Biomechanical characteristics of "All-on-4" concept analyzed by three-dimensional finite element method / 中国组织工程研究

BACKGROUND:With the increasing demand for edentulous jaw restoration,"All-on-4"concept is widely used.The load transfer mode of implant is different from that of natural tooth.The three-dimensional finite element analysis can study the stress distribution of implants and surrounding bone tissues under functional loading.On this basis,it provides research methods for finding suitable implant materials,optimizing implant geometry,and designing clinical surgical protocols. OBJECTIVE:To review researches related to three-dimensional finite element analysis in"All-on-4"concept. METHODS:Relevant literature published from 2003 to 2023 was searched in CNKI and PubMed databases with the search terms of"finite element method;All-on-4;edentulous;biomechanics"in Chinese and English.Finally,65 articles were included for review. RESULTS AND CONCLUSION:(1)In the case of insufficient horizontal bone mass,we can choose to apply narrow diameter implants,but we need to pay attention to the effect of the presence of the cantilever on the stress distribution and reduce the risk of failure.(2)The"All-on-4"concept reduces the stress distribution of bone by tilting the distal middle implant,but the ideal angle of the distal implant tilt in different jaw types requires further study.(3)The presence of cantilevers increases the risk of implant failure,and keeping the cantilever length/AP distance ratio at 0.9 helps to minimize mechanical complications.(4)When a framework is made of a material with a lower elastic modulus,the stress on the framework itself will be smaller,but it will increase the stress on the implant,prosthetic screw,abutment and peri-implant bone.On the contrary,when a material with a higher elastic modulus is used,it can reduce the stress on the prosthetic components,implants and peri-implant bone in the restoration,but the stress on the framework itself is higher.(5)The"All-on-4"concept allows for a better mechanistic balance,but requires the development of a long-term,effective treatment program that is tailored to the patient's specific situation.(6)Proper occlusal scheme is the key to the success of implant treatment,and there is no difference between canine-guide occlusion and group function occlusion in terms of the longevity of the restoration.However,there are many factors that influence occlusal design,and further in vitro experiments as well as a number of clinical studies are needed to explore the ideal occlusal design of the"All-on-4".

Narrow single tooth implants for congenitally missing maxillary lateral incisors: a 5-year follow-up.

INTRODUCTION: The maxillary lateral incisor epidemiologically represents the second most common congenitally absent teeth. In literature, different approaches have been proposed, such as canine teeth substitution, traditional prosthetic rehabilitation, adhesive restoration or single-tooth implant. The aim of this investigation was to evaluate the clinical and radiographical effectiveness of narrow single tooth implant treatment for missing maxillary lateral incisors. MATERIALS AND METHODS: A total of 11 subjects, in seven cases bilaterally, were treated in the Department of Medical, Oral and Biotechnological Sciences, University "G. D'Annunzio" of Chieti-Pescara, with a radiographical follow-up at 5 years from the loading. RESULTS: At the follow up, no bone defects or pathological gingival probing were present around the peri-implant tissues. No mechanical complications, such as loss of the crown fixation screws or fracture, were reported. CONCLUSIONS: Narrow implants represent a predictable optional treatment for maxillary lateral incisor restoration, with a high-level aesthetic and functional outcome of the rehabilitation.

In vitro interface changes of two vs three narrow-diameter dental implants for screw-retained bar under fatigue loading test.

The mechanical failure of a dental implant is clinically related to a prosthetic overload dissipated on the fixture/abutment complex. The aim of this investigation was to evaluate the fracture strength of two vs three narrow-diameter dental implant configurations for screw-retained bars. Different configurations of screw-retained bars on two narrow-diameter dental implants (Group I) and screw-retained bars on three narrow-diameter dental implants (Group II) were tested under a static fracture loading. A total of 20 specimens, 10 for each group were evaluated. The fracture loading point was significatively higher in Group I (p<0.05). The experimental groups reported high levels of fracture strength under loading that encourages the clinical application of screw-retained bars supported by multiple narrow-diameter implants.

