Biomedical subjects

K J Söderholm

Publications and source records attributed to K J Söderholm.

At least 19 recordsLinked to original sources

PubMed2001

Clinical wear performance of eight experimental dental composites over three years determined by two measuring methods.

The effect of matrix selection, filler composition, filler silanization, operator variations, and test site (dental clinic) on the wear rate of eight composites were evaluated. The wear was measured on replicas using both a microscopic and a laser scanning measuring method. The average wear rate on contact-free surfaces was 9.2 +/- 4.2 microm/month with the microscopic measurement and 8.5 +/- 3.7 microm/ month with the laser scanner over the 36-month period. The urethane-based composites performed significantly better than those which were bisGMA-based. Restorations placed at one dental clinic showed significantly lower initial wear. There was also a significant difference between the operators that was most pronounced during the first 6 months. The other variable (filler composition and silane treatment) did not affect the wear rate significantly.

Barium Compounds↗

PubMed2001

Shear strength of dentin and dentin bonded composites.

PURPOSE: The objective of this study was to compare the shear strength of dentin with the shear strength of dentin bonded composites, and to determine how variables such as composite strength and blade width used during shear testing influence shear strength values. MATERIALS AND METHODS: Dentin test samples (n = 36) were made by milling the anatomical molar crowns to a shape similar to a composite rod bonded to a flat dentin surface. Dentin bonding was accomplished by bonding composites to flat dentin surfaces (n = 72) using Scotchbond MP and Z100 (n = 36) or Silux Plus (n = 36) composites. Shear testing was conducted using a guillotine-like device with a flat blade embracing half the dentin or composite cylinders. The blade thickness was either 0.25, 0.5, 0.75, 1.0, 1.25, or 1.50 mm. Six samples per material and blade thickness were tested. In addition to the above study, the bond strength of Z100 (n = 6) and Silux (n = 6) bonded with Scotchbond MP and tested with an orthodontic edgewire loop were also tested and compared with the bond strength of the Z100 and Silux samples tested with the 0.5 thick blade. All shear testing was done at a load rate of 0.5 mm/min. The results were analyzed using ANOVA and Duncan's multiple range test. RESULTS: The shear strength values when tested with the blades were: dentin = 39.7 +/- 13.0 MPa, Z100 = 29.3 +/- 7.2 MPa, and Silux = 21.1 +/- 4.9 MPa; each group had significantly different values (p < 0.05). The blade thickness had no significant effect on strength (p = 0.471). Comparing the 0.5-mm-wide blade with the edge wire (width = 0.45 mm) revealed a significant difference (p = 0.0014) favoring the blade. Z100 performed better than Silux (p = 0.0014). CONCLUSION: The shear strength of the tested bonding agent is significantly lower than the shear strength of dentin. The shear strength depends on testing method (blade vs loop) and composite material.

Analysis of Variance↗

PubMed2001

Comparison of shear and flexural bond strength tests versus failure modes of dentin bonding systems.

PURPOSE: To (1) measure the shear and flexural bond strengths of three different bonding agents that use different application techniques, (2) determine whether the shear and flexural bond tests rank the three materials similarly, and (3) determine whether the fractured surface produced with the flexural test, facilitates studies of failures within the adhesive interphase region. MATERIALS AND METHODS: Scotchbond MP (SBMP), Single Bond (SNGB) and Clearfil SE (CLSE) were evaluated. For each material, 16 samples were bonded. Eight of these samples were bonded for shear testing and the other 8 samples for flexural bond strength testing. After the bonding was completed, all samples were stored in water at 37 degrees C for 30 days. Shear bond strength was measured using an orthodontic edge wire loop and flexural strength was measured using a 4-point bending device. The samples used for the flexural test consisted of 3 mm x 3 mm x 20 mm beams in which center a 1 mm thick dentin wafer had been bonded perpendicularly to the length of the beam. An indentation with a microhardness tester was placed at one of the dentin-composite interfaces to serve as an induced flaw. This flaw was placed on the surface in tension during flexural testing. The data were analyzed using ANOVA. Scanning electron microscopy was used to examine each specimen and assign its failure mode. Percent occurrence of failure mode was determined for each material and overall for both test methods. When there was uncertainty regarding failure location, electron dispersive spectroscopy x-ray analysis was used to identify elements present on the fractured surface. RESULTS: No significant difference (P > 0.05) in bond strength was observed within each test group, while significant differences (P < 0.05) existed between the two test methods (shear: SBMP = 21.2 +/- 4.0 MPa, SNGB= 24.3 +/- 4.7 MPa, CLSE= 24.6 +/- 4.4 MPa; flexural strength: SBMP= 34.6 +/- 9.3 MPa, SNGB = 31.9 +/- 6.9 MPa, CLSE= 34.3 +/- 4.7 MPa). Shear bond test specimens failed mostly within dentin (54.2%), followed by failures within the adhesive interphase (41.6%), and failures in composite (4.2%). Flexural strength specimens failed mostly within the adhesive interphase (83.3%), followed by failure in composite (16.7%). Bond strengths were similar for all three adhesive systems within each test method group. Failure mode analysis revealed significant differences (P < 0.0001) among the two test methods.

