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PubMed2001

Tooth preparations for complete crowns: an art form based on scientific principles.

STATEMENT OF THE PROBLEM: No recent literature has reviewed the current scientific knowledge on complete coverage tooth preparations. PURPOSE: This article traces the historic evolution of complete coverage tooth preparations and identifies guidelines for scientific tooth preparations. MATERIAL AND METHODS: Literature covering 250 years of clinical practice was reviewed with emphasis on scientific data acquired during the last 50 years. Both a MEDLINE search and an extensive manual search were used to locate relevant articles written in English in the last 50 years. RESULTS: Teeth should be prepared so that they exhibit the following characteristics: 10 to 20 degrees of total occlusal convergence, a minimal occlusocervical dimension of 4 mm for molars and 3 mm for other teeth, and an occlusocervical-to-faciolingual dimension ratio of 0.4 or greater. Facioproximal and linguoproximal line angles should be preserved whenever possible. When the above features are missing, the teeth should be modified with auxiliary resistance features such as axial grooves or boxes, preferably on proximal surfaces. Finish line selection should be based on the type of crown/retainer, esthetic requirements, ease of formation, and personal experience. Expectations of enhanced marginal fit with certain finish lines could not be validated by recent research. Esthetic requirements and tooth conditions determine finish line locations relative to the gingiva, with a supragingival location being more acceptable. Line angles should be rounded, and a reasonable degree of surface smoothness is desired. CONCLUSIONS: Nine scientific principles have been developed that ensure mechanical, biologic, and esthetic success for tooth preparation of complete coverage restorations.

Bicuspid↗
PubMed2006

Peer assessment of dental attractiveness.

INTRODUCTION: The objectives of the study were to determine the relative importance of various dental features that contribute to overall dental attractiveness and to test the validity of the concepts of golden proportion and golden percentage as applied to the human dentition. METHODS: Sixty 30-year-old subjects (29 men, 31 women) were selected from the 20-year longitudinal Cardiff Survey. Color photographs of the subjects' dentitions were taken with the lips retracted so that their teeth and gums were clearly exposed. Twelve nondentists, aged 32 to 33 years, equally divided according to sex, rated the subjects' dental appearances on a 5-point Likert attractiveness scale. The maxillary anterior teeth were measured, and relevant ratios were calculated and compared with the golden proportion. Factor analyses and linear regression were used to investigate the hierarchy of dental features, and variance components analysis was used to estimate interrater agreement. RESULTS AND CONCLUSIONS: Overall dental attractiveness did not depend on any particular feature of the dentition. A hierarchy of various features was established, with crown shape ranked highest, and tooth and gum color ranked lowest. The golden proportion and the golden percentage were not decisive factors in determining dental attractiveness.

Adult↗
PubMedDate not supplied

Tooth-supported telescopic crown-retained dentures: an up to 9-year retrospective clinical follow-up study.

PURPOSE: This study evaluated outcome and quality of treatments with telescopic crown-retained dentures. MATERIALS AND METHODS: A total of 72 subjects (27 men and 45 women; mean age 67 years) wearing 75 telescopic crown-retained dentures (18 in the mandible and 57 in the maxilla) participated in the study. There were a total of 368 abutment teeth, 272 in the maxilla and 96 in the mandible. Each patient was clinically examined. Using the CDA evaluation system, four calibrated evaluators also examined, independently, the inner crowns for margin integrity and the superstructure for retention, occlusion, stability, wear, and esthetic appearance. Observer consistency was measured with Cohen's kappa. RESULTS: The observation period varied from 9 months to 9.3 years (mean 3.8 years). One telescopic crown-retained denture was lost, and 24 abutment teeth (7%) were extracted during the observation period. In 49 abutment teeth (13%), technical complications had occurred, and a total of four framework fractures (5%) were observed. Based on the CDA criteria, most of the characteristics were evaluated as satisfactory. The characteristics "condition of denture-supporting soft tissue" and "superstructure wear" showed the highest frequencies of not acceptable ratings, 44% and 45%, respectively. CONCLUSION: In this retrospective follow-up study, satisfactory outcome was found for tooth-supported telescopic crown-retained dentures over a mean observation period of 3.8 years.

Adult↗
PubMed1999

[The restoration of the anterior teeth with crown-root fractures].

The author suggests repair of the front teeth after crown-root fractures making use of the remaining crown. Due to precise coincidence of the fracture surfaces of both fragments of the tooth and fixation with a cast pin and composite materials, good results were attained.

Adolescent↗
PubMed2001

Maxillary anterior implant treatment: a protocol for aesthetic success.

