Eruptive Tooth Movement May Be Prevented Or Modified by a Variety of Clinical Interventions

PRACTICE

IN BRIEF ● Eruption is both a developmental and adaptive process, and continues throughout life. ● Overeruption can be expected to occur when an opposing tooth is lost. ● Overeruption of an unopposed tooth may present challenges for restoration. VERIFIABLE ● Eruptive tooth movement may be prevented or modified by a variety of clinical interventions. CPD PAPER ● Considerations of the possible consequence of leaving a tooth unopposed, need to be addressed as part of the general treatment planning.

Eruptive tooth movement — the current state of knowledge

H. L. Craddock1 and C. C. Youngson2

How the dentition erupts, and what controls it, is fundamental to almost all aspects of clinical dentistry, yet the mechanisms behind this have not yet been fully elucidated. When the process continues into space that has been created through toothwear or tooth loss, problems in placing restorations can be encountered. This review examines the possible mechanisms of tooth eruption. Differences between processes in animals and humans are highlighted. The limitations of conclusions drawn from animal studies are then discussed with reference to human dental conditions. The differing forms of overeruption in humans are described and the treatment options for overerupted teeth, including prevention of the situation arising, are provided with a discussion of the quality of the evidence base behind these.

INTRODUCTION by members of several dental disciplines, SELECTION CRITERIA Understanding of eruptive tooth movement and the possible consequences of this A Medline literature search was carried out is not only relevant to orthodontists and must therefore be appreciated by them all, into the mechanisms of eruption, progress paediatric dentists, but should also be to aid in both the decision making throughout adulthood, physiological factors appreciated by all dentists in order to pro- process, and in the planning of future limiting or modifying eruptive movement vide the most appropriate care for some of tooth replacement. and clinical interventions capable of modi- their adult patients. Orthodontists take advantage of this fying or preventing vertical tooth move- Eruptive tooth movements continue physiological movement at certain stages ment. Key search words were: tooth erup- throughout life, and are most conspicuous- in corrective treatment, and in the growing tion — physiology, compensatory eruption, ly seen in the overeruption of unopposed patient the extent of this can be fairly pre- overuption, supereruption, supraeruption, teeth, and in wear cases, where occlusal dictable. They are equally aware that this hypereruption, axial tooth movement, vertical dimension is maintained. In the predictability is far less in adults. Restora- occlusal vertical dimension, correction of Western population, the numbers of these tive dentists regularly see what is some- overeruption and Dahl appliance. A total of types of cases are seen with increasing reg- times a dramatic loss of interocclusal space 433 references were identified from the ularity, and an understanding of the effects following an extraction of an opposing search. of these types of movements is important tooth. However in order to understand why The vast number of papers on eruptive in the management of both the simple and this takes place a knowledge of the mecha- tooth movement that have been published advanced restorative case. nism of eruption is needed. over the previous century necessitates The decision to extract a tooth, which some criteria for inclusion in this review. will render the unopposed tooth at risk of PURPOSE OF THE REVIEW Many theories are not yet fully proven and vertical positional changes, will be made This review of the literature was undertaken commonly held beliefs cannot be dis- with a view to increasing the understand- proved. The review included papers that: ing of vertical positional changes that may 1*Lecturer in Restorative Dentistry, 2Senior Lecturer in Restorative Dentistry, Division of Restorative Dentistry, occur throughout life, including: • Were available in English Leeds Dental Institute, Worsley Building, Clarendon Way, • The mechanisms that occur during • Provide clear contemporary evidence Leeds LS2 9LU *Correspondence to: H. L. Craddock developmental eruption • Form the basis for the commonly taught Email: [email protected] • Eruption in the adult texts on this subject • Factors preventing and limiting erup- • Illustrate limitations of previous studies Refereed Paper on which current belief is based doi:10.1038/sj.bdj.4811712 tion, and Received 20.12.02; Accepted 29.07.03 • Clinical interventions which may pre- • Suggest hypotheses, backed by strong © British Dental Journal 2004; 197: 385–391 vent and reverse eruptive movements. evidence, but not yet proven

