Old age has been associated with patients exhibiting a highly compromised dentition with regard to number of teeth, periodontal disease, bone loss, and caries; hence, planning for a fixed prosthesis becomes extremely difficult. Edentulism is a debilitating and irreversible condition and is described as “ultimate marker of disease burden for oral health.”¹ The rate of edentulousness differs much between countries, and it has declined dramatically during the last few decades since it is related to a number of factors, such as socio-economy, tradition, oral health resources, and not only to dental diseases. The overall prevalence of edentulism is about 16.3% in India among older adults (50 years and above).²

The most common practically approached treatment plan for such patients is the fabrication of a conventional complete denture. In general, the patients are satisfied with the provision of such dentures with about 30% of them having unrealistically high expectation toward the functioning of their dentures.³ With continuous use of such prosthesis, the oral functions, nutritional intake, communication, and the overall confidence is put at risk of creating psychosocial problems.⁴ The desire of patients to have an intact arch of functional and aesthetically pleasing teeth may pose dentists with various challenges.⁵

Ledger in 1856 was the first to use natural teeth as an anchorage for removable dentures and aid in stabilization.⁶ In 1950s. the concept of using dentures superimposed on natural teeth was popularized by Rehm, Brill, and Miller which improved the functional efficiency.⁷,⁸,⁹ In 1969, Morrow et al. and Lord and Teel came out with various concepts, techniques, and textbooks suggesting the reduction of a few millimeters of natural teeth to support dentures.¹⁰,¹¹ In 1996, Prieskel gave an elaborative explanation regarding overdentures guiding the dentists about how to approach a case.¹²

The ultimate goal of maintaining the roots was to prevent alveolar bone resorption, provide better load transfer to the underlying structures, maintain sensory feedback and achieve better stability. Furthermore, the patient feels that he/she is not completely edentulous and thereby improving the psychological aspect also. Mericske-Stern et al. in 1994, had come to a conclusion that the tooth-supported overdenture was an effective alternative approach to complete dentures.¹³

Brånemark et al. came up with an idea of a fixed prosthesis on 5–6 implants as a viable treatment for edentulous jaws, and during many years this was the dominating concept with extremely successful long-term results. In the mid-1980s, treatments with mandibular implant overdentures were introduced as being less expensive and less complicated but yet successful.¹⁴ The level of satisfaction experienced by the patients with severely resorbed mandibles provided by implant-supported overdentures can be compared with the satisfied wearers of conventional dentures with improvement in chewing comfort and better stability.¹⁵ There have been studies that demonstrate implant-supported overdentures being as efficient as a fixed prosthesis for parameters such as masticatory function and patient satisfaction. The implant-supported overdentures have certain advantages over tooth-supported overdentures as the caries risk is nonexistent and can offer a variety of denture designs. The disadvantages being reduced sensory feedback because of the absence of periodontal receptors and higher costs.¹⁶

This systematic review compares the functional efficiency of tooth-supported and implant-supported overdentures in patients requiring oral rehabilitation and come to a conclusion whether the teeth be saved or replaced with implants when both the methods are accessible and acceptable to a patient.

Protocol and registration

This systematic review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines 2015. The detailed protocol was registered at the National Institute for Health Research PROSPERO International prospective register of systematic reviews under the registration number CRD42021234190.

Focused question

The systematic review aimed to answer the following question: Is there any difference in the functional efficiency in humans who have undergone oral rehabilitation by tooth-supported overdentures and implant-supported overdentures?

The population, intervention, comparisons, outcomes format was used to define a focused clinical question.

Population/Participants: Humans who have received tooth-supported overdentures and implant-supported overdentures for oral rehabilitation

Inclusion criteria

Following studies were included:

Randomized control trials, case–control studies, cohort studies, systematic reviews, review literature

Exclusion criteria

Following studies were excluded: Reviews, case reports, case series, abstracts, editorials, letters, studies including animal experiments and historical reviews, in vitro studies, studies that were not performed comparing the two groups and incomplete data that did not allow the collection of information.

Information sources

Electronic databases

PubMed/Medline, Google Scholar, and Cochrane Library were searched for studies in English without time restrictions, reporting functional efficiency in tooth-supported versus implant-supported dentures patients.

The last search was performed in February 2021.

Search strategy

Two reviewers independently performed the search (A. K and S. W). Combinations of controlled terms (MeSH), keywords and Boolean operators were used whenever possible. A detailed description of the search strategy is given in Table 1.{Table 1}

Study selection

After duplicate records were removed, two investigators (A. K and S. W) independently performed the study selection by initially screening the title and abstract according to the inclusion criteria. The inclusion of articles for the full text analyses was performed only after a mutual agreement between the two. Where there were disagreements, it was resolved by means of a consensus discussion presided over by the third reviewer (A. Kh). Inter-reviewer agreement was measured through Cohen's kappa (k = 0.84).

