Journal of Dental Implant Research 2022; 41(1): 1-14  https://doi.org/10.54527/jdir.2022.41.1.1
Mandibular implant overdenture - treatment modalities and maintenance - an integrative overview
Hariharan Ramakrishnan , Maniamuthu Ragupathi
Department of Prosthodontics & Implantology, Ragas Dental College & Hospital, Uthandi, Chennai 600119 , India
Correspondence to: Hariharan Ramakrishnan, https://orcid.org/0000-0003-4466-5744
Department of Prosthodontics & Implantology, Ragas Dental College & Hospital, 2/102, East Coast Road, Uthandi, Chennai 600119, India. Tel: +044-24530006, Fax: +044-52123995, E-mail: abcv2005@yahoo.com
Received: November 22, 2021; Revised: February 2, 2022; Accepted: February 25, 2022; Published online: March 30, 2022.
© The Korean Academy of Implant Dentistry. All rights reserved.

This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract
Implant overdenture treatment planning should be carried out meticulously to ensure positive treatment outcomes over several years. Various factors, namely the number of implants to be placed, their length and diameter, type of abutment, nature of the residual edentulous ridge, available bone density, interarch distance, jaw relation, mouth opening, soft tissue architecture, design of the prosthesis, including the type of teeth and their size, and type of attachment to be used should all be taken into consideration while planning the treatment. The maintenance phase of the implant therapy includes the implant, prosthesis, and attachments. The treatment connects the dentist, patient, and hygienist triad. The dentist with the support of the hygienist should provide detailed explanations regarding the treatment and motivate the patient, and the patient, in turn, should sincerely follow the protocol for maintenance as explained by the dentist. The patient should also come back for periodic recall visits as scheduled by the prosthodontist/implantologist. This overview covers the evolving and changing aspects of mandibular implant overdenture treatment and maintenance.
Keywords: Clinical protocols, Dental prosthesis, Implant-supported, Dentures, Dental implants, Oral hygiene
INTRODUCTION

Implantology is a boon to the field of prosthodontics because it aids in overcoming the state of edentulousness and tries to mimic the natural tooth through its artificial way. Even though implants were in trend because of the phenomenon called osseointegration introduced by Branemark in the 1980s, the evolution of implants continues1). Conventional root form implants and their components were then modified for ease of understanding and usage. Development in 3D imaging and manufacturing technology helps develop customized implants and immediate placement in the extraction socket. The evolution of implants incorporates technology and includes materials such as alumina, zirconia, polymers, and various surface modifications with different particle sizes that improve osseointegration and pave the way for successful treatment2). Thorough knowledge and understanding of implant design, position, bone density, residual ridge resorption, prosthetic movement and biomechanics, patient's oral hygiene, cost factor are essential to decide the treatment option. This article describes the overdenture treatment options and after-care.

Data search included articles of various types including clinical reports, invitro studies, invivo studies, clinical trials published between 1990 and June 2021. Short communications, editorials, conference proceedings were dropped from search. Search engines included Google scholar, Pubmed, Web of science. Articles strictly related to mandibular implant overdenture (MIOD), were selected and evaluated for scientific description of treatment planning, treatment designs, maintanence aspects, patient perspectives.

The purpose of this overview was to describe the various treatment options available for completely edentulous mandible using overdenture as a prosthetic option, and elucidate in detail the biomechanics involved in the use of two to five implants in the interforamina region of mandible.

TREATMENT MODALITIES IN MANDIBULAR OVERDENTURES

There are definitive functional benefits obtained by edentulous patients who wear diverse designs of implant overdentures. These benefits include improved denture stability, enhanced patient satisfaction and comfort, improved chewing, and residual bony ridge height preservation1,3).

Misch had originally classified implant fixed and implant removable prosthesis as FP1, FP2, FP3, RP4, and RP5. FP stands for fixed prosthesis, RP stands for removable prosthesis. RP4 (Fig. 1) is a completely implant supported prosthesis both in the anterior and posterior regions of mandible and well splinted with a suitable bar without any cantilever. This kind of prosthesis is also known ISP, implant supported prosthsis. RP5 is a IRP prosthesis, which means implant retained prosthesis. five treatment options exist for RP5 or IRP and each option had been explained below. a novel way of assimilated and abbreviated naming had been mentioned for all the five types for the purpose of unified understanding of the treatment options4).

