BACKGROUND: Class II cavity preparations in restorative dentistry pose a risk of iatrogenic damage to adjacent teeth as they could increase their susceptibility to caries and the need for additional restorative procedures. While previous research has explored this issue through in vitro and limited in vivo investigations, the direct clinical observation of proximal protection usage to prevent iatrogenic damage during class II cavity preparations is still limited.
OBJECTIVE: This in vivo study aimed to assess the prevalence of proximal protection usage and extent of iatrogenic damage induced to adjacent surfaces upon occurrence during class II cavity preparations via direct visual inspection under magnification.
METHODS: Data were collected from restorative dentistry consultants supervising fourth-year undergraduate students. Information regarding cavity preparations, proximal protection usage, and iatrogenic damage was gathered through an electronic evaluation form via direct clinical observations once class II cavity preparations were finished. Statistical analyses, including ordinal logistic regression models, were employed to investigate associations and compute odds ratios (ORs).
RESULTS: We examined 82 teeth adjacent to class II cavity preparations in in vivo settings. The prevalence of proximal protection use was 72%, while the prevalence of iatrogenic damage was 17.1% overall, increasing to 47.8% when not using protection and 5.1% when using protective measures. Polishing and restoration of the induced damage were the primary management approaches. The use of protective measures, particularly matrix bands, significantly reduced the risk of iatrogenic damage (P < 0.05). Several factors, including arch, tooth surface, time, operator gender, and the state of the adjacent tooth before treatment, were examined but did not yield statistically significant associations.
CONCLUSIONS: Our study shows that most undergraduate dental students use proximal protection during class II cavity preparations, which are significant in reducing iatrogenic damage to the adjacent tooth. However, the literature shows that general practitioners often do not use proximal protection. The use of proximal protection should be reinforced and even required for the successful and safe treatment of proximal cavities. Future research with larger and more diverse samples is needed to understand the barriers to the use of proximal protection and develop interventions to promote its adoption.

This study aims to compare the different modes of cavity preparation while evaluating the effect of low-level laser therapy (LLLT) on dentine before bonding in terms of shear bond strength between composite resin and dentine. Fifty human molar teeth were mounted on acrylic blocks and dentine specimen were prepared after which they were randomized into four equal groups. Cavity preparation mode differed in respective groups. After etching, bonding; composite resin was placed and polymerized on the prepared dentine surfaces. The specimens were kept in an environment simulating oral cavity and then shear tested in a universal testing machine. The failure surfaces of the specimen teeth were subjected to SEM micrographic evaluation. The cavity prepared with diamond abrasive points had a higher shearing load at failure that was statistically significantly different from the ones prepared with laser. That with diamond abrasive points followed by LLLT of the cavity surface with Nd:YAG laser had a higher bond strength than the ones prepared with just Er:YAG laser and there was no statistically significant difference between these and the ones prepared with diamond abrasive points alone. SEM analysis of the failure mode in bur-cut dentine showed the presence of a hybrid layer at the interface. Surface conditioning of the same with Nd:YAG laser before etching suggested a recrystallisation of dentine due to the heat produced. Cavity preparation with Er:YAG laser leads to reduced shear bond strength to adhesive restorative materials when compared with that using burs and high-speed handpiece.

Reparative dentin formed by dental cavity preparation (DCP) is frequently used in clinical operations and plays a pivotal role in pulp protection. Recent reports have shown that senescent cells induced by various stressors aggravate many diseases. They can be treated using senolytics, which are drugs that selectively eliminate senescent cells. However, the association between DCP, senescent cells, and senolytics remains unclear. In this study, we established a rat model of DCP and analyzed the spatiotemporal localization of senescent cells in the pulp. The results showed that p21- and p16-positive senescent cells appeared mostly around the pulp horn (PH) under DCP. Furthermore, administration of senolytics (dasatinib and quercetin) successfully eliminated these senescent cells, thereby restoring the volume of reparative dentin formation. These data indicate that senescent cells induced by DCP may hamper the formation of reparative dentin. Senescent cells may be targets for the development of new restorative dentistry therapies.

