Balancing the risks and benefits associated with cosmetic dentistry - a joint statement by UK specialist dental societies.

Cosmetic dentistry has become increasingly popular, largely as a result of social trends and increased media coverage. This understandable desire for the alleged 'perfect smile' needs to be tempered with an appropriate awareness of the significant risks associated with invasive cosmetic procedures such as veneers and crowns. Patients need to be properly informed that elective removal of healthy enamel and dentine can result in pulpal injury and poorer periodontal health in the longer term, particularly if they are young. The duty of candour means that they ought to be informed that aggressive reduction of sound tooth tissue is not biologically neutral and results in structural weakening of their teeth. Less invasive procedures such as bleaching on its own or for example, combined with direct resin composite bonding, can satisfy many patient's demands, while still being kinder to teeth and having much better fall-back positions for their future requirements. It is the opinion of the British Endodontic Society, British Society for Restorative Dentistry, Restorative Dentistry UK, Dental Trauma UK, British Society of Prosthodontics and the British Society of Paediatric Dentistry that elective invasive cosmetic dental treatments can result in great benefit to patients, but that some aggressive treatments used to achieve them can produce significant morbidities in teeth which were previously healthy. This is a worrying and growing problem with many ethical, legal and biologic aspects, but many adverse outcomes for patients who request cosmetic dental improvements are preventable by using biologically safer initial approaches to treatment planning and its provision.

Recessive oligodontia linked to a homozygous loss-of-function mutation in the SMOC2 gene.

OBJECTIVE: Recently, several genes have been reported with mutations or variants that underlie a number of syndromic and non-syndromic forms of oligodontia including MSX1, PAX9, AXIN2, EDA and WNT10A. This study aimed to identify the causal mutations in a consanguineous Pakistan family with oligodontia and microdontia. DESIGN: Exome sequencing was performed in two of affected members of the Pakistan family. RESULTS: The exome sequencing data revealed that the affected individuals were homozygous with a novel mutation in exon 8 of the SMOC2 gene, c.681T>A (p.C227X). CONCLUSIONS: This is the second report describing SMOC2 mutations with oligodontia and microdontia underlining the key role for this signalling molecule in tooth development.

Tooth size patterns in patients with hypodontia and supernumerary teeth.

AIMS: Anomalies of tooth number may not be isolated conditions but may have wider associations in the development of the dentition including tooth size. This study aimed to examine links between hypodontia, supernumerary teeth and crown size, considering the effect on the development of the whole dentition and so increase understanding of the aetiology of these conditions. METHODS AND RESULTS: The patients, who were all of European ancestry, were 60 young adults (30 males and 30 females) with hypodontia and 60 age and sex matched controls together with 60 young adults (39 males and 21 females) with supernumerary teeth and 60 age and sex matched controls. Hand measurements of mesiodistal and buccolingual dimensions were made of the teeth on dental study models using Mitutoyo electric callipers. The mean value of two measurements was used and intra-operator and inter-operator reliability determined. Patients with hypodontia had smaller teeth than the control group and this difference was statistically significant (p<0.05) for all teeth except the MD dimensions of 13, 23, 24 and 44. The difference in size was greatest for the BL dimensions in hypodontia patients. Further, the greater the number of missing teeth the smaller the tooth size. The hypodontia patients also showed higher variability in tooth dimensions than the control group. Patients with supernumerary teeth had larger teeth than the controls, with the greatest differences in the MD dimensions. In both hypodontia and supernumerary patients the differences in tooth size were generalised throughout the dentition. CONCLUSIONS: In anomalies of tooth number the size of teeth is also involved. In patients with hypodontia and supernumerary teeth the crown size of the whole dentition is affected. These findings are compatible with a multifactorial aetiology of these conditions.

3D X-ray microscopic study of the extent of variations in enamel density in first permanent molars with idiopathic enamel hypomineralisation.

