Oral rehabilitation of resorbed mandibular ridges utilizing various techniques for implant-supported prosthesis through conventional and digital approach: A case series

Abstract

Residual ridge resorption (RRR) is an inevitable physiological process occurring after the extraction of teeth. The annual rate of resorption is thought to be more in the mandible as compared to the maxilla leading to loss of support and retention in the mandibular conventional prosthesis. The compromised retention and stability of conventional dentures in the mandible lead to the denial of a patient to wear the prosthesis. Rehabilitation of resorbed ridges using implant-supported prosthesis has led to enhanced retention and an increase in chewing efficiency, leading to better acceptance of prosthesis by the patient. This case series describes the rehabilitation of mandibular resorbed ridges using various approaches for implant-retained prosthesis utilizing both conventional and digital means.

INTRODUCTION

Residual ridge resorption (RRR) is a multifactorial process occurring after the extraction of teeth. Although complete dentures have been the most traditional means of rehabilitation of edentulous ridges, patient satisfaction with lower complete dentures is poor and associated with poor denture stability.[1,2] The issue of stability and retention of complete dentures has given rise to the development of implant-retained prosthesis as a viable solution. It has been demonstrated that implants minimize bone loss, denture instability, sore spots, and discomfort, which improves the masticatory efficiency leading to higher levels of patient satisfaction.[3] Implant-retained prostheses have shown a significant increase in the biting force and chewing efficiency, leading to enhanced quality of life of the patient. This case series focuses on the rehabilitation of mandibular resorbed ridges using All-on-2, All-on-4, and All-on-6 concepts utilizing both conventional means and digital technology.

CASE REPORTS

Case report 1

A 60-year-old man reported the chief complaint of a previous loose denture and wanted a more retentive prosthesis. Past medical history was insignificant. Past dental history revealed the extraction of multiple teeth due to periodontal involvement followed by replacement with maxillary and mandibular complete denture. Extraoral examination revealed sunken cheeks with sagging lips. Intraoral examination revealed completely edentulous maxillary and mandibular arches with overlying healthy mucosa [Figure 1a and b]. Radiographic examination was performed following the placement of radiopaque markers lingual to the canine region bilaterally in the duplicated denture [Figure 1c] fabricated using the agar container method. The template denture was inserted in the patient’s mouth, and a cone-beam computed tomography (CBCT) was performed. CBCT revealed adequate length and width of the bone in the canine region corresponding to the radiopaque markings satisfactory for conventional implant placement. Treatment options including implant-supported overdenture and implant-retained fixed prosthesis were advised to the patient, and he opted for implant-supported overdenture over the fixed prosthesis due to financial constraints. Informed consent was obtained from the patient regarding the treatment protocol.

Figure 1.

(a) Intraoral view of the maxillary arch, (b) intraoral view of the mandibular arch, (c) intraoral frontal view of duplicate denture, (d) osteotomy site preparation, (e) placement of paralleling pins, (f) application of torque using a torque wrench, (g) suture placement, and (h) OPG following implant placement

Surgical phase

The surgical site was prepared, and an inferior alveolar nerve block with 2% lignocaine and 1:80,000 epinephrine was given bilaterally. An envelope-like incision was placed on the alveolar ridge extending mesiodistally from the right premolar to left premolar regions, and mucoperiosteum was reflected, following which the disinfected template denture was placed inside the oral cavity and drilling was done through the denture until a concavity was made in the alveolar ridge. The template denture was now removed, and the osteotomy site was prepared in the canine region bilaterally through sequential drilling [Figure 1d]. Parallelism was further evaluated using the paralleling pins [Figure 1e]. Implants of 4 mm diameter and 12 mm length (SuperLine, Dentium, USA) were placed in the osteotomy site, and a torque of 35 Ncm was verified [Figure 1f]. The cover screws were placed, and flaps were sutured to achieve primary closure [Figure 1g]. An orthopantomogram (OPG) was performed immediately after implant placement to ensure the correct positioning of implants [Figure 1h]. Postoperative instructions were delivered, and the patient was recalled for follow-up after a week for suture removal. The surgical site reflected adequate tissue healing and good oral hygiene maintenance. The intaglio surface of the previous denture was relieved and relined with tissue conditioning material to be used as an interim prosthesis.

