[Crowns construction on a devitalized tooth (I)].
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Crowns↗
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Partial pulpotomy and tooth reconstruction of a crown-fractured permanent incisor: a case report.
Pulp exposure due to traumatic injuries in the anterior permanent teeth of adolescents is a common occurrence. A vital permanent maxillary incisor with complex crown fracture and pulp exposure was treated by partial pulpotomy and assessed clinically through pulpal sensitivity tests and radiographically for periapical healing. Partial pulpotomy consisted of pulp tissue removal to a depth of only 1 to 2 mm, then capping the pulpal wound with calcium hydroxide, lining with resin-modified glass-ionomer cement, and restoration with resin composite. At each recall (7, 15, 21, 50, 90, 150, and 250 days), no spontaneous pain was observed; the pulp showed signs of vitality and absence of periapical radiolucency after 90 days. For long-term success, partial pulpotomy is recommended as an option for cases of traumatic pulp exposure in permanent incisors with crown fractures.
Adolescent↗
Assessment of convergence angles of tooth preparations for complete crowns among dental students.
OBJECTIVES: Convergence angles for complete crown preparations have been recommended at 4-12 degrees . However, practitioners have difficulty meeting these recommendations. This study measured and compared the convergence angles of tooth preparations for complete crowns prepared at three Colleges of Dentistry: the University of Tanta, Egypt, King Abdulaziz University, Saudi Arabia, and The Ohio State University, Columbus, Ohio. METHODS: The convergence angles of 499 tooth preparations for complete crowns were evaluated. These comprised of a random sample of 262 teeth prepared by third-year dental students at the University of Tanta on extracted molars under normal preclinical conditions, 37 preparations on molar teeth on typodonts done by first-year dental students. The Ohio State University and 200 molar typodont complete crown preparations done by fourth-year dental students at King Abdulaziz University, Saudi Arabia. The bucco-lingual and mesio-distal convergence angles of each preparation were measured with a goniometer microscope. Mean convergence angles were calculated, and differences between groups were tested for statistical significance with analysis of variance (ANOVA) at 5% level of confidence. RESULTS: Convergence angle measurements were significantly different between the groups and the dimensions (P<0.001). The greatest convergence value (19.8+/-10.0) was for bucco-lingual measurements prepared by Egyptian dental students. The smallest convergence value (14.1+/-3.8) was for mesio-distal measurements prepared by Saudi dental students. CONCLUSIONS: This study emphasized the difference between what is taught at dental schools (what is theoretically possible) and the school results of actual practice. There was a considerable disparity between the convergent angles recorded in this study and the ideal configurations recommended in fixed prosthodontic textbooks and the dental literature.
Crowns↗
Dentition and occlusion development in African American children: mesiodistal crown diameters and tooth-size ratios of primary teeth.
PURPOSE: The aim of this study was to evaluate the mesiodistal primary tooth size diameter and posterior sagittal tooth-size ratio in an African American population and compare to existing African American and European American norms. METHODS: A sample of 1,124 African American children, 564 males and 560 females, was used to record crown size diameters employing indirect (cast) and direct (intraoral) measurement techniques. RESULTS: African American males showed larger crown diameters than African American females for each of the 5 classes of primary teeth (a=0.05 level). Sexual dimorphism averaged 3.5% in the maxilla and 3.2% in the mandible. When inter-racial primary crown size comparisons were made between African American and European American children, African American males showed larger mean crown diameters for each class of primary teeth compared to European American males. The inter-racial comparisons in crown diameters of females showed fewer statistically significant differences in primary teeth classes. When crown size comparisons of the primary dentition's posterior segments were made, African American males and females showed a larger primary posterior sagittal tooth-size-ratio compared to European American children. CONCLUSIONS: While intra- and inter-racial sex differences exist in the primary teeth of African American and European American children, with few exceptions, the mesiodistal crown size differences and sexual dimorphism appear to be larger for the African American population. African American children show a larger primary posterior sagittal tooth-size ratio (0.96) compared to European American children (0.94).
Black or African American↗
Light-force technique for the early treatment of an ectopic tooth.
