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PubMed1998

The significance of locating and filling the canal isthmus in multiple root canal systems. A scanning electron microscopy study of the mesiobuccal root of maxillary first permanent molars.

The mesiobuccal (MB) roots of 50 randomly selected maxillary first permanent molars were examined to evaluate the different configurations of canal isthmus and their incidences. Sections of the roots at 3.4, and 5 mm from the apex were prepared, acid etched, washed and dried. The apical side of each section was sputter coated with gold, examined by a Hitachi S-2500 scanning electron microscope and photographed. 36% of the mesiobuccal roots had one canal, whereas 64% had two canals. In the roots with two canals 31.25% contained either a complete isthmus, or accessory canals between the two main canals 31.25% showed partial isthmus formation. The significance of the different configurations is discussed. Our present findings indicate that the mesiobuccal roots of maxillary first permanent molars exhibit complex anatomy. Prudent judgement is essential in the canal isthmus preparation so that operators must provide meticulous skill and care to the patients.

Dental Pulp Cavity↗

PubMedDate not supplied

A multidisciplinary approach to the treatment of an intruded maxillary permanent incisor complicated by the presence of two mesiodentes.

Treatment of a traumatically intruded maxillary incisor with an immature apex remains controversial. Treatment options include observation, surgical repositioning, or orthodontic forced eruption. Likewise, the ideal timing of surgical removal of a mesiodens is highly controversial: immediate versus delayed intervention. The complications associated with untreated supernumerary teeth include: overretention of primary teeth, delayed eruption of permanent incisors, rotations, impaction, diastema, pulp necrosis and root resorption. Less common sequelae include enlarged follicular sacs, cystic degeneration and nasal eruption. This paper describes another risk factor associated with delayed removal of a mesiodens previously not mentioned in the dental literature, namely potential complications arising from a traumatic injury, in particular intrusion, of the maxillary permanent incisors.

Child↗

PubMed1997

Incidence of root face alteration after ultrasonic retrograde cavity preparation.

PROBLEM: Ultrasonic root end preparation is now a recognized clinical procedure. Advantages claimed include improved access to the surgical site (because of reduced root end bevel), and faster more conservative preparation of the root end cavity. However, cracking of the root face has been reported after preparation. OBJECTIVES: The aim of this study was to determine the incidence of root end cracking at varying ultrasonic power levels with a replica technique and scanning electron microscopy. STUDY DESIGN: The root canals of 55 single-rooted teeth were prepared to size 40 apically and obturated with laterally condensed gutta perch and sealer. Root ends were resected at 90 degrees 3 mm from the apex. Class 1 cavities (n = 5) were prepared with retro tips in a Neosonic handpiece with different power settings. Time of preparation and load applied were constant. Another experimental group (n = 5) was prepared with a no. 1 rotary bur. A replica technique with addition-cured silicone impression material and epoxy resin was used to prevent drying artefacts. Specimens were viewed under scanning electron microscope for alterations of the root face. RESULTS: Results showed no root face cracking across the full range of instrument power settings, although chipping of the retrograde cavity margins was observed. No cracking was noted in bur-prepared teeth.

Analysis of Variance↗

PubMed2000

Canal filling in primary teeth. Description of two particular cases.

Endopedodontics is that branch of child dentistry that regards pulp treatment in childhood. It involves endodontic treatment of all primary teeth and incisives, and of the first permanent molars with immature apex. The pedodontist has to exactly evaluate the techniques and the material to use in treating his patients. It is important to realize that we are facing a continuously evolving and absolutely unstable dentition. Therefore, the success of our work is the result of a careful evaluation of diagnostic parameters and of the techniques and the material. In the current clinical cases it is obvious how the lack of only one of the parameters listed, could represent the cause of severe damage to the patient's dental health and it could lead to psychological discomfort (if not damage), considering the age of the patient.

Child↗

PubMedDate not supplied

Composite morphology of the bone and associated support-tissue interfaces to osseointegrated dental implants: TEM and HVEM analyses.

