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Effects of various temperature regimens on enamel ultrastructure were examined by scanning electron microscopy in 70 rat incisors. The study has revealed a deep restructuring of the enamel during overheating in the course of tooth preparation, which necessitates the use of appropriate agents for the prevention and correction of the changes developing in dental tissue.
The conservative aesthetic restoration of unsightly anterior teeth has been revolutionized by the introduction of laminate veneers. Although direct composite veneers and pre-fabricated acrylic veneers have been used, the long-term clinical results are not as completely satisfactory as the laboratory-fabricated veneers. At present, indirect laboratory-made resin veneers and porcelain laminate veneers have become the two major modalities of treatment when conservative aesthetic restoration of anterior teeth is needed. In this article, details on these two types of veneers and steps of bonding them to the teeth are presented. Furthermore, colour modifications prior to veneer cementation, temporization of tooth preparations, long-term gingival response to veneer margins, and durability of the veneers have been reviewed.
This study evaluated 115 etched porcelain laminate veneers placed by a single operator at New York University Dental Center between 1982 and 1985. The restorations were divided into two groups. Group I consisted of 43 restorations placed without any tooth preparation; Group II consisted of 72 restorations placed using a chamfer preparation. The U.S.P.H.S. criteria was used to record cavosurface marginal discoloration, marginal integrity, and presence of caries. A clinical examination also revealed the number of debonds and/or the number of fractures of porcelain. A periodontal evaluation included the use of baseline and recall stone replicas of restored teeth to measure the height of the free gingival margin taken mid-facial to the incisal edge of the restoration. Any changes in gingival contour were also noted. Plaque and gingival indices were also recorded. The low fracture and debond rate found in the study combined with no incidence of caries seem to indicate that these restorations are functioning satisfactorily and with minimal negative periodontal response.
This article presents the treatment of several patients directed at the prevention of periodontal disease and restoration of an occlusion from an eating disorder. The disruption of the harmony between the anterior and posterior determinants of occlusion can lead to the loss of teeth. The lack of anterior guidance can create a molar-guided occlusion producing unfavorable occlusal interferences with destructive balancing side prematurities. Conversely, if the posterior teeth are permitted to drift into unstable occlusal relationships, the posterior dentition would develop an irregular guidance despite a suitable anterior guidance. The goal of the profession is preventing occlusal deterioration or disharmony between the anterior and posterior occlusal determinants and restore compromised occlusions when necessary. Etched metal retainers were fundamental to the treatment of specific patients while patient selection and perceptive tooth preparation were essential for success.
A provisional restoration must protect the prepared tooth, provide comfort and function and be esthetically acceptable and color stable. This study measured the degree of color change of provisional restorations. Five commercially available resins were evaluated: Trim, Tab, Kind, Snap and Duralay. Five cylindrical samples of each resin were fabricated by mixing the powder and the liquid to a predetermined ratio and pouring the mix into a mold. The Minolta Chroma Meter II Reflectance was used to establish the baseline color L* a* b*. The resins were then subjected to accelerated in vitro aging in a Weather-O-Meter and color readings were recorded. The color differentials on delta E* were computed for each sample (delta E*ab = [(delta L*)2+(delta b*)2]1/2). The difference is a quantitative measurement of color change. The National Bureau of Standards describes delta E* as units (NBS Unit = delta E*ab x 0.92). With this parameter only the allowable delta E*ab need be specified rather than the range of allowable L*, a*, b* values. This is important for color comparison and quality control functions. The results showed that Kind had a slight color change delta E* = -1.72, Trim demonstrated the most color change delta E* = -13.84, while the remaining resins demonstrated a noticeable change in color due to in vitro aging.
This evaluation consisted of a photographic evaluation of eight brands of commercially available #330 burs; comparisons were made to the standard as set by Dr Miles Markley. They were also evaluated as to their meeting ADA Specification No 23 for dental burs. In a second portion of the study, the burs were used to prepare channels in extracted teeth, and the pattern produced was evaluated. The results indicate that there is a great difference in the shape of the burs produced by the various manufacturers, as there was in the pattern they produced in preparing tooth structure.
The coordination of perceptive tissue management, diligent tooth preparation and prudent selection of the impression material for specific clinical conditions ensures the success of cast and ceramic restorations. The introduction of a knitted cord (Ultrapak with Astringedent) has alleviated the arduous aspects of tissue displacement and the new impression materials have displayed exceptional accuracy but healthy tissue is fundamental.
