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PubMed1980

Vital root retention in humans: a final report.

A research protocal for submucosal vital root retention in humans has been developed based on laboratory animal studies. Procedures, patient management, and statistical results have been reported in a series of three articles. Changes in techniques have also been reported, along with explanation of a flowchart for tooth root retention and alveolar ridge preservation. Some ideas for future investigations are presented. Vital root retention in humans appears to be a valid means of retaining residual bony ridge tissues to a greater degree than when patients are rendered totally edentulous.

Alveolar Process↗

PubMed2000

[Cementum formation in rat molar roots].

Cementum is the calcified tissue covering roots of teeth and serves as attachment sites of the periodontal ligament. Although recent studies have suggested that extracellular matrix of cementum is very similar to that of bone, cementogenesis on a biological basis is still poorly understood. There are variations in the distribution and mineral contents of cementum depending on animal age, tooth species and position within the tooth roots. This paper reviews the formation and age-related changes of cellular and acellular cementum in rat molar roots, and discusses the effect of mechanical stress to the cementum formation.

Animals↗

PubMed2004

Local and systemic complications in a cat after poorly performed dental extractions.

This case report describes a cat that was presented with infected oral tissues and signs of systemic inflammatory response. Incomplete dental extractions had been performed 10-days earlier During a second dental procedure, 22 tooth root remnants were removed. Diabetic ketoacidosis and possible thromboembolism complicated the cat's recovery period After 13-days of hospitalization, the patient was stable enough to be sent home. Postoperative examinations at 1, 3, 6, 12, 16, 24, and 52-weeks indicated continued improvement with moderate glycemic control and chronic but stable renal failure. The patient died from further complications of diabetic ketoacidosis 20-months following root remnant extractions.

Animals↗

PubMed2005

Root growth in the teeth of 46,XY females.

The subjects of this study are women with a male sex chromosome complement or 46,XY females who show the complete form of the testicular feminization syndrome (CTF). The basic endocrine defect is end organ insensitivity to androgens. They are on average tall individuals and also show an increase in head and face dimensions relative to normal females. A size increase is likewise evident in permanent tooth crowns and here we report permanent tooth root lengths in eight 46,XY females, their five female relatives and population control females and males. Measurements were made from panoramic radiographs by a digital calliper according to established procedures on both sides of the jaws. The results show increased root lengths of 46,XY females relative to control females with values similar to those in population control males. The root and crown findings point to evident irreversible growth excesses in 46,XY females beginning 3 years after birth up to the age of 14 years expressing an effect which apparently is influencing in a continuous way. Excess root growth conceivably would develop independently of the possible androgen influence, and it is suggested that the increase results from the direct effect of the genes on the Y chromosome. It is possible that these genes on the Y chromosome are the same that promote tooth crown growth.

Androgen-Insensitivity Syndrome↗

PubMed1997

Determination of energy density threshold for laser ablation of bacteria. An in vitro study.

The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.

Dose-Response Relationship, Radiation↗

PubMed1977

Photoelastic analysis of post core restorations.

Photoelastic models were used to analyse the effects of stress distribution around post-core systems. Parallel post designs were found to distribute stress more evenly to the tooth root, as compared to tapered posts. Screwed posts were found to be more undersirable.

Crowns↗

PubMed1998

Ideal arch force systems: a center-of-resistance perspective.

The analysis of force systems from an ideal arch has shown that the ratio of the moments produced by a straight wire connecting two malaligned brackets depends on the ratio of the angulations of the brackets to the interbracket axis. Although this result permits assessment of the relative forces and moments, prediction of future tooth movement requires knowledge of the position of center of resistance as well. In this study, the forces and moments produced by a straight portion of an arch wire were transferred from the brackets to the center of resistance. The purpose was to compare the force system at the brackets to the force system at the center of resistance and to assess whether bracket geometry can be applied to predict initial tooth movement. A computer model was used to simulate two teeth connected by a straight portion of wire. Forces and moments were calculated with the use of equations derived from elementary beam theory. The results show that the force system at the center of resistance may be of an entirely different "geometry" type than that at the bracket. Factors that influence the force system include the interbracket distance, the angulation of the teeth, the length of the tooth root, and the width of the bracket.

