Influence of probiotics on the periodontium, the oral microbiota and the immune response during orthodontic treatment in adolescent and adult patients (ProMB Trial): study protocol for a prospective, double-blind, controlled, randomized clinical trial.

BACKGROUND: Orthodontic treatment with fixed appliances is often necessary to correct malocclusions in adolescence or adulthood. However, oral hygiene is complicated by appliances, and prior studies indicate that they may trigger oral inflammation and dysbiosis of the oral microbiota, especially during the first 3 months after insertion, and, thus, may present a risk for inflammatory oral diseases. In recent periodontal therapeutic studies, probiotics have been applied to improve clinical parameters and reduce local inflammation. However, limited knowledge exists concerning the effects of probiotics in orthodontics. Therefore, the aim of our study is to evaluate the impact of probiotics during orthodontic treatment. METHODS: This study is a monocentric, randomized, double blind, controlled clinical study to investigate the effectiveness of daily adjuvant use of Limosilactobacillus reuteri (Prodentis®-lozenges, DSM 17938, ATCC PTA 5289) versus control lozenges during the first three months of orthodontic treatment with fixed appliances. Following power analysis, a total of 34 adolescent patients (age 12-17) and 34 adult patients (18 years and older) undergoing orthodontic treatment at the University Hospital Erlangen will be assigned into 2 parallel groups using a randomization plan for each age group. The primary outcome measure is the change of the gingival index after 4 weeks. Secondary outcomes include the probing pocket depth, the modified plaque index, the composition of the oral microbiota, the local cytokine expression and-only for adults-serum cytokine levels and the frequencies of cells of the innate and adaptive immune system in peripheral blood. DISCUSSION: Preventive strategies in everyday orthodontic practice include oral hygiene instructions and regular dental cleaning. Innovative methods, like adjuvant use of oral probiotics, are missing. The aim of this study is to analyse, whether probiotics can improve clinical parameters, reduce inflammation and prevent dysbiosis of the oral microbiota during orthodontic treatment. If successful, this study will provide the basis for a new strategy of prophylaxis of oral dysbiosis-related diseases during treatment with fixed appliances. TRIAL REGISTRATION: This trial is registered at ClinicalTrials.gov in two parts under the number NCT04598633 (Adolescents, registration date 10/22/2020), and NCT04606186 (Adults, registration date 10/28/2020).

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.

Impression material accuracy for palatal orthodontic miniscrews.

PURPOSE: This study investigates the accuracy of abutment transfer with current impression materials and provides a concise overview, including other relevant factors, in order to enable clinicians to make an informed decision about the optimal impression for this treatment procedure. METHODS: In all, 96 impressions of a cadaver head with two orthodontic miniscrews in place were taken with four common impression materials by two observers and using two methods of application. After pouring with a standard type IV stone and abutment transfer, all models and the upper jaw (which had been separated from the head) were scanned in a standard model scanner (Zirkonzahn® [Zirkohnzahn GmbH, Gais, Italy] S600 ARTI) and evaluated using a computer-aided design (CAD) program (GOM-Inspect [Gesellschaft für optische Messtechnik m.b.H., Braunschweig, Germany]). The deviations were measured at six points per screw and statistically evaluated with SPSS® (IBM, Chicago, IL, USA). RESULTS: Optimal values were obtained with biphasic polyvinylsiloxane, while monophasic polyvinylsiloxane, alginate and polyether also resulted in acceptable accuracy. Observer experience showed no effect and the method of application had only a minor effect on accuracy. CONCLUSIONS: Within the limitations of this study, it seems that all impression materials are suitable for miniscrew abutment transfer, provided that methods of intraoral adaptation of the orthodontic appliance can be employed. If higher accuracy is needed or for clinicians with less experienced, a biphasic polyvinylsiloxane impression with the putty-wash technique should be used as this combination reduces setting time. The most cost-effective version, alginate, can be used if the consequences of greater deviations can be handled. Caution is advised with polyether if undercuts are present.