OPERATIVE PROCEDURES FOR CHILDREN.
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An in vitro study evaluating the effect of ferrule length on fracture resistance of endodontically treated teeth restored with fiber-reinforced and zirconia dowel systems.
STATEMENT OF PROBLEM: There are few published studies analyzing the effects of different ferrule lengths of endodontically treated teeth in relationship to newly developed fiber-reinforced and zirconia dowel systems. PURPOSE: This in vitro study compared the effect of 3 different ferrule lengths on the fracture resistance and fracture patterns of crowned endodontically treated teeth restored with 4 different esthetic dowel systems. MATERIAL AND METHODS: The crowns of 123 human maxillary canines were removed at the cementoenamel junction and the roots were endodontically treated. Three master tooth models were prepared to ferrule lengths of 1.0 mm, 1.5 mm, and 2.0 mm to produce 3 master analogs. Each root was embedded in autopolymerizing resin with a 0.2-mm layer of silicone impression material to simulate the periodontal ligament. Forty analogs of each master tooth, with ferrule lengths of 1.0 mm, 1.5 mm, and 2.0 mm were produced with copy-milling (Celay system). Each group was further subdivided into 4 groups of 10 specimens each and restored with 4 different esthetic dowel systems (quartz fiber, glass fiber, glass fiber plus zirconia, and zirconia). All dowels were luted with adhesive resin cement (RelyX ARC), restored with composite cores (Valux Plus), and Ni-Cr alloy (Wiron 99) complete crowns. All specimens were loaded at 130 degrees to the long axes in a universal testing machine at a crosshead speed of 1 mm/min until fracture. Fracture patterns were classified as failures above or below the incisal third of the roots. The data were analyzed with 2-way ANOVA and Tukey HSD tests (alpha=.05). A Fisher exact test was conducted for evaluation of the mode of failure (alpha=.05). RESULTS: Mean failure loads (kg) for quartz fiber, glass fiber, glass fiber plus zirconia, and zirconia groups, respectively, with the 3 ferrule lengths were: 1.0-mm ferrule specimens: 98.09 +/- 2.90, 85.36 +/- 2.82, 80.24 +/- 1.88, 70.11 +/- 2.48; 1.5-mm ferrule specimens: 101.0 +/- 2.88, 87.58 +/- 2.83, 89.8 +/- 2.09, 82.71 +/- 2.14; 2.0-mm ferrule specimens: 119.5+/-1.78, 99.84+/-1.23, 98.6 +/- 1.64, 95.42 +/- 1.02. Teeth prepared with 2.0-mm ferrules demonstrated significantly higher fracture thresholds (P<.001). There were no significant differences in fracture patterns. CONCLUSION: Increasing the ferrule length of the endodontically treated teeth from 1 mm to 1.5 mm in specimens restored with quartz-fiber and glass-fiber dowels did not produce significant increases in the failure loads (P=.084, P=.119, respectively). No significant difference was detected between glass-fiber and glass-fiber plus zirconia dowels with 1.5-mm and 2.0-mm ferrules (P=.218, P=.244, respectively). However, fracture thresholds were higher for all 4 dowel systems when the specimens were prepared with a 2.0-mm ferrule length (P<.001).
Analysis of Variance↗
Developing natural aesthetics with direct composite restorations.
Contemporary direct restorations have significantly evolved since their initial development, allowing clinicians to develop natural-looking restorations. Composite resins can be applied for restoration of cavities, anterior tooth reconstruction, core preparation for crowns, splinting, provisionalization, placement of orthodontic brackets, and cementation. The development of hybrid and microfilled composite materials has further improved the clinician's ability to deliver minimally invasive treatment options. This article demonstrates a stratification process in the interproximal and incisal edge reconstruction of maxillary right and left central incisors using a small-particle hybrid composite resin to develop an optimal aesthetic result.
Adult↗
Evaluation of the 1-year clinical performance of dentin-bonded ceramic crowns and four case reports.
