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BACKGROUND: To prevent the absorption and collapse of the labial bone plate of the anterior teeth, immediate implantation and socket shield technique have been increasingly applied to anterior dental aesthetic implant restoration. OBJECTIVE: To provide a biomechanical basis for implant restoration of maxillary anterior teeth, finite element analysis was used to investigate the stress peak and distribution in different anatomical sites of natural teeth, conventional immediate implantation and socket shield technique. METHODS: Three maxillary finite element models were established, including a maxillary incisor as a natural tooth, a conventional immediate implantation and a socket shield technique. A mechanical load of 100â¯N was applied to simulate and analyze the biomechanical behavior of the root, periodontal ligament (PDL), implant and surrounding bone interface. RESULTS: The stress distribution of the natural tooth was relatively uniform under load. The maximum von Mises stress of the root, periodontal ligament, cortical bone and cancellous bone were 20.14â¯MPa, 2.473â¯MPa, 19.48â¯MPa and 5.068â¯MPa, respectively. When the conventional immediate implantation was loaded, the stress was mainly concentrated around the neck of implant. Maximum stress on the surface of the implant was 102â¯MPa, the cortical bone was 16.13â¯MPa, and the cancellous bone was 18.29â¯MPa. When the implantation with socket shield technique was loaded, the stress distribution of the implant was similar to that of immediate implantation. Maximum stress on the surface of the implant was 100.5â¯MPa, the cortical bone was 23.11â¯MPa, the cancellous bone was 21.66â¯MPa, the remaining tooth fragment was 29.42â¯MPa and the periodontal ligament of the tooth fragment was 1.131â¯MPa. CONCLUSIONS: 1. Under static loading, both socket shield technology and conventional immediate implantation can support the esthetic restoration of anterior teeth biomechanically. 2.Under short-term follow-up, both immediate implant and socket shield technology achieved satisfactory clinical results, including bone healing and patient satisfaction. 3.The stress distribution is mainly located on the buccal bone surface of the implant and is associated with resorption of the buccal bone plate after implant replacement in both socket shield technology and conventional immediate implantation. 4.The presence of retained root fragment had an impact on the bone graft gap. In immediate implantation, the peak stress was located in the cortical bone near the implant position, while in socket shield technology, the peak stress was at the neck of the cortical bone corresponding to the retained root fragment.
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BACKGROUND: Osseous condition of the mandible was regarded as a key factor influencing stability of implants in the early stage. Finite element analysis was used to assess the effect of bone mass density and alveolar bone resorption (double factors) on stress in a four-unit implant restoration of a free-end edentulous posterior mandible. METHODS: A 3D finite element model was constructed for a single-sided free-end edentulous mandible (from mandibular first premolar to mandibular second molar) containing threaded dental implants. Mandible sensitivity modes were constructed with different alveolar bone resorption levels for normal conditions as well as mild, moderate and severe periodontitis, respectively. Based on the mass density of cancellous bone for four types of bones as the sensitivity parameter, two implant design modes were constructed: Model A (four-unit fixed bridge supported by three implants, implant positions were 34, 36 and 37) and model B: 34 × 36, 37 (37: a single implant crown) (34 × 36: three-unit fixed bridge supported by two implants, implant positions were 34 and 36). A total of 32 sensitivity-based finite element models, grouped in two groups, were constructed. Stress distribution and maximum von Mises stress on cortical bone and cancellous bone around the implant, as well as the surface of implant were investigated by using ABAQUS when vertical loading and 45° oblique loading were applied, respectively. RESULTS: When vertical loading was applied on the implant, maximum von Mises stress on the cortical bone around the implant was assessed to be 4.726â¯MPa - 13.15â¯MPa and 6.254â¯MPa - 13.79â¯MPa for groups A and B, respectively; maximum stress on the cancellous bone around the implant was 2.641â¯MPa - 3.773â¯MPa and 2.864â¯MPa - 4.605â¯MPa, respectively; maximum stress on the surface of implant was 14.7â¯MPa - 21.17â¯MPa and 21.64â¯MPa - 30.70â¯MPa, respectively. When 45° oblique loading was applied on the implant restoration, maximum von Mises stress on the cortical bone around the implant was assessed to be 42.08â¯MPa - 92.71â¯MPa and 50.84â¯MPa - 102.5â¯MPa for groups A and B, respectively; maximum stress on the cancellous bone around the implant was 4.88â¯MPa - 25.95â¯MPa and 5.227â¯MPa - 28.43â¯MPa, respectively; maximum stress on the surface of implant was 77.91â¯MPa - 124.8â¯MPa and 109.2â¯MPa - 150.7â¯MPa, respectively. Stress peak on the cortical bone and that on cancellous bone around the implant increased and decreased with the decrease in bone mass density, respectively. Stress peak on alveolar bone increased with alveolar bone resorption when oblique loading was applied. CONCLUSION: 1. Both alveolar bone resorption and bone mass density (double factors) are critical to implant restoration. Bone mass density may exhibit a more pronounced impact than alveolar bone resorption. 2. From the biomechanical perspective, types I and II bones are preferred for implant restoration, while implantation should be considered carefully in the case of type III bones, or those with less bone mass density accompanied by moderate to severe alveolar bone loss. 3. Splinting crowns restoration is biomechanically superior to single crown restoration.
