Dental Hypotheses
Volume:13 Issue: 4, Oct -Dec 2022

We aimed to systematically review the animal studies that have investigated the efficacy of periodontal ligament stem cells (PDLSCs) in bone regeneration.

Web of science, Scopus, PubMed, Embase, Cochrane Library, and ProQuest were searched to September 2022 for animal studies investigating bone regeneration using PDLSCs.

Twenty studies were included. Calvaria and alveolar defects were treated with stem cells. The cells were mainly carried with hydrogel, hydroxyapatite, and collagen scaffolds. PDLSCs promoted osteogenesis compared with cell-free scaffolds, except in one study where biphasic calcium phosphate block scaffolds alone or with Bone morphogenic protein 2 had superior outcomes in calvaria defects. Controversial results were reported when comparing the osteogenic potential of PDLSCs and bone marrow stem cells. Two studies reported higher potential in BMSCs, and two others reported higher bone formation and more bone quality in PDLSCs.

With the limitations of this study, PDLSCs might have promising potential to accelerate bone regeneration in artificial defects; however, due to high heterogeneity in the outcomes of the present studies, before moving forward to human experiments, further preclinical in vivo studies are needed.

This study aimed to assess the remineralization of shallow and deep artificial white spot lesion (WSL) by the application of three fluoride releasing varnishes.

Sixty-four extracted premolars were subjected to acid attack inducing two depths of WSLs. Using a DIAGNOdent pen, teeth were divided into two groups according to the WSL depth: shallow enamel (SE) and deep enamel (DE). Then each was subdivided into four intervention groups of eight teeth each: MI varnish, Clinpro White varnish, Clinpro XT, or control (artificial saliva). Laser fluorescence were measured via DIAGNOdent pen at baseline, demineralization stage, 24 h, 4 weeks, and 8 weeks after intervention.

For each lesion depth, there were statistically significant differences among the agents after intervention (P < 0.01) and among time intervals for each group (P < 0.01).

MI varnish is more effective than Clinpro White varnish or Clinpro XT in remineralizing two depths of WSLs at different time points.

The goal of this study was to compare the impact of NaOCl, EDTA, and chitosan on the cyclic fatigue of 2Shape, HyFlex EDM, and RACE EVO.

A total of 120 new 2Shape (n=40), HyFlex EDM (n=40), and RACE EVO (n=40) files were subdivided randomly into four groups (n=10): Group (A) with no immersion, Group (B) with immersion in 5.25% NaOCl for 5 min, Group (C) with immersion in 17% EDTA for 5 min, and Group (D) with immersion in 0.2% chitosan for 5 min. The files were rotated in an artificial canal with a 5 mm radius and a 60° curvature at body temperature until they fractured, and the number of cycles to fracture was measured. ANOVA test and Tukey post-hoc test were used to analyze the data.

Immersion of the files in NaOCl, EDTA, or chitosan solutions had no significant effect on the number of cycles to fracture (P > 0.05).

The irrigation solutions did not have any influence on the cyclic fatigue of the tested files.

To evaluate the shade matching of teeth restored with OMNICHROMA using four different teeth shade-selection techniques.

Thirty sound upper first premolar teeth were used. Shade was taken by the VITA Linearguide 3D-MASTER, the VITA Easyshade V, digital photography, and the TRIOS 3 intraoral scanner for the cervical area. Subsequently, a Class V cavity was prepared and filled with an OMNICHROMA filling, and another reading for the shade was taken.

Value of ΔE in all groups were significantly higher than the clinically acceptable value (ΔE: 3.7) (P < 0.001). One-way ANOVA measurements showed statistically significant differences among the groups (P < 0.001).

OMNICHROMA composite showed some degree of mismatch with the surrounding tooth structure. This in vitro model could not simulate complex oral situation and more clinical studies are necessary.

The aim of this study was to compare the marginal microleakage between bulk-fill, preheated bulk-fill, and bulk-fill flowable composite resins above and below cemento-enamel junction (CEJ) using micro-computed tomography.

Sixty freshly extracted premolar teeth were prepared with a slot shaped cavities of a total of 120 Class II: 3 mm (bucco-lingual), 2 mm (mesio-distal) with mesial gingival margin located 1 mm coronal to CEJ, and distal gingival margin located 1 mm apical to the CEJ. The samples were randomly divided into two main groups according to the restorative material (Tetric EvoCeram and 3M Filtek), and each group was further sub-divided into three subgroups according to the consistency (bulk fill, preheated bulk fill, and bulk fill flowable). The specimens were thermocycled (500 cycles, 5–55 °C, 30 seconds dwell time) and immersed in a 50% ammonical silver nitrate for 24 hours. Microleakage was evaluated using micro-CT. Data analyzed via three-way ANOVA and random forest model (a machine learning algorithm).

