Influence of implant number on the biomechanical behaviour of mandibular implant-retained/supported overdentures: A three-dimensional finite element analysis

Objective

The aim of this study was to evaluate strain distribution in peri-implant bone, stress in the abutments and denture stability of mandibular overdentures anchored by different numbers of implants under different loading conditions, through three-dimensional finite element analysis (3D FEA).

Methods

Four 3D finite element models of mandibular overdentures were established, using between one and four Straumann implants with Locator attachments. Three types of load were applied to the overdenture in each model: 100 N vertical and inclined loads on the left first molar and a 100 N vertical load on the lower incisors. The biomechanical behaviours of peri-implant bone, implants, abutments and overdentures were recorded.

Results

Under vertical load on the lower incisors, the single-implant overdenture rotated over the implant from side to side, and no obvious increase of strain was found in peri-implant bone. Under the same loading conditions, the two-implant-retained overdenture showed more apparent rotation around the fulcrum line passing through the two implants, and the maximum equivalent stress in the abutments was higher than in the other models. In the three-implant-supported overdenture, no strain concentration was found in cortical bone around the middle implant under three loading conditions.

Conclusions and clinical significance

Single-implant-retained mandibular overdentures do not show damaging strain concentration in the bone around the only implant and may be a cost-effective treatment option for edentulous patients. A third implant can be placed between the original two when patients rehabilitated by two-implant overdentures report constant and obvious denture rotation around the fulcrum line.     

Prosthetic aspects of osseointegrated fixtures supporting overdentures. A 4-year report

Eighty-six consecutive patients, provided with 84 resilient and two nonresilient overdentures (six in the upper and 80 in the lower jaw), were examined. The overdentures were supported by a total of 173 osseointegrated titanium fixtures (the standard Branemark abutment), with a mean loading time of 19.1 months (range 4 to 48 months). In each jaw only two fixtures anchored the overdentures. No failures occurred during the observation period but two fixtures were lost before loading. The radiographic annual bone loss around fixtures in the lower jaw was -0.8 mm for the first year and less than -0.1 mm for the following years. The change in marginal bone height did not correlate with parameters such as the occlusion and articulation pattern, the presence or absence of a soft liner around the abutments, and the magnitude of the interabutment distance. The patients' reactions to overdenture treatment were, on the whole, positive concerning chewing function, phonetics, and comfort. The need for maintenance care of the clip-bar attachment was minimal.     

套筒冠义齿用于牙周病修复治疗后的根周骨质变化

目的：对套筒冠义齿用于牙周病修复治疗后基牙的骨质变化进行定量追踪观察。方法：采用平行投照技术，获得11例牙周病患者套筒冠义齿修复治疗前及治疗后1、2、3年牙周病患牙(91颗基牙)的系列标准牙片。运用牙科图像分析处理软件对每一基牙的根周骨高度和骨密度进行测量并进行统计学分析。结果：在所研究的时间内，患牙牙槽骨的骨高度有一定程度的增加，但无统计学意义；而骨密度在治疗后一年内有显著增加，而后趋于平缓。结论：套筒冠义齿有利于牙周病患牙根周骨质的稳定与恢复。     

下颌固定桥基牙牙槽骨单侧吸收对基牙应力分布的影响

目的:研究双端固定桥基牙牙槽骨单侧吸收对基牙应力分布的影响。方法:采用螺旋CT扫描获取健康人下颌骨、牙齿、牙周支持组织的二维图像,通过图像合成软件建立三维数字模型,并应用三维有限元分析软件生成下颌后牙三单位固定桥的三维有限元分析模型。在相同垂直和水平载荷情况下,分析基牙牙槽骨单侧吸收时固定桥各基牙的应力分布。结果:当前磨牙端基牙牙槽骨单侧吸收达25%、磨牙端基牙牙槽骨无吸收时,前磨牙端基牙开始出现应力集中;当磨牙端基牙牙槽骨单侧吸收达35%、前磨牙端基牙牙槽骨无吸收时,磨牙端基牙开始出现应力集中。结论:下颌后牙双端固定桥基牙应力分布与基牙牙槽骨吸收形式密切相关,但二者之间不是线性关系而是存在临界区,基牙牙槽骨单侧吸收的程度对基牙应力分布的影响弱于多侧吸收。     

Management of a failed mandibular staple implant: a clinical report

A 48-year-old woman sought treatment because her staple implant-retained overdenture was no longer retentive, and the denture was worn over the abutments. After unsuccessfully attempting to move the retentive nuts along the transosseous posts of the staple implant, the posts were cut off at the level of the bone. Two endosseous implants were placed around the staple implant, and a new implant-retained overdenture was fabricated and inserted using ball attachments for retention. This article describes the treatment for this patient, who has been wearing the new dentures successfully for the past 4 years.     

