Digital Versus Conventional Impression CAD\CAM Constructed 4- Implant Supported Mandibular Overdenture Base
Condition: Implant Complication
Study type: Interventional

Summary: 
      This clinical study was done to compare between digital with conventional impression used in
      the CAD/CAM constructed 4- implant supported mandibular overdenture base regarding their
      effect on the bone height changes
    

Detailed description: 
      The patients were classified randomly into two equal groups according to impression
      techniques of mandibular implants and residual ridge:

      Group 1: conventional impression group (CIG). Group 2: digital impression group (DIG).

      For group 1 :

        -  Unscrew the provisional acrylic denture from the implants

           . - The long transfer copings (implant level) were screwed to the implants.

        -  The transfer copings were splinted with orthodontic ligature wire and light cure
           composite resin before impression making to prevent movement of the transfer coping
           during impression procedure.

        -  A stock/special tray was perforated to allow passing of the transfer copings through it
           without interference and permit unscrewing of the transfer after setting of the
           impression

             -  - If there is large opening occurred, the opening was closed off using base plate
                wax to support the impression material, with the guide pins perforating the wax

             -  - Inject the light body rubber base impression around the transfer coping. Fill the
                tray with a heavy body impression material and insert it intraorally till the tips
                of all the guide pins are appeared, clean the guide pin access holes from excess
                impression material.

        -  Unscrew the long transfer coping from the opining of the tray to allow it to be removed
           with the impression material.

        -  Implant analogues was screwed into the transfer coping.

        -  The impression was poured to obtain master cast then attachments(ball and socket
           attachments) were screwed to the implant analogues and metal housings placed on their
           position on master cast.

        -  The lower master cast was scanned using extra oral 3D scanner (DOF Swing dental scanner,
           Correa) to obtain the standard tessellation language (STL) file format.

      For group 2 :

        -  A digital scanner (shining 3D scanner, Germany) was utilized to fabricate the definitive
           prostheses. The attachments were screwed to the implants intra orally and metal housing
           on their position which scanned by using intra oral scanner.

        -  Intra oral scanner transformed into a virtual volume the three-dimensional geometry of
           dental arches using the principle of structured light. A scanning stitching strategy
           carried out by the same experienced investigator and applied to DIG group for the
           attachments on their position on implants.

        -  IOS light source formerly kept parallel to the occlusal plane and started from the
           distal implant of the left quadrant and moved toward the anterior implant of the
           contralateral quadrant (right side); it was then moved back to the distal implant of the
           left side, tilting it toward the palatal side; the occlusal plane was crossed toward the
           buccal side and the camera moved again from the starting scanning point of the left side
           to the anterior implant of the right side trying to keep it perpendicular to the
           occlusal plane.

        -  The image was then inspected and missing regions were filled by fast passages of the
           camera over the related areas.

        -  The same scanning procedure was performed with the other half, from the anterior implant
           of the left quadrant to the distal implant of the contralateral quadrant (right side).

        -  The software automatically was applied a stitching algorithm in order to merge the two
           halves, based on the area between the two anterior implants, shared by both the separate
           scans.

        -  The virtual model was created of the dental implant and attachments in position which
           used to obtain 3d printed master cast by using 3D printer (WANHAO desktop 3D printer,
           Zhejiang, China).

      Then for both groups

        1. After approval of the virtual design preview of the permanent denture base by the
           investigator and technician, a pre polymerized denture base material (Ava Dent Digital
           Dental solutions HQ, Scottsdale, USA) were fabricated by CAD-CAM milling machine
           (DENTSPLY Sirona In Lab MC X5 laboratory milling machine, Germany) according to
           manufacturer' instructions.

        2. The denture base was milled from Pre-polymerized CAD-CAM PMMA acrylic plates (98-mm
           diameter×25-mm thick) by using milling machine.

        3. After the CAD-CAM permanent denture base milled, female parts (metal housing) of the
           attachments cemented on the prepared positions on the fitting surface of the denture
           base by using dual cure glass ionomer resin cement extra orally and cement excess
           removed from the lingual vents on the prepared positions of metal housing .

        4. Record blocks were constructed on the master casts and used to record Maxillo-mandibular
           jaw relation by using milled permanent denture base.

        5. Mounting of the maxillary cast was done on a semi-adjustable articulator† by the aid of
           maxillary face bow and the mandibular cast mounting was done in relation to the
           maxillary cast by centric inter occlusal wax wafer record.

        6. Protrusive wax record was used for adjusting the horizontal condylar angle of the semi
           adjustable articulator, while the lateral condylar angle was adjusted according to Hanau
           equation: L = H / 8 + 12. Where H represents the horizontal condylar path inclination in
           degrees as established by a protrusive record and L represents the lateral condylar path
           inclination in degrees.

        7. Maxillary anatomical and mandibular flat acrylic teeth‡ were arranged for lingualized
           balanced occlusion and try in was done in the patient's mouth.

        8. For the lower permanent denture base teeth cemented on their positions by using self
           cure acrylic resin .

        9. For the upper denture , flasking and processing was done into heat cured acrylic resin
           by the long curing cycle.

       10. After finishing and polishing, the dentures were remounted to adjust any occlusal
           discrepancies and to ensure proper contact in centric and eccentric positions. Final
           adjustment of the occlusion was done intraorally.

       11. The patient was instructed for proper insertion, removal, home care and hygiene and to
           use the denture until the evaluation session.
    

Intervention name(s): conventional impression group; digital impression group
Intervention type(s): Other; Other
Intervention description(s): Silicon impression material loaded on plastic tray and inserted inside the patient mouth; direct scanning was done using intraoral scanner to the female housing of the attachments on position
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment