Dye penetration in dry and water-filled gaps along root fillings

AIM: The aim of this study was to investigate the influence of hydration in voids along root fillings on methylene blue penetration. METHODOLOGY: A total of 80 human root canals were prepared using a step-back technique and filled with a zinc oxide based sealer and gutta-percha. Leakage along the fillings was measured by a transport fluid model and classified into three categories: gross leakage (GL), slight leakage (SL) and no leakage (NL). Specimens with NL and SL were immersed into methylene blue (MB) 2% for 24 h (group I). Specimens with GL which had wide gaps filled with water were randomly divided into two groups (II, III). Transport air was applied to remove water from gaps only in specimens of group III. All tested specimens from groups II and III were also immersed into MB 2% for 24 h. Each specimen was then split longitudinally and linear measurements of dye penetration were recorded. RESULTS: Group III (with dry gaps) showed significantly more dye penetration than group II. No significant difference was found between group I and group II. CONCLUSIONS: Methylene blue penetrates along root fillings more easily in dry gaps than in water-filled gaps.     

Fluid transport and bacterial penetration along root canal fillings

Convective transport of water from the coronal to the apical end of obturated root canals was determined by the movement of an air bubble in a capillary glass tube connected to the apex of the experimental root section using a headspace pressure of 120 kPa (1.2 atm). Water transport through existing voids in the obturated canals could be measured reproducibly in this way. The root canals of 60 human maxillary canines were filled with gutta-percha and sealer by the cold lateral condensation technique. Thirty of these were first exposed to a small motile bacterium, Pseudomonas aeruginosa, growing in a reservoir at the coronal end of each root. After 50 days, two specimens allowed penetration of bacteria to a reservoir at the apical end. All the roots were then assessed quantitatively for convective transport of water. The results were divided into three defined categories: 39 obturated canals were in the‘bacteria tight’category, 14 canals in the 'slight leakage’and 7 canals in the‘gross leakage’category. The two specimens that showed bacterial penetration fell into the slight and gross leakage categories. The previous test for bacterial passage did not statistically influence the fluid transport pattern of these roots which was measured subsequently. These findings indicate that fluids transport through obturated root canals, most of which do not allow the passage of bacteria.     

Leakage along apical root fillings in curved root canals. Part I: effects of apical transportation on seal of root fillings

Occurrence of apical transportation (AT) may complicate the root filling procedure and result in a compromised seal. In part I of this study, human mandibular premolars with single, curved (21 to 39 degrees), or straight canals were prepared by Lightspeed or a step-back hand filing technique. An AT index was determined using a double exposure radiographic technique. The prepared canals were obturated using lateral condensation of gutta-percha. Leakage along the apical 3 mm of root filling was measured with a fluid transport model. After hand filing, AT and perforation occurred in 87% of the curved canals. The AT indices were > or = 0.4 mm. After Lightspeed preparation, AT occurred in only 19% of the curved canals. The hand filing/curved group leaked statistically significantly more than the hand filing/straight and Lightspeed/curved groups (p = 0.002). We conclude that occurrence of AT is a factor that negatively influences the apical seal when curved canals are obturated by lateral condensation of gutta-percha.     

Utilization of gutta-percha for retrograde root fillings

Abstract – Just as gutta‐percha used with a root canal sealer is a recommended material for orthograde root fillings, it could similarly be the material of choice for retrograde fillings. Unfortunately, clinical accessibility and visibility do not always facilitate such a technique. The aim of this article is to present a new technique which enables retrograde fillings to be achieved with gutta‐percha and a sealer. After the apex had been resected, a hole was drilled perpendicular to the plane of section of the apex about 1 mm coronally. The bucco‐lingual depth required to reach the main canal was calculated. The cavity was then dried, coated with the sealer, and obturated with gutta‐percha in accordance with thermo‐mechanical compaction techniques. After excess filling material had been removed, the gutta‐percha was cold burnished and the angles of the root were smoothed. Clinical cases illustrating healing of the periapical tissues are shown.     

Utilization of gutta-percha for retrograde root fillings

Just as gutta-percha used with a root canal sealer is a recommended material for orthograde root fillings, it could similarly be the material of choice for retrograde fillings. Unfortunately, clinical accessibility and visibility do not always facilitate such a technique. The aim of this article is to present a new technique which enables retrograde fillings to be achieved with gutta-percha and a sealer. After the apex had been resected, a hole was drilled perpendicular to the plane of section of the apex about 1 mm coronally. The bucco-lingual depth required to reach the main canal was calculated. The cavity was then dried, coated with the sealer, and obturated with gutta-percha in accordance with thermo-mechanical compaction techniques. After excess filling material had been removed, the gutta-percha was cold burnished and the angles of the root were smoothed. Clinical cases illustrating healing of the periapical tissues are shown.     