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• Suggest clinically useful interventions dogs, showed the tooth itself played no part the dental follicle. These experiments how- and recommendations. in the eruptive process. In this investigation ever, provide no evidence that the follicle is tooth germs were removed and replaced involved in determination of final tooth Whenever possible human studies were with dead crown shells, synthetic substi- position. cited, and when animal studies were used tutes or given no form of replacement. The their limitations were discussed. Using follicular changes and the path of eruption Periodontal ligament these criteria 31 papers were selected and were no different from that seen in normal- Ten Cate1 looked for evidence to support are discussed in the following sections. ly erupting teeth, with the exception of the the theory of the periodontal ligament hav- group which used methyl methacrylate ing a major role in determining tooth erup- MECHANISM OF ERUPTION replica teeth. The methacrylate substitute tion. Strong evidence exists to show that Eruptive tooth movements are involved in group did not erupt, and inflammatory the periodontal ligament, which is derived primary eruption, supraeruption, impaction, changes were seen in the follicle. Although from the dental follicle, provides the force alveolar compensation following wear, as small sample sizes were used in this study, required for eruption. The cells thought to well as failure of eruption. For the purposes the results were nonetheless conclusive, be responsible are the fibroblasts within the of this paper, eruption into an initial func- and also serve to illustrate that inflamma- periodontal ligament, which have contrac- tional position and post-eruptive move- tion and disruption of the follicle may tile potential. An early paper by Ten Cate ment will be considered as two distinct impede eruption. This followed on from the et al.6 discussed the role of fibroblasts in phases of eruptive movement, although earlier study by the same group,3 designed the remodelling of the periodontal liga- some of the mechanisms may be similar. to assess the relative importance of the ment, citing various studies indicating the Meaningful scientific study of erup- gubernaculum dentis, tooth root, tooth role of fibroblasts in phagocytosis during tion is difficult in that tooth structure and crown and the dental follicle in the process re-modelling, increased fibroblastic activi- eruption vary from one species to anoth- of eruption. The dental follicle was found to ty during eruption and the distribution of er, and that histological studies in be the only structure necessary for an erup- fibroblasts within the periodontal ligament humans are rarely possible because of the tive pathway to develop and eruption to as indicators that fibroblasts play a key role inaccessibility of tissue for sampling and proceed. Again, relatively small numbers of in physiologic tooth movement. Although ethical considerations. subjects produced conclusive evidence. informative, this study consisted of histo- Many of our standard undergraduate Tooth morphology in the dog is sufficiently logical observations, and did not provide texts on eruption rely heavily on the evi- similar to that of humans to indicate that sufficient data on the origins of the tissues dence of animal experiments to explain the this study of primary eruption may also be studied (ie species, age, whether eruption mechanisms involved in tooth eruption. applicable to humans. was occurring) to enable the reader to Whilst providing valuable background accurately extrapolate the findings to knowledge of the processes likely to be Hydrostatic pressure eruptive tooth movement in humans. Ten involved in eruptive movement, this can- A number of studies exist to demonstrate Cate's theories have been further studied by not be directly extrapolated to the mecha- that there is a hydrostatic pressure differ- Berkovitz,7 who also agreed that no one nisms involved in humans for reasons that ential between the tissues investing the hypothesis can fully explain the mecha- will be explained. erupting tooth crown and its apical nism of tooth eruption. He proposed a mul- extent. tifactorial concept of tooth eruption, which ERUPTION The hydrostatic theory was investigat- embraces Ten Cate's favoured theory of Tooth eruption is defined as the process ed by Van Hassel and McMinn4 again fibroblast contraction, although recognis- whereby a tooth moves from its develop- using dogs, who found that the tissue ing the limitations of in vitro tissue studies. mental position within the jaws to emerge pressure apical to the erupting tooth was He also noted that there was no difference in the oral cavity. This is usually in an axial greater than occlusally, theoretically gen- in the quantities of metabolic structures direction, but may also occur in other erating an eruptive force. However, no within fibroblasts found in the periodontal planes during the life of the tooth. association was demonstrated between ligament of rapidly erupting teeth from Ten Cate1 recognized that the process of the magnitude of the force and the rate of those of fully erupted teeth. Berkovitz con- tooth eruption is not precisely understood, eruption. This was a relatively small cluded that there is no evidence that one and that text described the four possible study (six dogs) with fairly crude and hypothesis fully explains tooth eruption, mechanisms for eruption, that have been invasive methods of measurement, and and that eruption is likely to be a multi- investigated. These are: only compared pressure differentials factorial process. between the tissues immediately superior 1. Root formation, during which space for to the erupting tooth and the intra-coro- CONTROL OF ERUPTION the growing root is accommodated by nal pressure. Less invasive studies, such occlusal movement of the tooth crown. as those by Moxham5 in which the tissue Hormonal control mechanisms 2. Hydrostatic pressure within the periapi- pressures were modified pharmacologi- Risinger and Proffit8 investigated premolar cal tissues pushing the tooth occlusally. cally, showed changes in the rate of erup- eruption in human subjects and determined 3. Bony remodelling tion in rabbits, somewhat supporting the that a circadian rhythm of eruption existed. 4. Pulling of the tooth in an occlusal direc- hydrostatic theory. Using detailed monitoring of physiological tion by the cells and fibres of the peri- changes, the rate of eruption was measured odontal ligament. Bony remodelling over an 11-hour period. The methods used The Marks and Cahill2 study eloquently were accurate and the eruptive state of the Root formation demonstrated that the dental follicle needs teeth under investigation was less than half Clinical experience of the presence of to be present for tooth eruption. Bony erupted, as previous studies had shown that unerupted teeth, showing extensive root remodelling occurs around the erupting eruption was most rapid in the earlier development, suggests that root growth follicle regardless of the presence of a tooth stages of eruption. The authors concluded alone is unlikely to be responsible for erup- crown or tooth, suggesting that the remod- that eruption was probably under hormon- tion. A study by Marks and Cahill2 using elling process may be under the control of al control, most likely due to the effects of

