Genome-wide analysis in 756,646 individuals provides first genetic evidence that ACE2 expression influences COVID-19 risk and yields genetic risk scores predictive of severe disease.

SARS-CoV-2 enters host cells by binding angiotensin-converting enzyme 2 (ACE2). Through a genome-wide association study, we show that a rare variant (MAF = 0.3%, odds ratio 0.60, P=4.5×10-13) that down-regulates ACE2 expression reduces risk of COVID-19 disease, providing human genetics support for the hypothesis that ACE2 levels influence COVID-19 risk. Further, we show that common genetic variants define a risk score that predicts severe disease among COVID-19 cases.

Early failure of Class II resin composite versus Class II amalgam restorations placed by dental students.

Using the information from remake request slips in a dental school's predoctoral clinic, we examined the short-term survival of Class II resin composite restorations versus Class II dental amalgam restorations. In the student clinic, resin composite is used in approximately 58 percent of Class II restorations placed, and dental amalgam is used in the remaining 42 percent. In the period examined, Class II resin composite restorations were ten times more likely to be replaced at no cost to the patient than Class II dental amalgam restorations. A total of eighty-four resin composite restorations and six amalgam restorations were replaced due to an identified failure.

What is different in operative dentistry?

There have been both large and small changes in operative dentistry in the last 30 years. Extension for prevention is no longer the mantra. The design features of amalgam preparations have moved into the smallest preparations possible to gain full access to the carious dentin. The default Class 2 amalgam or resin composite is a slot preparation with no preparation of the occlusal fissures. Class 1 fissure caries once implied the entire fissure system was to be cut out. Now only the known carious portions of the fissure are cut away, the tooth is restored, and the remaining fissures in that tooth are sealed. Resin composite preparations have no depth requirements and saucer shaped boxes are more favorable for lowering shrinkage strains on the bonded walls. Re-mineralization of proximal lesions that can be seen on a radiograph is now a proven successful service for many lesions that are at or just into the dentin by radiographic interpretation. The largest paradigm shift has been in the decision that in vital teeth with normal pulps soft dentin can be left over a vital asymptomatic pulp with every expectation that the direct restoration will be successful long term.

A clinician's guide to purchasing surgical loupes.

Magnification using loupes is expanding within dental professions. Loupes offer enhanced vision of fine detail and critical ergonomic advantages. To achieve the maximum benefit from loupes, the dental professional should consider key features at the time of purchase. Proper fitting and adjustment are essential elements in the successful use of loupes. Though more expensive than simple, diopter lenses, the inherent advantages of compound and prism telescopic loupes make them superior choices when dental magnification is being considered.

Efficacy of bonded and nonbonded amalgam in the treatment of teeth with incomplete fractures.

BACKGROUND: This clinical study compared the efficacy of adhesive-retained vs. pin-retained complex amalgam restorations in the treatment of molars with incomplete fractures. Both relief of chewing pain and cold sensitivity were evaluated at two weeks, three months and one year. METHODS: The authors treated 38 patients with a chief complaint of chewing sensitivity on vital molar teeth (40 teeth in the study). A random-number generator determined the treatment method for each tooth. Twenty teeth received bonded amalgam restorations. Twenty teeth received amalgapins or threaded pins to retain the amalgam. Teeth were evaluated for postoperative chewing sensitivity. A visual analog pain scale was used to evaluate cold response to a skin-refrigerant-soaked cotton pellet at each visit. After 12 months, all 40 teeth were available for evaluation. RESULTS: Chewing pain was completely eliminated in all but one tooth. A Student's t-test found no significant difference (P > .05) in preoperative cold sensitivity between the bonded and nonbonded groups. A paired t-test comparison indicated that the teeth in the bonded group were significantly less sensitive to cold after three months and 12 months than they were at the time of the baseline measurements (P < .0001). A paired t-test indicated no significant difference between preoperative and postoperative cold sensitivity scores for teeth in the nonbonded group (P > .05). CONCLUSIONS: Both adhesively bonded and mechanically retained complex amalgam restorations were successful in resolving chewing sensitivity in cracked molars. For 39 of 40 teeth, chewing sensitivity did not return during the one-year follow-up period. At three months and 12 months, cold sensitivity was reduced in the bonded restorations. At all three time periods, cold sensitivity remained similar to baseline levels for the mechanically retained restorations. CLINICAL IMPLICATIONS: Incomplete tooth fracture in molars can be successfully treated by covering fractured cusps with amalgam restorations. This study excluded teeth with prolonged sensitivity to a cold stimulus or those with periodontal evidence of root fracture. With these exclusions, elimination of chewing sensitivity was predictable. Teeth restored with bonded restorations experienced a decrease in sensitivity to a cold stimulus at three months and at 12 months, but not at two weeks. The cold sensitivity of teeth restored with nonbonded restorations was similar at baseline, two weeks, three months and one year.

Tensile bond strength of resin-modified glass-ionomer cement to microabraded and silica-coated or tin-plated high noble ceramic alloy.

