ZBLC MasterClass

It has been suggested in the literature that implant position in relation to bone level might influence bone stability. Therefore, depending on its’ design, implant placement can be supracrestal, crestal or subcrestal. Only if implant is placed according to its design in appropriate position, surgical bone stability will be achieved. It is interesting to note, that not all implants can be placed subcrestally. In addition, implant-abutment connection stability becomes very important, if located subcrestally.

It is suggested that thin tissues might be thickened during implant placement, thus reducing bone resorption. Special guidelines how to work in vertical thin mucosal tissues are necessary, usually starting from subcrestal implant placement. Subcrestal implant position is suggested to cause controlled bone remodeling, but not bone loss, if special requirements are met. The depth of implant placement may depend on various factors – implant/abutment connection stability, absence or presence of platform switching and other. Finally, unique immediate transmucosal multiunit (stay-in abutment), which enables “1 abutment-1 time” theory in practice can be used.

Another option to increase soft tissues vertically, might be recontouring of the bone during basic implant bed preparation, especially if narrow ridge is present. Careful reduction and smoothening of the narrow ridge not only will provide a flat bone surface and enlarged platform area of bone for implant positioning, but also would increase soft tissue thickness as well. The third possibility to augment the tissues vertically is “tent-pole” technique, however there are some limitations, which should be considered, before undertaking this procedure.

If bone height is not sufficient for subcrestal implant placement, vertical augmentation of the soft tissue is recommended with different soft tissues grafts - autografts, xenografts or allografts. Procedures can be performed both in single or 2-stage approaches, depending on primary implant stability and nature of the augmentation material. Autografts produce significant soft tissue increase, however harvesting is difficult, also some studies indicate crestal bone loss after going autogenous. Collagen-matrix xenografts result in less boost of volume, since some shrinking is likely to occur, however bone stability is improved. Up to 6 years follow-up results are here.

Current recommendations allow clinicians to place cementation margins up to 2 mm subgingivally. Recent research has proved that the deeper the position of the margin, the greater amount of residual cement is left undetected. Cement remnants should be considered as a predisposing factor in development of chronic peri-implant disease. The relation between position of cement excess in the peri-implant sulcus, periodontal status of the patient and severity of peri-implant disease is explained. Lecture summarizes how to control cement remnants after cementation, by using supragingival margins and individual abutments.

Titanium base abutments, better known, as Ti-bases, form the foundation of prosthetic rehabilitation in Prosthetic Part of Zero bone loss concepts. To avoid cement excess, finished implant restoration with occlusal opening is cemented on titanium base in laboratory and restoration is attached to the implant intraorally by an abutment screw. Engaging and non-engaging versions should be used accordingly to situation, even poorly positioned implants now can be restored with angulated screw-retained solutions. And indeed, screw-retained Ti-base supported solutions can cover all aspects of implant restorations - single, angulated, FPDs and full-arch.

Titanium bases do possess important aspects in their design. Namely, gingival height and retentive height. Although, they seem similar, yet are different. Gingival height of Ti-base directly influences crestal bone stability, forming the part of the emergence profile of the restoration. It is important, that implant system would have Ti-bases with different gingival heights in their portfolio. Retentive part is important for retention of the finished restoration and must be sufficient to avoid decementation. The issue of sandblasting of titanium bases before cementation is discussed profoundly and recommendations provided.

Zirconium as a material is considered to be one of the best for peri-implant soft tissues. However, it is evident that it must be treated in special manner – to be polished to a certain extent. So clear polishing protocol must be created, that this procedure would be under control. It is important not to make “Zr without Zr” restorations, when veneering porcelain covers zirconia in subgingival zone of the restoration and does not allow the direct contact between soft tissues and zirconium. In that way the biocompatibility effect might be reduced. Other materials, like polished or glazed lithium disilicate, titanium and feldspathic porcelain are discussed as well.

Not only biological, but also technical requirements are important for successful outcome of the treatment. Several restorative materials are available for supragingival part of implant restorations, like anatomical zirconia, lithium disilicate or veneering porcelain. All of them have advantages and disadvantages, which are broadly analyzed. A special technique, which combines fusing of zirconia framework with lithium disilicate will be presented, where zirconia is designed to have contact with soft peri-implant tissues for adhesion and monolithic ceramics is responsible for subtle restorative strength for occlusion.

Step-by-step high quality videos in a pig model show all 4 methods of vertical soft tissue thickening, according to Puisys & Linkevicius (2015) algorithm. Subcrestal implant placement, using 5 mm healing abutment or stay-in abutment for “1 abutment-1 time” concept is demonstrated, along with vertical soft tissue thickening using soft tissue grafts. Practical demonstration is ended with tent-pole method, which includes positioning of 2 mm healing abutment and presentation of special suturing approach, comprised of deep matrix and single interrupted sutures.

Deep position of the implant results in condition, when stability of open tray transfer might be reduced, due to lack of the contact between transfer and impression material. This might lead to less accurate model and subsequently, restoration. A method, suggested by prof. T. Linkevicius (2012) is aimed directly to solve this situation, when slow-setting occlusal registration material is used together with conventional impression silicones to increase open tray coping stability.