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PubMed2001

Experimental evaluation of initial tooth displacement, center of resistance, and center of rotation under the influence of an orthodontic force.

The purpose of this study was to determine the location of the center of resistance and the center of rotation of the maxillary central incisors under the influence of a single simple force and to investigate related geometric parameters of the teeth and the surrounding periodontal tissues. By measuring the initial displacement of the central incisors with a magnetic sensing system, the location of the center of resistance and the centers of rotation associated with various forces were determined in 3 human subjects. The results show that the location of the center of resistance of the maxillary central incisor depends on the palatal bone level and is at approximately two-thirds of the palatal alveolar bone height, measured from the root apex. A greater moment-to-force ratio is needed for any controlled movement of the maxillary incisors during retraction in patients with reduced palatal alveolar bone height. This study suggests a method for estimating the location of the center of resistance of a tooth.

Alveolar Bone Loss↗
PubMed2002

The prognostic value of several periodontal factors measured as radiographic bone level variation: a 10-year retrospective multilevel analysis of treated and maintained periodontal patients.

BACKGROUND: Assigning a prognosis to a periodontal patient is one of the greatest challenges in clinical practice. Many different factors can affect the result of periodontal therapy. The purpose of this study was to evaluate the prognostic value of some clinical, genetic, and radiographic variables in predicting bone level variation in periodontal patients (aged 40 to 60) treated and maintained for 10 years. METHODS: Sixty consecutive non-smoking patients (mean age 46.77 +/- 4.96) with moderate to severe chronic periodontitis were treated with scaling and root planing (SRP). Some patients also underwent additional surgical treatments. All patients were maintained in the same private practice for 10 years. At baseline (T0) and at least 10 years later (T2), the following clinical variables were evaluated: probing depth (PD), tooth mobility (TM), presence of prosthetic restorations (PR), and molar teeth (MT). In addition, radiographic measurements were taken of the mesial and distal distances from the cemento-enamel junction (CEJ) to the bottom of the defect (BD), to the bone crest (BC), and to the root apex (RA). At T2, a genetic test to determine the IL-1 genotype and genetic susceptibility for severe periodontal disease was performed for all 60 patients. Based on the results of this assay, the patients were categorized as IL-1 genotype positive (G+) or negative (G-). The differences between the bone levels measured at T0 and T2 (ABD), indicating the bone level variation, was used as the outcome variable. Different predictor variables were then tested using a 3-level statistical model (multilevel statistical analysis; patient, tooth, and site level). At the patient level these were: age, gender, and interaction between mean bone loss and the IL-1 genotype (mean CEJ-BD(T0) x IL-1 genotype). At the tooth level the variables were: TM(T0), PR(T0), MT(T0); and at the site level the evaluated factors were: the infrabony component of the defect (CEJ-BD(T0) - CEJ-BC(T0), PD(T0), bone level (CEJ-BD(T0)), and the residual supporting bone (BD-RA(T0)). RESULTS: Among the considered predictor parameters, the following were significantly associated with the outcome variable: 1) mean CEJ-BD(T0) x IL-1 genotype (P = 0.0019); 2) TM(T0) (P < 0.0000); 3) CEJ-BD(T0) (P < 0.0000); 4) CEJ-BD(T0) - CEJ-BC(T0) (P < 0.0000); 5) PD(T0) (P = 0.0010). Deeper probing depths at a site and tooth mobility at baseline were associated with worst prognosis. Greater CEJ-BD(T0) distance and infrabony component at a site at baseline were associated with a better prognosis. The interaction between mean CEJ-BD measurement at baseline and IL-1 genotype was significantly associated both with a good or a poor prognosis. The other parameters evaluated - age, gender, presence of molars and prosthetic restorations, and residual supporting bone - were not significantly associated with bone level variation. CONCLUSIONS: Within the scope of this study design, many traditional prognostic factors were ineffective in predicting future bone level variation and therefore were of no prognostic value. Conversely, a few specific factors at each level emerged as valuable prognostic factors. At the patient level, the prognostic factor was initial mean bone level in conjunction with a positive IL-1 genotype. At the tooth level, the prognostic factor was tooth mobility. At the site level, the significant prognostic factors were initial bone level at a site, the infrabony component of a defect, and initial probing depth at a site. The use of these factors may be of value to clinicians as predictors of bone level variation when assigning a prognosis to a patient, a tooth, or a site.

