Degree of conversion of nano-hybrid resin-based composites with novel and conventional matrix formulation

Objectives

This study aimed to determine the degree of conversion (DC) of two nano-hybrid resin-based composites (RBCs) with novel monomer composition based on dimer acid derivates (hydrogenated dimer acid) and tricyclodecane–urethane structure compared to three nano-hybrid materials containing conventional matrices. DC was evaluated at 0.1, 2, and 6 mm depth at varying irradiation times (10, 20, and 40 s) and layering techniques (bulk and incremental).

Materials and methods

DC was measured in real time by a Fourier transform infrared spectroscopy (FTIR) spectrometer with attenuated total reflectance accessory. The FTIR spectra were recorded on the bottom of the samples in real time for 5 min from photoinitiation. Results were compared using one- and multiple-way ANOVA, Tukey's HSD post hoc test (α?=?0.05), and partial eta-squared statistic.

Results

After 5 min of measurement, DC showed no significant difference by varying cure time for specimens of 0.1 mm thickness. At 2 mm depth, the DC significantly increased after a cure time of 20 s compared to 10 s, remaining equal after 40 s of irradiation. At 6 mm depth, bulk curing showed significantly lower DC compared to incremental curing for all polymerization times. Specimen geometry revealed a strong effect on DC (η ²?=?0.90) followed by curing time (η ²?=?0.39).

Conclusions

The RBCs containing the dimer acid and tricyclodecane–urethane structure showed a relatively low decrease of DC with increasing incremental thickness compared to the conventionally formulated materials. The former reached the highest DC among the tested materials.

Clinical relevance

For the tested RBCs, increments of 2 mm and irradiation time of at least 20 s may be recommended for clinical practice. The two materials containing novel monomer composition might be applied for enlarged increments because of the low decrease of DC they demonstrated for 6-mm increments.     

In vitro fracture load of monolithic lithium disilicate ceramic molar crowns with different wall thicknesses

Objectives

The objective of this in vitro study was to assess the effect of wall thickness on the fracture loads of monolithic lithium disilicate molar crowns.

Material and methods

Forty-eight extracted molars were prepared by use of a standardized preparation design. Lithium disilicate crowns (e.max CAD, Ivoclar/Vivadent, Schaan, Liechtenstein) of different wall thicknesses (d?=?0.5, 1.0, and 1.5 mm; n?=?16 for each series) were then constructed and milled (Cerec MC-XL, Sirona, Bensheim, Germany). After placement of the teeth in acrylic blocks (Technovit, Heraeus Kulzer, Hanau, Germany), the crowns were adhesively luted (Multilink, Ivoclar Vivadent). In each series, eight crowns were loaded without artificial aging whereas another eight crowns underwent thermocycling (10,000 cycles, THE-1100, SD Mechatronik) and chewing simulation (1.2 million cycles, Willytec CS3, SD Mechatronik, F _max?=?108 N). All specimens were loaded until fracture on one cusp with a tilt of 30° to the tooth axis in a universal testing machine (Z005, Zwick/Roell). Statistical assessment was performed by use of SPSS 19.0.

Results

Crowns with d?=?1.0 and 1.5 mm wall thickness did not crack during artificial aging whereas two of the crowns with d?=?0.5 mm wall thickness did. The loads to failure (F _u) of the crowns without aging (with aging) were 470.2?±?80.3 N (369.2?±?117.8 N) for d?=?0.5 mm, 801.4?±?123.1 N (889.1?±?154.6 N) for d?=?1.0 mm, and 1107.6?±?131.3 N (980.8?±?115.3 N) for d?=?1.5 mm. For aged crowns with d?=?0.5 mm wall thickness, load to failure was significantly lower than for the others. However, differences between crowns with d?=?1.0 mm and d?=?1.5 mm wall thickness were not significant.

Conclusions

Fracture loads for posterior lithium disilicate crowns with 0.5 mm wall thickness were too low (F _u?<?500 N) to guarantee a low complication rate in vivo, whereas all crowns with 1.0 and 1.5 mm wall thicknesses showed appropriate fracture resistances F _u?>?600 N.

Clinical relevance

The wall thickness of posterior lithium disilicate crowns might be reduced to 1 mm, thus reducing the invasiveness of the preparation, which is essential for young patients.     

Effect of radical amplified photopolymerization (RAP) in resin-based composites

Objective

The objective of this study was to evaluate the effect of irradiation time and specimens thickness on the polymerization kinetic and variation in micro-mechanical properties of two commercial resin-based composites (RBCs) based on radical amplified photopolymerization (RAP) technology?, and to compare them with four camphorquinone (CQ)/amine-based RBCs.