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the late evening secretion of growth hormone and thyroid hormone. Most eruption occurred in late evening, although intrusion tended to occur in the early hours of the morning. There appeared to be no asso- Tooth erupted beyond the occlusal plane ciation with haemodynamic changes or functional activity. It would be erroneous to assume that eruptive movement is only present in children and adolescents with developing occlusions, although the rate The gingival margin has followed The gingival margin remains and control mechanisms may vary. tooth eruption at its original level A study by Leache et al.9 of children Periodontal growth Active eruption with growth deficit concluded that children with delayed growth due to growth hormone deficit or low genetically determined height had delayed tooth eruption. Howev- er those with delayed growth for other reasons show normal dental development. The gingival margin recedes, while the tooth This was a large study of children who were remains positioned at the occlusal plane shorter than average for their chronologi- cal age, although the numbers in each Passive eruption group studied were relatively small. Larger studies are required to support these find- Fig. 1 Classification of eruption/overeruption (after Compagnon and Woda, 1991) ings and provide more substantial evidence for the role of growth hormone in eruption. 45, although there are some ambiguities in The use of post-mortem specimens of Physical control mechanisms the number of subjects within each group ancient and primitive populations where A number of both animal and (relatively and a small difference in the upper age tooth wear was widespread has produced few) human studies have been carried out limit between groups. The results indicated interesting, though limited findings. to determine the forces generated during that the majority of overeruption occurred An anthropological study by Kerr and eruption in order to propel the tooth in the early years following opposing tooth Ringrose13 found that, in order to maintain towards the occlusal plane. loss. In later years loss of periodontal sup- occlusal vertical dimension, teeth continue Gierie et al.10 studied the effects of force port may be superimposed on the picture. to erupt and expose root surface in the application to erupting human premolars. In healthy individuals they noted that the absence of breakdown due to periodontal This was a relatively small study, (only gingival margin remained at its original disease. It is open to question however, eight child subjects). Although very accu- level on the tooth during this occlusal tooth how periodontal disease, other than bone rate measurement was possible, there were movement. This movement, where the peri- loss, could be assessed on the dried skulls. difficulties in observing changes over a odontal ligament and bone develop togeth- It has long been recognised that the prolonged period of time due to the some- er with tooth movement, was described as width of attached gingivae increases with what uncomfortable nature of the meas- periodontal growth. The study found that age. Ainamo and Talari14 compared the urement conditions. The teeth observed after 10 years of remaining unopposed, this widths of attached gingiva in two subject were seen to undergo periods of eruption periodontal migration reversed and root groups, 20 in each group, using radi- and intrusion. Light intermittent forces exposure occurred. Compagnon and Woda ographs to compare the relative distances such as those produced by soft tissue or described this as passive eruption, (as dis- between the lower border of the mandible, muscular contact, were capable of deflect- tinct from active eruption where the tooth the muco-gingival junction and the ing or halting eruption although they did continues to move in an occlusal direction cemento-enamel junction. They found that not increase the rate of intrusion during the in the absence of periodontal growth). the distance from the muco-gingival junc- intrusive phases. This fits well with the From these findings it is obvious that the tion to the lower border of the mandible Equilibrium Theory postulated by Wein- appearance of over-eruption may have remained constant, but the distance from stein et al.11 in relation to determination of several components, including periodontal the muco-gingival junction to the cemen- tooth position. This theory postulated that growth, passive eruption and active erup- to-enamel junction increased with age, teeth remained in a position within the tion. These are shown diagrammatically in indicating a continued eruptive tendency jaws where forces acting in equal and Figure 1. of teeth. It is unlikely that this study could opposite directions cancelled each other. Not all the groups examined were simi- be repeated in today's climate of radiation These forces are likely to arise from the oral lar in terms of the time since extraction of dosage limitation as it relied heavily on the musculature, soft tissue pressures, mastica- the opposing tooth, and some of the results use of marked orthopantomograms. The tory forces, and eruptive force. Habits may need to be treated with caution for number of subjects would be regarded as involving extra-oral foreign bodies such as several reasons. The group with evidence of low by today's standards. pencils and digits may also have an effect. periodontal disease only comprised ten The effect of the loss of an antagonist on subjects. The groups investigated were rel- tooth eruption was investigated by Ainamo POST-ERUPTIVE MOVEMENT atively small and the measurement meth- and Ainamo15 looking at the change in the Compagnon and Woda12 studied the unop- ods were crude. No measure of examiner width of the attached gingiva. Again a very posed upper first molar in both healthy reliability was mentioned. small sample size (13 subjects) was used mouths and those with some periodontal Other human studies of post-eruptive and the authors noted that unopposed teeth pathology present. This study involved 85 movement centre on the maintenance of continue to erupt following the loss of an adult subjects between the ages of 18 and occlusal face height following tooth wear. antagonist, with the supporting structures

