Adding mechanobiological cell features to finite element analysis of an immediately loaded dental implant.

Finite element analysis (FEA) has been used to analyze the behavior of dental materials, mainly in implantology. However, FEA is a mechanical analysis and few studies have tried to simulate the biological characteristics of the healing process of loaded implants. This study used the rule of mixtures to simulate the biological healing process of immediate implants in an alveolus socket and bone-implant junction interface through FEA. Three-dimensional geometric models of the structures were obtained, and material properties were derived from the literature. The rule of mixtures was used to simulate the healing periods-immediate and early loading, in which the concentration of each cell type, based on in vivo studies, influenced the final elastic moduli. A 100 N occlusal load was simulated in axial and oblique directions. The models were evaluated for maximum and minimum principal strains, and the bone overload was assessed through Frost's mechanostat. There was a higher strain concentration in the healing regions and cortical bone tissue near the cervical portion. The bone overload was higher in the immediate load condition. The method used in this study may help to simulate the biological healing process and could be useful to relate FEA results to clinical practice.

Effects of hyperbaric oxygen treatment on implant osseointegration in experimental diabetes mellitus.

OBJECTIVE: To evaluate whether hyperbaric oxygen (HBO) treatment has a favorable effect on implant osseointegration in diabetic rabbits. MATERIAL AND METHODS: An experimental diabetes model was induced in 32 New Zealand rabbits through IV injection of alloxan. After the state of diabetes had been confirmed, one dental implant was placed in the metaphysical region of each animal's tibia. After the implants' placements, the animals were divided into two groups. Half of the animals underwent HBO treatment, while the other group did not receive HBO treatment and served as the control group. The animals were euthanized at the 4th and 8th weeks. The osseointegration of the implants were compared by histomorphometry and resonance frequency analysis (RFA). RESULTS: The Bone Implant Contact (BIC) values were significantly higher in the HBO group than in the control group at the 4th week. There was no difference in the BIC values between the groups at the 8th week. There was no significant difference in the RFA scores between the groups both at the 4th and 8th weeks after the operation. CONCLUSION: Histomorphometry findings suggest that HBO has positive effect on implant osseointegration in the early healing period in diabetic rabbits. However, implant stability is not affected by HBO treatment.

Oral implant osseointegration model in C57Bl/6 mice: microtomographic, histological, histomorphometric and molecular characterization.

INTRODUCTION: Despite the successful clinical application of titanium (Ti) as a biomaterial, the exact cellular and molecular mechanisms responsible for Ti osseointegration remains unclear, especially because of the limited methodological tools available in this field. OBJECTIVE: In this study, we present a microscopic and molecular characterization of an oral implant osseointegration model using C57Bl/6 mice. MATERIAL AND METHODS: Forty-eight male wild-type mice received a Ti implant on the edentulous alveolar crest and the peri-implant sites were evaluated through microscopic (µCT, histological and birefringence) and molecular (RealTimePCRarray) analysis in different points in time after surgery (3, 7, 14 and 21 days). RESULTS: The early stages of osseointegration were marked by an increased expression of growth factors and MSC markers. Subsequently, a provisional granulation tissue was formed, with high expression of VEGFb and earlier osteogenic markers (BMPs, ALP and Runx2). The immune/inflammatory phase was evidenced by an increased density of inflammatory cells, and high expression of cytokines (TNF, IL6, IL1) chemokines (CXCL3, CCL2, CCL5 and CXC3CL1) and chemokine receptors (CCR2 and CCR5). Also, iNOS expression remained low, while ARG1 was upregulated, indicating predominance of a M2-type response. At later points in time, the bone matrix density and volume were increased, in agreement with a high expression of Col1a1 and Col21a2. The remodelling process was marked by peaks of MMPs, RANKL and OPG expression at 14 days, and an increased density of osteoclasts. At 21 days, intimate Ti/bone contact was observed, with expression of final osteoblast differentiation markers (PHEX, SOST), as well as red spectrum collagen fibers. CONCLUSIONS: This study demonstrated a unique molecular view of oral osseointegration kinetics in C57Bl/6 mice, evidencing potential elements responsible for orchestrating cell migration, proliferation, ECM deposition and maturation, angiogenesis, bone formation and remodeling at the bone-implant interface in parallel with a novel microscopic analysis.

