Continuing Education Activity

Retained dental roots arise most commonly due to prior dental extraction procedures, during which they are intentionally or unintentionally left behind. They can also arise from facial trauma that results in dental fractures. Their removal may be warranted to make way for a future dental implant or dental prosthesis or due to odontogenic pain, infection, or associated pathology. The extraction of retained root tips is a surgical procedure frequently performed in the outpatient setting by dentists and dental specialists. Appropriately managing retained roots requires knowledge of dental morphology, current root removal techniques, indications, and contraindications. This activity reviews the proper evaluation and treatment strategies used to extract dental roots. Additionally, it highlights the roles and responsibilities of healthcare team members when performing this type of surgery.

Objectives:

• Describe the morphogenesis and anatomical considerations of tooth roots.
• Review indications, contraindications, and preparatory considerations for the extraction of tooth roots.
• Summarize techniques commonly employed in the extraction of tooth roots.
• Outline potential complications associated with root extraction surgery and explain the importance of clinical proficiency in managing fractured and retained root fragments.

Introduction

The retained tooth root is a common consequence of tooth fracture, which may occur for various reasons. Tooth roots are a significant contributor to the ease or complexity of dental extraction surgery and often require unique management approaches not typically employed in routine exodontia. This article outlines various surgical and non-surgical considerations, instruments, and techniques helpful in extracting retained tooth roots to promote efficiency, improve patient-centered outcomes, and minimize complications.

Anatomy and Physiology

The root is one of the more unique characteristics of the tooth. It enables a single tooth to serve as a functional unit within the masticatory system through a firm, resilient skeletal anchorage and balanced transmission of occlusal force. Blood supply and sensation to our teeth are made possible by the neurovascular connection the root provides to neighboring nerves and vessels of the jaws.[1] A critical concept to be aware of is the high frequency of variability between the size, shape, length, and number of roots certain teeth can possess. These variations can impact a surgeon's difficulty extracting a given tooth, which is why a sound understanding of dental morphology is vital to surgical success in exodontia.

Tooth development proceeds reciprocally from cellular crosstalk between epithelial and mesenchymal cells. With the formation of the dental lamina, various cell types begin the process of organic tissue deposition. Enamel, a highly mineralized tissue forming the external layer of the crown, is deposited by differentiated cell types derived from the epithelium called ameloblasts. Dentin, which begins as a tissue matrix and lies just deep to enamel, is another mineralized substance deposited during tooth development and is produced by mesenchymal derivatives called odontoblasts. This back-and-forth deposition of mineralized tissue between ameloblasts and odontoblasts gives rise to the crown. Eventually, the deposit of enamel terminates at the level of the cementoenamel junction, which is the delineation between the most inferior extent of the crown and the most superior extent of the root.

The root of the tooth begins formation following the completion of crown development. Hertwig's epithelial root sheath, or HERS, acts as the growth center for root formation.[1] It also guides the deposition of the outer mineralized layer of the root.[1] This mineralized layer, called cementum, connects the root to the alveolar bone circumferentially through the periodontal ligament.[1] Various signaling pathways involved in tooth formation have been suggested in recent literature and are believed to promote the number and shapes of roots directly.[1] However, the mechanisms by which many of these pathways contribute to root formation, especially in humans, still require a more profound understanding.[1]

Root morphology tends to follow a pattern in most individuals. In the maxilla, central and lateral incisors traditionally have single, straight, and typically conical roots.[2] Maxillary canines are also single-rooted and are the longest of all tooth roots. The maxillary first premolar often has a long root trunk with bifurcated buccal and palatal roots, but single root variants exist.[3] Maxillary premolar roots are typically thin.[3] Because of the length of the root trunk, which often spans half the length of the root, maxillary first premolars are commonly associated with inadvertent root tip fractures during extraction. Unlike the maxillary first premolar, the maxillary second premolar is usually single-rooted and rarely presents with two roots or a bifurcated root phenotypically.

