Effect of zirconia surface conditioning before glazing on the wear of opposing enamel: an in vitro study.

OBJECTIVES: This in vitro study aimed to evaluate the wear of natural teeth opposing 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) with different surface conditions. MATERIALS AND METHODS: Sixty 3Y-TZP specimens were randomly assigned to six groups (n = 10), differing in surface condition. In three groups, the samples underwent glazing-with the glaze applied to roughened (i.e., 106-µm-grit diamond-finished), as-sintered, and polished zirconia. The three remaining groups consisted of unglazed specimens: solely polished samples and diamond-finished samples (106-µm-grit and 46-µm-grit) without further conditioning. Two-body wear was evaluated at extracted, non-carious molars (n = 60), which served as antagonists in chewing simulation (10,000 masticatory cycles, 49N load). As a control, natural teeth with intact enamel surfaces were tested against natural molars (n = 10). All samples were 3D-scanned before and after the chewing simulation (7 Series, Straumann). Volume loss was calculated (Inspect Software, GOM), and statistically analyzed (SPSS Statistics 24, IBM). RESULTS: Volume loss of the natural antagonists decreased in the following order: 106-µm-grit diamond-finished zirconia (4.6 ± 2.5 mm3), glazed 106-µm-grit diamond-finished zirconia (3.8 ± 1.1 mm3), glazed as-sintered zirconia (3.5 ± 0.9 mm3), 46-µm-grit diamond-finished zirconia (1.7 ± 0.6 mm3), control (1.6 ± 0.7 mm3), glazed polished zirconia (1.4 ± 0.5 mm3), and solely polishing (0.4 ± 0.2 mm3). Even when polishing the surfaces before glazing, volume loss was not mitigated to the same extent as after polishing alone. CONCLUSIONS: The zirconia surface condition beneath the glazing influences antagonist wear. Although polishing before glazing resulted in acceptable levels of antagonist wear, this approach did not yield as favorable results as polishing alone. CLINICAL RELEVANCE: For operators favoring glazing, pre-polishing the zirconia surface could be advantageous to reduce wear.

Zirconia Primers Improve the Shear Bond Strength of Dental Zirconia.

PURPOSE: Various resin cements and priming agents are available for adhesive luting of zirconia restorations. The purpose of this study was to investigate how cement type and priming protocol affect the shear bond strength on zirconia ceramics. MATERIALS AND METHODS: Yttria-stabilized tetragonal zirconia polycrystalline ceramic cylinders were bonded to flat zirconia ceramic surfaces using 7 commercially available resin cements. Ten specimens of each cement group were pretreated with a universal primer, and 10 specimens per group were bonded without pretreatment. In addition, 10 specimens per group were pretreated with system-specific zirconia primers, which were available for 3 cements. Altogether, 170 bonded specimens were water-stored, thermal-cycled, and then submitted to shear bond strength tests. The shear bond strength and the fracture types were documented. Differences in shear bond strengths were assessed using 2-way ANOVA with post-hoc test (α = 0.05). A point-biserial correlation was run between the fracture patterns and the shear bond strengths. RESULTS: The mean shear bond strengths of cements in the unprimed group showed large variations between 2.52 ± 3.01 (mean ± SD) MPa and 33.15 ± 7.35 MPa. Pretreating the specimens with a universal primer improved the shear bond strengths significantly in all groups (p < 0.05) with a range of 21.80 ± 12.51 to 57.20 ± 11.40 MPa. The system-specific primers also improved the shear bond strength significantly, compared to the unprimed group (p < 0.01); however, only one system-specific primer achieved a shear bond strength superior to the universal primer (p < 0.01). There was also a statistical correlation between the fracture type and the shear bond strength (p < 0.0005), with cohesively fractured specimens showing higher shear bond strengths (37.24 ± 19.87 MPa) than adhesively fractured specimens (23.10 ± 17.65 MPa) (p < 0.001). CONCLUSION: Using universal primer can enhance the maximal shear bond strength of zirconia.

CAD/CAM produces dentures with improved fit.

