August 9, 2022
by Faisal Al Assadi, BDS, PGCert HPE
Dental implants have been the recommended treatment of choice as a conservative approach in replacing missing teeth while preserving adjacent tooth structure when compared to fixed dental prostheses.1 The ability of the implant supported crown to replicate natural tooth like emergence profile provides the advantage of achieving higher aesthetic results in the anterior zone.2 Their high survival rate of 98.6 percent following 5 years of implant loading have supported implant therapy to be a highly predictable treatment option.3 However, careful planning related to implant position and angulation prior to implant placement allows for screw retained implant supported crowns to be used avoiding the complications related to cement retained crowns.4 Moreover, the importance of building the emergence profile of the restorations plays a major role in preserving the peri-implant soft and hard tissues hence influencing the long term success and survival.
According to previous studies, the stability of the surrounding crestal bone depends on the integrated junctional and connective tissue around the implant. This soft tissue barrier protects the underlying osseointegrated crestal bone from bacterial invasion and therefore increasing the success and survival rate of the implant. Berglundh et al termed the connective tissue zone as “connective tissue integration”.5 The vertical biologic width from the bottom of the junctional epithelium to the bone level ranges from 1 to 1.5mm where the sulcular and junctional epithelium range between 2 and 2.5mm.6 If the biological width is lacking, the bone will resorb to form the “appropriate biological dimension” reestablishing the biologic width.7 The depth of the biologic width also allows for a smoother emergence profile to be created forming connective tissue contour and junctional epithelium contour with no steep emergence from the implant platform to the extracoronal structure of the crown. Therefore, a well-designed provisional crown with smooth emergence profile connecting the implant platform to the contours of the prosthetic crown will avoid blanching of the soft tissue and allow the gingiva to grow and maintain the biologic width.
The importance of achieving a healthy and stable vertical soft tissue barrier around the implant is vital for the long-term success of implant therapy. This is especially important in the anterior aesthetic zone providing favorable emergence profile of the prosthetic crown to avoid impinging of the surrounding soft tissues allowing for healthy growth.8 To achieve an ideal emergence profile, it is important to mold the surrounding soft tissues prior to fabrication of the final implant supported crown. This can be done utilizing customized provisional crown to build or modify the curvature of the labial free gingiva and provide the required lateral support to interproximal papillae. Consequently, achieve a stable tissue form which can then be replicated by the lab technician into the final restoration.9 Depending on the timing of the implant placement, immediate or delayed/conventional placement, the time taken for the soft tissues to achieve the stability varies.
With recent advancements in digital dentistry, implant placement and restorations can be optimized with a digital wax-up and 3D implant planning software. The implant planning software can merge cone beam computed tomography (CBCT) as a DICOM file with the digital intraoral scan of the patient along with the virtual wax up which are usually an STL file format. This allows for a prosthetically driven implant placement or as described by Garber and Belser “restoration-driven implant treatment planning”10 and therefore permit the use of screw retained restorations predictably. Based on the planned position, the provisional crown can then be fabricated through additive or subtractive CAD-CAM technology or made at chairside. This case report demonstrates a technique used to fabricate a chairside implant supported provisional crown in the anterior zone with conventional loading utilizing a digital wax-up based on the 3D implant planned position and a prefabricated Tempshell with bilateral wings using a 3D printed dental model resin.
A 70-year-old female patient was presented with horizontal fracture at the gingival level of tooth supported crown #11. Due to the fracture level and the lack of ferrule to support a new tooth supported, the tooth was deemed unrestorable and recommended for extraction. Single implant supported crown following conventional loading was the treatment of choice. Subsequent to stage II surgery, the implant platform was exposed and healing abutment placed. (Figs. 1 & 2) A digital wax-up was used to print a 3D dental model resin and a silicon matrix of the wax-up was made. Using the silicon matrix and previous cast with missing tooth #11, a customized provisional crown was fabricated following ideal digital wax-up and bilateral wing extensions to provide a reproducible accurate seating of the Tempshell. (Fig. 3) The Tempshell was seated intraorally and a titanium temporary abutment was used to pick-up the Tempshell with flowable composite resin. (Fig. 4) The abutment was then unscrewed from the implant and the wings were trimmed and the emergence profile was built extraorally from the coronal contour of the crown to the implant abutment junction with flowable composite. (Fig. 5) The provisional crown was then finished, polished and tried-in ensuring no blanching of the soft tissues was observed. The provisional crown was hand tightened and screw access channel was sealed with Teflon tape and fermit. The custom-built emergence profile will then be used in fabricating the final
The ability to follow a prosthetically driven approach based on 3D digital planning allowed for a screw retained prosthetic option to be utilized. The screw access channel was placed on the palatal side of the crown hence improving esthetics and avoiding complications of possible residual cements if cement retained crowns were to be used. This have also allowed for a more predictable provisionalization procedure following the digital wax up, building a smooth emergence profile to adapt the peri-implant soft tissues prior to final crown fabrication. Furthermore, any modifications to the shape and dimensions of the provisional crown can be done clinically and copied into the final prosthesis. A digital scan of the soft tissue emergence profile and the crown can then be taken and sent to the lab technician for
fabrication of the final prosthesis.
Alternatively, a customized impression coping can be used with a conventional open tray impression to replicate the soft tissue profile in the impression. The emergence profile will remain identical in the final crown and hence providing better soft tissue integration preserving the underlying osseointegrated crestal bone resulting with improved aesthetics and prognosis of the treatment.
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About the Author
Faisal Al Assadi completed his Bachelor degree of Dental Surgery, BDS, in Saudi Arabia and PG Certificate in Health Professions Education at the University of Glasgow. I am currently a second year MSc candidate and Graduate Prosthodontics resident at the Faculty of Dentistry, University of British Columbia. I have no financial interests to be disclosed. firstname.lastname@example.org – 6090 Iona Drive, V6T 0B6 Vancouver, BC, Canada.