This case represents how predictable results can be obtained in a difficult situation if a tried-and-true protocol is closely followed. An atraumatic surgical technique, followed by controlled healing through correct implant placement and the use of a custom-healing abutment, set up the success of the soft tissue component of the case. Meticulous laboratory communication, combined with correct restoration selection, was the final step in the creation of lifelike results.

Adult↗
PubMed2005

[Short-term observation of gold-plating unprecious metal ceramic crown in restoring anterior tooth].

PURPOSE: To evaluate the short-term effect of gold-plating technique used in Ni-Cr metal ceramic crown in restoring anterior teeth. METHODS: 64 teeth from 38 cases were divided into two groups. Each group consisted of 32 teeth. All the teeth were restored with Ni-Cr metal ceramic crown. The restorations in group 1 had no treatment while those in group 2 were treated with gold-plating technique in the base metal alloy.Gingiva discoloration, bleeding on probing (BOP), plaque index (PLI) and sulcular bleeding index (SBI) were examined 1 and 12 months after restoration. Chi-square test and Wilcoxon rank sum test were used for statistical analysis. RESULTS: Gingiva discoloration was found in both groups after bonding. According to the percentage of gingival discoloration, there was no significant difference between group 1 and group 2 (12.5% vs 28.1%) (P>0.05). However, 12 months later, significant difference was found between the two groups (15.6% vs 37.5%)(P<0.05). According to PLI, BOP and SBI, there was no statistical difference between two groups (P>0.05). CONCLUSION: Gold-plating was a good method in solving the problem of gingival discoloration in unprecious metal ceramic crown.

Chromium Alloys↗
PubMed2005

Intermaxillary tooth size discrepancy and mesiodistal crown dimensions for a Turkish population.

INTRODUCTION: The aims of this study were to determine the size of individual permanent teeth, tooth-size ratios for the maxillary and mandibular dentitions, and sex differences for those variables in a Turkish population, and to compare the figures obtained with those of the Bolton analysis. METHODS: The data were derived from dental casts of 150 Turkish subjects (72 men, mean age 22.09 +/- 3.11 years; 78 women, mean age, 21.11 +/- 2.08 years) with normal occlusions. The mean, standard deviation, and minimum and maximum values were calculated for individual tooth size, and overall and anterior ratios, separately for men and women. To determine whether there are sex differences in intermaxillary tooth size discrepancies, an independent samples t test was performed. RESULTS: The mesiodistal dimensions of the maxillary teeth showed greater variability than the mandibular teeth, with the first molar dimensions having the greatest variability. The overall and anterior ratios were found to be 89.88 +/- 2.29 and 78.26 +/- 2.61, respectively. A statistically significant sex difference was found only in overall ratio (P < .001). According to Bolton's mean values, a discrepancy in the overall ratio was found in 18% of Turkish normal occlusion subjects, and anterior ratios outside 2 standard deviations from the Bolton mean were found in 21.3% of our sample. CONCLUSIONS: These findings indicate that population-specific standards are necessary for clinical assessments. Bolton's original data do not represent Turkish people, and therefore it is appropriate to use Turkish norms in daily orthodontic practice for Turkish patients.

Adult↗
PubMed1989

Three dimensional shape measurement of teeth by the system of laser displacement meter and computer controlled scanning machine. 2. The improvement of accuracy by means of the divisional measurement method.

The accuracy of the three dimensional shape measurement of teeth was improved. The system was composed of a laser displacement meter and a computer controlled scanning machine. The compensation of errors which were observed when the reflected beam was shaded by the model teeth itself was attempted by connecting the data which were measured by rotating the model tooth at 180 degrees on the going stage. The accuracy of measurement was examined at the slope of 7 crown abutment tooth. When the model tooth were measured without tilting, the difference between the true value and the measured data was -240 microns (-2.8%). However, by tilting the model tooth at +/- 20 degrees on the going stage and connecting the two couples of data obtained, the difference considerably decreased into +/- 10 microns (+0.1%). In order to measure a complete crown abutment tooth with high accuracy and without error at the shaded portion, the model tooth was tilted +/- 30 degrees and rotated 180 degrees on the going stage and measured divisionally at four regions. The four partial data thus obtained were combined by using the software program. By the present procedure, the margin of the abutment tooth was recognized and the error data were eliminated. The overlapped data upon divisional measurements were excluded and the complete data of the single abutment tooth were saved into a file. They are possible to be the basic data for the future production of prostheses by means of CAM technique.