Figure 1. Description of manidibular implant overdenture, removable prosthesis type 4. MIOD_RP4.

1. MIOD1_RP5 (type 1 mandibular implant overdenture and removable prosthesis type 5)

OD - 1 (overdenture) is indicated primarily when the cost is the most significant patient factor. The patient's desires must be minimal. Maxillary and mandibular Posterior ridge form should be an inverted U shape, with high parallel walls with good to excellent anatomic conditions for conventional denture retention, support, and stability. The problem with the existing denture should relate only to the amount of retention. The alphabets A∼E had been used in description of the five types of RP5. All these five alphabets had been described in figure and refers to the implant positions in the bilaterally present interforamina region.starting from patient’s right side of edentuluous mandible. the alphabets A and E are implant positions immediately before the bilateral mental foramen, B and D are bilateral canine regions. And C is the middle and central area of mandible. These five implant positions are also equally divided into five zones.Under these conditions, two implants may be inserted in the B and D positions The implants remain independent of each other and are not connected with a superstructure. The type of attachment used in OD-1 is an O ring design, and the prosthesis movement should be clinically possible in all directions3). (PM-6), prosthesis movement which denotes movement in all possible directions. Relatively simple two-implant mandibular overdentures improve patients’ evaluations of function and general satisfaction (Fig. 2).

Figure 2. Description of mandibular implant overdenture type 1, removable prosthesis type 5. MIOD1_ RP5.

It is a better prosthetic option in OD -1 to have the implants in the B and D positions rather than the A and E regions. Individual implants in the A and E positions permit more restoration rocking than the B and C regions. In B and C positions, the anterior movement of the prosthesis is reduced. The stability of the prosthesis is gained from the mandible’s anatomy and the prosthesis's design, which is like a conventional complete denture. The implant support mechanism is limited because stress relief is permitted in any plane4).

Cost factor brings OD 1 option into clinical consideration. The existing restoration may be adapted with a rebase procedure around the implants and attachments. Other clinical indications are when the span between the implants is too long and insufficient space exists to accommodate attachments on a bar and in arches that are markedly tapering anteriorly3). The bar would be either cantilevered too far or would interfere with speech and mastication. Hygiene procedures can be done with independent bar attachments5). The disadvantages of OD- 1 includes relatively poor implant support and stability, compared with the other options, because of the independent nature of the implants. it should be noted that bone loss in the edentulous regions of the mandible is not significantly reduced because only two implants are inserted2,4).

The implant-retained overdenture supported by two implants in the mandible had a success rate of 100% for loaded implants5-9). It is a relatively simple treatment recommended for edentulous patients who are dissatisfied with conventional dentures or have a resorbed mandibular ridge. In masticatory performance, treatment with an implant overdenture improves more than a traditional complete denture in persons with resorbed mandibular ridges. In contrast, little difference in performance was seen with adequate to good ridges5,9). clinicians should consider the amount of mandibular ridge resorption before recommending implant overdenture therapy to improve the ability to masticate food9).

2. MIOD2_RP5 (type 2 mandibular implant overdenture and removable prosthesis type 5)

The second treatment option for mandibular overdenture (OD - 2), (Fig. 3) is selected only on rare occasions. Criteria include posterior ridge form is an inverted U shape and provides good-to excellent support and lateral stability. Patient complaints are usually related to retention. The patient requires a new prosthesis and is willing to invest slightly more time and money. Implants are placed in locations B and C and are splinted together with a superstructure without any distal cantilever. The retentive element may be of a clip design depending on the interarch distance available3,4,10).

Figure 3. Description of mandibular implant overdenture type 2, removable prosthesis type 5. MIOD2_RP5.

