Root Furcation Research Articles

Bone availability for mandibular molar distalization in adults with mandibular prognathism.

To investigate the retromolar space available for molar distalization in patients with mandibular prognathism. Using cone-beam computed tomography, the posterior mandibular dimensions in 110 consecutive patients with Class I or Class III malocclusion were measured (mean age, 27.0 ± 7.1 years). The shortest linear distances from the distal root of the right mandibular second molar to the inner border of the mandibular cortex were measured at the level of root furcation and 2, 4, and 6 mm apical to the furcation along the sagittal line and the posterior line of occlusion. The retromolar distances were compared between the Class I and Class III malocclusion groups using general linear mixed models. The retromolar space measured through the sagittal line showed no significant intergroup difference. Among the distances measured through the posterior line of occlusion, the space measured at depths 0 and 2 mm to the furcation were significantly greater in the Class III group than in the Class I group. Patients with Class III malocclusion have greater retromolar space for mandibular molar distalization along the posterior line of occlusion only at the level of the second molar furcation.

Mineral trioxide aggregate improves healing response of periodontal tissue to injury in mice

Mineral trioxide aggregate (MTA) is a biomaterial used in endodontic procedures as it exerts beneficial effects on regenerative processes. In this study, we evaluate the effect of MTA on healing of periodontal ligament (PDL) and surrounding tissue, following injury, in a transgenic mouse model and on the differentiation of murine mesenchymal progenitor cells in vitro. We used an inducible Cre-loxP in vivo fate mapping approach to examine the effects of MTA on the contributions of descendants of cells expressing the αSMA-CreERT2 transgene (SMA9+ ) to the PDL and alveolar bone after experimental injury to the root furcation on the maxillary first molars. Col2.3GFP was used as a marker to identify mature osteoblasts, cementoblasts and PDL fibroblasts. The effects of MTA were examined 2, 17 and 30days after injury and compared histologically with sealing using an adhesive system. The effects of two dilutions of medium conditioned with MTA on proliferation and differentiation of mesenchymal progenitor cells derived from bone marrow (BMSC) and periodontal ligament (PDLC) in vitro were examined using the PrestoBlue viability assay, alkaline phosphatase and Von Kossa staining. The expression of markers of differentiation was assessed using real-time PCR. Histological analyses showed better repair in teeth restored with MTA, as shown by greater expansion of SMA9+ progenitor cells and Col2.3GFP+ osteoblasts compared with control teeth. We also observed a positive effect on differentiation of SMA9+ progenitors into osteoblasts and cementoblasts in the apical region distant from the site of injury. The in vitro data showed that MTA-conditioned medium reduced cell viability and osteogenic differentiation in both PDLC and BMSC, indicated by reduced von Kossa staining and lower expression of osteocalcin and bone sialoprotein. In addition, cultures grown in the presence of MTA had marked decreases in SMA9+ and Col2.3GFP+ areas as compared with osteogenic medium, confirming reduced osteogenesis. MTA promotes regeneration of injured PDL and alveolar bone, reflected as contribution of progenitors (SMA9+ cells) into osteoblasts (Col2.3GFP+ cells). In vitro, MTA-conditioned medium fails to promote osteogenic differentiation of both PDLC and BMSC.

Effect of local hIL-10 gene therapy on experimental periodontitis in ovariectomized rats

Objective: To investigate the effect of local hIL-10 gene therapy on experimental periodontitis in rats and to elucidate the mechanism underlying this effect.Material and methods: Experimental periodontitis was induced in ovariectomized (OVX) rats using a silk ligature. We then injected 5 μg of hIL-10 plasmid with 5 μl of liposomes or 5 μg of vector plasmid with 5 μl of liposomes into the palatal side of the gingival mucosa of the upper left second molar once every two days. The rats were killed 48 hours after the seventh injection. The body weight; bone mineral density of the whole body, pelvis and spine; resorption of the alveolar bone; and number of cytokine-positive cells were measured to determine the effects of hIL-10 on the periodontal tissue.Results: hIL-10 was expressed in periodontal tissues after local gene delivery. The expressed hIL-10 protein inhibited alveolar bone resorption and downregulated IL-1β, IL-6, TNF-α, RANKL and MMP-8 in the periodontal ligament in the root furcation region.Conclusions: Local hIL-10 gene transfer suppressed alveolar bone resorption in OVX rats, and this effect was probably associated with the decline in the expression of pro-inflammatory cytokines in the periodontal tissues.

