Dental Hypotheses
Volume:15 Issue: 1, Jan -Mar 2024

We aimed to assess the effect of the type of finish line and ferrule on fracture resistance of lithium disilicate endocrowns.

The literature search was done in Pubmed, Scopus, Dimensions, and Web of Science till August 2023, without language restrictions, using the following terms: ("endocrown" OR "endocrowns" OR "endo-crown" OR "endodontic crown" OR "endodontically treated crown") AND ("preparation" OR "preparation design") AND "fracture resistance" AND "lithium disilicate" AND "molars". Grey literature was similarly investigated via WorldCat, Open Grey, and Google Scholar. An artificial intelligence-powered software, SWIFT-Review, is employed for text mining at the selection stage. Risk of bias among included studies according to the QUIN was also assesed.

From 49 articles resulted from a systematic search of databases, four of them qualified as eligible studies to be reviewed. All included articles were reports of in vitro studies and their outcome were controversial. Koosha et al. and Naji et al. reported non-significant differences between specimens with ferrule and shoulder finish lines and buttjoint finish lines. However, Einhorn et al., indicated that restorations with ferrule exhibited significantly higher fracture resistance than butt-joints. Amin et al., concluded ferrule design would improve fracture resistance. All included studies in the review are evaluated as medium risk. Furthermore, no study had considered blinding in the methods.

Outcomes of included studies were controversial, and concerning the methodological limitations of included studies it is not that easy to reach a clear and definitive conclusion.

 We aimed to assess the effect of finger-sucking, nail-biting, and salivary levels of growth hormone on the type of malocclusion among primary school students. 

This study was conducted among 10–11-year-old (4th and 5th class of the elementary schools) students in the center of Karbala city from February to June 2021 using a multistage cluster random sampling technique. Data related to oral habits were obtained using questionnaires, which were distributed among the students and collected the next day after being answered and signed by the parents. Unstimulated saliva samples were collected, and salivary levels of growth hormone were assessed using the enzyme-linked immunosorbent assay (ELISA) method. Data were analyzed via multinomial logistic regression using R software. 

The finger sucking was a significant predictor for class 2 malocclusion (p < 0.001). Night-time finger sucking was a significant predictor for class 3 malocclusion (p = 0.031). Salivary levels of growth hormone and nail-biting were not significant predictors for malocclusion (p ˃ 0.05). Also, finger sucking was a marginally nonsignificant predicator for class 3 malocclusion (p = 0.057). 

 Cross-sectional studies capture data at a single point in time, and they cannot establish a cause-and-effect relationship. More cohort studies are required to reach a conclusion about the effect of non-nutritive sucking habits such as finger sucking, nail-biting and salivary level of growth hormone on type of malocclusion.

We aimed to evaluate the shear bond strength of acrylic denture teeth to flexible and heat-cured denture base material after surface treatments with argon plasma, chemical bonding agent (PALFIQUE universal), and combination.

A total of 80 incisor acrylic denture teeth were treated with a argonplasma, chemical bond (PALFIQUE universal bond), and a combination with 10 samples for each group. The neck (gingival portion) of teeth was cut at a 45° angle, and the teeth were attached to heat-cured acrylic resin and flexible denture base material. All the specimens were stored in artificial saliva for 7 days in an incubator (37 °C). A shear bond strength test was conducted using an Instron universal testing machine. Data were analyzed by the analysis of variance (ANOVA) and the Tukey’s honest significant difference post hoc test using R 4.2.3.

A statistically significant difference was found among study groups regarding the type of base, surface treatment with bond, plasma, and combination of bond and plasma (P < 0.00). The Tukey’s test showed that in a heatcured base, the difference between the control and surface treatment with bond was not significant (P Ë 0.05). Also, in the flexible base group, the difference between the control and surface treatment with plasma was not significant (P=0.162).

In heat-cured denture-base group, the shear bond strength increased significantly with the combination of surface treatment with argon plasma and a chemical bonding agent (PALFIQUE universal). In the flexible denture-base group, the shear bond strength increased significantly with use of a surface treatment with a chemical bonding agent (PALFIQUE universal).

We aimed to assess the effects of the addition of boron nitride nanoplatelets on the physical and mechanical properties of the geopolymer prepared by natural kaolinite.

The compressive strength and diametral tensile strength tests were conducted according to BS 1881-116:1983 and ASTM E9-89a(2000) using an atomic force max instrument. The surface microhardness of the geopolymer was evaluated using a Digital Vickers microhardness tester, following the guidelines outlined in ASTM E92-82(2003). The contact angle (wettability) tests were carried out according to ASTM D7334-08(2022).

There were statistically significant differences among all study groups regarding compressive strength, diametral tensile strength, surface hardness, and wettability (p < 0.001).

The boron nitride nanoplatelets reinforcement has a significant impact on the compressive strength, diametral tensile strength, surface microhardness, and wettability of the geopolymer, providing valuable insights for future research and development in this field.

This study aimed to evaluate the impact of ozonated water on water sorption and solubility of heat-cure acrylic resin.

Thirty-three samples of heat-cured acrylic resin were manufactured and divided into three groups: control, immersion for 10 and 20 minutes in ozonated water. Water sorption and water solubility tests were carried out in line with ADA Standard No. 12 for denture-base acrylic resin. Data were analyzed using one-way ANOVA at a significance level of 5%.

There was a nonsignificant difference between the control and experimental groups regarding water sorption (P =0.273) and was significant for water solubility (P < 0.001). Tukey’s post-hoc test showed significant differences between control and intervention (OZ-10 and OZ-20) groups regarding water solubility (P < 0.001) and nonsignificant differences between OZ-10 and OZ-20 groups (P=0.811).

Immersion for 10 and 20 minutes in ozonated water can increase water solubility.