Maxillary first molars typically have two buccal roots and one larger palatal root.[4] Roots may splay and have variable curvature.[4] Both the maxillary first and second molars have distal root inclinations, with the second molar often to a greater degree than the first. The second molar also traditionally has three roots that are usually less splayed than the first molar.[5] In some cases, the roots may fuse on the buccal aspect. The maxillary third molar has the most significant anatomical variability of all teeth. The roots of the maxillary third molar tend to be fused and shorter than the maxillary first and second molars.[5]

In the mandible, central and lateral incisors have single roots, with central incisors often lacking apical curvature.[6] If present in either tooth, apical curvature tends to be distally inclined.[6] Mandibular canines usually present with single roots, but one unique difference between maxillary and mandibular canines is that mandibular canines may have bifurcated roots similar to those seen in maxillary first premolars.[6] The mandibular first and second premolars typically present with single roots but may have bifurcated roots in rare situations. The root tips are often inclined distally, and the mandibular second premolar's root is usually longer than the first premolar's.[7] The mandibular first and second molars usually have two distally tilted roots: a mesial and a distal root. The mandibular second molar's roots are usually shorter with less splay than the first molar roots.

Finally, the mandibular third molars typically have two shorter, often parallel, mesial, and distal roots with a more pronounced taper than the first or second mandibular molars.[8] Like the maxillary third molar, the mandibular third molar can have significant morphological variation.[8]

Indications

Retained dental roots may present with one or many indications for removal. Some of the most common indications for the extraction of root fragments are:

• The presence of acute or chronic infection
• Partial or complete fracture of the crown
• Future dental implant placement
• Pain 
• Vertical root fractures
• Periodontal disease
• Caries 
• Presence of pathology
• Future prosthetic restoration of the site with a fixed or removable prosthesis
• Preservation of vital adjacent teeth and structures
• Patient esthetic concerns

Sometimes retained roots are removed prophylactically, even in the asymptomatic patient. A patient may require prophylactic root removal when their future access to care is known to be limited or non-existent (e.g., patients deploying in the military). Another example of when prophylactic extraction may be necessary is in patients planning to undergo radiation therapy to the head and neck for cancer treatment or in patients requiring medications known to contribute to osteonecrosis of the jaw. It is the surgeon's responsibility to discuss all applicable indications, risks, and benefits for root removal for the patient to provide informed consent for surgery.[9]

Contraindications

Specific scenarios exist where the benefit of root extraction does not necessarily outweigh the potential risks associated with removal. Additionally, it may be necessary to leave retained roots for some time until just before implant placement. Retaining vital root segments can preserve alveolar bone, which may make the surgical site more favorable for a dental implant. After completing a thorough risk-benefit analysis, the surgeon can decide if surgical removal is warranted or if it may be necessary to leave the retained root fragment. Root fragments may be intentionally undisturbed when there is an increased risk of damage to adjacent teeth or neurovascular structures like the inferior alveolar nerve (IAN).[10][11] 

The increased risk of unintentional displacement of fragments into nearby spaces such as the maxillary sinus, fracture of supporting alveolar bone, or development of an oroantral communication may also preclude removal.[12] Sometimes, prosthetics replacement drives the decision to keep or remove root segments. Retaining vital root segments could preserve alveolar bone. This approach is referred to as root submergence and may be the approach of choice when considering future prosthodontic options.[12] Alternatively, root fractures occurring at the time of surgery in the setting of a vital pulp with no marked root mobilization and appropriate wound closure can often be left indefinitely to allow for healing. Lastly, always consider the patient's desires for treatment. Patients may decline treatment despite indications for removal.[9] Therefore, a patient's declination of treatment is always a contraindication to root extraction.

Equipment

Extraction of dental roots requires many of the same surgical instruments in conventional exodontia. The typical surgical setup usually includes a combination of the following:

• Elevators
• Luxators
• Forceps
• Root tip picks
• Retractors
• Curets
• Dental explorers
• Dental mirrors
• Scissors
• Scalpels
• Hemostats
• Periodontal Probes
• Rongeurs
• Bone files
• Local anesthetic needles and syringes
• Irrigation needles and syringes
• Local anesthetic
• Sterile gauze
• Sutures
• Surgical handpiece
• Surgical bur
• Sterile saline
• Sterile water
• Bite block

Optimal lighting is critical in dental surgery, especially when extracting roots. The operatory and the surgical site should be well-lit for adequate visualization during the procedure. Though not required, many dentists and surgeons prefer to wear some form of magnification, such as surgical loupes.[13] In addition, surgical headlamps are often worn and can improve the operator's field visibility during surgery. Every surgical team member must don proper personal protective equipment (PPE) and ensure the patient has been adequately prepped and draped. Over the years, various adjuncts to the traditional exodontia armamentarium have been developed to facilitate root extraction. Depending on the technique employed when extracting root segments, one can use endodontic files, periotomes, luxators, a vertical extraction system, and Piezosurgery to facilitate extraction.[14] Appropriate instrumentation best facilitates predictable outcomes in oral surgery. This is particularly true when extracting retained roots.

Personnel

Required personnel for this procedure may vary based on individual state guidelines and the level of anesthesia provided during the case. However, a minimum of one dentist or surgeon and one surgically trained assistant are usually sufficient to complete this procedure under local anesthesia. While the surgeon operates, the surgical assistant provides suction and irrigation. They also may anticipatorily hand instruments to the surgeon as needed. Additional personnel may be required if the patient completes the procedure under sedation or general anesthesia.[15] Roles and responsibilities of team members may change depending on the mode of anesthesia delivery. For instance, an assistant trained in anesthesia monitoring is responsible for constant assessment and support of intraoperative airway patency. They also make the team aware of notable changes to vital signs or patient status during the procedure.[15][16]

Outpatient anesthesia in a dental or oral and maxillofacial surgery clinic requires a licensed anesthesia provider who has received extensive training in anesthesia delivery and anesthetic-related patient management. This could be the surgeon or dentist, but it could also be a certified registered nurse anesthetist (CRNA), an anesthesiologist, or a dental anesthesiologist.[16] Ancillary staff members perform crucial administrative tasks such as confirming informed consent, updating the patient’s medical history and allergies, and all necessary pre-procedural verifications. When operating effectively, all surgical team members help foster a culture of safety and efficiency in the outpatient surgical setting.[17][18]

Preparation

Every surgical procedure requires a thorough patient evaluation before treatment. At a minimum, this includes a physical examination and review of the patient's medical history and medications. A complete acknowledgment of the patient's medical status allows the surgeon to mitigate intra-operative and post-operative complications.[14] It will also help guide post-operative management strategies for pain and healing of the surgical site. The surgeon should assess the surgical site intraorally and evaluate diagnostic radiographs before surgery. The intraoral and radiographic examination gives the surgeon an idea of the health of the associated periodontium, the extent of caries at the surgical site, the root segment's mobility, and the condition of adjacent teeth. Pre-operative evaluation will also aid in selecting specific instrumentation and hemostatic agents.[9]

Radiographic examination is particularly important when dealing with retained roots. With the increasing availability and popularity of cone-beam computed tomography (CBCT), it has become much easier to determine the specific depth, position, size, curvature, and proximity of remaining root fragments to nearby anatomical landmarks like the maxillary sinus and the inferior alveolar nerve.[14] This is the primary limitation of traditional two-dimensional radiographs, though they are still indicated in the initial assessment of retained roots. Not all exodontia cases require a CBCT evaluation, but it becomes valuable when the anticipated surgery increases the risk of iatrogenic damage. Pre-operative evaluation not only gives the surgeon the means to generate an appropriate diagnosis but also determines the proper course of treatment.[14] The surgeon must exercise sound clinical judgment and base their decision-making on empirical evidence and best practices when treating retained root tips. Lastly, the surgeon must decide if they have the clinical skills and armamentarium necessary to perform the procedure safely and effectively. It is never the wrong answer to refer a patient to a higher level of care or to a provider with known expertise in treating a particular condition.[9]

Technique or Treatment

Once consent is obtained and all team members agree with the planned procedure, the patient is locally anesthetized, and the anesthetic is allowed time to take effect before initiating surgery. There is much data to support atraumatic teeth extraction whenever feasible. With the advent of new materials and technology, today’s surgeon is responsible for knowing how to extract teeth in a way that facilitates optimum preservation of bone and soft tissue. However, it is essential to note that no extraction is entirely devoid of trauma, and all forms of tooth loss result in some alveolar bone resorption.[19] There are a variety of methods at the surgeon’s disposal uniquely focused on the removal of root segments:

