Effects of xylitol mouthrinse on Streptococcus mutans

Objectives

This study aimed to measure the effect of xylitol mouthrinse on salivary Streptococcus mutans counts.

Methods

Subjects in the study group (n = 25) used xylitol mouthrinse for 4 weeks, while another group (n = 25) used saccharine mouthrinse. S. mutans were measured before and after intervention.

Results

At the baseline the mean S. mutans scores were 3.9 (SE = 0.03) and 3.9 (0.04) for the xylitol group and control group respectively, while the scores were 2.8 (0.13) and 3.9 (0.07) after the intervention. Significant reductions (p < 0.01) in the scores of S. mutans were found after the four week use of xylitol mouthrinse.

Conclusions

Significant reductions in the scores of S. mutans were found after the four week use of 20% xylitol mouthrinse. The bacteriostatic effect of xylitol mouthrinse on S. mutans may be comparable to other xylitol products. Further studies are needed to confirm both the short and long term effects of xylitol mouthrinse.     

Fatigue loading and R-curve behavior of a dental glass-ceramic with multiple flaw distributions

Objectives

To determine the effects of surface finish and mechanical loading on the rising toughness curve (R-curve) behavior of a fluorapatite glass-ceramic (IPS e.max ZirPress) and to determine a statistical model for fitting fatigue lifetime data with multiple flaw distributions.

Materials and methods

Rectangular beam specimens were fabricated by pressing. Two groups of specimens (n = 30) with polished (15 μm) or air abraded surface were tested under rapid monotonic loading in oil. Additional polished specimens were subjected to cyclic loading at 2 Hz (n = 44) and 10 Hz (n = 36). All fatigue tests were performed using a fully articulated four-point flexure fixture in 37 °C water. Fractography was used to determine the critical flaw size and estimate fracture toughness. To prove the presence of R-curve behavior, non-linear regression was used. Forward stepwise regression was performed to determine the effects on fracture toughness of different variables, such as initial flaw type, critical flaw size, critical flaw eccentricity, cycling frequency, peak load, and number of cycles. Fatigue lifetime data were fit to an exclusive flaw model.

Results

There was an increase in fracture toughness values with increasing critical flaw size for both loading methods (rapid monotonic loading and fatigue). The values for the fracture toughness ranged from 0.75 to 1.1 MPa m^1/2 reaching a plateau at different critical flaw sizes based on loading method.

Significance

Cyclic loading had a significant effect on the R-curve behavior. The fatigue lifetime distribution was dependent on the flaw distribution, and it fit well to an exclusive flaw model.     

Resin composites: Modulus of elasticity and marginal quality

Objective

To investigate how the modulus of elasticity of resin composites influences marginal quality in restorations submitted to thermocyclic and mechanical loading.

Methods

Charisma, Filtek Supreme XTE and Grandio were selected as they were found to possess different moduli of elasticity but quite similar polymerization contraction. MOD cavities (n = 30) were prepared in extracted premolars, restored and then subjected to thermocyclic and mechanical loading. Marginal quality of the restorations before and after loading was analyzed on epoxy replicas under a scanning electron microscope. The percentage of gap-free margins and occurrence of paramarginal fractures were registered. Modulus of elasticity and polymerization contraction were analyzed with parametric and margins with nonparametric ANOVA and post hoc Tukey HSD or Wilcoxon rank-sum tests, respectively. The number of paramarginal fractures was analyzed with exact Fisher tests (α = 0.05).

Results

Grandio demonstrated significantly more gap-free enamel margins than Charisma and Filtek Supreme XTE, before and after loading (p < 0.01), whereas there was no difference between Charisma and Filtek Supreme XTE (p > 0.05). No significant effect of resin composite (p = 0.81) on the quality of dentine margins was observed, before or after loading. Deterioration of all margins was evident after loading (p < 0.0001). More paramarginal enamel fractures were observed after loading in teeth restored with Grandio when compared to Charisma (p = 0.008).

Conclusions

The resin composite with the highest modulus of elasticity resulted in the highest number of gap-free enamel margins but with an increased incidence of paramarginal enamel fractures.

