A survey of radiographic measurement estimation in assessment of dental implant length.

The aim of this study is to survey radiographic measurement estimation in the assessment of dental implant length according to dentists' confidence. A 19-point questionnaire with closed-ended questions was used by two graduate students to interview 69 dentists during a dental implant meeting. Included were 12 questions related to over- and underestimation in three radiographic modalities: panoramic (P), conventional tomography (T), and computerized tomography (CT). The database was analyzed by Epi-Info 6.04 software and the values from two radiographic modalities, P and T, were compared using a chi2 test. The results showed that 38.24% of the dentists' confidence was in the overestimation of measurements in P, 30.56% in T, and 0% in CT. On the other hand, considering the underestimated measurements, the percentages were 47.06% in P, 33.33% in T, and 1.92% in CT. The frequency of under- and overestimation were statistically significant (chi2 = 6.32; P = .0425) between P and T. CT was the radiographic modality with higher measurement precision according to dentists' confidence. In conclusion, the interviewed dentists felt that CT was the best radiographic modality when considering the measurement estimation precision in preoperative dental implant assessment.

Accuracy of impression techniques for implants. Part 1 - Influence of transfer copings surface abrasion

Purpose: This study evaluated the influence of surface abrasion of transfer copings to obtain a precise master cast for a partially edentulous restoration with different inclinations. Materials and Methods: Replicas (N = 30) of a metal matrix (control group) containing two implants at 90° and 65° in relation to the benchtop were obtained using a polyether impression material and three impression techniques: square impression copings splint with dental floss and autopolymerizing acrylic resin (TRS), square impression copings abraded with aluminum oxide (TA), and square impression copings abraded with aluminum oxide and adhesive-coated (TAA). The replicas obtained in type V stone were digitalized, and the images were exported to AutoCAD software to perform the readings of possible degree alterations in implant inclinations. The results were submitted to analysis of variance (ANOVA) and Tukey test (α < 0.05). Results: Comparing the techniques with regard to the 90° implant inclination, no statistical difference was observed between the three techniques and the control group. Analyzing the three techniques with regard to the 65° implant inclination, no significant difference was seen between technique TA and the control group. Conclusions: Technique TA presented more accurate master casts than TRS and TAA techniques. The angulated implant (65°) tended to generate more imprecise master casts than implants perpendicular to the surface. © 2008 by The American College of Prosthodontists.

Evaluation of titanium implants with surface modification by laser beam. Biomechanical study in rabbit tibias

The purpose of the present study was to evaluate, using a biomechanical test, the force needed to remove implants with surface modification by laser (Nd:YAG) in comparison with implants with machined surfaces. Twenty-four rabbits received one implant with each surface treatment in the tibia, machined surface (MS) and laser-modified surface (LMS). After 4, 8 and 12 weeks of healing, the removal torque was measured by a torque gauge. The surfaces studied were analyzed according to their topography, chemical composition and roughness. The average removal torque in each period was 23.28, 24.0 and 33.85 Ncm for MS, and 33.0, 39.87 and 54.57 Ncm for LMS, respectively. The difference between the surfaces in all periods of evaluation was statistically significant (p < 0.05). Surface characterization showed that a deep and regular topography was provided by the laser conditioning, with a great quantity of oxygen ions when compared to the MS. The surface micro-topography analysis showed a statistical difference (p < 0.01) between the roughness of the LMS (R a = 1.38 ± 0.23 μm) when compared to that of the MS (R a = 0.33 ± 0.06 μm). Based on these results, it was possible to conclude that the LMS implants' physical-chemical properties increased bone-implant interaction when compared to the MS implants. © 2009 Sociedade Brasileira de Pesquisa Odontológica.

Cyclosporine-a and bone density around titanium implants: A histometric study in rabbits