Closed Surgical Technique: This technique involves elevating, luxating, and delivering the root segment from the coronal aspect of the socket without creating a mucoperiosteal flap. Once appropriate surgical visualization of the root segment is achieved, dental elevators can be used in succession using one of three fundamental physics concepts: (1) a wheel, (2) a lever, and (3) a wedge. When using an elevator as a wheel, a rotational arc between the elevator tip and the body of the root develops to lift the root out coronally. Cryer elevators perform well when used in this manner. When using an elevator as a class 1 lever, a fulcrum point is created between the alveolar crest and the root. This concept requires a reliable purchase point so that force can be applied without instrument slippage or misdirection.[14] If the current purchase point is inadequate, it may be necessary to create a bony trough using a surgical handpiece or osteotome adjacent to the root.[14]

Additionally, sectioning the root may allow for segmental delivery. A hole can be drilled in the root to allow for a crane pick or similar instrument to lever the root coronally.[14] When used as a wedge between the root and supporting interradicular bone, the instrument’s tip is oriented parallel to the root, and a consistent application of apical pressure is transmitted. As the elevator continues apically, the periodontal ligament fibers begin to sever from the root, and the bony alveolus expands outward. A void forms between the walls of the socket and the root, allowing for a broader range of elevator tip motion and more alveolar expansion. Eventually, the force delivered will be greater than what the remaining periodontal ligament fibers can resist, allowing for the coronal displacement of the segment.[14]

Depending on the physical characteristics of the root fragment to be removed, a surgeon may attempt all three of these principles - often simultaneously - until the root mobilizes. With time, the surgeon can predictably retrieve the root with forceps. A periotome is a handy instrument to use when desiring to preserve gingival and alveolar architecture. Manual and powered versions are available. The periotome uses a thin blade-like working end wedged within the periodontal ligament space, severing the ligamentous attachment encircling the root. The periotome avoids the need for excessive cortical bone removal.[20]

Another modern advancement in atraumatic tooth extraction is Piezosurgery. This cutting system creates osteotomies through ultrasonic vibrations, which promotes cleaner surgical cuts compared to oscillating saws or surgical burs. Piezosurgery permits the surgeon to remove only the necessary bone to facilitate root extraction. It also does not cause harm to soft tissues or neurovascular structures, unlike surgical burs or oscillating saws that obliterate hard and soft tissue indiscriminately.[20] Surgical skill comes with knowledge and consistent practice. As the surgeon gains experience in exodontia, they will be able to feel when their application of force is appropriate, promoting efficiency and safety during the surgery.

Open Surgical Technique: Removal of root segments using an open surgical technique involves the reflection of a tissue flap to improve visualization and gain surgical access to the root. Removal of cortical bone is often necessary following mucosal flap reflection. Removing roots may warrant a full-thickness flap, meaning the mucosal flap of soft tissue carries an adherent periosteal layer. Although alveolar bone loss does not develop from mucosal flap reflection alone, much of the blood supply to the alveolus originates from the periosteum. It, therefore, impacts the amount of alveolar bone remaining post-extraction.[20] The open surgical technique is a considerable approach when other less-invasive methods have proven ineffective. In many cases, creating a tissue flap and removing bone may be the only option to remove a root fragment or tip.

With the invention of the rotary surgical drill, the transition from simple to surgical exodontia has never been easier. Some say surgical drills are one of the greatest innovations in modern exodontia.[14] They minimize operating time and allow the surgeon to access points of the tooth that were previously inaccessible through simple exodontia methods.[14] When indicated, cortical bone can be drilled away, or roots can be sectioned to increase purchase points and allow for a more profound apical orientation of elevators. When multi-rooted teeth require sectioning with a drill, it is advantageous to treat each root as a single-rooted tooth when extracting, as it promotes less trauma to the supporting alveolus.[21] Maxillary molar roots are traditionally sectioned at the furcation level in a Y or T configuration.[20] In contrast, mandibular molar roots and other 2-rooted teeth are sectioned horizontally through their respective furcations.[22]