OBJECTIVES: Resin polymerisation shrinkage reduces the congruence of the denture base with denture-bearing tissues and thereby decreases the retention of conventionally fabricated dentures. CAD/CAM denture manufacturing is a subtractive process, and polymerisation shrinkage is not an issue anymore. Therefore, CAD/CAM dentures are assumed to show a higher denture base congruence than conventionally fabricated dentures. It has been the aim of this study to test this hypothesis. MATERIALS AND METHODS: CAD/CAM dentures provided by four different manufacturers (AvaDent, Merz Dental, Whole You, Wieland/Ivoclar) were generated from ten different master casts. Ten conventional dentures (pack and press, long-term heat polymerisation) made from the same master casts served as control group. The master casts and all denture bases were scanned and matched digitally. The absolute incongruences were measured using a 2-mm mesh. RESULTS: Conventionally fabricated dentures showed a mean deviation of 0.105 mm, SD = 0.019 from the master cast. All CAD/CAM dentures showed lower mean incongruences. From all CAD/CAM dentures, AvaDent Digital Dentures showed the highest congruence with the master cast surface with a mean deviation of 0.058 mm, SD = 0.005. Wieland Digital Dentures showed a mean deviation of 0.068 mm, SD = 0.005, Whole You Nexteeth prostheses showed a mean deviation of 0.074 mm, SD = 0.011 and Baltic Denture System prostheses showed a mean deviation of 0.086 mm, SD = 0.012. CONCLUSIONS: CAD/CAM produces dentures with better fit than conventional dentures. CLINICAL RELEVANCE: The present study explains the clinically observed enhanced retention and lower traumatic ulcer-frequency in CAD/CAM dentures.

Intraoral Vacuum-Assisted Closure Therapy-A Pilot Study in Medication-Related Osteonecrosis of the Jaw.

PURPOSE: For approximately 2 decades, vacuum-assisted closure (VAC) therapy has been widely used for the management of complex wounds and soft tissue defects on the external surface of the body. As yet, this technique has not been studied for intraoral wound management. Therefore, this study evaluated the feasibility, safety, and effectiveness of intraoral VAC therapy in patients with medication-related osteonecrosis of the jaw (MRONJ). PATIENTS AND METHODS: After successful construction of an intraoral device providing sufficient airtight sealing, individually manufactured appliances were used in a prospective clinical trial of 3 patients using the VAC therapy system. RESULTS: Intraoral VAC therapy showed some success and did not produce serious side effects. Different positive effects, such as formation of new granulation tissue, cessation of pain, and pus suppuration, were found. CONCLUSION: This prospective proof-of-principle study showed that intraoral VAC therapy is feasible and safe. It could play a role in the management of MRONJ and other types of intraoral wounds (eg, osteoradionecrosis, postoperative wound dehiscence, etc).

Do CAD/CAM dentures really release less monomer than conventional dentures?

OBJECTIVES: Computer-aided design (CAD)/computer-aided manufacturing (CAM) dentures are assumed to have more favourable material properties than conventionally fabricated dentures, among them a lower methacrylate monomer release. The aim of this study was to test this hypothesis. MATERIALS AND METHODS: CAD/CAM dentures were generated from ten different master casts by using four different CAD/CAM systems. Conventional, heat-polymerised dentures served as control group. Denture weight and volume were measured; the density was calculated, and the denture surface area was assessed digitally. The monomer release after 7 days of water storage was measured by high-performance liquid chromatography. RESULTS: Whole You Nexteeth and Wieland Digital Dentures had significantly lower mean volume and weight than conventional dentures. Baltic Denture System and Whole You Nexteeth had a significantly increased density. Baltic Denture System had a significantly smaller surface area. None of the CAD/CAM dentures released significantly less monomer than the control group. CONCLUSIONS: All tested dentures released very low amounts of methacrylate monomer, but not significantly less than conventional dentures. A statistically significant difference might nevertheless exist in comparison to other, less recommendable denture base materials, such as the frequently used autopolymerising resins. CLINICAL RELEVANCE: CAD/CAM denture fabrication has numerous advantages. It enables the fabrication of dentures with lower resin volume and lower denture weight. Both could increase the patient comfort. Dentures with higher density might exhibit more favourable mechanical properties. The hypothesis that CAD/CAM dentures release less monomer than conventional dentures could, however, not be verified.

