Introduction

Implants are generally a successful and well‐established treatment for tooth replacement. However, like everything in dentistry, things can and will fail and clinicians placing implants need to be well versed in algorithms of diagnostic assessment [1]. Profound knowledge in therapeutic interventions in order to save an ailing implant is equally important as skillsets in procedures where implants have not succeeded and are deemed to fail. The consequences of implant removal jeopardize the clinician’s efforts to accomplish satisfactory function and esthetics. For the patient, this usually involves further costs and additional procedures.

The current literature provides ample data on the high success rates of dental implant treatment, which range from 90 to 97% [2–5]. But over time, the percentage of dental implants that fail increases. Clinicians must be knowledgeable in different methods regarding removal of dental implants [6–8] on the basis of several clinical and anatomical factors and the patient’s desire for reimplantation in failed implant site. Regardless of the reason for explantation, being able to safely remove an osseointegrated implant is imperative.

Most late‐failing implants are not mobile and remain at least partially osseointegrated in the apical aspect. The attempt to remove the implants can therefore still be very challenging; the explantation might be invasive, and neighbor teeth or vital structures can also be potentially harmed [9].

Once the decision for the removal of an implant has been made, the selection of the appropriate removal technique should be addressed. The selected option should be fast, as minimally traumatic as possible and cost‐effective for patient and dentist. Because the implant bed configuration is of outmost importance to a stable implant placement, the expected morphology of the remaining defect should also guide the choice over the method of the implant removal.

Multiple explantation techniques have been reported in the literature with variable success rates. But thus far, very little is known regarding the different aspects of each technique with respect to benefits, limitations, and overall success rates. Moreover, universal explantation protocols with clear indications and guidelines are still lacking.

Since studies on the potential advantages and disadvantages of different removal techniques are still scarce, the basic techniques are summarized according to the available literature. Ideally, the explantation procedure should be followed either by the installation of another implant or by guided bone regeneration (GBR), or both procedures during the same session, when indicated.

Overview of Removal Techniques and Factors for Decision‐making

Implant removal is quite different from extracting a tooth. Great caution has to be exercised not to remove a buccal or lingual plate during explanation. Therefore, numerous techniques were identified as seen in Figure 16.1:

Factors for Decision‐making

Proper planning is fundamental in order to minimize treatment time, side effects, and costs. The quantity of peri‐implant residual bone, the proximity of vital anatomical structures, and the implant’s design should be evaluated. Maximal preservation of bone and the feasibility of future implant placement should be prioritized. Clinical and anatomical factors that may govern the explantation protocol (Table 16.1) also have to consider the retrievability of the prosthetic suprastructures. Their complete destruction may sometimes be required in order to access the implant’s inner structure. Broken screws or damaged abutments could also complicate implant removal and limit the choice between different explantation techniques.

Clinical factors	Anatomical factors
Type of Implant/abutment connection/suprastructures	Bone density
Implant diameter	Proximity of vital anatomical structures (maxillary sinus and inferior alveolar nerve)
Remaining level of osseointegration and mobility of implant	Width of buccal and lingual cortical plates
Presence of peri‐implant inflammation/ infection	Distance from adjacent teeth or implants
Timing of future implant placement

Removal is easier when the implant driver connects directly to the internal connector. Therefore, an implant with an internal connection is much easier to remove than one with an external hex or spline connection because the internal connection is usually more rigid [9].

However, complications may occur when removing an implant with an internal “trilob” connections using the counter‐torque ratchet. The neck portion of this type of implant system, especially those with smaller diameters (i.e. 3.5 mm), has been observed to fracture during removal procedure if the reverse torque is more than 45 Ncm [9].

Increased thread depth – which is the distance between the outer diameter and the implant body – is another characteristic of overall implant geometry, which can make implant removal more difficult.

A tapered implant with the same platform diameter as a straight‐walled implant has a decreasing outer diameter because of the taper. Thus, the thread depth decreases toward the apical region. The tapered, threaded implant has less implant‐to‐bone contact in the apical region and is, therefore, easier to remove with a more conservative technique.

