The objectives of jaw cyst resection are to terminate the pathological process, promote the restoration of jaw bone tissue, and restore the anatomical and physiological functions of the teeth in the cyst area [15, 16]. According to traditional surgical methods, root canal therapy and apical resection should be adopted as long as the tooth can be retained, regardless of the pulp activities in the cystic area [4, 5]. Although this surgical method decreased the possibility of postoperative infection in the lesion area, it also destroys the anatomical structure and pulp activity of the teeth, consequently reducing the stability and physiological function of involved teeth, despite that the pulp vitality of involved teeth generally does not have inflammation. We also found that growth of the bone around the involved teeth in the cavity is accompanied by the reconstruction of bone around the root apex and recovery of pulp activity after the fenestration [10]. Therefore, if the involved teeth apex is properly preserved and treated, the integrity of tooth and pulp activity of the involved teeth will be well protected and restored [10, 12].
In this study, to protect the root integrity and pulp activity of the involved teeth during operation, the following improvements of surgical methods were made.
-
The involved teeth and pathogenic teeth should be diagnosed before surgery, and root canal therapy should not be performed on the involved teeth.
-
The upper boundary of chiseling of the apical area of the alveolar bone should be 5 mm above the root tip of the involved teeth to protect the nerve and blood supply of the apex and to preserve the integrity and activity of pulp stem cells and periodontal ligament cells.
-
Only the epithelial lining of the capsule wall and part of the fiber lining is cut under direct vision in the area around the involved teeth. The fiber lining can be partially retained to avoid posing a threat to papillary stem cells, multifunctional pulp stem cells, periodontal stem cells, and blood vessels in the root tip.
-
During the operation, the cyst and the root tips of the pathogenic teeth are completely removed, but those of the involved teeth are not excised or cauterized. Then, irrigation of the chamber with sterile saline solution ensures sterile conditions and non-inflammatory factors in the cystic space.
-
The root tips of the involved teeth should be covered with some blood clots, which would facilitate development of a physiological basis for the regeneration of normal tissues around the area and the restoration of blood vessels and nerves in the pulp.
In the clinical research, we found that the root and pulp vitality of the involved teeth located in a jaw cyst could be effectively preserved; meanwhile, the anatomical and physiological functions of the teeth would not be involved if the inclusion criteria and standard surgical methods are strictly followed and performed. (The root integrity of the 63 teeth and pulp vitality of the 53 teeth were well preserved.) Currently, dental pulp revascularization, that is, a process of tissue regeneration in an inactive tooth, has gained increasing recognition since Lwaya et al. [17] first put forward this technology in 2001. Dental pulp revascularization takes advantage of the endodontic blood channel in vitro, letting the dentin in the root canal of the permanent tooth continue its generation, thus leading to the closure of the apical pore and the growth of the root [19]. Neha et al. [20] deduced that if a sterile tissue matrix can be provided for the growth of new cells, viable pulp can regenerate, and dental pulp revascularization is the result of replantation or allograft of dead teeth. This result suggests that if a sterile tissue matrix is provided for the growth of new cells, these cells could grow in the root canal and help rebuild the blood supply to the pulp, gradually replacing the diseased tissue[19, 20]. Studies of dental pulp revascularization on chronic periapical periodontitis and tooth trauma in young permanent teeth are quite common, and many animal experiments and clinical studies, both domestic and overseas, have shown good results[23, 24].
In some cases, a tooth with incomplete root formation may be able to reestablish blood supply after autotransplantation or replantation [25, 26]. Through a large number of clinical observations, we find that most of the pulp of the involved teeth is free of inflammation, and the blood flow and nerve activity of the involved pulp in jaw cyst treated by fenestration decompression can be preserved and restored. The endodontic vessels and nerves are abundant; in addition to the apical vessels, the endodontic vessels can communicate with the periodontal ligament and some accessory root canals [27]. Endodontic nerves are divided into myelinated fibers that conduct pain and some non-myelinated fibers nerves that regulate vasoconstriction and relaxation. Myelinated nerve fibers that conduct pain are also divided into Aδ fibers and C fibers. The pulp vitality test does not accurately reflect endodontic blood flow and nerve condition of involved teeth. Involved teeth with jaw cyst have more complete pulp tissue structure and activity than the transplantation teeth. Therefore, the blood flow and nerves of involved teeth should be easier to be preserves and regenerated than the transplantation teeth.
Especially for pediatric patients, some factors occur: apex may not have completed the root maturation at the time of intervention; the pulp activity of their teeth is easier to regenerate; moreover, the lack of compliance may require a treatment in general anesthesia. Therefore, it is important to carefully evaluate the maintenance of teeth, because any cyst recurrence would increase the burden of care[28]. Through improvement of this surgical method and the principle of treatment of involved teeth, the involved teeth with normal or insensitive pulp can be preserved effectively. The operation effect is good, the anatomical structure and vitality of the involved teeth can be preserved well and the cyst also did not recur. This surgical method is worth being developed and popularized in clinical work because not only does it reduce the cost and time of treatment for patients, it also preserves the physiological and anatomical functions of patients' teeth. However, this paper as the initial study of the involved teeth preservation, the classification of cysts is not precise enough and the number of samples is small, therefore, the obtained data cannot accurately reflect the surgical effect and the pulp situation of vascular and nerve functions after this modified operation. Therefore, in the future work, we will increase the number of cases, respectively for odontogenic cyst and non-odontogenic cyst for long-term follow-up of the surgical effect and pulp activity of the involved teeth, in order to obtain more scientific and accurate experimental results.
Our results showed that preservation of the involved teeth pulp for the treatment of jaw cyst by this improved operation method was effective.