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PubMed1988

Longitudinal study of electrometric sensitivity of young permanent incisors.

Electrometric sensitivity of permanent maxillary central incisors was studied longitudinally in 34 children at 6-month intervals over 2 1/2 yr (mean age of the children at the beginning of the study: 94.6 months). Root development stages were determined from radiographs obtained at the beginning of the study, after 1 yr, and after 2 1/2 yr. An increase in sensitivity was found over the study period, but large variations were found from child to child and even within the same child. Especially at the first examinations a few children showed very low sensitivity. Statistical analysis showed that examination number, root development and side of the mouth (right or left central incisor) all were statistically significantly related to sensitivity. Statistically significant differences were also found between the individuals.

Child↗
PubMed1994

Effect of hypocalcemic state on enamel formation in rat maxillary incisors.

Several authors have proposed that hypocalcemia can interfere with amelogenesis, resulting in enamel aberrations. Therefore, the purpose of this investigation was to study the effects of a diet-induced hypocalcemic state in young rats on enamel formation of the maxillary incisors. The experimental rats were fed a special diet, free from vitamin D and very low in calcium. The control rats were fed a normal diet. The experimental period was 3 wk. After termination, the blood analysis showed that the experimental rats had developed hypocalcemia with very low values of both total and ionized blood calcium. The experimental rats were smaller than their controls after 3 wk, with smaller skulls and teeth. At the light microscope level, the enamel and the ameloblasts did not seem to be affected, except in one rat, the smallest, which showed enamel hypoplasias in both maxillary incisors and a delayed increase of the mineral content during the maturation stage process. It is concluded that the hypocalcemic state induced did not greatly affect enamel formation. However, occasional enamel aberrations may occur.

Ameloblasts↗
PubMed1998

Demonstration of putative Ca-binding domains in dentin matrix of rat incisors after daily injections of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP).

In order to clarify the initial process of dentin mineralization, the inhibitory effect of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP) on dentin mineralization was investigated. Rats (100 g) were subcutaneously injected with HEBP (8 mg P/kg) for 7 or 14 d, and the incisors were processed for Ca histochemistry and/or electron microscopy. HEBP-treated incisors demonstrated ladder-like alternate rows of mineralized and non-mineralized dentin at the apical end. GBHA revealed moderate Ca reactions in the non-mineralized circumpulpal dentin matrix where electron microscopy revealed rich distribution of fine mesh-like electron-dense material. Non-mineralized mantle dentin matrix was negative for Ca but contained numerous matrix vesicles (MVs) filled with crystalline and/or amorphous mineral deposits. Mineralization of circumpulpal dentin occurred independently of MV-rich mantle dentin layer in affected specimens. Our data provide histochemical evidence of possible Ca-binding property of the circumpulpal dentin matrix and its absence in the mantle dentin where MV-mediated mineralization occurs. In the mantle dentin, HEBP does not interfere with crystal growth in MVs but inhibits its outgrowth after membrane rupture. It is proposed that circumpulpal dentin matrix has a potential to mineralize independently of MV-mediated mineralization of mantle dentin, although MVs determine the initial site and timing of dentin mineralization.

Aminophenols↗
PubMed1998

Blood vessels and nerve fibers in rat incisor pulp. Immunoelectron microscopic observation with anti-substance P antibody.

The distribution of nerve fibers with special reference to their positional relationship with blood vessels in the pulp of the rat mandibular incisor was investigated by light and electron microscopic immunohistochemistry using polyclonal anti-substance P antibody. In the center of the pulp, numerous immunoreactive nerve fibers with varicosities were found along larger blood vessels. In the periphery of the pulp, there were two layers of capillary plexus; an odontoblastic and a subodontoblastic. Many nerve fibers, showing varicosities, were located in the subodontoblastic region, and some revealed a close association with pericytes of capillaries of the subodontoblastic plexus. A few nerve fibers entered the odontoblast layer, but no nerve fibers were seen to be associated with the odontoblastic capillary plexus. The results suggest that the local regulation of blood flow takes place not only in larger blood vessels but also in the capillaries of the rat incisor pulp.

Animals↗
PubMed2006

Evidence by signal peptide trap technology for the expression of carbonic anhydrase 6 in rat incisor enamel organs.