Clinical significance

The results from this study suggest that the marginal quality of restorations can be improved by the selection of a resin composite with modulus of elasticity close to that of dentine, although an increase in paramarginal enamel fractures can result as a consequence.     

Decreased bone marrow stromal cells activity involves in unilateral anterior crossbite-induced early subchondral bone loss of temporomandibular joints

Objective

Subchondral bone loss in mandibular condyles was reported to be induced by experimentally created unilateral anterior crossbite (UAC) which altered the occlusal load distribution and hereafter the temporomandibular joint (TMJ) remodelling process. However, the initial cellular responses are poorly understood. In the present study, changes in osteoblast and osteoclast activities in TMJ subchondral bone were investigated using the rats treated with UAC.

Design

Forty rats were randomly divided into UAC and control groups, and sampled at 2 weeks after the operation. Subchondral bone loss was evaluated by micro-CT. Osteoclast and osteoblast activities were analyzed by real-time PCR. The osteoblast differentiation of the locally isolated BMSCs from TMJ subchondral bone was assessed by Alizarin red staining. The migration of BMSCs was detected by transwell assays.

Results

Compared with the age-matched controls, TMJ subchondral bone loss was observed in the UAC-treated rats (p < 0.05). The osteoblast activity evaluated by real-time PCR and osteoblast number revealed by immunohistochemical staining were reduced in the TMJ subchondral bone of UAC rats (p < 0.05), and the capability of proliferation, migration and osteoblast differentiation were all decreased in the locally isolated BMSCs from the UAC group (p < 0.05).

Conclusions

The present data demonstrated an involvement of reduced BMSCs activity in the initiation of the mandibular subchondral bone loss at the early stage of installation of the aberrant prostheses.     

Fatigue and damage accumulation of veneer porcelain pressed on Y-TZP

Objectives

This study compared the reliability and fracture patterns of zirconia cores veneered with pressable porcelain submitted to either axial or off-axis sliding contact fatigue.

Methods

Forty-two Y-TZP plates (12 mm × 12 mm × 0.5 mm) veneered with pressable porcelain (12 mm × 12 mm × 1.2 mm) and adhesively luted to water aged composite resin blocks (12 mm × 12 mm × 4 mm) were stored in water at least 7 days prior to testing. Profiles for step-stress fatigue (ratio 3:2:1) were determined from single load to fracture tests (n = 3). Fatigue loading was delivered on specimen either on axial (n = 18) or off-axis 30° angulation (n = 18) to simulate posterior tooth cusp inclination creating a 0.7 mm slide. Single load and fatigue tests utilized a 6.25 mm diameter WC indenter. Specimens were inspected by means of polarized-light microscope and SEM. Use level probability Weibull curves were plotted with 2-sided 90% confidence bounds (CB) and reliability for missions of 50,000 cycles at 200 N (90% CB) were calculated.

Results

The calculated Weibull Beta was 3.34 and 2.47 for axial and off-axis groups, respectively, indicating that fatigue accelerated failure in both loading modes. The reliability data for a mission of 50,000 cycles at 200 N load with 90% CB indicates no difference between loading groups. Deep penetrating cone cracks reaching the core–veneer interface were observed in both groups. Partial cones due to the sliding component were observed along with the cone cracking for the off-axis group. No Y-TZP core fractures were observed.

Conclusions

Reliability was not significantly different between axial and off-axis mouth-motion fatigued pressed over Y-TZP cores, but incorporation of sliding resulted in more aggressive damage on the veneer.     

Impairment of nasal airway under intermittent hypoxia during growth period in rats

Objective

To clarify the influences of intermittent hypoxia (IH) on the growth and development of the midfacial area, including the nasal cavity, in growing rats.

Design

Seven-week-old male Sprague–Dawley rats were divided into two groups: the experimental group (n = 5), which was exposed to IH for 8 h during light periods at a rate of 20 cycles/h (nadir, 4% O₂ to peak, 21% O₂ with 0% CO₂), and the control group (n = 5), which was exposed to room air. After 3 weeks, the maxillofacial structures in both groups were evaluated with respect to the height, width, length, surface area, cross-sectional area, and volume of the nasal cavity using soft X-ray and micro-CT.