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also developing vertically to follow tooth eruption. These patients were mainly mid- Occlusal Plane dle aged. Loss of an antagonist in younger Alveolar Crest patients (mean age 21–22 years) following orthodontic extraction was observed by Smith.15 This study incorporated a larger subject group (42 subjects) and the results were compared with an age and sex matched control group. Measurements were also assessed for reliability. Overerup- tion of the unopposed teeth was found to Fig. 2 The continuously growing tooth be statistically significant, and the problem was mainly confined to the distal aspect of the teeth due to tilting. The findings refuted same in all species, and therefore the rele- involved a split mouth trial of tooth posi- previously held beliefs that tooth position vance to mechanisms occurring in humans tional changes following the extraction of can be maintained by partial occlusal con- is questionable. a first molar. During the 2-year follow-up tact, as the study demonstrated that tilting The continuously extruding tooth period overeruption occurred in all cases, was likely to occur if only partial occlusal (Fig. 3) will ultimately extrude from the with no change in attachment levels. contact was maintained mesially with the alveolar supporting tissues, exposing an Studies such as this on animals with simi- distal portion of the occlusal surface of the increasing amount of root surface. In lar dentitions and occlusal arrangement to opposing first molar. species where there is a marked differentia- humans produce a much more accurate Kiliaridis et al.16 identified that overe- tion into crown and root, there will be an model of the probable outcome in humans, ruption greater than 2 mm occurs in 24% occlusally directed movement of the amelo- yet are still not directly transferable. of unopposed teeth, with 18% having no cemental junction. This type of eruption is demonstrable overeruption at all. This found in grazing animals such as sheep and PREVENTION OF OVERERUPTION leaves a group demonstrating some overe- cattle. Attrition in animals results in the The work of Gierie et al.10 demonstrated ruption of 82%, which in terms of restora- eventual loss of teeth towards the end of that intermittent light forces can prevent tion could have a clinical significance. As their life. It is also seen to some extent in the eruption of an actively erupting tooth there was no measurement of the overerup- humans. Figure 3 shows a constant and it is a commonly held belief that simi- tion beyond 2 mm, it is conceivable that occlusal plane, stabilised by tooth wear. lar intermittent forces generated during within these 24% of subjects, some overe- However, if the tooth were unopposed, chewing against an antagonst will have the ruptions may have been extreme. Mea- overeruption would be seen. same effect. On this basis, the replacement surements were made directly on models of In the continuously erupting tooth, the of an extracted tooth with a fixed or the dentition using a fairly crude method, alveolar supporting structures follow the removable prosthesis would prevent the although reproducibility was found to be occlusally directed development of overeruption of its antagonist provided it good. This study has several flaws in that the tooth, and no exposure of root surface was carried out before vertical movement measurement of overeruption was made is seen. When wear takes place, the occlusal had taken place and this principle is from straight lines drawn between points, level may remain constant, with the alveo- described in current undergraduate and rather than the anatomically determined lar bone becoming closer to the occlusal postgraduate texts (Davenport et al.19 and occlusal curve. plane (Fig. 4). Pameijer20). Both of the latter types of eruptive Another option for dealing with an LIMITATIONS OF ANIMAL STUDIES movement are seen in humans and are unopposed tooth would be to remove it, Many experiments on the mechanisms and described by Compagnon and Woda12 should it not be a key tooth for future rate of tooth eruption have been carried out using different descriptive terms. restorative options. This principle is well on other species, mainly rats and rabbits, Primate studies may provide us with illustrated in the concept of the ‘shortened whose teeth are continuously growing and data most closely applicable to humans. dental arch' as described by Kayser.21 are anatomically different to the teeth of Anneroth and Ericsson18 conducted a A more novel concept, described by primates. Steedle and Proffit17 described study on 28 monkeys, with a dentition Solnit et al.22 employed an etched metal three distinct types of mammalian tooth closely resembling that of man. This splint to bond the unopposed tooth to its eruption. 1. Continuously growing 2. Continuously extruding Occlusal Plane 3. Continuously erupting Anatomically, the continuously growing tooth (Fig. 2) is different from the other Alveolar Crest two categories in that there is no distinc- tion between the crown and the root structures. The fact that growth is continuous and rapid in these teeth makes them useful for eruption studies, as well as the ease of availability and housing of these small animals. However, because new root formation continues throughout life at a rapid rate, there is no evidence available to show that the histological mechanisms are the Fig. 3 The continuously extruding tooth

