Effect of silver diammine fluoride and glass ionomer on remineralisation of natural dentine caries

OBJECTIVES

Silver diammine fluoride (SDF) is a caries-arresting agent for dentine lesions. This study investigated the effect of application frequency of SDF when used with glass ionomer cement (GI) for remineralising carious dentine.

METHODS

Freshly extracted human posterior teeth with advanced caries were used. After superficial removal of infected dentine, single (G3), double (G4), triple (G5) applications of SDF (Advantage Arrest SDF 38 %) followed by a layer of GI (GC Fuji IX GP) were compared to no treatment (negative control-G2), and GI only (G1). All teeth were stored in artificial saliva between treatments and for 2-weeks after final treatment. Micro-computed X-ray tomography (NSI) scans were obtained at each stage and analysed to plot mineral density-depth profile, lesion depth (LD) and mineral loss (ΔZ). Data was statistically analysed at a significance level of 0.05.

RESULTS

Mean LD values were 837 μm, 735 μm, 841 μm, 1008 μm, 707 μm at baseline and 785 μm, 727 μm, 712 μm, 855 μm, 639 μm after treatment for groups G1 to G5, respectively. Mean ΔZ values were 6327 vol%μm, 5995 vol%μm, 10014 vol%μm, 7192 vol%μm, 5649 vol%μm at baseline and 3686 vol%μm, 5126 vol%μm, 5539 vol%μm, 2327 vol%μm, 3218 vol%μm after treatment for groups G1 to G5, respectively. Paired t-test showed that LD and ΔZ changed significantly within all groups from baseline to treatment weeks following storage (p < 0.05) except LD in the control (p > 0.05). ANCOVA showed significant difference among groups in net lesion depth recovery and net mineral gain (p < 0.05), and G3 and G4 showed the highest mineral gains.

CONCLUSION

One or two applications of SDF prior to placement of GI, were effective in remineralising advanced dentine lesions, while additional applications, when combined with GI, did not demonstrate additional benefit in this study.

CLINICAL SIGNIFICANCE

This short-term laboratory research study showed that one or two applications of SDF followed by GI coverage could remineralise advanced dentine caries in the presence of artificial saliva. This procedure carries potential in the treatment of difficult lesions where conventional restorations would require significant tooth structure removal through traumatic procedures.

The effect of digital diagnostic setups on orthodontic treatment planning

INTRODUCTION

This study aimed to evaluate whether viewing digital treatment simulations influenced orthodontic treatment planning decisions or practitioners' confidence in their selected plans.

METHODS

Records of 6 patients representing different case types (eg, missing teeth, crowding, sagittal discrepancies) were collected. A total of 22 orthodontists and 7 orthodontic residents viewed these records and formulated treatment plans for each case, indicating their most recommended plan and up to 2 alternative plans. After treatment planning each case, digital setups of each treatment plan indicated by the practitioner were shown. The practitioners were then asked if they still recommended their original plan, or if they would now recommend a different plan. Their confidence levels in the success of their plans were recorded before and after viewing the setups.

RESULTS

After viewing the digital setups, there was a significant change in the treatment plan for 9.2% of the cases. These included modifications like changing the extraction pattern or proposing space closure rather than opening space for an implant. In an additional 14.4% of the cases, treatment plans underwent partial changes, like adding interproximal reduction or temporary anchorage devices. Practitioner confidence levels increased after viewing the setups. In cases where the treatment plan changed, the practitioner's confidence level in the plan increased the most, and the final confidence level was uniformly high among all practitioners. Practitioners reported the most helpful features of digital setups were the ability to superimpose the setup with the original model, determine the amount of tooth movement needed, check the final incisal relationship (overjet and overbite), and establish the amount of interproximal reduction required.

CONCLUSIONS

Viewing digital setups resulted in changes to the treatment plans in about 24% of the cases. The use of digital setups was associated with higher levels of confidence in the selected plans.

Dental School Patient Preferences for Receiving and Returning Patient Satisfaction Surveys

The aims of this study were to investigate dental school patient, parent, and caregiver preferences for receiving and returning patient satisfaction surveys and to determine how modes of receiving and returning surveys impacted return rates. Two studies were conducted, both of which are reported. In Study 1, adult patients, parents of child patients, and caregivers of patients with special needs were asked to indicate their preferred mode of receiving and returning surveys. In Study 2, patients, parents, and caregivers were randomly assigned to different modes of receiving and returning surveys, and return rates were compared between modes and according to whether the individuals had been assigned to their preferred mode or not. The overall response rates were 90.4% for the first study and 48.1% for the second study. In both studies, the preferred mode was receiving and returning the survey in the clinic (chi-square=84.902 and 32.116; df=3; p<0.001). Younger respondents were more likely to prefer receiving and returning the survey by email (K-W statistics=13.406, 10.241; df=3; p=0.004 and 0.017). In Study 2, respondents were significantly more likely to return surveys in the clinic (chi-square=44.994; df=2; p<0.001) and were also significantly more likely to return surveys if they had received them in their preferred mode (binomial test p<0.001). Although receiving and returning the survey in the clinic was the preferred mode, these respondents' preferences were also related to their age. These results suggest that dental school clinics may be able to expect higher return rates if they can follow patients' preferences for receipt and delivery of surveys.

