上切牙区双端悬臂梁种植固定桥的应力分析

目的：通过分析双端悬臂梁种植义齿修复上颌切牙区牙列缺损的种植体在不同加载条件下的周围骨应力分布及位移量,进而探讨临床修复的可行性。方法：应用CT断层扫描技术对上颌骨及上颌牙列的大致轮廓进行三维重建,后于上中切牙区植入种植体,完成牙冠修复并建立模型。通过三维有限元技术模拟载荷,比较不同加载条件下种植体的周围骨组织应力分布及位移量。结果：经统计学分析,种植体-骨界面的皮质骨唇侧、舌侧、近中、远中、根尖部五个部位应力值的差异有统计学意义（P〈0.001）,五个部位的位移量的差异也有统计学意义（P〈0.001）。模型在各种加载条件下的应力分布及位移量的特征大致相同,且变化趋势相似,种植体颈部及周围骨皮质为应力集中区。在各种不同的加载条件中,30°加载角度时种植体周围骨应力分布更为科学。结论：在适当的负重条件下,双端悬臂梁种植义齿是临床修复切牙区缺失可供选择的一种设计方案。     

Level of satisfaction in patients with maxillary full-arch fixed prostheses: zygomatic versus conventional implants

PURPOSE: To evaluate the satisfaction of patients with maxillary fixed prostheses supported by conventional and/or zygomatic implants. MATERIALS AND METHODS: Patients restored with complete maxillary implant-supported fixed prostheses were included in the study. They were divided into 2 groups: those with at least 1 zygomatic implant (the zygomatic group) and those with no zygomatic implants (the nonzygomatic group). Twelve months after prosthesis delivery, subjects indicated their satisfaction with the new prosthesis on a visual analog scale. Prostheses were rated in terms of general satisfaction, comfort and stability, ability to speak, easy of cleaning, esthetics, self-esteem, and functionality. RESULTS: Forty-six patients participated in the study (23 in each group). The mean level of satisfaction was high; the groups differed significantly only in satisfaction with esthetics. Patients in the zygomatic group had a higher average score for esthetics than those in the nonzygomatic group. Those who had previously worn conventional removable prostheses gave a higher score for functionality to the implant-supported fixed prosthesis compared to the removable prosthesis. CONCLUSION: Patient satisfaction with zygomatic implant-supported fixed prostheses was similar to that for fixed prostheses supported by conventional implants.     

Biomechanical three-dimensional finite-element analysis of maxillary prostheses with implants. Design of number and position of implants for maxillary prostheses after hemimaxillectomy

The present study analyzed stress distributions in craniofacial structures around implant-supported maxillary prostheses. Using post-hemimaxillectomy computed tomography (CT) of a patient, the authors constructed a three-dimensional (3D) solid model using Digital Imaging and Communications in Medicine data (DICOM data) for maxillofacial and cranial bones. The effects of different prosthesis designs on stress distributions in craniofacial bones and osseous tissues around the implants were biomechanically investigated using 3D finite-element analysis. Maxillary prostheses were designed with 2 implants in the zygoma on the affected side and 2–3 implants in the maxillary alveolar bone on the unaffected side, without using a cantilever. Zygomatic implants provided suitable stress dispersal to the zygomatic and craniofacial bones on the affected side. This information is useful for designing maxillary prostheses.     

Evaluating the clinical performance of the Osseotite implant: defining prosthetic predictability

