Comparison between micro‐computed tomography and transverse microradiography of sound dentine treated with fluorides and demineralized by microcosm biofilm

The study aimed to apply micro‐computed tomography (micro‐CT) and transverse microradiography (TMR) to measure dentine demineralization and to test the preventive effect of titanium tetrafluoride (TiF₄) under microcosm biofilm. Sound dentine specimens from bovine root were treated for 6 h with: (i) 4.0% titanium tetrafluoride (TiF₄) varnish [pH 1.0, 2.45% fluoride (F?); (ii) 5.42% sodium fluoride (NaF) varnish (pH 5.0, 2.45% F); (iii) 2% chlorhexidine (CHX) gel (pH 7.0); (iv) placebo varnish (pH 5.0); or (v) no agent (untreated). Dentine specimens were then exposed to human saliva mixed with McBain saliva for 8 h. Thereafter, McBain saliva containing 0.2% sucrose was applied daily, for 5 d, onto dentine specimens to stimulate formation of microcosm biofilm. Although a high correlation was found between the results of both methods regarding integrated mineral loss, the results of the methods did not show good agreement in Bland–Altman plots, with significant biases in calculations of lesion depth. Fluoride varnishes were able to reduce dentine demineralization (P < 0.05), while CHX failed to do so. Fluorides are still the best option to reduce dentine demineralization. Micro‐CT may be used to measure dentine mineral loss, but not the lesion depth, for which TMR is superior.     

Mandibular mesial root canal morphology using micro‐computed tomography in a Brazilian population

To assess the root canal system morphology of mandibular molars by means of micro‐computed tomography, one hundred and four mandibular first molars were investigated and the following were evaluated: Vertucci's classification, the presence of lateral canals and the number of apical foramina. Mesial root canal surface area and volume were obtained by the CTAn and CTvol software. The type of root canal isthmi was classified applying the Hsu & Kim and Fan criteria. The most frequent root canal configuration was Vertucci type IV (46.2%). Lateral canals were observed in all root canal thirds and the average number of apical foramina was 3.15 ± 1.77. Regarding the presence of isthmus, Types I and II were the most prevalent, according to Hsu & Kim and Fan et al. criteria, respectively. Mesial root canals of mandibular molars showed high morphology variability.     

Inactivation of local root canal medicaments by dentine: an in vitro study

AIMS: The aim of the study was to investigate the inactivation by dentine of the antibacterial activity of various commonly used local root canal medicaments. METHODOLOGY: The medicaments tested were saturated calcium hydroxide solution, 1% sodium hypochlorite, 0.5% and 0.05% chlorhexidine acetate, and 2/4% and 0.2/0.4% iodine potassium iodide. Dentine was sterilized by autoclaving and crushed into powder with a particle size of 0.2-20 microns. Aliquots of dentine suspension were incubated with the medicaments in sealed test tubes at 37 degrees C for 24 h or 1 h before adding the bacteria. In some experiments bacteria were added simultaneously with dentine powder and the medicament. Enterococcus faecalis A197A was used as a test organism. Samples for bacterial culturing were taken from the suspensions at 5 min, 1 h and 24 h after adding the bacteria. RESULTS: Dentine powder had an inhibitory effect on all medicaments tested. The effect was dependent on the concentration of the medicament as well as on the length of the time the medicament was preincubated with dentine powder before adding the bacteria. The effect of calcium hydroxide on E. faecalis was totally abolished by the presence of dentine powder. Similarly, 0.2/0.4% iodine potassium iodide lost its effect after preincubation for 1 h with dentine before adding the bacteria. The effect of 0.05% chlorhexidine and 1% sodium hypochlorite on E. faecalis was reduced but not totally eliminated by the presence of dentine. No inhibition could be measured when full strength solutions of chlorhexidine and iodine potassium iodide were used in killing E. faecalis. CONCLUSIONS: The dentine powder model appears to be an efficient tool for the study of interactions between local endodontic medicaments, dentine, and microbes.     