A Review of Hydroxapatite and its use as a Coating in Dental Implants

At present, no standard manufacturing guideline exists for depositing hydroxyapatite (HA) on implant surfaces. Although animal and in vitro studies have reported on the benefits of using HA-coated implants as well as the risks of dissolution, these short-term studies did not demonstrate that the dissolution of the HA coating leads to a loss of implants. In addition, many in vivo and clinical studies did not include the chemical and structural characterization of the coatings, and thus comparisons between studies are difficult. In the clinics, the recommendation is that HA-coated screw implants be used for the anterior maxilla and posterior mandible where the bone depth exceeds 10 mm and when the cortical layer is thinner and spongiosia is less dense. In the posterior maxilla or when the cortical layer is very thin with low density, the use of HA-coated cylindrical implants is recommended. However, there are concerns for using HA-coated implants. The clinician needs to take into consideration the enhanced bacterial susceptibility of HA coatings compared with titanium implants. In addition, the clinician needs to consider the possible failure of HA coatings as a result of coating-substrate interfacial fracture. Finally, besides the surgical skills, it is also important that the clinical investigators be well versed with the materials characterization needed for HA-coated implants, the problems associated with the current HA coatings, and the indications for use. In addition, the correlation between well characterized coatings and their effect on bone formation rate and long-term implant success, coating-implant interfacial strength, and alternative superior coating process need to be investigated further.

Fluoride-Releasing Effect of a Modified Resin Denture Containing S-PRG Fillers on Salivary Fluoride Retention: A Randomized Clinical Study

This study aimed to evaluate the clinical effect of a resin denture base containing 20wt% surface prereacted glass ionomer (S-PRG) fillers on saliva fluoride concentrations as a surrogate evaluation of caries control. The study was a double-blind randomized clinical trial with a total of 110 participants aged 35-60 years who wore a removable partial resin denture for 1.5 years. Subjects were randomly assigned to receive a partial resin denture fabricated either with or without 20wt% S-PRG fillers (n = 55 per group). After 14 days of wearing the dentures, 5,000 ppm fluoride gel was applied nightly on both sides of the denture before storing it in a denture box overnight every night for 1.5 years. The salivary fluoride concentration was measured at baseline, on days 1, 14, and 15, and at 3 months and 1.5 years of wearing the denture. A significant increase in salivary fluoride concentration in the S-PRG denture group was observed from baseline to day 1, followed by a significant decrease to an approximate baseline level. After recharge with 5,000 ppm fluoride gel, salivary fluoride increased markedly on day 15 and remained elevated at month 3 through to 1.5 years. The resin denture base containing 20wt% S-PRG fillers demonstrated an initial fluoride release that increased saliva fluoride concentrations, but the fluoride release from within the material was short lived. The long-term effect of sustained fluoride release from the denture when combined with a regular fluoride recharge regimen may be beneficial for caries prevention.

Bleachorexia-an addictive behavior to tooth bleaching: a case report

Bleachorexia, addiction to tooth bleaching, is a behavioral disorder similar to anorexia. The patient feels that their teeth are always not white enough and continues to use whiteners to obtain a “perfect” smile. Such behavior falls under the category of a body dysmorphic disorder and may need medical counseling.

Effects of carbodiimide dentin surface treatment on resin-dentin bonding

PURPOSE

To assess the effects of ethanol-based 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide (EDC) dentin surface treatment on resin-dentin bonding and dentin collagen fibril biodegradation.

METHODS

Acid-etched dentin surfaces were pretreated with different concentrations of ethanol-based EDC solutions (0.01-2M) for 60 seconds, followed by two-step etch-and-rinse dentin adhesive application and resin composite bonding. Dentin surfaces pretreated with either ethanol alone or no pretreatment were used as controls. The specimens were subjected to microtensile bond strength testing after storage in 0.9% NaCl solution at 37°C for either 24 hours or 90 days. Furthermore, demineralized dentin slabs with and without ethanol-based EDC pretreatment were exposed to a collagenase solution for 24 hours, and subsequent hydroxyproline release was measured using ELISA. Data were analyzed with ANOVA and multiple comparison tests at α= 0.05.

RESULTS

The bond strength values were significantly lower for dentin surfaces pretreated with 1 and 2 M ethanol-based EDC than for the control surfaces (P< 0.05). The 0.01, 0.1, and 0.3 M ethanol-based EDC pretreated groups obtained significantly higher bond strength values at 90 days compared to controls. Hydroxyproline release measurements revealed that there were significantly lower levels released in the 0.3 and 1 M ethanol-based EDC pretreated specimens than for controls (P< 0.05).

