Anatomy of the root apex and its histologic changes with age

Morphology of the Physiological Foramen: II. Maxillary and Mandibular Premolars

INTRODUCTION

Information concerning the anatomy of the physiological foramen is still limited. The aim of this study was to investigate the distance between the physiological and anatomic apex, the shape and diameter of the physiological foramen in maxillary (Mx) and mandibular premolars (Mn).

METHODS

The anatomy of the apex of 229 maxillary (first: MxP1; second: MxP2) and 221 mandibular premolars (first: MnP1; second: MnP2) from a mixed Swiss-German population was investigated by means of microcomputed tomography and 3-dimensional software imaging.

RESULTS

The following results were obtained in the presence of a main physiological foramen. 1. The distance between the physiological and anatomic foramen was 0.29-0.99 mm (MxP1), 0.21-1.03 mm (MxP2), 0.13-0.8 (MnP1), and 0.15-1.41 (MnP2). 2. The mean narrow and wide diameters of the physiological foramen were 0.19-0.33 mm (MxP1), 0.25-0.42 mm (MxP2), 0.28-0.37 (MnP1), and 0.28-0.40 (MnP2). 3. The most common physiological foramen shape was oval (66.7% MxP1, 89.7% MxP2, 91.8% MnP1, 64.4% MnP2).

CONCLUSION

Considering the recommended preparation sizes based on a size corresponding to the friction, that is at the narrowest point in the area of the apical constriction (physiological foramen), and within the limitations of this ex vivo microcomputed tomography study, a final preparation size could be chosen when considering the pertaining morphologic considerations; yet, to a minimum ISO 30 size.

A literature review of local and systemic considerations for endodontic treatments in older adults

OBJECTIVES

The aim of this literature review was to summarise the clinical important findings on the endodontic treatment outcome in older patients (≥60 years old) with pulpal/periapical disease considering local and systemic factors from a body of knowledge that is heterogeneous in methods or disciplines.

BACKGROUND

Due to the increasing number of older patients in the endodontic practice, and the current trend for tooth preservation, the need for clinicians to have a better understanding of age-related implications that may influence the required endodontic treatment in older adults to retain their natural dentition is indispensable.

METHODS

PubMed/Medline and Embase was searched by a medical librarian using specific terms based on inclusion/exclusion criteria. The reference list was hand-seached for additional relevant publications between 2005-2020. A combination of these terms was performed uing Boolean operators and MeSH terms.

RESULTS

Of the 1577 publications identified manually and electronically, 25 were included to be fully reviewed by the examiners. The data was derived from three systematic reviews, one systematic and meta-analysis, three case series, four prospective and 14 retrospective cohorts. Overall, there was heterogeneity in reporting as well as limitations in most studies.

CONCLUSIONS

The outcome of endodontic treatment (ET) either nonsurgical or surgical or combination of these is not affected by older age. ET can be the treatment of choice in older patients wiht pulpal/periapical disease. There is no evidence that older age per se affects the outcome of any type of endodontic treatment.

The Complexity of the Root Canal Anatomy and Its Influence on Root Canal Debridement in the Apical Region: A Review

The main goal of root canal treatment is to eliminate the infection in the complex root canal system for the long-term preservation of a functional tooth. Proper debridement of the root canal system, especially in the apical portion, is essential for successful root canal treatment. The complexity of the canal anatomy in the apical region plays a crucial role in reducing the microbial load. Therefore, clinicians must have a thorough knowledge of the anatomy of the root canal system and its variations, especially in the apical portion. Root canal configurations in cross-section have been classified as round, oval, long oval, flattened, or irregularly shaped. Treating oval, long oval, flattened, or irregularly shaped canals is challenging and should be approached differently than a circular canal. Recognizing the root canal shape and apical anatomy determines the different strategies to be used in cleaning, shaping, and obturation to achieve the best result of root canal treatment. The recent development of the instrumentation system improves the treatment outcome for clinicians and patients. This review aimed to discuss the definition, prevalence, and instrumentation for cleaning and shaping in the apical area with the complexity of root canal systems. Therefore, with the aid of this review, we can better understand the variations in the anatomy of the root canal, especially at the apical portion.

