氢氧化钙封药载体的研究进展

氢氧化钙是近年临床上应用广泛的根管消毒剂,因其封药载体的不同,所产生的药效也存在差异.常用的氢氧化钙封药载体分水溶性、黏性和油性,探讨不同载体对氢氧化钙抗菌性能的影响是近年来的研究热点.本文就氢氧化钙封药载体的研究现状进行综述.     

Calcium hydroxide-based pastes used in endodontics

The aim of the present study is to propose a classification of calcium hydroxide pastes on the basis of the vehicle that retains the calcium hydroxide. The vehicle determines the working characteristics of the calcium hydroxide: viscous and only vehicles prolong the action of the calcium hydroxide as compared with water-soluble substances. Physicochemical properties of the vehicle may limit the effectiveness in disinfecting the entire root canal system. As calcium hydroxide is not effective against all bacterial species found in root canal infections, associations with other medicaments have been proposed to enhance the efficacy of the intracanal medication.     

Properties and applications of calcium hydroxide in endodontics and dental traumatology

Calcium hydroxide has been included within several materials and antimicrobial formulations that are used in a number of treatment modalities in endodontics. These include, inter-appointment intracanal medicaments, pulp-capping agents and root canal sealers. Calcium hydroxide formulations are also used during treatment of root perforations, root fractures and root resorption and have a role in dental traumatology, for example, following tooth avulsion and luxation injuries. The purpose of this paper is to review the properties and clinical applications of calcium hydroxide in endodontics and dental traumatology including its antibacterial activity, antifungal activity, effect on bacterial biofilms, the synergism between calcium hydroxide and other agents, its effects on the properties of dentine, the diffusion of hydroxyl ions through dentine and its toxicity. Pure calcium hydroxide paste has a high pH (approximately 12.5-12.8) and is classified chemically as a strong base. Its main actions are achieved through the ionic dissociation of Ca(2+) and OH(-) ions and their effect on vital tissues, the induction of hard-tissue deposition and the antibacterial properties. The lethal effects of calcium hydroxide on bacterial cells are probably due to protein denaturation and damage to DNA and cytoplasmic membranes. It has a wide range of antimicrobial activity against common endodontic pathogens but is less effective against Enterococcus faecalis and Candida albicans. Calcium hydroxide is also an effective anti-endotoxin agent. However, its effect on microbial biofilms is controversial.     

Influence of mixing vehicle on dissociation of calcium hydroxide in solution

The antimicrobial effects of aqueous preparations of calcium hydroxide have been demonstrated in the past. Calcium hydroxide, when dissolved in water, dissociates into hydroxide and calcium ions. The presence of hydroxide ions in a solution makes it antimicrobial. Recently it was shown that the use of glycerin as a mixing vehicle facilitates placement of calcium hydroxide in the root canals. The influence of nonaqueous mixing vehicles on the dissociation of calcium hydroxide is not clearly understood. In this study the conductivity of aqueous and nonaqueous solutions of calcium hydroxide was measured. The conductivity values for saturated solutions of calcium hydroxide in water was 7.3+/-3 mS/cm. The conductivity of calcium hydroxide in pure glycerin or propylene glycol was essentially zero. It was concluded that use of nonaqueous mixing vehicles may impede the effectiveness of calcium hydroxide as a root canal dressing.     

Apexification: review of the literature

Five methods for the treatment of teeth with an incompletely formed apex (open apex) and a necrotic pulp are discussed. The methods discussed include the use of (1) a customized cone (blunt-end, rolled cone); (2) a short-fill technique; (3) periapical surgery (with or without a retrograde seal); (4) apexification (apical closure induction); and (5) one-visit apexification. The apexification techniques, which use various formulations of calcium hydroxide to induce closure, are stressed. Based on the review of the literature and clinical experience of the authors, it was concluded that successful treatment of an immature pulpless tooth can partly result from the antibacterial and calcification-inducing action of calcium hydroxide.     

