The effects of infraocclusion: Part 1. Tilting of the adjacent teeth and local space loss

Restorative dentistry clinical decision-making for hypodontia: retained primary molars

Primary molar teeth that are retained beyond their exfoliation pose a clinical decision-making challenge for dental teams. The retention of these teeth may be due to absence of a permanent successor. As a result, careful planning is required to determine if retention or extraction is necessary. This article aims to discuss the prevalence of retained primary molars, assessment and treatment planning considerations, from both orthodontic and restorative perspectives.

Prevalence and Manifestations of Dental Ankylosis in Primary Molars Using Panoramic X-rays: A Cross-Sectional Study

Dental ankylosis is a serious condition defined as the process that causes the fusion between the dentin or the cementum of the root and the alveolar bone, with the obliteration of the periodontal ligament becoming progressively replaced by bone tissue. The aim of the study was to determine the prevalence, location, severity, and association of dental ankylosis in primary molars with other dental anomalies such as the agenesis of permanent buds. For this study 150 panoramic x-rays were selected from patients with temporary or mixed dentition, aged six to twelve years old, from a private dentistry office and from the Pediatric Dentistry Department of UMFST in Targu-Mures, Romania. In order to identify the cases with dental ankylosis, the presence and severity of the infraocclusion, displacements of the neighboring teeth, the appearance of the root area, and the relationship with the bone tissue were examined. For evaluation of the categorical data we used Fischer’s exact test and the Chi-squared test and the chosen significance level was set at 0.05. The results showed that the highest percentage of cases with ankylosis was found in the first group (six to nine years old), respectively, with 72% of cases compared with the second group (ten to twelve years old) with 28% of cases. Findings showed that there was no positive association between dental ankylosis and gender, but a strong correlation was found regarding the location on the dental arches. Most cases were identified on the lower arch with a higher percentage in quadrant three. Of the two primary molars, the most affected by ankylosis was the first molar in quadrant three, followed by the second molar, and finally the first molar in quadrant four. Most cases diagnosed with ankylosis had a mild to moderate degree of infraocclusion; therefore, changes in the functional balance of the dental arch and on neighboring teeth were insignificant. There were some differences obtained between our results and studies from the literature, especially regarding the localization in the lower left dental arch, but these differences can be attributed to the number of the subjects selected and from the methodology of dental ankylosis diagnosis. Based on the data obtained, it was concluded that ankylosis is a dental condition which occurs in children in early mixed dentition, especially in the lower arch, with the first primary molar being the most affected tooth. The presence of infraocclusion and the absence of dental mobility, especially during the stage of primary molars’ root resorption, are the main signs which must be followed to make an early diagnosis and prevent further complications.

Treatment of ankylosed deciduous molars with or without permanent successors in children and adolescents: a systematic review

INTRODUCTION

The aim of this systematic review was to provide guidelines for decision-making during orthodontic treatment planning of infra-occluded deciduous molars with or without their successors in children and adolescents.

EVIDENCE ACQUISITION

Computerized search was conducted on Medline via PubMed, and Cochrane Library. Articles published until 2020 in English language were analyzed following the Preferred Reporting Items for Systematic Reviews (PRISMA) Checklist. Observational and interventional longitudinal studies reporting the treatment of ankylosed deciduous molars with or without successor tooth in 3 to 15-year-old patients were included.

EVIDENCE SYNTHESIS

In case of ankylosis with presence of successor, exfoliation took place in 77% of teeth, while extraction involved 23%. Infra-occlusion happened in 53% of teeth (worsening in 52%), alveolar bone loss in 37%, mesial tipping of first permanent molar in 5%, and over-eruption of antagonist in no cases (after exfoliation and eruption of successor). In case of ankylosis without successor, exfoliation took place in 1% of teeth, progression of infra-occlusion in 42%, progression of root resorption in 58%, development of mesial tipping of first permanent molars in 25%, while no case of antagonist over-eruption was reported.

CONCLUSIONS

When the permanent tooth is present and the ankylosed tooth is slightly or moderately infra-occluded, observation is appropriate. In case of severe infra-occlusion or absence of successor, tooth extraction may be considered together with orthodontic space closure, transplantation, or prosthetic replacement. Alternatively, nonextraction and a prosthetic build-up may be considered.