Cervical Dentin Changes in Curved Root Canals after Using WaveOne and Reciproc Files with Full Rotation versus Reciprocation Movement: An Ex vivo Study.

Aim:The aim of the current study was to compare the effect of WaveOne and Reciproc files in reciprocation versus reverse full rotation movements on cervical dentin thickness by virtue of cone beam computed tomography (CBCT) analysis in curved mesial canals of mandibular first molars.Methods:Mesiobuccal canals of 60 mandibular molars were randomly divided into 4 groups (n = 15): Group 1; WaveOne/Reciprocation, Group 2; WaveOne/Full-Rotation, Group 3; Reciproc/Reciprocation, and Group 4; Reciproc/Full-Rotation. Pre- and post-instrumented CBCT scans were prepared for assessment of cervical dentin thickness changes (2 mm, 4 mm below the highest point of the root furcation) in both groups. Data statistically analyzed using two-way ANOVA test.Results:There was no statistically significant difference between four experimental groups in terms of remaining dentin thickness at 2 and 4 mm levels below the highest point of the furcation (P > 0.05). No separation of instruments occurred in any group.Conclusion:WaveOne and Reciproc files with two different motions have similar effects on cervical of root canals in terms of dentin thickness changes.

Repair of human periodontal bone defects by autologous grafting stem cells derived from inflammatory dental pulp tissues.

BackgroundRecently, stem cells derived from inflammatory dental pulp tissues (DPSCs-IPs) have demonstrated regenerative potential, but the real effect remains to be examined. This pilot study attempted to isolate DPSCs-IPs from two patients and to evaluate the feasibility and the effect of reconstructing periodontal intrabone defects in each patient.MethodsDPSCs-IPs were harvested from two patients with periodontal intrabone defects with their approval. After discussing the biological characteristics of DPSCs-IPs in each patient, DPSCs-IPs were loaded onto the scaffold material β-tricalcium phosphate and engrafted into the periodontal defect area in the root furcation. After 1, 3, and 9 months, the outcome was evaluated by clinical assessment and radiological study. Furthermore, new samples were collected and the biological characteristics of DPSCs-IPs were further studied compared with normal dental pulp stem cells. The primary cell culture success rate, cell viability, cell cycle analysis, and proliferation index were used to describe the growth state of DPSCs-IPs. In-vitro differentiation ability detection was used to further discuss the stem cell characteristics of DPSCs-IPs.ResultsAs expected, DPSCs-IPs were able to engraft and had an effect of regeneration of new bones to repair periodontal defects 9 months after surgical reconstruction. Although the success rate of primary cell culture and growth status was slightly inhibited, DPSCs-IPs expressed comparable levels of stem cell markers as well as retaining their multidifferentiation ability.ConclusionsWe developed a standard procedure that is potentially safe and technological for clinical periodontal treatment using human autologous DPSCs-IPs.Trial registrationAccording to the editorial policies, the present study is a purely observational study, so trial registration is not required.