PURPOSE: The purpose of this study was to evaluate the influence of alloy surface microabrasion, silica coating, or microabrasion plus tin plating on the tensile bond strengths between a resin-modified glass-ionomer luting cement and a high-noble alloy. Bond strength between the microabraded alloy specimens and conventional glass-ionomer cement or resin cement were included for comparison. MATERIALS AND METHODS: One hundred twenty uniform size, disk-shaped specimens were cast in a noble metal alloy and divided into 6 groups (n = 10 pairs/group). The metal surfaces of the specimens in each group were treated and cemented as follows. Group 1: No surface treatment (as cast, control), cemented with a resin-modified glass-ionomer cement. Group 2: Microabrasion with 50-microm aluminum oxide particles, resin-modified glass-ionomer cement. Group 3: A laboratory microabrasion and silica coating system, resin-modified glass-ionomer cement. Group 4: Microabrasion and tin-plating, resin-modified glass-ionomer cement. Group 5: Microabrasion only, conventional glass-ionomer cement. Group 6: Microabrasion and tin-plating, conventional resin cement. The uniaxial tensile bond strength for each specimen pair was determined using an Instron Universal Testing Machine (Instron Corp, Canton, MA). Results were analyzed using a one-way analysis of variance (alpha = 0.05) and a Tukey post-hoc analysis. RESULTS: Mean bond strength: Group 1: 3.6 (+/- 1.5) MPa. Group 2: 4.2 (+/-0.5) MPa. Group 3: 6.7 (+/- 0.9) MPa. Group 4: 10.6 (+/- 1.8) MPa. Group 5: 1.1 (+/- 0.4) MPa. Group 6: 14.6 (+/- 2.3) MPa. Group 6 was significantly stronger than Group 4. The bond strength of specimens cemented with the resin-modified glass-ionomer cement using microabrasion and tin-plating (Group 4) was significantly stronger than all other groups except the resin cement with microabrasion and tin-plating (Group 6). CONCLUSION: Microabraded and tin-plated alloy specimens luted with the resin-modified glass-ionomer cement resulted in the greatest mean tensile strengths for the resin-modified glass-ionomer cement groups. This strength was 73% of the mean tensile strength of microabraded specimens luted with resin cement.

Cuspal reinforcement in endodontically treated molars.

UNLABELLED: This in vitro study compared the ability of horizontal pins and a dental adhesive to reinforce the facial cusps of endodontically treated mandibular molars. Seventy-two mandibular molars were divided into six groups and mounted in acrylic blocks (n = 12). In Groups 1-5 standardized endodontic access and instrumentation in the coronal one-third of each root canal were completed. In Groups 1-4 the lingual cusps were reduced, leaving the buccal cusps intact. The facial cusps of the teeth in each group received one of the following modes of reinforcement: Group 1--no reinforcement; Group 2--dentin adhesive (Amalgambond Plus); Group 3--two horizontal TMS Minim pins; Group 4--two horizontal TMS Minim pins and Amalgambond Plus. Teeth in Group 5 were prepared for and restored with a complete cuspal coverage amalgam restoration using four vertical TMS Minim pins. Group 6 consisted of intact natural teeth. Using an Instron Universal Testing Machine, the lingual slope of the facial cusp of each specimen was loaded to failure using a compressive force applied at an angle 60 degrees to the long axis of the tooth. The mean fracture strengths for all groups were analyzed using a one-way ANOVA and Student-Newman-Keuls multiple range test (alpha = 0.05). Fracture patterns and modes of failure were also evaluated. RESULTS: The intact teeth (Group 6) were significantly more fracture resistant than all other groups, with the exception of Group 4 (combination of pins and adhesive). Group 1 (non-reinforced teeth) was significantly weaker than all other groups. Groups 2-4 (specimens with reinforced cusps) were not significantly different from each other. The use of horizontal pins or a combination of horizontal pins plus dentin adhesive for cuspal reinforcement resulted in significantly more teeth demonstrating favorable fracture patterns than did the use of adhesives alone. CONCLUSION: The buccal cusps of endodontically treated mandibular molars reinforced with a combination of horizontal pins and dentin adhesive were not significantly weaker than intact teeth. Of the restored teeth, those which had buccal cusps reinforced with horizontal pins and those treated with complete cuspal coverage amalgam restorations exhibited the most favorable restorative prognosis following cusp fracture.

Effect of saliva contamination on the bond of dentin to resin-modified glass-ionomer cement.

This in vitro study compared the shear bond strength of a resin-modified glass-ionomer restorative material (Fuji II LC) bonded to saliva-contaminated dentin versus non-contaminated dentin. Seventy-five extracted human molar teeth were randomly divided into five groups of 15 samples each. The dentin was treated with 10% polyacrylic acid for 20 seconds, rinsed, and dried. The acid-treated dentin surfaces in Groups 1-4 were contaminated with saliva. In Group 1, the saliva was air thinned. In Groups 2-4, saliva was dried completely with compressed air. The saliva-contaminated dentin in Group 3 was rinsed and dried. The saliva-contaminated dentin in Group 4 was rinsed, dried, treated with 10% polyacrylic acid, and dried. Specimens in Group 5 received no contamination. The resin-modified glass-ionomer cement restorative material was mixed and applied to the dentin surfaces. Following placement of the restorative material and 7 days of storage, the specimens were thermo-cycled 300 times. Using the Instron Universal Testing Machine, a shear force was applied to the restorative material. Shear bond strength values were compared among the groups using a one-way ANOVA and Student-Neuman-Keuls Multiple Range Test (alpha = 0.05). The non-contaminated specimens (Group 5) were significantly stronger than the contaminated specimens (Groups 1-4). There were no significant differences in bond strength among the groups containing contaminated specimens. Salivary contamination occurring after dentin etching significantly reduced the bond strength of the resin-modified glass-ionomer restorative material to dentin. Neither rinsing nor rinsing and re-etching resulted in bond strengths as great as to non-contaminated dentin.