REVIEW Year : 2021  |  Volume : 21  |  Issue : 1  |  Page : 3-10

Survival rates of axial and tilted implants in the rehabilitation of edentulous jaws using the All-on-four™ concept: A systematic review

Sneha Harishchandra Gaonkar, Meena Ajay Aras, Vidya Chitre, Kennedy Mascarenhas, Bhavya Amin, Praveen Rajagopal
Department of Prosthodontics, Goa Dental College and Hospital, Bambolim, Goa, India

Date of Submission10-Mar-2020Date of Decision15-May-2020Date of Acceptance20-Sep-2020Date of Web Publication29-Jan-2021

Correspondence Address:
Dr. Sneha Harishchandra Gaonkar
Department of Prosthodontics, Goa Dental College and Hospital, Bambolim, Goa
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jips.jips_100_20

Aim: The aim of this review was to evaluate the survival rate of axial and tilted implants in rehabilitation of edentulous jaws using all on four concept.
Setting and Design: Systematic Review.
Materials and Methods: A literature review was performed in MEDLINE, PubMed Central (PMC), Google scholar, Embase, Cochrane Central Register of Controlled Trials. Hand searches were conducted of the bibliographic of related journals and systematic reviews. A total of 380 articles were obtained from the intial screening process. Of these articles, 25 articles fulfilled the inclusion criteria. The authors performed evaluation of articles independently as well as data extraction and quality assessment.
Statistical Analysis Used: Qualitative analysis.
Results: The major prosthetic complication was the fracture of the acrylic prosthesis. The mean cumulative survival rate of implants (72-132 months) were 94% to 98%. The prosthesis survival rate (12 months) was between 99% to 100%. The averaged bone loss was 1.3 ±0.4 mm (12-60 months). No Significant difference was found between survival rates of axial and tilted implants nor between maxilla and mandible.
Conclusion: All on four concept can be employed successfully in the edentulous patients with resorbed ridges while improving their quality of life and reducing morbidity. However,randomized clinical trials with large sampling size and long term follow up should be incorporated.

Keywords: All-on-four™, axial implants, mandible, maxilla, tilted implants

How to cite this article:
Gaonkar SH, Aras MA, Chitre V, Mascarenhas K, Amin B, Rajagopal P. Survival rates of axial and tilted implants in the rehabilitation of edentulous jaws using the All-on-four™ concept: A systematic review. J Indian Prosthodont Soc 2021;21:3-10
How to cite this URL:
Gaonkar SH, Aras MA, Chitre V, Mascarenhas K, Amin B, Rajagopal P. Survival rates of axial and tilted implants in the rehabilitation of edentulous jaws using the All-on-four™ concept: A systematic review. J Indian Prosthodont Soc [serial online] 2021 [cited 2021 Dec 5];21:3-10. Available from: https://www.j-ips.org/text.asp?2021/21/1/3/308184   Introduction 

The occurrence of edentulism among elderly patients has been shown to have a negative impact on their quality of life.[1] It is a debilitating and irreversible condition leading to functional impairment and physical, psychological, and social disability. The treatment options available for these patients are complete dentures and removable or fixed implant-supported prosthesis.

Prosthetic rehabilitation of completely edentulous patients with implants is a reliable mode of treatment, but its success depends on the availability of good quality and quantity of bone. Patients with severe resorption of the alveolar bone require prior surgical intervention such as bone augmentation and sinus lift procedures for a successful outcome.[1],[2],[5] These techniques increase patient morbidity and treatment fees and can have associated complications. To overcome these disadvantages, the concept of “All-on-four™” was introduced by Paulo Malo in 2003.[70] This concept demonstrates placing two anterior implants in an axial position and two posterior implants with a tilt of up to 45° to support a full-arch fixed restoration. Bone grafting is avoided by tilting the posterior implants, thus utilizing the available bone. Advantages of tilting implants are that it eliminates the need for invasive procedures such as sinus floor augmentation and bone augmentation, preserves anatomical structures such as sinus floor in the maxilla and inferior alveolar nerve in the mandible, allows for placement of longer implants with good cortical anchorage, and increases interimplant space, thus reducing cantilever length in jaws and helping in better force distribution, thus reducing load on the implants.[1],[2],[3],[4],[6],[11],[13],[15],[18],[26] Disadvantages of tilting implants include the technical sensitivity of the procedure and the need of computer-guided surgical stent for implant to be placed in an optimal position.[6],[11],[13],[18] The purpose of this review article is to evaluate the survival rate (SR) of axial and tilted implants to rehabilitate completely edentulous maxilla and mandible.

Objectives of the study

The objectives of the study are to evaluate the survival rates of tilted and axial implants placed in human either in the maxilla or mandible using All-on-four treatment concept, bone level changes around these implants, and survival rates of fixed dental prostheses on these implants.

  Materials and Methods 

Search method and identification of studies

A literature review was performed in MEDLINE, PubMed Central, Google Scholar, Embase, and Cochrane Central Register of Controlled Trials.

Keywords such as “All on 4,” “All-on-four,” “tilted implant,” “angled implant,” “upright implant,” “axial implant,” “four implants,” “edentulous patient,” “edentulous mandible,” and “edentulous maxilla” were used alone or in combination.

Types of studies

Clinical trials reporting on the survival rates of axial and tilted implants, survival rates of full-arch fixed prosthesis, and changes in the bone levels around implants with a minimum follow-up period of 1 year were considered.