Correlated transmission electron and high-voltage electron microscopic analyses examined the undecalcified bone and associated support tissues of 60 endosseous titanium blade and titanium and ceramic root-form implants in dogs. The implants supported fixed partial dentures for up to 2 years. Data obtained from this investigation suggest that a range of tissues, both mineralized and unmineralized, support osseointegrated dental implants. This study examined the tissues apposing not just isolated aspects of the implant surface, but the entire length of the implant, and found that mineralized and unmineralized tissues existed concurrently. Much of the implant surface was apposed by mandibular bone, and both root-form and blade implants osseointegrated. The densely mineralized collagen fibril matrix was often separated from the implant by only a 20-nm to 50-nm electron-dense, ruthenium-positive deposit. High-voltage electron microscope stereology demonstrated that cellular processes extended directly to the implant from underlying osteocytes. In the same implants, areas containing an unmineralized collagen matrix interposed between the bone and implant surface were observed. In this region osteoblasts interacted with this matrix, and Howship's lacunae, containing vascular elements and osteoclasts, were also observed. The remodeling activities appear to be a homeostasis of catabolic activity (osteoclasts) and metabolic activity (osteoblasts). The apex of the implant was often apposed by a fibrofatty stroma. The support tissue response appears to be the result of the interrelations of osteoblasts, osteocytes, and osteoclasts in association with vascular elements. Therefore, the support tissue response to osseointegrated implants is a dynamic activity that involves the healthy interaction of these cells and tissues along the entire length of the implant.

Adipose Tissue↗

PubMed1982

An instrument for measuring root canal length and apex location. A rapid technique.

The invention of a new instrument (the Apexfinder) for measuring the root length and apex location is reported. This instrument is an accurate and reliable tool for the apex determination. The application method is based on the insertion of a plastic, fine-tapered barbed shaft through a beveled tube into the root canal. When resistance to withdrawal is felt, which indicates that one of the barbs has engaged the apical margin, the shaft is marked at the level of the cusp tip. The distance between the mark and the barbs which caused the resistance is measured. These barbs will show apical inclination, which would be opposite to the direction of the rest of the barbs. The practitioner can rely on this technique in the majority of cases provided that a full range of plastic shafts, with different dimensions, is available for use with the outer tube.

Dental Pulp Cavity↗

PubMed1995

In defense of the guidance theory of palatal canine displacement.

From the foregoing debate it will be quite clear that Peck et al. have provided ample evidence that may be used to fuel the arguments of both sides: 1. Their material does not contradict the possibility that environmental factors may give rise to palatal displacement of canines generated by genetic anomaly of the adjacent teeth. 2. The buccally displaced canine finds itself similarly environmentally compromised by the different factor of crowding which leads to its characteristic buccally ectopic guidance pattern. 3. (a) Canines that are transposed with the premolar, (b) others that have erupted ectopically, high in the buccal sulcus and in the absence of crowding, and (c) certain palatal canines whose root apex is located markedly distant from their designated site, may all be labeled as genetically controlled with a fair degree of confidence. 4. In between these clearly defined entities there exists a "gray area" in which it is probable that the etiology of the individual displaced teeth may be linked to a combination of circumstances that obey premise number 1 and premise number 2, to varying degrees. The guidance theory cannot provide the complete answer to the etiology of the palatally displaced canine. Were this so, we would find PDC every time there was an anomalous or missing lateral incisor. Equally, it may not yet be discounted out of hand and certainly not on the basis of the evidence provided in the article in question.

Cuspid↗

PubMed1990

Root canal anatomy of mandibular second molars. Part I.

The root canal anatomy of 149 mandibular second molars was studied using a technique in which the pulp was removed, the canal space filled with black ink and the roots demineralized and made transparent. Of the 149 teeth, 22 per cent had single roots, 76 per cent had two roots and 2 per cent had three roots. In the single-rooted teeth, three canals were most common, while in the mesial root of the two-rooted teeth, two canals that joined near the apex and one canal in the distal root were most frequent. Round canals were most common in two-rooted teeth and C-shaped canals in single-rooted teeth. Transverse anastomoses were found in 33 per cent of roots, most commonly in the middle third of the root. Lateral canals were found in 72 per cent of roots, most commonly in the apical third of the root. The apical foramen was positioned at the apex in only 33 per cent of roots, and apical deltas were found in 35 per cent. The patient's age and race affected canal shape, with more round canals present in patients over 35 years of age, and more C-shaped canals in Asians. The sex of the patient and the side of the mouth affected the presence of apical deltas, with more being found in males and on the left side. Single-rooted teeth had more complex root canal systems than two-rooted teeth, with more lateral canals, transverse anastomoses, apical deltas and C-shaped canals.

