Effect of incisal preparation design on the fracture strength of monolithic zirconia-reinforced lithium silicate laminate veneers.

PURPOSE: This study aimed to assess the fracture resistance of monolithic zirconia-reinforced lithium silicate laminate veneers (LVs) fabricated on various incisal preparation designs. MATERIALS AND METHODS: Sixty maxillary central incisors with various preparation designs were 3D-printed, 15 each, including preparation for: (1) LV with feathered-edge design; (2) LV with butt-joint design; (3) LV with palatal chamfer; and (4) full-coverage crown. Restorations were then designed and manufactured from zirconia-reinforced lithium silicate (ZLS) following the contour of a pre-operation scan. Restorations were bonded to the assigned preparation using resin cement and following the manufacturer's instructions. Specimens were then subjected to 10,000 thermocycles at 5 to 55°C with a dwell time of 30 s. The fracture strength of specimens was then assessed using a universal testing machine at a crosshead speed of 1.0 mm/min. One-way ANOVA and Bonferroni correction multiple comparisons were used to assess the fracture strength differences between the test groups (α = 0.001). Descriptive fractographic analysis of specimens was carried out with scanning electron microscopy images. RESULTS: Complete coverage crown and LV with palatal chamfer design had the highest fracture resistance values (781.4 ± 151.4 and 618.2 ± 112.6 N, respectively). Single crown and LV with palatal chamfer had no significant difference in fracture strength (p > 05). LV with feathered-edge and butt-joint designs provided significantly (p < 05) lower fracture resistance than complete coverage crown and LV with palatal chamfer design. CONCLUSION: The fracture resistance of chairside milled ZLS veneers was significantly influenced by the incisal preparation designs tested. Within the limitation of this study, when excessive occlusal forces are expected, LV with palatal chamfer display is the most conservative method of fabricating an indirect restoration.

Isolated effect of filler particle size on surface properties of experimental resin composites before and after toothbrush abrasion.

OBJECTIVE: This study aimed to isolate the relationship between filler size and the surface properties of roughness and gloss before and after toothbrush abrasion for experimental resin-based composites (RBCs) containing uniform spherical fillers. MATERIALS AND METHODS: Five experimental light-cured RBCs with different spherical filler sizes and three commercial RBCs were studied. Forty specimens were polished using silicon carbide papers. Gloss was measured after 0, 90, 180, and 360 min of simulated toothbrushing, and surface roughness was measured before and after 360 min of toothbrushing. Two-way ANOVA/Tukey's multiple comparison tests were used to compare the RBCs, and the correlation between particle size and surface roughness or gloss was also determined. RESULTS: After polishing and toothbrushing, RBCs with smaller fillers exhibited significantly higher gloss and lower surface roughness, and RBCs with larger fillers exhibited lower gloss and higher surface roughness. A significant correlation was found between filler particle size and gloss and surface roughness both before and after toothbrush abrasion. CONCLUSIONS: Gloss of RBCs containing fillers with larger particle sizes was significantly reduced. After toothbrushing abrasion, the surface roughness increased for all RBCs, except those containing the finest-sized fillers. The particle size of the filler is a critical determinant of the surface roughness and gloss of RBCs, after polishing and after toothbrushing. CLINICAL SIGNIFICANCE: Increased surface roughness caused by toothbrush abrasion reduces the gloss of resin-based composites. Resin-based composites containing finer fillers best maintain glossiness after routine tooth brushing.

Bond Strength of Two Resin Cements with Leucite-reinforced Ceramic Using Different Bonding Agents.