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Perda do Osso Alveolar , Implantes Dentários , Humanos , Perda do Osso Alveolar/cirurgia , Análise de Elementos Finitos , Software , Dente Pré-Molar , Mandíbula/cirurgia , Estresse Mecânico , Análise do Estresse Dentário , Prótese Dentária Fixada por ImplanteRESUMO
BACKGROUND: Apical periodontitis directly affects the stress state of the affected tooth owing to the destruction of the periapical bone. Understanding the mechanical of periapical bone defects/tooth is clinically meaningful. In this study, we evaluate the effect of periapical bone defects on the stress distribution in teeth with periapical periodontitis using finite element analysis. METHODS: Finite element models of normal mandibular second premolars and those with periapical bone defects (spherical defects with diameters of 5, 10, 15, and 20 mm) were created using a digital model design software. The edges of the mandible were fixed and the masticatory cycle was simplified as oblique loading (a 400 N force loaded obliquely at 45° to the long axis of the tooth body) to simulate the tooth stress state in occlusion and analyze the von Mises stress distribution and tooth displacement distribution in each model. RESULTS: Overall analysis of the models: Compared to that in the normal model, the maximum von Mises stresses in all the different periapical bone defect size models were slightly lower. In contrast, the maximum tooth displacement in the periapical bone defect model increased as the size of the periapical bone defect increased (2.11-120.1% of increase). Internal analysis of tooth: As the size of the periapical bone defect increased, the maximum von Mises stress in the coronal cervix of the tooth gradually increased (2.23-37.22% of increase). while the von Mises stress in the root apical region of the tooth showed a decreasing trend (41.48-99.70% of decrease). The maximum tooth displacement in all parts of the tooth showed an increasing trend as the size of the periapical bone defect increased. CONCLUSIONS: The presence of periapical bone defects was found to significantly affect the biomechanical response of the tooth, the effects of which became more pronounced as the size of the bone defect increased.
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Periodontite Periapical , Software , Humanos , Análise de Elementos Finitos , Estresse Mecânico , Dente Pré-Molar , Análise do Estresse DentárioRESUMO
AIM: To evaluate the effects of root canal treatment (RCT) and post-crown restoration on stress distribution in teeth with periapical bone defects using finite element analysis. METHODOLOGY: Finite element models of mandibular second premolars and those with periapical bone defects (spherical defects with diameters of 5, 10, 15, and 20 mm) were created using digital model design software. The corresponding RCT and post-crown restoration models were constructed based on the different sizes of periapical bone defect models. The von Mises stress and tooth displacement distributions were comprehensively analyzed in each model. RESULTS: Overall analysis of the models: RCT significantly increased the maximum von Mises stresses in teeth with periapical bone defects, while post-crown restoration greatly reduced the maximum von Mises stresses. RCT and post-crown restoration slightly reduced tooth displacement in the affected tooth. Internal analysis of tooth: RCT dramatically increased the maximum von Mises stress in all regions of the tooth, with the most pronounced increase in the coronal surface region. The post-crown restoration balances the internal stresses of the tooth and is most effective in periapical bone defect - 20-mm model. RCT and post-crown restoration slightly reduced the tooth displacement in all regions of the affected tooth. CONCLUSIONS: Root canal treatment seemed not to improve the biomechanical state of teeth with periapical bone defects. In contrast, post-crown restoration might effectively balance the stress concentrations caused by periapical bone defects, particularly extensive ones.
