Lateral periodontal cyst (LPC) is a relatively uncommon, usually asymptomatic developmental odontogenic cyst occurring on the lateral aspect of a vital tooth. They are defined as rare nonkeratinized and noninflammatory developmental odontogenic cyst representing 0.4% of all odontogenic cysts and 0.7% of all cysts of the jaw bones. The first well documented case was reported by Standish and Shafer. Most LPCs are found adjacent/lateral to the root of a vital tooth predominantly in the mandibular premolar region followed by anterior maxillary process. They are most prevalent in adults in the 5th–7th decade of life showing no gender preponderance. They are usually detected during routine radiography and are intraosseous and interradicular. The present case reports one such lesion which clinically looked like a periodontal abscess but proper diagnosis and conservative management improved the prognosis of the tooth.
A 36-year-old systemically healthy female reported with pain in gums, occasional pus discharge, and sensitivity to cold in lower front teeth since 2 months. There was no reported history of trauma. On examination, the patient had satisfactory oral hygiene status, tooth #41 had gingival recession (lingually) of about 3 mm, probing depth of 5 mm, grade II mobility, mild tenderness to vertical percussion, and the tooth was vital [Figure 1a and b]. There was diastema between #31 and #41. There were no periodontal pockets elsewhere. Based on the clinical presentation, a provisional diagnosis of chronic periodontal abscess was made.
The intraoral periapical radiograph was advised and it showed a well-defined radiolucency over mid-root level of #41 with a sclerotic border toward its cervical region [Figure 1c and d]. The alveolar crestal bone was intact. There were no significant findings in the periapical region. The radiographic features suggested it to be a cystic lesion and surgical curettage was planned.
Oral prophylaxis was done. Anticipating periapical exposure during the surgical intervention, endodontic treatment was performed for #41 [Figure 1e]. Routine blood investigations were advised which came out within normal limits. The case was planned for surgical cyst enucleation/surgical curettage under local anesthesia. The patient was explained the procedure and consent was taken.
A submarginal/parasulcular horizontal incision was given 1 mm above the mucogingival junction. A full-thickness flap was reflected from #43 to #33. The lesion was accessed from labial aspect of mid-root level of #41 through a bony window [Figure 2a]. Conservative surgical curettage was performed. Autogenous corticocancellous bone graft from the symphyseal region was harvested using trephine [Figure 2b]. The surgical site was sutured. Lower anterior teeth were splinted to aid in undisturbed healing and to avoid any masticatory trauma [Figure 2c]. Extraoral pressure bandage was given over the chin for 3 days and patient was given antibiotics and anti-inflammatory medicines. Healing was uneventful at both the sides. The curetted specimen was submitted for histopathological examination.
The hematoxylin and eosin-stained section showed bundles of collagen fibers suggestive of a cystic wall. Few inflammatory cells (lymphocytes) were seen between the collagen fibers. There was no evidence of cystic epithelium in the tissue being examined [Figure 3]. The histopathological examination was suggestive of a developmental odontogenic cyst.
The patient is regularly followed up with no recurrence yet (5 years) and an improving bone-fill of the defect [Figure 4a-d].
LPC is an uncommon developmental cyst that is defined as nonkeratinized and noninflammatory developmental cysts usually seen along the lateral surfaces of the roots of vital mandibular canine and premolar. It accounts for <1% of the jaw cysts. Various theories have been suggested to explain the origin of LPCs. The possible causes by which LPCs may arise are (1) an early dentigerous cyst left after tooth eruption, (2) A primordial cyst, (3) cell rests of Malassez, (4) reduced enamel epithelium, and (5) dental lamina remnants.
The literature shows that there are very few cases of LPCs reported with single case reports or case series with few cases. de Andrade et al. reviewed the 264 cases of LPCs published in English literature and found that most of the cases occurred in the fifth and the seventh decade of life (mean age of occurrence: 50.8 years), unlike our case, with a male preponderance (Male: Female: 1.3:1).
LPCs occur interradicularly and intraosseously, most commonly in the mandibular canine-premolar region followed by maxillary lateral incisor and canine region. It is usually asymptomatic, usually detected during routine radiography. Whenever they are apparent clinically, they usually present as small, soft-tissue swelling in the interdental papillary region, making it easily misdiagnosed as periapical or periodontal abscess. This makes it important to check for the tooth vitality. In the present case, the associated tooth was vital but a periodontal pocket of 5 mm was present along with gingival recession and grade II mobility. Based on the clinical presentation, a provisional diagnosis of periodontal abscess was made and a radiograph was advised.
