Crown forms and gingival phenotypes: Insights from a diverse Asian population

Objective

This study aimed to classify the crowns of maxillary central incisors into distinct categories and to examine the associations between these crown forms and morphometric characteristics in an ethnically diverse Asian population. This is significant for the treatment planning and management of cases, especially for the anterior teeth, from the restorative and aesthetic points of view.

Method and Materials

Clinical measurements and photographic data were collected from 160 participants, comprising students, staff, and patients of the Faculty of Dentistry, Universiti Kebangsaan Malaysia. The crown length, crown width, contact surface, papilla height, papilla fill, keratinized mucosa width, and gingival tissue thickness were measured. Cluster analyses were performed to identify the different crown form categories and corresponding characteristics.

Results

The mean crown width measured 7.093 ± 0.637 mm, while the mean crown length was 10.209 ± 0.966 mm. Three crown-form clusters were identified: triangular (50 %), square/tapered (23.1 %), and square (26.9 %) shapes. The triangular cluster had a significantly higher mean papilla height (4.64 mm ± 0.818) and the highest incidence of incomplete papilla fill (17.5 %). The chi-squared test showed a significant difference in crown forms between the different ethnicities, χ2 (2, 160) = 0.033.

Conclusion

Within this diverse Asian population, the crown form demonstrates three clusters: triangular, square/tapered, and square, characterized by a notably small average crown width and crown length. Most participants predominantly exhibited triangular crown forms with reduced crown width, crown length, and crown width/ crown length ratio. Furthermore, noticeable variations in crown forms and their morphometric attributes were observed among the three ethnic groups: Malays, Chinese, and Indians.

AKT from dental epithelium to papilla promotes odontoblast differentiation

Epithelial-mesenchymal interactions occur during tooth development. The dental epithelium (DE) is regarded as the signal center that regulates tooth morphology. However, the mechanism by which DE regulates the differentiation of mesenchyme-derived dental papilla (DP) into odontoblasts remains unclear. Using miniature pigs as a model, we analyzed the expression profiles of the DE and DP during odontoblast differentiation using high-throughput RNA sequencing. The phosphatidylinositol-3-kinase (PI3K)/AKT pathway is one of the most enriched pathways in both DE and DP. The PI3K/AKT pathway was first activated in the inner enamel epithelium but not in the DP on embryonic day 50. This pathway was then activated in the odontoblast layer on embryonic day 60. We showed that AKT activation promoted odontoblast differentiation of DP cells. We further demonstrated that activation of PI3K/AKT signaling in the DE effectively increased the expression levels of AKT and dentin sialophosphoprotein in DP cells. Additionally, we found that DE cells secreted collagen type IV alpha 6 chain (COL4A6) downstream of epithelial AKT signaling to positively regulate mesenchymal AKT levels. Therefore, our data suggest that PI3K/AKT signaling from the DE to the DP promotes odontoblast differentiation via COL4A6 secretion.

Revisiting the measurement of keratinized gingiva: a cross-sectional study comparing an intraoral scanner with clinical parameters

PURPOSE

The aim of this study was to investigate the relationships between gingival thickness (GT) and keratinized gingiva width (KGW), papilla height (PH), and crown ratio (CR) by employing transgingival probing and an intraoral scanner (IOS).

METHODS

This cross-sectional study examined 360 maxillary anterior teeth from 60 patients. GT was assessed using transgingival probing with an endodontic spreader. KGW, CR, and PH were measured using an IOS. One-way analysis of variance, the Student's t-test, and Spearman correlation coefficients were employed for statistical analysis.

RESULTS

Higher GT was significantly associated with thinner KGW in the central region (P=0.019). There was no statistically significant difference in GT between teeth (P=0.06). PH was lower in lateral teeth than in canines (P=0.047), with a PH of 2.99 mm in lateral teeth. The KGW was narrower in canines than in central teeth (P=0.007). A moderate correlation was observed between KGW and PH in the central region (P=0.01), while a weak negative correlation was found between KGW and CR (P=0.043).