Simultaneous repair and rebase of a removable partial denture.

A patient presented a unique dental problem: the evulsion of mandibular canines, and the restoration of anterior alveolar bone associated with periodontal disease. A mandibular removable partial denture, bilaterally supported by the canines, premolars, and molar abutments of blade implants, had been worn for more than ten years. The open clasps in the canine areas were irritating the oral tissues, and the space under the anterior saddle of the denture was retaining food. Both situations needed immediate consideration. The evulsed canines were reproduced in autocured acrylic and secured in the clasps of the denture. The space under the saddle was rebased with autocured acrylic. Since both areas were adjacent to each other, they were splinted together simultaneously. The patient was satisfied with having the old denture repaired without being deprived of the prosthesis for an extended period of time.     

Effect of 5.25 % Sodium Hypochlorite on Color Stability of Acrylic and Silicone Based Soft Liners and a Denture Base Acrylic Resin

The purpose of the current study was to investigate the effect of a chemical disinfectant (sodium hypochlorite 5.25 %) on color stability of a denture base acrylic resin and two processed soft denture lining materials of two different types (acrylic-based and silicone-based). Ten specimens from each type of materials tested were made (2 × 20 × 20 mm). All specimens were immersed in sodium hypochlorite (5.25 %). Colorimetric measurements for each specimen were taken before immersion, and after 24 h and 7 days of immersion. Color changes were evaluated using the CIE L*a*b* colorimetric system. Data were statistically analyzed with one-way analysis of variance (ANOVA) (α = 0.05). ANOVA was followed by Bonferroni test to determine which groups differed from each other. ΔE and ΔL* of the silicone-based liner at the 1st and 7th days of immersion were significantly more than of denture base acrylic resin and acrylic-based liner. Change in ΔL* values of denture base acrylic resin and acrylic-based liner was small and statistically insignificant after 24 h of its immersion. However, the increase in ΔL* values of the acrylic-based liner after 7 days of immersion was considerably more than of denture base acrylic resin. Color changes in denture base acrylic resin and soft denture liners tended to increase with longer immersion times, and the color stability of the soft denture liners was influenced by its chemical type.     

即刻负载的下颌套筒冠种植义齿在重度牙周病患者中的应用研究

目的介绍即刻负载的下颌套筒冠种植义齿在重度牙周炎患者中的应用,并评价其临床疗效。方法选择22位重度牙周炎患者,下颌颏孔区之间共植入88枚Ankylos种植体,采用Syncone套筒冠基台进行即刻修复、即刻负载,3个月后用纯钛支架义齿进行永久修复。修复完成后随访12~27个月,观察种植体周围软硬组织状况,计算存留率和成功率,调查患者满意度。结果 12~27个月观察期内,88枚种植体无脱落,存留率100%;仅有2枚边缘骨吸收大于2 mm,成功率达到97.73%;软组织状况均明显好转,牙周袋深度减小,探诊出血百分比降低,具有统计学差异;90.9%的患者都认为套筒冠义齿固位力足够,81.8%的患者认为使用12~27个月后,固位力无明显下降,95.46%的患者对这种义齿感到"比较满意"或者"非常满意"。结论即刻负载的下颌套筒冠种植义齿具有很高的存活率、成功率和患者满意度,有利于促进牙周病患者的软硬组织健康。     

Force versus time profiles of selected heat-processed denture liners.

The potential correlation of the force versus time behavior of four resilient lining materials and their acceptance by patients was investigated. Two modified acrylic resins and two silicone denture lining materials were tested. The response of the soft lining materials to a programmed indentation test was used to define a parameter for each denture liner product. A parameter defined as the "Rebound Index," using force-time data obtained from the indentation measurements, was significantly different for the modified acrylic resins compared to the silicone materials. Improved patient acceptance was correlated with higher values of this index.     