The effectiveness of various disinfectants used as endodontic intracanal medications: an in vitro study

The purpose of this study was to compare in vitro the suitability of four disinfectants as intracanal medications: calcium hydroxide, chlorhexidine gel, chlorhexidine in the form of a controlled-release delivery system (PerioChip), and the combination of chlorhexidine gel with calcium hydroxide. Saline was used as the control. The disinfectants were tested at three different time periods (3, 8, and 14 days) by using human tooth specimens that had been previously contaminated with Enterococcus faecalis. Calcium hydroxide worked very efficiently in killing E. faecalis in the 3-day group and 8-day group. It was not as effective in the 14-day group. The different chlorhexidine formulations were also found to be effective for all time periods. More specifically, the combination of chlorhexidine gel with calcium hydroxide and the chlorhexidine gel worked slightly better than the PerioChip, but there was no significant difference among the medications.     

Thermal diffusion through amalgam and cement base: comparison of in vitro and in vivo measurements.

Thermal diffusion was measured in vitro and in vivo through amalgam and amalgam underlaid with bases of zinc phosphate, zinc oxide-eugenol, and calcium hydroxide cements. Although the magnitudes differed, there generally was good agreement between in vitro and in vivo data with respect to the relative rates of thermal diffusivity through amalgam restorations underlaid with bases of each of the three materials. In all tests, both in vitro and in vivo, the zinc oxide-eugenol base proved to be the best thermal insulator. Calcium hydroxide was the next best thermal barrier and was followed by zinc phosphate cement. In vitro tests indicated dentin to be a better thermal insulator than zinc phosphate cement but inferior to the zinc oxide-eugenol and calcium hydroxide base materials used here. Although a method has been presented here for the in vivo assessment of the efficacy of thermal insulating bases and a number of in vivo experiments were conducted, much research remains to be done in this area. Additional investigation is needed to better define the parameters of thermal change beneath various types of restoratives and also to establish more exactly the role of base thickness in providing thermal protection beneath clinical metallic restorations.     

Calcium hydroxide: a review

Calcium hydroxide is a multipurpose agent, and there have been an increasing number of indications for its use. Some of its indications include direct and indirect pulp capping, apexogenesis, apexification, treatment of; root resorption, iatrogenic root perforations, root fractures, replanted teeth and interappointment intracanal dressing. The purpose of this paper is to review the properties and various indications for the use of calcium hydroxide.     

The Effect of Long-term Dressing with Calcium Hydroxide on the Fracture Susceptibility of Teeth

Introduction

Calcium hydroxide has been widely used to treat immature teeth to achieve periodontal healing and to promote the formation of an apical barrier. However, retrospective clinical studies have shown a high incidence of cervical root fractures with long-term calcium hydroxide dressing. The alkalinity of calcium hydroxide has been suggested to weaken the root. In vitro studies using ovine teeth show conflicting results on fracture strength of dentine, although different commercial products may have influenced the results. The purpose of this study was to investigate the effects of 2 commercial products used in prior studies (Calasept Plus and UltraCal XS), as well as a new product (Calmix) that uses a nonaqueous vehicle that allows for a higher pH, on the fracture strength of dentine over time.

In vitro antibacterial effect of calcium hydroxide combined with chlorhexidine or iodine potassium iodide on Enterococcus faecalis

Several studies have shown a higher success rate of root canal therapy when the canal is free from bacteria at the time of obturation. Treatment strategies that are designed to eliminate this microflora should include agents that can effectively disinfect the root canal. Enterococcus faecalis is often associated with persistent endodontic infections. While in vivo studies have indicated calcium hydroxide to be the most effective all-purpose intracanal medicament, iodine potassium iodide (IKI) and chlorhexidine (CHX) may be able to kill calcium hydroxide-resistant bacteria. Supplementing the antibacterial activity of calcium hydroxide with IPI or CHX preparations was studied in bovine dentine blocks. While calcium hydroxide was unable to kill E. faecalis in the dentine, calcium hydroxide combined with IKI or CHX effectively disinfected the dentine. The addition of CHX or IKI did not affect the alkalinity of the calcium hydroxide suspensions. It may be assumed that combinations also have the potential to be used as long-term medication. Cytotoxicity tests using the neutral red method indicated that the combinations were no more toxic than their pure components.     