Evaluation of Maxillary Sinus Septa Prior to Dental Implant Therapy: A Cone Beam Computed Tomography Study / Evaluación del Septo del Seno Maxilar Antes del Tratamiento con Implantes Dentales: Un Estudio con Tomografía Computarizada de Haz Cónico

SUMMARY: The objective of this study was to investigate the prevalence and location of maxillary sinus septa prior to dental implant therapy in different age groups by cone beam computed tomography (CBCT) and identify the most helpful orthogonal plane for this purpose. CBCT scans of 200 patients were selected. The final sample was divided into four groups according to age: (1) 30-39 y.o.; (2) 40-49 y.o.; (3) 50-59 y.o.; (4) +60 y.o. Three calibrated examiners assessed the presence and location (anterior, middle, posterior) of sinus septa using all orthogonal slices. The prevalence of septa per region and plane was compared by chi-square test. Among 359 maxillary sinuses evaluated, it was observed at least one septum in 163 sinuses (45.4 %). Overall, the anterior region was the most prevalent. However, when the age groups were considered, the anterior region was only the most prevalent in groups 2 and 3. The middle and posterior regions were more prevalent in groups 4 and 1, respectively. In conclusion, the prevalence of maxillary sinus septa in patients who were candidate to dental implant therapy was notably high. It was observed that the anterior region of the sinus was the most prevalent and the axial slice was the most representative.

RESUMEN: El objetivo de este estudio fue investigar la prevalencia y localización del septo del seno maxilar antes del tratamiento con implantes dentales en diferentes grupos etarios, por medio de la Tomografía Computarizada de Haz Cónico (TCHC). Fueron seleccionadas TCHC de 200 pacientes. La muestra final fue dividida en cuatro grupos de acuerdo con la edad: (1) 30-39 años; (2) 40-49 años; (3) 50-59 años y (4) +60 años. Tres examinadores calibrados evaluaron la presencia y localización (anterior, media o posterior) del septo del seno maxilar usando todas las secciones ortogonales. La prevalencia del septo por región y plano fue comparada mediante el test x-cuadrado. Entre los 359 senos maxilares evaluados, fue observado por lo menos un septo en 163 senos (45,4 %). Generalmente la región anterior fue la más prevalente. Sin embargo, cuando fueron considerados los grupos etarios, solamente la región anterior fue la más prevalente en los grupos 2 y 3. Las regiones media y posterior fueron las más prevalente en los grupos 4 y 1, respectivamente. La prevalencia del septo del seno maxilar en pacientes que son candidatos a tratamiento con implantes dentales fue notablemente alta. Se observó que la región anterior fue la más prevalente siendo las secciones axiales las más representativas.

Oral implant osseointegration model in C57Bl/6 mice: microtomographic, histological, histomorphometric and molecular characterization

Abstract Despite the successful clinical application of titanium (Ti) as a biomaterial, the exact cellular and molecular mechanisms responsible for Ti osseointegration remains unclear, especially because of the limited methodological tools available in this field. Objective: In this study, we present a microscopic and molecular characterization of an oral implant osseointegration model using C57Bl/6 mice. Material and Methods: Forty-eight male wild-type mice received a Ti implant on the edentulous alveolar crest and the peri-implant sites were evaluated through microscopic (μCT, histological and birefringence) and molecular (RealTimePCRarray) analysis in different points in time after surgery (3, 7, 14 and 21 days). Results: The early stages of osseointegration were marked by an increased expression of growth factors and MSC markers. Subsequently, a provisional granulation tissue was formed, with high expression of VEGFb and earlier osteogenic markers (BMPs, ALP and Runx2). The immune/inflammatory phase was evidenced by an increased density of inflammatory cells, and high expression of cytokines (TNF, IL6, IL1) chemokines (CXCL3, CCL2, CCL5 and CXC3CL1) and chemokine receptors (CCR2 and CCR5). Also, iNOS expression remained low, while ARG1 was upregulated, indicating predominance of a M2-type response. At later points in time, the bone matrix density and volume were increased, in agreement with a high expression of Col1a1 and Col21a2. The remodelling process was marked by peaks of MMPs, RANKL and OPG expression at 14 days, and an increased density of osteoclasts. At 21 days, intimate Ti/bone contact was observed, with expression of final osteoblast differentiation markers (PHEX, SOST), as well as red spectrum collagen fibers. Conclusions: This study demonstrated a unique molecular view of oral osseointegration kinetics in C57Bl/6 mice, evidencing potential elements responsible for orchestrating cell migration, proliferation, ECM deposition and maturation, angiogenesis, bone formation and remodeling at the bone-implant interface in parallel with a novel microscopic analysis.