Materials and methods

The materials were analysed by assessing the polymerization kinetic and the degree of cure (DC) at 0.1 mm and 2 mm depth during 5 minutes after photoinitiation, after curing for 10 s, 20 s and 40 s (Elipar Freelight2). The variation in micro-mechanical properties (Vickers hardness (HV), indentation modulus (E), and depth of cure (DOC)) was assessed in 100 μm steps on 6-mm-high specimens irradiated as above and stored in the water for 24 h at 37 °C.

Results

The results were statistically compared using one-way ANOVA with Tukey HSD post hoc test (α?=?0.05) and a general linear model. The parameter material exerted the strongest effect on DC (partial eta-squared η _p ²?=?0.83), followed by irradiation time (η _p ²?=?0.27), and depth (η _p ²?=?0.09). The polymerization kinetic, well described by an exponential sum function, showed in all materials a faster decrease in carbon–carbon double bonds at 0.1 mm than at 2 mm depth. The materials based on RAP achieved the highest DC values and a faster polymerization at both depths. The irradiation time exerted the strongest effect on the mechanical properties (DOC, η _p ²?=?0.96; HV, η _p ²?=?0.89; E, η _p ²?=?0.86), followed by depth (HV, η _p ²?=?0.63; E, η _p ²?=?0.54) and material (HV, η _p ²?=?0.40; E, η _p ²?=?0.67). At the most favorable curing conditions (40 s, surface), the mechanical properties of the analyzed materials varied between 11.38 (0.80) GPa in Estelite® Sigma Quick and 20.80 (1.42) GPa in Estelite® Posterior for E, and between 74.33 (3.56)?N/mm² in Tetric EvoCeram® and 120.71 (6.24)?N/mm² in Estelite® Posterior for HV.

Conclusions

RAP-initiated material demonstrated a higher increase in DOC with prolonged irradiation time than the analyzed CQ/amine based materials.

Clinical relevance

An irradiation time of 20 s is also recommended for RAP-initiated RBCs.     

Light curing through glass ceramics with a second- and a third-generation LED curing unit: effect of curing mode on the degree of conversion of dual-curing resin cements

Objectives

The aim of this study was to measure the degree of conversion (DC) of five dual-curing resin cements after different curing modes with a second- and a third-generation light-emitting diode (LED) curing unit. Additionally, irradiance of both light curing units was measured at increasing distances and through discs of two glass ceramics for computer-aided design/manufacturing (CAD/CAM).

Materials and methods

Irradiance and spectra of the Elipar FreeLight 2 (Standard Mode (SM)) and of the VALO light curing unit (High Power Mode (HPM) and Xtra Power Mode (XPM)) were measured with a MARC radiometer. Irradiance was measured at increasing distances (control) and through discs (1.5 to 6 mm thickness) of IPS Empress CAD and IPS e.max CAD. DC of Panavia F2.0, RelyX Unicem 2 Automix, SpeedCEM, BisCem, and BeautiCem SA was measured with an attenuated total reflectance–Fourier transform infrared spectrometer when self-cured (negative control) or light cured in SM for 40 s, HPM for 32 s, or XPM for 18 s. Light curing was performed directly (positive control) or through discs of either 1.5- or 3-mm thickness of IPS Empress CAD or IPS e.max CAD. DC was analysed with Kruskal–Wallis tests followed by pairwise Wilcoxon rank sum tests (α?=?0.05).

Results

Maximum irradiances were 1,545 mW/cm² (SM), 2,179 mW/cm² (HPM), and 4,156 mW/cm² (XPM), and all irradiances decreased by >80 % through discs of 1.5 mm, ≥95 % through 3 mm, and up to >99 % through 6 mm. Generally, self-curing resulted in the lowest DC. For some cements, direct light curing did not result in higher DC compared to when light cured through ceramic discs. For other cements, light curing through ceramic discs of 3 mm generally reduced DC.

Conclusions

Light curing was favourable for dual-curing cements. Some cements were more susceptible to variations in curing mode than others.

Clinical relevance

When light curing a given cement, the higher irradiances of the third-generation LED curing unit resulted in similar DC compared to the second-generation one, though at shorter light curing times.     

Herpes simplex virus reactivation and dental procedures

Objectives

Dental extraction is reported to trigger recurrent herpes labialis (RHL).

Aim

This aims to prospectively study the clinical occurrence of RHL and the oral herpes simplex virus type 1 (HSV-1) viral shedding before and 3 days after different dental procedures.

