Comparative evaluation of two collagen-based biomaterials with different compositions used for bone graft: An experimental animal study.

A large number of materials with different compositions and shapes have been proposed and studied for the purpose of bone tissue regeneration. Collagen-based materials have shown promising results for this application, with improved physicochemical properties. The aim of the present in vivo animal study was to evaluate and compare two commercially available collagen-based biomaterials for bone regeneration, with these being implanted in circumferential bone defects created in the calvarium of rabbits. Twenty rabbits received bilateral parietal osteotomies, performed with the aid of a 6.5 mm diameter trephine. Two groups were created: the BC group, where the defect was filled with a scaffold composed of 90% bovine bone particles and 10% porcine collagen, and the EG group, where the defect was filled with a scaffold composed of 75% hydroxyapatite particles of bovine origin and 25% bovine collagen. Ten animals were sacrificed at 30 days and another 10 at 45 days after implantation, and the samples were processed and histologically analyzed. In the evaluations of the samples at 30 days, no important differences were found in the results. However, in the samples at 45 days after surgery, the EG group showed better results than the BC group samples, mainly in terms of the amount of bone matrix formation (P < 0.0001) and the volume in area measured in each sample, where the EG group had a value 65% higher than that in the BC group samples. Based on the results obtained, we conclude that the amount of collagen and the particle characteristics present in the composition of the scaffolds can directly influence the amount of neoformation and/or bone regeneration.

Effects of the technique and drill design used during the osteotomy on the thermal and histological stimulation.

The objective of our in vivo study was to compare the effects of the osteotomy on the thermal alterations, the bone healing and count of polymorphonuclear cells, comparing the drill design (cylindrical or conical) using continuous or intermittent movement. Twelve rabbits were used, which were made four osteotomies (n = 2 per tibia) to simulate the surgical drilling sequence for the installation of a dental implant at 8 mm of length and regular diameter. Four groups were proposed: group G1, cylindrical drill with continuous movement; group G2, cylindrical drill with intermittent movement; group G3, conical drill with continuous movement; and, group G4, conical drill with intermittent movement. Thermal mean variation was 6.91 ± 1.4 °C in group 1, 4.30 ± 1.3 °C in group 2, 2.78 ± 0.6 °C in group 3, and 2.77 ± 0.7 °C in group 4. Whereas the mean area of new bone formation was 1.00 ± 0.3 mm2 in group 1, 1.48 ± 0.3 mm2 in group 2, 2.20 ± 0.4 mm2 in group 3, and 2.43 ± 0.4 mm2in group 4. The mean count of polymorphonuclear cells, in the group 1 was 62.4 ± 5.9 cells, group 2 was 50.7 ± 4.2 cells, group 3 was 44.4 ± 3.7 cells, and group 4 was 42.4 ± 3.7 cells. The conical drill sequence produced a significantly smaller increase in temperature during both techniques (continuous and intermittent), more effective new bone formation and a smaller number of polymorphonuclear cells. During the osteotomy for the installation of implants, the professional must take to consider the drill design to perform a less traumatic surgical technique, which can improve and facilitate the healing of peri-implant tissues.

Histological and Histomorphometrical Evaluation of a New Implant Macrogeometry. A Sheep Study.

Decompression or healing chambers between the threads have been proposed to improve and accelerate the osseointegration process of dental implants. The aim of the present work was to test, in an in vivo sheep study, if healing chambers between the threads could produce a better osseointegration process. Thirty titanium implants (15 conventional design (control) and 15 implants with healing chambers (test)) were inserted in a random fashion in the tibia of 3 sheep. The animals were euthanized after 30 days of healing, and the retrieved specimens treated to obtain thin ground sections. Histological observations showed that the quantity of newly formed bone growing in an apical direction was lower in the control group (1095 µm) when compared to the Test group (1658 µm). This difference was statistically significant. Moreover, a layer of osteogenic matrix was present around the portion of implants immersed in the marrow spaces. This osteogenic tissue was thicker in the test group. In conclusion, the present study confirmed the very good results in implants with healing chambers that presented a higher percentage of new bone formation.

Impact of Different Titanium Implant Thread Designs on Bone Healing: A Biomechanical and Histometric Study with an Animal Model.

