Comparative in vivo study of alloy titanium implants with two different surfaces: biomechanical and SEM analysis.

OBJECTIVES: The purpose of this study was to evaluate the biomechanical behavior of the interface formed between bone and implants with machined surfaces (MS) and those modified by Al2O3 sandblasting and acid etching (SBAS). MATERIALS AND METHODS: Before surgery, topographic characterization was performed by SEM-EDX and by mean roughness measurements. Ten Albinus rabbits received randomly 20 Ti-6Al-4V implants on its right and left tibiae, with one implant placed in each tibia. After implant insertion, the implant stability quotient (ISQ) was measured by means of resonance frequency analysis (RFA). After 3 and 6 weeks, the ISQ was again measured, followed by torque removal measurements. Analysis of variance and Tukey tests were used to analyze the data. The surface of the implants removed was evaluated by SEM-EDX. Immunohistochemical analysis of osteopontin (OPN) and osteocalcin (OC) protein was performed in bone tissue. RESULTS: The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of SBAS group were statistically higher than MS. Overall, higher statistically significant ISQ values were observed in the SBAS group compared to the MS group (p = 0.012). The intra-group comparison of ISQ values in the SBAS group showed statistically significant differences between 0 and 3 weeks (p = 0.032) and 0 and 6 weeks (p = 0.003). The torque removal measurements of group SBAS were statistically higher when compared with the torque removal measurements of group MS in the time intervals of 3 weeks (p = 0.002) and 6 weeks (p < 0.001). SEM-EDX of the implant surfaces removed in SBAS group showed greater bone tissue covering and mean values atomic in percentage of Ca, P, and O statistically superior (p < 0.05) than MS group. Immunohistochemical reactions showed intense OC immunolabeling at 6 weeks postoperative for SBAS group. CONCLUSIONS: The topographical modifications made in group SBAS allowed a better mechanical interlocking between the implant and bone tissue.

In vitro analysis of the microbiological sealing of tapered implants after mechanical cycling.

OBJECTIVE: The aim of this in vitro study was to evaluate the mechanical behavior and bacterial microleakage at the implant/abutment-tapered interface following mechanical cycling. MATERIALS AND METHODS: Two groups of screwless (Morse taper) implants (G1 and G2) and two groups of prosthetic screwed implants (G3 and G4) were tested. One group from each model (G2 and G4) were submitted to mechanical cycling, 500,000 cycles per sample, at a load of 120 N at 2 Hz prior to analysis. Microbiological analysis was performed via immersion of all samples in an Escherichia coli-containing suspension, incubated at 37 °C. After 14 days, the abutments were removed from their respective implants, registering the removal force (G1 and G2) or reverse torque (G3 and G4), and the presence of bacterial leakage was evaluated. Scanning electron microscopy (SEM) was performed to analyze the tapered surfaces of the selected samples. The Student t, binomial, and G tests were used for statistical analysis at a 5 % significance level. RESULTS: The results showed no significant difference between removal force, reverse torque, and contamination values when comparing implants of the same type. However, when the four groups were compared, contamination differed significantly (p = 0.044), with G1 having the least number of contaminated samples (8.3 %). SEM analysis showed superficial defects and damage. CONCLUSIONS: The abutment removal force or torque was not affected by mechanical cycling. Bacterial sealing of the implant/abutment tapered interface was not effective for any condition analyzed. Imprecise machining of implant parts does not allow a sufficient contact area between surfaces to provide effective sealing and prevent bacterial leakage. CLINICAL RELEVANCE: The microscopic gap caused by unsatisfactory implant/abutment adaptation, surface irregularities, and plastic deformation of all parts enabled bacterial contamination of the oral implants.

Vestibuloplasty by modified Kazanjian technique in treatment with dental implants.

