months follow-up) and T3 (12 months follow-up). Biological parameters such as bone level around the implants (CBL) were evaluated, CBL alteration (CBLC), total crown length (TCL) and implant/crown ratio (ICR) were digitally calculated. All implants included in the study were submitted to the analysis of the implant stability quotient (ISQ) at the time of implant installation (T0) and at 12 months of prosthetic function (T3). Data were statistically tested. The ICR was higher in the test group than in the control group (p<0.0001). The CBL measurements at the beginning of the study were 0.21±0.19 mm and 0.32±0.38 mm and at 12 months 0.65±0.24 mm and 0.87±0.34 mm, respectively in the test and control groups. CBLCs and CBL were similar at all times (p>0.05). No correlation was found between CBLC and ICR parameters, as well as between ISQ and implant length. We may conclude that standards and extra short implants can provide similar clinical results in prosthetic rehabilitation of the atrophic jaw over 12 months of follow-up.

Comparative clinical study using short and conventional implants in bilateral jaw posteriors

Abstract The aim of this study was to clinically and radiographically compare extra short and standards implants. Forty-two implants were installed in 10 selected patients. They received prosthetic loading only after the conventional waiting time for osseointegration and the prostheses were made ferulized. Radiographic shots were performed to evaluate vertical and horizontal bone losses at times T1 (prosthetic installation), T2 (6 months follow-up) and T3 (12 months follow-up). Biological parameters such as bone level around the implants (CBL) were evaluated, CBL alteration (CBLC), total crown length (TCL) and implant/crown ratio (ICR) were digitally calculated. All implants included in the study were submitted to the analysis of the implant stability quotient (ISQ) at the time of implant installation (T0) and at 12 months of prosthetic function (T3). Data were statistically tested. The ICR was higher in the test group than in the control group (p<0.0001). The CBL measurements at the beginning of the study were 0.21±0.19 mm and 0.32±0.38 mm and at 12 months 0.65±0.24 mm and 0.87±0.34 mm, respectively in the test and control groups. CBLCs and CBL were similar at all times (p>0.05). No correlation was found between CBLC and ICR parameters, as well as between ISQ and implant length. We may conclude that standards and extra short implants can provide similar clinical results in prosthetic rehabilitation of the atrophic jaw over 12 months of follow-up.

Resumo O objetivo deste estudo foi comparar clínica e radiograficamente implantes extra curtos e padrões. Quarenta e dois implantes foram instalados em 10 pacientes selecionados. Eles receberam carga protética somente após o tempo de espera convencional para a osseointegração e as próteses foram feitas ferulizadas. As imagens radiográficas foram realizadas para avaliar as perdas ósseas verticais e horizontais nos tempos T1 (instalação protética), T2 (6 meses de acompanhamento) e T3 (12 meses de acompanhamento). Parâmetros biológicos como nível ósseo ao redor dos implantes (CBL) foram avaliados, alteração CBL (CBLC), comprimento total da coroa (TCL) e relação implante / coroa (ICR) foram calculados digitalmente. Todos os implantes incluídos no estudo foram submetidos à análise do quociente de estabilidade do implante (ISQ) no momento da instalação do implante (T0) e aos 12 meses de função protética (T3). Os dados foram testados estatisticamente. A ICR foi maior no grupo teste do que no grupo controle (p<0,0001). As medidas de CBL no início do estudo foram de 0,21±0,19 mm e 0,32±0,38 mm e em 12 meses 0,65±0,24 mm e 0,87±0,34 mm, respectivamente nos grupos teste e controle. CBLCs e CBL foram semelhantes em todos os momentos (p>0,05). Não foi encontrada correlação entre os parâmetros CBLC e ICR, bem como entre o ISQ e o comprimento do implante. Podemos concluir que padrões e implantes extra curtos podem fornecer resultados clínicos semelhantes na reabilitação protética da mandíbula atrófica ao longo de 12 meses de acompanhamento.

Three-dimensional finite element analysis of two angled narrow-diameter implant designs for an all-on-4 prosthesis.

