Micro-computed tomography analysis of calcium hydroxide delivery efficacy in C-shaped canal system of mandibular second molars.

BACKGROUND: Calcium hydroxide [Ca(OH)2] is widely accepted as a biocompatible interappointment intracanal medicament. This study aimed to analyze the efficacy of Ca(OH)2 placement into the C-shaped canal system of mandibular second molars using the syringe method with and without lentulo spiral utilizing micro-computed tomography (micro-CT). METHODS: Twenty-four extracted mandibular second molars were instrumented and classified into C-shaped floors (n = 12) and non-C-shaped floors (n = 12). Both groups were placed with Ca(OH)2 using the syringe system, then all teeth were scanned and cleaned, and placed with Ca(OH)2 again but with the syringe system followed by lentulo spiral and rescanned. The specimens were scanned using micro-CT to analyze the volume, volume percentage, uncontacted surface area, and uncontacted surface area percentage of Ca(OH)2 with the two delivery methods in the entire canal and at the apical 4 mm of the canal. Mann-Whitney test and Wilcoxon signed-rank test were used to determine the statistical differences among the groups. RESULTS: Syringe administration used in conjunction with lentulo spiral presented lower uncontacted surface area, a lower percentage of uncontacted surface area, larger volume, and a higher percentage of volume than syringe without lentulo spiral (P < 0.05). There was no significant difference between the C-shaped floor group and the non-C-shaped floor group (P > 0.05) in the Ca(OH)2 uncontacted surface area, volume, and percentages at different regions of canals and among different delivery techniques groups. CONCLUSIONS: The lentulo spiral and syringe technique combination can increase the volume and contacted surface area of Ca(OH)2 in the C-shaped canal system of mandibular second molars.

Microcomputed tomography analysis of the radicular residual dentin thickness in mandibular second molars after virtual fiber post placement: Identification of danger zones.

STATEMENT OF PROBLEM: Mandibular second molars have variable root, pulp chamber floor, and radicular groove morphologies, potentially affecting residual dentin thickness and post placement suitability. However, an identification of the danger zones is lacking. PURPOSE: The purpose of this in vitro study was to investigate the residual dentin thickness in the danger zone of mandibular second molars after virtual fiber post placement by using a simulation method based on microcomputed tomography (µCT). MATERIAL AND METHODS: A total of 84 extracted mandibular second molars were scanned using µCT and classified according to root morphology (separate or fused) and pulp chamber floor morphologies (C-shaped, non-C-shaped, or no pulp chamber floor). Fused-root mandibular second molars were further classified based on the radicular groove type (V-, U-, or Ω-shaped). All specimens were accessed, instrumented, and rescanned with µCT. Two types of commercial fiber posts were also scanned. Clinical fiber post placement was simulated in all prepared canals by using a multifunctional software program. The minimum residual dentin thickness of each root canal was measured and analyzed by using nonparametric tests to identify the danger zone. Perforation rates were calculated and recorded. RESULTS: Larger fiber posts decreased minimum residual dentin thickness (P<.05) and increased perforation rate. In regard to mandibular second molars with separate roots, the distal root canal exhibited a significantly higher minimum residual dentin thickness than the mesiobuccal and mesiolingual root canals (P<.05). However, no significant difference in minimum residual dentin thickness was found between the different canals in fused-root mandibular second molars with C-shaped pulp chamber floors (P<.05). Fused-root mandibular second molars with Ω-shaped radicular grooves had a lower minimum residual dentin thickness than those with V-shaped radicular grooves (P<.05) and demonstrated the highest perforation rate. CONCLUSIONS: The morphologies of the root, pulp chamber floor, and radicular groove were correlated with residual dentin thickness distribution in mandibular second molars after fiber post placement. A comprehensive understanding of mandibular second molar morphology is essential for determining the suitability of post-and-core crown restorations after endodontic treatment.

Micro-computed tomography analysis of root canal morphology and thickness of crown and root of mandibular incisors in Chinese population.