Condylar Erosion in Patients With Chronic Temporomandibular Joint Arthralgia: A Cone-Beam Computed Tomography Study.

PURPOSE: The objective of this study was to assess the association between temporomandibular joint (TMJ) condylar erosion and chronic TMJ arthralgia. MATERIALS AND METHODS: Based on a sample size estimation, this case-and-control study involved 198 patients 16 to 73 years old recruited from a routine clinical practice (99 cases, patients with chronic TMJ arthralgia and mean pain duration of 16.4 months; 99 controls, asymptomatic patients without a history of orofacial pain). The clinical diagnosis of arthralgia was made according to the Research Diagnostic Criteria for Temporomandibular Disorders. Cone-beam computed tomographic (CBCT) images were evaluated for the presence or absence of erosive osseous changes of the TMJ condyle. Severity of TMJ condylar erosion was classified as grade 0 (absence of erosion), grade I (slight erosion), grade II (moderate erosion), or grade III (extensive erosion). Logistic regression analysis was used to assess the association between chronic TMJ arthralgia and condylar erosion, adjusting for age, gender, number of missing posterior teeth, and number of dental quadrants with missing posterior teeth. RESULTS: TMJ condylar erosion was found in 59.6% of cases and 21.2% of controls. There was a significant association between TMJ arthralgia and degree of condylar erosion (P < .001). The odds ratio that a TMJ with condylar erosion grade II might belong to the TMJ arthralgia group was strong (3.1:1; 95% confidence interval [CI], 1.17 to 8.09) and significant (P = .023). Significant increases in risk of TMJ arthralgia occurred with condylar erosion grade III (7.7:1; 95% CI, 3.09 to 19.18; P < .001). CONCLUSIONS: The study provides evidence of an association between TMJ condylar erosion and chronic TMJ arthralgia.

In Vitro Analysis of the Fracture Resistance of CAD/CAM Denture Base Resins.

Computer-aided design and computer-aided manufacturing (CAD/CAM) denture base manufacturers claim to produce their resin pucks under high heat and pressure. Therefore, CAD/CAM dentures are assumed to have enhanced mechanical properties and, as a result, are often produced with lower denture base thicknesses than conventional, manually fabricated dentures. The aim of this study was to investigate if commercially available CAD/CAM denture base resins have more favourable mechanical properties than conventionally processed denture base resins. For this purpose, a series of three-point bending tests conforming to ISO specifications were performed on a total of 80 standardised, rectangular CAD/CAM denture base resin specimens from five different manufacturers (AvaDent, Baltic Denture System, Vita VIONIC, Whole You Nexteeth, and Wieland Digital Dentures). A heat-polymerising resin and an autopolymerising resin served as the control groups. The breaking load, fracture toughness, and the elastic modulus were assessed. Additionally, the fracture surface roughness and texture were investigated. Only one CAD/CAM resin showed a significantly increased breaking load. Two CAD/CAM resins had a significantly higher fracture toughness than the control groups, and all CAD/CAM resins had higher elastic moduli than the controls. Our results indicate that CAD/CAM denture base resins do not generally have better mechanical properties than manually processed resins. Therefore, the lower minimum denture base thicknesses should be regarded with some caution.

Crestal Sinus Floor Augmentation Using Hydraulic Pressure and Vibrations: A Retrospective Single Cohort Study.