Morphotypes of the apical constriction of maxillary molars: a micro-computed tomographic evaluation

Objectives

The aim of this study was to evaluate and compare the apical constriction (AC) and apical canal morphology of maxillary first and second molars, using micro-computed tomography (micro-CT).

Materials and Methods

The anatomical features of 313 root canals from 41 maxillary first molars and 57 maxillary second molars of patients with known age and sex were evaluated using micro-CT, with a resolution of 26.7 µm. The factors evaluated were the presence or absence of AC, the morphotypes, bucco-lingual dimension, mesio-distal dimension, and the profile (shape) of AC and the apical root canal. The apical root canal dimensions, location of the apical foramen (AF), AC to AF distance, and presence of accessory canals in the apical 5 mm were also assessed. Descriptive and analytical statistics were used for data evaluation.

Results

AC was present in all 313 root canals. Patients’ age and sex did not significantly impact either AC or the apical canal dimensions. The most common AC morphotype detected was the traditional (single) constriction (52%), followed by the parallel (29%) morphotype. The mean AC dimensions in maxillary first molars were not significantly different from those in maxillary second molars. Sixty percent of AF were located within 0.5 mm from the anatomic apex.

Conclusions

The most common morphotype of AC detected was the traditional constriction. Neither patients’ age nor sex had a significant impact on the dimensions of the AC or the apical root canal. The majority of AF (60%) were located within 0.5 mm from the anatomic apex.

Relation between Apical Seal and Apical Preparation Diameter: An In Vitro Study

Background:

The current recommendations for the apical preparation diameter, one of the most important mechanical imperatives in the apical third preparation, are to preserve the apical foramen in its original position along with its narrowest diameter to avoid any complication such as tearing, zipping, or transport of the foramen. The aim of our study was to see the correlation between apical seal and apical preparation diameter.

Materials and Methods:

In total, 90 extracted maxillary incisors were randomly allocated into three groups of 30 teeth each according to the apical preparation size: Group 1: finishing file F1 corresponding to size 20 reached the working length, Group 2: prepared up to size 30 corresponding to finishing file F3, and Group 3: prepared up to size 50 corresponding to finishing file F5. After the filling of the root canals, the teeth were isolated and immersed in a dye solution, then cut longitudinally, photographed, and the dye penetration were calculated using a computer software.

Results:

Comparison of the three different apical preparation sizes showed no statistically significant differences regarding the apical microleakage.

Conclusion:

The most important value of the dye penetration was observed in the group with the largest apical diameter.

Root Canal Anatomy of Myanmar Permanent Mandibular Incisors in Mandalay Region

Introduction

Incomplete understanding of the root canal system leads to endodontic failure. Missed canal was the fourth most common endodontic failure, which needed retreatment. There were a few studies on internal morphology of posterior teeth of Myanmar population. However, there was no report on root canal anatomy of anterior teeth. So, the aim of the in vitro study was to investigate root canal anatomy of Myanmar permanent mandibular incisors in Mandalay Region by the staining and clearing method.

Materials and Methods

A total of 96 teeth from the tertiary hospitals and one academic department in Mandalay Region were selected according to inclusion and exclusion criteria. Then, they were cleaned, drilled, stained with Indian ink, and decalcified with 5% nitric acid for 3 days. After that, they were dehydrated with ascending concentration of ethanol (80% overnight, 90% for 1 hour, and full strength for three hours). Finally, they were clarified with 98% methyl salicylate and investigated by calibrated observer in case of Vertucci's classification, allocation of apical foramen, and the detailed anatomy.

Result

Almost 70% of the teeth had type Ι followed by 21.8% type ΙΙΙ, 4% 1-2-1-2-1 and type ΙΙ, and 1-3-2 and 2-3-1 comprised 1% each. Nearly 70% of apical foramen at central allocation of the root and 14% of detailed anatomy were seen in the sample teeth.

Conclusion

Most of the sampled Myanmar teeth comprised one canal and one foramen followed by type ΙΙΙ. However, unusual anatomies, such as 1-2-1-2-1, 1-3-2, and 2-3-1, were also seen. Contrastively, proportions of central location of apical foramen and of detailed anatomy were differed from the former reports. This study summarized that 3 in 10 mandibular incisors comprised the evidence of second or third canal configuration. Three types of intercanal calcifications, fusiform, islet, and bead, were additionally explored.