OBJECTIVES: The aim of this study was to investigate the root canal morphology and the thickness of crown and root of mandibular incisors in a Chinese subpopulation by micro-computed tomography (micro-CT). METHODS: In total, 208 mandibular incisors were scanned using micro-CT. The anatomical features of the canals (canal configuration, apical constriction, foramen-to-apex distance, accessory canal vertical distribution, and canal geometrical parameters) and the thickness of the crown and root 2/3 were evaluated. RESULTS: Three canal categories, labeled as Single (77.88%), Merged (15.87%), and Separated (6.25%), were summarized. The most frequent constriction type in main foramina was single constriction (42.53%). Wide and narrow diameters in a single main foramen were 0.37 ± 0.14 mm and 0.26 ± 0.07 mm, respectively. The distance from the anatomical foramen to the physiological foramen and the anatomical apex was 0.49 ± 0.20 mm and 0.36 ± 0.28 mm, respectively. During the virtual root-end resection, 97.12% of roots underwent successful resection at the 2-mm level, with the foramina visible on the resection surface. During 2-D cross-sectional analyses, the shape parameters of the root and canal showed significant positive correlation (P < 0.05). The thickest and thinnest walls were the incisal and proximal walls (P < 0.05) of the crown, respectively. The buccal walls were significantly thicker than the lingual walls on the crown (P < 0.05), whereas the lingual walls were thicker on the root 2/3 (P < 0.05). CONCLUSIONS: This study provides detailed information about the root canal morphology and thickness of the crown and root of mandibular incisors in a Chinese population. An understanding of morphology can benefit endodontic treatment. CLINICAL RELEVANCE: Adequate knowledge of the crown, root, and canal morphology, as well as the thickness distribution of the crown and root, is essential for successful root canal therapy and prevention of complications.

Mechano-chemical coupling of irrigation enhances endodontic biofilm debridement.

The complexity of the root canal system results in areas where mechanical instrumentation is impossible during endodontic treatment. To disinfect these areas, the effect of irrigation on biofilm debridement is of great significance but has not yet been well explored. Using an in vitro Enterococcus faecalis biofilm model and a biofilm reactor, the present study provides a better understanding of the relative contributions of mechanical and chemical effects of irrigation on biofilm removal, as well as the factors influencing their coupling efficiency. The results clearly demonstrate that, the mechanical effect of irrigation alone does not significantly influence the stability of biofilms. However, the mechanical effect promotes biofilm eradication by coupling with the chemical effect. In addition, both the irrigant concentration and the irrigant-biofilm contact time are among the key factors affecting the mechano-chemical coupling. This knowledge may serve to better direct endodontists in designing irrigation regimes during root canal therapy.

Evaluation of Secondary Alveolar Bone Grafting for Unilateral Complete Cleft Alveolus: A Retrospective Cone Beam Computed Tomography-Based Study.

Background: In patients with cleft lip and palate (CLP), secondary alveolar bone grafting (SABG) with particulate cancellous bone marrow (PCBM) is recommended. Objective: To compare bone graft outcomes in patients with unilateral CLP, when SABG is completed before or after canine tooth eruption (ACE or BCE), as measured by cone beam computed tomography (CBCT). Methods: Patients were allocated into two cohorts, ACE and BCE. The outcomes were evaluated using CBCT, followed by univariate and multifactorial analyses. Results: A total of 468 patients (age 11.61 ± 4.03 years; male/female 288/180) were analyzed, including 282 in the BCE group (9.41 ± 1.59 years, 175/107) and 186 in the ACE group (14.95 ± 4.31 years, 113/73). Although 5-level assessment revealed no significant difference in clinical success rate (>4 points) between the BCE and ACE groups (53.90% vs. 47.85%, p = 0.20), BCE group showed significantly higher rate of bone bridges formation (73.05% vs. 62.90%, p = 0.02), which can be attributed to variations in orthodontic participation and follow-up time. Independent predictors of graft failure were wide cleft, severe oronasal fistula, no palatal bone wall, and insufficient PCBM filling (p < 0.01). Conclusions: SABG should be performed before canine eruption with more aggressive PCBM filling and oral fistula management.

Internal and external morphological analysis of fused-rooted mandibular second molars in the Chinese population: A micro-computed tomographic study.

