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PubMed1989

Proximal bone loss adjacent to periodontally "hopeless" teeth with and without extraction.

Extraction of teeth with severe attachment loss ("hopeless" teeth) is common practice in the dental office. Recent evidence questions the validity of this approach. The purpose of the present study was to examine the alveolar bone changes adjacent to "hopeless" teeth with and without extraction. A total of 145 teeth from 129 patients were included in this retrospective study. Teeth were defined as "hopeless" when Class III furcation involvement was present, or when alveolar bone loss exceeded 50%. Patients were pooled into two groups: A, 82 "hopeless" teeth (71 patients) that were retained throughout the experimental period, and B, 63 "hopeless" teeth (58 patients) that were extracted. The average observation period was 4 years with a minimum of 2 years. Alveolar bone changes were measured as a percentage of the anatomic root (radiographic apex-CEJ) using a Schei ruler. Results revealed significantly greater bone loss adjacent to teeth flanking retained "hopeless" teeth, 3.12% per year, at a rate 10 times that of the 0.23% annual bone loss in teeth flanking "hopeless" teeth that were extracted (P less than 0.0001). This study confirms that without periodontal treatment, the retention of teeth with severe periodontal breakdown has a negative effect on the adjacent teeth.

Bone Resorption↗
PubMed1989

[The finite element analysis of the bicuspid and molar of mandible].

Recently, the finite element method has been adopted in the study of tooth structure as well as the stress distribution of dental prosthesis. In order to understand the loading state of the supporting tissues and the stress distribution of the teeth in various shapes under the pressure of loading, the author of this essay has applied the two-dimensional finite element method to the study of the stress distribution of the periodontal supporting tissues at the time when the second bicuspid and the second molar are vertically and obliquely loaded. Finally, the results of the quantitative analysis are obtained and a curve of the stress distribution of the teeth is also drawn up. The conclusion is as follows: 1. When the vertical loading is applied to the occlusal surface of the bicuspid and molar, the stress distribution of periodontal supporting tissues is uniform. 2. The stress concentration is on the marginal ridge and thedistal apex of bicuspid under the oblique loading. 3. When the oblique loading is applied to the occlusal surface of the molar, the stress concentration is only on the marginal ridge, and it is small.

Alveolar Process↗
PubMed1993

The use of E-speed film for root canal length determination.

This study compared the use of D-speed and E-speed dental X-ray film for assessing the working length of root canals. Root canal files of varying size (ISO 06, 08, 10 and 15) were placed in the root canals of a maxillary molar and a mandibular molar in a dried skull and mandible. Files were set at various lengths relative to the radiographic apex. The X-ray projections were kept constant. Exposure settings for the two film types that gave comparable radiographic density were selected. Films were developed manually under standardized conditions. A total of 48 films of each type were examined at various magnifications by four trained examiners for the estimation of distance between the file tip and radiographic apex. There were no differences between examiners in estimating working length. The effect of file size, root and magnification were also not significant. The differences between the film types were not significant (P > 0.05). It is concluded that clinicians should use E-speed film instead of D-speed film for root canal length measurement, because the exposure time was reduced by over 40% but the quality of the radiographic image was not significantly different.

Dental Pulp Cavity↗
PubMed1984

Apical root anatomy of impacted maxillary canines. A clinical and radiographic study.

When planning autotransplantation of impacted maxillary canines, it is advantageous to know not only the position but also the root anatomy. Radiographic and clinical findings on the root anatomy of 65 impacted maxillary canines were compared. The apices were judged as straight or deflected. The positions of the canines were also recorded. Twenty-eight canines (43%) had a straight and 37 (57%) a deflected apex. The radiographic diagnosis was confirmed in 49 canines, which means a diagnostic accuracy of 75%. The misinterpretation, consisting of seven false-positive and nine false-negative diagnoses, was due to insufficient radiographic examination (7 canines), observation errors (7 canines), and limitations of radiographic examination (2 canines). No association was found between the root anatomy and position. The results show than an optimal radiographic examination and knowledge of any apical deflection are valuable aids to operative assessment of impacted maxillary canines.

Adolescent↗
PubMed1992

Sealing ability of two intermediate restorative materials in bleached teeth.

This study compared the radicular penetration of bleaching agents in endodontically treated teeth containing an IRM base, a Cavit base, and no base. Forty-five extracted human maxillary central incisors treated with conventional endodontic therapy with laterally condensed gutta percha and sealer were randomly divided into three groups: (1) Cavit base, (2) IRM base and (3) no base. In groups 1 and 2, a 3.5 mm thickness of base material was placed at the time of obturation. After storage in saline for 1 week, the teeth were bleached with a mixture of 35% hydrogen peroxide and sodium perborate, combined with a 10% methylene blue dye solution, using a combination thermocatalytic and non-thermocatalytic bleaching technique. The apical distance of dye penetration was measured. The control group demonstrated dye penetration to the apex, indicating that a base is required to prevent leakage of bleaching agents when this combination of bleaching techniques is used. The mean distance of leakage was 3.43 mm (+/- 1.14) for the Cavit group and 5.94 mm (+/- 1.72) for the IRM group. Analysis with a t-test revealed that Cavit was a more effective barrier to leakage than IRM (T = 4.20, P less than 0.001).

