Physical effects of non-cavitated explorer probing on enamel smooth-surface carious lesions.

PURPOSE: To assess the physical effects of explorer probing on non-cavitated smooth-surface enamel carious lesions. METHODS: Extracted teeth with white enamel decalcification (ICDAS 2) were used. Indentations were made in decalcified and non-decalcified regions with a #23 explorer using "scratch" or "poke" application and 100g, 300g or 600g force. Specimens were imaged with SEM and polarizing light microscopy. Indentation widths were measured digitally. Two-way ANOVA with pair-wise comparisons was used to assess interactions of force and enamel condition (normal or carious) on indentation groove width. RESULTS: No or minimal effect was seen on normal enamel surface morphology. For the decalcified regions, defects were seen in SEM and polarizing light images. Findings included a smear layer, open clefts, lateral debris and micro-fractures. Two-way ANOVA for effects of force and enamel quality on mean groove width showed statistically significant differences for both variables for all teeth tested.

Preliminary Evidence That Bioactive Cements Occlude Artificial Marginal Gaps.

PURPOSE: The objective of this preliminary laboratory study was to explore whether bioactive dental cements have the ability to seal marginal gaps as compared with other classes of dental cements. MATERIALS AND METHODS: Tooth discs (dentin/enamel) were positioned adjacent to a second disc of one of five possible dental cements (two bioactive and three conventional) and separated by a 50-µm Mylar film, creating a controlled gap between the two discs. The edges of the tooth segments were abraded to expose dentin such that the dentin interface was positioned opposite the cement. The artificial gap assembly was stabilized with adhesive and composite resin. Artificial gap assemblies for each cement type were immersed in a phosphate-containing, simulated body fluid (phosphate buffered saline) for up to 8 months. Occlusion of artificial marginal gaps (including deposition of crystal-like, mineralized deposits within the gaps) was observed and scored categorically during the observation period. Deposition of radiodense material within the artificial marginal gap space was confirmed by micro-computerized tomography analysis. RESULTS: There was no evidence of marginal gap occlusion for the three conventional control cements, whereas both bioactive, surface apatite-forming cements demonstrated occlusion of the artificial marginal gaps. CONCLUSIONS: The preliminary findings of this initial study suggest the possible capability of surface apatite-forming, calcium-based, bioactive dental cements to seal or reseal artificial marginal gaps in simulated aqueous physiological conditions. CLINICAL SIGNIFICANCE: The results of this laboratory study, although preliminary in nature, suggest a new functional property for bioactive dental materials, namely the ability to significantly improve marginal stability with tooth/restorative material interface. Such behavior in a restorative material could improve the survival and serviceability of dental restorations.

Conventional polishing techniques versus a nanofilled surface sealer: preliminary findings regarding surface roughness changes and analysis.

OBJECTIVE: To evaluate the effect ofa nanofilled resin surface sealer (Seal&Protect) on the surface roughness of a hybrid composite resin. METHODS: Twelve 15 mm x 2 mm disc composite resin specimens (TPH Spectrum Shade C-2) were fabricated and light-cured under controlled conditions. Specimens were divided into six groups of two discs each. The positive control group was no finishing (Mylar Surface-MS); the remaining five group specimens were all standardized by finishing with an Enhance Finishing Disc prior to a final polishing/surface treatment step or sequence, which included: (1) polishing with a 1 micron aluminum oxide polishing paste; (2) polishing with a sequence of 1 micron and 0.3 micron aluminum oxide polishing pastes; (3) polishing with a one-step diamond polishing cup; (4) application and curing of the nanofiller resin surface sealer; and (5) no further treatment-Enhance finishing disc surface (negative control). Surface roughness (Ra) values (6 Ra values per specimen; 12 Ra values per group) were measured using a Surfcorder SE 1700 profilometer. Data were analyzed by a one-way ANOVA (p < or = 0.05). RESULTS: Polishing or surface treatment techniques significantly affected the surface roughness (Ra) values of the "finished" hybrid composite resin. Enhance Finishing Disc gave the highest Ra values; Mylar Surface gave the lowest. Application of the nanofilled resin surface sealer, after finishing with the elastomeric bonded-abrasive finishing disc, resulted in significantly lower surface roughness (Ra) values (p < 0.001). Other polishing techniques also significantly reduced the surface roughness of the composite resin surface. CONCLUSION: Use of a nanofilled, low-viscosity surface sealer may, after additional laboratory and clinical testing, present an alternative/adjunctive technique in final "polishing"/surface treatment of certain composite resin restoratives.

