Chinese Journal of Dental Research, 02/2019

The continual growth of cystic lesions of the jaws can cause bone expansion, facial deformity, impacted teeth, occlusal disorder and displacement and loosening of the originating tooth or adjacent teeth. The management of teeth associated with cystic lesions of the jaws has been widely debated. When standing teeth with vital pulp are associated with cystic lesions, especially when tooth roots protrude into the cyst cavity, different treatment options have been recommended to support tooth preservation. However, there is no consensus about the extraction of the affected tooth in cases of root involvement by odontogenic keratocyst (OKC). In addition, there is controversy around whether root canal therapy should be considered a necessary treatment to be carried out prior to or after enucleation when standing teeth are associated with cystic lesions. An impacted tooth enclosed in the cavity of a developmental cyst may be treated by various approaches such as marsupialisation or decompression, or enucleation in combination with extraction or coronectomy, depending on the patient's age, root development and the angle and depth of the tooth in the jaw. Successful results obtained in pulp revascularisation after autotransplantation or endodontic regeneration treatments have been reported and pulp tissue functionality after cyst enucleation or apicetomy is a serious concern. In this article, we present an overview of the management of teeth associated with cystic lesions of the jaws. Keywords: cystic lesions, tooth, enucleation, marsupialisation, apicetomy

The repair of large bone defects remains a huge challenge for bone regenerative medicine. To meet this challenge, a number of bone substitutes have been developed over recent years to overcome the drawbacks of traditional autograft and allograft therapies. Thus, the improvement of the osteoinductive ability of these substitutes has become a major focus for research in the field of bone tissue engineering. It has been reported that some metallic ions play an important role in bone metabolism in the human body, and that bone repair could be enhanced by incorporating these ions into bone substitutes. Moreover, it is well documented that ions released from these substitutes such as magnesium, zinc, and strontium can increase the osteogenic and angiogenic properties of bone repair scaffolds. However, the mechanisms of action of these ions on cellular bioactivity are currently unclear. Therefore, in the present article, we highlight the recent use of bioactive ions in bone tissue engineering and discuss the effects of these ions on osteogenesis and neovascularisation. Keywords: bioactive ions, bone regeneration, tissue engineering, osteogenesis, angiogenesis

Objective: To investigate the immunoinflammatory response in the crosstalk of human oral keratinocytes (HOKs) with selected periodontal commensals and pathogens. Methods: Four representative viable oral bacteria, including periodontal commensals (Streptococcus mutans, Sm; and Actinomyces israelii, Ai) and pathogens (Aggregatibacter actinomycetemcomitans, Aa; and Porphyromonas gingivalis, Pg), were selected. A viable bacteria-HOKs interactive model was tested under various conditions of oxygen, antibiotics, duration and multiplicity of infection (MOI). The expression of IL-6 and IL-8 in HOKs was assessed by real-time qPCR and ELISA. Results: An MOI of 1 was determined to be the appropriate ratio of bacteria and HOKs with substantial amounts of viable bacterial cells and HOKs in an antibiotic-free medium under aerobic conditions for 2 h. Sm and Pg significantly upregulated the expression of IL-6 and IL-8 (P 0.05), while Ai and Aa could not induce significant levels of these cytokines with reference to the control. Conclusion: Within the limitations of this study, the current findings suggest that periodontal commensals and pathogens may differentially modulate immunoinflammatory response in human oral keratinocytes. Keywords: commensals, periodontopathogens, human oral keratinocytes, bacteria-host interaction, cytokines

Objective: To determine the number, shape and diameter of apical foramina as well as changes in root apex morphology of permanent teeth with failed endodontic treatment. Methods: Clinical records were collected for teeth diagnosed with posttreatment periapical periodontitis that subsequently underwent endodontic microsurgery. Resected root apices were examined with stereomicroscopy. The number, shape and diameter of apical foramina were recorded. Scanning electron microscopy (SEM) was used to investigate the presence and extent of apical external root resorption and evaluate how it was influenced by sex, age, tooth position, periapical radiolucency size and periapical lesion biopsy results. External root resorption was classified according to site (periforaminal or foraminal), and the extent of resorption was graded as 0, 1, 2 or 3. Results: A total of 112 teeth with 112 apices were examined. The mean diameter of the main apical foramina was 420.78 µm. The apical foramen was most commonly irregularly shaped (68.39%). The incidence of multiple foramina was 48.21%. SEM revealed that 96.43% of apices had periforaminal resorption (PR) and 94.64% had foraminal resorption (FR). The existence and extent of external root resorption were not correlated with sex, age, tooth position, periapical radiolucency size or periapical lesion biopsy results (P > 0.05). Conclusion: Apical foramina of permanent teeth with failed endodontic treatment were commonly irregularly shaped, with a mean diameter of approximately 420 µm. Nearly half of the samples had multiple foramina. There was a high prevalence of apical external root resorption. A relationship may exist between morphological changes in the root apex and treatment failure. Keywords: root canal therapy, endodontic surgery, apical foramen, root resorption, posttreatment periapical periodontitis

