Laser curing of dental materials.

Research supports the use of the argon laser in dentistry. Used at powers of 250 mW +/- 50 mW for 10 seconds per increment, the argon laser provides good curing of light-activated restorative materials in a shorter period of time with equal or better physical properties as compared to the conventional halogen curing light. When used at approximately 1.5 W, it is a good soft tissue surgical instrument that cuts with little or no bleeding and minimal postoperative pain. The future looks bright for the use of the argon laser in other areas, such as decay prevention or pulpal treatments for primary teeth as well as an adjunct to endodontic therapy.

Effect of argon laser irradiation on shear bond strength of orthodontic brackets: an in vitro study.

Argon lasers, due to their significant time savings over conventional curing lights, are being investigated for use in bonding orthodontic brackets. They are also being investigated for their ability to confer demineralization resistance on enamel. The purpose of this study was to evaluate the effects of argon laser irradiation on bond strength at 3 different laser energies (200, 230, and 300 mW) and at 3 unique time points of laser application (before, during, or after bracket placement). One hundred-fifty human posterior teeth were divided into 9 study groups and 1 control group. After debonding, the adhesive remnant index was scored for each tooth. There was no evidence of an effect of energy level on bond strength, P =.903, or of an interaction between timing of bracket placement and energy level, P =.858. When combining data across energy levels, the mean bond strength was significantly different between all 3 bracket placement groups, P <.001. In addition, the mean bond strength of teeth lased after bonding was significantly higher than the control group, P <.05. There were no statistically significant differences between adhesive remnant index scores among the 10 groups. Lasing the enamel before or after bonding does not adversely affect bond strength. Use of the argon laser to bond orthodontic brackets can yield excellent bond strengths in significantly less time than conventional curing lights, while possibly making the enamel more resistant to demineralization.

Caries resistance in enamel by laser irradiation and topical fluoride treatment.

PURPOSE: The purpose of this in vitro study was to compare caries resistance of sound human enamel following argon laser (AL) irradiation, as well as, combinations of topical fluoride foams and AL irradiation. METHODS AND MATERIALS: Thirty extracted human teeth were sectioned into four buccal windows and assigned to one of the following treatment groups: (1) no treatment/control; (2) low fluence (11.5 J/cm2) AL irradiation for 10 seconds; (3) 1.23% APF foam for 4 minutes followed by low fluence AL irradiation; (4) 2.0% NaF foam for 4 minutes followed by low fluence AL irradiation. Caries-like lesions were created by submerging the teeth in ten Cate solution (pH 4.5). Following a 96-hour exposure period, 100 microns longitudinal sections were prepared for polarized light evaluation. Visilog 5.1.1. image analysis software was used to obtain quantitative lesion depths. The Scheffe F-test was used to compare the lesion depths for each of the four treatment groups. RESULTS: Lesion depths were: 16.1 +/- 6 microns for control; 13.7 +/- 4 microns for AL irradiation alone; 12.1 +/- 4.3 microns for 1.23% APF foam before AL irradiation; and 11.4 +/- 5.9 microns for 2.0% NaF foam before AL irradiation. Significant difference (p < 0.05) was found between the control group and the 2.0% NaF foam before AL irradiation group. AL irradiation alone reduced lesion depth by 15% compared with the control lesion. When AL irradiation was combined with 1.23% APF foam treatment, lesion depth decreased by 25% compared with control lesions, and by 29% when combined with 2.0% NaF foam. CONCLUSION: Combining AL irradiation and 2.0% NaF foam treatment significantly enhances the resistance of sound enamel to an in vitro cariogenic challenge.

Laser and curing light induced in vitro pulpal temperature changes.

OBJECTIVE: This study was conducted to compare in vitro pulp chamber temperature changes induced by conventional curing light and argon laser under common conditions. SUMMARY BACKGROUND DATA: Previous in vitro studies have shown that impacting the surface of teeth with either an argon laser or conventional curing light causes pulp temperature increases of various degrees. METHODS: The sample tooth had a class V composite restoration placed with 2.48-mm distance from the surface of the composite to a Thermister Thermometer. The thermometer was inserted into the cutaway pulp chamber to measure the temperature increase from stabilized room temperature, which was caused by exposure to argon laser or conventional curing light. RESULTS: Temperature increases for the argon laser for the recommended curing time were 3 degrees F or less. The longer the exposure times for either method of curing, the higher the temperature increased. CONCLUSION: At recommended curing times, in vitro pulp chamber temperature increases from laser units were significantly lower than those of the conventional curing lights.