STATEMENT OF PROBLEM: Although the concept of angulated dental implants has been used for the rehabilitation of the completely edentulous maxilla, its use has yet to be validated with narrow-diameter implants. Proper estimation of narrow-diameter implant dimensions and angulations is essential for the correct use of these implants. PURPOSE: The purpose of this 3D finite element analysis study was to compare the stress levels and distributions of 2 narrow-diameter angled implant arrangements supporting a maxillary fixed complete prosthesis. MATERIAL AND METHODS: Two commercially available narrow-diameter implants (3.5×11.5 mm, Unitite Prime; 2.9×11.5 mm, Unitite Slim) were compared for their performances under axial and oblique loading (masticatory force: 100 N) in simulated situations of all-on-4 treatment (2 parallel anterior implants perpendicular to the bone crest and 2 posterior implants angled at 30 degrees). An edentulous maxilla model generated from computed tomography and a prosthesis parametric computer-aided design (CAD) model were combined with computational models of implants and prosthetic components to represent implant-supported maxillary fixed complete prostheses. A condition of complete osseointegration was assumed. Peri-implant bone was analyzed by the Mohr-Coulomb criterion. Implants, abutments, and screws were analyzed by the von Mises criterion, and frameworks by the Rankine criterion. RESULTS: The 3.5-mm model showed higher axial load values for peri-implant bone, implants, and abutments than the 2.9-mm model. As for oblique load, values were higher for right-sided peri-implant bone, implants, abutments, and frameworks in the 3.5-mm model than in the 2.9-mm model. The 3.5-mm model had a 16% lower risk of peri-implant bone loss for the axial load and 4% for the oblique load. CONCLUSIONS: The biomechanical behavior of an angled 2.9-mm implant was comparable with that of a 3.5-mm implant for an all-on-4 prosthesis. However, despite a lower risk of peri-implant bone loss, the 3.5-mm model had higher peak stress on implants and abutments than the 2.9-mm model.

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.

Bone Volume Dynamics and Implant Placement Torque in Horizontal Bone Defects Reconstructed with Autologous or Xenogeneic Block Bone: A Randomized, Controlled, Split-Mouth, Prospective Clinical Trial.

PURPOSE: The aim of this study was to evaluate volumetric stability of autologous and xenogeneic block grafts and primary stability of implants in maxillary grafted areas. MATERIALS AND METHODS: Each patient received one autologous block and xenogeneic block, both covered with a membrane. Bone thickness measurements clinically and tomographically were made before, immediately, and 6 months postoperatively. After 6 months, identical implants were placed in each grafted area, and primary stability was measured. RESULTS: Eight patients with anterior horizontal bone defects were selected. Clinical outcomes at 6 months postgrafting in the autologous block revealed a mean thickness of 7.4 ± 1.6 mm, with an initial mean measurement of 3.4 ± 1.7 mm and 2.6% resorption, whereas the mean in the xenogeneic block was 8.9 ± 1.5 mm, 3.3 ± 1.6 mm, and 7.3%, respectively. Tomographic evaluation of the thickness at 6 months postgrafting in the autologous block was a mean 7.8 ± 1.8 mm, with an initial mean of 3.7 ± 1.6 mm and resorption of 0%, while the mean in the xenogeneic block was 9.3 ± 1.6 mm, 3.6 ± 1.4 mm, and 2.1%, respectively. No significant difference in bone thickness was observed immediately or 6 months after the procedure. The mean implant placement torque was 32 ± 22 Ncm in the autologous block and 18 ± 9 Ncm in the xenogeneic block (P = .004). CONCLUSION: Xenogeneic block was shown to be a suitable alternative to reconstruct horizontal defects in the alveolar ridge that had undergone extensive resorption, though lower insertion torques were obtained during implant placement.

Influence of the Diameter of Dental Implants Replacing Single Molars: 3- to 6-Year Follow-Up.