OBJECTIVE: Dentin-bonded crowns are a comparatively recent addition to the dentist's armamentarium. Although 1-year data cannot predict the long-term performance of restorations, it may be useful for new treatment modalities, given that it will describe early, catastrophic failures. In this study, the 1-year performance of 109 dentin-bonded crowns was assessed. METHOD AND MATERIALS: The crowns were placed in two locations (Glasgow, Scotland, and Belfast, Northern Ireland) for 27 patients. The principal reasons for crown placement were tooth substance loss, esthetic reasons, and tooth fracture. Minimal preparations were used. Ninety-eight crowns were available for review at 1 year. RESULTS: Ninety crowns were found to be intact, six had a crack visible on transillumination and two had fractured. No crowns had debonded. No secondary caries was noted. No unsatisfactory scores were recorded for marginal adaptation, adjacent gingival health, or color match. CONCLUSION: The dentin-bonded crowns placed during this study provided good overall performance at 1 year.
Adolescent↗
Inhibition of morphogenesis and stimulation of vascular proliferation in embryonic tooth cultures by a sarcoma growth factor preparation.
Sarcoma growth factor (SGF) induces proliferation and anchorage-independent growth of nonmalignant cells. It competes with epidermal growth factor (EGF) for the EGF-receptors at the cell surface. SGF-like factors have recently been isolated from embryos, suggesting that SGFs may represent embryonic forms of EGF. Therefore, we have tested whether SGF preparations affect organogenesis and differentiation of cultured embryonic tissues. The embryonic tooth rudiments were cultivated in the presence of SGF and EGF. Stimulation of vascularization was seen in both of these organ cultures. Therefore, we propose that endothelial cells may be target cells for SGF, and SGF may be involved in the control of vascularization during embryogenesis. SGF and also, to a certain extent, EGF profoundly inhibited morphogenesis and differentiation of the tooth germ, with concomitant stimulation of vascularization. Analysis of cell proliferation revealed that some cell types of the tooth germ did not respond to SGF by proliferation, while a stimulation by EGF was observed. Nevertheless, tooth morphogenesis was also slightly inhibited by EGF, suggesting that growth factors which enhance proliferation do not necessarily stimulate morphogenesis and differentiation. Since the SGF preparations contain several factors, the effects observed could be due to the action of one or more factors.
Animals↗
Composite resin inlays: a single appointment technique.
This article presents a time efficient technique for the fabrication and subsequent placement of a composite resin inlay. An inlay preparation is cut into a tooth and a polyvinylsiloxane impression is made. A polyether impression of the polyvinylsiloxane impression forms a die, then a composite resin inlay is fabricated on the die. The inlay is contoured and polished on the die and occlusion is evaluated clinically. The inlay has a final polymerization under intense light and vacuum pressure, then is cemented with a mixture of unfilled resin and hybrid composite. The technique allows an esthetic restoration to be placed in one appointment. The die provides easy access and rapid inlay fabrication. There is no need to place a separator on the prepared tooth, no chance of premature tooth bonding, and interproximal contact is easily achieved.
Adult↗
Impression technique for arches requiring both implant and natural tooth restorations.
Implant impression copings reduce access to prepared teeth during the impression-making process. If the impression copings and teeth are in close proximity, it may be difficult to extrude impression material circumferentially around the margins of the tooth preparations. A technique is described that allows the impressions of the prepared teeth to be made without the implant impression copings interfering. The advantages and disadvantages of the technique are discussed.
Dental Abutments↗
Porcelain versus composite inlays/onlays: effects of mechanical loads on stress distribution, adhesion, and crown flexure.
