Preventing Peri-implantitis with a proper Cementation Protocol and with the consideration of alternatives to Cement-Retained Implant Restorations

Successful implant restoration is depending on an adequate surgical and prosthetic protocol. In the last few years an increase in Peri-Implantitis has been attributed, in part, to the excess cement left around the implant collar and threads, leading in many cases to bone loss and even the complete failure of the implant treatment [1-5]. This article will attempt: 1. To describe a proper cementation protocol for cement-retained implant restorations to reduce cement induced implant failures, and 2. To review the alternative implant restorative options to cement-retained crowns such as screw-retained restorations, screwless and cementless implant restorations, screw-retained-cemented implant crown, angulated screw channel restorations, the lingual locking screw-retained restorations and the multi-unit abutment restorations. Case Report Preventing Peri-implantitis with a proper Cementation Protocol and with the consideration of alternatives to Cement-Retained Implant Restorations Tony Daher1*, Robert G Mokbel2 and Vahik P Meserkhani3 1Private Practice Limited to Prosthodontics and Implant Dentistry, La Verne, California, USA 2Private Practice Limited to Prosthodontics and Implant Dentistry, Fountain Valley, California, USA 3Private Practice Limited to Prosthodontics and Implant Dentistry, Glendale, California, USA *Address for Correspondence: Tony Daher, Private Practice Limited to Prosthodontics and Implant Dentistry, La Verne, California, USA, Email: tonydaher@verizon.net Submitted: 23 October 2018 Approved: 25 October 2018 Published: 26 October 2018 Copyright: © 2018 Daher T, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited


Introduction
The dental implant should be placed in an optimum position according to the predetermined prosthetic restoration. A Screw-Retained Implant Crown (SRIC) is mostly desirable when possible [4]. When an implant is not adequately placed, and the access hole does not end up in the middle of the occlusal surface or to the lingual of the incisal edge, an implant cement-retained restoration is commonly indicated. Residual excess cement after placement of single or ixed partial dentures has been associated with clinical and radiographic signs of peri-implant disease in 81% of the cases [4] (Figure 1). Once the residual excess cement is removed surgically with the administration of an antibiotherapy regimen, clinical signs of the peri-implantitis will resolved in 74% of the tested implants (Figures 2,3). During the cementation of such restorations, it was demonstrated that a risk of leaving excess cement behind in the implant gingival cuff exists [4].
When a cement-retained implant restoration is indicated, an adequate cementation protocol must be followed so no excess cement is wedged in the implant gingival sulcus [3] (Figure 4).
For a successful cement-retained implant restoration, it was demonstrated that the presence of adequate thick and attached gingiva, an adequate abutment margin placement at or above the gum level ( Figures 5,6), an adequate abutment height and taper for proper resistance and retention form, (Figure 6), and adequate cementation protocol as described below (Figure 4).

Implant restoration cementation protocol [3] (Figure 4)
Once the restoration has been adjusted, then its seating is con irmed with a radiograph and approved by the patient, the cementation process proceeds as follows: 1. Fabricate a chairside duplicate abutment using a PVS bite registration material.
Squirt the PVS bite material inside the crown and form a handle-base outside the crown(s).
2. Place the implant abutment over the implant in the patient mouth, using a new clinical screw, torque it to implant company speci ication. (Most companies recommend 30 to 35 Ncm).
3. The screw should be allowed to relax for 10 min. to reduce deformation elongation. Then the screw is unscrewed and then torqued a second time before proceeding with the cementation procedure.
4. If the margins of the custom or milled abutment are subgingival (often on the facial), tacking a cord around the neck of the abutment can help catch most of the cement that may still leak inside the sulcus.
5. Fill the crown with a radio-opaque cement such as Temp-Bond after cleaning the crown intaglio surface(s) with alcohol and seat fully the abutment duplicate(s) into the crown(s). This will remove most excess cement outside the mouth. Keep in mind that you need to work fast.
6. Add a tiny dap of temporary cement inside the crown at the gingival area then seat the crown on the abutment, clean any excess and remove the cord.
7. Make a inal periapical radiograph for veri ication purposes.

