T. Hu

Use of CBCT to identify the morphology of maxillary permanent molar teeth in a Chinese subpopulation

AIM To investigate variations in root canal configuration in the maxillary permanent molar teeth of a Chinese subpopulation using cone-beam computed tomography (CBCT). METHODOLOGY A total of 269 patients with healthy, untreated, well-developed maxillary molars were enrolled, including those suffering facial trauma, and those who required a pre-operative assessment for implants. Radiographic examination by CBCT was conducted as part of their routine examination, diagnosis and treatment planning. Overall, 299 maxillary first and 210 maxillary second molar teeth were examined in vivo by CBCT. The number of roots, the number of canals per root, the canal configuration and the presence of additional mesiobuccal canals were recorded. Vertuccis classification for root-canal configurations was utilized. RESULTS All maxillary first molars had three separate roots; however, 52% of mesiobuccal (MB) roots had two canals with the remainder having one. All distobuccal and palatal roots had Vertucci Type I canal configurations. When the MB2 canal was present, 14, 69 and 16% of MB roots had Type II, IV and V canal configurations, respectively. The root canal system of the maxillary first molar teeth could be categorized into two variants: one with three separate roots with one canal in each of the distobuccal and palatal roots and two canals in the MB root, and the other with three separate roots with one canal in each root. Of 210 maxillary second molars, 10% had one root, 8% two roots and 81% three roots. Of the MB roots, 22% had two canals with the remainder having one. When the MB2 canal was present, 18%, 58%, 10% and 3% of MB roots had type II, IV, V and VI canal configurations, respectively. The root canal system of the maxillary second molar could be categorized into eight variants. CONCLUSIONS Mesiobucccal roots of maxillary molar teeth had more variation in their canal system than the distobuccal or palatal roots. The root canal configuration of the maxillary second molars was more variable than that of the first molars. CBCT can enhance detection and mapping of the mesiobuccal root-canal system with the potential to improve the quality of root canal treatment.

Use of cone-beam computed tomography to evaluate root and canal morphology of mandibular molars in Chinese individuals

AIM To evaluate the root canal configuration of permanent mandibular first and second molar teeth in a Chinese subpopulation using cone-beam computed tomography (CBCT). METHODOLOGY Patients who required CBCT radiographic examinations as part of their routine examination, diagnosis and treatment planning, were enrolled. Cases where the anatomy was compromised by physiological or pathological processes and the original root canal morphology was not clear were excluded. A total of 389 healthy, untreated, fully developed mandibular molars in Chinese individuals were included. The following observations were recorded: (i) the number of roots and their morphology; (ii) the number of canals per root; (iii) the canal configuration; (iv) the frequency of distolingual roots in the mandibular first molars and (v) the frequency of C-shaped canals in the mandibular second molars. The root canal configurations were classified according to the method of Vertucci (Oral Surgery, Oral Medicine, and Oral Pathology58, 1984, 589). RESULTS The majority of mandibular molars (70% of first molars, 76% of second molars) had two separate roots; however, three roots were identified in 29% of first molars. C-shaped roots occurred in 29% of second molars. Three canals were found in 56% of mandibular first molars and 43% had four canals. In the mandibular second molars, 46% had three canals and 38% had two canals. Most distal roots had a simple type I configuration, whereas mesial roots had more complex canal systems, with more than one canal. There were seven variants of the root canal morphology amongst the mandibular first molars and eight variants amongst the mandibular second molars, without considering the various root types. CONCLUSIONS Three-rooted mandibular first molars and C-shaped mandibular second molars occurred frequently in this Chinese population. CBCT is an effective tool for the detection of additional distolingual roots and C-shaped roots/canals, and it is a valuable aid for dentists providing root canal treatment.

Dental erosion and severe tooth decay related to soft drinks: a case report and literature review.

Soft drinks have many potential health problems. The inherent acids and sugars have both acidogenic and cariogenic potential, resulting in dental caries and potential enamel erosion. In this report we present a 25-year-old man complaining with the severe worn-out of the front teeth during the past 3 years. He had a history of drinking cola for more than 7 years and had a poor oral hygiene. Severe decays were present in the incisors and the canines, while less severe lesions were noted on the premolars and the molars. The review is to show the relationship between dental erosion and caries and soft drinks. Some efforts have been taken to reduce the harmful effect of soft drinks.

Interleukin-6 polymorphisms modify the risk of periodontitis: a systematic review and meta-analysis

ObjectiveTo clarify the association of IL-6 polymorphisms and periodontitis, a meta-analysis of case-control studies and a systemic review were conducted.Material and methodsWe performed a literature search using PubMed and Medline database to May 2009, with no restrictions. We also reviewed references from all retrieved articles. Six case-control studies involving 1 093 periodontitis cases and 574 controls were selected for meta-analysis to assess the purported associations between IL-6 polymorphisms and the risk of periodontitis. IL-6 −174 G/C and −572 C/G polymorphisms were included in the present meta-analysis, and the association between IL-6 −6331 T/C polymorphism and the risk of periodontitis was adequately reviewed as well.Results and conclusionThe present meta-analysis indicates that the IL-6 −174 G allele could not modify the risk of chronic periodontitis, but increased the risk of aggressive periodontitis. And −572 C/G polymorphism is associated with the pathogenesis of periodontitis, including chronic periodontitis or aggressive periodontitis.