Results

The experimental group showed a significantly smaller cross-sectional area and volume than did the control group. The surface area exhibited no significant differences between the two groups, although it tended to be smaller in the experimental group than in the control group. The nasal volume divided by the length of the tibia (for comparison with whole-body growth) was significantly smaller in the experimental group than in the control group.

Conclusions

These data suggest that IH exposure suppresses growth and development of the nasal cavity and may result in nasal breathing disturbance.     

Effects of surface treatment,hydration and application method on the bond strength of a silorane adhesive and resin system to dentine

Objectives

To evaluate the effects of surface treatment, surface hydration (SH) and application method (AM) on the tensile bond strength of the Silorane Adhesive System (SAS) to dentine.

Methods

Ninety bovine teeth were used. For the control group (n = 10), each dentine surface was treated according to the manufacturer's instructions of the SAS. The remaining teeth were randomly distributed into two groups (n = 40), according to the type of dentine surface treatment (ST)—37% phosphoric acid or Er:YAG Laser prior to the application of the SAS. Each group was further divided into 2 subgroups (n = 20), according to the SH status: dry (D) or wet (W). Each subgroup was further divided into 2 subgroups (n = 10), according to the application method [AM: Active (AC) mode or Passive (PA) mode]. A coat of resin composite (Filtek P90) was applied on the surface. Artificial ageing was performed with a thermo-mechanical cycling machine. The specimens were sectioned into 1 mm × 1 mm × 10 mm sticks and stressed to failure using a universal testing machine. The remaining teeth in each group were used for Scanning Electron Microscopy to examine the fractured area. Data were subjected to a three-way ANOVA, Tukey's test and Dunnet's test (α = 0.05).

Results

The ANOVA showed significant differences for SH and AM, but not for ST. For SH, the results of Tukey's test were (in MPa): D – 14.9(±3.8)^a, W – 17.1(±4.3)^b; and for AM: PA – 14. 9(±4.2)^a, AC – 17.1(±3.9)^b.

Conclusions

Acid etching, when combined with a moist dentine surface and the use of primer agitation, improves the bond strength of the SAS to dentine.

Clinical Significance

According to the results of the present in vitro study, modification of the application protocols for the silorane-based adhesive system may improve its clinical performance.     

Fit of 4-unit FDPs made of zirconia and CoCr-alloy after chairside and labside digitalization – A laboratory study

Objectives

To analyse the marginal fit of 4-unit fixed dental prostheses (FDPs) and the accuracy of three-dimensional cast-datasets using both approaches to Computer Aided Design (CAD)/Computer Aided Manufacturing (CAM): direct and indirect digitalization.

Methods

A titanium model of a 4-unit FDP was digitized by an intraoral scanning device (iTero, Align Technology, Carlstadt, US; DD, n = 12). Additionally 12 conventional impressions were taken and referring master casts were digitized by a laboratory scanner (CS2, Straumann, Basel, Switzerland; ID, n = 12). Frameworks were fabricated (CARES CADCAM GmbH, Straumann, Markkleeberg, Germany) from base metal alloy (coron, Straumann; DD-C: n = 12; ID-C: n = 12) and zirconia (zerion, Straumann; DD-Z: n = 12; ID-Z: n = 12) from the same datasets. The marginal fit of the resulting frameworks and the accuracy of the underlying datasets from DD and ID were evaluated. Data were analyzed by unpaired two sample Student's t-test with Levene-test (p < 0.05).

Results

Frameworks from group DD-C showed significantly better marginal fit than ID-C (DD-C: 56.90 ± 27.37 μm, ID-C: 90.64 ± 90.81 μm). For zirconia frameworks no differences between both digitalization methods (DD-Z: 127.23 ± 66.87 μm, ID-Z: 141.08 ± 193.17 μm) could be observed. Base metal alloy frameworks exhibited significantly better marginal fit than zirconia frameworks (DD: p < 0.001; ID: p = 0.022). Regarding the accuracy group DD showed significantly higher “trueness” than ID.