During screening of a rat incisor enamel organ cDNA library by signal peptide trap technology, we identified a DNA fragment matching a predicted translation sequence for rat carbonic anhydrase 6 (CA6). This result was unexpected because CA6, to date, has been associated primarily with secretions from glandular tissues. To further characterize this observation, reverse transcription-polymerase chain reaction (RT-PCR) amplifications were carried out on total RNA extracted from freeze-dried secretory and maturation-stage rat incisor enamel organs. A cDNA fragment of the expected size was detected in control samples from rat salivary glands as well as within maturation-stage enamel organ samples. This CA6 RT-PCR fragment was further cloned and sequenced and found to match the nucleotide sequence 770-1079 from clone XM_216584 of GenBank. Northern blot analyses with the rat CA6 cDNA fragment confirmed its expression relative to maturation-stage enamel organ samples. It is at present unclear whether the CA6 expressed by enamel organ cells is secreted into the enamel layer or into the intercellular spaces of the enamel organ itself to assist in neutralizing excess protons arising from the growth of apatite crystals during the maturation stage of amelogenesis.

Amelogenesis↗
PubMed2006

Formation of the dentino-enamel interface in enamelysin (MMP-20)-deficient mouse incisors.

An anomalous dentino-enamel junction (DEJ), manifested by delamination of the enamel layer, was reported in enamelysin [matrix metalloproteinase-20 (MMP-20)] knockout (KO) mice. To better understand the possible role of MMP-20 in the formation of the DEJ, we performed transmission electron microscopy (TEM) studies of the DEJ at early stages of tooth morphogenesis in KO mice. Our TEM analysis revealed that in the incisors from KO mice the mantle dentin is hypomineralized at the onset of enamel mineralization. At this early stage, TEM revealed no apparent differences in nascent aprismatic enamel between the KO mice and the controls. Hypomineralized mantle dentin was also observed in the incisors from KO mice, as assessed by back-scattered SEM at the secretory and early maturation stages, but not in the late-maturation stage, suggesting that the mineralization of mantle dentin is not completely arrested, but rather postponed. Histological studies indicate that the organic content in the initial enamel layer remains very high throughout amelogenesis. These results imply that MMP-20 is involved in the regulation of mineralization in mantle dentin and demonstrate the complex nature of DEJ formation. They also suggest that the structural and functional properties of the DEJ are determined during the initial mineralization stages.

Amelogenesis↗
PubMed2006

Comparison of three methods for enamel protein extraction in different developmental phases of rat lower incisors.

Protein extraction methods [urea, trichloroacetic acid (TCA), and acetic acid] were compared for protein recovery from rat incisor developing enamel in the S phase (intermediate/late secretion), M1 phase (early maturation), M2 phase (intermediate maturation), and M3 phase (final maturation). We compared the protein recoveries with the percentage of enamel matrix dry weight burnt off by incineration. Our results indicate that TCA and urea were equally efficient for the extraction of S-stage proteins (85% and 90% recovery, respectively), while urea was the best for M1-stage proteins (92% recovery), and TCA the best for M2-stage (99% recovery) and M3-stage (60% recovery) proteins. The other methods yielded less than 30% recovery in comparison to incineration for M2 and M3 stages. The fact that urea extraction works well in the S and M1 stages and not thereafter is probably related to the changes in the proteins during enamel development and the amount of mineral that needs to be dissolved. TCA is the single method that effectively recovered proteins from all developmental stages of the rat incisor enamel.

Acetic Acid↗
PubMed2004

Pulp canal obliteration in an unerupted permanent incisor following trauma to its primary predecessor: a case report.

Trauma to a primary tooth may result in damage to the underlying developing permanent tooth bud because of the close proximity between the root of the primary tooth and its permanent successor. We report an unusual case where injury to the primary dentition resulted in pulp canal obliteration (PCO) of a permanent maxillary central incisor prior to its eruption. The other permanent maxillary central incisor was diagnosed as malformed because of trauma to the primary dentition at an earlier age. The occurrences of PCO or crown malformation dose not routinely disrupt the eruption of those teeth. Periodic assessment is required to determine the need for endodontic intervention.

Child↗
PubMed1990

Replacing resorbed maxillary central incisors with mandibular premolars.