Dentists are often faced with extensively resorbed mandibular ridges with shallow buccal vestibule and high insertion of the mentalis muscle in relation to the crest of the ridge, causing the displacement of the prosthesis. Vestibuloplasty techniques aim at eliminating the muscle insertions, reposition the mucosa, and increase the area chapeável, giving more stability to the prosthesis. Among the techniques to deepen the vestibule are submucosal vestibuloplasties by secondary epithelialization and with mucosal and skin grafts. We will discuss vestibuloplasty by secondary epithelialization with emphasis on the so-called modified Kazanjian technique. This technique provides an appropriate result and does not require hospitalization, additional surgery at the donor, or prolonged periods without the use of prosthesis.

Influence of the implant diameter with different sizes of hexagon: analysis by 3-dimensional finite element method.

The aim of this study was to evaluate the stress distribution in implants of regular platforms and of wide diameter with different sizes of hexagon by the 3-dimensional finite element method. We used simulated 3-dimensional models with the aid of Solidworks 2006 and Rhinoceros 4.0 software for the design of the implant and abutment and the InVesalius software for the design of the bone. Each model represented a block of bone from the mandibular molar region with an implant 10 mm in length and different diameters. Model A was an implant 3.75 mm/regular hexagon, model B was an implant 5.00 mm/regular hexagon, and model C was an implant 5.00 mm/expanded hexagon. A load of 200 N was applied in the axial, lateral, and oblique directions. At implant, applying the load (axial, lateral, and oblique), the 3 models presented stress concentration at the threads in the cervical and middle regions, and the stress was higher for model A. At the abutment, models A and B showed a similar stress distribution, concentrated at the cervical and middle third; model C showed the highest stresses. On the cortical bone, the stress was concentrated at the cervical region for the 3 models and was higher for model A. In the trabecular bone, the stresses were less intense and concentrated around the implant body, and were more intense for model A. Among the models of wide diameter (models B and C), model B (implant 5.00 mm/regular hexagon) was more favorable with regard to distribution of stresses. Model A (implant 3.75 mm/regular hexagon) showed the largest areas and the most intense stress, and model B (implant 5.00 mm/regular hexagon) showed a more favorable stress distribution. The highest stresses were observed in the application of lateral load.

Stress analysis in platform-switching implants: a 3-dimensional finite element study.

The aim of this study was to evaluate the influence of the platform-switching technique on stress distribution in implant, abutment, and peri-implant tissues, through a 3-dimensional finite element study. Three 3-dimensional mandibular models were fabricated using the SolidWorks 2006 and InVesalius software. Each model was composed of a bone block with one implant 10 mm long and of different diameters (3.75 and 5.00 mm). The UCLA abutments also ranged in diameter from 5.00 mm to 4.1 mm. After obtaining the geometries, the models were transferred to the software FEMAP 10.0 for pre- and postprocessing of finite elements to generate the mesh, loading, and boundary conditions. A total load of 200 N was applied in axial (0°), oblique (45°), and lateral (90°) directions. The models were solved by the software NeiNastran 9.0 and transferred to the software FEMAP 10.0 to obtain the results that were visualized through von Mises and maximum principal stress maps. Model A (implants with 3.75 mm/abutment with 4.1 mm) exhibited the highest area of stress concentration with all loadings (axial, oblique, and lateral) for the implant and the abutment. All models presented the stress areas at the abutment level and at the implant/abutment interface. Models B (implant with 5.0 mm/abutment with 5.0 mm) and C (implant with 5.0 mm/abutment with 4.1 mm) presented minor areas of stress concentration and similar distribution pattern. For the cortical bone, low stress concentration was observed in the peri-implant region for models B and C in comparison to model A. The trabecular bone exhibited low stress that was well distributed in models B and C. Model A presented the highest stress concentration. Model B exhibited better stress distribution. There was no significant difference between the large-diameter implants (models B and C).

Successful Osseointegrated Implants in Hypertensive Patients: Retrospective Clinical Study.

