RESUMO
STATEMENT OF PROBLEM: Consideration of the thickness of alveolar bone on both the palatal and labial sides and the inclination angle of teeth is important for immediate implant placement in the maxillary anterior region. However, comprehensive research exploring how sex and age influence the thickness of bone and tooth angle in the maxillary anterior region is lacking. PURPOSE: The purpose of this clinical study was to investigate the effect of sex and age on the thickness of labial and palatal bone and on the tooth inclination angle of maxillary central and lateral incisors using cone beam computed tomography (CBCT) images in an Asian population. MATERIAL AND METHODS: The labial and palatal bone thickness and the inclination angle of maxillary central and lateral incisors were measured from the CBCT images of 149 participants aged between 20 and 65 years. The correlation between the angles of the maxillary central and lateral incisors and sex and age on the tooth angles and thicknesses of labial and palatal bone was determined statistically. RESULTS: A high correlation (R=0.73) was found between the angle of maxillary central and lateral incisors. Men had higher angles of the maxillary central and lateral incisors and thicker palatal bone at the middle and root of the teeth compared with women. In both sexes, the angle and palatal bone thickness of maxillary central incisors were significantly higher than those of maxillary lateral incisors. The angle of both maxillary central and lateral incisors decreased gradually with age, with a difference in angle of over 10 degrees. CONCLUSIONS: The study revealed that women exhibited relatively thinner palatal bone compared with men. Additionally, participants aged between 40 and 65 years exhibited significantly thicker palatal bone compared with younger age groups, potentially providing a larger site for implant placement. Furthermore, tooth angle gradually decreases with age in the maxillary anterior region.
RESUMO
OBJECTIVE: This study proposed a new classification method of bone quantity and quality at the dental implant site using cone-beam computed tomography (CBCT) image analysis, classifying cortical and cancellous bones separately and using CBCT for quantitative analysis. METHODS: Preoperative CBCT images were obtained from 128 implant patients (315 sites). First, measure the crestal cortical bone thickness (in mm) and the cancellous bone density [in grayscale values (GV) and bone mineral density (g/cm3)] at the implant sites. The new classification for bone quality at the implant site proposed in this study is a "nine-square division" bone classification system, where the cortical bone thickness is classified into A: > 1.1 mm, B:0.7-1.1 mm, and C: < 0.7 mm, and the cancellous bone density is classified into 1: > 600 GV (= 420 g/cm3), 2:300-600 GV (= 160 g/cm3-420 g/cm3), and 3: < 300 GV (= 160 g/cm3). RESULTS: The results of the nine bone type proportions based on the new jawbone classification were as follows: A1 (8.57%,27/315), A2 (13.02%), A3 (4.13%), B1 (17.78%), B2 (20.63%), B3 (8.57%) C1 (4.44%), C2 (14.29%), and C3 (8.57%). CONCLUSIONS: The proposed classification can complement the parts overlooked in previous bone classification methods (bone types A3 and C1). TRIAL REGISTRATION: The retrospective registration of this study was approved by the Institutional Review Board of China Medical University Hospital, No. CMUH 108-REC2-181.
Assuntos
Implantes Dentários , Humanos , Estudos Retrospectivos , Tomografia Computadorizada por Raios X , Arcada Osseodentária , Tomografia Computadorizada de Feixe Cônico , Densidade ÓsseaRESUMO
PURPOSE: Reconstruction plates are frequently used to treat mandibular segmental defects. The aim of this study is to compare the biomechanical performance of a 3-dimensional-printed self-designed titanium alloy reconstruction plate with that of the traditional reconstruction plate in mandible reconstruction. The analyzed parameters of the self-designed reconstruction plate, including plate length (100 mm and 125 mm), plate thickness (2.1, 2.4, and 2.7 mm), and bone mass (100, 75, and 50%), were also evaluated. METHODS: An artificial mandible with anatomical geometry was used to develop the self-designed reconstructed plate. Both in vitro experiments and finite element simulations were performed for the biomechanical comparison of the self-designed and traditional reconstruction plates. In finite element analysis, 3 major muscle forces of mandible movement were set as the loading condition, and the displacement of the condyle was fixed in all directions as the boundary condition. RESULTS: The biomechanical performances (stresses in the plate and strains in bone) of the self-designed reconstruction plate were superior to those of the traditional plate. Factorial analysis indicated that plate length and thickness had significant effects on decreasing stresses of the plate and mandibular bone. CONCLUSIONS: The self-designed reconstruction plate might have a benefit to reduce the stresses/strains in plate itself and surrounding bone.