Cluster of differentiation 146 (CD146) is known to localize in stem cells and precursor cells of various tissues. In this study, to analyze the function of CD146 in odontoblast differentiation, immunohistochemical localization of CD146 was examined during rat molar tooth development and after cavity preparation. At the cap and bell stages, many CD146-positive cells were visible around the blood vessels in the dental papillae. On Postnatal day 2, osterix-positive odontoblasts were arranged in the dentin sialoprotein (DSP)-positive predentin, and many CD146-positive cells were observed near these odontoblasts with blood vessels. Some perivascular CD146-positive cells overlapped with Smad4-positive cells. However, the immunoreactivity for alpha-smooth muscle actin (α-SMA), one of the markers for undifferentiated cells, was negligible. Furthermore, the number of these cells decreased in the dental pulp on Postnatal day 28. On Day 4 after cavity preparation, Osterix-positive odontoblasts appeared lining the reparative dentin. Most of the blood vessels near the reparative dentin showed immunoreactivities for CD146. Reparative odontoblasts actively formed DSP-positive dentin matrix because these cells were positive for Smad4 and Osterix, but not for α-SMA. After 7 days, the number of CD146-positive cells near blood vessels decreased in the dental pulp beneath the cavity. These results suggest that the CD146 is expressed in the perivascular area of the dental pulp and induces vascularization in the vicinity of dentin formation, and some CD146-positive cells are activated by the bone morphogenetic protein signaling pathway and differentiate into odontoblasts in the early stages of dentin formation and repair.

UNASSIGNED: Endodontically treated premolars are currently restored with direct bonded techniques in conservative manner enabling them to bear functional stresses homogeneously.
UNASSIGNED: The study aimed to evaluate the effect of placement of compactable glass fibers in reinforcing the endodontically treated teeth in a novel conservative manner.
UNASSIGNED: Research laboratory, in vitro study.
UNASSIGNED: Seventy-five extracted maxillary premolars were procured. Fifteen teeth were left untreated (Group A) and the remaining teeth were endodontically treated followed by standardized mesio-occluso-distal preparation and randomly assigned to experimental groups (n = 15) as follows: (B) no restoration, (C) restoration with composite, (D) EverStick® POST followed by composite, and (E) vertical glass fibers within 3 mm of the coronal root canal space and buccopalatal flaring of the coronal fibers followed by composite. After conditioning and thermocycling, specimens were loaded under a universal testing machine to evaluate fracture resistance and fracture pattern of specimens.
UNASSIGNED: Obtained scores were statistically analyzed using one-way analysis of variance test for stress analysis, post hoc Tukey\'s test for intergroup comparison, and Chi-square test for analysis of favorable and unfavorable fracture.
UNASSIGNED: The fracture resistance was highest to lowest as follows: Group A > E > C > D > B (P < 0.001).
UNASSIGNED: EverStick®POST used in conservative manner improved fracture strength of teeth significantly.

UNASSIGNED: The erbium-doped yttrium aluminium garnet (Er:YAG) laser has been revealed to effectively ablate dental hard tissues, and its utilisation to caries eradication and cavity preparation is envisaged. Nevertheless, only a limited research has been performed on the Er:YAG laser\'s capacity to treat caries.
UNASSIGNED: The efficiency of caries elimination with an Er:YAG laser in vitro was equated to that of traditional mechanical therapy in this study.
UNASSIGNED: The investigation made use of teeth that had suffered from root caries. The Er:YAG laser was used to treat half of each tooth, while the other half was either removed with a conventional bur or left untouched as a control. Each therapy was evaluated in terms of how long it took to remove cavities, histological examinations of decalcified serial sections, scanning electron microscopy (SEM) analyses and the density of the dentin.
UNASSIGNED: A longer treatment time was required for the Er:YAG laser to completely eradicate carious dentin because of its precise irradiation strategy. However, the Er:YAG laser was effective in removing diseased and softening carious dentin with little heat injury to neighbouring intact dentin, much as the bur treatment. It was also shown that the Er:YAG laser treatment had a lower amount of vibration than other methods. The SEM study of the lased dentin surface revealed characteristic micro-irregularities.
UNASSIGNED: The Er:YAG laser system appears to be a potential novel technical option for caries therapy, based on our findings.

For hard tissue formation, cellular mechanisms, involved in protein folding, processing, and secretion play important roles in the endoplasmic reticulum (ER). In pathological and regeneration conditions, ER stress hinders proper formation and secretion of proteins, and tissue regeneration by unfolded protein synthesis. 4-Phenylbutyric acid (4PBA) is a chemical chaperone that alleviates ER stress through modulation in proteins folding and protein trafficking. However, previous studies about 4PBA only focused on the metabolic diseases rather than on hard tissue formation and regeneration. Herein, we evaluated the function of 4PBA in dentin regeneration using an exposed pulp animal model system via a local delivery method as a drug repositioning strategy. Our results showed altered morphological changes and cellular physiology with histology and immunohistochemistry. The 4PBA treatment modulated the inflammation reaction and resolved ER stress in the early stage of pulp exposure. In addition, 4PBA treatment activated blood vessel formation and TGF-β1 expression in the dentin-pulp complex. Micro-computed tomography and histological examinations confirmed the facilitated formation of the dentin bridge in the 4PBA-treated specimens. These results suggest that proper modulation of ER stress would be an important factor for secretion and patterned formation in dentin regeneration.