Either Dolder or Hader design can be used. Cross-section view is ideally ovoid (Dolder) or with an apron type or any other shape than round to increase its strength and reduce its flexibility. The bar should be more than 2 mm away from the soft tissue in a vertical dimension to facilitate easy access for hygiene aids. A narrow space impairs oral hygiene procedures and may cause food debris impaction and mild tissue inflammation. It should be parallel to the plane of occlusion as an angled bar will not permit rotation of the prosthesis to load the posterior soft tissue. It should be aligned perpendicular to a line bisecting the angle between the posterior edentulous ridges to allow prosthesis rotation. The bar is connected to the facial aspect of each implant coping, allowing the lingual flange of the prosthesis to remain within the contour of a conventional denture. The prosthesis movement should have a PM–3 to PM 6 or more excellent range of motion. A reduction of loading forces exerted on two anterior implants when splinted with a bar compared with individual implants10,11). In vivo force measurements in three dimensions with two mandibular implants revealed that bars contributed to load sharing between two implants.

The two splinted implants should not be in the A and E positions because this results in a curved arch form. The superstructure follows the anterior curve of the arch causes an improved lingual contour of the restoration. Six edentulous mandibular curvatures correspond to an increased length, the flexibility of the superstructure. Since the bar is under the anterior teeth, anterior to the implants, a more extraordinary moment of force is also created. The prosthesis attachment system to the superstructure may also be compromised if clips are improperly used for retention12,13). The clips must be perpendicular to the path of rotation and closer to implants to prevent rotation. Prosthesis, when designed to rest against the sides of the curved bar, the prosthesis movement may be reduced to PM-0. This places a much greater lateral load on the implant system. Bars that run tangentially may not permit friction-free movement of the prosthesis and are likely to exert more significant torsional loading on the implants10).

The flexibility of the superstructure is related to the length. As a result, there is five times more flexure if the implants were in the B and D locations. The increase in superstructure movement may result in the loosening of the coping screws. Once this occurs, the remaining attached implant receives a dramatic increase in moment of forces from the long lever arm of the superstructure, increase in pressure might result in bone loss, mobility of the implant, and even fracture of an implant component11,12).

The distance between the implants is in the 20 to 22 mm range or B and C positions. Implants placed too close to each other will result in reduced prosthesis stability. In the case of AE positioned implants, joining them is the sagittal position of the superstructure. When the bar is straight and doesn't follow the arch, it clinically occupies a lingual position to the arch. The overdenture’s lingual flange extends ten mm long and seven mm vertically to accommodate the attachment connected over the superstructure13). In addition, because the teeth are set over, or anterior to the crest of the ridge, anterior to the superstructure, rotation, and tipping of the prosthesis become more prevalent. Moment of force for a straight bar connecting implants in the A and E positions are twice for implants in the B and C locations13). first premolar region often illustrates minimal attached gingiva. Implants placed in this region often lack adequate attached gingiva on the facial aspect of the implant. Muscle attachments are also more common in this area, and soft tissue corrections may be indicated to improve long-term maintenance.

Implants splinted in A and E positions have more significant potential load per surface area than implants placed in B and C regions. The bite force increases in the posterior regions. More significant vertical load is associated with increased stresses. Though the A and E positions give more lateral stability to the prosthesis than the B and C positions, only two implants resist this lateral load. The B and C positions can increase lateral movement13). Place two implants in the A and E positions is strongly discouraged. The anatomic ridge should be good to excellent, and the overdenture should have excellent support and retention independent of the implants. The two implants should not be splinted because they are too far apart. The internal aspect of a bar-retained overdenture should not be processed against the sides of the abutment, as this will limit rotation.

3. MIOD3_RP5 (type 3 mandibular implant overdenture and removable prosthesis type 5)

The use of more than two implants has been recommended to support a mandibular overdenture in clinical scenarios that will require increased retention, such as high muscle attachments, prominent mylohyoid ridges, or prominent gaggers, knife-edged residual ridges, superficial mental foramina, or sensitive mucosa have also been indicated for multiple implants3,14-17). Three root-form implants are placed for a mandibular overdenture (OD-3). A superstructure connects the implants but without a distal cantilever. Posterior ridge form determines the posterior lingual flange extension of the denture, limiting lateral movement of the restoration. Poor lateral stability places additional forces on the anterior implants. If the posterior ridge form is good, implants are placed in the A, C, and E areas, and a prosthesis movement of PM-2 to PM-6 range of motion can be expected. The greater the stress to the prosthetic system, the more prosthesis movement (Fig. 4).