Prosthetic phase

The patient was kept on a regular follow-up for three months, following which a radiographic examination was performed to assess the implants and gingival height was measured. Second-stage surgery was performed, and cover screws were replaced with healing abutments. Gingival tissue was allowed to mature, following which locator abutments (Positioner Abutment, Dentium, USA) of adequate gingival height were placed [Figure 2a]. The fabrication of a complete denture prosthesis was performed in a conventional manner [Figure 2b and c], following which the pickup of metal caps with plastic sockets was done. Block-out spacers were placed on positioner abutments, and metal caps were connected to the abutments intraorally [Figure 2d]. Two troughs were created in the intaglio surface of mandibular complete denture, and positioning of denture was done over metal sockets. Once the positioning was verified, autopolymerizing resin was placed inside troughs, following which the patient was asked to maintain light occlusal pressure in centric relation until the resin was completely set. The metal sockets were picked up in denture, following which finishing and polishing were performed [Figure 2e]. The prosthesis was inserted in the mouth [Figure 2f], and oral hygiene instructions were delivered. The patient was kept on a regular follow-up and was satisfied with the outcome of the treatment [Figure 2g].

Figure 2.

(a) Placement of locator attachment, (b) maxillary and mandibular final cast, (c) try-in stage, (d) placement of metal housings, (e) pickup of female components, (f) insertion of overdenture, and (g) post-rehabilitative smile view

CASE REPORT 2

A 55-year-old male patient reported the chief complaint of completely missing teeth in the lower arch. Past medical history was not significant. Past dental history revealed extraction of multiple teeth due to periodontal involvement. Intraoral examination revealed a partially edentulous maxillary arch opposing a completely edentulous mandibular arch with RRR in the posterior region [Figure 3a and b]. The patient was willing to receive a fixed treatment, so a CBCT was advised to the patient. Radiographic examination revealed adequate bone length and width in the mandibular arch within the interforaminal region. Hence, a full-arch All-on-4 fixed implant-supported prosthesis was planned for rehabilitation of mandibular arch. An informed consent regarding the treatment protocol was obtained from the patient.

Figure 3.

(a) Intraoral view of the maxillary arch, (b) intraoral view of the mandibular arch, (c) inferior alveolar nerve block using local anesthesia, (d) elevation of mucoperiosteum, (e) placement of Malo Guide, (f) osteotomy site preparation, (g) intraoral view following implant placement, and (h) OPG following implant placement

Surgical phase

The surgical site was prepared, and local anesthesia of 2% lignocaine with 1:80,000 epinephrine was given [Figure 3c]. A midcrestal incision was placed extending mesiodistally from the right molar to left molar regions, and the mucoperiosteal flap was reflected [Figure 3d], following which mental nerve foramen was located in the mandible. A 2-mm hole was drilled in the middle of the mandibular arch to insert and adapt the Malo Guide (Nobel Biocare AB, Goteborg, Sweden) for guiding the positioning of implants [Figure 3e]. First, the osteotomy site of two distal implants was prepared at the premolar region with an inclination of 45° relative to the occlusal plane, following which the osteotomy sites of anterior two axial implants were prepared in the lateral incisor region for a favorable implant distribution [Figure 3f]. The parallelism of anterior implants was verified with paralleling pins, following which implants were placed (SuperLine, Dentium, USA) [Figure 3g], and a torque of 35 NCm was verified. Cover screws were placed, and flaps were sutured to achieve primary closure, following which an immediate OPG was performed to ensure the correct positioning of implants [Figure 3h]. Postoperative instructions were delivered, and the patient was recalled for a follow-up after a week for suture removal. The surgical site reflected adequate tissue healing, following which an interim prosthesis was delivered to the patient.

