Mandibular Overdentures When Treating Failing Dentition With Immediate Prosthetic Loading

Patients may present with failing mandibular dentition involving the entire or partial arch. This report presents a partial arch case in which the patient utilizes a partial denture to replace the missing teeth. Finances may limit full arch restoration with an all-on-X concept. The patient’s goal is a stable prosthesis that does not move when eating or speaking. Overdentures can fulfill that goal and provide a stable restored arch at a lower treatment cost than treatment with a fixed hybrid prosthesis. Additionally, an overdenture allows easier oral hygiene homecare and maintenance for the patient than the fixed hybrid prosthetic approach.

Traditionally, when these types of cases have been treated, the remaining dentition has been extracted, and implants are placed depending on the availability of bone. Those typically were left to osseointegrate and loaded several months later with a delayed loading approach. This requires relining the denture and requiring the patient to have a loose, nonstable prosthesis during that healing phase. Frequently, in these cases, the crest requires some reduction, especially when the superior aspect of the crest is thin, which is related to bone loss due to periodontal disease leading to tooth loss or resorption of edentulous areas of the arch. Reducing the crest to provide a flat area with sufficient width buccal lingually to accommodate implant placement and have adequate bone adjacent to the implant reduces the stability and retention of a standard denture on that arch. Thus, providing an immediate stable retentive full arch mandibular removable prosthesis (overdenture) by immediate activation of overdenture attachments (ie, Locators) aids the patient in reaching their goals without delays in treatment.

The mandibular bone presents denser bone than is found in the maxilla. It is typically classified as D1 or D2.¹  This denser bone allows better initial stability at implant placement to allow immediate loading of those implants. Literature has supported the idea that the implant can be loaded immediately when an insertion torque of 35 Ncm or greater is achieved.^2,3  When implants are being utilized in an overdenture approach in the mandible, less force is placed on the individual implants as the lateral surfaces of the arch limit the lateral displacement of the denture. Therefore, the prognosis for immediate loading mandibular overdentures when sufficient insertion torque is achieved is high, and consideration of this approach improves patient treatment satisfaction and decreases overall treatment time. The key is the placement of 4 implants spread around the arch to prevent anterior-posterior rocking of the prosthesis under function to limit off-axis loading of those implants—locator abutments and attachments (Zest Dental Solutions, Carlsbad, CA). Locator attachments allow divergence of the individual implants.⁴  When the implants are placed with some angulation, increased wear is observed in the plastic Locator attachment, so ideally, placement as parallel as possible is recommended. The Locator attachment has also demonstrated better long-term retention with the overdenture than ball-type attachments, providing better patient satisfaction and retention over time.⁵  Ideally, placing the implants bilaterally at the first molar and canine positions provides the best stability and retention when anatomy allows for that posterior placement position. For those patients who have been missing the molars and have had resorption of the arch in that region, implants can be placed mesial to the mental foramen, and improved retention is reported by those patients treated compared to their standard denture.

This article will present 2 case examples of mandibular arches with failing dentition related to caries and periodontal issues and their treatment with immediate implant placement and loading with Locator attachments. Long-term follow-up of 1 year and 8 months in 1 case and 33 months in the other case demonstrate crestal bone stability with this immediate overdenture loading protocol.

A 40-year-old female patient presented for a consultation on treating her lower dentition, indicating she was aware of issues with those teeth and had 2 on the left posterior quadrant broken at the gingiva. A review of her medical history showed she was taking 10 mg olanzapine, 20 mg citalopram daily, and Ventolin as needed. She had been informed the remaining mandibular dentition was failing and expressed she did not want to wear a lower denture that might move around when she talked and ate. The patient expressed a desire to remove the mandibular dentition related to her long-term struggles with dentistry. The patient was wearing a complete maxillary denture and indicated she was satisfied with that and, at this time, wished only to address the lower arch. Medical history was reviewed, and the patient was being treated for schizophrenia, bipolar depression, anxiety, gastroesophageal reflux disease, and insomnia. She reported a moderate level of xerostomia, which related to the medications she was taking for her medical conditions.

