Cervical Margin Research Articles

Effect of Silver Diamine Fluoride and Potassium Iodide on Microleakage of Composite Resin in Anterior Primary Teeth.

One of the preventive interventions for early childhood caries is the use of silver diamine fluoride (SDF), which works uniquely in the prevention of caries. The suggested method to minimize the discoloration of SDF is the use of potassium iodide (KI). However, there are concerns about the bonding properties of dentin after the application of SDF-KI. Therefore, this study aimed to investigate how SDF-KI affects composite resin microleakage in primary teeth. In this in vitro study, class V cavities were created on the buccal surfaces of 60 extracted primary canines. The samples were divided into three groups: Group I: 38% SDF solution was applied to the cavity; Group II: SDF-KI solution was applied to the cavity; and group III: the cavities were irrigated with distilled water. All cavities were filled with composite resin and subjected to a thermocycling regime (500 cycles). The dye penetration of samples was evaluated following a 24-h immersion in 1% methylene blue. Microleakage at the occlusal and gingival margins was evaluated using a stereomicroscope at 40× magnification. Data were analyzed using the Chi-squared test (p < 0.05). There was no statistically significant difference between microleakage scores at the occlusal margin (p = 0.128). At the cervical margin, the SDF-KI group had significantly more microleakage than the SDF and control groups (p = 0.001). Applying the SDF-KI significantly increased microleakage in the cervical margin but had no significant effect on the occlusal margin. Regarding the beneficial effects of SDF in preventing and arresting dental caries, application of it before composite resin is suggested in controlling caries without the negative effects on microleakage. How to cite this article: Meraji A, Asadian F, Hekmatfar S. Effect of Silver Diamine Fluoride and Potassium Iodide on Microleakage of Composite Resin in Anterior Primary Teeth. J Contemp Dent Pract 2024;25(7):691-695.

Management of subgingival proximal defects

Deep proximal cavities can be progressively elevated by a restorative procedure known as deep margin elevation (DME), which improves margins for either direct or indirect restorations. Dietschi and Spreafico (1998) introduced the non-surgical alternative procedure of DME for crown lengthening. Other names for the DME concept include “coronal margin relocation,” “proximal box elevation,” and “cervical margin relocation.” A DME treatment’s therapeutic effectiveness depends on a proper indication, and its clinical efficacy is largely dependent on how well the DME is adjusted. In addition to maintaining periodontal health, a suitable DME adaption may be able to lessen bacterial buildup and the occurrence of secondary caries. Here, we report on three cases of DME that were performed when adequate isolation was possible, and caries was progressing subgingivally.

Three-Dimensional Internal Voids and Marginal Adaptation in Deep Margin Elevation Technique: Efficiency of Highly Filled Flowable Composites.

To evaluate interfacial three-dimensional adaptation and internal voids of different flowable materials before and after cyclic fatigue in a simulated deep-margin elevation scenario. Eighty (n &#61; 80) extracted premolars were selected and two Class II cavities were prepared. The mesial one with cervical margin 1 mm above the cementum-enamel junction (CEJ) and the distal one with cervical margin 1 mm below the CEJ. After performing adhesive procedures, specimens were divided into four groups according to the employed materials for 2 mm horizontal deep-margin relocation: nanohybrid composite (Clearfil ES2, Kuraray); conventional viscosity flowable composite (Tetric Flow, Ivoclar); medium viscosity flowable composite (Majesty ES2 Low Flow, Kuraray); high viscosity flowable composite (Majesty ES2 Super Low Flow, Kuraray). All restorations were finalized by oblique layering with nanohybrid composite (Clearfil ES2, Kuraray). To reveal interfacial and internal gap progression, specimens were scanned with a micro-CT (SkyScan 1172), before and after 500,000 cycles of mechanical chewing simulation (50 N, 1 Hz). Data were imported into Mimics software after smoothing and region growing. Only the 2 mm margin relocation volumes were considered. Obtained masks were analyzed for noise removal and volume calculation. At baseline, interfacial gap progression and internal voids, expressed in mm3, were collected and statistically analyzed with two-way ANOVA (α 0.05) for the variables substrate and restorative materials followed by Tukey post-hoc test. An additional two-way ANOVA test, followed by Tukey post-hoc test, was performed to evaluate variation in interfacial gap progression after mechanical aging. At baseline, the ANOVA test showed a significant difference for the variable restorative materials (p &#61; 0.01). More specifically, the Tukey post-hoc test revealed that the highly filled medium viscosity composite performed better than the conventional viscosity composite at baseline for the interfacial gap. The internal voids ANOVA test at baseline reported no significant differences for the variable tested. Analysis of variance for internal gap progression after thermocycling showed no differences for both substrate and restorative material employed. Highly filled medium viscosity composite performed significantly better than the conventional viscosity flowable composite for what concern baseline interfacial gaps. Artificial aging with a chewing simulator and thermocycling did not affect interfacial gap progression on enamel and dentin. The tested restorative materials performed equally after aging.