PURPOSE: To evaluate the sinus membrane perforation and implant survival rate after crestal minimally invasive sinus floor augmentation using hydraulic pressure and vibrations. MATERIALS AND METHODS: In this retrospective single cohort study, all patients who underwent minimally invasive sinus floor augmentation between 2007 and 2015 using hydraulic pressure and vibrations were included. The sinus membrane is elevated by physiologic saline at 1.5 bar. The fluid is then set into vibration to further separate the sinus membrane from the bony floor. The endpoints were sinus membrane perforation and the survival rate of implants. RESULTS: The hydraulic pressure and vibration technique was applied in 156 patients. Seven patients with perforations of the sinus membrane were treated with the lateral window approach and excluded from the follow-up analysis. In the remaining 149 patients, 184 crestal sinus floor augmentations were performed and 184 implants were placed. In 10 of these 184 cases, a perforation was suspected in the postoperative computed tomography (CT) scan. In total, the perforation rate was 8.9% (17/191). Nineteen implants were lost during the follow-up period ranging from 0.2 to 8.4 years with a median of 2.3 years. The cumulative implant survival rates after 1, 3, and 5 years were 94.4%, 87.7%, and 87.7%, respectively. No severe perioperative complications were noted. CONCLUSION: The hydraulic pressure and vibration technique allows a minimally invasive crestal sinus augmentation with a perforation rate less than 10% and implant survival rates of approximately 90%.

Comparing the effect of strontium-functionalized and fluoride-modified surfaces on early osseointegration.

BACKGROUND: Studies have shown that medical devices comprising strontium contribute to bone healing and osseointegration. The aim of this study was to evaluate the in vivo performance of surface-functionalized implants (Ti-Sr-O) showing predictable release characteristics of strontium and compare it to performance a commercially available fluoride-modified surface. METHODS: Ti-Sr-O functionalized, fluoride-modified,  Grade 4 titanium implants were inserted in the femoral condyle of adult male New Zealand white rabbits. Atomic absorption spectrometry (AAS) was utilized to monitor strontium blood serum levels. Two weeks after insertion, histomorphometric evaluation was performed with respect to bone-to-implant contact (BIC%) and bone formation (BF%) using defined regions of interest. RESULTS: Mean values for BIC% showed a comparable degree of osseointegration for Ti-Sr-O and the fluoride-modified surface, while BF% revealed a significant difference in increased BF with Ti-Sr-O. AAS measurements did not indicate any influence of the Ti-Sr-O modified implants on the strontium blood serum concentrations. CONCLUSIONS: Within the limitations of this study, it was shown that the Ti-Sr-O coating, with sustained release characteristics of strontium, enhanced bone apposition and, thus, could find practical applications, e.g., within the field of medical implantology.

Dental age is more appropriate than chronological age for evaluating the mandibular movement range in children.

PURPOSE: The measurement of excursive jaw movements is an important instrument for evaluating the functional condition of the temporomandibular system. Dento-maxillofacial development differs widely within different age, weight or height clusters. Tooth eruption is part of the development of the temporomandibular system. Therefore, the dental developmental stage might reflect temporomandibular development more appropriately. The aim of this study was to investigate whether the dental age is a more suitable parameter for evaluating the mandibular movement range of children in the mixed dentition stage than chronological age. MATERIALS AND METHODS: In a prospective study, the mandibular movement range and relevant temporomandibular findings of 146 children aged 8-10 yr were assessed clinically. Alginate impressions were taken and dental casts were generated. Dental age was assessed from the casts. RESULTS: The mean mouth opening capacity was 46.2 mm (SD = 5.2); the mean laterotrusion to the left was 10.1 mm (SD = 1.9) and to the right 10.0 mm (SD = 1.8). For protrusion, the mean value was 9.1 mm (SD = 2.0). There was a statistically highly significant correlation between dental age and maximal active mouth opening extent. Statistically significant correlations between chronological age and active jaw movement capacity could not be shown. CONCLUSIONS: In children in the mixed dentition stage, dental age seems to reflect the developmental stage of the temporomandibular system more adequately than chronological age. Therefore, dental age-related normative values could be more appropriate for evaluating the temporomandibular system in children. CLINICAL TRIAL REGISTRATION NUMBER: 20100302-161.

Orthodontic Treatment Need of Austrian Schoolchildren in the Mixed Dentition Stage.