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Periodontite Periapical , Coroa do Dente , Humanos , Análise de Elementos Finitos , Cavidade Pulpar , Coroas , Periodontite Periapical/terapiaRESUMO
BACKGROUND: With periodontal disease having an increasing incidence, mandibular free-end edentulism caused by periodontitis is clinically more common. Finite element analysis and clinical case reports were used to evaluate the influence of different designs on the load distribution of implant prosthesis in mandibular posterior free-end edentulism. METHOD: A finite element model of a mandible with posterior free-end edentulism was established. Considering the implant position and selection of single crown repair or splint repair, four designs were conducted including model A: 3435 × 37(four-unit fixed bridge supported by three implants, implant positions were 34, 35, 37); model B: 34,35 × 37, (34: a single implant crown) (35 ×37: three-unit fixed bridge supported by two implants, implant positions were 35, 37); model C: 34 × 3637(four-unit fixed bridge supported by three implants, implant positions were 34, 36, 37); and model D: 34 × 36, 37(37: a single implant crown)(34 ×36: three-unit fixed bridge supported by two implants, implant positions were 34, 36). Stress distribution and the Von Mises stress value of the implants, the crown and the bone around the implants were analyzed at vertical and 45° inclined load. RESULTS: Stress in the cortical bone was mainly concentrated around the implant neck, and maximum Von Mises stress (MVMS) of the four models was 11.6-16.1 MPa at vertical load and 61.74-96.49 MPa at 45° inclined load. Stress in the cancellous bone was concentrated around the implant base, and MVMS of four models was 3.075-3.899 MPa at vertical load and 5.021-6.165 MPa at 45° inclined load. Stress of the restoration crowns was mainly concentrated in the connector of the bridge, and MVMS of four models was 23.38-26.28 MPa at vertical load and 53.14-56.35 MPa at 45° inclined load. Stress of the implant interface was mainly concentrated on the surface of the smaller implants near the bridge, and MVMS of four models was 21.12-33.25 MPa at vertical load and 83.73-138.7 MPa at 45° inclined load. CONCLUSION: There was favorable stress distribution of the four models at vertical load and 45° inclined load. Design of a three-unit fixed bridge combined with a partial crown may be an available option for devising patient treatment plans with mandibular free-end edentulism.
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Implantes Dentários , Mandíbula , Humanos , Análise de Elementos Finitos , Estresse Mecânico , Dente Pré-Molar , Mandíbula/cirurgia , Prótese Parcial Fixa , Análise do Estresse Dentário , Prótese Dentária Fixada por Implante , Planejamento de Prótese DentáriaRESUMO
OBJECTIVE: This study aimed to evaluate timing of fixation to retard bone absorption using finite element analysis(FEA). METHODS: Volunteer CT images were used to construct four models of mandibles with varying degrees of alveolar bone resorption. By simulating occlusal force loading, biomechanical analysis was made on the periodontal membrane, tooth root and surrounding bone (both cancellous and cortical) of mandibular dentition. RESULTS: The von Mises stress value of the periodontal structures was positively related with the degree of alveolar bone resorption, and the von Mises stress at the interface between the periodontal membrane and tooth root was increased significantly in moderate to severe periodontitis models. The von Mises stress at the interface between the periodontal cortical bone and cancellous bone was increased significantly in the severe periodontitis model. And the von Mises stress value with oblique loading showed significantly higher than vertical loading. CONCLUSION: Teeth with moderate to severe periodontitis, loosened tooth fixation can be used to retard bone absorption.
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Perda do Osso Alveolar , Periodontite , Raiz Dentária , Perda do Osso Alveolar/diagnóstico por imagem , Análise do Estresse Dentário , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Mandíbula , Estresse Mecânico , Raiz Dentária/cirurgiaRESUMO
BACKGROUND: To apply CBCT to investigate the anatomical relationship between the mandibular molar and alveolar bone, aimed to provide clinical guidelines for the design of implant restoration. METHODS: 201 CBCT data were reevaluated to measure height of the alveolar process (EF), width of the alveolar process (GH), width of the basal bone (IJ), the angle between the long axis of the first molar and the alveolar bone (â a) and the angle between the long axis of the alveolar bone and basal bone (â b). The angle and width were measured to determine the implant-prosthodontic classification of the morphology in the left lower first molar (36) and right lower first molar (46). All measurements were performed on the improved cross-sectional images. RESULTS: EF, GH and IJ were measured as (10.83 ± 1.31) mm, (13.93 ± 2.00) mm and (12.68 ± 1.96) mm for 36, respectively; and (10.87 ± 1.24) mm, (13.86 ± 1.93) mm and (12.60 ± 1.90) mm for 46, respectively. No statistical significance was observed in EF, GH, IJ, â a and â b between 36 and 46 (all P > 0.05). The morphology was divided into three categories including the straight (68.7-69.2%), oblique (19.9-20.4%) and concave types (11%). Each type was consisted of two subcategories. CONCLUSIONS: The proposed classification could provide evidence for appropriate selection and direction design of the mandibular molar implant in clinical. The concave type was the most difficult to implant with the highest risk of lingual perforation. The implant length, width, direction required more attention.