Computer Simulation↗

PubMed1996

Complications of rigid internal fixation for mandibular fractures.

The application of rigid internal fixation to maxillofacial trauma is among the truly great advances that have been made in the field. The use of rigid internal fixation techniques has resulted in many advantages for the patient. Unfortunately, complications have occurred with this technology that are often devastating in their consequences for treatment outcomes. This article addresses some of the problems that stem from the use/misuse of rigid fixation devices in the treatment of mandibular fractures. It presents the most common complications and their management, including malunion, fibrous union, infection/osteitis, and impalement of the tooth roots and/or inferior alveolar canal.

Alveolar Process↗

PubMed1998

The decade of overdentures: 1970-1980.

Jaw bones resorb when teeth are lost. People cannot function as well with complete dentures compared with their natural teeth. As more people are living longer and these cumulative effects become increasingly documented, dentists in the 1970s attached more importance to keeping teeth. The concept of overdentures developed as a simple and economic alternative to prolong the retention and function of the last few teeth in a compromised dentition. The previous option was extensive fixed prosthodontics. An overdenture is a complete or removable partial denture that has one or more tooth roots to provide support. Rather than extracting all compromised teeth, the crowns, and pulpal tissue of selected teeth (usually two anterior teeth) are removed. The remaining root projecting through the mucosa is restored and/or contoured. With the crown removed, there is space to cover the area with a denture. The root has less mobility, and its retention retards bone resorption. Overdentures with roots are more stable, and patients can chew better than with dentures supported on residual alveolar bone and mucosal tissue alone. Keeping even a few teeth has a strong psychological value for some patients. Patients who have lost teeth, adjacent tissue, and bone need replacement of more oral structures than tooth crowns alone can provide. A complete denture with flange contours can restore tissue and appearance. The conventional tooth-supported overdenture concept continues to be an accepted treatment modality and has now been adapted to implants.

Alveolar Bone Loss↗

PubMed2000

Fixed lingual arch appliance for compliance-free unilateral molar distalization in the mandible. Three case studies.

An asymmetrically activated lingual arch appliance enables rapid, unilateral molar distalization in the mandible without active patient compliance. Using the segmented arch technique, the biomechanics involve only the tooth moved, in accordance with the 2-tooth concept, with a large, multi-rooted tooth segment acting as an anchoring unit. The anchorage system requires no maxillary involvement.

Activator Appliances↗

PubMed1988

Use of antimicrobial containing acrylic strips in the treatment of chronic periodontal disease. A three month follow-up study.

Local antimicrobial therapy has been considered for use in the treatment of chronic periodontal disease. This study evaluated chlorhexidine, metronidazole, and tetracycline delivered into periodontal pockets in an acrylic resin vehicle and compared the results with root planed and untreated sites over a three-month follow-up period. One site per patient where pocketing greater than or equal to 6 mm associated with a single rooted tooth was randomly allocated to one of the five possible regimens. Baseline and follow-up measurements included probing depth, loss of attachment, bleeding on probing, crevicular fluid flow, and dark-field microscopy of a subgingival plaque sample. Intratreatment evaluations revealed no significant changes in any parameter for untreated sites. Significant improvements in many parameters occurred with all four therapies although the magnitude and duration were greater in metronidazole and root planing groups. The more important intertreatment comparisons indicated that most treatments produced significant benefits compared with the control group; however, again these were greater with metronidazole and root planing. Furthermore, significantly greater effects were noted for metronidazole and root planing compared with tetracycline and more particularly chlorhexidine. It is concluded that some locally delivered antimicrobials alone may be useful in the treatment of chronic periodontal disease. However, at this time local antimicrobial therapy should be considered as adjunctive to conventional debridement techniques.

Adult↗

PubMed1992

Potential attachment area of the first mandibular molar in dogs.