OBJECTIVE: To measure mineral concentration distributions within teeth with idiopathic enamel hypomineralisation, a condition in which developmental defects are seen in first permanent molars, and/or incisors. DESIGN: X-ray microtomographic and 3D x-ray microscopy. SETTING: UK University, 2001. MATERIALS AND METHODS: X-ray microtomographic measurements of the extent of hypomineralisation in two affected molars and two contralateral controls extracted from the same patient. RESULTS: The control molars were visibly normal. The affected molars showed hypomineralised yellow opaque enamel with regions of breakdown. X-ray microtomographic images showed; a 20% reduction in mineral concentration of affected enamel (most cases involved full enamel thickness); hypomineralised enamel had a mineral concentration gradient opposite to that of normal enamel; regions of hypomineralisation distributed randomly throughout affected teeth, (apart from cervical region which was less severely affected). CONCLUSIONS: The pattern of mineral concentration suggests a disturbance during the maturation process. Differences in susceptibility of the ameloblasts during different stages of dental development may explain the asymmetric distribution of the defects. Topical fluoride applications may help promote post eruption maturation of the surface layer in these teeth. The use of fissure sealants and adhesive materials appears to prevent further breakdown.

Tooth size and morphology in twins.

OBJECTIVE: To assess concordance of tooth size and occlusal morphology in monozygotic (identical) and dizygotic (non-identical) twins compared to unrelated controls in order to determine how much these dental traits are related to inheritance. METHODS: Mesiodistal and bucco-lingual dimensions of tooth size in 34 pairs of twins were measured with dial calipers. In addition, the occlusal morphology of nine pairs of teeth was assessed using a co-ordinate measuring machine with a non-contact laser probe. RESULTS: The results showed greater concordance in tooth size for both mesiodistal and bucco-lingual dimensions within twin pairs compared to twin and unrelated controls. Furthermore, monozygotic (MZ) twins showed greater concordance than dizygotic (DZ) twins for all permanent teeth with statistically significant variance for the mesiodistal dimension (P = 0.01) but not bucco-lingual dimension. Superimposed computer models of the digitized occlusal surfaces showed a high degree of similarity for MZ twins compared to DZ twins. The mean intrapair deviation was 147 microm for MZ, 209 microm for DZ and 258 microm for unrelated controls. CONCLUSIONS: The remarkable similarity in the tooth size and morphology of monozygotic twins suggests a strong inheritability factor to tooth size and shape and that these may be useful as additional tools for zygosity determination along with other dental traits.

Detection of a novel mutation in X-linked amelogenesis imperfecta.

Amelogenesis imperfecta (AI) is a heterogeneous group of inherited disorders of defective enamel formation. The major protein involved in enamel formation, amelogenin, is encoded by a gene located at Xp22.1-Xp22.3. This study investigated the molecular defect producing a combined phenotype of hypoplasia and hypomineralization in a family with the clinical features and inheritance pattern of X-linked amelogenesis imperfecta (XAI). Genomic DNA was prepared from buccal cells sampled from family members. The DNA was subjected to the polymerase chain-reaction (PCR) in the presence of a series of oligonucleotide primers designed to amplify all 7 exons of the amelogenin gene. Cloning and sequencing of the purified amplification products identified a cytosine deletion in exon VI at codon 119. The deletion resulted in a frameshift mutation, introducing a premature stop signal at codon 126, producing a truncated protein lacking the terminal 18 amino acids. Identifying mutations assists our understanding of the important functional domains within the gene, and finding another novel mutation emphasizes the need for family-specific diagnosis of amelogenesis imperfecta.

Mechanisms of risk in preterm low-birthweight infants.

The periodontal diseases share many common risk factors with preterm low birth weight. Examples are, age, socioeconomic status and smoking (Fig. 5). Studies to date have only shown an association between the two conditions, and this does not indicate a causal relationship. However, since the inflammatory mediators that occur in the periodontal diseases, also play an important part in the initiation of labor, there are plausible biological mechanisms that could link the two conditions. The challenge for the future is to characterize the nature of the factors that predispose a mother to give birth prematurely to infants less than 2500 g and to assign relative probabilities to each. Studies are taking place in many parts of the world to determine the probability of a preterm low-birth-weight outcome, the interdependence of the factors that contribute to a birth event and possible casual relationships between these factors. Further information about the details of the effects of maternal infection will come from intervention studies, animal studies and more detailed examination of the mechanisms.