Adhesives↗

PubMed2000

Filler particle leachability of experimental dental composites.

We studied the effect of matrix selection, filler composition, and filler silanization on filler leachability after storage in distilled water or artificial saliva. We evaluated 2 matrix systems, 2 filler systems and 2 silane treatment procedures, combined into 8 different dental composite materials. A total of 128 batches were made, and 2 specimens per batch were prepared. Of these 2 specimens per batch, one was stored in distilled water and the other in artificial saliva, both at 37 degrees C. We transferred the specimens each 30th day during a 3-yr period to new vials containing either freshly distilled water or newly mixed artificial saliva and analyzed the solutions the specimens had been stored in regarding Si, Ba and Al concentrations. The analyses revealed that storage solution, filler composition, and total time in the storage solution had strong effects on leachability. The average monthly leakage of the three elements was linear with time and higher in the artificial saliva. The Ba-containing filler leached Si faster in artificial saliva than in distilled water, and roughly twice as much as the quartz filler. The storage effect approached an order of magnitude, while the filler effect was roughly a factor of two. Filler leaching was linear over time.

Algorithms↗

PubMed2000

Calcium leaching from dentin and shear bond strength after etching with phosphoric acid of different concentrations.

Based on the H2O-P2O5-CaO phase diagram, we hypothesize that a phosphoric acid concentration around 27 wt% leaches most calcium from dentin. We also hypothesize that bond strength is affected by resin infiltration, and that resin infiltration becomes incomplete when calcium leakage exceeds a certain value. Dentin disks were cut from human molars. Eight phosphoric acid concentrations were prepared (15.7-51.2 wt%). For each acid group, there were four etch time subgroups (15, 30, 60 and 120 s). The dentin disks were etched in acid and rinsed in water for times corresponding to 15 s, 30 s, 60 s and 120 s. The calcium concentrations were analyzed using atomic absorption spectroscopy. Composite cylinders were bonded to the remaining parts of the teeth using the same etching protocol, and shear bond strength was determined. The 29.2 wt% group demonstrated the highest and the 15.7 wt% group the lowest calcium leaching value. Even though there were trends towards lower bond strength for longer etch times, a statistically significant difference was only found between 30 and 120 s. There was no significant correlation between calcium leaching and bond strength. The results support the tested hypothesis that the highest leaching value would be around 27 wt% phosphoric acid.

Acid Etching, Dental↗

PubMed1999

BIS-GMA--based resins in dentistry: are they safe?

BACKGROUND: The authors critically surveyed research dealing with the release of resin components from dental composites and the potential of these agents to mimic or disrupt estrogenic cell responses. TYPES OF STUDIES REVIEWED: The studies reviewed included those on synthetic methods used to make bisphenol A glycidyl methacrylate, or BIS-GMA, and the biological effects of this resin in cell culture and animals. The estrogenic effect of bisphenol A was targeted because bisphenol A is present as an impurity in some resins (BIS-GMA) and as a degradation product from other resins (bisphenol A dimethacrylate, or BIS-DMA). RESULTS: The outcomes of this review revealed that short-term administration of BIS-GMA and/or bisphenol A in animals or cell cultures can induce changes in estrogen-sensitive organs or cells. However, considering the dosages and routes of administration and the modest response of estrogen-sensitive target organs, the authors conclude that the short-term risk of estrogenic effects from treatments using bisphenol A-based resins is insignificant. Long-term effects need to be investigated further. CLINICAL IMPLICATIONS: Commonly used dental resins should not be of concern to the general public; however, pharmacological evaluation of dental materials is needed to ensure biologically safe and therapeutically effective substances.