Aim: Cyclosporine A (CsA) is an immunosuppressive agent commonly used to prevent organ transplantation rejection. It has been demonstrated that CsA may negatively affect osseointegration around dental implants. Therefore, the aim of this study was to evaluate the effect of CsA administration on bone density around titanium dental implants. Materials and Methods: Fourteen New Zealand rabbits were randomly divided into 2 groups with seven animals each. The test group (CsA) received daily subcutaneous injection of CsA (10mg/kg body weight) and the control group (CTL) received saline solution by the same route of administration. Three days after the beginning of immunosuppressive therapy, one machined dental implant (7.00 mm in lenght and 3.75 mm in diameter) was inserted bilaterally at the region of the tibial methaphysis. After 4 and 8 weeks the animals were sacrificed and the histometrical procedures were performed to analyse the bone density around the first four threads of the coronal part of the implant. Results: A significant increase in the bone density was observed from the 4- to the 8 week-period in the control group (37.41% + 14.85 versus 58.23% + 16.38 - p <0.01). In contrast, bone density consistently decreased in the test group overtime (46.31% + 17.38 versus 16.28 + 5.08 - p <0.05). In the 8-week period, there was a significant difference in bone density between the control and the test groups (58.23 + 16.38 eand16.28 + 5.08 - p= 0.001). Conclusion: Within the limits of this study, long-term CsA administration may reduce bone density around titanium dental implants during the osseointegration process.

Prosthetic approaches for immediate implants in esthetic areas: Aliterature review and clinical cases

The placement of implants in fresh extraction sockets followed for provisionalization allows soft tissues preservation and alveolar ridge, however for this some requisites are necessary. This article describe the factors involved in immediate implants and the prosthetic approachs for this type of therapy. Addtionaly two clinicals case were presented showing diferents approachs for in prosthetic stage for maintenance the aesthetic aperance of soft tissues of the immediate implants.

Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals, Inc.

Healing outcomes at implants installed in sites augmented with particulate autologous bone and xenografts. An experimental study in dogs

Aim: To evaluate the integration of implants installed at the interface of pristine and grafted tissue augmented with particulate autologous bone or deproteinized bovine bone mineral (DBBM), concomitantly with a collagen membrane. Material and methods: In 6 Labrador dogs, the distal root of 3P3 and 4P4 was endodontically treated and hemi-sected, and the mesial roots extracted concomitantly with the extraction of 2P2. The buccal bony walls were removed, and two box-shaped defects, one larger and one smaller, were created. After 3 months, flaps were elevated, and the defects were filled with particulate autologous bone or DBBM in the right and left side of the mandible, respectively. Collagen membranes were used to cover the grafted areas. Three months later, flaps were elevated, and a customized device was used as surgical guide to prepare the recipient sites at the interface between grafts and pristine bone. One implant was installed in each of the four defects. After 3 months, biopsies were harvested and ground sections prepared for histological evaluation. Results: The augmentation technique was effective at all sites and all the foreseen implants were installed. In the histological analysis, all implants were integrated in mature bone, at both the buccal and lingual aspects. The most coronal bone-to-implant contact and the top of the buccal bony crest were located at a similar distance between test and control implants. However, these distances were higher at the larger compared with the smaller defects. Especially in the large defect, residual particles of DBBM were found embedded into connective tissue and located outside the bony crest. Conclusions: Particulate autologous bone as well as DBBM particles used to augment horizontally the alveolar bony process allowed for the osseointegration of implants installed after 3 months of healing. © 2012 John Wiley & Sons A/S.

Effect of microthread presence and restoration design (screw versus cemented) in dental implant reliability and failure modes

Objectives: This study evaluated the reliability and failure modes of implants with a microthreaded or smooth design at the crestal region, restored with screwed or cemented crowns. The postulated null hypothesis was that the presence of microthreads in the implant cervical region would not result in different reliability and strength to failure than smooth design, regardless of fixation method, when subjected to step-stress accelerated life-testing (SSALT) in water. Materials and methods: Eighty four dental implants (3.3 × 10 mm) were divided into four groups (n = 21) according to implant macrogeometric design at the crestal region and crown fixation method: Microthreads Screwed (MS); Smooth Screwed (SS); Microthreads Cemented (MC), and Smooth Cemented (SC). The abutments were torqued to the implants and standardized maxillary central incisor metallic crowns were cemented (MC, SC) or screwed (MS, SS) and subjected to SSALT in water. The probability of failure versus cycles (90% two-sided confidence intervals) was calculated and plotted using a power law relationship for damage accumulation. Reliability for a mission of 50,000 cycles at 150 N (90% 2-sided confidence intervals) was calculated. Differences between final failure loads during fatigue for each group were assessed by Kruskal-Wallis along with Benferroni's post hoc tests. Polarized-light and scanning electron microscopes were used for failure analyses. Results: The Beta (β) value (confidence interval range) derived from use level probability Weibull calculation of 1.30 (0.76-2.22), 1.17 (0.70-1.96), 1.12 (0.71-1.76), and 0.52 (0.30-0.89) for groups MC, SC, MS, and SS respectively, indicated that fatigue was an accelerating factor for all groups, except for SS. The calculated reliability was higher for SC (99%) compared to MC (87%). No difference was observed between screwed restorations (MS - 29%, SS - 43%). Failure involved abutment screw fracture for all groups. The cemented groups (MC, SC) presented more abutment and implant fractures. Significantly higher load to fracture values were observed for SC and MC relative to MS and SS (P < 0.001). Conclusion: Since reliability and strength to failure was higher for SC than for MC, our postulated null hypothesis was rejected. © 2012 John Wiley & Sons A/S.