Reliability of the Assessment of Periodontal Disease in Historical Populations

Periodontal disease is the destruction of all portions of periodontium. However, only periodontitis, based on whether attachment loss has occurred, can be detected in archaeological material. Therefore, several methods have been used to assess the frequency of periodontitis in past populations. The main scope of this study is to determine whether diagnoses of periodontitis through various methods are consistent with diagnoses obtained using the radiographic method. The samples (35 individuals, 576 teeth) were selected from Radom Cemetery's collection (in use between 1790 and 1811). For each individual, a periodontal status assessment was made using the following parameters: (i) measuring the distance between the cement–enamel junction (CEJ) and the crest of the alveolar bone (AC); (ii) the degree of root exposure; (iii) presence of the inter-dental septum; (iv) dental calculus; (v) scoring system on the texture of the alveolar bone (Kerr's method) and (vi) radiography. In the studies, a correlation was found between the radiographic images and Kerr's method (r = 0.92) and root furcation (r = 0.96). Increasing degree of change on the alveolar bone is connected with increases in the CEJ–AC distance. A relationship between the frequency of the prevalence of dental calculus and changes on the alveolar bone was found. It means that the radiographic method, which is not always possible to use in archaeological collections, can be replaced by the presented macroscopic methods. Copyright © 2016 John Wiley & Sons, Ltd.

Temporo-spatial requirement of Smad4 in dentin formation

The TGF-β/BMP family plays an important role in multiple stages of tooth development. TGF-β/BMP signaling is required for odontoblast differentiation and dentin formation; however, the precise molecular mechanisms underlying dentin formation remain unclear. To address the role of TGF-β/BMP signaling in dentin formation, we analyzed mice in which Smad4, a key intracellular mediator of TGF-β/BMP signaling, was subjected to tissue-specific ablation under the control of Dspp, OC, or Col1a1 promoters. Three independent Smad4 conditional knockout mice exhibited various dentin defects in the crowns and roots of their molars depending on the transactivator. In all mutant molars, crown dentin thickness was thinner than that of the control. In addition, impaired dentin was found in the cervical region and root furcation area. Although the initial differentiation of odontoblasts was normal, odontoblast polarity abruptly decreased and the expression of Col1a1, OC, and Dspp was reduced in the odontoblasts of mutant molars. In Dspp-Cre-mediated Smad4 disruption mice, primary dentin formation was slightly delayed, while secondary dentin formation was severely affected in the cervical region of the molars. These results indicate that TGF-β/BMP signaling is required for odontoblast maturation and dentin formation in a stage- and site-dependent manner.

The Importance of Clinical Genotype in Patients with Klinefelter Syndrome. A Genetic Disorder Asociated to Taurodontism

Taurodontism is a clinical condition found in the molar teeth of humans whereby the body of the tooth and pulp chamber is enlarged vertically at the expense of the roots. As a result, the floor of the pulp and the furcation of the tooth is moved apically down the root. It is due to the failure or late invagination of Hertwig’s epithelial root sheath, which is responsible for root formation and shaping causing an apical shift of the root furcation. The constriction at the amelocemental junction is abnormally formed. Taurodontism is most commonly found in permanent dentition although the term is traditionally applied to molar teeth. It has been reported that taurodontism follows an autosomal dominant type of inheritance. Meanwhile, Mutations or chromosome aberrations are considered alterations in the chromosome number or structure. They are mainly considered due to gametogenesis inborn error at meiosis, where DNA loses are seen due to DNA repair processes deficiency. Some chromosome studies were performed were 34.6% (1596 patients) showed different chromosome alterations. Among the studies population, male and female pediatric patients with sexual genetic diseases were chosen. These chromosome changes are classified as numeric or structural alterations, respectively. A wide variety of pediatric patients with genetic diseases chromosome alterations are described in this study analyzing their clinical characteristics, medical, surgical treatments and their clinical evolution according to the genetic disease.

Alterations of the Danger Zone after Preparation of Curved Root Canals Using WaveOne with Reverse Rotation or Reciprocation Movements.

Introduction:The aim of this study was to compare the changes that occur in the danger zone (DZ) after preparation of curved mesiobuccal (MB) canals of mandibular first molars with WaveOne instruments in two different movements [reciprocation (RCP) and counter-clockwise rotation (CCWR)] by means of cone-beam computed tomography (CBCT). Methods and Materials:MB canals of 30 mandibular molars were randomly divided into 2 groups (n=15); WaveOne/RCP and WaveOne/CCWR. Pre- and post-instrumentation CBCT images were assessed for changes in the dentin thickness in DZ (2 and 4 mm below the highest point of the root furcation) in both groups. Data was analyzed using the repeated measures ANOVA test. Results:There was no statistically significant difference between two experimental groups in terms of remaining dentin thickness at 2 and 4 mm levels below the highest point of the furcation (P>0.05). Conclusion:The efficacy of WaveOne instrument on changes of the dentin thickness in the DZ was not affected by different file movements.