This study used 2-D finite element modeling to simulate cuspal flexure and stresses at the surface and tooth-restoration interface of a restored maxillary molar using three restorative materials; the influence of four inlay/onlay preparation configurations on stress distribution within the complex was also investigated. A buccolingual cross-section of an intact molar was digitized and used to create 2-D models restored with different restorative materials (feldspathic porcelain, high- and low-elastic modulus composites) and tooth preparations (small and large inlays, small and large onlays). Two simulated 25-N oblique loads were applied to the cusps. The tangential stress for each finite element node located at the tooth surface, interfacial stress, and relative cuspal flexure were analyzed. All materials and tooth preparations exhibited similar surface tangential stress patterns, with a definite compressive area at the external cusp ridges, a tensile zone at the occlusal surface, and compression stress peaks at the CEJ. The low-elastic modulus composite showed reduced tensile stresses at its surface but increased tension at the dentin-adhesive interface when compared to ceramics. All types of onlays demonstrated a majority of compressive interfacial stresses, while inlays showed a majority of tensile stresses. The interfacial tension at the dentin level increased with the flexibility of the restorative material. Only the large ceramic onlay displayed almost pure compression at the interface. Composite-restored teeth exhibited increased crown flexure, while porcelain-restored teeth showed increased crown stiffness. Porcelain inlays/onlays featured more detrimental stresses at the occlusal surface but better potential protection against debonding at the dentin-restoration interface compared to composite inlays/onlays. Ceramic onlays/overlays seem to represent an effective answer to restore severely damaged posterior teeth.
Composite Resins↗
A study into the variations in the labial reduction of teeth prepared to receive porcelain veneers--a comparison of three clinical techniques.
OBJECTIVES: Various techniques have been suggested to enable the operator to produce an even reduction of 0.5 mm of labial tooth enamel during preparation for a porcelain veneer. For example, in addition to the traditional free hand method, longitudinal or horizontal depth orientation grooves and the use of small round burs to produce dimples as depth guides have been suggested. However, there is no published data that compares how effective these techniques are at producing the 'ideal' veneer preparation. In this study three techniques were compared using the technique of co-ordinate metrology. METHOD: A single operator using the above three techniques prepared 84 extracted teeth. Impressions of the prepared and unprepared teeth were scanned using a co-ordinate measuring machine (CMM). Measurements of maximum labial reduction along the mid-labial plane were taken and analysed. RESULTS: The study showed that among the three techniques studied the use of small round burs (D001-012), when used side on at an angle of 45 degrees to the tooth surface to produce dimples as depth guides, resulted in the greatest frequency of tooth reductions closer to the 'ideal' depth chosen for this study, ie within the 0.4 mm-0.6 mm range. CONCLUSION: The study concluded that even after using techniques designed to produce consistent preparations, a single operator still produced preparations with considerable variation from the ideal. The study showed that among the three techniques compared the use of small round burs, when used side on at an angle of 45 degrees to the tooth surface to produce dimples as depth guides, resulted in the greatest frequency of tooth reduction closer to the 'ideal' depth chosen for this study only, ie within the 0.4 mm-0.6 mm range. It is stressed that this range may not be the ideal in all clinical situations.
Analysis of Variance↗
Production of nitric oxide-derived reactive nitrogen species in human oral cavity and their scavenging by salivary redox components.
Nitrite is reduced to nitric oxide (NO) in the oral cavity. The NO generated can react with molecular oxygen producing reactive nitrogen species. In this study, reduction of nitrite to NO was observed in bacterial fractions of saliva and whole saliva. Formation of reactive nitrogen species from NO was detected by measuring the transformation of 4,5-diaminofluorescein (DAF-2) to triazolfluorescein (DAF-2T). The transformation was fast in bacterial fractions but slow in whole saliva. Salivary components such as ascorbate, glutathione, uric acid and thiocyanate inhibited the transformation of DAF-2 to DAF-2T in bacterial fractions without affecting nitrite-dependent NO production. The inhibition was deduced to be due to scavenging of reactive nitrogen species, which were formed from NO, by the above reagents. The transformation of DAF-2 to DAF-2T was faster in bacterial fractions and whole saliva which were prepared 1-4 h after tooth brushing than those prepared immediately after toothbrushing. Increase in the rate as a function of time after toothbrushing seemed to be due to the increase in population of bacteria which could reduce nitrite to NO. The results obtained in this study suggest that reactive nitrogen species derived from NO are continuously formed in the oral cavity and that the reactive nitrogen species are effectively scavenged by salivary redox components in saliva but the scavenging is not complete.