Effects of a 36% tooth bleaching gel on zinc phosphate cement.

PURPOSE: To assess the effect of a 36% hydrogen peroxide bleaching gel on the roughness, microhardness, indentation modulus, and micromorphology of zinc phosphate cement aged 24 h or 1 week, compared to cement not exposed to bleaching gel. METHODS: Dynamic indentation was performed for microhardness and indentation modulus. Contact profilometry was performed for surface roughness. Scanning electron microscopy assessed micromorphology. Means for microhardness, indentation modulus, and roughness were analyzed for differences among groups (No. 1 = 24 h/control; No. 2 = 24 h/treatment; No. 3 = 1 week/control; No. 4 = 1 week/treatment). RESULTS: Means (SD) for groups 1-4 respectively: Vickers Microhardness (HV): 34.2(8.7)a, 32.8(10.9)a, 24.8(5.0)b, 41.5(7.4)c; Indentation Modulus (EIT, GPa): 14.2(6.9)a,b, 10.6(3.6)a, 11.2(3.8)a, 14.7(2.8)b; and Surface Roughness (Ra, microns): 1.08(0.38)a, 1.21(0.55)a, 1.55(0.21)b, 1.52(0.29)b. Means labeled with the same superscript were not statistically significantly different. Scanning electron microscopy of groups 1 and 2 revealed similar details. Group 3 surfaces had plate-like crystals not present on the group 4 surfaces. CONCLUSIONS: Bleaching gel exposure increased hardness and indentation modulus and caused limited changes in surface morphology, but the cement was not adversely affected by the bleaching protocol.

Comparison of detachment forces of two implant overdenture attachment types: effect of detachment speed.

PURPOSE: To compare detachment (retentive) force for overdenture retainers used with conventional and "mini" implant designs over a range of different detachment (separation) speeds. METHODS: Two dental implant fixtures [Sendax MDI ("mini" dental implant) and Replace Select (conventional dental implant design)] with ball attachments were mounted in brass cylinders. Corresponding attachments were processed into acrylic denture resin blocks and connected to the ball attachments on the implants. The fixture/attachment assemblies were placed in an Instron testing system under ambient room temperature and humidity conditions (approximately 72 degrees F and 35-65% relative humidity). The assemblies were separated under tensile load at 11 speeds from 10-500 mm/minute with 10 replicates at each speed. Maximum detachment (separation) force was recorded. Mean, minimum, maximum, standard deviation and range of maximum detachment (separation) force was calculated. To test the hypothesis "the Sendax MDI and the Replace Select have the same average detachment force, at a given detachment speed", one-way ANOVA was performed. To test the hypothesis that "all detachment speeds have the same average maximum detachment force", one-way ANOVA was performed. To test the hypothesis that "the distribution of maximum detachment forces is the same for all detachment speeds", non-parametric Kruskal-Wallis analysis was performed. RESULTS: For Replace Select, the mean of the maximum force varied from 6.02-3.46 N with a downward trend as detachment speed increased. For Sendax MDI, the mean of the maximum force varied from 3.43-2.86 N. One-way ANOVA and Kruskal-Wallis analyses supported rejection of the hypotheses stated above with more than 99.99% confidence. Within the limitations of this study, the retentive properties of the Sendax MDI and the Replace Select attachment properties were different. Detachment speed had an effect on separation force for the two attachments in this study. Given the range of velocities possible in masticatory function; implant overdenture attachments, optimally, should be evaluated at more than one detachment speed to evaluate clinically-relevant, strain-rate behavior.

The Relative Location of the Dye Staining Endpoint Indicated With Polypropylene Glycol-Based Caries Dye versus Conventional Propylene Glycol-Based Caries Dye.