PURPOSE: The aim of this study was to evaluate the influence of the implant diameter on marginal bone remodeling around dental implants replacing single molars after a follow-up period of 3 to 6 years. MATERIALS AND METHODS: Patients who received dental implants with an external hexagon platform in healed sites to support a single metal-ceramic crown in the molar region were recalled to the office. The implantation sites and implant length information were recorded, and the implants were divided according to the implant diameter: regular (RP) or wide (WP). Each implant was assessed by digital periapical radiography, using a sensor holder for the paralleling technique. The marginal bone remodeling was determined as the distance from the implant platform to the first bone-to-implant contact, and the known implant length was used to calibrate the images in the computer software. The follow-up measurements were compared with those obtained from the radiograph taken at the time of prosthetic loading to determine the late bone remodeling. The independent t test was used to compare data. RESULTS: A total of 67 implants from 46 patients were evaluated with a mean follow-up period of 4.5 ± 1.0 years. The RP group comprised 36 implants from 29 patients (mean age: 58.3 ± 10.6 years), while 31 implants from 17 patients (mean age: 56.9 ± 11.5 years) were included in the WP group. The RP group presented lower survival rates (86.1%) than the WP group (100.0%). Similar marginal bone loss (P < .05) was identified for the RP and WP groups (1.35 ± 0.96 mm and 1.06 ± 0.70 mm, respectively). CONCLUSION: Although wide-diameter implants exhibited lower incidence failures, the bone levels were similar after the prosthetic loading around regular- and wide-diameter implants supporting single molar crowns.

Retrospective Evaluation of the Influence of the Collar Surface Topography on Peri-implant Bone Preservation.

PURPOSE: To evaluate the influence of the collar surface topography on peri-implant marginal bone preservation. MATERIALS AND METHODS: A total of 156 patients who received at least one cylindrical implant of regular diameter with an external-hexagon platform in the posterior region of the maxilla or mandible were recalled to the office for a retrospective evaluation. Implantation sites and implant length information were recorded, and implants were divided according to the collar surface topography: machined (M) or rough (R) surface. Each implant was assessed by digital periapical radiography, using a sensor holder for the paralleling technique. The marginal bone remodeling was determined as the distance from the implant platform to the first bone-to-implant contact, and the known implant length was used to calibrate the images in the computer software. The follow-up measurements were compared with those obtained from the radiograph taken at the time of prosthetic loading to determine the late bone remodeling. An independent t test was used to compare data. RESULTS: From 138 patients who attended the recall, 242 implants (M = 126; R = 116) were evaluated with a mean follow-up period of 4.6 ± 0.9 years. Similar success rates were found in both groups (M = 95.0%; R = 95.9%). Late bone remodeling in the maxilla was not influenced by the implant collar (P = .504); however, lower marginal bone loss was observed in the R group (1.20 ± 0.52 mm) compared with the M group (1.58 ± 0.73 mm) in the mandible (P = .007). CONCLUSION: Although the implant collar design did not influence the success rate of dental implants, the rough collar design reduced the late marginal bone remodeling around external-hexagon implants in the mandible. The maxilla was not benefited by the rough collar design.

Analysis of the distribution of stress and deformation in single implant-supported prosthetic units in implants of different diameters / Análise da distribuição das tensões e deformações em reabilitações implanto-suportadas unitárias com implantes de diferentes diâmetros

Introduction: When stress and strain levels in the bone-implant system exceed It's capacity, a mechanical fatigue occurs, resulting in collapse and loss of osseointegration. Objective: Analyze biomechanical behavior in single implant-supported prosthesis with implants of different diameters in the posterior mandible. Material and method: Three different finite element models of Cone-Morse implants with the same height were created, varying the diameter (3.3 mm, 4.1 mm and 4.8 mm). The mandibular first molar area was the location of the implant, with It´s component and overlying prosthetic crown. The jawbone was composed of cortical and cancellous bone. Refined mesh of 0.5 mm was created in the critical interfaces to be analyzed. The loading of the models was performed at the point of occlusal contact with an occlusal load of 400 N. Result: Maximum stress and strain occurred in the cervical regions of the implants in all groups, either in the implants or in components as well as in the analysis of cortical bone. The greater the diameter, the lower the stress and strain found in the implant. The 3.3 mm group had the highest strain in peri-implant cortical bone, and the 4.1 mm group had the smallest deformation, significantly lower than in the 4.8 mm group. Conclusion: Although the biggest implant diameter (4.8 mm) appears to have lower values of stress and strain, the group of intermediate implant diameter (4.1 mm) showed less deformation rate in the cortical peri-implant bone. Therefore it is concluded that the 4.1 mm implant platform presented a more biomechanically effective peri-implant bone maintenance.