Endodontic File Technique: Using endodontic files to retrieve retained root segments involves the insertion of an endodontic file through the visible root canal orifice from the coronal aspect and advancing it apically until friction develops within the canal.[23] The more contact surface area the file has within the canal, the more generated force when pulling the root segment coronally.[23] The type and size of endodontic file best suited for extraction in root tips have yet to be well-studied, but it has been shown that a #25 Hedstrom file generates a tremendous pullout force in all roots, regardless of the length of the root. Factors such as root length and PDL attachment significantly impact the use of this technique. Shorter root segments and tips offer the greatest likelihood of technique success. Barbed broaches, size #40 or #50 endodontic reamers, and even file sizes up to #80 were all identified as potential adjuncts.[23][24] However, larger file sizes may restrict the distance of apical advancement of the file within the canal, limiting the amount of frictional force. Also, due to the significant amount of friction generated within the canal, imprudent amounts of rotational force can cause files to break, further complicating the extraction.[25]

Local Anesthetic Needle Technique: Following adequate luxation of the root segment, it may be possible to advance a traditional 25-gauge local anesthetic syringe needle through the visible root canal orifice in an apical direction.[23] The needle should develop retentive friction within the canal to generate enough pullout force to lift the root segment from the socket. This technique tends to be more effective on smaller, more apical root segments but helps retrieve retained roots without concomitant removal of supporting bone. Vertical Extraction Technique: This minimally invasive procedure involves attaching a pin within the body of the retained root (usually within the pulp chamber), followed by applying the extraction system and stabilizing it against the dental arch.[26] The use of this technique does not require flap surgery in most circumstances. The mechanism of virtually all vertical extraction methods relies purely on the severance of the periodontal ligament without destroying the alveolar bone.[26]

Stabilization often involves the use of putty or impression material (commonly silicone-based). The pin is attached to the extraction system using a cable or wire. With the apparatus firmly held against the arch, increasing traction forces sever the periodontal ligament attachment entirely and lift the root from the socket. This technique is best used on single-rooted teeth and individual root segments but showed reduced effectiveness in multi-rooted teeth without a previous history of root canal therapy.[26] 

The Benex device (Benex, Lucerne, Switzerland) is the most frequently cited vertical extraction system on the market today. However, some notable disadvantages of the Benex system are that the technique is time-consuming, and its mechanism is achievable only by counterbalancing against the dental arch, placing adjacent teeth and alveolar bone at risk for accidental fracture.[25] Additionally, the system is costly when compared to more conventional armamentaria. For these reasons, vertical extraction systems may not be the most practical means for the atraumatic extraction of teeth and roots. On the contrary, some have suggested a more cost-effective alternative to the Benex extraction system using a similar variation of the vertical extraction principle used by Benex. The technique requires using a miniplate screw fixated within the radicular canal and with a wire wound under the head of the screw. The wire-screw-root combination extrudes coronally using a wire twister and the nearby palatal bone as the fulcrum.[27][28]

Regardless of the technique employed to extract the retained tooth root, the surgeon should finish the procedure with copious irrigation of the socket with sterile saline to flush away surgical debris, as they can contribute to the development of infection post-operatively. Wound edges should be re-approximated when reflecting mucoperiosteal flaps.[14] To promote hemostasis after the procedure, sterile gauze moistened with sterile saline may be placed over the surgical site with light biting pressure.

Complications

Mitigation of surgical risk occurs through proper planning and good technique, but untoward events can still manifest intraoperatively or during the postoperative period. Most are not unique to root extractions and are just as likely to present in simple or surgical exodontia cases. Complications of all tooth extractions include:

• Pain
• Bleeding
• Infection
• Fracture of bone or jaws
• Osteomyelitis
• Osteonecrosis
• Alveolar osteitis
• Prosthetic defects
• Impaired wound healing
• Burns [9]