The Effect of Different Separated File Retrieval Strategies on the Biomechanical Behavior of a Mandibular Molar: A Finite Element Analysis Study

IntroductionThis study evaluated the effects of retrieval strategies of separated nickel-titanium files on the biomechanical behavior of endodontically treated teeth by finite element analysis. MethodsSix FE models were created: intact tooth; simulated a scenario where the apical 3 mm of a nickel-titanium file is separated and retained; TD, simulated application of a trephine drill to expose 1 mm of the separated file; simulated troughing of 180° at the inner wall of root canal for an extra 1 mm of the separated file beyond the staging platform; simulated circumferential ultrasonic troughing done for an extra 1 mm after the TD; and PM, simulated iatrogenic perforation sealed using MTA. Occlusal loading followed the occlusal fingerprint of the tooth before maximum von Mises stresses, maximum principal stresses, safety factor, and number of cycles till failure were determined. The cervical region of the teeth and mid-root sections including the separated file was chosen as the areas of interest for further analysis. ResultsIntact tooth recorded the highest number of cycles till failure and safety factor. Other models showed a narrow range of variation in all aspects with the PM recording the lowest number of cycles till failure. The highest von Mises stress was recorded at the mesiobuccal line angle of the PM near its cervical margin, while the lowest was found at the intact tooth. ConclusionUnder the limitation of this study, various file retrieval strategies removing the surrounding root dentin within the amounts of general guidelines do not affect the biomechanical behavior of the tooth.

Influence of cervical margin relocation on marginal integrity of resin composite restoration after thermo mechanical loading.

Influence of cervical margin relocation on marginal integrity of resin composite restoration after thermo mechanical loading.

Orthodontic Extrusion of Fractured Tooth with Clear Retainer

Tooth fracture at the cervical margin is frequently seen, and orthodontic extrusion of the same can be carried out to achieve a “ferrule effect” for successful restoration. Various techniques incorporating conventional removable and fixed orthodontics have been employed to facilitate orthodontic extrusion of the fractured tooth. The clear aligner can be used to facilitate the extrusion of a fractured tooth using the “bootstrap” arrangement. Bootstrap mechanics involve placing bonded buttons at the gingival margins on the facial, lingual, or both surfaces of a tooth that is lagging. In this pearl, an innovative and economical prerestorative orthodontic method, based on the biomechanical principles of the “bootstrap” arrangement used in aligners, is developed for the successful extrusion of a fractured tooth using a clear retainer and orthodontic elastics. The amount of extrusion of the fractured tooth was 2.5 mm and was achieved in a time frame of 3 weeks. The appliance is patient-friendly and cost-effective. Moreover, the appliance omitted the use of fixed orthodontic treatment mechanics.

Comparative evaluation of marginal integrity of three esthetic restorative materials in class V cavities under stereomicroscope: an in-vitro study

Aims: The aim of this invitro study was to compare the marginal integrity among three esthetic restorative materials. Methods and Material: This study was conducted on 60 freshly extracted human premolars in which Standardized Class V cavities were prepared. Teeth were equally assigned to three groups : GC- Aenial Anterior Composite(Group A), Tetric N- Ceram(Group B), Palfique LX5(Group C). Each group containing 20 teeth were restored and then stored in distilled water for 1 week at 37°C. The specimens were dried and painted with two coats of nail varnish on the teeth except 2mm around the cervical margins of the restoration and air dried. After that the teeth were kept in 2 % methylene blue solution for 24 hours. After sectioning the teeth, the sectioned halves were then evaluated for dye penetration under stereomicroscope. Statistical analysis used: The statistical analysis was performed using the Kruskal-Wallis test along with post hoc pairwise comparison by Mann Whitney U test. Results: The findings suggested that Tetric N-Ceram was superior to the other two composite materials Conclusions: Marginal leakage scores of novel restorative material, Tetric N- Ceram was minimal and within acceptable limits compared to other tested material.