AIM: To compare the bond strength of two resin cements to leucite-reinforced ceramics using three different boding agents and evaluate the compatibility of bonding agents. MATERIALS AND METHODS: Twenty extracted sound human molars were sectioned horizontally 2-3 mm above the cementoenamel junction (CEJ). CAD/CAM ceramic blocks for inLab were also sectioned to create 4 mm thick and bonded to the dentin. The adhesive groups assigned were divided into four adhesive groups: Group I: Variolink II dual-cure resin cement and Scotchbond Multi-Purpose Plus adhesive, group II: Multilink Automix dual-cure resin cement and Multilink primers, group III: Multilink Automix and Clearfil SE bond 2 (CSE2) adhesive, group IV: Multilink Automix and CSE2 with light curing after adhesive application. Five specimens of each group were sectioned perpendicular to obtain six microsticks of 1 × 1 mm width from each sample. Microtensile bond strength data were expressed in MPa. Fracture modes (FrMs) analyzed for the surfaces were divided into six patterns. Microtensile bond strength data were statistically analyzed with one-way ANOVA and Tukey post hoc tests (α = 0.05). T-test was performed at the 5% significance level to analyze groups III and IV with and without light curing. RESULTS: Group I showed the highest µTBS average of 13.67 MPa, group IV showed 12.26 MPa, group III showed 12.15 MPa, and group II showed the lowest average of 10.84 MPa. No significant differences were found between the bonding agents. However, the six types of failure modes, although all observed, were characterized by the adhesive system: Type I: adhesive failure of laminated dentin and ceramic; type II: adhesive failure of laminated ceramic; type III: adhesive failure of laminated dentin; type IV: cohesive failure of luting agent; type V: cohesive failure of dentin, and type VI: mixed failure of adhesion and cohesion. As a result, the FrM most commonly observed was the adhesive failure at the luting cement-ceramic block interface. CONCLUSION: The combination of resin cements and bonding agents did not significantly affect the bond strength of CAD/CAM ceramic restorations and dentin. CLINICAL SIGNIFICANCE: Several universal bonding agents are currently available for direct and indirect bonding, and using the same bonding agent for direct and indirect restorations could simplify inventory and benefit routine clinical practice. How to cite this article: Aida N, Koi K, Amaya-Pajares SP, et al. Bond Strength of Two Resin Cements with Leucite-reinforced Ceramic Using Different Bonding Agents. J Contemp Dent Pract 2023;24(11):859-863.

Development and maintenance of surface gloss of dental composites after polishing and brushing: Review of the literature.

OBJECTIVE: To describe the effect of the composites' composition to produce high surface smoothness/gloss using finishers/polishers, and to assess maintained smoothness/gloss under toothbrush abrasion. MATERIALS AND METHODS: PubMed papers published from January 01, 2000 to September 01, 2021 were included, and keywords used were: filler particle size, shape, amount of dental composites; finishing/polishing, gloss/roughness, and toothbrush abrasion of composites. Seventy-five in-vitro studies were included in this literature review. Forty-six articles assessed filler particle size/composition/shape and distribution to obtain high gloss/smoothness on different formulations; and the finishers/polishers effect on these materials. Twenty-nine papers assessed toothbrush abrasion of composites. RESULTS: Suprananofill/nanofill/microfills typically showed the smoothest and glossiest surfaces compared to nanohybrid, microhybrid and hybrid composites. Microfill (0.04-0.07 µm, 71-88 GU); suprananofill (0.001-0.8 µm, 52-92 GU), microhybrids (0.05-0.35 µm, 35-95 GU) and nanohybrids (0.05-0.21 µm, 66-97 GU). Composites with small, spherical particles tend to show smoother, glossier surfaces and more wear resistant compared to resin composites with larger or irregular particles. Several studies showed higher roughness and reduced gloss after toothbrush abrasion. CONCLUSIONS: Within the limitations of this study, suprananofill/nanofill/microfill composites tended to show the smoothest/glossiest surfaces due to smaller particle size. Composites with small, spherical particles tended to show smoother/glossier surfaces. Overall, toothbrush abrasion showed higher surface roughness and reduced gloss. CLINICAL SIGNIFICANCE: Suprananofills/nanofills/microfills had good polishability and polish retention due to their smaller particle size. The effectiveness of a polishing system is material-dependent. In general, Enhance-PoGo, Sof-Lex discs, and Sof-Lex Spiral wheels showed similar level of smoothness.

Influence of 38% silver diamine fluoride application on bond stability to enamel and dentin using universal adhesives in self-etch mode.

