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PubMed1989

Use of an electronic apex locator in the treatment of teeth with incomplete root formation.

An electronic apex locator was used to determine length and control apical bridge formation in the treatment of teeth with incomplete root formation. Measurements were taken in 10 teeth in which apexification therapy had just started and in 11 teeth where the formation of the apical barrier was considered to be complete. In the beginning of the apexification therapy, when the apical foramen was still open, endometric measurements gave incorrect results in all instances. After apical closure had occurred and definite obturation of the root canal seemed possible, the apex locator in all teeth gave correct results and complete agreement was obtained between the radiographs and the electronic tests. Even in teeth in which complete apical closure could not be obtained, the results of electronic measurements were correct. Electronic apex locators may be used as auxilliary devices in controlling apical hard tissue closure in the treatment of teeth with incomplete root formation.

Adolescent↗

PubMedDate not supplied

Stress concentrations at the apex of pinned, implanted teeth.

Stress in the alveolus at the apex is reduced when the implant is held by a pin through the alveolar wall. This stress reduction is effected by transfer of part of the coronal force to the alveolar wall by the pin. Pin positions centrally located between the apex and the alveolar crest provide the greatest reduction of stress concentration in the alveolus at the apex. Since the bone is especially fragile near the alveolar crest, care must be taken when the pin is positioned in this region. Positioning the pin near the apex has the least effect on reducing the stress in the alveolus at the apex. Although no data were obtained relating to stress in the alveolar wall at points of pin penetration, results given here do indicate that from 7 to 30% of the intrusion component of the coronal force is transmitted to the alveolar wall by the pin. Additional research is needed to determine the effects of stress at the pin through the alveolar wall because of load transfer by the pin from the implant to the alveolar wall. The situation in the alveolar wall would be one of creation of a completely unnatural stress rather than reduction of an existing stress, as was the case at the apex. Whether the reduction of stress at the apex and the creation of stress at the pin through the alveolar wall are of physiological benefit is a question that must yet be answered.

Alveolar Process↗

PubMed2004

C-shaped canal system in mandibular second molars: Part I--Anatomical features.

The purpose of this study was to investigate the anatomical features of C-shaped root canal system in mandibular second molars using micro-computed tomography (microCT). Fifty-eight extracted mandibular second molars with fused roots were collected from a native Chinese population. The teeth were scanned into layers of 0.5-mm thickness by microCT and measurements were made at eleven levels. The ratio of the depth of the deepest part of the groove to the buccal-lingual thickness of the cross-section of the root was calculated for each tooth. The canal shapes of the scanned cross-sections were assessed and classified according to a modified Melton's method. Results were subject to the Kruskal-Wallis test. Of the 58 molars, 54 had a C-shaped canal system with a mean groove-to-thickness ratio of 47.96%; the four teeth without a C-shaped canal had a mean ratio of 14.82%. Most orifices (98.1%) were found within 3 mm below the cementoenamel junction. Of teeth with a C-shape canal system, a majority demonstrated an orifice with an uninterrupted "C" configuration. Seventeen canals divided in the apical portion, most of which did so within 2 mm from the apex. The cross-sectional shape varied drastically along the length of the canal. Teeth with a high groove-to-thickness ratio had at least one section with C1, C2, or C3 configuration. The canal shape in middle and apical thirds of C-shaped canal systems could not be predicted on the basis of the shape at the orifice level. Section 2 of this paper addressed the correlation between the radiographic appearance and these microCT images.

Anatomy, Cross-Sectional↗

PubMedDate not supplied

Immediate implants after extraction. A review of the current situation.

Immediate implants are positioned in the course of surgical extraction of the tooth to be replaced. The percentage success of such procedures varies among authors from 92.7-98.0%. The main indication of immediate implantation is the replacement of teeth with pathologies not amenable to treatment. Its advantages with respect to delayed implantation include reduced post-extraction alveolar bone resorption, a shortening of the rehabilitation treatment time, and the avoidance of a second surgical intervention. The inconveniences in turn comprise a general requirement for membrane-guided bone regeneration techniques, with the associated risk of exposure and infection, and the need for mucogingival grafts to seal the socket space and/or cover the membranes. The surgical requirements for immediate implantation include extraction with the least trauma possible, preservation of the extraction socket walls and thorough alveolar curettage to eliminate all pathological material. Primary stability is an essential requirement, and is achieved with an implant exceeding the alveolar apex by 3-5 mm, or by placing an implant of greater diameter than the remnant alveolus. Esthetic emergence in the anterior zone is achieved by 1-3 mm sub-crest implantation. Regarding guided regeneration of the alveolar bone, the literature lacks consensus on the use of membranes and the type of filler material required. While primary wound closure is desirable, some authors do not consider it to be of great relevance.