单端固定桥连接体部米塞氏应力分析

目的：分析单端固定桥连接体米塞氏（Von Mises)的应力情况。方法：用三 维有限元方法，通过改变基牙牙槽骨高度、基牙数目和桥体长度进行分析和计算基牙与桥体间的连接体部Von Mises的应力情况。结果：较高的Von Mises应力集中在连接体部，降低牙槽骨高度或增加骨高度或增加桥体长度均会提高Von Mises应力，而增加基牙数目则会减小其应力。结论：为了减少单端固定桥连接体部的疲劳和断裂，应增加基牙数目，减短桥体长度。     

Overdenture retention of four resilient liners over an implant bar

STATEMENT OF PROBLEM: Resilient denture liners offer an alternative method of designing implant-retained overdentures. Space is provided in the overdenture to envelop the implant bar with a resilient liner to be applied chairside or processed in the laboratory. The degree of retention may vary and these materials change over time. PURPOSE: This study evaluated the retention on an implant/bar prosthesis with overdentures lined with 4 resilient denture lining materials, after cyclic insertion and removal over a simulated 1.5-year period. MATERIAL AND METHODS: Four implants were placed in a mandibular edentulous cast and a gold bar superstructure was made. Overdentures were processed in Lucitone-199 and Tokuyama, Luci-Sof, Molloplast-B, and PermaSoft (with and without sealer) lining materials, cured according to manufacturers' instructions. Each of 5 overdentures contained each liner and were cycled 2740 times (simulating 1.5 years of service at 5 insertions daily) in 37 degrees C water in an Instron at 20 cm/min. Insertion and retention force were measured. RESULTS: The 3 silicone rubber liners were 3 to 5 times more retentive than the plasticized acrylic liner initially. After cycling, Tokuyama soft liner (autopolymerized silicone) gained 14% retention, Luci-Sof (heat-cured silicone) gained 8%, Molloplast-B (heat-cured silicone) lost 12%, whereas PermaSoft (autopolymerized plasticized acrylic) with sealer lost 43%, and without sealer lost 60%. PermaSoft lining material also chafed and crumbled after cycling and was significantly less retentive in most statistical comparisons. CONCLUSIONS: All the silicone-based resilient liners retained the overdentures well. The plasticized acrylic was less retentive initially, and lost significant retention after 2740 cycles, compared with silicone-based resilient liners.     

微型种植体在无牙颌患者覆盖义齿修复中的初步应用

目的探讨微型种植体在无牙颌患者修复中的临床初步应用。方法2002年5至8月，为4例全身健康情况不良伴牙槽骨重度吸收的无牙颌患者植入14枚微型种植体，磁性固位体覆盖义齿修复。术前、术后即刻、术后每年评估种植体周围皮质骨高度及周围牙龈健康状况，检查修复体戴用情况，评估患者满意度。结果14枚种植体至今全部存留，未发生种植体周围炎，X线片检查显示：种植体周围皮质骨高度稳定。除1枚下颌种植体磁性基台折断，余无异常。全部患者对修复体满意。结论利用微型种植体为无牙颌且伴有牙槽骨吸收的患者行覆盖义齿修复是可行的。本组随访3年的临床效果满意，长期效果尚待进一步观察。     

The influence of resilient liner and clip attachments for bar‐implant‐retained mandibular overdentures on opposing maxillary ridge. A 5‐year randomised clinical trial

This study aimed to compare the influence of resilient liner and clip attachments for bar‐implant‐retained mandibular overdentures on opposing maxillary ridge after 5 years of denture wearing. Thirty edentulous male patients (mean age 62·5 years) received two implants in the anterior mandible after being allocated into two equal groups using balanced randomisation. After 3 months, implants were connected with resilient bars. New maxillary complete dentures were then constructed, and mandibular overdentures were retained to the bars with either clips (group I, GI) or silicone resilient liners (group II, GII). The prosthetic and soft tissue complications of the maxillary dentures were recorded 6 months (T_6 m), 1 year (T1), 3 years (T3) and 5 years (T5) after overdenture insertion. Traced rotational tomograms were used for measurements of maxillary alveolar bone loss. The proportional value between bone areas and areas of reference not subject to resorption was expressed as a ratio (R). Change in R immediately before (T0) and after 5 years (T5) of overdenture insertion was calculated. Maxillary denture relining times and frequency of flabby anterior maxillary ridge occurred significantly more often in GI compared with GII. The change of R in anterior part of maxilla was significantly higher than change of R in posterior part in both groups. GI showed significant resorption of anterior residual ridge compared with GII. Relining times and frequencies of flabby ridge were significantly correlated with change in R. Within the limitations of this study, resilient liner attachments for bar‐implant‐retained mandibular overdentures are associated with decreased resorption and flabbiness of maxillary anterior residual ridge and fewer maxillary denture relining times when compared with clip attachments.     

