Alignment efficiency and three-dimensional assessment of root resorption after alignment with conventional and copper-nickel-titanium archwires: A randomized controlled trial

OBJECTIVE

To compare alignment efficiency and root resorption between nickel-titanium (NiTi) and copper-nickel-titanium (CuNiTi) archwires after complete alignment in mandibular anterior region.

METHODS

In this two-arm parallel single-blind randomized controlled trial, forty-four patients with Class I malocclusion with mandibular anterior crowding were recruited form orthodontic clinic of All India Institute of Medical Sciences (Jodhpur, India). Patients were randomly allocated into NiTi and CuNiTi groups, with a 1:1 allocation. Alignment was performed using 0.014-in, 0.016-in, 0.018-in, 0.019x0.025-in archwire sequence in the respective groups, which terminated in 0.019 x 0.025-in stainless-steel working archwire. The primary outcome was alignment efficiency, measured on study models from baseline (T0) to the first, second, third, fourth and fifth-month (T5). Secondary outcome was root resorption, measured from CBCT scans taken at T0 and T5. Mixed-factorial ANOVA was used to compare Little's Irregularity Index (LII). For assessing the proportion of patients with complete alignment at the end of each month, Kaplan-Meier survival curve was built and time to treatment completion was compared between groups using log rank test. Paired t-test was used to assess external apical root resorption (EARR) within groups, whereas independent t-test was used to evaluate LII and EARR between the groups.

RESULTS

Twenty-two patients were recruited in each group. One patient was lost to follow-up in the CuNiTi group. No statistically significant differences were observed in alignment efficiency between the groups (p>0.05). Intergroup comparison revealed that the changes in root measurement in three-dimensions were not statistically significant (p>0.05), except for mandibular right central incisor, which showed increased resorption at root apex in NiTi group (p<0.01).

CONCLUSION

The two alignment archwires showed similar rate of alignment at all time points. Root resorption measurement did not differ between the NiTi and CuNiTi groups, except for the mandibular right central incisor, which showed more resorption in NiTi group.

The prevalence, characteristics, and risk factors of external cervical resorption: a retrospective practice-based study

OBJECTIVES

External cervical root resorption (ECR) is a poorly understood and aggressive form of resorption. The purpose of this study was to examine the prevalence, characteristics, and risk factors associated with the occurrence of ECR in patients seeking endodontic care from private practice settings.

MATERIALS AND METHODS

Records of 343 patients with 390 teeth diagnosed with ECR were identified from 3 private endodontic practices from 2008 to 2022. The patients' demographic information, systemic conditions, and dental history were recorded. The characteristics of the cases including Heithersay classification, pulpal and periapical status, and their management were documented. The association between case severity and potential predisposing factors was examined using chi-square analysis.

RESULTS

The overall prevalence of ECR among patients seeking endodontic care was low (< 1%). However, there was a greater than twofold increase in the pooled prevalence from 2016 to 2021 (0.99%) compared to the data from 2010 to 2015 (0.46%). The most commonly affected teeth were anterior teeth (48.7%). Class II (30.0%) and class III (45.4%) defects were the most often identified. Patients with a history of trauma or orthodontic treatment were significantly more likely to be diagnosed with severe cervical resorption (class III or IV) (p < 0.05).

CONCLUSIONS

There has been an increase in the prevalence of ECR in patients seeking endodontic care. A history of orthodontic treatment and traumatic dental mechanical injuries may predict the severity of resorption.

CLINICAL RELEVANCE

The upward trend in the occurrence of ECR warrants close monitoring of the patients at high risk of developing the condition to facilitate early detection and management.

Management of Multiple Idiopathic Root Resorption in a Rheumatoid Arthritis Patient: A Case Report with 4-year Follow-up

Cervical root resorption is a rare destructive disease that originates from the external cervical root surface. It has a multifactorial etiology. Cervical root resorption may affect several teeth and its treatment can be complicated due to the size, location, and extension of the resorptive defect. Rheumatoid arthritis is a chronic inflammatory autoimmune disease that has systemic effects. The objective of this article was to report a rare case of multiple idiopathic cervical resorptions in a patient with rheumatoid arthritis. A 52-year-old male patient with a 20-year history of rheumatoid arthritis was diagnosed with multiple idiopathic cervical resorptions through cone-beam computed tomography (CBCT) and clinical examination. All known causes for cervical resorption were ruled out after a detailed anamnesis. This report details inflammation due to rheumatoid arthritis as a possible cause of idiopathic cervical resorption. The systemic alterations wrought by rheumatoid arthritis could be related to the etiopathogenesis of cervical root resorption. Non-surgical endodontic treatment was done for the maxillary left canine. The defect was surgically repaired using bioceramic putty. The 12-month recall revealed the good healing of the periodontal and periradicular conditions with no obvious clinical symptoms. At the 36-month recall visit, clinical and radiographic evidence of deterioration in the repair material was observed. At the 54-month follow-up, deterioration of repair material was observed with an increase in the extension of resorption in tooth 14 was detected. Reasons for this deterioration remain unclear. Ruling out all other factors for cervical root resorption, how rheumatoid arthritis contributes to cervical root resorption is still lacking/unclear. Dental care providers must be vigilant for signs of cervical root resorption in vulnerable patients with rheumatoid arthritis for early diagnosis and prompt treatment. Keywords: External root resorption, Inflammatory markers, Multiple root resorption, Rheumatoid arthritis, Resorption repair.

