Analysis of factors influencing the amount and localisation of residual ridge reduction of mandible

The objective of this study was to determine, on a certain number of edentulous patients, the correlation between some parameters of residual ridge reduction (RRR)--(age of patients; parodontopathy as cause of teeth extraction; period of edentulousness; period of denture wearing and reasons of renewed dentures) and classes and sub-classes of RRG in the frontal and molar regions. The aim of these comparisons was to precisely determine the possible presence of loccus minoris of reduction in relation to the studied zones and the mentioned factors of the loss of residual ridge (RR). The study concerned 35 lateral head films of edentulous patients chosen at random. By intersection of data and by their statistical processing, it was established that all reduction parameters, except the age of patients, were important factors or co-factors of this process. They had no specific effect RR. The finding that the molar region was more jeopardized by reduction was explained by the fact that the period of edentulousness and denture wearing were in function of the time, due to an unequal rate of teeth extraction, and that they became the true reason of a more severe reduction and the molar region a more susceptible area to this process.     

Symptomatic osteoporosis: a risk factor for residual ridge reduction of the jaws.

The purpose of this study was to clarify if symptomatic osteoporosis is a risk factor for severe residual ridge reduction of the jaws. The analysis included 12 edentulous women with osteoporotic fractures, otherwise normal, and 16 normal edentulous women matched with respect to age, menopausal age, and period of edentulousness. The bone mineral content measured in vivo by dual-photon scanner was significantly lower in the mandible and the forearm bones (that is, in the skeleton) of the osteoporotic group than it was in the normal group. No significant difference between the two groups was demonstrated with respect to the size of the mandibular sagittal area, measured on identical lateral cephalograms, while the sagittal maxillary area was significantly smaller in the osteoporotic group. Symptomatic osteoporosis therefore seems to be a severe risk factor for smaller residual ridge reduction off the maxillae, while this does not seem to be the case in the mandible.     

Posterior segmental osteotomy of maxillary edentulous ridge: an alternative to vertical reduction

The posterior segmental maxillary osteotomy (PSMO) can be used as an alternative procedure to vertical reduction of the edentulous posterior maxilla. Surgical intrusion of the segment resulted in an adequate interarch space for prosthetic restoration without cortical bone loss and widening of the edentulous ridge and the mobilized keratinized mucosa as would be the case if vertical alveolar reduction had been performed.     

Systemic bone diseases and reduction of the residual ridge of the mandible; primary hyperparathyroidism. A preliminary report

Twenty-five edentulous patients with established hyperparathyroidism were evaluated to establish a possible relation between extreme reduction of the height of the mandible and systemic bone loss. As an important parameter of the severity of the systemic bone loss, the level of the intact biologically active molecule of the parathormone was used. In this study no relation between hyperparathyroidism and reduction of the residual alveolar ridge could be established. In only two patients the reduction could be classified as "severe." Furthermore the level of the active, intact, circulating parathormone or the duration of the hyperparathyroidism could not be identified as an important factor in relation to the local phenomenon of reduction of the alveolar ridges.     

Reconstruction of the alveolar ridge with hydroxyapatite

Diagnosis, classification, surgical and prosthetic techniques, supporting research, and clinical trials are described for reconstruction of the deficient alveolar ridge with dense, nonresorbable hydroxyapatite. The use of particulate and solid forms for preservation of the alveolar ridge, facial reconstruction, and orthognathic surgery are discussed.     

Studies of residual ridge resorption. II. The relationship of dietary calcium and phosphorus to residual ridge resorption

This report presents results of an original investigation of the relationship between dietary calcium and phosphorus and alveolar bone resorption in edentulous patients.The diets of subjects with minimal bone resorption were compared with the diets of subjects with severe alveolar destruction. The results indicate a positive correlation among low calcium intake, calcium/phosphorus imbalance, and severe ridge resorption. Relationships among actual volume intake of these minerals, recommended allowances, and clinical findings were described.Emphasis was placed on the importance of considering dietary factors in the diagnosis and treatment of prosthodontic problems which arise from the excessive resorption of residual ridges.     

Continuing changes in the contour of the maxillary residual alveolar ridge

Using a cast measuring technique, the change in contour of the residual maxillary alveolar ridge of patients who have worn dentures for a number of years and are then fitted with new dentures, has been investigated. The study confirmed that even after 30 years of denture wearing, further bone resorption may occur beneath new dentures.     

