Carlsson GE Critical review of some dogmas in prosthodontics. J Prosthodont Res. 2009; 53:3-10
Farias-Neto A, Carreiro Ada F Complete denture occlusion: an evidence-based approach. J Prosthodont. 2013; 22:94-97
In: Zarb GA, Bolender CL, Eckert SE (eds). St Louis: Mosby; 2003
Bonwill WGA The science of the articulation of artificial dentures. Dent Cosmos. 1878; 20:321-324
Marklund S, Wanman A A century of controversy regarding the benefit or detriment of occlusal contacts on the mediotrusive side. J Oral Rehabil. 2000; 27:553-562
Heydecke G, Akkad AS, Wolkewitz M Patient ratings of chewing ability from a randomised crossover trial: lingualized vs. first premolar/anine-guided occlusion for complete dentures. Gerodontology. 2007; 24:77-86
Farias-Neto A, Mestriner Junior W, Carreiro Ada F Masticatory efficiency in denture wearers with bilateral balanced occlusion and canine guidance. Braz Dent J. 2010; 21:165-169
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For more than a hundred years, it has been supposed that canine guidance should be avoided in conventional complete dentures, since it would result in denture instability. Thus, bilateral balanced articulation has been held by many authors as fundamental for treatment success. However, randomized clinical trials have shown that balanced articulation is not as important as previously thought. The issue about which occlusal concept is the most appropriate for individual needs is clinically and economically relevant for both the dentist and dental technician. Therefore, the purpose of this study is to provide an evidence-based update on complete denture occlusion.
Clinical Relevance: The issue about which occlusal concept is the most appropriate for individual needs is clinically and economically relevant.
Article
Using evidence-based dentistry, Carlsson1 presented a list of old and current dogmas in prosthodontics:
The role of occlusion in the aetiology of temporomandibular disorders;
The belief that teeth that are lost must be replaced if the health of the masticatory system is to be maintained;
The value of the face-bow in jaw relation records; and
The concept that complete dentures need bilateral balanced articulation.
The author concluded that many procedures regarding prosthodontic interventions are based more on belief than scientific evidence.1
Current scientific evidence suggests that bilateral balanced articulation is not essential for successful treatment with conventional complete dentures. A recent systematic review revealed that canine-guided dentures do not seem to affect masticatory function and patient satisfaction.2 The issue about which occlusal concept is the most appropriate for individual needs is clinically and economically relevant. For the dentist and dental technician, the construction of a set of dentures with bilateral balanced articulation is more complex and time consuming than the construction of canine-guided dentures. Therefore, the purpose of this study was to provide an evidence-based update on complete denture occlusion.
Bilateral balanced articulation
For more than a hundred years, it has been supposed that oblique and lateral forces, like those present during canine guidance, should be avoided in conventional complete dentures, since this kind of force would result in denture instability (Figure 1). Thus, the bilateral balanced articulation has been held by many authors as fundamental for treatment success. This occlusal concept presents posterior contacts on both sides of the mandible (working side and balancing side) during eccentric movements (Figure 2). According to those who advocate the need for a balanced articulation, this occlusal concept improves retention and stability, and provides better masticatory function.3
Figure 1. Historically, it has been supposed that canine-guided dentures should be avoided because it would result in denture instability.Figure 2. In a balanced articulation, posterior contacts on both sides of the mandible (working side and balancing side) are present during eccentric movements.
The concept of a balanced articulation was first developed by Bonwill in 1878.4 He advocated that bringing the largest amount of grinding surfaces into contact at each movement would equalize the action of the muscles on both sides simultaneously. This would result in equal pressure and force distribution on both sides of the dental arches. Spee compared occlusal functions to ‘grinding millstones’ and stated that:
‘As forward and backward gliding of the mandible takes place in a path of circular motion, such displacements can occur over longer distances without any need for the arches to separate from each other. Thus, masticatory efficiency is guaranteed. This ought to be considered in the construction of dentures, not only to enable better mastication but also in order to avoid lever effects during chewing. These levering effects are less manifest with increased length of contact surface in every position of the firmly occluded teeth’.5
However, during functional activities, such as eating, drinking, speaking or singing, there is no balancing contact. During mastication, we can say that ‘when bolus in, balance out’ (Figure 3). Balancing contacts are not found during mastication and probably are not physiologically necessary. With the food bolus between the teeth, the occlusal surfaces do not make contact with each other, but with the food. Thus, is bilateral balanced articulation necessary for successful denture treatment? Where is the scientific evidence?