Assuntos
Mandíbula , Reconstrução Mandibular , Fenômenos Biomecânicos , Placas Ósseas , Análise de Elementos Finitos , Humanos , Mandíbula/cirurgia , Reconstrução Mandibular/métodos , Impressão Tridimensional , Estresse MecânicoRESUMO
BACKGROUND/PURPOSE: Incisor liability is the discrepancy in the sum of the mesiodistal crown width between the primary and permanent incisors. Incisor liability affects the integrity and eruption of the permanent incisors during the transition from the primary to permanent dentition. This study investigated the incisor liability in the primary dentition of Taiwanese children. METHODS: The digital periapical films of 203 upper arches of 105 boys and 98 girls and 195 lower arches of 119 boys and 76 girls aged between 3 and 6 years were selected in this retrospective study. The mesiodistal crown widths of the primary and permanent incisors were measured using the medical imaging software for both arches. Differences in incisor liability values were statistically analyzed. RESULTS: The mean ± standard deviation of the incisor liability values were 8.32 ± 1.88 and 6.91 ± 1.13 mm for the upper and lower arches, respectively, in all children. The incisor liability was closely related with the total crown widths of the permanent incisors for upper and lower arches. The incisor liability values were higher among boys than girls for the upper but not lower arch. CONCLUSION: Incisor liability differs depending on ethnicity. In Taiwanese children, incisor liability was closely related with the crown widths of the permanent incisors. The incisor liability values of boys were higher than those of girls in the upper arch but not the lower arch.
Assuntos
Incisivo , Erupção Dentária , Povo Asiático , Criança , Pré-Escolar , Feminino , Humanos , Masculino , Estudos RetrospectivosRESUMO
OBJECTIVE: The study objective was to investigate four common occlusal modes by using the finite element (FE) method and to conduct a biomechanical analysis of the periodontal ligament (PDL) and surrounding bone when orthodontic force is applied. MATERIALS AND METHODS: A complete mandibular FE model including teeth and the PDL was established on the basis of cone-beam computed tomography images of an artificial mandible. In the FE model, the left and right mandibular first premolars were not modeled because both canines required distal movement. In addition, four occlusal modes were simulated: incisal clench (INC), intercuspal position (ICP), right unilateral molar clench (RMOL), and right group function (RGF). The effects of these four occlusal modes on the von Mises stress and strain of the canine PDLs and bone were analyzed. RESULTS: Occlusal mode strongly influenced the distribution and value of von Mises strain in the canine PDLs. The maximum von Mises strain values on the canine PDLs were 0.396, 1.811, 0.398, and 1.121 for INC, ICP, RMOL, and RGF, respectively. The four occlusal modes had smaller effects on strain distribution in the cortical bone, cancellous bone, and miniscrews. CONCLUSION: Occlusal mode strongly influenced von Mises strain on the canine PDLs when orthodontic force was applied. CLINICAL RELEVANCE: When an FE model is used to analyze the biomechanical behavior of orthodontic treatments, the effect of muscle forces caused by occlusion must be considered.
Assuntos
Ligamento Periodontal , Técnicas de Movimentação Dentária , Dente Pré-Molar/diagnóstico por imagem , Fenômenos Biomecânicos , Simulação por Computador , Análise de Elementos Finitos , Ligamento Periodontal/diagnóstico por imagem , Estresse MecânicoRESUMO
BACKGROUND/PURPOSE: Impact of the implant shape on the biomechanical performance of all-on-four treatment of dental implant is still unclear. This study evaluated the all-on-four treatment with four osseointegrated implants in terms of the biomechanical effects of implant design and loading position on the implant and surrounding bone by using both in vitro strain gauge tests and three-dimensional (3D) finite element (FE) analyses. METHODS: Both in vitro and 3D FE models were constructed with placing NobelSpeedy and NobelActive implants as well as a titanium framework in an edentulous jawbone based on the concept of all-on-four treatment. Three types of loads were applied: at the central incisor area (loading position 1) and at the molar regions with (loading position 2) and without (loading position 3) the denture cantilever. For the in vitro tests, the principal bone strains were recorded by rosette strain gauges and statistically evaluated using Wilcoxon's rank-sum test. The 3D FE simulations analyzed the peak von-Mises stresses in the implant and surrounding cortical bone. RESULTS: The peak stress and strain in the surrounding bone were typically 36-62% (3D FE analysis) and 47-57% (in vitro test) (p < 0.001)higher for loading position 3 than for loading positions 1 and 2. Between those two implant designs, the bone strains and bone stresses did not differ significantly. CONCLUSION: For all-on-four treatment with four osseointegrated dental implants, altering the implant design does not appear to affect the biomechanical performance of the entire treatment, especially in terms of the stresses and strains in the surrounding bone.
