P. Gehrke¹, A. Strohecker², G. Dhom¹

Introduction: Reliable peri-implant soft tissue regeneration represents a complex surgical and prosthetic challenge. Due to clinical limitations, group-specific perceptions of gradual soft tissue alterations versus ideal situations seem to be of special interest especially if the viewer’s profession is taken into account.

Aim: The aim of the study was to assess the influence of papilla length and position of the interproximal contact space in symmetric and asymmetric situations by comparing the esthetic perception of dental professionals and laymen. Furthermore, it was determined which factors have affected the evaluation in case of deviations from the optimal standard in the anterior region.

Material and Methods: Based on an ideal, digitally optimized reference picture of an anterior region, sequential alterations of papillary length and position of crown-contact point were performed by digital imagery. The digitally altered pictures were rated and assessed based on a questionnaire by 105 dentists and 106 laymen. Statistical analysis included description and assessment of scaling parameters according to the Mann-Whitney U test, the Kruskal-Wallis test and the Chi quadrant test. A possible influence of age and gender in both groups as well as the professional and educational background of laymen and the professional degree of dental specialists were considered.

Results: The phenomenon of papillary loss with a resulting “black triangle” in the midline was detected at an early stage both by laymen and dental specialists. However, they were evaluated differently with respect to esthetic consequences. Laymen tolerated the gradual loss of papilla as long as the remaining interproximal space was filled completely with mucosa due to prolongation of the contact point and if a “black triangle” could be avoided. Asymmetric alterations of the contact point or papillary length in the lateral arch were assessed significantly more critically by clinicians.

Keywords: Interproximal papilla length; symmetric; asymmetric; perception of implant esthetics1 Indroduction

Predictability of osseointegration in implant dentistry with documented long-term results of more than 95 % resulted in extending the solely functional treatment spectrum of edentulous patients to esthetic single-tooth restorations in the anterior region [13]. Since, besides the eyes, the mouth influences the impression on facial balance the most, implant-supported restorations replacing upper incisors and their peri-implant soft tissue are an important esthetic aspect of the smile. The shape, the absolute and relative crown size, the quality and quantity of the peri-implant mucosa as well as the interproximal papillae are relevant for the success or failure of an esthetic implant-supported restoration in the anterior region. While today peri-implant integration of hard tissues is a matter of routine, the esthetic integration of implant-supported restorations and surrounding tissues are still a challenge.

The anterior maxilla of the natural dentition displays a significant range of variation. Nevertheless, a number of basic parameters positively influencing the esthetics of the anterior region can be defined. Three basic shapes of upper middle incisors can be distinguished with differing emer-gence profiles from human to human: triangular, oval or square. The width of natural upper incisors ranges between 8.3 and 9.3 mm, while the length usually ranges between 10.4 to 11.2 mm [28, 34, 48]. The length-to-width ratio of middle incisors is around 80 % [4, 42, 52]. Other authors have limited the optimal quotient between 75–80 % [9]. These scales are independent of the absolute tooth size and convey the distinctive look to upper incisors. Unfortunately, this ideal scale matching (“golden proportions”) of the six upper anterior teeth can be found only in 17 % of all natural dentitions [38]. Analogous, the lateral incisors of maxillary implant-supported restorations should look smaller by the factor 0.618 as compared to the canines. On the other hand, the middle incisors should be 1.618 larger than the lateral ones [25]. Application of this rule is however restricted to front viewing. Therefore, restoring esthetics has to be customized for each patient. Subjective preferences and the variations of natural dentitions have to be considered [41].

In addition, a smile becomes even more esthetic if the number of interdental contact points between the middle incisors and the canines is high. An imaginary line runs along the interdental contact points parallel to the emergence of the incisal plane and the lower lip line [27, 31, 40]. The incisal profile is determined cervically by the marginal gingiva and by the peri-implant mucosa for implants. According to Kois, two distinctive periodontal patterns of soft tissue are present in the oral cavity: the thin scalloped biotype and the thick flat biotype [4]. Each type has distinctive morphological characteristics. The thick flat biotype is charcterized by adequate amounts of masticatory mucosa. It is dense and fibrous in nature with minimal height difference between the highest and lowest points on the proximal and facial aspects of the marginal gingival; therefore, it is called flat. Larger-sized teeth that are most likely square characterize this type of periodontium. The typical reaction of this tissue type to trauma is inflammation and apical migration of the junctional epithelium. The thin scalloped biotype of periodontium exhibits its own distinctive features. These include thin, friable gingiva with a narrow band of attached masticatory mucosa, and a thin facial bone that usually exhibits dehicencies. The tooth crown shape generally exhibits a triangular form, and the contact points are smaller and located in a further incisal location. The gingival biotype of the implant site decisively influences contour, texture and transparency (colour) of the soft tissue for risk analysis. These parameters have been reported in the literature as relevant for differentiating between esthetic success and failure [2, 8, 21]. A typically scalloped peri-implant mucosa is achieved if papillae are present in the interproximal space and their tips lie more coronally between the canine and the middle incisors. In naturally-looking implant-supported rehabilitations the shape of the interproximal papilla adjusts to the position and size of the interproximal crown contact point [10, 49]. In case of single tooth implants, its position decisively influences the presence of papillae and should not exceed 3–5 mm to the crestal bone of the adjacent tooth [11, 32, 33, 50, 51]. In fact, the papilla will be supported by the approximal bone of the tooth, not by the surrounding bone of the implant. A biotype with thick tissue can be of clinical advantage for single tooth crowns in the anterior region since, as a rule, it is more resistant to recession. This biotype is characterized by a strongly attached tissue stripe. In case of a weak biotype, the thin, fragile soft tissue favors the formation of approximal papillae, but is more prone to recession which significantly increases the esthetic risk [19, 20].