Animals↗

PubMed1998

The in vivo effects of bisGMA on murine uterine weight, nucleic acids and collagen.

The aim of this investigation was to evaluate the ability of commercial bisGMA to stimulate growth in an estrogen-sensitive target tissue. Adult, female, Swiss-Webster mice were ovariectomized and received either oil, estradiol (100 microg/kg), or one of two bisGMA doses (25 microg/kg or 100 microg/kg). Starting on the day of surgery, the hormone, drug or oil was injected subcutaneously 3 times a week. After 3 wk of treatment, the animals were sacrificed, the uteri removed, weighed and stored at -80 degrees C for biochemical analysis. The uteri from ovariectomized mice receiving high dose (100 microg/kg) bisGMA or estradiol showed a significant increase in normalized wet weight that was 29% and 786%, respectively, greater than the ovariectomized control uterine normalized weights. In the low bisGMA dose (25 microg/kg) group, normalized uterine wet weights were not statistically significant from ovariectomized controls. Biochemical analyses of uterine tissues revealed that estradiol resulted in maintaining DNA content, RNA content, RNA/DNA ratios and collagen content significantly above the ovariectomized control. Neither the low nor high doses of bisGMA stimulated RNA content, DNA content or RNA/DNA ratios above ovariectomized controls. However, the high dose (100 microg/kg) of bisGMA caused a significant increase above ovariectomized controls in uterine collagen content.

Animals↗

PubMed1998

Determinants of quality in operative dentistry.

The definition of quality in operative dentistry has often, at least in part, been related to how well a cut preparation compares with an ideal preparation. The ideal preparation follows well-defined design principles. These design principles have their roots in empirical dentistry and scientific evaluations, the latter often being conducted in vitro. Because of the complexity of following these design principles practically, a large portion of dental education consists of perfecting cavity preparations. By focusing on how to cut these cavity preparations as closely as possible to the ideal preparation, dentists with high psycho-motor skills have been able to provide the public with restorative procedures of high standards over the years. However, because of the tendency of relating quality in operative dentistry to the ideal preparation, we found it justifiable to review the literature dealing with the cavity design principles of the Class II amalgam preparation. What triggered this review was a request from the International Dental Federation (FDI) to start a process leading to a scientifically based quality definition of dental restorations, a definition that determines how different factors, including cavity design principles, affect the longevity of both tooth and restoration. From our review, we conclude that patient response and restoration performance over time, rather than how closely a cavity preparation compares with the ideal preparation, will be of more significance in determining the longevity of a Class II amalgam restoration.

Dental Amalgam↗

PubMed1998

Effect of primer solvent, primer agitation, and dentin dryness on shear bond strength to dentin.

PURPOSE: To evaluate the shear bond strength of acetone- or water-based primers applied with or without agitation to either wet or dry dentin. MATERIALS AND METHODS: Forty-eight caries-free extracted human premolars were embedded in gypsum and flat dentin surfaces were prepared. The teeth were randomly divided in eight groups with six specimens each. After acid etching and rinsing, either a HEMA and acetone (Ac) or a HEMA and water (Wa) primer were applied to dry (D) or wet (W) dentin. The primer was placed with (Y) or without (N) agitation according to the following combinations: Group 1: D-Ac-Y; Group 2: D-Ac-N; Group 3: D-Wa-Y; Group 4: D-Wa-N; Group 5: W-Ac-Y; Group 6: W-Ac-N; Group 7: W-Wa-Y; Group 8: W-Wa-N. The primed surface was dried, covered with a bonding resin and light-cured, whereupon a composite cylinder was bonded to the dentin surface. The shear bond strength was determined after 30 days in water. RESULTS: The mean and standard deviations, expressed in MPa, were: Group 1: 13.1 +/- 3.42; Group 2: 15.9 +/- 4.84; Group 3: 19.8 +/- 6.64; Group 4: 18.6 +/- 5.18; Group 5: 16.5 +/- 5.25; Group 6: 25.5 +/- 4.79; Group 7: 21.9 +/- 4.94; Group 8: 17.4 +/- 4.50. The results were analyzed using ANOVA and Waller-Duncans K-ratio t-test. The acetone-based primer gave the highest bond strength to wet dentin without agitation. When the acetone-based primer was used on dry dentin a significant decrease in bond strength occurred (P < 0.05). No significant difference (P > 0.05) was found for the water-based primer on wet or dry dentin. Agitation improved the bond strength for the water-based primer, but decreased the bond strength for the acetone-based primer.