A 5-year prospective, multicenter study is in progress at four private dental practices to determine the cumulative implant survival rate and prosthetic outcome when using the Osseotite dental implant in posterior maxillary and mandibular areas. An interim evaluation after 34.4 months of study progress is presented. A total of 219 Osseotite implants were placed in 74 patients (34 women and 40 men with a mean age of 57.8 +/- 15.2 years) using a conventional two-stage surgical protocol and 3- to 6-month healing time. Subsequently, patients were restored with fixed or removable restorations. Nineteen of the 74 patients reported smoking an average of 13.2 cigarettes per day. Restorative treatments included 40 single-unit restorations; 53 splinted 2-, 3-, 4-, and 5-unit implant-supported maxillary and mandibular prostheses; 4 full-arch fixed maxillary prostheses; 1 mandibular fixed/detachable hybrid prosthesis; and 1 mandibular overdenture. The mean time from implant placement to second stage surgery was 6.2 +/- 2.0 months; from restoration and implant loading to the most recent follow-up evaluation was 20.9 +/- 6.8 months. Of the 219 implants placed, three posterior maxillary implants developed infections and were removed prior to second stage surgery. No implant failures occurred at second stage surgery or after implant loading. Using the Kaplan-Meier method, the cumulative implant survival rate was 100% for anterior implants and 98.4% for posterior implants at 28.5 +/- 5.7 months. The cumulative postloading implant survival rate was 100% for both anterior and posterior implants. The results of this study indicate that the Osseotite dental implant achieved a high rate of integration that remained stable during nearly 2 years of implant function. In addition, because no postloading implant failures have occurred, the Osseotite implant has provided a high level of prosthetic predictability.     

Photoelastic analysis of biomechanical behavior of single and multiple fixed partial prostheses with different prosthetic connections

The aim of this study was to evaluate the stress distribution on external hexagon, internal hexagon, and Morse taper implant in single and 3-unit implant-supported fixed partial prostheses (FPPs) using photoelasticity. Six models were fabricated with the photoelastic resin PL-2: 3 models for the 3-unit implant-supported FPP with implants of 4.0 × 10.0 mm in the region of the second premolar and molar including 1 model for each type of implant connection, and 3 models for the single prosthesis for each implant type. The prostheses fabrication was standardized. A circular polariscope was used, and axial and oblique (45 degrees) loads of 100 N were applied in a universal testing machine. The results were photographed and analyzed qualitatively. The internal hexagon implant exhibited better stress distribution and lower intensity of fringes followed by the external hexagon and Morse taper implants for the models with the 3-unit prostheses. For the single implants, the Morse taper implant presented better stress distribution, followed by the internal and external hexagon implants. The oblique loading increased the number of photoelastic fringes in all models. It was concluded that the internal hexagon implant exhibited better biomechanical behavior for the 3-unit implant-supported FPP, whereas the Morse taper implant was more favorable for the single implant-supported prosthesis. The oblique loading increased the stress in all models.     

Photoelastic analysis of implant-retained and conventional obturator prostheses with different attachment systems and soft relining

Complete and partial loss of maxillary bone may jeopardize oral physiology and generate complications as oral-sinus-nasal communication. Palatal obturator prostheses are a treatment alternative for rehabilitation of these patients. The aim of this study was to assess stress distribution, through photoelasticity, on palatal obturator prostheses associated with different attachment systems (o'ring, bar clip, and o'ring/bar clip) of implants and submitted to relining. Two photoelastic models were fabricated according to an experimental maxillary model with oral-sinus-nasal communication. One model did not present implants, whereas the other included 2 implants with 13.0 mm in length in the left ridge. Four colorless maxillary obturator prostheses were fabricated and relined with soft silicone. One of these prostheses presented no attachment system, whereas the remaining prostheses included attachment systems adapted to the implants. The assembly (model/attachment system/prosthesis) was positioned in a circular polariscope during loading with 100 N at 10 mm/s. The results were based on observation during the experiment and photographic records of stress on the photoelastic model. The bar clip system exhibited the highest stress concentration followed by o'ring/bar clip and o'ring systems. The attachment systems presented different stress distribution with greater concentration surrounding the implants and homogenous stress distribution on the photoelastic model without implants. The highest concentration of fringes occurred, in ascending order, with o'ring, o'ring/bar clip, and bar clip systems.     

