Atraumatic removal of a root remnant in the retromolar region

Piezo surgery supports atraumatic procedure in osteotomy close to nerves

Surgical removal of third molars or wisdom teeth is one of the most frequent procedures in oral surgery. The risk of complications associated with it is determined, among other things, by the operating technique and the patient’s age, and also by the tooth’s anatomy and position in the jaw bone (angle, depth of displacement) (1). The procedure may traumatize two adjacent molars (2), lead to perioperative bleeding complications or cause postoperative dysaesthesia, infections and pain (3). Fractures of the ascending ramus are possible in the mandible and oro-antral communications often occur in the maxilla.

Nerve damage

Particular care must be taken with regard to the position of the lingual nerve and inferior alveolar nerve when performing extraction in the mandible. In approximately 1 percent of cases, damage to both nerves together may result in anaesthesia, hypaesthesia, hyperaesthesia and disturbances in taste perception. Dysaesthesias are permanent in approximately 1 percent of cases (3-5) but it is not uncommon for them to last for longish periods (4).

With adequate preoperative radiological diagnostics (orthopantomogram), injuries to the inferior alveolar nerve are mostly foreseeable and therefore preventable. Where it is suspected that an impacted third molar is in close proximity to this nerve, a three-dimensional image (DVT, CT) may additionally be indicated (6, 7).

When wisdom teeth are extracted or osteotomized, root portions may fracture and remain behind (3). Generally speaking, radices relictae must be removed if they can be identified intra- or postoperatively. Depending on how the operation proceeds, leaving them in place may lead to postoperative infections and corresponding discomfort, including dysaesthesias.

Role of the operating technique

The access route (buccal or lingual), flap design, protection of the nerves in the operating area and the preparation technique all play a role in the operating technique. However, there are very few comparative studies that provide evidence that any one specific technique has significant advantages (8).

Osteotomies are traditionally performed with rotary round burs and bone burs. Alternative piezo surgical systems that may be used work with micro-oscillation which, according to clinical observations, can improve control during preparation. Slipping – as is possible with rotary instruments – is prevented in piezo surgery (9-11).

In the case of preparation close to nerve tissue, piezo surgery has the decisive advantage when used correctly that soft tissue is protected due to the specific micro-oscillating mode of operation (12, 13).

Conservative treatment and fracture prevention

One additional advantage of piezo surgical instruments is their diameter, which in the case of saws is only 0.25 to 0.5 millimetres depending on the system. Common Lindemann burs by comparison have a diameter of 1.6 mm, and even the latest products still have a diameter of 1.2 mm. Surgical round burs are available above a diameter of 1.0 mm. Spherical piezo surgical instruments which can be used as an alternative to round burs also have a minimum diameter of approximately 1.0 mm.

Overall, an unnecessarily large amount of bone is removed with rotary as opposed to piezo surgical instruments due to their size. The wound area becomes larger, increasing the risk of postoperative pain and infections. Additionally, depending on the anatomical situation, the jaw bone may be unnecessarily weakened. According to clinical experience, even conventional rotary or oscillating saws remove a relatively large amount of bone substance (9, 14).

In contrast, with piezo surgical instruments it is possible to expose impacted teeth – and also normally erupted teeth or root remnants – very selectively and therefore with as little trauma as possible to the tissue. The fine instruments and the cavitation effect arising as a result of micro-oscillation ensure a good view making it easier to prevent injuries and unnecessary loss of substance.

Case description

A 26-year old patient had recurring pain in the operative area six months after osteotomy of tooth 38 (LL8) and complained of hyposensitivity in the area innervated by the inferior alveolar nerve. He was referred by the referring dentist, who had not performed the original tooth extraction himself, to the Department of Oral Surgery at the University Dental Clinic Vienna.

The autogenous tissue was removed with the scraper-shaped section of the working part of the instrument and stored in a physiological saline solution until further use (cf. Fig. 13).

To expose the root remnant with as little trauma as possible to the tissue, a further instrument was used (Piezomed S2) that is primarily indicated for preparing the lateral window in augmentations of the sinus floor. The diamond-coated ball was additionally used to smooth sharp bone edges (Fig. 6 and 7). All the Piezomed attachments were used with the relevant automatic default setting without booster function.