Acetone↗

PubMed1997

The effect of comonomer composition, silane heating, and filler type on aqueous TEGDMA leachability in model resin composites.

Experimental composites using either bisGMA/TEGDMA or UEDMA/ TEGDMA matrices, quartz or barium glass fillers, and 2 different filler silanization methods were evaluated regarding monomer leachability in distilled water. The leached amount was detected and quantified using gas chromatography. The results showed that twice as much TEGDMA is leached from a bisGMA/TEGDMA based composite than from an UEDMA/ TEGDMA based composite, when both contain 50 wt% TEGDMA. The hypothesis suggested that the higher degree of cure of UEDMA/TEGDMA based composites would be reflected in a lower monomer leaching value, and this hypothesis was supported by the findings. Whether such a correlation exists within groups of UEDMA/TEGDMA based matrices having different degrees of cure was not determined and needs to be investigated in future studies. Variables such as filler composition and silane treatment did not affect the leaching values of TEGDMA in water. That finding suggests that future studies should target differences in matrices, and that the need for considering effects of filler composition and silane treatment methods should not receive the same priority.

Analysis of Variance↗

PubMed1996

Filler leachability of composites stored in distilled water or artificial saliva.

Though dental composite materials leach filler elements when stored in distilled water, it is not known whether similar leaching occurs in saliva. The hypothesis to be tested was that due to ion exchange occurring at the filler surfaces, more filler elements leach from composites stored in a salt solution simulating saliva than from composites stored in distilled water. Another aim was to determine how matrix selection, filler composition, and filler silanization affect filler leachability of composites after storage in the simulated saliva and water media. We made 128 batches of experimental composites. Half of these used a bis-GMA/TEGDMA matrix and the other a UEDMA/TEGDMA matrix. Either silica or barium glass filler particles were incorporated into these matrices. Filler silanization was followed by a filler drying at 60 degrees C for 24 h. Half of the silanized particles received an additional heat treatment for 1 h at 110 degrees C in vacuum. One specimen per batch was stored in distilled water and the other in artificial saliva at 37 degrees C. After each 30-day interval for one year, the specimens were transferred to either freshly distilled water or newly mixed artificial saliva. The "old" solutions were analyzed by ICP for determination of the Si, Ba, and Al concentrations. Analysis of variance revealed that storage solution, filler composition, and total time in the storage solution had strong effects on the leachability (p < 0.0001 in all cases). The average monthly leakage of Si for quartz-filled composites was 0.22 +/- 0.20 microgram/mL (distilled water) and 2.80 +/- 1.20 microgram/mL (artificial saliva). For barium-glass-filled composites, the corresponding Si leaching values were 0.73 +/- 0.48 microgram/mL and 5.00 +/- 2.20 microgram/mL. The monthly means of the barium leaching values were 2.00 +/- 1.00 microgram/mL (distilled water) and 3.10 +/- 1.80 microgram/mL (artificial saliva). The large difference between leaching in artificial saliva and in distilled water, as well as the interaction between storage medium and filler, cast doubt on the clinical relevance of in vitro studies using distilled water.

Aluminum↗

PubMed1995

Some effects of water on dentin bonding.

OBJECTIVES: The goals of this study were to determine how: 1) the bond strengths of hydroxyethylmethacrylate (HEMA)-based dentin primers are affected by different solvents (water or acetone), 2) the application time of these primers affect the bond strength, and 3) the conversion of water contaminated bonding resins. METHODS: HEMA (35%), mixed with water or acetone, was placed on moist dentin for 30 or 120 s, dried, covered with a bonding resin, and light-cured. Composite cylinders were bonded to these surfaces, and the shear bond strength was determined after 30 d of water storage at 37 degrees C. The conversion of bonding resins containing 0.05, 0.1, 0.2, 0.4 and 0.8 mL water per mL of bonding resin was determined with FTIR. RESULTS: The two acetone groups gave significantly (p<0.5) higher bond strength values (sigma 30s=22.2 +/- 2.1 MPa and sigma 120s=21.5 +/- 3.2 MPa) than the two water groups (sigma 30s=7.0 +/- 3.3 MPa and sigma 120s=16.2 +/- 4.8 MPa). In contrast to the acetone-based primer, the water-based primer improved its bond strength with increased priming time without reaching that of the two acetone groups. The conversion of the bonding resin was 53.5%, which decreased to approximately 25% when 0.2 mL or more water was added per mL resin. SIGNIFICANCE: Compared to acetone, water is inferior as a solvent for HEMA-based dentin primers and gives both lower bond strength and requires longer priming time than acetone. A possible explanation of these results is the ability of water to interfere with the polymerization of the resin systems.