Materials used for deep margin elevation (Review article)

Abstract: Deep margin elevation (DME) is considered a conservative approach for restoring the deep proximal margin by applying resin composite increments over the preexisting cervical margin to relocate it coronally and facilitate the insertion of indirect restoration. Different materials have been applied in DME. Materials and methods: An analysis of the research publications in the literature dealing with the different restorative materials used for DME regarding their fracture resistance, microleakage, marginal quality, and marginal adaptation that have been published from 2000 until 2023 using MEDLINE (PubMed) and Google Scholar databases. Results. The studies showed that enamel margin had the best gap-free margins, followed by direct bonding to dentine, DME required careful layering of 1 mm increment to show fewer gaps, and there was no significant difference compared with those without margin elevation. DME didn't significantly influence the fracture strength in all of the materials utilized for DME except that elevated with bulk-fill Smart Dentin Replacement. Conclusions: This review included 16 in vitro studies concerning the different restorative materials used for DME. The samples in multiple layers of 1 mm increment of DME showed similar results to those where the indirect restorations bonded directly to dentine. On the other hand, in clinical practice, DME assists in making indirect restoration cementation easier, faster, and more reliable. Therefore, further research and clinical observations are needed.

Influence of 3D models choice on cervical outline measurements of teeth

Abstract. Among different study techniques, which are used in dental research, measurements of teeth play one of the most important roles. However classical measurement techniques usually show consistent results on morphologically complete objects, while teeth can be found in different conditions, depending, for instance, on the natural wear degree. In order to increase the sample, which is especially important when findings are not abundant, and to improve the analytical part, alternative techniques have been proposed, among which cervical measurements are considered to be informative, especially taking into consideration morphological and methodological importance of the cervical area. Algorithms of automated digital measurement techniques also use the cervical area for providing stability of results. Visualisation of the tooth cervical margin and reconstruction of its projections can be achieved by two conventional imaging techniques, which are tomography (preferably high-resolution) and intra-oral confocal optical scanning. They both were used for obtaining 3D reconstruction of upper premolar taken from palaeoanthropological materials. In line with applying the same automated coordinate system setting algorithm to both types of reconstructions, contours of their enamel cervical margins were defined and their projections to horizontal plane were obtained and measured. Despite the fact that 3D reconstructions from different imaging sources technically can serve for running automated odontometry, measurement results, especially in comparative studies, should be handled with attention.

The Evaluation of the Cervical Marginal Sealing of Direct vs. Indirect Composite Resin Restorations in MOD Cavities.

The aim of this in vitro study was to compare the quality of marginal sealing at the cervical margins of indirect and direct composite resin restorations in mesio-occluso-distal (MOD) cavities. MOD preparations were performed on 30 extracted teeth. The mesial cervical margin of each tooth was relocated using a flow composite resin (Enamel Plus HRi Flow, Micerium, Avegno, GE, Italy), then the samples were divided into three groups. In group A, the cavities were directly restored using a nanohybrid composite resin (Miris 2 Coltène Whaledent, Altstaetten, Switzerland) and a universal adhesive (ScotchBond Universal, 3M ESPE, St. Paul, MN, USA) by the etch-and-rinse strategy, for group B, the restoration procedure was similar but the self-etch strategy was used, and the samples in group C were filled using the inlay technique. Each sample was stored for 48 h in a 2% methylene blue solution, then it was cut in a mesio-distal direction using a Struers Secotom 50 device (Cleveland, OH, USA). The marginal sealing and adhesive interface were assessed for each sample at the cervical margin by optical microscopy (OM) and scanning electron microscopy (SEM). One-way ANOVA and Bonferroni post-hoc tests were used with a significance level of 0.05. Significant differences were recorded within groups A and C, between mesial and distal margins (p = 0.02 in group A and p = 0.043 in group C). The marginal sealing is more effective in MOD inlay restoration compared to direct restorations. Relocation of the cervical margin with flow composite resin and the use of different adhesive strategies do not improve the marginal sealing.