Scleroderma and multiple teeth with invasive cervical resorption: is there a connection?

Scleroderma is a chronic connective tissue disease generally classified as an autoimmune rheumatic disease. Symptoms may include thickening of the skin, calcifications, Raynaud syndrome, and esophageal problems. Invasive cervical resorption is an aggressive form of external resorption localized in the cervical part of the tooth. Its etiology remains uncertain. This case report describes invasive cervical resorption affecting 4 teeth in a 44-year-old woman with scleroderma and speculates on the possible relationships between these disease entities.

Decision criteria influencing the therapeutic approach to invasive cervical resorption: a case series

Invasive cervical resorption (ICR) is a dental lesion starting in the cervical region and involving the loss of dental hard tissue as a result of odontoclastic action. Due to its localization and invasive pattern, this process represents a challenging clinical situation. When feasible, the major aim of an ICR treatment is to completely remove the pathologic tissue (specifically at the entry point of the lesion) and to seal the resulting defect, without compromising tooth rehabilitation. In this context, choosing how to access the resorptive lacuna is essential. Two main options have been described in the literature: an external approach, requiring the surgical exposure of the resorptive lacuna, and an internal approach, taking advantage of the endodontic access cavity. However, there are no guidelines that indicate which approach to choose for the treatment of an ICR. This article is based on four clinical cases. It aims to provide specific clinical and radiologic features that should be considered in order to take the most appropriate decision, when choosing between the internal and the external approaches. It is proposed to base the therapeutic strategy on the accessibility and the size of the portal of entry of the lesion. When the entry point is wide, its extension along the root must also be taken into account. Other important parameters are the circumferential and vertical extents of the lesion in the radicular dentin. Although it is not a determining factor, the pulpal involvement of the lesion can also be considered.

Florid hypercementosis synchronous with periodontitis: a case report

Excessive cementum formation, referred to as hypercementosis (HC), is an uncommon nonneoplastic process that principally occurs with permanent teeth. Widespread tooth involvement has been confined mostly to Paget disease of bone. Only a limited number of reports of HC coincident with periodontitis has appeared in the literature. The aim of this article is to present the clinical, radiographic, and histopathologic findings of a 44-year-old female with moderate to severe periodontitis synchronous with 22 HC-affected teeth. A list of other etiologies associated with HC is provided.

Are breeding teeth in Atlantic salmon a component of the drastic alterations of the oral facial skeleton?

Upriver spawning migration of starving Atlantic salmon (Salmo salar) involves drastic skeletal alterations, among which a toothless stage followed by the appearance of a new set of so-called breeding teeth has been described. To investigate this phenomenon, we examined the patterns of tooth replacement on the lower jaws in different life stages of wild animals before and after spawning. Prior to spawning, every position held either a functional or a replacement tooth, both in first-time (grilse) and repetitive (salmon) spawners. Teeth were in a similar developmental stage every three positions along the tooth row. A functional tooth occurred in every third position and intermediate positions were taken by developing teeth. Within the process of replacement, teeth were resorbed and not shed. Our observations on an uninterrupted tooth replacement pattern provided no evidence of an intermediate toothless stage nor of a specialized breeding-teeth generation. Only animals that survived spawning (kelts) showed a highly variable tooth pattern, but with the initial "every third position" pattern still recognizable in some animals. We hypothesise that previous accounts describing a complete tooth loss/replacement relate to proliferation of the oral mucosa that conceals the teeth prior to the breeding period and to the use of maceration techniques that could have removed all teeth with an incompletely mineralised base.

[Observation of osteoclasts on the root surface during human deciduous teeth resorption]

OBJECTIVE

To observe osteoclasts on the resorbing surface of human deciduous teeth.

METHODS

After fixing the collected deciduous teeth, we prepared the tooth slices without decalcification, treated them with HE and TRAP dyestuff, and observed the osteoclasts under light and scanning electron microscope.

