The effect of ultrasonic access cavity preparation on dentinal inner walls: a micro-CT study on cadaveric samples.

OBJECTIVE: The objective of this study is to evaluate the occurrence of coronal dentinal micro-cracks after access cavity refinement using high-speed burs and ultrasonic tips by means of micro-computed tomography (micro-CT) analysis. METHODS: In this study, 18 mandibular cadaveric incisors were divided into two groups according to the protocol of the preparation of the conventional access cavity. The diamond bur 802 # 12 was used until the perforation of the pulp roof. Then, the Endo-Z bur was used for the group #1 and the ultrasonic tip Start-X # 1 for the group #2 to finish and refine the access cavity. The preparation time of each access cavity has been recorded. The teeth underwent a micro-CT scan before and after the preparation of the access cavity. Fisher's exact test, the Chi-square test, the Kolmogorov-Smirnov test, the Mann-Whitney test, and the Student's test were used for statistical evaluation. RESULTS: The percentage of teeth with new micro-cracks is not significantly different between the two groups (-p-value < 0.5). The number of newly formed micro-cracks and extension size were not significantly different between the two groups. The direction of extension of the micro- cracks was occluso-apical. The average duration of the access cavity is significantly smaller with the Endo-Z system (-p- value < 0.001). The roughness of walls surfaces has no statistically difference between the two groups. CONCLUSION: The use of ultrasound, although slower, is considered safe in the creation of dentinal micro-cracks, in the preparation of the access cavity.

5-year retrospective evaluation of direct composite restorations in orthodontically treated patients.

OBJECTIVES: In patients affected by dimensional discrepancy between size of anterior maxillary and mandibular teeth, orthodontic therapy could be necessary to solve occlusal problems. However, anterior restorations are indicated to finalize the aesthetic aspect of the therapy. The aim of the present retrospective clinical study was to evaluate the long-term outcomes of direct additive composite restorations performed to correct anterior teeth discrepancies persisting after orthodontic treatment. METHODS: Patients with dimensional teeth discrepancy, subjected to a combined orthodontic-restorative treatment, between January 2009 and January 2019, were recalled for the present retrospective evaluation and divided in two groups according to the restoration performed: G1) diastema closure; G2) tooth shape modification. All patients, after ortho therapy, were subjected to a standardized restorative rehabilitation of the anterior area. All restorations were performed by a single experienced operator employing the same materials. During recall visits, two calibrated examiners evaluated the restorations and recorded USPHS data. Kaplan-Meier estimator and Cox-regression analysis were performed. Statistical significance was set for p < 0.05. RESULTS: 53 patient were included, with a total of 169 restoration (G1:110;G2:59). The mean study time period was 5 year (ranging from 6 month to 10 years). The overall survival rate of additive restoration was 2,59% (G1:2,07%; G2:0,47 p < 0.05). Chipping of the material was the most frequent adverse event (G1:13,64%; G2:1,69), followed by composite wear (G1:9,09%; G2:5,17). CONCLUSIONS: Based on the obtained results, good clinical performances were shown at a 5-year interval. A low number of failures were collected and most of them were classified as reparable. Only few cases needed complete reintervention. CLINICAL SIGNIFICANCE: Showing that a direct approach in restoring anterior teeth for diastema closure or shape modification is a valid alternative in terms of durability and aesthetics to more invasive procedure such as indirect restorations.

Tridimensional Evaluation of the Interfacial Gap in Deep Cervical Margin Restorations: A Micro-CT Study.

CLINICAL RELEVANCE: Using a material that optimizes marginal seal when using a margin elevation technique to manage deep class II cavities should enhance clinical outcomes. SUMMARY: Objectives: The purpose of this laboratory study was to perform a tridimensional interfacial gap evaluation of class II cavities with enamel and dentin cervical margins, before and after cyclic fatigue, restored with different nanohybrid resin composites.Methods and Materials: Standardized class II cavities were performed on 48 intact maxillary premolars, placing the mesial cervical margin 1 mm above the cement-enamel junction (CEJ) and the distal cervical margin 1 mm below the CEJ. Specimens were treated with two-step self-etch adhesive (Clearfil SE Bond2) and divided into six groups according to the restoration technique. Microcomputed Tomography imaging was executed before and after 1,000,000 cycles of chewing simulation at 50 N. Tridimensional interfacial gaps, expressed as cubic millimeters, were analyzed through a standardized software flowchart (Mimics). Data were analyzed with a two-way analysis of variance and Tukey post hoc tests (α=0.05).Results: Restoration technique (p=0.001) and chewing simulation (p=0.00001) significantly influenced interfacial gap on dentin but not on enamel. The post hoc test showed that, on dentin margins, flowable resins had a lower gap at baseline but a higher gap after chewing simulation, especially when a 2-mm-thick layer was applied, compared with nanohybrid and bulk-fill composites.Conclusions: Based on the obtained results, no differences in interfacial gap volume were found on enamel margins. On dentin margins, flowable resins showed better marginal seal at baseline, but they seem to be more prone to interfacial degradation during chewing simulation than traditional composites.

