Defining Aesthetics
Anterior dental aesthetics concerns both the teeth and soft tissue envelope. The teeth display variance and nuances, showing individuality in a given dentition in terms of their size, shape, intra- and inter-arch relationships. The size of anterior teeth is determined by the mesio-distal width divided by the inciso-gingival length, which yields the width/length (w/l) ratio. General guidelines state that the w/l ratio of a central incisor should range from 0.75 to 0.8 and that this tooth type should be the dominant element in the anterior dental composition [1]. The shape of the teeth otherwise is genetically determined and show differences based on age, sex and race.
In relation to the dental hard tissues, the factors influencing the aesthetic perspective of the soft tissue envelope include the anatomy of the dentogingival complex, osseous crest level, periodontal biotype, tooth contact points, tooth position and extra-oral skeletal and soft tissue landmarks. In cross section, the dentogingival complex is composed of three entities: the supra-crestal connective tissue attachment, epithelial attachment and sulcus. The connective tissue and epithelial attachments have been shown to be the most consistent in thickness, while the sulcus depth varies enormously. This attachment is known as the biologic width, which has been quoted as being 2.04 mm [3,4]. Assuming that the osseous crest is in a normal position, this measurement of around 2 mm, together with a sulcus depth of 1 mm, yields 3 mm for the entire dentogingival complex. It is crucial that this equilibrium of 3 mm is maintained and not violated by any clinical procedure.
A thin periodontal biotype, being friable, increases the risk of recession following endodontic surgery. Conversely, a thick biotype is fibrotic and resilient, making it resistant to the surgical procedure, but has a tendency toward pocket formation, as opposed to gingival recession. Gingival recession with the formation of ‘black triangles’ is also more evident in triangular teeth with pronounced scalloping of the gingiva.
A further factor that contributes to anterior dental aesthetics is the extra-oral anatomy, where the peri-oral skeletal and soft tissues forming of the lower third of the face should harmonize with the dentition. During a relaxed ‘ideal smile’, the upper lip exposes the cervical aspects of the maxillary anterior teeth, where the gingival margins should be symmetrical and at the same height, with up to 3 mm of exposure being aesthetically acceptable. For patients with a high smile line, the contact points of the maxillary teeth are relevant for ensuring optimal aesthetics. Tarnow produced the ‘5 mm rule’, which states that when the distance from the contact point to the interproximal osseous crest is 5 mm or less, there is complete fill of the gingival embrasures with an interdental papilla [5].
Perception of Aesthetics
What may seem like an attractive smile may be perceived differently due to subjective inter-individual variations in expectations and beliefs. Chan et al (2017) utilised different photographs showing the lips and teeth in both retracted and relaxed positions, to determine whether the perception of ‘beauty’ differed between dentists, non-dentists, males and females [6]. They found that all groups demonstrated statistically significant agreement in the perception of beauty, and that both the teeth and lips seemed to contribute similarly to the attractiveness of a smile. Nomura et al (2018) found that the gingival zenith differences greater than 1 mm were detectable in the smile attractiveness, both by laypeople, general dentists and orthodontists [7]. The aesthetic change in the central incisors were more noticeable than those performed in the lateral incisors. Orthodontists and general dentists were more critical in the evaluation of the gingival zenith changes, with laypeople only perceiving this change from 1 mm of maxillary right central incisor asymmetrical change. The age of the layperson has also been shown to impact smile perception; where an older group of laypeople were more tolerant of a black triangle ranging from 1 to 2.5 mm between the maxillary central incisors, compared to a younger group of laypeople. A gingival display of 0 and 2 mm were considered attractive by both groups, whereas an excessive gingival display of 6 mm was scored as unattractive by both groups.
Negative Aesthetic-based Outcomes
As surgical endodontic procedures involve the intentional wounding of soft tissues, aesthetic-based outcomes should consider the soft tissue healing and its related complications. Flap procedures may lead to complications such as scarring, attachment loss, gingival recession, flap necrosis, flap tearing and tissue dehiscence. In wounds that heal by secondary intention, continuous local inflammation, infection, wound dehiscence and foreign bodies are important contributory factors that lead to scar formation [8]. Visual and physical signs of inflammation within and around wounds are primarily caused by neutrophil leukocytes, together with the complement proteins, aided and abetted by tissue mast cells. Excessive protease and reactive oxygen species release by neutrophils cause major collateral damage to a wound [9]. The scarring may clinically manifest as an elevated or depressed site, with an alteration of the mucosal texture and colour and changes in the biomechanical properties of the tissues [10]. This presents as a significant aesthetic problem in patients with a high smile line. In a study which assessed the scarring of the gingiva and alveolar mucosa 1 year following apical surgery, Von Arx et al (2008) found that more substantial scarring was noted in the alveolar mucosa compared with the gingiva. This may be due to the increased mobility, elevated risk of wound dehiscence and greater dissection area of the mucosa. Female patients and patients undergoing surgery for the first time had significantly more changes in scarring of the alveolar mucosa. The submarginal and papilla-saving incisions resulted in more changes in gingival scarring compared with the papilla-based and intrasulcular incisions [10].