种植体数目与分布对下颌种植覆盖义齿骨组织应力变化的影响

目的：建立下颌种植覆盖义齿三维有限元模型,研究咬合力作用下种植体数目与位置分布对牙槽骨组织应力分布的影响因素。方法：临床采集患者下颌骨及其原有义齿CT数据,使用逆向工程软件建立种植体数目与位置不同的下颌种植覆盖义齿实体模型。通过Abaqus有限元软件分析咬合力作用下种植体数目与位置分布对种植体周围以及下颌后端牙槽骨应力变化的影响。结果：在咬合力作用下,下颌骨Mises应力主要分布在种植体周围骨组织,种植体远中颈部呈现应力集中,下颌后端区域应力较小且分布均匀。随着种植体数目的增加,后端种植体周围骨应力上升,远端牙槽骨应力降低。当牙弓前、后端种植体距离增加时,种植体周围骨应力增大,远端牙槽骨应力降低。结论：采用2植体支持的下颌种植覆盖义齿种植体周围骨吸收风险较小,但远端牙槽嵴骨吸收风险增大。4植体义齿所承受的咬合力主要由植体承担,修复时应注意前后植体的距离和咬合力在义齿上的合理分布。     

Resilient liner vs. clip attachment effect on peri‐implant tissues of bar‐implant‐retained mandibular overdenture: a 1‐year clinical and radiographical study

Purpose: The aim of this study was to compare between the effects of resilient liner and clip attachments of bar‐implant‐retained mandibular overdenture on peri‐implant tissues. Materials and methods: In a randomized‐controlled clinical trial, 30 edentulous male patients (mean age 62.5 years) were equally assigned to two groups. In each patient, two implants were inserted in the canine area of the mandible using a two‐stage surgical protocol. After 3 months, the implants were connected with resilient bars. Mandibular overdentures were retained to the bars with either clips (group I) or silicone‐resilient liners (group II). Peri‐implant tissues were evaluated clinically (with regard to plaque scores, gingival scores and probing depths) and radiographically (with regard to peri‐implant vertical and horizontal alveolar bone changes). Evaluations were performed at the time of overdenture insertion (T0), 6 months (T6) and 12 months (T12) after overdenture insertion. Results: After 12 months of using bar‐implant‐retained mandibular overdenture, the resilient liner attachment had significantly decreased peri‐implant plaque score, gingival score, probing depth, vertical and horizontal bone loss when compared with the clip attachment. Conclusion: Within the limitations of this study, and in terms of peri‐implant tissue health of bar‐implant‐retained mandibular overdenture, we recommend resilient liner rather than clip attachment. To cite this article:
Elsyad MA, EL Shoukouki AH. Resilient liner vs. clip attachment effect on peri‐implant tissues of bar‐implant‐retained mandibular overdenture: a 1‐year clinical and radiographical study.
Clin. Oral Impl. Res. 21 , 2010; 473–480
doi: 10.1111/j.1600‐0501.2009.01879.x     

磁性附着体种植覆盖义齿修复下颌牙槽骨重度吸收无牙颌患者的临床观察

目的：探讨磁性附着体种植覆盖义齿修复下颌牙槽骨重度吸收无牙颌患者的临床效果。方法：对下颌牙槽骨重度吸收、牙槽嵴低平的患者,在下颌尖牙位置植入2枚种植体,3—6个月后完成磁性附着体覆盖义齿修复。每隔6个月复诊一次,观察覆盖义齿使用情况,并结合口内检查和X线检查评价使用效果。结果：修复完成后2—3年,种植体骨结合良好,未见明显骨吸收;义齿固位良好,患者对美观及功能效果满意。结论：磁性附着体种植覆盖义齿修复下颌牙槽骨重度吸收无牙颌患者,能明显示改善义齿固位和咀嚼效果。     

The effect of different mandibular dentures on antagonistic maxillary ridge

PURPOSE: Is to evaluate the antagonistic, maxillary ridge resorption for different prosthetic modalities mainly mucosa-supported mandibular complete overdentures, combined mucosa implant-supported mandibular complete overdenture, and lower conventional complete dentures. MATERIALS AND METHODS: Fifteen completely edentulous patients were divided into 3 groups; 5 patients each. Group I patients received maxillary conventional denture and mandibular overdentures retained by magnet attachment on 2 implants (mainly mucosa-supported overdenture). Group II patients received maxillary conventional denture and mandibular overdentures retained by bar attachment on 2 implants (combined mucosa implant-supported overdenture). Group III patients received upper and lower conventional complete denture. All patients were evaluated clinically and radiographically immediately after insertion and after 1 and 2 years. Panoramic radiographic film was used to evaluate the antagonistic maxillary ridge resorption. RESULTS: Indicated a more pronounced annual bone resorption of the antagonistic maxillary ridge after 2 years in patients with conventional complete denture wearers when compared with patients with combined mucosa implant-supported mandibular complete overdenture and mainly mucosa-supported mandibular complete overdenture groups. CONCLUSION: Using a combined mucosa implant-supported mandibular complete overdenture the amount of antagonistic maxillary alveolar bone resorption increases when compared with the mainly mucosa-supported complete overdenture.     