Micro-CT evaluation of several glide path techniques and ProTaper Next shaping outcomes in maxillary first molar curved canals.

AIM: To evaluate the ability of ProGlider instruments, PathFiles and K-files to maintain canal anatomy during glide path preparation using X-ray computed micro-tomography (micro-CT). METHODOLOGY: Forty-five extracted maxillary first permanent molars were selected. Mesio-buccal canals were randomly assigned (n = 15) to manual K-file, PathFile or ProGlider groups for glide path preparation. Irrigation was achieved with 5% NaOCl and 10% EDTA. After glide path preparation, each canal was shaped with ProTaper Next X1 and X2 to working length. Specimens were scanned (isotropic voxel size 9.1 µm) for matching volumes and surface areas and post-treatment analyses. Canal volume, surface area, centroid shift, canal geometry variation through ratio of diameter ratios and ratio of cross-sectional areas were assessed in the apical and coronal levels and at the point of maximum canal curvature. One-way factorial anovas were used to evaluate the significance of instrument in the various canal regions. RESULTS: Post-glide path analysis revealed that instrument factor was significant at the apical level for both the ratio of diameter ratios and the ratio of cross-sectional areas (P < 0.001), with an improved maintenance of root canal geometry by ProGlider and PathFile. At the coronal level and point of maximum canal curvature, ProGlider demonstrated a tendency to pre-flare the root canal compared with K-file and PathFile. PathFile and ProGlider demonstrated a significantly lower centroid shift compared with K-file at the apical level (P = 0.023). Post-shaping analysis demonstrated a more centred preparation of ProGlider, compared with PathFile and K-files, with no significant differences for other parameters. CONCLUSIONS: Use of ProGlider instruments led to less canal transportation than PathFiles and K-files.

Postoperative quality of life following single-visit root canal treatment performed by rotary or reciprocating instrumentation: a randomized clinical trial.

AIM: To compare the impact of rotary and reciprocating instrumentation on postoperative quality of life (POQoL) after single-visit primary root canal treatment. METHODOLOGY: A randomized controlled clinical trial was designed and carried out in a University endodontic practice in northern Italy. Healthy subjects with asymptomatic irreversible pulpitis, symptomatic irreversible pulpitis or pulp necrosis with or without apical periodontitis (symptomatic or asymptomatic) scheduled for primary root canal treatment were enrolled. Single-visit root canal treatment was performed with ProTaper™ S1-S2-F1-F2 (rotary group, n = 23) and WaveOne™ Primary (reciprocating group, n = 24). Irrigation was performed with 5% NaOCl and 10% EDTA. Root canal filling was performed with the continuous-wave technique and ZOE sealer. POQoL indicators were evaluated for 7 days post-treatment. The variation of each indicator over time was compared using anova for repeated measures (P < 0.05). The impact of each variable on POQoL was analysed with a multivariate logistic regression model (P < 0.05). RESULTS: Pain curves demonstrated a more favourable time-trend in the rotary group (mean, P = 0.077; maximum, P = 0.015). Difficulty in eating (P = 0.017), in performing daily activities (P = 0.023), in sleeping (P = 0.021) and in social relations (P = 0.077), was more evident in the reciprocating group. Patients' perception of the impact of treatment on POQoL was more favourable in the rotary group (P = 0.006). Multirooted tooth type and pre-existing periradicular inflammation were associated with a decrease in POQoL. CONCLUSION: Reciprocating instrumentation affected POQoL to a greater extent than rotary instrumentation.