Adolescent↗

PubMedDate not supplied

Clinical evaluation of root canal obturation methods in primary teeth.

PURPOSE: This study evaluated in vivo 2 different obturation techniques (lentulo spiral mounted in a slow-speed handpiece and hand-held) in primary teeth. METHODS: The study was carried out on 24 children (mean age = 6.71 years) who had received 50 single-visit zinc oxide and eugenol (ZOE) pulpectomies in primary molars. The root canal filling materials were deposited into the canals either by a lentulo spiral mounted in a slow-speed handpiece or by a hand-held lentulo spiral. Evaluation of pulpectomized molars was performed by both authors immediately and 6 months following treatment using specific clinical and radiographic criteria. In cases of disagreement, the lower rank was selected. RESULTS: The study found 64% (16/25) optimal filling (if 1 or more of the canals having ZOE ended at the radiographic apex or up to 2 mm short of the apex) when the lentulo spiral mounted in the slow-speed handpiece was used. It also found a 96% (21/22) clinical success rate in the group obturated by the lentulo spiral mounted in a slow-speed handpiece vs 48% (12/25) optimal filling and a 92% (23/25) clinical success rate in the group obturated by a hand-held lentulo spiral. The radiographic success for over- and optimally filled canals, when combining both lentulo groups, was significantly greater than underfilled root canals (P = .009). CONCLUSIONS: There was no statistically significant difference between the 2 techniques of obturation, according to the quality of the root canal filling or success rate.

Child↗

PubMed2002

An experimental study on mandibular expansion: increases in arch width and perimeter.

The purpose of this study was to estimate the increase in arch perimeter associated with mandibular lateral expansion. The mandibular expansion was simulated using a three-dimensional (3D) finite element method (FEM) and a computer graphics technique (3D simulation). The centre of rotation of molars during movement accompanied by lateral expansion was calculated using 3D FEM. The geometry of the model was determined using the mandibular bone of an East Indian skeletal specimen and 1 mm computer tomogram (CT) slices. The 3D set-up simulation was then conducted using 3D computer graphics instead of performing a manual set-up. Rotational movement was induced in the buccal segment, from the first premolar to second molar, in the 3D set-up model around the location of the centre of rotation (4.5 mm below the root apex of the first molar) derived from the FEM. According to 3D simulation, the model showed an opening space of 1.43 mm between the canine and first premolar, and thus a change in arch perimeter of 2.86 mm. The tip of the mesio-lingual cusp of the first molar moved 3.88 mm laterally, resulting in a change in inter-molar width of 7.76 mm. These values mean that a 1 mm increase in arch width resulted in an increase in arch perimeter of 0.37 mm. This result would be of value clinically for prediction of the effects of mandibular expansion.

Biomechanical Phenomena↗

PubMed1985

Variation in the developing root cone angle of the permanent mandibular teeth of modern man and certain fossil hominids.

The radiographic appearance of the developing root apex of 461 mandibular teeth was studied using ellipsopantomographs of 77 individuals. The angle formed by the mesial and distal aspects of the developing root cone was measured for each quarter of root development in the permanent mandibular teeth of each subject. Large values for this angle in the more coronal part of the root gradually decreased towards the root apex where values were small in all teeth studied. This gradual decrease in the angle of the developing root cone is concordant with the faster increase in root length but slower rates of dentinogenesis reported for the apical region of human teeth in the literature, as the decrease is likely to reflect the increasing numbers of odontoblasts that become involved in root formation as it proceeds apically. The developing root cone angles of one of the five fossil hominid specimens studied (KMN-ER 820) fall outside the range for the developing root cone angle of the developing premolar and permanent second molar roots in modern Homo sapiens and is evidence of a faster rate of root elongation than is typical for modern man.