CONCLUSIONS

A moderate negative correlation was found between GT and KGW, as well as between PH and KGW in central teeth. In contrast, a weak negative correlation existed between CR and KGW. The PH (2.99 mm) was lower in lateral teeth than in canines. The traditional paradigm, which suggests a positive correlation between KGW and GT, was re-evaluated by measuring KGW using an IOS.

Do different incision techniques for implant surgery affect gingival papilla height around dental implants? A retrospective study of 115 cases

BACKGROUND

Surgical incision designs are considered closely correlated to gingival papilla of dental implants. This study aims to explore whether different incision techniques for implant placement and second stage surgery affect gingival papilla height.

METHODS

Cases using different incision techniques (intrasulcular incisions or papilla sparing incisions) between November 2017 and December 2020 were selected and analyzed. A digital camera was used to capture images of gingival papilla at different time points. Ratio of papilla height to crown length using different incision techniques were measured and statistically compared.

RESULTS

A total of 115 papillae (68 patients) were eligible according to the inclusion/exclusion criteria. The average age was 39.6 years. Decreased postoperative papilla height were observed after implant placement surgery in all groups without statistical difference. However, for second stage surgery, intrasulcular incisions lead to more atrophy in gingival papilla compared to papilla sparing incisions.

CONCLUSIONS

Selection of incision techniques in implant placement surgery does not significantly affect papilla height. For second stage surgery, intrasulcular incisions significantly leads to more papilla atrophy compared with papilla sparing incisions. Trial registration KQCL2017003.

Recurrent Primordial Odontogenic Tumor: Epithelium-Rich Variant

Primordial odontogenic tumor (POT) is a rare, mixed odontogenic neoplasm composed of spindled and stellate-shaped cells in myxoid stroma resembling dental papilla, surfaced by cuboidal-to-columnar odontogenic epithelium. Most POTs present in the posterior mandible as a well-demarcated radiolucency associated with a developing tooth in children and adolescents. POT is treated conservatively with no recurrences documented to-date. To describe the clinicopathological features of a recurrent POT. A 19-year-old female presented with an asymptomatic swelling, and panoramic radiograph revealed a multiloculated radiolucency in the mandibular body and ramus, with buccal and lingual perforation. The tumor was composed of plump spindle and stellate cells in a delicately collagenous and myxoid stroma, surfaced by columnar epithelial cells with reverse nuclear polarization. There was extensive epithelial proliferation forming invaginations within the tumor mass and organoid/enamel organ-like structures with enameloid-like deposits, dentinoid, and dystrophic calcifications. This was similar to the POT that had been excised four years prior from the same location. The patient underwent hemi-mandibulectomy and currently is free of disease at a thirteen-month follow-up. This report describes the first recurrent POT exhibiting extensive epithelial proliferation.

Primordial odontogenic tumour: A systematic review of the common but also unusual features of this novel entity

BACKGROUND

Primordial odontogenic tumour (POT) is a novel entity that was described in 2014 and that is included in the group of benign mixed epithelial and mesenchymal odontogenic tumours. In recent years, several papers have added new cases with some clinical and histopathological aspects that slightly differ from those described in the original report. The aim of this systematic review is to update all available data on POT published in the literature and to identify those features of the neoplasm that require further investigation.

MATERIALS AND METHODS

A systematic review of literature was conducted using PubMed, Embase, Web of Science and Scopus. Additional sources were also checked. Publications reporting cases with enough clinicopathological information were included, without any time or language restrictions. Histopathological or radiological studies were considered for qualitative analysis.

RESULTS

A total of 30 publications were included. Seventeen papers were used for quantitative analysis while 13 papers were used only for qualitative analysis. A total of 18 cases of POT were identified. Some clinical, radiographic, histopathological and therapeutic features were common in all reported cases, while other aspects of the neoplasm were inconsistent through published cases. This inconsistency was particularly remarkable when dealing with the histopathological features of the neoplasm.

DISCUSSION

Some issues about POT remain unclear and deserve to be clarified by future reports. The description of the odontogenic epithelium covering the ectomesenchyme is often contradictory, while it remains debatable whether peripheral ameloblastic epithelial islands or hard dental tissue deposition can occasionally occur within the tumour.