In order to evaluate the influence of 38% silver diamine fluoride (SDF) application on enamel and dentin bond stability of universal adhesives in self-etch mode, a 38% SDF and three universal adhesives were used in this study. Initial shear bond strength (ISBS), fatigue bond strength (FBS), and shear bond strength of survivors (SBSS) to enamel and dentin of universal adhesives in self-etch mode, with and without SDF application, were determined. SDF was applied to the polished enamel or dentin surface for 1 min, water-rinsed and air-dried for comparison with controls. The universal adhesives were applied to the prepared samples and composite resin was bonded using a mold-enclosed method. Enamel bond stability of universal adhesives with SDF (ISBS: 14.7-20.4 MPa; FBS: 5.5-7.4 MPa and SBSS: 14.4-21.5 MPa) was significantly weaker than those without SDF (ISBS: 28.0-29.2 MPa; FBS: 12.1-15.6 MPa and SBSS: 28.4-34.4 MPa). Dentin bond stability with SDF (ISBS: 14.8-20.9 MPa; FBS: 7.1-8.2 MPa and SBSS: 17.3-21.8 MPa) was also significantly weaker than without SDF (ISBS: 19.3-36.1 MPa; FBS: 11.0-13.7 MPa and SBSS: 22.2-34.6 MPa). The results suggest that SDF application on enamel and dentin reduces the bond stability of universal adhesives in self-etch mode.

Relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives.

The relationship between enamel bond fatigue durability and surface free-energy characteristics with universal adhesives was investigated. The initial shear bond strengths and shear fatigue strengths of five universal adhesives to enamel were determined with and without phosphoric acid pre-etching. The surface free-energy characteristics of adhesive-treated enamel with and without pre-etching were also determined. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were higher than those to ground enamel. The initial shear bond strength and shear fatigue strength of universal adhesive to pre-etched enamel were material dependent, unlike those to ground enamel. The surface free-energy of the solid (γS ) and the hydrogen-bonding force (γSh) of universal adhesive-treated enamel were different depending on the adhesive, regardless of the presence or absence of pre-etching. The bond fatigue durability of universal adhesives was higher to pre-etched enamel than to ground enamel. In addition, the bond fatigue durability to pre-etched enamel was material dependent, unlike that to ground enamel. The surface free-energy characteristics of universal adhesive-treated enamel were influenced by the adhesive type, regardless of the presence or absence of pre-etching. The surface free-energy characteristics of universal adhesive-treated enamel were related to the results of the bond fatigue durability.

Comparison between universal adhesives and two-step self-etch adhesives in terms of dentin bond fatigue durability in self-etch mode.

This aim of this study was to compare universal adhesives and two-step self-etch adhesives in terms of dentin bond fatigue durability in self-etch mode. Three universal adhesives - Clearfil Universal, G-Premio Bond, and Scotchbond Universal Adhesive - and three-two-step self-etch adhesives - Clearfil SE Bond, Clearfil SE Bond 2, and OptiBond XTR - were used. The initial shear bond strength and shear fatigue strength of resin composite bonded to adhesive on dentin in self-etch mode were determined. Scanning electron microscopy observations of fracture surfaces after bond strength tests were also made. The initial shear bond strength of universal adhesives was material dependent, unlike that of two-step self-etch adhesives. The shear fatigue strength of Scotchbond Universal Adhesive was not significantly different from that of two-step self-etch adhesives, unlike the other universal adhesives. The shear fatigue strength of universal adhesives differed depending on the type of adhesive, unlike those of two-step self-etch adhesives. The results of this study encourage the continued use of two-step self-etch adhesive over some universal adhesives but suggest that changes to the composition of universal adhesives may lead to a dentin bond fatigue durability similar to that of two-step self-etch adhesives.

Influence of duration of phosphoric acid pre-etching on bond durability of universal adhesives and surface free-energy characteristics of enamel.

The purpose of this study was to evaluate the influence of duration of phosphoric acid pre-etching on the bond durability of universal adhesives and the surface free-energy characteristics of enamel. Three universal adhesives and extracted human molars were used. Two no-pre-etching groups were prepared: ground enamel; and enamel after ultrasonic cleaning with distilled water for 30 s to remove the smear layer. Four pre-etching groups were prepared: enamel pre-etched with phosphoric acid for 3, 5, 10, and 15 s. Shear bond strength (SBS) values of universal adhesive after no thermal cycling and after 30,000 or 60,000 thermal cycles, and surface free-energy values of enamel surfaces, calculated from contact angle measurements, were determined. The specimens that had been pre-etched showed significantly higher SBS and surface free-energy values than the specimens that had not been pre-etched, regardless of the aging condition and adhesive type. The SBS and surface free-energy values did not increase for pre-etching times of longer than 3 s. There were no significant differences in SBS values and surface free-energy characteristics between the specimens with and without a smear layer. The results of this study suggest that phosphoric acid pre-etching of enamel improves the bond durability of universal adhesives and the surface free-energy characteristics of enamel, but these bonding properties do not increase for phosphoric acid pre-etching times of longer than 3 s.

Relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive.

The purpose of this study was to determine the relationship between mechanical properties and bond durability of short fiber-reinforced resin composite with universal adhesive. As controls, micro-hybrid and nano-hybrid resin composites were tested. The universal adhesives used were Scotchbond Universal, Adhese Universal, and G-Premio Bond. The fracture toughness and flexural properties of resin composites, and shear bond strength and shear fatigue strength of universal adhesive with resin composite using both total-etch and self-etch modes were determined. In the results, short fiber-reinforced resin composite showed significantly higher fracture toughness than did micro-hybrid and nano-hybrid resin composites. The flexural strength and modulus of short fiber-reinforced and nano-hybrid resin composites were significantly lower than were those of micro-hybrid resin composites. Regardless of etching mode, the shear bond strength of universal adhesives with short fiber-reinforced resin composite did not show any significant differences from micro-hybrid and nano-hybrid resin composites. The shear fatigue strength of universal adhesives with short fiber-reinforced resin composite and micro-hybrid resin composites were significantly higher than that of nano-hybrid resin composites. The results of this study suggest that the mechanical properties of short fiber-reinforced resin composite improve their bond durability with universal adhesive.

Sex- and age-based differences in single tooth loss in adults.

The aim of this study was to investigate sex- and age-based differences in single tooth loss in adults. The data were obtained from the results of a periodontal disease examination carried out under a health promotion law in a city in Japan in 2005. Baseline data from a total of 3,872 participants aged 40 or 60 years comprising 1,302 men and 2,570 women were available. Only participants with 27 present teeth were eligible for inclusion in the analysis, giving a total of 218 men and 428 women. Third molars were excluded from the study. The bilateral total of each type of tooth was obtained. The mandibular first molar was missing in 26.7% of the men and 36.2% of the women among 40-year-olds and 35.3% of the men and 29.8% of the women among 60-year-olds. The mandibular second molar was missing in 14.7% of the men and 12.5% of the women among 40-year-olds, and 17.6% of the men and 18.4% of the women among 60-year-olds. Significant differences were observed between men and women in the mandibular second premolars and first molars among 40-year-olds. These results suggest that we need to pay more attention to individual teeth which are at particularly high risk for tooth loss, namely the mandibular first and second molars, and especially the mandibular first molars in middle-aged women.

An in vitro comparison of the effects of various air polishing powders on enamel and selected esthetic restorative materials.

