Review Article
Applications of Piezoelectric Surgery in Endodontic Surgery: A Literature Review Francesc Abella, DDS, MSc, Joan de Ribot, DDS, MSc, Guillermo Doria, DDS, MSc, Fernando Duran-Sindreu, DDS, PhD, and Miguel Roig, DDS, PhD Abstract Introduction: Piezosurgery (piezoelectric bone surgery) devices were developed to cut bone atraumatically using ultrasonic vibrations and to provide an alternative to the mechanical and electrical instruments used in conventional oral surgery. Indications for piezosurgery are increasing in oral and maxillofacial surgery, as in other disciplines, such as endodontic surgery. Key features of piezosurgery instruments include their ability to selectively cut bone without damaging adjacent soft tissue, to provide a clear operative field, and to cut without generating heat. Although piezosurgery instruments can be used at most stages of endodontic surgery (osteotomy, rootend resection, and root-end preparation), no published data are available on the effect of piezosurgery on the outcomes of endodontic surgery. To our knowledge, no study has evaluated the effect of piezosurgery on root-end resection, and only 1 has investigated root-end morphology after retrograde cavity preparation using piezosurgery. Methods: We conducted a search of the PubMed and Cochrane databases using appropriate terms and keywords related to the use and applications of piezoelectric surgery in endodontic surgery. A hand search also was conducted of issues published in the preceding 2 years of several journals. Two independent reviewers obtained and analyzed the full texts of the selected articles. Results: A total of 121 articles published between January 2000 and December 2013 were identified. This review summarizes the operating principles of piezoelectric devices and outlines the applications of piezosurgery in endodontic surgery using clinical examples. Conclusions: Piezosurgery is a promising technical modality with applications in several aspects of endodontic surgery, but further studies are necessary to determine the influence of piezosurgery on rootend resection and root-end preparation. (J Endod 2014;40:325–332)
Key Words Apical surgery, cone-beam computed tomography imaging, endodontic surgery, piezoelectric device, piezosurgery
O
ne goal of endodontic surgery is to treat apical periodontitis in cases in which healing has not occurred after nonsurgical retreatment or, in certain instances, after primary root canal therapy (1). Such cases include patients with persistent or refractory intracanal infection after iatrogenic changes to canal anatomy (2) or those with microorganisms in proximity to the constriction (3) and apical foramen (4). Other indications include extraradicular infections, such as the presence of bacterial plaque on the apical root surface (5) or bacteria within the lesion itself (6). The outcome of endodontic surgery for periapical lesions depends on several factors. Modern surgical endodontic treatment involves the use of a magnification device, such as a dental operative microscope. This enables precision, with no or minimal bevel or root-end resection and retrograde canal preparation to a depth of 3–4 mm using an ultrasonic tip (7). Advantages of modern surgical endodontic treatment include easier identification of root apices; smaller osteotomies; and shallower resection angles, which preserve cortical bone and root length (8). The modern technique shows a much higher success rate than the traditional technique (9). Recently, Tsesis et al (10) reported that modern surgical endodontic treatment yields a successful outcome rate of 89%. The introduction of cone-beam computed tomography (CBCT) scanning is particularly useful for both diagnosis and treatment planning (11) (Fig. 1A–N). Figure 1 shows the benefits of the use of CBCT imaging during endodontic surgery including elimination of the superimposition of anatomic structures, such as the zygomatic buttress, alveolar bone, maxillary sinus, and other roots (12), and early detection of the presence and dimensions of apical lesions and changes in apical bone density (13, 14). CBCT imaging also provides clinicians with a clear view of the anatomic relationship between root apices and neighboring structures, such as the mandibular canal (15), mental foramen, and maxillary sinus (16, 17). Furthermore, CBCT