Immediate functional loading of implant-supported mandibular prostheses with customized UCLA’S attachments with distal extension: A case report

Abstract

Implant-supported complete dentures are a common procedure for patients with mandibular edentulism problems. This article documents the protocol for immediate functional loading of fixed transient mandibular prostheses with fully moldable attachments and distal extensions to prevent fractures. A 56-year-old female patient was referred to the Oral Rehabilitation and Implantology Service due to periodontal problems, difficulty in chewing capacity and aesthetic compromise. The patient was treated in a single surgical procedure with dental extractions, guided regularization of the alveolar process and guided placement of five interforaminal implants and placement of functional fixed mandibular prostheses with immediate loading with personalized UCLA’S, distal extensions and short arc occlusal scheme. At 3 months postoperatively, the definitive placement of fixed mandibular metal acrylic prostheses and conventional upper prostheses was performed. The functional and aesthetic integrity of the fixed mandibular prosthesis implant preserved with UCLA’S documents that implant placement in the interforaminal zone with an immediate loading protocol is a viable treatment option for prosthetic rehabilitation of the fully edentulous mandibular arch and that design with distal extensions in the posterior sector of the mandibular arch is an effective option to avoid fracture of the prostheses, presenting a survival of the five mandibular implants of 100% at 1 year postoperatively.

Introduction

Aging increases the risk of numerous oral disorders and systemic diseases that affect the quality of life of older people, affecting their essential biological functions such as chewing, swallowing, and speaking. Among them, xerostomia or dry mouth can cause root decay, chapped lips, and fissured tongue, while periodontal diseases lead to tooth loss.1 The long-term trend in the burden of edentulism in older adult patients demands that medical sciences, especially geriatric dentists and prosthodontists, pay more attention to this vulnerable group of patients.2 Prosthetic treatment planning is essential; However, the patient’s economic, social, psychological and motor state must also be taken into account.3

The stable anchorage of implant-supported overdentures and implant-supported fixed complete dentures represents successful clinical treatment approaches in partial and complete edentulous patients.4 Numerous studies confirm both the success of the placement of osseointegrated implants that retain mandibular prostheses5-7 and the patient’s edentulous satisfaction.8 Xie et al.9 in their prospective study demonstrated that implant placement today improves stress conditions, aesthetic perception and quality of life related to oral health.

Immediate and delayed loading procedures are very well-documented and safe methods. A recent systematic review demonstrated that immediate loading protocols have high survival rates for both fixed and removable prostheses. ¹⁰ To allow immediate placement or provisionalization, good initial implant stability (>35 N cm²) and an implant stability coefficient value >60 are required. However, good primary stability is not always possible, some factors such as local anatomy, bone density, implant drilling protocol, and implant macro-design could influence this. In addition, in fully edentulous patients, immediate loading procedures require a minimum of four implants connected to prostheses with high initial stability and good-quality bone, which will allow a good prognosis for the patient. ¹¹ The research indicates that success rates are greater in the mandibular jaw and better when the implants are placed anteriorly in the mandible’s interforaminal region.^12,13 Studies indicate that lower stress values were seen in the peri-implant bone and implants in the overdenture as the number of implants increased. ¹⁴ For this reason, this article aims to document a protocol for the immediate loading of transitional fixed prostheses with fully castable attachments and distal extensions to prevent them from fracturing. This will allow graduate students and clinical specialists to document the construction of an improved implant-supported prosthetic device in the treatment of a patient with complete mandibular edentulism.

Case description

A 56-year-old married female patient was referred to the Department of Implantology and Oral Rehabilitation with complaints of severe periodontal problems that hindered masticatory ability and compromised esthetics. The patient had no relevant personal pathological history.

Initially, the patient presented a diagnosis of periodontitis stage III/grade C, with grade II mobility sequelae in teeth 37, 34, 33, 32, 32, 31, 41, 42, and 43 (International Dental Federation Numbering System). ¹⁵ She presented endoperiodontal lesion in tooth 17 with sequelae of right maxillary sinusitis of dental origin. He had a misaligned maxillary overdenture with overcontoured and misaligned crowns in teeth 17 and 27, as well as misaligned mandibular removable prostheses of flexible material. Given the characteristics of the patient, the treatment planning consisted of the following: extraction of teeth 17 and 27, placement of immediate monomaxillary prostheses, and implant-supported mandibular prostheses with immediate loading (Figure 1(a)–(d)).

Figure 1.

(a) Panoramic X-ray. (b–d) Intraoral photographs.