Analysis of the cells isolated from epithelial cell rests of Malassez through single-cell limiting dilution

The epithelial cell rests of Malassez (ERM) are essential in preventing ankylosis between the alveolar bone and the tooth (dentoalveolar ankylosis). Despite extensive research, the mechanism by which ERM cells suppress ankylosis remains uncertain; perhaps its varied population is to reason. Therefore, in this study, eighteen unique clones of ERM (CRUDE) were isolated using the single-cell limiting dilution and designated as ERM 1-18. qRT-PCR, ELISA, and western blot analyses revealed that ERM-2 and -3 had the highest and lowest amelogenin expression, respectively. Mineralization of human periodontal ligament fibroblasts (HPDLF) was reduced in vitro co-culture with CRUDE ERM, ERM-2, and -3 cells, but recovered when an anti-amelogenin antibody was introduced. Transplanted rat molars grown in ERM-2 cell supernatants produced substantially less bone than those cultured in other cell supernatants; inhibition was rescued when an anti-amelogenin antibody was added to the supernatants. Anti-Osterix antibody staining was used to confirm the development of new bones. In addition, next-generation sequencing (NGS) data were analysed to discover genes related to the distinct roles of CRUDE ERM, ERM-2, and ERM-3. According to this study, amelogenin produced by ERM cells helps to prevent dentoalveolar ankylosis and maintain periodontal ligament (PDL) space, depending on their clonal diversity.

Guided autotransplant of a first premolar to replace a maxillary ankylosed incisor using a custom-designed osteotome

BACKGROUND

Autotransplantation is a highly successful technique to replace ankylosed teeth. The authors propose a modified therapeutic approach to guide the autotransplant of an immature maxillary premolar using a tooth-shaped osteotome.

CASE DESCRIPTION

A 9-year-old boy reported an avulsion of his maxillary permanent left central incisor with a delayed replantation. An autotransplant of the immature maxillary right first premolar into the position of the affected tooth was planned. A surgical 3-dimensional guiding template and a tooth-shaped osteotome were manufactured to prepare the neo-alveolus (referring to the creation or modification of an alveolus to house the tooth) modification. Although the donor tooth was placed in the recipient socket with the buccal side of the root fully exposed, the transplant outcome was successful.

PRACTICAL IMPLICATIONS

The use of 3-dimensionally designed surgical osteotome could improve accuracy and surgical handling of a donor tooth autotransplant, even with substantial bone defects in the recipient site.

Early replacement of ankylosed first molar via mesial root movement facilitates bone formation and normal eruption of the third molar

Ankylosis of a molar during active growth leads to a significant vertical bone defect, extrusion of the opposing molar, and inclination of adjacent teeth. Treatment timing is an essential factor for the patient's quality of life. Early extraction of the ankylosed molar and protraction of the second molar is challenging because of the difficulty of tooth movement and the uncertainty of the normal eruption of the third molar. In view of the uncertainty of eruption of the mandibular third molar, it is essential to assess the potential for eruption according to the developmental stage of the third molar and to secure sufficient space for eruption. In this case report, a girl with an ankylosed right mandibular first molar and an advanced vertical bone defect was treated via early extraction of the ankylosed molar along with the intrusion of the maxillary molar and mesial root movement of the second molar before the initiation of third molar root formation. Restoration of the vertical bone defect was noted at the end of treatment. In addition, spontaneous eruption of the third molar was observed, which was in contrast to the mesioangular impaction of the contralateral third molar. This case emphasizes the importance of treatment timing to increase the chance of utilization of the third molar.

Transcriptome analysis of ankylosed primary molars with infraocclusion

Primary molar ankylosis with infraocclusion can retard dental arch development and cause dental asymmetry. Despite its widespread prevalence, little is known about its molecular etiology and pathogenesis. To address this, RNA sequencing was used to generate transcriptomes of furcal bone from infraoccluded (n = 7) and non-infraoccluded (n = 9) primary second molars, all without succeeding biscuspids. Of the 18 529 expressed genes, 432 (2.3%) genes were differentially expressed between the two groups (false discovery rate < 0.05). Hierarchical clustering and principal component analysis showed clear separation in gene expression between infraoccluded and non-infraoccluded samples. Pathway analyses indicated that molar ankylosis is associated with the expression of genes consistent with the cellular inflammatory response and epithelial cell turnover. Independent validation using six expressed genes by immunohistochemical analysis demonstrated that the corresponding proteins are strongly expressed in the developing molar tooth germ, in particular the dental follicle and inner enamel epithelium. The descendants of these structures include the periodontal ligament, cementum, bone and epithelial rests of Malassez; tissues that are central to the ankylotic process. We therefore propose that ankylosis involves an increased inflammatory response associated with disruptions to the developmental remnants of the dental follicle and epithelial rests of Malassez.

To extract or not to extract? Management of infraoccluded second primary molars without successors

Infraocclusion is a term used to describe a tooth which has stopped its relative occlusal growth into the arch after the period of active eruption; as a result, the tooth becomes depressed below the occlusal plane. Although many aetiological mechanisms have been proposed, ankylosis is considered the primary cause of infraocclusion. Complex cases benefit from multidisciplinary management. This paper concentrates on the diagnosis and management of infraoccluded second primary molars, without permanent successors and without significant malocclusion, and provides clinicians with a treatment decision tree to aid in treatment planning.