Assuntos
Mandíbula , Fenômenos Biomecânicos , Implantes Dentários , Análise do Estresse Dentário , Dentaduras , Análise de Elementos Finitos , Humanos , Técnicas In Vitro , Mandíbula/cirurgia , Estresse MecânicoRESUMO
BACKGROUND: In this study, we explored how various preprocessing approaches can be employed to enhance the capability of dental CBCT to accurately estimate trabecular bone microarchitectural parameters. METHODS: In total, 30 bovine vertebrae cancellous bone specimens were used for in study. Voxel resolution 18-µm micro-computed tomography (micro-CT) and 100-µm dental CBCT were used to scan each specimen. Micro-CT images were used to calculate trabecular bone microarchitectural parameters; the results were set as the gold standard. Subsequently, before the dental CBCT images were converted into binary images to calculate trabecular bone microarchitectural parameters, three preprocessing approaches were used to process the dental CBCT images. For Group 1, no preprocessing approach was applied. For Group 2, images were sharpened and despeckable noises were removed. For Group 3, the function of local thresholding was added to Group 2 to form Group 3. For Group 4, the air pixels was removed from Group 3 to form Group 4. Subsequently, all images were imported into a software package to estimate trabecular bone microarchitectural parameters (bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular number (TbN), and trabecular separation (TbSp)). Finally, a paired t-test and a Pearson correlation test were performed to compare the capability of micro-CT with the capability of dental CBCT for estimating trabecular bone microarchitectural parameters. RESULTS: Regardless of whether dental CBCT images underwent image preprocessing (Groups 1 to 4), the four trabecular bone microarchitectural parameters measured using dental CBCT images were significantly different from those measured using micro-CT images. However, after three image preprocessing approaches were applied to the dental CBCT images (Group 4), the BV/TV obtained using dental CBCT was highly positively correlated with that obtained using micro-CT (r = 0.87, p < 0.001); the correlation coefficient was greater than that of Group 1 (r = -0.15, p = 0.412), Group 2 (r = 0.16, p = 0.386), and Group 3 (r = 0.47, p = 0.006). After dental CBCT images underwent image preprocessing, the efficacy of using dental CBCT for estimating TbN and TbSp was enhanced. CONCLUSIONS: Image preprocessing approaches can be used to enhance the efficacy of using dental CBCT for predicting trabecular bone microarchitectural parameters.
Assuntos
Osso Esponjoso/diagnóstico por imagem , Tomografia Computadorizada de Feixe Cônico/veterinária , Arcada Osseodentária/diagnóstico por imagem , Animais , Bovinos , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , Sensibilidade e Especificidade , Microtomografia por Raio-XRESUMO
BACKGROUND: Intermittent parathyroid hormone (PTH) can be used to treat osteoporosis of the spine and hip. However, whether it can be used to treat osteoporosis of the mandible is unclear. The purpose of this study was to explore the influence of applying intermittent PTH to ovariectomized rats on the trabecular bone microarchitecture of the mandible and femoral head. METHODS: Eighteen female rats were divided into three groups: the healthy group, ovariectomized (OVX) group, and OVX + PTH group. The OVX group and OVX + PTH group had an OVX at 8 weeks of age. The OVX + PTH group received intermittent PTH therapy for 12 weeks. The mandibles and femurs of all rats were removed at 20 weeks and were then scanned using microcomputed tomography (micro-CT). RESULTS: From the micro-CT analysis, the trabecular bone microarchitecture of the mandible and femoral head are offered as follows: (1) The bone volume fraction and trabecular thickness in the OVX group were lower than those in the healthy group. (2) The bone volume fraction and trabecular thickness in the OVX + PTH group approximated those in the healthy group. CONCLUSION: The conclusions of this study regarding the trabecular bone microarchitecture of the mandible and femoral head are offered as follows: (1) The BV/TV and TbTh in the OVX group were lower than those in the healthy group. (2) The BV/TV and TbTh in the OVX + PTH group approximated those in the healthy group, therefore, intermittent PTH displayed high efficacy for treating femoral or mandibular deterioration of bone microstructure resulting from loss of ovarian function. Osteoporosis of the femur or mandible in the rats was ameliorated by intermittent PTH therapy.