Introdução: Quando os níveis de tensão e compressão gerados no sistema osso-implante excederem a capacidade óssea ocorre uma fadiga mecânica, resultando em colapso e perda da osseointegração. Objetivo: Analisar o comportamento biomecânico em próteses unitárias implanto-suportadas com implantes de diferentes diâmetros na região posterior de mandíbula. Material e método: Foram criados três modelos de elementos finitos de implantes cone-Morse de mesmo comprimento, variando-se o diâmetro: 3,3 mm, 4,1 mm e 4,8 mm. A localização do implante foi a região de primeiro molar inferior, com componente e coroa protética sobrejacentes. A mandíbula foi composta por osso cortical e medular. Foi criada malha refinada de 0,5 mm nas interfaces criticas a serem analisadas. O carregamento dos modelos foi realizado nos pontos de contatos oclusais, com uma carga oclusal de 400 N. Resultado: Tensão e deformação máximas ocorreram nas regiões cervicais dos implantes em todos os grupos, tanto na análise dos implantes e componentes quanto na análise do osso cortical. Quanto maior foi o diâmetro, menores foram tensão e deformação encontradas no implante. O grupo 3,3 mm apresentou a maior deformação em osso cortical periimplantar, tendo o grupo 4,1 mm a menor deformação, significantemente menor em relação ao grupo 4,8 mm. Conclusão: Apesar de o implante de maior diâmetro (4,8 mm) ter apresentado os menores valores de tensão e deformação, o grupo do implante de diâmetro intermediário (4,1 mm) mostrou menor taxa de deformação em osso cortical periimplantar. Portanto conclui-se que o implante de plataforma 4,1 mm apresentou-se mais efetivo biomecanicamente para manutenção óssea periimplantar.

Guidelines for Selecting the Implant Diameter During Immediate Implant Placement of a Fresh Extraction Socket: A Case Series.

This prospective case series proposes a method for selecting the diameter of immediate postextraction anterior implants and guiding the placement position of the implant based on the buccolingual dimension with the goal of preserving the buccal bone wall. The socket buccolingual distance was measured to determine the appropriate implant diameter, considering a 3-mm gap to the buccal wall. Pre- and postoperative cone-beam computed tomography images were compared to evaluate the buccal bone. The socket width measurements were not significantly different (P = .931). The mean widths of the postoperative buccal bone were 3.01 ± 0.18 mm, 2.92 ± 0.38 mm, and 2.83 ± 0.42 mm for the crestal bone at the implant platform and at 2 and 4 mm apically, respectively, after 35 months of follow-up. This new diameter selection method for implants demonstrated predictable buccal plate preservation.

Evaluation of bone remodeling around single dental implants of different lengths: a mechanobiological numerical simulation and validation using clinical data.

Algorithmic models have been proposed to explain adaptive behavior of bone to loading; however, these models have not been applied to explain the biomechanics of short dental implants. Purpose of present study was to simulate bone remodeling around single implants of different lengths using mechanoregulatory tissue differentiation model derived from the Stanford theory, using finite elements analysis (FEA) and to validate the theoretical prediction with the clinical findings of crestal bone loss. Loading cycles were applied on 7-, 10-, or 13-mm-long dental implants to simulate daily mastication and bone remodeling was assessed by changes in the strain energy density of bone after a 3, 6, and 12 months of function. Moreover, clinical findings of marginal bone loss in 45 patients rehabilitated with same implant designs used in the simulation (n = 15) were computed to validate the theoretical results. FEA analysis showed that although the bone density values reduced over time in the cortical bone for all groups, bone remodeling was independent of implant length. Clinical data showed a similar pattern of bone resorption compared with the data generated from mathematical analyses, independent of implant length. The results of this study showed that the mechanoregulatory tissue model could be employed in monitoring the morphological changes in bone that is subjected to biomechanical loads. In addition, the implant length did not influence the bone remodeling around single dental implants during the first year of loading.

