Causes of Complete Dentures Renewal

Causes of Complete Dentures Renewal

Dr. Héla Haloui – Resident, departement of complete denture
Dr. Oumaima Tayari – Resident, departement of complete denture
Prof. Jaouadi Jamila (j.jaouadi@yahoo.fr) – Director, department of prosthodontics
Prof. Ali Ben Rahma – Head of Service, departement of complete denture

Clinic of dentistry of Monastir, Department of Prosthetic Dentistry, University of Monastir, Laboratory of oro-facial rehabilitation and oral health (LR12ES11)

Dental News March issue 2019

Abstract

During the replacement of the missing teeth, it is imperative that consideration should also be given to the amount of soft tissue which needs to be restored. A restoration can be termed functional only when it provides sufficient support to the extraoral and intraoral tissues while assisting proper speech, esthetics, and mastication.

The nursing and the medical staff in particular should be informed via appropriately designed educational materials and other resources specific to the oral health needs of older adults.

Prosthodontic replacement aims to reach high absolute patient satisfaction with the new prosthesis as well as improvement of satisfaction when comparing new and old dentures.

Key words: Complaints, complete dentures, denture replacement, oral and general health status, Compression-molded

Introduction

Conventional removable dentures still play an important role in the treatment of lost teeth. A thorough understanding of the parameters that influence patient satisfaction is useful for deciding whether denture replacement is meaningful. From a clinical perspective, factors that can be measured before starting treatment are relevant ¹⁴.

Replacement of missing teeth and the associated structures are done with the help of artificial prosthesis. Acrylic resin, by virtue of its excellent properties is widely used as a material of choice for fabrication of denture base. In spite of its higher esthetic quality, tissue compatibility and ease of manipulation, it has an inherent deficiency that it is prone to fracture. Acrylic resin, which came into market in 1950s, was widely accepted as denture base material, because of its excellent properties like good esthetic value, ease of manipulation, ease of repair and also for economical factors ¹². The expectations of patients can profoundly influence treatment outcome. 

Many prosthetic failures may result not from technical problems but from a lack of communication between the dentist and the patient with regard to the treatment outcome. Patient education should help to create a positive attitude by informing the patient about the limitations associated with complete dentures like being placed on a resilient base and masticatory inefficiency. The patient should be motivated on ways to overcome or compensate for these problems as well as proper oral and denture hygiene⁹. A thorough understanding of the parameters that influence patient satisfaction might help to predict treatment outcome and could hence be useful in deciding whether denture replacement is helpful ¹³.

This paper aims to review the factors associated with an increased risk of failure in complete denture patients since identifying potential problems will help to improve outcomes for edentulous patients treated with conventional complete dentures.

Causes of renewal

The clinical management of some edentulous patients can be a source of frustration for both patient and clinician as, despite the best efforts, patients remain unable to adapt to wearing the dentures that have been provided. Often the patients who fall into this category have had poor previous experience of denture-wearing and may arguably have unrealistic expectations. Nonetheless, repeated adjustments, or even remakes, can significantly add to the cost of denture construction and this can result in a negative experience for both the clinician and the patient ¹¹.

1. Related to health

Presently, one of the major problems in dentistry is the dental care for elderly patients. In order to solve this problem, most of the developed countries have investigated the dental and general health status of their elderly. Although the health care and dental needs of the elderly are known in developing countries, there are no studies or a worldwide system to organize social services according to the needs and demands of the patients.

On the other hand, while oral disorders are rarely life-threatening, they can have a significant impact on the social and psychological well-being of elderly people. It is often assumed that improved oral health will improve the quality of life. 

In older adults, this becomes more significant because many of these persons have substantial disabilities and handicaps that could impair oral care. This situation may consequently lead to poor oral health or development of oral diseases in the elderly that could become an important public health issue ¹⁵.

Studies assessing both the medical and oral health of older adults are not common; clearly dental treatments are not within their priorities; In some studies it has been demonstrated that edentulous subjects have inadequate dentures ranging between 31% and 80%. It is very difficult to identify whether this was due to biological and physiological changes in the mouth or was a consequence of malpractice during denture construction ⁷.

2. Bases’ defaults

The most common causes of denture fracture may be either extra-oral cause like fall from patient’s hand to the hard surfaces or intra-oral during function. One has to depend mostly upon the users’ version for the cause of the denture fracture. (Fig. 1, Fig. 2)

Inside the mouth, fracture can happen for various reasons like improper occlusion, placement of artificial teeth in the buccal slope of the ridge or against the palate, pressure from opposing natural teeth, poor retention and stability, prolonged use causing wear of artificial teeth and resorption of residual ridge, presence of high frenal attachments, prominent mid palatine suture, palatal or lingual torus, hard or soft tissue undercut, etc.

Defects in the denture may also be created during laboratory procedure. This may include thin denture base, placing the artificial teeth in the buccal slope of the ridge, incorporation of metal strengtheners, inclusions like plaster or air bubbles within the material, porosity, deep scratches which act as a stress raiser and predispose the denture to fracture ¹².

3. Obstacles related to Residual ridges

Dentures have to function in a dynamic environment. The tongue being the most versatile muscle in the body, it can be used to control the denture. Post-placement denture problems have been classified by various authors. Heartwell and Rahn classified post-placement problems as incompatibility with the surrounding oral environment, problems with mastication, disharmony with functions like speech, respiration and deglutition, dissatisfaction with aesthetics and deterioration of soft tissues or bony support  ¹¹.

Failure to recognize the cardinal importance of tooth position and flange form and contour often results in dentures which are unstable and unsatisfactory, even though they were skillfully designed and expertly constructed.