Borates↗
PubMed1994

An in vivo comparative study of two apex locators.

Two different electronic apex locators were used before extraction to determine working length in 116 root canals belonging to 34 molars. The results were then compared with postextraction working length measurements. The determinations were made before and after eliminating the canal contents and drying the interior. The results showed that 84.8% and 79.3% of the Odometer, and 89.6% and 88.7% of the Endocater readings for dry and nondry canals, respectively, occurred within the two 0.5-mm intervals closest to the apical constriction.

Dental Pulp Cavity↗
PubMed2000

The retraction of upper incisors with the PG retraction system.

The aim of this study was to evaluate the effect on the dentoalveolar structures of the application of PG springs for retraction of upper incisors and to compare the outcome with the effect of a closed coil spring retraction system. Thirty-six subjects with Angle Class I or Class II malocclusions were selected for the study. Each subject had the two upper first premolars extracted and presented a symmetrical extraction space of at least 3 mm distal to the lateral incisors after canine retraction. The subjects were divided into two groups, the PG group with 17 subjects and the coil group with 19 patients. One group had the incisors retracted by PG universal retraction springs, whereas in the other a closed coil spring system was used. The average chronological ages were 18 years 4 months for the PG group, and 18 years 7 months for the coil group. In both groups the springs were activated to produce an initial force of 150 g per side. To examine the type of movement of the anterior and posterior teeth, and the time and rate of space closure, 20 parameters were measured and evaluated statistically with Wilcoxon and Mann-Whitney U-tests. In both groups the incisor retraction was accompanied by mesial movement of the buccal segments. Distal movement of the root apex of the incisors was observed in both groups, although more pronounced in the PG group (P < 0.01). A significant incisor intrusion resulting in a decrease in overbite was found in the PG group, whereas the deep bite increased significantly in the coil spring group. The PG spring produced a three-dimensional control in the movement of the upper incisors, so that application of additional intrusive mechanics after completion of the incisor retraction became unnecessary.

Adolescent↗
PubMed1987

The calcifying potential of the pulpless open apex in untreated teeth of dogs.

Pulpectomies were performed on 22 immature premolars (44 root canals) from 3 young dogs. The root canals remained unfilled and the access cavities were sealed with amalgam. After observation periods of 7, 15 and 45 days, the apical and periapical regions of the teeth were evaluated histopathologically. Hard tissue formation was found in 32 open apices. The apical calcification occurred only in specimens with intracanal vital tissue. The severity of periapical inflammatory response had no relationship to the presence or absence of apical hard tissue formation. No apical bridging was seen in specimens where epithelial proliferation had occurred.

Animals↗
PubMed1987

An evaluation of xeroradiographs and radiographs in length determination in endodontics.

Twelve block sections of mandibles containing incisors, canines, premolars, and molars were dissected from human cadavers (total, 26 teeth). Endodontic access was achieved, and a No. 10 k-type endodontic file was inserted to a point approximately 1 to 2 mm short of the radiographic apex. By securing the mandible and Rinn instrument with plaster mounts, exposures were made from identical angles and film and jaw placement remained constant in both techniques. Conventional film images were recorded on Kodak Ultraspeed film with six to eight impulses. Xeroradiographic images were recorded with four to five impulses. Radiographs and xeroradiographs were evaluated with the use of light from a masked viewbox. A magnifying glass was used to evaluate visualization of the following entities: the root apex; the periodontal ligament; the trabecular pattern; and the measuring instruments. The images were examined and categorized by three examiners, who used the following scores: 3, optimal for diagnostic information; 2, adequate for diagnostic information; 1, poor but providing diagnostic information; and 0, unacceptably poor. In all categories examined, the information provided by xeroradiographs was significantly greater than that provided by conventional radiographs (p less than .05). In terms of diagnostic value and lower patient dose, xeroradiographs are preferred to conventional radiographs.

Dental Pulp Cavity↗
PubMed1993

Human cellular mixed stratified cementum: a tissue with alternating layers of acellular extrinsic- and cellular intrinsic fiber cementum.