三种缓冲机制的根面附着体式覆盖义齿的电测应力分析研究

目的 分析不同加载情况下,太极扣、球帽、磁性根面附着体支持的覆盖义齿基牙周围牙槽骨及缺牙区牙槽嵴的应力差异,为临床根面附着体的选择提供参考.方法 采用电阻应变测量法,体外模拟覆盖义齿受力情况,测量基牙牙颈部牙槽骨、下颌牙弓前部中央及第一磨牙相对应缺牙区牙槽嵴处的应力,并比较分析三种附着体式覆盖义齿在不同加载情况下应力差异.结果 不同缓冲机制附着体式覆盖义齿在相同加载情况下,义齿会出现一定程度的滑动(磁性附着体式覆盖义齿)或旋转(三种附着体义齿),基牙牙颈部不同部位牙槽骨、牙弓前部及游离端缺牙区牙槽嵴应力分布明显不同.结论 太极扣式覆盖义齿适应条件相对最广泛,其次为磁性附着体式覆盖义齿.     

Prosthetic aspects and patient satisfaction with two-implant-retained mandibular overdentures: a 10-year randomized clinical study

PURPOSE: This study aimed to compare the prosthetic aspects and patient satisfaction with prosthetic care in two-implant-retained mandibular overdentures, whether implants were splinted with a bar or left with magnets or ball attachments. MATERIALS AND METHODS: Thirty-six completely edentulous patients had two Br?nemark implants placed in the mandibular canine area. A randomized procedure allocated patients into three groups of equal size, each with a different attachment system: bars, magnets, or balls. Prosthesis retention and mechanical as well as soft tissue complications were recorded in addition to patient satisfaction. A linear mixed model was fitted with attachment type and time as classification variables and adjusted by Turkey's multiple range test. RESULTS: Ball-retained overdentures showed at year 10 the greatest vertical retention force (1,327 g), followed by bars (1,067 g) and magnets (219 g). In the ball group, need for tightening of abutment screws was the most common mechanical complication; in the magnet and bar groups, respectively, the most common complications were wear and corrosion, and the need for clip activation. Prosthesis stability and chewing comfort for the overdenture were rated significantly lower for the magnet group compared to the ball and bar groups. Prosthesis stability of the maxillary denture was rated significantly lower in the bar group compared to ball and magnet groups. CONCLUSION: The ball group scored best in relation to retention of the overdenture, soft tissue complications, and patient satisfaction at year 10. The bar group scored lower for comfort and stability of the maxillary denture. Magnets offered patients the least comfort.     

A prospective evaluation of Frialoc implants with ball-abutments in the edentulous mandible: 1-year results

Several surgical and prosthetic concepts for the treatment of patients with mandibular atrophy and related lower denture problems are proposed and described in the literature. The present study discusses and evaluates the use of a new single-stage implant and overdenture with ball-attachment for this purpose. This study evaluates the clinical performance of the implants and abutments and addresses surgical and prosthetic complications that were encountered. Eighteen fully edentulous patients received two, single-stage Frialoc implants (Friadent, Mannheim, Germany). The implants were left to osseointegrate for 3 months and were subsequently provided with ball-abutments and loaded through a mandibular overdenture. After 1-year of clinical service, two implants were lost, which accumulated to a 1-year survival rate of 93.9% (SE 4.2%). Patient satisfaction was high, and prosthetic complications and postinsertion maintenance were minimal. Three abutments loosened, one of which subsequently broke after 5 months of loading. Retightening of the attachment (gold matrix) was performed on seven occasions in four patients. Soft tissue response was excellent. Although minor hypertrophy of the peri-implant mucosa was observed, hardly any marginal bone loss between baseline and 1-year observations occurred. Short-term results indicate that mandibular implant overdenture treatment by means of two ball-abutments, using Frialoc implants and prosthetic components, leads to good clinical results, both from an objective and a subjective perspective.