CLINICAL SIGNIFICANCE

Pretreatment of dentin surfaces with ethanol-based EDC solution ≤ 0.3M before resin composite bonding can improve the stability of the resin-dentin bond and prevent dentin collagen fibril biodegradation.

Antibacterial activity of gold-titanates on Gram-positive cariogenic bacteria

Objective: Gram-positive cariogenic bacteria are etiological agents in dental caries; therefore, strategies to inhibit these bacteria to reduce the incident of this disease have intensified. In this study, we investigated antibacterial activities of titanates and gold-titanates against Lactobacillus casei (Lc) and Streptococcus mutans (Sm).

Materials and methods: Monosodium titanate (MST), nanomonosodium titanate (nMST) and amorphous peroxo-titanate (APT), which are inorganic compounds with high-binding affinity for specific metal ions, were used. Total bacterial proteins were measured to represent bacterial cell mass after 24 h incubation with gold-titanates. We further examined the effect of nMST-Au(III) concentrations (10,200,400 mg/L) on Lc and Sm cell viability over time via Live/Dead fluorescent staining and colony forming units (CFUs). Transmission electron microscopy (TEM) was used to determine specific locations on the bacterial cells affected by the nMST-Au(III).

Results: We found all gold-titanates and APT alone reduced bacterial protein for Lc (p value <0.001) while only MST-Au(III) and nMST-Au(III) affected Sm growth (p value <0.001). Overall, nMST-Au(III) showed the most effectiveness against both Lc and Sm at 400 mg/L. The Live/Dead staining showed all concentrations of nMST-Au(III) affected Lc growth but only 200 and 400 mg/L nMST-Au(III) interrupted Sm growth. The growth curves based on CFUs/mL showed all nMST-Au(III) concentrations affected growth of both Lc and Sm. TEM images showed nMST-Au(III) attached to Lc and Sm cell wall and were internalized into both cells.

Conclusions: nMST-Au(III) demonstrated potential antimicrobial activity against Gram-positive cariogenic bacteria. These results support further development of nMST-Au(III) as a potential novel material to prevent dental caries.

The Accuracy of Optical Scanning: Influence of Convergence and Die Preparation

The purpose of this study was to determine the reliability of the data acquisition and modeling process of laser and white light scanners by evaluating the reproducibility of digitized simulated crowns with different convergences. A secondary purpose was to analyze the influence of die preparation by testing this hypothesis with a set of dies without ditching compared with a set with well-defined margins. Ditching or trimming the die defines the position of the margin and acts as a guide to gingival contour when the restoration is being waxed. Two light scanners (a white light optical scanner [Steinbichler Gmbh, Neubeuern, Germany] and red laser light scanner [TurboDent System, Taichung, Taiwan]) were evaluated. Two sets of simulated crowns were fabricated as cone frustrum models with a total occlusal convergence (TOC) of 0°, 5°, 10°, 15°, 20°, and 25° and a 9-mm base and 3-mm height using a precision milling machine and computer-aided design/computer-aided manufacturing (CAD/CAM) technique. One set of the dies was ditched immediately below the finish line to enhance marginal definition. Each die was optically digitized five times directly with the two different measuring systems. The area of each triangle in the scan that is occlusal to the margin line was calculated and summed to produce the final surface area measurement provided. The digitizing error was compared with the computed surface area of the original master die sets and compared with a paired t-test (df=4; 95% CI). There was no difference in accuracy of the untrimmed dies between the two systems evaluated. We also did not find any difference in the 0° (p=0.12) and 5° degree (p=0.21) groups among the ditched dies. However, when the TOC exceeded 5°, there was a significant difference between the two groups, with the laser groups having a smaller error percentage. Three-dimensional light scanning was not affected by the convergence angle except in the 0°-5° range. Trimming the dies greatly affected the accuracy of scanning.

Management of idiopathic subgingival amalgam hypertrophy--the common amalgam overhang

An amalgam overhang is defined as an extension of amalgam restorative material beyond the confines of a cavity preparation. The pseudo pathology term "idiopathic subgingival amalgam hypertrophy" is used in the title for shock effect and as a scare tactic to catch the attention of our readers. From various studies, it is apparent that such overhangs are alarmingly common. The overhang is largely iatrogenic, caused by poor operator skill exacerbated by unusual dental morphology. Creep may also play a role in the gingival overhang of large amalgam restorations. Maybe we, as clinicians, are becoming complacent and lax in our techniques and matrixing while restoring such a routine restoration. This article revisits the pros and cons of different methods of amalgam overhang management with clinical cases for illustration.