Dental Implant Treatment with Computer-assisted Surgery for Bilateral Agenesis of Maxillary Lateral Incisors: A Case Report.

Here, we report a case of dental implant treatment involving computer-assisted surgery for bilateral agenesis of the maxillary lateral incisors. The patient was a 39-year-old woman with the chief complaint of functional and esthetic disturbance due to maxillary and mandibular malocclusion. The treatment plan comprised non-extraction comprehensive orthodontic treatment and prosthodontic treatment for space due to the absence of bilateral maxillary lateral incisors. A preliminary examination revealed that the mesiodistal spaces left by the absent bilateral maxillary lateral incisors were too narrow for implant placement (right, 5.49 mm; left, 5.51 mm). Additional orthodontic treatment increased these spaces to approximately 6 mm, the minimum required for implant placement if risk of damage to the adjacent teeth due to inaccuracies in directionality of drilling is to be avoided. For dental implant treatment with computer-assisted surgery, preoperative planning/simulation was performed using Simplant® ver.12 software and a toothsupported surgical template fabricated using stereolithography. Two narrow-diameter implants were placed in a two-stage procedure. It was confirmed that there was sufficient distance between the implant fixtures and the roots of the adjacent teeth, together with no exposure of alveolar bone. Following a 4-month non-loading period, second-stage surgery and provisional restoration with a temporary screw-retained implant crown were performed. Cement-retained superstructures made of customized zirconia abutment and a zirconia-bonded ceramic crown were fitted as the final restoration. At 5 years after implant surgery, there were no complications, including inflammation of the peri-implant soft tissue and resorption of peri-implant bone. Computer-assisted implant surgery is useful in avoiding complications in bilateral agenesis of the maxillary lateral incisors when only a narrow mesiodistal space is available for implant placement.

A 3 year prospective study of survival rate of narrow diameter implants

PURPOSE: The purpose of present study was to retrospectively analyze the survival rate of narrow diameter implant less than 3.6 mm by initial stability and radiographic measurements. MATERIALS AND METHODS: In total, 24 patients who received 38 narrow diameter implants (≤ 3.6 mm in diameter, ≥ 7 mm in length) were enrolled in this retrospective study. The cumulative survival rate was calculated and various factors were investigated according to the implant platform diameter, body diameter, length, position, concomitant use of guided bone regeneration in implant placement and final prosthesis type. Initial stability was investigated with implant stability quotient (ISQ) value. The mesial and distal marginal bone level (MBL) change was calculated with radiography. RESULTS: The overall survival rate was 92.11%. Mean ISQ value and MBL change of survival implants was 66.26 and 0.14 ± 0.31 mm, respectively. None of the implants with platform diameters larger than the body diameter failed. CONCLUSION: In conclusion, the findings of present study suggest that narrow diameter implant could be predictable treatment in narrow alveolar ridge.

Effectiveness of temporary implants in teenage patients: a prospective clinical trial.

AIMS: The objective of this study was to assess prospectively the outcomes of extra-narrow diameter implants (XNDI) placed in teenage patients as a temporary restorative option. MATERIAL AND METHODS: Twenty consecutive young patients presenting one or several missing teeth received XNDI that were immediately restored with composite, Polymethylmethacrylate (Acrylic) or ceramic crown. Clinical and radiographical outcomes were assessed for a minimum follow-up period of 1 year. Additionally, each patient completed retrospectively a satisfaction questionnaire using Visual Analog Scale (VAS). RESULTS: A total of 30 implants were placed and followed for a period of 1-7.4 years (mean: 3.59 years). One implant failed after 3 weeks and was replaced successfully. No further biological complications occurred during the follow-up period, leading to an implant survival rate of 96.6%. The patient satisfaction evaluations displayed high levels of comfort and function. CONCLUSION: Immediately restored XNDI to replace missing teeth on teenager patients seems to be an effective temporary restorative option to replace missing teeth in young patients. Composite or ceramic crowns should be preferred. Clinical trials with long-term follow-ups and the assessment of passive egression are needed.

