This randomized clinical trial aimed to evaluate the radiographic and clinical evaluations of mandibular implant-supported overdentures supported d by two different bar materials。 Completely edentulous patients received two implants in the mandibular canine region and were rehabilitated with overdentures supported by a conventional cobalt-chromium bar and a zirconia CAD/CAM bar。 Radiographic marginal bone loss around implants, crestal bone height changes posteriorly and clinical peri-implant parameters were assessed at baseline,6 months, and 12 months to compare the performance of both bar materials。

This randomized clinical trial was conducted to compare the radiographic and clinical outcomes of mandibular implant-supported overdentures supported by conventional cobalt-chromium bars and zirconia CAD/CAM bars。 Eligible completely edentulous patients were selected according to predefined inclusion and exclusion criteria。

All participants received two endosseous dental implants placed in the mandibular canine regions following a standardized surgical protocol。 After a healing period, patients were randomly allocated into two groups。 In the first group, overdentures were supported by using a conventional cast cobalt-chromium bar, while in the second group, overdentures were supported by using a zirconia CAD/CAM-fabricated bar。

Radiographic evaluations of marginal bone loss around implants and crestal bone height changes posteriorly were performed using cone beam computed tomography and clinical peri-implant parameters, including pocket depth, plaque index, bleeding index, and mobility were evaluated at baseline,6 months and after 12 months。

The primary outcome of this study was the evaluation of radiographic marginal bone loss around implants and crestal bone height changes posteriorly, while secondary outcomes included peri-implant soft tissue health parameters。 The collected data were statistically analysed to compare bone stability and clinical performance associated with the two bar materials over the observation period。

Inclusion Criteria:

• • Patients age range was between 50-60 years old.

  • Only male patients were selected to participate in this study.
  • All patients were apparently free from any systemic or debilitating diseases that might affect bone metabolism or delay post-operative healing.
  • Patients were free from any temporo-mandibular joint disorders.
  • Patients were free from any neuromuscular or bony disorders, and medically free from any neurologic disorder affecting the neuro-muscular system.
  • Patients' residual alveolar ridges were covered with firm, healthy mucosa, free from any signs of inflammation, ulceration, or flabby tissue.
  • Mandibular edentulous alveolar ridge areas had sufficient width and height of alveolar bone.
  • Patients exhibited Angle Class I maxillo-mandibular relationship and sufficient inter-arch space.
  • Patients had good oral hygiene.
  • A period of at least six months up to one year had elapsed from the last extraction.

Exclusion Criteria:

• • Patients with systemic diseases that might affect bone quality, contribute to bone resorption, increase surgical risk, or delay/complicate post-operative healing.

  • Patients with parafunctional habits such as bruxism, clenching, or grinding.
  • Patients with residual ridge covered by inflamed, ulcerated, or flabby mucosa.
  • Patients with inadequate inter-arch space.
  • Patients with abnormal tongue behavior and/or size.
  • Patients with xerostomia or excessive salivation.
  • Heavy smoker patients and alcoholic patients.