Reasons for Implant Removal

There are multiple reasons identified in the literature for removal of implants and the prostheses retained to these implants (Figure 16.2). Some of these, but not limited to, are broadly categorized into the following groups:

1. Mobility of the implant
2. Extensive crestal bone loss
3. Chronic pain, including sinus problems, close proximity to the canal with neurological disturbances or nerve damage
4. Advanced peri‐implantitis
5. Fractured implant
6. Malpositioned and unrestorable implant

There is also an established association between biocorrosion, presence of titanium particles (titanium intolerance) and other different metals alloys, and peri‐implant aseptic bone loosening leading to a failure of implant osseointegration [10, 11]. Since no metal or alloy is completely inert in vivo, the possible detrimental immunological consequences of its by‐products are contributing factors of clinical implant failure requiring removal of these fixtures [10, 11].

Irrespective of the reasons mentioned above: if radiographically, an implant has a radiolucent line along the entire implant surface, the implant is tender to percussion and/or mobile, the only option is removal of the implant.

Implant Removal Techniques

Non‐bone Removal Techniques

Tooth Extraction Set

Dental implants, which are mobile or show only little residual bone‐to‐implant contacts, can usually be removed with instruments, which are also used for tooth extraction including elevators and/or extraction forceps. If the threads oppose no resistance, rotating movements are not even required.

The application of counter‐torque techniques has been proposed as another conservative and atraumatic alternative for the explantation of clinically stable dental implants. Counter‐torque technique (CTT) and the reverse screw technique (RST) may be useful, where damage to the surrounding tissues is to be avoided. Both of these techniques engage the implant and with a counterclockwise force and reverse screw the implant out of the bone.

Counter‐torque‐Technique

The treatment is performed using an implant removal kit (i.e. Biomet 3i Implant removal kit^®, Figures 16.3 and 16.4) that allows the application of a counter‐torque to the bone‐implant interface.

The procedure commences with the removal of the cover screw or the abutment of the implant to be removed. The technique is applied by placing an abutment or an engaging extraction tool into the implant and reverse torquing the implant counterclockwise (Figure 16.3). The need to raise a flap or not is made according to the surgical needs. A ratchet is engaged into the implant connection and then a counter‐torque is exerted by a wrench in counter‐clockwise direction. When the reverse torque reaches 200 Ncm without success, a piezoelectric device can be utilized to remove the coronal third (3–4 mm) of the bone‐implant contacts. If not available, trephine drills or burs can be utilized at low speeds and under copious saline irrigation. The implant explantation is then continued with the reverse torque wrench.

The CTT has a high success rate but is not exempt from complications, although at a very low rate. Typical complications are usually identified as fractures of the implant [12]. As a minimally invasive technique, Solderer et al. [5] have recommended the CTT as the first option for the removal of failed nonmobile dental implants.

This technique is recommended in predominantly poor bone quality (∼maxilla). In higher bone density, bone damage or fracture of the implant body or adjacent bone may occur. The existing bone density is the most critical factor, which affects the ease of implant removal via the CTT or RST.

Reverse Screw Technique

A reverse screw removal drill is usually indicated when the internal connection of the implant (threads) is damaged, or an external connection implant requires removal and the Counter torque technique (CTT) technique may not be advisable, or when the counter‐torque method is unsuccessful.

A screw removal device is inserted clockwise into the implant and tightened using the torque to engage the implant. This technique is recommended only for poorly dense bones. In higher bone density bone, damage or fracture of the implant body or adjacent bone may occur. The existing bone density is the most critical factor which affects the ease of implant removal via the CTT or RST. Caution is also advised with smaller‐diameter internal implants (∼3.0 mm) because fracture of the implant body may occur.

The counter‐torque tool kit (Figure 16.4) is made up of three components:

1. internal implant removal screw, which is screwed into the implant
2. implant remover driver, which is screwed on the implant removal screw anticlockwise
3. torque ratchet which has two torque gauges – one side measures the correct torque for the implant removal screw to be driven into the implant, and the other side measures the correct torque for the removal of the implant.

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