Blood Flow Alterations in the Anterior Maxillary Mucosa as Induced by Implant-Retained Overdenture.

PURPOSE: Blood flow disturbance from functional pressure may lead to ischemia and accumulation of metabolites leading to residual ridge resorption (RRR) underneath complete dentures. The purposes of this study were to determine the effect of mandibular complete denture (CD) and implant-retained overdenture (IRO) on blood flow disturbance in the opposing denture bearing-mucosa of maxillary CD and to compare the blood flow disturbance to RRR of the anterior maxilla. MATERIALS AND METHODS: The test group included 9 participants rehabilitated by maxillary CD opposing mandibular IRO, while the control group consisted of 4 participants with CDs. Blood flow was measured by laser Doppler flowmetry (LDF) after denture removal for 0, 30, 60, and 90 minutes. RRR was quantified as reduction in bone volume a year post-treatment. The measurement of blood flow was then compared to the quantification of RRR. RESULTS: The mean blood flow measure for the IRO group was significantly lower than CD after immediate denture removal and 30 minutes later. After 60 minutes, the mean difference was not significant between groups, and at 90 minutes, the mean blood flow of both groups equalized to reach a steady state of 377 BPU. The mandibular IRO had reduced the initial blood flow measure in the opposing anterior maxilla mucosa to almost a quarter (103 BPU) of the steady state value (377 BPU) compared to the CD, which reduced it to only about one half (183 BPU), suggesting greater blood flow disturbance in the IRO group. This result is in tandem with the greater reduction of bone volume observed in the IRO group, which was 7.3 ± 1.3% after a year, almost three times higher than CD group at 2.6 ± 1.7%. CONCLUSION: IRO may cause significantly higher blood flow disturbance than CD and may have contributed to greater RRR in the anterior maxilla.

Premaxilla Stress Distribution and Bone Resorption Induced by Implant Overdenture and Conventional Denture.

PURPOSE: To relate the principal stress, strain, and total deformation in the premaxilla region beneath a complete denture to the pattern of premaxilla bone resorption when opposed by a conventional complete denture (CD) or by a two-implant-retained overdenture (IOD) using finite element analysis (FEA). MATERIALS AND METHODS: Three-dimensional solid models of the maxilla, mucosa, and denture of a selected edentulous patient were created using Mimics and CATIA software. The FEA model was created and duplicated in ANSYS 16.0 to perform two simulations for the IOD and the CD models. The values of maximum stress and strain and total deformation were obtained and compared to the outcomes of premaxilla resorption from a parallel clinical study. RESULTS: The maximum principal stress in the premaxilla in the IOD model ranged from 0.019 to 0.336 MPa, while it ranged from 0.011 to 0.193 MPa in the CD model. The maximum principal strain in the IOD model was 1.75 times greater than that in the CD model. Total deformation was 1.8 times higher in the IOD model. Greater bone resorption was observed in regions of higher stress, which were on the occlusal and buccal sides of the premaxilla residual ridge. CONCLUSION: Stress, strain, and total deformation values present in the premaxilla area beneath a CD were approximately two times greater in a comparison between an opposing mandibular two-IOD and an opposing mandibular CD. The results were consistent with a parallel clinical study in which the rate of premaxilla bone resorption was almost three times greater in the IOD group.

Mandibular Implant-Retained Overdentures: Potential Accelerator of Bone Loss in the Anterior Maxilla?

PURPOSE: To compare the residual ridge resorption (RRR) of the anterior maxillary bone beneath complete dentures when opposed by mandibular complete dentures (CD) and implant-retained overdentures (IRO). MATERIALS AND METHODS: 18 patients were rehabilitated with maxillary CD opposing mandibular IRO, and 4 patients were prescribed with conventional CD. Cone beam computed tomography (CBCT) scans of the maxilla were acquired before and 1 year post-treatment and converted into 3D models using Mimics research software. RRR was quantified by measuring the changes in bone volume following superimpositioning and sectioning of these models at the anterior maxillary region. Subsequently, the sectioned 3D models of the anterior maxilla were exported to 3-Matic software to reveal the predominant region and depth of RRR. RESULTS: The mean reduction in bone volume of the anterior maxilla in the CD group was 2.60% (SD = 1.71%, range = -4.89 % to -0.92%, median = -2.30%), while the mean reduction in the IRO group was almost three times higher at 7.25% (SD = 3.16%, range = -13.25 to -1.50, median = -7.15%). The predominant areas of RRR were on the buccal and occlusal ridge of the anterior maxilla. CONCLUSION: Within the limits of this study, it may be concluded that an IRO caused significantly higher RRR of the anterior maxilla than a CD.