Fracture Strength of Implant-Supported Ceramic Crowns with Customized Zirconia Abutments: Screw Retained vs. Cement Retained.

PURPOSE: To compare the fracture resistance before and after cyclic fatigue assays of ceramic crowns with customized zirconia abutments when screw retained and cemented onto implants. MATERIALS AND METHODS: The sample of this study consisted of 40 ceramic crowns with zirconia infrastructure fixed onto external hexagonal implants. The crowns were distributed into two groups (n = 20): Screw-retained and cemented crowns. Half the crowns of each group (n = 10) underwent compression until fracture and the other half (n = 10) underwent cyclic fatigue and subsequent compression until fracture. The cyclic fatigue test was carried out using an electromechanical fatigue device (loads from 0 to 100 N, 2 Hz frequency, in distilled water, at 37 °C for a period of 1 million cycles). The compression test was carried out using a universal testing machine with a 0.5 mm/min speed and 5 KN load cell. After fracture, the crowns were classified according to the type of fracture. Student's t test (p < 0.05) was used for statistical analysis. RESULTS: The cyclic fatigue altered neither the mean fracture resistance of the screw-retained crowns (before = 1068.31 N, after = 891.49 N; p > 0.05) nor that of the cemented crowns (before = 2117.78 N; after = 2094.81 N; p > 0.05); however, the mean fracture resistance of the cemented crowns was higher than that of the screw-retained crowns both before (p < 0.001) and after (p < 0.001) the cyclic fatigue. Fractures occurred most frequently in the ceramic veneer, followed by fracture of some of the copings. CONCLUSION: The ceramic crowns cemented onto the customized zirconia abutments offered greater fracture resistance than ceramic crowns with customized zirconia abutments screw retained onto implants. The cyclic fatigue did not seem to influence the fracture resistance of these crowns, whether cemented or screw retained onto implants. Fracture of the veneering ceramic was the predominant failure in this study.

Clinical evaluation of ceramic inlays and onlays fabricated with two systems: 12-year follow-up.

OBJECTIVES: The aim of this study was to evaluate the 12-year clinical performance of sintered (Duceram, Dentsply-Degussa, Dentsply International Inc., PA, USA)-D and pressable (IPS Empress, Ivoclar-Vivadent, Schaan, Leichtenstein)-IPS ceramic inlay and onlay restorations. METHODS: Eighty-six restorations were placed in 35 patients with a median age of 33 years by a single operator. The restorations were luted with dual-cured resin luting material (Variolink II, Ivoclar-Vivadent, Schaan, Leichtenstein) and Syntac Classic adhesive under rubber dam. The evaluations were conducted by two independent investigators at the baseline, 1, 2, 3, 5, and 12 years using the modified USPHS criteria. RESULTS: At the 12-year recall, 22 patients were evaluated (62.86 %), totalling 48 (55.81 %) restorations. Seven restorations were fractured (one from Duceram and six from IPS), eight restorations presented secondary caries (three from Duceram and five from IPS), nine restorations showed unacceptable defects at the restoration margin and needed repair or replacement (two from Duceram and seven from IPS), and four IPS restorations presented pulp sensitivity. CONCLUSION: Chi-square and Mann-Whitney tests revealed that IPS Empress system showed the best results for color match and surface texture (p < 0.05) but a significant worse result for fracture (p = 0.05). Wilcoxon test showed significant differences in relation to color match, surface texture, marginal discoloration, and marginal integrity between the baseline and 12-year recall for both ceramic systems. CLINICAL SIGNIFICANCE: This long-term clinical study observed that the main reasons for failure of ceramic restorations were related to fracture, recurrent caries, and decreased marginal integrity over time. Carefully monitoring of the ceramic-tooth interface may extend their clinical longevity.