Root and canal morphology of maxillary first premolars in a Chinese subpopulation evaluated using cone-beam computed tomography

AIM To evaluate the external and internal anatomy of maxillary first premolar teeth in a Chinese subpopulation using cone-beam computed tomography (CBCT). METHODOLOGY A total of 300 CBCT images involving maxillary first premolar teeth were obtained from 241 patients who underwent CBCT scanning as part of an oral and dental examination for bone mass before placement of implants or to locate impacted teeth before orthodontic therapy. Tooth position, number of roots, canal configuration, number of canals and number of apical foramina per root were investigated. The Fishers exact test was used to analyse the correlation between root number and tooth position. RESULTS Overall, 66% (n = 198) of teeth had one root and 33% (n = 100) had two roots; the remaining 1% (n = 2) had three roots. This frequency distribution showed no statistical significance between left and right sides. The most frequent canal configuration of these maxillary first premolars was type IV (n = 153; 51%), followed by type II (n = 70; 23%), with only 1% (n = 2) of teeth having type VIII. One-rooted teeth with canal bifurcations and/or combinations (types II, III, V, VI and VII) accounted for nearly 50% (n = 98) of the sample. Eighty-five per cent (n = 255) of the teeth examined had two root canals (types II-VII), and 14% (n = 43) had one. Amongst the 59 patients with bilateral teeth, 38 had a symmetrical pattern of tooth anatomy, including the same number of roots and the same types of canal configurations. CONCLUSIONS There was a high frequency of one-rooted teeth amongst maxillary first premolars, with most having one root with two canals (types II-VII). The morphology of the canal in one-rooted teeth was highly variable.

Lipopolysaccharide-induced dental pulp cell apoptosis and the expression of Bax and Bcl-2 in vitro.

Lipopolysaccharide exerts many effects on many cell lines, including cytokine secretion, and cell apoptosis and necrosis. We investigated the in vitro effects of lipopolysaccharide on apoptosis of cultured human dental pulp cells and the expression of Bcl-2 and Bax. Dental pulp cells showed morphologies typical of apoptosis after exposure to lipopolysaccharide. Flow cytometry showed that the rate of apoptosis of human dental pulp cells increased with increasing lipopolysaccharide concentration. Compared with controls, lipopolysaccharide promoted pulp cell apoptosis (P < 0.05) from 0.1 to 100 μg/mL but not at 0.01 μg/mL. Cell apoptosis was statistically higher after exposure to lipopolysaccharide for 3 days compared with 1 day, but no difference was observed between 3 and 5 days. Immunohistochemistry showed that expression of Bax and Bcl-2 was enhanced by lipopolysaccharide at high concentrations, but no evident expression was observed at low concentrations (0.01 and 0.1 μg/mL) or in the control groups. In conclusion, lipopolysaccharide induced dental pulp cell apoptosis in a dose-dependent manner, but apoptosis did not increase with treatment duration. The expression of the apoptosis regulatory proteins Bax and Bcl-2 was also up-regulated in pulp cells after exposure to a high concentration of lipopolysaccharide.

Finite element analysis of the effects of three preparation techniques on stresses within roots having curved canals

AIM To compare stress distribution within roots having curved canals prepared by three preparation techniques when subjected to occlusal loads and condensation loads as a consequence of different filling techniques. METHODOLOGY Three preparation techniques (crown-down, step-back and reverse-flaring) were compared by finite element analysis (FEA). Based on an established FEA model within curved canal, three modified models prepared by different preparation techniques were established by replacing original canal with prepared ones. FEA was performed to investigate the stress distribution under occlusal forces, which were simulated by loads of 500 N in four directions (buccal, lingual, mesial and distal), at 0 (vertical), 30, 45 and 60 degrees to the longitudinal axis of the tooth. In addition, vertical and lateral condensation processes at the curvature were simulated to determine the influence of different canal filling techniques on stress distribution. RESULTS When the occlusal and the filling loads were applied, stress distribution around the curvature and the orifice had little change on the three modified prepared models. The reverse-flaring technique resulted in the least stress with the lateral condensation process. In the case of vertical condensation, the maximum von Mises stress (46.205 MPa) occurred near the loading site. The model also revealed a tendency for stress concentration (30.635 MPa) just below the compacting level. CONCLUSIONS The study confirms that appropriate canal preparation techniques in simulated curved canals have little influence on stress distribution around the curvature or the orifice. However, vertical compaction induced high stress in the region just below the loading site.