Significance

Direct and indirect digitalization lead to clinically acceptable marginal fit of 4-unit FDPs from base metal alloy and zirconia. Higher accuracy of datasets from DD leads to better marginal fit of frameworks from base metal alloy but not for ones from zirconia.     

Effect of the Nd:YAG laser on sealer penetration into root canal surfaces: A confocal microscope analysis

Objectives

The objective of this in vitro study was to evaluate the use of the Neodymium:Yttrium-Aluminium-Garnet (Nd:YAG) laser as part of the root canal treatment on the penetration of sealer into dentinal tubules.

Methods

Eighty extracted lower premolars were randomly assigned to two groups (n = 40 each): Control group (CG), subjected to a conventional protocol of endodontic instrumentation and obturation; and Laser group (LG), in which Nd:YAG laser irradiations were combined with conventional preparation and obturation. Endodonted samples were sectioned at 3 and 5 mm from the apex and observed under a confocal scanning microscope (CLSM). The penetration depth into the dentinal tubules and the extension of the intracanal perimeter infiltrated by sealer were measured. The Student–Newman–Keuls test was run for between-group comparisons (α = .05).

Results

The depth of sealer penetration into dentinal tubules did not differ among groups. LG samples showed the significantly highest percentage of penetrated perimeter at 3 mm from the root apex. Within each group, the greatest depth of penetration (P = .0001), and the major percentage of penetrated perimeter (P < .001), were recorded at 5 mm.

Conclusions

The application of the Nd:YAG laser after instrumentation did not improve the depth of sealer penetration into the dentinal tubules. The laser enlarged the total penetrable perimeter near the apex.

Clinical significance

The Nd:YAG laser may be an appropriate complement in root canal treatment, as it enhances the sealer adaptation to the dentinal walls in the proximity of the apex.     

Effect of proximal box elevation with resin composite on marginal quality of resin composite inlays in vitro

Objectives

To evaluate marginal quality and resin–resin transition of lab made resin composite inlays in deep proximal cavities with and without 3 mm proximal box elevation (PBE) using resin composites before and after thermo-mechanical loading (TML).

Methods

MOD cavities with one proximal box beneath the cementoenamel junction were prepared in 40 extracted human third molars. Proximal boxes ending in dentine were elevated 3 mm with different resin composites (G-Cem, Maxcem Elite as self-adhesive resin cements and Clearfil Majesty Posterior as restorative resin composite in one or three layers bonded with AdheSE), or left untreated. Clearfil Majesty Posterior inlays were luted with Syntac and Variolink II (n = 8). Marginal quality as well as the PBE-composite inlay interface was analyzed under an SEM using epoxy resin replicas before and after thermomechanical loading (100,000 × 50 N and 2500 thermocylces between +5 °C and +55 °C).

Results

Bonding resin composite inlays directly to dentine showed similar amounts of gap-free margins in dentine compared to PBE applied in three consecutive layers (p > 0.05). The groups with self-adhesive resin cements for PBE exhibited significantly more gaps in dentine (p < 0.05).

Significances

With layered resin composite, PBE is effective in indirect resin composite bonding to deep proximal boxes. Self-adhesive resin cements are not suitable for this indication.     

The temporomandibular joint of California sea lions (Zalophus californianus): Part 1 – Characterisation in health and disease

Objectives

This study aimed to characterise the histologic, biomechanical and biochemical properties of the temporomandibular joint (TMJ) of California sea lions. In addition, we sought to identify structure–function relationships and to characterise TMJ lesions found in this species.

Design

Temporomandibular joints from fresh cadaver heads (n = 14) of California sea lions acquired from strandings were examined macroscopically and microscopically. The specimens were also evaluated for their mechanical and biochemical properties. Furthermore, if TMJ arthritic changes were present, joint characteristics were described and compared to healthy joints.