There was no statistically significant three-way interaction between type of composite, location of gingival margin related to CEJ, and filling technique (P=0.103). However, the random forest model (a machine learning algorithm) showed type of composite is the most influential factor.

Within the limitations of this study, considering the importance of the type of composite, the teeth restored with preheated bulk fill composite showed decrease in microleakage in comparison with bulk fill flowable composite.

We aimed to assess the expression of p63 among different clinical types of oral lichen planus.

The current study includes 44 oral lichen planus cases from the oral pathology laboratory, oral diagnostic department, Baghdad University. P63- PRM114P used as primary monoclonal antibodies. The intensity of immunohistochemistry activity was calculated utilizing the following criteria: weak intensity: one positive cell, moderate intensity: two positive cells, and strong intensity: three or more positive cells (magnification 20×).

The mean age of participants was 52.82 ± 12. No significant relationship found between gender and expression of p63 (P= 0.65). The p63 expressed in all clinical types of oral lichen planus (OLP). Yet, expression of p63 was not significantly related to the clinical type of OLP (P= 0.98).

We could not found relationship between expression of p63 among different clinical types of oral lichen planus. With respect to the limited sample size of this study, some larger scale studies among different populations are need to reach to a definitive conclusion regarding relationship between expression of p63 among different clinical types of oral lichen planus.

Aim of this study is to compare shear bond strength of different luting materials used in fixed space maintainer cementation.

Thirty intact extracted human third molars randomly divided into three equal groups: group A: RelyX luting 2 (resin modified glass ionomer); group B: TOTALCEM (self-adhesive resin cement/ dual cure); group C: Transbond plus (compomer). After bonding procedures, the samples were kept in distilled water at 37°C for 24 hours prior to the shear bond strength test. Data were analyzed blindly by one-way ANOVA test and the Tukey post hoc test using R software.

There were statistically significant differences between the three luting materials (P < 0.001).

TOTALCEM showed significantly higher shear bond strength than RelyX luting 2 and Transbond plus. With respect to limitations of in vitro studies, long-term clinical studies required.

This study aimed to determine whether there was a difference in the duration it required to extract impacted molars based on the sex of the patient.

In this study, 108 patients with impacted mandibular third molars who attended the Tikrit Dental College (50% of them were men, aged 18–30) were included. The impactions were classified using the Winter’s method. The surgery duration was defined as the time between incision and final suturing. Data were analyzed by point-biserial correlation and chi-squared test using R software.

The frequencies of different types of impactions were similar between males and females (P > 0.05). The most common type of impaction was mesioangular, followed by distoangular, straight, and horizontal. Negatively very weak correlation found between gender and third molar surgery duration (r=−0.15, P= 0.11, 95% CI −0.037–0.331).

No significant correlation among gender and duration of surgery was found. To validate the findings of this study, further research with a larger sample size is needed.

We aimed to compare solubility between zinc oxide eugenol and zinc oxide eucalyptus.

One hundred and twenty standardized plastic ring molds were constructed and filled with zinc oxide eugenol and zinc oxide eucalyptus. The specimens were allowed to dry for 24 hours and then weighed to the nearest 0.0001 g. Then divided randomly into three groups and immersed in distilled water for 1, 7, and 21 days. Then samples were removed from the solution and allowed to dry for 24 hours. Then they were weighed again, the percentage of weight loss was then determined as solubility. Data analyzed by two-way repeated measures ANOVA and the Tukey’s post-hoc test using MedCalc 20.104.

Zinc oxide eucalyptus solubility is more than zinc oxide eugenol. All tests of between-subjects effects and withinsubjects effects showed statistically significant differences (P < 0.001).

The 1st day results showed solubility of not more than 3% following storage in distilled water which meet the requirements of ISO 6876, where both zinc oxide-eugenol (ZOE) (0.05%) and zinc oxide eucalyptus (0.15%) satisfied these criteria.

We aimed to evaluate the microleakage of composite resin and self-cure glass ionomer (GI) restorations in primary molars when the restorations were applied at the same day of silver diamine fluoride (SDF) treatment, and after 14 days.

Class V cavities made at the buccal surface of 64 deciduous molars. For the experimental group of 32 teeth treated with SDF (eight teeth filled with composite and eight teeth filled with GI after 1 day and 14 days), the remaining 32 teeth without application of SDF served as a control group. All samples were then thermocycled and immersed in 2% methylene before being molded in epoxy resin to facilitate cutting into two sections. The dye penetration was then measured using a stereomicroscope at 20× magnification.