Assuntos
Cabeça do Fêmur/efeitos dos fármacos , Cabeça do Fêmur/diagnóstico por imagem , Mandíbula/efeitos dos fármacos , Mandíbula/diagnóstico por imagem , Ovariectomia/efeitos adversos , Hormônio Paratireóideo/administração & dosagem , Animais , Feminino , Ovariectomia/tendências , Ratos , Ratos Wistar , Microtomografia por Raio-X/métodosRESUMO
BACKGROUND/PURPOSE: This study investigated the effects of three three-dimensional (3D) bone-to-implant contact (BIC) parameters-potential BIC area (pBICA), BIC area (BICA), and 3D BIC percentage (3D BIC%; defined as BICA divided by pBICA)-in relation to the implant diameter on primary implant stability, as well as their correlations were also evaluated. METHODS: Dental implants with diameters of 3.75, 4, 5, and 6 mm and artificial bone specimens were scanned by microcomputed tomography to construct 3D models for calculating pBICA, BICA, and 3D BIC%. Indexes of the primary implant stability including the insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ) were measured after implants with various diameters were placed into bone specimens. The Kruskal-Wallis test, Wilcoxon rank-sum test with Bonferroni adjustment, and Spearman correlations were all performed as statistical and correlation analyses. RESULTS: The implant diameter significantly influenced pBICA and BICA, but not 3D BIC%. ITV and PTV were more sensitive to implant diameter than was ISQ. The coefficients of determination were high (>0.92) for the correlations between pBICA (or BICA) and indexes of the primary implant stability. CONCLUSION: This study revealed how the implant diameter and the three-dimensional (3D) BIC influence the primary stabilities of dental implant. ITV and PTV were more sensitively influenced by the implant diameter than ISQ. The pBICA and BICA seem to be more important than 3D BIC % for using wider implant in treatment plan, since those two parameters are highly predictive of variations in the primary stability of dental implant.
Assuntos
Implantes Dentários , Análise do Estresse Dentário , Humanos , Microtomografia por Raio-XRESUMO
BACKGROUND: The influences of potential bone-to-implant contact (BIC) area (pBICA), BIC area (BICA), and three dimensional (3D) BIC percentage (3D BIC%; defined as BICA divided by pBICA) in relation to the implant length on initial implant stability were studied. Correlations between these parameters were also evaluated. METHODS: Implants with lengths of 8.5, 10, 11.5, and 13 mm were placed in artificial bone specimens to measure three indexes of the initial implant stability: insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ). The implants and bone specimens were also scanned by microcomputed tomography, and the obtained images were imported into Mimics software to reconstruct the 3D models and calculate the parameters of 3D bone-to-implant contact including pBICA, BICA, and 3D BIC%. The Kruskal-Wallis test, Wilcoxon rank-sum test with Bonferroni adjustment, and Spearman correlations were applied for statistical and correlation analyses. RESULTS: The implant length affected ITV more than PTV and ISQ, and significantly affected pBICA, BICA, and 3D BIC%. A longer implant increased pBICA and BICA but decreased 3D BIC%. The Spearman coefficients were high (>0.78) for the correlations between the three 3D BIC parameters and the three indexes of the initial implant stability. CONCLUSIONS: pBICA, BICA, and 3D BIC% are useful when deciding on treatment plans related to various implant lengths, since these 3D BIC parameters are predictive of the initial implant stability.
