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Open Access Publications from the University of California

Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Francisco Electronic Theses and Dissertations (2016)

BACKGROUND:

Hard and soft tissue LASERs continue to gain popularity in dentistry. Most published literature on enamel and dentin bond strength after LASER use were carried out utilizing Er:YAG, ErCr:YSGG and 10.6µm CO2 LASER, respectively. The LASER bond strength literature lacks studies using a 9.3 µm short-pulsed CO2 LASER.

OBJECTIVES:

The objective of this study was to test, whether 9.3 μm short-pulsed CO2 LASER irradiation has an influence on the bond strength of human enamel following different LASER treatments for pit and fissure sealants as well as for composite restoration placements in a laboratory study in comparison to non-LASER treated enamel by measuring the bond strength of a total-etch adhesive system, using shear-bond strength testing 24 hours after flowable composite placement.

METHODS:

The laboratory study was carried out in four stages. Stage 1 of the study was performed on bovine enamel, and stage 2 was carried out on human enamel samples, respectively. For stage 1 and 2 samples were “hand irradiated” while in stage 3 a computer controlled motor-driven stage was used to move the sample while irradiating with the CO2 LASER. Stage 4 was used as negative control comparing LASER treatment alone without etching to a no-etched control.

In the first three stages, the control group was treated with 37% phosphoric acid-etch (Scotchbond™ Universal etchant, 3M™ ESPE™, St. Paul, MN) and bonded with Adper Single Bond Plus (3M™ ESPE™, St. Paul, MN) followed by the placement of Z250 Filtek™ supreme flowable composite (3M™ ESPE™, St. Paul, MN). The test group samples were treated with a short-pulsed 9.3 µm CO2 LASER (Solea, Convergent Dental, Inc., Natick, MA) at different energy settings followed by total-etch bonding. After debonding of the composite with the UltraTester™ (Ultradent™ Products, Inc., South Jordan, UT), the shear-bond strength values were compared between the groups with ordinary one-way ANOVA followed by Bonferroni’s multiple comparison tests.

RESULTS:

The bovine treatment groups showed an increase in shear-bond strength in comparison to the non-irradiated control group. However, statistically the increased bond strength values were not significantly different. LASER hand irradiation on human enamel showed an increase in shear-bond strength by 27.4%. LASER irradiation treatment using a stage motor showed an increase in shear-bond strength by 20.2%. Those differences were statistically significant for some of the treatment groups. The negative control groups with no etching after LASER treatment showed a significant, 79.5% reduced shear-bond strength in comparison to the total-etch control group.

CONCLUSION:

The study results suggest that when used with total-etch technique and 3M™ ESPE™ Adper Single Bond Plus, SOLEA 9.3 µm short-pulsed CO2 LASER treatment increases composite shear-bond strength to enamel by up to 27.4% in comparison to non-LASER treated enamel. Using the LASER settings for caries prevention resulted in the highest shear-bond strength increase. The study also showed that CO2 LASER treatment by itself is not a substitute for acid etching. In conclusion, when SOLEA 9.3 µm short-pulsed CO2 LASER irradiation is used to render enamel caries-resistant, the shear-bond strength of the dental sealant to the enamel is increased.

    Cover page: In Vitro Study of Enamel Bond Strength Following 9.3 μm CO2 LASER Treatment
    • Article
    • Peer Reviewed
    UC San Francisco Previously Published Works (2016)

    Introduction

    The regular collection of 3-dimensional (3D) imaging data is critical to the development and implementation of accurate predictive models of facial skeletal growth. However, repeated exposure to x-ray-based modalities such as cone-beam computed tomography has unknown risks that outweigh many potential benefits, especially in pediatric patients. One solution is to make inferences about the facial skeleton from external 3D surface morphology captured using safe nonionizing imaging modalities alone. However, the degree to which external 3D facial shape is an accurate proxy of skeletal morphology has not been previously quantified. As a first step in validating this approach, we tested the hypothesis that population-level variation in the 3D shape of the face and skeleton significantly covaries.

    Methods

    We retrospectively analyzed 3D surface and skeletal morphology from a previously collected cross-sectional cone-beam computed tomography database of nonsurgical orthodontics patients and used geometric morphometrics and multivariate statistics to test the hypothesis that shape variation in external face and internal skeleton covaries.

    Results

    External facial morphology is highly predictive of variation in internal skeletal shape ([Rv] = 0.56, P <0.0001; partial least squares [PLS] 1-13 = 98.7% covariance, P <0.001) and asymmetry (Rv = 0.34, P <0.0001; PLS 1-5 = 90.2% covariance, P <0.001), whereas age-related (r(2) = 0.84, P <0.001) and size-related (r(2) = 0.67, P <0.001) shape variation was also highly correlated.

    Conclusions

    Surface morphology is a reliable source of proxy data for the characterization of skeletal shape variation and thus is particularly valuable in research designs where reducing potential long-term risks associated with radiologic imaging methods is warranted. We propose that longitudinal surface morphology from early childhood through late adolescence can be a valuable source of data that will facilitate the development of personalized craniodental and treatment plans and reduce exposure levels to as low as reasonably achievable.
      Cover page: Facial surface morphology predicts variation in&nbsp;internal skeletal shape
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