Evaluation of root maturation after revitalization in immature permanent teeth with nonvital pulps by cone beam computed tomography and conventional radiographs.

AIM: To investigate the response of immature permanent teeth with nonvital pulps after revitalization procedures using cone beam computed tomography imaging and conventional radiograph. METHODOLOGY: Clinical records of patients who had undergone revitalization between 1997 and 2014 were collected. Seventeen patients attended the follow-up examination. Clinical examination and radiographic examination by means of CBCT imaging and conventional radiographs were conducted to evaluate treatment outcomes, especially the dimensional changes of the root and the pattern of root maturation. Statistical analysis was conducted using Fisher's exact test and Monte Carlo test to investigate the effect of potential outcome predictors. RESULTS: For the follow-up period as far as 96 months, thirteen teeth (76%) were classified as a 'success'. Conventional radiographs showed various degrees of dimensional changes in the immature roots ranging from 0% to 73% changes. The mean percentage changes of root length and root wall thickness were 14.38 ± 20.92% and 13.82 ± 11.17%, respectively. CBCT images illustrated various patterns of root maturation including incomplete root development with wide-open apices and fully formed roots with various apical shapes. Root canal contents varied radiographically from empty canals to many degrees of unpredictable patterning of radiopaque deposits. CONCLUSION: Revitalization in immature teeth with nonvital pulps resulted in unpredictable responses in terms of continued root development. Various types of root maturation and root canal contents were observed radiographically, which were different from typical root development.

Thermal transfer in extracted incisors during thermal pulp sensitivity testing.

AIM: To measure the temperature distribution within tooth structure during and after application of thermal stimuli used during pulp sensitivity testing. METHODOLOGY: Extracted intact human maxillary anterior teeth were investigated for temperature changes at the labial enamel, the dentino-enamel junction (DEJ) and pulpal surface during and after a 5-s application of six different thermal stimuli: hot water (80 degrees C), heated gutta-percha (140 degrees C), carbon dioxide dry ice (-72 degrees C), refrigerant spray (-50 degrees C), ice stick (0 degrees C) and cold water (2 degrees C). J-type thermocouples and heat conduction paste were used to detect temperature changes, together with a data acquisition system (Labview). Data were analysed using analysis of variance, with a confidence level of P < 0.05. RESULTS: Temperature change was detected more quickly at the DEJ and pulpal surface with the application of hot water, heated gutta-percha and refrigerant spray than with carbon dioxide dry ice and ice (P < 0.05). Cold water and refrigerant spray were in the same range in terms of time to detect temperature change at both the DEJ and pulpal surface. Thermal stimuli with greater temperature difference from tooth temperature created a greater thermal gradient initially, followed by a greater temperature change at the DEJ and the pulpal surface. In this regard, ice and cold water were weaker stimuli than others (P < 0.05). CONCLUSIONS: Thermal stimuli used in pulp testing are highly variable in terms of temperature of the stimulus, rate of thermal transfer to the tooth and extent of temperature change within tooth structure. Overall, dry ice and refrigerant spray provide the most consistent stimuli, whereas heated gutta-percha and hot water were highly variable. Ice was a weak stimulus.

An investigation of thermal stimulation in intact teeth.

OBJECTIVES: To investigate the response of extracted intact teeth to thermal stimulation in terms of fluid movement, in relation to temperature change within tooth structure. METHODS: Dentinal fluid movement was measured in response to thermal stimuli applied to enamel. Freshly extracted teeth with intact crowns were investigated for the effects of thermal stimulation; namely, hot water (80 degrees C), iced water (2 degrees C) and carbon dioxide dry ice (-72 degrees C) for 5s application. Two capillary-based methods were used to measure fluid flow. To measure temperature changes at the dentino-enamel junction (DEJ) and pulpal wall in response to the same stimuli, fine J type thermocouples were used. RESULTS: Thermal stimuli caused fluid movement, which occurred before the temperature changed at the pulp wall. Sealing the dentinal tubules resulted in a delayed response time. In general, fluid movement occurred coincident with the temperature change detected at the DEJ. However, many teeth showed a "bidirectional" response to thermal stimulation. The initial fluid movement in the bidirectional response was detected before the earliest temperature change observed at the DEJ, and was in the opposite direction to the main fluid movement. CONCLUSION: Our results imply that thermal contraction and expansion of dentinal fluid may not be the complete explanation for dentinal fluid movement in intact teeth. Enamel may serve not only as a temperature transfer medium but may also expand or contract when subjected to thermal stimulation.

A cleaning protocol for rotary nickel-titanium endodontic instruments.

BACKGROUND: The cleaning of endodontic and all dental instruments prior to sterilization is a prerequisite for their processing for re-use. This study aimed to develop a clinically practical cleaning protocol for rotary nickel-titanium (NiTi) endodontic files prior to sterilization. METHODS: Cleaning experiments were conducted on six different types of files that had been used on human teeth. The experiments involved three components of mechanical and chemical removal of root canal debris from the files: the use of sponges soaked with chlorhexidine to remove gross debris, pre-soaking, and ultrasonication. After cleaning, the files were immersed in Van Gieson's solution and examined under magnification for stained debris. New unused files were also examined. RESULTS: Macroscopically, there were no instances of visible debris and all files appeared clean after all cleaning sequences. Microscopically, new files showed both stained and unstained debris, and several experimental cleaning regimens produced files that were free of stained debris. Combining elements of the most effective cleaning sequences resulted in a cleaning protocol that predictably produced clean files. CONCLUSIONS: The results do not support the recommendation for the single use of endodontic files based on inability to clean files between uses. Under experimental conditions the cleaning protocol developed rendered rotary NiTi files 100 per cent free of stained debris. The protocol comprises 10 vigorous strokes in a scouring sponge soaked in 0.2 per cent chlorhexidine solution, a 30 minute pre-soak in an enzymatic cleaning solution, 15 minutes ultrasonication in the same solution, and a 20 second rinse in running tap water. The protocol can be applied to all endodontic files.

Cleaning of rotary nickel-titanium endodontic instruments.

AIM: To develop and evaluate an effective cleaning procedure for rotary nickel-titanium (NiTi) endodontic instruments. METHODOLOGY: New rotary instruments (ProFile size 25/.04) were contaminated by preparing canals of extracted teeth. Three factors were evaluated to develop an effective cleaning sequence: dry or moist storage before cleaning; mechanical removal (brushing); and chemical dissolution in 1% NaOCl with ultrasonication. Debris on flutes was scored after staining in situ with Van Gieson's solution at x45 magnification. Debris was classified as stained or unstained particulate debris and organic film, and rated as none, slight, moderate or heavy. The effectiveness of a recommended cleaning sequence was tested on different instrument types and in private endodontic practices. RESULTS: All new instruments showed metallic spurs and fine particulate debris on the surfaces. After contamination, brushing alone removed most particulate debris, but did not remove organic film. NaOCl effectively removed organic film. Under laboratory conditions, the sequential cleaning procedures (moist storage, brushing followed by immersion in 1% NaOCl and ultrasonic cleaning) totally removed organic debris. Dry storage before cleaning or autoclaving with debris present reduced cleaning effectiveness (P<0.001, one-way ANOVA). In three private practices, the cleaning protocol substantially reduced biological contamination, but complete cleaning was not always achieved (87% clean). CONCLUSION: Complete removal of organic debris from instruments is feasible using a combination of mechanical removal and chemical dissolution, but requires meticulous attention to details.