Tooth root and root trunk surface area measurements were taken from 20 first mandibular molar (M1) teeth obtained randomly from canine cadaver specimens. The mean root surface area for all teeth was 497.1 +/- 116.2 mm2. The cumulative surface areas of the mesial (MR) and distal (DR) roots were 251.4 +/- 70.2 mm2 and 211.7 +/- 51.9 mm2, respectively. The root trunk surface area was 34.0 +/- 21.4 mm2. Surface area measurements for individual roots and the root trunk were significantly different. Cumulative individual root surface area (MR + DR) was 93.2% of total root surface area. The MR surface area contributed most to total root surface area (50.6%) and cumulative individual root surface area (54.3%). The mean distance from the beginning of the root trunk to the furcation was 2.1 mm. On the basis of the linear variation of the percentage of root surface area of the M1, 44.6% of the total root surface area was 3 to 7 mm apical to the most coronal aspect of the cementoenamel junction. The MR was heart-shaped, compared with the more cylindrical shape of the DR.

Animals↗

PubMed2004

Outcomes of vital primary incisor ferric sulfate pulpotomy and root canal therapy.

PURPOSE: To compare ferric sulfate (FS) pulpotomy and primary tooth root canal therapy (RCT) in cariously exposed vital pulps of primary incisors. METHODS: A total of 133 incisors in 50 children were randomly selected to be treated by FS pulpotomy (64) or RCT (69). RESULTS: Two years after treatment, 77 incisors (41 FS pulpotomy, 36 RCT) were available for clinical and radiographic examination. There was no clinical evidence of pathosis in 78% of FS pulpotomy-treated and 100% of RCT-treated incisors. Two independent pediatric dentists evaluated periapical radiographs of the treated incisors. Incisors were classified into 1 of 4 treatment outcomes: N, normal treated incisor; H, nonpathologic radiographic change present; PO, pathologic change present, but not requiring immediate extraction; PX, pathologic change present, extract immediately. Survival analysis was applied. A moderate level of agreement between raters was found for incisors with outcome PX (K = 0.54). Intra-rater reliability was substantial for incisors with outcome PX (K = 0.61). No difference was demonstrated in the proportion of FS pulpotomy- and RCT-treated incisors rated PX at the 2-year recall (x2 = 0.6). RCT incisors demonstrated a significantly higher survival rate than FS pulpotomy incisors at 2 years (p = 0.04). CONCLUSIONS: Treatment outcomes for RCT incisors were not significantly different from FS pulpotomy-treated incisors at 2 years; however, at 2 years the survival rate of RCT incisors was statistically greater than that of FS pulpotomy-treated incisors.

Child, Preschool↗

PubMed2000

Application of bone remodeling theories in the simulation of orthodontic tooth movements.

A numerical model that calculates bone apposition and resorption around a tooth root on the basis of bone remodeling theories was developed to simulate orthodontic tooth movements. The model was used to calculate different kinds of orthodontic tooth movements, that were then compared with the expected movements based on clinical experience. For simulation of the movements the root of a canine was modeled in an idealized way in the form of an elliptical paraboloid and was processed with a finite element program. The finite element model was loaded with defined force systems. Two model assumptions were used to calculate the bone remodeling process. The mechanical loads firstly in the periodontal ligament and secondly in the alveolar bone were taken to simulate the following tooth movements: 1. mesial tipping around the center of resistance (force system at the bracket: isolated torque MY = 5 Nmm), 2. rotation around the long axis of the tooth (MZ = 5 Nmm), 3. uncontrolled tipping around the root tip (FX = 1 N, MZ = 5 Nmm), 4. canine retraction (FX = 1 N, MY = -9.5 Nmm, MZ = 5 Nmm), 5. and 6. extrusion/intrusion (FZ = +/- 0.5 N, MX = +/- 2.5 Nmm). Comparison with clinical experience was performed by calculating the orthodontic tooth movements based on the assumption of a fixed position of the center of resistance. It could be demonstrated that the numerical model of orthodontic bone remodeling can be used to calculate orthodontic tooth movements. However, the results are strongly dependent on the model assumptions. The model simulating the bone remodeling on the basis of the loading of the periodontal ligament delivers results that are in very good accordance with the biomechanical assumptions of the position of the center of resistance. However, marked side effects occurred with the second model, especially in the simulations of uncontrolled tipping, translation and intrusion/extrusion. Clinically, these side effects cannot be observed.

Bone Remodeling↗

PubMed2005

[Effects of expansion fashion and expansion quantity on retention of cement-expanded composite screw post].