Three-dimensional analysis of the physiological foramen geometry of maxillary and mandibular molars by means of micro-CT

The aim of this study was to investigate the physiological foramen diameter, shape and distance between physiological and anatomical apex of maxillary and mandibular first and second molars. Accurate knowledge of the physiological foramina morphology; thus, inherent mechanical shaping technical hindrances, is decisive when taking the corresponding root canal final preparation decision. The morphological dimensions of a total of 1727 physiological foramina were investigated by means of micro-computed tomography. Mean narrow and wide (to a high number, oval) diameters of the physiological foramen were 0.24, 0.22 and 0.33 mm and 0.33, 0.31 and 0.42 mm in mesiobuccal (MB), distobuccal (DB) and palatal (P) roots in maxillary first molars; 0.24, 0.22 and 0.33 mm and 0.41, 0.33 and 0.44 in MB, DB, and P roots in maxillary second molars. Mandibular first molars showed mean narrow and wide diameters of 0.24 and 0.30 mm and of 0.39 and 0.46 mm in mesial (M) and distal (D) roots; second mandibular molars showed 0.25 and 0.31 mm and 0.47 mm in M and D roots. The mean distance between the physiological foramina and anatomical apex was 0.82, 0.81 and 1.02 mm and 0.54, 0.43 and 0.63 mm in MB, DB and P roots of the maxillary first and second molars, respectively. A mean distance of 0.95 mm (M) and 1.05 mm (D) in the first and 0.78 mm (M) and 0.81 mm (D) in the second mandibular molars was observed. Based on the results obtained, assumable recommendations for final preparation size of the physiological foramen were calculated. However, when taking into consideration, the resulting standard deviations of marginal errors must be cautiously considered when taking a final decision in clinical endodontic treatment.

Controversies in Endodontics

Diseases of the dental pulp often have an infectious origin, and treatments are aimed to control infections of the root canal system. Endodontic treatment principles originally evolved on the basis of trial and error, and only in recent decades have scientific methods been adopted to support clinical strategies. Yet, relevant research on the disease processes, their diagnoses, and efficient treatment are rare in the endodontic literature. Hence, the advancement of biologically based knowledge significant to clinical endodontics has been slow. Therefore, many differences of opinion still prevail in this field of dentistry. This review highlights and analyzes the background of some of the more heavily debated issues in recent years. Specifically, it deals with disagreements regarding the clinical management of pulpal exposures by caries in the adult dentition, definitions of success and failure of endodontic therapy, and causes of and measures to control infections of the root canal system. Clearly, a most apparent gap in the published endodontic literature is the lack of randomized clinical trials that address the more significant controversial matters relating to the management of pulpal wounds, medication, and the number of appointments required for the treatment of infected root canals. However, trials in endodontics require extremely long follow-up periods if valid conclusions are to be generated. Therefore, it is not to be expected that there will be rapid solutions to these issues in the foreseeable future.

Cementum as an age determinant: A forensic view

CONTEXT

Forensic age estimation (FAE) defines an expertise in forensic medicine, which aims to define in the most accurate way to determine the unknown chronological age of the person involved in judicial or legal proceedings. Dental cementum is a vital tissue which demonstrates continuous apposition throughout the life of the tooth. This appositional changes of cementum helps in approximation of age inforensic investigations.

AIMS

To correlate age by measuring the overlap or coronal migration of thecementum at thecementoenamel junction (CEJ) and the thickness of the cementum at the apical third of the root.

SETTINGS AND DESIGN

A hundred freshly extracted teethfrom patients ranging from ages 17-55were longitudinal buccolingually ground sectioned using a mounted lathe wheel and Arkansas stone.

MATERIALS AND METHODS

100 freshly extracted teeth of age group ranging from 17-55 years were taken. These teeth were longitudinally ground sectioned to a thickness of 8-10μm using a mounted lathe wheel and Arkansas stone. Afterwards the teeth were examined under a light microscope using a micrometer eyepiece for measuring the overlap or coronal migration of the cementum at the CEJ and the thickness of the cementum at the apical one-third of root.

STATISTICAL ANALYSIS

Measurements of the overlap or the coronal migration of the cementum at the CEJ and the thickness of the cementum at the apical one-third of the root are correlated with age.

