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Registration of maxillomandibular relationship through a fully digital workflow for complete-mouth rehabilitation with screw-retained fixed implant-supported prostheses: A clinical report
Corresponding author: Dr Rania E. Ramadan, Department of Prosthodontics, Faculty of Dentistry, Alexandria University, Champlion St, Azarita, Alexandria, EGYPT
Digital recording of the maxillomandibular relationship by using intraoral scanning in completely edentulous patients for computer-aided design and computer-aided manufacture implant-supported prostheses can be challenging. This clinical report describes the fabrication of complete-arch, screw-retained implant-supported prostheses in a completely edentulous patient with a fully digital workflow.
Implant dentistry has advanced greatly in the era of digital technology.
Computer-aided design and computer-aided manufacture (CAD-CAM) technology can be applied not only in implant planning but also in fabricating implant-supported prostheses to restore function and esthetics with predicted efficiency and to save time by eliminating multiple appointments.
with screw-retained prostheses having the advantage of being retrievable compared with cement-retained prostheses, facilitating prosthesis maintenance.
Implementing a fully digital implant-prosthetic protocol in these patients has many challenges with respect to the implant position, digital scanning of the soft tissue, and digital registration of the maxillomandibular relationship, which includes occlusal plane orientation, vertical dimension of occlusion (VDO), centric relation (CR), and eccentric relation. Previous authors
A digital approach integrating facial scanning in a CAD-CAM workflow for complete-mouth implant-supported rehabilitation of patients with edentulism: a pilot clinical study.
Use of a digitally planned and fabricated mandibular complete denture for easy conversion to an immediately loaded provisional fixed complete denture. Part 1. Planning and surgical phase.
have proposed digital techniques to record the VDO. However, these techniques have limitations in that they require a specific system or additional equipment.
A digital approach integrating facial scanning in a CAD-CAM workflow for complete-mouth implant-supported rehabilitation of patients with edentulism: a pilot clinical study.
Use of a digitally planned and fabricated mandibular complete denture for easy conversion to an immediately loaded provisional fixed complete denture. Part 1. Planning and surgical phase.
The purpose of this clinical report was to present a fully digital workflow for the fabrication of complete-arch, screw-retained implant-supported prostheses in a completely edentulous patient.
Clinical report
A 54-year-old completely edentulous man presented to the Prosthodontic Department, Faculty of Dentistry, Alexandria University, Egypt seeking maxillary and mandibular fixed prostheses. Maxillary and mandibular complete-arch fixed implant-supported restorations were presented as a treatment option, and written consent was provided before treatment.
Maxillary and mandibular complete dentures were made on a semiadjustable articulator (Bio-Art A7 plus; Bio-Art) at an appropriate maxillomandibular relationship. The Bennett and condylar inclination angles were recorded by making protrusive and lateral records from the patient using an occlusal registration material (Futar D; Kettenbach GmbH) and then transferring the records to the articulator to be subsequently inserted into a virtual articulator (Bio-Art A7 plus; Bio-Art) during the design of the implant-supported prostheses.
Fiducial markers were attached to the dentures, and a dual cone beam computed tomography (CBCT) scan (PaX-i3D; Vatech) was obtained. Upon CBCT assessment, a decision to rehabilitate the maxillary and mandibular arches with screw-retained complete-arch implant-supported prostheses on 6 implants per arch placed in the lateral incisor, first premolar, and first molar locations. The denture scans were aligned to the maxillary and mandibular CBCT scans using a software program (OnDemand 3D; CyberMed Inc) allowing prosthetically driven implant planning.
The implant sites were planned virtually, and surgical guides were designed in the software program so that all teeth were sectioned from the surgical guide leaving an anterior stop on the central incisors and bilateral posterior stops at the second molars. These stops were to maintain the established VDO and CR of the presurgical complete denture (Fig. 1). The surgical guides were then 3D printed in a desktop printer (Form 2; Formlabs).