Bone healing around titanium implants in two rat colitis models

Objective: Crohn's disease is a chronic inflammatory process that has recently been associated with a higher risk of early implant failure. Herein we provide information on the impact of colitis on peri-implant bone formation using preclinical models of chemically induced colitis. Methods: Colitis was induced by intrarectal instillation of 2,4,6-trinitro-benzene-sulfonic-acid (TNBS). Colitis was also induced by feeding rats dextran-sodium-sulfate (DSS) in drinking water. One week after disease induction, titanium miniscrews were inserted into the tibia. Four weeks after implantation, peri-implant bone volume per tissue volume (BV/TV) and bone-to-implant contacts (BIC) were determined by histomorphometric analysis. Results: Cortical histomorphometric parameters were similar in the control (n = 10), DSS (n = 10) and TNBS (n = 8) groups. Cortical BV/TV was 92.2 ± 3.7%, 92.0 ± 3.0% and 92.6 ± 2.7%. Cortical BIC was 81.3 ± 8.8%, 83.2 ± 8.4% and 84.0 ± 7.0%, respectively. No significant differences were observed when comparing the medullary BV/TV and BIC (19.5 ± 6.4%, 16.2 ± 5.6% and 15.4 ± 9.0%) and (48.8 ± 12.9%, 49.2 ± 6.2 and 41.9 ± 11.7%), respectively. Successful induction of colitis was confirmed by loss of body weight and colon morphology. Conclusions: The results suggest bone regeneration around implants is not impaired in chemically induced colitis models. Considering that Crohn's disease can affect any part of the gastrointestinal tract including the mouth, our model only partially reflects the clinical situation. © 2012 John Wiley & Sons A/S.

Impact of diabetes mellitus and metabolic control on bone healing around osseointegrated implants: Removal torque and histomorphometric analysis in rats

Objectives: To evaluate bone healing around dental implants with established osseointegration in experimental diabetes mellitus (DM) and insulin therapy by histomorphometric and removal torque analysis in a rat model. Materials and methods: A total of 80 male Wistar rats received a titanium implant in the tibiae proximal methaphysis. After a healing period of 60 days, the rats were divided into four groups of 20 animals each: a 2-month control group, sacrificed at time (group A), a diabetic group (group D), an insulin group (group I), and a 4-month control group (group C), subdivided half for removal torque and half for histomorphometric analysis. In the D and I groups the DM was induced by a single injection of 40 mg/kg body weight streptozotocin (STZ). Two days after DM induction, group I received subcutaneous doses of insulin twice a day, during 2 months. Groups C and D received only saline. Two months after induction of DM, the animals of groups D, C and I were sacrificed. The plasmatic levels of glucose (GPL) were monitored throughout the experiment. Evaluation of the percentages of bone-to-implant contact and bone area within the limits of the implant threads was done by histomorphometric and mechanical torque analysis. Data were analyzed by anova at significant level of 5%. Results: The GPL were within normal range for groups A, C and I and higher for group D. The means and standard deviations (SD) for histomorphometric bone area showed significant difference between group D (69.34 ± 5.00%) and groups C (78.20 ± 4.88%) and I (79.63 ± 4.97%). Related to bone-to-implant contact there were no significant difference between the groups D (60.81 + 6.83%), C (63.37 + 5.88%) and I (66.97 + 4.13%). The means and SD for removal torque showed that group D (12.91 ± 2.51 Ncm) was statistically lower than group I (17.10 ± 3.06 Ncm) and C (16.95 ± 5.39 Ncm). Conclusions: Diabetes mellitus impaired the bone healing around dental implants with established osseointegration because the results presented a lower percentage of bone area in group D in relation to groups C and I resulting in a lowest torque values for implant removal. Moreover, insulin therapy prevents the occurrence of bone abnormalities found in diabetic animals and osseointegration was not compromised. © 2012 John Wiley & Sons A/S.