Overall model test showed statistical significant difference among study groups (P < 0.001). Post hoc test showed significant difference for usage of silver diamine fluoride (P < 0.001) and non-significant differences for type of restoration (P=0.21) and time (P=0.43).

There was a significant reduction in microleakage following the usage of SDF before restoration over time.

Composite have evolved significantly due to the increase in the demand for a more esthetic and conservative approach in dentistry. Modifications have been made on the filler particle size and loading, followed by alterations in the resin matrix substance. Methacrylate-based composite with the addition of nanoparticles to the filler has been introduced in the market, providing improved esthetics and lower polymerization shrinkage. The present study was done to compare the fracture resistance of teeth restored using two newer methacrylate-based composite materials, along with the flexural strength of the composites.

Sixty mandibular premolars were divided into two control groups of 10 teeth each and two experimental groups of 20 teeth. Group I − intact teeth with no preparations (n=10), Group II − prepared but unrestored teeth (n=10), Group III − teeth prepared and restored with a stackable nanohybrid methacrylate-based composite material (IPS Empress DirectTM), and Group IV − teeth prepared and restored with a packable submicron methacrylate-based composite material (Brilliant EverglowTM), respectively. The teeth were embedded in resin-filled PVC rings, and a compressive loading test was carried out for all groups at a cross-head speed of 0.5 mm/min. The flexural strengths of the two composite materials were also analyzed using three-point bending test using Universal Testing Machine. The statistical significance (P < 0.05) of the differences between the experimental groups was analyzed by ANOVA and Tukey post hoc test.

The mean fracture resistance was highest in Group IV (1877.37 ± 494.79) followed by Group III (1763.69 ± 392.51), Group I (1607.08 ± 283.48), and Group II having the least (1442.08 ± 373.66). The mean fracture resistance overall differed significantly between the four groups (P=0.048). Tukey test showed fracture resistance differed significantly between Group II and Group IV (P=0.042) and no significance among other groups.

Fracture resistance was highest in the group restored with the packable submicron hybrid composite material. The packable submicron methacrylate-based composite material also showed higher flexural strength than stackable nanohybrid composite material.

Adenoid hypertrophy (AH), an immune response of the body against infections, is common in children and has adverse effects on their physical and mental health.

The hypothesis: 

We hypothesized that mouth breathing (MB) may induce AH, and that they interact with each other.

Evaluation of The Hypothesis: 

AH may cause upper airway obstruction, which can induce the patient to switch from nasal breathing to mouth breathing (MB). However, MB does not involve the processes of warming, humidifying, and cleaning the inhaled air, which leads to changes in the oral environment and increases the risk of inflammation of the upper respiratory tract. This study discussed the relationship between MB and AH. The importance of this hypothesis is that attention should be paid to the status of MB or AH while treating them in order to block the interaction and thus improve the efficiency of treatment.

In 2019, Wuhan city of China announced the epidemic of COVID-19 as a public health disaster which has been recognized as an uncommon type of single stranded RNA virus belonging to Coronaviridae family and then quickly spread all over the world. Clinically symptomatic patients are identified as the primary source of COVID-19 transmission. Most of dental procedures require the use of high-speed handpieces which leads to aerosol generation. Implant dentistry is the field of dentistry which deals with prosthetic rehabilitation with minimal aerosol generation ensuring an aseptic surgical environment. There are several decisive recommendations regarding COVID-19 precautions that should be appreciated in implant dentistry. Sharp drills in slow speed drilling machines are preferred during surgery. Regular irrigation with high volume suction is greatly encouraged. Osteotomes are encouraged over ultrasonic devices to minimize the generation of aerosols during surgical procedures. Immediate implants placement is more preferred as the number of visits to the dentists is reduced. Impression techniques should be shifted to the digital approach instead of conventional methods. Full mouth rehabilitation cases requiring complex procedures should be accomplished restrictedly.

Limited evidence is available on adhesive dentistry in the management of amelogenesis imperfecta (AI). The presentation, the conservative management with adhesive techniques, and the outcome of hypoplastic AI are discussed.

Case Report: 

Autosomal dominant, hypoplastic AI was diagnosed, on a 36-year-old woman, presented with unesthetic teeth and a history of frequent decay with subsequent complications. Following the hygienic phase, stabilization of caries and root canal treatment (RCT) were done. Coronal restoration of endodontically treated teeth and light-cured direct composite veneering were done in the restorative phase. Surveyed crowns, mucosa-borne partial denture, and a resin-bonded bridge were prescribed in the prosthetic phase. The patient was pleased with the improved masticatory ability and esthetics.

A stepwise least invasive, yet esthetically acceptable treatment options based on adhesive techniques are successful in hypoplastic AI.