scanning establishes where access osteotomies can be performed, enabling minimally invasive surgery. Finally, in 70% of patients, CBCT scanning reveals clinically relevant information not identified by periapical radiography (13). Although many published studies advocate the use of modern approaches, limited information is available on the applications of piezosurgery (piezoelectric bone surgery) in endodontic surgery. The introduction of piezoelectric instruments that vibrate within the ultrasonic frequency range represents a major advance in oral surgery (18). Piezosurgery is a meticulous and soft tissue–sparing system for bone cutting based on ultrasonic microvibrations. The first piezoelectric device is still being devel-
From the Department of Restorative Dentistry and Endodontics, Universitat Internacional de Catalunya, Sant Cugat del Valles, Barcelona, Spain. Address requests for reprints to Dr Miguel Roig, Universitat Internacional de Catalunya, Dentistry Faculty, C/Josep Trueta s/n, 08195 Sant Cugat del Valles, Barcelona, Spain. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2014 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2013.11.014
JOE — Volume 40, Number 3, March 2014
Piezoelectric Surgery in Endodontic Surgery
325
Review Article
Figure 1. (A and B) Periapical radiographs showing an apical lesion associated with tooth #9. (C) Endodontic surgery was the treatment of choice. (D) White MTA (ProRoot MTA; Dentsply Maillefer, Ballaigues, Switzerland) root-end filling was used. (E) A follow-up radiograph at 1 year showed almost complete periapical healing. A CBCT scan (Sirona Galileos CBCT System; Sirona Dental Systems GmbH, Bensheim, Germany) was taken of the previously mentioned tooth as a complementary examination. (F) Coronal and (G) sagittal (G) reconstructed CBCT images revealed that the periapical radiolucency was larger than that seen radiographically. Note that the apical lesion affected the buccal cortical plate. (H) The clinical view of maxillary anterior teeth; note that tooth #9 had a metalceramic crown. (I and J) Enucleation of the apical lesion. (K–N) Images showing the root-end resection and root-end preparation of tooth #9. (N) Cavity preparation (3 mm deep) along the long axis of the root using an ultrasonic tip.
oped and widely debated in studies by Vercellotti et al (18, 19), who pioneered its application in periodontal surgery. Piezoelectric surgery devices operate with principles that are similar to the piezoelectric dental scaler devices, but the latter are not capable of 326
Abella et al.
cutting through hard tissues. Selective cutting is the most innovative feature of the piezoelectric surgery device. Although piezosurgery cuts mineralized tissues such as bone, it does not cut soft tissues such as blood vessels, nerves, and mucosa (19). JOE — Volume 40, Number 3, March 2014
Review Article Indications for the use of piezosurgery devices are increasing in oral and maxillofacial surgery, as in other disciplines, such as endodontics (20). Currently, piezoelectric instruments can be used at most stages of endodontic surgery, reducing the risk of damage to soft tissues. We conducted a literature review on the uses and applications of piezoelectric surgery in endodontic surgery supported by clinical cases.
Search Methodology and Study Selection We conducted a search of the PubMed and Cochrane databases using appropriate Medical Subject Headings terms and keywords related to the use and applications of piezoelectric surgery in endodontic surgery. The following keywords were used to identify a list of potential papers: piezosurgery AND (endodontics OR endodontic surgery OR apical surgery OR apicoectomy) AND (piezoelectric OR piezoelectric bone surgery). To enrich the results, a hand search was conducted of issues published in the preceding 2 years of the following journals: International Endodontic Journal, Journal of Endodontics, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology. Cross-referencing continued until no new articles were identified. Two independent reviewers obtained and analyzed the full texts of the selected articles. One hundred twenty-one articles published between January 2000 and December 2013 were identified using Medical Subject Headings headings and keywords. Useful information from each study was collected for this review.