Adult↗
PubMed1998

Cortical bone remodeling/tooth movement ratio during maxillary incisor retraction with tip versus torque movements.

The validity of the postulate "bone traces tooth movement" was examined on 40 Angle Cl II cases. It was hypothesized that a 1:1 cortical bone remodeling/tooth movement ratio is preserved during maxillary incisor retraction. The sample was divided into retraction with tip (13 patients), retraction with torque (18 patients), and control (9 patients) groups. Two time point cephalograms were analyzed with two superimposition techniques, SN at S and a newly developed static tooth analysis, with the maxillary left central incisor serving as a reference object. In both retraction with tip and retraction with torque groups, the postulate bone traces tooth movement was not preserved and a bone remodeling/tooth movement ratio of 1:2 and 1:2.35 was obtained, respectively. In retraction with tip movement, the apical one third of the root tipped labially reducing the superior area of labial maxillaris by 19%. However, due to the compensating effect of the retraction movement, no apex approximation to the labial cortical plate occurred (eliminating the hazard of root resorption, dehiscence, or fenestration). In retraction with torque movement, the increase in both superior (28%) and inferior (65%) labial maxillaris areas was indicative for the hazard of root approximation to the palatal cortical bone. It is recommended to use the 1:2 bone remodeling/tooth movement ratio as a guideline to determine the biocompatible range of orthodontic tooth movements. Furthermore, a judicious interplay between the two modes of retraction can prevent major biologic impairments associated with the ratio and can extend the orthodontic range of treatment.

Bone Remodeling↗
PubMed2001

An evaluation of dental radiograph accuracy in the measurement of enamel thickness.

Many studies have employed lateral radiographs to measure the thickness of tooth enamel in recent human and fossil hominid samples, but the accuracy of measurements obtained by this technique has not been assessed. In this study, 20 isolated human maxillary permanent molars were radiographed using the parallel film technique. The crowns were then sectioned longitudinally through the tips of the buccal cusps. Measurements of enamel cap area, and of linear enamel thickness in the occlusal basin and over the metacone apex, were made from the radiographs and corresponding sectioned surfaces. Comparisons of the two sets of values revealed that radiographs generally overestimated enamel thickness but there was considerable variability in the error by which measurements from radiographs either under- or overestimated the true value. Lateral radiographs may provide a rough visual impression of whether a tooth has thin or thick enamel but they do not generally provide for accurate measurement of enamel thickness. Quantitative data on enamel thickness from studies that have employed lateral radiographs should be viewed with circumspection.

Anatomy, Cross-Sectional↗
PubMed2005

Three canals in the mesiobuccal root of a maxillary first molar: a case report.

This article describes the identification and treatment of a maxillary first molar exhibiting three canals in the mesiobuccal root. An 18-yr-old male patient presented for nonsurgical root canal therapy of tooth #3. After accessing the pulp chamber, and probing with 2.5x magnification, only one canal was located in the mesiobuccal root initially. Subsequent to troughing the groove between the mesiobuccal and palatal canals with a #2 round bur, two additional canals were located. An electronic apex locator was utilized to ensure a perforation of the pulpal floor had not occurred. A working film confirmed the presence of three canals in the mesiobuccal root, and the canals were cleaned, shaped, and obturated.

Adolescent↗
PubMed1994

[Three dimensional finite element analysis of stress induced by orthodontic forces in the periodontal tissue].