PURPOSE: The aim of this study was to investigate the association of hypertension and antihypertensive drugs with the failure of osseointegrated dental implants. MATERIALS AND METHODS: This study conformed to STROBE Guidelines regarding retrospective studies. Data from 602 medical records of patients who received rehabilitation treatment with osseointegrated implants between 2000 and 2017, completed at least 6 months before the study, were analyzed. Data on age, sex, presence or absence of hypertension, use or not of antihypertensive drugs, number of placed and lost implants, and type of prosthetic rehabilitation were collected. Statistical chi-square tests and the Fisher exact test were used to analyze the variables with implant loss, using a significance level of P < .05. RESULTS: One thousand eight hundred eighty-seven implants were placed with a success rate of 97.51% (47 implants lost in 41 patients). Of the 602 patients, 71.43% (432) were normotensive and 28.36% (171) were hypertensive. The success rate of implants in the normotensive group was 93.28%, and in the hypertensive group, it was 92.99%, with no statistical difference between the groups (P = .958). Of these patients, the success rate among the hypertensive group was similar for medication users (92.5%) and for nonusers (94.1%), with no statistically significant difference (P = .939). CONCLUSION: The presence of hypertension, as well as the use of antihypertensives, could not be associated with the failure of osseointegrated implants.

Sialolithiasis of the submandibular gland.

Sialolithiasis of the salivary gland is a benign pathology that occurs most frequently in the submandibular gland because of its anatomic features. Depending on the sialolith size and calcification degree, it can be visible in radiographic examinations. Commonly, patients may experience pain and/or edema, when the ducts are obstructed. The authors report the case of sialolithiasis of the submandibular gland in a 42-year-old, female, white-skinned patient, noticed during routine dental examination. Following diagnosis confirmed by clinical and radiographic examinations, the treatment plan consisted of surgery for removal of the calcified mass. The prognosis is often good, and generally there is no recurrence.

Influence of implant angulation with different crowns on stress distribution.

The aim of this study was to perform a photoelastic analysis of stress distribution on straight and angulated implants with different crowns (screwed and cemented). Three models were made of photoelastic resin PL-2: model 1: external hexagon implant 3.75×10.00 mm at 0 degrees; model 2: external hexagon implant 3.75×10.00 mm at 17 degrees; model 3: external hexagon implant 3.75×10.00 mm at 30 degrees. Axial and oblique (45 degrees) load (100 N) was applied with a universal testing machine. The photoelastic fringes on the models were recorded with a digital camera and visualized in a graphic software for qualitative analysis. The axial loading generated the same pattern of stress distribution. The highest stresses were concentrated between medium and apical thirds. The oblique loading generated a similar pattern of stress distribution in the models with similar implant angulation; the highest stress was located on the cervical region opposite to implant angulation and on the apical third. It was concluded that the higher the implant angulation, the higher the stress value, independent of crown type. The screwed prostheses exhibited the highest stress concentration. The oblique load generated higher stress value and concentration than the axial load.

Biomechanical and microscopic response of bone to titanium implants in the presence of inorganic grafts.

This study evaluated the biomechanical and microscopic response of previously grafted bone to titanium implants. The lower incisors of 16 rabbits were surgically extracted, and bilateral perforations communicating with the remaining sockets were created distally. A socket/perforation defect on each mandible was chosen at random to be immediately filled with a xenogenic graft, whereas the contralateral perforation was left to heal naturally and served as a paired control. After 60 days, titanium implants were installed in the previously operated areas. After periods of 2 and 6 months, the animals were killed, and the force necessary to retrieve implants as well as the bone-implant contact (BIC) and bone mass (BM) were quantified and statistically compared by 2-way analysis of variance and Tukey's test (α  =  .05). No significant differences in removal torque were observed, either by time or by treatment condition. Differences in BIC and BM between experimental and control groups were not statistically significant through the intervals studied (P < .05). The presence of a xenogenic graft did not influence the microscopic tissue response to titanium implants or fixation into newly formed or mature bone.

Clinical concepts of dry socket.

Dry socket is one of the most studied complications in dentistry, and a great number of studies have searched for an effective and safe method for its prevention and treatment. One of the great clinical challenges since the first case was reported has been the inconsistency and differences in the various definitions of dry socket and the criteria used for diagnosis. The pathophysiology, etiology, prevention, and treatment of dry socket are very important in the practice of oral surgery. The aim of the present report was to review and discuss each aspect.

Photoelastic stress analysis in screwed and cemented implant-supported dentures with external hexagon implants.