Overview Ultrasound is sound energy with a frequency above the range of human hearing, which is 20 kHz. For clinical purposes, ultrasound is generated by transducers, which convert electrical energy into ultrasonic waves. This is usually achieved either by magnetostriction or piezoelectricity (21). Magnetostrictive dental scaler devices undergo changes in their physical dimensions when placed within a magnetic field. This is achieved by placing a ferromagnetic stack within a solenoid through which direct current is passed. Magnetostrictive instruments operate between 18 and 25 kHz (21). When electric current passes through a wire coil in the handpiece, a magnetic field is created around the stack or rod transducer, causing it to constrict. Alternating current then produces an alternating magnetic field that causes the tip to vibrate (22). Piezoelectric scaler units are based on the piezoelectric effect, which was first described in 1880 by Jacques and Pierre Curie, who claimed that some ceramics and crystals deform when an electric current is passed across them, resulting in oscillations of ultrasonic frequency without producing heat (23). Currently, lead zirconate titanate is the most widely used piezoelectric material. The resultant vibration produces tip movement that is primarily linear in direction and generally allows only 2 sides of the tip to be active at any time. Piezoelectric scaler units have some advantages over earlier magnetostrictive units because they offer more cycles per second (24). The tips of these units work in a linear, back-and-forth, ‘‘piston-like’’ motion, which is ideal for endodontics. Magnetostrictive units, on the other hand, rely on an elliptic movement of the ultrasonic tip, which is not ideal for either surgical or nonsurgical endodontic use. One further drawback of magnetostrictive units is that the stack generates heat, necessitating adequate cooling (24). Piezosurgery was introduced as an alternative to the traditional instrumentation used in oral bone surgery (23). Piezosurgery is a new and innovative method that uses piezoelectric ultrasonic vibrations to perform precise and safe osteotomies. It was developed in 1988 by the Italian oral surgeon Tomaso Vercellotti (25) to overcome the limitations of conventional bone surgery. The instrument uses a modulated ultrasonic frequency that permits the cutting of hard tissues. The vibrations obtained are amplified and transferred to a vibration tip, which, JOE — Volume 40, Number 3, March 2014
when applied with slight pressure to bone tissue, results in a cavitation phenomenon—a mechanical cutting effect that occurs exclusively in mineralized tissue (25). Piezosurgery uses a specifically engineered surgical instrument approximately 3 times as powerful as a conventional ultrasonic instrument (a piezoelectric scaler unit). The unique feature of the piezosurgery technique is that cutting occurs when the tool is applied to mineralized tissue but stops when soft tissue is encountered. The vibration frequency (between 25 and 30 kHz), cutting power, and irrigation are adjustable. This vibration frequency causes microvibrations of 60–210 mm in amplitude, providing the handpiece with a power exceeding 5 W (23). Given that piezosurgery requires adequate irrigation, the flow rate of the cooling solution must be regulated to prevent the bone overheating. Heating osseous tissue in excess of 47 C for 1 minute significantly reduces bone formation and is associated with irreversible cellular damage and fatty cell infiltration (26). Eriksson et al (27) showed that local bone necrosis occurs in cases in which the temperature exceeds 47 C for 1 minute as a result of contact with rotating tools. The light handpiece pressure and integrated saline coolant spray of piezosurgery maintain a low temperature and allow clear visibility of the surgical site (28).
Bone-tissue Management Piezosurgery is useful when bone must be cut close to important soft tissues, such as nerves, vessels, the Schneiderian membrane, and the dura mater, or when mechanical or thermal injury must be avoided. Trauma to the mental nerve caused by blunt dissection in this area can cause temporary paresthesia but is less likely to leave permanent injury. Schaeren et al (29) concluded that direct exposure of a peripheral nerve to piezosurgery, even in the worst case scenario, does not dissect the nerve. This makes piezosurgery a promising tool for osteotomy procedures in close proximity to nerves during endodontic surgery. The cutting characteristics of piezosurgery depend on the degree of bone mineralization (density), the design of the insert, the pressure applied to the handpiece, and the speed of operation. Ultrasonic vibration frequency (Hz), power level (W), and saline coolant spray are parameters adjustable according to the intended procedure (25). Recently, methods that use CBCT imaging have been used to determine bone quality, which can be expressed numerically using Hounsfield units (HUs) (30). de Oliveira et al (31) reported that the distribution of anterior mandibular bone is equivalent to type 1 of the Lekholm and Zarb classification (>850 HU) (32). Types 2 and 3 are between 500 and 800 HU, and type 4 is 500 HU. Hence, bone quality can be evaluated with CBCT scanning before endodontic surgery and the appropriate power level selected. Piezosurgery requires only minimal pressure unlike conventional microsaws or drills (23). Piezosurgery devices provide a clear surgical site; they maintain a blood-free field during bone cutting through an air-water cavitation effect. Figure 2A–I shows that this cavitation effect and constant irrigation provide a bloodless procedure that ensures a clear visibility of the surgical site (25). Cavitation involves the formation and immediate implosion of cavities within a liquid (small liquid-free zones or ‘‘bubbles’’). In piezoelectric surgery, cavitation describes the processes of vaporization, bubble generation, and subsequent bubble implosion into many microscopic gas bubbles. It occurs in a flowing liquid as a result of oscillations in pressure caused by ultrasonic vibrations (33). Walmsley et al (34) suggested that cavitation fragments bacterial cell walls and therefore has an antibacterial function.