Threads of dental implants with healing chamber configurations have become a target to improve osseointegration. This biomechanical and histometric study aimed to evaluate the influence of implant healing chamber configurations on the torque removal value (RTv), percentage of bone-to-implant contact (BIC%), bone fraction occupancy inside the thread area (BAFO%), and bone and osteocyte density (Ost) in the rabbit tibia after two months of healing. Titanium implants with three different thread configurations were evaluated: Group 1 (G1), with a conventional "v" thread-shaped implant design; Group 2 (G2), with square threads; and Group 3 (G3), the experimental group with longer threads (healing chamber). Ten rabbits (4.5 ± 0.5 kg) received three implants in each tibia (one per group), distributed in a randomized manner. After a period of two months, the tibia blocks (implants and the surrounding tissue) were removed and processed for ground sectioning to evaluate BIC%, BAFO%, and osteocyte density. The ANOVA one-way statistical test was used followed by the Bonferoni's multiple comparison test to determine individual difference among groups, considering a statistical difference when p < 0.05. Histometric evaluation showed a higher BAFO% values and Ost density for G3 in comparison with the other two groups (G1 and G2), with p < 0.05. However, the RTv and BIC% parameters were not significantly different between groups (p > 0.05). The histological data suggest that the healing chambers in the implant macrogeometry can improve the bone reaction in comparison with the conventional thread design.

Microgrooves and Microrugosities in Titanium Implant Surfaces: An In Vitro and In Vivo Evaluation.

The physical characteristics of an implant surface can determine and/or facilitate osseointegration processes. In this sense, a new implant surface with microgrooves associated with plus double acid treatment to generate roughness was evaluated and compared in vitro and in vivo with a non-treated (smooth) and double acid surface treatment. Thirty disks and thirty-six conical implants manufactured from commercially pure titanium (grade IV) were prepared for this study. Three groups were determined, as described below: Group 1 (G1), where the samples were only machined; group 2 (G2), where the samples were machined and had their surface treated to generate roughness; and test group 3 (G3), where the samples were machined with microgrooves and the surface was treated to generate the roughness. For the in vitro analysis, the samples were submitted to scanning microscopy (SEM), surface profilometry, the atomic force microscope (MFA) and the surface energy test. For the in vivo analyses, thirty-six implants were placed in the tibia of 9 New Zealand rabbits in a randomized manner, after histological and histomorphometric analysis, to determine the level of contact between the bone and implant (BIC%) and the bone area fraction occupancy (BAFO%) inside of the threads. The data collected were statistically analyzed between groups (p < 0.05). The in vitro evaluations showed different roughness patterns between the groups, and the G3 group had the highest values. In vivo evaluations of the BIC% showed 50.45 ± 9.57% for the G1 group, 55.32 ± 10.31% for the G2 group and 68.65 ± 9.98% for the G3 group, with significant statistical difference between the groups (p < 0.0001). In the BAFO% values, the G1 group presented 54.97 ± 9.56%, the G2 group 59.09 ± 10.13% and the G3 group 70.12 ± 11.07%, with statistical difference between the groups (p < 0.001). The results obtained in the evaluations show that the surface with microgrooves stimulates the process of osseointegration, accelerating the healing process, increasing the contact between the bone and the implant and the area of new bone formation.

Biomechanical and Histological Analysis of Titanium (Machined and Treated Surface) Versus Zirconia Implant Materials: An In Vivo Animal Study.

OBJECTIVES: The aim of this study was to perform an in vivo histological comparative evaluation of bone formation around titanium (machined and treated surface) and zirconia implants. For the present study were used 50 commercially pure titanium implants grade IV, being that 25 implants with a machined surface (TiM group), 25 implants with a treated surface (TiT group) and, 25 implants were manufactured in pure zirconia (Zr group). The implants (n = 20 per group) were installed in the tibia of 10 rabbits. The implants distribution was randomized (n = 3 implants per tibia). Five implants of each group were analyzed by scanning electron microscopy and an optical laser profilometer for surface roughness characterization. Six weeks after the implantation, 10 implants for each group were removed in counter-torque for analysis of maximum torque value. The remaining samples were processed, included in historesin and cut to obtain non-decalcified slides for histomorphological analyses and histomorphometric measurement of the percentage of bone-implant contact (BIC%). Comparisons were made between the groups using a 5% level of significance (p < 0.05) to assess statistical differences. The results of removal torque values (mean ± standard deviation) showed for the TiM group 15.9 ± 4.18 N cm, for TiT group 27.9 ± 5.15 N cm and for Zr group 11.5 ± 2.92 N cm, with significant statistical difference between the groups (p < 0.0001). However, the BIC% presented similar values for all groups (35.4 ± 4.54 for TiM group, 37.8 ± 4.84 for TiT group and 34.0 ± 6.82 for Zr group), with no statistical differences (p = 0.2171). Within the limitations of the present study, the findings suggest that the quality of the new bone tissue formed around the titanium implants present a superior density (maturation) in comparison to the zirconia implants.

Peri-Implant Bone Behavior after Single Drill versus Multiple Sequence for Osteotomy Drill.