RESULTS

There were large quantity of various forms of overlapping and huge osteoclasts with many nuclei and silk-like protuberances on the resorbing surface of deciduous teeth. The multinucleated osteoclasts align on the surface of coarse dentin.

CONCLUSION

On the resorbing surface of human deciduous teeth there are large amount of osteoclasts which can be used as a source of studying human osteoclast.

Histogenesis and disappearance of the teeth of the Mekong giant catfish, Pangasianodon gigas (Teleostei)

Juveniles of the Mekong giant catfish, Pangasianodon gigas (Teleostei), have 3 sorts of tooth-upper and lower jaw teeth, palatal teeth, and pharyngeal teeth--but adults are toothless. To investigate the histogenesis and disappearance of the teeth, we made serial sections of the mouth and teeth of juvenile fish at 10 developmental stages (from ca. 8.5 to ca. 30 cm in total length) and examined them under scanning electron microscope and light microscope. Observations of teeth and surrounding tissues in the serial sections revealed the process of tooth resorption by active odontoclast-like cells. Numbers of jaw and palatal teeth decreased with age. When the fish reached ca. 14 cm in total length, the numbers of functional upper jaw teeth and successional tooth germs decreased rapidly, and the developmental rate of successional tooth germs slowed. When the fish reached ca. 24 cm, no teeth existed in the upper jaw. It is clear that tooth disappearance results from the shedding of functional teeth and the lack of replacement tooth germs.

Expression of matrix metalloproteinase-9 mRNA and protein during deciduous tooth resorption in bovine odontoclasts

Matrix metalloproteinase-9 (MMP-9, or gelatinase B) is an extracellular proteinase that is highly expressed in osteoclasts and has been postulated to play an important role in their resorptive activity. Although MMP-9 has been reported to play a role in bone resorption, the association of this enzyme during deciduous tooth resorption has not yet been clarified. The purpose of the present study was to increase our understanding of the role of MMP-9 during deciduous tooth resorption. Reverse transcription-polymerase chain reaction (RT-PCR) and northern blot analysis of total RNAs extracted from bovine root-resorbing tissues, which lie between the root of a deciduous tooth and its permanent successor, revealed the expression of mRNA for MMP-9 in the tissue. These results indicate that MMP-9 may be involved in the process of deciduous tooth resorption. In addition, in situ hybridization and immunohistochemistry were also performed to identify the cells that produced MMP-9 in bovine root-resorbing tissue. MMP-9 mRNA was highly expressed in odontoclasts that were aligned along the surface of the tissue. Immunohistochemistry confirmed the predominant localization of MMP-9 in odontoclasts. The present data demonstrate that odontoclasts in deciduous root resorption express MMP-9, which may participate in proteolysis during root resorption of deciduous tooth.

Immunolocalization of vacuolar-type H+-ATPase, cathepsin K, matrix metalloproteinase-9, and receptor activator of NFkappaB ligand in odontoclasts during physiological root resorption of human deciduous teeth

To investigate the cellular mechanisms of physiological root resorption in human deciduous teeth, the authors examined the immunocytochemical localization of vacuolar-type H+-ATPase, a lysosomal cysteine proteinase, cathepsin K, matrix metalloproteinase-9 (MMP-9), and receptor activator of NFKB ligand (RANKL) in odontoclasts. H+-ATPase, cathepsin K, and MMP-9 are the most important enzymes for decalcification of apatite crystals and degradation of type-I collagen. In addition, RANKL is one of the key regulatory molecules in osteoclast formation and functions. Odontoclasts developed extensive ruffled borders and clear zones apposed to the resorbing root dentine surfaces. On immunoelectron microscopy, the expression of vacuolar-type H+-ATPase was detected along the limiting membranes of pale vacuoles and the ruffled border membranes of odontoclasts. Cathepsin K in odontoclasts was localized within pale vacuoles, lysosomes, the extracellular canals of ruffled borders, and the underlying resorbing dentine surfaces. MMP-9 localization in odontoclasts was similar to those of cathepsin K. RANKL was detected in both mononuclear stromal cells and odontoclasts located on resorbing dentine surfaces. These results suggest that (1) odontoclasts are directly involved in decalcification of apatite crystals by active extrusion of proton ions mediated by H+-ATPase and (2) extracellular degradation of dentine type-I collagen by both cathepsin K and MMP-9, and (3) odontoclast differentiation and activity are regulated, at least in part, by RANKL, possibly produced by mononuclear stromal cells and odontoclasts themselves in the resorbing tissues. Thus, the cellular mechanisms of physiological root resorption appear to be quite similar to those of osteoclastic bone resorption.