RESULTS

Results of the study indicated that the cementum at the CEJ migrated coronally during theaging process in case of the impacted teeth. There is also a significant increase in the thickness of the cementum at the apical onethird of rootin the case of both the impacted and erupted teeth.

CONCLUSION

Approximation of age by measuring overlap or coronal migration of the cementum at the CEJ and the thickness of the cementum at the apical one-third of the rootsets new alleys in FAE.

Micro-Computed Tomography Analysis of the Root Canal Morphology of Palatal Roots of Maxillary First Molars

INTRODUCTION

A thorough knowledge of root canal anatomy is critical for successful root canal treatments. This study evaluated the internal anatomy of the palatal roots of maxillary first molars with micro-computed tomography (microCT).

METHODS

The palatal roots of extracted maxillary first molars (n = 169) were scanned with microCT to determine several anatomic parameters, including main canal classification, lateral canal occurrence and location, degree of curvature, main foramen position, apical constriction presence, diameters 1 and 2 mm from the apex and 1 mm from the foramen, minor dentin thickness in those regions, canal volume, surface area, and convexity.

RESULTS

All canals were classified as Vertucci type I. The cross sections were oval in 61% of the canals. Lateral canals were found in 25% of the samples. The main foramen did not coincide with the root apex in 95% of the cases. Only 8% of the canals were classified as straight. Apical constriction was identified in 38% of the roots. The minor and major canal diameters and minor dentin thickness were decreased near the apex. The minor dentin thickness 1 mm from the foramen was 0.82 mm. The palatal canals exhibited a volume of 6.91 mm(3) and surface area of 55.31 mm(2) and were rod-shaped.

CONCLUSIONS

The root canals of the palatal roots were classified as type I. However, some factors need to be considered during the treatment of these roots, including the frequent ocurrence of moderate/severe curvatures, oval-shaped cross-sections, and lateral canals, noncoincidence of the apical foramen with the root apex, and absence of apical constriction in most cases.

Endodontics and the ageing patient

Patients are living longer and the rate of edentulism is decreasing. Endodontic treatment is an essential part of maintaining the health and well-being of the elderly. Retention of natural teeth improves the quality of life and the overall health and longevity of ageing patients. Also, teeth that might be otherwise extracted may be strategically valuable to retain a prosthesis, and elderly patients are more likely to have medical complications that may prevent dental extractions from being safely performed. The technical goals of endodontic treatment in the elderly are the same as those for younger patients. However, the pulpo-dentinal complex undergoes calcific changes over time, which may pose challenges for the clinician. The purposes of this review are to discuss age changes in the pulp and the challenges posed by diagnosing, treatment planning and treating the elderly endodontic patient.

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

PURPOSE

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.

METHODS

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.

RESULTS/CONCLUSIONS

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.

Accuracy of working length determination using 3 electronic apex locators and direct digital radiography

OBJECTIVES

The objectives of this study were to assess the accuracy of working length determination using 3 electronic apex locators and direct digital radiography and to compare the results with those obtained using the visual method (control measurement).

STUDY DESIGN

Twenty extracted human maxillary premolars were selected: 17 two-rooted and 3 single-rooted (total of 37 canals). Working length was measured using electronic apex locators Elements Diagnostic, Root ZX, and Just II. Subsequently, teeth were positioned in the alveolar bone of a dry skull and submitted to direct digital radiography. A variation of ±1 mm was considered as acceptable. Results were analyzed using the Wilcoxon and the χ(2) tests.

RESULTS

Results presented an accuracy of 94.6% for Elements Diagnostic, 91.9% for Root ZX, 73.0% for Just II, and 64.9% for direct digital radiography when considering the margin of ±1 mm in relation to the control measurement. Comparisons with the actual control measurements resulted in accuracy results of 13.51%, 13.51%, 10.10%, and 2.70%, respectively.

CONCLUSIONS

Root ZX and Elements Diagnostic are more accurate in determining working length when compared with Just II and Schick direct digital radiography.