Animals↗

PubMed1989

A diagnostic case involving an incisive canal cyst.

An incisive canal cyst was misdiagnosed as an endodontic lesion. The patient's chief complaint was pain on mastication with increasing intensity for the last 2 days. The single original periapical radiograph revealed a well-circumscribed radiolucency related to the apex of the maxillary right central incisor. The patient was referred with a request for endodontic therapy. A subsequent angled radiograph revealed an interroot location of the lesion, and pulp testing showed a normal response. The patient was then referred for surgical treatment. Following removal of the lesion, the histopathologic examination confirmed the diagnosis of an incisive canal cyst. One-year follow-up showed complete healing and maintained tooth vitality, and the patient was asymptomatic.

Adult↗

PubMed1992

Asymmetry of the root canal foramen.

Deviation of the major apical foramen from the anatomical root apex is a recognized phenomenon. To determine the frequency, position and mean distance of the major apical foramen from the anatomical root apex, 230 roots of permanent teeth were examined stereomicroscopically and radiographically. Radiographic analysis was used to establish how accurate the conventional radiograph was in displaying such a deviation. The frequency of deviation of the major foramen, determined stereomicroscopically, was 76%, and depended on the type of teeth examined. Radiographic analysis of the same sample revealed 57% of root canals had asymmetry of the root canal foramen. Agreement of stereomicroscopic and radiographic findings was found to be 61%. The most frequent deviation of the major foramen was on the distal root surface (29%), but this was not statistically significant. The mean distance between the deviation of the major foramen and the anatomical root apex was 0.99 mm. The study indicates that the clinician should consider deviation of the foramen during root canal treatment, as the deviation could not easily be detected radiographically.

Adolescent↗

PubMed1995

In vitro radiographic representation of the extent of voids within obturated root canals.

The aim of this study was to determine whether radiographs provide an accurate representation of the degree of root canal obturation following a cold lateral condensation technique. A total of 40 extracted single-rooted lower premolar teeth were prepared using either a standardized step-back technique or an ultrasonic device by one of two operators. The four groups each of 10 teeth were obturated using lateral condensation by a third operator. To assess apical leakage the obturated teeth were coated with nail varnish to within 2 mm of the apex and immersed in methylene blue for 48 h. The teeth were then radiographed in bucco-lingual and mesio-distal planes prior to subsequent sectioning in a bucco-lingual plane. Sections and radiographs were analysed using an image analysis apparatus to determine the proportion of root canal occupied by gutta-percha, void and/or sealer. Mean percentages of void calculated from the bucco-lingual radiographs, mesiodistal radiographs and tooth sections were 4.14%, 5.98% and 4.98%, respectively. Statistical analysis showed no significant differences between the radiographic views and the tooth sections (P > 0.05). Both planes of radiograph accurately represented the proportion of void when compared with the tooth section.

Analysis of Variance↗

PubMed1998

[Relapse after endodontic treatment: endodontic retreatment or apex resection?].

In many cases, unsuccessful endodontic treatment is followed by apicoectomy. Endodontic retreatment, however, could be an appropriate alternative for apicoectomy more frequently. In this paper indications, specific problems and treatment methods are presented for endodontic retreatment, apicoectomy and intentional replantation.

Apicoectomy↗

PubMedDate not supplied

Non carious cervical lesions. A review.

Non-carious cervical lesions (NCCL) are characterized by a loss of hard dental tissue near the cement-enamel-junction. Commonly, their shape is like a wedge with the apex pointing inwards. Other times, they appear as regular depressions, like a dome or a cup. Their main characteristic is the presence of hard-mineralized tissue. According to the literature, the prevalence of cervical lesions is 85%, while their incidence is about 18% among permanent teeth. NCCL are currently classified as erosion, abrasion, or abfraction. Their etiology seems to be related to different factors: hexogen and endogen acids, mechanical abrasive action, tooth flexion under axial and non-axial loads. Moreover, it seems that a fundamental role is ascribable to tooth bending phenomena due to the strength components parallel or oblique to the occlusal level, which occur during the normal function as well as during parafunctions. The frequent therapeutic failures are probably due to the same factors causing the onset of the original lesion. Several materials have been proposed to restore NCCL: amalgam (abandoned), glass-ionomer cements, compomers, and composite resins. Early failures of these restorations have often been reported in the literature, probably due to the same factors which originally caused the lesions. Further investigations are required to determine more reliable restorative therapies.