The following articles were excluded:

Systematic reviewsCase reportsBiomechanical trialsFinite-element analyses andTrials including more than four implants, zygomatic implants, and pterygoid implants.

Types of participants

Studies involving only human subjects were included.

Types of outcome measurements and data collection

For each study, the following data were collected: name of the authors, type of study design, number of jaws investigated, total number of implants, number of implants in the maxilla and mandible, implant survival rates, prosthesis survival rates, and marginal bone loss.

  Results 

The electronic search yielded a total of 380 articles. The search results were combined, and articles including the words “case report,” “literature review,” and “finite element analysis” in the title were excluded and seventy papers were considered. Of these, 45 trials were excluded after reading full texts for the initial screening process [Table 1],[Table 2],[Table 3], and 25 articles fulfilled the inclusion criteria. Fourteen studies reported were prospective studies and 11 studies reported were retrospective studies [Table 2] and [Table 4].

Outcomes of the studies

During the follow-up period, it was seen that the majority of implant failures were seen within 12 months of surgical placement. The reasons for failure were reported to be lack of osseointegration and infections.

There was no significant difference in the outcome of tilted versus axial implants in the maxilla and the mandible. In addition, no significant difference was found between tilted and axial implants in their respective jaws [Table 4].

The most common prosthesis-related problem reported was fracture of the provisional acrylic prosthesis. Other problems reported were wear patterns in the opposing dentition and prosthetic screw loosening in the cases of bruxers.

In all the studies, bone-level changes were evaluated based on the measurements of the distance between the implant neck and the first sign of bone-to-implant contact radiographically. Marginal bone loss level was reported separately for both tilted and axial implants in 15 trials. It was found that there was no significant difference for bone loss values for both tilted and axial implants and also for maxillary and mandibular implants.

  Discussion 

The “All-on-4” concept to support fixed full-arch prostheses has been gaining popularity because it offers a predictable treatment option to rehabilitate edentulous patients while eliminating regenerative procedures and complications inherent to these procedures. The patient is benefitted by the provision of a fixed full-arch prosthesis on the day of the surgery, a shorter treatment time due to elimination of time-consuming bone-grafting procedures, and the low cost of the treatment compared to conventional implant treatment modalities.

Out of 380 publications, only 25 papers provided substantial information about the all-on-4 concept to evaluate the SR of axial and tilted implants, fixed prostheses, and marginal bone-level changes.

Most of the studies reported were of retrospective or prospective. None of the studies were designed as a randomized controlled trial (RCT).

Malo et al.[18] reported the results of implant SR up to 132 months (cumulative survival rate [CSR] 94.8%) and a SR up to 72 months (CSR 98%). In this review, no statistically significant difference was observed in the SR of axial and tilted implants. Due to the absence of RCT, the efficacy of immediate rehabilitation supported by axial and tilted implants cannot be evaluated definitely, However, based on the included studies in the review, it is seen that prognosis of the implant is excellent.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19],[20],[22],[23],[26],[27]

Regarding marginal bone level changes, no significant difference was found between axial and tilted implants. Most of the included studies reported limited marginal bone loss on an average of <1.5 mm for axial and tilted implants for a follow-up period of 12 months.[1],[2],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[19],[22],[23],[26],[27] The studies by Maló et al.[26] and Krennmair et al.[27] reported limited marginal bone loss of 1.74 mm and 1.17 mm for axial implants and 1.76 mm and 1.24 mm for tilted implants, respectively, for a follow-up period of 5 years. Only one study defined success criterion for bone loss as no more than 1.5 mm by the end of the 1st year of functional loading or 0.2 mm/year in the subsequent years.[5]

In addition, when comparing either the maxilla and mandible, no statistically significant differences were found in the SR of implants.

The above-mentioned studies suggest that the placement of implant in the jaws (maxilla/mandible) or angulation of implant using the “All-on-4” concept does not affect the bone levels.

The prostheses were incorporated within 48 h after the surgery in all the included studies. The most common complication reported was the fracture of the acrylic prosthesis. This was mainly seen in bruxers due to progressive wear of the resin material. Therefore, it is recommended to reinforce definitive prostheses with cast metal frameworks.

Limitations

This review is based only on prospective and retrospective studies which gave limited information on the prognosis of the All-on-4 technique for a short term. To determine the efficacy of this, RCTs with large sample size and long-term follow-up should be incorporated.

  Conclusion 

The All-on-four treatment concept seems to be an approach for edentulous jaws according to the common demand of a cost-effective treatment concept, decreased treatment times, and higher patient quality of life compared to extended surgical approaches. The results obtained from the studies indicate an implant SR of 98% to 94.8% for a follow-up period of 72–132 months. The marginal bone loss of 1.5 mm to 1.7 mm for axial and tilted implants was reported for a follow-up period of 12–60 months. The prosthesis SR was reported between 99% and 100% for the follow-up period of 12 months. Proper patient selection, thorough evaluation of patients, and good surgical skills of the operator are important to establish predictable treatment outcomes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

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  [Table 1], [Table 2], [Table 3], [Table 4]
This article has been cited by1 Clinical success between tilted and axial implants in edentulous maxilla: A systematic review and meta-analysis ShrutiParthiv Mehta, PriyankaVaibhav Sutariya, MansoorkhanRafikahmed Pathan, HemilHitesh Upadhyay, SurbhiRavi Patel, NidhiDhaval Gupta Kantharia The Journal of Indian Prosthodontic Society. 2021; 21(3): 217 [Pubmed] | [DOI]