Milled in Versus Round Bar for Mini-implant Retained Mandibular Overdentures
Condition: Bone Loss
Study type: Interventional

Summary: 
      purpose: The primary purpose of this retrospective radiographic study were conducted to
      compare between milled bar and round bar for mini implant retained overdentures (IODs) on
      peri-implant bone changes and posterior mandibular ridge resorption .Study Design: A
      convenience sample of 18 completely edentulous participants were selected for this
      retrospective study from patients originally available at the start of the trial .

      The null hypothesis was that there were no significant difference between milled in and round
      bar attachment retained implant supported overdentures in posterior ridge resorption and
      peri-implant bone changes.
    

Detailed description: 
      Study Design:

      A convenience sample of 18 completely edentulous participants were selected for this
      retrospective study from patients originally available at the start of the trial. The
      patients were informed about the study objectives and they were signed an informed consent
      and the protocol were approved by the Ethical Committee, Faculty of Dentistry, Mansoura
      University.

      The patients were equally divided into two groups at the start of the trial. The patients
      (average age 45-60 years) were selected for this study from outpatient clinic of Removable
      Prosthodontics Department, Faculty of Dentistry, Mansoura University.

      Patients' criteria:

      Completely edentulous maxillary and mandibular residual alveolar ridges covered with healthy
      mucosa without any remaining roots or local inflammation as detected by digital panoramic
      x-ray and clinical examination.. Anterior mandibular bone length was sufficient to allow
      proper implant placement as assessed by digital panoramic radiograph. Patients were of class
      I Angel's maxillo-mandibular relation with at least 22mm of restorative space allow for bar
      construction as detected by tentative jaw relation, and good bone quality (classes 1 to 3
      according to Lekholm and Zarb). Participants with diabetes mellitus, osteoporosis,
      immunological dysfunction, anticoagulant medication, radiation to the head and neck region,
      smoking habits ,and systemic diseases that interfere with implants osseointegration were
      excluded from the study .For each patient, overdentures assisted by four splinted mini dental
      implants According to type of bar attachment used for splinting the four MDIs, patients were
      divided into two equal groups where: Group I: Received milled-in bar and Group II: Received
      round bar joint attachment. O-Ball impression copings were snapped directly onto each O-Ball
      MDI Implant. A Pick-Up closed tray impression technique was made using polyether impression
      material. MDI Lab Analog was pressed into the coping until a snap fit was observed .The
      impression was poured into dental stone to form a stone model for scanning Bar construction

      Milled-in bar construction for group I:

      The cast was scanned using 3SHAPE TRIOS and the bar constructed throughout the production
      steps:

      Step 1: Order Creation ,Step 2: scan the lab analog of MDI on the stone model scanned with
      D700 scanner. Step 3: CAD Designing (first select preparation in teeth view from canine to
      canine-click abutment button-choose restoration type (bar)-choose restoration material (wax)
      .Step 4: Sending to CAM for Manufacturing, Step 5: Manufacturing (cutting from disc of
      modeling wax). After casting into cobalt chromium alloy, the metal bar was secured into
      position on the cast and adjusted to the table of the milling machine. The facial and lingual
      guide planes were refined and the bar was finished and polished to a high shine.

      Round bar fabrication for group II:

      Prefabricated plastic bar pattern (RHIN 83 OT BAR multi use) was pre scanned for
      standardization of all cases. After cast scanning the abutment copy was designed and again
      standardized for all MDI. The pre scanned bar was inserted over the copies. The same
      procedure for manufacturing was followed as that of milled -in bar.

      The finished bar is brought to the patient's mouth, seated accurately. The denture is then
      tried, fitted and extensions adjusted in the usual manner. The denture fitting surface was;
      the hygienic space under the bar was blocked-out with wax.

      For group I: Metallic Retentive clips were directly fastened to the bar. After the occlusion
      was rechecked, the clips were picked-up using auto-polymerized acrylic resin while the
      patient was instructed to close lightly in centric occlusion.

