Molecular and biochemical approach for understanding the transition of amorphous to crystalline calcium phosphate deposits in human teeth.

Calcium phosphate (CaP) deposition during bone mineralization starts with the aggregation of Posner's clusters Ca9(PO4)6 into amorphous Ca-phosphate (ACP), which then transforms into crystalline CaP and finally maturates to hydroxyapatite (HA). Using dentin/enamel of human teeth as a model system, we show that the physiological inorganic polymer polyphosphate (polyP), a phosphate donor in mineralization, prevents the transition from amorphous to crystalline CaP at concentrations> 15 wt%. Stabilization of the amorphous phase of CaP by polyP is reversed by hydrolysis of the polymer by alkaline phosphatase (ALP), an enzyme that releases phosphate for mineralization. It is still present in calcified enamel and dentin, as shown here by immunostaining and enzyme activity measurements. The phase transfer into crystalline CaP can be prevented by the ALP inhibitor levamisole. Besides TEM and SEM, the modulating effects of polyP and ALP on the kinetics of the phase transition from amorphous to crystalline CaP are demonstrated and confirmed by XRD and FTIR analyses. Molecular modeling studies show that the polyP chains, due to their dimensions, are able to penetrate into the channels between the Posner molecules, preventing cluster association to ACP and impairing HA crystal formation.

Consequences of the COVID-19 Pandemic and Governmental Containment Policies on the Detection and Therapy of Oral Malignant Lesions-A Retrospective, Multicenter Cohort Study from Germany.

(1) Background: In response to the global COVID-19 pandemic, governmental measures have been undertaken. The impact of the crisis on the healthcare of patients with cancer is largely unexplored. This multicenter cohort study aimed to investigate a potential screening delay and its consequences in patients with oral cancer (OC) during the pandemic. (2) Material and Methods: Data of patients who were first diagnosed with OC during different periods were collected, especially in terms of OC incidence, tumor stage/entity and time to intervention. The periods lockdown (LD) (13 March-16 June 2020), post-lockdown (PLD) (17 June-1 November 2020), and the corresponding equivalents in 2018/19 were differentiated and compared. (3) Results: There was no obvious trend towards a higher incidence of OC or higher tumor stages, whereas a trend towards a shorter time to intervention during the LD2020 could be observed. Subgroup analyses revealed an increased incidence in OC within the PLD2020 in Mainz, which might be explained by the partial closure of dental practices in this federal state during LD. (4) Conclusions: While there was no overall higher incidence of OC, we found closure of practices during LD to possibly delay cancer diagnosis. Therefore, measures must be taken to identify patients at risk and to ensure basic healthcare, especially in the context of dental screening measures.

Clinical long-term and patient-reported outcomes of dental implants in oral cancer patients.

BACKGROUND AND PURPOSE: The aim of this clinical study was to investigate the clinical long-term and patient-reported outcome of dental implants in patients with oral cancer. In addition, analysis of the influence of radiation therapy, timing of implant insertion, and augmentation procedures on implant survival was performed. MATERIAL AND METHODS: This retrospective study investigated the clinical outcome of 711 dental implants in 164 oral cancer patients, inserted by experienced surgeons of the Department of Oral and Maxillofacial Surgery, University Medical Center Mainz, Germany. Oral health-related quality of life (OHRQoL) was evaluated. RESULTS: Cumulative 5-year and 10-year implant survival rates for all included implants were 87.3% and 80.0%. Implants placed straight after ablative surgery (primary implant placement) and implants placed after completing the oncologic treatment (secondary implant placement) showed a comparable implant survival (92.5% vs. 89.5%; p = 0.635). Irradiation therapy had no significant influence on implant survival of secondary placed implants (p = 0.929). However, regarding implant site (native bone vs. augmented bone) and radiation therapy (non-irradiated bone vs. irradiated bone), implants inserted in irradiated bone that received augmentation procedures showed a statistically significant lower implant survival (p < 0.001). Patients reported a distinct improvement in OHRQoL. CONCLUSIONS: Promising long-term survival rates of dental implants in patients after treatment of oral cancer were seen. In addition, patients benefit in form of an improved OHRQoL. However, bone augmentation procedures in irradiated bone may result in an impaired implants' prognosis.

Biofilm and Orthodontic Therapy.

Dental biofilms can cause major oral diseases like gingivitis, periodontitis, and caries. Orthodontic appliances promote supra- and subgingival biofilm accumulation, alter the oral microbiome, and hamper oral hygiene. Orthodontic treatment can be associated with adverse effects, such as enamel decalcification, gingivitis, and periodontal disease. The aim of this review is to summarize the changes in supra- and subgingival biofilm and periodontal tissues during and after orthodontic treatment. Studies have reported elevated levels of Streptococcus mutans and periodontopathogenic bacteria in patients undergoing orthodontic treatment. In general, the microbial changes and periodontal parameters decreased to pretreatment levels after appliance removal. Nevertheless, some adverse effects associated with orthodontic treatment are not reversible, such as enamel decalcifications caused by metabolic products of high levels of cariogenic bacteria. The evidence suggests that the roughness and constituents of the orthodontic materials influence the bacterial colonization. Therefore, several antibacterial orthodontic bonding systems, which show antibacterial effects in vitro, have been developed. The importance of adequate oral hygiene should be emphasized to all orthodontic patients. They should be frequently reminded and motivated to obtain a good oral hygiene. The evidence from the current literature suggests the safest way for orthodontic treatment in periodontally diseased patients may be after successful completion of the periodontal therapy. However, the exact time point needs to be better clarified in future studies.