Materials and methods

Oral HSV-1 DNA was measured by real-time PCR before and 3 days after dental procedures of the inferior dentition in 57 immunocompetent patients (mean age 32.4 years) who were selected and divided into four distinct subgroups (dental inspection without anesthesia, n?=?19; dental filling under local anesthesia, n?=?14; molar extraction under local anesthesia, n?=?15; and molar extraction under general anesthesia, n?=?9) and compared to 32 healthy controls (mean age 33 years).

Results

None of the patients suffered from RHL at day 3. Oral HSV-1 DNA was detected before and after procedure in 1.7 % (1/57) and 5.3 % (3/57), respectively [dental inspection without anesthesia, 5.3 % (1/19); molar extraction under local anesthesia, 6.7 % (1/15); and molar extraction under general anesthesia, 11 % (1/9)]. None of the controls presented RHL or detectable oral HSV-1 DNA. There was no statistically significant difference between the study groups and controls.

Conclusion

Molar extraction increases the risk of oral HSV-1 shedding but not of RHL. Procedure-related nerve damage probably accounts for HSV reactivation.

Clinical relevance

Antiviral prophylaxis for RHL is not routinely recommended for dental procedures, regardless of a prior history of RHL.     

Clinical results of lithium-disilicate crowns after up to 9 years of service

Objectives

The purpose of this prospective study was to evaluate the clinical outcome of anterior and posterior crowns made of a lithium-disilicate glass–ceramic framework material (IPS e.max Press, Ivoclar Vivadent).

Materials and methods

A total of 104 single crowns were placed in 41 patients (mean age, 34?±?9.6 years; 15 male, 26 female). Eighty-two anterior and 22 posterior crowns were inserted. All teeth received a 1-mm-wide chamfer or rounded shoulder preparation with an occlusal/incisal reduction of 1.5–2.0 mm. The minimum framework thickness was 0.8 mm. Frameworks were laminated by a prototype of a veneering material combined with an experimental glaze. Considering the individual abutment preconditions, the examined crowns were either adhesively luted (69.2 %) or inserted with glass–ionomer cement (30.8 %). Follow-up appointments were performed 6 months after insertion, then annually. Replacement of a restoration was defined as failure.

Results

Four patients (10 crowns) were defined as dropouts. For the remaining 94 crowns, the mean observation time was 79.5 months (range, 34–109.7 months). The cumulative survival rate according to Kaplan–Meier was 97.4 % after 5 years and 94.8 % after 8 years. Applying log rank test, it was shown that the location of the crown did not significantly have an impact on the survival rate (p?=?0.74) and that the cementation mode did not significantly influence the occurrence of complications (p?=?0.17).

Conclusions

The application of lithium-disilicate framework material for single crowns seems to be a reliable treatment option.

Clinical relevance

Crowns made of a lithium-disilicate framework material can be used clinically in the anterior and posterior region irrespective of an adhesive or conventional cementation when considering abutment preconditions.     

Effect of seating forces on cement–ceramic adhesion in microtensile bond tests

Objectives

The aim of this study was to evaluate the effect of different seating forces during cementation in cement–ceramic microtensile bond strength (μTBS).

Materials and methods

Forty-five blocks (5?×?5?×?4 mm³) of a glass-infiltrated alumina-based ceramic (In-Ceram Alumina) were fabricated according to the manufacturer’s instructions and duplicated in resin composite. Ceramic surfaces were polished, cleaned for 10 min in an ultrasonic bath, silica coated using a laboratory type of air abrasion device, and silanized. Each treated ceramic block was then randomly assigned to five groups (n?=?9) and cemented to a composite block under five seating forces (10 g, 50 g, 100 g, 500 g, and 750 g) using a dual-cured resin cement (Panavia F). The ceramic–cement–composite assemblies were cut under coolant water to obtain bar specimens (1 mm?×?0.8 mm²). The μTBS tests were performed in a universal testing machine (1 mm/min). The mean bond strengths values were statistically analyzed using one-way ANOVA (α?≤?0.05).

Results

Different seating forces resulted in no significant difference in the μTBS results ranging between 13.1?±?4.7 and 18.8?±?2.1 MPa (p?=?0.13) and no significant differences among cement thickness.

Conclusions

Excessive seating forces during cementation seem not to affect the μTBS results.

Clinical relevance

Excessive forces during the seating of single all-ceramic restorations cementation seem to display the same tensile bond strength to the resin cement.     

Effect of fluoride gels supplemented with sodium trimetaphosphate in reducing demineralization

Objectives

The objective of this study was to evaluate the in vitro effect of low-fluoride (F) gels supplemented with sodium trimetaphosphate (TMP) on enamel demineralization.