Free crown tipping can be useful when teeth do not erupt in their physiologic sequence and a real intraosseous migration and eruption of a single tooth into a distant ectopic position can be observed. This article presents a case of an ectopic mandibular lateral incisor treated early, with the light-force technique and uncontrolled forces, and finished with the bidimensional edgewise appliance. A Caucasian female patient, 10 years 10 months of age, had a mandibular left lateral incisor displacement, with the lateral incisor crown positioned mesial to left second primary molar. An early treatment was planned to correct the mandibular left lateral incisor displacement and to allow proper eruption of the mandibular left canine and first premolar. A second phase of treatment, in permanent dentition, was planned for the dental Class II subdivision on the right and deep bite correction. Phase 1 treatment was completed after 10 months; phase 2 treatment was initiated in the permanent dentition and lasted 18 months. Treatment achieved the following outcomes: (1) mandibular lateral incisor in corrected position; (2) full canine and molar Class I relationship; (3) overjet and overbite within the normal limits; (4) symmetric arches; and (5) a balanced profile. The radiograph evaluation revealed good root parallelism and mandibular left lateral incisor light root resorption. The light-force technique is not only a possible alternative but the ideal appliance for treatment in the mixed dentition, when the permanent teeth should be controlled.
Child↗
Thin layer alpha-Al2O3:C beta dosemeters for the assessment of current dose rate in teeth due to 90Sr intake, and comparison with electron paramagnetic resonance dosimetry.
The use of thin-layer alpha-Al2O3:C thermoluminescent detectors (TLDs) for the assessment of current beta dose rate in human teeth due to 90Sr intake is investigated. The teeth used in this study were collected from members of the Techa river population who were exposed to radiation as a result of releases of the Mayak plutonium production facilities (Southern Urals-Russia) between 1949 and 1956. The beta dose rates from different parts of the tooth (enamel, crown dentine, and root) were determined by storing the detectors over the samples in a shielded environment. The cumulative dose measured by electron paramagnetic resonance (EPR) in different dental tissues is found to be proportional to current dose rate obtained from alpha-Al2O3:C thermoluminescence dosemeters. The retention of 90Sr in various parts of the teeth is discussed.
Aluminum Oxide↗
Pulpal healing following acute dental trauma: clinical and radiographic review.
Successful treatment of tooth luxations, crown fractures, and root fractures is often compromised by the emergency nature of the injury. Precise radiographic and clinical evaluation is required to facilitate healing and treatment selection. While traditional treatment protocols indicate that dental injuries implying pulpal ischemia require immediate endodontic therapy to avoid healing complications, the clinical investigations discussed herein suggest that a variety of etiologies for pulp survival/pulp necrosis exist. This article discusses the long-term prognosis of pulp necrosis following traumatic dental injuries, and clinical and radiographic criteria for its diagnosis.
Clinical Protocols↗
Functional and esthetic considerations for single-tooth Ankylos implant-crowns: 8 years of clinical performance.
PROBLEM: Following the loss of an anterior natural tooth, the mucogingival complex begins to collapse. The early placement of endosseous dental implants can prevent or reduce the extent of this collapse. If there is a long interval between the loss of the natural tooth and the placement of the implant prosthetic replacement, this collapse tends to increase significantly. PURPOSE: This paper will report on the clinical success of this implant product in the fabrication of esthetic, functional, and harmonious replacements for missing single, natural teeth for a period of 8 years. METHOD: A total of 275 single Ankylos implant tooth restorations in the anterior and posterior jaw regions were placed and monitored for 8 years. Of these, 264 implants were restored using the titanium Balance abutments, and only 11 were restored using ceramic abutments. The final restorations were either metal-ceramic or full-ceramic crowns and were cemented with glass ionomer cement. RESULTS: The survival rate was 98.2%, with only 5 implants being lost during the healing phase. There were no other implant losses in the postloading period that averaged 3.2 years. To date, there have been no mechanical complications associated with the prosthetic components (ie, screw loosening, screw breaking, or crown breaking) for either the titanium or the ceramic abutments. CONCLUSIONS: Experience with the Ankylos system with single-tooth replacement indications may be considered positive with regard to the esthetic and functional results of the treatment. The lack of mechanical complications and problems with the hard and soft tissue in the loading phase of the implants suggests the functional safety of the tapered connection between implant and abutment.
