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According to our examination, the anatomical shape of the root canal can influence the function of the examined instrument, therefore it's advisable to pay attention to the canal's curve at the selection of the root canal cutting instrument. Concerning the examined instruments, the least effective was the ultrasonic instrument.
Certain asymmetry of root canal preparation can be observed in the straight root canal group, as well. The modification of original root canal shape in this group usually is not substantial. Using hand instruments for shaping curved canals special tecniques are required to minimize the asymmetry. Though tendencies of different shaping characteristics can be observed on the mesiodistal and oro-vestibular views there are no statistically significant differences between the asymmetries measured on the oro-vestibular and mesio-distal views. The three dimensional form of canals usually exclude the possibility of forming the same asymmetry on both projections, but the difference between the two views is not striking, therefore the conventional clinical radiographs usually do not give complete information about the asymmetry of preparation.
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The surgical microscope, today used almost exclusively by endodontists, will eventually be used by general dentists as well. This will give them the ability to perform a myriad of tasks and achieve superior results.
PURPOSE OF STUDY: To examine factors which may predispose to tooth fracture, and to assess the compressive strengths of foods and sweets which are associated with tooth fracture in vivo. POPULATION STUDIED: Consecutive dental patients presenting with one or more fractured posterior teeth at the surgeries of three general dental practitioners, over a four-month period. METHOD: A pro forma was designed to elicit information on the factors associated with tooth fracture and the nature and extent of such fractures. Three general dental practitioners were requested to complete a pro forma for each patient presenting with a fractured posterior tooth over a four-month period. Foods and sweets considered to be associated with tooth fracture were identified and their compressive strengths tested. FINDINGS: A total of 129 cases of fractured posterior teeth were recorded, of which 48% occurred in the mandibular arch and 52% in the maxillary arch. In the mandible, 75% of tooth fractures occurred in molars while in the maxillary arch 50% occurred in molars. In 57% of cases assessed, no identifiable causative item was noted. Forty-five per cent of fractures were in teeth which had been restored on three or more surfaces. Compressive forces of 0.16KN to 2.2KN were obtained for food items implicated in tooth fractures. CONCLUSION: As mesio-occlusodistal restorations were identified as a major predisposing factor to tooth fracture in this study, with mandibular first molar teeth particularly affected, placement of cuspal coverage restorations may be considered to be a justifiable preventative measure in teeth identified as being at risk.
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This article reviews the recent literature on clinical trial studies of acid-etch bridges. Due to long-term retention problems, acid-etch bridges are not as yet considered among the permanent types of bridge prosthesis. When failure of acid-etch bridges occurs, the weak link seems to be the enamel-resin junction rather than the metal-resin junction. A modified posterior acid-etch bridge design is described in detail. This design, which incorporates a major retention-promoting component, is meant to improve long-term retention of posterior acid-etch bridges. Cast projections are added to the bridge design. These fit loosely into slot cavities made in the abutment teeth. Following bridge cementation, the slot cavities are restored with posterior composite. As a result, the cast metal projections are locked into the abutment teeth. This added retention device will maximize the long-term retention of posterior acid-etch bridges.
PURPOSE: To evaluate the shear bond strength to the dentin of permanent teeth and failure site of Dentastic hydrophilic dentin bonding agent. MATERIALS AND METHODS: Forty permanent noncarious molar teeth stored in distilled water were obtained. The teeth were cleaned with pumice and a rubber cup. The mesio-buccal surface of the teeth was ground flat with hand pressure with a series of SiC paper ending with the 600 grit to provide a uniform surface on dentin to which the resin composite could be applied. After preparing the tooth surface, the teeth were stored in distilled water for 48 hours. They were then divided at random into four groups of 10 specimens each: Group 1: Dentastic, five coats of primer; Group 2: Dentastic, three coats of primer; Group 3: Dentastic, five coats of primer, light-cured adhesive before resin bonding; Group 4: Dentastic, three coats of primer, light-cured adhesive before resin bonding. All specimens were thermocycled (500x) and sheared in a testing machine. After shear testing, the debonded sites of all samples were examined with a stereomicroscope and a scanning electron microscope. RESULTS: The results in MPa were: Group 1: 22.63 +/- 6.24; Group 2: 23.35 +/- 5.14; Group 3: 23.58 +/- 5.66; Group 4: 27.26 +/- 8.22. ANOVA and Student-Newman-Keuls showed no statistically significant difference between the groups. In all groups, all specimens failed at the dentin (dentin cohesive failure = dentin fracture) or at the resin (resin cohesive failure = resin fracture). This means that the bond strength of the product is stronger than the cohesive strengths of the dentin and the resin.