The odontoclasts of Ambystoma mexicanum

The resorption of teeth in Ambystoma mexicanum during postembryonal ontogenesis and induced metamorphosis occurs by means of light-microscopic detectable giant-cells. These have morphological and functional characters similar to those of odontoclasts of other vertebrates. The multinucleated odontoclasts resorb not only the pedicel (base), but the stalk of the tooth, too. When active, the cells form a ruffled border and a sealing zone. In this way they are able to demineralize the hard tissues of teeth (dentin and mineral of the pedicel) and to dissolve the extracellular matrix. Resorption of enamel has not been observed. Marks of resorption resemble the Howship's lacunae of other tetrapods. TRAP as a typical enzyme of odontoclasts could not be detected histochemically. Dependence of PTH, which is supposed to be necessary for the formation and activation of odontoclasts as well as of thyroxine can be excluded, although the resorbing cells are functionally and cytologically identical with those of other vertebrates. This demands some other mechanism for the formation and regulation of the odontoclasts in A. mexicanum.

Ultrastructural study of the root dentine surface resuming resorption on human deciduous teeth

Resorption of deciduous teeth is not continuous, but alternates with periods of repair or rest. Dentine surfaces in periods of rest or repair resume resorption by odontoclasts during physiological root resorption of the deciduous teeth. However, no observations of such dentine surfaces have been shown. The characteristic feature of the dentine surfaces resuming resorption remains unknown. Tartrate-resistant acid phosphatase activity (TRAP) was detected on human deciduous teeth. The root resorbing surfaces on these teeth were photographed with a whole-mount light microscope, and the photographed areas were serially sectioned into 0.5 micron semithin sections. Preodontoclasts and odontoclasts were three-dimensionally reconstructed. On root resorbing surfaces, areas with small scattered TRAP-positive cells were observed among areas with many TRAP-positive resorbing odontoclasts and TRAP-negative areas. The sections showed that areas with small scattered TRAP-positive cells have features similar to those of TRAP-negative areas, but there were three kinds of characteristic TRAP-positive cells: preodontoclasts, odontoclasts forming small lacunae, and preodontoclasts, and odontoclasts with cytoplasmic processes extending to the dentine surface, which is covered with cells. These results suggest that the areas with small scattered TRAP-positive cells could be at the stage of resuming resorption, and show that the presence of preodontoclasts and odontoclasts with cytoplasmic processes extending to the covered dentine surface is a characteristic feature of the dentine surface at this stage.

Mononuclear odontoclast participation in tooth resorption: the distribution of nuclei in human odontoclasts

Osteoclasts and odontoclasts have been considered multinucleated giant cells which resorb hard tissue by ruffled borders. Recently, the authors reported the presence of a mononuclear osteoclast and odontoclast with a ruffled border. However, the relative frequency of such cells and the distribution of the number of nuclei including mononuclear cells in them have not been elucidated. Six human deciduous teeth were used in this study. After fixation and decalcification, tartrate-resistant acid phosphatase (TRAP) activity was detected with the azo dye method, and then TRAP-positive cells were observed on resorbing areas of teeth by light microscopy. The cells for investigation were serially sectioned by semithin sections to observe the presence of resorptive lacuna and the number of nuclei. The TRAP activity was detected in both multinucleated and mononuclear odontoclasts from serial semithin sections, and 242 TRAP-positive cells which formed lacunae on dentin were investigated to determine the frequency distribution of the number of nuclei. The mean number of nuclei per cell was 5.3, and median was 4. Only 2.9% of odontoclasts were mononucleus and 93.8% had 10 or fewer nuclei. The majority of odontoclasts forming lacunae on the dentin were cells with 10 or fewer nuclei, and mononuclear odontoclasts participated in human deciduous tooth resorption together with multinucleated ones.

Normal human peripheral blood mononuclear cells mobilized with granulocyte colony-stimulating factor have increased osteoclastogenic potential compared to nonmobilized blood