Crowns↗
Width/length ratios of normal clinical crowns of the maxillary anterior dentition in man.
The purpose of this investigation was to analyze the clinical crown of the 3 tooth groups of the maxillary anterior sextant of the permanent dentition of normal subjects with respect to (i) width, length and the width/length ratios and (ii) determine if there is a correlation between tooth dimensions or tooth group ratios and subject height. Subjects (> or = 20 y.o.) were recruited for this study if (i) the free gingival margin on the facial surface of teeth in the maxillary sextant was positioned apical to the cervical bulge, (ii) there was no evidence of attachment loss; as determined by lack of a detectable CEJ and (iii) the marginal tissue was knife edged in form, firm in consistency and coral pink in color. Teeth were excluded if (i) there was evidence of gingival alteration, i.e., gingival overgrowth/hyperplasia, inflammation, altered passive eruption, attachment loss, gingival recession or history of periodontal surgery, or (ii) there was evidence or history of incisal edge/proximal tooth alteration as in, i.e., restorative intervention, traumatic injury or occlusal wear into dentin. At least 1 suitable tooth from each tooth group of the maxillary anterior dentition had to be present. A maxillary impression was taken and poured in yellow die stone. The widest mesial-distal portion and the longest apical-coronal portion of the test teeth were measured. Gender, ethnicity and subject height (SH) were recorded for each participant. Due to a limited ethnic diversity only data from the Caucasian group were analyzed. The mean coronal tooth width (mm) of males versus females was CI: 8.59 versus 8.06, LI: 6.59 versus 6.13 and CA: 7.64 versus 07.15. The mean coronal tooth length (mm) of males versus females was CI: 10.19 versus 9.39, LI: 8.70 versus 7.79 and CA: 10.06 versus 8.89. All width and length measures were significantly greater for males than for females. The mean coronal tooth width/length ratios for males versus females was CI: 0.85 versus 0.86, LI: 0.76 versus 0.79 and CA: 0.77 versus 0.81. A comparison between genders of the width/length ratios of the CI and LI were found not to differ, however the CA ratio for females was significantly greater than for males. A statistically significant difference was found to exist between the mean (cm) SH for males versus females: 181.2 versus 164.0. A positive correlation (p < or = 0.0001 to 0.0691) was found to exist between tooth group width/height ratios within genders. No significant correlation was found between any of the tooth dimensions or tooth group ratios and SH. The results of this study indicate that within male and female Caucasians, the mean width/length ratio of the maxillary 3 anterior tooth groups is 0.81. As well, within both genders there is a positive correlation between tooth group width/length ratios. The significance of these findings with respect to periodontal mucogingival plastic surgical procedures is discussed.
Adult↗
Eruption of third permanent molars after the extraction of second permanent molars. Part 1: Assessment of third molar position and size.
The eruptive path of third molars after extraction of second molars was examined in 63 patients. Panoramic radiographs from the start and the end of active treatment and 3 or more years after treatment were assessed. Study models were used to compare the size of the second and third molars and to assess the final position of the third molars. All third molars erupted; none became impacted. During eruption, maxillary third molar crowns uprighted and maintained their angulation as they came into occlusion. Mandibular third molar crowns continued to upright significantly mesiodistally after active treatment, with space closure the result of horizontal translation rather than mesial tipping. Further uprighting occurred once occlusion was established, although few became as upright as the second molars they replaced. However, mandibular third molar roots were frequently curved distally, thus the third molar crown position was invariably better than the overall tooth angulation would suggest, by 16.5 degrees on average. Model analysis (Richardsons' scoring system) showed 96% of mandibular and 99% of maxillary third molars erupted into a good or acceptable position. Limitations of this scoring system are discussed. The mesiodistal size of third molars was suitable to replace second molars; on average, mandibular third molars were 0.55 mm larger and maxillary third molars were 0.7 mm smaller than second molars.
Adolescent↗
Double facial and a lingual trace talon cusps: a case report.
Talon cusp is an uncommon odontogenic anomaly, presented as an accessory cusp like structure on the crown of an anterior tooth. Their presence may create diagnostic, esthetics, occlusal, pulpal and periodontal problems. This case report describes an unusual double facial talon cusp along with lingual trace talon on left maxillary central incisor.