A panoramic radiograph and cone-beam computed tomography (CBCT) were taken to evaluate the remaining dentition and available bone for potential implant placement (Figure 1). A clinical examination was performed (Figures 2 and 3). Teeth 20 and 21 (mandibular left premolars) had prior endodontic treatment and minimal coronal tooth structure remaining. Cervical facial composite restorations with recurrent decay were noted on all anterior teeth (#22–27). The right premolars (#28 and 29) and first molar (#30) presented large multisurface amalgam restorations with recurrent decay noted on each tooth. Structurally, the remaining dentition could have been a better candidate for preservation by eliminating decay and crown placement.

Clinical findings were discussed with the patient, and the remaining dentition was recommended to be extracted. Due to finances, 4 implants would be placed, and restoration would be with an overdenture utilizing Locator attachments on the implants. Utilization of an overdenture would allow easier homecare and hygiene. Additionally, treatment costs would be lower than using an All-on-X approach, and future prosthesis replacement due to wear and aging would be cost-effective for the patient. The patient was informed that an immediate placement and loading protocol could be utilized if sufficient insertion torque could be achieved at implant placement. Patient questions were answered, and she agreed to the treatment plan presented. Impressions were taken of the maxillary denture intraorally and the mandibular arch. An occlusal bite registration was taken with the maxillary denture and how it occluded with the mandibular dentition. Consent forms were reviewed and signed by the patient, and then was scheduled for the surgical appointment. The restoring practitioner has taken impressions and a bite to fabricate an immediate complete denture.

The patient presented for the surgery appointment, and local anesthetic was administered utilizing bilateral inferior alveolar and mental injections. A full-thickness flap was elevated, and then the mandibular dentition was extracted. An incision was made with a scalpel at mid-crest from the retromolar pad to the retromolar pad across the arch. A full-thickness flap was reflected on the buccal and lingual to expose the ridge. The ridge was leveled and reduced with a carbide bur in a surgical handpiece. Osteotomies were created for the planned 4 implants at sites #19, 22, 27, and 30, utilizing the extraction sockets to guide orientation and placement. Implants were placed at those prepared sites utilizing Megagen AnyOne OneStage tissue level implants as follows: #19 a 4 × 8.5 mm, #22 a 3.5 × 13 mm, #27 a 3.5 × 13 mm, and #30 a 4.5 × 10 mm, which were countersunk 0.5–1 mm subcrestally (Figure 4). An insertion torque of 35–50 Ncm was achieved on the implants. Locator abutments were placed on each implant with a cuff height of 2 mm and an insertion torque of 35 Ncm (Figure 5). The flap margins were reapproximated and trimmed as needed to achieve primary closure across the ridge and around the Locator abutments present and secured with 5-0 Monoglyc (PGA-PCL) sutures (Figure 6).

Male Locator attachments in their metal housing were placed on the Locator abutments. The mandibular immediate denture was inserted, and the metal housings were marked in the denture to permit relief and allow the denture to sit fully on the ridge with soft tissue contact on the ridge. Occlusion with the maxillary denture was verified and adjusted to achieve uniform contact upon occluding the arches. The wells that had been created at each Locator position (Figure 7). CHAIRSIDE Attachment Processing Material was injected into each well to partially fill the well, and the overdenture was inserted intraorally to pick up the male housings. Placing too much pickup resin into the overdenture may prevent full seating of the prosthesis and may, in this case, trap the sutures, leading to issues when the overdenture is removed. The patient was instructed to wait to remove the overdenture until her follow-up appointment so that any soft tissue inflammation would not prevent reinsertion during the initial healing. For the first 2 weeks, the patient was instructed only to remove the complete upper denture (CUD) nightly. The patient rinsed with chlorhexidine bid for 2 weeks with the lower implant-retained overdenture in place. The patient was shown how to remove and re-insert the lower prosthesis at the 2-week mark and instructed to remove and rinse with saline after each meal and then remove both prostheses at night.

The patient returned at 2 weeks postimplant placement and immediate loading of the overdenture for a post-operative check and suture removal. The overdenture was removed, and the soft tissue demonstrated a lack of inflammation and complete coverage of the ridge (Figure 8). A panoramic radiograph was taken to document the implants in relation to the surrounding bone crestally (Figure 9). Sutures were removed, and the patient was instructed to insert and remove the overdenture, along with oral hygiene practices.