In vivo caries-like lesion prevention with argon laser: pilot study.

OBJECTIVE: This clinical pilot study was conducted to investigate the effectiveness of argon laser irradiation to reduce demineralization or loss of tooth structure in vivo. SUMMARY BACKGROUND DATA: In vitro research previously demonstrated the ability of argon laser irradiation to reduce demineralization or loss of tooth structure. METHODS: Using the Ogaard model of producing demineralization, the experimental teeth were irradiated with argon laser of 250 mW (producing approximately 12 J/cm2) prior to banding. Polarized light evaluation of the sectioned, extracted teeth was used to determine the amount of demineralization. RESULTS: Results showed a 29.1% reduction in demineralization in the experimental teeth as compared to the bilateral control teeth. CONCLUSION: Low-power argon laser irradiation significantly reduced demineralization clinically.

Combined effects of acidulated phosphate fluoride and argon laser on sound root surface morphology: an in vitro scanning electron microscopy study.

OBJECTIVE: The purpose of this in vitro scanning electron microscopy (SEM) study was to evaluate the effects of combining low fluence argon laser (AL) irradiation and acidulated phosphate fluoride (APF) treatment on the surface morphology of sound human root surfaces. SUMMARY BACKGROUND DATA: Previous in vitro investigations have shown that combined APF and AL irradiation of root surfaces provided a protective effect against cariogenic challenges. MATERIALS AND METHODS: Twelve extracted human molars were sectioned into quarters, and each quarter assigned to 1 of 4 treatment groups: (1) no treatment/control; (2) low fluence (11.5 J/cm2) AL irradiation; (3) 1.23% APF for 4 minutes; (4) APF treatment followed by low fluence AL irradiation. Surface morphology alterations were compared among groups using SEM techniques. RESULTS: AL irradiation alone produced irregular textured surfaces with adherent globular material and fine microporsities in the background. APF treatment, alternatively, only created relatively smooth surface coatings that masked the original underlying root surface. Combining APF treatment followed by AL irradiation resulted in a surface coating composed of relatively small (2 to 3 microns) spherical to avoid precipitates, morphologically resembling calcium fluoride. CONCLUSION: Combining APF with AL irradiation may create a more reactive surface that possesses fluoride-rich mineral deposits and protects the underlying root surface from cariogenic challenges.

Argon laser irradiation effects on sound root surfaces: in vitro scanning electron microscopic observations.

OBJECTIVE: The purpose of this in vitro scanning electron microscopy (SEM) study was to evaluate the effect of low fluence (energy density of 11.5 J/cm2 and 100 J/cm2) argon laser irradiation on the surface morphology of sound root surfaces. SUMMARY BACKGROUND DATA: Previous laboratory investigations have shown that argon laser irradiation of root surfaces provided a protective effect against in vitro cariogenic challenges. METHODS: Root surfaces of extracted human molars were sectioned into treatment quarters: 1) mesiobuccal--no treatment control; 2) mesiolingual--low fluence argon laser irradiation (0.231 Watts, 11.5 J/cm2 for 10 seconds); 3) distobuccal--no treatment control; and 4) distolingual--higher fluence argon laser irradiation (2.0 Watts, 100 J/cm2 for 10 seconds). All surfaces were critical-point dried, coated with platinum and paladium under vacuum, and evaluated qualitatively for intactness, surface morphology, surface deposits, and porosities in a blinded fashion by scanning electron microscope. RESULTS: The argon lased root surfaces demonstrated alterations of root surfaces with creation of surface globular particulate material, microporosities, and depressions. Both low- and high-fluence lased root surfaces showed areas with plaque-like plates with fine punctuate oval particulate material on their surfaces. CONCLUSIONS: Argon laser irradiated root surfaces produce surface granular to globular deposits that may provide readily mobilized tooth mineral, which may become redeposited into the underlying root surface during a cariogenic challenge and enhance resistance to caries formation. In addition, microporosities created by the argon laser may provide a means for bonding fluoride-releasing restorative and preventive materials to root surfaces and further improve the root surfaces' ability to resist cariogenic challenges.

Root caries in vitro after low fluence argon laser and fluoride treatment.