Single-cell suspensions of granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood mononuclear cells (G-PBMC) cultured in alpha minimal essential medium (alphaMEM) containing 10% fetal bovine serum formed multicellular aggregates within 24 hours. In six separate experiments, formation of aggregates appeared to be dependent on cell density per surface area, so that 5.8 +/- 1.3 aggregates formed per 1 x 10(5) cells when G-PBMC were cultured at densities greater than or equal to 1 x 10(5) cells/cm2. The frequency of aggregate formation was less than 1 per 10(5) cells when G-PBMC were cultured at densities less than 1 x 10(5) cells/cm2. Once formed, aggregates became adherent within 72 hours, and then, over the course of 21 days, released CD3/CD4/CD25-positive cells into the supernatant. This T-cell production peaked between days 7 and 14, reaching a total of 1,269 +/- 125.9 cells released per aggregate by day 21. Between days 14 and 21, the aggregates also generated macroscopic clusters of adherent mononuclear and giant multinucleated cells that stained positive for tartrate-resistant acid phosphatase (TRAP). At 4 weeks, the macroscopic foci coalesced into monolayers. Multinucleated TRAP-positive cells were distinguished from macrophage polykaryons by the absence of CD14 expression and the presence of osteoclast-specific membrane receptors for calcitonin and alphavbeta3-vitronectin. The osteoclast nature of these cells was further demonstrated by their ability to form resorption lacunae on dentine slices. Comparable osteoclast formation was not detected in cultures of normal marrow or normal nonmobilized peripheral blood.

Morphology of the deciduous tusk (tush) of the African elephant (Loxodonta africana)

The tusk of the African elephant is preceded by a deciduous tooth generally known as the tush. Tushes from nine elephant fetuses and six calves younger than 1 year were exposed by dissection and described morphologically. All tushes consisted of a crown, root and pulpal cavity, the formation of which is completed soon after birth. They reached a maximum length of 5 cm, appeared not to erupt through the skin and were pushed aside and resorbed during enlargement of the distally located primordium of the tusk. Dental enamel, which covered the crown, could easily be removed and consisted of rods with an interwoven arrangement; the dentine-enamel junction was flat. Cellular cementum extended for variable distances over the crown and the dentine was tubular in nature. Although the tush apparently has no function, it provides the anlage and orientation for the development of its permanent successor.

[Physiology and pharmacology of hard tissues--effect of chemicals on the formation and the resorption mechanism of tooth and bone]

This review described the effects of several drugs on the formation and the resorption mechanism of tooth and bone. The enamel formed during high fluoride exposure showed marked hypocalcification, and the organic substances appeared on the incisors in these regions. Such changes following fluoride administration appear to indicate an inhibition of the mineral deposition and/or an inhibition of organic matrix withdrawal. The successive bisphosphonate (HEBP) injections reduced both the progress of the mineral deposition and the formation of the enamel matrix. Colchicine showed a remarkable inhibitory effect on the matrix-forming cells of the dentin and enamel in teeth through its striking inhibitory action on the cytoskeletal system and secretary function. The dentin formation in rabbit and rat incisor dentin was reduced markedly. Colchicine induced reparative dentinogenesis in dental pulp and ectopic calcification in the bone marrow. Both sodium salicylate and aspirin reduced dentin formation through a mechanism that reduces the incorporation of collagen precursors into odontoblasts. Sodium salicylate also inhibited the growth of the upper jaw and tibia in rats. The recruitment of osteoclast-like multinucleated cells was inhibited by sodium salicylate in vitro. A pharmacological approach for studying the formation and resorption mechanism of hard tissue is useful tool for developing hard tissue research.

Odontoclastic resorption of the superficial nonmineralized layer of predentine in the shedding of human deciduous teeth

Resorption by odontoclasts of a superficial nonmineralized layer of predentine that occurs in prior to the shedding of human deciduous teeth was studied by light and electron microscopy. As resorption of the tooth roots neared completion, multinucleate cells appeared on the predentine surface of the coronal dentine between the degenerated odontoblasts, excavated characteristic resorption lacunae in the nonmineralized predentine. These multinucleate cells had the same ultrastructural characteristics as odontoclasts and histochemical demonstration of tartrate-resistant acid phosphatase activity in the multinucleate cells revealed intense staining in numerous small granules identified as lysosomes. Occasionally, the multinucleate cells simultaneously resorbed both nonmineralized and calcospherite-mineralized matrix in the predentine. The study demonstrates that multinucleate odontoclasts can resorb nonmineralized predentine matrix in vivo, probably in the same way as they resorb demineralized organic matrix in the resorption zone underlying their ruffled border.

Odontoclastic resorption at the pulpal surface of coronal dentin prior to the shedding of human deciduous teeth

Histological and histochemical observations of more than 150 extracted human deciduous teeth revealed that, prior to shedding, odontoclastic resorption as a rule takes place at the pulpal surface of coronal dentin. We also found that this phenomenon occurs in all kinds of deciduous teeth. The process of this internal resorption of coronal dentin of deciduous teeth clearly showed time-related histological changes. During the time the roots were actively being resorbed, the pulpal tissue retained its normal structure. However, when root resorption neared completion, inflammatory cells started to gradually infiltrate into the pulp, and odontoblasts began to degenerate. After that, multinucleate odontoclasts appeared, and resorption proceeded from the predentin to the dentin. The odontoclastic activity was initially detected only on the pulpal surface at the bottom areas of the crown. It gradually spread towards the pulpal horn regions along the wall of the pulp chamber. However, this internal resorption of coronal dentin did not continue until the teeth were finally shed. After the elimination of resorption, the resorbed dentin surface was repaired by a cementum-like deposition or covered with fibrous connective tissue.