Enucleation of Radicular Cysts One important application of piezosurgery is in the enucleation of radicular cysts. Figure 3A–I shows the surgical procedure for
Piezoelectric Surgery in Endodontic Surgery
327
Review Article
Figure 2. (A) A clinical image of tooth #3. (B) A periapical radiograph showing a small apical lesion associated with the mesial root of the right maxillary first molar. The patient complained of pain on the buccal aspect of this tooth. (C–E) A CBCT scan (ProMax 3D s; Planmeca Oy, Helsinki, Finland) was performed before endodontic surgery. (C) Sagittal, (D) axial, and (E) coronal images confirmed a circumscribed apical lesion in the mesial root. Note that the apical lesion affected neither the buccal nor palatal cortical plates. (F) A Piezosurgery Insert OT1 (Mectron) (flattened, diamond-coated file) was used to cut bone in proximity to the maxillary sinus. Minimal bleeding of the surgical site is apparent. (G) The final size of the osteotomy. (H) This procedure was performed with Biodentine (Septodont Laboratoires, Saint-Maur-des-Fosses, France) as the root-end filling material. (I) A periapical radiograph taken 6 months after treatment. Note that the Biodentine is not as radiopaque as other calcium silicate–based materials.
enucleation of a lateral periodontal cyst using piezosurgery and the Piezosurgery Retrosurgical Kit (Mectron, Carasco, Italy), which is specifically designed for endodontic surgery. Diamond-coated inserts can be used to remove the bone lamina over the cyst, whereas dull, bellshaped inserts can be used for the dissection of the cyst epithelium from the bone (23). The use of piezosurgery in the treatment of jaw cysts is a new development, and few cases have been reported (35, 36). Atraumatic handling of soft tissues is required for the complete removal of cystic lesions and is technically comparable to handling the sinus membrane during sinus bone grafting (37). The main advantage of enucleation is that it facilitates a pathologic examination of the entire cyst. Another advantage is that total excisional biopsy treats the lesion appropriately (37). Kocyigit et al (35) compared piezosurgery with conventional surgery for radicular cyst enucleation. They evaluated 29 patients prediagnosed with radicular cysts in the jaw region using radiology and cytology. Nineteen patients were treated using piezosurgery and 10 using conventional procedures. Piezosurgery was more successful than conventional surgery in terms of intraoperative hemorrhage, epithelial perforation, postoperative complications, and recurrence, but it increased the overall duration of the surgical procedure. Yaman and Suer (36) evaluated the performance of piezosurgery in removing odontogenic cysts. They concluded that piezosurgery increased operation time but also markedly increased visibility in the operating field. In cases in which cyst enucleation is necessary in difficult areas requiring delicate manipulation, the use of piezosurgery carries a lower risk of damage to vital structures, such as neurovascular tissues.
Root-end Resection Minimization of the bevel angle during root resection is one of the most important developments in endodontic microsurgery (38). The traditional technique uses a bevel angle of 45 –60 to facilitate access and visibility when using large surgical instruments. The mod328
Abella et al.