Changes in resin-infiltrated dentin stiffness after water storage

Plasticization of polymers by water sorption lowers their mechanical properties in a manner that is predictable by the polarity of their component resins. This study tested the hypothesis that when adhesive resins were used to create resin-infiltrated dentin, the reductions in their flexural moduli after water storage would be lowered proportional to their hydrophilic characteristics. Three increasingly hydrophilic resin blends were used to fabricate polymer beams and macro-hybrid layer models of resin-infiltrated dentin for testing with a miniature three-point flexure device, before and after 1-4 weeks of water storage. Flexural modulus reductions in macro-hybrid layers were related to, and more extensive than, reductions in the corresponding polymer beams. Macro-hybrid layers that were more hydrophilic exhibited higher percent reductions in flexural modulus, with the rate of reduction proportional to the Hoy's solubility parameters for total intermolecular attraction forces (delta(t)) and polar forces (delta(p)) of the macro-hybrid layers.

Clinical Evaluation of the Soft-Start (Pulse-delay) Polymerization Technique in Class I and II Composite Restorations

Class I and II composite restorations placed with a Soft-Start technique showed no significant changes in post-op sensitivity to cold or any decreased signs of marginal stress.

Effect of solvent type and content on monomer conversion of a model resin system as a thin film

OBJECTIVE

The purpose of this study was to examine the effect of solvent concentration on the degree of conversion of a model photo-activated resin formulation when placed as a thin film in ambient air.

METHODS

A photo-activated co-monomer mixture (ethoxylated bis-GMA/TEGDMA) (Bisco Inc.) was diluted into six concentrations (from 1.0 to 13.0M) with either acetone or ethanol. A controlled volume of diluted, uncured resin was placed on the horizontal surface of an attenuated reflectance unit and the infrared (IR) spectrum obtained. A light emitting diode light-curing source (Bluephase, Ivoclar/Vivadent) then immediately irradiated the specimen for 10s (n=5). Five minutes after exposure, IR spectra of the cured material were obtained, and monomer conversions were calculated using standard methods that monitored changes in aliphatic-to-aromatic CC absorbance ratios in the uncured and cured states.

RESULTS

In the acetone/model resin system, maximum conversion occurred with 2.5-5.0M solvent. In the ethanol/model resin system, conversion peaked at 2.5M solvent. Above 5.0M solvent, conversion values declined rapidly for both solvents. A 13.0-M solution resulted in near 0% conversion for both solvents. At 2.5 and 5.0M acetone, conversions exceeded those of equivalent concentrations of the ethanol-based system.

CONCLUSIONS

For both an acetone- and ethanol-solvated model resin system, conversion did not immediately decrease with addition of solvent, but instead increased over that of the model resin alone. At higher solvent content (greater than 2.5M ethanol and 5.0M acetone), conversion rapidly declined, with ethanol causing less conversion at equal-molar solvent concentrations.

Mathematical modeling of molar tooth preparations for complete crowns

OBJECTIVES

This study used both cone frustum and right truncated pyramids mathematical methods to evaluate and characterize molar tooth surface area. Previous mathematical modeling studies evaluated only the total surface area. We attempted to analyze both the top surface and lateral surface areas.

METHODS

The computations were performed according to the published formulas. The vertical heights of both models were assigned to be 3 and 4mm and the horizontal base width chosen to be 9 and 10mm for both models. Three total occlusal convergences: 10 degrees , 15 degrees , and 20 degrees were selected to be the tested parameters.

RESULTS

The calculated data revealed that the top surface area represented a relatively large proportion of the total surface area in both models. We also found that the effect of increasing the total occlusal convergence has a much greater effect on the overall top surface area than the lateral surface and total surface areas.

CONCLUSIONS

The models previously used to report and compare surface areas of prepared natural teeth were found to be overestimating the overall surface area. More complex configurations including two-plane reductions, anatomy of cusps and retentive features such as slots and grooves need to be included in future modeling protocols.

Sialolith characterization by scanning electron microscopy and X-ray photoelectron spectroscopy

The objective of this study has been to characterize sialolith, a calcium phosphate deposit that develops in the human oral cavity, by high-resolution field emission scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The morphological and chemical data obtained helped in the determination of their formation mechanism in salivary glands. Sialoliths in the submandibular salivary glands may arise secondary to sialodenitis, but not via a luminal organic nidus. We believe this is the first study that characterizes a sialolith by XPS.

Tensile bond strength of dual curing resin-based cements to commercially pure titanium

OBJECTIVES

The aim of this study was to evaluate the tensile bond strength of dual curing luting resin cements to commercially pure titanium at 10 min and 24h after removal of the oxide layer.

METHODS

One hundred and twenty titanium discs were obtained by casting and polishing with silicon carbide papers. The titanium discs were sandblasted with 50 microm aluminum oxide, ultrasonic cleaned and bonded in pairs with the resin-based cements Panavia F and Rely X ARC at 10 min and 24h after the sandblasting. The tensile test was performed with a crosshead speed of 0.5mm/min in an Instron Universal testing machine.