The central (intraosseous) calcifying odontogenic cyst: an analysis of 215 cases

This study reviews and analyzes the clinical, radiographic, and histomorphologic features of the 215 cases of central calcifying odontogenic cyst (CCOC) reported in the literature. Based on the present information, a clinicopathologic classification of calcifying odontogenic cyst is proposed. The CCOC is also compared with its peripheral counterpart and the differences discussed.

[Autotransplantation of an impacted supernumerary tooth]

The Authors report on a case of interesting tooth transplantation using a supernumerary in the site of a lower premolar root affected by periapical granuloma. Irrespective of local unfavourable conditions, the good result of surgical operation is demonstrated by up to now vitality and stability of transplanted tooth.

Evidence for an inhibitor of osteoclast attachment in dentinal matrix

The ability of osteoclasts to colonize in vitro different preparations of dentin extracted with guanidinium hydrochloride (GuHCl) was studied in order to establish morphological evidence for an extractable inhibitor of osteoclast spreading within dentin. Osteoclasts were isolated from neonatal rats and seeded onto pieces of fully mineralized dentin, demineralized dentin and predentin extracted with GuHCl. Osteoclasts were also seeded onto unextracted tissues. The results were evaluated with scanning electron microscopy. Osteoclasts colonized and resorbed fully mineralized dentin, whereas clastic cells were not observed on unextracted demineralized dentin and predentin. In contrast to this, osteoclasts attached and spread on demineralized dentin and predentin extracted with GuHCl. It was concluded that the non-collagenous organic component of dentin contains an extractable inhibitor of osteoclastic attachment and spreading. It is tempting to speculate that the inhibitor may be responsible for the naturally occurring resistance of dentin to resorption.

Short root anomaly

A case of generalised short root anomaly is described. All permanent teeth had abnormally short roots, associated with microdontia, hypodontia and a dens invaginatus. Members of the patient's family were similarly affected.

[Experimental study on the effect of replantation of immature permanent teeth on the periapical and periodontal tissues]

Replantation and semi-rigid fixation were performed on canine immature permanent teeth, and one week after replantation the teeth were treated by root filling with calcium hydroxide. The root apex and periodontium of the teeth with replantation were examined for changes regularly during the experiment by microradiographic, fluorescence microscopic, polarizing microscopic and X-ray observation of undecalcified horizontal continual ground sections. The results obtained were as follows: 1) Immediately after replantation, root formation was observed, but its formation was found to cease at a relatively early time. No site of the root showed any inflammatory resorption. 2) The dentine of the teeth with replantation was narrow, and the whole tooth substance showed discoloration due to penetration of calcium hydroxide. 3) the periodontal space surrounding the teeth with replantation was decreased daily by new bone actively formed from the alveolar bone proper and by a thin cementum layer added on the periodontal surface. This change occurred from one week after replantation. 4) The width of the periodontal space of the teeth with replantation, which had been wider than that of a control tooth, was increased and decreased daily at the cervix and root apex and the central part of the root, respectively. 5) Collagen fibers of the periodontal membrane were present in the periodontal space of the teeth with replantation, together with regeneration of the periodontal membrane that had been cut by extraction. 6) There were no changes due to replantation in the two teeth adjacent to the tooth with replantation or the lateral jaw.

A transmission electron microscope study of fibroblast changes in human deciduous tooth pulp

The coronal pulps of four primary canines, free from radicular resorption, and of three primary teeth, with roots entirely resorbed, were prepared for electron microscopy. Mature fibroblasts, similar to those reported in the pulps of permanent teeth, were present in the pulps of the clinically mature teeth. Regression of fibroblasts, evident in the pulps of deciduous teeth at the root resorption stage, was characterized by cytoplasmic changes, modifications in the cytoskeleton and dissociation of cells and fibrils. Deciduous teeth might provide a model for studying pulp fibroblast ageing.

A quantitative comparison of osteoclasts in the teeth of the anuran amphibian Xenopus laevis

An image-analysing computer was used to measure transectional areas of osteoclast cytoplasm and nuclei, the number of nuclei per osteoclast transection, odontoblast height and dentine thickness on serial sections of resorbing, erupting and ankylosed teeth from 3 groups of female frogs of different snout-vent lengths. All parameters except nuclear size were increased significantly between the small and large frogs, suggesting that larger teeth are resorbed by larger osteoclasts. Because more time is required for resorption of the thicker dentine of large frogs, the increased size and nuclear number of the osteoclasts in large specimens may be related to the increased time available for fusion of mononuclear precursor cells. However, in large frogs the proportional increase in cytoplasmic area of osteoclasts was greater than the increase in number of nuclei. This may be related to osteoclast activity, as the height of the odontoblasts also increased with dentine thickness.