Figure 4. Description of mandibular implant overdenture type 3, removable prosthesis type 5. MIOD3_RP5.

If the anterior or posterior ridge form is poor, the implants are placed in the B and D positions. This will increase the restoration's posterior movement but decrease stress on the implants and screw-retained bar. If the patient with poor posterior ridge form requires more stability, more than three implants are indicated3,15). The prosthesis movement for three implants in the B∼D areas should PM-3 to PM-6 ranges of motion. There are several advantages of splinting A, C, and E implants over implants in the B and D positions. The other implant provides a six-fold reduction in flexion of the superstructure. Screw loosening is less frequent because three coping screws retain the superstructure. Forces are reduced in the presence of a third implant as compared with two implants. The greater surface area of the implant to bone following osseointegration allows for optimal distribution of forces. Three implants distribute stresses more efficiently and minimize crestal bone loss. Because the crestal bone is the first region to be affected, this represents a significant advantage. There is twice in a reduction in the maximum moment of force for a three implant system when compared with two implants in the A and E regions15,16).

Implants splinted in the A, C, E positions should not form a straight line. The C implant is anterior to the more distal A and E implants. Prosthesis benefits from vertical implant support in the anterior arch. Greater the anteroposterior (A-P) distance of the A, C, E implants, the greater the biomechanical advantage of the bar in reducing stress on the implant and the better the lateral stability of the implant bar and attachments. However, rotation of the prosthesis may be more limited when compared with overdenture OD-1 and OD-215).

A PM-2 or greater can be designed with three A, C, and E anterior implants. The prosthesis should not form any contact angles with the superstructure, resulting in too rigid of a system. When clips are planned for the overdenture, the bar may connect the facial of the A and E implant copings and the lingual of C coping. As a result, a straight bar perpendicular to the path of rotation may be fabricated. The connecting bar is placed parallel to the plane of occlusion, and the attachments should be placed at the same height along the bar. This is needed for the prosthesis to rotate during function effectively. No cantilever should be designed in this three-implant system. Implants placed in the B∼D regions are indicated with poor posterior ridge form. The increased horizontal movement of the prosthesis causes a greater lateral force on the implants. The prosthesis movement should be PM–3 or greater to reduce the stress on the B∼D implants16,17).

4. MIOD4_RP5 (type 4 mandibular implant overdenture and removable prosthesis type 5)

Mandibular overdenture option (OD-4) provides four implants to be placed in the A, B, D, and E positions. These implants offer sufficient support and include a distal cantilever approximately 1.5 times the A-P distance of about 10 mm on each side. The cantilevered superstructure is a feature of four or more implants for two reasons: the increase in implant support, compared with OD-1 to OD-3. The second is related to the additional retention of the superstructure, which limits the retention, the risk of screw loosening, and associated complications18). Indications for OD-4 include poor posterior ridge anatomy, causing a lack of retention and stability, presence of soft tissue abrasions, difficulty in speech, edentulous posterior mandible is more resorbed than the anterior region, the external oblique line is high, and the mylohyoid ridge corresponds to the crest of the residual ridge, patient's complaints and desires are more demanding (Fig. 5).

Figure 5. Description of mandibular implant overdenture type 4, removable prosthesis type 5. MIOD4_RP5.

The prosthesis movement may have more stability, a PM-2 range of motion is clinically seen. Attachments are placed in the distal cantilevers and the midline. The prosthesis is an RP-4 and has the least soft tissue support compared with other soft tissue-supported overdentures. The anterior attachment must allow the prosthesis to lift from the bar to permit rotation of the distal attachments. Clips, which help in the rotation, are challenging to use on cantilevered superstructures. To allow movement, the clip should be placed perpendicular to the path of rotation and not along the cantilevered bar where its functions for retention18,19).