An anatomical investigation of the mandibular second molar using micro-computed tomography.

An understanding of root anatomy is an important foundation for providing successful endodontic treatment. The aim of this study was to use micro-computed tomography (micro-CT) to investigate the root anatomy of the mandibular second molar. Eighteen mandibular second molars were scanned using micro-CT. Images were reconstructed, and measurements and observations were recorded regarding pulpal floor anatomy, canal configuration, root wall thickness along the root, presence of calcifications in the pulp chamber and in canals, and apical anatomy. The most frequently found mesial root canal configuration was Vertucci Type 7 (1-2-1-2), which was seen in 33.3% of samples. Distal canals were most frequently Vertucci Type 1 (one canal), with 61.1% of samples showing this configuration. 11.1% of samples had two canals, 44.4% of samples had three canals, 33.3% of samples had four canals, and 11.1% of samples had five canals at some point along the length of the roots. Average root wall thickness between the mesiobuccal canal and the furcation was 1.23 mm. Mesiolingual canal root wall thickness was on average 1.29 mm, and the distal root furcation wall thickness averaged 1.41 mm. 77.8% of samples had calcifications present in both the pulp chamber and within the canals.

The characteristics of epithelial cell rests of Malassez during tooth eruption of development mice

It has been demonstrated that Hertwig's epithelial root sheath (HERS) has an important role in root development, closely related to development of cementum epithelial rests of Malassez (ERM) as the residuum after HERS fragment, and is the exclusive epithelial structure in the mature periodontal ligament. Some studies reported that ERM may play a role in maintaining a stable environment of periodontal, and likely to be involved in regeneration of periodontal tissue, especially of cementum. However, the function of the ERM is not well understood. In this study, we observed the morphology and biological characteristics of ERM of the maxillary 1st molar with surrounding periodontal tissues of BALB/c mice during the period of tooth cusp erupted out of the gingiva to occlusion stability. Immunohistochemistry revealed ERM predominately located at the cervical and root furcation regions of the periodontal ligament. The number of ERM cells at the cervical and root furcation regions of the post-built occlusion stage decreased compared to pre-built occlusion stage and occlusion building stage. Transmission electron microscopy analysis showed that epithelial cell nuclei with typical features of apoptosis were observed at the post-built occlusion stage, and consistent with positive bodies labeled by TUNEL(terminal deoxy-transferase (TdT)-mediated dUTP-biotin nick end labeling), while proliferating cell nuclear antigen positive bodies mainly located at occlusion built stage. It suggests that ERM may regulate in alveolar bone remodeling in association with the periodontal ligament during tooth erupting to occlusion stability and may play important roles potentially in regeneration and homeostasis of the periodontal tissues.

Periodontal diseases at the transition from the late antique to the early mediaeval period in Croatia

ObjectiveWe tested the hypothesis that the transition from the late antique to the early mediaeval period in Croatia had a negative impact on the periodontal health. Methods1118 skulls were examined for dental calculus, alveolar bone resorption, fenestrations, dehiscences and root furcation involvement. ResultsThe prevalence of teeth with calculus varied from 40.7% in the LA sample of continental parts of Croatia to 50.3% in the LA sample of Adriatic Croatia. The prevalence of alveolar bone resorption ranged between 21.2% in the EM sample from continental Croatia and 32.3% in the LA sample from Adriatic Croatia. The prevalence of individuals with alveolar bone dehiscences varied from 8.6% in the LA sample from continental Croatia up to 15.0% in the EM sample from Adriatic Croatia. The prevalence of individuals with alveolar bone fenestrations varied from 21.5% in the LA sample from Adriatic Croatia up to 36.2% in the LA sample from continental Croatia. The prevalence of individuals with exposed root bifurcations or trifurcations varied from 9.0% in the EM sample from Adriatic Croatia up to 20.7% in the EM sample from continental Croatia. Statistically significant differences were found between samples. ConclusionThe transition from the late antique to the early mediaeval period in Croatia did not have a negative impact on periodontal health. Studies of periodontal health of ancient populations should be performed to provide a better and more reliable reconstruction of living conditions in the past.