The East London Study of Maternal Chronic Periodontal Disease and Preterm Low Birth Weight Infants: study design and prevalence data.

The influence of subject-based and environmental factors on the balance between the subgingival microbial challenge and the host response in periodontal diseases illustrates the intimate link between oral and systemic health. From this stems the hypothesis that the persistent Gram-negative challenge and associated inflammatory sequelae in periodontal disease may have consequences extending beyond the periodontal tissues themselves. This paper addresses the design of a case-control study to examine the relationship between preterm low birth weight (PLBW) and maternal periodontal disease. We present preliminary data on the prevalence of these 2 conditions in a group of mothers at the Royal Hospitals Trust, London, U.K. Cases are defined as mothers delivering an infant weighing less than 2,500g before 37 weeks gestation and controls as mothers delivering an infant of more than 2,500g after 38 weeks. We estimated that a study involving 800 mothers (1:3 case:control) should have sufficient power to detect an association with a minimum odds ration of 3 at the 5% significance level. Demographic details of 177 subjects demonstrated that they were representative of the local population, and the prevalence of PLBW was within the expected range. However, the extent and severity of periodontal disease were higher than predicted and may have reflected elevations in gingival inflammation associated with pregnancy. The final outcome of the study should help determine the need for further interventionist studies to demonstrate a causal relationship between periodontal disease and PLBW, as well as provide information on the prevalence of periodontal diseases in this study population.

Environmental causes of enamel defects.

A large number of causes of enamel defects, both environmental and genetic, have been described. However, many of these are derived from case histories and studies of individual conditions. What is needed now is a systematic investigation of the problem. The first requirement in exploring the aetiology further is the standardization of both the clinical diagnosis and the descriptive terminology. This has been provided by the Fédération Dentaire Internationale Developmental Defects of Enamel Index. Comparing studies using standardized methods, including this index, has highlighted areas for closer investigation. The total prevalence of enamel defects in a population needs to be established as a baseline for studies on aetiology. Sixty-eight per cent of 1518 school children in London have enamel defects in the permanent dentition, with 10.5% having 10 or more teeth affected and 14.6% having hypoplasia, i.e. missing enamel. These findings are in contrast to the 37% with hypoplasia found in a group of third to fifth century Romano-Britons from Dorset, England, suggesting further consideration of possible environmental and genetic differences between the two populations. An overall long-term study of dental development in low birth weight children has shown significantly more (P < 0.001) enamel defects related to major health problems during the neonatal period. By using standardized, reproducible criteria in prevalence studies to gain an overview of the problem and then studying specific groups or conditions, it is possible to identify general and specific factors in the aetiology of enamel defects and investigate further the varying role of genetic and environmental effects.

Planning future general anaesthetic services in paediatric dentistry on the basis of evidence: an analysis of children treated in the Day Stay Centre at the Royal Hospitals NHS Trust, London, between 1985-95.

This study aimed to provide evidence for future planning of general anaesthetic services in Paediatric Dentistry. An audit was carried out on children (< or = 17 years) with special needs who were treated under general anaesthesia in the Day Stay Centre at The Royal Hospitals NHS Trust, London, between 1985-95. During these years, 586 child patients were treated, of which 350 had medical complications and/or mental disabilities. Although the number of peri-operative admissions were low (11 planned and 9 emergency), it highlighted the necessity for these patients to be treated in a hospital. Comprehensive dental treatments were carried out which included 1630 deciduous and 596 permanent tooth restorations, and 1382 deciduous and 261 permanent tooth extractions. These patients had follow-up preventive support in the Dental Institute and the readmission rate for further dental treatment under general anaesthesia was low (14 per cent). Comparing the results between 1985-87, 1988-91 and 1992-95 periods, there was a trend for more patients, travelling longer distances, to be treated in the latter periods. It is suggested that more centres with appropriate equipment and trained staff need to be established to meet the increased demand.