OBJECTIVES: The present study aims to compare the drilling protocol effect on osseointegration event in three commercially available titanium dental implants with different drill protocol using a rabbit tibia model. MATERIALS AND METHODS: Three different drilling sequences were compared as follows: drilling sequence using a single unique drill of 4.2 mm conical implant (Group 1), drilling sequence using 3 consecutive cylindrical drills for a 4.1 mm cylindrical implant (Group 2), and drilling sequence using 3 consecutive conical drills for a 4.3 mm conical implant (Group 3). For each group, 18 drilling procedures and implant placements were performed, totalizing 54 commercially available titanium dental implants. The samples were removed 6 weeks after implantation. Resonance frequency analyses (RFA) were performed immediately after the implantation, and at 6 weeks removal torque test (RTt) and histological analysis were performed. RESULTS: The RFA measured showed statistical difference between the groups in time 1 and no significant statistical differences in time 2 (p > 0.05). In the RTt no significant difference was found between the 3 groups tested. Histomorphometric analysis showed no significant difference between groups in the bone-to-implant contact% (p > 0.05). CONCLUSION: In the present preclinical study, osteotomy using a single bur did not show differences regarding the proposed and evaluated tests parameters for assessing the peri-implant behavior.

Análise comparativa in vivo do potencial de osseointegração entre três marcas de implantes líderes no mercado europeu / In vivo comparative analysis of the osseointegration potential among three leading implant brands in the European market

Objetivos: avaliar in vivo (histomorfometricamente) o potencial de osseointegração de três marcas comerciais de implantes consideradas como de primeira linha no mercado mundial. Material e métodos: seis coelhos New Zealand, de mesmo peso e idade, receberam 24 implantes de diâmetros similares e comprimentos iguais, de três marcas com tratamentos de superfície variados: G1 (Nobel Biocare, Nobel Replace), G2 (MIS, V3) e G3 (Straumann, Bone Level). Os implantes foram colocados nas metáfises proximais e distais seguindo os protocolos de osteotomia. Após anestesia e sacrífi co dos animais, os implantes foram retirados 45 dias depois para análise histomorfométrica. Ainda, um implante de cada marca foi submetido à análise por MEV (Philips XL30) com diferentes aumentos, sendo as imagens obtidas no modo BSEs. A porcentagem de contato osso-implante entre os grupos foi analisada pelo teste Anova (α=0,05). Resultados: os três modelos de tratamento superficial produziram alta osteocondutividade e boa formação óssea, não havendo diferença entre os valores BIC (p=0,94). Conclusão: as três superfícies testadas apresentaram um grau de osseointegração muito similar.

Objectives: to evaluate by histomorphometrical methods (in vivo) the osseointegration potential of three different implant brands in the world market. Material and methods: six New Zealand rabbits of similar weight and age received 24 dental implants of similar diameters and same length, with three different implant surfaces G1 (Nobel Biocare, Nobel Replace), G2 (MIS, V3), e G3 (Straumann, Bone Level). The implants were installed at the proximal mesial and distal surfaces according the recommend osteotomies. After anesthesia and sacrifice, the implants were retrieved 45 days later for histomorphometrical analysis. Also, one implant from each company was evaluated under SEM BSE mode. The BIC percentage among groups was compared by statistical analysis (One-way ANOVA, 5% level of significance). Results: all three different implant surfaces provided high osteoconductivity and good bone formation, with no significant differences (p=0.94). Conclusion: similar osseointegration patterns were verified among the three tested implant brands.

DNA damage in dental pulp mesenchymal stem cells: An in vitro study.

The aim of this study was to evaluate the potential use of a DNA comet assay, DNA fragmentation fluorimetric assay and reactive oxygen species levels as potential biomarkers of genome conditions of dental pulp stem cells (DPSCs) isolated from dog canine teeth. Mesenchymal stem cells were isolated from the dental pulp collected from dog teeth. The results obtained suggest the ideal moment for clinical application of cellular therapy for this type of cell. The cell culture was maintained with Dulbecco's modified Eagle's medium supplemented with 10.00% fetal bovine serum for eight passages. During each passage, cell proliferation, oxidative stress and level of DNA fragmentation were assessed by3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium (MTT) assay, testing 2,7 dichlorodihydro-fluorescein-diacetate and PicoGreen®, respectively. There were important differences among the first three DPSC passages compared to passages 4-8 and a large number of nuclei with some levels of DNA damage (30.00 to 40.00% in initial DPSC passages and > 50.00% in late passages), indicating in vitro DPSC genomic fragility. Within the limitations of this study, the results suggest these relatively simple and inexpensive approaches - comet and DNA fragmentation assays - could help sort stem cells with less DNA damage for use in research or therapies.

The influence of drill length and irrigation system on heat production during osteotomy preparation for dental implants: an ex vivo study.