Age-related changes in crown and root length in Sri Lankan Sinhalese

Exploration of the relationship between tooth dimensions, body size, and age is important in paleontology, forensic odontology and aesthetic dentistry. It is reasonable to speculate that tooth length is associated with stature since teeth contribute to facial height. This study aimed to determine whether there was an association between tooth length and stature and age in a sample of Sri Lankan Sinhalese. Extracted teeth of adults, whose age, sex and standing height were known, were used for measurements. The total tooth length (TTL), crown length (CL) and root length (RL) of permanent maxillary central (68) and lateral (67) incisors were measured using a caliper. Statistical analyses were performed with the software MINITAB version 14.0 (Minitab Inc, USA). Mean age and standing height were 47.81 yr and 152.15 cm, respectively. There was no significant correlation between stature and tooth lengths of incisors. However, age was found to have a significant correlation with RL, (r = 0.26, P < 0.05) and CL (r = -0.28, P < 0.05). Absence of an association between tooth length and stature indicated that the genetic linkage between tooth size and stature was weak, suggesting that determination of stature from tooth lengths is unwarranted. The association between tooth length and age indicates the importance of root length in age determination.

The fundamental operating principles of electronic root canal length measurement devices

It is generally accepted that root canal treatment procedures should be confined within the root canal system. To achieve this objective the canal terminus must be detected accurately during canal preparation and precise control of working length during the process must be maintained. Several techniques have been used for determining the apical canal terminus including electronic methods. However, the fundamental electronic operating principles and classification of the electronic devices used in this method are often unknown and a matter of controversy. The basic assumption with all electronic length measuring devices is that human tissues have certain characteristics that can be modelled by a combination of electrical components. Therefore, by measuring the electrical properties of the model, such as resistance and impedance, it should be possible to detect the canal terminus. The root canal system is surrounded by dentine and cementum that are insulators to electrical current. At the minor apical foramen, however, there is a small hole in which conductive materials within the canal space (tissue, fluid) are electrically connected to the periodontal ligament that is itself a conductor of electric current. Thus, dentine, along with tissue and fluid inside the canal, forms a resistor, the value of which depends on their dimensions, and their inherent resistivity. When an endodontic file penetrates inside the canal and approaches the minor apical foramen, the resistance between the endodontic file and the foramen decreases, because the effective length of the resistive material (dentine, tissue, fluid) decreases. As well as resistive properties, the structure of the tooth root has capacitive characteristics. Therefore, various electronic methods have been developed that use a variety of other principles to detect the canal terminus. Whilst the simplest devices measure resistance, other devices measure impedance using either high frequency, two frequencies, or multiple frequencies. In addition, some systems use low frequency oscillation and/or a voltage gradient method to detect the canal terminus. The aim of this review was to clarify the fundamental operating principles of the different types of electronic systems that claim to measure canal length.

Evaluation of the accuracy of three electronic apex locators using glass tubules

AIM

To evaluate the accuracy of three different electronic apex locators (EALs) using glass tubules.

METHODOLOGY

Forty-eight glass tubules with different diameters and an agar model were used to mimic root canals. A size 15 stainless steel K-file was used as the measuring electrode. The Root ZX, Propex and Neosono Ultima EZ were used to measure the tubule length with tubules dry, or filled with 0.9% NaCl, 3% H(2)O(2), 2.5% NaOCl or 17% EDTA. The distance between the real length (RL) and measured length (ML) of the tubules was recorded. The range of RL +/- 0.5 mm and RL +/- 1 mm was used to evaluate the accuracy of the EALs. Results were subject to correlation analysis and Friedman's test.

RESULTS

In dry tubules, the accuracy of Root ZX was 75-91.7% for RL +/- 0.5 mm and 100% for RL +/- 1 mm, whilst the measurements of the other two EALs were all within the RL +/- 0.5 mm. No influence from the increase in tubule diameter on the accuracy of all three EALs was observed in dry tubules. In tubules filled with electrolyte, the accuracy of the Root ZX decreased as tubule diameter increased (R(d) > 0, P < 0.05). The RL-ML distance recorded by Propex was inversely related to the tubule diameter (R(d) < 0, P < 0.05). The accuracy of Propex was 75-100% for RL +/- 0.5 mm and 100% for RL +/- 0.5 mm when the tubule diameter was not more than 0.80 mm, but decreased in tubules with diameter over 0.80 mm and filled with 2.5% NaOCl or 17% EDTA. Nearly, all the measurements (except for six tubules) using Neosono Ultima EZ were within 1 mm shorter than RL despite the contents in tubules and the increase of tubule diameter.