Restoration of a vertical alveolar bone defect by orthodontic relocation of a mesially impacted mandibular first molar

An impacted mandibular first molar tends to cause serious bone defects of the adjacent teeth. When choosing between the 2 typical treatment options-extraction or orthodontic relocation of the impacted tooth-the decision should be based on assessment of the prognosis. A 22-year-old man with severe mesioangulation and impaction of the mandibular first molar and a related vertical bone defect on the distal side of the second premolar was treated with extraction of the second molar and orthodontic relocation of the first molar with a retromolar miniscrew. Comprehensive orthodontic treatment involving premolar extraction was conducted. Strategic extraction of the molar and adequate orthodontic movement helped to restore the bone structure on the affected side. This case report suggests the effectiveness of restoration of bone defects by using viable periodontal tissues around the impacted tooth for the longevity of the periodontium.

Management of ankylosed primary molars with premolar successors: a systematic review

BACKGROUND

The authors conducted a systematic review to determine the clinical prognosis of and methods of managing ankylosed primary molars with permanent successors.

METHODS

The authors searched electronic databases (PubMed, Scopus, MEDLINE, Cumulative Index to Nursing and Allied Health Literature, Web of Science, Cochrane Database of Systematic Reviews and Google Scholar) up to April 2012 with the assistance of a librarian specializing in health sciences databases. They also searched the gray literature. They selected clinical studies in which investigators assessed the prognosis of ankylosed primary molars with permanent successors; they also hand searched references of the selected articles to identify any additional studies that the electronic search may have missed.

RESULTS

The authors identified 3,529 original articles from the electronic database search and none from the hand search. Once selection criteria were applied, only four articles met all inclusion criteria and were included. The number of patients studied ranged from 15 to 107. The number of ankylosed primary molars investigated ranged from 26 to 263.

CONCLUSIONS

Ankylosed primary molars often manifest with mild to moderate progressive infraocclusion. Conservative monitoring of ankylosed primary molars is recommended. The clinician should consider extraction if the permanent successor has an altered path of eruption, if the ankylosed primary molar is severely infraoccluded with the adjacent teeth tipping to prevent the successor from erupting, or both. The ankylosed molar often exfoliates spontaneously within six months; however, when exfoliation is more delayed, arch-length loss, occlusal disturbance, hooked roots or impaction of permanent successors may occur. Practical Implications. Ankylosed primary molars initially should be monitored closely for up to six months. If they do not exfoliate spontaneously, they should be removed, because arch-length loss, alveolar bone defects, impacted permanent successors and occlusal disturbances often occur when the removal is delayed.

Ankylosis of permanent first molars: genetics or environment? A case report of a discordant twin pair

The rare condition of secondary retention has been reported in the literature as being of genetic origin, with some authors suggesting an autosomal dominant pattern. We report the unusual case of two monozygotic biamniotic, bichorionic male twins, who were discordant for permanent first molar secondary retention, involving ankylosis. Twin A showed normal occlusion and eruption patterns, whereas Twin B displayed a left open bite, in relation with a totally submerged primary second molar leading to retention of the underlying premolar (35), and severe infraocclusion of the adjacent permanent molar (36). After orthodontic failure to close the open bite, ankylosis of 36 was confirmed, whereas 26 became severely infraoccluded.The mother had a history of bilateral molar ankylosis and presented reduced posterior alveolar height. Discordance in this twin pair demonstrates that environmental influences, in addition to epigenetic and local factors, may play a role in secondary retention, which is difficult to diagnose and challenging to treat.

Orthosurgical treatment including anchorage from a palatal implant to correct an infraoccluded maxillary first molar in a young adult

Tooth ankylosis during adolescence and early adulthood can lead to infraocclusion and several interrelated, adverse sequelae at the intra-arch and interarch levels. An orthosurgical treatment modality that includes surgical luxation and immediate orthodontic traction is recommended as a conservative approach in many patients. The key to success in this approach is the timely delivery of relatively heavy and continuous forces to the luxated tooth to prevent its reankylosis. Because high reactive forces are inevitably generated, it is crucial to create a reliable source of anchorage. This report describes the successful use of an osseointegrated orthodontic implant to reinforce the anchorage during the orthosurgical repositioning of an infraoccluded molar in a young adult.

Late diagnosis of dentoalveolar ankylosis: impact on effectiveness and efficiency of orthodontic treatment

Dentoalveolar ankylosis is a local etiologic factor of malocclusion that can have deleterious effects on normal dental development. Therefore, it is of paramount importance to diagnose the problem as early as possible so that interception can be performed at the correct time. This case report demonstrates the consequences of late diagnosis of dentoalveolar ankylosis and discusses its effects on development of the occlusion and how it can increase orthodontic biomechanical complexity and treatment time.

