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PubMedDate not supplied

Generation of 3-D finite element models of restored human teeth using micro-CT techniques.

PURPOSE: This article describes the development of a three-dimensional finite element model of a premolar based on a microscale computed tomographic (CT) data-acquisition technique. The development of the model is part of a project studying the optimal design and geometry of adhesive tooth-colored cusp-replacing restorations. MATERIALS AND METHODS: The premolar was digitized with a micro CT scanner with a resolution of 13 microns. Surface contours were fitted to the various materials, after which a 3-D finite element mesh was constructed to the contours. To demonstrate the potential use of the resulting model, it was applied to a cusp-replacing resin composite restoration. RESULTS: The stress patterns generated in the composite material were truly 3-D. Stress concentrations were found at the surface where the load was applied and in the vicinity of the dentin-composite bonding surface, where the interface had its complex geometry. CONCLUSION: The described procedure is an easy method to produce a highly detailed 3-D finite element model of a premolar with an adhesive cusp-replacing restoration.

Bicuspid↗
PubMedDate not supplied

In vitro comparison of cuspal fracture resistances of posterior teeth restored with various adhesive restorations.

PURPOSE: This study compared the cuspal fracture resistances of posterior teeth restored with five different adhesive restorations. MATERIALS AND METHODS: Eighty-four sound human molars were included in this study. Sample molars were divided into seven groups. The first five groups received mesio-occlusodistal cavity preparations and were restored with (1) amalgam combined with urethane dimethacrylate cement, (2) posterior composite, (3) direct composite inlay, (4) cast-metal inlay, and (5) complete ceramic inlay. The sixth and seventh groups were introduced in the study as controls. Samples of group 6 were prepared but were tested without restoration (prepared-only group). Samples of group 7 were intact teeth and were tested as unprepared. All samples were loaded axially until failure. RESULTS: While the unprepared teeth had a significantly higher resistance than all other groups, the prepared-only teeth were the weakest. No significant differences were found in resistance to cuspal fracture among the restoration groups. CONCLUSION: The difference between the mean cuspal fracture resistance of the unprepared and prepared-only groups was statistically significant. Restoration groups were stronger than the prepared-only group. However, differences between the restoration groups were insignificant.

Adult↗
PubMed2001

Effects of restorative and adhesive curing methods on dentin bond strengths.

PURPOSE: To evaluate the shear bond strengths of "one-bottle" adhesives to dentin when used with self-cured composite. MATERIALS AND METHODS: 100 bovine teeth were ground to expose superficial dentin, which was polished to 600-grit. The dentin was etched for 15 s with 35% phosphoric acid, rinsed, and blotted with tissue paper. The surface remained visibly moist for all specimens. The following adhesives were applied to the etched dentin according to manufacturers' directions: Scotchbond Multi-Purpose (in its visible light-cured [VLC] and self-cure modes) as a control, One-Step (VLC only), OptiBond Solo Plus (VLC only), Prime & Bond NT (VLC) and Prime & Bond NT Dual-Cure. For each adhesive, specimens were bonded with a self-cure composite, while 10 were bonded with a VLC composite as a control. After 24 hrs water storage, shear bond strengths were determined using an Instron universal testing machine. Data were analyzed using two-way ANOVA, Tukey's test, and Student's t-tests. RESULTS: Using the light-cured composite, mean bond strengths ranged from 11.0 MPa for light-cured Prime & Bond NT to 26.3 MPa for OptiBond Solo Plus. Using the self-cure composite, mean bond strengths ranged from 0.0 for light-cured Prime & Bond NT to 21.4 MPa for One-Step. Two adhesives, light-cured Prime & Bond NT and OptiBond Solo Plus, had significantly lower bond strengths when used with the self-cure composite. CLINICAL SIGNIFICANCE: Some "one-bottle" dentin adhesives may not provide acceptable bonding to tooth structure when they are used with self-cure composites.

Acid Etching, Dental↗
PubMedDate not supplied

Treatment of cariously involved fused maxillary primary lateral and central incisors.

A 3-and-a-half-year-old male child presented with fused cariously involved right maxillary primary central and lateral incisors as well as a previously traumatized non-vital left primary central incisor with a draining fistula. The child also had other restorative needs and the decision taken was to address all needs under a G.A. With respect to the fused incisors, these were split and root canals treatment was performed for all three incisors which were then restored with stainless steel crowns with esthetic facings.

Child, Preschool↗
PubMedDate not supplied

Shrinkage stresses associated with incremental composite filling techniques in conservative Class II restorations.