Child↗
An 18-year retrospective survival study of full crowns with or without posts.
PURPOSE: This study of full crowns investigated long-term survival in relationship to biologic and technical variables. MATERIALS AND METHODS: A total of 1,037 full crowns in 456 patients, made in an undergraduate university clinic, were evaluated over an 18-year period. All patients were offered a supportive maintenance program. Failures of full crowns were classified as irreversible (loss of full crown and/or tooth) or reversible (full crown intact after conservative treatment) complications and as biologic or technical/patient-related failures. RESULTS: The Kaplan-Meier survival rate after 18 years was 78%. No statistically significant differences were found between restorations in the maxilla and mandible (P= .150); between restorations on molars, premolars, and anterior teeth (P = .671); and between restorations on posts and cores compared to restorations without posts and cores (P = .602). For the surviving restorations, the improved plaque score over time was statistically significant (P = .001). Biologic failures (66.4%) resulting in removal were more common than technical and patient-related failures (33.6%). Caries was the most frequent reason for failure (irreversible complication). CONCLUSION: The survival of full crowns made in an undergraduate university clinic during an 18-year period is comparable to the results published by university departments or private practitioners. Plaque scores and bleeding on probing were not directly related to failures. Occurrence of a previously reversible complication is a predicting factor for an irreversible complication. A reversible complication within the first 2 years will probably lead to an early irreversible complication.
Adolescent↗
[A new approach to the description of the anatomical characteristics of the surfaces of human teeth].
A new approach to the anatomical structure peculiarities description of the crown part of the tooth surface by the system of the parallel sections is suggested. It helps to make their graphic picture and analytical description producing a new anthropometric system of assessing normal and pathological conditions.
Anthropometry↗
Factorial analysis of variables influencing stress in all-ceramic crowns.
OBJECTIVE: The objective of this investigation was to evaluate the relative contribution of variables in the crown-cement-tooth system that can influence magnitude of maximum principal stress in all-ceramic crowns. METHODS.: Factorial analysis was performed to calculate the coefficients of main and interactive effects of seven variables on maximum stress distribution in a series of finite element models of an axisymmetric stylized ceramic crown-cement-tooth system. Variables investigated at two levels were selected for their clinical relevance and included those relating to crown material and geometry (thickness and cuspal incline), cement modulus and thickness, supporting tooth core, and position at which the occlusal load was applied. RESULTS: The average principal stress for all combinations of all variables was 135.1 MPa but stress magnitude ranged from 73.7 to 214.0 MPa. Crown material and thickness are of primary importance in stress magnitude but other variables (cement modulus, load position, and supporting tooth core) also contribute to the stress magnitude. Interactions between these variables can have an important influence, particularly since the stress in the crown is not necessarily sensitive to the same factors for all crown material systems. SIGNIFICANCE: Comprehensive evaluation of stress in a crown of a crown-cement-tooth system must integrate the influence of single variables and their interactions.
Aluminum Silicates↗
Endodontic treatment of a mature tooth with an abnormal clinical crown.
In this report, a case of a mature tooth with abnormal crown morphology, which created plaque retentive areas was presented. The pulp was necrosed due to the periodontal disease, and the anomaly was thought to be an aberration of a talon cusp. Therapy involved the reshaping and the endodontic treatment of tooth.
Child↗
[The planning of the design of combined crowns with regard to tooth display during conversation and smiling].
Analysis of the type of teeth crown exposure in talking and smiling, carried out in 798 subjects, has shown that the perigingival third of the crowns is not exposed in the majority of the examinees. This permitted employment of cast combined crowns with wide perigingival metal rims to support the clasp dentures to make them look better when supplying 73 patients with partial removable dentures.
Crowns↗
Tooth surface loss. 11. Surgical crown lengthening.
Restoration of worn teeth can be made easier by surgical crown lengthening. It improves appearance and facilitates tooth preparation. Anatomical features can limit the height that can be gained.
Crown Lengthening↗
CROWN DEVELOPMENT IN HUMAN DECIDUOUS MOLAR TEETH.
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Anatomy↗