PURPOSE: The purpose of this finite element analysis study was to evaluate the biomechanical behavior (stress distribution pattern) in the mandibular overdenture, mucosa, bone, and implants when retained with 2 standard implants or 2 mini implants under unilateral or bilateral loading conditions.
MATERIAL AND METHODS: A patient with edentulous mandible and his denture was scanned with cone beam computed tomography (CBCT), and a 3D mandibular model was created in the Mimics software program by using the CBCT digital imaging and communications in medicine (DICOM) images. The model was transferred to the 3Matics software program to form a 2-mm-thick mucosal layer and to assemble the denture DICOM file. A 12-mm-long standard implant (Ø3.5 mm) and a mini dental implant (Ø2.5 mm) along with the LOCATOR male attachments (height 4 mm) were designed by using the SOLIDWORKS software program. Two standard or 2 mini implants in the canine region were embedded separately in the 3D assembled model. The base of the mandible was fixed, and vertical compressive loads of 100 N were applied unilaterally and bilaterally in the first molar region. The material properties for acrylic resin (denture), titanium (implants), mucosa (tissue), and bone (mandible) were allocated. Maximum von Mises stress and strain values were obtained and analyzed.
RESULTS: Maximum stresses of 9.78 MPa (bilaterally) and 11.98 MPa (unilaterally) were observed in 2 mini implants as compared with 3.12 MPa (bilaterally) and 3.81 MPa (unilaterally) in 2 standard implants. The stress values in the mandible were observed to be almost double the mini implants as compared with the standard implants. The stresses in the denture were in the range of 3.21 MPa and 3.83 MPa and in the mucosa of 0.68 MPa and 0.7 MPa for 2 implants under unilateral and bilateral loading conditions. The strain values shown similar trends with both implant types under bilateral and unilateral loading.
CONCLUSIONS: Two mini implants generated an average of 68.15% more stress than standard implants. The 2 standard implant-retained overdenture showed less stress concentration in and around implants than mini implant-retained overdentures.
PURPOSE: The purpose of this retrospective study was to investigate the clinical factors affecting the occlusal re-establishment and short-term complications of RBFPDPs cemented at an increased OVD.
MATERIAL AND METHODS: Occlusal re-establishment and clinical complications were reviewed in 109 participants (155 RBFPDPs) treated at the Faculty of Dentistry, Universiti Teknologi MARA from January 2013 to May 2018. Types of complications and risk factors were assessed from clinical data. Demographic factors, clinical factors, and prosthesis factors were distinguished and their association with occlusal re-establishment analyzed by using multiple regression analysis.
RESULTS: A total of 155 RBFPDPs (42 anterior, 113 posterior) were placed in 109 participants. All achieved occlusal re-establishment, 89.9% complete occlusal re-establishment and 10.1% partial occlusal re-establishment, a minimum of 4 months after the RBFPDPs had been placed at an increased OVD. The design of the metal retainer coverage was found to be a significant factor affecting occlusal re-establishment and decementation (P
PURPOSE: The purpose of this clinical study was to investigate the occlusal force and occlusal contact reestablishment of RBFPDPs cemented at an increased occlusal vertical dimension (the Dahl concept) and to evaluate the factors affecting them.
MATERIAL AND METHODS: A prospective clinical study was carried out on 28 participants receiving cantilevered RBFPDPs at an increased occlusal vertical dimension at the Faculty of Dentistry, University Teknologi MARA. Maximum occlusal forces were recorded at precementation, postcementation, and 12-week review visit by using pressure indicating film, while occlusal contact reestablishment was assessed at the precementation stage and 12-week review visit by using shim stock foils. The Wilcoxon signed-rank and chi-squared tests were used for statistical analysis (α=.05).
RESULTS: Significant differences were found for maximum occlusal force between the precementation and the postcementation and between the postcementation and the 12-week review of RBFPDPs (P.05).
