ADVANTAGES AND LIMITATIONS OF BARS AND LOCATOR ATTACHMENT

Headnote

Abstract

Edentulous patients face many problems, like mastication and phonation difficulties, discomfort, poor stability, poor retention, and of course, a decrease in selfconfidence because of the aesthetics. Implant-supported overdentures represent a modern method that helps restore the above disfunctions. Two treatment cases are presented, one for bar system and one for locator overdentures. The reasons to choose the one or the other were bone support, the divergence of the implants axis, available space, technical difficulty, and price. The bar and locator overdentures offer the stability and retention of a fixed prosthesis and the advantages of classic removable prostheses. Overdentures are easy to maintain, their costs are moderate, but regular visits to the dentist for maintenance and possible future repairs should not be neglected.

Keywords: locator over dentur es, bar overdentures, edentulous, supported implant.

1.INTRODUCTION

The problem of the edentulous patient is widespread throughout the world. Because of various problems like dental and periodontal disease, congenital defects or trauma, the teeth are lost and, if the situation progresses, total edentulism can set in. Also, unfortunately, there is evidence to support this negative correlation between edentulism and a low socioeconomic status, which will influence patients in choosing the type of prosthesis [1].

When edentulous patients use conventional complete dentures, they often have difficulties because of poor retention, reduced support and stability and decreased phonetic and chewing ability [2]. Implant-supported overdenture helps restore the above disfunctions. This type of rehabilitation is documented as a successful and financially viable method [3], with many advantages over the classic prosthetic options, namely: increased retention and stability, limited lateral movements, less traumatized soft tissues, ease of adaptation of the patient to the new situation and increased self-confidence. Another benefit for patients with implant overdentures is that they experience a low amount of bone resorption, compared to those with conventional complete dentures. Also, the surgery is a simple process, not requiring a large number of implants and the osseous and peri-implant response to overdenture was noticed to be a favorable one [4].

The locator and the bar systems are implant overdenture systems used to solve most clinical cases. Each of these systems has strong and weak points and must be used according to their recommendation. Over time, the clinical studies comparing the locator with other attachment systems have shown that the system locator has the highest level of maintenance among attachments [5,6].

Aim

The purpose of this article is to identify the advantages and limitations of the bar and locator systems for implant-supported overdentures. We support our opinion with a presentation of two treatment cases, one for each system discussed.

2.MATERIALS AND METHODS

As a starting point, an electronic search of the scientific literature was performed on PubMed, using keywords such as locator overdentures and bar overdentures. A total number of 963 articles published between 1999 and 2021 were found using keywords such as locator overdentures (378 articles), bar overdentures (585 articles). The inclusion criteria refer to the content of relevant information, provided in English, while the exclusion criteria eliminated studies irrelevant to the aim of our article. The reasons to choose one or another of the presented systems were bone support, divergence of the implants axis, available space, technical difficulty, and price.

The anchoring system must be chosen according to the anatomy and features of the edentulous patient, the degree of parallelism of the implants, the height of the peri-implant gum, the position and number of implants, the need for retention, antagonists and occlusion, patient's level of hygiene, age of the patient, so that he can easily and safely maneuver the overdenture, and of course, patient's budget [7].

Bar Overdenture

The bar system uses a cast metal bar that performs a rigid interconnection between implants. This is the right choice when more than 2 implants are used, but there are cases when the system uses only 2 implants; in these situations, they are usually placed in straight line on the crest of the ridge. The characteristic of this system is the connection between the basis of the prosthesis and the bar that secures the attachment retentive quality. The prosthesis rests on the adjacent mucosa for support and, at the same time, it is made to fit passively and attach to the bar.

The ideal length of a single bar to provide good retention and support should be around 20-22 mm, but it is adapted to each clinical case. There are many types of bars with different shapes on cross sections, like inverted U-shape, ovoid, circle, or round shape. The bar can be made from different materials like plastic, Co-Cr, ZrO2 prefabricated like type IV gold, titanium grade 4, 5 or of pure titanium, which can be milled by CAD/CAM [8-10].