The effect of lysophosphatidic acid and Rho-associated kinase patterning on adhesion of dental pulp cells

AIM To investigate the effects of lysophosphatidic acid (LPA) and the Rho/Rho-associated kinase (ROCK) pathway on adhesion of dental pulp cells (DPCs). METHODOLOGY Human DPCs were cultured ex vivo. After treatment of LPA and Y-27632, a specific ROCK inhibitor, changes in focal contacts (FCs) were examined by immunofluorescent staining. Activation of FCs proteins was examined by measuring tyrosine 397 phosphorylation of focal adhesion kinase (FAK) and paxillin using immunoblotting. The data were analysed by Students t-test. RESULTS The immunofluorescent staining indicated LPA stimulation induced larger focal adhesion in the cell periphery, compared with the control. Inhibition of ROCK by Y-27632 decreased the formation of FCs markedly, even in the LPA-stimulated cells. LPA also increased the level of tyrosine phosphorylation of paxillin at 30min (P<0.05) and FAK at 5 and 30min (P<0.05). Furthermore, p-paxillin levels declined immediately after Y-27632 treatment and remained low at 5, 30, 60min. Y-27632 also suppressed the effects of LPA on p-paxillin and p-FAK at 5 and 30min (P<0.05). CONCLUSION LPA activated Rho and then subsequently activated ROCK, suggesting that LPA influences the FCs of DPCs by modulating tyrosine phosphorylation of FAK and paxillin via the Rho/ROCK pathway.

Root canal curvature

Dear Editor We wish to share with readers a simple method to record and evaluate the degree of severity of canal curvature in human teeth. As is known to all, substantial curvatures in root canals lead to increased difficulty in root canal preparation (Schneider 1971, Alodeh & Dummer 1989, Alodeh et al. 1989, Dummer et al. 1989, Schäfer et al. 2002, Willershausen et al. 2008, Unal et al. 2009, Zheng et al. 2009). To describe the severity of curved canals, Schneider (1971) initially put forward the concept of the angle of root canal curvature. Later, Lim & Webber (1985) suggested that a landmark at the apical limit of instrumentation should be identified and that this position should be incorporated in any description of canal curvature, rather than the use only the root apex. Dummer and coworkers (Alodeh & Dummer 1989, Alodeh et al. 1989, Dummer et al. 1989) included a third factor in their work on simulated canals, that is, the position of the beginning of the curve and the radius of the arc of the curved portion of the canal. Schäfer et al. (2002) also took these landmarks as being of importance and pointed out that to define the canal curvature mathematically and unambiguously, the angle, the radius, and the length of the curve should be determined and described. Such parameters have been accepted widely and used (Burklein & Schäfer 2006, Schäfer et al. 2006 Zheng et al. 2009). However, this complex description of curved root canals is difficult to communicate simply to other dentists and the patient; thus, it has limited value as a useful means of describing the status of canal shape and complexity. In this letter, because of the difficulty in identifying the apical constriction on radiographs, it is proposed that the measurement of a curved canal is associated with the apical foramen, according to the method of Schneider (1971). In addition, several improvements have been identified in terms of the previous descriptions of canal shape (Schneider 1971, Dummer et al. 1989, Schäfer et al. 2002) and a mathematical derivation described. A more simple and intuitive way to describe the curved root canals is proposed. Based on the definition of the angle of canal curvature initiated by Schneider (1971), this new method can be used to intuitively record simultaneously the other two indicators depicting the degree of the root canal curvature: the radius of curvature and the length of the curved part. First, the angle of the curvature is defined according to Schneider (1971). As shown in Fig. 1, point A denotes the apical foramen. The point where the canal begins the curvature is marked as point B. A line is then drawn parallel to the long axis of the canal through point B, and a point C is chosen on this line such that the distance between B and C is equal to that between A and B. The angle a formed by lines AB and BC is the angle of curvature. From E and F, the midpoints of AB and BC, respectively, two lines are drawn perpendicular to the lines AB and BC, which would meet at the circumcentre O of triangle ABC. The distance between O and A, B or C is the radius (R) of the circumference, which determines the magnitude of the curve. From Fig. 1, we can see that:

Use of cone-beam computed tomography to evaluate the prevalence of root fenestration in a Chinese subpopulation

AIM To use cone-beam computed tomography (CBCT) to evaluate the prevalence of root fenestration (RF) in a Chinese subpopulation. METHODOLOGY A total of 306 patients were selected from patients receiving a routine CBCT examination; those with a malocclusion, a history of trauma or nondental pathosis were excluded. Overall, CBCT images of 4387 teeth were evaluated by two endodontists and one radiologist, and final agreements on findings were agreed for each tooth. The distribution, prevalence, types of RF and the degree of periapical bone of RF teeth were recorded using a newly developed classification system. RESULT The overall prevalence of RF by tooth type ranged from 0.18% to 10.46% and was higher in the maxilla (5.37% of teeth) than in the mandible (1.00% of teeth). RF appeared most frequently in maxillary first premolars (10.46%), followed by maxillary lateral incisors (7.80%) and maxillary canines (7.58%). RF appeared significantly more often on the labial/buccal side (99.98%) than the palatal/lingual side (0.02%). The two most common types of RF were Type I (54.73%) and Type IV (27.03%), and most periapical bone defects were Level I (92.57%). CONCLUSION The prevalence of root fenestration was lower in this Chinese subpopulation than that reported previously in other ethnic groups. CBCT was an effective and convenient tool for identifying and diagnosing RF.