Materials and methods

Bovine enamel blocks (n?=?160) were selected based on surface hardness (SH) and divided into eight treatment groups (n?=?20 per group): no F or TMP (placebo), 3 % TMP (3 %TMP), 5 % TMP (5 %TMP), 4,500 μg F/g (4,500), 4,500 μg F/g?+?3 % TMP (4,500 3 %TMP), 4,500 μg F/g?+?5 % TMP (4,500 5 %TMP), 9,000 μg F/g (9,000), and 12,300 μg F/g (acid gel). Blocks were subjected to demineralization/remineralization cycling for 5 days. Subsequently, surface hardness (SH₁) and integrated loss of subsurface hardness (ΔKHN) were assessed, and the concentrations of loosely bound (CaF₂-like) and firmly bound (FA-like) formed and retained F were determined.

Results

The 4,500 5 %TMP and acid gel groups showed similar results and had the lowest mineral loss (SH₁ and ?KHN). The acid gel group had the highest concentration of CaF₂-like F, but the formation and retention of FA-like F was greater in the 4,500 5 %TMP group than in the acid gel group (p?<?0.05).

Conclusion

It is possible to inhibit enamel demineralization with low-F gels supplementing these gels with 5 % TMP.

Clinical relevance

The low-F gel containing TMP can be regarded as a safer alternative for clinical use from a toxicological point of view since it contains half of the amount of a conventional formulation while promoting similar anticaries effect.     

Light transmittance and micro-mechanical properties of bulk fill vs. conventional resin based composites

Objectives

The aim of this study was to quantify the blue light that passes through different incremental thicknesses of bulk fill in comparison to conventional resin-based composites (RBCs) and to relate it to the induced mechanical properties.

Materials and methods

Seven bulk fill, five nanohybrid and two flowable RBCs were analysed. Specimens (n?=?5) of three incremental thicknesses (2, 4 and 6 mm) were cured from the top for 20 s, while at the bottom, a spectrometer monitored in real time the transmitted irradiance. Micro-mechanical properties (Vickers hardness, HV, and indentation modulus, E) were measured at the top and bottom after 24 h of storage in distilled water at 37 °C. Electron microscope images were taken for assessing the filler distribution and size.

Results

Bulk fill RBCs (except SonicFill) were more translucent than conventional RBCs. Low-viscosity bulk fill materials showed the lowest mechanical properties. HV depends highly on the following parameters: material (η_p ²?=?0.952), incremental thickness (0.826), filler volume (0.747), filler weight (0.746) and transmitted irradiance (0.491). The bottom-to-top HV ratio (HV_bt) was higher than 80 % in all materials in 2- and 4-mm increments (except for Premise), whereas in 6-mm increments, this is valid only in four bulk fill materials (Venus Bulk Fill, SDR, x-tra fil, Tetric EvoCeram Bulk Fill).

Conclusions

The depth of cure is dependent on the RBC’s translucency. Low-viscosity bulk fill RBCs have lower mechanical properties than all other types of analysed materials. All bulk fill RBCs (except SonicFill) are more translucent for blue light than conventional RBCs.

Significance

Although bulk fill RBCs are generally more translucent, the practitioner has to follow the manufacturer’s recommendations on curing technique and maximum incremental thickness.     

In vitro comparison of mechanical properties and degree of cure of bulk fill composites

Objectives

The aim of our study was to measure and compare degree of conversion (DC) as well as micro- (indentation modulus, E; Vickers hardness, HV) and macromechanical properties (flexural strength, σ; flexural modulus, E _flexural) of two recently launched bulk fill resin-based composites (RBCs): Surefil® SDR? flow (SF) and Venus® bulk fill (VB).

Materials and methods

DC (n?=?6) was investigated by Fourier transform infrared spectroscopy (FTIR) in clinical relevant filling depths (0.1, 2, and 4 mm; 6 mm bulk, 6 mm incremental) and irradiation times (10, 20, 40 s). Micro- (n?=?6) and macromechanical (n?=?20) properties were measured by an automatic microhardness indenter and a three-point bending test device after storing the specimens in distilled water for 24 h at 37°C. Furthermore, on the 6-mm bulk samples, the depth of cure was determined. A field emission scanning electron microscope was used to assess filler size. Results were evaluated using one-way analysis of variance, Tukey’s honest significance test post hoc test, a multivariate analysis (α?=?0.05) and an independent t test. Weibull analysis was used to assess σ.