The effect of flowable composite and glass ionomer liner on the marginal integrity of class II composite resin restorations

Aim of the study To evaluate the effect of flowable composite and glass ionomer liner on the marginal integrity of Class II composite resin restorations. Materials and methods A total of thirty non-carious human maxillary molar teeth were mounted in acrylic blocks. Simple Class II cavity with parallel walls was prepared. The cervical margin was established 1.5 mm above the cemento- enamel junction. The overall dimensions and depth of the cavities were standardized as follow: 4 mm length occlusocervically, 4 mm width buccolingulaly and 2 mm depth axially. Specimens were randomly divided into three equal groups (10 each). Group 1: The cavities were restored with Xtra Fil bulk fill composite without liner. Group 2: Xtra base flowable composite (1 mm thickness) was applied, followed by Xtra Fil bulk fill. Group 3: Ionoseal glass ionomer was applied as a base (1 mm thickness), followed by Xtra Fil bulk. Specimens were then subjected to 500 thermal cycles from 5 to 55oC with 30 s dwell time, and 15 s transfer time. Impressions of the teeth were made using a polyvinyl siloxane material, poured with epoxy resin. These replicas were left 24 h for complete setting. Then, Gold sputtered to be examined under scanning electron microscopy (SEM). Results were expressed as percentage of open margins for the total margin length for proximal and cervical margins and also the width of the gap were measured. The recorded data was collected, tabulated, and statistically analyzed using SPSS version 25. Results It was found that there was a significant difference in total gap length between group 1 and group 2 with P value = 0.000. Where group 1 has the biggest marginal gap length and the smallest marginal gap length belongs to Group 2. While there was no significant difference between group 1 and group 3 with P value 0.124. It was also found that there was no significant difference between groups in marginal gap widths. Conclusions The use of flowable composite and glass ionomer as liner could reduce microleakage of bulkfill composite restorations.

Residual cervical H-SIL after cervical conization with positive margins. Is there any associated risk factor?

Introduction: Cervical cancer is the second leading cause of death from gynecological cancer. In Argentina, it is estimated that nearly 4,500 new cases are diagnosed each year and 1,800 women die from this disease. The human papillomavirus (HPV) is a necessary but not a major cause to develop this type of cancer and it is responsible for producing both low-grade (L-SIL) and high-grade (H-SIL) squamous intraepithelial lesions (SIL) depending on the viral serotype in addition to other factors specific to the infected patient. Cervical intraepithelial neoplasia (CIN) is treated by local ablation or excision techniques with lower morbidity. The choice of treatment depends on the degree and extent of the disease, as well as the patient age, risk factors and immunity to generate spontaneous regression or persistence/recurrence. Objective: To identify clinical or pathological factors in patients who presented residual lesion (H-SIL) in the surgical specimens of both re-conization and hysterectomy (HT). Materials and methods: A retrospective, observational study was carried out at Sanatorio Güemes, Buenos Aires, Argentina. All patients that underwent cervical conization with an electric scalpel and had positive margins in the surgical specimen between January 2017 and May 2022 inclusive were analyzed. Data was obtained from 43 patients who had positive cervical conization specimen margins at our institution in the time period described above. Two patients who only had the exocervical margin involved and also 11 patients who did not meet the inclusion criteria were excluded. Among patients (30), all were reoperated (16 underwent re-conization, while in 14 patients it was decided to have a total hysterectomy). Among all the patients who underwent a new surgical procedure, residual disease was found in 10 patients (33.3%), while 20 patients (66.6%) had no residual lesion. Results: The highest percentage of patients (66.6%) did not present residual lesions in the posterior resection specimens. The parameter exhibiting the most substantial influence in our analysis was the proportion of lesion extension, exerting a significant effect on the persistence/recurrence of the disease in subsequent surgical samples (Relative Risk [RR] 7.87, 95% Confidence Interval [CI] 1.13-54.66, p &lt; 0.01). Conclusion: This information brings us even closer to the new reports of bibliographical data: although the presence of the compromised endocervical margin is valuable for estimating the risk of disease persistence/recurrence, it is not sufficient. Therefore, there is a lack of information about the importance of other factors to predict this situation.

