A finite element study on stress distribution of two different attachment designs under implant supported overdenture

Objective

This study aimed to evaluate stress patterns generated within implant-supported mandibular overdentures retained by two different attachment types: ball and socket and locator attachments.

Materials and methods

Commercial CAD/CAM and finite element analysis software packages were utilized to construct two 3D finite element models for the two attachment types. Unilateral masticatory compressive loads of 50, 100, and 150 N were applied vertically to the overdentures, parallel to the longitudinal axes of the implants. Loads were directed toward the central fossa in the molar region of each overdenture, that linear static analysis was carried out to find the generated stresses and deformation on each part of the studied model.

Results

According to FEA results the ball attachment neck is highly stressed in comparison to the locator one. On the other hand mucosa and cortical bone received less stresses under ball and socket attachment.

Conclusions

Locator and ball and socket attachments induce equivalent stresses on bone surrounding implants. Locator attachment performance was superior to that of the ball and socket attachment in the implants, nylon caps, and overdenture. Locator attachments are highly recommended and can increase the interval between successive maintenance sessions.     

A Double-Blind Randomized Controlled Trial (RCT) of Titanium-13Zirconium versus Titanium Grade IV Small-Diameter Bone Level Implants in Edentulous Mandibles - Results from a 1-Year Observation Period

Background: The use of endosseous dental implants has become common practice for the rehabilitation of edentulous patients, and a two‐implant overdenture has been recommended as the standard of care. The use of small‐diameter implants may extend treatment options and reduce the necessity for bone augmentation. However, the mechanical strength of titanium is limited, so titanium alloys with greater tensile and fatigue strength may be preferable. Purpose: This randomized, controlled, double‐blind, multicenter study investigated in a split‐mouth model whether small‐diameter implants made from Titanium‐13Zirconium alloy (TiZr, Roxolid?) perform at least as well as Titanium Grade IV implants. Methods and Materials: Patients with an edentulous mandible received one TiZr and one Ti Grade IV small‐diameter bone level implant (3.3 mm, SLActive®) in the interforaminal region. The site distribution was randomized and double‐blinded. Outcome measures included change in radiological peri‐implant bone level from surgery to 12 months post‐insertion (primary), implant survival, success, soft tissue conditions, and safety (secondary). Results: Of 91 treated patients, 87 were available for the 12‐month follow‐up. Peri‐implant bone level change (?0.3 ± 0.5 mm vs ?0.3 ± 0.6 mm), plaque, and sulcus bleeding indices were not significantly different between TiZr and Ti Grade IV implants. Implant survival rates were 98.9 percent and 97.8 percent, success rates were 96.6 percent and 94.4 percent, respectively. Nineteen minor and no serious adverse events were related to the study devices. Conclusion: This study confirms that TiZr small‐diameter bone level implants provide at least the same outcomes after 12 months as Ti Grade IV bone level implants. The improved mechanical properties of TiZr implants may extend implant therapy to more challenging clinical situations.     

Implant overdenture using a locator bar system by drill and tapping technique in a mandible edentulous patient: a case report

Various options have been introduced for the selection of implant overdenture attachments. Attachment wear due to the repeated insertion and removal of dentures has caused problems such as decreased retention and the requirement for suprastructure remanufacturing. In these cases, a Locator bar system was applied using the drill and tapping technique to achieve total retrievability. In a 55-year-old female patient who showed three degrees of mobility in most of her teeth due to severe alveolar bone loss, a complete denture in the maxilla and an implant supported type overdenture in the mandible were planned after extracting all the remaining teeth. Six implants were placed from canine region to the distal molar region, and the locator was connected to the milled bar using the drill and tapping technique. For a 61-year-old female edentulous patient who complained of poor retention with old denture, a complete denture in the maxilla and an implant-tissue supported type overdenture in the mandible were planned. Four implants were placed in front of mental foramen, and the Locator was also connected to the Hader bar using the drill and tapping technique. With this technique, female parts can be easily replaced, and retention can be continuously maintained.     

A Prosthesis Retention System for Full‐Arch,Fixed, Implant‐Supported Prosthesis

Full‐arch, fixed, implant‐supported prostheses can be designed to be cement‐ or screw‐retained. Both retention mechanisms have a few inherent disadvantages. A fixed attachment system has been introduced to circumvent the disadvantages of both screw and cement retention. This system eliminates the screw access holes and the use of cement. The number of intraoral procedures required is also reduced. The purpose of this article is to report a case using the Locator F‐Tx Attachment System to facilitate fabrication of an esthetic, clinician‐retrievable, full‐arch implant‐supported fixed dental prosthesis.     