ern technique uses a shallow bevel angle of 0 –10 to expose fewer dentinal tubules (8). The use of a microscope minimizes access to the root apex, and the use of angled micromirrors permits observation of the complex root anatomy (39). However, there is no consensus on how much of the root must be resected to satisfy biologic principles. De Deus et al (40) showed that a large number of apical ramifications and lateral canals exist at least 3 mm from the root end. Thus, root-end amputations of
Applications of Piezoelectric Surgery in Endodontic Surgery: A Literature Review Francesc Abella, DDS, MSc, Joan de Ribot, DDS, MSc, Guillermo Doria, DDS, MSc, Fernando Duran-Sindreu, DDS, PhD, and Miguel Roig, DDS, PhD Abstract Introduction: Piezosurgery (piezoelectric bone surgery) devices were developed to cut bone atraumatically using ultrasonic vibrations and to provide an alternative to the mechanical and electrical instruments used in conventional oral surgery. Indications for piezosurgery are increasing in oral and maxillofacial surgery, as in other disciplines, such as endodontic surgery. Key features of piezosurgery instruments include their ability to selectively cut bone without damaging adjacent soft tissue, to provide a clear operative field, and to cut without generating heat. Although piezosurgery instruments can be used at most stages of endodontic surgery (osteotomy, rootend resection, and root-end preparation), no published data are available on the effect of piezosurgery on the outcomes of endodontic surgery. To our knowledge, no study has evaluated the effect of piezosurgery on root-end resection, and only 1 has investigated root-end morphology after retrograde cavity preparation using piezosurgery. Methods: We conducted a search of the PubMed and Cochrane databases using appropriate terms and keywords related to the use and applications of piezoelectric surgery in endodontic surgery. A hand search also was conducted of issues published in the preceding 2 years of several journals. Two independent reviewers obtained and analyzed the full texts of the selected articles. Results: A total of 121 articles published between January 2000 and December 2013 were identified. This review summarizes the operating principles of piezoelectric devices and outlines the applications of piezosurgery in endodontic surgery using clinical examples. Conclusions: Piezosurgery is a promising technical modality with applications in several aspects of endodontic surgery, but further studies are necessary to determine the influence of piezosurgery on rootend resection and root-end preparation. (J Endod 2014;40:325–332)
Key Words Apical surgery, cone-beam computed tomography imaging, endodontic surgery, piezoelectric device, piezosurgery
O
ne goal of endodontic surgery is to treat apical periodontitis in cases in which healing has not occurred after nonsurgical retreatment or, in certain instances, after primary root canal therapy (1). Such cases include patients with persistent or refractory intracanal infection after iatrogenic changes to canal anatomy (2) or those with microorganisms in proximity to the constriction (3) and apical foramen (4). Other indications include extraradicular infections, such as the presence of bacterial plaque on the apical root surface (5) or bacteria within the lesion itself (6). The outcome of endodontic surgery for periapical lesions depends on several factors. Modern surgical endodontic treatment involves the use of a magnification device, such as a dental operative microscope. This enables precision, with no or minimal bevel or root-end resection and retrograde canal preparation to a depth of 3–4 mm using an ultrasonic tip (7). Advantages of modern surgical endodontic treatment include easier identification of root apices; smaller osteotomies; and shallower resection angles, which preserve cortical bone and root length (8). The modern technique shows a much higher success rate than the traditional technique (9). Recently, Tsesis et al (10) reported that modern surgical endodontic treatment yields a successful outcome rate of 89%. The introduction of cone-beam computed tomography (CBCT) scanning is particularly useful for both diagnosis and treatment planning (11) (Fig. 1A–N). Figure 1 shows the benefits of the use of CBCT imaging during endodontic surgery including elimination of the superimposition of anatomic structures, such as the zygomatic buttress, alveolar bone, maxillary sinus, and other roots (12), and early detection of the presence and dimensions of apical lesions and changes in apical bone density (13, 14). CBCT imaging also