A comparison of the antimicrobial efficacy of three calcium hydroxide formulations on human dentin infected with Enterococcus faecalis

This study compared the antibacterial efficacy of three different formulations of calcium hydroxide by using human dentin specimens that were infected with Enterococcus faecalis. After exposure to three forms of calcium hydroxide (calcium hydroxide mixed with distilled water, calcium hydroxide mixed with 0.2% chlorhexidine, and calcium hydroxide mixed with camphorated paramonochlorophenol) for 7 days, dentin powder from the infected specimens was obtained and assessed for bacterial quantity by spectrophotometry. It was found that calcium hydroxide mixed with camphorated paramonochlorophenol killed all of the Enterococcus faecalis inside the dentinal tubules. This result was better than that obtained with calcium hydroxide mixed with distilled water or with 0.2% chlorhexidine (p < 0.05). Calcium hydroxide mixed with distilled water and calcium hydroxide mixed with 0.2% chlorhexidine were ineffective against these bacteria.     

Monoinfection of root canal with Pseudomonas aeruginosa

Abstract A successful treatment of a persisting endodontic infection with Pseudomonas aeruginosa is described together with a review of its presence in saliva and root canal infections. The treatment included ethanol irrigation and prolonged calcium hydroxide therapy in addition to thorough mechanical preparation. The minimum pH value of calcium hydroxide for in vitro killing of the isolated strain was found to be above 10.     

An in vitro comparison of pH changes in root dentine following canal dressing with calcium hydroxide points and a conventional calcium hydroxide paste

AIM: This study aimed to measure and compare pH changes at apical and cervical sites on the external root surface of extracted teeth dressed with calcium hydroxide in two different formulations. METHODOLOGY: Root canals of 45 single-rooted extracted human teeth were accessed and shaped using a step-down technique with rotary instrumentation. Standard cavities were prepared on the external root surface at specific apical and cervical sites. The teeth were randomly allocated to three groups. Teeth in group A were dressed with calcium hydroxide points, those in group B were dressed with an aqueous calcium hydroxide paste and teeth in group C were left unfilled. Following storage in humid conditions, the pH of the dentine at apical and cervical sites was measured at baseline and then at 24 h, 72 h, 1 week, 10 days, 2 weeks and 3 weeks. RESULTS: The pH of the root dentine at both apical and cervical sites was significantly greater (P < 0.001) in teeth dressed with aqueous calcium hydroxide paste compared with those dressed with calcium hydroxide points, when averaged out across all time periods. For all groups, there was a significant difference between the mean apical and cervical pH values for each tooth with lower values for the apical sites (P < 0.001). CONCLUSION: The results of this study indicate that an aqueous calcium hydroxide paste was more effective than calcium hydroxide points at raising the pH on the external root surface of extracted teeth.     

Tertiary dentinogenesis with calcium hydroxide: A review of proposed mechanisms

Calcium hydroxide has been used extensively in dentistry for a century. Despite its widespread use as a pulp‐capping agent, its mechanisms of action still remain ambiguous. Understanding its modes of action will lead to a broader understanding of the mechanisms associated with induced dentinogenesis and help in optimizing the currently available agents to target specific regenerative processes to obtain the best possible clinical outcomes. A literature search relating to mechanisms of dentinogenesis of calcium hydroxide up to December 2011 was carried out using pubmed and MEDLINE database searches as well as manual searching of cross‐references from identified studies. Resulting suggestions regarding dentinogenic mechanisms of calcium hydroxide range from direct irritating action of the material to induction of release of biologically active molecules. The purpose of this article is to discuss various mechanisms through which calcium hydroxide may induce tertiary dentinogenesis in the light of observations made in included studies.     

Pulpal reactions in rat incisors to Caridex™

This study examined the in vivo effects of Caridex, a chemomechanical caries removal system, on rat pulpal tissue. Rat incisors were opened and the pulps exposed to Caridex or physiological saline and sealed with calcium hydroxide. After various time periods, teeth were extracted and examined by light microscopy. Histological evaluation revealed an almost identical response in both test and control teeth which consisted of a transient inflammatory reaction and a limited necrosis in adjacent pulp tissue. Within seven days, formation of hard tissue matrix was seen below the necrotic area and on pulpal walls. It was suggested that the high pH of Caridex may have contributed to the necrotizing effect of calcium hydroxide in adjacent pulp tissue and the formation of hard tissue matrix. Additionally, the solution is most probably bactericidal. The results suggest that the system can be used as a caries removal agent on humans without unfavourable side effects on the dental pulp.     

