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PubMed1999

Effect of appliance reactivation after decay of initial activation on osteoclasts, tooth movement, and root resorption.

Clinical orthodontists frequently reactivate appliances following decay. Studies of tooth movement and tissue responses following reactivations indicate that linear tooth movement and rapid recruitment of osteoclasts can be achieved if reactivation is timed to coincide with the latter part of the bone remodeling cycle initiated by the first activation. Both can be delayed if reactivations are timed for the early part of the previous cycle. The objective of this study was to examine tooth movement, root resorption, and osteoclast recruitment following appliance reactivation after the first activation had decayed. Bilateral orthodontic appliances were activated with 40 cN in 144 rats to mesially tip the maxillary molars. After 16 days, rats were randomized into two groups of 72. In group 1, appliances were reactivated in precisely the same manner as the first activation. In group 2, appliances were sham-reactivated. Rats were sacrificed at 1, 3, 5, 7, 10, and 14 days. Orthodontic movement was measured cephalometrically; changes in osteoclasts and root resorption were assessed at both compression and tension sites histomorphometrically; tartrate-resistant acid phosphatase (TRAP) was measured in alveolar bone and serum biochemically. Orthodontic tooth movement was linear in group 1, but osteoclasts required 3 to 5 days to appear. There were no group- or time-related differences in root resorption. Bone TRAP levels were elevated in both groups but dropped significantly (p<0.01) in group 2 at day 7. Appliance reactivations that followed decay of the first activation produced efficient tooth movement without increased risk of root resorption, but these changes were not accompanied by rapid osteoclast recruitment at compression sites. Timing appliance reactivations for the latter portion of the previous bone remodeling cycle could have significant clinical advantages because the delay period seen in tooth movement following a single activation or short-term reactivation can be avoided.

Activator Appliances↗
PubMed1995

The force requirements for tooth movement. Part II: Uprighting and root torque.

In orthodontic treatment tooth root movement is essential, not only to obtain mesio-distal paralleling of individual tooth roots, but also to achieve correct axial inclinations in relation to basal bones and inter-incisal angles in the anterior segments. This article describes a pilot study in which paired teeth on opposite sides of the mouth and which required root paralleling as a part of orthodontic treatment, were subjected to known moments of force. The forces were exerted using helical torsion springs of predetermined load-deflection characteristics. Average weekly moments of force were related to the weekly rates of angular movement of eight teeth in a group of four patients. The experiments lasted for up to seven weeks and were designed so that the movement of the paired teeth in each patient were concurrent.

Cuspid↗
PubMed1985

[Color change in dental tissue as a sign of thermal damage].

The appearance of hard human tissue after thermal damage permits certain conclusions to be drawn with regard to fire parameters. In addition to morphological destruction, the change in color of dental tissues like enamel, dentine, and cement is also important. We studied teeth extracted from 330 human males and females under well-defined time and temperature conditions. Using the DIN and RAL color indexes, the color phenomenon was evaluated on the basis of the amount of glowing obtained when the teeth were heated. It is easiest to determine the color change in cement, as no calculus or hindering plaques are on the root surface. In addition to this, destruction of the tooth root takes place only during extreme combustion conditions. Determining the dentine color is more difficult and is possible only after the enamel splits. Also, the different dentine thicknesses hinders the observation of color. When the enamel was tested, it was found that the differences in color caused by high temperatures are unimportant. Moreover, the enamel burst into small particles. The effect we observed regarding the anthracite lustre using low temperatures was typical, and the best results were obtained in dental roots with eight color scales. All three dental hard tissues have in common that the variations in color appear regularly and successively according to ascending temperature or duration of time: natural dental color, black, brown, blue, grey, white, and pink. In these processes, the temperature and combustion time are inversely proportional to the velocity of color change. The literature is discussed that deals with temperature- and time-dependent color phenomena of dental hard tissues destroyed as a result of thermal damage.

Burns↗
PubMed1977

Effects of overdentures upon remaining oral structures.