For the elaboration of the prostheses, the following was carried out: Physiological impressions were taken with polymethylxilosane (Zhermack™) rubber in heavy and light consistencies, then the working models were obtained with type IV plaster, the registration of craniomandibular relations, and transfer to the semi-adjustable articulator (Hanau). The articulation of three-layer acrylic artificial teeth (Vita MFT™) was carried out, with a short-arch occlusal scheme (Figure 2). The dentures were processed with heat-curing acrylic (Lucitone™) and characterized with acrylic pigments (Vipident™), obtaining immediate prostheses. Cone Beam computed tomography was performed. The placement of five interforaminal implants (Nobel Biocare™) of 4.3 mm in diameter by 13 mm in length was planned with the help of Mimic’s software (Figure 3). Crestal bone implant insertion using a fully limiting stereolithographic surgical template supported by the mucosa. ¹⁶ Two customized UCLA’S were made with distal extensions in base metal, chromium-nickel alloy (Remanium™). All remaining teeth were extracted. The surgical guide was placed on the alveolar ridge, fixed with screws, and a Nobel Biocare drilling protocol ¹⁷ was performed (Figures 4 and 5). A platform was made with the help of an acrylic regularization guide (Figure 6) and the implants were placed obtaining a primary stability of 45 N/cm² in the implants in positions 33, 41, 42, and 43, only on 31 a primary stability of 20 N/cm² was obtained (Figure 7). Immediate loading was performed by trapping the 4.3 mm diameter titanium attachments on implants 31, 41, and 42 and the UCLA’S with customized distal extension on implants 33 and 43 with low shrinkage resin (Triad, Dentsply™) to achieve passivity and rigidity of the prostheses (Figure 8). Subsequently, the monomaxillary denture was placed and the provisional mandibular fixed prostheses were screw-retained at 15 N/cm² torque. During the first postoperative month, the case was followed up weekly for occlusal adjustment and evaluation of the healing, showing an adequate evolution (Figure 9). Three months after implant placement, impressions of the five implants were taken with single-phase polyvinylsiloxane (Zhermack) with a customized impression tray. After splinting, the impression pins with low-shrinkage self-curing acrylic (Duralay™) (Figure 10). The upper denture was duplicated in clear acrylic for physiological impression taking with polyvinylsiloxane (Zhemarck), which was used to record the craniomandibular relationships and their transfer to the Hanau articulator (Figure 11). From the articulation of the five-layer artificial teeth (Premier, Kulser™), the metallic structure of the implant-supported prostheses was made with nickel–chromium alloy (Remanium) (Figure 12). Subsequently, the monomaxillary prostheses and the mandibular hybrid prostheses were acrylated with characterized heat-curing acrylic (Anaxdent™). Finally, the final placement of the implant-supported fixed mandibular prostheses was performed with a torque of 35 N/cm², rectifying simultaneous occlusal contacts and occlusal scheme of canine and anterior guides (Figure 13). The distal prostheses cantilever measured 15 mm on the right side and 10 mm on the left side.

Figure 2.

Vita MFT™ teeth articulator.

Figure 3.

4.3 mm × 13 mm Nobel Replace™ implant planning.

Figure 4.

Dental extractions.

Figure 5.

Alveolar process regularization guide.

Figure 6.

Restrictive guide.

Figure 7.

Nobel replace implants placed.

Figure 8.

Splinting of prosthetic attachments with low shrinkage resin.

Figure 9.

Conventional upper immediate prostheses antagonizing with implant-supported immediate fixed mandibular prostheses.

Figure 10.

Impression with polyvinylsiloxane.

Figure 11.

Upper physiological impression and registration of craniomandibular relations.

Figure 12.

Nickel–chromium alloy metal framework.

Figure 13.

(a and b) Finished prostheses.

Outcomes and follow-up

Once the denture was in place, instructions were given on denture care and maintenance of good oral hygiene. The patient was kept under observation for the first 24 h in case the prostheses bothered the patient, or a high point had to be removed. Since then, a periodic follow-up was performed after 1 month, 6 months, 1 year up to 2 years, so until that date, the survival rate of the interforaminal implants and both prostheses was 100%, with no signs of mobility of the implants and fracture of prostheses. The patient quickly adapted to wearing the prostheses and showed significant functional, esthetic, and psychological improvement.

Discussion

Nowadays, immediate loading procedures of dental implants have gained much popularity due to their advantages of reduced treatment time, improved esthetics, and patient acceptance.^10,11 Therefore, the purpose of this report was to document the construction of a prosthetic appliance on five interforaminal implants placed using an immediate loading protocol that will assist with normal oral function, improving the quality of life of the complete edentulous patient.