This study investigated the root canal morphology of fused-rooted mandibular second molars based on the pulp chamber floor (PCF) and analysed the correlation between the external morphology of the radicular groove, and the internal morphology of the PCF and root canal configuration. A total of 291 fused-rooted teeth collected from the Chinese population were scanned using micro-computed tomography and a dental operating microscope was used for observing the PCFs. The classification of the PCF and root canal configuration were identified according to modified Min et al.'s and Gao et al.'s classifications, respectively. Additionally, a new radicular groove classification was proposed. The correlation among these morphological characteristics was investigated using the chi-square test and Fisher's exact test (p < 0.05). The results showed that 74.2% of teeth had C-shaped PCFs, while 21.0% had non-C-shaped PCFs. As for the root canal configurations, 37.5% of teeth were merging type, 40.9% were symmetrical type, and 14.8% were asymmetrical type. Statistical analysis revealed a significant correlation between the PCF types and the root canal configurations (p < 0.001). The dominant root canal types for teeth with C-shaped PCFs were merging and symmetrical types, while the asymmetrical type was not identified in non-C-shaped PCFs. In addition, significant morphological association between the root canals and radicular grooves was also revealed (p < 0.001). Teeth with different PCF morphologies exhibit specific patterns of root canal category distribution. Understanding the morphological nuances of the root canal based on the PCF can assist clinicians in predicting and identifying the canal configuration beneath the visible orifice.

Intraoral Scanning Evaluation Of Maxillary Arch Changes Post Modified Sommerlad Palatoplasty For Around Three Years.

BACKGROUND: To investigate the postoperative effect of dental arch changes in cleft palate patients with modified Sommerlad palatoplasty by intraoral scanning technique in early deciduous dentition children. METHODS: Patients (n=60) with non-syndromic unilateral complete cleft lip with palate (UCLP) or cleft palate only (CPO) treated by modified Sommerlad palatoplasty without relaxed excision before 18 months old and 95 healthy controls without cleft were included. Three-dimension images of the maxillary dental arches of all subjects aged 3 to 4 years were obtained by intraoral scanning (IOS) technique. Seven parameters including anterior dental arch width (Ar-Al), middle dental arch width (Fr-Fl), posterior dental arch width (Sr-Sl), anterior palatal arch width (Cr-Cl), posterior palatal arch width (Mr-Ml), anterior dental arch length (IP-D) and entire dental arch length (IP-O) were measured. RESULTS: Compared with male group, the Mr-Ml distance of controls in female group statistically decreased (p=0.039) and the Fr-Fl, Sr-Sl, Mr-Ml distance of female patients decreased (p=0.013, p=0.002, p=0.005). The IP-D, IP-O distance of children in UCLP group was shorter than those of CPO children (p＜0.0001, p＜0.0001). Patient group showed decreased distance of Ar-Al, Cr-Cl, IP-D and IP-O and increased distance of Sr-Sl and Mr-Ml compared with control group (p=0.0002, p=0.002, p<0.0001, p<0.0001, p=0.007, p=0.027). CONCLUSION: The results indicated that the modified palatoplasty showed no growth inhibition in the middle, posterior dental arch width, and palatal arch width, though slightly but significantly inhibition in the length of anterior and entire dental arch. CLINICAL QUESTION/ LEVEL OF EVIDNCE: Risk, III.

Assessment of the Effectiveness of Supplementary Methods for Residual Filling Material Removal Using Micro-computed Tomography: A Systematic Review and Meta-analysis of In Vitro Studies.

A systematic review and meta-analysis were conducted to evaluate the effectiveness of auxiliary methods in removing residual filling material (RFM). This systematic review has been registered with the International Prospective Register of Systematic Reviews (registration number CRD42020197482). A comprehensive literature search was conducted to identify relevant articles in electronic databases (PubMed, Embase, Cochrane) from January 2005 to March 2021. In vitro studies investigating or comparing at least one type of supplementary method or technique were included. A total of 26 studies were selected from the 239 records obtained after screening the databases. Ten of the included studies were suitable for meta-analysis. Strong evidence showed that ultrasonically activated irrigation (UAI) [SMD (95% CI): -0.52 (-0.88 to -0.16, P=0.266)] and XP-Endo Finisher R (XPR) [SMD (95% CI): -0.55 (-0.89 to -0.20, P=0.136)) contributed significantly to increase the removal procedure, and XPR has no significant superiority over UAI [SMD (95% CI): 0.36 (-0.12 to 0.84, P=0.994)]. Strong evidence was found to support the increased cleaning efficiency of the supplementary use of the Gentle Wave system, laser irradiation, XP Endo Finisher, and self-adjusting file. In contrast, conflicting evidence was found to support the use of sonic to improve the removal of RFM, and limited evidence was found to support the efficiency of Tornado Brush. Under in vitro conditions, UAI and XPR increase the removal of RFM from the root canal system during retreatment procedures.

