Edentulism, defined as the complete loss of all dentition, is a worldwide phenomenon. Edentulism occurs because of biologic disease processes, such as dental caries, periodontal diseases, trauma, and oral cancer. Edentulism is accompanied by several comorbidities that can significantly influence an individual. Although the rate of edentulism is declining, the number of edentulous patients continues to rise because of the increase in population. The management of edentulous patient has been addressed since the early days of dentistry. This article describes complete dentures and their maintenance, and advanced technology in complete dentures, and in implant-retained and implant-supported prosthesis.
Key points
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Edentulism is a global phenomenon and it is projected to remain in high numbers for many countries.
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Complete dentures are widely used for edentulous patients and proper maintenance, timely recall, and patient education are essential for their success.
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With advanced technology in CAD/CAM, digital dentures may provide advantages in its material, method of fabrication, and favorable clinical outcomes.
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As dental implants have improved the treatment of edentulous patients the use of fewer numbers of implants has led to alternative treatment options.
Introduction
Prevalance of Edentulism
Edentulism, defined as the complete loss of all dentition, is a worldwide phenomenon. According to the World Health Organization criteria, edentulous patients are considered physically impaired, disabled, and handicapped because of their inability to properly masticate and speak.
Edentulism occurs because of biologic disease processes, such as dental caries, periodontal diseases, trauma, and oral cancer. Social and/or behavioral factors that have led to this disease state include poor access to care or third-party payer or insurance systems that may limit the types of care the patient receives.
The estimated edentulous population in the United States is greater than 36 million. For adults 18 and older, approximately 10% (9.7%) are edentulous, with the rate increasing with age. About 26% of the population in the United States between the ages of 65 years and 74 years, approximately 23 million people, are completely edentulous and another 12 million are edentulous in one arch. Among the geriatric population that is greater than 65 years, the ratio of edentulous individuals to dentate individual is 2 to 1. In Europe, prevalence of edentulism ranges from 15% to 72% for the elderly 65- to 74-year age group population in various countries. Ren and colleagues reported that in China adults aged 65 to 74 were 11 times more likely to become edentulous, and adults older than 75 were 24 times more likely to become edentulous compared with the 45 to 54 age group.
Although the trend of edentulism has been reported to have declined in prevalence in many countries, because of an increase overall in the elderly population, the number of edentulous individuals has not declined. In the United States, the rate of edentulism has been declining and is projected to be reduced to a rate of 2.6% by 2050. It is projected that there will be less than 9 million edentulous people by 2050. Other areas of the world are foreseeing an increase among their adult population. A study by Cardoso and colleagues reported edentulous patients in Brazil were declining in the teenage and middle-aged adults, but will increase among the elderly population, reaching more than 64 million by 2040. Therefore, the need to restore edentulous patients to function will not only remain but will increase in the future globally.
The latest trends show that there are no gender biases for edentulism. Men and women are nearly equally likely to become edentulous. However, socioeconomic status does seem to play a role. There are higher percentages of edentulism shown in those who are below the poverty level (14.3%). By race, Wu and others reported that Native Americans had the highest prevalence (23.98%) for edentulism, followed by African Americans (19.39%), white persons (16.90%), Asians (14.22%), and Hispanics (14.18%) for adults older than the age 50.
Edentulism is accompanied by several comorbidities that can significantly influence an individual. According to Felton, edentulous patients were associated with poor dietary habits and nutritional intake, osteoporosis, and increased risk of having hypertension and coronary artery disease. The literature has reported edentulous patients are more likely to be smokers and have smoking-associated diseases, such as asthma, emphysema, and cancer. Health-related quality-of-life studies indicate that edentulism can affect the quality of life, where patients report to have unsatisfactory esthetics and lowered self-esteem. Socially, denture wearers have revealed they keep their dentures a secret from friends, siblings, and spouses. Furthermore, some denture wearers may avoid certain social situations, such as eating at weddings and parties, and avoiding job interviews and networking with other professionals.
Complete denture as replacement of teeth
Complete denture rehabilitation remains one of the most popular and traditional prosthodontic treatment options for edentulous patients who have systemic, anatomic, and/or financial limitations ( Fig. 1 ). Successful outcomes of complete denture patients may depend on prognostic factors, such as age of patient, patient demographic, psychological factors and personal traits, previous denture experience, expectation and attitudes, residual ridge form and anatomy, method of construction, quality of dentures and changes over time, and esthetics. Although there has been much debate on the influence or significance of these factors on the outcome of denture therapy, one thing that is certain is the sequelae of prolonged denture use.