CONCLUSIONS

The accuracy of the Root ZX decreased as the tubule diameter increased when tubules were filled with electrolytes. The electrolytes in the tubules decreased the accuracy of Propex when the tubule diameter was large. The electrolytes in tubules and tubule diameter had no influence on the accuracy of Neosono Ultima EZ. The Propex and Neosono Ultima EZ were more accurate than the Root ZX under various conditions in this laboratory study.

An Evaluation of Root ZX and Elements Diagnostic Apex Locators

The purpose of this study was to compare the accuracy of the Root ZX and Elements Diagnostic electronic apex locators under clinical conditions. Thirty-six teeth planned for extraction were used. Each tooth was decoronated, coronally flared with Orifice Shapers, and irrigated with 2.6% sodium hypochlorite. Working lengths were measured with K-files using both electronic apex locators. The files were cemented at the last measured working length and the teeth were extracted. The apical 4-mm of each canal were exposed and photographed under 15x and 30x magnification. Images of each apex were projected and the distance from the file tip to the minor diameter was determined. The mean distances from the file tip to the minor diameter were 0.346 mm for the Elements Diagnostic and 0.410-mm for the Root ZX beyond the minor constriction. In locating the minor constriction the Root ZX was accurate 75% of the time to +/-0.5 mm, 83.3% +/-0.75 mm, and 88.9% to +/-1 mm. The Elements Diagnostic was accurate 75% of the time to +/-0.5 mm, 88.9% to +/-0.75 mm, and 91.7% to +/-1 mm. There was no statistically significant difference between the accuracy of the two electronic apex locators in locating the minor diameter (p < 0.05).

Remaining Dentin Thickness in the Apical 4 mm Following Four Cleaning and Shaping Techniques

The aim of this study was to determine the remaining dentin thickness (RDT) in the apical 4 mm following four cleaning and shaping techniques. Sixty human adult extracted mandibular incisors and 60 mesial buccal canals of mandibular molars were assigned to five groups of 12 teeth for each tooth type: Step-down stainless steel hand instrumentation, Lightspeed, Profile GT and 0.4 taper, K3 "g pack," control group. After instrumentation the teeth were sectioned at 0.5, 1.5, 2.5, and 3.5 mm short of working length (WL) and evaluated for the minimum RDT at each level. ANOVA of RDT showed significant differences among levels and techniques. For incisors, no technique yielded greater RDT than the other techniques (p < 0.0001). For molars, K3 had greater RDT than the other techniques (p = 0.0006) at the 1.5, 2.5, and 3.5 mm levels. While there were significant statistical differences in RDT among techniques at different levels, further study would be required to determine any significant clinical difference in RDT.

The Role of Apical Instrumentation in Root Canal Treatment: A Review of the Literature

The issue of final apical preparation size remains controversial despite considerable clinical and in vitro research. The astute clinician must be aware of this research before choosing any instrumentation system because the informed clinician's decision must be guided by the best available evidenced-based information. This review article generated a Medline-based search strategy to disclose these studies and provides a critique and summary of the results.

Electronic apex locators

Prior to root canal treatment at least one undistorted radiograph is required to assess canal morphology. The apical extent of instrumentation and the final root filling have a role in treatment success, and are primarily determined radiographically. Electronic apex locators reduce the number of radiographs required and assist where radiographic methods create difficulty. They may also indicate cases where the apical foramen is some distance from the radiographic apex. Other roles include the detection of root canal perforation. A review of the literature focussed first on the subject of electronic apex location. A second review used the names of apex location devices. From the combined searches, 113 pertinent articles in English were found. This paper reviews the development, action, use and types of electronic apex locators.

Morphology of the Physiological Foramen: I. Maxillary and Mandibular Molars

Information concerning the anatomy of the physiological foramen is limited. The aim of this study was to investigate the distance between the physiological and anatomical apex, accessory foramina frequency, and the shape and diameter of the physiological foramen in maxillary and mandibular molars. The apical anatomy of 523 maxillary and 574 mandibular molars from an Egyptian population was investigated by means of a computer-aided stereomicroscope (40 x magnification). The following results were obtained:

Human teeth with periapical pathosis after overinstrumentation and overfilling of the root canals: a scanning electron microscopic study

AIM

The aim of this study was to determine whether overinstrumentation followed by immediate overfilling could be a potential risk in the treatment of infected root canals.