Results

VB showed, in all depth, significant higher DC (VB, 62.4–67.4 %; SF, 57.1–61.9 %), but significant lower macro- (VB, E _flexural?=?3.6 GPa; σ?=?122.7 MPa; SF, E _flexural?=?5.0 GPa; σ?=?131.8 MPa) and micromechanical properties (VB, E?=?7.3–8.8 GPa, HV?=?40.7–46.5 N/mm²; SF, E?=?10.6–12.2 GPa, HV?=?55.1–61.1 N/mm²). Both RBCs showed high reliability (VB, m?=?21.6; SF, m?=?26.7) and a depth of cure of at least 6 mm at all polymerization times. The factor “RBC” showed the strongest influence on the measured properties (η ²?=?0.35–0.80) followed by “measuring depth” (η ²?=?0.10–0.46) and “polymerization time” (η ²?=?0.03–0.12).

Conclusions

Significant differences between both RBCs were found for DC, E, σ, and E _flexural at all irradiation times and measuring depths.

Clinical relevance

Curing the RBCs in 4-mm bulks for 20 s can be recommended.     

Long-term performance of posterior InCeram Alumina crowns cemented with different luting agents: a prospective,randomized clinical split-mouth study over 5 years

Objectives

This prospective, randomized clinical split-mouth study investigated the 5-year performance of InCeram Alumina posterior crowns cemented with three different luting cements. 4-META- and MDP-based cements were used for adhesive luting. Glass ionomer cement served as control.

Materials and Methods

Sixty patients were treated with 149 (n?=?62 Panavia F/MDP; n?=?59 SuperBond-C&B/4-META; n?=?28 Ketac Cem/glass ionomer) InCeram Alumina crowns on vital molars and premolars in a comparable position. Follow-up examinations were performed annually up to 5 years after crown placement using the modified United States Public Health Service (USPHS) criteria. Kaplan–Meier survival analysis comprised secondary caries, clinically unacceptable fractures, root canal treatment and debonding. Kaplan–Meier success rate included restorations with minimal crevices, tolerable color deviations (<1 Vitashade), and clinically acceptable fractures. Logistic regression models with a random intercept were fitted.

Results

The 5-year Kaplan–Meier survival probabilities were: SuperBond-C&B 88.7 %, Panavia F 82.8 %, Ketac Cem 80.1 % with no significant difference (p?=?.813). Endodontical treatment was carried out on 7.4 % of all abutment teeth, and 5.4 % revealed secondary caries. Unacceptable ceramic fractures were observed in 7.4 %. Debonding was a rare complication (1.3 %). The 5 year Kaplan–Meier success rate was 91.6 % for SuperBond-C&B-, 87.4 % for Ketac Cem- and 86.3 % for Panavia F-bonded restorations with no significant difference (p?=?.624). All cement types showed significant marginal deterioration over time (p?<?.0001).

Conclusions

Posterior InCeram Alumina crowns showed acceptable long-term survival and success rates independent of luting agent used. Ceramic fractures, endodontical treatments and secondary caries were the most frequent failures.

Clinical relevance

Glass-infiltrated Alumina crowns in combination with adhesive as well as conventional cementation can be considered as a reliable treatment option in posterior teeth.     

Efficacy and cytotoxicity of a bleaching gel after short application times on dental enamel

Objectives

This study aimed to evaluate and correlate the efficacy and cytotoxicity of a 35 % hydrogen peroxide (HP) bleaching gel after different application times on dental enamel.

Materials and methods

Enamel/dentin disks in artificial pulp chambers were placed in wells containing culture medium. The following groups were formed: G1, control (no bleaching); G2 and G3, three or one 15-min bleaching applications, respectively; and G4 and G5, three or one 5-min bleaching applications, respectively. Extracts (culture medium with bleaching gel components) were applied for 60 min on cultured odontoblast-like MDPC-23 cells. Cell metabolism (methyl tetrazolium assay) (Kruskal–Wallis/Mann–Whitney; α?=?5 %) and cell morphology (scanning electron microscopy) were analyzed immediately after the bleaching procedures and the trans-enamel and trans-dentinal HP diffusion quantified (one-way analysis of variance/Tukey’s test; α?=?5 %). The alkaline phosphatase (ALP) activity was evaluated 24 h after the contact time of the extracts with the cells (Kruskal–Wallis/Mann–Whitney; α?=?5 %). Tooth color was analyzed before and 24 h after bleaching using a spectrophotometer according to the Commission Internationale de l’Eclairage L*a*b* system (Kruskal–Wallis/Mann–Whitney; α?=?0.05).

Results

Significant difference (p?<?0.05) in cell metabolism occurred only between G1 (control, 100 %) and G2 (60.6 %). A significant decrease (p?<?0.05) in ALP activity was observed between G2, G3, and G4 in comparison with G1. Alterations on cell morphology were observed in all bleached groups. The highest values of HP diffusion and color alterations were observed for G2, with significant difference among all experimental groups (p?<?0.05). G3 and G4 presented intermediate color change and HP diffusion values with no statistically significant differences between them (p?>?0.05). The lowest amount of HP diffusion was observed in G5 (p?<?0.05), which also exhibited no significant color alteration compared to the control group (p?>?0.05).