Malocclusal traits can impair dental health and aesthetical appearance. The index of orthodontic treatment need (IOTN) identifies the patients who benefit the most from orthodontic treatment. The aim of this study was to assess the malocclusion frequencies and the orthodontic treatment need among Austrian children in the mixed dentition stage, since there is no pre-existing data from Austria. In the present study, 157 children aged between 8 and 10 years were examined. Following an anamnesis questionnaire, which included a question about the parents' perceived treatment need, the children were examined clinically and dental impressions were taken. The sagittal molar relationship, overjet, overbite and the presence of cross- or scissor bite were registered. The treatment need was assessed using the dental health component (DHC) of the index of orthodontic treatment need (IOTN). 64.3% (95% CI [56.8, 71.8]) of the children showed Angle class I molar relation, 33.1% (95% CI [25.8, 40.5]) class II and 2.5% (95% CI [0.1, 5.0]) Angle class III relation. Crossbite was found in 36.3% (95% CI [28.8, 43.8]) of the participants. A treatment need for medical reasons (IOTN 4 or 5) was found in 30.6% (95% CI [23.4, 37.8]). There was no statistically significant relationship between objective treatment need and the parents' perception. The malocclusion frequencies and the treatment need assessed in the present study appeared to be comparable to those assessed in other countries. The data supports the opinion that orthodontic screening is important and necessary at this stage of dental development, also due to the discordance between objective and perceived treatment need.

Evaluation of Currently Available CAD/CAM Denture Systems.

PURPOSE: The introduction of computer-aided design/computer-assisted manufacture (CAD/CAM) technology into removable denture prosthodontics enables denture adaptation in fewer patient visits, an advantage that appeals to dentists and patients. Since manufacturers follow very different approaches, an evaluation of the different clinical CAD/CAM complete denture fabrication protocols is desirable. The aim of this article is to assess and evaluate the different clinical fabrication protocols of currently available CAD/CAM denture systems to provide decision support for dental practitioners. MATERIALS AND METHODS: The information for the present article was gathered by questionnaires from (in alphabetical order) Global Dental Science, Merz Dental, Wieland Dental + Technik, Ivoclar Vivadent, VITA Zahnfabrik, and Whole You, and complemented with results from the authors' clinical experience. RESULTS: Wieland Digital Denture involves four patient visits. Both AvaDent digital dentures and Whole You Nexteeth enable denture fabrication in three (including a try-in session) or two (without try-in) visits. Baltic Denture System stipulates complete denture fabrication in two visits, and VITA VIONIC material system is an open system enabling choice between different treatment protocols. It can be combined with several open scanners, CAD software options, and milling machines. CONCLUSION: The available CAD/CAM denture fabrication systems provide a variety of advantages, and the decision on a system should depend on the dentist's prosthodontic expertise, patient throughput rate, and requirements regarding denture individualization.

Is Cognitive Status Related to Oral Hygiene Level and Appropriate for Determining Need for Oral Hygiene Assistance?

BACKGROUND: With declining general health, the maintenance of oral health becomes increasingly difficult. Unfortunately, health care resources are limited. An assessment tool for detecting a patient's need for oral health care assistance would promote its adequate distribution. The aim of this study is to evaluate if the Shulman clock-drawing test score is a suitable assessment tool for determining the need for oral hygiene assistance. METHODS: Data collected from recent dental checkups of 126 inhabitants of five Austrian residential care facilities were analyzed. The Shulman clock-drawing test score was used as a measure for cognitive abilities and related to tooth and denture hygiene indices, which were assessed using the approximal space plaque index (API) and the denture plaque index (DPI). RESULTS: Shulman score values were distributed almost evenly in the study population. The mean API was 83.6% (SD 20.2%) for the maxilla and 94.9% (SD 15.6%) for the mandible. The mean DPI was 43.9% (SD 31.4%). Cognitive impairment was not statistically related to the dental or denture hygiene index. CONCLUSIONS: A high Shulman clock-drawing test score indicates the need for oral hygiene assistance, but it is not suitable as a single tool to assess this need. Patients with other disabilities might equally qualify for assistance. Dentures, however, can be cleaned quickly and efficiently independently of patient compliance; therefore, cleaning the patients' dentures should be part of nursing personnel's daily care routine for every patient.