Analysis of resin tags formation in root canal dentine: a cross sectional study

Aim  To evaluate the length, density and quality of resin tags formed by penetration of various types of adhesive systems into dentinal tubules at various cross section levels of the root canal in correlation to the density of dentinal tubules.
Methodology  Thirty mandibular premolars were instrumented and fibre posts were inserted with three different adhesive systems with and without activator: etch & rinse XP Bond and XP Bond/Self Cure Activator; self-etch (two-step) AdheSE and AdheSE/AdheSE DC Activator and self-etch (one-step) Hybrid Bond and Hybrid Bond/Hybrid Brushes. The resin tags were evaluated from slices obtained from sections perpendicular to the long axis of the teeth at 3, 6, and 9 mm from the root apex under a Confocal Laser Scanning microscope.
Results  In all groups, lack of continuity of resin tag length, density and quality was observed not only from the cervical to the apical region of each root canal, but also in a mesio-distal direction to the long axis of the root. Application of etch & rinse adhesive in contrast to the self-etch adhesives provided the formation of the shorter, but considerably denser, more homogeneous and not interrupted resin tags with similar length. Use of the activator for all types of adhesives significantly increased the completeness ( P  = 0.014) and continuity ( P  = 0.024) of resin tags.
Conclusions  None of the investigated adhesives were able to completely infiltrate the dentinal tubules in the entire root canal. Use of the etch & rinse adhesive system and the activators significantly increased the density and the quality of resin tags.     

上颌前磨牙牙根及根管形态的锥形束CT研究

目的研究上颌前磨牙牙根形态、三根管的发生率和根管解剖形态,为临床诊疗提供参考。方法选取珠海市口腔医院412名患者,共779颗上颌第一前磨牙,728颗上颌第二前磨牙的锥形束CT(cone-beam computed tomography,CBCT)扫描数据,分析上颌前磨牙的牙根及根管形态,三根管的发生率、双侧对称性、根管分叉位置等。结果上颌第一前磨牙三根管发生率为1.8%,上颌第二前磨牙三根管发生率为0.3%,上颌第一前磨牙三根管发生率显著高于上颌第二前磨牙(X^2=8.304,P=0.004)。上颌第一前磨牙三根管对称率为27.3%,上颌第二前磨牙无对称三根管结构出现。上颌前磨牙解剖形态可为单根、双牙根或三牙根,其内部根管形态复杂,存在七种Vertucci根管类型,上颌第一前磨牙以VertucciⅣ型为主,上颌第二前磨牙则以VertucciⅠ型常见。三根管上颌前磨牙的根管分叉位置多见于根中或根上1/3,16颗三根管上颌前磨牙都具有三个独立的根尖孔。结论上颌前磨牙根管形态复杂多变,CBCT对发现变异和额外根管具有重要辅助作用。     

Evaluation of root canal morphology of maxillary premolars: a cone‐beam computed tomography study

The aim of this study was to evaluate the root canal configuration of maxillary premolars using cone‐beam computed tomography (CBCT). CBCT images of 999 maxillary premolars from a database were analysed to determine the frequency of the number of roots, root canals and Vertucci's classification. The associations among these variables were evaluated by Chi‐square test (P < 0.05). In the first premolars, 42.2% of single‐rooted teeth had a type II configuration, whereas 98.7% of 2‐rooted teeth showed type IV. In the second premolars, type I was the most prevalent (49.9%). The presence of two roots was more prevalent in first premolars, and the presence of one root was more prevalent in second premolars (P < 0.05). Male patients had a higher percentage of two roots compared with female patients (P < 0.05). Type IV and I was more prevalent in first and second premolars respectively (P < 0.05). There was a high frequency of 2‐rooted and single‐rooted teeth among maxillary first and second premolars respectively.     

Canal transportation using Mani GPR or HyFlex NT during the retreatment of curved root canals: A micro‐computed tomographic study

This study assessed the apical transportation using Mani GPR or HyFlex NT during the retreatment of curved root canals. Thirty‐eight roots were analysed using micro‐CT for the comparison of apical transportation produced by two retreatment systems. Longitudinal transportation, horizontal transportation, variation in the canal angle of curvature and variation in the canal/root width ratio were analysed. Longitudinal transportation was frequently observed, regardless of the system used. The canals retreated with Mani GPR showed a significantly higher horizontal transportation at 1 mm from the root apex (P < 0.01) and greater variation of the canal curvature angle (P < 0.01). The canal/root width ratio was similar between groups (P > 0.05). In conclusion, longitudinal transportation occurred more frequently in the mesial canal walls. Mani GPR showed greater horizontal transportation at 1 mm short of the apex, and higher variation of the canal curvature angle compared with HyFlex NT.     

Inactivation of root canal medicaments by dentine,hydroxylapatite and bovine serum albumin

