Role of dendritic cell-mediated immune response in oral homeostasis: A new mechanism of osteonecrosis of the jaw.

Dendritic cells are an important link between innate and adaptive immune response. The role of dendritic cells in bone homeostasis, however, is not understood. Osteoporosis medications that inhibit osteoclasts have been associated with osteonecrosis, a condition limited to the jawbone, thus called medication-related osteonecrosis of the jaw. We propose that disruption of the local immune response renders the oral microenvironment conducive to osteonecrosis. We tested whether zoledronate (Zol) treatment impaired dendritic cell (DC) functions and increased bacterial load in alveolar bone in vivo and whether DC inhibition alone predisposed the animals to osteonecrosis. We also analyzed the role of Zol in impairment of differentiation and function of migratory and tissue-resident DCs, promoting disruption of T-cell activation in vitro. Results demonstrated a Zol induced impairment in DC functions and an increased bacterial load in the oral cavity. DC-deficient mice were predisposed to osteonecrosis following dental extraction. Zol treatment of DCs in vitro caused an impairment in immune functions including differentiation, maturation, migration, antigen presentation, and T-cell activation. We conclude that the mechanism of Zol-induced osteonecrosis of the jaw involves disruption of DC immune functions required to clear bacterial infection and activate T cell effector response.

MTA as modulator of periapical tissue healing in rat molar: A histological study.

Background: Periapical surgery has been suggested as a treatment option for teeth with periapical lesions when those lesions continue despite receiving root canal therapy. Since sealing the apical region is the operation's primary goal, the choice of the root-end filling material affects how the surgery turns out. The retrofilling materials Zinc Oxide Eugenol (ZOE) and Mineral trioxide aggregate (MTA) are both known to have antibacterial characteristics. The purpose of this study is to determine how MTA affects as a Modulator of Periapical Tissue Healing through histological examination in Rat Molar. Methods: A dental fissure bur measuring 0.7 mm is used to remove the buccal root apex from the buccal alveolar bone's surface, creating the cavity. One of the following is placed within each cavity: Group 1: MTA, Group 2: ZOE. For each material series, six samples were used. We classified the healing outcomes for each MTA and ZOE retrograde filling material into three groups based on histological analysis: the amount of newly generated bone, the number of fibroblasts, and the infiltration of neutrophils into the surgical site. Results: On the 6th day of examination, fibroblasts were seen in the area around the wound. A significant inflammatory response, including neutrophil infiltration, was seen around the ZOE after retrograde filling. On the 16th day, the new alveolar bone structure showed a slight increase. After filling the MTA on the 6th day of examination, the immediate inflammatory response was insignificant. Neutrophils were observed to enter the region surrounding the retrofilled MTA, and a small number of osteoclasts were observed to be resorbing bone. Around the wound site, fibroblasts can also be detected. On the 16th day, unlike ZOE, a lot of new bone grows close to this material. Conclusion: MTA has the ability to modulate periapical healing in rat molar.

A comparative analysis of postoperative morbidity and alveolar bone regeneration following surgical extraction of impacted lower third molar teeth using piezosurgery and conventional instruments: a split-mouth clinical investigation.

BACKGROUND-OBJECTIVE(S): This randomized, split-mouth study aimed to compare postoperative complications following the surgical extraction of impacted lower third molars using piezosurgery versus conventional rotary instruments. MATERIALS AND METHODS: Twenty-one patients, aged 18-35 years, with bilaterally and symmetrically impacted lower third molars, were randomly assigned to undergo extraction using piezosurgery on one side and conventional rotary instruments on the other. RESULTS: The piezosurgery method required a longer operation time. However, it resulted in quicker resolution of postoperative swelling by the 7th day compared to the conventional method, where swelling persisted longer. Mandibular angle-tragus measurements were significantly higher with the conventional method on the 1st, 3rd, and 7th postoperative days. Although mouth opening decreased significantly after piezosurgery, it returned to preoperative levels by the 7th day, outperforming the conventional method. Postoperative pain was notably higher with the conventional method during the first four days but showed no significant difference from the 5th day onward. Alveolar bone healing was significantly better with piezosurgery at the 3rd and 6th months. Temporary paresthesia occurred in one patient from the conventional group, resolving within four weeks. Neither method resulted in alveolar osteitis. CONCLUSION(S): Within the study's limitations, piezosurgery demonstrated a reduction in postoperative discomfort, suggesting its advantage in enhancing patient recovery following lower third molar extractions. CLINICAL SIGNIFICANCE: Piezosurgery, when used appropriately, can reduce postoperative complications compared to conventional methods. Clinicians should be aware of its indications, benefits, and potential challenges. Trial registration This study was registered as a clinical trial to the ClinicalTrials.gov, and the registration ID is NCT06262841 ( https://clinicaltrials.gov/study/NCT06262841 ).