The purpose of this study was to investigate the stress induced in the periodontal tissue of the upper central incisor by application of orthodontic forces. A three dimensional finite element model consist of tooth, periodontal ligament (PDL), cancellous and compact bone was established and the following results were obtained: (1) The highest stresses were observed on the root surface, the intermediate on the alveolar bone and the lowest in the PDL. (2) Stress condition on the surface of root and alveolar bone is very complex. The maximum, intermediate and minimum principle stresses on the same area are quite different, but the three principal stresses in the PDL are similar. (3) Regarding to tipping and torque movement, the stress value varied largely from the cervix to the apex, and there is stress concentration at the cervix and the apex. For bodily movement when M/F is -10.30, the stress induced is homogeneous and the difference of the stress values from the cervix to the apex is little, which seems to be more physiological.

Alveolar Process↗
PubMedDate not supplied

[A technic for performing tooth-preserving operations in treating radicular cysts and chronic periodontitis of the permanent teeth in children and adolescents].

A high incidence of complications developing during and after removal of teeth with chronic periodontitis and radicular cysts has made the dentists resort to conservative surgical methods of treatment of such conditions. These methods are replantation, resection of radical apex, hemisection, radicular amputation, granulectomy, crown-radicular separation, crown-radicular amputation, hemireplantation, and inter-radicular granulectomy. The technique of such treatment is described in detail. Conservative surgical methods of treatment include the following stages: (1) conservative therapy; (2) surgical treatment; (3) orthodontic treatment; (4) dynamic follow-up till complete recovery of osseous tissue. The recommended modalities are not difficult but rather effective and may be performed at pedodontic clinics.

Adolescent↗
PubMed1976

The investigation of microleakage in root canal therapy. An electrochemical technique.

An electrochemical technique employing zero-resistance ammetry is described for evaluating the quantity, rate, and areas permeated in the canal system of a root-filled tooth by 1 per cent potassium chloride. Single-rooted extracted teeth were root-filled by a vertical condensation gutta-percha technique. The teeth were coated from the cementoenamel junction to 3 mm. from the apex with a stopping-off medium, so that the apical foramen and the accessory canals in the area would play a role, but not the lateral canals in the gingival area. The teeth were placed in a potassium chloride solution. When the potassium chloride permeated the apical seal and reached a mild steel rod placed through the occlusal access opening extending 2 mm. into the coronal end aspect of the canal, corrosion of the steel was established and was measured for quantity and rate. This technique suggests the possibility of another pathway for tissue fluid to effect coronal dentinal discoloration. The technique also suggests a quantitative means of measuring apical sealing procedures.

Corrosion↗
PubMed1989

[Dental study of hypophosphatasic child].

Hypophosphatasia is a hereditary disease characterized by congenital deficiency of tissue alkaline phosphatase. One of its dental features is the shedding of teeth. We have experienced a case which was referred to our clinic with the chief complaints of loss and shedding of lower deciduous central incisors and was diagnosed to be highly suspected of hypophosphatasia as a result of hematological examination at the pediatric clinic. As a result of close systemic and dental examination and further study of changes in the course for two and a half years, the following findings were obtained: 1. Low serum alkaline phosphatase level and hypercalcemia were the systemic findings of the disease. 2. There was no delayed ossification in terms of carpal bone age. 3. X-ray cephalography revealed no particular cephalic abnormality, except the lack of development of frontalis and mandibular. 4. Dental findings comprised marked resorption of upper alveolar bone in the front teeth area and pronounced instability of front deciduous teeth. 5. As for changes in oral symptoms, extraction of A because of pronounced instability was followed by spontaneous shedding of A. About one year later, A was extracted because of marked instability. At the time of this writing, A was slightly instable without any abnormality in the other teeth. 6. Pathohistological study of the extracted teeth disclosed only a little resorption of cement of root apex and dysgonic periodontium without any marked tissue changes.

Alkaline Phosphatase↗
PubMed2003

Technical quality of root canal treatment in Taiwan.