A case report is presented on autotransplantation of a lower premolar into the upper central incisor area. A traumatized upper central incisor lost because of external root resorption was replaced by a premolar transplant taken from a crowded mandibular arch. The transplant showed excellent adaptation and the periapical inflammation noticed a few years after the operation was treated successfully with apicectomy.

Bicuspid↗
PubMed1990

Effect of topical application of doxycycline on pulp revascularization and periodontal healing in reimplanted monkey incisors.

Maxillary incisors in 47 monkeys, 54 in the experimental group (I) and 117 in the control group (II), were extracted and reimplanted, either immediately or after 30 or 60 min wet or dry storage. Incisors in the experimental group I were additionally kept 5 min in a suspension of 1 mg doxycycline in 20 ml physiologic saline, freshly prepared for each of the 15 animals before reimplantation. The observation time varied from 6 to 8 weeks. The teeth were removed in tissue blocks, histologically processed and evaluated for occurrence of complete pulp revascularization (CPR), presence of the micro-organisms in the pulpal lumen and ankylosis or inflammatory root resorption. Then the results were statistically evaluated, using log-linear analyses and chi-square tests (SAS, 1985) for the comparisons between group I and group II. These analyses revealed that topical application of doxycycline increased the frequency of complete pulp revascularization (P less than 0.002) and decreased the frequency of micro-organisms in the pulpal lumen (P less than 0.001). Furthermore, the frequencies of ankylosis (P less than 0.05) and inflammatory root resorption (P less than 0.001) were also decreased compared with the control group of teeth. It was concluded that the effect of topical treatment with doxycycline was most probably exerted on the micro-organisms that contaminated root surface during the extra-alveolar time; contamination of necrotic pulp tissue from the mechanical damage in the cervical part of the root surface was not affected.

Animals↗
PubMed1990

Traumatic injury to maxillary incisor teeth in a group of South Wales school children.

This study examines, from photographic records, the prevalence of accidental damage to maxillary incisor teeth in a group of 968 11/12-year-old South Wales school-children; 15.3% showed evidence of trauma ranging from enamel fractures or discolouration to actual loss of a tooth. Boys (19.4%) showed a higher prevalence of trauma than girls (11%). Maxillary central incisors were the most at risk from trauma, with coronal fractures being the most commonly sustained injury. Those subjects who showed evidence of trauma had an statistically (p less than 0.001) but not clinically significantly greater overjet than did those who had none. The percentage of subjects suffering trauma increased significantly with increasing overjet, but lip incompetence did not affect the prevalence of accidental damage. Though statistically unsupported due to the small numbers involved in this cohort, it appeared that the rougher nature of boys activities and their more active participation in sports were of greater importance than the magnitude of their overjet in determining whether their teeth were at risk from trauma. In contrast, it was the magnitude of the overjet which was the dominant factor in girls. Despite the wide availability of relatively simple means of restoration and, in the majority of cases, regular dental examinations, only 14.8% of traumatised teeth had received treatment at this age.

Child↗
PubMed1991

Delayed endodontic and prosthetic treatment of two traumatized incisors.

This case report describes the delayed endodontic and prosthetic treatment of two maxillary central incisors in a 16-year-old patient. Both teeth had been traumatized eight years previously. The examination revealed arrested root formation with wide open apices, periapical inflammation and inflammatory resorption. Endodontic treatment with calcium hydroxide led to formation of hard tissue barriers in both teeth so that definite obturation could be performed. One tooth was lost due to a deep crown-root-fracture and replaced by an intraosseous implant, whereas the other incisor was retained for nearly four years.

Adolescent↗
PubMed1992

Morphology of the mineralizing front and observations of reparative dentine following induction and inhibition of dentinogenesis in the rat incisor.

An extra oral approach was made to 26 pairs of Wistar rat incisors and a small bur used to expose the pulps which were then dressed with either calcium hydroxide paste (Pulpdent) zinc oxide-eugenol cement (Kalzinol) or a triamocinolone acetonide/tetracycline containing cement (Ledermix). Animals were sacrificed at 7 days, incisors removed, a window cut to the pulp opposite the site of exposure, soft tissues removed with 7% NaOCl for 30 minutes before teeth were dehydrated in graded concentrations of acetone and gold coated for examination under SEM. Calcium hydroxide produced rapid complete repair with a remarkably regular formation of calcospherites, except for a zone of relative inhibition perforated by nutrient canals at the periphery of each lesion. Both zinc oxide-eugenol and triamcinolone acetonide cements inhibited both bridging of the defect created by the exposure and dentine formation in the surrounding pulpal wall. Data was grouped according to the degree of hard tissue repair. The results were statistically significant (Chi-square p < or = 0.001). This method demonstrated qualitative and quantitative differences in the repair process resulting from chemical variations in the dressings applied.