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Implantes Dentários , Tomografia Computadorizada de Feixe Cônico Espiral , Tomografia Computadorizada de Feixe Cônico , Humanos , Mandíbula/diagnóstico por imagem , Dente Molar/diagnóstico por imagemRESUMO
BACKGROUND: Currently, insufficient bone volume always occurs in the posterior maxilla which makes implantation difficult. Short implants combined with transcrestal sinus floor elevation (TSFE) may be an option to address insufficient bone volume. PURPOSE: The clinical performance of short implants combined with TSFE was compared with that of conventional implants combined with TSFE according to the survival rate. METHOD: In this systematic review and meta-analysis, we followed the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines. Articles were identified through PubMed, Embase, the Cochrane Library, and manual searching. Eligibility criteria included clinical human studies. The quality assessment was performed according to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. The odds ratio (OR) with its confidence interval (CI) was considered the essential outcome for estimating the effect of short implants combined with TSFE. RESULTS: The registration number is INPLASY202050092. Eleven studies met the inclusion criteria, including 1 cohort study and 10 cross-sectional studies. With respect to the 1-year survival rate, no significant effect was observed between short implants (length ≤ 8 mm) and conventional implants combined with TSFE (I2=0%, OR=1.04, 95% CI: 0.55-1.96). Similarly, no difference was seen between the two groups regarding the survival rate during the healing period (I2=10%, OR=0.74, 95% CI: 0.28-1.97) and 3-year loading (OR=1.76, 95% CI: 0.65-4.74). CONCLUSION: There was no evidence that the survival rate of short implants combined with TSFE was lower or higher than that of conventional implants combined with TSFE when the residual bone height was poor and the implant protrusion length of short implants was less than or similar to conventional implants. Nevertheless, the results should be interpreted cautiously due to the lack of random controlled trials in our meta-analysis.
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Levantamento do Assoalho do Seio Maxilar , Estudos de Coortes , Estudos Transversais , Seio Maxilar , Estudos Observacionais como Assunto , Taxa de SobrevidaRESUMO
BACKGROUND: Transcrestal sinus floor elevation (TSFE) has been widely used in the oral clinic when the residual bone height (RBH) exceeds 5 mm. However, when there is insufficient RBH in the posterior maxilla, two-stage TSFE may be an option. CASE SUMMARY: This article introduces the concept of two-stage TSFE. Six patients had osseointegration failure after TSFE. For the first-stage surgery, we restricted the vertical bone augmentation as much as possible. At the second-stage surgery, the increased RBH was 3.28 ± 1.55 mm, which was beneficial for surgery. Five implants functioned successfully on schedule, but one implant failed again during the healing period. A third surgery was performed, and the implant functioned successfully. CONCLUSION: When RBH was less than 5 mm, two or more procedures of TSFE might result in a higher RBH.
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PURPOSE: To systematically evaluate the accuracy of clinical applications of digital guides. METHODS: First, PubMed and Embase databases were searched using the PICO standard. Eligible articles were included. Second, the eligible articles were classified according to the different types. Next, the NOS and ROB2 as evaluation indicators were used to evaluate the bias of those included articles. Finally, sensitive factors were excluded through the outcomes and data analyses were retrieved. RESULTS: More than 1,562 articles were retrieved, and 38 in vivo research documents were systematically analyzed after screening according to the inclusion criteria, which mainly listed three aspects of the coronal, apical, and angular implant data, and integrated the same type of articles in the study. To test its heterogeneity, the P-values of those articles included in the analysis were all less than 0.05. Finally, in the comparison between the guide group and the free-hand group after excluding sensitive factors, the standardized mean difference (Std.MD) of the angle was 1.26 (95% CI 1.06, 1.47), the Std.MD of the apical point was 1.38 (95% CI 1.12, 1.63), and the Std.MD of the coronal point was 0.98 (95% CI 0.66, 1.29). Comparing the maxillary and mandibular groups after excluding sensitive factors, the Std.MD of the coronal point was -0.31 (95% CI -0.52, -0.09), the Std.MD of the apical point was -0.15 (95% CI -0.34, 0.03), and the Std.MD of the angle is -0.23 (95% CI -0.46, 0.01). Comparison between the smoking group and the nonsmoking group, and between the flap group and the flapless group showed that there was not enough evidence to make a reliable assessment. CLINICAL SIGNIFICANCE: Compared with free-hand operation, a digital guide is more accurate in the apex, the coronal point and the angle, and the accuracy in the angle was very high. The difference in accuracy between the maxillary and mandibular groups was not statistically significant. Other factors such as smoking habit and flap need more clinical data.