Residual ridge resorption is a phenomenon that describes the life-long remodeling of the alveolar ridge after dental extractions, where the size of the residual ridge is reduced most rapidly in the first 6 months and continues throughout life at a slower rate. Residual ridge resorption has been described as being chronic, progressive, irreversible, and catabolic. There are several studies that have examined this phenomenon in the past; describing the process by using standardized measurements in panoramic radiographs, lateral cephalographs, and diagnostic casts. The rate of resorption can differ based on the individual and jaw location. It is influenced by different anatomic, prosthetic, metabolic and systemic, and functional factors. Additionally, studies have investigated the association of residual ridge resorption and systemic conditions, such as osteoporosis, menopause, age, and gender. There was a higher tendency for narrower ridges with elderly women, estrogen deficiencies, and vitamin supplements helped with minimizing ridge resorption. Different prosthetic and functional factors have been evaluated in their roles in residual ridge resorption, such as immediate dentures, zero degree teeth, and duration of denture wearing. Previous studies have reported increased amount of ridge resorption associated with immediate dentures, zero degree or nonanatomic teeth, and prolonged denture use.
As the by-product of residual ridge resorption, adaptation of the denture base can change significantly. Ill-fitting dentures can cause the following mucosal changes: traumatic ulcers, denture stomatitis, candida infection, angular chelitis, and soft tissue hyperplasia. Resilient lining material compensates for the resorbed tissue and allows tissue recovery to take place. Reline is defined as “the procedure used to resurface the tissue side of a removable dental prosthesis with new base material, producing an accurate adaption to the denture foundation area.” Resilient lining materials are either an elastomeric silicone or plasticized acrylic resin. Over time, the plasticizers can leach out of the reline material and become much harder, whereas elastomeric silicone is more dimensionally stable. However, the bonding of the silicone to the denture base is unreliable long-term.
Commercially available denture cleansers can roughen the surface of the lining materials, leading to biofilm formation and Candida albicans colonization. Therefore, prolonged use of a resilient liner, compared with more stable laboratory rebasing, should be cautioned.
Denture relining materials are often used to accommodate hard and soft tissue changes during healing periods. When this is the case, the duration of need for the denture reline is unpredictable because of variability in healing times of individual patients. A recent study by Puri and colleagues showed that bone turnover markers known as serum osteocalcin and C-terminal telopeptides, which are easily assessed in blood, were linked with increased number of relines among denture patients. Therefore, in the future, certain biologic markers may potentially inform the clinician of the proper timing to perform the laboratory rebase.
Fit, retention, and stability of the prosthesis are hallmark to successful complete denture therapy. Therefore, establishing a recall regimen and consistent and periodic monitoring of soft and hard tissue health is essential for successful complete denture therapy. Felton and colleagues published guidelines for proper care and maintenance for complete dentures. Properly educating patients regarding the significance of denture care and maintenance is recommended. Several key points, such as storage, biofilm formation, disinfection, and use of denture adhesives, were described in detail. It was recommended that biofilm on dentures should be removed every day with an effective, nonabrasive cleaner; dentures should never be placed in boiling water or bleach solution for more than 10 minutes; and although use of denture adhesives is helpful, the period of usage should not exceed 6 months and assessment of oral health care provider for supporting tissue is recommended at that time. Teaching patients to recognize the changes occurring in their own mouth and to return to their dental provider can prevent further problems and successfully prolong the use of their prostheses.
Advancement in complete dentures
The methods of conventional complete denture fabrication have remained unchanged for the past 70 years since the introduction of polymethylmethacrylate in 1936. Over the decades, acrylic resin has demonstrated improvements in its physical properties and polymerization processes with the introduction of autopolymerizing, compression-molded, microwave-processed, and injection-molded techniques. The conventional protocol for fabrication of complete dentures involves a complex sequence of clinical and laboratory steps. On average, this process requires at least five clinical appointments ; which can consist of recording the horizontal and vertical relationships of the jaws and transferring it accurately to the semiadjustable articulator, patient approval of the esthetics, and the unavoidable postinsertion adjustment visits. This minimum number of appointments may discourage clinicians from offering rehabilitation of edentulism with complete dentures as part of their services.
Computer-aided design/computer-aided manufacturing (CAD-CAM) has made significant contributions in dentistry since its early introduction in the 1980s. With the advent of this technology and its successful application in the realm of maxillofacial, fixed, and implant prosthodontics, CAD-CAM technology was recently applied to the fabrication of complete dentures to simplify the clinical and laboratory procedures, and to establish cost- and time- efficient protocols that would provide favorable outcomes for edentulous patients.
These advancements in digital fabrication have had a significant impact on conventional complete denture fabrication processes. The methods for construction of complete denture using CAD-CAM technology have been previously reported ( Figs. 2 and 3 ). These methods simplify and shorten the number of patient visits. A recent review by Steinmassl and colleagues described six different commercially available CAD-CAM denture systems and their methods of fabrication and the number of patient visits required. Most of the companies described use subtractive technology to mill the dentures (ie, Wieland Digital Denture, Baltic Denture System Global Dental Sciences), whereas others use additive manufacturing with three-dimensional printing (ie, Dentca). In both techniques, scanning of the clinical records obtained either through master casts or definitive impressions are digitized and allow for designing and milling of the monolithic prosthesis or the denture bases.
