Update in clinical procedures
Prosthetic considerations when rehabilitating implants in the aesthetic zone
In the aesthetic area, four considerations are essential: form, colour, biocompatibility and mechanical performance. When considering aesthetics, perception is key. The patient’s perception is their subjective interpretation, and it should be carefully explored. An efficient and effective line of communication between the patient, dentist and technician is a prerequisite for good results. With this in mind, we must know which cases can compromise aesthetics over function, or function over aesthetics. The speaker presented three cases to illustrate these concepts (fig 9).
Case 1: congenitally missing upper lateral incisors
The patient wanted to replace their missing teeth. He had an average smile line, narrow restorative spaces, mild soft tissue volume deficiencies, an unfavourable canine relationship, increased vertical overlap and low value, high opacity teeth.
The first step is to prepare a wax-up and a mock-up to plan the aesthetic appearance and to guide implant surgery (fig 10). Provisional restorations guide the soft tissue by the critical and subcritical contours (Su et al., 2010) and the shape of the papilla by the position of contact points (Wittneben et al., 2013). The soft tissue profile is also influenced by times the number of times the abutment has been re-connected: the more disconnections, the more tissue is lost.
Then, the supra- and infra-gingival shapes should be communicated to the lab and the material must be selected. Zirconia abutments can provide good aesthetic results (Brodbeck et al., 2003), but they are vulnerable to fatigue. Intraoral forces can break the abutments (Stimmelmayr et al, 2012, Klotz et al., 2011) or the implant platform may be damaged by the zirconia abutment (Kim 2013).
The alternative is to use zirconia-titanium in the abutment and a titanium-titanium connection between the abutment and implant platform (Guilherme et al., 2016). Although this option maintains the integrity of the implant platform, complications may still occur. Debonding of the titanium base or fracture (either of the titanium base or of the zirconia part) must be addressed by re-cementing the abutment base or replacing the whole abutment (Putra et al., 2019). Other biological complications may arise directly from veneered zirconia reconstructions cemented extraorally on non-original titanium bases. The significant increase in PD and BoP values observed in these cases may be due to the wide diameter and reduced height of the non-original bases (Asgeirsson et al., 2019).
Alternatively, whole titanium abutments can be chosen. These can also be gold coloured. It has been shown that patients do not perceive these abutments as unaesthetic (Bidra & Rungruanganunt, 2013). In this patient’s case, customised gold-coloured titanium abutments were used to prevent potential mechanical problems in the narrow spaces, and zirconia copings with ceramic crowns were cemented over them (fig 11–12).
To prevent the cement from flowing into the sulcus when the crown is inserted, a smaller copy of the abutment should be used (Wadhwani & Piñeyro, 2009).
Case 2: fractured upper central incisor
In this case, the fracture was in the crest level. Although controversial, the patient decided to extract the tooth and replace it with an implant. The coronal fragment of the tooth was attached with composite to a titanium cylinder and used as an immediate provisional (fig 13). To prepare the new provisional from the lab, a customised transfer was used to transmit the subgingival contour to the technician (fig 14). Additionally, pictures – normal and polarized – and videos of the patient smiling and talking were sent by email, and a telephone conversation was held to help explain the details. To perform the few changes required in the shape, a second provisional was made as an exact replica of the first one that was sent to the lab. The patient was travelling from Switzerland to Portugal and so there was limited clinical time with her available. By giving her a second provisional while maintaining the first one made out of the tooth fragment, the shade matching ability was improved. Cross-polarized pictures were also used, which can be very helpful for carrying out a virtual try-in of the final restoration. For this reason one single central incisor restoration was delivered in only one take. A virtual try-in was made before the definitive prosthesis was fabricated. The whole process demonstrates how difficult it is, and the effort required to achieve comprehensive communication with the technician in the quest for perfection.
The three disconnections in this case led to a degree of soft tissue volume loss, which has been established in the literature (Degidi et al., 2011; Grand et al., 2012; Koutouzis et al., 2017) (fig 15).
Case 3: acquired mucogingival deformities
The third case involved a young patient who wanted a pretty smile. They presented with missing soft tissues in 21–22 caused by periodontitis and a high smile line. Overcorrection by orthodontic extrusion was performed, and the surgical guide was then made to extract 21–22 and place two implants (fig 16–17). The early provisionals guided the cicatrisation; they looked good, but the patient didn’t like them because the teeth weren’t white enough and looked too wide. This feedback was communicated to the lab, and the veneers were cemented and new impressions of the two implants were sent with customised transfers. The final result was successfully accepted by the patient.
- form and colour are both important, but in the end the colour changes we perceive as dentists are not perceived by the majority of our patients if the remaining aesthetic parameters are met
- communication with the lab is of paramount importance
- the sub- and supra-gingival contours should be transferred
- videos with explanations can be more illustrative of the changes that need to be made in the laboratorial side, and polarised pictures make it easier to communicate exact colours
- we can compromise on aesthetics over function in cases involving colours low in value and high opacity teeth
- close attention must be paid to patients with a high smile line
- we can compromise on function over aesthetics when there is enough restorative space (both horizontal and vertically) and with aesthetically driven patients