Deciduous enamel defects in low-birth-weight children: correlated X-ray microtomographic and backscattered electron imaging study of hypoplasia and hypomineralization.

Enamel does not remodel, and disturbances occurring during development may remain in the tooth as a permanent record of the upset. Mineralization in prenatal and postnatal deciduous enamel was studied in the shed deciduous incisors of low-birth-weight (LBW: < 2kg) children. The specific objective was to gain further insight into the mechanism of formation of developmental defects of enamel. Sections at a resolution of 22-40 microns were reconstructed using X-ray microtomography (microCT) giving absolute measurements of linear absorption coefficient for AgK alpha radiation. Detail to ca. 1 micron resolution was obtained using automated, digital backscattered electron (BSE) imaging of PMMA-embedded material. Matching the histograms of BSE and microCT images made possible the calibration of the mean atomic number-dependent signal in the BSE images. The comparison of abnormal, affected enamel regions and post-recovery, normal, unaffected regions could be made in the same teeth, since these zones were easily recognized from the distribution of hypoplasia and hypomineralization. The microCT values, converted to calculated mineral densities, ranged from 2.3 g cm-3 to 2.6 g cm-3 in LBW hypoplastic, and between 2.65 and 2.78 g cm-3 in control primary enamel and post-defect, post-natal LBW enamel. Hypoplasia with or without minimal hypomineralization indicated recovery of the ameloblasts in the maturation phase. Disturbance during late matrix formation and early maturation resulted in hypoplasia and hypomineralization.

Small primary tooth-crown size in low birthweight children.

As part of a longitudinal study of dental development in a group of low birthweight children (LBW), study models of 72 children at age 7 years were measured to determine the tooth-crown size of primary molars and canines and to compare the findings with equivalent measurements in 60 normal birthweight (NBW) controls. Mesiodistal (length) and buccolingual (width) dimensions were measured manually, using dial calipers. Primary canines and molars were smaller in the LBW than the controls, with significance values ranging from P < 0.001 for the mesiodistal dimension of maxillary and mandibular canine (> 4% difference) to a non-significant difference P < 0.2 for the buccolingual dimension mandibular first primary molar (1.8% difference). Within the LBW group there was a positive correlation between birthweight and mesiodistal tooth size. Small primary tooth size in LBW children may be influenced by both genetic and environmental factors. The shorter prenatal growth period and poor perinatal and early postnatal development may influence the developing deciduous dentition. Small primary tooth-crown size, associated with LBW, should be considered in all population studies of tooth size.

Unerupted incisors: a case report illustrating an attractive solution.

A case is described in which, after removal of midline supernumerary teeth on two separate occasions, an unerupted central incisor was brought into the arch with the aid of neodymium-iron-boron magnets. Once the incisor was visible, a pre-adjusted upper edgewise appliance was used to guide the tooth into its correct position.

Enamel defects in the primary dentition of children born weighing less than 2000 g.

The findings for enamel defects in the primary dentition of a group of low birthweight (LBW) children were related to their perinatal medical histories. Examination of 110 LBW children and 93 control children aged 5 years showed that significantly more of the LBW children (71%) had hypoplasia than controls (15%), but there was no difference in opacities alone (LBW 25%, control 26%). In the LBW group, defects were seen more often in children classified as ill during the perinatal period, who received ventilator support or intravenous alimentation and in those children born at less than 32 weeks gestation, compared to the LBW children without these perinatal problems. It is speculated that the high incidence and the cause of enamel defects in sick preterm infants may be due to oxygen deprivation and mineral substitute depletion.

Favourable spontaneous eruption of severely displaced maxillary canines with associated follicular disturbance.

Cases of severely displaced unerupted maxillary canines are presented, related to disturbance of the follicle. Removal of the deciduous predecessor produced favourable eruption of the permanent canine and should be considered as a treatment option in similar cases.