Objective: To evaluate the mineralisation response of lipopolysaccharide (LPS)-induced dental pulp cells (DPCs) to betamethasone and the potential benefit of betamethasone application on the recovery of injured dental pulp. Methods: The proliferation influence of betamethasone on DPCs was analysed through the cell counting kit-8 assay. To assess the anti-inflammatory effects of betamethasone, the expression levels of inflammatory factors IL-6, IL-1ß and TNF-∂ were determined by real-time polymerase chain reaction (PCR). Mineralisation was investigated through the detection of the mineralisation-related biomarkers alkaline phosphatase (ALP), dentine sialophosphoprotein (DSPP) and osteocalcin (OCN) through the ALP activity assay, immunohistochemistry staining, Alizarin Red and tissue nonspecific alkaline phosphatase (TNAP) staining, the reverse transcriptase PCR technique and western blot. Results: A low concentration of betamethasone (1 µ/mL) promoted the proliferation of DPCs. The real-time PCR results demonstrated that inflammatory cytokines were downregulated by betamethasone treatment. The mineralisation outcome in DPCs treated with betamethasone was better than in those treated without betamethasone. Conclusion: Betamethasone promoted the proliferation of DPCs. Betamethasone enhanced mineralisation in LPS-stimulated DPCs. Keywords: LPS-stimulated dental pulp cells (DPCs), betamethasone, mineralisation

Objective: To evaluate the effect of premature delivery and birth weight (BW) on primary tooth eruption. Methods: A total of 2,230 children aged 3 to 36 months from urban and rural areas in Beijing, China, were classified for analysis by gestational age at delivery (89 preterm and 2,141 full term) and BW (low, normal and high). The tooth eruption status of these children was examined and recorded every 3 months. Results: The timing of first primary tooth eruption was significantly delayed in preterm infants (8.4 months versus 7.3 months for full term; P 0.05). Furthermore, the number of teeth was significantly less for the preterm and low-BW groups at 12 to 18 and 24 to 30 months, but the number of teeth caught up with normal-BW children by 30 to 36 months. In contrast, the time of first tooth eruption of high-BW children was earlier, while the erupted teeth at each month range was more than the normal-BW group. This research also demonstrated a negative correlation (r = -0.202; P = 0.009) between the time of first primary tooth eruption and BW as well as a positive correlation between the number of erupted teeth and BW. Conclusion: Premature delivery and BW were the influencing factors for the timing of primary tooth eruption in children from Beijing, China. Recommendations for feeding habits and oral healthcare implementation may vary according to different primary tooth eruption status among individuals. Keywords: tooth eruption, primary teeth, premature delivery, birth weight (BW)

Mandibular canines are usually considered to be single-canal teeth. However, more than one canal and, more rarely, two roots may also occur. Three clinical cases are reported in order to illustrate endodontic anatomical variants in the human mandibular canine. All procedures were performed in conformity with the current state-of-the-art practices in endodontics, which included effective local anaesthesia, rigorous clinical and radiographic pre-access analysis, appropriate tooth restoration to ensure watertight rubber dam installation and surgical microscopic manipulations for precision. The first case involved a mandibular canine with only one root but two canals, including a lateral canal. The second case was a retreatment of a mandibular canine with two roots, two canals and a broken stainless steel K-File in the buccal canal. The third case involved a mandibular canine that revealed a rare root canal configuration (1-3-1): a Sert and Bayirli's type XVII canal. To avoid missing the presence of any root canals in endodontic treatment, clinicians should have a thorough knowledge of the anatomic variants of the root canal system and should take the necessary time to perform a rigorous pre-access analysis. The systematic use of a surgical microscope and ultrasonic endodontic tips facilitates and standardises access cavity preparation and canal localisation. Keywords: endodontic anatomy, mandibular canine, pre-access analysis