Histological and histomorphometrical alterations of the periodontal ligament in gerbils submitted to teeth extraction

This study verified the effect of unilateral teeth extraction on the periodontal ligament in gerbils (Meriones unguiculatus). Ten adult male gerbils weighing about 50 g had induced occlusal alterations by upper left molar extractions while the other ten animals, only submitted to surgical stress, were considered as controls. The periodontal ligament was characterized by qualitative and quantitative analysis, histological description and histomorphometric quantification. Significant alterations were observed on the left side of the experimental group (P < 0.05), the hypofunctional region, when it was compared with the contralateral side and the corresponding region of the control group. Two months after occlusal alterations induced by unilateral teeth extraction, atrophic histological alterations and a decrease in the periodontal space on the ipsilateral side characterized the periodontal ligament. In this study it was possible to conclude that the gerbil can be used in experimental models attempting to correlate the periodontium's biological response to various mechanical stresses, as the periodontal ligament was shown to be highly sensitive to occlusal alterations.

Diagnosis and management of the infraerupted primary molar

An infraerupted tooth is a tooth that has failed to erupt to be in line with adjacent teeth in the vertical plane of occlusion. The general dentist may be faced with this predicament which requires careful attention and thoughtful consideration in terms of long-term patient goals. It is important to diagnose infraerupted teeth and treat them in a timely fashion to help prevent unwelcome sequelae. Important interdisciplinary communication is vital between the dentist and the orthodontist to ensure that precious space and time are not lost. Here we present a review article of complications and considerations that must be taken into account when faced with a patient who has an infraerupted tooth.

Spontaneous uprighting of permanent tooth germs after elimination of local eruption obstacles

Four clinical cases are presented to demonstrate the self-correcting potential of aberrant tooth germs after the elimination of eruption obstacles (in 2 cases cysts, in 2 other cases severely infraoccluded primary teeth). In the case of the submerging deciduous teeth, the tilted adjacent teeth were orthodontically uprighted after the surgical procedure. Possible causative mechanisms are discussed.

Cortical bone remodeling/tooth movement ratio during maxillary incisor retraction with tip versus torque movements

The validity of the postulate "bone traces tooth movement" was examined on 40 Angle Cl II cases. It was hypothesized that a 1:1 cortical bone remodeling/tooth movement ratio is preserved during maxillary incisor retraction. The sample was divided into retraction with tip (13 patients), retraction with torque (18 patients), and control (9 patients) groups. Two time point cephalograms were analyzed with two superimposition techniques, SN at S and a newly developed static tooth analysis, with the maxillary left central incisor serving as a reference object. In both retraction with tip and retraction with torque groups, the postulate bone traces tooth movement was not preserved and a bone remodeling/tooth movement ratio of 1:2 and 1:2.35 was obtained, respectively. In retraction with tip movement, the apical one third of the root tipped labially reducing the superior area of labial maxillaris by 19%. However, due to the compensating effect of the retraction movement, no apex approximation to the labial cortical plate occurred (eliminating the hazard of root resorption, dehiscence, or fenestration). In retraction with torque movement, the increase in both superior (28%) and inferior (65%) labial maxillaris areas was indicative for the hazard of root approximation to the palatal cortical bone. It is recommended to use the 1:2 bone remodeling/tooth movement ratio as a guideline to determine the biocompatible range of orthodontic tooth movements. Furthermore, a judicious interplay between the two modes of retraction can prevent major biologic impairments associated with the ratio and can extend the orthodontic range of treatment.

Orthodontic and restorative procedures for retained deciduous teeth in the adult

The restorative dentist will occasionally be confronted with complex treatment planning such as (1) tooth-to-arch dimensional discrepancies, (2) teeth tilted from the vertical midline, (3) teeth overlapped with root contact, (4) horizontal loss of arch dimension from retained deciduous teeth, (5) an impacted adult canine tooth, and (6) peg lateral incisors. Pretreatment diagnostic tooth positioning on replica casts, radiographs, pertinent clinical information, and strategic prosthodontic and orthodontic therapy can ensure predictable treatment. Orthodontic and restorative procedures for three patients with these described discrepancies are detailed to support the direction of treatment planning.

The effects of infraocclusion: Part 3. Dental arch length and the midline

The third and final article in this series examines the effect of infraocclusion on the midline of the mandibular dental arch. From clinical observation, a shift in the dental midline to the side affected by infraocclusion seemed very common, and this could be explained within the terms of the hypothesis proposed in the first article. A method was devised on a panoramic radiograph to define and to distinguish the anatomic (skeletal) midline and the dental midline. This confirmed the existence of a dental shift to the affected side. The hemiarch length of each side was measured on the film, from the distal of the second deciduous molar/second premolar to both constructed midlines, and was found to be longer on the affected side, confirming an abnormally distal position of the first molar on that side.