Locator Overdenture

The locator system is available in different dimensions, with heights from 1 to 6 mm and different angles. This system stood out through its ability to self-align, as it can tolerate a divergency up to 40° of the implant axis. Usually, two implants are sufficient for this method to be effective. In the case of total mandibular edentation, it is preferable that they be placed at a sufficient distance from each other, the ideal location being the positions of the first premolar. This is meant at minimizing any possible anteroposterior rotation, which would happen if positioned on the central incisors, for example. The attachment components ensure the retentive quality for these systems, while the basis of the prosthesis contacts the mucosa correctly [11-13].

Since 2001, locator attachment has started to be used. This system is characterized by using implants as independent units, which are connected separately to an overdenture. This method assures easy insertion and disinsertion, dual retention, with no splinting of implants [14].

3.RESULTS / CASE REPORTS

Bar supported overdenture

A 55 year-old non-smoker and healthy female visited the dentist to rehabilitate her edentulous mandible. After a detailed consultation, radiography and CBCT, it was decided that the patient will be prosthetically rehabilitated with a bar overdenture. Two surgeries were successfully performed. In the first one, two Alpha Bio implants were inserted in 4.3 and 3.3 places and a bar overdenture was anchored over the osseointegrated implants (Fig. 1). After three years, a second surgery was performed and two ICX-Premium implants were inserted in 4.4 and 3.4 places for a future fixed prosthesis on implants. The patient declares that she was satisfied along the three years with overdenture, she had no problems with masticatory and phonetic function and oral hygiene was also easy to maintain (Fig. 2).

Locator supported overdenture

A 68 year-old smoker male patient visited the dentist for complete oral rehabilitation. After a detailed consultation, radiography and CBCT, it was decided that he will be prosthetically rehabilitated with locator overdenture. In the first stage, the old prostheses were removed and then the remaining teeth 1.7, 1.5,1.2, 1.1, 2.1, 2.3, 2.7 needed to be extracted. In the following surgery stages, 4 ICX-ActiveMaster implants: 1.5, 2.5, 3.4, 4.4 were inserted (Figs. 3,4). The patient was rehabilitated with locator overdentures and, as in the previous case, he declared that he is satisfied and can easily perform the chewing and phonetic functions (Figs. 5-7).

Both procedures described above are modern and effective methods of overdentures, each having a number of advantages and disadvantages.

The locator system can be defined as a nonrigid connection anchorage which uses modern solitary attachments. The locator is characterized by a number of advantages, the first being the self-alignment and tolerance for implant divergency up to 40°. So, given the advantages described above, if we have a suboptimal insertion of implants, it is preferable to use the locator anchoring system to correct the implantation axis [15].

Also, if we use the locator, we will need just a minimum vertical height and a minimal number of implants. Usually, two implants are sufficient, but there are ideal situations that involve low prices, being also minimally invasive, in which only one implant can be used. It has been observed that the complications are minimal and the success rate is relatively high [16]. Another advantage that should not be neglected refers to the technical part. They are easy to manufacture and involve simple repairs when needed [17].

Despite these advantages, this system has a number of limitations that should be taken into account. First, the divergence that can be allowed between the implants has limits. Also, over time, bone resorption is installed, especially in the posterior areas, so that regular visits to the dentist are necessary in order to maintain or replace the attachments [18]. If we talk about maintenance costs, they can be usually high, so the patient needs to be informed of future costs and future visits to the dentist [19].

However, the locator system is a wise choice for rehabilitation, the survival rate of the implant being, according to some studies, 95.2% [20].

The other system, bar overdenture, also has a success rate from 96.3% to 98.2%, according to literature [21]. Some authors have concluded that a bar overdenture is a great choice, especially when the splint is needed and parallelism between implants is difficult to obtain.

An advantage of the bar system is that it offers a very good stability and retention, but it should 4. DISCUSSION

be noted that this retention could lead to functional limitations of the tongue, because it interferes with the anatomy of the jaw. Anyway, patients associated the bar system with good chewing efficiency and a great satisfaction [22].