RESULTS

The Rely X ARC reached the highest tensile strength value at 24h after sandblasting (18.27 MPa), but there was no statistically significant difference between the two dual curing resin cements for both times tested. All specimens showed a mixture of cohesive fracture in the resin cement and adhesive failure. However, the predominant failure mode for Panavia F was cohesive in resin cement, and the Rely X ARC exhibited a greater proportion of specimens with adhesive failure between the alloy and resin luting cement at 10 min and 24h.

SIGNIFICANCE

Both cements had, statistically, the same tensile bond strength. But in the fracture mode analysis, the adhesive predominant fracture mode of Rely X ARC cement indicates a premature clinical adhesive failure. On the other hand, the cohesive predominant fracture mode of Panavia F indicates a longer clinical adhesive bond with titanium.

A Case for Rubber Dam Application—Subcutaneous Emphysema After Class V Procedure

Subcutaneous emphysema after dental treatment occurs frequently, especially in older patients. Dentists should be aware of the etiology, the differential diagnosis and how to avoid and properly treat such situations.

Standardized method to produce tetracycline-stained human molar teeth in vitro

OBJECTIVE

This study tested the hypothesis that exposure of human molar teeth to tetracycline (TCN) derivatives in vitro results in tooth discoloration resembling the clinical presentation of TCN staining.

METHOD AND MATERIALS

The effects of exposure of 20 extracted human molar teeth to distilled water, chlortetracycline, doxycycline, or minocycline were compared. The baseline color of each tooth was analyzed with a dental spectrophotometer. The pulp chambers were each filled with a TCN derivative solution and then sealed. The teeth were placed in a centrifuge tube and then centrifuged at 2800 rpm for 20 minutes. Color change was monitored weekly for 7 weeks. Digital images of the surfaces were recorded. For each specimen at every evaluation period, color change from baseline was calculated using Commission Internationale d'Eclairage (CIE) Delta E 2000 (deltae00).

RESULTS

There was a significant association between the type of derivative used and deltae00, as well as between the evaluation period and deltae00. There was also a significant association between the interaction term, derivative x evaluation period, and deltae00. Results of the Holm-Sidak post hoc test demonstrated that all 3 TCN derivatives were associated with significantly larger deltae00 than the control group (P < or = .05).

CONCLUSIONS

All 3 TCN derivative solutions produced significant color changes as time progressed. Different TCN derivatives produced a different L* (lightness), C* (chroma), and H* (hue), with minocycline behaving distinctly differently from chlortetracycline and doxycycline. The model could be used to study the underlying mechanisms of TCN staining as well as many aspects of vital tooth

Provisional anterior tooth replacement using nonimpregnated fiber and fiber-reinforced composite resin materials: a clinical report

The loss of anterior teeth is often a serious esthetic concern. While conventional fixed partial dentures and implant-supported restorations may be the treatments of choice, nonimpregnated fibers (NFs) and fiber-reinforced composite (FRC) resins offer a conservative alternative for improving esthetics. This article describes 2 clinical situations in which NF glass ribbon and FRC were successfully used to provisionally restore anterior edentulous areas in an esthetic, functional, and timely manner.

Microtensile bond strength testing and failure analysis of hybrid and flowable composites

PURPOSE

Few studies have been performed on the cohesive tensile strength of flowable resin composites and hybrids, or on the coupling strength of flowables to hybrid composites. Thus, the purpose of this study was to measure interfacial microtensile bond strengths between hybrid resin composite and flowable resin composite/compomer.

MATERIALS AND METHODS

A polyvinyl siloxane mold was used to fabricate specimens for 9 groups, each consisting of 15 rectangular beams (2 x 2 x 20 mm). Flowable and hybrid resin composites and their paired couplings with each manufacturer's product line were tested. Materials include Heliomolarflow, Revolution, and Dyractflow as representative flowable resin composites and compomer. Heliomolar HB, Prodigy, and Esthet X were selected as representive hybrid resin composites. Resin specimens were cured for a total of 80 s and immersed in water for 7 days. A microspecimen former was used to trim rectangular specimens into specimens with a circular cross section (diameter = 1.0 mm) with a 2 mm gauge length. Specimens were subjected to tensile forces in a passive-gripping space mounted on a Vitrodyne machine.

RESULTS

The results are expressed in MPa. Kruskal-Wallis one-way ANOVA on ranks demonstrated significant differences in microtensile bond strength among groups (p < 0.001).

CONCLUSION

The cohesive tensile strength of resin composites were material dependent. Flowable and hybrid composites from the same manufacturer have comparable cohesive tensile strengths. The coupling strength of flowable/hybrid combinations were comparable to cohesive strength of the hybrid composites with the exception of Esthet X/Dyractflow, where the coupling was stronger than the cohesive strength of either resin composite alone.