Alternative options to the cement-retained implant restorations
Screw-Retained Implant Restorations (Figure 7): A well-placed implant will allow appropriate contours of the restoration and the access hole for a screw retained restoration will be placed in either on the occlusal or lingual surfaces. This will result in a functional and esthetic restoration. Weber et al. [6], in a prospective clinical study, evaluated the plaque index (MPI), sulcus bleeding index (SBI), keratinized mucosa (KM), gingival level (GL), around ifty-nine crowns (38.82%) were cement retained, while 93 (61.18%) crowns were screw retained, during a 3-year follow-up period following prosthetic rehabilitation, they found that peri-implant soft tissues responded more favorably to screw-retained crowns when compared with cementretained crowns. However, no soft-tissue recession was observed in either type of crowns. Cement-retained crowns were preferred by dentists, while patients were equally satis ied with either type of crowns they received.
A systematic review of screw versus cement-retained implant-supported ixed restorations study by Sherif et al. [7] showed that "there is no signi icant difference a b between cement-and screw-retained restorations for major and minor outcomes with regard to implant survival or crown loss. This is important data, as clinicians use both methods of restoration, and neither is a form of inferior care."

Screwless and Cementless Implant Restorations (Figure 8):
The Integrated Abutment Crown (IAC) (Bicon, LLC.) [8], is an implant restoration where the implant abutment and the crown material are one unit. The abutment-crown complex is connected to the implant with a locking taper. This technique does not use cement to retain the crown or screws to retain the abutment.
Urdaneta et al. [9], conducted a 3-year retrospective cohort study and found that the clinical outcome of this screwless and cementless system for the single implant restorations compares favorably with the experience of screw-and cement-retained restorations within the observation period.
The Screw Retained-Cemented Implant Crown (SR-CIC) ( Figure 9): This procedure eliminates the cement interface inside the mouth, and avoid the pitfalls of cementation, and renders affordable the implant restoration a screw-retained type. A Ti-base and CAD/CAM or stock abutment achieve these objectives.
The objective is to fabricate a regular crown with a hole that its over the prepared stock abutment (similar to a custom-abutment). The custom abutment or UCLA type abutment is more expensive then the stock abutment procedure. The cost of the SR-CIC is comparable to a regular cemented crown over a stock abutment. This technique provides the same outcome as the UCLA type abutment with being less expense.
The procedure is a follow: 1. A custom abutment, a Titanium-base of a UCLA abutment or a prepared stock abutment, is fabricated, or selected, or milled in the lab or in the of ice. The abutment margins can be juxta-gingival or subgingival, especially in the esthetic areas. Sandblast, and if necessary, apply an opaquer onto the abutment in case of an all ceramic. 3. Make any necessary adjustment to it and adapt the 2-pieces together.
4. Silane the crown as needed and cement outside the mouth using a resin cement keeping the crown access hole free of cement as much as possible.
5. Remove all excess cement outside the mouth and polish the assembled abutment crown.
6. Try-in and torque the SR-CIC as required. Verify seating with an X-ray. 7. Fill the access hole with a Te lon tape or with a light PVS plug and seal it with an appropriate bonded composite restoration. Cotton pellet should never be used as the potential of bacterial.

The screw-retained implant restoration using Angulated Screw Channel (ASC) or the Dynamic Screw Channel (DSC) concept (Figures 10,11)
When the implant is mal-positioned, the access hole for a screw retained restoration would be esthetically unacceptable. In this situation a cement retained restoration is indicated. One way to reduce the dependence on the cement-retained restoration when a screw-retained restoration is not feasible, is the Angled Screw Channel (ASC) abutment or the Dynamic Screw Channel (DSC) abutment (Figure 9), rendering the placement of the screw opening at the lingual surface or at the occlusal surface. The Dynamic Abutment system developed by Talladium International implantology 10 consists of two pieces connected together by an elbow that works as a joint, the system has full freedom of movement in circumference between 0° and 20°. In 2004, an abutment called the Dynamic Abutment (Talladium International Implantology) became commercially available. This abutment can allow a deviation of the restoration screw access angle to the implant angle of up to 28 degrees. This will allow a screw-retained restoration to be connected directly to the implant.
The purpose of using a ASC or DSC is to move the anterior screw access hole lingually ( Figure 11) or to move the posterior screw access opening towards the middle of the occlusal surface rendering the restoration a screw-retained restoration. The technique is as follows: 1. Fabricate a master cast from an implant level impression.
2. Order a dynamic angulated screw channel Titanium-Base abutment or a UCLA Dynamic abutment.
3. Mill a Zirconia crown and cement it over Ti-base abutment. When a metalloceramic restoration is indicated, use a dynamic UCLA abutment (from Preat Corp.), do a full-contoured wax pattern, then make a silicone index, followed by a wax cut-back making less than a 2mm of space for ceramic application. Cast the wax pattern with precious metallo-ceramic alloy, then apply porcelain.