OBJECTIVES: This study determined the difference in the location of the caries dye staining endpoint of 1% Acid Red dye in propylene glycol versus that of 1% Acid Red dye in polypropylene glycol. METHODS: Freshly extracted permanent molar crowns with primary occlusal carious lesions were chisel-split axially to expose the lesion in cross-section on both halves. One half was stained with propylene glycol-based dye and the other with polypropylene glycol-based dye. For the control group, both halves were stained with propylene glycol-based dye. The dye staining front was marked on digital images of the stained split surfaces, and the images were aligned using reference notches. The distance between the marked staining front lines was measured in five locations, and the measurement protocol was repeated. Weighted averages and a 95% confidence interval for the distance between marked staining front lines were calculated for the control and experimental groups. RESULTS: The weighted average distance for the experimental group (0.298 mm, 95% confidence interval 0.240 mm - 0.357 mm) was about four times that of the control group (0.070 mm, 95% confidence interval 0.051 mm - 0.089 mm). Generally, the marked staining line for the polypropylene glycol-based dye specimens was located shallow (occlusal) to the propylene glycol-based staining line (range -0.12 mm to 0.66 mm). CONCLUSIONS: The staining endpoint of 1% Acid Red dye in polypropylene glycol is shallower than that of 1% Acid Red dye in propylene glycol. The method is useful for comparing staining endpoints of caries dye formulations. (Eur J Dent 2008;2:29-36).

Evaluation of laser fluorescence for differentiating caries dye-stainable versus caries dye-unstainable dentin in carious lesions.

PURPOSE: To assess the performance of laser fluorescence (DIAGNOdent, "DD") for differentiating carious versus non-carious dentin during caries excavation using caries dye as the gold standard. METHODS: The superficial carious dentin surfaces of lesions in 25 teeth were exposed, and the surface evaluated by DD. Next, caries dye was applied and the surface was observed for dye staining. The lesion was then excavated approximately 0.5 mm with a round bur. The resulting surface was evaluated by DD, and the above sequence was repeated until three non-stained surfaces were evaluated by DD. Using "caries dye staining" as the gold standard, correct classification proportion was calculated at each DD cutpoint in the dataset. Using the optimal cutpoint, sensitivity, specificity and likelihood ratios were calculated. Non-parametric ROC analysis was performed and AUC calculated. RESULTS: With an optimal cutpoint of 11 or 12, DD was highly accurate in discriminating between dye-stainable and dye-unstainable surfaces, producing a correct classification proportion of over 98% and an AUC of 0.999 for all 176 surfaces. These results support further refinement of DD for use in caries excavation and further research relating DD to other caries excavation endpoints.

Staining of non-carious human coronal dentin by caries dyes.

This study tested the hypothesis that commercially available caries dyes stain non-carious human coronal dentin in freshly extracted teeth. Multiple sections were cut from 10 non-carious and two control carious teeth using a water-cooled saw. Each section was stained with one of five caries dyes. The location of staining, if any, was noted and the staining intensity was scored on a four-point scale. One of the sections from each tooth was subsequently decalcified and processed for observation under a light microscope using four histologic staining techniques to evaluate morphology, collagen distribution and bacterial content. The association between the stain intensity scores on the undecalcified sections and the five dyes was evaluated using the Kruskal-Wallis One-Way ANOVA by Ranks test. Outer carious dentin in the control specimens stained intensely with each of the five dyes. In the undecalcified, non-carious sections, all had at least one area of staining. However, this staining could be differentiated from the intensity of dye staining in the carious controls, except in two instances. The association between stain intensity scores and the five dyes was not statistically significant. In the histologic sections, numerous bacteria were seen within the dentinal tubules of carious lesions of the two control specimens; however, no bacteria were found in any of the sections from non-carious specimens. Histologically, no differences were observed in the morphology or staining pattern within mantle or circumpulpal dentin in areas stained with caries dye, and in only one unique instance within the main body of the dentin. These results suggest that the five dyes evaluated in this study can stain non-carious dentin, however, this stain can be differentiated from the staining of outer carious dentin in vitro.