A new congenital cleft palate New Zealand rabbit model for surgical research.

Cleft palate repair is a challenging procedure for cleft surgeons to teach, and in research, it can be difficult to evaluate different techniques and develop new treatments. In this study, a congenital cleft palate New Zealand rabbit model has been described and could be beneficial in future studies concerning cleft palate repair. Pregnant New Zealand rabbits received 1.0 mg dexamethasone injection intramuscularly once a day from the 13th gestation day (GD13) to GD16. On GD31. Newborn rabbits were delivered by cesarean sections, fed with a standardized gastric tube feeding method, and divided into two groups. The rate of survival and the incidence of cleft palate was calculated. Weight, appearance, behavior, maxillary occlusal view, and regional anatomic and histological comparisons were recorded within 1 month after birth. Infants from the two groups with similar physiological conditions were selected for continuous maxillofacial and mandibular Micro-CT scan and three-dimensional reconstruction analysis. Ten pregnant rabbits gave birth to 48 live infants. The survival and cleft palate rates were 65.6% and 60.4% respectively. Both groups survived over 1 month with no difference in weight, appearance, and behavior. The cleft type was stable, and anatomical defects, histological characteristics, and nasal-maxillary abnormalities of the cleft were similar to those of humans. There was no statistically significant difference in maxillary and mandible development between the two groups within one month after birth. This congenital cleft palate model is considered to have more research possibilities with efficient cleft induction, reliable feeding methods, stable anatomical defects, and maxillofacial development similar to those seen in humans.

Casein phosphopeptide-amorphous calcium phosphate modified glass ionomer cement attenuates demineralization and modulates biofilm composition in dental caries.

The study investigated the effects of the modified conventional glass ionomer cement (GIC) incorporated with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on biofilm composition of dental caries. Shear bond strength, durability tests, adhesive remnant index (ARI) and scanning electron microscope were used to measure the physical properties. Microhardness and ions release were determined to evaluate anti-demineralization effects; growth of the biofilm and its composition were assessed using MTT assay and Q-PCR assay. All experimental groups exhibited a significant stimulation of ions release, and reduced attenuation of microhardness. Nearly 39% reduction in the bacterial biofilm was observed with 5% CPP-ACP group. The regulation ability is mainly manifested in the inhibition of S. mutans and promotion of S. gordonii. The modified GICs by exhibiting anti-demineralization effects potentially lead to a reduction in the cariogenicity of plaque and can serve as a putative promising remineralization system with both enhanced antimicrobial and remineralization properties.

Rotating a Segmental Maxilla to Close a Serious Vertically Displaced Alveolar Cleft.

In recent years, alveolar bone grafting has emerged as the first treatment choice for space closure in the secondary dentition. Despite this, a high possibility of failure still exists for patients with a vertical discrepancy of cleft segments. This is attributed to the absence of valid contact between the grafted bone and the surfaces of bone segments in the cleft region. In cases of minor discrepancies, the vertical distance can be reduced orthodontically, allowing for subsequent alveolar bone grafting.1 However, in severe cases, isolated orthodontic treatment is not viable due to a high risk of periodontal problems and increased tooth mobility. Under the circumstances, surgical intervention is essential. Herein, we report a case in which the alveolar segment is aligned using a novel application of segmental maxillary osteotomy to rotate the segment with a subperiosteal tunnel. Rigid fixation of the segment in the desired position is then performed with concurrent bone grafting. Therefore, performing segmental maxillary osteotomy before bone grafting could be an alternative to correcting the vertical discrepancy encountered in cleft patients.