Results

Five male and 9 female specimens demonstrated macroscopically normal fibrocartilaginous articular surfaces and fibrous discs in the TMJ. Out of the 9 female specimens, 4 specimens had TMJ lesions were seen either in the articular surface or the disc. Histologically, these pathologic specimens demonstrated subchondral bone defects, cartilage irregularities and inflammatory cell infiltrates. The normal TMJ discs did not exhibit significant direction dependence in tensile stiffness or strength in the rostrocaudal direction compared with the mediolateral direction among normal discs or discs from affected joints. The TMJ discs were not found to be anisotropic in tensile properties. This feature was further supported by randomly oriented collagen fibres as seen by electron microscopy. Furthermore, no significant differences were detected in biochemical composition of the discs dependent upon population.

Conclusion

The TMJ and its disc of the California sea lion exhibit similarities but also differences compared to other mammals with regards to structure–function relationships. A fibrous TMJ disc rich in collagen with minimal glycosaminoglycan content was characterised, and random fibre organisation was associated with isotropic mechanical properties in the central region of the disc.     

Mechanical properties and modeling of drug release from chlorhexidine-containing etch-and-rinse adhesives

Objectives

To evaluate the effects of chlorhexidine (CHX) addition in different concentrations into simplified etch-and-rinse adhesives on the ultimate tensile strength (UTS), water sorption (WS), solubility (SO) and the rate of CHX release over time.

Methods

We added CHX diacetate to Ambar [AM] (FGM) and XP Bond [XP] (Dentsply) in concentrations of 0, 0.01, 0.05, 0.1 and 0.2 wt%. For UTS (n = 10 for each group), adhesive specimens were constructed in an hourglass shape metallic matrix with cross-sectional area of 0.8 mm². Half of specimens were tested after 24 h and the other half after 28 days of water storage in tension of 0.5 mm/min. For WS and SO (n = 10 for each group), adhesive discs (5.8 mm × 1.0 mm) were prepared into a mold. After desiccation, we weighed and stored the cured adhesive specimens in distilled water for evaluation of the WS, SO and the cumulative release of CHX over a 28-day period. For CHX release (n = 10 for each group), spectrophotometric measurements of storage solution were performed to examine the release kinetics of CHX. We subjected data from each test to ANOVA and Tukey’ test (α = 0.05).

Results

XP Bond adhesive showed significantly more WS and SO and lower UTS than Ambar. In general, the addition of CHX did not alter WS, SO and UTS of the adhesives. XP showed a higher CHX release than AM (p < 0.05) in all concentrations and the final amount of CHX release was directly proportional to the initial CHX concentration added to the adhesives. After 28 days of water storage, approximately 20% of CHX was released from XP and 8.0–12.0% from AM.

Conclusions

Addition of CHX to commercial adhesive is a feasible method to provide a controlled release of CHX over time without jeopardizing WS, SO and UTS of the adhesives.

Significance

Manufacturers should consider adding CHX to commercial adhesives to provide a controlled release of CHX over time.     

An in vitro investigation of the effect of bevel design on the penetration and withdrawal forces of dental needles

Objectives

To compare the effect on insertion and withdrawal forces using needles with a standard atraumatic bevel to those with a novel asymmetrical bevel in vitro.

Methods

Maximum needle penetration forces were measured using a 10 N load cell mounted on an Instron universal testing machine. Forces were determined during insertion through a 0.4 mm polyurethane membrane mounted at 90° (n = 30 of each design), 30° (n = 16 of each design) and 150° (n = 16 of each design) to the needle bevel and during a 10 mm insertion into a polyvinyl siloxane block mounted at 90° to the bevel (n = 16 of each design). In all tests the rate of insertion was 50 mm/min.

Results

The novel design required less force to penetrate the membrane at 30° and 150° compared to the standard design (mean forces at 30° being 0.75 N and 0.98 N for novel and standard designs respectively [p < 0.001] and at 150° 0.52 N and 0.66 N respectively [p < 0.001] but more force at 90° penetration tests (0.60 N and 0.46 N respectively [p < 0.001]). The novel design required less force to insert 10 mm into the polyvinyl siloxane (1.80 N and 2.54 N respectively [p < 0.001]).