Effects of hyperbaric oxygen treatment on implant osseointegration in experimental diabetes mellitus

Abstract Objective To evaluate whether hyperbaric oxygen (HBO) treatment has a favorable effect on implant osseointegration in diabetic rabbits. Material and Methods An experimental diabetes model was induced in 32 New Zealand rabbits through IV injection of alloxan. After the state of diabetes had been confirmed, one dental implant was placed in the metaphysical region of each animal's tibia. After the implants' placements, the animals were divided into two groups. Half of the animals underwent HBO treatment, while the other group did not receive HBO treatment and served as the control group. The animals were euthanized at the 4th and 8th weeks. The osseointegration of the implants were compared by histomorphometry and resonance frequency analysis (RFA). Results The Bone Implant Contact (BIC) values were significantly higher in the HBO group than in the control group at the 4th week. There was no difference in the BIC values between the groups at the 8th week. There was no significant difference in the RFA scores between the groups both at the 4th and 8th weeks after the operation. Conclusion Histomorphometry findings suggest that HBO has positive effect on implant osseointegration in the early healing period in diabetic rabbits. However, implant stability is not affected by HBO treatment.

Impact of Inorganic Xenograft on Bone Healing and Osseointegration: An Experimental Study in Rabbits.

PURPOSE: To evaluate if an inorganic graft applied before implant insertion interferes with osseointegration. MATERIALS AND METHODS: The bilateral mandibular incisors of 12 rabbits were extracted. One of the sockets was randomly filled with an inorganic xenogenic bone graft, whereas the remaining socket was allowed to heal naturally and served as a control. After 60 days, titanium implants were inserted into healing areas. The animals were killed 60 days after. Bone depositions were marked with fluorochrome oxytetracycline, alizarin, and calcein and evaluated using confocal laser scanning microscopy. Bone-to-implant contact (BIC) and bone area (BA) within the limits of the implant threads were analyzed. Data were compared statically by paired t tests, one-way ANOVA, and Bonferroni post hoc tests (α = 0.05). RESULTS: No differences between the control and experimental groups in bone deposition for each marker, in either the BIC or BA analysis were observed. The bone deposition marked by alizarin (14-21 days) was the highest, followed by oxytetracycline (0 and 7 days) and calcein (45 and 52 days) in both groups (P < 0.05). CONCLUSION: The bone healing or the course of osseointegration was not impaired by the use of an inorganic xenogenic graft before insertion of a titanium implant.

Effect of the long-term administration of Cyclosporine A on bone healing around osseointegrated titanium implants: A histomorphometric study in the rabbit tibia.

The aim of this study was to investigate the effect of cyclosporine A (CsA) therapy on bone healing around osseointegrated implants in the rabbit by means of descriptive histologic and histomorphometric analyses. Eighteen rabbits received one implant each in the right tibia proximal metaphysis. After the bone-healing period of 3 months, 6 randomly selected animals were sacrificed (Group CTL-12) before the immunosuppression therapy initiation to obtain a standard of implant integration. Another six randomly selected animals were submitted to a daily subcutaneous (sc) injection of 10 mg/kg CsA (Group CsA) whereas the six remaining animals received daily sc injections of saline solution (Group CTL-24). Groups CTL-24 and CsA were sacrificed after another 12 weeks. Bone-to-implant contact (BIC), and bone area fraction occupancy (BAFO) within the implant threads were measured. Bone density (BD) and descriptive histological analyses were also accomplished. Rabbits under CsA therapy presented statistically lower percentage of BIC (33.28 ± 6.19) compared to the animals of CLT-24 (55.6 ± 17.73). No differences were found between CsA and CTL-12 (38.7 ± 7.87). Significant decreased percentage of BAFO between the implant threads in the CsA (48.43 ± 9.48) group compared to the CTL-24 (72.26 ± 11.72) was observed. No differences were found between CsA and CTL-12 (61.99 ± 13.94) groups. BD analysis showed significant lower BD in the CsA (48.56 ± 9.32) group compared to the CTL-12 (68.74 ± 10.89) and CTL-24 (77.96 ± 4.96) groups. Collectively, our findings demonstrated that CsA therapy negatively affect the bone healing around osseointegrated implants due to the significant lower values for BIC, BAFO, and BD.

