Contemporary Restoration of Endodontically Treated Teeth. Nadim Z. Baba
of follow-up, the lesion was not probeable yet. The repair was made with amalgam at the time; today that repair would be accomplished with mineral trioxide aggregate, a material that has been shown to be very suitable for perforation repairs.
Finally, developmental malformations can lead to unusual periradicular lesions. Radicular invaginations or grooves are one example of this situation. As long as an intact epithelial attachment remains, the periodontium is maintained in a healthy status. However, once the attachment is broken, the invagination is extremely difficult to manage and often creates a self-sustaining infrabony pocket.49
Resorption
Root resorption complicates treatment of teeth; it is unpredictable both in terms of appearance of the lesion and response to treatment. For practical purposes, resorption can be classified into the following categories: eruption-related (which is resorption of primary teeth as part of succedaneous tooth eruption and will not be discussed further in this chapter); trauma-related; pressure-related; cervical invasive; and idiopathic resorption.
Trauma-related root resorption follows traumatic dental injuries and is related to damage to the root cementum and the PDL. Initial resorption after dental trauma is termed repair-related resorption and involves only cementum. It is difficult to demonstrate this type of resorption radiographically. However, it plays a role in the repair process after injury to the PDL during which new PDL fibers are inserted into the new cementum that forms as part of this process. Trauma-related resorption requires no treatment and is of concern only if it continues so that the resorption begins to involve the subjacent dentin. The resorptive process then may take one of two pathways (occasionally both can occur simultaneously): (1) infection-related (inflammatory) and (2) ankylosis-related (replacement) resorption.
Infection-related root resorption has a dual etiology when it occurs following a traumatic dental injury (Fig 2-13). First there is damage to the PDL with subsequent resorption of cementum; if resorption progresses to the dentin, then the second etiologic factor arises, that is, the presence of bacteria in the pulp space. The bacteria will have a stimulating effect, through the dentinal tubules, on the osteoclasts to aggressively resorb both tooth structure and surrounding bone. If this infected necrotic pulp tissue is not removed (by RCT), the bacterial presence will stimulate continued resorption of both tooth structure and adjacent alveolar bone. This process is the basis for recommending endodontic evaluation and treatment of teeth involved in traumatic dental injuries. It has been well established that RCT in these types of trauma-related resorptions will both prevent infection-related resorption and arrest the resorption if it has already started.50
Fig 2-13 Infection-related resorption. Radiograph taken 6 months after replantation of the mandibular central incisors, which had been avulsed in an accident. Failure to perform RCT in a timely manner (ideally within 2 weeks following replantation) allowed the pulps to become infected, which stimulated both infection-related root resorption and bone resorption. This type of resorption is the result of initial damage (from the accidental avulsion) to the cementum and PDL and the presence of bacteria in the pulp tissue. Infection-related (inflammatory) resorption can be predictably prevented with timely RCT.
A variation of the resorption just described is infectionrelated resorption that takes place inside the root canal, referred to as internal resorption (Fig 2-14). This is a very rare type of resorption and is often confused radiographically with external invasive resorption (to be described in the following paragraphs).51 The mechanism is very similar to that of the external variety in that bacteria are necessary to stimulate the resorptive process, and there probably has to be some damage or disruption in the predentin layer, allowing clastic cells to resorb underlying dentin.
Fig 2-14 Internal resorption. (a) The resorptive cavity is centered in the root of the tooth. (b) RCT will successfully arrest the resorption. (Courtesy of Dr Steve Morrow, Loma Linda, CA.)
The resorptive process is in some ways self-limiting in that the resorption will stop when the pulp undergoes necrosis from the presence of the bacteria. The treatment for internal resorption is RCT—after a careful diagnosis has been established so that a case of external invasive resorption, which can initially look like internal resorption, is not mistreated.
The second type of trauma-related root resorption is called ankylosis-related resorption because it occurs as a result of bony fusion (ankylosis) with dentin, resulting in a gradual replacement of the root structure with bone (Fig 2-15). This type of resorption is related to extensive damage to the PDL, followed by resorption of cementum without subsequent repair, thus exposing the dentin to osteoclastic removal followed by replacement with bone. This process cannot be arrested once begun, and the status of the pulp in the tooth (healthy or diseased) is immaterial. In a young person who is still growing, ankylosis prevents the tooth from erupting and the adjacent alveolar process from developing.52 Fortunately, there is now a procedure—decoronation—that can be used to allow continued bone formation.52 In adults, teeth undergoing replacement resorption can last for many years even when ankylosed.
Fig 2-15 Ankylosis-related resorption. (a) The left central incisor of a 13-year-old girl has ankylosed 4 years after a traumatic intrusion. Intruded teeth in young patients (younger than 15 years) should be allowed to spontaneously reerupt. In this case, the tooth did not reerupt but became ankylosed. (b) Ankylosis-related (replacement) resorption has prevented normal eruption. The pulp is vital, illustrating that the pulp plays no role in ankylosis-related root resorption.
Pressure-related resorption is that seen when an erupting tooth causes pressure on an adjacent tooth (Fig 2-16) or when some lesions cause pressure as they grow in size. The resorption that results from orthodontic movement is also pressure related; interruption of the orthodontic movement will arrest the resorption.
Fig 2-16 Pressure-related root resorption. (a) In this case, a third molar has exerted pressure against the distal aspect of the second molar. (b) The effect of the pressure on the second molar can be seen clearly after removal of the third molar. RCT is not indicated, but a periodontal problem may result if the bone does not fill in on the distal aspect of the tooth.
Cervical invasive resorption (Fig 2-17) is probably the most frustrating of resorptive entities. It can occur without any warning and may not always be associated with an event—trauma or otherwise—that would predict its occurrence. A history of trauma is often recognized, but other events such as orthodontic treatment and other dental procedures have been implicated.53 A lack of recognizable etiology is not uncommon. This is also a type of resorption that has no connection with the status of the pulp.
Fig 2-17 Cervical invasive resorption. (a) The resorption (arrow) may have resulted from trauma to the cervical cementum during removal of the third molar. Although the pulp is not directly affected by the resorptive process, management of this tooth would probably include RCT. (b) The radiograph of a canine with invasive resorption (arrow) illustrates the conditions sometimes observed years after a traumatic injury. Treatment options in such cases may include