The actual cantilever length is determined from the prosthesis movement, not the size of the superstructure bar. A bar may be cantilevered 10 mm beyond the distal implant. However, if the prosthesis does not move, the cantilever is extended until the prosthesis movement is evident. This is often several millimeters beyond the end of the bar and is known as the hidden cantilever. If the attachments are too rigid or incorrectly placed, the prosthesis may become stiff, and the cantilever can be extended to the retromolar pad. If the arch form is square and the A-P distance reduced, the implants may be placed in the A∼C locations for patients chewing primarily on the right side. The C implant is placed as far forward as clinically under the incisors of the restoration. This increases the A-P and therefore increases the amount of distal cantilever. If the A-P distance is less than 4 mm, no cantilever should be designed, and a PM 3 to PM 6 restoration is indicated. The patient benefits from the four implants because there is more excellent vertical support and lateral stability. The prosthesis only loads the soft tissue over the second molar and retromolar pad regions3,20,21).

5. MIOD5_RP5 (type 5 mandibular implant overdenture and removable prosthesis type 5)

Five implants are usually inserted in the A∼E positions. The superstructure is cantilevered distally a maximum of 2.5 times the A-P distance of approximately 15 mm (Fig. 6), placing it under the first molar area22). It is designed for patients with moderate to severe problems related to a conventional prosthesis. The needs and desires are often most demanding and may include limiting the bulk of the prosthesis; major patient concerns might be one or more of function or stability, sore spots, and inability to wear existing mandibular dentures. Usually, four to six retentive elements are included in the bar design, namely O-rings and Hader clips. Because of their number and distribution, they provide retention and oppose prosthesis movement. Typically four O-rings are evenly distributed (two anterior and two posteriors to the distal implants). A Hader bar clip is placed distal to the last O-rings on each cantilevered section22-24).

Figure 6. Description of mandibular implant overdenture type 5, removable prosthesis type 5. MIOD5_RP5.

At delivery, the O-rings may be the only attachments used. The Hader clip may be added as a backup system (or additional retention, if an O-ring stud breaks, or if the vertical dimension of occlusion does not permit the use of a high profile retentive O-ring causes repeated fracture of the overlying acrylic denture. This bar design also allows for a reduction in stress to the bar and implants if screw loosening or bone loss around the implants are identified. The Hader clip and bar may be sectioned off the bar. The RP-4 prosthesis is converted to an RP-5 since it may rotate on the two O-rings placed just distal to the implants. The forces exerted on implants connected with a bar design and RP-4 prostheses have been documented extensively. A constant finding was the most distal implant received stresses 2 to 3 times greater than the other implants. The highest concentration of stresses was at the crest level distal to the most distal implant on the loaded side. The stresses increased with the length of the cantilever. Therefore stress factors need to be carefully evaluated before an extended cantilever is designed25-27).

Five implants also allow the superstructure and prosthesis to be cantilevered forward from the anterior ridge. This is of particular clinical benefit for angle’s skeletal Class II patients23). Traditional mandibular dentures reconstruct the horizontal overjet, so the lower anterior teeth position does not impinge on the neutral zone during rest or function. However, in an RP-4 restoration, the teeth may be set in a skeletal Class I pattern, providing the best esthetic result. This also increases the amount of function in the anterior region. The distal cantilever is reduced to decrease the lever force. Because these patients are Class II, the forward anterior tooth position also places the molars forward, and the need for a distal cantilever is reduced25).

MAINTENANCE OF OVERDENTURES

Implant overdentures require routine maintenance. Den Dunnen et al.28), concluded that most of the Edentulous patients treated with mandibular implant-retained overdentures require professional hygiene care, adjustments, and treatment of complications29). Biologic maintenance therapy to control inflammation and prevent peri-implant disease is necessary, as well as mechanical maintenance that may involve repair and replacement of implant abutments and superstructure components. Mericske et al.30) described the treatment outcomes with implant-supported overdentures. The most common prosthodontic complications were denture base adjustments and tightening of the ball attachment mechanism. Given the distal extension nature of the implant-supported overdenture, a reline maintenance protocol was also required. In addition, overdentures may also need to be periodically rebased.

Prosthetic complications with magnetic attachments are higher than ball attachments and bar clips. Wear, corrosion of the magnets can occur. Loosening of abutment screws and exchange of the O–rings and O–ring retainers were encountered for ball attachments. The most common complication for the bar group was the need for reactivation of clips. Education and assessment of patients before beginning any implant therapy is a crucial first step for ensuring success. If a patient cannot care for their natural teeth or prosthesis, the same risk cannot be taken with implants. It is important to note that the patient realizes that treatment is not complete after the placement of the implants and prosthesis and that maintenance shall never end. Hygiene techniques, sterile instrumentation, and antimicrobials should be used in the care of dental implants. Likely, using more refined dental materials and new framework designs in implantology may result in fewer complications in the future31-35).