Rehabilitation of severely resorbed maxillae with zygomatic implants: an evaluation of implant stability, tissue conditions, and patients' opinion before and after treatment

PURPOSE: The aim of the present study was to describe experiences of 11 consecutively treated patients who received zygomatic implants. Patient results were assessed through clinical and radiographic evaluations of tissue conditions, including resonance frequency analysis (RFA). MATERIALS AND METHODS: Eleven patients were treated with implant-retained fixed prostheses. A total of 64 implants were placed, 22 of which were placed in the zygoma. Fixed prostheses were removed to allow clinical and radiographic evaluations at a follow-up visit 18 to 46 months following implant placement. RFA was performed on all implants. A visual analog scale was used to assess patient satisfaction before and after treatment. RESULTS: All patients received implant-supported prostheses. All zygomatic implants demonstrated clinical signs of osseointegration. One anterior implant was lost during follow-up. Mean ISQ values for the zygomatic and anterior implants were 65.9 (range, 42 to 100) and 61.5 (range, 48 to 71), respectively. Twenty-four implants showed moderate inflammation, with 3 exhibiting severe inflammation. Most anterior implants (75.6%) showed a marginal bone recession of 1 thread or less. Four zygomatic implants showed bone loss of 4 to 5 threads, and 5 zygomatic implants exhibited no marginal bone support. Patients described significant improvement in chewing ability and esthetics but did not describe changes in speech. DISCUSSION: The use of zygomatic implants can help the clinician avoid the need for bone grafting and reduce morbidity. In addition, it can shorten the treatment time considerably. CONCLUSION: This preliminary report demonstrates that zygomatic implants can provide posterior support to fixed prostheses in patients who lack bone volume to place conventional implants without encroaching upon the maxillary sinus.     

Stress distribution around maxillary implants in anatomic photoelastic models of varying geometry. Part II

STATEMENT OF PROBLEM: Insufficient buccal bone volume can be a significant problem when loading dental implants in the maxilla. Increased potential for buccal fenestration and dehiscence can result in an exposed implant surface, mucosal irritation, decreased support, and potential implant failure. PURPOSE: The objective of this study was to model the stress distribution around maxillary implants by comparing simulated occlusal loading of maxillary implants in a 2-dimensional photoelastic anatomic model and a dry skull model. MATERIAL AND METHODS: Two model systems were used. First, a 2-dimensional photoelastic anatomic frontal skull sectional model was prepared in the first molar region. Left and right maxillary metal cylinder implant analogues inclined at 0 and 25 degrees to the sagittal plane were loaded in simulated intercuspation. Second, a dry skull lined with a photoelastic coating on the buccal aspect over an embedded cylinder implant was prepared in the first molar region. Principal stress concentration was photographed on axial and nonaxial implant loading. RESULTS: On simulated intercuspal loading, maximum stress concentration occurred at the buccal concavity in both the 2-dimensional anatomic photoelastic and skull models. There was no stress concentration at the apices of the maxillary implants in the 2-dimensional model. On lateral loading of the skull model, stress was distributed along the entire buccal aspect of bone adjacent to the implant, with a higher concentration at the buccal concavity. CONCLUSION: Preservation of buccal supporting bone volume is desirable to obtain a physiological modeling response and to enhance the facial plate. Insufficient bone volume may result in buccal fenestration or dehiscence, which can precipitate mucosal irritation, decreased support, and potential implant failure.     

Stress distribution around maxillary implants in anatomic photoelastic models of varying geometry. Part I

STATEMENT OF PROBLEM: It is unclear which implant inclination and position are most favorable in relation to the supporting anatomy and loading direction in the maxilla. PURPOSE: This study was designed to examine stress distribution around implants in a 2-dimensional photoelastic anatomic model. MATERIAL AND METHODS: Two 2-dimensional photoelastic models were prepared with opposing 8-degree cylinder metal implant and molar teeth analogues. A frontal anatomic sectional plate model based on a CT section at the first molar was symmetrically loaded through its long axis. A midfacial rectangular model based on the same section was loaded in a different direction with varying supporting geometries. RESULTS: Stress distribution around the maxillary implant was highest in the buccal concavity at the apical buccal third and in the lingual concavity on intercuspal loading. No stress concentration occurred at the implant apex under the sinus for axial and nonaxial loading in both anatomic model geometries. On lateral loading, stress concentration was observed at the buccal concavity and at the implant neck. In the midfacial block model, principal stresses were concentrated at the maxillary implant neck on nonaxial loading and at the apex on axial loading. CONCLUSION: This 2-dimensional skull model showed different patterns of stress distribution among the maxillary implant, mandibular implant, and teeth. The highest principal stress concentration was seen at the buccal concavity of the maxillary implant; this may play a role in osseointegration with highly angled implants in the posterior maxilla. Differences in stress distribution between anatomic and nonanatomic models showed how the supporting geometry (for example, sinus/nasal anatomy), boundary conditions, and loading direction influence stress distribution.     