Conclusions

HP diffusion through dental tissues and its cytotoxic effects were proportional to the contact time of the bleaching gel with enamel. However, shorter bleaching times reduced bleaching efficacy.

Clinical relevance

Shortening the in-office tooth bleaching time could be an alternative to minimize the cytotoxic effects of this clinical procedure to pulp tissue. However, the reduced time of bleaching agent application on enamel may not provide adequate esthetic outcome.     

Clinical longevity of ceramic laminate veneers bonded to teeth with and without existing composite restorations up to 40 months

Objectives

This study evaluated the survival rate of ceramic laminate veneers bonded to teeth with and without existing composite restorations (ECR).

Materials and methods

Twenty patients (mean age: 49.7 years) received 92 feldspathic ceramic laminate veneers (Shofu Vintage AL) on the maxillary teeth (intact teeth: n?=?26; teeth with ECR: n?=?66). Preparations with incisal overlap were made, and ECR of good quality were not removed but conditioned using silica coating (CoJet) and silanization (ESPE-Sil). Enamel and dentin were etched with 38 % H₃PO₄ for 15–30 s and rinsed 30 s; adhesive resin (Excite) was applied, and laminate veneers were then cemented (Variolink Veneer). Restorations were evaluated at baseline and thereafter every 6 months using modified United States Public Health Service criteria.

Results

Mean observation period was 21.6 months. Overall, five absolute failures were encountered (fractures: n?=?3; chipping: n?=?1; debonding: n?=?1), resulting in a survival rate of 94.6 % (Kaplan–Meier). Survival rates of the laminates bonded to teeth without (96 %) and with ECR (93.5 %) did not show significant differences (p?>?0.05). Slight marginal defects (16 of 87 laminates) and slight marginal discoloration at the margins were noted (12 of 87 laminates) until the final recall. Secondary caries and endodontic complications were not detected in any of the teeth.

Conclusion

The clinical survival of ceramic laminate veneers up to 40 months was not significantly influenced when they were bonded onto intact teeth or onto teeth with ECR.

Clinical relevance

When no caries is present, it may not be necessary to replace existing composite restorations prior to cementation of ceramic laminate veneers.     

Randomized clinical evaluation of a light-cured base material for complete dentures

Objectives

The purpose of this study was to compare plaque adhesion, tissue reaction, and technical complications for complete dentures based on visible light-cured resin (VLCR) or on conventional poly(methyl methacrylate) (PMMA).

Materials and methods

A stratified randomized cohort study was designed with 52 patients treated with a complete denture in the maxilla (n?=?28), the mandible (n?=?2), or both (n?=?22). Seventy-four dentures were manufactured, 38 of PMMA and 36 of VLCR. Investigators and patients were unaware of the nature of the denture base material. Plaque adhesion, tissue reaction, and technical complications were investigated 4 weeks after denture insertion (baseline). Recall investigations were performed after 6, 12, and 24 months.

Results

After 6, 12, and 24 months, plaque adhesion was significantly higher for VLCR dentures than for PMMA dentures. Tissue reaction was comparable for both groups, however. After 6, 12, and 24 months, need for repair was significantly greater for VLCR prostheses. The mean number of additional aftercare sessions per patient after 24 months was 50 % higher for VLCR than for PMMA.

Conclusions

Good oral hygiene must be established by patients treated with VLCR dentures, to remove biofilm from these dentures. Increased aftercare must also be taken into account when this material is used.

Clinical relevance

VLCR might be a viable alternative to PMMA for patients with allergic reactions to residual monomer or benzoyl peroxide.     

Characterization of maxillary central incisor: novel crown–root relationships

Objectives

The periodontal biotype includes crown features of the maxillary central incisor (MCI), whereas root measures have been less studied. The aim of our study was to morphologically characterize MCI and search relationships between crown and root measures.

Material and methods

One hundred-fifty MCIs were used. On each tooth, several crown and root reference points were marked and the following measures were done: On crown: mesio-distal (MD?=?major, md?=?minor), axial (crown length, cervical convexity) and buccolingual diameters (Cbl); On root: mesio-distal (Rmd) and buccolingual diameters (Rbl); and tooth length. A ratio between md and MD was made in order to assess dental forms. Root diameter prediction was assessed by means of multiple and single linear regression analyses, with variable selection by backward method. Reliability of measurements was estimated by the Pearson correlation coefficient.