provides clinicians with a clear view of the anatomic relationship between root apices and neighboring structures, such as the mandibular canal (15), mental foramen, and maxillary sinus (16, 17). Furthermore, CBCT scanning establishes where access osteotomies can be performed, enabling minimally invasive surgery. Finally, in 70% of patients, CBCT scanning reveals clinically relevant information not identified by periapical radiography (13). Although many published studies advocate the use of modern approaches, limited information is available on the applications of piezosurgery (piezoelectric bone surgery) in endodontic surgery. The introduction of piezoelectric instruments that vibrate within the ultrasonic frequency range represents a major advance in oral surgery (18). Piezosurgery is a meticulous and soft tissue–sparing system for bone cutting based on ultrasonic microvibrations. The first piezoelectric device is still being devel-
From the Department of Restorative Dentistry and Endodontics, Universitat Internacional de Catalunya, Sant Cugat del Valles, Barcelona, Spain. Address requests for reprints to Dr Miguel Roig, Universitat Internacional de Catalunya, Dentistry Faculty, C/Josep Trueta s/n, 08195 Sant Cugat del Valles, Barcelona, Spain. E-mail address: [email protected] 0099-2399/$ - see front matter Copyright ª 2014 American Association of Endodontists. http://dx.doi.org/10.1016/j.joen.2013.11.014
JOE — Volume 40, Number 3, March 2014
Piezoelectric Surgery in Endodontic Surgery
325
Review Article
Figure 1. (A and B) Periapical radiographs showing an apical lesion associated with tooth #9. (C) Endodontic surgery was the treatment of choice. (D) White MTA (ProRoot MTA; Dentsply Maillefer, Ballaigues, Switzerland) root-end filling was used. (E) A follow-up radiograph at 1 year showed almost complete periapical healing. A CBCT scan (Sirona Galileos CBCT System; Sirona Dental Systems GmbH, Bensheim, Germany) was taken of the previously mentioned tooth as a complementary examination. (F) Coronal and (G) sagittal (G) reconstructed CBCT images revealed that the periapical radiolucency was larger than that seen radiographically. Note that the apical lesion affected the buccal cortical plate. (H) The clinical view of maxillary anterior teeth; note that tooth #9 had a metalceramic crown. (I and J) Enucleation of the apical lesion. (K–N) Images showing the root-end resection and root-end preparation of tooth #9. (N) Cavity preparation (3 mm deep) along the long axis of the root using an ultrasonic tip.
oped and widely debated in studies by Vercellotti et al (18, 19), who pioneered its application in periodontal surgery. Piezoelectric surgery devices operate with principles that are similar to the piezoelectric dental scaler devices, but the latter are not capable of 326
Abella et al.
cutting through hard tissues. Selective cutting is the most innovative feature of the piezoelectric surgery device. Although piezosurgery cuts mineralized tissues such as bone, it does not cut soft tissues such as blood vessels, nerves, and mucosa (19). JOE — Volume 40, Number 3, March 2014
Review Article Indications for the use of piezosurgery devices are increasing in oral and maxillofacial surgery, as in other disciplines, such as endodontics (20). Currently, piezoelectric instruments can be used at most stages of endodontic surgery, reducing the risk of damage to soft tissues. We conducted a literature review on the uses and applications of piezoelectric surgery in endodontic surgery supported by clinical cases.
Search Methodology and Study Selection We conducted a search of the PubMed and Cochrane databases using appropriate Medical Subject Headings terms and keywords related to the use and applications of piezoelectric surgery in endodontic surgery. The following keywords were used to identify a list of potential papers: piezosurgery AND (endodontics OR endodontic surgery OR apical surgery OR apicoectomy) AND (piezoelectric OR piezoelectric bone surgery). To enrich the results, a hand search was conducted of issues published in the preceding 2 years of the following journals: International Endodontic Journal, Journal of Endodontics, Oral Surgery, Oral Medicine, Oral Pathology, Oral Radiology, and Endodontology. Cross-referencing continued until no new articles were identified. Two independent reviewers obtained and analyzed the full texts of the selected articles. One hundred twenty-one articles published between January 2000 and December 2013 were identified using Medical Subject Headings headings and keywords. Useful information from each study was collected for this review.