Evaluation of the ceramic laminate veneer-tooth interface after different resin cement excess removal techniques.

To compare, in vitro, resin cement excess removal techniques at the veneer-tooth interface. Anterior human teeth were restored with ceramic veneers and randomly divided according to the following techniques (n = 10): removal of excess resin cement with brush and dental floss, followed by light-curing with Valo (Group 1) or Elipar (Group 2) for 1min and 40s; tack-curing with Valo (Group 3) or Elipar (Group 4) for 1s; and tack-curing with Valo (Group 5) or Elipar (Group 6) for 5s. The tack-curing was followed by removal of excess with probe and dental floss and light-curing for 1min and 40s. The area of excess resin cement (mm2) was measured in micro-CT images using AutoCAD program. The failures at the cervical margin in the X, Y, and Z axes (µm) of greater value were measured using the DataViewer program. The specimens were submitted to microleakage with 2% basic fuchsin. According to the Kruskal-Wallis and multiple comparison test, the highest area of excess resin cement was found in Group 1 (5.06 mm2), which did not differ statistically from Groups 2 (3.70 mm2) and 5 (2.19 mm2). Groups 2, 3 (1.73 mm2), 4 (1.14 mm2), and 5 (2.18 mm2) did not differ statistically. Group 6 (0.77 mm2) obtained the lowest value, which did not differ statistically from Groups 3 and 4. According to the Kruskal-Wallis and Dunn test, there was no significant difference in failures in X (p = 0.981), Y (p = 0.860), and Z (p = 0.638) axes and no significant difference in microleakage (p = 0.203) among the groups. Tack-curing for 1s or 5s, followed by removal of excess resin cement using a probe and a dental floss, tended to result in a lower amount of excess material around the margin. The technique used for resin cement excess removal influences the amount of excess leaved at the veneer-tooth interface. Tack-curing for 1s or 5s is recommended to mitigate the excess resin cement.

Evaluate the effects of low-intensity pulsed ultrasound on dental implant osseointegration under type II diabetes.

Objective: The objective of this study is to assess the impact of low-intensity pulsed ultrasound (LIPUS) therapy on the peri-implant osteogenesis in a Type II diabetes mellitus (T2DM) rat model. Methods: A total of twenty male Sprague-Dawley (SD) rats were randomly allocated into four groups: Control group, T2DM group, Control-LIPUS group, and T2DM-LIPUS group. Implants were placed at the rats' bilateral maxillary first molar sites. The LIPUS treatment was carried out on the rats in Control-LIPUS group and T2DM-LIPUS group, immediately after the placement of the implants, over three consecutive weeks. Three weeks after implantation, the rats' maxillae were extracted for micro-CT, removal torque value (RTV), and histologic analysis. Results: Micro-CT analysis showed that T2DM rats experienced more bone loss around implant cervical margins compared with the non-T2DM rats, while the LIPUS treated T2DM rats showed similar bone heights to the non-T2DM rats. Bone-implant contact ratio (BIC) were lower in T2DM rats but significantly improved in the LIPUS treated T2DM rats. Bone formation parameters including bone volume fraction (BV/TV), trabecular thickness (Tb.Th), bone mineral density (BMD) and RTV were all positively influenced by LIPUS treatment. Histological staining further confirmed LIPUS's positive effects on peri-implant new bone formation in T2DM rats. Conclusion: As an effective and safe treatment in promoting osteogenesis, LIPUS has a great potential for T2DM patients to attain improved peri-implant osteogenesis. To confirm its clinical efficacy and to explore the underlying mechanism, further prospective cohort studies or randomized controlled trials are needed in the future.

Comparison of Various Commonly Used Luting Cements on the Success of Composite Inlays Assessed by the Levels of the Microleakage-An In vitro Study.