Results

Dental form groups were: Stout type 56.67 %, Intermediate type 22.67 %, and Strangled type 20.67 %. A significative association was found between Rbl and Cbl (p?=?0,000), Rmd with md (p?=?0.000), and Rmd with MD (p?=?0.000). The results allow predicting root diameters through crown measures.

Conclusions

There is a direct relationship between crown and root features, which allows the prediction of root diameters with a high accuracy (95 %), regardless of tooth form.

Clinical relevance

The morphometric data assess tooth diameters more accurately and could improve treatment planning, offering a more comprehensive approach to the periodontal biotype concept.     

Vomer flap for hard palate repair is related to favorable maxillary growth in unilateral cleft lip and palate

Objective

Vomer flap repair is assumed to improve maxillary growth because of reduced scarring in growth-sensitive areas of the palate. Our aim was to evaluate whether facial growth in patients with unilateral cleft lip and palate was significantly affected by the technique of hard palate repair (vomer flap versus two-flap).

Materials and methods

For this retrospective longitudinal study, we analyzed 334 cephalometric radiographs from 95 patients with nonsyndromic complete unilateral cleft lip and palate who underwent hard palate repair by two different techniques (vomer flap versus two-flap). Clinical notes were reviewed to record treatment histories. Cephalometry was used to determine facial morphology and growth rate. The associations among facial morphology at age 20, facial growth rate, and technique of hard palate repair were assessed using generalized estimating equation analysis.

Results

The hard palate repair technique significantly influenced protrusion of the maxilla (SNA: β?=??3.5°, 95 % CI?=??5.2-1.7; p?=?0.001) and the anteroposterior jaw relation (ANB: β?=??4.2°, 95 % CI?=??6.4-1.9; p?=?0.001; Wits: β?=??5.7 mm, 95 % CI?=??9.6-1.2; p?=?0.01) at age 20, and their growth rates (SNA p?=?0.001, ANB p?<?0.01, and Wits p?=?0.02).

Conclusions

The results suggest that in patients with unilateral cleft lip and palate, vomer flap repair has a smaller adverse effect than two-flap on growth of the maxilla. This effect on maxillary growth is on the anteroposterior development of the alveolar maxilla and is progressive with age. We now perform hard palate closure with vomer flap followed by soft palate closure using Furlow palatoplasty.

Clinical relevance

These findings may improve treatment outcome by modifying the treatment protocol for patients with unilateral cleft lip and palate.     

Fluoride release and mechanical properties after 1-year water storage of recent restorative glass ionomer cements

Objectives

The objective of this study was to evaluate the relationships between fluoride release and mechanical properties after 1-year water storage of five recent restorative glass ionomer cements (GICs).

Materials and methods

Five GICs, FujiIX GP EXTRA (FEX), FujiIX GP (FIX), GlasIonomer FX-II (GFX), Ketac Molar Easymix (KME), and Riva Self Cure (RSC), were examined. Cumulative fluoride release, compressive strength, and surface hardness were measured up to 1-year storage (n?=?5), and analyzed with one-way or two-way ANOVA and Tukey HSD test (α?=?0.05). Elemental compositions before and after 1-year storage were also examined (n?=?3).

Results

The amounts of fluoride release were significantly different among the products. The highest amount of fluoride release occurred during the first day. Then, the amount of fluoride release rapidly decreased and still continued until 1-year storage. Compressive strengths indicated that two main factors were significant (GFX?<?FEX?=?RSC?<?FIX?<?KME; 1 day?<?1 week?=?1 month?=?3 months?=?6 months?=?1 year), but surface hardness showed a slightly different tendency (GFX?=?RSC?<?FEX?=?FIX?=?KME; 1 year?<?1 day?<?1 week?=?1 month?=?3 months?=?6 months). Significant correlation was found between decrease of silicon and decrease rate of the surface hardness.

Conclusions

Fluoride releases were detected up to 1-year storage, but the mechanical properties slightly decreased due to decrease of Si after 1-year storage. Elution of Si instead of fluoride release was considered more critical to deteriorate the mechanical properties of GICs.

Clinical relevance

Fluoride released for 1-year water storage will contribute to secondary caries prevention. The amount of fluoride release did not affect these mechanical properties. These results indicate the usefulness of these GICs.     

Changes in mastication after an immediate loading implantation with complete fixed rehabilitation

Objective

This study aimed to measure modifications of mastication after immediate loading full-arch prosthesis (ILFAP) rehabilitation.