Longevity of class 2 direct restorations in root-filled teeth: A retrospective clinical study.

OBJECTIVES: To evaluate retrospectively the longevity of endodontically treated teeth restored with direct resin composite without cusp coverage, with or without the insertion of fibre posts. The null hypothesis was that direct restorations with fibre posts perform better than those without fibre posts. METHODS: Patients recruited for this study were treated in the Department of Cariology and Operative Dentistry, University of Turin, between 2008 and 2011. In total, 247 patients with 376 root treated posterior teeth, restored with direct resin composite, were recalled for a control visit. Only second-class cavities were considered. Two groups were defined based on the absence (Group A) or presence (Group B) of fibre post. Failures and complications, such as periodontal failure, endodontic failure, tooth extraction, root fracture, post fracture, post debonding, replacement of restoration, crown displacement, and coronal-tooth fracture, were noted. Functional restoration quality was evaluated following the modified USPHS criteria. Data were evaluated statistically with ANOVA. RESULTS: Group A consisted of 128 patients with 178 restorations (88 premolars, 90 molars) with a median follow-up of 34.44 months. Group B consisted of 119 patients with 198 teeth (92 premolars, 106 molars) with a median follow-up of 35.37 months. Direct restorations with fibre posts were statistically significantly more functional (95.12% success) than those without fibre posts (80% success) because of less marginal discolouration, better marginal integrity, and higher restoration integrity. CONCLUSIONS: The null hypothesis was accepted because direct post-endodontic restorations with fibre posts performed better than restorations without posts after 3 years of masticatory function. CLINICAL SIGNIFICANCE: An evaluation of the longevity of post endodontic direct restoration would seem to enhance the fiber post insertion within a composite restoration to reduce clinical failures.

Fibre post adaptation and bond strength in oval canals.

AIM: To evaluate ex vivo the bond strength and adaptation of fibre posts with oval and circular cross sections luted in oval canals with post spaces prepared using dedicated drills or ultrasonic tips. METHODOLOGY: Forty extracted premolars with oval canals were root filled, then randomly divided into four groups according to the post space preparation device and the shape of the luted fibre post: dedicated drill + round post, dedicated drill + oval post, ultrasonic tip + round post and ultrasonic tip + oval post. Posts were cemented with a self-adhesive cement (RelyX Unicem 2; 3M ESPE). Samples were sectioned in 1-mm-thick slices and observed under a microscope, and the area occupied by the post within the post space area was calculated. Bond strength was then measured using a push-out test, and the failure modes were evaluated with a stereomicroscope at 40× magnification. Fibre post adaptation and push-out test results were evaluated by analysis of variance (P < 0.05). RESULTS: Fibre posts, both round and oval, were better adapted to the apical region of the post space (P = 0.001). In oval canals, the bond strength was significantly higher in coronal regions, when the post space was prepared with a dedicated drill and an oval post was luted (P < 0.0001). Adhesive failures between cement and post were the most frequent type of failure in all groups. CONCLUSIONS: Circular and oval posts achieved similar adaptation to oval canals, but the use of ultrasonic tips and round posts resulted in reduced bond strength values.

Antibacterial efficacy and drug-induced tooth discolouration of antibiotic combinations for endodontic regenerative procedures.

Elimination of microbial contamination from the root canal system is a precondition for successful root canal treatment. Teeth with immature root development, necrotic pulps and apical periodontitis present multiple challenges for successful treatment. Disinfection is achieved by irrigation followed by the placement of an intracanal medicament. A mixture of ciprofloxacin, metronidazole and minocycline (3-MIX S) has been shown to be very effective in eliminating endodontic pathogens in vitro and in vivo. Among the components of the mixture, minocycline can induce tooth discolouration after long-term oral use. Therefore, the elimination of minocycline from the above-mentioned combination has been suggested to prevent the occasion of this undesirable effect. The aim of this study was to investigate the potential antimicrobial efficacy of alternative antibiotic combinations [3-MIX C (clarithromycin); 3-MIX F (fosfomycin)] against bacteria from infected root canals. An additional objective was to evaluate their discolouration potential as possible alternatives to minocycline-based intracanal medicaments. Our in vitro results clearly demonstrated that 3-MIX C and 3-MIX F had a greater antimicrobial activity than 3-MIX S, underlying that clarithromycin still had a higher capacity to kill endodontic pathogens in vitro compared to fosfomycin. Both 3-MIX C and 3-MIX F were able to avoid the permanent staining effect of the crown.