Animals↗

PubMed1995

Morphologic criteria for root canal treatment of primary molars undergoing resorption.

The endodontic anatomy of primary molars is difficult to predict because of the balance of resorption and hard tissue deposition. In particular, the resorption causes perforating lacunae across the wall of the root, even at the furcation level, and modifies shape, dimension and position of endodontic apex. The phenomenon can be so deep as to compromise endodontic therapy. The first aim of the study was to verify if reliable criteria can be found for treatability in primary molars undergoing resorption, i.e. if it is possible to predict if perforating lacunae are present or not. The second aim of the study was to verify if other informations needed for endodontic treatment, as shape, dimension and location of the apex, and curvature of the root canal can be predicted. For the study, 80 extracted primary molars, 75 of which pulpally involved by caries, were selected. The treatability was evaluated in term of root length, root shape, dimension and shape of endodontic apex, age of the patient and X-ray index of resorption. The association between variables was performed by multiple correspondence analysis. The results suggested that root length was the most reliable criterion of the integrity of the root. The borderline of treatability was at the length of 4 mm. The position of endodontic apex related to anatomical apex, and the lingual related to the buccal root length were analyzed by linear regression analysis. The canal length was often similar to the root length (i.e. the endo and anatomical apices were very close) in lower and upper molars. However, in lower molars, if two or more canals were present in the same root, a discrepancy was observed between buccal and lingual root length. This finding was constant in first lower molars. In addition regression analysis provided a linear function between the lengths of the buccal and lingual side of the same root in lower molars. Its coefficient b was 0.73.

Analysis of Variance↗

PubMed2002

Location of canal isthmus and accessory canals in the mesiobuccal root of maxillary first permanent molars.

BACKGROUND: Failure in surgical endodontics may be caused by many factors. Failure is commonly due to improper preparation for the root-end filling and a lack of seal of the resected root end. The aim of this study was to investigate the morphology of resected mesiobuccal (MB) root ends of maxillary first molars and to evaluate the location of the canal isthmus and accessory canals between the MB canals. METHODS: From 50 selected first permanent molars, sections of the MB root at 3, 4 and 5 mm from the apex were prepared, acid-etched, washed and dried. The apical side of each section was sputter-coated with gold, examined by a scanning electron microscope and photographed. RESULTS: Overall, 18 (36%) of the 50 MB roots had one canal, whereas 32 (64%) had 2 canals. Of the roots with 2 canals, 10 (31.25%) contained either a complete isthmus or accessory canals or both between the 2 main canals. Another 10 (31.25%) showed partial isthmus formation. CLINICAL SIGNIFICANCE: MB roots exhibit a variety of canal configurations. On the basis of these findings, we propose a classification of the resected root surface of the MB root. Prudent judgement in preparing the canal isthmus, meticulous skill and comprehensive knowledge of root canal anatomy are essential for successful treatment.

Dental Pulp Cavity↗

PubMed1996

An evaluation of the Canal Master, balanced force, and step-back techniques.

The step-back (SB), balanced-force (BF) , and Canal Master (CM) instrumentation techniques were compared in 53 mesial canals of mandibular molars using two different instrument types: Flex-R and CM. Canal angulation changes from preoperative to postrotary and postinstrumentation were measured using the Schneider technique (ST) and the long-axis technique (LAT). Instrumentation times were recorded, and then the roots were sectioned at 1, 3, and 5 mm from the apex. Measurements were made of the minimal remaining root structures and canal diameter. Rotary instrumentation resulted in a average loss of curvature of 2.37 degrees, as measured by the ST. The ST showed significant changes in canal angulation between CM (-7.74 degrees) and SB (-5.28 degrees) groups, with p < 0.05. LAT showed significant changes for CM versus BF and SB (p<0.001), with a mean change in angulation of -7.69 degrees, -1.68 degrees, and _0.1 degrees respectively. The BF technique (5.5) was significantly faster than either SB (7.1 min) or CM (8.3 min), with p < 0.05. The remaining mesial-distal root structure at all levels was similar among groups.

