OBJECTIVETo learn retention and stability of linear occlusal complete dentures by investigating the subjective feelings of patient and the value of retention force.

METHODSStatic retention forces of maxillary and mandibular dentures were measured for 25 patients wearing linear occlusal dentures by using Hz-1 retention dynamometer. The subjective feelings of patients in functional state were gained simultaneously through questionnaire.

RESULTSLinear occlusal dentures demonstrate good retention in static and dynamic state. Among patients with severe resorption of residual ridge (RRR), mandibular linear occlusal dentures (shown good retentive subjective feelings) demonstrate significantly smaller retention force than those with slight or medium degree of RRR. There is no correlation between the subjective feelings and the values of retention forces of mandibular dentures. The subjective feelings of patients wearing new linear occlusal dentures are much better than that of old anatomic occlusal dentures.

CONCLUSIONLinear occlusal dentures improve the performances of dentures by enhancing their stability during mastication movement.

Aged ; Aged, 80 and over ; Dental Occlusion ; Denture Design ; standards ; Denture Retention ; Denture, Complete ; standards ; Denture, Complete, Lower ; standards ; Denture, Complete, Upper ; standards ; Female ; Humans ; Male ; Middle Aged

OBJECTIVETo analyze stress distribution in alveolar bone around implants of implant supported overdentures (ISO) with linear occlusion and with anatomic occlusion at lateral mandibular position, and to justify the possibility of decreased injurious force around implants in ISO with linear occlusion.

METHODSComputerized tomography scan and finite element analysis (FEA) were used to set up two 3-D FEA models of maxillae and mandible with severe residual ridge resorption. The mucosa, linear and anatomic occlusal ISO with bar attachments, and two implants inserted between mandibular foramina were also established in the models. With the condition of imitating the loading of masseter muscles, these models were loaded to simulate the stress distributions in alveolar bone around implants under ISO at lateral occlusion position.

RESULTSAt lateral occlusion, the stress distributions in alveolar bone around implants under ISO with anatomic occlusion were mainly on the lingual and distal sides of the working side implants. However, stress distributions under ISO with linear occlusion were on the distal sides of bilateral implants. Both the stress peaks of ISOs with linear occlusion and with the anatomic one appeared in the working side. In anatomic occlusion model, sigma(z): -6.47 MPa and 6.81 MPa, sigma(1): -4.20 MPa and 7.20 MPa (negative value: compressive stress, positive value: tensile stress); in linear occlusion model, sigma(z): -4.86 MPa and 3.04 MPa, sigma(1): -3.48 MPa and 5.33 MPa.

CONCLUSIONSAt lateral occlusion, when comparing the ISO with two different occlusion schemes, stress peak in alveolar bone around implants in the linear occlusion model was lower than that in the anatomic occlusion model at equal loading situation. Stress in the alveolar bone under ISO with linear occlusion distributed more evenly than that under ISO with anatomic occlusion.

Dental Implantation ; Dental Occlusion ; Denture, Complete, Lower ; Finite Element Analysis ; Humans ; Mandible ; physiology ; Models, Anatomic ; Models, Biological ; Stress, Mechanical

OBJECTIVETo analyze the energy relieving effect of different thickness of mucosa beneath mandibular complete denture and try to analyze clinical question of prosthodontics using energy analysis methods.

METHODSA 3-DFE model of the mandibular complete denture and its supporting tissue were set up. Their elastic deformed energy and the percentage in the whole system were respectively calculated when mucosal thickness was different.

RESULTSThe percentage of mucosal elastic deformed energy grew from 44.53% to 52.91% and 57.91% with its different thickness under static loads.

CONCLUSIONSThe energy relieving effect of mucosa grows with its thickness and the approach of energy analysis is one of effective method on oral biomechanics questions.

Biomechanical Phenomena ; Dental Stress Analysis ; Denture, Complete, Lower ; Elasticity ; Finite Element Analysis ; Humans ; Mouth Mucosa ; anatomy & histology

OBJECTIVETo investigate the profile of mandibular denture polished surface in edentulous patients with different residual ridge resorption (RRR) using neutral zone record.

METHODSTwenty randomly selected edentulous patients with different category of RRR were investigated, which were divided into three groups according to ridge resorption grade and the relationships between upper and lower jaws: group 1: Class I edentulous patients (n = 6), group 2: Class II edentulous patients (n = 7), group 3: Class III edentulous patients and crossbite jaw relationship (n = 7). All subjects were asked to perform sufficient functional movement with silicon registration material in their mouth to record the shape, which were interpreted as the ideal shape of denture polished surface. Three-dimensional laser scanner was used to record the data of the outline of the maxillary and mandibular ridge and the silicon record of the polished surface. Digital model reconstruction was then conducted on the workstation. Sagittal surface of the model in the cut-in point on first molar and first premolar was made and data of the outline of these surfaces was collected.

RESULTSBoth the buccal and the lingual polished surfaces were concave, straight or slight protuberant and inclined respectively in group 1, 2 and 3. The average angles between the horizontal and the lingual polished surface were (80.40 +/- 3.51) degrees, (90.38 +/- 2.71) degrees and (96.59 +/- 5.00) degrees respectively.

CONCLUSIONSThe polished surfaces were changed with different progress of RRR in edentulous patients. It was suggested that the degree of residual ridge resorption and the relationship between upper and lower jaws should be considered when clinicians design the polished surface of denture.

Aged ; Aged, 80 and over ; Alveolar Bone Loss ; Denture Bases ; Denture Design ; Denture, Complete, Lower ; Female ; Humans ; Lasers ; Male ; Microscopy, Electron, Scanning ; Middle Aged ; Mouth, Edentulous ; Pilot Projects ; Surface Properties

OBJECTIVETo evaluate the in vivo retentive forces of mandibular complete overdenture with Magfit attachments, as well as the relation between the location of magnetic attachments and the retentive forces of the denture.

METHODS5 patients were selected and treated with mandibular complete overdentures retained by Magfit EX600 and MD800 attachments. A strainometer was used to measure the retentive forces in anterior, central and posterior parts of the overdenture before and after magnets were set. The vertical and anterior-upper 60 degrees retentive forces of the overdenture were measured one month later.

RESULTSThe retentive forces of the overdentures after setting magnets were significantly greater than that before magnets were set (P < 0.05). There was no significant difference in retentive forces between the different parts (P > 0.05). The retentive force in vertical direction was greater than that in anterior-upper 60 degrees direction (P < 0.025).

CONCLUSIONMagnetic attachments can significantly improve the retention of mandibular complete overdenture. The location of magnetic attachments greatly influences the retentive force of the overdenture.

Aged ; Aged, 80 and over ; Dental Prosthesis Design ; methods ; Dental Prosthesis Retention ; instrumentation ; Dental Stress Analysis ; Denture Precision Attachment ; Denture, Complete, Lower ; Denture, Overlay ; Electromagnetic Fields ; Female ; Humans ; Magnetics ; instrumentation ; Male ; Materials Testing ; Stress, Mechanical