Effect of different implant placement depths on crestal bone levels and soft tissue behavior: a randomized clinical trial.

OBJECTIVES: This randomized clinical trial analyzed crestal bone changes and soft tissue dimensions surrounding implants with an internal tapered connection placed in the mandible anterior region at different depths (equicrestal and subcrestal). MATERIALS AND METHODS: Eleven edentulous patients (five implants per patient) were randomly divided in a split-mouth design: G1, 28 equicrestal implants; and G2, 27 subcrestal implants. All implants were immediately loaded. Correlation between keratinized tissue width (KTW) and vertical mucosa thickness (MT) with soft tissue recession was analyzed. Intraoral radiographs were used to evaluate crestal bone changes. Patients were assessed immediately, 4-, and 8-months after implant placement. Rank-based ANOVA-type statistical test was used for comparison between groups (α = 0.05). RESULTS: Fifty-five implants (G1 = 28 and G2 = 27) were assessed in 11 patients. Implant survival rate was 100% for both groups. Both tested implant placement depths presented similar crestal bone loss (P > 0.05). Significant crestal bone loss for each group was found in the different measurement times (T4 and T8) (P < 0.05). Implant placement depths, KTW, and vertical MT had no effect on soft tissue recession (P > 0.05). CONCLUSIONS: Different implant placement depths do not influence crestal bone changes. Soft tissue behavior is not influenced by different implant placement depths or by the amount of keratinized tissue.

Effects of metformin on bone healing around titanium implants inserted in non-diabetic rats.

OBJECTIVE: To evaluate the effects of metformin on bone healing around titanium implants inserted in non-diabetic rats. METHODS: Twenty Wistar rats were randomly assigned to one of the following groups: control group (n = 10): rats without metformin treatment; MT group (n = 10): rats treated with metformin (40 mg/kg/day by gavage). At thirty days after implant placement, animals were euthanized. Histometric measurements of bone-to-implant contact (BIC) and bone area (BA), in addition to immunohistochemical analysis of the number of cells stained for RANKL and OPG, were assessed in the cortical and medullary areas around implants. RESULTS: The percentages of BIC and BA in the cortical bone were significantly lower in the MT group than in the control group (P < 0.05). Furthermore, the medullary bone around the implants inserted in the metformin-treated animals exhibited an increased number of RANKL-stained cells than that around the implants inserted in the control animals (P < 0.05). CONCLUSIONS: Metformin negatively affected osseointegration by reducing the percentages of BIC and BA and increasing the expression of RANKL around titanium implants inserted in non-diabetic rats.

Functional investigation of bone implant viability using radiotracers in a new model of osteonecrosis.

OBJECTIVES:: Conventional imaging methods are excellent for the morphological characterization of the consequences of osteonecrosis; however, only specialized techniques have been considered useful for obtaining functional information. To explore the affinity of radiotracers for severely devascularized bone, a new mouse model of isolated femur implanted in a subcutaneous abdominal pocket was devised. To maintain animal mobility and longevity, the femur was harvested from syngeneic donors. Two technetium-99m-labeled tracers targeting angiogenesis and bone matrix were selected. METHODS:: Medronic acid and a homodimer peptide conjugated with RGDfK were radiolabeled with technetium-99m, and biodistribution was evaluated in Swiss mice. The grafted and control femurs were evaluated after 15, 30 and 60 days, including computed tomography (CT) and histological analysis. RESULTS:: Radiolabeling achieved high (>95%) radiochemical purity. The biodistribution confirmed good blood clearance 1 hour after administration. For 99mTc-hydrazinonicotinic acid (HYNIC)-E-[c(RGDfK)2, remarkable renal excretion was observed compared to 99mTc-methylene diphosphonate (MDP), but the latter, as expected, revealed higher bone uptake. The results obtained in the control femur were equal at all time points. In the implanted femur, 99mTc-HYNIC-E-[c(RGDfK)2 uptake was highest after 15 days, consistent with early angiogenesis. Regarding 99mTc-MDP in the implant, similar uptake was documented at all time points, consistent with sustained bone viability; however, the uptake was lower than that detected in the control femur, as confirmed by histology. CONCLUSIONS:: 1) Graft viability was successfully diagnosed using radiotracers in severely ischemic bone at all time points. 2) Analogously, indirect information about angiogenesis could be gathered using 999mTc-HYNIC-E-[c(RGDfK)2. 3) These techniques appear promising and warrant further studies to determine their potential clinical applications.

