Abstract
The aim of this study was to determine the correlation between the papilla deficit and the distance between the bone crest at the neighbouring tooth and the contact point of the clinical crown (distance 4) for immediate and delayed zirconia implants. This prospective observational study included 78 patients with 82 implants investigated at the 1-year follow-up. Patients received single-unit zirconia implants (Straumann PURE Ceramic Implant with ZLA surface) that were placed using either the delayed (group A) or immediate (group B) protocol after tooth extraction. The distance of the alveolar crest of the neighbouring tooth to the height of the interdental papilla and the absence of the papilla were also assessed. There was a strong correlation between the papilla deficit and distance 4 in group A (Spearman’s rho = 0.64). However, in group B, only a weak correlation between the two distances was found (Spearman’s rho = 0.28). A full soft tissue margin was generated when distance 4 was 7–8 mm or less. Delayed implant placement showed a critical distance between the alveolar crest at the neighbouring tooth and the contact point of the crown risking a visible papilla deficit of between 7 mm and 8 mm.
More than 90% of patients show so-called ‘pink and white’ aesthetics regarding the upper lip line. Two possible surgical approaches to achieve a highly aesthetic result, particularly in the anterior region, are the early placement of implants after tooth extraction and delayed implant placement. Immediate implant placement requires carefully considered patient selection and a high level of surgical experience; integrity of the buccal alveolar wall and ideal preoperative hard and soft tissue levels should be present.
The soft tissue margin and the interdental papilla formation are very important for an aesthetic outcome. When titanium implants are used in the sensitive aesthetic zone, a gray metal shadow, particularly in those with thin mucosa types of a thickness less than 3 mm, may reduce the aesthetic success. In contrast, zirconia implants (ZrO 2 ) have a natural tooth-like colour and thus eliminate the problem of dark shadows showing through the gingiva. During the healing process and integration of titanium implants, recession of the soft tissue and bony alveolar structures may negatively affect the level of the facial mucosa. In this context, the worst case scenario is a total loss of the interdental papilla formation, leading to so-called ‘black triangles’.
The new full ceramic material zirconia has been shown to be comparable to titanium with respect to their properties. The integration of magnesium, aluminium, or yttrium ions has led to an extremely stable and reliable product. Furthermore, a monotype full ceramic implant with a micro-rough surface has been developed and shown to deliver almost identical values for removal torque and histomorphometric parameters (such as bone density and bone contact ratio) in animal experiments. Customer bias against zirconia implants as a result of the degraded surfaces and material failure seen in the past has declined with the development of new more mechanically stable products.
Generating full papillary fill, especially in the interdental space, is a challenging task. Several authors have assessed the peri-implant distances that affect the presence or absence of the interdental papilla. The distance from the contact point of the crown to the alveolar crest, the bone contact at the implant, and the bone crest at the neighbouring tooth influence the papilla height. Nevertheless, the most powerful effect on the papilla height has been described for the distance between the bone crest at the neighbouring tooth and the contact point of the clinical crown (termed ‘distance 4’ in the present study).
Long-term studies on the behaviour of the peri-implant hard and soft tissues and the assessment of the outcome of immediate implantation of zirconia monotype implants after tooth extraction are scarce in the published literature. Therefore, the aim of this 1-year follow-up study was to evaluate the relationship between the papilla height and the alveolar crest level of both teeth neighbouring a zirconia monotype implant. It was hypothesized that immediate implant placement would present the same results as delayed implant placement regarding the correlation between the papilla height and distance 4.
Materials and methods
Study design
All patients were treated between July 2012 and August 2014. The exclusion criteria for implantation included systemic disease (e.g., uncontrolled diabetes), endodontic lesions, mucosal disease, untreated periodontitis, smoking, missing contact point between the crowns, and gingivitis. The study protocol was approved by the ethics committee of the medical faculty. This prospective observational study was performed in compliance with the STROBE statement (strengthening the reporting of observational studies in epidemiology). Two experienced surgeons conducted the implant treatment, and one examiner performed the follow-up assessment. The clinic for prosthodontics controlled all measurements.
Full zirconia monotype implants (Straumann PURE Ceramic Implants with ZLA surface; Straumann AG, Basel, Switzerland) of three lengths (8, 10, and 12 mm) and with two abutment sizes (4 and 5.5 mm) were used. The implant had a diameter of 4 mm in the part placed in the bone, a thread pitch of 0.8 mm, and was of a self-cutting design.
In group A (66 implants in 62 patients), delayed implant placement was performed 3 months after tooth loss or bone augmentation based on a healed and remineralized stable bony morphology, as required for a safe integration process. Implant placement, sometimes with accompanying augmentation, was followed by a period of 3 months without prosthetic loading. For conditioning of the soft tissues, a provisional crown was placed after successful implant osseointegration. To ensure physiological implant integration, the patients received a deep-drawing template for placement over the adjacent teeth and implant. The patients were instructed to use the template during food intake. Finally, the full ceramic definitive crown was positioned. Patients who underwent a two-step augmentation procedures were excluded from group B and were included in group A. In these cases, an additional time period of 3 months from augmentation to implant placement was necessary ( Fig. 1 ).
In group B (16 implants in 16 patients), based on favourable initial conditions, implant insertion took place immediately after tooth extraction. This was done with accompanying augmentation in most cases. To ensure physiological implant integration, patients were briefed to avoid hard food for 1 month. The immediately placed temporary crown was taken out of any loading contact to allow undisturbed osseointegration of the implant. After 3 months, the final prosthetic crown was cemented ( Fig. 2 ). Exclusion criteria for an immediate implantation were as follows: inflammation in the implant region, extensive alveolar deficit, traumatically induced tooth extraction, unfavourable tooth axis, and lack of primary stability of the implant; these patients were included in group A.
Data collection
The primary outcome variables were distances 1–4, and whether a relationship between the papilla height and the alveolar crest level of both neighbouring teeth could be evaluated. In addition, implant success was assessed. The four distances were determined by radiographic and clinical evaluation ( Fig. 3 ; Table 1 ). The assessment was performed according to a previously published method.