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adults using this type of appliance. The findings of their 1980 study,27 investigat- Occlusal Plane ing 20 patients with attrition, were that intrusion was on average 1.05 mm and eruption was1.47 mm, and that more eruption than intrusion appeared to take place in the younger subjects. They also noted Alveolar Crest that the use of the splint did not initiate symptoms of TMD and was well tolerated by the wearer. The methodology relied on measurement of radiographic reference points located with metallic implants, before and after appliance treatment, and did not appear to have good inter-examiner reliability. It was suggested that this was caused by difficulties in agreeing reference points on the implants. This study did Fig. 4 The continuously erupting tooth highlight large differences between subjects in intrusion and eruptive potential. adjacent opposed tooth. Provided the bond cated in young patients and the correction Dahl and Krogstad28 observed the effects of between the teeth remains intact this of overeruption can take place alongside permanently increasing the occlusal verti- should theoretically prevent overeruption. other planned tooth movements. Leveling cal dimension in adults, over a five and a Jepson and Allen23 suggested the use of of the arch, which is the first stage in half year period. In some cases there was a adhesive distal cantilever bridges to straight wire fixed orthodontic treatment, reduction in the initial increase in vertical increase the length of shortened dental often deals with overeruptions without any dimension, but in no case did the OVD arches to improve function and aesthetics. specific movements of these teeth. There return to its pre-treatment level. Again, no An additional use for this type of appliance are a number of novel approaches to the precipitation of TMD occurred in the could be to stabilise the tooth position fol- orthodontic correction of overeruption in patients involved. lowing extraction and prevent undesirable adults. Gazit et al.24 reported on a treated Other workers have sought to modify eruptive movement. adult case where all the interocclusal clear- and improve on the basic Dahl appliance The main considerations to be made ance for prosthetic replacement of missing described above. Briggs et al.29 described when deciding on the necessity of prevent- teeth was lost to overeruption. Interoc- the original removable metal onlay appli- ing vertical tooth movement could include: clusal space was created by the intrusion of ance, a fixed modification using metal several mandibular teeth with fixed ortho- adhesive anterior onlays, and definitive 1. Is the tooth a key tooth for future dontic therapy. In adults, the need for restorations prepared at an increased verti- restorative options? orthodontic repositioning may be due to cal dimension. The authors stressed the 2. Has the tooth remained unopposed for teeth drifting following loss of periodontal need for further study into this concept. some time without signs of overerup- support. A particularly useful case report Ricketts and Smith30 mentioned the above tion? by Steffensen and Storey25 describes the treatment options and provide the clinician 3. Would the overeruption of the tooth intrusion of an incisor with a fixed/remov- with a useful means of measuring and present restorative or occlusal difficul- able orthodontic appliance, following the monitoring the relative axial tooth move- ties? elimination of active periodontal pathology. ment taking place. Another variation on 4. Overall state of the dentition. Following treatment a good level of peri- the Dahl appliance is described by Gough 5. Patient preferences and tolerance. odontal attachment was maintained. It and Setchell,31 this time producing axial 6. Aesthetic considerations. must be recognized that these are merely tooth movement in both anterior and pos- 7. Other planned restorative treatment for case reports and not controlled studies, and terior teeth. These authors reported on the unopposed tooth and the edentulous further research is needed in this area. observations in 50 adult subjects and space. As already intimated, the wearing of found that: In many cases the dentist may conventional orthodontic appliances by 1. 94% of patients had no pulpal symptoms encounter a situation requiring prosthetic adults is not always acceptable. The ortho- in the treated teeth, although 2% had restoration where the tooth has already dontic ‘intrusion' of lower incisors using a symptoms requiring endodontic treat- overerupted to some extent. In this case the bite plane is a well accepted, and generally ment. options for correction need to be consid- successful, way of reducing an increased 2. 4% of the teeth suffered loss of vitality. ered. In cases of moderate movement, the overbite. This principle has been adopted in 3. 94% of patients reported no new TMD overerupted tooth may be safely reduced in the development of the ‘Dahl' appliance in symptoms. length, although where a greater degree of the treatment of tooth wear. This was ini- 4. 10% of patients reported mild periodon- 26 overeruption is encountered repositioning tially a single case described by Dahl et al. tal symptoms in the form of tenderness of the tooth may be necessary. where an anterior bite plane was placed on biting. between the upper and lower incisors, and CORRECTION OF OVERERUPTION they concluded that the interocclusal space The overall success rate for this treat- Conventional orthodontic treatment ade- gained between the incisors after wearing ment group was 96%, appearing to make quately corrects many overeruptions, but the appliance, was due not only to incisal this procedure very predictable in its out- tends to be more acceptable to children and intrusion, but also caused by the eruption come. The duration of treatment was from adolescents than adults, mainly due to peer of the posterior segments. This group per- 0.93 to 24 months with a median of 5.9 pressure and aesthetic considerations. formed two further studies into the effect of months. This study was a retrospective Other orthodontic corrections may be indi- increasing the occlusal face height in clinical audit, with no randomisation of