Active application of liquid etching agent improves adhesion of fibre posts to intraradicular dentine.

AIM: To assess the effectiveness of an active application of liquid etching, compared with the standard gel formulation on smear layer removal from post space walls and push-out bond strength of luted fibre posts. METHODOLOGY: Human extracted teeth were collected and root filled. After post space preparation and cleaning with 10% ethylenediaminetetraacetic acid for 30 s, teeth were assigned to four groups (n = 11) according to etching procedure: (i) 37% phosphoric acid (H3 PO4 ) gel; (ii) 37% H3 PO4 liquid applied with an endodontic needle; (iii) 37% H3 PO4 liquid applied with an Endovac; (iv) no etching procedure (control group). Three teeth per group were sectioned longitudinally and prepared for SEM examination to evaluate the presence of smear layer, debris, sealer/gutta-percha remnants, and the number of open tubules. Eight teeth per group were bonded with an etch-and-rinse adhesive, and fibre posts were luted with a resin-based cement. After cutting, specimens were prepared for a push-out test. Data were analysed by anova and post hoc tests (P < 0.05). RESULTS: Improved smear layer removal was obtained in Group 2, followed by Group 1, Group 3, and the control group (P < 0.05). The mean values for the bond strength of the push-out test were: Group 1, 8.3 ± 2.9 MPa (coronal); 7.7 ± 3.0 (middle); 3.3 ±1.9 MPa (apical); Group 2, 7.8 ± 2.1 MPa (coronal); 6.9 ± 3.9 MPa (middle); 3.7 ± 1.3 MPa (apical); Group 3, 9.7 ± 2.8 MPa (coronal); 8.6 ± 2.1 MPa (middle); 6.9 ± 2.3 MPa (apical); and Group 4, 2.9 ± 3.0 MPa (coronal); 2.6 ± 2.0 MPa (middle); 1.1 ± 2.0 MPa (apical). CONCLUSIONS: Liquid phosphoric acid applied with an endodontic needle yielded better canal wall smear layer removal and higher bond strength values when an etch-and-rinse system was used.

Atypical facial pain related to apical fenestration and overfilling.

AIM: To report a case of apical fenestration and overfilling in which unusual pain characteristics made differential diagnosis challenging. SUMMARY: A 32-year-old woman with diffuse, spontaneous, moderate pain in the maxillary left posterior sector, exacerbated by masticatory and facial muscle movement, with intense sporadic electric-shooting pain, underwent clinical examination and 3D cone beam computed tomography (CBCT). Apical fenestration with protrusion of the mesial root of tooth 26 beyond the buccal cortical plate, extrusion of canal filling material into the soft tissues and a periosteal reaction were detected. Surgery was performed under the operating microscope. The filling material and surrounding fibrous tissue were located, dissected from healthy soft tissues and removed. The mesiobuccal root apex was resected with a bur to within the bony crypt. A root end was prepared and filled with Tech Biosealer RootEnd™ (Isasan, Como, Italy). At the 2-week recall, the patient had complete resolution of the symptoms and good soft-tissue healing. The 1-year recall examination and intra-oral radiography confirmed complete resolution of the symptoms and health of periradicular tissues. KEY LEARNING POINTS: Apical fenestration may occur in 9% of cases and may be considered an anatomic predisposing factor for persistent pain after root canal treatment. This complication provides a considerable differential diagnostic challenge and is often misdiagnosed and mistreated. When correctly diagnosed through an accurate, multidisciplinary approach, it may be managed with a simple surgical procedure in which the endodontist should play a key role. Misdiagnosis and over treatment of apical fenestration, through the surgical management of chronic facial pain conditions, could lead to severe exacerbation of chronic pain, which may potentially become persistent or, indeed, intractable.

Comparative evaluation of the enamel margins roughness obtained with different finishing devices.