The aim of this study was to assess the stress distribution of the retention systems (screwed and cemented) for implant-supported fixed partial dentures by means of photoelastic method. Two models were made of photoelastic resin PL-2 with 2 implants (phi = 4.00 x 10 mm) located in the second premolar and molar region in each photoelastic model, varying the retention system (screwed and cemented). The implant-supported fixed partial dentures were standardized and made of Ni-Cr alloy. Axial and oblique (45 degrees) forces of 100 N were applied on the occlusal surface by means of a Universal Testing Machine (EMIC-DL 3000; São José dos Pinhais, Paraná, Brazil). The results were observed and photographed in the field of a circular polariscope and qualitatively analyzed with the aid of computer software (Adobe Photoshop, San Jose, CA). The screw retention system presented the highest number of fringes when the loads were applied on the premolar, pontic, and molar and showed this behavior in all load applications, under axial and oblique loads. It was concluded that there was a better stress distribution and lower magnitude of stress on the cemented implant-supported dentures, under axial and oblique loads. Oblique load caused an increase in stress concentrations in all the models.

Photoelastic analysis of the influence of platform switching on stress distribution in implants.

The aim of this study was to evaluate the stress distribution of platform switching implants using a photoelastic method. Three models were constructed of the photoelastic resin PL-2, with a single implant and a screw-retained implant-supported prosthesis. These models were Model A, platform 5.0 mm/abutment 4.1 mm; Model B, platform 4.1 mm/abutment 4.1 mm; and Model C, platform 5.00 mm/abutment 5.00 mm. Axial and oblique (45°) loads of 100 N were applied using a Universal Testing Machine (EMIC DL 3000). Images were photographed with a digital camera and visualized with software (AdobePhotoshop) to facilitate the qualitative analysis. The highest stress concentrations were observed at the apical third of the 3 models. With the oblique load, the highest stress concentrations were located at the implant apex, opposite the load application. Stress concentrations decreased in the cervical region of Model A (platform switching), and Models A (platform switching) and C (conventional/wide-diameter) displayed similar stress magnitudes. Finally, Model B (conventional/regular diameter) displayed the highest stress concentrations of the models tested.

Influence of cusp inclination on stress distribution in implant-supported prostheses. A three-dimensional finite element analysis.

PURPOSE: The aim of this study was to assess the influence of cusp inclination on stress distribution in implant-supported prostheses by 3D finite element method. MATERIALS AND METHODS: Three-dimensional models were created to simulate a mandibular bone section with an implant (3.75 mm diameter x 10 mm length) and crown by means of a 3D scanner and 3D CAD software. A screw-retained single crown was simulated using three cusp inclinations (10 degrees, 20 degrees, 30 degrees). The 3D models (model 10d, model 20d, and model 30d) were transferred to the finite element program NeiNastran 9.0 to generate a mesh and perform the stress analysis. An oblique load of 200 N was applied on the internal vestibular face of the metal ceramic crown. RESULTS: The results were visualized by means of von Mises stress maps. Maximum stress concentration was located at the point of application. The implant showed higher stress values in model 30d (160.68 MPa). Cortical bone showed higher stress values in model 10d (28.23 MPa). CONCLUSION: Stresses on the implant and implant/abutment interface increased with increasing cusp inclination, and stresses on the cortical bone decreased with increasing cusp inclination.

Remodeling of calvarial graft in increased atrophic maxillary thickness. A prospective clinical study.

PURPOSE: This study evaluated the autogenous graft resorption rate in a calvarial block graft in the anterior region of an atrophic maxilla and compared it with the thickness of the remaining ridge. MATERIALS AND METHODS: Twelve patients were included in the study. They were submitted to cranial calotte graft surgery, and there were 40 blocks in total. The thicknesses of the ridges in the crest, middle and apical regions of the blocks were evaluated by computed tomography scan at the times: preoperative (T0), 48 hours (T1) and 6 months (T2) after the reconstructions. RESULTS: The resorption of the blocks from T1 to T2 was 13.4%. The greatest remodeling occurred in the alveolar bone crest (20.07%), followed by the middle portion (12.28%), and the apical region (9.5%), but the three regions did not significantly differ between times T1 and T2 (crest P = .07, middle P = .124, apical P = .131). Recipient site with the lowest thickness had the greatest resorption rates (up to 2 mm = 17.6%; from 2 to 4 mm = 17.52%) while than those with a thickness greater than 4 mm had a mean resorption of 8.81%. CONCLUSIONS: The resorption of the grafts in this study was 13.4%. Higher resorption rates were observed in the alveolar crest areas, where the ridges were less thick.