Assuntos
Osso e Ossos/diagnóstico por imagem , Implantes Dentários , Análise do Estresse Dentário , Desenho de Prótese , Humanos , Imageamento Tridimensional , Modelos Dentários , Microtomografia por Raio-XRESUMO
BACKGROUND/PURPOSE: Small-diameter dental implants are associated with a higher risk of implant failure. This study used both three-dimensional finite-element (FE) simulations and in-vitro experimental tests to analyze the stresses and strains in both the implant and the surrounding bone when using one-piece (NobelDirect) and two-piece (NobelReplace) small-diameter implants, with the aim of understanding the underlying biomechanical mechanisms. METHODS: Six experimental artificial jawbone models and two FE models were prepared for one-piece and two-piece 3.5-mm diameter implants. Rosette strain gauges were used for in-vitro tests, with peak values of the principal bone strain recorded with a data acquisition system. Implant stability as quantified by Periotest values (PTV) were also recorded for both types of implants. Experimental data were analyzed statistically using Wilcoxon's rank-sum test. In FE simulations, the peak value and distribution of von-Mises stresses in the implant and bone were selected for evaluation. RESULTS: In in-vitro tests, the peak bone strain was 42% lower for two-piece implants than for one-piece implants. The PTV was slightly lower for one-piece implants (PTV = -6) than for two-piece implants (PTV = -5). In FE simulations, the stresses in the bone and implant were about 23% higher and 12% lower, respectively, for one-piece implants than those for two-piece implants. CONCLUSION: Due to the higher peri-implant bone stresses and strains, one-piece implants (NobelDirect) might be not suitable for use as small-diameter implants.
Assuntos
Implantes Dentários/classificação , Análise do Estresse Dentário/métodos , Maxila/diagnóstico por imagem , Estresse Mecânico , Fenômenos Biomecânicos , Dente Suporte , Análise de Elementos Finitos , Humanos , Imageamento TridimensionalRESUMO
STATEMENT OF PROBLEM: Use of a small diameter implant may increase the stress on bone around the implant neck; however, an expanded platform design may mitigate these stress concentrations. To date, no study has compared the biomechanical effect of regular platform and extended platform designs on an implant. PURPOSE: The purpose of this in vitro study was to evaluate the biomechanical effects of an expanded platform-switching design for immediately loaded small diameter implants on bone strains. MATERIAL AND METHODS: Three groups of artificial jawbone models were prepared for small diameter (3.25-mm) and standard diameter (4.0-mm) implants with expanded or regular platform designs. Platform-switching implant design was implemented by assembling implants with a smaller connected abutment. Specimens were tested under both vertical and lateral static loads at 190 N. Peak values of the principal microstrain of bone were recorded and analyzed statistically with Kruskal-Wallis test and multiple comparisons Bonferroni test (α=.05). The initial stability of each implant was also measured for 3 types of implant. RESULTS: Under vertical loading, the bone strain was lowest for the regular type of immediately loaded small diameter implant. Under lateral loading, peak bone strain around the expanded platform small diameter implant with platform switched abutment was up to 74.9% lower than that of the regular type of small diameter implant. Increasing the implant diameter from 3.25 mm to 4.0 mm on the expanded platform implants reduced the bone strain by approximately 10% and 30% under lateral and vertical loading, respectively. The initial implant stability did not vary significantly among the implants tested. CONCLUSIONS: Using the expanded platform small diameter implant with a platform-switched abutment may decrease the marginal bone strains around immediately loaded small-diameter implants under lateral loading.
Assuntos
Dente Suporte , Projeto do Implante Dentário-Pivô , Fenômenos Biomecânicos , Implantes Dentários , Humanos , Estresse MecânicoRESUMO
The quality of maxillary bone is generally lower than that of mandibular bone; consequently, complete arch immediate implant-loading treatment is not as predictable in the maxillary as in the mandibular arch. The All-on-4 concept has proven to be an effective and successful treatment protocol. However, the survival rate of All-on-4 implants in the maxilla is lower than of those in the mandible. In this report, 2 anterior wide-diameter implants were used with the All-on-4 concept for a maxillary rehabilitation to provide biomechanical benefits with better primary stability while still achieving a functional and esthetic result. The clinical challenges of using wide-diameter implants in the anterior region are also discussed and should be considered during treatment planning.