CONCLUSIONS: Overall, occlusal force was reestablished after 12 weeks, and occlusal contact was completely reestablished in most participants after placement of RBFPDPs at an increased occlusal vertical dimension.
PURPOSE: The purpose of this prospective clinical study was to evaluate the changes in masticatory function from baseline (T0) to 3 months (T1) and 3 years (T2) in participants with MODs and to assess the effect of baseline mandibular bone height and volume on masticatory function after 3 years.
MATERIAL AND METHODS: Participants were assessed for masticatory function by using masticatory performance involving paraffin wax cubes as an objective measure and by using masticatory ability involving a questionnaire as a subjective measure. Edentulous individuals presenting for replacement dentures were provided with conventional mucosa-supported prostheses and evaluated for masticatory function after a 3-month settling-in period (baseline measure). Before implant placement, baseline measures of bone height and volume were recorded from cone beam computed tomography (CBCT) images. The prostheses were then converted to implant-stabilized mandibular overdentures while any maxillary prostheses remained supported by the mucosa. Masticatory function was reassessed at 3 months and 3 years after insertion of the mandibular overdentures, and the mean changes from baseline were analyzed with the Wilcoxon signed-rank test. The effect of variables on masticatory function was determined by using multivariate linear regression analyses.
RESULTS: A total of 23 participants were included in the study, with only 1 participant not completing the 3-year assessment. Significant improvement was observed in the masticatory performance (mixing ability index) (P
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.
PURPOSE: The purpose of this 3D finite element analysis study was to evaluate the biomechanical behavior of 2-implant mandibular overdentures (2IMO) and their individual components by using implants of different diameters.
MATERIAL AND METHODS: A 3D mandibular model was obtained from the cone beam computed tomography (CBCT) images of a 59-year-old edentulous man, and a 3D denture model was developed from intraoral scanning files in the Mimics software program. A 3D model of different diameters of implants (2.5 mm, 3.0 mm, 3.5 mm, and 4.0 mm) with a LOCATOR attachment was developed in the Solidworks software program. Two same-sized implants were inserted in the mandibular model at 10 mm from the midline in the 3Matics software program. A vertical load of 100 N was applied on the first molar region on the right side or both sides in the ANSYS software program. The maximum von Mises stresses and strains were recorded and analyzed.
RESULTS: Stresses within the implants decreased with an increase in diameter (from 2.5 mm to 3 mm, 3.5 mm, and 4.0 mm) of the implants. The highest stresses were observed with 2.5-mm-diameter implants (0.949 MPa under unilateral and 0.915 MPa under bilateral loading) and the lowest with Ø4-mm implants (0.710 MPa under unilateral and 0.703 MPa under bilateral loading). The strains on the implants ranged between 0.0000056 and 0.0000097, and those on the mandible ranged between 0.0000513 and 0.0000566 across all diameters of the implants without following a specific trend.
CONCLUSIONS: In 2IMO, the stresses in the implants and mandible decreased with an increase in the diameter of the implants. The implants of lesser diameter (2.5 mm) exhibited the highest stresses and strains, and the implants of the largest diameter (4 mm) exhibited the lowest stresses and strains under unilateral and bilateral loading conditions.
BACKGROUND: Literature lacks information on various unsplinted attachment systems and their effect on peri-implant tissue health. A focus question (as per PICOS) was set as follows: Does one particular unsplinted attachment system (I) compared with another (C) results in better peri-implant outcomes (O) in two implant-retained mandibular overdentures (P) using randomized controlled trials (RCTs) (S)? The literature search was conducted in the PubMed, MEDLINE and Cochrane Central Register of Controlled Trials (CENTRAL) databases between January 2011 and December 2021. The keywords used were "denture, overlay," "denture," "overlay" AND "dental prosthesis, implant supported," "dental implants," "dental implant abutment design" AND "jaw, edentulous," "mouth, edentulous" AND "mandible." Only RCTs on two implant-retained mandibular overdentures using unsplinted attachment systems measuring peri-implant tissue outcomes with minimum 1-year follow-up were selected. In total, 224 studies were identified in initial search, and 25 were shortlisted for full-text evaluation. Four studies were included for systematic review upon considering inclusion and exclusion criteria. The risk of bias was evaluated using Cochrane Risk of Bias Tool 2.0 (RoB 2.0).