Osteopromotion Capacity of Bovine Cortical Membranes in Critical Defects of Rat Calvaria: Histological and Immunohistochemical Analysis.

Membranes that aid the guided bone regeneration (GBR) process have been the subject of studies of compatible biomaterials that contribute to this repair process. The present study compared different membranes used in critical-size defects of rat calvaria by assessing GBR as well as histological, histomorphometric, and immunohistochemical reactions. Forty-eight male albino Wistar rats were randomly allocated into four groups (n = 12 each), namely, C: membrane-free control group (only blood clot, negative control group); BG: porcine collagen membrane group (Bio-Gide®, positive control group); GD: bovine cortical membrane group (first experimental group); and GDF: thicker bovine cortical membrane group (second experimental group). Rats were euthanized at 30 and 60 days postoperatively. Quantitative data from the histometric analysis were submitted to two-way ANOVA and Tukey's posttest when p < 0.05. Histomorphometric results of the thicker bovine cortical membrane at 30 and 60 days were promising, showing improved new bone formation values (p < 0.05), and the CD group presented similar results in both analysis periods, being surpassed only by the GDF group (p < 0.05). The immunohistochemical results were associated with the histomorphometric data. A less-thick membrane also assisted in GBR. All membranes promoted GBR, especially the positive control and experimental groups.

Evaluation of Osteoconduction of a Synthetic Hydroxyapatite/ß-Tricalcium Phosphate Block Fixed in Rabbit Mandibles.

(1) Background: This study aimed to evaluate the incorporation of hydroxyapatite/ß-tricalcium phosphate blocks grafted in rabbit mandibles. (2) Methods: Topographic characterization of biomaterial was performed through scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). Ten rabbits randomly received autogenous bone graft harvested from the tibia (Autogenous Group-AG) or synthetic biomaterial manufactured in ß-tricalcium phosphate (Biomaterial Group-BG) at their right and left mandibular angles. Euthanasia was performed at 30 and 60 postoperative days; (3) Results: SEM-EDX showed a surface with the formation of crystals clusters. Histological analyses in BG at 30 days showed a slower process of incorporation than AG. At 60 days, BG showed remnants of biomaterial enveloped by bone tissue in the anabolic modeling phase. Histometric analysis showed that mean values of newly formed bone-like tissue in the AG (6.56%/9.70%) were statistically higher compared to BG (3.14%/6.43%) in both periods, respectively. Immunohistochemical analysis demonstrated early bone formation and maturation in the AG with more intense osteopontin and osteocalcin staining. (4) Conclusions: The biomaterial proved to be a possible bone substitute, being incorporated into the receiving bed; however, it showed delayed bone incorporation compared to autogenous bone.

Histological and histomorphometric evaluation of efficacy of a polypropylene barrier in guided bone regeneration and modified guided bone regeneration in critical defects in rodent cranial vaults.