Prosthetic phase

The patient was kept on a regular follow-up for three months, following which second-stage surgery was performed. Cover screws were replaced with the healing abutments, and the gingival tissue was allowed to mature to facilitate the development of a proper gingival emergence profile for the anticipated restoration. Multiunit abutments of adequate gingival height and angulation were placed [Figure 4a]. Impression copings were placed, and intraoral splinting of copings was performed using floss and autopolymerizing pattern resin [Figure 4b]. The pickup impression of splinted copings was made using polyvinyl siloxane material, and implant analogs were placed. The gingival mask was injected [Figure 4c], and the working model was obtained [Figure 4d]. The jig was fabricated on a definitive cast using autopolymerizing pattern resin and verified intraorally for passive fit. The metal bar was fabricated through conventional casting, and the screw-retained metal bar was checked for passive fit intraorally [Figure 4e] followed by an OPG to assess the proper fit of the metal bar [Figure 4f]. Jaw relation and try-in were performed in the conventional manner, following which the processing of hybrid prosthesis was done [Figure 4g]. The prosthesis was inserted, and a final torque of 30N was given to the retention screws. The access holes were secured using composite [Figure 4h], and postoperative instructions regarding oral and prosthesis hygiene were given to the patient. The patient was kept on a regular follow-up and was satisfied with the treatment.

Figure 4.

(a) Placement of multiunit abutments, (b) intraoral splinting of impression copings, (c) pickup impression followed by gingival mask application, (d) mandibular definitive cast, (e) intraoral view following metal bar placement, (f) OPG following metal bar try-in, (g) final hybrid prosthesis, and (h) insertion of final prosthesis

CASE REPORT 3

A 52-year-old female patient reported the chief complaint of an unesthetic appearance due to missing teeth in the lower arch. Past dental history revealed the extraction of multiple teeth due to periodontal involvement. Intraoral examination revealed a partially edentulous maxillary arch opposing partially dentulous mandibular arch with periodontally compromised remaining teeth [Figure 5a and b]. The patient was willing to receive a fixed treatment, so a CBCT was advised to the patient. A radiographic examination revealed adequate bone length and width in the mandibular arch. Hence, a full-arch All-on-6 fixed implant-supported prosthesis was planned for the rehabilitation of mandibular arch. The implant-supported prosthesis was not possible in the maxillary posterior region due to inadequate bone height and width. A maxillary flexible partial denture was planned opposing the mandibular fixed prosthesis. An informed consent regarding the treatment protocol was obtained from the patient.

Figure 5.

(a) Intraoral view of the maxillary arch, (b) intraoral view of the mandibular arch, (c) Malo Guide placement, (d) osteotomy site preparation, (e) placement of paralleling pins, (f) application of torque using a torque wrench, (g) intraoral view following implant placement, and (h) OPG following implant placement

Surgical phase

After achieving local anesthesia, a full-thickness crestal incision was made from the right molar to left molar regions. The remaining teeth were extracted, and curettage was performed followed by irrigation using clindamycin injection. Malo Guide was stabilized [Figure 5c], and the osteotomy site was prepared using a sequential drilling protocol [Figure 5d]. Parallelism was assessed using the paralleling pins [Figure 5e], and implants were placed. Four implants (4 * 12 mm) (SuperLine, Dentium, USA) were placed anteriorly in the interforaminal region and two implants (4 * 10 mm) (SuperLine, Dentium, USA) posteriorly in the molar region. A final torque of 35 N/cm was verified [Figure 5f], and cover screws were placed [Figure 5g]. Flaps were sutured to achieve primary closure, and a postoperative OPG was performed to evaluate implant placement [Figure 5h]. The patient was recalled after a week to assess soft tissue healing and suture removal. The interim prosthesis was relieved and delivered to the patient.