Postsurgical care following implant placements should be gentle and clean. Tissues are tender after implant placement, resulting in the problematic maintenance of adequate hygiene and debridement. The presence of sutures can cause plaque formation; food retention can result in poor healing or infection. Patient instructions may include the use of chlorhexidine gluconate because of its substantivity and ability to destroy oral bacteria. Chlorhexidine gluconate can be used as a rinse or applied with cotton swabs or tufted brushes, depending on the patient's individual needs. When the healing period is in process, clinical and home hygiene procedures must be practical and noninvasive to avoid disturbing the healing tissues. At the same time, the patient must be aware that gentle debridement will only be adequate while tissues are healing. The use of a soft toothbrush could be advantageous. Once healing and restoration are complete, a new hygienic procedure will be established, learned, and followed. Temporary restorations and prostheses need adequate home care to avoid the harboring of bacterial plaque. A patient's compliance to a strict home care regimen is put to the test during provisionalization. Changes and modifications in oral hygienic tools and usage may be necessary to maintain adequate plaque control. Hygiene recall should be specific to the patient's needs and ensure the health of the peri-implant tissues36-39).

Maintenance consists of a triad formed by the patient, prosthodontist/implantologist, and dental technician especially for those prostheses involving fractures. Various measures include the use of interdental brushes, either hand or motorized, use of non-staining mouthwashes, flosses. plaque control should be adequate. If a pathologic condition is present, it should be gently probed. Supragingival scaling or slight subgingival should be done on every recall visit around the implants. Overdenture patients should be assessed every 3 to 4 months. Radiographs are to be taken at least once a year. If an implant needs repair, a graft with guided bone regeneration can be used. Home care procedures must be individualized for each patient based on his desires40). Edentulous patients who are not used to caring for an oral cavity may have difficulty acquiring the skills necessary to care for their implants. Hygiene instruction may at times need to be modified or changed based on patient response and ability. Patient skills must also be evaluated. Medical situations such as arthritis, carpal tunnel syndrome, Parkinson's disease, and strokes can make a relatively easy task like toothbrushing extremely difficult or even impossible. Automatic and mechanical brushes, chemotherapeutic mouth rinses must be enlisted to aid in plaque control for this kind of patient.

Education is an important step when delivering prosthesis to a patient. Clear and proper explanation, education, and visual demonstration are crucial to successful maintenance. A complete record of the oral hygiene aids prescribed, the education given, and how well the patient can carry them out must be well documented. Multiple hygiene aids can cause a patient to become discouraged and poorly motivated. A trial-and-error approach and a previous history of the usage of hygiene aids by the patients may help determine what the best adjunct and regular brushing can be prescribed41,42).

The patient needs to understand that the abutment is a connection between the implant and bone. Visit the hygienist should occur weekly for approximately one month to evaluate and educate the patient. If good oral hygiene cannot be achieved during this phase of implant therapy, subsequent steps should be delayed. If there is plaque retention after Stage II surgery, often the tissue will overgrow onto the healing cap or abutment. The patient must understand how detrimental this development is to the success of the implant. Proceeding with the restorative phase of treatment without ensuring complete patient plaque control can be perceived as encouraging implant failure. Meticulous documentation of records showing recommendations, instructions, and the patient's compliance and effectiveness is essential in evaluating long-term success for each implant patient. Any non-compliant patient behaviors that may surface during this stage need to be promptly addressed.

