Views: 268 Author: Kaylee Publish Time: 2023-09-21 Origin: Site
Patients who are completely edentulous, have significantly resorbed ridges, and have unfavorable jaw relations frequently experience problems with their traditional denture because of a reduced ability to support weight, particularly in the lower arch. Implant-retained overdentures, or IODs, have been suggested as a successful rehabilitation strategy for these patients in order to improve their level of happiness and restore both function and aesthetics.The McGill consensus from 2002 states that the least amount of care that patients should receive for an edentulous mandible is a 2-implant retained overdenture.Since single implant mandibular overdentures are easier for elderly patients to remove and do not differ significantly from two implant-retained overdentures, some authors have also suggested single implant mandibular overdentures as a therapeutic alternative for elderly patients experiencing discomfort and functional difficulties with conventional mandibular overdentures (Srinivasan et al. 2014; Passia et al. 2015). 1-IODs, however, call for longer-term research and a wider spectrum of functional, prosthodontic, and patient-related results.Although implant-overlay dental prostheses (IODs) have certain drawbacks as compared to fixed dental prostheses supported by implants, they may be cleaned more readily by senior patients, need fewer implants, and are less expensive overall (Borges et al. 2020). IODs are made up of various parts, including the implant, mucosa, bone, denture, and attachments. There are a number of attachments available, and each has a unique capacity to withstand stress and strain. At the moment, the most widely utilized form of attachment for mandibular overdenture restoration is the Locator attachment. IODs are subjected to a range of forces in various directions during oral function, which are applied along the hinge axis, which serves as the attachments' fulcrum line (Tokuhisa et al. 2003). According to Yang et al. (2011), the retention that these attachments provide to prevent withdrawal along the insertion path causes lateral forces surrounding the attachment assemblies and implant during function. These pressures can result in a number of mechanical and biological issues. Various parameters, including as implant position, implant angulation, implant depth, and attachment height, influence these lateral dislodging forces. These contributing elements are outlined in this article and, if properly managed, can improve patient satisfaction, lower the need for maintenance, and extend the long-term life of IODs. To guarantee consistent outcomes, the paper ends with therapeutic advice and suggestions.
The remaining mandibular ridge may have an impact on implant placement sites as bone resorption takes place (Swasty et al. 2009), which could have an impact on treatment outcomes and surgical planning. There is ongoing debate on the optimal location for implant placement in 2-IODs, with suggestions including the premolar, canine, and lateral incisor regions. Research supporting canine or lateral implant placement point to benefits for bone preservation and a reduction in marginal bone loss (Elsyad et al. 2018; Elsyad et al. 2016). However, the fulcrum line around which overdentures typically rotate is relocated more posteriorly when implants are positioned in the premolar region (Hong et al., 2012). This increases the "seesaw effect" and transfers the strain to the implants. Less of this is visible in the lateral and canine zones. The proximity of implants to the first molar area, where edentulous patients frequently apply the largest occlusal forces due to contraction of the levator muscles, is another factor contributing to greater bone loss surrounding implants in the premolar position (Sadowsky et al. 2004). The amount of bone available in both positions—which is typically higher in the canine region—should be considered by the practitioner when selecting between the lateral and canine placements. Furthermore, it is preferable to place the implants in the lateral incisor region if the patient wants to upgrade the restoration from a mandibular overdenture to a fixed prosthesis, like an all-on-four concept, in the future.Aspects Influencing Mandibular Implant Overdenture Long-Term Success Rate a. Implant Position
The remaining mandibular ridge may have an impact on implant placement sites as bone resorption takes place (Swasty et al. 2009), which could have an impact on treatment outcomes and surgical planning. There is ongoing debate on the optimal location for implant placement in 2-IODs, with suggestions including the premolar, canine, and lateral incisor regions. Research supporting canine or lateral implant placement point to benefits for bone preservation and a reduction in marginal bone loss (Elsyad et al. 2018; Elsyad et al. 2016). However, the fulcrum line around which overdentures typically rotate is relocated more posteriorly when implants are positioned in the premolar region (Hong et al., 2012). This increases the "seesaw effect" and transfers the strain to the implants. Less of this is visible in the lateral and canine zones. The proximity of implants to the first molar area, where edentulous patients frequently apply the largest occlusal forces due to contraction of the levator muscles, is another factor contributing to greater bone loss surrounding implants in the premolar position (Sadowsky et al. 2004). The amount of bone available in both positions—which is typically higher in the canine region—should be considered by the practitioner when selecting between the lateral and canine placements. Furthermore, it is preferable to place the implants in the lateral incisor region if the patient wants to upgrade the restoration from a mandibular overdenture to a fixed prosthesis, like an all-on-four concept, in the future.
The morphology of the existing bone tissues, anatomical structures, or a surgeon with inadequate skill may prevent the prosthetically desired implant inclination or location from being clinically attained. According to Mericske-Stern et al. (1993), implants should ideally be positioned as perpendicular to the occlusal plane as possible and parallel to each other in order to achieve uniform stress distribution. This is important for maintaining the level of bone surrounding the implants and reducing lateral or axial forces, which could increase the mechanical risks associated with IODs, such as attachment loosening and attachment assembly fracture.