Assuntos
Prótese Dentária Fixada por Implante/métodos , Prótese Parcial Fixa , Carga Imediata em Implante Dentário/métodos , Estética Dentária , Feminino , Humanos , Maxila , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Before extracting impacted lower third molars, dentists must first identify the spatial relationship between the inferior alveolar nerve (IAN) and an impacted lower third molar to prevent nerve injury from the extraction. Nevertheless, the current method for describing the spatial relationship between the IAN and an impacted lower third molar is deficient. Therefore, the objectives of this study were to: (1) evaluate the relative position between impacted lower third molars and the IAN; and (2) investigate the relative position between impacted lower third molars and the IAN by using a cylindrical coordinate system. METHODS: From the radiology department's database, we selected computed tomography images of 137 lower third molars (from 75 patients) requiring removal and applied a Cartesian coordinate system by using Mimics, a medical imaging software application, to measure the distribution between impacted mandibular third molars and the IAN. In addition, the orientation of the lower third molar to the IAN was also measured, but by using a cylindrical coordinate system with the IAN as the origin. RESULTS: According to the Cartesian coordinate system, most of the IAN runs through the inferior side of the third molar (78.6 %), followed by the lingual side (11.8 %), and the buccal side (8.9 %); only 0.7 % is positioned between the roots. Unlike the Cartesian coordinate system, the cylindrical coordinate system clearly identified the relative position, r and θ, between the IAN and lower third molar. CONCLUSIONS: Using the cylindrical coordinate system to present the relationship between the IAN and lower third molar as (r, θ) might provide clinical practitioners with a more explicit and objective description of the relative position of both sites. However, comprehensive research and cautious application of this system remain necessary.
Assuntos
Nervo Mandibular/diagnóstico por imagem , Dente Serotino/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Dente Impactado/diagnóstico por imagem , Adulto , Idoso , Humanos , Nervo Mandibular/anatomia & histologia , Pessoa de Meia-Idade , Dente Serotino/patologia , Estudos Retrospectivos , Tomografia Computadorizada por Raios X/métodos , Dente Impactado/patologia , Adulto JovemRESUMO
OBJECTIVE: Small-diameter implants have been available since the 1990s, but few studies have analyzed their mechanical properties. This study evaluated the effects of the implant material and the implant-abutment connection designs on the primary stability and the marginal bone strain of small-diameter implant subject to immediate loading. MATERIALS AND METHODS: Insertion torque value (ITV), implant stability quotient (ISQ), and Periotest value (PTV) of three implant systems with four parameters (titanium, titanium alloy, internal and external hexagon connections) were measured after placing implants into artificial type 2 jaw-bone models. Specimens were tested under both vertical and oblique static loads at 190 N. Peak values of the principal bone strain were recorded and analyzed statistically by the Kruskal-Wallis test and multiple-comparisons Bonferroni test. RESULTS: PTV and ISQ were higher for the NIOSM311 (internal-hex and Ti alloy) and FOSM311 (external-hex and pure Ti) implants, respectively, than for the NOSM311 (external-hex and Ti alloy) implant. Under vertical loading the peak value of peri-implant bone strains did not differ significantly among these three implant systems. However, the peak bone strains were at least 32 % lower for the NIOSM311 and FOSM311 implants than for the NOSM311 implant under lateral loading. CONCLUSIONS: The implant material and the implant-abutment connection design significantly influence the peri-implant bone strain of immediately loaded small-diameter implants, but barely affect their primary stability. CLINICAL RELEVANCE: A commercially pure titanium implant with an internal connection has the potential to reduce the risk of implant failure of small-diameter implant related to biomechanical complications.
Assuntos
Dente Suporte , Carga Imediata em Implante Dentário , Fenômenos Biomecânicos , Projeto do Implante Dentário-Pivô , HumanosRESUMO
BACKGROUND: The study compared the implant mobility and surrounding bone strain between the titanium-zirconium (Ti-Zr) alloy and the commercial pure (CP) Ti implants. METHODS: The mobility--quantified as the implant stability quotient (ISQ) and Periotest value (PTV)--of implants constructed from Ti-Zr alloy and CP Ti placed into artificial type-2 jawbone models were measured. Specimens were tested by applying 190 N vertically or at 30 degrees laterally. Peak values of the principal strains of bone were recorded by rosette strain gauges with a data acquisition system and were analyzed statistically using Wilcoxon rank-sum test. RESULTS: PTV and ISQ values did not differ significantly between the Ti-Zr and CP Ti implants (P > 0.01). Under vertical loading, the peak bone strains did not differ significantly between the Ti-Zr and CP Ti specimens (P > 0.006). However, the peak strains were 52% lower around the Ti-Zr implant than around the Ti implant on the buccal side of bone under lateral loading (P < 0.001). CONCLUSIONS: The implant material (Ti-Zr alloy vs CP Ti) had no effect on the mobility of small-diameter dental implants. However, using Ti-Zr alloy as an implant material decreased the periimplant bone strain under lateral loading in this pilot study.