This study provided the following guidelines in the selection of specific designs for overdenture abutments: 1. The Dolder bar, which exhibits more cross-arch involvement than the Zest anchor, will share the occlusal load across the arch, between the abutments and the supporting structures. 2. The posterior edentulous regions will receive some physiologic stimulation with the Dolder bar, for it shares more stress here than the Zest anchor. 3. The forces on the Dolder bar produce stress directed more apically than that from the Zest anchor. Since this force is better tolerated, use of the Dolder bar may be indicated for a short-rooted tooth with less supporting bone. 4. The greater stress concentrated around the abutment teeth by the Zest anchor makes use of this design in a tooth that is periodontally sound and has a long root structure well imbedded in supporting bone seem logical.

Dental Abutments↗
PubMedDate not supplied

Tissue-engineered hybrid tooth and bone.

Tooth loss accompanied by alveolar bone resorption presents a significant clinical problem. We have investigated the utility of a tissue-engineering approach to provide corrective therapies for tooth-bone loss. Hybrid tooth-bone tissues were bioengineered as follows. Tooth implants were generated from pig third molar tooth bud cells seeded onto polyglycolide (PGA) and polyglycolide-colactide (PLGA) scaffolds, and grown for 4 weeks in the omenta of adult rat hosts. Bone implants were generated from osteoblasts induced from bone marrow progenitor cells obtained from the same pig, seeded onto PLGA fused wafer scaffolds, and grown for 10 days in a rotational oxygen-permeable bioreactor system. The tooth and bone implants were harvested, sutured together, reimplanted, and grown in the omenta for an additional 8 weeks. Histological and immunohistochemical analyses of the excised hybrid tooth-bone constructs revealed the presence of tooth tissues, including primary and reparative dentin and enamel in the tooth portion of hybrid tooth-bone implants, and osteocalcin and bone sialoprotein-positive bone in the bone portion of hybrid tooth-bone constructs. Collagen type III-positive connective tissue resembling periodontal ligament and tooth root structures were present at the interface of bioengineered tooth and bone tissues. These results demonstrate the utility of a hybrid tooth-bone tissue-engineering approach for the eventual clinical treatment of tooth loss accompanied by alveolar bone resorption.

Animals↗
PubMed2001

Prevention of the ingress of a known virulent bacterium into the root canal system by intracanal medications.

Contamination of the root canal system by persistent, enteric bacteria via leakage through interim restorations has been well documented. This in vitro study evaluated the ability of interappointment medications to prevent contamination of the root canal system by Enterococcus faecalis. Coronally unsealed, medicated tooth roots fixed in a closed system were contaminated daily with a standardized, aerobic, broth culture of E. faecalis. Four medications were evaluated (n = 15): group A, calcium hydroxide/methylcellulose paste; group B, camphorated parachlorophenol/calcium hydroxide paste; group C, 1% chlorhexidine/methylcellulose gel; and group D, calcium hydroxide points. The mean number of days to contamination as indicated by turbidity in the closed system was the following: group A, 37; group B, 46; group C, 16; group D, 5; and a positive control (no medication), 3. A one-way analysis of variance with a Scheffe post hoc test (p = 0.05) detected significant differences in effectiveness with A and B superior to C and D, and C superior to D.

Analysis of Variance↗
PubMedDate not supplied

Replantation of avulsed primary anterior teeth: treatment and limitations.

In addition to the successful replantation of avulsed permanent teeth, the replantation of primary anterior teeth may also be indicated. The decision is based on age and stage of tooth development, development of dentition, storage of the avulsed tooth and the way it is transported to the treatment site, the appropriate in vitro treatment of the tooth before reinsertion, and the willingness of the child to cooperate. A method involving retrograde filling of the primary tooth root with calcium hydroxide after resecting the root apex has proved successful. Other commercially available root filling materials and pins are not indicated. Calcium hydroxide allows the tooth to heal in place without reaction and prevents the development of apical periodontitis. As regards any surgical intervention, the attending dentist in this case has to weigh the benefits against the risks.