The patient returned after 4 months to check healing and integration. The clinical exam noted a lack of inflammation, and healthy soft tissue was evident (Figure 10). A panoramic radiograph was taken to check the crestal bone levels after 4 months of immediate loading with the overdenture (Figure 11). Bone stability around the immediately placed implants and improving fill of the extraction sockets were noted.

A panoramic radiograph was taken at a recall appointment at 1 year and 8 months postsurgery, demonstrating bone maintenance around the immediately loaded implants for the overdenture (Figure 12). The clinical exam noted healthy soft tissue with no inflammation across the arch in contact with the Locator abutments (Figure 13). The patient expressed satisfaction with the retention of the overdenture and indicated no issues with the prosthesis.

A 74-year-old female patient presented with a complaint of pain in the remaining mandibular teeth. A medical history review indicated the patient was taking Ramipril 5-mg daily and no other meds. Examination noted the patient was wearing a cast partial mandibular denture and the only remaining teeth were the left second molar, first premolar and canine (Figure 14). The patient indicated that the right first molar had been extracted recently due to periodontal issues. Grade 1 mobility was noted on the 3 remaining teeth, and periodontal probing noted deep probing on the mesial of the second molar and canine. A panoramic radiograph and CBCT were taken to evaluate the teeth and available bone (Figure 15). Evaluation of the radiograph noted a defect at the prior extracted right first molar and on the mesial of the canine where the left incisors would be positioned. A deep angular defect was noted on the mesial of the left first molar, which had prior endodontic treatment and was restored with a crown. A review of the patient’s medical history noted a history of high blood pressure, which was being controlled with medication by her physician. The patient also disclosed an allergy to sulfa-based antibiotics.

The patient expressed a desire for improved stability on the lower arch. A treatment discussion with the patient reviewed the clinical findings, and the remaining mandibular teeth were in poor periodontal condition, so they were recommended to be extracted. The recommended treatment would be placing 4 implants spread across the arch and restoration with a Locator retained overdenture. The patient was advised that should adequate insertion torque be achieved at implant placement; the implants would be immediately loaded with the overdenture. Questions from the patient were answered, and she indicated she wished to proceed with the recommended treatment. The restoring practitioner took an impression of both arches and an interocclusal record to fabricate a complete arch denture to be utilized as an immediate denture. Consent forms were reviewed and signed by the patient, who was scheduled for the surgical appointment.

The patient presented for the surgical visit. Local anesthetic was administered utilizing bilateral inferior alveolar and mental injections. The mandibular dentition was extracted (Figure 16, left). An incision was made with a scalpel at mid-crest from the retromolar pad to the retromolar pad across the arch. A full-thickness flap was reflected on the buccal and lingual to expose the ridge (Figure 16, middle). The ridge was leveled and reduced with a carbide bur in a surgical handpiece (Figure 16, right). Osteotomies were created avoiding the extraction sockets and spaced around the arch for best stability with the planned Locator attachments. Osteotomies were made for the planned 4 implants at sites #19, 23, 27, and 31, avoiding the extraction sockets. Implants were placed at those prepared sites utilizing Hiossen SS3 implants: #19 a 4.0 × 7.0 mm, #23 a 3.5 × 11.0 mm, #27 a 3.5 × 11.0 mm, and #31 a 4.0 × 7.0 mm were placed (Figure 17). An insertion torque of 45 Ncm was achieved on the implants. Locator abutments were placed on each implant with a cuff height of 2 mm with an insertion torque of 35 Ncm. The flap margins were reapproximated and trimmed as needed to achieve primary closure across the ridge and around the Locator abutments present and secured with 4-0 Supramid (polyamide 6.6) sutures. Locator attachments were placed on each of the Locator abutments. The denture was relieved over the Locator abutments and attachments to allow the denture to seat on the arch without contacting the Locators and fully seating on the ridge.

CHAIRSIDE Attachment Processing Material was injected into each well on the tissue side of the denture to partially fill the well, and the overdenture was inserted intraorally to pick up the male housings. The patient was guided into occlusion, and the resin was allowed to set. Upon setting, the overdenture was removed, and any residual resin on the adjacent denture base was removed and the area polished. The overdenture was then reinserted, and the patient was instructed to wait to remove the overdenture until her follow-up appointment so that any soft tissue inflammation would not prevent reinsertion during the initial healing. As with case 1, the patient was instructed only to remove the CUD nightly. The patient rinsed with chlorhexidine bid for 2 weeks with the lower implant-retained overdenture in place. The patient was shown how to remove and re-insert the lower prosthesis at the 2-week mark and instructed to remove and rinse with saline after each meal and remove both prostheses at night.