Tilted and Short Implants Supporting Fixed Prosthesis in an Atrophic Maxilla: A 3D-FEA Biomechanical Evaluation

Purpose: This study compared the biomechanical behavior of tilted long implant and vertical short implants to support fixed prosthesis in an atrophic maxilla. Materials and Methods: The maxilla model was built based on a tomographic image of the patient. Implant models were based on micro-computer tomography imaging of implants. The different configurations considered were M4S, four vertical anterior implants; M4T, two mesial vertical implants and two distal tilted (45°) implants in the anterior region of the maxilla; and M6S, four vertical anterior implants and two vertical posterior implants. Numerical simulation was carried out under bilateral 150N loads applied in the cantilever region in axial (L1) and oblique (45°) (L2) direction. Bone was analyzed using the maximum and minimum principal stress (σmax and σmin), and von Mises stress (σvM) assessments. Implants were analyzed using the σvM. Results: The higher σmax was observed at: M4T, followed by M6S/L1, M6S/L2, M4S/L2, and M4S/L1 and the higher σvM: M4T/L1, M4T/L2 and M4S/L2, M6S/L2, M4S/L1, and M6S/L1. Conclusions: The presence of distal tilted (all-on-four) and distal short implants (all-on-six) resulted in higher stresses in both situations in the maxillary bone in comparison to the presence of vertical implants (all-on-four). © 2013 Wiley Periodicals, Inc.

Stress analysis in bone tissue around single implants with different diameters and veneering materials: A 3-D finite element study

The aimof this study was to evaluate the stress distribution on bone tissue with a single prosthesis supported by implants of large and conventional diameter and presenting different veneering materials using the 3-D finite elementmethod. Sixteenmodels were fabricated to reproduce a bone block with implants, using two diameters (3.75 × 10 mmand 5.00 × 10 mm), four different veneering materials (composite resin, acrylic resin, porcelain, and NiCr crown), and two loads (axial (200 N) and oblique (100 N)). For data analysis, the maximum principal stress and vonMises criterion were used. For the axial load, the cortical bone in allmodels did not exhibit significant differences, and the trabecular bone presented higher tensile stresswith reduced implant diameter. For the oblique load, the cortical bone presented a significant increase in tensile stress on the same side as the loading for smaller implant diameters. The trabecular bone showed a similar but more discreet trend. There was no difference in bone tissue with different veneering materials. The veneering material did not influence the stress distribution in the supporting tissues of single implant-supported prostheses. The large-diameter implants improved the transference of occlusal loads to bone tissue and decreased stress mainly under oblique loads.Oblique loading was more detrimental to distribution stresses than axial loading. © 2013 Elsevier B.V. All rights reserved.

Assessment of the Correlation Between Insertion Torque and Resonance Frequency Analysis of Implants Placed in Bone Tissue of Different Densities

The primary stability of dental implants is fundamental for osseointegration. Therefore, this study aimed to assess the correlation between insertion torque (IT) and resonance frequency analysis (RFA) of implants placed in mandibles and maxillas of different bone densities. Eighty dental implants were placed in maxillas and mandibles, and IT and the implant stability quotient (ISQ) were measured at the time of implant insertion. Bone density was assessed subjectively by the Lekholm and Zarb index. The type I and II densities were grouped together (group A)as were the type III and IV densities (group B). The IT in group A was higher (Student t test, P = .0013) than in group B (46.27 +/- 18.51 Ncm, 33.62 +/- 14.74 Ncm, respectively). The implants placed in group A showed higher ISQ (Student t test, P = .0004) than those placed in group B (70.09 +/- 7.50, 63.66 +/- 8.00, respectively). A significant correlation between IT and the ISQ value was observed for group A (Pearson correlation test; r = 0.35; P = .0213) and for group B (r = 0.37; P = .0224). Within the limitations of this study, it was possible to conclude that there is a correlation between IT and RFA of implants placed in mandibles and maxillas of different bone densities.

Stress analysis in oral obturator prostheses over parallel and tilted implants: photoelastic imaging

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