Report of a Case of Hypodontia due to Ectodermal Dysplasia: Early Rehabilitation with Overdenture

Alveolar ridge is underdeveloped in ectodermal dysplasia (ED). The available treatment plans include fixed, removable or implant-supported prostheses, alone or in combination.A 5 year-old boy was referred for treatment to the Department of Prosthodontics, Tehran University of Medical Sciences with the chief complaint of missing teeth. Prosthodontic treatment was performed to improve mastication, esthetics, phonetics, and psychological support. Altering the alveolar height also provided a more pleasant musculocutaneous profile. Series of overdentures were fabricated in the same conventional manner to compensate for the patient’s growth.Early treatment had a major impact on self-esteem, masticatory function, speech and facial esthetics of our patient. However, long-term success depends on regular recall appointments.

Microtensile Bond Strength between Zirconia Core and Veneering Porcelain after Different Surface Treatments

Objectives: The long-term clinical success of all-ceramic restorations requires sufficient bond strength between the veneering ceramic and substructure. The present study compared the effects of three methods of surface treatment on the microtensile bond strength of the veneering porcelain to zirconia. Materials and Methods: Twelve zirconia blocks were randomly divided into four groups of aluminum oxide (Al2O3) air abrasion, carbon dioxide (CO2) laser irradiation, erbium-doped yttrium aluminum garnet (Er:YAG) laser irradiation, and control samples (no surface treatment). After surface treatment, the zirconia blocks were veneered with porcelain. To assess the surface topographies, four surface-treated specimens were left uncoated. Microtensile bond strength was tested in each group and was statistically analyzed by one-way ANOVA and post-hoc Tukey's test. Surface topographies were examined by using scanning electron microscopy (SEM). Results: The highest and lowest microtensile bond strength values were recorded in the Al2O3 (43.6±10.0 MPa) and control groups (34.7±8.2 MPa, P<0.05). The bond strengths in the CO2- and Er:YAG-irradiated groups were equal to 40.4±6.5 MPa and 38.2±7.5 MPa, respectively. The majority of the failures (mean=92.44%) were of cohesive nature located in the veneer, followed by mixed fractures (mean=7.6%). The milling marks of the computer-aided design/computer-aided manufacturing (CAD/CAM) machine were apparent in the control samples, while desert-like micro-cracks were observed on the surfaces treated with CO2 and Er:YAG lasers. Al2O3 air abrasion produced the roughest topography. Conclusions: Al2O3 air abrasion resulted in a higher microtensile bond strength compared to CO2 or Er:YAG laser irradiation. Cohesive failure mode was predominant. No pure adhesive failures were observed

Three Dimensional Finite Element Analysis of Distal Abutment Stresses of Removable Partial Dentures with Different Retainer Designs

Objectives: This finite element method study aimed to compare the amount of stress on an isolated mandibular second premolar in two conventional reciprocal parallel interface designs of removable partial dentures (RPDs) and the same RPD abutment tooth (not isolated). Materials and Methods: A Kennedy Class 1, modification 1 RPD framework was simulated on a 3D model of mandible with three different designs: an isolated tooth with a mesial rest, an isolated tooth with mesial and distal rests and an abutment with a mesial rest (which was not isolated); 26 N occlusal forces were exerted bilaterally on the first molar sites. Stress on the abutment teeth was analyzed using Cosmos Works 2009 Software. Results: In all designs, the abutment tooth stress concentration was located in the buccal alveolar crest. In the first model, the von Mises stress distribution in the contact area of I-bar clasp and cervical portion of the tooth was 19 MPa and the maximum stress was 30 MPa. In the second model, the maximum von Mises stress distribution was 15 MPa in the cervical of the tooth. In the third model, the maximum von Mises stress was located in the cervical of the tooth and the distal proximal plate. Conclusion: We recommend using both mesial and distal rests on the distal abutment teeth of distal extension RPDs. The abutment of an extension base RPD, which is not isolated in presence of its neighboring more anterior tooth, may have a better biomechanical prognosis.      

Comparative Evaluation of Retentive Properties of Two Compatible Ball Attachments in Mandibular Implant-Retained Overdentures: An In Vitro Study

Objectives: The retentive properties of implant-retained overdentures (IRO) may be influenced by the type of attachments. The aim of this research was to compare the retention of two dental implant systems with compatible ball attachments, namely Straumann® system (SS) and Rhein83 SRL system (RS) after fatigue testing. Materials and Methods: Two laboratory models consisting of two parallel Straumann® fixtures at a distance of 22 mm were prepared. Five pairs of each systems' ball attachments were examined (n=5). The samples were soaked in artificial saliva. The retention strength values (RSV) were recorded before the fatigue test and after 1100, 2200, 3300, 4400, and 5500 insertion and removal cycles at a speed of 51 mm/minute with a 50-N load cell in a universal testing machine. The data were analyzed by repeated measures analysis of variance (ANOVA) followed by independent sample t-test with Bonferroni corrections. Results: There was a decrease in the RSV in both systems after 5500 cycles of insertion and removal. There was a significant statistical difference between the RSV of the normal Sphero Block of the RS (17.52±0.68 N) and that of the Spare Lamella retention inserts of the SS (19.72±0.74 N, P=0.001). Conclusions: Although the RSVs of the RS and SS were almost similar before the fatigue test, as the number of insertion and removal cycles increased, the RSV decreased more significantly in the RS compared to the SS