Conclusion

The novel design needed less force than the standard version to penetrate a thin membrane when used at 30° and 150° to the surface and to penetrate a polyvinyl siloxane block to a depth of 10 mm but required more force to penetrate a thin membrane at 90°.

Clinical significance

Needle bevel design affects the penetration and withdrawal forces of dental needles in vitro.     

Alpha 2 integrin gene (ITGA2) polymorphism in renal transplant recipients with and without drug induced gingival overgrowth

Background

Variances in fibroblasts’ α2β1 integrin intensity may lead to altered adhesion to type I collagen and consequently to suppression of phagocytosis which may be one of the mechanisms for drug induced gingival overgrowth. The present study aimed to evaluate the genotype and allele frequencies of α2 integrin +807 gene in renal transplant patients with and without gingival overgrowth.

Material and methods

Seventy renal transplant patients with cyclosporine A (CsA)-induced gingival overgrowth (CsA GO+) were enrolled. Renal transplant patients without GO medicated with CsA (CsA GO−; n = 79) and tacrolimus (Tac; n = 52) served as controls. DNA was obtained from peripheral blood and ITGA2 +807C/T polymorphism was genotyped by polymerase chain reaction and restriction fragment length polymorphism method. Clinical parameters including probing depth and plaque, papilla bleeding and hyperplasia indexes were recorded. Chi-square, Kruskal–Wallis and Mann–Whitney tests were used in statistical analysis.

Results

Clinical parameters of CsA GO+ group were significantly higher than those of the CsA GO− and Tac groups (p < 0.05). ITGA2 807C/T genotype and allele frequencies of study groups were similar (p > 0.05).

Conclusion

Within the limits of the present study it can be concluded that ITGA2 +807 gene polymorphism is not associated with susceptibility to CsA-induced GO.     

Impact of different adhesives on work of adhesion between CAD/CAM polymers and resin composite cements

Objective

To determine the impact of pre-treatment of adhesive systems on the work of adhesion (WA) between CAD/CAM polymers and resin composite cements and compare with conventional tests of previous studies.

Methods

Surface parameters were measured by contact angle measurement (2700 measurements) and WA was calculated. Five CAD/CAM polymers were used for fabrication of specimens (n = 75/subgroup): artBloc Temp (A), Telio CAD (B), Nano Composite CFI-C (C), exp. CAD/CAM nanohybrid composite (D), and LAVA Ultimate (E). Then, air-abraded specimens were pre-treated (n = 15 per group): Ambarino P60 (I), Monobond Plus/Heliobond (II), visio.link (III), VP connect (IV), and no pre-treatment (V). Resin composite cement specimens (n = 75) were smoothed out homogeneously on a glass plate (n = 15/group): RelyX ARC (RXA), Variolink II (VAR), Panavia F2.0 (PAN), RelyX Unicem (RXU), and Clearfil SA Cement (CSA). Contact angles were determined with 3 drops of distilled water and diiodomethane each. Data were analyzed using Kruskal–Wallis-H test and Spearman-Rho correlation (p < 0.05).

Results

CAD/CAM materials (B), (A), and (C) showed higher WA compared to (D) and (E). (II) and (IV) resulted in higher WA than (I), (III) and (V). VAR had the significantly lowest WA, followed by RXU, RXA, CSA and PAN. No correlation occurred between WA and TBS/SBS whereas polar component of surface free energy of CAD/CAM resin and spreading coefficient showed significant positive correlation with TBS/SBS.

Conclusions

Determination of WA is not a proper method to draw conclusions about the bond between resin materials. Destructive test methods are not dispensable.

Clinical significance

The successful outcome of fixed dental restorations depends, among others, on the quality of bonding between the tooth and the restoration. Additional pre-treatment of the dental CAD/CAM resin restoration by bonding systems can be recommended for clinical use. Pre-treatment showed a significant impact on the surface properties.     

Comparison of incidence of complications and aesthetic performance for posterior metal-free polymer crowns and metal–ceramic crowns: Results from a randomized clinical trial

Objectives

The purpose of this randomized clinical study was to evaluate the clinical performance of posterior, metal-free polymer crowns after follow-up for up to six years, and to compare it with the performance of metal–ceramic crowns.