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subject selection, and which did not quan- tify the total relative tooth movement. There was a mixture of fixed and removable appliances, and the relative efficacy of each was not stated. Only 16 subjects were undergoing treatment for the distortion of the occlusal plane following undesirable eruptive changes. Further work in this area would add weight to these findings, and give guidance as to which patients would Fig. 5 Periodontal most benefit from this type of appliance. growth altering In all of the papers using anterior ‘Dahl' aesthetics and appliances, a flat cingulum surface was available space for restoration designed to permit vertical transmission of occlusal forces down the long axis of the tooth, to prevent proclination or forward drifting of the teeth. This is highlighted clearly by Briggs et al.29 It would appear that we can expect overeruption to be the norm when opposing teeth are lost16 and this has the potential to significantly reduce the space available for fixed or removable tooth replacement. Traditional methods of dealing with this problem have the potential disadvantages of being either very destruc- tive ( crowning to a new occlusal plane) or protracted (orthodontic treatment). Fig. 6 Active eruption with dentinal exposure More novel techniques appear, from the UL6 (26) limited data available, to be associated with few complications, are relatively simple and are also less expensive. As with involving x-ray exposure and invasive fy or treat undesirable tooth movements, most conditions however, prevention of the procedures. In any literature review, the and thereby create a mechanical and bio- problem arising is often the best solution reader needs to be aware of publication logical environment more conducive to and this review aims to raise awareness of bias, ie only positive findings tend to find successful restorative treatment. Aware- the complications of overeruption and pre- their way into publication, and many stud- ness of the likelihood of undesirable tooth ventive measures, by the profession. ies never reach the public forum. movement following the loss of an antago- From the evidence reviewed in this nist, may encourage practitioners to plan SUMMARY paper, several trends appear: for the sequelae of tooth loss, or perhaps Two types of post-eruptive tooth move- counsel their patients in the benefits of 1. Eruption is both a developmental ment may take place: avoiding extraction. process, bringing an erupting tooth into • Periodontal growth, where the attach- its functional position, and an adaptive 1. Ten Cate A R. Oral histology: Development, structure ment apparatus moves in an occlusal process, maintaining occlusal vertical and function. Mosby Company. 5th ed, pp268-285, direction with the tooth. dimension following wear. 1998. 2. Marks S C Jr, Cahill D R. Experimental study in the dog • Active eruption where the tooth erupts 2. Primary eruption appears to be con- of the non-active role of the tooth in the eruptive and the attachment apparatus comes to trolled by the secretion of growth and process. Archs Oral Biol 1984; 29: 311-322. lie apically to its original position. thyroid hormones, there is no evidence 3. Cahill D R, Marks S C Jr. Tooth eruption: Evidence for as to whether this is the case in post- the central role of the dental follicle. J Oral Path 1980; Both of these scenarios may create 9: 189-200. eruptive tooth movement. problems in restoration. Periodontal 4. Van Hassell H J, McMinn R G. Pressure differential 3. The dental follicle, from which the peri- favouring tooth eruption in the dog. Archs oral Biol growth may change the dento-gingival odontal ligament is derived, is essential 1972; 17: 183-190. proportions, creating changes in aesthet- to the eruptive process. 5. Moxham B J. The effects of some vaso-active drugs ics that may be unacceptable to the on the eruption of the rabbit mandibular incisor. 4. A cyclical pattern to eruption, involving patient and difficult to correct (Fig. 5). Archs Oral Biol 1979; 24: 681-688. both eruption and intrusion at different 6. Ten Cate A R, Deporter D A, Freeman E. The role of The exposure of dentine and cementum, times of the day, seems to occur. fibroblasts in the remodeling of periodontal ligament and the changing cervical morphology during physiological tooth movement. Am J Orthod 5. Eruption may be halted or reversed by may complicate treatment in the latter 1976; 69: 155-168. intermittent or continuous force applica- 7. Berkovitz B K. How teeth erupt. Dent Update 1990: scenario (Fig. 6). tion. 206-210. Although when viewed individually 8. Risinger R K, Proffit W R. Continuous overnight 6. Direction of eruption may be modified many of the studies on tooth eruption observation of human premolar eruption. Archs oral by uneven application of occlusal load- Biol 1996; 41: 779-789. appear weak, the evidence as a whole sug- ing during eruption. 9. Leache E B, Maranes Pallardo J P, Mourelle Martinez M gests interesting concepts to be considered R, Moreno Gonzales J P. Tooth eruption in children by members of all dental disciplines. Fur- Bearing in mind the processes involved with growth defecit. J Int Ass Child 1988, 19: 29-35. ther research is needed to support existing in eruption outlined in this paper, dentists 10. Gierie W V, Paterson R L, Proffit W R. Response of erupting human premolars to force application. Arch evidence, and current ethical guidelines may well wish to use some of the tech- Oral Biol 1999; 44: 423-428. may prevent the repeat of early studies niques described to predict, prevent, modi- 11. Weinstein S, Haack D C, Morris L Y, Snyder B B,