Functional investigation of bone implant viability using radiotracers in a new model of osteonecrosis

OBJECTIVES: Conventional imaging methods are excellent for the morphological characterization of the consequences of osteonecrosis; however, only specialized techniques have been considered useful for obtaining functional information. To explore the affinity of radiotracers for severely devascularized bone, a new mouse model of isolated femur implanted in a subcutaneous abdominal pocket was devised. To maintain animal mobility and longevity, the femur was harvested from syngeneic donors. Two technetium-99m-labeled tracers targeting angiogenesis and bone matrix were selected. METHODS: Medronic acid and a homodimer peptide conjugated with RGDfK were radiolabeled with technetium-99m, and biodistribution was evaluated in Swiss mice. The grafted and control femurs were evaluated after 15, 30 and 60 days, including computed tomography (CT) and histological analysis. RESULTS: Radiolabeling achieved high (>95%) radiochemical purity. The biodistribution confirmed good blood clearance 1 hour after administration. For 99mTc-hydrazinonicotinic acid (HYNIC)-E-[c(RGDfK)2, remarkable renal excretion was observed compared to 99mTc-methylene diphosphonate (MDP), but the latter, as expected, revealed higher bone uptake. The results obtained in the control femur were equal at all time points. In the implanted femur, 99mTc-HYNIC-E-[c(RGDfK)2 uptake was highest after 15 days, consistent with early angiogenesis. Regarding 99mTc-MDP in the implant, similar uptake was documented at all time points, consistent with sustained bone viability; however, the uptake was lower than that detected in the control femur, as confirmed by histology. CONCLUSIONS: 1) Graft viability was successfully diagnosed using radiotracers in severely ischemic bone at all time points. 2) Analogously, indirect information about angiogenesis could be gathered using 999mTc-HYNIC-E-[c(RGDfK)2. 3) These techniques appear promising and warrant further studies to determine their potential clinical applications.

Avaliação histológica e histomorfométrica da energia superficial e molhabilidade em implantes de titânio grau IV e grau V: estudo experimental em coelhos / Histologic and histomorphometric evaluation of surface energy and wettability in dental implants of titanium grade IV and V: experimental study in rabbits

O presente estudo teve como objetivo avaliar a resposta biológica ao redor de implantes de titânio grau IV (titânio comercialmente puro) e grau V (Ti6Al4V), com diferentes tipos de tratamentos de superfície através da análise do contato ossoimplante (bone implant contact - BIC) e da área de neoformação óssea com e sem fluorocromo (bone area BA e BAfluo) das 3 primeiras roscas em contato ósseo de cada implante. Para isso, utilizou-se um total de 90 implantes Cone Morse de titânio grau IV (Drive 45 implantes) e titânio grau V (Facility 45 implantes), com dimensões de 3.5x8mm e 2.9x7mm, respectivamente. Estes dois tipos de implantes foram avaliados em três tratamentos de superfícies diferentes: a) superfície com jateamento com partículas abrasivas seguido de tratamento ácido - NeoPoros (NP) - em embalagem seca (Grupo Controle); b) superfície jateada seguido de tratamento ácido e energia de superfície, armazenado em líquido (ESm); c) superfície jateada seguido de tratamento ácido com energia de superfície e embalado a seco (ESs); totalizando 6 grupos, distribuídos em 15 coelhos New Zealand, em cada um foram instalados 6 implantes, sendo 3 em cada tíbia. Após 15 dias de osseointegração, os coelhos passaram por eutanásia e as tíbias seccionadas, fixadas e incluídas para a avaliação histológica e histomorfométrica. Mensurações no analisador de imagens ImageJ foram realizadas e a análise dos dados estatísticos, de todos os grupos foram avaliados através da análise de variância a dois critérios e do teste de Tukey para comparações múltiplas grupo a grupo, adotando o nível de significância de 5% (p<0,05). Os resultados mostraram que não houve diferença estatisticamente significante entre os dois tipos de titânio, porém houve diferença estatisticamente significante entre os tipos de superfície em relação ao BIC, BA e BAfluo; também, não houve interação entre titânio e superfície. Na análise do contato osso-implante (BIC) a superfície ESm teve melhor desempenho em relação ao NP, que por sua vez foi semelhante ao ESs. Quanto à área óssea (BA), a superfície NP teve menor desempenho em relação à ESs, este obteve semelhante desempenho a ESm. Quanto a área ósseo neoformada com presença de fluorocromo (BAfluo), NP teve menor desempenho em relação ao ESs, o qual obteve semelhante comportamento a ESm. Com isso, concluiu-se que implantes de titânio de gau IV e grau V obtiveram respostas biológicas equivalentes, enquanto que a energia de superfície com a molhabilidade podem ser consideradas como vantagem, uma vez que otimizam o processo de osseointegração.(AU)

