Dental devices; reclassification of tricalcium phosphate granules and classification of other bone grafting material for dental bone repair. Final rule.

The Food and Drug Administration (FDA) is reclassifying tricalcium phosphate (TCP) granules for dental bone repair from class III to class II (special controls), classifying into class II (special controls) other bone grafting material for dental indications, and revising the classification name and identification of the device type. Bone grafting materials that contain a drug that is a therapeutic biologic will remain in class III and continue to require a premarket approval application. The classification identification includes materials such as hydroxyapatite, tricalcium phosphate, polylactic and polyglycolic acids, or collagen. This action is being taken to establish sufficient regulatory controls that will provide reasonable assurance of the safety and effectiveness of these devices. Elsewhere in this issue of the Federal Register, FDA is announcing the availability of the guidance document that will serve as the special control for the class II devices.

A thorough physicochemical characterisation of 14 calcium phosphate-based bone substitution materials in comparison to natural bone.

Fourteen different synthetic or biological bone substitution materials were characterised by high-resolution X-ray diffractometry, infrared spectroscopy, thermogravimetry, and scanning electron microscopy. Thus, the main parameters chemical composition, crystallinity, and morphology were determined. The results are compared with natural bone samples. The materials fall into different classes: Chemically treated bone, calcined bovine bone, algae-derived hydroxyapatite, synthetic hydroxyapatite, peptide-loaded hydroxyapatite, and synthetic beta-TCP ceramics.

Dental calculus composition following use of essential-oil/ZnCl2 mouthrinse.

PURPOSE: To test the hypothesis that anticalculus agents cannot completely inhibit calculus formation but can influence the types of calcium phosphate which form, i.e., they can influence the composition of the inorganic component of human dental calculus (HDC). MATERIALS AND METHODS: The composition of HDC specimens obtained from a 16-week multi-center clinical study using three regimens were analyzed, investigators blinded. The treatment regimens were: (a) standard dentifrice (SD), (b) pyrophosphate antitartar dentifrice, and (c) SD with Tartar Control Listerine Antiseptic mouthrinse (containing essential oils and 0.09% zinc chloride). 25 individual samples and eight pooled samples from each group were analyzed using X-ray diffraction, infrared spectroscopy, and scanning electron microscopy. RESULTS: (1) relative frequency of occurrence for: (a) bacteria: Group A = 100%, Group B = 60%, and Group C = 25%; (b) Carbonate hydroxyapatite (CHA): Groups A, B, and C = 100%; (c) dicalcium phosphate dihydrate (DCPD): Group A = 55%; Group B = 45%; Group C = 80%; (2) The relative amount of DCPD is inversely proportional to that of CHA in HDC: the higher the amount of DCPD, the lower the amount of CHA. Group C regimen with essential oil/ZnCl2 mouthrinse and standard dentifrice showed a significant anti-microbial effect and favored the formation of DCPD, the most soluble Ca-P.

A dual constant-composition titration system as an in vitro resorption model for comparing dissolution rates of calcium phosphate biomaterials.

It has been postulated that the in vivo resorption rates of calcium-phosphate bone-graft materials are closely related to their dissolution rates in demineralizing solutions having ionic compositions mimicking the acidic environment produced by osteoclasts. Thus, it should be possible to use an in vitro model to produce dissolution-rate data of calcium-phosphate materials as a starting point for predicting in vivo resorption properties. Direct pH measurements of the extracellular fluid from bone-resorbing cells showed that the pH was as low as 3. In the present study, a dual constant-composition dissolution system was used as an in vitro resorption model to compare dissolution rates of different calcium-phosphate materials. NIST standard reference hydroxyapatite (HA), dicalcium-phosphate dihydrate (DCPD), and calcium-phosphate cement (CPC) discs of known dimensions (6-mm d x 3-mm h) were allowed to dissolve at 37 degrees C in a solution that had an inorganic composition similar to that of serum ([Ca] = 1.15 mmol/l; [P] = 1.2 mmol/l; [KCl] = 133 mmol/l) and a pH of 3.0. A Ca ion-specific electrode and a pH electrode were used to control the addition of titrants to compensate for the increases in calcium and phosphate concentrations, respectively, in the demineralizing solution. The rate and stoichiometry (Ca/P molar ratio) of dissolution were obtained from the titration data. Each solid dissolved at an approximately constant rate during the dissolution process. The dissolution rates, expressed in mg cm(-2) min(-1), (mean +/- standard deviation, n = 5) were for HA: 6.58 +/- 1.22; DCPD: 21.0 +/- 2.6; and CPC: 8.21 +/- 0.73. DCPD dissolved three times faster than HA (p < 0.05). CPC dissolved 1.2 times faster than HA but the difference was not statistically significant (p > 0.05). This model can be used to study the rate and stoichiometry of dissolution of calcium-phosphate bone-graft materials and coatings under a wide range of mineral saturation conditions.