Figure 1Surgical guide designed with anterior stop at central incisors and bilateral posterior stops at second molars at established vertical dimension of occlusion and centric relation position of presurgical complete denture.
On the day of surgery, an index was made from silicone putty (Zetaplus; Zhermack SpA) to be inserted between each surgical guide and the opposing denture to position each guide precisely in its corresponding arch (Fig. 2). Then, each guide was stabilized using 3 fixation pins sequentially. Six implants (IS implant; NeoBiotech) were inserted in each arch through a guided flapless surgical approach,
cover screws (IS cover screw; NeoBiotech) were placed, and a postoperative panoramic radiograph was made. The maxillary and mandibular complete dentures adjacent to the implant sites were relieved with an acrylic resin trimming bur (Robot carbide HP cutter; SHOFU Inc) and relined with a silicone soft liner (Mollosil; DETAX GmbH) in occlusion. The patient was provided with oral hygiene instructions, prescribed 1 gm amoxicillin and clavulanic acid (Augmentin; GSK), 600 mg ibuprofen (Brufen; Abbott Laboratories Inc) every 12 hours, and chlorhexidine mouthwash (Hexitol; ADCO) and instructed to adopt a soft diet.
Figure 2Surgical guide in place using silicone index. A, Maxillary surgical guide with mandibular complete denture and index. B, Mandibular surgical guide with maxillary complete denture and index.
After 4 months, the implants were uncovered, and 12 multiunit abutments (IS multiunit abutment; NeoBiotech) with an appropriate collar height and angulation were attached to the implants and tightened to 30 Ncm with a manual torque wrench (Torque wrench; NeoBiotech). Multiunit healing screws (IS healing cap; NeoBiotech) were screwed to the abutments and left for 2 weeks for soft tissue healing (Fig. 3). After soft tissue healing, the healing screws were removed, and the surgical guide holes were slightly widened opposite the abutments with the acrylic resin trimming bur to ensure proper seating of the guide.
Figure 3Multiunit healing screws in place. A, Maxillary arch. B, Mandibular arch.
To digitally register the established maxillomandibular relationship with the complete dentures, 2 indices were made from an occlusal registration material (Futar D; Kettenbach GmbH). The first index was made between the maxillary and mandibular surgical guides using the anterior and posterior stops to register the VDO and CR (Fig. 4A). The second index was made between the maxillary complete denture and the mandibular surgical guide to register the occlusal plane (Fig. 4B). Then, the maxillary and mandibular guides were sectioned into 2 halves along the midline.
Figure 4A, Index between surgical guides using anterior and posterior stops to register vertical dimension of occlusion and centric relation. B, Index between maxillary complete denture and mandibular surgical guide to register occlusal plane.
Multiunit scan bodies (Multiunit scan body; NeoBiotech) were hand tightened on the abutments according to the manufacturer’s recommendations, and an intraoral digital scan of the maxillary and mandibular arch was captured with an intraoral scanner (CEREC Omnicam; Dentsply Sirona) (Fig. 5).
Figure 5Multiunit scan bodies in place. A, Intraoral view of maxillary arch. B, Intraoral scanning of maxillary arch. C, Intraoral view of mandibular arch. D, Intraoral scanning of mandibular arch.
All the scan bodies were removed except for the left mandibular ones; then, the right maxillary and mandibular surgical guide halves were firmly secured in place with the aid of the first index in closure. Intraoral scanning of the contralateral side with mandibular multiunit scan bodies was made; thus, the VDO and CR were digitally recorded. This procedure was necessary as stitching of the scans could not be achieved when both maxillary and mandibular scan bodies were in place (Fig. 6).
Figure 6Registration of maxillomandibular relationship. A, Intraoral view of sectioned guides at correct VDO and CR. B, Registration of VDO and CR with intraoral scanner. C, Intraoral view of maxillary denture, sectioned mandibular guide, and scan bodies at contralateral side. D, Registration of occlusal plane with intraoral scanner. CR, centric relation; VDO, vertical dimension of occlusion.