Since the late 1950s, porcelain-fused-to-metal (PFM) restorations have remained a standard modality for rehabilitation of anterior dentition. This article discusses recent modifications to improve aesthetics, using clinical cases to present the multifaceted potential of this type of restoration. Color and contour are discussed. The use of a combination of laminate veneers and PFM restorations is presented in cases where the crown restorations of the adjacent teeth are not necessary, but color and contour require enhancement to achieve an aesthetic result. The learning objective of this article is to review the utilization of the improved porcelain laminates and the modified PFM crowns.
The importance of the mucogingival complex in any restorative procedure has long been recognized, and various surgical and nonsurgical procedures have been developed to restore the compromised gingiva to its original health. The learning objective of this article is to review nonsurgical restorative techniques to manipulate the soft tissue surrounding the cervical aspect of the restored tooth into a more favorable contour. The techniques presented are applicable to direct and indirect restorations. Six case reports are used to illustrate the various clinical procedures. The techniques include: Supragingival direct restorative techniques, such as recontouring intact dentition; and intracrevicular indirect techniques, such as recapturing the soft tissue of deficient crown restorations, re-engineering recessed injured tissue, re-creation of hyperplastic injured tissue, re-engineering hyperplastic recessed posttrauma tissue, and re-engineering the periprosthetic envelope.
Until the 1980s, aesthetic dentistry focused its attention primarily on the replication and improvement of tooth structure by developing modifications of porcelain-fused-to-metal crown restorations, incorporated in porcelain systems in combination with adhesive technology. The introduction of new, improved, or modified periodontal surgical techniques addresses nearly all mucogingival challenges, except for the loss of papillae. Therefore, it is of critical importance to develop and define aesthetic guidelines for treatment of the mucogingival complex. In these guidelines, the aesthetic analysis of a treatment is divided into an evaluation of the mucogingiva and that of the tooth structure. Correction of mucogingival discrepancies is a prerequisite for aesthetic success in dental treatment. The learning objective of this article is to review the mucogingival discrepancies and examine a variety of potential solutions.
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Splinting is a well-accepted clinical treatment that has been us many years to control irreversible tooth mobilities through mechanical stabilization. With contemporary demands for quality-of-life dentistry, extracoronal or unesthetic splints can fall short of patient expectations. This article examines the rationale and technique for placing an intracoronal esthetic splint when full coverage restorations are no indicated or desired. This type of splint using bondable ceramic ropes is imperceptible both visually and to the patient's tongue, lips, and cheeks proprioceptively.
The development of porcelain laminate veneers has added a new dimension to dentistry in the treatment of unsightly anterior teeth. It is a less invasive procedure than the conventional crown restoration in the treatment of aesthetic problems. This paper highlights some of the considerations in the successful use of porcelain veneers.
The usefulness of splinting of severely loosened teeth in advanced periodontitis has been discussed extensively, both positively and negatively. Retention of patients own teeth through the aid of this simple and inexpensive resin composite splint provides a satisfactory solution for many affected patients. The fabrication and placement techniques for splints for the anterior and posterior regions are described, as are additional indications for such splints, which are fabricated from resin composite and glass fiber bundles. Such splinting can be provided even for severely loosened, periodontally diseased teeth without danger of intraoperative tooth loss. Long-term retention of such teeth can be ensured only through a risk-oriented postoperative program of oral hygiene and regular examination of the splint.