Methods

Eighty single crowns, manufactured from a polymer composite resin, were set on posterior teeth. Half of these received a glass–fibre framework (group 1) whereas half were prepared without framework stabilization (group 2). As the control group, 40 conventional metal–ceramic crowns were inserted. Primary endpoints were incidence of complications, investigated on a time-to-event basis, plaque status, and aesthetic performance.

Results

Thirty clinically relevant complications occurred after a median time of 2.3 years. Median follow-up time was four years. The most frequent complications were delamination (n = 24) and root-canal treatment (n = 4) of the crowns; the incidence of complications was not significantly different among crown materials (p = 0.60). Twenty crowns had to be replaced (six polymer crowns in group 1, nine polymer crowns in group 2, four crowns in the control group, and one tooth (in group 1) had to be extracted). Mean plaque and gingival indexes for the test groups did not differ from those for the control group.

Conclusions

Within a median follow-up period of four years, the clinical performance of posterior polymer crowns with and without a glass–fibre framework was not significantly different from that of metal–ceramic crowns, although the number of catastrophic failures of composite crowns was higher than that of the metal–ceramic crowns.

Clinical significance

On the basis of the study results, posterior polymer crowns may be an alternative to metal–ceramic crowns, although additional research is needed before they can be recommended, without reservation, as permanent restorations.     

Influence of procedural variations during the laboratory phase of complete denture fabrication on patient satisfaction and denture quality

Objectives

To compare subjective and objective outcomes of complete dentures fabricated with standard clinical protocols, but omitted selected steps during the laboratory phase.

Materials and methods

Forty-three edentulous patients (mean age 58.1 years, SD 9.9, range 35–78), were consecutively recruited and randomly assigned to one of four groups according to selected variations of laboratory steps: Group 1 (n = 10), omission of secondary casts obtained from impressions in border moulded custom trays; Group 2 (n = 10), omission of secondary casts and face-bow articulator mounting; Group 3 (n = 10), omission of face-bow mounting; Group 4 (n = 13), no steps omitted (control). Clinical procedures for all groups were identical, and performed by senior dental students under supervision of prosthodontists, all of whom were blinded to the Group. At 1-, 4- and 12-weeks after delivery, patients rated their overall satisfaction, as well as a range of functional factors using visual analogue scales. An independent blinded prosthodontist similarly rated four domains of denture quality at the 1-week follow-up.

Results

No significant differences were noted among the groups in all aspects of patients’ assessments at all the time points (P > 0.1). There were no significant differences in prosthodontists’ ratings of denture quality in any of the domains examined (P > 0.1).

Conclusion

Selected omissions of steps (face-bow mounting and/or secondary casts) during the laboratory phase of complete denture fabrication has only a minor role, if any, in subjective and objective outcomes, contrasting with the common belief that such omissions will adversely affect outcomes.

Clinical significance

General practitioners provide most complete dentures. Many do not follow all the procedures they were taught at dental school. Our finding that omitting frequently advocated steps made no difference to patient satisfaction or to denture quality suggests that cost-effectiveness through simplifications be considered in practice and in education.     

Analysis of age-related changes in the functional morphologies of salivary glands in mice

Background and Objectives

Salivary glands in the elderly commonly exhibit salivary dysfunction resulting dry mouth, poor oral hygiene, and dental caries. However, in vivo changes of salivary glands during aging have not been well documented in the literature. This study was undertaken to determine age-related morphometric and functional changes of salivary glands using an aging mouse model.

Methods

Male C57BL/6 mice were divided into three groups, group A (10 weeks old; n = 10), group B (30 weeks old; n = 10), and group C (90 weeks old; n = 10). Body weights, salivary gland weights, salivary flow rates, and salivary lag times were measured and compared. Histomorphometric examinations and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays were performed. In addition, changes in salivary uptake and excretion were observed by single-photon emission computed tomography (SPECT).