The subtractive manufacturing process uses prepolymerized resin pucks fabricated under high heat and pressure, which supposedly results in less monomer release, higher density, and less microporosity and polymerization volumetric shrinkage. The decrease in monomer residual and porosity have been linked with having less microbial colonization on denture surfaces and increased biocompatibility with the oral environment compared with its conventional counterpart. This method of fabrication eliminates the errors of conventional denture processing, which include denture warpage, volumetric and linear shrinkage, porosity, and crazing.
According to Goodacre and colleagues, CAD-CAM monolithic complete dentures produced the most accuracy, reproducibility, and least overall denture tooth movement during fabrication when compared with other methods of complete denture fabrication. In regards to the accuracy of the available CAD-CAM systems, Steinmassl and colleagues determined that AvaDent Digital Dentures system exhibited the highest precision in denture fit when compared with traditionally fabricated dentures. Further research in long-term prospective outcomes of the denture material, stability in the oral environment, and clinical outcome is still needed.
Intraoral scanning of the edentulous tissues has been suggested and attempted with promising results. However, difficulty lies in the digital program algorithm to recognize appropriately extended denture borders because of the functional movements and displaceability of the edentulous tissues.
Kattadiyil and colleagues have reported improved retention of the denture and reduced clinical chair time for milled dentures compared with the conventional dentures. Steinmassl and colleagues supported these findings and reported that CAD-CAM systems were able to precisely reproduce the master cast surface in comparison with the traditional methods.
Bidra and colleagues reported that one of the most important advantages of this technology is the decrease in clinical appointments whereby definitive impressions, maxillomandibular records, and tooth selection are completed in one appointment thus reducing the number of patient visits. Patient satisfaction has been measured through survey studies and it has been determined that patients are generally pleased and satisfied with their overall treatment outcome and experience with digital technologies suggesting that, regardless of the operator training and expertise, this method of denture fabrication may be predictable as long as prosthodontic fundamentals are applied. “Electronically archiving” the patient and denture data for future fabrication has been another advantage of CAD-CAM dentures.
Bidra and colleagues also advocated that CAD-CAM fabricated complete dentures can positively influence patient care, dental curriculums, and research. A study surveying US dental schools showed 52% of program directors and 12% of restorative chairs that completed the questionnaire reported implementing this technology into their curriculum. However, growing concerns exist because of the high cost of implementation compared with the low-cost traditional fabrication techniques.
Although most outcomes were favorable, a few minor complications of CAD-CAM dentures having poor esthetic outcomes or altered phonetics with the prostheses, and discrepancies with occlusal vertical dimension and tooth arrangements have been reported. Some studies reported having additional appointments for small percentages of patients than what the manufacturers stated. Saponaro and colleagues reported that 17 patients out of 48 (35.4%) needed an extra appointment for their two-visit protocol. A direct correlation exists between the number of postinsertion adjustments and patient satisfaction. The lower the number of recall visits, higher scores documented for patient satisfaction.
In their systematic reviews, Kattadiyil and colleagues published that careful patient selection seems critical for the success of computer-engineered dentures. The authors recommended that complex prosthodontic patients should be treated with caution to avoid the cost associated with prosthesis remakes. Although the available literature on CAD-CAM dentures is scarce, this method using the latest technology has shown promising short-term results with improved material offering good fit, retention, and mechanical properties. Prospective clinical studies involving edentulous patients requiring CAD-CAM complete dentures are needed to improve patient-centered outcomes. Further research is needed, with substantial sample sizes and longer follow-up periods to validate the performance of this treatment alternative.
Tooth-retained overdenture
With the high expenses associated with dental implant treatment, saving a few teeth to fabricate a tooth-supported overdenture ( Fig. 4 ) is a viable option for managing edentulous patients. Carlsson in 2014 reiterated the continuous and unpredictable loss of residual bone after extraction and while using complete denture. It was suggested to not extract all remaining dentition but to preserve several teeth to fabricate overdentures to provide denture stability and retention. This classical modality of simply using the reduced mandibular canines sealed with amalgam restorations has been shown to delay the ridge resorption process by eight times more than using a conventional complete denture in the mandible. Sensory feedback from the periodontal receptors and enhancement of the masticatory system have been advocated as an advantage for the use overdentures for the edentulous patient compared with conventional complete dentures. However, additional need for treatment before denture fabrication usually requires more time and cost on the patient’s behalf, and third-party payment may have restrictions for tooth-supported overdentures.