Adult↗
Posterior composite Class II restorations: in vitro comparison of preparation designs and restoration techniques.
The aim of this study was to evaluate conservative preparation designs for the restoration of Class II lesions with posterior resin composite. Fourteen primary and 14 permanent molars were obtained. Conservative modified MO and DO preparations were placed in half the teeth; conventional MO and DO preparations were placed in the remaining teeth. Randomly, a glass-ionomer liner was placed over the exposed dentin in one preparation of each tooth, a calcium hydroxide liner was placed in the remaining preparations. Posterior resin composite was placed in all teeth, and the teeth were loaded with a 17-kg force. Teeth were thermocycled, stored in 37 degrees C water, then immersed in 50% silver nitrate solution and placed in developer. The teeth were sectioned and photographed. Microleakage was calculated according to the depth of dye penetration, on a 6-degree scale. Results demonstrated the conservative modified restorations and conventional restorations, when glass-ionomer liner was used, to have less marginal microleakage, in both primary and permanent teeth, than their calcium hydroxide counterparts.
Calcium Hydroxide↗
Three-dimensional computer vision for tooth restoration.
If a person with carious lesions needs or requests crowns or inlays, these dental fillings have to be manufactured for each tooth and each person individually. We survey computer vision techniques which can be used to automate this process. We introduce three particular applications which are concerned with the reconstruction of surface information. The first one aims at building up a database of normalized depth images of posterior teeth and at extracting characteristic features from these images. In the second application, a given occlusal surface of a posterior tooth with a prepared cavity is digitally reconstructed using an intact model tooth from a given database. The calculated surface data can then be used for automatic milling of a dental prosthesis, e.g. from a preshaped ceramic block. In the third application a hand-made provisoric wax inlay or crown can be digitally scanned by a laser sensor and copied three dimensionally into a different material such as ceramic. The results are converted to a format required by the computer-integrated manufacturing (CIM) system for automatic milling.
Adolescent↗
Assessment of the amount of remaining coronal dentine in root-treated teeth.
OBJECTIVES: There is currently no standardised technique to measure the amount of coronal dentine remaining in a root-treated tooth after crown preparation. The aim of this study was to develop a method of measuring remaining coronal dentine in root-treated teeth and to propose an index for grading tooth restorability. METHODS: The study recruited 20 patients who had completed molar endodontic treatment at the Eastman Dental Hospital and had been prescribed an amalgam coronal-radicular core with a full coverage cast restoration. Using a series of interlocking special trays and impressions, a method was devised to produce a cast of the amount of remaining dentine coronal to the finish line after crown preparation. This cast was scanned using a laser profilometer and the volume of remaining dentine was calculated. A tooth restorability index (TRI) was developed to assess the strategic value of the remaining dentine. The TRI allowed scores of 0-3 in each sextant with a maximum score of 18 per tooth. RESULTS: Twenty teeth were scored by three examiners and the TRI scores varied from 2 to 13. The volume of coronal dentine varied from 61.73 to 232.22 mm(3). CONCLUSIONS: A tooth restorability index has been devised to assess the strategic value of remaining dentine. A Kappa statistic was calculated to produce values of 0.584, 0.688 and 0.720, giving moderate-good agreement between the examiners.
Crowns↗
Fracture resistance of endodontically-treated premolars adhesively restored.