The lingual locking screw for implant-retained restorations [11] (Figure 12)
The advantage of implant-borne screw-retained prostheses is the ability to retrieve it. The removal of cement-retained implant crowns has often proven dif icult due to a multitude of variables, including locating the access and stripped screws and saveguarding the underlying custom abutment. To facilitate its removal a photo of the abutment is made before cementing the crown over. This photo is kept in patient chart to help locate the access hole and retrieve the restoration when it is needed [12] ( Figure 13). A better way that it is available to the practicing dentist is the use of a vertically or horizontally secondary screw to lock the implant crown superstructure to the implant abutment. The concept of a secondary locking horizontal screw [11] or the cross-pin 12 at the crown level allows latitude in ixture position, good aesthetics, and especially retrievability ( Figure 12). The technique of lingual set screw is well described at www.preat.com. The crosspin technique is described in the article of Gervais MJ et al. [13].
The general principles in using either technique, are as follow: 1. These screws are smaller than the abutment screws and not able to withstand occlusal forces without the abutment protection. Designing the abutment in a manner to provide optimum resistance and retention form is a must. This provides protection to the lingual screws against destructive shearing forces.
2. The lab technician must provide a lingual location with an easy clinical access for the placement of the lingual screw. For example, the cingulum area of the anterior teeth, the lingual surfaces of the maxillary and mandibular premolars and maxillary molars and mesio-lingual angle of the mandibular molars due to the position of the tongue.
3. It is imperative to establish the inal shape of the prosthesis early for proper abutment design and contour. This can be established by providing a full contoured wax patterns of the inal restoration on a cast or digitally on a computer.

4.
A medical silicone or just a light viscosity polyvinyl siloxane is used to seal the space between the crown and the abutment during placement procedure. This will prevent any seepage of food in that space. Then the lingual screw(s) will secure the prosthesis to the abutment(s).
The use of multi-unit abutment to overcome mal-aligned implants: When multiple implants are misaligned in the posterior quadrants, multi-unit (MU) abutments could be used to overcome the misalignment by moving the implant internal connection to a taper external connection and render the restoration screwretained ( Figure 14). By using such abutments, the occlusal stress will be moved from the implant screw to the MU abutment small screw. In case of the prosthesis small screw breaks, it is easily replaced and even the MU abutment can be removed and replaced with a similar one. The prosthesis is placed back over. These abutments can be either straight or angulated types are used especially for 4-implant screw-retained prosthesis concept (Figure15).

Summary
The ability to retrieve a restoration is often cited as an advantage of screwretained prostheses. Cemented-retained prostheses have been promoted to allow the restoration of mal-aligned implants. When needed, proper cementation technique must a b c Figure 14: Multi-unit (Octa) abutments for a partially edentulous situation. a) 2 Dentis TM multi-unit octa type abutments. b) 3 Implant connected screw-retained crowns over octa type abutments. c) Occlusal view of the prosthesis in place.
be used to avoid cement implant complication. It is always advisable to plan a screwretained restoration whenever possible. When an implant angulation is present, an alternative to the cement-retained restoration is to use the Angulated Screw Channel concept, the lingual set of screws, and the multi-unit abutment restoration. Soft tissues may respond more favorably to screw-retained crowns when compared to cementretained crowns.
The management of peri-implant disease is not yet fully investigated, the complexity of the etiology and the lack of a uni ied treatment modality make the treatment even less evident. Restorative treatment is part of the problem and new restorative guidelines should be established.