Age Factors↗
PubMed1986

Quantitative comparisons of potentially cariogenic microorganisms cultured from noncarious and carious root and coronal tooth surfaces.

Potentially cariogenic microorganisms cultured from noncarious and carious root and coronal (enamel) surfaces were quantitatively compared in patients 22 to 84 years of age (mean, 52 years). We collected 150 plaque specimens from 26 in situ teeth with initial root lesions and from 25 extracted teeth with advanced root lesions. The frequencies of isolation of Streptococcus mutans, Actinomyces viscosus, and Lactobacillus spp. were, respectively, 94, 72, and 51% at the noncarious root site; 98, 71, and 54% at the root lesion; 84, 61, and 44% at the noncarious enamel site; and 100, 66, and 90% at the enamel lesion. The streptococci made up the largest mean proportion of the total anaerobic cultivable microflora, ranging from 31.2% at the noncarious enamel site to 37.6% at the root lesion, while S. mutans varied between 18% at the noncarious enamel and root surfaces and approximately 24% at both the enamel and root lesions. The proportion of actinomyces ranged from 12.3% at the root lesion to 23.6% at the noncarious root site, while A. viscosus varied from 7.8% at the root lesion to 15.1% at the noncarious root site. The largest mean proportion of lactobacilli (4.2%) was recovered at the enamel lesion site. Proportions of Candida spp. made up less than 0.1% at all sites. Proportions of microorganisms did not differ significantly between noncarious enamel and root sites, but the noncarious coronal and root sites had higher (P less than 0.05) proportions of actinomyces than did the root lesion. Also, enamel lesions had a greater (P less than 0.05) percentage of Lactobacillus spp. than did root lesions. The number of streptococci recovered from the root lesion was greater (P less than 0.01) than the number of actinomyces at the same site. S. mutans was recovered from initial root lesions in greater numbers (P less than 0.001) than were actinomyces and lactobacilli. The number of S. mutans recovered at the initial root lesions was greater (P less than 0.01) than that recovered from the advanced root lesions.

Actinomyces↗
PubMed1998

Morphometrical analysis of main and accessory canals in apical root portion of frontal teeth.

Reviewing radiographs may often lead to a wrong conclusion regarding root canal ending (apical constriction) and anatomical apex of the tooth root. Anthropological measurements may help clinicians to understand better root canal ending aberrations in a sense to decide whether to do a revision of the root canal filling or not. The object of this investigation was to examine the deviation frequency, the distance of the major apical foramen from the anatomical apex and occurrence and number of accessory canals in the apical third of the frontal teeth roots. A total of 156 randomly chosen upper and lower permanent incisors and canines, after extraction due to periodontal disease were prepared for the investigation. The access cavity was prepared and root canal therapy was initiated just to prepare endodontic space for methylene blue dye injection. Methylene blue clearly dyed all root canal exits and after that the teeth were cut and examined with a stereomicroscope and a sliding scale. Results indicate that deviation frequency was found in 60.25% of the cases and the mean distance between deviated major foramen and the anatomical root apex was 0.35 mm. Accessory canals were found in 33.33% of the cases in the apex third of the root. Data were statistically elaborated with the method of Chi-square test.

Dental Pulp Cavity↗
PubMed2002

Methodology of three-dimensional determination of root surface roughness.