AIM: To evaluate the current technical quality of root canal treatment (RCT) in Taiwan. METHODOLOGY: A total of 1085 RCT cases, randomly selected from a large sample and representative of the Taiwanese population from April to September 2000, were evaluated by eight endodontic specialists. The qualitative evaluation of RCT cases was based on two variables: length of the root filling and density of the obturation. A root canal with both adequate filling length (the apical termination of the root filling within 2 mm of the radiographic apex) and complete obturation (no lateral or apical canal lumen visible in the apical one-third of the root canal) was defined as having good-quality endodontic work (GQEW). A tooth was defined as having a GQEW when all its canals were categorized as GQEW. RESULTS: From a total of 1867 root canals, overfilling occurred in 235 (12.6%), adequate filling length in 1152 (61.7%), underfilling in 466 (25.0%) and no filling in 12 (0.6%). Of the 1867 root canals, 710 (38.0%) demonstrated complete obturation and 1157 (62%) demonstrated incomplete obturation. GQEW was found in 650 (34.8%) root canals and 329 (30.3%) teeth. The percentage of teeth with GQEW in hospital cases (38.1%) was significantly greater (P < 0.001) than that in private clinic cases (24.3%). In addition, the frequency of teeth with GQEW in the anterior teeth (40.4%) or in the premolars (33%) was significantly greater (P < 0.001) than that in the molars (18.4%). CONCLUSIONS: Approximately 70% of the teeth receiving RCT in Taiwan were either of inadequate filling length or sealing density.

Bicuspid↗
PubMed1981

Remodelling processes following transplantation of dental germs in dogs.

Dental germs with different amounts of root development were transplanted from the left side to the right side, and vice versa, in young beagle dogs. The unerupted premolars had been taken out by osteotomy. After transplantation, the dental germs were covered with mucosa. The observation period lasted 7 postoperative weeks. Histological examination of the remodelling processes of the bone and tooth-tissue was carried out by polychromatic sequential labelling. All the transplanted dental germs remained vital, and the eruption continued to the normal occlusion level. From this, it follows that eruption of teeth does not depend on root development alone. In some cases, root length growth stopped immediately as a result of transplantation. Either a stumpy apex was formed, or resorption took place. In other cases root growth continued. There was a bend in the root at the point of transplantation, and the subsequently formed root section was shorter and thinner than in normal teeth.

Animals↗
PubMed2005

Facial cellulitis arising from dens evaginatus: a case report.

Dens evaginatus is a developmental anomaly that produces a tubercle on the occlusal surface of a tooth. It is found most frequently in the mandibular premolars. The occlusal tubercle easily causes occlusal interferences. Attrition or fracture of the tubercle can lead to pulpitis, pulp necrosis, periapical pathosis, and periapical infection. This case report illustrates the treatment of facial cellulitis arising from dens evaginatus with open apex. Calcium hydroxide was used for the apexification procedure. One year after canal obturation, radiography revealed no apical pathosis and the apical seal was evident.

Adult↗
PubMed1994

Age estimation with the aid of tooth development: a new method based on objective measurements.

The common methods of age determination with the aid of teeth have been criticized because they rely on subjective estimations of tooth development, as seen in radiographs, and subsequent comparisons with pictures and descriptions in compiled dental charts. The distribution around an estimated age with these methods is usually more than +/- 2 yr between the 10th and 90th percentiles. In an attempt to avoid subjective estimations, objective measurements of developing teeth were correlated with subjects' chronologic ages. The structures measured were crown height, apex width, and root length. With the aid of a multiple regression model, a linear relationship between some of these distances and age was shown. The distances which were best correlated with age differed according to sex and age. This method has a 95% C.I. of about +/- 2 yr around an estimated age. It therefore seems to be more accurate than the earlier methods. Thus, the individual variation in tooth development is of the same order of magnitude, and a better estimation can therefore not be done in children 6-14 yr of age.

Adolescent↗