Acetone↗

PubMed1995

The impact of recent changes in the epidemiology of dental caries on guidelines for the use of dental sealants: clinical perspectives.

When used properly, sealants result in improved dental health. However, their use on all occlusal tooth surfaces for preventive reasons will result in wasted dental care resources. To optimize the preventive effects of sealants, a delivery model should be initiated that uses specially trained dental hygienists or dental assistants who visit schools to explain oral health-related issues, conduct visual inspections of clinical oral health status, identify patients at risk for dental caries, and generate a central database for program operation. When a high-risk patient is identified, auxiliary personnel could place sealants and recall the patient for a new visual inspection six months later. If caries is suspected at that time, the patient could be sent to a dentist for additional treatment. To offset the negative effects caused by overutilization of sealants, their usage should be divided into two categories. First, a preventive option should be available, and the fee for use of sealants in this option should be lower compared to the fees used today. By using specially trained auxiliary personnel to place such sealants, the fee could be kept reasonably low. Second, a sealant treatments option that targets treatments of incipient lesions also should be available. The fee for such a treatment should be close to that of the traditional occlusal restoration, and the application should be by a dentist. By using such a fee structure based on market forces, one would expect that sealant usage would increase among patients suffering from early carious lesions, while the usage of preventive sealants would remain the same or decline. This utilization pattern for dental sealants would contribute to improved efficiency of sealant usage in the treatment of dental caries, particularly at a time when caries frequency is declining. The improved efficiency could release dental care resources that should be used to target risk groups with improved education in dental health. By using such a strategy, the long-term effect would be not only the placement of fewer restorations, but an improvement in dental health among adolescents and adults.

Adolescent↗

PubMed1995

Effects of treatment and storage conditions on ceramic/composite bond strength.

During the past few years, the interest in using ceramic inlays and veneers has increased. New materials and methods have been introduced to bond these restorations to resinous materials. Since our knowledge of how to optimize such bonding is limited, the objective of this study was to test the hypothesis that various surface treatment variables and combinations of these variables affect the strength of the ceramic/composite interphase of ceramic inlays differently. The influences of material composition, surface-roughening method, silane treatment, silane heat treatment, and storage condition on bond strength were investigated. Three ceramics (Dicor, Mirage, Vitabloc), three surface-roughening methods (etching, sandblasting, grinding), three silane treatments (gamma-methacryloxypropyltrimethoxysilane [MPS], MPS+paratoluidine, vinyltrichlorosilane), two heat treatments (20 degrees C for 60 s, 100 degrees C for 60 s), and two storage conditions (24-hour dry, one yr in water at 37 degrees C) were studied. For each of the 108 combinations, five specimens were tested. Ceramic cylinders were treated according to group assignment and bonded to blocks of the same ceramic material with a dual-cured resin. The shear bond strength was determined, and the experimental factors were evaluated by analysis of variance. The results showed that surface-roughening method had the strongest effect on bond strength, while ceramic selection had the least significant effect. Of the surface-roughening methods, etching was associated with higher bond strength values than either sandblasting or grinding.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum Oxide↗

PubMed1995

Does resin based dentine bonding work?

