Early-Loaded One-Stage Implants Retaining Mandibular Overdentures By Two Different Mechanisms: 5-Year Results

Purpose: To compare the biologic and prosthetic outcomes of implants loaded early to retain mandibular overdentures by means of two different attachment systems. Materials and Methods: Patients were screened according to specific inclusion/exclusion criteria and randomly allocated to treatment groups involving two-implant-supported early loaded mandibular overdentures retained by ball attachments or Locator attachments. Marginal bone loss, Plaque Index, peri-implant infection, Bleeding Index, prosthetic complications, and Kaplan-Meier survival estimates of the groups were assessed at the 5-year recall. Results: Among the 29 patients (58 implants) who completed the study, one implant was lost during healing; all implants survived after prosthesis delivery. Bone loss in the ball attachment group (0.77 +/- 0.05 mm) was significantly greater than that in the Locator group (0.59 +/- 0.03 mm). The Plaque and Bleeding indices of both groups were comparable, and peri-implant inflammation scores in both groups were zero for all implants. The frequencies of activation of the matrix, replacement of the matrix, and denture reline in the ball attachment group were significantly higher than those observed in the Locator group. While assessments for the absence of any complication showed that the 1- and 3-year Kaplan-Meier survival probabilities of both groups were comparable, when activation of the retainer was excluded, survival probabilities of the ball attachment group were higher. Conclusions: The biologic outcomes of early loaded mandibular overdentures retained by ball attachments or Locators were comparable. Although the frequency of prosthetic complications with ball attachments was higher, this did not decrease the survival probability for the treatment

CAD/CAM Glass Ceramics for Single-Tooth Implant Crowns: A Finite Element Analysis

Purpose:To evaluate the load distribution of CAD/CAM mono-ceramic crowns supported with single-tooth implants in functional area.Materials and Methods:A 3-dimensional numerical model of a soft tissue-level implant was constructed with cement-retained abutment to support glass ceramic machinable crown. Implant-abutment complex and the retained crown were embedded in a O 1.5 x 1.5 cm geometric matrix for evaluation of mechanical behavior of mono-ceramic CAD/CAM aluminosilicate and leucite glass crown materials. Laterally positioned axial load of 300 N was applied on the crowns. Resulting principal stresses in the mono-ceramic crowns were evaluated in relation to different glass ceramic materials.Results:The highest compressive stresses were observed at the cervical region of the buccal aspect of the crowns and were 89.98 and 89.99 MPa, for aluminosilicate and leucite glass ceramics, respectively. The highest tensile stresses were observed at the collar of the lingual part of the crowns and were 24.54 and 25.39 MPa, respectively.Conclusion:Stresses induced upon 300 N static loading of CAD/CAM aluminosalicate and leucite glass ceramics are below the compressive strength of the materials. Impact loads may actuate the progress to end failure of mono-ceramic crowns supported by metallic implant abutments