The patient returned at 2 weeks postimplant placement and immediate loading of the overdenture for a postoperative check and suture removal. The overdenture was removed, and the soft tissue demonstrated a lack of inflammation and complete coverage of the ridge (Figure 18). A panoramic radiograph was taken to document the implants in relation to the surrounding bone crestally (Figure 19). Sutures were removed, and the patient was instructed on inserting and removing the overdenture, along with oral hygiene practices.

The patient returned for regular recalls. Panoramic radiograph was taken at a recall appointment at 33-months postsurgery and immediate loading demonstrating bone maintenance around the immediately loaded implants for the overdenture (Figure 20). A clinical exam noted healthy soft tissue with no inflammation across the arch when in contact with the Locator abutments. The patient expressed satisfaction with the retention of the overdenture and indicated no issues with the prosthesis.

Patients with failing mandibular dentition that will necessitate edentulation of the arch are frequently treated with implants utilizing a fixed prosthetic approach. However, an overdenture approach may be better suited for that patient due to finances or an improved ability to do homecare than would be present with a fixed approach. The higher density of the mandibular bone allows the practitioner to achieve higher insertion torque, permitting immediate loading that may permit immediate loading of the arch with free-standing implants and overdenture attachments. A recently published 5-year study that followed 32 participants reported that immediately placed and loaded mandibular implant overdentures using locator attachments showed acceptable plaque index, bleeding index, and peri-implant pocket depth. Although greater marginal bone loss was observed from baseline to follow-up, that was within acceptable limits.⁶  This was supported by another study that found that gingival and bleeding indexes of the patients were not influenced by any free-standing (unsplinted) overdenture attachment available.⁷ 

But is there a difference between free-standing overdentures and bar-overdentures? A study reported no difference in implant survival between Locator free-standing overdentures and bar-overdentures over a 9-year follow-up period. However, bar-overdentures were associated with slightly more complications. While patients in the Locator free-standing group were able to maintain better oral hygiene.⁸  Numerous articles have been published utilizing 2 free-standing implants with a Locator or other attachments, reporting a positive long-term effect for the patient.⁹  A 12-year study reported that early loading at 6 weeks postimplant placement had a 94.5% success rate.¹⁰  Using 2 implants with attachments to retain the overdenture allows anterior-posterior “rocking” type motion under function, especially when biting with the anterior teeth during mastication. This may lead to premature wear of the overdenture attachment males and give the patient a less stable feel to the prosthesis. The authors of this article feel that utilization of 4 implants with Locator attachments with the implants ideally placed in the first molar and canine positions bilaterally provides greater stability to the prosthesis under function and decreases the wear potential of the attachment males.

Oral hygiene homecare is the key to patient maintenance and avoidance of peri-implantitis. As those patients losing the mandibular dentition often had poor home care, leading to periodontal issues and other issues leading to tooth loss, a fixed or bar-overdenture may hamper oral hygiene homecare for patients. Many patients being treated with implants for a jaw that is or will be edentulous are geriatric patients. A study reported that treatment of those patients with fixed rehabilitations, although clinically successful, had a high prevalence of peri-implant disease related to an inability to perform adequate oral hygiene homecare under that fixed prosthesis. This would also include bar-overdentures, as access for oral hygiene homecare is similar to fixed prosthetics.¹¹  One 20-year implant overdenture survival study in mandibular edentulous geriatric patients reported a success rate of 92.5%. Plaque index, bleeding index, and probing depth increased slightly over time, while radiographic analysis revealed minor marginal bone loss during the first 10 years and no further loss thereafter. Participants indicated great satisfaction with their overdenture and reported a good quality of life.¹² 

Patients are nervous when presenting with failing dentition; part of that concerns being in a loose denture during part of the treatment process. Immediate implant placement and loading the planned overdenture eliminate those issues and improve patient expectations and satisfaction. Distribution of the implants allows better stability of the overdenture with the elimination of anterior-posterior rocking when functioning. Using an overdenture also provides treatment at a lower total cost and easier oral hygiene maintenance for the patient than a fixed approach.