Indirect composite restoration is one of the commonly followed procedures in the posterior teeth. The success of this is dependent on many factors, one being the luting cement. Hence, the current study explores the microleakage of the two luting cements at 2 different times. Eighty extracted human teeth were taken, and class II cavities were made that were to receive the composite inlays. They were grouped as supragingival and subgingival, which for further divided as were further subdivided to be observed for marginal leakage at cervical and occlusal margins, at the end of a day and 1 month. Each group had ten specimens. The luting cements that were evaluated were Variolink N and RelyX Unicem. After the composite inlay restoration was done for all the specimens, the sections were put on slides, and a stereomicroscope was used to measure the amount of dye penetration. Leakage was evaluated and compared using Mann-Whitney U test. At the end of 1 day, there was no significant alteration in the microleakage in the occlusal or cervical regions for either region supragingivally or subgingivally between the two luting cements. Significant difference between the two cements at the cervical borders at the end of a month was seen for both the margins. When compared supragingivally and subgingivally at the end of 1 day or at the end of 1 month, there was not a significant difference for any of the cements. Within the constraints of the current investigation, it can be said that there was similar microleakage for both Variolink N and RelyX Unicem at the conclusion of a day's storage time. After a 1-month storage period, RelyX Unicem showed more cervical microleakage than Variolink N.

Effect of a modified laminate veneer preparation design on absolute margin discrepancy and marginal overhang

Veneer preparation designs impact veneer accuracy. However, whether a modified design could reduce absolute margin discrepancy and marginal overhangs is unclear. The purpose of this in vitro study was to investigate whether a modified veneer preparation design enhances the absolute margin discrepancy and marginal overhang. The absolute margin discrepancy and the marginal overhang of 3 different veneer preparation designs on a typodont tooth (n=20): feather edge, shoulder, and shoulder with wings were measured. The feather edge design was prepared first and subsequently modified to create the shoulder and shoulder with wings preparations. Ceramic veneers were fabricated using computer-aided design and computer-aided manufacture with each veneer assessed for fit before cementation. Ten specimens were cut vertically, and 10 were cut horizontally in each group. The absolute margin discrepancy and marginal overhangs were measured for each cross-section with scanning electron microscopy. Descriptive data analysis and hypothesis testing were conducted using the nonparametric Kruskal Wallis test (α=.05). On the vertical sections, the shoulder with wings preparation had the best absolute margin discrepancy and overhang. The design was also best for mesial overhang and mesial absolute margin discrepancy when measuring horizontally. The shoulder with wings preparation design produced the smallest cervical absolute margin discrepancy and overhang. This design also produced absolute margin discrepancy and overhangs comparable with those of the shoulder design in the proximal areas.

In Vitro Effect of the Length of Relocated Cervical Margin with Casting Post and Core, Prefabricated Fiber Post, and Polyethylene Fiber with a Composite Core on Fracture Resistance and Marginal Integrity.

This study aimed to assess the effect of length of the relocated cervical margin with casting post and core (CP), prefabricated fiber post and composite core (PFP), and polyethylene fiber-reinforced composite (PEFRC) on fracture resistance and marginal integrity. In this in vitro study, 70 sound human maxillary premolars were divided into seven groups according to the type of post and core system and length of the relocated cervical margin (n = 10): control (no preparation), PFP-3, PEFRC-3, CP-3 with 3 mm of cervical margin relocation (CMR), PFP-6, PEFRC-6, and CP-6 (with 6 mm of CMR). The samples were restored with zirconia crowns (except the control group). Epoxy resin replicas were fabricated before and after thermomechanical loading. Marginal integrity was assessed at the luting cement-core, core-tooth, and luting cement-enamel interfaces under a scanning electron microscope (SEM) (×200). Fracture resistance and failure mode were subsequently assessed. Data were analyzed by independent t-test, paired t-test, ANOVA, Tukey-Games Howell, Mann-Whitney, Kruskal-Wallis, Wilcoxon, Mann-Whitney with Bonferroni correction, and Fisher-Freeman-Halton tests (α = 0.05). The marginal integrity of the groups with 3 mm of CMR followed the following order: PEFRC > PFP > CP at all interfaces (P < 0.05). In 6-mm CMR groups, this order was CP < PFP = PEFRC at the luting cement-core and (CP < PEFRC) = PFP at the core-tooth interface. No significant difference was found in fracture resistance when comparing the 3-mm CMR groups with each other (P > 0.05). PFP-6 showed higher FR than CP-6 (P < 0.001). PEFRC-6 had no significant difference with PFP-6 and CP-6 (P > 0.05). In each post and core system, 3-mm CMR groups showed higher marginal integrity and fracture resistance (P < 0.05). Increasing the length of the relocated cervical margin decreased the marginal integrity and fracture resistance of all three systems of CP, PFP, and PEFRC.