Predictors of Non-carious Loss of Cervical Tooth Tissues

In this sample of subjects, age, premolars and the presence of corrosive factors were found to be significantly associated with NLCTT. The long-term success of treating such a lesion is dependent on properly identifying and eliminating the etiologic factors.

Measurement of clinical wear of two packable composites after 6 months in service

Original large-particle composites exhibited poor wear characteristics. With the packable composites, there has been a reintroduction of large particles. The clinical wear characteristics of such packable composites are relatively unknown. The purpose of this study was to compare wear between two types of packable composites: Alert (Jeneric Pentron) and Surefil (Dentsply Caulk). Each material was compared with and without a surface sealant. Fifty-two subjects were included. Subjects had to have two to four eligible teeth, be 21 years of age, in good health and in need of moderate to large class 2 restorations on molars, and/or a two-surface class 1 on molars. Wear was assessed, using the Moffa-Lugassy (ML) scale, by evaluating stone models made from polyvinyl siloxane (PVS) impressions taken at baseline and 6 months. Rating was done by four calibrated examiners using a forced consensus model. The use of a surface sealant with Alert significantly reduced the median wear rate at 6 months compared with that of the SureFil restorations.

Effect of preparation convergence on retention and seating discrepancy of complete veneer crowns

The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate cement using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0 degrees to 70 degrees and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4.58 +/- 1.13 to 73.13 +/- 78.32 microm. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4.03 +/- 0.61 to 12.12 +/- 0.33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0.62), and retention (r = -0.91). Crown retention and marginal discrepancy were influenced by the preparation convergence design.

SEM evaluation of contemporary self-etching primers applied to ground and unground enamel

PURPOSE

This study evaluated the etching effect of self-etching priming agents applied to intact and ground enamel.

MATERIALS AND METHODS

Thirty-two human molars were used. Each tooth was divided into two halves. The buccal or lingual mid-coronal surface of 32 half-teeth was ground with 600-grit silicon carbide paper. The other half-teeth were left intact (control). Teeth were treated with Clearfil SE Bond (SE), Prompt L-Pop (PLP) or Adper (AD). Those in the control group were etched with 35% phosphoric acid. The etching effect of such systems on enamel surfaces was assessed by three different approaches using scanning electron microscopy: 1) in situ or direct morphological examination of the etched enamel; 2) indirect morphological examination, that is, evaluation of the etching pattern left on resin reproductions; 3) adhesive interface examination.

RESULTS

SE exhibited the least aggressive dissolution of the intact and ground enamel, with many sites of the intact enamel remaining completely unetched. SE monomer infiltration into etched enamel was restricted to the superficial layer. PLP and AD produced equivalent etching patterns on intact and ground enamel, which resemble that produced by the phosphoric acid control group. PLP and AD monomer penetration extended along the porous subsurface enamel layer.

CONCLUSION

SE produced mild morphological changes on intact and ground enamel surface, resulting in a very superficial resin infiltration particularly into intact enamel. No differences were evident among the etching and resin infiltration pattern produced by both all-in-one self-etching adhesives, PLP and AD, and the phosphoric acid system.

Practical fluoride and remineralization protocols for adult patients

There is a wealth of information on preventive measures and procedures that can be used to care for paediatric and adolescent patients. However, few studies have been conducted in adult or geriatric populations, and an understanding of preventive and non-surgical treatment regimens for these patients is lacking. Traditionally, caries incidence is high among risk groups of low income, low dental IQ and certain ethnic subgroups, but we are now witnessing a high incidence of caries among middle-income and healthy adult patients with an imbalance of protective factors and cariogenic factors. We will direct our attention to the adult population and attempt to address some of the most common questions.

Effect of preparation convergence on retention and seating discrepancy of complete veneer crowns

The purpose of this study was to evaluate the retention and marginal seating discrepancy of complete veneer crown cemented with zinc phosphate using various preparation convergence designs. The method employed was that of cementing cast metal crowns onto 46 metal dies fabricated as complete veneer crown preparations with various convergence angles ranging from 0 degrees to 70 degrees and a shoulder finish line. The marginal discrepancy was calculated by measuring the change in crown height before and after cementation using an optical measuring microscope. The force required to remove the crowns from the dies in a vertical direction was determined using an Instron universal testing machine and recorded as retention. The increase in preparation convergence exhibited a wide variation of seating discrepancy between specimens, ranging from 4.58 +/- 1.13 to 73.13 +/- 78.32 microm. Significant tilting of crown was observed as the convergence angle of preparation increased. The retention values ranged from 4.03 +/- 0.61 to 12.12 +/- 0.33 MPa. The Pearson analysis revealed statistically significant correlations between preparation convergence and marginal discrepancy (r = +0.62), and retention (r = -0.91). Complete veneer crown retention and marginal discrepancy were influenced by the preparation convergence design.

