Nature vs. nurture in dental caries

Characterization of enamel with variable caries risk

Small angle X-ray scattering (SAXS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) have been used to look at enamel from nine premolars, three each from individuals in low, medium and high risk caries groups. Only SAXS was able to detect consistent differences between any of the groups. In enamel from the high caries risk group, the micropores between the hydroxyapatite crystals were laminar. In enamel from the low caries risk group, the micropores were cylindrical. Other parameters varied between teeth but were not correlated with caries risk.

The association of basic proline-rich peptides from human parotid gland secretions with caries experience

To address whether there are associations between the peptide composition of human parotid saliva and dental decay (caries) experience, we have characterized the peptides from parotid ductal saliva collected from nine adults who have remained free from dental caries (mean age = 59.2; Decayed Missing Filled Surfaces index [DMFS] = 0) and nine individuals who have experienced caries (mean age = 51.2; mean DMFS = 38.4). Ethanol-soluble peptides were size-fractionated on columns of Bio-Gel P-2; the salivary peptides derived from caries-susceptible subjects appeared larger than those found in the saliva of caries-free subjects. Peptides were then resolved into 19 species by cation exchange HPLC. Sequence analysis identified 18 peptides that appear to be proteolytic cleavage products of the basic proline-rich proteins IB-4, IB-5, IB-7, IB-8b, and P-B. The peptides that were more abundant in saliva obtained from the caries-free group differed from those isolated from the caries-susceptible group. The median peptide concentration of one possible precursor protein, IB-7, was found to be higher in saliva collected from caries-free individuals than in that from caries-susceptible individuals. Although differences were found in the phenotypes of proline-rich proteins expressed by these groups of caries-free and caries-susceptible subjects, no statistically significant associations were observed among proline-rich phenotypes and the level of any peptide. Collectively, our results indicate that proteolytic processing of parotid salivary proteins differs among individuals who have remained caries-free and those who have experienced dental decay.

The impact of molecular genetics on oral health paradigms

As a result of our increased understanding of the human genome, and the functional interrelationships of gene products with each other and with the environment, it is becoming increasingly evident that many human diseases are influenced by heritable alterations in the structure or function of genes. Significant advances in research methods and newly emerging partnerships between private and public sector interests are creating new possibilities for utilization of genetic information for the diagnosis and treatment of human diseases. The availability and application of genetic information to the understanding of normal and abnormal human growth and development are fundamentally changing the way we approach the study of human diseases. As a result, the issues and principles of medical genetics are coming to bear across all disciplines of health care. In this review, we discuss some of the potential applications of human molecular genetics for the diagnosis and treatment of oral diseases. This discussion is presented in the context of the ongoing technological advances and conceptual changes that are occurring in the field of medical genetics. To realize the promise of this new molecular genetics, we must be prepared to foresee the possibilities and to incorporate these newly emergent technologies into the evolving discipline of dentistry. By using examples of human conditions, we illustrate the broad application of this emerging technology to the study of simple as well as complex genetic diseases. Throughout this paper, we will use the following terminology: Penetrance--In a population, defined as the proportion of individuals possessing a disease-causing genotype who express the disease phenotype. When this proportion is less than 100%, the disease is said to have reduced or incomplete penetrance. Polymerase chain reaction (PCR)--A technique for amplifying a large number of copies of a specific DNA sequence flanked by two oligonucleotide primers. The DNA is alternately heated and cooled in the presence of DNA polymerase and free nucleotides, so that the specified DNA segment is denatured, hybridized with primers, and extended by DNA polymerase. MIM--Mendelian Inheritance in Man catalogue number from V. McKusick's Mendelian Inheritance in man (OMIM, 1998).