Data extraction

Data extraction was performed independently by the two reviewers (A. K and S. W) according to the aims of the present systematic review and was reciprocally blinded to each other's extraction. Disagreements between the review authors were discussed and resolved with a third review author (A. Kh). The data extracted, comprises the characteristics of the eligible studies which were put into a customized data extraction form.

Study selection

We followed the PRISMA guidelines for methodology. The study selection process is summarized in Figure 1 (PRISMA flow chart). The total number of hits was 4004. After removing the duplicates, 3469 hits were scrutinized for inclusion in the study. All the titles and abstracts were screened based on the selection criteria. The studies that did not meet the inclusion criteria were excluded. Subsequently, the full text of selected articles was assessed independently by two reviewers. Five articles were selected from screening. Following careful examination, discussion was conducted depending on the selection criteria amongst the reviewers. Any discrepancies in opinion were resolved by the third reviewer. Ultimately, five articles were finalized for further analysis. All the statistical analysis were performed using the statistical software Review Manager version 5.3 (The Nordic Cochrane Centre, Copenhagen, Denmark).Figure 1

PRISMA flow diagram showing the studies exclusion and final inclusion with reasons. PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

According to the World Health Organization criteria, people with no teeth are considered physically impaired. Edentulous patients could also be considered disabled, due to their inability to eat and speak effectively, which are two of the essential tasks of life; they could be considered handicapped, as they tend to avoid eating and speaking in public.¹⁷ Having a functional masticatory system is critical for the individual to replace the body's nutrients and maintain optimal overall health. To minimize bone loss, chronic mucosal irritation, and functional problems for the denture patient, provision of tooth-supported complete denture therapy and low-cost dental implant therapies, along with establishment of routine recall systems for these patients, should be the ultimate goal for the dental professional.¹⁸

The concept of conventional tooth-retained overdentures is a simple and cost-effective treatment than the implant overdentures. When few firm teeth are present in an otherwise compromised dentition, they can be retained and used as abutments for overdenture fabrication. This helps improve the retention and stability of the final prosthesis significantly. The concept of overdentures may not be the elixir, but it is a positive means for delaying the process of complete edentulism and helps in the preservation of bone. To top it all, it gives the patient the satisfaction of having prosthesis with his natural teeth still present.¹⁹

Osseointegrated dental implants revolutionized the conventional prosthodontic treatment. Implant-retained or supported prostheses produce a greater biting force and masticatory efficiency than conventional dentures.²⁰

This systematic review aimed at comparing the functional efficiencies of tooth-supported and implant-supported overdentures.

Carlsson defines masticatory ability as an individual's own assessment of his or her masticatory function, whereas masticatory/chewing efficiency is defined as the capacity to reduce food during mastication or to achieve a certain particle size reduction. Bates et al. defined masticatory performance as the particle size distribution of food when chewed for a given number of strokes. Hence, masticatory performance is an objective masticatory function which has often been measured by clinical mastication tests, while masticatory ability is a self-assessed masticatory function studied by interviewing subjects or questionnaires based on their oral function.²¹,²² A total of five articles were shortlisted out of which four studies were clinical trials and 1 was a questionnaire based follow-up study.

Fontijn-Tekamp et al. used three parameters namely unilateral bite force, maximum bite force and chewing efficiency.²³ The bite force was measured using a miniature strain-gauge bite force transducer with a vertical height of 3.8 mm. Subjects were instructed to bite on two force levels: (1) equivalent to force they use when chewing and (2) maximum force. The unilateral bite force of implant-supported overdentures was comparable to that of the root-overlay dentures whereas maximum bite force was higher for subjects with dental implants. The possible reason for these differing statistics may be because of the negative feedback from periodontal receptors as well as painful compression of the marginal gingiva of the remaining roots. However, on comparing the chewing efficiency, the subjects with natural roots under overdentures had a significant edge over the subjects with dental implants. Most of the implant subjects had enough force to pulverize the food but were unable to manipulate it adequately between posterior teeth which led to poor chewing efficiency.