REVIEW RESULTS: A total of 41 patients received ball attachments (in 3 studies), 36 patients received low-profile attachments (in 3 studies), 16 patients received magnet attachments (in 1 study), and 13 patients received telescopic attachments (in 1 study). All four studies used standard sized implants, however, differed in implant manufacturers. Two studies which compared ball attachments low-profile attachments revealed-similar peri-implant tissue health parameters but differed in crestal bone-level changes. One study compared ball with telescopic attachments and revealed similar results in crestal bone-level changes and all four peri-implant tissue health parameters. Single study compared magnets with low-profile attachments and shown lesser bone loss with magnet attachments. Single study was judged to have low risk of bias, single with some concerns, and remaining two to have high risk of bias.
CONCLUSION: Gingival index and bleeding index of the patients were not influenced by any of the unsplinted overdenture attachment (stud, magnet, telescopic) system. Inconclusive results found among the studies evaluated comparing crestal bone loss and plaque index.
CLINICAL SIGNIFICANCE: This review manuscript has simplified comparative analysis of different unsplinted attachment systems used in two implant mandibular overdentures to help clinicians choose correct system in such situation.
MATERIAL AND METHODS: Thirty-four patients (mean age 60.70 ± 8.7 years) received telescopic crown or locator attachments for ISOD and completed OHIP-14 (Malaysian version) and DS questionnaires, at baseline (T0 ) with new conventional complete dentures (CCD) and 3 months (T1 ) and 3 years (T2 ) after ISOD conversion. Mandibular bone volume was calculated from cone beam computed tomography (CBCT) datasets using Mimics software. Mean changes (MC) in OHIP-14 and DS at intervals were analyzed using the Wilcoxon signed-rank test and effect size (ES). The association of bone volume, implant attachment type, and other patient variables with the change in OHIP-14 and DS were determined using multivariate linear regression analysis.
RESULTS: The MC in OHIP-14 and DS scores from T0 to T1 and T2 showed significant improvement with moderate and large ES, respectively. Regression analyses for the change in OHIP-14 score from T0 to T2 showed significant association with implant attachment type (P = 0.043), bone volume (P = 0.004), and baseline OHIP-14 (P = 0.001), while for DS, the association was only significant with baseline DS score (P = 0.001).
CONCLUSION: Improvement in patients' OHRQoL and satisfaction with ISOD was associated with their baseline ratings. Mandibular bone volume had a stronger association for improvement in OHRQoL compared to type of attachment.
MATERIALS AND METHODS: Sixmaster dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Ten copings of 0.6 mm thickness were fabricated from each type of ceramic, for a total of thirty copings. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented with resin luting cement Panavia F according to manufacturer's instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37 degrees C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min.
RESULTS: The results of the present study showed the following mean loads at fracture: Turkom-Cera (2184 +/- 164 N), In-Ceram (2042 +/- 200 N), and Procera AllCeram (1954 +/- 211 N). ANOVA and Scheffe's post hoc test showed that the mean load at fracture of Turkom-Cera was significantly different from Procera AllCeram (p < 0.05). Scheffe's post hoc test showed no significant difference between the mean load at fracture of Turkom-Cera and In-Ceram or between the mean load at fracture of In-Ceram and Procera AllCeram.
CONCLUSION: Because Turkom-Cera demonstrated equal to or higher loads at fracture than currently accepted all-ceramic materials, it would seem to be acceptable for fabrication of anterior and posterior ceramic crowns.