Safety and efficacy of a nightguard bleaching agent containing sodium fluoride and potassium nitrate

OBJECTIVES

Transient sensitivity during bleaching is generally reported to affect 67% of patients. While most people tolerate this sensitivity, some find it impossible to continue treatment. The purpose of this study was to determine the safety and efficacy of an experimental, low-sensitivity bleaching agent.

METHOD AND MATERIALS

Twenty-two participants bleached for a minimum of 6 hours per night over a 2-week period. The bleaching agent used, Experimental Product E, is a 10% carbamide peroxide gel containing potassium nitrate and sodium fluoride. Evaluations were performed at baseline and 1,2,13, and 26 weeks. Color change was measured using a value-ordered Vita classic shade guide and a colorimeter. Sensitivity of the teeth, gingiva, tongue, and/or throat was measured daily using a patient log.

RESULTS

The median color change after 2 weeks was eight tabs. Approximately 36% reported sensitivity during the active whitening phase of the study. As a group, participants reported sensitivity during 13.7% of the total days spent whitening.

CONCLUSION

Experimental Product E was shown to be safe. Participants experienced minor sensitivity during the active bleaching phase only. Experimental Product E was shown to be an effective bleaching agent for the subjects tested in this study.

Technique on restoring sub-gingival cervical lesion

This article outlines an atraumatic isolation approach and a conservative instrumentation sequence, followed by use of a highly viscous, rapid-setting, capsulated glass ionomer cement to manage a difficult deep proximal-cervical Class V lesion.

Application of rapid prototyping to operative dentistry curriculum

Computers are becoming an integral part of dental education and dental practice. Rapid prototyping is a technique for the production of solid objects from computer models. The variety of rapid prototyping devices and materials that can be processed is increasing all the time. In this article, the authors present a discriminative learning device and associated exercises for developing visual recognition skills and examine the potential for the application of rapid prototyping to the operative dentistry curriculum. Other rapid prototyping technologies as applied in dentistry are also discussed.

Occluding effect of dentifrices on dentinal tubules

OBJECTIVES

The objective of this study was to evaluate the tubule occluding ability of three commercial available dentifrices (Sensodyne, Emoform and Sorriso) by Scanning Electron Microscopy.

METHODS

Fifty cervical areas from buccal and lingual surfaces of sound third human molars were used. Cervical enamel was wet abraded to expose flat dentin surfaces and further polished with diamond pastes. Specimens were randomly divided into five groups (n=10): G1-no brushing; G2-brushing without dentifrice; G3-brushing with Sensodyne; G4-brushing with Emoform; G5-brushing with Sorriso. Brushed specimens were treated for 4 min per day, for 7 days in a toothbrushing machine. Specimens were prepared and observed under SEM for calculation of the percentage of occluded tubules. In addition, slurries of toothpastes were analyzed by X-ray microanalysis. Data were statistically analyzed by ANOVA and Tukey test (p<0.05).

RESULTS

Means of occluded tubules in descending order were: G5-98.83+/-3.31% (a), G4-96.02+/-5.24% (a), G3-80.12+/-24.65% (a), G1-37.31+/-24.22% (b); G2-22.92+/-15.19% (b). The three tested dentifrices produced increased dentinal occlusion as compared to controls (p<0.05) but equivalent occlusion among each other. Calcium from calcium-carbonate abrasive was identified in all dentifrices.

CONCLUSIONS

Results indicated that the use of all dentifrices occluded tubules more than no brushing and brushing without dentifrices groups. Thus, the tested dentifrices seem effective for desensitization by tubule occlusion.

Antibacterial and conventional self-etching primer system: morphological evaluation of intact primary enamel

The aim of this study was to analyze the etching effect of a new dental adhesive system that uses an antibacterial and self-etching primer agent. Non-carious primary human molars were divided into three groups: 35% phosphoric acid etching (3M-ESPE), self-etching primer (Clearfil SE Bond--Kuraray) and antibacterial self-etching primer (ABF experimental system--Kuraray) for SEM evaluation of surface, resin replicas and interface. Both self-etching primers produced shallow grooves and no defined etching morphologies. Phosphoric acid produced definite etching patterns at the enamel surface.

Modified matrix adaptation for sub-gingival Class II amalgam restorations

Proper placement of the matrix and wedge is critical for the success of Class II amalgam restorations. Improper placement of matrix and wedges can result in poor contours or contacts, overhangs or weakness resulting from poorly condensed restorative material. This paper presents a technique for adaptation of a combination of matrix bands in cases where the gingival cavosurface margin extends deep sub-gingivally.

