Publications by authors named "P S Ungar"

94 Publications

Grit your teeth and chew your food: Implications of food material properties and abrasives for rates of dental microwear formation in laboratory (Primates).

Palaeogeogr Palaeoclimatol Palaeoecol 2021 Dec 20;583. Epub 2021 Sep 20.

Department of Integrative Anatomical Sciences, University of Southern California, Los Angeles, California.

Dental microwear analysis has been employed in studies of a wide range of modern and fossil animals, yielding insights into the biology/ecology of those taxa. Some researchers have suggested that dental microwear patterns ultimately relate back to the material properties of the foods being consumed, whereas others have suggested that, because exogenous grit is harder than organic materials in food, grit should have an overwhelming impact on dental microwear patterns. To shed light on this issue, laboratory-based feeding experiments were conducted on tufted capuchin monkeys [] with dental impressions taken before and after consumption of different artificial foods. The foods were (1) brittle custom-made biscuits laced with either of two differently-sized aluminum silicate abrasives, and (2) ductile custom-made "gummies" laced with either of the two same abrasives. In both cases, animals were allowed to feed on the foods for 36 hours before follow-up dental impressions were taken. Resultant casts were analyzed using a scanning electron microscope. We asked five questions: (1) would the animals consume different amounts of each food item, (2) what types of dental microwear would be formed, (3) would rates of dental microwear differ between the consumption of biscuits (i.e., brittle) versus gummies (i.e., ductile), (4) would rates of dental microwear differ between foods including larger- versus smaller-grained abrasives, and (5) would rates of dental microwear differ between molar shearing and crushing facets in the animals in these experiments? Results indicated that (1) fewer biscuits were consumed when laced with larger-grained abrasives (as opposed to smaller-grained abrasives), but no such difference was observed in the consumption of gummies, (2) in all cases, a variety of dental microwear features was formed, (3) rates of dental microwear were higher when biscuits versus gummies were consumed, (4) biscuits laced with larger-grained abrasives caused a higher percentage of new features per item consumed, and (5) the only difference between facets occurred with the processing of biscuits, where crushing facets showed a faster rate of wear than shearing facets. These findings suggest that the impact of exogenous grit on dental microwear is the result of a dynamic, complex interaction between (at the very least) grit size, food material properties, and time spent feeding - which is further evidence of the multifactorial nature of dental microwear formation.
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December 2021

Three-Dimensional Surface Texture Characterization of In Situ Simulated Erosive Tooth Wear.

J Dent Res 2021 10 14;100(11):1236-1242. Epub 2021 Apr 14.

Indiana University School of Dentistry, Indianapolis, IN, USA.

This in situ erosive tooth wear (ETW) study tested enamel 3-dimensional (3D) surface texture outcomes for the detection and differentiation of ETW lesions simulated in clinically relevant conditions. Twenty participants enrolled in this 3-arm crossover intraoral ETW simulation and wore their own partial denture for 14 d holding 2 human enamel specimens (per arm). In each arm, participants were assigned to 1 of 3 different dental erosion protocols: severe (lemon juice/pH 2.5), moderate (grapefruit juice/pH 3.5), and no erosion (bottled drinking water, control). Enamel specimens were evaluated by white-light scanning confocal profilometry for 3D surface texture and surface loss (ETW model validation). Individual point clouds were analyzed using standard dental microwear texture characterization protocols for surface roughness and anisotropy. Fractal complexity (), texture aspect ratio (), and arithmetical mean height () values were generated at baseline, 7 d, and 14 d. Data were analyzed by analysis of variance models suitable for the crossover design with repeated measurements, and correlation coefficients were used to examine the relationship between outcomes. and differentiated ETW severity (no erosion < moderate < severe, < 0.001) at days 7 and 14. and were lower at baseline compared to days 7 and 14 ( < 0.001) for moderate and severe challenges. increased from day 7 to 14 ( = 0.042) for the severe challenge. For , ETW severity did not have a significant effect overall ( = 0.15). and were highly positively correlated ( = 0.89, < 0.001), while and were not correlated overall with ( < 0.1, ≥ 0.25). Enamel surface loss increased with ETW severity (no erosion < moderate < severe, < 0.001) at days 7 and 14, validating the ETW simulation model. Complexity () and roughness () outcomes were able to detect and differentiate ETW levels, with being able to monitor the progression of severe lesions. No clear characterization of ETW lesions could be provided by the anisotropy () parameter.
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October 2021

Objective assessment of simulated non-carious cervical lesion by tridimensional digital scanning.