Orthograde retreatment and apexification after unsuccessful endodontic treatment, retreatment and apicectomy

AIM: To describe a case where a second orthograde retreatment was successful in the management of an infected mandibular right first molar that previously had received both orthograde and retrograde treatments. SUMMARY: Periapical surgery is unlikely to be successful unless the root canal system has been adequately debrided and sealed. A case is described where orthograde endodontic treatment, retreatment and apicectomy were unsuccessful in the management of and infected mandibular right first molar. The periapical radiolucency eventually disappeared following a second orthograde retreatment. Teh second retreatment included 12 months of intracanal calcium hydroxide placement to promote apexification, thus allowing subsequent controlled obturation with gutta percha and AH26. At a 5-year review following completion of treatment, the tooth remained asymptomatic and was in normal function. KEY LEARNING POINTS: Orthograde retreatment is a treatment option to manage refractory lesions in teeth that have previously received endodontic treatment, retreatment and apicectomy. Orthograde retreatment using long-term intracanal calcium hydroxide can help promote root-end closure of a resected apex.     

A comparison of the surface tension of calcium hydroxide mixed with different vehicles

The aim of this study was to evaluate and compare the surface tension of different liquids that are used as potential agents to mix with calcium hydroxide in root canal treatment. We also tried to evaluate final surface tension values of the calcium hydroxide mixed with glycerin, Ringer's solution, anesthetic solution, and saline. Surface tension values were measured using a "Du Noüy" tensiometer. The results showed statistically significant differences between vehicles alone and the calcium hydroxide combinations and also indicated that anesthetic solution (p = 0.018, p < or = 0.02) is the most favorable vehicle with the lowest surface tension values.     

The pH changes of four different calcium hydroxide mixtures used for intracanal medication

The purpose of this study was to determine the pH values of calcium hydroxide mixtures in combination with either distilled water, two different local anaesthetic solutions or physiological saline solution, which are commonly used as a dressing materials during endodontic treatment. The pH of each vehicle prior to mix with calcium hydroxide and subsequently each prepared combination was determined using a digital pH meter. The pH measurements were determined at 3 min, 10 min, 1 h, 24 h, 48 h and 7 days. The results of this study indicated that four different water-based vehicles demonstrated similar pH changes range within pH 11-12 when mixed with calcium hydroxide.     

The history of direct pulp capping

The first method of capping exposed pulps, using gold foils, was described by Pfaff in 1756. Thereafter, numerous agents for direct pulp capping have been recommended. Until the end of the 19th century, most materials were used empirically with the idea that the pulp tissue must be irritated by etching or cauterization to heal. Later, more attention was drawn to disinfecting agents, because it became obvious that microorganisms were the reason for pulp inflammation - but these agents were cytotoxic. Since insufficient or inappropriate diagnoses were made before treatment, even necrotic pulps were capped. The first scientific clinical study to compare different capping materials was made by D?twyler in 1921, whereupon zinc oxide-eugenol showed the best results. One year later, Rebel performed the first animal experiments with disastrous results, so he regarded the exposed pulp as a doomed organ. In 1920 Hermann, introduced calcium hydroxide for root canal fillings. Between 1928 and 1930 he studied the reaction of vital pulp tissue to calcium hydroxide to prove that it was a biocompatible material. Since then, calcium hydroxide has been recommended by several authors for direct pulp capping, but it took until the middle of 20th century until it was regarded as the standard of care.     

Endodontic treatment of teeth associated with a large periapical lesion

AIM: To report the healing of a large periapical lesion following non-surgical root canal treatment. SUMMARY: A 12-year-old male with a large periapical lesion around the apices of his mandibular incisors is described. The lesion formed after trauma to the mandibular anterior teeth 5 years previously. During root canal treatment, chlorhexidine gluconate was used for irrigation, and calcium hydroxide was used both for the intracanal dressing and as a base of the root canal sealer. Periapical healing was observed 3 months after obturation and continued at the 12-month review. Key learning points Root canal treatment, including the use of chlorhexidine gluconate and calcium hydroxide for infection control, led to substantial healing of a large periapical lesion. This report confirms that large periapical lesions can respond favourably to non-surgical treatment.