This study aimed to evaluate the biological response around grade IV (commercially pure titanium) and grade V (Ti6Al4V) titanium implants with different types of surface treatments by analyzing bone-implant contact (BIC) and the bone formation area with and without fluorochrome (BA and BAfluo) of the 3 first threads on bone contact of each implant. To this end, this study used 90 Morse Taper grade IV (Drive - 45 implants) and grade V (Facility - 45 implants) titanium implants, measuring 3.5x8mm and 2.9x7mm, respectively. Both types of implants were evaluated in three different surface treatments: a) blasted/acid-etched implant surface - NeoPoros (NP) - dry pack (control group); b) blasted/acid-etched implant surface and surface energy, stored in liquid (ESm); c) blasted/acid-etched implant surface with surface energy and dry packed (ESs); totalizing 6 groups, distributed in 15 New Zealand rabbits. Six implants were placed in each rabbit, 3 in each tibia. After 15 days of osseointegration, the rabbits were euthanized and the tibias sectioned, fixed and embedded for histologic and histomorphometric evaluation. Measurements were carried out using the image analysis program ImageJ and the assessment of statistical data concerning all groups was done through the two-way analysis of variance and the Tukey test for multiple comparisons group to group, adopting the significance level of 5% ( p <0.05). The results showed no statistically significant difference between the types of titanium used. However, there were statistically significant differences between the types of surface in relation to the BIC, BA and BAfluo. In addition, there was no interaction between titanium and the surface. Concerning the analysis of bone-implant contact (BIC), the ESm surface had better performance compared to the NP, which, in turn, was similar to the ESs. As for bone area (BA), the NP surface had lower performance in relation to the ESs surface, as the latter had a similar performance to the ESm surface. Concerning the newly formed bone area with presence of fluorochrome (BAfluo), the NP had lower performance if compared to the ESs, which behaved similarly to that of the ESm surface. Thus, this study concluded that grade IV and grade V titanium implants showed equivalent biological responses, while the surface energy, together with its wettability, can be considered an advantage, enhancing the osseointegration process.(AU)

Stress Distribution Around Dental Implants Placed at Different Depths.

INTRODUCTION: The progressive bone loss at the neck of dental implant is a clinical concern since it affects the maintenance of dental aesthetics. The current study evaluated the influence of insertion depth, prosthetic connection, and type of loading on the stress distribution around dental implants, using photoelastic evaluation. MATERIALS AND METHODS: A total of three blocks of photoelastic resin for each type of implant connection (external hexagon, external hexagon flattened, internal hexagon, and Morse taper) were built. Each block differed in the position of the implant platform in relative to the upper margin of the block: I (2 mm below), II (at the same level), and III (2 mm above). A force of 100 N was applied to both straight and tilted abutments. Totally, 4 selected points were evaluated at 1 side of the implant. Quantitative data were collected for the statistical analysis. RESULTS: A multiple linear regression showed the relation between the stress distribution and the insertion depth. For all the implant types, both with straight and tilted abutments, group I presented the lowest stress concentration around the fixture when compared with group II and III (P < 0.05). CONCLUSIONS: Within the limitations of this study, it could be concluded that the deeper the insertion, the lower the stress concentration.

The influence of the connection, length and diameter of an implant on bone biomechanics.

BACKGROUND: Regardless of the multiple options of connections, diameters and heights for dental implants, the clinician should know the biomechanical behavior of the bone to plan the treatment according to the biological and anatomical conditions of each patient, without risk to the long-term treatment success. REVIEW: The following review attempts to summarize the relevant literature to establish guidelines for clinicians based on the scientific evidence regarding the influence by the implant's connection, diameter and length on the bone biomechanics. CONCLUSIONS: The length, diameter and connection of each implant have a degree of influence in bone biomechanics. Despite the influence of different implant connections, diameters and lengths on peri-implant bone stress and strain, these characteristics should remain within the physiological limits to avoid a pathological overload, bone resorption and consequent risk to the long-term success of implant-prosthetic treatment.

