As a commonly used disinfectant and pulp capping agent in the treatment of dental pulp diseases, calcium hydroxide has been widely used, and a lot of experimental research and clinical observations have been made on this. With the gradual deepening of research, the application of calcium hydroxide and its preparations in children’s dental diseases is becoming more and more common.
1. The mechanism of action of calcium hydroxide
Calcium hydroxide is a white powder in normal state, with stable chemical properties. It is soluble in water and can be dissociated into calcium ions and hydroxide ions in a small amount. It is strongly alkaline, with a pH value of up to 12.3. The pulp capping agent and disinfectant commonly used in dental clinical treatment have the following pharmacological effects: ① antibacterial; ② inactivating endotoxin; ③ inducing hard tissue formation and promoting repair.
1.1 Antibacterial Calcium hydroxide has strong alkalinity, and its pH value can reach 12.3 after being dissolved in water, which has a certain bactericidal effect on bacteria that damage dentin. Leung et al. used calcium hydroxide preparation for indirect pulp capping of deep caries. After 4 weeks, the residual carious dentin in the cavity was removed and found that the bacteria in the carious dentin decreased by 93%, while the bacteria in the control group increased. 2 times. Brannstrom et al. used streptococcus inoculation on dog teeth to cause pulp infection. After 2 days, the pulp was capped with calcium hydroxide. After 10 weeks, histological examination showed that the infection was limited to the vicinity of the perforation, and there were different degrees of calcification. barrier formation. Various studies have shown that calcium hydroxide has certain antibacterial properties for endodontic treatment of teeth.
1.2 Inactivation of endotoxin Endotoxin is the cell wall component of Gram-negative bacteria, which is composed of two major parts: polysaccharide and lipid A. The fatty acid in lipid A is the toxic basis of endotoxin. Calcium hydroxide can hydrolyze fatty acid, thereby changing the The structure of lipid A, resulting in loss of endotoxin activity. The dominant microorganisms in the infected root canal are Gram-negative bacteria, which release endotoxins in the cell wall when they multiply or die, which can stimulate the body to produce some inflammatory mediators such as prostaglandins, leading to cytokine secretion, complement activation, and triggering localized host and systemic immune response. Endotoxin can also directly act on the periapical tissue of the host, resulting in significant damage to the host cells. In the process of root canal treatment, pathogenic bacteria can be removed, but endotoxin can remain in the dentin wall and apical area for a long time, and continue to stimulate the periapical tissue, resulting in long-term non-healing of periapical lesions. Silva et al believe that endotoxin can cause inflammatory cell infiltration in the periapical tissue, destruction of collagen fibers, resorption of alveolar bone and cementum, resulting in serious damage to the periapical tissue, and calcium hydroxide can effectively reduce endotoxin in the root canal. level, preventing its damage to the periapical tissue.
1.3 Induce the formation of reparative dentin The strong alkalinity of calcium hydroxide can cause superficial pulp necrosis, the surface layer of the pulp and calcium hydroxide will be destroyed and decomposed, and the necrotic layer will stimulate the deep pulp tissue, induce its repair potential, and make Interstitial cells and fibroblasts proliferate, and fibrous proliferations are gradually arranged from a disordered state to become perpendicular to the superficial layer and penetrate deep into the collagen matrix. Fibroblasts gradually differentiated into odontoblasts, forming tubular and osteoid dentin, after which calcium salts were deposited, dentin bridges were calcified, and the coagulated necrotic layer disappeared. The dentin bridge layer was identified. Wen Lingying et al. exposed the pulp of 24 young permanent teeth and then directly capped the pulp with calcium hydroxide preparations. Histological studies showed that the exposed pulp surface covered with calcium hydroxide showed superficial tissue necrosis and mild inflammation, and then a defensive reaction occurred. and repair, a thicker dentin bridge was formed 8 weeks after the operation. Due to the strong alkalinity of calcium hydroxide, the pulp tissue is degenerated and necrotic, and the defense and repair of the pulp cells are stimulated, thereby eliminating inflammation and infection on the pulp surface, and forming a dentin bridge on the healthy pulp surface. Due to the self-repairing ability of dental pulp, calcium hydroxide can be used as an inducing factor for pulp repair and dentin bridge formation and one of the methods for preventing dental pulp infection.
Calcium hydroxide has a strong and stable ability to induce dentin formation, and Ca2+ has the function of transmitting information, promoting the formation of new dentin cells, regulating the synthesis and secretion of cells, and promoting the formation of dentin bridges. OH- may promote cell division and proliferation by increasing cytoplasmic pH. Calcium hydroxide is an initiating factor rather than a repair substrate, which can reduce the permeability of newly formed capillaries, reduce the formation of intercellular fluid, increase the concentration of Ca2+ in the tissue, and make the coke that inhibits tissue mineralization. The decrease in phosphate concentration increases the activity of Ca2+-dependent alkaline phosphatase, and the increase in pH also provides favorable environmental conditions for tissue mineralization.