Because the numbers of dentate elderly are increasing, root caries prevention has become a great concern to the dental profession. This in vitro study evaluates the influence of combining low fluence argon laser treatment and acidulated phosphate fluoride treatment on caries initiation and progression in human root surfaces. The combination of low energy laser treatment and fluoride treatment increased the caries resistance of root surfaces when compared with no treatment and with laser irradiation treatment alone.

Placement and restoration of implants by predoctoral students: the Creighton experience.

Teaching of implant dentistry in the predoctoral dental curriculum has evolved dramatically over the past 20 years. In 1974, only one third of American dental schools addressed the topic of implants. Today, 48 of the 54 American dental schools have predoctoral curricula. The Creighton University experience offers some unique and instructive insights into a 10-year process of developing and implementing a predoctoral implant dentistry curriculum. All interested students may perform both the surgical placement and restoration of implant prostheses. Clinical instruction involves all restorative and surgical faculty members. Favorable 3-year (91%) and 5-year (87%) surgical success rates have been maintained. This article presents one university's program for examination and discussion.

Response of associated oral soft tissues when exposed to Argon laser during polymerization of dental resins.

BACKGROUND AND OBJECTIVE: Polymerization of dental resins with Argon laser produces restorations with improved physical properties when compared to conventional visible-light polymerization techniques. However, the possibility of damaging adjacent soft tissues has not been addressed. STUDY DESIGN/MATERIALS AND METHODS: In this study, Argon laser (488/514 nm) was used for the polymerization of composite resins to determine effects on the parakeratinized gingiva adjacent to both restored and unrestored teeth in six dogs, using 10-, 20-, and 30-second polymerization exposures. RESULTS: Gingival tissues removed at 24 hours, 72 hours, or 5 days revealed desiccated, disrupted, hyalinized connective tissue. Tissues exposed for 10 seconds showed minimal change. This minimal degree of change was most evident at 72 hours and returned to normal limits at 5 days. The 20-second exposure produced alterations evident through all time periods. Tissues exposed for 30 seconds exhibited necrosis, severe disruption, and vessiculation, which was still unresolved at 5 days. CONCLUSION: This study demonstrates that clinically relevant Argon laser exposure (10 seconds) of parakeratinized gingiva adjacent to teeth undergoing restoration does not cause lasting damage.

Surface morphology of sound enamel after argon laser irradiation: an in vitro scanning electron microscopic study.

Argon laser irradiation (ALI) at relatively low fluences (energy densities) enhances the caries resistance of sound enamel. The purpose of this SEM study was to compare the effects of argon laser irradiation at relatively low fluences (11.5 Joules/cm2 and 100 Joules/cm2) on enamel surface morphology. Following a fluoride-free prophylaxis, 12 extracted caries-free human molars were sectioned into tooth quarters. Tooth quarters were treated as follows: 1) Mesiobuccal-ALI at 11.5 J/J/cm2 for 10; 2) Distobuccal-Control; 3) Mesiolingual-ALI at 100 J/J/cm2 for 10; and 4) Distolingual-Control. Enamel surface morphology was compared among the two argon laser irradiation groups and matched non-treated control enamel surfaces by SEM. Argon laser treatment resulted in considerable alterations in the surface morphology compared with matched controls. Control enamel surfaces showed relatively smooth contours with occasional termination of enamel prisms at the surface. Both argon laser treatment groups had intact enamel surfaces lacking prism end markings and cratering of the enamel surface. A discontinuous granular surface permeated by numerous microporosities of < 1.0 micron in diameter was created with both argon laser treatment groups. Globular deposits of approximately 0.5 to 2 microns in maximum dimension composed the surface coatings. These deposits were admixed with areas of fine microporosities. Argon laser irradiation at relatively low fluences produces surface coatings which may act as reservoirs for mineral phases during an acidogenic attach of the enamel and may provide a certain degree of protection against a cariogenic challenge.

Bond strengths to enamel and dentin with indirect and direct resin composites.