Since Buonocore, in the mid 1950s, introduced enamel etching to be used to bond resinous restorations to enamel, different resin based bonding procedures have continuously found their way into dental practise. Today, dentists bond materials not only to enamel, but also to dentine. Up until recently, the clinical success with dentine bonding agents had been unreliable at best, and many clinicians had become sceptical as to whether it would ever be possible to bond to dentine. In this paper, some of the important break-throughs in the field of dentinal adhesives are reviewed in an attempt to throw some light on the question, does resin based dentine bonding work? The technical procedure used to optimise dentine bonding is reviewed, emphasising the significance of etching dentine, placing the primer on a slightly moist dentine surface, avoiding oxygen inhibition of the bonding resin, and maximising the degree of cure. In addition, emphasis is also placed on the significance of variations in dentine structure, and how sclerotic dentine may make dentine bonding less efficient. The conclusion of the entire review is that although significant improvements have been made in the field of dentine bonding during the last few years, it is still too early to conclude that dentine bonding will survive several years of clinical service.

Acid Etching, Dental↗

PubMed1993

Molecular orientation of silane at the surface of colloidal silica.

The objective of this study was to investigate the silica-silane bond formation present at the filler interface of dental composites. Diffuse reflectance infrared Fourier transform spectroscopy was used, and the spectra of pyrogenic silica (Cab-O-Sil) treated with different concentrations of gamma-methacryloxypropyltrimethoxysilane (MPS) were analyzed. The outcome of the study suggested that the gamma-methacryloxypropyltrimethoxysilane (MPS) molecules oriented parallel to the colloidal silica surface (Cab-O-Sil) and formed two types of bonds. One of these bonds was a siloxane bridge formed by a condensation reaction between the silanol groups of both the silica surface and the hydrolyzed silane. Water formed during this reaction and soon became recaptured by the silanol groups of the silica surface. These water molecules were not available for additional hydrolyzation reactions of the unhydrolyzed silane under the experimental conditions. The intensity of the isolated OH-groups decreased because of this reaction. Simultaneous with the condensation reaction, the carbonyl group of the MPS molecule formed hydrogen bonds. This hydrogen bond formation resulted in a peak shift of the carbonyl band from 1718-1720 cm-1 to 1700-1702 cm-1. This hydrogen bond formation also occurred with the isolated OH-groups. After consumption of the isolated OH-groups, no additional surface reaction occurred because no further OH-groups were available for additional condensation reactions or hydrogen bond formation. The findings suggest that the amount of silane needed for filler treatment depends on the number of isolated OH-groups available on the filler surface.

Composite Resins↗

PubMed1993

Crystal precipitation on dentin by poly(acrylic acid) solutions containing SO4(2-) ions.

The ability of four different 40% poly(acrylic acid) (PAA) solutions, containing 4 or 6 wt-% of either Na2SO4 or (NH4)2SO4, to cause precipitation of CaSO4 on dentin surfaces was investigated. Each treatment consisted of exposing the dentin to one of the four solutions for either 1 or 2 min and was followed by a water rinse (1 min) and air drying (30 sec). The treated dentin surfaces were then evaluated in a scanning electron microscope (SEM), which showed that crystals precipitated on the dentin with these solutions. Of the four investigated PAAs, one performed better than the others with regard to crystal precipitation and blockage of the tubules. This solution was selected for additional studies of the effects of different PAA concentrations (10%, 20%, 30%, 40%, and 50%). In these solutions, 4 and 6 wt-% of either Na2SO4 or (NH4)2SO4 were dissolved. Additional dentin surfaces were then treated with these solutions as described earlier and evaluated in an SEM. This evaluation showed that solutions containing 30-50% PAA resulted in optimized crystal formation for all the different sulfate solutions and that the optimization occurred within 1 min. Besides optimizing crystal precipitation, these mixtures also minimized the frequency of open dentinal tubules.

Acid Etching, Dental↗

PubMed1992

Visual and profilometric wear measurements.

Wear of composites can be estimated by the degree of marginal discrepancy between the prepared cavity wall and the occlusal margins of composites. Such evaluations are done on casts by comparing and rating the marginal discrepancy with those on standard casts. We analyzed the reliability of this technique on metal and stone specimens. These specimens contained grooves of different width and depth. For the visual comparison we used stone casts of machined standards of known groove depth. We measured the depths of the metal specimens with a profilometer and made stone casts of these original specimens. Using the stone casts of the standards, five dentists estimated the unknown groove depths on the remaining stone casts. These estimates were done under standardized conditions and repeated by each dentist on five different occasions. The results showed that visual depth evaluations of die stone specimens underestimated the depths when compared with the values measured with a profilometer on the original metal models. One investigator gave significantly different (p less than 0.05) groove depth estimates at different occasions.

Calcium Sulfate↗