BACKGROUND: The last few years have detailed a number of surgical materials and techniques to stimulate guided bone regeneration (GBR). Polypropylene has been used as a mechanical barrier, intentionally designed to be exposed to the oral environment, isolating the regeneration area, and allowing the blood clot to remain protected in a confined space while pluripotent mesenchymal cells regenerate the alveolar bone tissue. AIM: Due to the lack of studies on polypropylene barriers (PB) (Bone Heal- Bone heal ind. e Com. LTDA - São Paulo, Brazil), this study aimed to evaluate the histological repair process of critical defects (7 mm) made in the rodent cranial vaults comparing its efficacy in GBR and modified GBR. MATERIALS AND METHODS: A total of 30 rats were divided into three groups. The control group consisted of 10 rats, wounds covered with just a blood clot. The second group consisted of an exposed/uncoated PB at the edges of the wound, and it was removed after 3 days. The third group used submerged PB with coaptation of the wound edges, and it was not removed. Five animals of each group were euthanized at 30 and 90 days postoperative and submitted to microscopic analysis and histomorphometric evaluation. RESULTS: Modified GBR (membrane exposed to the oral medium) provided earlier tissue organization at 30 days; however, the third group presented better bone neoformation at 90 days. CONCLUSION: Modified GBR provided earlier tissue organization compared with the control group, as well as promoting improved bone neoformation, while regeneration with the submerged membrane presented better bone neoformation in the long term.

Practice-Based Clinical Evaluation of Dental Implants Placed with Immediate or Delayed Loading Protocols: One-Year Follow-Up.

We evaluate bone remodeling and prostheses survival of immediately provisionalized with occlusal loading and delayed loading (DL) single implants placed in the posterior region after 1-yr follow-up in dental practices. Included in the study are patients selected to receive one regular implant (4 × 10 mm) for single tooth replacement in healed ridge sockets in the mandible and maxilla. Implants are immediately loaded or delayed functionally loaded with metal ceramic crowns, depending on peak insertion torque value. All implants are clinically and radiographically evaluated at T1, immediately postoperatively; T2, 60 d; T3, 180 d; and T4, 360 d. Measurements between implant platform and top of alveolar bone crest at distal and mesial areas are performed using periapical radiographs. Data are statistically evaluated through two-way repeated measures of analysis of variance following post hoc comparisons using the Tukey test (p < 0.05). Ten specialists working in ten different practices treat 36 patients who receive one implant each with internal conical connection (hybrid implant system, 4 × 10 mm) (Emfils; Itu, Brazil). Results show that bone-level alterations in immediate (IM; 0.56 mm; confidence interval [CI]: ± 0.21 mm) and delayed (0.65 mm; CI: ± 0.19 mm) groups are not significantly different (p = 0.515) during the course of the 1-yr observation period. In both groups, statistically significant progressive bone-level remodeling occurs through the evaluated follow-up time points (p < 0.047). All prostheses are rated "alpha," presenting 100% success at 1-yr follow-up. The loading method does not influence bone-remodeling levels around IM or DL at the posterior region after 1-yr follow-up. No prostheses complications are reported.

Assessment of bone repair in critical-size defect in the calvarium of rats after the implantation of tricalcium phosphate beta (ß-TCP).

OBJECTIVES: Evaluating the osteoconductive property of tricalcium phosphate beta (ß-TCP) in comparison to that of inorganic bovine bone for repair in a critical-size defect in the rat calvarium. MATERIALS AND METHODS: Critical-size defects of 7mm were made with a trephine in the calvaria of 48 Wistar rats. The animals were divided into four groups, and the defects in each group were filled with tricalcium phosphate beta (ß-TCP), inorganic bovine bone (Bio-Oss), autogenous bone, or left empty. The animals were euthanized at two different time points (30 and 60days post-operation). All defects were recovered with a absorbable membrane of bovine cortical bone. Histological, histometric, and immunohistochemical (osteocalcin) assessments were carried out at 30 and 60days post-operation. RESULTS: At 30days post-operation, all groups showed areas of bone formation, predominantly when autogenous grafts were used. However, there were no statistically significant differences between the treatment groups (p>0.05). After 60days, there were similarities in the bone formation patterns between the ß-TCP (26.32±) and Bio-Oss (17.35±) groups (p=0.549). In terms of the immunohistochemical assessment of osteocalcin, the clot group showed light to moderate staining at 30 and 60days. The autogenous group showed moderate staining at 30days and moderate to intense staining after 60days. The Bio-Oss group showed light to moderate staining after 30days and intense staining at 60days. The ß-TCP group showed moderate staining at 30 and 60days post-operation. CONCLUSION: ß-TCP is a good osteoconductive material with similar effects to those of inorganic bovine bone graft and is suitable for utilization in the repair of bone defects.