Disinfection of impressions by immersion or spraying with disinfecting solutions is considered nowadays mandatory for effective infection control. The purpose of this review was to examine existing evidence on the effects that chemical disinfection may have on critical qualities of impressions, namely dimensional accuracy and stability over time. A PubMed search was conducted to include original laboratory research articles written in English, published between 1980 and 2005 in peer-reviewed journals and investigating the effect of chemical disinfection, by immersion or spraying, on the dimensional changes that the impression materials experience after setting. Studies were also sought manually, by tracing the references cited in the retrieved articles. The reports on dimensional changes of disinfected impression materials, although rather numerous, are difficult to compare and analyze because of variations of the experimental design. The investigations broadly agree that the disinfection process does not generally affect the dimensional integrity of the impressions, in spite of the statistically significant differences occasionally found. However, the immersion in the disinfecting solution encourages water absorption phenomena in the case of the so-called hydrophilic impression materials, especially after the long-term immersion. Chemical interactions between impressions and disinfectants may occur, but they do not appear to influence the dimensional behaviour of the former. The overall effect of the disinfection is influenced not only by the changes experienced by the impression per se, but also by the alterations of the acrylic tray containing the impression and of the gypsum product poured in it.

Lesch-Nyhan syndrome (LNS) is an X-linked disorder originating from deficiency of the enzyme hypoxanthine guanine phosphoribosyl transferase. It is characterized by neurological manifestations, including the dramatic symptom of compulsive self-mutilation, which results in destruction of oral and perioral tissues. Several drug trials have been administered to improve the severe self-destructive behaviour, with questionable effectiveness. Invasive treatment approaches, such as extraction of teeth and orthognathic surgery, have been suggested with variable success. A conservative treatment with an intraoral appliance serving to prevent oral and peri-oral self-injury is presented in this report. The patient was a 14-year-old boy demonstrating the typical LNS behaviour, including compulsive self-biting, significant loss of lip and tongue tissue, spasticity and involuntary movements. An acrylic maxillary appliance was designed and constructed with an occlusal plate raising the bite. The appliance was retained by two Adams' clasps on the first premolars, along with three ball clasps between the incisors. Fabrication, insertion, and maintenance were uncomplicated and non-stressful to the patient. Periodic recall over 3-year period has confirmed the effective healing of the oral lesions and a high level of tolerance of the appliance.

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The prevalence of abnormal (retracted) position of the tongue at rest was examined in subjects with varying number of natural lower teeth. The aim of the study was to explore the relationship between tongue retraction and state of dentition and to identify potentially related parameters. The resting tongue positions were recorded in subjects partially edentulous in the lower jaw (n = 164) and compared with those met in dentate (n = 57) and completely edentulous participants (n = 84). Potentially related parameters, such as age, sex, duration of edentulism, palate vault and signs of temporomandibular disorders were also recorded. Tongue retraction was observed in a small percentage (12.3%) of the dentate, almost half (45.7%) of the partially edentulous and in the majority (67.8%) of the completely edentulous participants. The number of natural lower teeth correlated with the resting tongue position in the partially edentulous group. The tongue position at rest was also found weakly related to signs of temporomandibular disorders in the dentate group and to the sex and duration of edentulism in the partially edentulous group. It was concluded that the abnormal positioning of the resting tongue is increasingly observed with decreasing number of natural teeth, possibly in accordance with the morphological and functional alterations that result from teeth loss. The presence of a retracted tongue affects the complete denture construction; however, its effect on denture function remains questionable.