Assuntos
Ligas , Implantes Dentários , Titânio , Zircônio , Fenômenos Biomecânicos , Técnicas In Vitro , Projetos PilotoRESUMO
Background/purpose: Few studies have investigated the effects of abutment screw diameter in the stress of dental implants and alveolar bones under occlusal forces. In this study, we investigated how variations in implant diameter, abutment screw diameter, and bone condition affect stresses in the abutment screw, implant, and surrounding bone. Materials and methods: Three-dimensional finite element (FE) models were fabricated for dental implants with external hex-type abutments measuring 4 and 5 mm in diameter. The models also included abutment screws measuring 2.0 and 2.5 mm in diameter. Each implant model was integrated with the mandibular bone comprising the cortical bone and four types of cancellous bone. In total, 12 finite element models were generated, subjected to three different occlusal forces, and analyzed using FE software to investigate the stress distribution of dental implant and alveolar bone. Results: Wider implants demonstrated lower stresses in implant and bone compared with standard-diameter implants. The quality of cancellous bone has a minimal impact on the stress values of the implant, abutment screw, and cortical bone. Regardless of occlusal arrangement or quality of cancellous bone, a consistent pattern emerged: larger abutment screw diameters led to increased stress levels on the screws, while the stress levels in both cortical and cancellous bone showed comparatively minor fluctuations. Conclusion: Wider implants tend to have better stress distribution than standard-diameter implants. The potential advantage of augmenting the abutment screw diameter is unfavorable. It may result in elevated stresses in the implant system.
RESUMO
PURPOSE: Finite element analysis and an in vitro experiment were employed to investigate the loading effects of angled abutments, comparing various customized angled abutments derived from the average angle of incisors in patients with a commercial 15°∆ angled abutment, on both the implant and surrounding bone. METHODS: Four customized angled abutment models (21.9°∆, 24.15°∆, 20.22°∆, 33°∆) were developed using cone-beam computed tomography (CBCT) images of incisor inclination from various age groups of patients. 3D maxillary bone models were created from CBCT images of four individual patients. Finite element analysis and in-vitro strain gauge experiments were conducted, applying 100N or 50N of axial or oblique force, to assess the differences in stress/strain between the customized and the commercial 15°∆ angled abutments in both the implants and surrounding bone. RESULTS: Under axial loading, the stress values in the dental implant and surrounding bone were elevated due to the relatively higher angles of the customized angled abutments (21.9°∆, 24.15°∆, 20.22°∆, 33°∆) when compared to the commercial 15°∆ angled abutment; however, under oblique loading the commercial 15°∆angled abutment exhibited higher stress values in both the implant and surrounding bone. For in vitro experiment, there is no statically difference in bone strain between the customized (21.9°∆) and the commercial 15°∆ angled abutments in axial loading. Nevertheless, in oblique loading using a commercial 15°∆ angled abutment induced the higher bone strains. CONCLUSION: Customized angled abutments offer lower stress/strain under oblique loads but higher stress/strain under axial loads compared to commercial ones. Therefore, in the design and application of angled abutments, careful consideration of the occlusal load direction is paramount for achieving biomechanical success of dental implant.
RESUMO
Background/purpose: Augmented reality (AR) is gaining popularity in medical applications, which may aid clinicians in achieving improved clinical outcomes. The purpose of this study was to determine the positional and angle errors of orthodontic miniscrew placement by using a self-developed AR aided system. Materials and methods: Cone beam computed tomography (CBCT) and patient printed models were used in in vitro experiments. The participants were divided into a control group and an AR group, in which traditional orthodontic methods and the AR-aided system were used respectively. After the information obtained from the CBCT images and navigation system was combined on the display device, the AR-aided system indicated the planned miniscrew position to guide the clinicians during the placement of miniscrews. Both methods were compared by a senior and a junior dentist, and the position and angle of miniscrew placement were statistically analyzed using Wilcoxon's signed-rank and Mann-Whitney U tests. Results: When the AR-aided system was used, the accuracy of miniscrew placement in the mesiodistal position considerably increased (83%) when the procedure was performed by a senior clinician. In addition, the accuracy of miniscrew placement in the mesiodistal position and the angle of miniscrew placement considerably increased by approximately 67% and 72%, respectively, when the procedure was performed by a junior clinician. The position error of miniscrew placement was smaller for the junior clinician when the AR-aided system was used than for the senior clinician. Conclusion: The AR-aided system improved the accuracy of miniscrew placement regardless of the clinician's level of experience.