Mastication after surgical reconstruction of the mandibular residual ridge

A group of thirty-one female denture patients who underwent surgical reconstruction of their deficient residual ridges with ridge extension and skin graft or ridge augmentation with bone graft were evaluated with regard to their masticatory function before surgery, then at 8 months and 12 months post-operative with their new dentures. Two objectives tests of masticatory efficiency were used. The masticatory efficiency index (MEI), based on the size of chewed almond particles, determined the potential capacity of patients to masticate while the masticatory performance (MP) based on the time required to masticate food before swallowing assessed the individual ability of each patient to chew food. A subjective index of difficulty (SD) provided information on the patient's own assessment of chewing difficulty of certain foods selected for their hard texture. The evolution of each index and their interrelationship were statistically evaluated. It was shown that the masticatory performance (MP) and the subjective index of difficulty (SD) both improved significantly during the rehabilitation period and even more rapidly than the masticatory efficiency index (MEI). The discrepancy between the objective and the subjective tests and the overestimation from the patients indicate that the real benefit of the rehabilitation is not limited to improved chewing, but also to an acquired self-confidence in mastication.     

Relationship between the stress distribution and the shape of the alveolar residual ridge – three-dimensional behaviour of a lower complete denture

PURPOSE: For a complete denture to function effectively, the denture must be stabilized during mastication. The alveolar ridge has various forms, and we must choose the artificial tooth arrangement that is most suitable to the form of the alveolar ridge. The purpose of this study was twofold: (i) to examine the relationship between the alveolar ridge form and the stress distribution on the mucosa, and (ii) to model the contact condition between the denture base surface and mucosa. MATERIALS AND METHODS: In this study, the three-dimensional finite element method was used for the analysis. Four types of alveolar ridge were prepared. As a loading condition, three load places were prepared: the mesial position, the central position and the distal position. We utilized the 'contact option (MARC)' to simulate the true behaviour of the denture. RESULTS: We were able to model the contact condition by using the 'contact option'. Maximum stresses were distributed on the alveolar ridge in which the absorption is severe. And, the distal load produced large compressive stresses on the inclined plane of posterior alveolar ridge in which alveolar form.     

延长垂直下斜方肌岛状肌皮瓣修复重建大型头颈部缺损

颈横动脉供血的延长垂直下斜方肌岛状肌皮瓣(extended vertical lower trapezius island myocutaneous flap,eVLTIMF)用于修复重建大型头颈部缺损安全可靠。该瓣制备较简单,成活率高。供区较隐蔽,可直接关闭缝合,并发症少,肩部运动受影响较小;还可制备成折叠瓣,合并其他带蒂瓣或合并肩胛骨骨肌皮瓣修复特大洞穿性缺损或下颌骨缺损。eVLTIMF在头颈部大面积缺损修复,尤其是在晚期复发性头颈部肿瘤挽救手术后巨大缺损修复重建中起着重要作用。本文对斜方肌的临床应用解剖、 eVLTIMF瓣制备及其在颅颌面、口腔颌面和颌颈区缺损修复中的应用作一阐述。     

Stress distribution prevents ischaemia and bone resorption in residual ridge

Objective

Intensive mechanical stress and/or inflammation are known to induce alveolar bone resorption. This study investigated whether a distribution of mechanical stress would reduce residual ridge resorption or improve ischaemia.

Design

Thirty rats were divided into six experimental groups (n = 5). The control group received no intentional stimulation, but rats in the experimental groups wore denture stimulators made of acrylic resin or a soft lining material. The stimulator transmitted masticatory pressure to the rats’ palates for four weeks. The four types of soft lining materials investigated in this study dispersed the applied pressure, with compressive stress ranging from 20.8 to 90.8 kPa. Volumes of blood flow and bone resorption of denture foundations were measured every week for 4 weeks. Statistical evaluation of these results was performed using two-way ANOVA and Holm-Sidak test within 5% error limits.

Results

Non-viscoelastic material clearly induced bone resorption and ischaemia of denture foundations, while viscoelastic materials reduced these phenomena to different extents according to their viscoelastic properties. Ischaemia in the alveolar ridge preceded residual ridge resorption, because the amount of residual ridge resorption and blood flow rate showed a simple linear regression.

Conclusion

Animal model of this study suggested that a distribution or reduction of mechanical stress could improve blood flow and decrease alveolar ridge resorption.     

Horizontal and vertical ridge augmentation for implant placement in the aesthetic zone

Lack of sufficient bone to place an implant at the functionally and aesthetically most appropriate position is a common problem, especially in the upper anterior jaw. A surgical technique is proposed to augment the alveolar ridge for vertical and horizontal defects through a localized alveolar osteotomy and interpositional bone graft. Three bone cuts (two vertical and one horizontal) are made in the alveolar bone. This portion of bone is carefully down-fractured. The gap between this bone box and the alveolar bone is filled with an interpositional bone graft. An on-lay bone graft is placed in the buccal side of the defect and fixed with titanium osteosynthesis screws. The aim of this surgical technique is to achieve bone graft healing in a short period of time. The broad vascular pedicle on the palatal side is maintained to ensure a nutritional supply for the down-fractured bone and interposed bone graft. The on-lay bone graft augments the palatal-buccal dimension and the interposed graft guarantees vertical augmentation.