Incorrect tooth placement and arbitrary shaping of the polished surfaces may have an adverse effect on the success of the prosthesis.

One of the methods used to solve this problem is the neutral zone technique. 

The artificial teeth can then be set up in the correct positions. (Fig. 3) The basal area of the denture foundation greatly influenced the masticatory efficiency, suggesting that the masticatory efficiency in complete denture wearers was limited by their own residual ridges and patients should be informed about the limitation of the recovery of masticatory ability before the beginning of denture treatment  ¹.

4. Occlusal defaults

A period of 6-8 weeks is necessary to establish new memory patterns for the masticatory muscles. In a study by Goiato et al. patients experienced improved masticatory efficiency after one year with their new dentures ³. Correction of the vertical and sagittal occlusal relationship by fitting new dentures has also been found to alter head and cervical spine postures significantly, to relieve signs and symptoms of CMD (cranio-mandibular disorders) and to have a positive effect on the masticatory muscles ⁶.

It has also been suggested that incorrect vertical dimension and centric relation were the most frequent causes of TMD (temporo-mandibular disorder).

Also, a decrease in vertical dimension contributes to cheek biting since the cheeks tend to collapse into the occlusal area.

Patients should be educated that the chewing efficiency of the denture wearer is less than one-sixth that of the subject with a natural dentition. The assessment and reestablishment of the occlusal vertical dimension (OVD) are considered important factors in the treatment of complete denture wearers. The long-term use of a complete denture can result in jaw displacement due to abrasion of the artificial teeth and residual ridge resorption, causing esthetic complications. 

Most patients with old dentures and incorrect OVD accept reestablishment of the OVD with new complete dentures, even if they were used to their old dentures. For this reason, it is usually believed that changes in the OVD should be conservative and for a trial period, with an interim prosthesis if necessary. It is a gradual process that allows assessing the patient’s tolerance, esthetics, and phonetics at the proposed restored OVD ² .

Occlusal checking should be performed via a remount procedure because denture base materials and fabrication procedures cannot provide dimensionally accurate complete dentures. 

Deflective occlusal contacts of denture teeth in centric occlusion can be eliminated by selective grinding and by tooth-guided excursive movements ¹⁵.  

However, if it is found that there is a large change in the vertical dimension of occlusion, producing an open bite of more than 3 mm, then any adjustments to the teeth to correct this, are going to result in a complete re-shaping of the occlusal surfaces and almost certainly a complete loss of the cuspal anatomy of the teeth. The only recourse is to remove the posterior teeth, re-take the jaw registration, remount on the articulator, and set and process new posterior teeth to the correct occlusal vertical dimension. 

When there is a discrepancy between centric relation and maximum intercuspation the clinician must first consider the size of the error: if it is the result of an incorrect recording of the centric relation position, and if the discrepancy is no more than the width of a cusp, the dentures must be remounted on the articulator using a new jaw relationship record (a “check bite”) and the occlusion corrected on the articulator. 

If the discrepancy is too large to be adjusted in this way (i.e. more than the width of a cusp), then the posterior teeth must be removed, a new jaw registration record made, the dentures must be remounted, and new teeth processed onto the base.

Finally; these new parameters can be adopted for a new complete denture ⁴. (Fig. 4, Fig. 5, Fig. 6)

5. Technical procedures

Most dentists will have examined a patient who is perfectly happy with his/her ill-fitting, mobile and maloccluded dentures. Indeed, patient ratings for satisfaction with their dentures have been shown to change significantly over time.

This illustrates the influence of adaptive capacity on patient satisfaction with dentures, however, this should not be used as an excuse for poor prosthodontic work, as the need to rely on adaptive capacity will be minimized by producing technically correct dentures. 

Not all patients display such adaptive capacity. 

Additionally, there is a small number of studies that demonstrate that technically correct dentures will better satisfy patients than poor quality ones ⁵.

The dental laboratory generally does not have detailed diagnostic and examination findings about the patient. Even if dental laboratory technicians have access to the information, they do not have the training to properly evaluate it and determine the appropriate treatment. Without a thorough understanding of biologic and physiologic principles, laboratory personnel could unknowingly place harmful forces on the patient’s dentition. 

Common errors are about failing to use accurate burn out temperatures and times. If the burn out temperature is too low and the burn out time is too short, the investment will not experience enough thermal expansion. As a result, the casting may fit the definitive cast too tightly. If the burn out temperature is too high, the investment will decompose and cause the casting to be pitted and rough ¹⁰.

However if, the flask is closed too rapidly to permit the resin to flow into all spaces, unequal pressure will be exerted and tooth displacement might occur.

A classical study reported that processing dentures by long cycle in a water bath is recommended, as it causes least dimensional changes and Slow cooling inside the water bath is recommended before deflasking to avoid high residual stresses generated by thermal expansion differences between the plaster mold and denture base ⁸.

Conclusion

Successful prosthodontic therapy is multi-factorial. Factors which have been shown to carry a high risk of failure include:

• Dentist-related factors;

• Inaccurate jaw relations;

• Not involving patients in aesthetic choices;

• Poor impression-taking;

• Patient-related factors;

• Neurotic patients;

• A severely resorbed ridge.

It is suggested that, if these patient-related factors are present, the patient should be considered high risk for non-adaptation to new complete dentures. This should be discussed with the patient prior to commencing treatment so that expectations can be appropriately managed ¹².

Mouth preparation should be given primary importance; to minimize the possibility of fracture, E-glass fiber reinforced PMMA, visible light polymerized resin, metal reinforced resin may be used. Last, but not the least, proper instruction should be given to the patients about the careful handling of the denture, as many of them broke due to sudden fall. Patients should clean the denture within a bowl filled with water ¹³.

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