Patients who are fully edentulous and undergo implant therapy may not be used to daily oral cleansing. These patients must relearn a routine of oral care and be compliant with the same. Overdentures and connector bars are a viable option, especially for patients with compromised manual dexterity. Connector bars offer flexibility when choosing an oral hygiene aid. Most oral hygiene aids are readily adaptable around a bar4). A patient needs to maintain plaque and debris-free overdentures. The patient should regularly inspect the overdenture to ensure that it is free of plaque and calculus43). Any attached to the overdenture could be in close or direct contact with the implant attachments, connector bars, and surrounding tissue. Daily soaking with denture tablets and thorough brushing prevents the overdenture from harboring bacteria. Undercuts, clips, o-rings, and ball attachments can have more plaque and calculus than the bar. Therefore denture brushing and soaking are critically essential to eliminate the accumulation of plaque and food debris. Inspection at recall visits will determine the need to scale, polish, or ultrasonically clean the overdenture. Attachments must be checked to confirm that no clips are missing or loose, thus ensuring that the patient has a secure connection to the implants30). For patients with a history of nocturnal parafunctional habits, removal of the overdenture may permit contact of the implant-abutment with opposing natural teeth, soft tissue, or prostheses, producing discomfort and possible wear or breakage of teeth, implants, or attachment components30). To prevent such occurrences, occlusal devices for the protection of implant abutments have been advocated. A technique for the fabrication of an occlusal device using O–rings to protect implant abutments that support overdentures from nocturnal parafunctional habits had been described in the Baker et al44).

To facilitate optimum home care at the gingival/implant junction, hygiene is accomplished most readily using an interdental brush, rotary uni-tufted brush, or ultrasonic brush41). The latter instrument is particularly effective in the posterior segment and from the lingual aspect where access is difficult. Patients should be educated in using the instrumentation, area by area, after insertion of the superstructure. The implantologist should give instruction immediately after placement of the prosthesis, and instruction should be part of the treatment protocol. The superstructure must be self-cleansing with adequate embrasures for access to hygiene instruments; it should not be unhygienic and lead to plaque accumulation and gingival inflammation. The patient should be placed on a three-month recall schedule for evaluation and further instruction until the level of care is satisfactory. The patient can later be on a six-month hygiene recall schedule as a minimum requirement. At annual appointments, the prosthesis is cleaned using an ultrasonic cleaner. screws are placed in identical positions when the prosthesis is replaced and secured41,42).

DISCUSSION

Patient selection criteria for type 1 includes presence of opposing maxillary arch,good anatomical inverted U shape arches in cross section, for type 2 it is driven by patient desires which are minimal and related to retention and also when they can afford cost of bar. Type 3 includes presence of moderate force factors,increased desire from patient for enhanced retention,type 4 and 5 includes failures if any encountered with the existing prosthesis of one of the first three types of RP5, by the patient and is willing to spend more on implants and superstructure4).

Patient satisfaction is the final factor that makes treatment successful. Patient with conventional denture feels better with implant-supported overdenture especially those who had undergone pre-prosthetic surgery. Meijer et al., in their study, compared the satisfaction scores between complete denture wearers and overdenture wearers and found the highest satisfaction scores with the latter6,37). In terms of prosthetic parts, both the removable and fixed implant prostheses are equally good. Feine et al. explained that removable implant prostheses are comfortable to clean and are more preferred by older adults; young aged persons liked fixed implant prosthesis32).

Implant-supported overdentures for the patient's edentulous state are both an alternate treatment option for atrophic ridges and a vital choice in preserving existing residual ridges39,43). Considerable advantages gained from implant-supported overdentures are preserving the remaining residual ridge, anchorage, improved stability, and retention, enhancing chewing efficiency. The treatment planning should include implant number, position, splinted or unpainted, removable or fixed prosthesis. The patient’s oral hygiene care and maintenance ability also play a vital role in the treatment planning45-50).

Antimicrobials facilitate the maintenance of implant surfaces. Therefore, oral rinse with mouthwash containing commercially available compounds such as phenolic agents, plant alkaloids, or chlorhexidine gluconate will benefit41,43). Chlorhexidine gluconate has demonstrated binding action to the tissues in the oral cavity. It is close to 100% bacterial kill of the oral bacteria in a 0.12% concentration after 5 hours after a 30-second rinse41). use of antimicrobials is also effective with the hand or motorized brushes to achieve maximum agent contact with the implant and soft tissue surfaces. The binding action of the compound to the soft tissues, tooth, and implant structures increases the efficacy of the home care procedures. Chlorhexidine may have the side effect of staining in some individuals; patients with multiple composite or tooth-colored filling materials should be counseled to use a cotton swab dipped in the antimicrobial and applied to the site. Other adverse effects include the possible change in taste perception42). lukewarm saltwater can help in reducing plaque accumulation. a Motorized brush dipped in the solution with subsequent application to the implant head and neck also can be done41).