Overview Ultrasound is sound energy with a frequency above the range of human hearing, which is 20 kHz. For clinical purposes, ultrasound is generated by transducers, which convert electrical energy into ultrasonic waves. This is usually achieved either by magnetostriction or piezoelectricity (21). Magnetostrictive dental scaler devices undergo changes in their physical dimensions when placed within a magnetic field. This is achieved by placing a ferromagnetic stack within a solenoid through which direct current is passed. Magnetostrictive instruments operate between 18 and 25 kHz (21). When electric current passes through a wire coil in the handpiece, a magnetic field is created around the stack or rod transducer, causing it to constrict. Alternating current then produces an alternating magnetic field that causes the tip to vibrate (22). Piezoelectric scaler units are based on the piezoelectric effect, which was first described in 1880 by Jacques and Pierre Curie, who claimed that some ceramics and crystals deform when an electric current is passed across them, resulting in oscillations of ultrasonic frequency without producing heat (23). Currently, lead zirconate titanate is the most widely used piezoelectric material. The resultant vibration produces tip movement that is primarily linear in direction and generally allows only 2 sides of the tip to be active at any time. Piezoelectric scaler units have some advantages over earlier magnetostrictive units because they offer more cycles per second (24). The tips of these units work in a linear, back-and-forth, ‘‘piston-like’’ motion, which is ideal for endodontics. Magnetostrictive units, on the other hand, rely on an elliptic movement of the ultrasonic tip, which is not ideal for either surgical or nonsurgical endodontic use. One further drawback of magnetostrictive units is that the stack generates heat, necessitating adequate cooling (24). Piezosurgery was introduced as an alternative to the traditional instrumentation used in oral bone surgery (23). Piezosurgery is a new and innovative method that uses piezoelectric ultrasonic vibrations to perform precise and safe osteotomies. It was developed in 1988 by the Italian oral surgeon Tomaso Vercellotti (25) to overcome the limitations of conventional bone surgery. The instrument uses a modulated ultrasonic frequency that permits the cutting of hard tissues. The vibrations obtained are amplified and transferred to a vibration tip, which, JOE — Volume 40, Number 3, March 2014
when applied with slight pressure to bone tissue, results in a cavitation phenomenon—a mechanical cutting effect that occurs exclusively in mineralized tissue (25). Piezosurgery uses a specifically engineered surgical instrument approximately 3 times as powerful as a conventional ultrasonic instrument (a piezoelectric scaler unit). The unique feature of the piezosurgery technique is that cutting occurs when the tool is applied to mineralized tissue but stops when soft tissue is encountered. The vibration frequency (between 25 and 30 kHz), cutting power, and irrigation are adjustable. This vibration frequency causes microvibrations of 60–210 mm in amplitude, providing the handpiece with a power exceeding 5 W (23). Given that piezosurgery requires adequate irrigation, the flow rate of the cooling solution must be regulated to prevent the bone overheating. Heating osseous tissue in excess of 47 C for 1 minute significantly reduces bone formation and is associated with irreversible cellular damage and fatty cell infiltration (26). Eriksson et al (27) showed that local bone necrosis occurs in cases in which the temperature exceeds 47 C for 1 minute as a result of contact with rotating tools. The light handpiece pressure and integrated saline coolant spray of piezosurgery maintain a low temperature and allow clear visibility of the surgical site (28).
Bone-tissue Management Piezosurgery is useful when bone must be cut close to important soft tissues, such as nerves, vessels, the Schneiderian membrane, and the dura mater, or when mechanical or thermal injury must be avoided. Trauma to the mental nerve caused by blunt dissection in this area can cause temporary paresthesia but is less likely to leave permanent injury. Schaeren et al (29) concluded that direct exposure of a peripheral nerve to piezosurgery, even in the worst case scenario, does not dissect the nerve. This makes piezosurgery a promising tool for osteotomy procedures in close proximity to nerves during endodontic surgery. The cutting characteristics of piezosurgery depend on the degree of bone mineralization (density), the design of the insert, the pressure applied to the handpiece, and the speed of operation. Ultrasonic vibration frequency (Hz), power level (W), and saline coolant spray are parameters adjustable according to the intended procedure (25). Recently, methods that use CBCT imaging have been used to determine bone quality, which can be expressed numerically using Hounsfield units (HUs) (30). de Oliveira et al (31) reported that the distribution of anterior mandibular bone is equivalent to type 1 of the Lekholm and Zarb classification (>850 HU) (32). Types 2 and 3 are between 500 and 800 HU, and type 4 is 500 HU. Hence, bone quality can be evaluated with CBCT scanning before endodontic surgery and the appropriate power level selected. Piezosurgery requires only minimal pressure unlike conventional microsaws or drills (23). Piezosurgery devices provide a clear surgical site; they maintain a blood-free field during bone cutting through an air-water cavitation effect. Figure 2A–I shows that this cavitation effect and constant irrigation provide a bloodless procedure that ensures a clear visibility of the surgical site (25). Cavitation involves the formation and immediate implosion of cavities within a liquid (small liquid-free zones or ‘‘bubbles’’). In piezoelectric surgery, cavitation describes the processes of vaporization, bubble generation, and subsequent bubble implosion into many microscopic gas bubbles. It occurs in a flowing liquid as a result of oscillations in pressure caused by ultrasonic vibrations (33). Walmsley et al (34) suggested that cavitation fragments bacterial cell walls and therefore has an antibacterial function.