Survival rate of zygomatic implants in atrophic or partially resected maxillae prior to functional loading: a retrospective clinical report

PURPOSE: The purpose of this article was to evaluate the survival rate of 34 remote anchorage implants placed in 18 patients from placement to uncovering, prior to any prosthetic loading. MATERIALS AND METHODS: A total of 18 patients (9 women and 9 men with a mean age of 63 years) who required rehabilitation with a fixed prosthesis because of severely atrophic maxillae (including 1 patient who had undergone primary and secondary cleft lip and palate repair), traumatic maxillary bone loss, and maxillectomy procedures received 1 or 2 zygomatic implants and 2 to 4 standard maxillary dental implants. The survival rate of the 34 zygomatic implants from placement to uncovering was investigated. Aspects of the placement technique or postoperative complications related to surgical procedures likely to affect the implant failure rate were detected and critically discussed. RESULTS: Osseointegration was evaluated using the reverse torque test and percussion after uncovering. Only 1 patient (5.6%) sustained postoperative clinical complications during the evaluation period which resulted in the loss of both zygomatic implants (5.9%). CONCLUSION: Although the handling of this anchorage implant system is somewhat complex, and the design has certain shortcomings, it might be an alternative to more extensive bone augmentation procedures. However, rehabilitation of partially or completely edentulous patients with fixed implant-supported prosthesis is only feasible when 2 to 4 standard implants are placed in the anterior maxilla and splinted with the zygomatic implants.     

Clinical outcome of 103 consecutive zygomatic implants: a 6-48 months follow-up study

The purpose of this study was to evaluate retrospectively, after a period of 6-48 months follow-up of prosthetic loading, the survival rate of 103 zygomatic implants inserted in 55 totally edentulous severely resorbed upper jaws. Fifty-five consecutive patients, 41 females and 14 males, with severe maxillary bone resorption were rehabilitated by means of a fixed prosthesis supported by either 1 or 2 zygomatic implants, and 2-6 maxillary implants. This retrospective study calculated the success and survival rates at both the prosthetic and implant levels. Out of 55 prostheses, 52 were screwed on top of the implants, while 3 were modified due to loss of standard additional implants and transformed in semimovable prosthesis. Although osseointegration in the zygomatic region is difficult to evaluate, no zygomatic implant was considered fibrously encapsulated and they are still in function. This study confirms that zygoma bone can offer a predictable anchorage and support function for a fixed prosthesis in severely resorbed maxillae.     

“All-on-four” concept and immediate loading for simultaneous rehabilitation of the atrophic maxilla and mandible with conventional and zygomatic implants

We report the simultaneous rehabilitation of an edentulous patient with a hybrid (zygomatic and conventional implants) all-on-four implant-supported prosthesis for the maxilla and a standard (conventional implants) all-on-four implant-supported prosthesis for the mandible. The transfer impression was made with a multifunctional guide and the upper and lower prostheses were placed 24 h postoperatively. Clinical and radiographic examinations showed no infection or bony resorption 2 years later. Simultaneous maxillary and mandibular rehabilitation with all-on-four immediate loading is a viable, fast and effective option for edentulous patients.     