Narrow-implant-retained overdenture in an atrophic mandibular ridge: a case report with 6-year follow-up.

When atrophic jaws compromise oral rehabilitation with conventional implants, narrow-diameter implants can be used. This case report describes treatment of an edentulous 75-year-old diabetic woman with a severely resorbed mandibular ridge. Her mandibular dentition was restored with an overdenture supported by 3 narrow implants and 1 mini implant. Her maxillary dentition was restored with a conventional complete denture. A 6-year clinical and radiographic follow-up confirmed that the narrow implants had provided effective stability for the overdenture, providing improvements in phonetics and masticatory ability at a low cost.

Clinical and radiographic evaluation of early loaded narrow-diameter implants: 3 years follow-up.

OBJECTIVE: To evaluate the clinical reliability of narrow implants placed in a one-stage procedure and early loaded in the upper and lower incisor region. MATERIAL AND METHODS: This is a prospective, single-arm, multicenter study in which patients with missing natural dentition in upper lateral and lower incisor positions were enrolled. Eligible implants (OsseoSpeed™ TX 3.0S, DENTSPLY Implants) were of three different lengths and of 3.0 mm in diameter. One-stage surgery was performed and healing abutment connection took place. Placement of the permanent single crown took place after a 6-10 weeks healing period. Clinical and radiographic checks were performed at implant placement, loading, and at the 6, 12, 24, and 36 months follow-up visits. RESULTS: A total of 69 subjects with 97 implants have been included in this study. From surgery to 36 months follow-up, 5.6% of the implants showed bone loss of more than 1 mm, while no bone loss at all were observed for 57.3% of the implants. The mean marginal bone level change from surgery to the 6, 12, and 36 months follow-up visits was -0.27, -0.11, and -0.09 mm, respectively. The total survival rate after 3 years is 95.5%. CONCLUSIONS: The data presented show stable marginal bone levels as well as healthy soft tissue around OsseoSpeed™ TX 3.0S implants, after 3 years of function. An interesting finding from this investigation was that a longer healing period before crown placement and loading contributed to statistically significant less marginal bone loss between loading and the 1-year follow-up visit (Galindo-Moreno et al. 2012). This finding, associated with a stable probing pocket depth and a stable crown-gingiva distance, using a one-stage surgical procedure helps to maintain the integrity of the peri-implant soft tissues. Narrow implants can be considered as a valid solution in the treatment of the localized narrow bony defects in the anterior area with reduced spaces between the natural teeth.

Long-term retrospective study of narrow implants for fixed dental prostheses.

OBJECTIVE: The objectives of this study were to analyze retrospectively the long-term survival and success rates of Narrow implants (NIs) placed with various implant systems, and the association with biological and technical complications. MATERIAL AND METHODS: In total, 338 patients (men = 45.6%, women = 54.4%) who received 541 NIs (≤3.5 mm in diameter) for fixed prostheses were enrolled in this retrospective study. The mean marginal bone level (MMBL) change was calculated. Life table analysis with the cumulative survival rate and success rate was calculated, and biological and technical complications were evaluated. RESULTS: The annual MMBL change was 0.07 ± 0.20 mm. The 12-year cumulative survival (success) rates of NIs were 98.1% (91.8%) and 98.5% (93.8%) for the implant- and subject-based analysis, respectively. During the observation period up to 12 years (mean 4.9 years), six implants were lost in the maxilla, whereas three implants were lost in the mandible. Technical complications were more frequent than biological complications. Infection was the most common underlying cause of biological complications and the most frequent technical complication was decementation. CONCLUSION: In conclusion, the findings of this study suggest that NIs could be used safely for narrow alveolar ridges or narrow mesiodistal spaces on the basis of their high survival rate.