2. Application of calcium hydroxide in children’s dental disease
2.1 Pulp capping is a common clinical condition due to deep caries, trauma, or accidental exposure of the pulp during dental operations. Appropriate treatment is required to preserve the viable pulp as much as possible, especially for young permanent teeth. At present, the commonly used pulp capping drugs are calcium hydroxide and its preparations. Many studies have proved that the use of calcium hydroxide to directly pulp the teeth with accidental pulp exposure when the pulp is not inflamed can promote the healing of the pulp and the formation of reparative dentin. , preserve the live marrow. Direct pulp capping is a treatment in which the exposed pulp is covered with medication to promote pulp healing and restoration, usually on healthy, freshly exposed pulp. Zhang Xiong et al. selected 203 teeth with accidental pulp exposure during dehumidification, no symptoms, normal electrical activity, and no periapical disease, and used visible light-cured calcium hydroxide for direct pulp capping. Follow-up review was performed at 2 weeks, 3 months, and 1 year after operation, and the longest follow-up time was 4 years, with a success rate of 95.07%. The results showed that pulp capping with calcium hydroxide had a good prognosis if there were no obvious symptoms or mild symptoms before surgery.
2.2 pulpotomy pulpotomy is an effective method for the treatment of accidental pulp exposure. The inflamed pulp tissue is cut 1-2 mm below the pulp exposure point. After sufficient hemostasis, the section is covered with calcium hydroxide preparation to promote the dentin bridge. Formed, preserved live pith. Blanco et al [collected 39 cases of anterior teeth with exposed pulp, and treated them with pulpotomy in which the pulp section was covered with calcium hydroxide preparation. After 3 months, dentin bridges began to form. The prognosis of the case is good.
2.3 Apical induction plasty When the root of a young permanent tooth is still in the developmental stage, due to some reasons, such as deformity, trauma, caries, etc., the pulp is necrotic, the root development stops, and the root tip is in an open state. Due to the large cavity of the root canal, the conventional method of dilating and frustrating the root canal is difficult to achieve thorough cleaning, and it is even impossible to fill the root canal tightly, which often results in inflammatory root absorption and eventually tooth loss. Since the 1960s, scholars have done a lot of research work, changing the simple mechanical filling method in the past, but using the method of apical induction to promote the continuous development of the root apex to achieve a sealing effect.
Chen Xiping selected 34 young permanent teeth with pulp necrosis, and made a paste with calcium hydroxide powder, iodoform and glycerin. Apical induction angioplasty was performed after conventional root canal preparation. At 3 months, 6 months and 12 months after operation, the success rate was 97.1%. Chi Zhengbing selected 138 traumatized young permanent anterior teeth from 1993 to 1995, and underwent apical induction with conventional calcium hydroxide preparation. After 6 months of prevention, 137 teeth finally reached basic or complete atresia of the apex, and the other one There was no discomfort in the tooth, but X-ray showed that the root and the alveolar bone had osseous adhesion, and the success rate was 99%. It is reported in foreign countries that the success rate of apical induction is between 70% and 100%, and the root apex can begin to form in 3 to 20 months, which is basically consistent with domestic reports.
2.4 Root canal disinfectants Most of the commonly used root canal disinfectants such as formaldehyde cresol, camphor phenol, clove oil, etc. have strong cytotoxicity or become haptens, causing damage to the body. In recent years it has been found that calcium hydroxide can control infection and reduce the occurrence of pain during root canal treatment, significantly better than traditional drugs such as formaldehyde cresol and camphorol. Studies have shown that calcium hydroxide has inhibitory and killing effects on Streptococcus, Staphylococcus aureus, Fusobacterium, Pseudomonas aeruginosa, Escherichia coli and other bacteria, and the longest effective time is 72 hours. Mixed bacterial infections can also be inactivated within 72 hours. Bacteriological studies have also found that the antibacterial efficacy of calcium hydroxide against Streptococcus mutans and Bacteroides gingivalis, which play an important role in endodontic diseases, is significantly higher than that of camphorphenol and formaldehyde cresol.
2.5 Root canal filling of deciduous teeth As a root canal filling material for deciduous teeth, it should have the following characteristics: it does not stimulate the periapical tissue, has antibacterial effect, is easy to introduce into the root canal, absorbs the excess part easily, X-ray blocking, can induce living periapical tissue Seal the root canal. At present, the commonly used root canal filling materials for deciduous teeth are zinc oxide clove oil paste and calcium hydroxide iodoform paste. The disinfection and sterilization, permeability and inactivation of endotoxin of calcium hydroxide ensure its ability to control root canal infection as a root filling paste. Mickel et al. found that although zinc oxide clove oil paste has stronger antibacterial effect than calcium hydroxide paste, calcium ions can react with apatite matrix in dentin to form calcium phosphate crystals, seal dentinal tubules and reduce the presence of bacteria , and the cytotoxicity is less than that of zinc oxide clove oil paste. After adding iodoform, it can slowly release free iodine when it encounters tissue fluid, fat or bacterial products after root filling, which has the effect of sterilizing and oxidizing cells. repair.