Clin Oral Investig 2021 Jun 19;25(6):4069-4074. Epub 2021 Jan 19.

Department of Cariology, Operative Dentistry and Dental Public Health, Indiana University School of Dentistry, 415 Lansing St, Indianapolis, IN, USA.

Objective: To explore the use of 3D intraoral scanner/image analysis for the detection and monitoring of simulated non-carious cervical lesions (NCCLs) in vitro.

Materials And Methods: A total of 288 NCCLs of different severities and simulated using a laboratorial model associating toothbrush stiffness (soft, medium, and hard) and toothpaste abrasivity (low, medium, high, and negative control) were analyzed. Dental impressions were taken from specimens before and after 35K and 65K brushing strokes, and then scanned with a CEREC Omnicam scanner. 3D models were analyzed for volumetric tooth loss. 3D optical profilometry was considered as the gold standard. Data were analyzed using ANOVA and Fisher's PLSD tests (alpha = 0.05), and agreement between methods by using intraclass correlation coefficient.

Results: Toothbrushes of hard and mid stiffness caused higher tooth loss than soft when associated with the highest abrasive, at 35K and 65K strokes (p < 0.001). Variation in slurry abrasivity led to differences in tooth loss (with control < low < medium < high, p < 0.0001) after both 35K and 65K strokes, regardless of the type of toothbrush used, except at 35K, wherein control = low (p = 0.55). 35K strokes caused less tooth loss than 65K for all abrasive slurries (p < 0.0001) except controls. The intraclass correlation coefficient for agreement between the test and gold standard methods was 0.85.

Conclusions: Analysis of 3D images from intraoral scanner could detect and monitor NCCL progression, although this ability was limited on incipient lesions. Overall good agreement was found between the test method and optical profilometry.

Clinical Relevance: The suggested method may be applicable to detect and monitor NCCLs clinically.
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June 2021

Monitoring of simulated occlusal tooth wear by objective outcome measures.

J Dent 2020 11 8;102:103467. Epub 2020 Sep 8.

Department of Cariology, Operative Dentistry and Dental Public Health, Indiana University School of Dentistry, 415 Lansing St., Indianapolis, IN, 46202, USA. Electronic address:

Objectives: This in vitro study explored quantitative outcome measures as clinical indicators of simulated occlusal tooth wear progression.

Methods: Ten sound, extracted human premolars were selected and submitted to occlusal tooth wear simulation in 0.5-mm steps (0/0.5/1.0/1.5 mm). At each step, enamel thickness on the buccal cusp tips was evaluated using cross-polarization optical coherence tomography (CP-OCT) and micro-computed tomography (μ-CT). The occlusal surface of each premolar was also scanned at each step using a 3D digital intraoral scanner, followed by morphological characterization using standard topography attributes (Slope, Relief, RFI, OPCr). Repeated measures ANOVA assessed differences in simulated wear levels for the μ-CT and CP-OCT data as well as the topography values. Correlations were also calculated between the μ-CT/CP-OCT and topography data.

Results: Significant differences were observed for enamel thickness at each simulation wear stage, for both CP-OCT (p < 0.001) and μ-CT (p < 0.001), with good agreement between methods (intraclass correlation: 0.89). For topography analysis, as wear increased, the average Slope, RFI, and Relief values decreased, and average OPCr values increased, with more significant differences shown for Slope. Slope showed significant (p < 0.05) positive correlations with CP-OCT. OPCr showed significant negative correlations with μ-CT, and CP-OCT (p < 0.05). RFI and Relief were not correlated with either μ-CT or CP-OCT (p > 0.05).

Conclusions: Our findings suggest the potential of PS-OCT for measuring enamel thickness changes in the cusp tips of the occlusal surface. Similarly, conventional intraoral scanners can serve effectively for monitoring overall tooth wear when combined with dental topographic analyses of resultant point clouds.

Clinical Significance: CP-OCT measures of enamel thickness and dental 3D topographic attributes showed potential as objective outcomes for the clinical monitoring of occlusal tooth wear. Their combination provided a comprehensive understanding of the tooth wear development process.
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November 2020