Following the first description of the formal genesis of acellular extrinsic- and cellular intrinsic fiber cementum on growing human teeth, the present paper introduces cellular mixed stratified cementum as a particular tissue. Based on a large and diverse material (human premolars and molars) that was examined by various methods, such as microradiography, light microscopy using transmitted and polarized light, and scanning- and transmission-electron microscopy, the composition and structure of this type of cementum is described. Cellular mixed stratified cementum covers the apex, the apical third of the roots or more, and the furcational aspects of human teeth. With all methods employed, it was shown that this tissue consists in principle of acellular extrinsic- and cellular intrinsic fiber cementum, i.e. two major types of cementum that alternate or are in irregular sequences deposited upon one another. The dynamics of this layering and the fact, that, temporarily, root surfaces may remain unsupported by Sharpey's fibers as a consequence of this layering, are discussed.

Adolescent↗
PubMed1983

Fine structure of the horny teeth of the lamprey, Entosphenus japonicus.

The fine structure of the horny teeth of the lamprey, Entosphenus japonicus, was examined by light- and electron-microscopy. Most of the horny teeth consisted of two horny and two nonhorny layers. The primary horny layer was well keratinized, and the cells were closely packed and intensely interdigitated, being joined together by many modified desmosomes. The plasma membrane of the horny cell, unlike the membranes of other vertebrates, was not thickened. The intercellular spaces were filled with electron-dense material. Microridges were seen on the free surface. Structures resembling microridges were found on the underside of the primary horny layer. The secondary horny layer displayed various stages of keratinization. The keratinization started at the apex and developed toward the base. In the early stage of keratinization, the superficial cells became cylindrical and were arranged in a row forming a dome-shaped line. Their nuclei were situated in the basal part of the cells. The appearance of the nonhorny layers varied according to the degree of keratinization of the horny layers beneath them. The nonhorny cells were joined together by many desmosomes and possessed many tonofilament bundles. The replacement and keratinization of the horny teeth are discussed in the light of these results.

Animals↗
PubMed1990

Periapical bacterial plaque in teeth refractory to endodontic treatment.

It has recently been found that bacteria are able to survive and maintain an infectious disease process in periapical lesions of nonvital teeth. The purpose of this study was to examine the surfaces of root tips removed during surgical-endodontic treatment for the presence of microorganisms. A full thickness flap was reflected under strict surgical asepsis and the periapical lesions were enucleated and removed. About 2-3 mm of the root was cut off, rinsed in sterile saline and placed in 10% neutral-buffered formalin. Upon fixation, the root tips were dehydrated, air-dried and given an electrically conducting coat of gold in a vacuum evaporator. The root tips were then studied in a Jeol, JSM-U3 scanning electron microscope, usually operated at 20 kV. The root surfaces were covered with soft tissue, except at the apex of the roots, where a continuous, smooth and structureless coating was seen, apparently adjacent to the apical foramen. At higher magnification a variety of bacterial forms were recognized in the smooth coating. A bacterial plaque was observed in irregularities of the surfaces between fiber bundles and cells and in crypts and holes. The bacteria were held together by an extracellular material and the plaque was dominated by cocci and rods. Fibrillar forms were recognized as well, often with cocci attached to their surfaces.

Bacteria↗
PubMed2000

Severe gingival recession in trisomy 18 primary dentition. A clinicopathologic case report of self-inflicted injury associated with mental retardation.

This clinicopathologic case report documents severe gingival recession in the primary dentition of a trisomy 18 patient. Primary molar and canine teeth exhibited recession extending beyond the midpoint of the buccal aspect of the root, occasionally reaching the root apex. Radiographic examination revealed taurodontism in both primary and permanent teeth. Clinical and histopathologic findings, along with case history, eliminated the possibility of prepubertal periodontitis and suggested a diagnosis of self-inflicted injury associated with mental retardation. Histologic examination of the primary teeth revealed normal cementum and dentin structure. Taurodontism, histologic structure of the dentition, and severe attachment loss in the primary dentition have not been described previously in trisomy 18.

Abnormalities, Multiple↗
PubMed1993

Adaptation of thermafil components to canal walls.

The desired result of the Thermafil system is described as a centered carrier encased by gutta-percha in apposition to the canal walls. This study examined, in curved canals, the intracanal relationships of: (a) the metal carrier; (b) the surrounding gutta-percha; and (c) the sealer. Following the manufacturer's recommended techniques, 20 resin blocks that had canals prepared with conservative flaring were obturated. Cross-sections were made in the cervical, middle, and apical thirds and were evaluated with a stereomicroscope and scanning electron microscope to determine the location of the Thermafil components. In an additional 20 resin canal preparations obturated with the Thermafil system, the sealer was stained with dye to evaluate coating patterns. Then, these blocks were sectioned at the apex and examined under the stereomicroscope for adaptation at the apical extent of the preparation. In most preparations, the carrier abutted the canal wall in the cervical and middle sections but was usually surrounded by gutta-percha in the apical one third. The adaptation of components showed the most variability at the most apical extent of the preparation; complete encasement of the carrier did not occur in any specimen. Sealer distribution was variable throughout, usually being absent in the apical canal.