AIM: The aim of this in vitro study was to compare the surface roughness of enamel margins resulting by the use of rotating, sonic and ultrasonic devices for cavity margins finishing. METHODS: Forty-eight anterior intact teeth were selected for this study. Each item was sectioned 1 mm below the CEJ, perpendicular to the long axis of the tooth, with the carborundum separating disk mounted on the high-speed handpiece. With the same bur the crown was separated into two parts along the midline vertically. At the end 96 "half-crowns" were obtained. The samples were divided into 6 groups of 8 samples each, according to enamel margin's finishing technique (A and B: diamond ultrasonic tip; C: multisteel ultrasonic tip; D: fine diamond rotating bur; E: ultra-fine diamond rotating bur; F: sonicflex prep). The surface roughness evaluation of the enamel of each sample has been carried out by using a profilometer. The statistical analysis was performed with a balanced hierarchical ANOVA. RESULTS AND CONCLUSION: The results of this in vitro study showed that the enamel roughness obtained with sonic and ultrasonic devices was significantly higher than roughness obtained with rotating burs. Within the sonic and ultrasonic tips, the multisteel ones gave better results, that were comparable to diamond sonic device.

Influence of sodium hypochlorite on fracture properties and corrosion of ProTaper Rotary instruments.

AIM: To evaluate the influence of immersion in NaOCl on resistance to cyclic fatigue fracture and corrosion of ProTaper NiTi Rotary instruments. METHODOLOGY: A total of 120 new ProTaper NiTi Rotary files (F2) were randomized and assigned to three different groups of 40 each. Group 1 was the control group; 20 mm (excluding the shaft) of group 2 instruments were immersed in 5% NaOCl at 50 degrees C for 5 min; instruments in group 3 were completely immersed in 5% NaOCl at 50 degrees C for 5 min. All instruments were then tested for cyclic fatigue, recording the time in seconds to fracture. Data were analysed by the Kruskall-Wallis test and post-hoc multiple comparisons (P < 0.05). Micromorphological and microchemical analyses were also completed by means of a field emission scanning electron microscopy (SEM) on those instruments in group 3 that had undergone early fracture. RESULTS: Instruments in group 3 had a significantly lower resistance to fracture because of cyclic fatigue than those in groups 1 and 2 (P < 0.001). In some instruments in group 3, early fracture occurred after only a few seconds of fatigue testing. SEM observations revealed evident signs of corrosion of the fractured instruments. CONCLUSION: Group 3 had significantly reduced resistance to cyclic fatigue compared with instruments in groups 1 and 2. The phenomenon of early fracture may be attributed to galvanic corrosion induced by the presence of dissimilar metals, where one acts as the cathode of a galvanic couple, established when the instrument is immersed in NaOCl solution. The NiTi alloy may acts as the anode and thus undergoes corrosion.

Primary and secondary closure of the surgical wound after removal of impacted mandibular third molars: a comparative study.

Primary and secondary closure techniques after removal of impacted third molars were compared in terms of post-operative pain and swelling. Two hundred patients with impacted third molars were randomly divided into two groups of 100. Panoramic radiographs were taken to assess degree of eruption and angulation of third molars. Teeth were extracted, and in Group 1 the socket was closed by hermetically suturing the flap. In Group 2 a 5-6 mm wedge of mucosa adjacent to the second molar was removed to obtain secondary healing. Swelling and pain were evaluated for 7 days after surgery with the VAS scale. The statistical analysis (*analysis of variance for repeated measures, P < 0.05) showed that pain was greater in Group 1, although it decreased over time similarly in the two groups (P = 0.081, F(6,198) = 3.073*). Swelling was significantly worse in Group 1 (P < 0.001, F(6,198) = 44.30*). In Group 1, dehiscence of the mucosa was present in 33% of patients at day 7, and 2% showed signs of re-infection with suppurative alveolitis at 30 days. Pain and swelling were less severe with secondary healing than with primary healing.

Third molar extraction. Current trends.

Extraction of third molars is the operation most frequently performed by oral and maxillofacial surgeons. The American National Institute of Health (1979) and the American Association of Oral and Maxillofacial Surgeons (1993) have organised consensus conferences to systematically analyse the scientific evidence and provide official guidelines for the management of third molars. However, some clinical aspects are still controversial: indications for preventive extraction, early extraction, prognosis of impacted teeth, continuous follow-up, relationship with anterior crowding and temporo-mandibular disorders. This article reviews the conclusions from the consensus conferences and integrates them with more recent data. The actual trend seems to justify a more conservative clinical approach rather than an aggressive extraction policy.