As disadvantages, the bar system is more expensive than the locator. Also, the use of the bar system will induce high bone stress that increases proportionally with the height of the bar, resulting in mechanical complications, periimplant stress and even installation of a vertical movement [23].

Selection of one of these methods depends on bone's condition at the time of examination. If the edentulous ridge is thick enough to stabilize the prosthesis when applying lateral forces, the locator is a good long-term choice. When bone resorption is important and movement may occur during chewing, the use of overdenture on the bar is recommended.

Both systems have been shown as effective in this respect, and studies have evidenced no significant differences between them [24].

Another important thing is patient's wellbeing, which must be closely monitored, because the prosthesis has an important effect on his psychic condition.

However, studies show that the patient is satisfied primarily when the prosthesis does not cause pain or discomfort, pain being the first thing the patient will notice and complain about. The masticatory function is also extremely important. If the patient can use his prosthesis to eat without problems, then he will definitely be satisfied. Two other important functions are phonation and aesthetics. Patient's well-being will be directly proportional to the performance of these functions without difficulty, increasing his self-confidence. Regarding patient's psyche, studies do not show any significant difference between these two methods, but a major difference between conventional prosthesis and overdenture, which is felt by the patient as a part of his body; also, patients with overdenture, especially the elderly ones, were satisfied with their quality of life related to oral health.

Both methods of attachment overdenture contribute to the well-being of the patient who can perform the functions described above, thus increasing his self-confidence [25,26].

5. CONCLUSIONS

The bar and locator overdentures offer the stability and retention of a fixed prosthesis and, at the same time, the advantages of classic removable prostheses. Overdentures are easy to maintain, their costs are moderate, but regular visits to the dentist for maintenance and possible future repairs should not be neglected.

Both types of systems have advantages and disadvantages, but there are no important differences between them. These two systems must be considered modern and effective methods of prosthesis application, overdenture being an alternative that offers stability and implicitly an efficient mastication, as well as an increased comfort to the totally edentulous patient.

It is important to examine the patient correctly, so that we can choose the best anchoring method for every case.

References

References

1. Al-Rafee MA. The epidemiology of edentulism and the associated factors: A literature Review. J Family Med Prim Care. 2020;30;9(4):1841-3.

2. Kim HY, Lee JY, Shin SW, Bryant SR. Attachment systems for mandibular implant overdentures: a systematic review. J Adv Prosthodont. 2012;4(4):197203.

3. Feine JS, Carlsson GE, Awad MA, Chehade A, Duncan WJ, Gizani S, et al. The McGill consensus statement on overdentures. Mandibular twoimplant overdentures as first choice standard of care for edentulous patients. Gerodontology. 2002;19(1):3-4.

4. Warreth A, Alkadhimi AF, Sultan A, Byrne C, Woods E. Mandibular implant-supported overdentures: attachment systems, and number and locations of implants-Part I. J Ir Dent Assoc. 2015;61(2):93-7.

5. Kleis WK, Kämmerer PW, Hartmann S, Al-Nawas B, Wagner WA Comparison of three different attachment systems for mandibulartwo-implant overdentures: one-year report. Clin Implant Dent Relat Res. 2010; 12(3):209-18.

6. Cakarer S, Can T, Yaltirik M, Keskin C. Complications associated with the ball, bar andLocator attachments for implant-supportedoverdentures. Med Oral Patol Oral Cir Bucal. 2011;16(7):e953-9.

7. Chee WW. Treatment planning: implant-supported partial overdentures. J Calif Dent Assoc. 2005;33(4):313-6.

8. Abdelrehim A, Abdelhakim A, ElDakkak S, Influence of different materials on retention behavior of CAD-CAM fabricated bar attachments. J Prosthet Dent,. 2021; doi:10.1016/j.prosdent.2021.01.012.