Prosthetic phase

The patient was kept on a regular follow-up for three months, following which second-stage surgery was performed. The healing abutments allow gingival tissue to mature and were replaced by multiunit abutments of adequate gingival height to facilitate the development of a proper gingival emergence profile. Multiunit impression copings were placed, and intraoral splinting of copings was performed using floss and composite material [Figure 6a]. The pickup impression of splinted copings [Figure 6b] was made using polyvinyl siloxane material, following which a gingival mask was injected and the working model was obtained [Figure 6c]. The jig was fabricated on a definitive cast using autopolymerizing pattern resin and verified intraorally for passive fit. The definitive cast was scanned using a laboratory scanner (Dentsply Sirona inEos X5), and a digital image of the cast was obtained. Designing the metal bar was performed using EXOCAD software [Figure 6d] followed by 3D printing of metal bar using the direct metal laser sintering (DMLS) technique [Figure 6e]. The screw-retained metal bar was obtained and checked for passive fit intraorally [Figure 6f] followed by an OPG to evaluate the proper fit [Figure 6g]. Jaw relation and try-in were performed in a conventional manner followed by processing of hybrid prosthesis. The finished and polished prosthesis was inserted [Figure 6h], and a final torque of 30N was given to the retention screws [Figure 6i]. Postoperative instructions regarding oral and prosthesis hygiene were given to the patient, and the patient was kept on a periodic follow-up.

Figure 6.

(a) Intraoral splinting of impression copings, (b) pickup impression, (c) mandibular definitive cast, (d) digital image of scanned mandibular cast with designing of metal bar framework, (e) 3D-printed metal bar, (f) intraoral view following metal bar placement, (g) OPG following metal bar try-in, (h) insertion of final prosthesis, and (i) post-rehabilitative view

DISCUSSION

Rehabilitation of resorbed ridges, especially that of the mandibular ridge, is challenging due to the reduced bone volume caused by long-term edentulism. Alveolar atrophy can be managed by various techniques including bone grafting and augmentation procedures. However, each of these techniques has biological and technological limitations, such as morbidity at the graft donor sites, postoperative discomfort, surgical complexity, uncertain predictability, and extended treatment times.[4] Implant-supported overdenture and fixed prosthesis were chosen for the present case series to eliminate the additional surgery for graft placement, financial expenditure, and time lag in treatment.

Mandibular implant-supported overdenture provides an effective solution in case I as the patient was wearing a prosthesis with suboptimal retention. Enhanced retention provided by the prosthesis leads to an increase in biting force and overall satisfaction of patient. The ability to easily remove prosthesis also facilitated greater access to maintenance of oral hygiene.[5] All-on-4 implant was chosen for case II as there was reduced bone in the posterior region, thereby tilted implant was chosen for posterior sites to avoid the placement of short implants and avoid the anatomical structures. The placement of long tilted implants in the posterior region provides biomechanical advantages including increase in A-P spread, reduced cantilever, improved load distribution, cross-arch stabilization, and preservation of marginal bone height.[6,7] Malo Guide was used to improve the accuracy and assure adequate inclination and positioning of implants.[8] The “All-on-6” concept was chosen for case III as the adequate bone was present in the posterior region, which enabled the maximal use of remaining bone in the lower jaw, avoiding regeneration techniques that increase patient morbidity, raise treatment costs, and additional complications. According to various studies, there is generally no discernible difference between the All-on-4 and All-on-6 groups in terms of long-term clinical outcomes. However, All-on-6 seems to be more predictable in several clinical assessments for some specific characteristics than All-on-4.[9] This could be attributed to the better stress distribution caused by the increased number of implants, increased A-P spread, decreased cantilever length, and improved prosthetic support. The two-stage surgical approach was utilized in all three cases as the marginal bone loss in the two-stage approach has been found to be less than that of the single-stage approach.[10]

CONCLUSION

The present case series describes the rehabilitation of mandibular ridges using various implant-supported modalities to fulfill the desired expectations of patients taking into consideration the treatment time and financial constraints. The implant-supported prosthesis has shown significant improvement in biting force and chewing efficiency. Moreover, the implant-retained prosthesis has been demonstrated to enhance speech and provide other psychological benefits, such as boost in confidence, enhanced social interactions, emotional well-being, and an overall improved quality of life.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given his consent for his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Self.