Dental implants in geriatric patients: a retrospective study of 47 cases

PURPOSE: To determine the overall success of dental implants placed in geriatric patients. PATIENTS: Dental implants were placed in 47 geriatric patients who were 79 or more years of age at the time of the procedure. The study group was composed of 27 men and 20 women, with a median age of 89 years and a range of 79 to 99 years of age at the time of implant surgery. A total of 73 dental implants were placed in the maxilla and 87 dental implants placed in the mandible. All implants were restored with fixed implant-supported prostheses or removable implant-supported prostheses. Eleven of the patients underwent maxillary sinus augmentation with porous hydroxyapatite and platelet-rich plasma. Seven patients had their implants immediately loaded. RESULTS: A total of 160 dental implants were placed in the 47 geriatric patients. One hundred fifty-nine integrated successfully. In the case of the failed implant, the site was grafted and another implant was placed 5 months subsequent to the initial failure. This replacement implant integrated and has been in function for 6 months. The survival rate for dental implants placed in the maxilla was 99% and in the mandible was 100% in our geriatric population. CONCLUSION: Treatment with dental implants can be predictable and safe for the rapidly growing geriatric population. Geriatric patients who are medically stable are suitable candidates for osseointegrated implant surgery, which facilitates oral function, comfort, and quality of life. A review of the 47 geriatric patients treated supports the conclusion that dental implants can be successfully placed and restored with fixed implant-supported or removable implant-supported prostheses.     

颧区垂直骨内种植和斜向骨内种植的生物力学三维有限元法对比研究

目的:比较上颌骨大型缺损后,行颧区成形术,在颧骨体底部垂直于牙合平面方向植入的种植体,与直接往颧骨体斜向30°植入的种植体在垂直牙合力作用下表现的生物力学行为差异。方法:按照两个不同种植体义颌的设计特点建立两个一侧上颌骨大型缺损种植体复合体的三维有限元模型,在相同的垂直于牙合平面加载100N,比较两者的受力情况。结果:斜向植入种植体颈部最大等效应力约是垂直植入种植体的4倍;最大拉应力约是垂直植入种植体的10倍;最大压应力约是垂直植入种植体的5倍;最大剪应力约是垂直植入种植体的4倍。虽然两者在颧骨体以外其余部位的应力分布均类似于颧突支柱的应力传导路径,但斜向种植体受侧向力后在主要传导路径上的最大应力值都要明显高于垂直种植体的轴向受力情况。结论:无论是颧骨体研究区的应力分布,还是颧骨体以外其余颅骨骨质的应力情况,垂直植入都要明显优于斜向植入。提示采用在颧区垂直种植的颧颊翼种植体义颌,比颧骨体斜向种植的常规种植体义颌具有优越的生物力学表现。     

Zygoma implant-supported prosthetic rehabilitation of a patient with a maxillary defect

This clinical report describes the successful management of a patient who underwent extensive resection of a maxillary cancer, by introduction of a maxillary obturator prosthesis using zygoma implants. The patient was a 57-year-old man with cancer of the upper anterior gingiva. The maxillary bone in the affected region had been extensively excised by radical surgery. Owing to loss of teeth retaining the denture, the existing prosthesis was unstable, and the patient experienced severe speech and mastication disorders. Four zygoma implants (two on each side), and two conventional dental implants (one each at both maxillary tuberosities) were used as denture retainers. The obturator prosthesis was stabilized by the implants, and the patient's oral function improved. High-level compatibility between the implant and surrounding tissue was obtained by mucosal regeneration around the implant. The results suggest that the combination of zygoma and conventional dental implants improves postoperative oral function by facilitating retention of the obturator prostheses.     

Restoration with implants in patients with recessive dystrophic epidermolysis bullosa and patient satisfaction with the implant-supported superstructure

PURPOSE: The use of endosseous implants in the prosthetic restoration of edentulous patients with recessive dystrophic epidermolysis bullosa (RDEB) may provide improved outcomes when compared with traditional prosthetic methods. The aim of this study was to evaluate the feasibility of placing endosseous implants in patients with RDEB and to compare the treatment outcomes of fixed and removable implant-supported restorations in the edentulous maxilla or mandible with the main emphasis on patient response. MATERIALS AND METHODS: Six patients with RDEB were treated with implants. All patients were completely edentulous in either the maxilla or mandible and had marked oral involvement, with alterations in the soft and hard tissues in all cases. Three patients were treated with fixed, screw-retained implant-supported prostheses, and 3 were treated with removable implant-supported prostheses. Six months after prosthetic restoration, patients were given a questionnaire to assess their psychologic well-being and satisfaction with the implant-supported restoration marked on a visual analog scale. RESULTS: A total of 38 dental implants (21 maxillary, 17 mandibular) were placed in 6 patients. The implant success rate was 97.9%. The average follow-up from implant placement was 5.5 years (range, 1 to 9). The fixed and removable implant-supported prostheses were associated with improvements in comfort and retention, function, esthetics and appearance, taste, speech, and self-esteem. The level of satisfaction was slightly higher in patients with a fixed prosthesis. CONCLUSION: These findings suggest that endosseous implants can be successfully placed and provide support for prostheses in patients with RDEB. Patients with fixed prostheses and overdentures were satisfied with their implant-supported prostheses in the edentulous maxilla and mandible.     