Measurement of elastic modulus and Vickers hardness of surround bone implant using dynamic microindentation--parameters definition.

The clinical performance of dental implants is strongly defined by biomechanical principles. The aim of this study was to quantify the Vicker's hardness (VHN) and elastic modulus (E) surround bone to dental implant in different regions, and to discuss the parameters of dynamic microindantion test. Ten cylindrical implants with morse taper interface (Titamax CM, Neodent; 3.5 mm diameter and 7 mm a height) were inserted in rabbit tibia. The mechanical properties were analyzed using microhardness dynamic indenter with 200 mN load and 15 s penetration time. Seven continuous indentations were made distancing 0.08 mm between each other perpendicularly to the implant-bone interface towards the external surface, at the limit of low (Lp) and high implant profile (Hp). Data were analyzed by Student's t-test (a=0.05) to compare the E and VHN values obtained on both regions. Mean and standard deviation of E (GPa) were: Lp. 16.6 ± 1.7, Hp. 17.0 ± 2.5 and VHN (N/mm2): Lp. 12.6 ± 40.8, Hp. 120.1 ± 43.7. No statistical difference was found between bone mechanical properties of high and low profile of the surround bone to implant, demonstrating that the bone characterization homogeneously is pertinent. Dynamic microindantion method proved to be highly useful in the characterization of the individual peri-implant bone tissue.

Influence of implant/abutment connection on stress distribution to implant-surrounding bone: a finite element analysis.

PURPOSE: The objective of this study was to analyze and compare the stress distribution in the cortical and trabecular bone between the internal hexagon and the Morse taper systems, both with straight abutments. MATERIALS AND METHODS: Two implant systems (Morse taper and internal hexagon connections) were simulated in maxillary bone. Loads of 100 N (axial) and 50 N (oblique) in relation to the implant axes were applied. The 3D finite element method was used to simulate and analyze the present study. The analyzed parameters were ultimate tensile strength and Von Mises stress. RESULTS: Both systems presented stresses below the bone tissue physiological limit as well as a similar distribution in quantitative values, with a higher concentration of tension in the cortical surface near the neck of the implant in the two conditions of applied loads, with higher values for the internal hexagon system. When the groups were evaluated individually, the internal hexagon system showed higher compressive stresses, while in the Morse taper system, the highest values were traction. CONCLUSIONS: There was a difference in the stress location on the prosthetic components of the systems studied; however, it did not influence trabecular bone stress generation.

Mechanical property assessment of bone healing around a titanium-zirconium alloy dental implant.

BACKGROUND: It has been reported that titanium-zirconium alloy with 13-17% zirconium (TiZr1317) implants show higher biomechanical stability and bone area percentage relative to commercially pure titanium (cpTi) grade 4 fixtures. PURPOSE: This study aimed to determine whether the higher stability for TiZr1317 implants is associated with higher mechanical properties of remodeling bone in the areas around the implants. MATERIALS AND METHODS: This study utilized 36 implants (n = 18: TiZr1317, n = 18: cpTi), which were placed in the healed ridges of the mandibular premolar and first molar of 12 mini pigs (n = 3 implants/animal). After 4 weeks in vivo, the samples were retrieved, and resin-embedded histologic sections of approximately 100 µm in thickness were prepared. In order to determine the nanomechanical properties, nanoindentation (n = 30 tests/specimen) was performed on the bone tissue of the sections under wet conditions with maximum load of 300 µN (loading rate: 60 µN/s). RESULTS: The mean (± standard deviation) elastic modulus (E) and hardness (H) for the TiZr1317 group were 2.73 ± 0.50 GPa and 0.116 ± 0.017 GPa, respectively. For the cpTi group, values were 2.68 ± 0.51 GPa and 0.110 ± 0.017 GPa for E and H, respectively. Although slightly higher mechanical properties values were observed for the TiZr1317 implants relative to the cpTi for both elastic modulus and hardness, these differences were not significant (E = p > 0.75; H = p > 0.59). CONCLUSIONS: The titanium-zirconium alloy used in this study presented similar degrees of nanomechanical properties to that of the cpTi implants.