Biomechanics and clinical implications of complete edentulous state

Effect of Different Definitive Impression Techniques for Resorbed Mandibular Ridge on Retention of a Lower Complete Denture

AIM

This study aimed to evaluate the effect of different definitive impression techniques for the resorbed mandibular ridge on the retention of lower complete dentures.

MATERIALS AND METHODS

Ten completely edentulous male patients with severe atrophic mandibular ridge were selected from the Prosthodontic Department's outpatient clinic, Faculty of Dentistry, Sinai University (Kantara branch). Each patient received four dentures. Dentures were divided into four groups according to the type of final impression, Group I: Conventional impression techniques (open mouth technique), Group II: Cocktail impression techniques, Group III: Modified functional impression technique, and Group IV: Wire impression technique. Each denture was used for one month and at the end of the month the retention test was carried out and the results were tabulated and statistically analyzed.

RESULTS

There is a statistically significant difference between the groups. The results also showed that the highest mean value was in group IV, whereas the lowest mean value of retention was in group I.

CONCLUSION

Wire impressions produce lower dentures with higher retention, whereas conventional impressions produce lower dentures with the lowest retention, so it is considered to be more advantageous.

CLINICAL SIGNIFICANCE

The wire impression technique is superior in the management of resorbed ridges as compared with other techniques.

A Fixed Reconstruction and Immediate Rehabilitation of Fully Edentulous Arch Using the All-on-Four Concept: Case Series

The implant survival largely depends on the mechanical setting in which they work as an independent entity. The implant design, number and position markedly affect the treatment plan. Deficient bone quantity and quality and presence of a vital anatomical landmark have often led the practitioners to conduct researches to find newer ways of implant insertion. One such technique is the 'All-On-4' concept, an alternative to the conventional implant therapy; lessens the amount of strain to the alveolar bone by increasing the antero-posterior spread with distal tilting the posterior implant. It is a cost-effective procedure that decreases the treatment time and the morbidity rate allowing a higher patient quality of life. The article demonstrates clinical cases describing rehabilitation of completely edentulous arches using the All-On-4 concept.

Importance of teeth in maintaining the morphology of the adult mandible in humans

Edentulism can negatively affect both masticatory performance and dietary intake by altering the patterns of biomechanical stress and strain, which in turn modifies the morphology of the different regions of the mandible. The morphological changes in the mandible caused by these stressors are unknown when comparing mandibles across varying dentition states. This study investigated differences in the morphology of human mandibles across various states of the dentition. In total, 498 mandibles of individuals between 20 and 80 yr of age at death were sourced from the Raymond A. Dart Collection of Human Skeletons. These included fully dentate (n = 95), partially edentulous (n = 333), and fully edentulous (n = 70) mandibles. Twelve linear anthropometric measurements of the mandible were derived from digitized landmarks located on its external surface. Data analysis included geometric morphometrics and multivariate analyses. Compared with dentate and partially edentulous mandibles, fully edentulous mandibles showed a shorter alveolar height (-0.4 mm), a shorter mandibular body length (-4 mm), a larger gonial angle (+4°), a more obtuse mental angle (+4.7°), a broader bicondylar width (+3.8 mm), and a taller ramus height (+1.6 mm). Thus, edentulous states are associated with an altered mandibular morphology, which may result from a reduction in jaw function.

Biomechanical factors related to occlusal load transfer in removable complete dentures

Owing to economic conditions, removable dentures remain popular despite the discomfort and reduced chewing efficiency experienced by most denture wearers. However, there is little evidence to confirm that the level of mucosal load exceeds the pressure pain threshold. This discrepancy stimulated us to review the current state of knowledge on the biomechanics of mastication with complete removable dentures. The loading beneath dentures was analyzed in the context of denture foundation characteristics, salivary lubrication, occlusal forces, and the biomechanics of mastication. The analysis revealed that the interpretation of data collected in vivo is hindered due to the simultaneous overlapping effects of many variables. In turn, problems with determining the pressure beneath a denture and analyzing frictional processes constitute principal limitations of in vitro model studies. Predefined conditions of finite element method simulations should include the effects of oblique mastication forces, simultaneous detachment and sliding of the denture on its foundation, and the stabilizing role of balancing contacts. This review establishes that previous investigations may have failed because of their unsubstantiated assumption that, in a well-working balanced occlusion, force is only exerted perpendicular to the occlusal plane, allowing the denture to sit firmly on its foundation. Recent improvements in the simulation of realistic biomechanical denture behavior raise the possibility of assessing the effects of denture design on the pressures and slides beneath the denture.