The objectives of tooth preparation for porcelain crowns are emphasized in this article. The forms of contour described by Gonon, LE Huche, Poggioli and Leibowitch are reviewed in the first part. In the second part, the profile of the cervical limits and their evolution are described, according to the materials used. The importance of the marginal fit, in relation to microleakage and esthetics, is related in the third part.
The success of a prosthesis, in the past was related only to the perfectness of construction and the occlusion. Nowadays the criterion for the acceptance of a prosthesis is its good relation to the gingival tissues. It would be a great error to isolate some parts of the prosthesis and study their possible influence to the gingival tissues. Instead of this, prosthesis should be seen on its whole. The proceeding for the prevention of the periodontal damage is related to all the stages of the construction of a prosthesis beginning from the tooth preparation, the impression till the fixation of the temporary prosthesis. According to these, the present study deals with the elements of the prosthesis which may affect the gingival tissues.
To discover the methods by which general dental practitioners instructed the commercial dental laboratories to make removable partial dentures and to ascertain whether the dental practitioners had surveyed and designed the dentures by themselves or not. The investigations were carried out in two commercial dental laboratories, the results of this survey showed that most of the dental practitioners did not give clear instructions on the order cards. Only a very small amount of the work (5.90%) had any traces of survey lines. Evidence of tooth preparations were found to be 30.12 percent and only 24.22 percent of the master casts had designs drawn on them. More than half the work (70.5%) was given to the technicians so that they could carry out the designs on their own initiative, although it should be the sole duty and responsibility of the dental practitioners themselves.
During the 30 years that have elapsed since the original report by Buonocore (1955), which demonstrated the increased retention of acrylic resins to an acid-etched enamel surface, the development of composite restorative materials in particular has enabled the clinician to offer a wider range of treatment alternatives to patients who present initially with problems directly related to their anterior teeth. Whilst the problem may be immediately apparent when the teeth erupt, professional advice is most often sought during adolescence. The provision of crowns for patients in this age group is contraindicated for many reasons, including compliance with extensive restorative procedures, large pulp cavities with the possibility of traumatic exposure during tooth preparation and inadequate crown height associated with an immature gingival margin.
A magnetic retention system has been used in more than 6000 complete and partial overdentures, sectional dentures and implant overdentures, with excellent clinical results and patient acceptability. For the overdenture application, decoronated, root-treated teeth are fitted with preformed or cast magnetisable alloy root elements, or 'keepers'. Following conventional denture construction, paired cobalt/samarium magnets in a special configuration are cured into the denture base so that with the denture inserted, the magnets grip the root elements with a retentive force of approximately 300 g per root. The paired magnet arrangement eliminates any external magnetic field and doubles the available retention. Magnetic retention has few of the problems encountered with other retention devices. It offers simplicity, low cost, self-adjustment, inherent stress-breaking, automatic repositioning after denture displacement, comparative freedom of lateral denture movement, reduces trauma to retained roots and eliminates the need for adjustment in service. For the sectional denture application, undesirable undercuts on the abutment teeth are used to provide passive, positive retention. The separate buccal and lingual sections are joined together by parallel pins fitting into matching tubes, assembly being maintained by magnetic attraction between a retention element in one section and a keeper in the other. Insertion and removal are more difficult than with a conventional denture but soft tissue coverage is minimal. There are no visible retainer arms and food traps are eliminated. Abutment tooth preparation is negligible, the laboratory procedures simple, and the treatment inexpensive and reversible. A clinical trial of magnetic overdenture retention in conjunction with osseointegrated titanium implants is now in progress. After 21 months acceptable clinical results have been obtained. An improved implant with an alumina core and a sintered hydroxyapatite coating is at present undergoing animal trials. Chemical bonding at the bone/implant interface is anticipated.
Small instructional models, such as replicas of tooth preparations, are used routinely in dental courses to encourage consistent instruction and evaluation. The option is available to fabricate models from molds rather than purchasing models from a manufacturer. Removal of small models from molds can be difficult, tedious, and time consuming. Also, the mold can be damaged by instruments during the removal of a model. A device that injects compressed air into the mold separates small models easily and quickly. The injector device can be assembled from parts available in the general market-place. Safety precautions should be observed.
