Machined and plastic copings in three-element prostheses with different types of implantabutment joints: a strain gauge comparative analysis

OBJECTIVE: Using strain gauge (SG) analysis, the aim of this in vitro study was quantify the strain development during the fixation of three-unit screw implant-supported fixed partial dentures, varying the types of implant-abutment joints and the type of prosthetic coping. The hypotheses were that the type of hexagonal connection would generate different microstrains and the type of copings would produce similar microstrains after prosthetic screws had been tightened onto microunit abutments. MATERIALS AND METHODS: Three dental implants with external (EH) and internal (IH) hexagonal configurations were inserted into two polyurethane blocks. Microunit abutments were screwed onto their respective implant groups, applying a torque of 20 Ncm. Machined Co-Cr copings (M) and plastic prosthetic copings (P) were screwed onto the abutments, which received standard wax patterns. The wax patterns were cast in Co-Cr alloy (n=5), forming four groups: G1) EH/M; G2) EH/P; G3) IH/M and G4) IH/P. Four SGs were bonded onto the surface of the block tangentially to the implants, SG 1 mesially to implant 1, SG 2 and SG 3 mesially and distally to implant 2, respectively, and SG 4 distally to implant 3. The superstructure's occlusal screws were tightened onto microunit abutments with 10 Ncm torque using a manual torque driver. The magnitude of microstrain on each SG was recorded in units of microstrain (µε). The data were analyzed statistically by ANOVA and Tukey's test (p0.05). The hypotheses were partially accepted. CONCLUSIONS: It was concluded that the type of hexagonal connection and coping presented similar mechanical behavior under tightening conditions

A Randomized Trial of Mineral Trioxide Aggregate Cements in Primary Tooth Pulpotomies

Purpose: The purpose of this study was to compare the outcome of primary tooth pulpotomies using two different white mineral trioxide aggregate (MTA) cements and calcium hydroxide (CH)

Age of majority assessment in Dutch individuals based on Cameriere's third molar maturity index

Radiological examination of the third molar is done in living individuals for estimation of chronological age, especially in the late adolescence. The aim of this study was to assess the application of Cameriere's third molar maturity index (I3M) to determine whether an individual is 18 years or older (adult) or younger than 18 years (minor) in a sample of Dutch individuals. The sample consisted of panoramic images of 360 individuals aged between 14 and 22 years old. Three observers performed the measurements. Gender was not statistically significant in discriminating adults and minors. The highest value of the Youden index of the receiver operating curve analysis was for the value of I3M < 0.08 in discriminating individuals as minor or adult. The specificity (Sp) and sensitivity (Se) results for females were 96.3% and 72.7% respectively. The Sp and Se for males were 95.0% and 84.0% respectively. The probabilities of correctly classified individuals were 83.3% and 88.9%, and Bayes post-test probability was 96.3% and 95.7% in females and males respectively. Obtained results showed that the specific cut-off point of I3M < 0.08 may be a useful and reliable method for adult age assessment in a Dutch population

Effects of different orthodontic adhesives and resin removal techniques on enamel color alteration

Objective: To investigate the color alterations in enamel following the use of different orthodontic bonding resins and adhesive residue removal burs. Materials and Methods: Metal brackets were bonded to extracted human premolars (n = 175) by using an etch-and-rinse adhesive system, a self-etch adhesive system (SEP), or a resin-modified glass ionomer cement (RMGIC). After 24 hours of photoaging, the brackets were removed and the adhesive residue on the tooth surfaces was cleaned with either a tungsten carbide bur or a Stainbuster bur. Tooth colors were measured with a spectrophotometer at baseline, after adhesive removal, and after additional photoaging. Color evaluation was made, and color differences induced by photoaging were calculated. Statistical evaluation was made using the Kruskal-Wallis test and the Mann-Whitney U-test, with Bonferroni correction. Results: All specimens showed discoloration at varying levels. The highest color change was observed in the etch-and-rinse adhesive/tungsten carbide bur group. When the etch-and-rinse and self-etch adhesives were used, adhesive-remnant removal with Stainbuster burs resulted in significantly lower discoloration. The type of bur did not affect the extent of enamel discoloration in the RMGIC group. Conclusions: Orthodontic treatment alters the original color of enamel, and both the adhesive system and the resin-removal methods are responsible for this change. When brackets are bonded with the etch-and-rinse system or the SEP, cleaning the adhesive residuals with Stainbuster burs is recommended for minimal change. RMGIC can be safely cleaned with tungsten carbide burs