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Abstract The need to rehabilitate severely compromised teeth is frequent in daily clinical practice. Tooth extraction and replacement with dental implant represents a common treatment choice. However, the survival rate for implants is inferior to teeth, even if severely damaged but properly treated. In order to reestablish a physiological supracrestal tissue attachment of damaged teeth and to arrange an efficient ferrule effect, three options can be considered: crown lengthening, orthodontic extrusion and surgical extrusion. Crown lengthening is considered an invasive technique that causes the removal of part of the bony support, while both orthodontic and surgical extrusion can avoid this inconvenience and can be used successfully in the treatment of severely damaged teeth. The aim of the present narrative review is to compare advantages, disadvantages, time of therapy required, contraindications and complications of both techniques. Keywords: orthodontic extrusion, surgical extrusion, rapid orthodontic extrusion, forced orthodontic eruption, crown–root fracture, orthodontics Go to: 1. Introduction “Severely damaged teeth” are considered as teeth with severe structural damage due to multiple factors: crown–root fractures, extensive carious lesions, cervical root resorption or other causes that lead to the loss of part of the clinical crown. Such teeth need to be rehabilitated, even considering the high prevalence of subgingival root caries among the elderly [1]. Nowadays, in the so-called “dental implant era” (Clark and Levin), clinicians often choose to extract compromised teeth and replace them with dental implants, even if less invasive options are feasible [2]. Moreover, the lower implants survival rate compared to teeth should be considered even in cases of severely compromised but properly treated and maintained teeth [2]. Placing a dental implant is not free from possible intraoperative and postoperative complications, such as neurological damage and sinus penetration. No less, extraction is an irreversible action that should be considered as the last resort. A fixed partial prosthetic denture may represent another alternative to implant placement to replace extracted teeth, but it requires the inevitable mutilation of healthy dental tissue of the adjacent abutment teeth. The main limit of this choice is associated with the lower long-term survival rate than both dental implants and post-endodontically restored teeth [3]. For all these reasons, the maintenance and rehabilitation of a compromised tooth still seems to be the most effective treatment. Due to prosthetic rehabilitation, it is crucial to create an effective ferrule effect for a desirable biomechanical behavior of the tooth [4]. The presence of 1.5–2 mm of sound supragingival dental tissue significantly increases tooth fracture resistance [4,5]. Even an adequate distance between crown margin and alveolar crest must be ensured to respect the supracrestal tissue attachment [4,6]. Supracrestal tissue attachment, commonly known as biological width, is defined as “the dimension of tissues placed coronally to the crest of the alveolar bone” [6,7]. Preserving it is a fundamental requirement for the health of periodontal tissues; any violation of its integrity can lead to gingival inflammation and consequent loss of clinical attachment and bone resorption [6]. Biological width is stated to be mm, which represents the sum of epithelial and connective tissue average measurements with a significant intra- and inter-individual variability [6,7,8]. Therefore, the clinician should measure the individual dimension of biological width by performing a bone sounding, or ensure at least a distance of 3–4 mm between the alveolar crest and the crown margin [4,9,10]. In the case of a severely damaged tooth without sufficient supra-alveolar structure to achieve an effective ferrule effect and to ensure the preservation of the supracrestal tissue attachment, the clinician should assess as treatment options: Surgical crown lengthening; Orthodontic extrusion; Surgical extrusion [11]. Surgical crown lengthening, when performed for restorative purposes, requires the execution of an apically repositioned flap with bone resection [12]. As a general rule, it is necessary to remove an amount of bone in order to expose at least 4 mm of healthy dental tissue. The exposed healthy dental tissue will be then covered by gingival proliferation during healing from 2 to 3 mm [12].