In comparing and evaluating the instruments that are used in root debridement, roughness constitutes a standard variable that is assessed. The purpose of this study was to describe the conditions and requirements for the three-dimensional roughness measurements of tooth roots using a laser profilometer. Impressions were made of 60 instrumented and 12 untreated root surfaces, which were then measured using a dynamically focussing optical profilometer (Mikrofocus, UBM, Karlsruhe, Germany). To separate roughness from the form of the tooth, a low pass filter was applied. This meant that the longer wavelengths - which roughly approximated the root forms - were subtracted from the measured profile. We then used an individualized Fourier transformation to define the threshold at which roughness becomes waviness. Roughness parameters were Ra (average roughness) and Rz (average roughness in the z dimension) for two- and three-dimensional measurements. To describe the requirements for the measurement, we studied the effect of pixel density and the field size on the average roughness value, Ra. We found that Ra increases with pixel density until 400 per mm is reached, after which it does not change meaningfully. Furthermore, Ra is highly dependent upon the area of the field to be scanned, increasing in line with the area, and does not approach one value within the surface available on one tooth. The correlation coefficients between the two-dimensional and three-dimensional Ra and Rz values ranged from 0.7 to 0.8. We conclude that roughness values are strongly dependent on the measurement conditions and the results of one study cannot be directly compared to another. In addition, it was found that two-dimensional measurements are sufficient for characterizing root surfaces.

Dental Scaling↗
PubMedDate not supplied

Two-year outcomes of primary molar ferric sulfate pulpotomy and root canal therapy.

PURPOSE: The objective of this outcome study was to compare ferric sulfate pulpotomy (FS) and primary tooth root canal therapy (RCT) on cariously exposed vital pulps of primary molars. METHODS: A total of 291 molars were treated in 130 children--182 molars received FS and 109 received RCT by random selection. RESULTS: At 2-year reassessment, 116 molars (73 FS, 43 RCT) were available for clinical and radiographic examination. There was no clinical evidence of pathosis in 96% of FS and 98% of RCT molars. Two independent pediatric dentists evaluated periapical radiographs of the treated molars. Molars were classified into 1 of 4 outcomes: (1) N--normal treated molar, (2) H--nonpathologic radiographic change present, (3) P(O)--pathologic change present, follow-up in 6 months, and (4) P(X)--pathologic change present, extract immediately. Survival analysis was applied. A good level of agreement between raters was found for molars with outcome P(X) (kappa=0.745). Intrarater reliability was good for molars with outcome P(X) (kappa=0.710). Significantly greater numbers of FS than RCT molars were rated P(X) at the 2-year recall (chi2=5.8; P=.02). No significant difference in survival between the 2 types of vital pulp treatments was detected in log rank tests (P=.22). CONCLUSIONS: Outcomes for FS were poorer than RCT outcomes at 2 years; however, at 2 years, the survival rates were not statistically different.

Chi-Square Distribution↗
PubMed2004

Identification of gammadeltaT lymphocytes in human periapical lesions.

Endodontic (root canal) therapy is required when the pulp of a tooth becomes necrotic due to a bacterial infection or trauma. A proportion of patients who receive endodontic therapy subsequently have periapical (around the tooth root) lesions detected by radiolucency. Currently, there are no means to identify susceptible patients. Although tissue from periapical lesions has been described as inflammatory, inflammatory cell types and their functions have been poorly characterized. For example, T lymphocytes were identified using pan specific anti-CD3 mAb, which recognizes both alphabeta and gammadeltaT cells. Using the current model of gammadeltaT cells as immunoregulatory cells; gammadeltaT cells can mediate protective or destructive milieus. We postulated that patients who have a periapical lesion, as identified by radiographic bone loss, mount a gammadeltaT cell response. We collected specimens removed by surgery from both periapical lesions and other oral tissues, generated total RNA and performed reverse-transcriptase polymerase chain reaction to identify rearranged delta genes. Results were confirmed with semi-nested polymerase chain reaction. In addition, we demonstrate that these lesions contain a population of CD3+ cells that are alphabetaT cell receptor negative, implying that these cells are gammadeltaT cells. Here we show that 36/37 of periapical lesions and only 2/11 of other lesions contain gammadeltaT cells (P<0.0001). Vdelta2+ T cells were the most common subtype identified (30/36) in these samples. This is the first report in the literature of the presence of gammadeltaT cells in human periapical lesions.

Adult↗
PubMed1993

Principles of dental extraction.