Conservative Class II preparations are widely utilized, however the stresses produced by incremental composite placement/curing has not been demonstrated. The purpose of this investigation was to visualize the stresses generated by composite resin placed into photoelastic models of conservative Class II preparations using different incremental techniques. Conservative Class II preparations on three different primary molar replicas were cast life-sized in a photoelastic material. Incremental placement/curing techniques used were oblique, gingival-occlusal, and facial-lingual and were compared with bulk placement/curing. The photoelastic stresses produced with conservative Class II restorations were of lower intensity than conventional Class II and larger composite restorations previously reported. Few differences in shrinkage-induced stresses were observed between the incremental placement/curing techniques tested. Lowest shrinkage stresses were generated by the bulk placement/curing technique.

Birefringence↗
PubMed2001

Presentation, diagnosis and initial management of patients referred to a hospital tooth wear clinic.

Information on presenting complaints, diagnosis and initial management strategy was recorded on a proforma for 114 consecutive patients referred to a hospital tooth wear clinic over a two-year period. Over twice as many male patients were referred as females. Twenty percent of patients had no presenting complaint and the others shared the common complaints concerning appearance, sensitivity and their deteriorating dentitions. The assessment of aetiology identified attrition as the most common cause of tooth wear in the subject group studied. About half the group were prescribed preventative treatment only and the other half were deemed to require restorative dental treatment.

Adolescent↗
PubMed2000

New filling materials--an occupational health hazard.

The acrylic content of dental composites poses a risk of adverse reactions. Although the quantities of the substances released are probably too small to cause systemic reactions, local skin or mucosal reactions may arise from direct contact with dental composites. In fact, epidemiological data suggest that most known side effects of dental resins are occupational dermatoses. They may either be due to irritation or allergy. In the Scandinavian countries, occupational dermatoses are relatively common among dental staff, sometimes entailing occupational disability and re-schooling. Most of these reactions can be avoided by observing precautions such as the minimization of the oxygen-inhibited-layer (OIL) in set composites and by using the resin-paste enamel bonding technique. The risk of occupational dermatoses could be reduced by the development of new bonding techniques and careful risk-benefit assessments in the use of dental composites.

Acrylic Resins↗
PubMed1999

Variable polymerisation shrinkage and the interfacial micropermeability of a dentin bonding system.

PURPOSE: Adhesive bonds are subjected to competing stresses whilst a restoration is setting. This study aimed to determine the effect of these stresses on a chemically- and light-activated dentin adhesive (Scotch Bond MultiPurpose Plus: SBMP+) by assessing the morphology and micropermeability of the interfacial region. MATERIALS AND METHODS: Restorative materials and techniques were selected to impart differing setting stresses to the adhesive interface. An amalgam (Dispersalloy), a light-activated composite (Z100) with a high- or low-intensity curing light, and chemically-activated composite (Adaptic) were placed either in bulk (4 mm thickness) or in one thin layer (2 mm) in occlusal cavities in 55 freshly extracted third molars. In addition, thin composite restorations were placed on 15 horizontally sectioned teeth using a glass slide as a rigid clear matrix. The pulp chambers of all samples were filled with rhodamine B dye solution for 4 hours. Samples were longitudinally sectioned and the interfacial dye leakage measured using a confocal optical microscope. Data were analysed using the Kolmogorov-Smirnov test. RESULTS: In occlusal cavities, Z100 had significantly more leakage than the amalgam and Adaptic. There was no significant difference in micropermeability between large and small increments, or curing light intensity for Z100, but when placed in bulk, there was evidence of incomplete composite polymerisation near the cavity floor, especially with the low intensity curing light. Cohesive failure of the deep resin composite and gap formation were a frequent finding with the high-intensity light curing. The least leakage for Z100 was achieved with a thin layer on flat dentin. In contrast, the chemically-activated composite performed well in bulk when the surface of the restoration was freely exposed, but badly when constrained by the glass matrix. CONCLUSION: Restoration setting stress is critical in the microscopic integrity of the adhesive bond to dentin.

Bisphenol A-Glycidyl Methacrylate↗
PubMed2000

Microleakage and retention of bonded amalgam restorations.

PURPOSE: To compare the microleakage and bond strength exhibited by two light-cured, filled dentin bonding agents, a resin cement, and cavity varnish. MATERIALS AND METHODS: The four test groups of lining agents for amalgam restorations included (LF) Light-cured, Filled resin (Clearfil Liner Bond 2); (LCF) light- and chemical-cured, Filled resin (Clearfil Liner Bond + Protect Liner); (RC) Resin Cement (Panavia 21); and (V) Varnish (Copalite). For each group, 20 Class V cavity preparations were cut in human extracted molars. Tytin amalgam was condensed into the preparation. After storage for at least 24 hrs in distilled water at 37 degrees C, all restorations were subjected to 2500 thermal cycles (8 degrees C to 48 degrees C). After 1 wk, specimens were tested. For the leakage tests, teeth were immersed in 45Ca, sectioned, and radiographs of sections were evaluated and then evaluated by Ridit analysis. Retention samples were tested to failure in tension using an Instron machine and peak load (kg) was recorded. RESULTS: Compared to varnish, the two dentin bonding agents (LF and LCF) significantly decreased microleakage at the cementum margin but not at the enamel margin. The two dentin bonding agents also exhibited significantly greater retentive strength than either the resin cement or the varnish.