An important point to consider when planning to extract any tooth is the proximity of root tips to adjacent anatomical landmarks like the maxillary sinus floor or the inferior alveolar nerve (IAN). Though uncommon, one of the most unfavorable outcomes of any extraction is accidentally displacing teeth or root segments into nearby anatomic spaces. This complication usually results from inadequate pre-surgical evaluation, excessive force application during extraction, poor surgical site visibility, and an under-reflected mucoperiosteal flap.[29]

Roots of posterior maxillary teeth commonly contact or protrude through the floor of the ipsilateral maxillary sinus. Maxillary molars demonstrated protrusion through the maxillary sinus in greater than 50% of cases, with the mesiobuccal root of maxillary second molars showing the most significant depth of protrusion of all maxillary posterior tooth roots.[30] Other anatomical areas of concern for root displacement are the submandibular, sublingual, buccal, and pterygomandibular spaces.[31]

Maxillary posterior teeth can even be displaced as far posteriorly as the infratemporal fossa, often requiring alternative surgical approaches for retrieval.[32] The displacement and even the retrieval of roots from any anatomic space in the head or neck can increase patient morbidity.[32] Best practices involve only attempting retrieval if the tooth or root is fully in-view and easily graspable at displacement time. Otherwise, an immediate specialist referral for evaluation and treatment is the prudent approach.[29] Iatrogenic nerve injury is another rare but serious complication associated with tooth and root removal, particularly with mandibular third molars. In some patients, the roots of the mandibular third molar can be in direct contact with the mandibular canal that houses the IAN. One study showed that the frequency of intimate positioning between the mandibular third molar roots and the mandibular canal was as high as 7.1%.[33] 

Another study showed that the location of the canal relative to the third molar apex was predominantly inferior (77%) but presented on the lingual side in 11.8% of cases and on the buccal side in 8.9% of cases.[10] The mandibular canal can also run between the roots, which was the case only 0.7% of the time. Complications of root segment extractions are rare but can occur quickly and without warning. Therefore, the surgeon must weigh the potential risks of retrieval of all root segments before proceeding with surgery. With sound surgical planning and technique, most unfavorable outcomes of tooth extraction are preventable.

Clinical Significance

Retained root fragments are not uncommon within the general population. Dentists and surgeons who routinely extract teeth often have a well-developed approach to removing retained roots to maintain clinical efficiency in the event of tooth fractures during surgery. Before this article, a formal review of root extraction techniques had yet to be published. As dentistry continues to evolve, general dentists are surgically extracting teeth and performing other dentoalveolar surgeries at a never-before-seen rate. As most dentists and dental specialists are aware, removing teeth can be a humbling endeavor, requiring the surgeon's consistent capability to convert to a surgical extraction, if necessary. Retained roots can add time and increase stress levels for the patient and the surgical provider. To minimize harm and promote favorable patient outcomes, the exodontist should have the knowledge base, skill level, and confidence to employ the latest surgical techniques.[22]

Enhancing Healthcare Team Outcomes

The benefits of a well-trained surgical staff cannot be understated. Before every surgery, all involved staff members should systematically verify the present patient's correctness and the planned procedure's accuracy. Instrumentation, supplies, and emergency equipment should all be available and accessible before starting the procedure. Tooth extraction is typically an ambulatory procedure, and indications for extraction rarely constitute an emergency. However, emergencies can and do happen in the outpatient surgical setting. Therefore, it is essential to ensure that every surgical team member understands their role since effective management of complications as they arise is a team effort.[17][18]

Time spent in surgery is costly, both financially and psychologically. It raises patient and provider anxiety and may also contribute to increased morbidity. One of the most fundamental ways to reduce surgical time is preparedness. Instrument anticipation by the assistant during surgery hastens every procedural step, especially during complex root removal.[18] Teaching staff how to manage intra-operative complications like bleeding or sinus perforation can also significantly reduce morbidity in dental surgery. Risk is inevitable in surgery, no matter the procedure, but the most significant risk often stems from a lack of preparation. Therefore, the surgeon and the surgical team must thoroughly prepare for every case and contingency without exception.[17]

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Disclosure: Parker Benton declares no relevant financial relationships with ineligible companies.

Disclosure: Paul Chang declares no relevant financial relationships with ineligible companies.