Numerous manual and automatic toothbrushes are available, and those which will suit each patient should be explored. A soft or extra-soft toothbrush will remove plaque and debris without traumatizing tissue. A motorized toothbrush with a taper can be used to access connector bars' undersurface or aid with interdental cleaning. Tufted brushes can be used in undercut areas41). They are instrumental in posterior lingual regions where a conventional toothbrush might not reach. They can be modified by heating the plastic handles with hot water or hot blue flame for use in certain patients42).

Patient instruction for the use of floss should be aimed at gentle insertion and motion to avoid trauma to gingival tissue. Threader may need to be used to access around connector bars. Numerous woven flosses with threaders built to help access and cleanse larger embrasure spaces and under connector bars. Yarns and loosely woven flosses can also be used, but these should not be considered if there is the possibility of fibers being retained on rough surfaces or around restorations. Braided flossing cords are more rigid than conventional floss but are easy to use in open areas in the mouth, where a floss threader may be too flimsy. Specific elastomeric cords can also be used, which prevents it from collapsing and shredding.. Designs in interdental brushes include straight and cone-shaped. The wire should be plastic or coated with nylon to prevent scratching of the titanium components30,41). Patients should also be instructed to inspect and change the brush when signs of wear are evident43). Foam tips can also be used to apply therapeutic agents interdentally. Proxy-Tip is an interproximal brush and stimulator. It has many soft, flexible, semicircular flanges that remove plaque and facilitate the application of antibacterial agents41). Oral irrigation helps remove plaque and debris from around dental implants and their restorations.. The flow of irrigation should be aimed to pass through contacts and never be directed into tissue. Incorrect use could cause trauma to tissues around the implant and could cause bacteremia42).

Liu et al.51) concluded oral hygiene in patients with implant overdentures was poor, and it contributed to increased risk of peri-implant mucositis. Prevelance in patients with poor oral hygiene was 11.9 times as much as that of those with proper oral hygiene. Patients wearing IOD should be educated about the hygiene of the attachments. magnetic attachments require more maintenanence than locator attachments and there are no differences in peri-implant vertical bone loss in mandibular overdentures with Locator and magnet attachments52), whereas, locator attachments for immediate loaded implants retaining mandibular overdentures are associated with decreased plaque accumulation, decreased implant stability, decreased interleukin-1β concentration in peri-implant sulcular fluid, increased per-implant vertical bone loss compared to magnetic attachments after one year53). single implant retained mandibular ovedenture (IMO), can also provide quality of life (QoL) or attachments over single, compared to patients with two IMO and this statement was further reinforced by comparison of crestal bone levels after one year follow up with immediate loading protocol for both single and dual implants54-59) ball attachments is the ideal choice in limited interarchclinical situations, telescopic attachments gave most favourable patient satisfaction and bar provided the most superior retention60). Immediate loading over locator attachments on single mandibular implants or dual implants is also a viable option61). Another study indicated no differences in peri-implant tissue indices, implant stability, and quality of life outcomes between the two loading protocols for two and four-implant supported mandibular overdentures62). Single mandibular implant in the edentulous mandible significantly increased patients' denture satisfaction, irrespective of loading protocol63,64). Semper et al.63) explained the fact that distal cantilever bar upto 12 mm was a treatment option in a clinical situation and didn't resulted in crestal bone losss. In another study64) CADCAM technique was utilized for achieving horizontal path of passive insertion for a bar supported overdenture.

CONCLUSION

Conventional dentures are the traditional treatment option in completely edentulous patients. However, implant-retained overdentures are an affordable alternative since flexibility in the cost factor is possible. In addition, overdentures are also advisable in terms of preserving oral hygiene and easy maintenance. Therefore, mandibular overdenture on a single or dual implants are a worthy economic and functional treatment option compared to fixed implant treatment options and also improve nutritional and psychologic quality of patient life.

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