PURPOSE: To investigate the differences in shear bond strengths between indirect and direct resin composites attached to enamel and dentin. MATERIALS AND METHODS: Sixty human molar teeth stored in distilled water since extraction were used in this study. Thirty of the teeth were prepared to form a flat enamel surface ground to 600 grit and 30 of the teeth were prepared to form a flat dentin surface ground to 600 grit. Cylinders constructed from Triad indirect resin composite were bonded to 15 enamel and 15 dentin surfaces and additional cylinders constructed from TPH direct resin were bonded to the remaining 15 enamel and 15 dentin substrates. Bond strengths were determined by shearing the specimens with an Instron testing machine. RESULTS: Mean shear bond strengths observed in this study were: Triad to enamel, 27.64 +/- 7.35 MPa; TPH to enamel, 27.43 +/- 3.37 MPa; Triad to dentin, 21.83 +/- 3.10 MPa; and TPH to dentin, 21.27 +/- 4.85 MPa. Two-way ANOVA demonstrated that significant differences existed between the four test groups and that this difference was primarily related to the surface to which the cylinders were attached (P = 0.000). No significant differences were discovered in shear bond strengths between restorative materials (P = 0.767) or between restorative materials bonded to a specific, common surface (P = 0.891). Turkey's post hoc test demonstrated that the shear bond strength of Triad to enamel was significantly greater than the shear bond strength of either Triad to dentin (P = 0.012) or TPH to dentin (P = 0.005). This test also pointed out that the shear bond strength of TPH to enamel was significantly greater than the shear bond strength of either TPH to dentin (P = 0.007) or Triad to dentin (P = 0.016). Finally, it was noted that the shear bond strength of Triad to enamel was essentially the same as TPH to enamel (P = 1.000) and that the bond strength of Triad to dentin was essentially the same as TPH to dentin (P = 0.990).

Effects of argon laser curing on dentin shear bond strengths.

Previous studies have demonstrated the ability of the argon laser to polymerize light-activated materials and improve enamel shear bond strengths. This study was conducted to evaluate the effects of the argon laser on dentin shear bond strengths of current dentin bonding systems. Argon laser (HGM Model 8) at 231 and 280 mW, 5 sec bonding agent, 10 sec composite, and a conventional curing light (Translux EC/Kulzer) at 10 sec bonding agent, 20 sec composite were used to polymerize samples of dentin bonding systems [Scotchbond Multi-Purpose Plus (3M) and Prime Bond (Dentsply/Caulk), both with TPH (Dentsply/Caulk) composite]. A flat dentin bonding site (600 grit) was prepared on the buccal surface of extracted human teeth. Twelve samples were made for each set of parameters for both laser and conventional light totaling 48 samples. Samples were stored in distilled water in light-proof containers for 24 h at 37 degrees C. Shear bond strengths (MPa) were determined for each sample on the Instron testing machine. Mean values were calculated for each set of data and ANOVA with Fisher PLSD were used for statistical analysis. The argon laser provided bond strengths that were 21-24% greater than those of the conventional curing light system.

4-year clinical study of castable ceramic crowns.

PURPOSE: To evaluate the 4-year clinical performance of castable glass ceramic crowns used to restore teeth in the posterior segments. MATERIALS AND METHODS: 101 castable ceramic (Dicor) full++ crown restorations were placed in 61 molar and 40 premolar teeth using a bonded resin cement. RESULTS: After 4 years of clinical performance, 15 of the original 101 restorations were known to have failed with 13 of those failures affecting molar restorations. All serviceable restorations were rated as excellent for color match, margin adaptation, proximal contact and gingival health. Cavosurface margin discoloration received a 93.5% alfa response. The results of this study show that Dicor crowns meet the esthetic and biological requirements for posterior restorations. The incidence of fracture of molar restorations in this study indicated that when used for restoring molars, careful case selection and caution must be employed.

Effects of argon laser irradiation and acidulated phosphate fluoride on root caries.

PURPOSE: To determine the effects of argon laser irradiation (ArI) and topical acidulated phosphate fluoride (APF) treatment on artificial caries formation in root surfaces. MATERIALS AND METHODS: After soft tissue debridement and fluoride-free prophylaxis, the teeth were divided into quarters and acid-resistant varnish was applied, leaving windows of sound root surface exposed. Each tooth received four separate treatments: (1) Control-mesiobuccal quarter; (2) ArI only--mesiolingual quarter; (3) ArI followed by APF- distobuccal quarter; (4) APF followed by ArI-distolingual quarter. ArI was for 10 seconds at 2W (100J/cm2) and APF treatment was for 4 minutes. After artificial lesion formation, sections were prepared and evaluated with polarized light. Mean lesion depths were determined and compared (ANOVA & DMR for a paired design). RESULTS: Mean lesion depths were: 347 +/- 41 microns--controls; 263 +/- 32 microns--ArI only; 158 +/- 21 microns--ArI followed by APF; and 149 +/- 17 microns -APF followed by ArI. Lesion depths were significantly different (P < 0.05) between the control group and each treatment group, and between ArI only group and either combined APF and ArI groups. No lesion depth difference (P > 0.05) was present between the combined APF and ArI groups. Argon laser irradiation significantly enhanced the resistance of root surfaces to demineralization. Combination of APF treatment with argon laser irradiation provided added protection against a constant artificial caries attack.