In the fabrication of crowns and inlays it is very important that all the details of the impression are exactly reproduced by the cast. These requirements prevail between elastomeric impression materials and dental stones as well as between waxes and investment materials. Inadequate filling of the details of the impression will result in rounded inner corners of the casting, which then may not properly seat on the prepared tooth. Two brands of elastomeric impression material, dental stone, wax, investment material and wetting agent were chosen to study the reproduction of details. A master model of stainless steel, shaped like a truncated cone with a convex top and 60 degrees threads, was used. The shape of this model made it possible to make microscopic measurements of the reproduced detail of the threads. No significant difference, by different prepouring treatment of the impressions was found in reproducing details with elastomeric impression materials and dental stones. All combinations of elastomeric impression materials and dental stones reproduced, however, significantly more details than combinations of waxes and investment materials. The relevance of transferring conclusions from the laboratory investigation to clinical conditions are discussed as well as the clinical value of reproducing details.
Dirt tattoos caused by accidents can be washed out nearly complete and without cicatrices using a hard nail-brush, emery cloth and prepared tooth brushes with plenty of 0,1% oxycyanate.
A newly designed specimen allowed strength testing of simulated collarless metal ceramic crowns. The design provided precision replication of specimens having ceramic veneers that were completely supported by metal or that were extended 1 and 2 mm beyond the metal support. Twelve specimens of each design were loaded to failure at angles of 90, 45, and 6 degrees. Specimens with unsupported extensions approximated the compressive strength of those with complete framework support (means of 291.6 MPa, 320.2 MPa, and 335.9 MPa, respectively, for 1 mm, 2 mm, and 0 mm of porcelain extension) when tested at 90 degrees. However, for corresponding porcelain lengths, mean resistance to fracture at an angle of 45 degrees was 7.3, 11, and 5.8 times smaller, and at an angle of 6 degrees, 45, 60, and 25 times smaller. The differences were highly significant (P < .001). These results suggest that collarless metal ceramic crowns having up to 2 mm of unsupported porcelain could resist the same axial pressure as those restorations with complete metal support, provided a 90-degree shoulder tooth preparation is used.
PURPOSE: To determine whether the use of Gluma as a desensitizing agent on tooth preparations has any effect upon the bond strength of a resin composite restoration cemented to dentin. MATERIALS AND METHODS: Forty extracted human molars which were caries and restoration-free were occlusally reduced to remove enamel. Twenty of the teeth received a Gluma desensitization treatment and 20 were untreated (controls). Following a 7-day storage period, simulated resin composite inlays were bonded to all of the dentin specimens, using either All-Bond 2 with All-Bond Crown & Bridge Cement or OptiBond with Porcelite Dual Cure. Twenty-four hours later, the shear bond strength of the specimens was determined. RESULTS: Statistical analysis (paired t-tests) indicated no significant difference in bond strength for Gluma-treated specimens when compared to controls, for either bonding material.
The objective of this clinical study was to evaluate the long-term efficacy of placing sealed posterior composite restorations for arresting active caries. The tooth preparation for this bonded and sealed restoration was limited to placing a bevel in the enamel only, without the removal of the carious lesion. The radiographic and clinical performance of these ultraconservative sealed composite restorations placed over caries (CompS/C) was compared over a period of nine years with: 1) ultraconservative, localized sealed amalgam (AGS) restorations with no extension for prevention, and 2) traditional, unsealed amalgam restorations (AGU) with the usual extension for prevention outline form. Sealant retention with > 50 percent to 100 percent of the margins occurred in 64 percent of CompS/C and 82.5 percent of AGS restorations. After nine years the cumulative failure rates were 16 percent for CompS/C, 2.5 percent for AGS, and 17.1 percent for AGU restorations. Thus, the clinical performance of CompS/C restorations was slightly superior to that of the traditional AGU restorations. The AGS restorations were definitely superior to the traditional AGU restorations and to the CompS/C restorations in both children and adults alike. Complete sealant retention over CompS/C and AGS restorations was equivalent between children and adults (P = 0.14 and 0.74, respectively). A higher percentage of open margins in CompS/C restorations was seen, however, in children (17.4 percent) than adults (1.94 percent). This study has shown that Class I caries can be arrested by the CompS/C restoration.