Observation of Osseous Healing after Intraoral Vertical Ramus Osteotomy (IVRO)

Intraoral Vertical Ramus Osteotomy (IVRO) is frequently performed as a form of mandibular osteotomy, but the process of osseous healing of the split bone fragments has not yet been reported. The purpose of this study was to clarify the process of osseous healing occurring in the tissue over time. The subjects were 35 patients who underwent IVRO. Sixty-one rami from these patients were studied at 1 month, 6 months, 1 year, and then 2 to 3 years after surgery by computed tomography (CT) . The plane passing through the mandibular foramen was designated as the upper plane, while the plane passing through the root furcation was designated as the lower plane. We examined all of the images between the two planes. We classified 5 types of bone fragments, from proximal to distal; these were classified on the basis of the CT cross- sectional images at 1 month after surgery. The 5 types were as follows: outer-side type (OS) , outer-proximal type (OP) , proximal type (PX) , inner-proximal type (IP) , and inner-side type (IS) . To elucidate the types of osseous healing, the progression of bone formation and the forms of the mandibular ramus proximal bone fragments were examined. In most cases, bone fragments were covered with callus-like structures at 6 months after surgery, and changed to cortical bone-like structures at 2 to 3 years after surgery. That is, the split bone fragments were in a transitional state at 2 to 3 years after surgery. In the majority of cases, the forms of the mandibular ramus proximal bone fragments were PX and OP. OP showed a significant difference in the amount of setback of the distal bone fragment. These aspects of osseous healing were discussed mainly because of the clinical importance of postoperative mouth opening and closing and the traction of the surrounding soft tissue.

Osteogenic effect of Drynariae rhizoma extracts and Naringin on MC3T3-E1 cells and an induced rat alveolar bone resorption model

ObjectiveTo investigate if Drynariae rhizoma (DR) and its main ingredient Naringin could reduce alveolar bone loss by stimulating the proliferation and differentiation of osteoblasts. Materials and methodsThe effect of DR water (DRWE), ethanolic extract (DREE), and Naringin on MC3T3-E1 cells was evaluated respectively by MTT method and by measuring the activity of alkaline phosphatase (ALP activity) as well as the level of osteocalcin in medium. Bone mineral density (BMD) detection, osteoclast counting by tartrate resistant acid phosphatase staining, and histopathological analysis were performed in an induced rat model of alveolar bone resorption after gastric perfusion with DR extracts or Naringin. ResultsDRWE and Naringin effectively increased the proliferation of MC3T3-E1 cells, whilst DREE and Naringin enhanced the differentiation of osteoblastic cells. The in vivo study indicated an elevated BMD value in the tooth-periodontal tissues from DRWE, DREE and Naringin treated groups after 10, 20 and 30 days of perfusion (P<0.05). In DRWE treated group, the number of osteoclasts at days 10, 20 and 30 decreased remarkably as compared to the corresponding negative controls (P<0.05), and no osteoclast could be found at day 30. New non-calcified bone-like matrix attached by osteoblasts at the root furcation was also shown. ConclusionsDR could be a supplementary medicine for periodontal therapy as it could reduce bone resorption in rat model of alveolar bone resorption and exert osteogenic effect on osteoblasts.

Alteration of bFGF expression with growth and age in rat molar periodontal ligament

To test the hypothesis that immunohistochemical changes in expression of basic fibroblast growth factor in the periodontal ligament do not change with age. Thirty male Wistar-ST rats were divided into growing groups (5, 9, and 15 weeks of age) and aging groups (6, 12, and 18 months of age). Serial sagittal sections (5 microm thick) were cut parallel at the distobuccal roots of the maxillary first molar. Paraffin-embedded tissue sections were stained with hematoxylin and eosin and rabbit polyclonal antibodies to basic fibroblast growth factor. The number and the area of basic fibroblast growth factor-immunoreactive cells in the periodontal ligament of the maxillary first molar decreased with age. The number of basic fibroblast growth factor-immunoreactive cells was much greater in the root furcation area, which experiences the greatest effect of occlusal force. Regardless of age, the production of basic fibroblast growth factor in the periodontal ligament may occur subject to functional demand. The hypothesis is rejected. The expression of basic fibroblast growth factor in the periodontal ligament decreased with age.