9. de la Rosa Castolo G, Guevara Perez SV, Arnoux PJ, Badih L, Bonnet F, Behr M. Implant-supported overdentures with different clinical configurations: Mechanical resistance using a numerical approach. J Prosthet Dent. 2019;121(3):546.e1-546.e10

10. Nogueira MCF, Bacchi A, Mesquita MF, Santos MBF, Consani RLX. Influence of Cross-Section Design and Vertical Misfit on Stress Distribution in Overdenture Retaining System: 3-Dimensional Finite Element Analysis. Implant Dent. 2018;27(4):445-51.

11. Schneider AL, Kurtzman GM. Restoration of divergent free-standing implants in the maxilla. J Oral Implantol. 2002;28(3):113-6.

12. Sadig W. A comparative in vitro study on the retention and stability of implant-supported overdentures. Quintessence Int. 2009;40(4):313-9.

13. Damghani S, Masri R, Driscoll CF, Romberg E. The effect of number and distribution of unsplinted maxillary implants on the load transfer in implantretained maxillary overdentures: an in vitro study. J Prosthet Dent. 2012;107(6):358-65.

14. Trakas T, Michalakis K, Kang K, Hirayama H. Attachment systems for implant retained overdentures: a literature review. Implant Dent. 2006;15(1):24-34

15. Tokar E, Uludag B. Effects of Low-Profile Stud Attachment Configurations on Stress Distribution Characteristics of Implant-Retained Overdentures. Int J Oral Maxillofac Implants. 2018; 33(4):754-63.

16. Padmanabhan H, Kumar SM, Kumar VA. Single Implant Retained Overdenture Treatment Protocol: A Systematic Review and Meta-Analysis. J Prosthodont. 2020; 29(4):287-97.

17. Chee W, Jivraj S. Treatment planning of the edentulous mandible. Br Dent J 2006;201(6):33-47.

18. Patodia C, Sutton A, Gozalo D, Font K. Cost and complications associated with implant-supported overdentures with a resilient-attachment system: A retrospective study. J Prosthet Dent. 2022;128(2):181-6.

19. Chaware SH, Thakkar ST. A systematic review and meta-analysis of the attachments used in implantsupported overdentures. J Indian Prosthodont Soc. 2020;20(3):255-68.

20. Wang F, Monje A, Huang W, Zhang Z, Wang G, Wu Y. Maxillary four implant-retained overdentures via Locator® attachment: Intermediate-term results from a retrospective study. Clin Implant Dent Relat Res. 2016;18(3):571-9.

21. Jivraj S, Chee W, Corrado P. Treatment planning of the edentulous maxilla. Br Dent J 2006;201(5):26179.

22. Seung-Ryong Ha, Sung-Hun Kim, Seung-Il Song, Seong-Tae Hong, Gy-Young Kim, Implantsupported overdenture with prefabricated bar attachment system in mandibular edentulous patient J Adv Prosthodont. 2012;4(4):254-8.

23. Joshi S, Kumar S, Jain S, Aggarwal R, Choudhary S, Reddy NK. 3D Finite Element Analysis to Assess the Stress Distribution Pattern in Mandibular Implantsupported Overdenture with Different Bar Heights. J Contemp Dent Pract. 2019;20(7):794-800.

24. Naert I, Gizani S, Vuylsteke M, Van Steenberghe D. A 5-year prospective randomized clinical trial on the influence of splinted and unsplinted oral implants retaining a mandibular overdenture: prosthetic aspects and patient satisfaction. J Oral Rehabil 1999;26(3):195-202.

25. Mahanna FF, Elsyad MA, Mourad SI, Abozaed HW. Satisfaction and Oral Health-Related Quality of Life of Different Attachments Used for Implant-Retained Overdentures in Subjects with Resorbed Mandibles: A Crossover Trial. Int J Oral Maxillofac Implants. 2020;35(2):423-31.

26. Kuoppala R, Näpänkangas R, Raustia A. Quality of Life of Patients Treated With Implant-Supported Mandibular Overdentures Evaluated With the Oral Health Impact Profile (OHIP-14): a Survey of 58 Patients. J Oral Maxillofac Res. 2013;4(2):e4.