OBJECTIVE: The purpose of this study was to investigate the effects of each of the commercially available air polishing powders on the surface characterization of human enamel, hybrid composite, and glass ionomer using a highly standardized protocol. The air polishing powders utilized in the study included aluminum trihydroxide, calcium carbonate, calcium sodium phosphosilicate, glycine, and sodium bicarbonate. METHODS: The hybrid composite and glass ionomer cement were mixed and photo light-cured for 40 seconds according to manufacturer's directions, and formed in a specially prepared mold that was coated using a Teflon aerosolized spray. The enamel samples were prepared by removing sections of human enamel from extracted unerupted third molars using a water-cooled, slow-speed diamond rotary saw. The enamel sections were approximately one centimeter in diameter and 3 mm thick. The enamel sections were flattened using a series of silicon carbide grit papers (600, 800, and 1200 grit) mounted on a rotating polishing wheel. A flat polished enamel surface, at least 5 mm in size, was produced and embedded in the hybrid composite material used for testing purposes, resulting in a sample approximately 10 mm in diameter and 2 mm thick. The restorative material samples were wet-polished to produce a uniform smooth surface and to remove the resin-rich surface layer, using the same series of silicon carbide grit papers used on the enamel (600, 800, and 1200 grit). The 1200 grit abrasive paper used is equivalent to a dental polishing disc commonly used to finish dental restorations. All samples were stored in distilled water at 37 degrees C prior to testing. Each of the three types of samples was treated with each air polishing powder for one, two, and five seconds. A test group of five samples each of hybrid composite, glass ionomer cement, and enamel was fabricated for each of the six types of abrasive powder and three-time exposures for the air polishing treatment, resulting in a total of 270 samples. The treatment samples were exposed to the air polishing powders for the three periods of time using a custom mounting jig and shutter device that was fabricated to standardize the air polishing treatments. The air polishing handpiece was placed in a mounting jig that positioned the tip of the handpiece at an 80 angle from the sample surface. The exposure to the air polishing air, water, and polishing powder was regulated by an articulated metal plate positioned between the tip and the test sample. The holder for the test sample kept the sample in a constant circular motion to simulate clinical use of the air polishing handpiece. A custom computer program was developed to activate a stepper motor that rotated the metal plate away from the sample for the controlled exposure times of one, two, and five seconds before the plate moved back to intercept the polishing spray mixture. RESULTS: The effect of the air polishing application on the surfaces of the tooth enamel and restorative materials was evaluated for changes in surface roughness and surface topography. The average surface roughness value was evaluated with a contact profilometer prior to and after the air polishing treatment. Changes in the surface characterization of each sample due to air polishing treatment were recorded using scanning electron microscopy. Epoxy resin replicas of representative test samples were made for evaluating under the scanning electron microscope. Samples were sputter-coated with gold palladium and the scanning electron photomicrographs were taken at a magnification of 25X and at a 45 degrees angle. Based on evaluation with the contact profilometer, there were statistically significant interactions between the type of powder and material, type of power and time, and type of material and time. The SEM photomicrographs were used to evaluate the clinical significance of the effects of the air polishing on each type of material. The SEM photomicrographs provided a visual quantitative analysis of the effects of air polishing powders on the restorative materials and the enamel. Any disruption of the surface characterization was considered to be clinically significant and represented volumetric loss and violation of the integrity of the restorative materials and/or enamel. CONCLUSIONS: Based on the results of this study, the air polishing powders that are compatible with use on hybrid composite and glass ionomer cements are EMS glycine and EMS sodium bicarbonate. The air polishing powders that are compatible for use on enamel include EMS glycine, Dentsply sodium bicarbonate, and EMS sodium bicarbonate.

Mechanical properties and color stability of provisional restoration resins.

PURPOSE: To evaluate the mechanical strength and color stability of provisional restoration materials. METHODS: For mechanical testing, four groups [Trim (PEMA), Alike (PMMA), Versatemp (bis-acrylic resin composite, BARC) and Perfectemp II (bis-acrylic fluoride enriched resin, BAFC)] of resin disks were prepared for fracture toughness and shear punch strength testing, respectively. Five samples were fabricated for each group; therefore, a total of 20 resin disks for each testing method was prepared. The load at fracture and shear punch values of each specimen were recorded after 24-hour storage in distilled water. The stress intensity factors (K(Ic)) were calculated by the formula reported by Atkinson et al. For shear strength, the following formula was used: Shear strength = Force (N)/section thickness (mm) x punch circumference (mm). Values of each group in both tests were analyzed using one-way-ANOVA and Tukey multiple comparison test. For color stability testing, provisional resin disk specimens of the above mentioned materials were fabricated. Five samples were prepared for each subgroup (with and without a surface coating agent - Permaseal) and three different solutions (distilled water, red wine and curry); a total of 120 disk specimens were fabricated. Color values of each group were measured using a spectrophotometer after 24 hours and 2 weeks of aging in the aforementioned solutions. The color differences (deltaE*ab) between before and after aging were calculated by CIE Lab color-difference formula. The interaction of deltaE*ab values were analyzed by two-way analysis of variance followed by Newman-Keuls Multiple comparison test. RESULTS: The highest fracture toughness value [(MPa (m)1/2)] was obtained by PMMA (0.89) followed by BARC (0.67), PEMA (0.54) and BAFC (0.42). Significant differences were observed among all test groups (P < 0.05). The highest shear punch strength (MPa) was obtained by BARC (160), followed by PMMA (141) and PEMA (132). The lowest value was obtained by BAFC (106). BARC showed a significantly higher mean value than the other groups (P < 0.05). PEMA and PMMA demonstrated better color stability than the two bis-acrylic resin composites. Wine and curry showed higher stainability than water, recording higher deltaE*ab values than the clinically perceptible difference level of deltaE*ab 3.3. The surface coating agent groups demonstrated more staining than the non-coated groups. All groups, except for BARC, demonstrated significant differences dependent upon surface coating and solutions (P < 0.05).