Computer Graphics↗
PubMed2002

Survival of intentionally retained permanent incisor roots following crown root fractures in children.

Retaining tooth roots, following crown loss, confers a number of benefits including the preservation of alveolar bone. Intentional root retention in adults has been widely investigated but little is known about this treatment approach in children. Therefore, the aim of the present study was to investigate the clinical outcomes associated with permanent anterior root retention in a young population. The study group comprised 53 children who had received treatment in the paediatric dentistry clinic, Charles Clifford Dental Hospital, Sheffield, UK, over the past 10 years, following a complicated crown root fracture of a permanent maxillary incisor at or below the gingival margin. Data relating to patient age at crown root fracture, gender, previous trauma history, tooth vitality, treatments performed and clinical outcomes were obtained retrospectively using patient records. The mean age of the subjects at initial crown root fracture was 12.1 years (range 8.3-15.8 years) and there were more than twice as many males (n = 37, 70%) as females (n = 16, 30%). In just over half of the cases seen (n = 29, 54%), the tooth involved was already nonvital at the time of crown root fracture. For the majority of these nonvital teeth (n = 27, 93%), primary treatment had comprised placement/replacement of a calcium hydroxide root dressing. The remaining two teeth did not require root treatment as a satisfactory gutta percha root filling was already present. A variety of treatments was undertaken for the 24 vital roots: in 15 (63%) cases the pulp was extirpated and calcium hydroxide placed; three (12%) cases were subject to a pulpotomy; five (21%) cases were left untreated with the hope that vitality would be maintained following gingival healing and in one case the radicular pulp was extirpated and immediately obturated with gutta percha. The mean time that the roots were kept under review was 2.6 years (+/- 1.57, range 0.6-6.8). During this period, only five roots (9%) had to be removed due to persistent periapical infection. There were no complications associated with the five cases where vital root submergence had been permitted but all three cases which had initially undergone a pulpotomy subsequently presented with pulpal necrosis necessitating pulpal extirpation and calcium hydroxide therapy. These findings indicate that efforts to retain permanent anterior roots in a young population are justified in view of the high clinical success rate of over 90% over a 2-year period.

Adolescent↗
PubMed2006

Molar development in common chimpanzees (Pan troglodytes).

Numerous studies have reported on enamel and dentine development in hominoid molars, although little is known about intraspecific incremental feature variation. Furthermore, a recent histological study suggested that there is little or no time between age at chimpanzee crown completion and age at molar eruption, which is unlikely given that root growth is necessary for tooth eruption. The study presented here redefines growth standards for chimpanzee molar teeth and examines variation in incremental features. The periodicity of Retzius lines in a relatively large sample was found to be 6 or 7 days. The number of Retzius lines and cuspal enamel thickness both vary within a cusp type, among cusps, and among molars, resulting in marked variation in formation time. Daily secretion rate is consistent within analogous cuspal zones (inner, middle, and outer enamel) within and among cusp types and among molar types. Significantly increasing trends are found from inner to outer cuspal enamel (3 to 5 microns/day). Cuspal initiation and completion sequences also vary, although sequences for mandibular molar cusps are more consistent. Cusp-specific formation time ranges from approximately 2 to 3 years, increasing from M1 to M2, and often decreasing from M2 to M3. These times are intermediate between radiographic studies and a previous histological study, although both formation time within cusps and overlap between molars vary considerably. Cusp-specific (coronal) extension rates range from approximately 4 to 9 microns/day, and root extension rates in the first 5 mm of roots range from 3 to 9 microns/day. These rates are greater in M1 than in M2 or M3, and they are greater in mandibular molars than in respective maxillary molars. This significant enlargement of comparative data on nonhuman primate incremental development demonstrates that developmental variation among cusp and molar types should be considered during interpretations and comparisons of small samples of fossil hominins and hominoids.

Age Determination by Teeth↗
PubMed1981

The nickel-chromium crown for restoring posterior primary teeth.

The differences between the recently marketed nickel-chromium crown and other crowns available for primary posterior teeth are compared. Indications for use of preformed crowns are reviewed and techniques of tooth preparation, crown adaptation, and cementation are described.

Cementation↗
PubMed1997

Crown-root fracture of lower molar--restorative procedures.

Endodontically treated teeth may undergo crown, crown-root, or root fractures. The treatment of fractured teeth can be complicated, sometimes because of difficulties with the final restoration. This case report describes a case of crown-root fracture of a left lower first molar in which endodontic treatment and rapid orthodontic eruption of the tooth made a good prosthetic restoration possible.

Adult↗