AIM: This study examined and compared the inhibition of the antibacterial effect of saturated calcium hydroxide solution, chlorhexidine acetate and iodine potassium iodide by dentine, hydroxylapatite and bovine serum albumin. METHODOLOGY: Enterococcus faecalis strain A197A prepared to a suspension of 3 x 10(8) cells per ml in 0.5% peptone water was used. Fifty microL of saturated calcium hydroxide solution, 0.05% chlorhexidine acetate or 0.2/0.4% iodine potassium iodide were incubated at 37 degrees C with 28 mg dentine powder (DP), hydroxylapatite (HA) or bovine serum albumin (BSA) in 50 microL water for 1 h before adding 50 microL of the bacterial suspension. Samples for bacterial culturing were taken from the suspension 1 and 24 h after adding the bacteria. In further experiments, the amount of dentine was stepwise reduced from 28 mg 150 microL-1 to 2.8 mg 150 microL-1. RESULTS: Calcium hydroxide was totally inactivated by the presence of 28 mg of DP, HA or BSA. Chlorhexidine (0.05%) was strongly inhibited by BSA and slowed down by dentine. However, HA had little or no inhibitory effect on chlorhexidine. The antibacterial effect of 0.2/0.4% iodine potassium iodide on E. faecalis was totally inhibited by dentine (28 mg), but was practically unaffected by HA or BSA. A stepwise reduction of dentine from 28 mg 150 microL-1 to 2.8 mg 150 microL-1 was followed by a similar reduction of the inhibition of the antibacterial activity of chlorhexidine. Iodine potassium iodide was not inhibited at all with dentine amounts less than 28 mg. However, the effect of saturated calcium hydroxide solution was totally eliminated by dentine, in all four concentrations. CONCLUSION: Inhibition by dentine of the antibacterial activity of calcium hydroxide, chlorhexidine and iodine potassium iodide occurs by different mechanisms. Different components of dentine may be responsible for the inhibition of these three medicaments. Calcium hydroxide was particularly sensitive to inhibition by both inorganic and organic compounds.     

A high-resolution computed tomographic study of changes in root canal isthmus area by instrumentation and root filling

Introduction

The aim of this study was to obtain a three-dimensional analysis of the isthmus area of the mesiobuccal root canal system in mandibular molars using high-resolution micro-computed tomography (μ-CT) scanning and to measure the amount of debris and root filling material in the isthmus after instrumentation/irrigation and root filling.

Methods

Mandibular molars with two separated mesial root canals (10 teeth) were scanned by using the Skyscan 1172 μ-CT system (Skyscan, Aartselaar, Belgium) before and after instrumentation and after filling using the Thermafil root filling technique. An isthmus was defined as the ribbon-shaped or thin connecting structure between two root canals after instrumentation. The characteristics of the isthmuses were quantitatively monitored during the whole treatment. The images were segmented and quantified. The surface area of the isthmus, volume of debris after rotary instrumentation, and volume of the filled space in the isthmus after obturation were evaluated.

Results

Of the seven mesial roots, two had isthmus/anastomoses somewhere along its length in the apical 5 mm, and five had an isthmus that was continuous all the way from the coronal part to the apical part. The average percentage of isthmus surface area and isthmus volume after instrumentation was 21.4% and 9.4% of the whole root canal system, respectively. About 35.2% of the isthmus volume was filled with apparent hard tissue debris after instrumentation/irrigation. The average percentage of volume of filling material in the isthmus areas was significantly lower (57.5%) than in the main root canals (98.5%, p < 0.001).

Conclusions

A considerable amount of dentin debris is produced and packed into the isthmus area during rotary instrumentation of mesial canals of lower molars despite continuous irrigation during and after instrumentation. The debris may partly prevent penetration of the filling material and sealer into the isthmus area.     

Cone-beam computed tomographic evaluation of root canal morphology of mandibular anterior teeth in a Saudi subpopulation,retrospective In-Vivo study

BackgroundThere is variability in the results of dental morphological studies between different ethnic populations. This study aimed to investigate the root canal morphology of mandibular anterior teeth in a Saudi subpopulation in the Riyadh region.MethodsWe examined a total of 1,769 cone-beam computed tomography (CBCT) images of the mandibular anterior teeth, including the central incisors (n = 587), lateral incisors (n = 590), and canines (n = 592). The number and configuration of the root canals were determined. Fisher's exact and Pearson’s chi-square tests were used to assess the differences between sexes and age groups, with a level of statistical significance was set at p < 0.05.ResultsOverall, Type I canal was the most frequent configuration among the mandibular anterior teeth (76.1%). However, the prevalence of Type III canal configuration in the central and lateral incisors was 36.5% and 31%, respectively. Additionally, the mandibular canines were mainly Type I canals (98.4%). The prevalence of canal configuration was predominantly Type I (95.7%), followed by Type III (2.7%), Type IV (0.4%), and Type V (1.2%). There was a statistically significant difference in the canal configurations between men and women (p = 0.02). Females more often had Type I root canals (60.6%), while Type III was more frequent in males (57.2%). However, there were no statistically significant differences between the age groups in canal configuration.ConclusionThe mandibular anterior teeth of the Saudi subpopulation had mainly one root canal. However, almost one-third of the central and lateral incisors had two canals. CBCT is a useful tool that can be used, if available, to investigate root canal morphology before root canal treatment.