Results

Body and gland weights increased with age. Gland weight was significantly higher in group B than in groups A and C. Salivary lag time was significantly greater in group C than in groups A and B, and salivary flow rate was significantly greater in group B than in groups A and C. Histologic evaluations exhibited acinar cell atrophy, cytoplasmic vacuolization, lymphocyte infiltration, small mucin component and more periductal fibrosis in salivary glands of group C. TUNEL assays revealed that apoptotic salivary epithelial cells were significantly more numerous in group C than in groups A and B. ^99mTc-pertechnetate excretion rate was significantly lower in group C than in groups A and B in SPECT.

Conclusion

Various morphometric and histopathological changes were observed in the salivary glands of aging mouse as well as relevant functional alterations, such as, decreased saliva production and excretion. Increased number of apoptotic salivary epithelial cells may contribute to the observed functional deterioration.     

Effect of luting cement and thermomechanical loading on retention of glass fibre posts in root canals

Objectives

To evaluate the effect of luting cement and thermomechanical loading on the retention of glass fibre posts in root canals.

Methods

One hundred and forty-four single-rooted human premolars were endodontically treated and restored with RelyX Fibre Posts. The teeth were divided into four groups according to the cements used (Fuji I, Fuji CEM, RelyX Unicem and RelyX ARC). Each group was further divided into two subgroups according to the method of ageing (immediately tested and after thermomechanical loading). Bond strength was evaluated using a pull-out test. Microleakage was examined quantitatively with dye penetration. The dentine–cement-post bonding interface was assessed using scanning electron microscopy. Data were analysed with two-way ANOVA (pull-out test) and Kruskal–Wallis analysis (microleakage).

Results

The pull-out bond strength and microleakage were significantly affected by the type of cement and ageing. Although RelyX ARC showed the highest bond strength before thermomechanical loading (p < 0.05), the sealing ability of this cement was worse than those exhibited in Fuji CEM and RelyX Unicem (p < 0.05). After thermomechanical loading, pull-out strengths of Fuji I and Fuji CEM were significantly increased, whereas that of RelyX ARC group significantly decreased (p < 0.05). The sealing ability of Fuji CEM was significantly better than the two resin cement groups (p < 0.05) after ageing.

Conclusion

Fuji CEM demonstrates increased pull-out strength after thermomechanical loading and favourable sealing ability compared with the other cements.

Clinical significance

Resin-modified glass ionomer cements have the potential benefit of achieving long-term retention when used for luting glass fibre post to root canal dentine. So it may be recommended for the cementation of glass fibre post in clinics.     

Outcome of single immediate implants placed in post-extraction infected and non-infected sites,restored with cemented crowns: A 3-year prospective study

Objectives

To compare the survival of immediate implants placed in postextraction infected and non-infected sites, restored with cemented crowns.

Methods

Thirty-six implants were immediately placed in non-infected sockets (control group (CG), n = 18), and in infected alveoli (test group (TG), n = 18) that had been debrided, curetted, cleaned with 90% hydrogen peroxide, irradiated with yttrium–scandium–gallium–garnet (Er,Cr:YSGG) laser, and irrigated with a sterile solution. Guided bone regeneration was performed under antibiotic coverture. All study patients had both a CG and a TG site. The implant osteotomy sites were extended 3–4 mm beyond the apical extent of the sockets to achieve primary stability for the implants. The prosthetic phase occurred 4.5 months after surgery. Success criteria were accepted as the presence of implant stability, absence of a radiolucent zone around the implants, absence of mucosal suppuration, and lack of pain. Clinical evaluations were performed at baseline, and at 12, 24, and 36 months of follow-up.

Results

All of the implants were osseointegrated 3 months after surgery. The 3-year survival rate was 94.44% for TG, and 100% for CG. The clinical and radiographic variables tested yielded no significant differences among groups at 36 months.

Conclusions

Under the tested conditions, immediate implant placement can be considered a predictable treatment option for the restoration of fresh postextraction infected sockets.

Clinical significance

Immediate implants may be indicated for replacing teeth lost due to chronic periapical lesions with endodontic failure history when appropriate preoperative procedures are taken to clean and decontaminate the surgical sites.