The All-on-Four Treatment Concept in Implantology- A Review Download PDF

Journal Name : SunText Review of Dental Sciences

DOI : 10.51737/2766-4996.2021.033

Article Type : Review Article

Authors : Shah K and Kulshrestha R

Keywords : Implants; Full mouth rehabilitation; Prosthesis

Abstract

      Generally, a complete edentulous arch requires 5-7 implants. This is not possible always because of biologic or economic factors. Such scenario pivots the need for treatment by All-on-4 concept. Though, biological, and mechanical complications can arise due to reduce implant support, but the success rates are quite satisfactory. This article describes the All-on-4 concept in general. This concept is mainly indicated to maximize the use of available alveolar bone and to allow for immediate function. It greatly increases patient’s satisfaction.

       


      Introduction

      The “All on four” treatment concept is used for full mouth rehabilitation in complete edentulous arch with either a denture or bridge supported by four implants [1]. In the early concept by Branemark, it was stated that use six implants in a mandible with sufficient ridge and 4 implants in severely deficient alveolar ridge [2]. The two anterior implants are placed axially and remaining two posteriors are angled and placed distally to minimize cantilever and aid in mastication. In addition, the posterior angulation also prevents implant’s interference with mandibular nerve in lower arch and maxillary sinus in upper arch [3]. Nobel Biocare was amongst the first company to identify the evolution of All-on-four technique for full mouth rehabilitation.


      Discussion

      The ill-fitting complete denture can result in soreness and atrophy of the jaws which is a discomfort to the patients [13]. The all-on-four concept offers comfortable solution for patients with atrophic jaws. The immediate implant-support restoration provides patient greater satisfaction. The outcome is better quality of patient’s life [14]. In the study of Lopes et al., difficulty in doing surgery was classified based on a score- low (residual ridge of > 5mm), moderate (irregular residual ridge of 4-5mm) and high (irregular residual ridge of < 4mm) [15]. The under drilling of implant site does enhance the insertion torque by preventing counter sinking to maximize stability of the implant. Biologically, this approach is justified because mechanical stimulation around a newly placed implant modulates the release of bone mediators [16]. Indiscriminately and immediately loading of dental implants is not always favourable because of unfavourable stress distribution and non-favourable cellular response during initial healing phase in un-splinted implants like in over dentures or partial fixed dental prosthesis [17]. Furthermore, high torque during insertion of implant at an under drilled site which is commonly used for immediate loading can reduce crestal bone-to-implant contact during initial healing phase [18]. To reduce the chance of patient’s morbidity, flapless surgery with the use of prefabricated customized guides are used. This makes the surgery more accurate and avoids interference with anatomical structures [19]. Primary stability is extremely important for osseointegration which can be achieved by greater insertion torque. For this splinting is recommended during a full arch restoration with immediate loading [20]. On contrary, extra high insertion torque can lead to wearing on the implant surface and cause a foreign body reaction because of titanium debris and ions that are emitted from the implant surface [21].


      Conclusion

      The all-on-four treatment concept had overall great success rate of more than 98% at 24 months follow up. The window technique to locate anatomic structures allows adequate implant insertion and safeguards sinus and nerve. To attain primary stability and to prevent countersinking of implant in cortical bone the implant bed was under-prepared. It is recommended to use guided surgery to ensure proper positioning and inclination of distal implants. Acrylic fracture and peri-implantitis are the complication of all-in-four implant treatment. Furthermore, there is a need for more follow-up studies to determine the effectiveness of all-on-4 implant concept.


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