Enucleation of Radicular Cysts One important application of piezosurgery is in the enucleation of radicular cysts. Figure 3A–I shows the surgical procedure for
Piezoelectric Surgery in Endodontic Surgery
327
Review Article
Figure 2. (A) A clinical image of tooth #3. (B) A periapical radiograph showing a small apical lesion associated with the mesial root of the right maxillary first molar. The patient complained of pain on the buccal aspect of this tooth. (C–E) A CBCT scan (ProMax 3D s; Planmeca Oy, Helsinki, Finland) was performed before endodontic surgery. (C) Sagittal, (D) axial, and (E) coronal images confirmed a circumscribed apical lesion in the mesial root. Note that the apical lesion affected neither the buccal nor palatal cortical plates. (F) A Piezosurgery Insert OT1 (Mectron) (flattened, diamond-coated file) was used to cut bone in proximity to the maxillary sinus. Minimal bleeding of the surgical site is apparent. (G) The final size of the osteotomy. (H) This procedure was performed with Biodentine (Septodont Laboratoires, Saint-Maur-des-Fosses, France) as the root-end filling material. (I) A periapical radiograph taken 6 months after treatment. Note that the Biodentine is not as radiopaque as other calcium silicate–based materials.
enucleation of a lateral periodontal cyst using piezosurgery and the Piezosurgery Retrosurgical Kit (Mectron, Carasco, Italy), which is specifically designed for endodontic surgery. Diamond-coated inserts can be used to remove the bone lamina over the cyst, whereas dull, bellshaped inserts can be used for the dissection of the cyst epithelium from the bone (23). The use of piezosurgery in the treatment of jaw cysts is a new development, and few cases have been reported (35, 36). Atraumatic handling of soft tissues is required for the complete removal of cystic lesions and is technically comparable to handling the sinus membrane during sinus bone grafting (37). The main advantage of enucleation is that it facilitates a pathologic examination of the entire cyst. Another advantage is that total excisional biopsy treats the lesion appropriately (37). Kocyigit et al (35) compared piezosurgery with conventional surgery for radicular cyst enucleation. They evaluated 29 patients prediagnosed with radicular cysts in the jaw region using radiology and cytology. Nineteen patients were treated using piezosurgery and 10 using conventional procedures. Piezosurgery was more successful than conventional surgery in terms of intraoperative hemorrhage, epithelial perforation, postoperative complications, and recurrence, but it increased the overall duration of the surgical procedure. Yaman and Suer (36) evaluated the performance of piezosurgery in removing odontogenic cysts. They concluded that piezosurgery increased operation time but also markedly increased visibility in the operating field. In cases in which cyst enucleation is necessary in difficult areas requiring delicate manipulation, the use of piezosurgery carries a lower risk of damage to vital structures, such as neurovascular tissues.
Root-end Resection Minimization of the bevel angle during root resection is one of the most important developments in endodontic microsurgery (38). The traditional technique uses a bevel angle of 45 –60 to facilitate access and visibility when using large surgical instruments. The mod328
Abella et al.
ern technique uses a shallow bevel angle of 0 –10 to expose fewer dentinal tubules (8). The use of a microscope minimizes access to the root apex, and the use of angled micromirrors permits observation of the complex root anatomy (39). However, there is no consensus on how much of the root must be resected to satisfy biologic principles. De Deus et al (40) showed that a large number of apical ramifications and lateral canals exist at least 3 mm from the root end. Thus, root-end amputations of