Estimated percentile curves of occluding pairs in an adult population.

The purpose of this study was to provide the estimated percentile curves of occlusal pairs (OPs) in adults for use in oral health instruction. Data on number of present teeth (PT) were obtained from the National Report on the Survey of Dental Disease in 2005. Data from 1,535 males and 2,248 females, ranging in age from 18 to 82, were analysed. The mean number of OPs were used from our previous report. In that report we can be estimated OPs from the number of PT. In this study, PT data were replaced by the mean number of OPs. Estimated percentile curves in males, the 10th percentile of OPs was 13.7 at 60 years of age and 12.5 at 70. The 50th percentile of OPs was 12.2 at 50 years of age, 11.2 at 60 and 5.4 at 70. The 90th percentile of OPs was 7.6 at 50 years of age, 2.1 at 60 and 0 at 70. There appeared to be a cut off point after 10 OPs where the 50th to 97th percentile curves of OPs dropped off rapidly. In females, the 10th percentile of OPs was 13.4 at 60 years of age and 12.7 at 70. The 50th percentile of OPs was 11.5 at 50 years of age, 10.2 at 60 and 6.2 at 70. The 90th percentile of OPs was 7.1 at 50 years of age, 2.4 at 60 and 0 at 70. In females again the percentile curves dropped off after 10 OPs. Our results suggest that the loss of OPs may be accelerated when the number of OPs drops below 10. This means that patients need at least 10 OPs in order to maintain a stable oral status. The estimated percentile curves given in this study should be made available for use in adult oral health education.

Age- and sex-specific differences in ratio of occluding pairs to number of present teeth.

The aim of this study was to determine age- and sex-specific differences in the ratio of occluding pairs (OPs) to number of present teeth (PT). The data were obtained from a periodontal disease examination carried out under a health promotion law in a city located northeast of Tokyo, Japan, in 2005. Data from a total of 5,131 (1,735 male and 3,396 female) 40-, 50-, and 60-year-old participants were analysed in this study. Occluding pairs were counted by analysing dental charts. Sex-related differences in the ratio of mean PT to OPs were found at 30 PT in 40-year-olds, at 22 PT and 28 PT in 50-year-olds, and at 24 PT and 28 PT in 60-year-olds. Age differences were only found at 28 PT in males. These differences in the ratio of PT to OPs were influenced by the presence of third molars and the type of tooth loss pattern. In some cases the PT-to-OP ratio is influenced by age and sex, but these differences are very small. Age and sex need to be considered when using PT to estimate OPs.

Relationship between Eichner Index and number of present teeth.

The aim of this study was to determine the percentage of participants in each of the six Eichner Index groups by number of present teeth (PT). The data were obtained from a periodontal disease examination carried out under a health promotion law in a city located northeast of Tokyo, Japan, in 2005. Data from a total of 1,549 (524 male and 1,025 female) 60-year-old participants were analyzed in this study. Number of occlusal supports was counted by analyzing dental charts. The Eichner Index was used to group the participants into six groups based on distribution of occlusal support teeth. The percentage of patients in Group A with 24 PT was 31.4%; none in Group A had fewer than 19 PT. The percentage in Groups A, B1, and B2 with between 20 and 28 PT was above 50%; the number of participants in these groups with fewer than 20 PT decreased rapidly. Those with fewer than 16 PT were almost found in Groups B3, B4 and C. Only a few patients in Group C had between 10 and 14 PT; those with fewer than 9 PT were only found in Groups B4 or C. Based on these results, the Eichner Index category of a given participant can be estimated from number of PT.

Digital Technologies for Restorative Dentistry.