The earliest history of immediate loading protocols was introduced by Ledermann, ¹⁸ who placed an overdenture on four interforaminal implants on the same day as the surgical procedure.

On the other hand, a study demonstrated that favorable and acceptable esthetic results can be achieved by placing implants after the extraction of teeth in the anterior part of both jaws. ¹⁹ The characteristics of dental implants that are favorable for immediate loading procedures are primary stability >35 N cm² with an implant stability coefficient value >60. ¹¹ However, scientific evidence has shown that the most frequent prosthetic complications and maintenance interventions in the mandible are fractures of prosthetic devices, prosthetic retention adjustments, pressure ulcers, and matrix exchanges. ²⁰ Therefore, implant-supported mandibular prostheses with fully castable attachments were planned to prevent its fracture, which after 2 years of follow-up has had an excellent survival rate.

A preliminary study ²¹ demonstrated that immediate loading of two-implant mandibular overdentures placed in the interforaminal region using flapless surgery with magnetic attachments tends to improve oral health-related quality of life and patient evaluation before what was observed in comparison with conventional loading. Similarly, Mohamed et al.’s ²² study demonstrated that the placement of four interforaminal implants following an immediate loading protocol, which supported fixed prosthetic restorations in patients with complete mandibular edentulism, provided high success rates after the 1-year follow-up period. On the other hand, a prospective study compared the immediate and conventional loading of four interforaminal implants supporting a mandibular overdenture with respect to survival stability and dental implant-related complications. In this study, 20 patients received 80 implants, of which 32 were loaded immediately, while the rest were loaded conventionally. The authors subsequently demonstrated that implant survival was similar in both groups after 36 months and no implants were lost. In addition, postoperative complaints such as swelling, hematoma, or wound dehiscence, as well as the need for prosthetic treatment due to abutment loosening or occlusal discrepancies, occurred in both study groups. Despite this, pressure marks and the number of visits were significantly higher in the conventional loading group compared to the immediate loading group. Finally, the authors concluded that, with sufficient initial stability >30 N cm², the procedures of immediate loading of four interforaminal implants in the mandible could be the preferred option for older adult patients, reducing the total treatment time and the number of visits. ⁴ A retrospective study consisting of a clinical and radiographic examination to evaluate changes in bone level (vertically) after the placement of unsplinted and immediately loaded interforaminal implants in an overdenture using ball attachments revealed a gradual acceptable bone loss with a mean of 0.27 ± 0.36 mm immediately after surgery, 0.47 ± 0.42 mm after 1 year, and 0.95 ± 0.98 mm after 10 years of follow-up, which reflects that it is a viable clinical treatment with a high rate of success of implants and prosthetic devices, partly also explained by a high level of patient satisfaction. ²³

The all-on-four protocol uses four implants in the anterior part of atrophic edentulous jaws to support an immediately loaded denture. The two most anterior implants are placed axially, while the two most posterior implants are placed distally and angled to increase arch width which improves masticatory efficiency. ²⁴ In the present study, the use of straight implants with an increased number of implants in the interforaminal zone with good bone quality is an alternative treatment to the all-on-four technique. In this case, the opposing denture was complete, and so the force transfer to the implants was not high. ²⁵

However, the presenting authors recommend more prospective controlled and randomized clinical studies need to be carried out with a larger number of patients and implants to verify the effectiveness of the method in comparison with the all-on-four technique and to compare it with patients who have fixed prostheses or natural dentition on the maxillary arch, where the masticatory forces will be higher.

In summary, the development of dental implants provides the dental prosthetic discipline with an extraordinary range of treatment options that have revolutionized the management of partially and completely edentulous patients. In this sense, the decision-making for the choice of treatment plan and the success of the treatment are a function of two critical factors:

• The understanding and implementation of basic biomechanical principles, and the ability and talent of the oral prosthetist to meet the functional and esthetic demands of the patient. In particular, the dental prosthetic rehabilitation of completely edentulous patients is guided by principles based on scientific evidence that has documented the survival of implants subjected to different loading protocols in the medium and long term.

• The duration times of the different treatment options.

• The risks, benefits, and patient satisfaction based on the physiological and esthetic results of the treatments.

• The level of difficulty of the prosthetic treatment and the cost-effectiveness of the procedures.

Conclusion

This clinical case demonstrates the feasibility of immediate loading in the interforaminal area with five fixed mandibular implant-retained UCLA’S prostheses with distal extensions to avoid fracture of the prostheses. A correct diagnosis and planning using an adequate surgical and prosthodontic protocol allows to achieve a successful alternative in the treatment of the patient with complete mandibular edentulism.