Chen et al. compared the masticatory efficiency, mandibular excursions and the electromyographic (EMG) analysis of implant-supported and tooth-supported overdentures.¹⁶ The mandibular excursions were recorded with a kinesiograph (K5AR, Myotronics Inc., Tukwila, Wash). The tracings were evaluated according to the standard chewing cycle outline of the classification of Ahlgren.²⁴ The EMG recording were performed with MEB-5508K EMG equipment (Nihon Kohden Inc., Tokyo, Japan). The masticatory efficiency, control of chewing cycles and centralization of end tracings in the cycles of implant-supported overdenture group, although not significant, had the tendency of being higher than that of the tooth-supported overdenture group (P > 0.05). On the contrary, the results showed a greater amplitude of EMG in temporal muscle in subjects with tooth-supported overdentures. Haraldson et al. demonstrated that in all masticatory muscles, only the amplitude of the temporal muscle is positively related to occlusal force.²⁵ Therefore, it can be inferred that the partly preserved periodontal proprioceptors might be beneficial to the preservation of masticatory muscle function. Slagter et al. showed that the peak amplitudes of masticatory muscles in chewing excursions were only slightly related to the reduction in particle size of chewed food.²⁶ This suggests that masticatory efficiency is more correlated to mandibular excursions and less correlated to masticatory muscle bioelectric activity.

Hug et al. evaluated the patient satisfaction after a 2-year follow-up through a prosthetic questionnaire using visual analogue scale.²⁷ All patients were asked to answer a 9-item questionnaire. The adjustments and repairs of the denture were observed more frequently in root-supported group especially in the 1^st year of the prosthesis delivery whereas all 9 questions showed a tendency of higher mean values with implant-supported group. Subjects of the root-supported group were dissatisfied because of frequent dislodgement of copings or activation of female components and some studies indicate a limited prognosis for roots because of their greater susceptibility to caries and periodontal problems. Caries rates of up to 35% were reported even in the presence of a high standard of oral hygiene.²⁸

Shah et al. compared the biting force using a force transducer and the EMG activity of the masseter muscle.⁴ No statistically significant difference in masseter muscles' EMG recording in the rest position between both the groups was observed. Decreased masseter muscles' EMG activity in tooth-supported overdenture group than implant-supported overdenture group during initial tooth contact position was recorded. Patients with implant-supported overdentures exhibited greater masseter muscles' EMG activity during maximum voluntary clench and experienced greater increase in the maximum biting force than tooth-supported overdenture group. Patients with tooth-supported prosthesis still had tactile proprioceptive reflex rising from periodontal ligament that alarm them against overload.

Gargari et al. developed a patient-based questionnaire about the functional differences between tooth-supported and implant-supported prosthesis with a follow-up of 1 year.²⁹ The questionnaire was developed with 6 questions, the themes of which were identified around social, emotional, and practical issues about eating. No statistically significant differences were found between tooth-supported and implant-supported overdentures and the patients show high level of satisfaction for masticatory function, esthetics, and phonetics in both the groups.

Different oral health conditions may be found with regard to the number of remaining teeth, dental and periodontal health, or type and quality of prostheses. Individual subjective treatment need is based on previous dental experience, self-esteem, self-assessment of general health, mental disorders, mobility, economics, and fear of dental treatment.³⁰

From recent investigations on implant-supported overdentures, one can conclude that this treatment concept is more successful than treatment with overdentures supported by natural roots. Therefore, a final question is posed: shall teeth be saved or instead replaced by implants? Apart from individual wishes and psychologic aspects, namely anxiety of the patients to undergo surgery, strong desire to retain their teeth, previous experience with removable partial prostheses or complete dentures, and predictability of success, some objective differentiations have to be made. More problems with maxillary implants were encountered and reported in various studies: thin bone, loose bone structure, large sinus that does not allow the placement of multiple implants, and divergent implant axes. Force distribution seems to be less favorable with maxillary implants than with fixed prostheses when maxillary dentures are loaded. These observations lead to the conclusion that natural roots should be maintained in the maxillae, preferably if their strategic position is favorable. If maxillary implants are planned for overdenture support in the edentulous patient, support should be provided by four implants with rigid connections. Only minor problems are faced with mandibular implants. Clinical experience gives evidence that two implants provide sufficient support. Therefore, it is advisable to abstain from heroic endodontics and extensive periodontal treatment to save a few remaining teeth. The cost-effectiveness of implants will be more favorable.

There have been several studies which have compared the functional efficiencies of conventional dentures with overdentures where it is a proven fact that overdentures have an upper edge over conventional dentures. However, when it comes to comparing the functional efficiencies within the overdenture group namely tooth-supported and implant-supported, there is very limited literature.

Out of the five articles selected for this systematic review, three were in favor of implant-supported overdentures, one was in favor of tooth-supported overdentures and one showed no statistically difference between the two groups.

Therefore, it is difficult to come to a conclusion as to which one is better than the other.

Nevertheless, the ultimate choice of treatment for the type of prosthesis is based on individual's needs and oral health conditions and the prognosis of the same depends on how well it is being maintained.

Financial support and sponsorship

Nil.

Conflicts of interest

The authors of this manuscript declare that they have no conflicts of interest, real or perceived, financial or nonfinancial in this article.