Although the accuracy of direct digitization of oral structure has been improved, indirect digitization is still required in specific situations such as full-arch scanning. Once accurate images are imported, efficient designing can be achieved by CAD software. Although smile design using a 3-dimensional facial scan better predicts planned restorations, further improvement in virtual articulators is needed for complex cases. Computer-aided manufacturing can be offered in several formats such as chairside, laboratory, or centralized fabrications. The subtractive technique is mainly used for restorations, and many chairside CAM materials are available now, but the additive technique has the potential to save materials and an advantage in fabricating complex geometries. Limited evidence is available in applying CAD/CAM technologies in implant restorations. However, it is used to fabricate custom implant abutments and crowns from various materials such as titanium, zirconia, and PEEK and hybrid crowns using stock titanium base abutments.

Novel translucent monolithic zirconia fixed restorations in the esthetic zone.

Novel translucent monolithic zirconia has improved optical properties, and it may fulfill patient's esthetic demands and overcome the chipping risk of bilayer metal-ceramic restorations. New zirconia's microstructures allow us to mimic natural teeth.

Effects of a paste-free prophylaxis polishing cup and various prophylaxis polishing pastes on tooth enamel and restorative materials.

The application of cleaning and polishing agents to a patient's dentition is a routine part of many dental practices. This study measured the surface roughness and surface gloss of tooth enamel, composite resin, and dental porcelain restorative materials when exposed to a paste-free prophylaxis polishing cup as well as a conventional prophylaxis polishing paste. Samples of human tooth enamel, a composite resin restorative material, and dental porcelain were prepared by a series of polishing papers to produce a flat smooth surface. The baseline average surface roughness (Ra) was measured using a contact stylus profilometer, and the surface gloss was measured with a glossmeter. The test samples were subjected to a standardized polishing routine using a paste-free prophylaxis polishing cup and a fine- or coarse-particle prophylaxis paste. Post-treatment surface roughness and gloss measurements were compared using a paired t statistical test. The conventional prophylaxis pastes increased surface roughness and decreased the gloss of the composite resin and tooth enamel test groups. The paste-free cups did not significantly affect the surface roughness of the enamel or the restorative materials. Dental porcelain surface roughness essentially was not affected by the application of paste-free cups and the fine and coarse pastes.

Number of occlusal units estimated from number of present teeth.

The aim of this study was to determine the relationship between number of present teeth (PT) and number of occlusal units (OUs). The data were obtained from a periodontal disease examination based on the health promotion law in Tokyo, Japan in 2005. Data from a total of 1,549 (524 male and 1,025 female) 60-year-old people were analyzed in this study. The number of OUs was counted by analyzing their dental charts. Any pair of opposing teeth of the same type was counted as one OU. The maximum number of OUs in a 28-tooth dentition was therefore 14. Our study revealed that the mean number of OUs decreased along with the number of PT. The OUs of the molars were lost first, followed by those of the premolars. The anterior OUs were last to be lost. The mean number of OUs was always lower than half the number of PT: 10.4 at 24 PT, 7.2 at 20 PT, 4.4 at 16 PT, and 1.3 at 10 PT. In the posterior region (premolars and molars), the mean number of OUs was 4.7 at 24 PT, 2.6 at 20 PT, and 1.0 at 16 PT. For molars, there were 1.4 OUs at 24 PT, 0.6 at 20 PT, and 0.4 at 16 PT. Participants with fewer than 20 PT had fewer than two OUs in the posterior region. This research demonstrates that the number of OUs can be estimated from the number of PT. This knowledge can be used to reveal more detailed information about the oral health status of a given population.

Successful development and implementation of a digital dentistry curriculum at a US dental school.

Introducing new technology in the dental school curriculum may face some uphill challenges navigating through university-level bureaucracy, financial ramifications, and influencing the mindset of certain faculty. A dental school that relies heavily on teaching traditional restorative procedures may particularly face many challenges to embrace new technology. The restorative department at a US dental school created a division of computer-aided design and computer-aided manufacturing (CAD/CAM) dentistry to introduce the concept of digital dentistry to dental students and faculty. This article describes methods that were adopted to improve acceptance and increase the productivity of chairside CAD/CAM restorations for both students and faculty at the dental school in US.