Despite major advances in the practice of veterinary dentistry during the past decade, extractions are still the most commonly performed dental procedures. A sound understanding of tooth root morphological and anatomic features is important to proper extraction. Tooth extraction techniques using sound surgical principles will permit efficient procedures, minimize trauma and discomfort to the animal patient, and encourage rapid healing. The keys to success are controlled forces and patience during the extraction process.

Animals↗
PubMed1976

Root resorption by ameloblastomas and cysts of the jaws.

Radiographs of 122 cases of a series of nonmalignant simple jaw cysts and ameloblastomas were examined and the frequency of resorption of adjacent tooth roots compared. The ameloblastomas proved to have a root resorptive potential far greater than the cystic lesions considered. Certain statistically significant differences were observed in the root resorption related to the cystic lesions. The dentigerous cyst showed a tendency to resorb roots (55%), whereas in this study no resorption was observed in primordial cysts. These differences may aid the clinician in the preoperative differential diagnosis. It is suggested that the capacity of the dentigerous cyst for root resorption may be the result of its origin from the dental follicle, which is associated with resorption of the roots of primary teeth during normal tooth succession.

Ameloblastoma↗
PubMed1997

Late failure of root canal therapy: a diagnostic and treatment planning challenge. Case report.

This report describes a case in which failure of conventional root canal therapy presented 17 years following initial treatment. The apical pathology was curetted, the tooth root resected and a root-end filling placed. The possible reasons for failure of the initial orthograde root canal therapy are discussed with the conclusion that the cause may not have been addressed fully by surgical intervention. The case highlights the challenge facing clinicians when assessing failed root fillings, not only in determining the exact cause of failure but deciding the appropriate treatment for the individual tooth and patient.

Adult↗
PubMed2005

Apical diffusion of calcium hydroxide in an in vitro model.

An in vitro agar model was developed to study the effect of intracanal medicaments on periapical tissues and was used to study the diffusion of three calcium hydroxide (Ca(OH)2) medicaments of varying viscosity through simulated root canals with various sizes of apical foramina. Experimental medicaments were added to pipette tips used to represent tooth roots, which were fixed in syringes containing brain heart infusion agar and calcium-reactive dye. OH and Ca concentrations were measured in the agar at 30 minutes and 24 hours. Ca concentration and pH increased with larger aperture sizes, and higher pH and Ca diffusion was produced by a 10% Ca(OH)2 solution than was produced by Pulpdent or a Ca(OH)2 paste. The results suggest that the properties of the Ca(OH)2-containing vehicle could affect the action of the medicament in the periapical tissues.

Analysis of Variance↗
PubMedDate not supplied

Effects of pulsed Nd:YAG laser radiation on action potential conduction in nerve fibres inside teeth in vitro.

OBJECTIVE: This study aimed to simulate the effects of lasing dentine on pulpal nerve function. METHODS: Rat spinal nerve roots were threaded through the prepared pulp canal of a 10 mm long tooth root segment which was mounted in a perspex bath. The protruding ends of the nerve were placed on platinum wire electrodes used to elicit and to record compound nerve action potentials (CAPs). Laser energy (average power = 0.3-3.0 W) was applied to the surface of the root segment using a pulsed Nd:YAG dental laser (dLase 300). RESULTS: With the laser probe tip placed in static contact with the tooth surface, the nerve CAP was irreversibly abolished within 60 s of lasing at 1.0-3.0 W power. When the laser tip was moved to and fro over the root surface in a scanning mode, similar levels of radiation produced less marked effects. In the latter mode, CAP attenuation increased with increasing power and duration of lasing. After 60 s lasing at 0.3 W, the CAP size was 95% (+/- 5, S.D.) of the prelasing controls value; with 2.0 W the CAP was reduced to 54% (+/- 33). The CAP recovered to 90% of control levels after lasing at powers up to 1.5 W, but reached only 72% of control values after lasing at 2.0 W power. CONCLUSIONS: Laser radiation applied to dentine caused a dose-dependent block of action potential conduction in nerve fibres in the underlying pulp chamber.

Action Potentials↗