Effect of different storage media on elemental analysis and microhardness of cervical cavity margins restored with a bioactive material.

This study aimed to investigate the elemental analysis and microhardness of a bioactive material (Activa) and marginal tooth structure after storage in different media. Fifteen teeth received cervical restorations with occlusal enamel and gingival dentin margins using the tested material bonded with a universal adhesive, 5 of them on the 4 axial surfaces and the other 10 on only the 2 proximal surfaces. The first 5 teeth were sectioned into 4 restorations each, then stored in 4 different media; deionized water, Dulbecco's phosphate buffered saline (DPBS), Tris buffer, and saliva. The storage period for deionized water was 24 hours while it was 3 months for the other media. Each part was analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis for different substrates/distances and the wt% of calcium, phosphorus, silica, and fluoride were calculated. The other 10 teeth were sectioned across the restoration, stored in either Tris buffer or saliva for 24 hours or 3 months, and were evaluated for microhardness of different substrates/areas. Data were analyzed using analysis of variance and Tukey's post hoc test. Enamel and dentin interfaces in the DPBS group exhibited a significant increase in calcium and phosphorus wt%. Both silica and fluoride significantly increased in tooth structure up to a distance of 75 μm in the 3-month-media groups than the immediate group. Storage media did not affect the microhardness values. SEM-EDS analysis suggests an ion movement between Activa and tooth structure through a universal adhesive while stored in DPBS.

Controversies in the treatment of early-stage oral squamous cell carcinoma

The treatment of early-stage oral squamous cell carcinoma (OSCC) is still a controversial issue. Thanks to the 8th edition of TNM by AJCC there is a better distinction between the stages of OSCC. However, Stages I and II still share the same treatment protocol, even if the prognosis is radically different. A retrospective study has been conducted including 70 previously untreated patients with Stage I or II OSCC, treated with tumorectomy and selective neck dissection. The study focuses on the link between pT1/2 and various other factors, particularly histological grading, vascular and perineural invasion, local and cervical recurrence, surgical margins and overall survival. These data reveal significant differences between pT1 and pT2 in histological grade, perineural invasion, cervical recurrence, surgical margins, and overall survival, emphasizing the necessity of different treatment protocols for T1 and T2 OSCC. Distinct strategies should be proposed to treat Stage I and II OSCC, with Stage II patients possibly benefitting from more aggressive treatments: following these data, a wait-and-see strategy should only be considered in Stage I, while certain treatments at the cervical level — such as prophylactic neck dissection and sentinel node biopsy — should always be considered for Stage II tumors.

Over-eruption in marsupial carnivore teeth: compensation for a constraint

Pronounced over-eruption of the canine teeth, causing the cervical enamel margin to extend beyond the alveolar bone and exposing the root, occurs with age and growth in Australian marsupial carnivores, much more than in eco-morphologically equivalent placental carnivores. Suppression of functional tooth replacement is characteristic of marsupials, where most placentals have the primitive diphyodont pattern of two generations of incisor, canine and premolar teeth. Canine and molar tooth dimensions of four species of marsupial carnivores (thylacine Thylacinus cynocephalus , Tasmanian devil Sarcophilus harrisii and two quolls Dasyurus spp . ) and canine dimensions of seven eco-morphologically equivalent placental carnivore species were measured from museum specimens. Canine dimensions were measured in a time series on live wild-living individual devils and quolls. The canine teeth and to a lesser extent the molar teeth of marsupial carnivores continue to erupt through life, resulting in a net increase in tooth height and diameter, a phenomenon not evident in placental carnivores. Potential mechanisms causing over-eruption include tooth wear and gradual release of occlusal pressure as the individual grows. Over-eruption in marsupial carnivores may be a compensatory response for tooth size limits imposed by monophyodont tooth replacement, ensuring that animal's teeth are scaled to jaw size from juvenile to adulthood.