Compomers↗

PubMed1990

[Relationship of caries and periapical lesions in children].

Periapical lesion is an alteration of the bone around the dental apex. We pretended study periapical lesions appear in children's population. We proved a great relation between periapical lesion and carries. Then it was measured stadistically the relationship between both parameters.

Child↗

PubMed1995

Radiography in endodontics.

In endodontics, the paralleling technique has a geometrical advantage over the bisecting angle technique and results in radiographs with less distortion. Distortion is undesirable for endodontic radiography as it can significantly alter the apparent position of an endodontic instrument relative to the root apex. However, there are instances where the bisecting angle is preferable, and consideration should be given to this technique to improve the image quality when it is used.

Dental Pulp Cavity↗

PubMed1996

Unmonitored apexification of wide open apex in nonvital, immature incisor: a case report.

Apexification is the accepted procedure to form an apical stop in nonvital teeth with incomplete root formation. A case is presented in which apexification with calcium hydroxide was performed on erupting maxillary central incisor in 7-year-old female child with immature root (half root) formation and wide open apex. Although it was an induced procedure, but unmonitored. Patient did not return until 18 months after his first visit. Treatment then concluded with gutta percha obturation against firm "cap shaped" apical stop.

Calcium Hydroxide↗

PubMed2005

Damping effects on the response of maxillary incisor subjected to a traumatic impact force: a nonlinear finite element analysis.

OBJECTIVES: The aim of this study was to evaluate the effects of damping on stress concentration in an impacted incisor. METHODS: Damping ratios of maxillary incisors were tested using an in vivo modal testing method. A finite element model of the upper central incisor was established for dental trauma analysis. To assess the effect of damping properties on induced stresses in the traumatized incisors, equivalent stresses in the finite element model with various damping ratios were calculated for comparison. The mechanisms of cushioning properties of the upper incisors on traumatic injuries were assessed by profiling the stress distributions in the incisor model sequentially with time. RESULTS: The measured damping ratio of maxillary incisors was 0.146+/-0.037. When the incisor was subjected to an impact force, high stresses were concentrated at the labial and lingual incisor edges, cervical ridge, and the area around root apex. When the damping ratios of the incisor model were set at 10- and 50-fold of the measured values, the peak stresses induced near the impact site of the incisor model were reduced from 24.0 to 23.2 and 15.9 MPa, respectively. On the other hand, the peak stress lagged and the stress existence period increased when the damping properties were taken into consideration. CONCLUSIONS: Damping properties of teeth provide protection to the tooth during traumatic injury by decreasing the peak stress magnitude due to release of strain energy over a longer period.

Adult↗

PubMed1992

Anatomical relationship of the mandibular canal to its surrounding structures in mature mandibles.

A lack of agreement exists in the literature regarding the anatomical relationship of the mandibular canal to its surrounding structures such as the root apices. The purpose of this investigation was to study the spatial relationship of the mandibular canal to the posterior teeth in dried human mandibles. Twenty-two mature dried mandibles were sectioned through the root apices of the first and second premolars and molars. Second premolars and second molars had the closest distances to the canal with a mean of 4.7 mm and 3.7 mm, respectively. With a mean of 6.9 mm, the apices of the mesial roots of the first molars were farthest from the canal. The canal pathway in mature mandibles followed in S-shaped curve in 31% of the cases. In 41% of the cases it was located lingual (19%), buccal (17%), or directly inferior (5%) to the apices of the posterior teeth. In 28% of the cases the canal could not be identified clearly in the second premolar and first molar regions. In a typical S-shaped configuration the canal was located buccal to the distal root of the second molar, crossed to the lingual below the second molar mesial root, ran lingual to the first molar, and crossed back to the buccal apical to the apex of the second premolar. Based on our results it appears that the mandibular second premolar and second molar are the most likely teeth to be involved in accidental damage to the mandibular canal during root canal therapy.

Bicuspid↗

PubMed1993

[Age-related changes in the pulp chamber and its wall in human canine teeth].