METHODOLOGY

Thirty-five human teeth with infected root canals were overinstrumented and overfilled approximately 45 min after their extraction. The experimental teeth were enlarged up to size 40 and the overinstrumentation and overfilling were checked with the aid of a magnifying glass. The specimens were fixed in glutaraldehyde plus sodium cacodylate solution and prepared for scanning electron microscope examination.

RESULTS

Bacteria were detected on the flute of the files and mostly at the root apices around the main foramen, remaining firmly attached to resorptive lacunae despite the fact that the apices had undergone great changes, including fracture or zipping. A control group consisting of 10 human teeth root canals containing vital pulps were also overinstrumented and overfilled. No bacteria were detected on the flutes of the files, at the apices or on the extruded master cone overfilling these samples.

CONCLUSIONS

The high percentage of bacteria adhering to the resorptive lacunae or in the flutes of files used in overinstrumented human teeth with infected root canals carry a potential risk for postoperative pain, clinical discomfort and flare-ups. The hazards observed in these circumstances do not support the one-visit treatment of teeth having acute or chronic periapical abscesses.

Coronal displacement of cementum: correlation between age and coronal movement of cementum in impacted teeth

This study was conducted on 48 impacted and 51 erupted maxillary permanent canine teeth extracted from healthy patients aged 13-73 years. Longitudinal buccolingual ground sections were prepared. The distance between the edges of cementum and enamel in each specimen was measured with an eyepiece micrometer. A correlation test was applied between age and the distance between enamel and cementum measurements. In impacted teeth, depending on age, cementum had a tendency to overlap the enamel; there was a linear correlation between age and coronal displacement of cementum (n-2 = 46, r = 0.69, distance (microgram) = 21.7* age (years) -440, p < 0.001). No correlation between age and coronal displacement was found in erupted teeth (n-2 = 49, r = -0.23, p > 0.05). Results of the study indicated that the cementum in impacted teeth migrated coronally during the ageing process. This may be related to continually erupting forces which affect the impacted teeth and may be a mechanism by which the teeth are protected at the cemento-enamel junction (CEJ). This phenomenon could be used in forensic dentistry to determine age. The absence of correlation in erupted teeth could be attributed to the masking effects of extrinsic factors.

Progressive changes in the pulpo-dentinal complex and their clinical consequences

With changes in the age structure and oral health in the population, changes in the pulpo-dentinal complex are becoming more relevant clinically. Age-related changes in the structure of dentine and pulp are reviewed. The influence of these changes on restorative dentistry are considered with particular emphasis on endodontics and the use of adhesive restorative materials.

Apical foraminal openings in human teeth. Number and location

One hundred forty extracted permanent human teeth were prepared for examination with a scanning electron microscope to determine the number of foramina, their distances from the apices, and their locations. In most of the specimens, the root canals deviated to one side and ended short of the apices. Some specimens showed interradicular openings; others had configurations on the top of the apices that were similar to the crest on a helmet.

Pararadicular cementum deposition as a criterion for age estimation in human beings

The purpose of this article is to ascertain if pararadicular cementum can be used as a reliable criterion for age estimation in human beings. Fifty-two nonrestorable teeth were extracted from 42 patients at the Veterans Administration Medical Center at Ann Arbor, Mich. The specimens were prepared to a thickness of 500 microns with a Buehler Isomet bone saw (Bronwell Scientific, Inc., Rochester, N.Y.). Longitudinal sections were cleaned of artifacts in an ultrasonic cleaner and stained with 1% alizarin red. Photomicrographs were taken of each prepared section. The cementum was composed of multiple light and dark bands that were counted on the photograph and added to the average eruption time of the individual tooth. There was an overall Pearson's product-moment correlation coefficient of r = 0.93 between the patient's predicted age with the use of cementum annulations as compared with the actual chronologic age of the person. Predicted age counts showed greater divergence from actual age in persons older than 55 years. A formula is presented to adjust for this discrepancy. The data indicate that quantitation of cementum annuli is a moderately reliable means for age estimation in humans.