Calcium Radioisotopes↗
PubMed2000

Effect of conditioner and restorative resin on enamel bond strengths.

PURPOSE: To evaluate the effect of three enamel conditioners and four restorative materials on enamel shear bond strengths. MATERIALS AND METHODS: 120 bovine incisors were polished to 600-grit and randomly assigned to three enamel adhesive systems (n=40): Syntac Single Component with phosphoric acid etching (PA-SSC), Syntac Single Component without phosphoric acid etching (SSC), and Experimental Prompt L-Pop (LPI), a self-etching adhesive. The specimens were restored with one of four resin restorative materials (n=10): (1) Compoglass F, a high-viscosity compomer; (2) Compoglass Flow, a low-viscosity compomer; (3) Tetric Ceram, a high-viscosity resin-based composite (RBC); and (4) Tetric Flow, a low-viscosity RBC. After thermocycling, shear tests were carried out with an Instron Universal Testing Machine. Mean enamel bond strengths were analyzed with ANOVA and Duncan post hoc test at P < or = 0.05. RESULTS: PA-SSC resulted in higher mean bond strengths than LP1, but the difference was not statistically significant. Both PA-SSC and LP1 resulted in statistically higher mean bond strengths than SSC at P < or = 0.0001. The lowest mean bond strengths of all the groups were obtained when SSC was used with an RBC (Tetric Ceram or Tetric Flow). SSC and PA-SSC resulted in statistically higher mean bond strengths when used with a compomer than when used with an RBC, regardless of the viscosity. Although recommended to be used only with compomers, LP1 resulted in statistically similar enamel bond strengths when used with the composite of corresponding viscosity (Tetric Ceram vs. Compoglass F; Tetric Flow vs. Compoglass Flow). LP1, however, resulted in higher enamel bond strengths when combined with Tetric Ceram than when combined with Tetric Flow. When the results were pooled for "viscosity", high-viscosity restorative materials resulted in higher bond strengths than low-viscosity materials at P < or = 0.041. When the data were pooled for "restorative material", compomers resulted in higher bond strengths than composites at P < or = 0.0001.

Acid Etching, Dental↗
PubMed2000

Fracture strength of fragment-bonded teeth. Effect of calcium hydroxide lining before bonding.

PURPOSE: To measure, in vitro the strength of intact teeth, fracture-bonded teeth, and fracture-bonded teeth bonded after a preliminary calcium hydroxide lining of the dentin part of the remaining tooth. MATERIALS AND METHODS: The study used 30 young, similarly aged sheep incisors. Twenty incisors were fractured 2.5 mm from the incisal edge and another 10 incisors remained non-fractured and served as control (Group 1). Group 2 comprised 10 fractured incisors, which after 3 weeks water storage were bonded by use of acid etching and a dentin bonding agent. In Group 3, the root part of 10 fractured incisors were lined with calcium hydroxide and kept in water for 3 weeks. Then the lining was removed with a hand instrument before bonding as above. The strength of the teeth in Groups 1-3 was measured and the mean fracture strengths representing the three groups were compared by Newman-Keuls' multiple range tests at a 5% level of significance. RESULTS: The mean fracture strength of the lined teeth (9.6 MPa) was significantly different from that of intact teeth (17.8 MPa) as well as from that of the bonded but unlined teeth (15.8 MPa). The latter two means were not significantly different. It is concluded that the use of calcium hydroxide on the fracture surfaces of fractured teeth before bonding lowers the fracture strength of the restored teeth.

Acid Etching, Dental↗
PubMed2001

A survey of referrals to a restorative dentistry department in a district general hospital.

This study reports on referrals to a specialist Restorative Dentistry service based in a district general hospital in the United Kingdom. The service encompasses the subspecialties of Endodontics, Periodontics and fixed/removable Prosthodontics and is part of the National Health Service. A prospective, cross-sectional, observational study of consecutive referrals to new patient clinics of a full-time consultant in Restorative Dentistry over a three-month period was undertaken. 277 patients were examined of which 63% were female. 86% of referrals were from general dental practitioners and 79% of patients were from Leicestershire. 44% of referrals were for treatment within the department and 57% were discharged to the practitioners with a treatment plan. The results illustrate the utilisation of a specialist service and show that requests for Endodontic and Periodontal treatment occur most frequently.

Adolescent↗