Subsequently, the autogenous bone tissue (Fig. 13) was placed into the alveole and the surrounding bone defect (Fig. 14). Collagen fleece covered the bone chips up to bone level as protection for the exposed nerve (Fig. 15). Sutures using vicryl thread, USP 4.0, were used to close the opened up soft tissue (Fig. 16). An Ibuprofen preparation (Seractil 400 mg, 3x1) and an antibiotic consisting of amoxicillin and clavulanic acid (Augmentin 1 g, 2x1) were prescribed postoperatively.

The wound healed without complications (Fig. 17) and the sutures were removed after seven days. The patient reported the return of proper sensitivity. There was no longer any pain.

Discussion

The complication risk for the surgical removal of wisdom teeth is determined, among other things, by the patient’s age, root anatomy and operating technique (1). It is very likely that the same parameters also influence the operating procedure and wound healing in the case of root remnant osteotomies.

Where root remnants are close to nerves and there is no discomfort, they can be left in place based on appropriate postoperative diagnosis (3). Since in our case study the patient was suffering from pain and paraesthesia, it was necessary to osteotomize the remnant despite the risk of nerves and surrounding tissue being damaged again and possibly more seriously. Had the radix relicta been left in place, ongoing pain and recurring infections would have been likely. Furthermore, pathological processes such as abscess formation, osteomyelitis or dental cysts might have occurred.

Based on his medical history, our patient (non-smoker, 26 years old) had a very good chance of a successful outcome. Due to indication of the root remnant’s close proximity to the inferior alveolar nerve on the OPG, digital volume tomography was used in addition (6).

The very close proximity discovered made it necessary to perform a precise and atraumatic osteotomy. In this case, clinical observations and comparative studies favour piezo surgery which has been available since the end of the 1990s (9-11). Due to the characteristic micro-oscillation of these systems, it is possible to remove bone selectively, thus enabling minimally invasive preparation.

Device-specific advantages

With the device used here (Piezomed, W&H), very effective cooling close to the instrument provides additional security. This also applies to the device’s ability to identify the instruments being used, which ensures automatically correct power settings. The device exhibits remarkably high and constant performance during osteotomies, which was relevant during the harvesting of bone chips in the case study. At the same time, due to the technical design, soft tissue, and therefore also nerve tissue, was preserved in the operating area. For example, this special piezo surgical characteristic enables the preparation of lateral bone windows during a sinus lift, with only slight risk of perforating the Schneiderian membrane (13).

In our example, a week after removal of the root remnant our patient reported a return of sensitivity in the innervated area of the inferior alveolar nerve. Postoperative checkups additionally showed very good, fast wound healing and an end to the pain symptoms that had gone on for six months. The procedure was carried out completely without rotary instruments. In the author’s experience, they would not have facilitated a comparably atraumatic operating technique.

Another advantage of the piezo surgical technique is the absence of bleeding during the procedure. This is attributed to the cavitation effect: the high-frequency ultrasound generates shock waves in the cooling liquid which result in micro-coagulation (15). The result is a better view and a safer procedure (11). In the system used, integrated illumination with six LEDs can improve the view at the operating site.

Widening of periodontal ligament space and harvesting of bone chips

Using the slender piezo surgical instrument Piezomed P1, it was possible to widen the periodontal ligament space in preparation and to remove the root elegantly by inserting the instrument into the root canal. The micro-oscillating mode of operation also proved advantageous here and flexible use of the technology is obvious. In contrast, rotary instruments do not offer comparable options.

In autogenous bone chips, harvested using a piezo surgical technique in the case study, bone cells appear to have a better chance of survival than when using rotary preparation (16). This is an advantage for wound healing. As is usual at the University Dental Clinic Vienna, to optimize hygiene and consequently the healing process, suction with bone filter was not used during the preparation.

Conclusions

The case study illustrates the tissue-conserving and at the same time powerful work of the Piezomed system. Due to the precise micro-oscillating mode of operation, it is also possible to protect nerves during challenging osteotomies thus allowing them to regenerate.

Literatur

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