Gingival recession may be caused by incorrect repositioning, compromised blood circulation or contraction of the flap. Von Arx et al (2009) evaluated gingival recession 1 year following endodontic surgery of 70 maxillary anterior teeth (including first premolars). The visual assessment using photographs did not demonstrate significant changes in gingival level or papillary height post-operatively. The parameters that were found to significantly influence changes in the gingival margin and clinical attachment levels at 1-year post-op were the gingival biotype, pre-operative probing depth and the type of incision [11]. A longer follow-up period of 5 years revealed that the patients’ age, smoking habit and type of periapical healing influenced these periodontal parameters [12].
Clinical manifestations of disturbed wound healing include excessive bleeding, dehiscence, perforations, flap necrosis or tearing, pus formation and chronic infections [13]. Flap necrosis may occur because of insufficient blood supply, caused by excessive force or crushing of the soft tissue, and poorly placed vertical releasing incisions. Flap tearing may occur as a result of poor flap design with a small and insufficient incision that causes excessive tension leading to tearing. Post-operative bleeding disturbs granulation tissue formation and slows the healing process. Partial or total separation of the wound margin causing dehiscence may manifest within the first week after surgery and is usually a result of infection from bacterial contamination of the incisional wound. Presence of foreign bodies such as remnant gutta percha, residual tooth fragments or bone sequesters can lead to poor wound healing and latent infections. General factors such as poor nutritional status, diabetes mellitus, alcohol abuse and smoking have negative effects on wound healing [13].
Soft Tissue Management in Surgical Endodontics
The goal of surgical endodontic procedures is to obtain both clinical and radiographic signs of healing, which ensures that the treated tooth remains functional and contributes to the patient’s quality of life. The informed consent process involves getting to know the patient’s specific concerns with the surgical procedure, including the determination of his or her aesthetic demands. This should follow detailed extra- and intra-oral examination and photographic documentation of the aesthetic zone and the anterior tooth to be treated. This allows the operator to identify the smile line, periodontal biotype and any pre-existing defects such as gingival recession, ‘black triangles’ and/or gingival or mucosal scarring.
The identification of the periodontal biotype is important in planning the type of surgical incision during endodontic surgery. It is characterized by specific anatomic characteristics, such as gingival thickness, gingiva width and bone morphotype [15] and is classified into thin-scalloped, thick and fat, or thick-scalloped [16]. The type of incision is an important predictor for complications following the surgery of a tooth with a thin biotype: higher probability for recession with an intra-sulcular incision, more scarring for the submarginal incision, flap tearing during elevation and difficulties in suturing which may lead to wound dehiscence.
To allow for proper tissue healing, it is important to avoid horizontal and severely angled vertical incisions which may impair flap blood supply. Contraction of the severed collagen fibers that run perpendicular to the incision line may result in flap shrinkage. Incisions should also facilitate flap repositioning over solid bone and should avoid major muscle attachments. In general, the flap should be full thickness, and can be of an intra-sulcular, submarginal, semilunar, or papilla-preservation design.
The papilla-preservation techniques were designed for guided tissue regeneration of intraosseous periodontal defects, where the flap design aims to provide primary wound closure, maintain flap integrity, and avoid early membrane exposure. It can be performed using the buccal papilla-based incision (PBI), or via a palatal approach to prevent scar formation at the aesthetic zone. Velvart et al (2004) showed that the type of marginal incision has both a short- and long-term effect on the degree of papillary recession. The PBI preserved papilla height and allowed predictable recession-free healing of up to 1 year. The complete mobilization of a papilla via a sulcular incision (SI) however resulted in a mean recession value of 0.98 mm at 1 year [18]. Taschieri et al (2016) also compared the PBI with SI but found no differences in recession change values [19]. A study by Azim et al (2020) found that despite the papillary height remaining constant, the mid-facial area of the tooth treated with endodontic microsurgery showed a high prevalence of gingival recession when SI or PBI were used [20]. A meta-analysis aiming to determine the effect of different incision designs in endodontic microsurgery on periodontal parameters identified six studies involving 401 teeth in 372 patients. There were no statistically significant differences between incision designs in any of the outcomes evaluated. However, the PBI presented the highest probability of being ranked the most effective incision to reduce buccal gingival recession, followed by the submarginal and intrasulcular incisions [21].
Passive repositioning and proper tissue approximation are crucial to avoid soft tissue healing complications. Improper use of sutures may lead to inflammation and delayed healing. The role of the suture is to attain wound closure and flap stabilization for several days. Synthetic, non-resorbable, monofilament suture materials are the most advantageous [22]. In vivo microbiological studies have shown that all sutures in all patients were found to contain bacteria. Overall, lower bacterial levels and better soft tissue healing were found around monofilament and synthetic sutures compared to multifilament and natural ones respectively [23,24,25].
Following closure of the soft tissue flap, adequate pressure must be placed to encourage haemotasis and reattachment of the periosteum. Post-surgical management is key to prevent any undesirable sequelae. This involves management of any post-operative bleeding, adequate wound care with gentle oral hygiene measures (toothbrushing and the use of an antibacterial mouthwash), soft diet and the avoidance of any strenuous activity. Although the incidence of undesirable post-operative sequelae is low, it should be reported immediately to the treating surgeon and managed promptly.
Conclusion
In patients undergoing surgical endodontic procedures in the aesthetic zone, each step of the procedure must be meticulously planned and executed by the treating clinician. The primary aim of eliminating disease should not detract from the secondary aim of ensuring an acceptable aesthetic outcome. Patients will have to be counselled on the risks involved and be given the appropriate options for corrective procedures in the event of complications.
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