PURPOSE: To investigate the cusp fracture resistance of endodontically treated teeth, adhesively restored with various materials. MATERIALS AND METHODS: MOD preparations and endodontic treatment was carried out on extracted sound maxillary premolars. The cavities were restored with the amalgam Valiant in combination with Superbond or Panavia bonding, the resin composites Z100, Herculite XRV or Clearfil RP with their respective bonding systems, Z100 in combination with the glass ionomers Ketac Fil, Fuji II and Vitremer, and Tetric in combination with Compoglass. Fracture resistance was measured by axial loading in an Instron testing machine. RESULTS: One of the restorative methods, resin composites in combination with dentin bonding systems in beveled MOD preparations rendered the tooth a cusp fracture resistance which did not differ significantly from that of sound natural teeth. Two other restorative methods, bonded amalgam and a sandwich of glass ionomer cement/resin composite in beveled preparations were significantly weaker in resisting cusp fracture than sound natural teeth, but still significantly stronger than the unrestored tooth with a MOD preparation. It was statistically apparent that several adhesive restorative systems could satisfactorily be used to restore teeth after endodontic therapy.
Analysis of Variance↗
Clinical research on bonded amalgam restorations. Part 1: SEM study of in vivo bonded amalgam restorations.
Exfoliated deciduous teeth, in which bonded or nonbonded amalgams had been placed two to three years previously, were examined directly and indirectly with the use of a scanning electron microscope (SEM). Bonding resin was found in the interface between the amalgam and the tooth structure, frequently obliterating the microspace. Several materials now are available that bond amalgam to tooth surfaces with bonding strength exceeding 10 MPa. Amalgam can be retained in preparations without undercuts, or in pits and fissures without any tooth preparation. The article consists of two parts: in part 1, results of a pilot study on bonded amalgam-tooth interfaces is presented. In part 2, the authors discuss further studies and clinical technique. Commercial products are compared; and other clinical trials now in progress, concerning amalgam bond strength adhesion and ability to eliminate microspace, are discussed.
Dental Amalgam↗
Clinical studies on marginal gingiva around abutment tooth (Part 3). Effect of tannin-fluoride preparation on gingival health.
It was examined whether the tannin-fluoride preparation (HY preparation), which might have a caries-reductive, plaque inhibiting and astringent action, could reduce the incidence of gingival inflammation around abutment teeth. Zinc oxide eugenol cement mixed with the HY preparation was packed in the cavity prepared in the resin base facing the abutment tooth. Gingival crevicular fluid (Periotron units:GCF), gingival index (GI), plaque index (PlI) and probing depth around the abutment teeth were measured over a 3 month period. The following results were obtained: 1. GCF decreased at month 1 and showed low values at months 2 and 3. 2. GI showed a decreasing tendency. 3. PlI and probing depth did not show obvious changes. These results indicate that the tannin-fluoride preparation reduces gingival inflammation around abutment teeth.
Adolescent↗
Etched porcelain veneer restoration of a primary tooth: a clinical report.
The treatment of a retained primary tooth in the adult dentition has always been a difficult clinical problem. In the anterior region of the mouth, the problem is further complicated by esthetic requirements. In this clinical report, a primary canine was recontoured both incisally and interproximally with an etched porcelain veneer to provide an esthetic result. The use of etched porcelain as an indirect veneer material, which has demonstrated clinical success, is an alternative to the requirements of conservative dentistry, namely, preservation of tooth substance and safeguarding primary tooth vitality. The procedure used in this clinical report differs from traditional procedures. The preparation was extended to the lingual surface of the tooth, which allowed for an increase of the incisal length and added a sufficient amount of porcelain. The etching procedure was performed twice by applying 30% phosphoric acid etchant gel to the prepared tooth.
Adult↗
Temperature rise during root canal preparation--a possible cause of damage to tooth and periodontal tissue.
Temperature rise on the surface of extracted human premolar roots was recorded during root canal preparation using a thermo-couple. It was found that time, pressure exerted on the reamer, type of reamer and rotational speed influenced the temperature rise. Starting from about 30 degrees C temperatures up to 87 degrees C were recorded, generally in less than 50 seconds' working time, using routine instrument and technique. Possible effects of this temperature rise on tooth substance, periodontal membrane and supporting bone are discussed.
Dental Instruments↗