Dental Pulp Cavity↗
PubMed1995

Effect of preflaring on tactile detection of the apical constriction.

The efficacy of tactile detection of the apical constriction in flared and nonflared root canals was examined in 120 root canals of adult patients. In 68 nonflared (group 1) root canals, a #15 or #20 K-file was used to detect ("feel") the apical constriction. In 52 teeth (group 2), Hedstrom files, Gates Gliden drills #2 to #4, and ultrasonic files were used to enlarge the canal orifice and flare the coronal portion of the root canals before testing the apical constriction. After placing a #15 or #20 file in each root canal, a radiograph was taken, and the distance between the tip of the file and the radiographic apex was measured. The location of the file tip was classified into three categories: (a) within 1 mm short of the radiographic apex; (b) underextended, more than 1 mm short of the radiographic apex; and (c) overextended beyond the radiographic apex. In group 1 (nonflared), 32.3% of the root canals were classified in category a, as compared with 75.0% in group 2 (preflared). Over 26% of the root canals in group 1 and approximately 4% of the canals in group 2 were included in category b. Files inserted in preflared root canals had a significantly lower incidence of overextension than those placed in nonflared canals (21% versus 41%). The ability to determine the apical constriction by tactile sensation was significantly increased when the canals were preflared (p < 0.0001).

Adult↗
PubMed1990

Root canal anatomy of mandibular second molars. Part II. C-shaped canals.

The root canal anatomy of 19 mandibular second molars with C-shaped canals was investigated by rendering the roots transparent and allowing the canal system to be observed by black ink infiltration. The presence of three root canals was most frequent, and lateral canals were found in all roots. Transverse anastomoses were found in 15 of the 19 roots. The apical foramen was most commonly situated away from the apex, and apical deltas were found in 16 of the 19 roots. The C-shaped canals were found more frequently in Asians than in other racial groups (P less than 0.02). The formation of C-shaped roots and their racial predilection is discussed. A case report of the root canal treatment of a C-shaped canal is included and suggestions are made concerning suitable procedures for use in root canal treatment of these complex canal systems.

Adolescent↗
PubMed2003

Maxillary incisor root forms in orthodontic patients in Nairobi, Kenya.

OBJECTIVE: To evaluate, radiographically, the root forms of maxillary incisors in a sample of patients seeking orthodontic treatment in Nairobi, Kenya. DESIGN: A retrospective study of maxillary incisor root forms based on periapical radiographs. SETTING: A private dental clinic in Nairobi, Kenya. MATERIALS AND METHODS: The study comprised 393 maxillary incisors in 100 consecutive subjects (51 boys, 49 girls) aged 9-24 years. Intra-oral periapical radiographs of the incisors were evaluated. An index was used to categorise the roots as follows: 0=normal, 1=short, 2=blunt, 3=apical bend, 4=pipette apex. RESULTS: Normal root form was recorded in 60%, short in 12.5%, blunt in 7%, apical bend in 13%, and pippete-apex in 7% of the roots. Sixty nine percent of the pippete-apex roots were in central incisors and 94% of the roots with apical bend were in lateral incisors. Seventy three percent of short roots were in females. CONCLUSION: Based on evidence from previous studies on risk of root resorption which indicates that pipette and blunt roots are the forms mostly involved in this phenomenon, the present data imply that about 14% of the roots may have been at risk of moderate to severe resorption during fixed orthodontic treatment.

Adolescent↗
PubMed1997

The ways and wherefores of immediate placement of implants into fresh extraction sites: a literature review.

A waiting period of 12 months or longer to allow total socket healing used to be accepted protocol for placing dental implants. More than 15 years of research and clinical practice were needed for the concept of immediate endossceous implantation into fresh extraction sites to be accepted. Today the dilemma is no longer when, but which, protocol to follow. The diverse recommendations found in the literature leave the practitioner confused as to the methodology of choice. The conclusions drawn after reviewing the relevant literature on immediate dental implantation are: 1) implants placed into fresh extraction sockets have a high rate of survival, ranging between 93.9% to 100%; 2) implants must be placed 3 to 5 mm beyond the apex in order to gain a maximal degree of stability; 3) implants should be placed as close as possible to the alveolar crest level (0 to 3 mm); 4) there is no consensus regarding the need for gap filling and the best grafting material; 5) the use of membrane does not imply better results-on the contrary, membrane exposure may carry complications in its wake; and 6) the absolute need for primary closure remains to be established.

Alveolar Process↗