OBJECTIVE: This study aimed to measure the influence of drill length and irrigation system on heat production during osteotomy preparation for dental implants using bovine bone rib as experimental model. MATERIALS AND METHODS: Three groups were created: Group 1: drilling with three consecutive burs with double irrigation (internal and external) for a 4.0 mm conical implant; and Group 2 and Group 3: drilling with three consecutive burs with external irrigation for a 4.1 mm cylindrical implant and for a 4.3 mm conical implant, respectively. Four lengths were tested: 10, 12, 14 and 16 mm; in site prepared on bovine ribs using a surgical unit linked to a testing device, to standardize and simulate implant drilling procedures. Bone temperature variations were recorded using three thermocouples in different positions as of the crestal bone: 2 mm, position (p1); 7 mm, position 2 (p2); and 12 mm, position 3 (p3). RESULTS: The highest temperature changes were invariably recorded during the process of withdrawal. Significantly lower temperature changes (P < 0.02) could be recorded at maximum drilling depths during the shearing process regardless of drilling depth or irrigation method. Double irrigation was associated with significantly lower temperatures compared with external irrigation by the use of implant drills (P < 0.01). CONCLUSIONS: Within the limitations of this ex vivo study was possible concluded that the use a double irrigation system in multiple conventional drill for osteotomy can decrease the heat generation when increase the drill length.

Analysis of Implant Strength After Implantoplasty in Three Implant-Abutment Connection Designs: An In Vitro Study.

PURPOSE: The aim of this in vitro study was to assess the resistance to static fatigue of implants with different connections before and after implantoplasty. MATERIALS AND METHODS: Sixty conical implants and 60 abutments were used; 4-mm-diameter versions were available for each model. Three groups (n = 20) were established based on the following implant connections: external hexagon (group 1), internal hexagon (group 2), and Morse taper (group 3). The implants of each group were submitted to a compressive load before (n = 10) and after the implantoplasty (n = 10). The wear was performed in a mechanical lathe machine using a carbide bur, and the final dimensions of each sample were measured. All groups were subjected to quasi-static loading at a 30-degree angle to the implant axis in a universal testing machine and 5 mm out of the implant support. RESULTS: After the implantoplasty, the mean final diameter was 3.13 ± 0.033 mm for group 1, 3.23 ± 0.023 mm for group 2, and 3.25 ± 0.03 mm for group 3. The mean fracture strengths for the groups before and after the implantoplasty were, respectively, 773.1 ± 13.16 N and 487.1 ± 93.72 N in group 1; 829.4 ± 14.12 N and 495.7 ± 85.24 N in group 2; and 898.1 ± 19.25 N and 717.6 ± 77.25 N in group 3. CONCLUSION: Resistance to loading decreased significantly after implantoplasty, and varied among the three implant connection designs.

Effects of different torque levels on the implant-abutment interface in a conical internal connection.

The fit of the implant-abutment interface was assessed by the metallographic technique and by scanning electron microscopy (SEM), using solid abutment types at different torque levels. Forty Morse taper connections and forty solid abutments were used at different torque levels (repeated after 10 minutes) in the following groups (n = 10): 25 Ncm (group g1), 30 Ncm (group g2), 35 Ncm (group g3), and 40 Ncm (group g4). The samples were embedded in a metallographic resin, sectioned lengthwise, and polished. SEM images were used to measure the linear contacts and the fits between abutments and the internal walls of the implant. The overall mean gap and standard deviation were as follows: 9.0 ± 1.36 µm for group g1, 7.9 ± 2.81 µm for group g2, 2.0 ± 0.76 µm for group g3, and 0.3 ± 0.40 µm for group g4. A significant difference was observed in the average fit values between the groups (p < 0.05). The linear area of contact between the abutment and the implant increased as torque augmented. This study demonstrated that higher insertion torque values in a conical internal connection increase the fit (contact) of the implant-abutment interface.

Effects of different torque levels on the implant-abutment interface in a conical internal connection

Abstract The fit of the implant-abutment interface was assessed by the metallographic technique and by scanning electron microscopy (SEM), using solid abutment types at different torque levels. Forty Morse taper connections and forty solid abutments were used at different torque levels (repeated after 10 minutes) in the following groups (n = 10): 25 Ncm (group g1), 30 Ncm (group g2), 35 Ncm (group g3), and 40 Ncm (group g4). The samples were embedded in a metallographic resin, sectioned lengthwise, and polished. SEM images were used to measure the linear contacts and the fits between abutments and the internal walls of the implant. The overall mean gap and standard deviation were as follows: 9.0 ± 1.36 µm for group g1, 7.9 ± 2.81 µm for group g2, 2.0 ± 0.76 µm for group g3, and 0.3 ± 0.40 µm for group g4. A significant difference was observed in the average fit values between the groups (p < 0.05). The linear area of contact between the abutment and the implant increased as torque augmented. This study demonstrated that higher insertion torque values in a conical internal connection increase the fit (contact) of the implant-abutment interface.