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Attaway H E. On an equilibrium theory of tooth 18. Anneroth G, Ericsson S G. An experimental in the treatment of periodontally compromised position. Angle Orthod 1963; 1: 1-26. histological study of monkey teeth without incisors: A case report. Int J Periodontics Restorative 12. Compagnon D, Woda A. Supra-eruption of the antagonist. Orthod Rev 1967; 18: 345-359. Dent 1993; 13: 433-439. unopposed maxillary molar. J Prosthet Dent 1991: 66: 19. Davenport J C, Basker R M, Heath J R, and Ralph J P. 26. Dahl B L, Krogstad O, Karlsen K. An alternative 29-34. A colour atlas of removable partial dentures. London: treatment in cases with advanced localised attrition. 13. Kerr N W, Ringrose T J. Do not confuse the bone loss Wolfe Medical Publications 1988: 11-13 J Oral Rehab 1975; 2: 209-214. of periodontitis with root exposure due to 20. Pameeijer J H N. Periodnontal and occlusal factors in 27. Dahl B L, Krogstad O: Long term observations of an supereruption. Br Dent J 1998; 184: 242-246. crown and bridge procedures. Dental Center for increased occlusal face height obtained by a 14. Ainamo J, Talari A. Eruptive Movements in Teeth in Postgraduate Courses. Amsterdam, 1985. combined orthodontic/ prosthetic approach. J Oral Human Adults. In: Poole D F G and Stack M V (eds). 21. Kayser A. Shortened dental arches and oral function. Rehab 1985; 12: 173-176. The Eruption and Occlusion of Teeth. London: J Oral Rehabil 1981; 8: 457-462. 28. Dahl B L, Krogstad O. The effect of a partial bite raising Butterworth 1976; 97-107. 22. Solnit G S, Aquilino S A, Jordan R D. An etched metal splint on the occlusal face height. Acta Odont Scand 15. Ainamo A, Ainamo J. The width of attached gingival splint to prevent the supereruption of unopposed 1980; 40: 17-24. on supraerupted teeth. J Periodontal Res 1978; 3: teeth. J Prosthet Dent 1988; 59: 381-382. 29. Briggs P F A, Bishop K, Djemal S. The clinical evolution 194-198. 23. Jepson N J A, Allen P F. Short and sticky options in the of the 'Dahl‘ Principle. Br Dent J 1997; 183: 171-176. 16. Kiliaridis S, Lyka I, Friede H, Carlsson G E, Ahlqvist M. treatment of the partially dentate patient. Br Dent J 30. Ricketts D N J, Smith B G N. Clinical techniques for Vertical position, rotation, and tipping of molars 1999; 187: 646-652. producing and monitoring minor axial tooth without antagonists. Int J Prosthodont 2000; 13: 24. Gazit E, Ausker Y, Lieberman M. a conservative movement. Eur J Prosthodont Rest Dent 1993; 2: 5-9. 480-486. orthodontic -prosthetic approach for a difficult 31. Gough M B, Setchell D J: A retrospective study of 50 17. Steedle J R and Proffit W R: The pattern and control clinical situation: A case report. Int J Adult Orthod treatments using an appliance to provide localized of eruptive tooth movements. Am J Orthod 1985; 87: Othodgnath Surg 1993; 8: 135-138. occlusal space by relative axial tooth movement. 56-66. 25. Steffensen B, Storey A T. Orthodontic intrusive forces Br Dent J 1999; 187: 134-139.