Radiographically, LPCs present a round or tear drop shaped, unicystic, well-defined radiolucency, <1 cm (in most cases) with sclerotic margin along the lateral surface of the root. They may cause root divergence, but do not cause resorption of adjacent teeth; loss of lamina dura with widened periodontal ligament space may be present. In the present case, the alveolar crestal margin of mandibular central incisor was intact but a well-defined radiolucency with sclerotic border was present over the mid-root level. The radiographic features changed the provisional diagnosis of periodontal abscess to some cystic lesion.
The differential diagnosis of LPC includes gingival cyst, lateral radicular cyst, odontogenic keratocyst (OKC), and radiolucent odontogenic tumors. Gingival cysts appear very similar to LPCs when the latter presents as gingival swelling. LPCs are considered to be the intraosseous counterpart of extraosseous gingival cysts of adult and should be differentiated on radiographic features. A radicular cyst may develop on the lateral surface secondary to pulp necrosis or infected lateral accessory root canal; in such cases pulp vitality and periodontal examination helps in differentiating the two lesions. OKCs can very easily be misdiagnosed as LPCs if occurring in mandibular premolar region as they are similar clinically and radiographically. They are defined as developmental, noninflammatory, odontogenic cysts with high recurrence rate and more aggressive nature with a greater tendency for cortical expansion. With similar radiographic appearance, OKCs are present about three times more in mandible, presenting as unilocular or multilocular presentation in about 41% cases in tooth bearing regions in the mandible as compared to 75.5% cases in maxilla. Once the inflammatory origin is excluded definitive diagnosis can be made based on surgical exploration and histopathological examination. Mendes and Waal opined that the histological diagnosis of LPC should be given more importance than the radiographic diagnosis.
Majority of the cases of LPCs reported in the literature were managed by enucleation and curettage based on the clinical and radiographic appearance. However, the confirmatory diagnosis of LPC can be made only postoperative after the histopathological evaluation of the curetted specimen as in our case.[1,8]
Histopathological features of LPC include 1–5 cell thick nonkeratinized stratified squamous epithelium resembling reduced enamel epithelium, along with the presence of epithelial thickenings or plaques and the presence of glycogen rich clear cells in the plaques or the superficial epithelium. Usually, no inflammatory cells are observed in the cystic wall. In the present case, the cyst was chronically inflamed as represented by the presence of lymphocytes; the clear cells or the epithelial plaques were missing. If they get secondarily infected, they mimic periodontal abscess.
The treatment of choice for LPCs is surgical removal aiming cystic enucleation along with thorough curettage removing all the remnants. The associated tooth is vital and does not require extraction or endodontic treatment. However in the present case the involved tooth was vital but as periapical exposure and surgery was anticipated during surgical exploration; intentional endodontic therapy was performed. Conservative surgical curettage was done and attempts were made to preserve the integrity of the tooth as much as possible. Autogenous corticocancellous bone graft from the symphyseal region was harvested using trephine. Autogenous bone grafts are considered the gold standard osteoinductive bone graft material. The advantages of harvesting autogenous bone graft from symphyseal region are that this area provides corticocancellous type of bone graft with good surgical access and minimum resorption of the bone graft; however, it may pose an esthetic concern (ptosis of chin), postoperative pain and edema, temporary or permanent alterations to lower incisors and surrounding soft tissues. To avoid second surgical site for procurement of bone graft, this site was chosen. The new safety guidelines for chin block harvesting are that the bone cut should be perpendicular to the cortex in a right angle to the vestibular plain of the symphysis, the depth should be safely maintained at 4 mm (to avoid any trauma to the incisors), the distance to the root apices should be kept at least 8 mm and the lower border should be kept intact with 5 mm safety distance from the mental foramen. Submarginal/attached gingiva incision was opted and it is the incision of choice whenever possible (minimum 3–5 mm of keratinized gingiva should be present); as it prevents gingival recession and crestal bone loss at the surgical site, causes less bleeding and edema with minimal trauma and good surgical access.
The present case highlights a rare case of LPC which clinically appeared as an innocuous periodontal abscess. The case could have been easily misdiagnosed and managed as an abscess draining through the periodontal pocket. The radiograph was suggestive of a cystic lesion without any sclerotic margin probably because of superimposed infection. The radiographic features changed the provisional diagnosis and the treatment plan. Upon surgical exposure, autogenous bone grafting was planned and the case was conservatively handled with regeneration as an intention behind bone grafting. The present case highlights the conservative management of a case of LPC that was very precisely diagnosed as some variation from the routinely occurring lesion like periodontal abscess followed by rehabilitation by autogenous bone grafting and regeneration. The focus was not only the treatment of the pathology but also the rehabilitation for better function and esthetics.
The case stresses upon doing a thorough clinical, radiographic, and histopathological examination of a seemingly routine case for the proper diagnosis, management, and follow-up.
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