OBJECTIVE: To study the effects of expansion fashion and expansion quantity on retention of cement-expanded composition screw post (CECSP). METHODS: Ninety simulated tooth roots made of polymethylmethacrylate were divided into ten groups, each fashion induded five groups. The expanded plastic sheath of tricuspid valve was made with the special separated valve device and cemented and tightened up into root with the screw post at the same time by ZPC. Then the root and screw post-core system was tested by the speed of 10 mm/min on the INSTRON 4302 and the retention force was recorded. RESULTS: It appeared that the difference between different expansion fashion and different expansion quantity were significantly (P < 0.05). The retention of expansion fashion one was significantly greater than those of fashion two. The retention was best when expansion quantity was within 10%. CONCLUSION: During clinic operation, we should apply definite fashion and control the expansion quantity within 10%, and the screw post should tighten up to the bottom of prepared root.

Bone Screws↗

PubMed1985

Early mouse molar root development: cellular changes and distribution of fibronectin, laminin and type-IV collagen.

We analysed epithelial-mesenchymal interactions that occur during the early stages of the formation of mouse molar roots using light and electron microscopy. Morphological changes observed in the cells of Hertwig's epithelial sheath, the pulp and the follicular mesenchyme are described. The Hertwig's epithelial cells lose their cuboidal form and become flattened, apparently intermixing with the cells of the follicular mesenchyme. At the light- and electron-microscope levels, immunoperoxidase techniques were used to localize fibronectin, laminin and type-IV collagen. These appear to be closely associated with cell differentiation and matrix deposition in developing tooth roots. In addition, at the ultrastructural level, intracellular immunoreactivity was detected. The rough endoplasmic reticulum and nuclear envelope of some cells of the periodontal ligament facing the acellular cementum exhibited specific reactivity with laminin and type-IV collagen. Moreover, these periodontal ligament cells express keratin, but not vimentin, filaments. Our results demonstrate that Hertwig's epithelial cells maintain their capacity to synthesize laminin and type-IV collagen, as well as to express keratin filaments, despite basement membrane fragmentation and the disorganization of Hertwig's epithelial sheath. Thus, some Hertwig's epithelial cells remain in the periodontal ligament intermixed with follicular mesenchyme cells.

Animals↗

PubMed1997

[Comparison of two methods of age determination in teeth of known age from wild carnivores].

Two age-determining methods were conducted on representatives of known age from the Order Carnivora (4 red foxes, 3 tree martens, 3 stone martens, 2 racoons, 2 badgers, 2 polecat and one otter). Age determination employed with the aid of tooth wear nearly agrees with the real age of the animals. Dating based on the formation of the age-dependent cement zone coincided well with the known ages of the individual specimens. However, in real foxes the figure one must be added to the number of cementum layers counted determining the definitive age of individuals. For representation of the cementum layers transverse sections of the apical part of the tooth root of canini, P2 and P3, stained with methylene blue, should be used. It is important to note that the dentino-cemental line should not be considered when counting the year rings in the cement.

Age Determination by Teeth↗

PubMed1992

Calcium and phosphorus content of roots exposed to the oral environment.

This study analyzed the calcium and phosphorus content of extracted tooth roots exposed to the in vivo oral environment. 20 teeth were obtained from 16 patients and divided into two groups of 10 teeth each. In group 1, the teeth had gingival probing depths of 5 mm or more, and teeth of group 2 had gingival recessions of 3 mm or more. Prior to extraction, the gingival margin location was recorded by placing a groove on the tooth surface. After extraction, the teeth were sectioned coronal-apically, air dried and coated with carbon. Energy dispersive X-ray spectra, excited in a scanning electron microscope, were analyzed to measure relative calcium and phosphorus contents and for calculation of their ratios. X-rays were collected from two positions on the sectioned root. Experimental positions were selected within the exposed portion of the roots of groups 1 and 2, and unexposed positions were selected from that portion of the same root with attached periodontal membrane. At each position, calcium and phosphorus content was measured at 4 depths into the root surface: in cementum, in dentin three-quarters of the distance to the pulp chamber, and at 2 locations in between on either side of the cemento-dentinal junction. Analysis of data demonstrated large variations in calcium and phosphorus content from surface to surface of individual teeth and from tooth to tooth in a subject. No statistically significant differences were found between experimental and unexposed locations. Calcium and phosphorus contents were greater in roots exposed to pockets when compared to roots exposed by recession at both experimental and unexposed locations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