Secondary bone grafting and orthodontic treatment in patients with bilateral complete clefts of the lip and palate

The results of secondary bone grafting and orthodontic treatment in 41 patients with bilateral complete clefts of the lip and palate are reported. Good bone formation was found in 98% of the cleft sites grafted before the eruption of the canines, and in 80% of the clefts grafted later. Closure of both cleft spaces by orthodontic means was achieved in 20 of the 21 patients in the first group, and in 14 of the 20 patients in the second group. The bone grafts failed in one cleft site in 4 patients, all of which were regrafted with satisfactory results. In 2 patients one of the canines was later affected by external root resorption, necessitating endodontic treatment. Both the failures and the root resorptions occurred in patients bone grafted at an older age than was considered optimal for bilateral clefts: 10 to 11 years. Seven patients needed a bridge prosthesis, 3 of these over one cleft space only. Even these patients benefited greatly from bone grafting.

Resorption of the mouse incisor after the application of cold to the periodontal attachment apparatus

In order to study in detail the processes leading to the resorption and ankylosis of teeth after trauma, the effects of cold application on the periodontal tissues were studied in the mouse. Liquid nitrogen was applied locally to the outer surface of the lower jaw which resulted in a freezing of the incisor and its surrounding tissues. The healing processes in the damaged periodontal ligament and the accompanying phenomena of ankylosis and dental root resorption were investigated histologically at both the light and electron microscopic levels. As a result of cold application, the cells in the periodontal ligament were killed. After a few days, the ligament started to be repopulated with cells like fibroblasts and macrophages. From 3 days on, mineral crystallites were deposited along the cementum covering the lingual, mesial, and lateral surfaces of the incisor, finally resulting in a 4-6 micron thick layer. During the period of 7-12 days following cold application, this layer of mineralized material started to be phagocytosed and degraded, presumably by mononuclear cells. Finally, extensive root resorption and some ankylosis between the tooth and the alveolar bone were observed. In the resorbed areas, cells were seen which could not be distinguished from osteoclasts. In some instances, their ruffled border was in close apposition with each of the three mineralized tissues--dentin, cementum, and alveolar bone. It is hypothesized that the deposition and subsequent phagocytosis of mineralized material along the root surface may be an important factor in the initiation of dental root resorption.

Intentional vital root transection: a 52-week histopathologic study in Macaca mulatta

Past studies dealing with the vascular supply to surgically mobilized dentoalveolar segments have mentioned occasional encounters with vital root transection and have noted varying degrees of pulpal response to this insult. The purpose of this investigation was to observe the pulpal and periapical responses of monkey dental tissues to intentional vital root transection over a 1-year postoperative period. Four adult Macaca mulatta monkeys were used in this study. All roots were surgically transected within the apical third with a bur. Maxillary and mandibular quadrants for 1, 2, 3, 4, 6, 12, 24, and 52 weeks following surgery were obtained after the animals were killed by perfusion of the left ventricle. The tissue blocks were prepared by routine histologic methods. The results demonstrated a disruption of the normal pulpal architecture, with initial pulpal degeneration and subsequent early replacement by the periodontal ligament tissue. A cellular cemental lining of the root canal occurred in all specimens. The periodontal ligament-like tissue continued to deposit cementum, resulting in almost total obliteration of the root canal and pulp chamber and leaving an intact but much reduced blood supply to the pulp chamber containing periodontal tissues.

Use of maxillary tooth development to estimate age in a group of Hereford cross Friesian steers

Visual and radiographic examination of maxillary tooth development was undertaken in a group of 76 Hereford cross Friesian steers, all but one slaughtered at the same weight (464 kg). Differences were found in the stages of second molar intraoral development between the various age groups. Radiographic inspection showed that stages of resorption of the temporary premolar roots and crown and root formation of the permanent cheek teeth varied with age. The maximum age range before animals could be differentiated into age groups using radiographic examination of maxillary tooth development was three months (one year from one year three months, one year three months from one year six months, one year four months from one year seven months, one year five months from one year eight months). In the carcase, radiography of the maxillary teeth provided a useful estimate of age. The first two maxillary molars were more advanced in crown and root formation than the permanent premolars. Except for the second permanent premolar all maxillary teeth were less advanced in development than their mandibular counterparts.