Animals↗
PubMed1993

Investigation of the children referred to a dental hospital with avulsed permanent incisor teeth.

The management of children referred to a dental hospital because of avulsed permanent incisor teeth was considered in a retrospective study. The group consisted of 49 children between the ages of 6 and 14 years. Most of the children (60%) had their avulsed teeth stored dry while only 7% had them stored in milk, and 19% in saliva. Following avulsion the majority of the children attended a dental surgeon or general hospital. Twenty-three children contacted health care personnel within 30 minutes but only 13 had their teeth replanted in this time period. Thirty-six children had 46 incisors replanted. No relationship was demonstrated between the place or personnel who replanted the teeth, and a successful outcome.

Adolescent↗
PubMed1994

Partially arrested root formation in a permanent maxillary central incisor subsequent to trauma to the primary dentition.

When the primary dentition sustains a traumatic insult, the development of the succedaneous teeth can be disturbed leading to a number of malformations. In this case report, the patient presented with a history of prior trauma to his primary maxillary incisors which resulted in partially arrested root formation for a permanent incisor. The considerations in formulating a treatment plan which included orthodontics are discussed.

Child↗
PubMed1995

Replantation of 400 avulsed permanent incisors. 3. Factors related to root growth.

Four hundred avulsed and replanted permanent incisors were examined for pulpal and periodontal healing. In 30 teeth, root formation was incomplete at the time of injury. Two teeth were excluded from the study due to nonphysiological extraalveolar storage (i.e. homemade saline). Of the 28 remaining replanted incisors, 7 showed subsequently completed root development, 8 partially completed root development and 13 arrested root development. Completed root development subsequent to replantation was found to be significantly related to pulpal revascularization, being rare in cases with pulp necrosis (5 of 15 teeth) and frequent after pulpal healing (11 of 13 teeth) (p = 0.01). Root development was not found to be significantly related to the extraalveolar storage period; but occurred slightly more frequently when the dry storage period was less than 45 min. (p = 0.13). Ingrowth of bone and formation of an internal periodontal ligament (PDL) was found in 6 teeth and was related to arrested root formation in cases with pulpal healing. The explanatory factor for these findings appeared to be damage to the Hertwig's epithelial root sheath.

Chi-Square Distribution↗
PubMed1995

Endodontic management of mandibular lateral incisor fused with supernumerary tooth.

In this article we report a case of a mandibular lateral incisor in which 3 separate root canals were located. Clinical and radiographic examinations suggested that fusion had occurred between the mandibular incisor and a supernumerary tooth. The endodontic management of the tooth is described, and repair of an apical periodontitis had occurred after 9 months.

Adolescent↗
PubMed1996

Prognosis of root-fractured permanent incisors.

The prognosis of 56 root-fractured permanent incisors was evaluated clinically and radiographically for 2 to 31 years. Information about initial case histories, examination and treatment of root-fractured teeth were recorded retrospectively from patient cards. Most of the root fractures occurred in the 16-20 year age group (38%) followed by the 11-15 year age group (29%). Males were involved more often than females. Fifty-two percent of the patients visited the dental clinic within the first week, while 48% did so 1 month-31 years later after the injury. The leading cause of root fractured injuries was falls (46%) and mostly involved one tooth (71%). Maxillary central incisors were the most often affected teeth (95%). The most common type of root fracture was in the middle third of the root (57%) followed by apical part (34%). About 59% of untreated or splinted teeth maintained their vitality. Healing with connective tissue was observed in 19 teeth, with calcified tissue in 15 teeth and with osseous tissue in only one tooth. There was partial or complete obliteration of the pulp space in these healed cases (62.5%). The formation of pulpal hard tissue produced no additional clinical problems. Partial or total pulp necrosis were noted in 21 (37.5%) teeth. Endodontic treatment was successful in 12 cases. The remaining 9 teeth were extracted due to the loss of marginal alveolar bone and apical periodontitis.

Adolescent↗