Effect of etching and airborne particle abrasion on the microstructure of different dental ceramics

STATEMENT OF PROBLEM

The ceramic composition and microstructure surface of all-ceramic restorations are important components of an effective bonding substrate. Both hydrofluoric acid etching and airborne aluminum oxide particle abrasion produce irregular surfaces necessary for micromechanical bonding. Although surface treatments of feldspathic and leucite porcelains have been studied previously, the high alumina-containing and lithium disilicate ceramics have not been fully investigated.

PURPOSE

The purpose of this study was to assess the surface topography of 6 different ceramics after treatment with either hydrofluoric acid etching or airborne aluminum oxide particle abrasion.

MATERIAL AND METHODS

Five copings each of IPS Empress, IPS Empress 2 (0.8 mm thick), Cergogold (0.7 mm thick), In-Ceram Alumina, In-Ceram Zirconia, and Procera (0.8 mm thick) were fabricated following the manufacturer's instructions. Each coping was longitudinally sectioned into 4 equal parts by a diamond disk. The resulting sections were then randomly divided into 3 groups depending on subsequent surface treatments: Group 1, specimens without additional surface treatments, as received from the laboratory (control); Group 2, specimens treated by use of airborne particle abrasion with 50-microm aluminum oxide; and Group 3, specimens treated with 10% hydrofluoric acid etching (20 seconds for IPS Empress 2; 60 seconds for IPS Empress and Cergogold; and 2 minutes for In-Ceram Alumina, In-Ceram Zirconia, and Procera).

RESULTS

Airborne particle abrasion changed the morphologic surface of IPS Empress, IPS Empress 2, and Cergogold ceramics. The surface topography of these ceramics exhibited shallow irregularities not evident in the control group. For Procera, the 50-microm aluminum oxide airborne particle abrasion produced a flattened surface. Airborne particle abrasion of In-Ceram Alumina and In-Ceram Zirconia did not change the morphologic characteristics and the same shallows pits found in the control group remained. For IPS Empress 2, 10% hydrofluoric acid etching produced elongated crystals scattered with shallow irregularities. For IPS Empress and Cergogold, the morphologic characteristic was honeycomb-like on the ceramic surface. The surface treatment of In-Ceram Alumina, In-Ceram Zirconia, and Procera did not change their superficial structure.

CONCLUSION

Hydrofluoric acid etching and airborne particle abrasion with 50-microm aluminum oxide increased the irregularities on the surface of IPS Empress, IPS Empress 2, and Cergogold ceramics. Similar treatment of In-Ceram Alumina, In-Ceram Zirconia, and Procera did not change their morphologic microstructure.

The effects of filling techniques and a low-viscosity composite liner on bond strength to class II cavities

OBJECTIVE

The aim of this study was to test the hypothesis that the effects of filling technique, cavity configuration and use of a low-viscosity composite liner influence resin bond strength to the dentin of class II cavities gingival floor; and analyze the failure modes of fractured specimens.

METHODS

Standardized class II cavities were prepared in the proximal surfaces of freshly extracted third molars, which were randomly assigned to 10 experimental groups. All prepared surfaces were acid-etched, bonded with Single Bond adhesive system and restored with TPH composite, according to each technique: G1 and G2-horizontal layering, G3 and G4-faciolingual layering, G5 and G6-oblique layering, G7 and G8-bulk filling, G9 and G10-control (flat dentin surfaces). Groups were tested, with or without a low-viscosity composite liner (Tetric Flow Chroma). After storage in water for 24h, teeth were vertically serially sectioned to yield a series of 0.8mm thick slabs. Each slab was trimmed into an hourglass shape of approximately 0.8mm(2) area at the gingival resin-dentin interface. Specimens were tested in tension at 0.5mm/min until failure. Fractured specimens were analyzed in an SEM to determine the failure modes.

RESULTS

No significant difference was found between groups restored with and without a low-viscosity composite liner (p>0.05). Among filling techniques, the bulk filling groups presented the lowest bond strength values (p<0.05), while incremental filling groups did not differ from control (flat dentin surfaces). Failure modes varied significantly among groups restored with and without the low-viscosity composite liner.

SIGNIFICANCE

Bond strengths were not improved when a low-viscosity composite liner was applied, but it remarkably influenced the failure modes. Incremental techniques improved bond strength.

Technique for repair of multiple abutment teeth under preexisting crowns

This technique describes a simple procedure for repairing multiple fractured or broken-down abutment teeth under existing crowns. The technique uses a Teflon tape polytetrafluoroethylene (PTFE) as a matrix and separating medium for fabrication of an autopolymerizing composite core material with digital pressure. This technique enables the dentist to solve an emergency clinical situation in a relatively short amount of time, pending further restoration with endodontic treatment and a cast post and core procedure.

Case report of a 40-year, five surface complex amalgam restoration

Reports of longevity for multi-surface amalgam restoration have been limited. This paper reports a case where a five-surface complex amalgam restoration has been followed and documented for 40 years. The pictorial series will help to identify some of the factors a dentist should consider before replacing the restoration.