Electronmicroscopic study of mineralization in induced heterotopic bone formation in guinea pigs

Mineralization of heterotopic bone was studied in a bone induction model using allogenic demineralized dentin implanted in the abdominal wall of guinea pigs. There was a high yield of newly formed osteoid and bone as well as some cartilage together with areas of resorption of the dentin, and fibroblast proliferation. The osteoid contained many matrix vesicles II and less of lysosome-like type I vesicles. Early cartilage formation had more type I vesicles. The implanted dentin contained no matrix vesicles. The first signs of mineralization occurred mainly as irregular clusters of mineral crystals in the matrix close to the surface of collagen fibrils. Crystal-like figures were also found inside some type II matrix vesicles, although most of these vesicles in the mineralization zone had no crystals. The type I vesicles of both bone and cartilage exhibited often crystals near the outer membrane. The mineralizing bone showed a reduction in the size and number of proteoglycan particles. Remineralization of the implanted dentin was also often found and the mineralization pattern resembled the mineralization of bone except for the absence of matrix vesicles. Electron diffraction of selected areas showed that the crystals in the new bone and the mineralized dentin were hydroxyapatite.

Dental root abnormalities and gingival overgrowth in epileptic patients receiving anticonvulsant therapy

Forty-six mentally retarded epileptic patients being treated with phenytoin and phenobarbital were studied to determine the root/crown length ratios. Forty-five mentally retarded patients not receiving anticonvulsant drugs provided the controls. Further, because serum phenytoin levels have been related to severity of gingival hyperplasia, efforts were made to determine if the hyperplasia was associated with dental root abnormalities and also whether these abnormalities could be related to epilepsy per se. Results showed that in certain teeth there was a smaller root/crown ratio in the patients taking anticonvulsant medication. The male patients were more affected than the female. The unusually short roots were not necessarily related to high serum phenytoin but the severity of gingival overgrowth was. Histologic study of teeth from patients taking anticonvulsants revealed developmental abnormalities and resorption.

Hard-tissue resorption and deposition after endodontic instrumentation

Hard-tissue resorption and deposition following endodontic instrumentation were studied histologically in forty-one monkey teeth after 2, 7, and 42 days. No medicaments and no root canal filling materials were used. The number and length of lacunae and areas of resorption of the root canal wall, the root surface, and the lamina dura were counted and measured. Resorption, stimulated by instrumentation, was observed after 7 days at all sites. Resorption was slight at the root canal wall and at the root surface and was significantly more severe than normal osteoclastic replacement in the adjacent lamina dura. After 42 days the reaction had subsided at the three sites, but none of the tissue had returned to normal. Inflammatory reaction due to infection of the root canal appeared to enhance resorption after 42 days at the root canal wall and the lamina dura, but this was not observed at the root surface.

The time scale of tooth development and replacement in Xenopus laevis (Daudin)

One hundred and seventy two larval specimens of Xenopus laevis were reared in such a way that their rates of development (as measured by external criteria) were similar, and so the course of dental development could be examined histologically in a cross sectional study. In this way the events of tooth development were observed, and a time scale constructed for these events. The teeth took an average time of 26 days to develop, erupt and become ankylosed to the bony pedestal, after which each tooth was in a functional position for only about 7 days. Individual tooth replacement was assessed to occur about every 16 days. By comparing the number and size of the odontoblasts responsible for dentinogenesis in 18 months old adult Xenopus laevis with the odontoblasts in the larval specimens, the conclusion was drawn that, despite the larger size of the adult teeth, the time involved in their development and replacement may well be of similar duration to the smaller larval teeth. The significance of the findings for the Zahnreihen Theory is discussed.

Oral aspects of osteopetrosis

The characteristic feature of osteopetrosis is a lack of osteoclastic activity, leading to a series of somatic problems for afflicted persons. The life span of osteopetrotic patients has increased in recent years, thereby making oral aspects of the disease more evident. Four children with malignant osteopetrosis, born between 1967 and 1975, were examined. In all patients the anterior teeth were of normal shape, and erupted on schedule. Primary molars and all permanent teeth were greatly distorted, and remained totally or partly embedded in basal bone. Vertical growth of alveolar ridge was very limited. Where a fenestration of overlaying mucosa had occurred, a localized progressive osteitis developed, leading to soft tissue inflammation and, in two cases, extraoral mandibular fistulas. Peridontal attachment was very poor, spontaneous exfoliation had occurred in all patients. In two children tooth germs and necrotic bone were surgically removed. No beneficial effect of the treatment was observed. Large doses of antibiotics were needed to control recurring infections. No means of curing progressive osseous destruction of mandibular bone has been found. The general prognosis is poor.