Materials and method

Fourteen patients were observed before and 6 months after ILFAP rehabilitation when masticating two natural, standardized foods (peanut and carrot) and three model foods with increasing hardness. The granulometry of the expectorated boluses from carrot and peanuts was characterized by median particle size (D50), determined at the natural point of swallowing. Chewing time (CT), number of chewing cycles (CC), and chewing frequency (CF) were video recorded. A self-assessment questionnaire for oral health-related quality of life [Geriatric Oral Health Assessment Index (GOHAI)] was also used.

Results

After ILFAP rehabilitation, the mean D50 values for carrot and peanuts were smaller [Repeated Model Procedures (RMP), F?=?41, p?<?0.001]. Mean CT and CC values recorded with the three model foods decreased, while CF increased regardless of the model food hardness (RMP, F?=?14, F?=?10, and F?=?11, respectively, p?<?0.001). The GOHAI score increased from 43?±?9 to 56?±?3 (t test, p?<?0.001).

Conclusion

ILFAP rehabilitation improves the ability to reduce the bolus particle size and the ability to discriminate between different food hardnesses in the 6 months post-surgery period.

Clinical relevance

This study encourages the clinical development of immediate loading implantation with a fixed full-arch prosthesis protocol.     

Dentofacial characteristics of patients with rheumatoid arthritis

Objectives

The aims of this study are to evaluate the dentofacial morphology of patients with rheumatoid arthritis (RA) and to compare the morphological data with those of healthy age- and sex-matched control subjects.

Methods

Twenty-seven RA patients (mean age, 45.77?±?8.64 years) and 25 healthy subjects (mean age, 44.80?±?8.24 years) participated in this prospective study. Clinical and functional evaluations of the RA patients were assessed. The erythrocyte sedimentation rate, C-reactive protein level, rheumatoid factor level, and anti-citrullinated peptide antibodies (ACPA) titers of RA patients were determined, and DAS28 scores were calculated. Linear and angular measurements were performed on cephalometric tracings and condylar erosion was evaluated on lateral panoramic radiographs. Statistical comparison of the two groups was performed with an independent samples t test. Pearson correlation analysis was used to assess the relationship between the clinical and laboratory parameters.

Results

Based on DAS28 scores, no patient with RA was in the remission period, 3 patients had low, 23 had medium, and 1 had high disease activity. Sixteen (59.26 %) patients with RA had positive ACPA titers. Lateral cephalometric radiographs revealed statistically significant difference between the two groups for the measurement of U1–NA (millimeter; p?=?0.047), U1–NA (degrees; p?=?0.031), L1–NB (degrees; p?=?0.030), IMPA (L1–MP; p?=?0.001), interincisal angle (U1–L1; degrees; p?=?0.022) and midface length (Co–A; millimeter; p?=?0.033). A significant positive linear correlation was found between disease duration time and DAS28 scores (r?=?0.066, p?=?0.040).

Conclusions

Dentoalveolar effects of RA on dentofacial morphology are more significant than the skeletal effects. Future studies with larger sample sizes are required to evaluate the exact effects of RA on dentofacial morphology.

Clinical relevance

Clinicians should consider the fact that RA-associated dentoalveolar changes can be observed and may affect the orthodontic treatment process.     

Salivary levels of mutans streptococci and Lactobacilli among Palestinian school children in East Jerusalem

Objectives

The aim of the present study was to investigate the distribution of oral cariogenic bacteria among 12-year-old Palestinian children attending schools in East Jerusalem.

Materials and methods

Salivary levels of mutans streptococci (MS) and Lactobacilli (LB) were examined by semi-quantitative commercial kits and then correlated to social–demographic parameters.

Results

Overall, 52.1 % of the examined children presented the highest possible ranking score categories for MS bacteria, with only 5.4 % in the lowest category. Only 12.6 % of the school children presented the highest LB score, while 25 % had the lowest ranking score. Salivary MS levels in children attending private schools were lower than those of children in government schools and United Nations Relief and Works Agency (UNRWA) schools. Conversely, levels of LB were lowest in children attending UNRWA schools compared to government and private schools. Girls had significantly higher amounts of MS and LB than boys (p?=?0.001). Lower MS levels were significantly related to the following socioeconomic variables: higher father’s education level (p?=?0.037), higher mother’s education level (p?=?0.063), mother’s employment status (p?=?0.012), and lower home density (p?=?0.001). For LB, the only significant socioeconomic variable was higher father’s employment level, which was related to lower LB level (p?=?0.025).

Conclusions

Levels of MS and LB were found to be strongly related with socioeconomic status among Palestinian children in East Jerusalem. The relatively high prevalence of cariogenic bacteria suggests that oral care prevention and treatment demands special attention from the health care institutions and authorities.