Initial in vitro evaluation of DIAGNOdent for detecting secondary carious lesions associated with resin composite restorations.

OBJECTIVE: To assess the potential of DIAGNOdent (DD) readings for detecting secondary enamel and dentin carious lesions associated with resin composite restorations in a set of preserved extracted adult teeth. METHOD AND MATERIALS: Thirty test sites adjacent to resin composite restorations in 15 extracted teeth were evaluated visually and with DD readings for enamel and dentin caries. The results were compared to gold standard diagnosis determined by sectioning through each site and subsequent microscopic observation. Sensitivity, specificity, accuracy, and likelihood ratios at optimum threshold values for enamel and dentin caries were determined. Receiver operator characteristic (ROC) analysis was performed to compare visual and DD diagnostic methods. RESULTS: Histologic incidence of enamel caries was 20% and dentin caries was 36.67%. All composite restorations in the sample teeth fluoresced (range 5 to 22). For enamel caries detection with DD, the optimum threshold of > or = 26 produced a sensitivity of .67 and a specificity of .79. For dentin caries detection with DD, the optimum threshold of > or = 22 produced a sensitivity of .73 and a specificity of .84. ROC analysis showed that the DD readings do contain diagnostic information. DD readings for dentin caries diagnosis produced better diagnostic results compared to visual readings for the 30 test sites in the study, but these results were not significantly different. CONCLUSION: DIAGNOdent readings may have potential for resin composite secondary enamel and dentin carious lesion detection. DIAGNOdent instrument design factors and technique should be optimized to improve performance prior to clinical trial for this application.

Predoctoral clinical curriculum models at U.S. and Canadian dental schools.

In fall 2002, the ADEA Section on Comprehensive Care and General Dentistry conducted a survey of the predoctoral clinical curriculum models at sixty-four North American dental schools. Fifty-eight percent of the schools reported that most patient care is provided in a comprehensive care clinic setting, 22 percent reported that most patient care is provided in discipline-specific settings, and 20 percent reported a hybrid of comprehensive care and discipline-specific settings. While ten Primarily Discipline-Based (PD) schools have instituted new Primarily Comprehensive Care (PCC) or Hybrid clinical curricula since 1997, one PCC school has converted to a Hybrid model, and one PCC school has converted to a PD model. PCC curriculum models were frequently associated with the following institutional factors: more densely populated metropolitan areas; private institutional sponsorship; location within a university medical center; larger class size; and more students enrolled in advanced training at the school. Curriculum factors frequently associated with PCC models included the following: increased use of simulation technology: higher proportion of clinical/teaching track faculty; higher proportion of part-time faculty; higher proportion of generalist faculty; same faculty supervising both treatment planning and patient treatment; and use of competency exams as the main requirement for completion of the curriculum.

New device for selective dentin caries removal.

OBJECTIVES: To develop prototype rotary selective dentin caries excavators and to demonstrate their ability to remove only carious dentin in extracted teeth. METHOD AND MATERIALS: Milled polymer prototype and formed wire loop prototype burs were made. They were tested on normal dentin with standardized force application and compared to carbide burs for ability to cut by weighing three extracted teeth at pre- and postcutting for each prototype version. They were tested on carious dentin of three teeth for each prototype version. The resulting excavated surfaces were analyzed with dentin caries dye, the teeth were decalcified and examined histologically, and the used prototypes were examined in light and scanning electron microscopes. RESULTS: For both prototypes, noncarious teeth did not lose weight from prototype instrumentation, but each lost 9 or 10 mg after instrumentation with the control carbide bur. Both prototypes quickly removed carious dentin in each of the carious teeth until a definitive cutting endpoint was reached. The excavated surfaces from the milled polymer prototypes did not stain with caries dye, but those from the wire loop prototypes stained lightly in some areas. In the light microscope, all sections of excavated carious teeth were bacteria-free. Light and scanning electron microscope images of the prototypes revealed scratch patterns on the wire loop prototypes and deformation of blades on the polymer prototypes. CONCLUSION: Both prototypes removed carious dentin but did not remove normal dentin in the extracted teeth used in this study. Further development is indicated.