The occlusal plane and 3D tooth position were digitally registered by inserting and scanning the maxillary complete denture. The left side was scanned using the second index between the maxillary denture and right half of the mandibular guide (Fig. 6). All the digital scans were exported as Polygon format (PLY) files. The following step was to make 2 extraoral photographs with the patient wearing the maxillary complete denture, retracted and smile images, to aid in the smile design.
The PLY files with the extraoral photographs were imported to a CAD design software program (Dental DB 3.0 Galway; exocad GmbH) to design maxillary and mandibular complete-arch, screw-retained fixed implant-supported prostheses. The maxillary prosthesis was designed as a single unit in the software program. Taking into consideration mandibular flexure,
the mandibular prosthesis was designed as 2 segments separated in the midline. The prostheses were designed with a group function occlusal scheme on the virtual articulator (Bio-Art A7 plus; Bio-Art) (Fig. 7A-D).
Figure 7Designing of screw-retained prostheses with exocad software program. A, Framework design. B, Design of prostheses. C, Prostheses design on virtual articulator. D, Smile creator.
A 3D-printed polymethyl methacrylate prototype (Tooth shade resin; Formlabs) was fabricated and evaluated intraorally secured by 12 prosthetic screws (Prosthetic screw; NeoBiotech) to determine accuracy, passive fit, esthetics, proper tooth arrangement, phonetics, and correct maxillomandibular relationship (Fig. 8A). Once evaluated, titanium frameworks were milled from a titanium disk (Starbond Ti5 disc; S&S Scheftner GmbH) using a 5-axis milling machine (Redon hybrid dental CNC; Redon Technology) and evaluated intraorally for passive fit using the Sheffield test, and periapical radiographs were made to verify the fit of the framework on the abutments
(Fig. 8B, C). High translucent zirconia crowns were milled as single crowns from zirconia disks (Ceramill Zolid; Amann Girrbach) and cemented in the laboratory with a resin cement (Duo-link Universal; Bisco Inc). Finally, the gingival part of the titanium frameworks was covered with a pink-colored composite resin (Visiolign; Bredent GmbH) to create natural esthetics (Fig. 9A-E).
Figure 8A, Three-dimensionally printed polymethyl methacrylate prototype for clinical evaluation. B, Milled titanium frameworks in place for clinical evaluation. C, Periapical radiographs of milled titanium frameworks to confirm passive fit.
After evaluating the occlusion, the screws were tightened to 15 Ncm, and Teflon (sterilized plumber’s tape) and light-polymerizing composite resin (Tetric N-Ceram; Ivoclar AG) were placed in the screw channels. Instructions on oral hygiene were provided, and the patient was scheduled for follow-up visits. A panoramic radiograph of the definitive restoration was made after 6 months (Fig. 9F).
Summary
This clinical report described the implementation of intraoral scanning for the registration of edentulous arches with a correct maxillomandibular relationship, producing well-fitting, passive, screw-retained implant-supported prostheses in a completely edentulous patient. This impression-free, time-saving digital workflow overcame drawbacks associated with the conventional procedures.
Acknowledgments
The authors thank Dr Mervat E. Abd-Ellah, Dr Akram F Neena, Dr Jasmin M. Ragheb, and Dr Khaled M. Farrag for their valuable help throughout the clinical treatment.
References
Papaspyridakos P.
Vazouras K.
Chen Y.W.
et al.
Digital vs conventional implant impressions: a systematic review and meta-analysis.
A digital approach integrating facial scanning in a CAD-CAM workflow for complete-mouth implant-supported rehabilitation of patients with edentulism: a pilot clinical study.
Use of a digitally planned and fabricated mandibular complete denture for easy conversion to an immediately loaded provisional fixed complete denture. Part 1. Planning and surgical phase.
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