Analysis of Variance↗

PubMed2006

Reinforcement of immature roots with a new resin filling material.

The purpose of this study was to compare the reinforcement and strengthening ability of Resilon, gutta-percha, and a self-curing composite resin (Bisfil 2B) in endodontically treated roots of immature teeth. Sixty single rooted teeth were divided into five groups of 12 teeth each. Teeth in all groups except the negative controls were prepared with a #5 Peeso (1.5 mm) through the apex (simulating immature roots) and root ends were filled with a 4 mm barrier of MTA. After smear layer removal, canals in the three experimental groups were backfilled with gutta-percha, Resilon, or Bisfil 2B. The remaining canal space in the positive control group was left unfilled. Negative controls received no treatment. A horizontal fracture was created in the root of each specimen using an Instron and the mean peak loads to fracture were recorded. ANOVA revealed no significant difference between any of the treatment groups. Based on the results of this study, canal wall reinforcement of teeth with a canal diameter of 1.5 mm or less may not be necessary.

Analysis of Variance↗

PubMed1995

Anatomic relationship of the genial tubercles to the dentition as determined by cross-sectional tomography.

PURPOSE: This study determined the anatomic location and the dimensions of the genial tubercles in relation to the apices of the mandibular central incisors. MATERIALS AND METHODS: Linear cross-sectional tomographic images were made of 41 adult human skulls. A 2-mm-thick section was produced through each central incisor. The vertical distance between the apex of each central incisor and the level of the superior aspect of the genial tubercle was measured on the radiographs. Additional measurements were taken on the dry skulls to determine the horizontal distance between the apices of the two central incisors and the width and height of the genial tubercle. RESULTS: Although 5 mm is considered a safe zone for geniotomies, 29 of the genial tubercles (35.4%) were less than 5 mm from the apices of the mandibular central incisors. The distance between the apices of these incisors ranged from 9 mm to 15 mm. CONCLUSION: Osteotomy of the genial tubercles can be performed within the confines of the mandibular central incisors, but care must be taken to avoid the root apices.

Adult↗

PubMed1995

A computerized method for the evaluation of root canal morphology.

The objective of this research was to develop a technique that would allow three-dimensional imaging of root canals utilizing computer image processing. Ten single-rooted permanent human teeth with mature apices were analysed. The teeth were decoronated and fixed on boards with the long axis of the root perpendicular to the board. The cross-sectioning started at the root apex and continued in the coronal direction, roughly perpendicular to the long axis of the ++root. The samples were divided into two groups. The first five samples were sectioned 15 times, each section being 0.5-mm thick, in order to obtain the three-dimensional reconstruction of the root and the root canal. The root apex of each sample was cross-sectioned 19 times and each section was 0.2-mm thick. After each section, the root canal contour was defined utilizing the calibrated net with coordinate system in the ocular of the stereomicroscope. The coordinates of the root canal cross-section contour thus determined, together with the value of the thickness of each cut, were relevant input data for the reconstruction of the root canal cross-sections, longitudinal sections and for the final three-dimensional rebuild of the root and the root canal model. this technique appears to be highly accurate in determining the anatomy of the root canal system and may also be applied in other fields of dental research.

Computer Simulation↗

PubMed1990

Clinical evaluation of five electronic root canal length measuring instruments.

A previous in vitro study has shown high accuracy, but no clinically significant differences in a group of five electronic root canal length measuring instruments. The purpose of this study was to evaluate and compare the performance of the same group of instruments under clinical conditions and to correlate their accuracy to radiographic estimates of canal length. Five electronic root canal length measuring instruments were used to measure the working length to the "apex" in 20 single-rooted teeth scheduled for extraction. After extraction, the actual canal length was measured visually to a point just within the apical foramen. This length was compared with instrument length as determined electronically. The accuracy of the instruments in determining canal measurement within +/- 0.5 mm from the apical foramen varied from 55 to 75%. The differences between the instruments were not statistically significant. On average, all of the instruments except for the Endocater gave canal length measurements that were beyond the apical foramen. The variability of the measurements, which was comparable to that of estimates of canal length from preoperative radiographs, indicated that radiographic verification of the working length is still desirable.

Adult↗