Disruption of periodontal integrity induces expression of apin by epithelial cell rests of Malassez

It has been suggested that epithelial cell rests of Malassez (ERM) may express enamel matrix proteins and play an important role in periodontal regeneration. Two novel proteins, apin (APIN) and amelotin (AMTN), produced by maturation-stage ameloblasts and junctional epithelium, have recently been identified. The objective of this study was to evaluate whether the ERM express APIN and AMTN under normal conditions and after periodontal challenge. Gingivectomy and orthodontic tooth movement were carried out on the left side of the maxillae of rats. The control group included the untreated contralateral side of these animals and the maxillae of normal, untreated rats. Animals were sacrificed by intracardiac perfusion on days 3 and 5 after the experimental procedures and maxillary molars were decalcified and processed for paraffin embedding. Immunohistochemistry was used to evaluate the expression of various ameloblast products, including APIN, AMTN, ameloblastin (AMBN) and amelogenin (AMEL). At 3 and 5 days after periodontal challenge, ERM were more evident in the periodontal ligament along the root surface and in the root furcations. Immunodetection of APIN, but not of the other three proteins, was observed in the ERM following the disruption of periodontal integrity. No immunolabeling for APIN, AMTN, AMBN and AMEL was detected in the ERM under normal conditions. The expression of APIN at an early time-point following disruption of periodontal integrity suggests that this protein may be part of the cascade of events leading to the activation of ERM during periodontal healing and regeneration.

Radiographic Characteristics of Furcation Involvements in Mandibular Molars as Prognostic Indicators of Healing After Nonsurgical Periodontal Therapy

The authors conducted a study to evaluate the radiographic characteristics of Class II mandibular furcation involvements as prognostic indicators of healing after nonsurgical periodontal therapy. Twenty-three patients with chronic periodontitis (Class II furcation involvements in mandibular molars, probing pocket depth [PPD] of 5 millimeters or greater and bleeding on probing [BOP]) were selected to receive nonsurgical periodontal treatment. The authors evaluated visible plaque index, BOP, position of the gingival margin, PPD, relative attachment level (RAL) and relative horizontal attachment level. On radiographs, the authors measured root trunk, bone attachment level in the furcation region, lesion height (Lh), furcation width at alveolar crest level inside furcation (Fw) and 2 mm apical to the fornix (Fw2), and the perpendicular distance from the horizontal line connecting mesial and distal radiographic alveolar crest to furcation fornix. They analyzed all data using linear multiple regression. Six months after treatment, the furcations showed a mean RAL gain of 1.08 mm (+/- 1.25 mm) and a PPD decrease of 2.74 mm (+/- 1.58 mm). The authors found a statistically significant influence between Fw and PPD (P = .0044), Fw2 and PPD (P = .0014), Lh and PPD (P = .0241), and Fw2 and RAL (P = .0037). Within the limitations of this study, the results suggest that Fw, Fw2 and Lh may influence the response of Class II mandibular furcations to nonsurgical periodontal therapy and may serve as prognostic indicators for this therapy. Thus, narrower and shorter root furcations would be expected to have better outcomes.