UK Dental Associations and Societies

The British Society for the Study of Prosthetic Dentistry (BSSPD)

The British Society for the Study of Prosthetic Dentistry is one The annual conference of the society is held immediately of the oldest of the specialist dental societies in the UK and was prior to Easter at a variety of venues around the UK. The founded in 1953. The worldwide membership is major part of the conference consists of a scien- approaching 500. Members have always been at tific programme during which papers, posters the forefront of scientific, clinical and academic and table demonstrations are presented, fol- dentistry. The society is established to advance lowed by active discussion. An enjoyable social education in prosthetic dentistry for the benefit of programme is also incorporated into the confer- the public. It aims to promote and carry out or ence, with the society’s annual dinner as the assist in promoting and carrying out research, centrepiece of the programme. surveys and investigations in prosthetic dentistry The society has published guidelines con- and the publication of such works. cerning the quality of design and construction Membership is open to dentists, doctors and of complete and partial dentures and of implant scientists who profess an interest in prosthetic based prostheses (Ed. Ogden, A. Quintessence, dentistry, and is by election. The large number London 1996). of members in practice has ensured that the The society is represented on national dental society has remained in touch with general committees such as the Specialist Advisory Com- practice as well as academic dentistry. Hon- mittee in Restorative Dentistry, the Association of orary membership is offered to distinguished individuals Consultants and Specialists in Restorative Dentistry Group and by unanimous election of the society. the British Standards Institution.

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