Periapical tissue reaction to root fillings with Sealapex

The histological response of periapical tissues to root canal fillings with Sealapex, pure calcium hydroxide and gutta-percha points was studied in dogs' teeth. After pulpal extirpation the root canals were enlarged, irrigated and dried. Teeth in the first group were filled with gutta-percha points alone, those in the second group were filled with pure calcium hydroxide and gutta-percha, and those in the third group were filled with Sealapex and gutta-percha. The animals were killed after 7, 30 and 90 days and histological sections of each specimen were prepared. It was concluded that hard tissue formation was more pronounced after root filling with Sealapex than with calcium hydroxide or gutta-percha points.     

Bypassing gutta-percha root fillings with an automated device

Endodontic retreatment using Canal Finder K files and chloroform was performed in 106 gutta-percha-obturated, curved root canals, 71 in vitro and 35 in vivo. The minimum time taken to bypass the obturation in a single root canal was 3 s and the maximum time 95 s. The mean times were 19 and 27 s in the two in vitro groups and 32 s in the in vivo group. Eighty-nine percent of the root canals which had been obturated short were bypassed apically in vivo. Root canal curvature was well maintained in all but two root canals. In these two cases apical transportation occurred. Breakage of files occurred three times in vitro, but this did not prevent the completion of bypassing with new files. These results are attributed to the mode of action of the Canal Finder system, which makes it an efficient root canal pathfinder. The advantages of the suggested technique are discussed in light of the clinical considerations of endodontic retreatment.     

Tissue response to glass ionomer retrograde root fillings

The periapical tissue response to glass ionomer cement retrograde root fillings was investigated both in the presence and in the absence of fillings in the root canals of eight upper incisor teeth of four monkeys. The pulps of the teeth were extirpated and one canal in each pair was filled with laterally condensed gutta-percha immediately after canal preparation. The other canal was prepared but left open to oral contamination. Apicectomies were performed on both teeth in each pair 1 week later, and glass ionomer cement retrograde root fillings were placed. After 5 months, the teeth and surrounding tissues were removed and prepared for histological examination. All four of the teeth without root canal fillings showed severe periapical inflammation, and bacterial were present in the interface between the dentine and the retrograde root filling. The teeth with root canal fillings showed little or no periapical inflammation. This study showed that adhesive retrograde root fillings were successful when the root canal was completely filled, but in the absence of a gutta-percha canal filling they failed to provide a seal.     

A Five-year study of Hudron root canal fillings

A prospective clinical and radiographic study was conducted in order to compare Hydron and laterally condensed gutta-percha/AH-26 root canal fillings. Paralleling technique periapical radiographs were taken preoperatively, postoperatively and at recall appointments at post-treatment intervals of 6 months, 1 year, 2 years, 3 years and 5 years. Clinical examination at the recall appointments revealed no adverse signs or symptoms amongst all the patients who attended (mean attendance 44.5% at each interval). Radiographs were scored according to the periapical status of the treated root, and comparable bone healing rates were observed between the two root-filling materials. Among the patients attending recall appointments, there were no radiographic signs of failure of any of the 39 gutta-percha/AH-26 root canal fillings. However, three of the 35 canals filled with Hydron were classified as failures, and four required further assessment after the 5-year recall appointment. This study indicated that Hydron and gutta-percha/AH-26 root canal fillings were well accepted but, on the basis of radiographic assessment, success with gutta-percha/AH-26 was more predictable.     

根管偏移对充填材料封闭根管能力的影响

目的 :研究弯曲根管预备后的根管偏移对充填材料封闭根管能力的影响。方法 :选取 73颗下颌单根管前磨牙作为研究对象 ,其中弯根管牙 46颗 ,直根管牙 2 7颗。A组 2 3颗弯根管牙用Lightspeed器械预备根管 ,B组 2 3颗弯根管牙、C组 17颗直根管牙以及对照组牙用K锉预备根管 ,预备方法为逐步后退技术。使用双曝光X线技术和Ehrlich法测量根管偏移指数 (ATI)的大小。使用侧向加压技术充填所有根管后 ,用流体传输模型测量每个根管内微渗漏的量。结果 :A组中有 19%的根管发生根管偏移 ,B组中有 85 %的根管发生根管偏移 ,两组之间ATI的大小有高度显著性差异。当ATI大于 0 .3mm时 ,根管内微渗漏的发生率明显增加。结论 :弯曲根管预备中出现的根管偏移会削弱充填材料封闭根管的效果。