球帽和Locator附着体种植覆盖义齿的临床疗效评价

目的:评价球帽附着体和Locator附着体应用于种植覆盖义齿的临床效果.方法:纳入无牙颌患者67例,共植入150颗Straumann或Bego种植体,完成球帽式或Locator式种植覆盖义齿修复.定期随访复查,包括修复后生物并发症和机械并发症情况和患者满意度调查.采用SPSS 17.0软件统计分析.结果:完成随访58例,球帽组35例,Locator组26例,球帽改Locator组7例.生物并发症比较显示,球帽组的牙龈增生发生率明显高于Locator组(P＜0.05);球帽组和Locator组的机械并发症发生率无显著差异(P＞0.05),但Locator组各类机械并发症的发生次数少于球帽组,球帽组平均修理频次为1.9次,Locator组为0.9次;Locator组患者对咀嚼和固位的满意度高于球帽组,不同性别的患者满意度无差异,满意度与患者的年龄和随访时间无相关性.结论:Locator式种植覆盖义齿相比球帽式种植覆盖义齿,临床效果具有一定优势.     

磁共振检查肢体病变定位器的研究与临床应用

目的探讨肢体病变定位方法,分析磁共振检查肢体病变定位器准确性。方法利用磁共振检查肢体病变定位器对38例患者肢体病变准确定位,施行穿刺或手术治疗。结果所有被检查患者肢体病变定位准确,对手术或穿刺治疗起到重要指导作用。结论磁共振检查肢体病变定位器在肢体占位性病变检查中,定位准确,有利于病变的诊断和治疗。     

Locator式和球帽式下颌种植覆盖义齿在牙槽嵴应力分布的光弹性研究

目的 分析比较含2个种植体的下颌种植覆盖义齿分别使用球帽附着体和Locator附着体在正中,侧向及前伸(牙合)应力加载时对其种植体和余留牙槽嵴的应力分布差异.方法 应用三维光弹实验的方法,在Atwood 3级无牙颌模型双侧至尖牙区域内各植入1枚种植体后制作环氧树脂光弹模型,进行3种咬合状态下的1kg垂直加载.应力冻结后,比较两者的应力分布差异.结果 正中及前伸(牙合)位加载时,2种附着体均可达到颊舌侧应力分布相近,球帽式牙槽嵴顶应力分布略大;侧向(牙合)加载时,球帽式覆盖义齿较Locator式覆盖义齿工作侧与平衡侧应力差更小;3种(牙合)位加载时,球帽式覆盖义齿种植体周围的应力均小于Locator式覆盖义齿,其中侧向(牙合)尤为明显.结论 (1)在下颌牙槽嵴重度吸收时,使用球帽附着式覆盖义齿较Loctor式覆盖义齿可能对种植体周围的骨质及剩余牙槽嵴有更好的保护作用,建议作为首选(2)在使用Locator附着体时建议选用可减少侧向力的(牙合)型,如舌向集中(牙合)等.     

Retentive Properties of O‐Ring and Locator Attachments for Implant‐Retained Maxillary Overdentures: An In Vitro Study

Purpose

To evaluate and compare retentive properties of O‐ring and Locator attachments for implant‐retained maxillary overdentures.

Materials and Methods

Four implant analogs were inserted in canine and second premolar areas of an acrylic edentulous maxillary model. A metal‐reinforced experimental acrylic overdenture was constructed and connected to the analogs using either O‐ring (group I) or Locator (group II) attachments. Locators were divided into 3 subgroups according the degree of retention of the patrix nylon insert: Locator extra‐light retention (group IIa), Locator light retention (group IIb), and Locator medium retention (group IIc). Vertical and oblique (lateral, anterior, and posterior) dislodging forces were measured at the beginning of the study (initial retention) and after 540 cycles of denture insertion and removal (final retention).

Results

For vertical, lateral, and anterior dislodging, group IIc recorded the highest initial and final retention, and group I recorded the lowest retention. For posterior dislodging, group I recorded the highest retention, and group IIa recorded the lowest retention. For group II, vertical dislodging recorded the highest initial and final retention, and lateral dislodging recorded the lowest retention. For group I, posterior dislodging recorded the highest initial and final retention, and lateral dislodging recorded the lowest retention. For all dislodging forces (except posterior dislodging), the highest retention loss was recorded in group I, and the lowest retention loss was recorded in group IIa.

Conclusion

Locator medium attachment was associated with favorable retention during axial (vertical) and nonaxial (anterior and lateral) dislodging compared to other types of Locator inserts and O‐ring attachments after a simulated 6‐month period of overdenture use.