Argon laser irradiation and acidulated phosphate fluoride treatment in caries-like lesion formation in enamel: an in vitro study.

The purpose of this in vitro study was to determine the combined effects of argon laser irradiation (ArI) and acidulated phosphate fluoride treatment (APF) on caries-like lesion formation in human enamel. Each specimen was divided into tooth quarters with each quarter assigned to one of four groups: 1) control; 2) ArI Only; 3) ArI before APF treatment; 4) APF treatment before ArI. After a fluoride-free prophylaxis, acid-resistant varnish was applied to the tooth quarters, leaving sound enamel windows exposed on buccal and lingual surfaces. Argon laser irradiation was at 2 watts for 10s (100J/cm2). APF treatment was with a 1.23% APF gel for 4 min. Lesions were created in sound enamel windows with an acidified gel. After lesion formation, sections were obtained and imbibed with water for polarized light study. Body of the lesion depths were determined and compared among the four groups. Lesion depths were: 195 +/- 23 microns for control; 129 +/- 17 microns for ArI only; 96 +/- 14 microns for ArI before APF; and 88 +/- 11 microns for APF before ArI. Significant differences (P < 0.05) were found between the control group and all treatment groups, and between the ArI only group and both combined APF and ArI groups. Significant difference (P > 0.05) was not found between the ArI before APF and the APF before ArI groups. Laser irradiation alone reduced lesion depth by 34% compared with control lesions. When ArI was combined with APF treatment, lesion depth decreased by more than 50% compared with control lesions, and by 26 to 32% when compared with lased-only lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Enamel caries initiation and progression following low fluence (energy) argon laser and fluoride treatment.

The aim of this study was to evaluate the effect of low fluence argon laser (AL) and acidulated phosphate fluoride (APF) treatment on caries initiation (CI) and progression (CP) in human enamel. Twenty caries-free molars were divided into tooth quarters. Tooth quarters from each specimen were assigned to one of four groups: 1) Control; 2) AL Only; 3) AL before APF; 4) APF before AL. AL was at 0.25 watts for 10 seconds (12.0 +/- 0.5 J/cm2). APF treatment was with a 1.23% gel for 4 minutes. Lesions were created in two treated, sound enamel windows per tooth quarter with an acidified gel. After CI and CP, sections were obtained and imbibed with water for polarized light study. Mean body of the lesion (BL) depths were determined and compared among groups (ANOVA & DMR). After CI, BL depths were: 189 +/- 29 micrometers for Control, 133 +/- 23 micrometers for AL only; 91 +/- 17 micrometers for AL before APF; and 83 +/- 14 micrometers for APF before AL. After CP, BL depths were: 321 +/- 43 micrometers for Control, 206 +/- 35 micrometers for AL only; 118 +/- 21 micrometers for AL before APF; and 114 +/- 19 micrometers for APF before AL. After CI and CP, argon laser irradiation alone resulted in significant reductions in lesion depth when compared with controls (p<0.05). APF treatment before or after argon laser exposure resulted in a significant reduction in lesion depth when compared with AL alone or control groups (p<0.05). Caries initiation and progression in vitro are affected to a significant extent when low fluence (energy) argon laser irradiation of sound enamel alone or in conjunction with APF treatment is done. This caries-protective effect occurs at an argon laser fluence (energy) that is capable of polymerizing visible light-cured resins.

Argon laser irradiation in root surface caries: in vitro study examines laser's effects.

Recent research shows that laser irradiation can improve enamel's resistance to caries. This in vitro study examines the effects of argon laser irradiation on root surface caries. Treated surfaces seemed more resistant to an artificial caries medium than control surfaces.