In a study by Patil et al., implants placed with a higher degree of angulation produced the maximum level of stress. The study evaluated the stress and strain distribution patterns under unilateral and bilateral loading in 2-mandibular IODs with different placements and angulations of implants. The denture and supporting mucosa showed the least increases in stress values, whereas the bone and implants showed the greatest alterations, according to the authors' research. Consequently, when implants are not positioned in a parallel arrangement, this increase in stress levels puts the implant and the attachment components at greater danger.
Denture displacement and the lateral forces applied to the implant are significantly influenced by the height of the attachment. According to Ying et al., attachments at a lower height caused less denture displacement because they applied a lesser lateral stress to the implant (Ying et al. 2017). The implant depth, gingival height, and vertical space are some of the parameters that influence the practitioner's attachment height decision. It is more difficult for the practitioner to fix this mis-leveling by utilizing different locator heights when the implants are placed at different depths. A rotational path of dislodgement caused by an uneven level of two Locator abutments may also result in a larger degree of cumulative tensile tensions. These forces may subsequently be transferred to the implant, causing undesirable stresses on the implant and adjacent alveolar bone (Sia et al. 2017). Therefore, in order to avoid a discrepancy in locator height, implants should be positioned at the same or a similar crestal level.
Despite the lack of evidence linking implant depth to tissue thickness, a thicker mucosal lining necessitates the adoption of a high collar attachment. Despite this, practitioners should nevertheless make an effort to insert implants at identical depths in order to prevent different tissue thickness levels during the prosthetic phase. Furthermore, vertical space—which is estimated to be an average of 8.5 mm for locator attachments (Ahuja et al., 2010) and 12–14 mm for bar attachments (Carpentieri et al., 2019)—must be taken into account when scenario designing an attachment overdenture. Figure 1, Tables 1 and 2, and the prosthesis space required for locator and bar attachment are different.
One method that has been suggested to reduce issues such as fractures or cracks in IODs is metal reinforcing. It is important to manufacture this reinforcement at a level that won't obstruct the attachment components. The placement of the metal reinforcement must also be carefully considered in order to avoid adding too much mass to the denture base, which could negatively impact phonetics and/or esthetics.
Appropriate extensions to the primary and secondary stress-bearing areas in the mandible offer posterior support and resist occlusal forces applied to the posterior lever arm, since an IOD is supported by both tissue and implant. Sufficient flange extensions, particularly in the buccal shelf region, are also necessary to seal food impaction, avoid it, and support the face.
Over the past ten years, improvements in computer technology and radiographic 3-dimensional imaging techniques have led to a breakthrough in implant placement accuracy and precision. Using computed tomography and 3D implant planning software, computer-aided implant placement procedures enable the visualization of implant position with respect to anatomical and prosthetic factors. Using computer-fabricated guides for static computer-aided implant placement (sCAIP), planned implant positions and digital data can be transferred to the real clinical setting in conjunction with advancements in computer-aided design/computer-assisted manufacturing (CAD/CAM) techniques (Jorba-García et al. 2021). On the other hand, real-time tracking of implant placement can be accomplished with markers and a tracking device using dynamic computer-aided implant placement (dCAIP) (Jorba-García et al. 2021). sCAIP or dCAIP can be used to ensure correct implant location, angulation, and depth in IODs. The relatively small amount of room in the oral cavity can make it difficult, even for a highly skilled practitioner, to place implants at the ideal location and inclination.
This case study highlights how crucial it is to use surgical guidance in IOD patients in order to have the best possible outcomes. A male patient, sixty years of age, arrived at the clinic with complaints regarding his non-retentive lower denture. Following a thorough clinical examination and case assessment, the patient and the doctor examined the available treatment options and enumerated the benefits, drawbacks, and dangers associated with each. The mandibular arch patient elected to have two implants with two locator attachments. The patient did not smoke, had a clean medical history, no current oral conditions, and no conditions that would prevent her from receiving implant therapy.
Initially, a dual-scan approach was utilized to implant two implants for locator attachments in the mandibular arch of the totally edentulous patient. With this approach, there are two scan steps: the first is a radiopaque marker-based CBCT of the patient's denture, and the second is a CBCT of the patient wearing the denture/radiographic guide. Using the radiographic markers as a point of reference, these two scans are acquired in order to superimpose the two files over one another, creating a model of the patient's bone and denture. After that, the scans were loaded into a planning program, which used a prosthetically driven concept to establish the orientation and position of the implants.
The guided surgery was carried out using a flapless technique. This method has the benefit of being less stressful during surgery if there is enough keratinized tissue. After that, tissues were punctured using the puncher that was called for in the surgical procedure. Before drilling, the guide was removed to remove the punctured tissues, and it was then re-secured so that implant bed preparations could continue using the guided surgery drills (Surgical Kit Guided Surgery, Institut Straumann). As previously scheduled, implants (RC Bone Level Tapered Implant 4.1, length 10 mm, Institut Straumann AG) were subsequently inserted into the prepared bed locations. The achieved parallelism and spacing between implants facilitate the insertion and removal of the overdenture and enable the use of the retentive components' maximum strength. The patient received post-operative instructions and healing abutments were inserted.
Mandibular implant-retained overdentures must, in general, be executed with precision to ensure long-term survival. This includes space analysis, treatment planning, and accurate diagnosis and prosthetic implementation. The interaction between the implant, surrounding tissues, and attachment assembly should be understood by the practitioner, as well as the biomechanical components of this therapeutic approach. With the use of digital technology, it is also crucial to have an informed relationship between the prosthodontist and the surgeon in order to assist prevent mistakes in implant placement.