      For group II: plastic clip was adapted to their metal sleeve, adapted to the bar, the
      occlusion was checked and then they were picked-up using auto-polymerized acrylic resin while
      the patient was instructed to close lightly in centric occlusion. After finishing and
      polishing procedures, the mandibular denture was clinically remounted to adjust any
      interferences in the centric and eccentric the occlusal contacts.

      The prosthodontic maintenance required for the IODs and opposing dentures were evaluated
      during a 8-year follow-up period and compared between the 2 bar design attachments for IODs.

      Patients' evaluation

      Radiographic Evaluation of peri-implani bone changes:

      A. Long cone paralleling technique and a film holder designed specifically for implant
      imaging will be used for intraoral radiograph. To maintain the same film- implant distance
      and cone implant distance, a modification will be carried out for the film holder. This
      modification is a hole drilled exactly above the implant fixture so the distance will be
      maintained during subsequent film exposures. Through this modification, standardized
      radiographs will be achieved.

      B. The long cone periapical radiographs will be taken using a digital photostimulable
      phosphor plate (PSP) aligned parallel to the implant and all radiographs will be taken by the
      same standard intraoral X-ray machine with exposure settings of 60 kV, 7 mA for 0.16 s.
      Subsequently, lines and reference points will be marked. Detect magnification error by
      comparing the implant dimensions in the radiographs with the actual implant dimensions this
      ratio allow us to obtain the actual values of the bone changes.

      C. For marginal alveolar bone changes, the distance between implant shoulder (A) and first
      bone to implant contact (B) indicated vertical bone level (DIB) in mm. Vertical bone loss
      (VBL) will be calculated by subtracting DIB at (T8) from DIB at T0. Alveolar bone changes
      will be measured mesially and distally. B. periapical x-ray will be done immediately at
      insertion (T0) ,the second one (T3), and after 8 years following the insertion (T8).

      Evaluation of Posterior Mandibular Alveolar Bone Changes:

      Posterior area index will be evaluated by proportional measurement of a posterior mandibular
      area like the method described by Wright and Watson. Two panoramic radiographs will be taken,
      one at time of insertion (T0) and the second one after 8 years following the insertion (T8).
      The reference points and lines will traced using AutoCAD 2018 software.

      The posterior mandibular area will outline by joining points at the gonion (G/G') to the
      lower border of the mental foramen (M/M') and the sigmoid notch (S/S'). (N/N') representing
      the center of the triangle joining the three points M-S-G/M'-S'-G'. Reference area will be
      represented by a line joining M-G-N/M'-G'-N'. The experimental area will determined
      A-P-G-M/A'-P'-G'-M' where A-L/A'-L' represents the crest of the mandibular ridge to the lower
      border of the mandible and perpendicular to the M-G/M'G' line. The area difference which
      represents the bone resorption will be calculated by the equation (X/Y+X'/Y')/2 where X/X'
      represents the experimental area and Y/Y' represents the reference area.
    

Intervention name(s): panoramic x-ray
Intervention type(s): Diagnostic Test
Intervention description(s): Long cone paralleling technique and a film holder designed specifically for implant imaging were used for intraoral radiograph. To maintain the same film- implant distance and cone implant distance, a modification were carried out for the film holder. This modification is a hole drilled exactly above the implant fixture so the distance were maintained during subsequent film exposures. Through this modification, standardized radiographs were achieved.
Other intervention name(s): periapical x-ray
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: A convenience sample of 18 completely edentulous participants were selected for this retrospective study from patients originally available at the start of the trial .
The patients were equally divided into two groups at the start of the trial. The patients (average age 45-60 years) were selected for this study from outpatient clinic of Removable Prosthodontics Department, Faculty of Dentistry, Mansoura University
Masking: Single (Investigator)
Primary purpose: Other
Keywords: milled bar; round bar