One of the current trends in dental education is to empower dental students on a global platform using advanced technology. Haptic virtual reality simulation (HVRS) is a relatively new technology in the field of teaching and learning operative dentistry. This study aims to assess the impact of haptic virtual reality simulation (HVRS) on dental students\' psychomotor skills acquisition in preclinical operative dentistry. Class I cavity preparations (CP) were performed at baseline by 21 novice dental students on plastic teeth. Duration of CP was recorded and cavity features were evaluated and scored. Then, students were exposed to HVRS training on CP. Another Class I CP was performed by each student on plastic teeth after HVRS training, then evaluated, and the duration was recorded. There was a statistically significant decrease in CP performance time after HVRS training (p < 0.001) and an increase in the mean total marks of CP after HVRS training (p < 0.001). The change in the students\' performance in the CP displayed a statistically significant improvement after HVRS training in smoothness of the pulpal floor (p = 0.047), pulpal floor direction (p = 0.029), buccal, lingual, and mesial wall direction (p = 0.004, p = 0.025, p = 0.002), mesial and distal wall smoothness (p = 0.01, p = 0.001), internal line angle (p = 0.024), and internal point angle (p = 0.029). Overall improved performance in psychomotor skills was found after HVRS training. It could be beneficial to incorporate HVRS training early in pre-clinical operative dentistry courses as an adjunct to conventional phantom head training.

UNASSIGNED: The authors have used an in vitro model to appraise the antimicrobial efficacy of diode lasers with two different power outputs on Streptococcus mutans (SM), Lactobacillus casei (LC), and Actinomyces naeslundii (AN).
UNASSIGNED: The coronal dentin of thirty human mandibular third molars was prepared with four cylindrical cavities left in contact with SM, LC, and AN for 72 h to facilitate bacterial penetration. Diode laser (810 nm for 30 s in two cycles) with 1.5 W (group I), 1 W (group II), and 2% chlorhexidine gluconate solution for 60 s (group III) was applied on three cavities and the fourth cavity was not subjected to any treatment (control). Similar amounts of dentin debris were collected from the cavity into sterile tubes. The bacterial count was determined by serial dilution and plate count method. Percentage of killing was calculated for comparative analysis.
UNASSIGNED: The percentage of SM killed after exposure was 73.68 ± 23.37, 51.75 ± 25.45, and 26.78 ± 21.8 in three groups, respectively, (P = 0.002; Kruskal-Wallis) with no significant difference between group I and group II (P = 0.089; Mann-Whitney). The percentage of AN killed after exposure was 37.77 ± 49.52, 22 ± 19.48, and 56.86 ± 23.93 in three groups, respectively, (P = 0.013; Kruskal-Wallis) with significant difference between group II and group III (P = 0.002; Mann-Whitney). The percentage of LC killed after exposure was 51.32 ± 39.07, 36.65 ± 38.48, and 75.41 ± 22.6 in three groups, respectively (P = 0.091; Kruskal-Wallis).
UNASSIGNED: Diode lasers exerted antibacterial effect of varying levels against all the three cariogenic bacteria. Although they are recommended as a supplementary antibacterial surface pretreatment technique for efficient removal of cariogenic bacteria, further clinical studies are required to confirm the in vitro findings.

As the member of erbium laser family, Erbium, Chromium: Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) has obtained the approval for caries removal and cavity preparation by Food and Drug Administration (FDA). However, there is still controversy over the beneficial effects of Er,Cr:YSGG preparations on microleakage. The present study is the first systematic review and meta-analysis to compare the microleakage of cavities prepared by Er,Cr:YSGG lasers with that by traditional burs. In addition, the effect of acid etching on the adhesive potential of self-etch and etch-and-rinse adhesives was assessed after laser preparation.
An electronic search was performed in Pubmed, EBSCO, Embase, and the Cochrane Controlled Register of Trials (CENTRAL).
Totally, 357 articles were identified. Finally, 13 met the inclusion criteria, of which 11 were selected for meta-analysis. All the included studies exhibited a moderate risk of bias. Based on the meta-analysis, no significant difference was observed between the Er,Cr:YSGG and traditional bur groups in terms of the incidence of microleakage. Self-etch adhesives, in combination with prior acid etching, showed less microleakage than those without acid etching in the laser-prepared cavities.
Current studies do not support the beneficial effects of Er,Cr:YSGG preparations on microleakage. Additional acid etching with self-etching adhesives is recommended after Er,Cr:YSGG preparations. Further high-quality studies are needed to draw a convincing conclusion in the future.