Characterizations of alveolar repair after mandibular second molar extraction: an experimental study in rats

Abstract Characterizations of rat mandibular second molar extraction socket with significantly different buccal and lingual alveolar ridge width remain unclear. Objective: To observe alterations in the alveolar ridge after extraction of mandibular second molars, and to examine processes of alveolar socket healing in an experimental model of alveolar ridge absorption and preservation. Methodology: Eighteen Wistar rats were included and divided into six groups regarding healing time in the study. Bilateral mandibular second molars were extracted. The rats with tooth extraction sockets took 0, 1.5, 2, 3, 4 and 8 weeks of healing. Histological observation, tartrate-resistant acidic phosphatase (TRAP) staining, Masson's trichrome staining, immunohistochemical staining and micro-computed tomography (micro-CT) were applied to estimate alterations in the alveolar ridge. Results: Different buccal and lingual alveolar ridge width led to different height loss. Lingual wall height (LH) decreased significantly two weeks after tooth extraction. Buccal wall height rarely reduced its higher ridge width. From two to eight weeks after extraction, bone volume (BV/TV), density (BMD), and trabecular thickness (Tb.Th) progressively increased in the alveolar socket, which gradually decreased in Tb.Sp and Tb.N. LH showed no significant change during the same period. Osteogenic marker OCN and OPN increased during bone repair from two to eight weeks. The reduced height of the lingual wall of the tooth extraction socket was rarely repaired in the later repair stage. Osteoclast activity led to absorption of the alveolar ridge of the alveolar bone wall within two weeks after operation. We observed positive expression of EMMPRIN and MMP-9 in osteoclasts that participated in the absorption of the spire region. Conclusion: Extraction of rat mandibular second molars may help the study of alveolar ridge absorption and preservation. The EMMPRIN-MMP-9 pathway may be a candidate for further study on attenuating bone resorption after tooth extraction.

Alveolar wound healing after implantation with a pool of commercially available bovine bone morphogenetic proteins (BMPs): a histometric study in rats

The capacity of a commercially available pool of bovine bone morphogenetic proteins (BMPs) to stimulate osteogenesis in the rat alveolar healing was investigated by histometric analysis. Male rats were anesthetized and had their upper incisor extracted. A pool of purified bovine BMPs adsorbed to microgranular resorbable hydroxyapatite was agglutinated with bovine collagen and saline before implantation into the alveolar socket. The implanted and control rats (n=30 per group) were sacrificed 1 to 9 weeks postoperatively, the hemi-maxillae were decalcified, processed for paraffin embedding and semi-serial longitudinal sections were obtained and stained with hematoxylin and eosin. The volume fraction of alveolar healing components was estimated by a differential point-counting method in histologic images. The results showed that in both, control and implanted rats, the alveolar healing followed the histologic pattern usually described in the literature. Quantitative data confirmed that the BMPs mixture did not stimulate new bone formation in the alveolar socket of implanted rats. These results suggest that the pool of BMPs adsorbed to hydroxyapatite and agglutinated with bovine collagen did not warrant incorporation of the osteoinductive proteins to a slow-absorption system that would allow a BMPs release rate compatible to that of new bone formation, and thus more adequate to osteoinduction.

No presente trabalho analisou-se histometricamente a capacidade de um material de origem nacional em estimular o reparo ósseo alveolar de ratos. Uma mistura de BMPs bovinas purificadas adsorvidas à hidroxiapatita microgranular absorvível foi aglutinada com colágeno bovino e soro fisiológico e implantada na cavidade de extração de incisivos superiores. Os ratos implantados e controles (n=30 por grupo) foram sacrificados após 1, 2, 3 e 9 semanas, as hemi-maxilas contendo os alvéolos em reparação foram descalcificadas e processadas para inclusão em parafina e obtenção de cortes semi-seriados, corados com hematoxilina e eosina. O volume percentual de tecido ósseo reparacional foi estimado por um método de contagem diferencial de pontos, em imagens histológicas analisadas sob uma ocular contendo um retículo com 100 pontos eqüidistantes. Nos ratos controles e implantados o reparo seguiu o padrão descrito na literatura. No grupo implantado, o material não estimulou o reparo ósseo alveolar em nenhum dos períodos analisados. Os resultados sugerem que a mistura de BMPs adsorvidas à hidroxiapatita microgranular absorvível não tenha garantido sua incorporação a um sistema carreador de absorção lenta que propiciasse sua liberação num ritmo compatível com o da neoformação óssea, portanto, adequado à osteoindução.