A total of 21 extracted, vital human canines (i.e., 8 maxillary and 13 mandibular) of patients between 40 and 78 years of age has been used to study, by means of X-rays and scanning electron microscopy, the age-related restriction of the pulp chamber and of the root canal, and the structure of its inorganic dentinal walls. This was done at the mesial and distal as well as the vestibular and oral aspects of the pulp chamber walls. In addition, the density of the openings of the dentinal tubules was, under standardized conditions, determined at the coronal part of the pulp chamber, in the middle of the root canal and apically on each of the four aspects of the pulp chamber, i.e. vestibularly, mesially, orally and distally. The results demonstrated that (1) pulp chamber and root canal of both maxillary and mandibular canines, with increasing age of the patients, does not become very much restricted in the vestibulo-oral direction and only very little or patchwise in the mesio-distal direction, (2) fibrodentin that causes such restriction, is deposited in greater amounts only after 60 to 70 years of age, and (3) the density of the tubules is very variable, rather similar in the coronal crown chamber and the middle of the root canal, both mesio-distally and vestibulo-orally, and decreases sharply towards the root apex. These findings are discussed mainly with respect to the age-related changes in the pulp chamber and root canals of human central and lateral incisors.

Adult↗

PubMed1994

Quantitative study of the apical nerve fibers of adult and juvenile rat molars.

The rat molar has become an important model for studies of interactions between nerves and the pulp-dentin complex, yet there is only limited quantitative information on the number and size distribution of axons entering the roots of this tooth. This study was undertaken to provide such a detailed characterization of the apical innervation of the rat molar. An additional objective was to compare the apical nerve composition of young, recently erupted rat molars with that of mature teeth in order to determine whether there is ongoing maturation of the innervation after the teeth have attained functional occlusion. A complete census was made of the nerve fibers entering the roots of both mature and recently erupted juvenile mandibular first molars in Sprague-Dawley rats. Each of the four roots of the first molars was processed for electron microscopy of thin sections near the apex. The majority of intradental nerve fibers entered the molar via the two larger (mesial and distal) roots. Within the apical root pulp, most, but not all, axons occurred within well-defined fascicles associated with blood vessels. Molars from adult animals (age 4 months) had a mean total of 232 (S.D. = 49, N = 7 teeth) myelinated fibers and 806 (S.D. = 143) unmyelinated axons entering the four roots. Fibers exceeding the A delta size range (circumference > or = 19 microns) accounted for only 4% of the myelinated axons at the apex. Molars from juvenile animals (age 4 weeks) had fewer myelinated fibers (mean 176, S.D. 18, N = 8), but more unmyelinated axons (mean 1,174, S.D. 160) than adults. The mean ratio of unmyelinated axons to myelinated axons was 6.6:1 for juveniles compared to 3.5:1 for adults. Juvenile teeth contained no myelinated fibers that exceeded 19 microns in circumference. These results indicate that the innervation of the rat molar resembles that of teeth of non-rodent mammals in that (1) innervation density is high, (2) there is a high ratio of unmyelinated axons, and (3) most of the myelinated fibers are of thin caliber. Furthermore, it appears that after the molar erupts, maturation of the nerve fiber composition continues with processes that include both a marked decrease in the number of unmyelinated axons and an increase in the number and size heterogeneity of myelinated fibers.

Animals↗

PubMed1991

Localization of anatomic structures before endodontic surgery with tomograms. Report of a case.

Tomograms taken before endodontic surgery can demonstrate the location of root apices relative to adjacent anatomic structures. This buccolingual perspective is not depicted on conventional periapical or panoramic radiographs. Accurate length determination from the root apex to the inferior alveolar canal is simplified, and the relationship of root surfaces to the buccal and lingual plates is well visualized on the tomographic images.

Adult↗

PubMed1976

The apical level of root fillings.

The apical level of root fillings made by general practitioners, undergraduate students and an endodontist was compared. In total, 3003 root fillings were grouped morphometrically in three classes. Class A fillings were ending at a distance from the radiographic apex. Class B fillings were ending flush with the radiographic apex or with an overfilling of not more than 1 mm, while class C consisted of fillings with a moderate (1-2 mm) or marked (greater than 2 mm) excess. For 2187 class A fillings the distance from the apical end of the root filling to the radiographic apex was measured to the nearest 0.5 mm. The 531 class B and 285 class C root fillings were given the distance 0.0 mm. A detailed classification of root fillings with regard to their length was then developed by calculating the average distances and standard deviations. A longer apex-distance was observed for root fillings made by the general practitioners than for those made by the undergraduates and the endodontist. Class B and C fillings were infrequently observed among fillings made by general practitioners. Roots from three-rooted teeth had been filled closer to the radiographic apex by the endodontist than by undergraduates. A higher relative number of class C fillings was observed for undergraduates than for the endodontist, while the opposite observation was made for class B cases.

Clinical Competence↗