Research on promoting periodontal regeneration with human basic fibroblast growth factor-modified bone marrow mesenchymal stromal cell gene therapy

Recently, it has been found that effective periodontal regeneration can be induced by bone marrow mesenchymal stromal cell (BMSC) transplantation or local application of basic fibroblast growth factor (bFGF). The aim of the present study was to assess, in dogs, the efficacy of periodontal regeneration via the delivery of BMSC transfected with bFGF to repair destruction of periodontal tissue. BMSC from dogs were isolated, cultured and purified via density-gradient centrifugation. Polymerase chain reaction (PCR) was employed to clone bFGF cDNA from human periodontal cells, and the product was then ligated into the eukaryotic expression vector pDC316-IREs-EGFP. BMSC transfected with pDC316bFGF-IREs-EGFP were transplanted into root furcation defects of beagle dogs. After 6 weeks, regeneration in defects was assessed via clinical examination, X-ray, histologic observation and micro-CT analysis. DNA sequence analysis showed that the bFGF sequence of recombinant plasmid pDC316bFGF-IREs-EGFP was consistent with that reported by GeneBank. bFGF expression was detected with Western blotting, and active bFGF in supernatant was also observed. Our animal experiment proved that the regenerating speed of periodontal bone tissue in groups transplanted with BMSC containing the modified bFGF gene was higher than in those transplanted with BMSC alone. A successfully constructed eukaryotic expression vector containing human bFGF in pDC316bFGF-IREs-EGFP could produce bioactive bFGF in vitro. bFGF overexpression mediated by the recombinant plasmid pDC316bFGF- IREs-EGFP accelerated periodontal regeneration.

Epidermal Growth Factor in Liposomes May Enhance Osteoclast Recruitment during Tooth Movement in Rats

To evaluate the effects of local administration of epidermal growth factor (EGF) located within liposomes on recruitment of osteoclasts during mechanical force in rats. An orthodontic elastic band was inserted between the left upper first and second molars, to move mesially the first molar. Rats were randomly divided into 4 groups (n = 8): EGF (2 ng/microL) located within liposomes (group 1), liposomes only (group 2), soluble EGF (2 ng/microL; group 3), or vehicle alone (group 4). The solutions were injected into the region of the root furcation of the left first molar after elastic band insertion. Tooth movement was measured using a plaster model of the maxilla, and the number of osteoclasts recruited at the pressure side of the first molar was histologically evaluated. Intergroup analysis showed that there was no significant difference between group 2 and group 4 (P > .05) and between group 1 and group 3 (P > .05). However, group 1 and group 3 exhibited greater differences in tooth movement than group 2 and group 4 (P < .05). On the other hand, group 1 showed greater tooth movement than groups 2 and 4 with statistical significance (P < .01). The increase in the number of osteoclasts in group 1 was significantly higher than in the other groups (P < .05). Exogenous EGF-liposome administration has an additive effect when compared with soluble EGF on the rate of osteoclast recruitment, producing faster bone resorption and tooth movement.

Evaluation of the risk of a stripping perforation with gates-glidden drills: serial versus crown-down sequences

The aim of this study was to evaluate the remaining dentine/cementum thickness using Gates-Glidden burs in serial and crown-down sequences and to observe which of the two sequences is the safest for preparing mesial roots of molars. Thirty-six left and right human mandibular first molars were selected. Standard access cavities were made and initially explored with Flexofiles sizes 10 and 15 until the tip was visible at the apex. The teeth were embedded in a muffle specially developed for this study using a PVC tube with two parallel metal rods in its lid. Each tooth-block was sectioned 3 mm apically to the furcation using a low-speed saw with a diamond disc. The tooth-block was examined under a microscope and an initial image was captured by a digital video system with 8 X and 12 X magnifications. Finally, the tooth-blocks were reassembled in the muffle so that the canals could be instrumented. After instrumentation the area of each mesial canal as well as the smallest distance to the root furcation were measured again. The mesio-buccal canals (crown-down order) and the mesio-lingual canals (serial sequence) presented an average area of 0.46 +/- 0.16 mm(2) and 0.88 +/- 0.27 mm(2) (P < 0.01), respectively. The mean values of the smallest distance to the furcation for the mesio-buccal and mesio-lingual canals were 0.66 +/- 0.19 mm and 0.39 +/- 0.13 mm (P < 0.01), respectively. The remaining dentine/cementum thickness using Gates-Glidden burs was greater in the crown-down sequence than in the serial sequence.