植入位点不同对颧骨种植义齿种植体周骨应力分布影响的研究

目的探讨植入位点不同时颧骨种植义齿种植体-骨界面的应力分布规律。方法计算机模拟建立上颌后牙区重度萎缩三维有限元模型,分别在第一前磨牙区、第二前磨牙区、第一磨牙区和第二磨牙区模拟颧骨种植义齿修复。进行垂直向、颊向30°和舌向30°加载100 N,统计分析植入位点不同时颧骨种植义齿种植体-骨界面的应力。结果1）第一前磨牙区颧骨种植体颊侧暴露较多,与临床不符。2）上颌后牙区拉应力峰值比较：选择第二磨牙区植入时最大,第二前磨牙区次之,第一磨牙区最小。上颌后牙区压应力峰值比较：选择第二磨牙区植入时最大,第一磨牙区次之,第二前磨牙区最小。颧骨区拉应力及压应力峰值比较：选择第二前磨牙区植入时最大,第一磨牙区次之,第二磨牙区最小。结论选择第一磨牙区颧骨种植义齿修复较好。     

修复材料对种植体周围骨组织应力的影响

目的：研究不同上部结构材料对种植体固定修复中种植体周骨组织的应力反应特点。方法：建立种植体支持固定桥力学模型，通过三维有限元方法分别计算出采用丙烯酸树脂，釉质瓷，瓷，金合金为上部结构材料时骨组织的应力状况，结果：每况工况下，种植体颈部周围皮质骨区所受的应力都是最大的，四种材料比较时使用丙烯酸树脂对种植体颈部骨组织的应力最小，其次为釉质瓷，瓷，最大为金合金，结论：修复材料的弹性模量会影响种植体周骨组织的应力分布，弹性模量低者对种植体颈部周围骨组织有保护作用，釉质瓷可能是较为理想的修复材料。     

上部结构材料对无牙下颌种植固定修复影响的三维有限元分析

目的:通过三维有限元方法探讨上部结构材料对无牙下颌种植固定修复生物力学的影响,为无牙颌修复治疗提供参考。方法:构建无牙下颌种植固定修复三维有限元模型,用6种牙科材料（纯钛、钴铬合金、金合金、氧化锆、聚醚醚酮及碳纤维增强聚醚醚酮）分别对种植上部结构进行赋值,得到6种模型,模拟斜向加载,对种植体、周围骨组织及上部结构进行应...     

Maxillary antral-nasal inlay autogenous bone graft reconstruction of compromised maxilla: a 12-year retrospective study.

During a 12-year period (1984-1996), 118 maxillary inlay autogenous bone grafts and 248 commercially pure titanium threaded root-form endosseous implants were placed in 54 consecutively treated patients with compromised maxillary bone. In this retrospective clinical study, 3 groups of patients were reviewed, group selection being based on anatomic location and surgical access to the recipient site. Group 1 included patients with bone grafts placed in the antrum floor via an intraoral antrostomy exposure, group 2 included patients with bone grafts placed in the nasal floor via an anterior intraoral nasotomy exposure, and group 3 included patients with bone grafts placed in the antral and nasal floor via an intraoral Le Fort I osteotomy downfracture exposure. Each patient received an implant-supported dental prosthesis. For the combined 3 groups, survival rates were 87% for endosseous implants and 100% for autogenous bone grafts. The success rate for the dental prostheses in the 3 groups was 95%. Sixty-nine dental prostheses functioned a mean of 57.1 months, whereas 3 prostheses required remaking because of implant loss. Of the medical and mechanical risk factors tabulated in this study, current use of nicotine, history of sinusitis, molar site implant placement, and shorter implant lengths had the most influence on implant failure.