Figure 3. During mastication, we can say that ‘when bolus in, balance out’. With the food bolus between the teeth, the occlusal surfaces do not make contact with each other, but with the food.
Do denture wearers need a balanced articulation?
Because the highest incidence of oblique forces capable of dislodging dentures occurs during mastication, it was supposed that canine-guided dentures would impair masticatory function. Therefore, a recent systematic review was conducted to investigate the influence of canine-guided dentures on treatment outcomes with conventional complete dentures.2 Inclusion requirements were randomized controlled trials comparing bilateral balanced and canine-guided dentures, and assessment of masticatory function and/or patients' satisfaction. By the end of the search phase, seven studies were considered eligible. Two studies presented better data for canine-guided dentures, one study for balanced dentures, and four studies presented no difference. The authors concluded that there is no scientific evidence to support that balanced dentures promote better masticatory efficiency, chewing experience or patient satisfaction.2
In most of the studies included in that systematic review,2 patients were assessed after experiencing both occlusal concepts for equal periods. In Heydecke et al,6 20 edentulous patients received two sets of new dentures. Patients were blinded to the study group and were not informed about the differences between the two types of dentures. The dentures were delivered in randomized order, and each was worn for 3 months. Patients' rating of chewing experience was significantly better with non-balanced dentures.6 In Farias-Neto et al,7 24 edentulous patients received one set of new dentures. The change from balanced articulation to canine guidance was performed clinically by the addition of light-cured composite resin in the lower canines. Patients were randomized into two groups with different treatment sequences, and each occlusal concept was worn for 3 months. The colorimetric method was used to perform a masticatory efficiency test. In that method, masticatory efficiency was measured on the basis of the concentration of extracted fuchsin, which was expressed in absorbance. A method for quantifying the overall satisfaction of denture wearers was used. Patients were asked to respond to questions with three-grade answers (well satisfied, satisfied, dissatisfied) regarding 8 factors: chewing, tasting, speech, pain, aesthetics, fit, retention, and comfort. No difference was observed between balanced and canine-guided dentures.
Paleari et al8 investigated complete denture movement during chewing. The results of the kinesiographic recordings demonstrated that canine guidance promotes lower maxillary complete denture movement better than bilateral balanced articulation. The occlusal scheme did not influence patient satisfaction. According to the authors, the differences between occlusal schemes, albeit statistically significant, probably have no clinical relevance because of their magnitude.
It has been suggested that bilateral balanced articulation protects against bone resorption because it promotes symmetrical distribution of stress on the alveolar ridges.9 No clinical trials have investigated that association. It is difficult to accomplish long-term controlled trials evaluating the influence of occlusal concepts on bone resorption due to patients' age and many other variables. However, because during mastication there is no balancing contact, there is no force distribution on both sides of the arches. To avoid problems in denture retention, stability, and bone resorption, it seems to be more reasonable for clinicians to instruct patients not to incise, to put small pieces of food in the mouth, and to masticate on both sides of the arch.
To summarize, randomized controlled trials suggest that bilateral balanced articulation does not improve masticatory function,6,7 patient satisfaction7,8 and denture stability8 of conventional complete denture wearers. These results are important because they encompass objective parameters as well as patients' perceptions. Further research should test if these findings may be extrapolated for patients presenting parafunctional activities or extremely resorbed ridges.
Conclusion
Current scientific evidence shows that treatment outcome is similar for both occlusal concepts. While it is not incorrect to construct dentures with balanced articulation, it seems that the needs and attitudes of individual patients may have been overestimated. If canine-guided dentures can be constructed with acceptable clinical results in a minimum amount of time and effort, clinicians should be aware of the evidence in order to make the decision that best suits their patients' needs. As was said by Leonardo da Vinci, ‘simplicity is the ultimate sophistication’.