Mycoplasma detection and elimination are necessary for the application of stem cell from human dental apical papilla to tissue engineering and regenerative medicine

BACKGROUND

Recently, postnatal stem cells from dental papilla with neural crest origin have been considered as one of potent stem cell sources in regenerative medicine regarding their multi-differentiation capacity and relatively easy access. However, almost human oral tissues have been reported to be infected by mycoplasma which gives rise to oral cavity in teeth, and mycoplasma contamination of ex-vivo cultured stem cells from such dental tissues and its effect on stem cell culture has received little attention.

RESULTS

In this study, mycoplama contamination was evaluated with stem cells from apical papilla which were isolated from human third molar and premolars from various aged patients undergoing orthodontic therapy. The ex-vivo expanded stem cells from apical papilla were found to express stem cell markers such as Stro-1, CD44, nestin and CD133, but mycoplama contamination was detected in almost all cell cultures of the tested 20 samples, which was confirmed by mycoplasma-specific gene expression and fluorescence staining. Such contaminated mycoplasma could be successfully eliminated using elimination kit, and proliferation test showed decreased proliferation activity in mycoplasma-contaminated cells. After elimination of contaminated mycoplasma, stem cells from apical papilla showed osteogenic and neural lineage differentiation under certain culture conditions.

CONCLUSION

Our study proposes that the evaluation of mycoplasma contamination and elimination process might be required in the use of stem cells from apical papilla for their potent applications to tissue engineering and regenerative medicine.

Neurogenic differentiation of human dental stem cells in vitro

Objectives

The purpose of this study was to investigate the neurogenic differentiation of human dental pulp stem cells (DPSCs), periodontal ligament stem cells (PDLSCs), and stem cells from apical papilla (SCAP).

Materials and Methods

After induction of neurogenic differentiation using commercial differentiation medium, expression levels of neural markers, microtubule-associated protein 2 (MAP2), class III β-tubulin, and glial fibrillary acidic protein (GFAP) were identified using reverse transcriptase polymerase chain reaction (PCR), real-time PCR, and immunocytochemistry.

Results

The induced cells showed neuron-like morphologies, similar to axons, dendrites, and perikaryons, which are composed of neurons in DPSCs, PDLSCs, and SCAP. The mRNA levels of neuronal markers tended to increase in differentiated cells. The expression of MAP2 and β-tubulin III also increased at the protein level in differentiation groups, even though GFAP was not detected via immunocytochemistry.

Conclusion

Human dental stem cells including DPSCs, PDLSCs, and SCAP may have neurogenic differentiation capability in vitro. The presented data support the use of human dental stem cells as a possible alternative source of stem cells for therapeutic utility in the treatment of neurological diseases.

Do dental stem cells depict distinct characteristics? - Establishing their "phenotypic fingerprint"

Dental tissues provide an alternate source of stem cells compared with bone marrow and have a similar potency as that of bone marrow derived mesenchymal stem cells. It has been established there are six types of dental stem cells: Dental pulp stem cells, stem cells from human exfoliated deciduous teeth, stem cells from apical papilla, periodontal ligament stem cells, dental follicle progenitor cells, oral periosteum stem cells and recently gingival connective tissue stem cells. Most of the dental tissues have a common developmental pathway; thus, it is relevant to understand whether stem cells derived from these closely related tissues are programmed differently. The present review analyzes whether stem cells form dental tissues depict distinct characteristics by gaining insight into differences in their immunophenotype. In addition, to explore the possibility of establishing a unique phenotypic fingerprint of these stem cells by identifying the unique markers that can be used to isolate these stem cells. This, in future will help in developing better techniques and markers for identification and utilization of these stem cells for regenerative therapy.

Expression pattern of zinc-finger transcription factor Odd-skipped related 2 in murine development and neonatal stage

The Odd-skipped gene, first identified as a Drosophila pair-rule zinc-finger transcription factor, plays an important role in Drosophila development. The mammalian homolog, Odd-skipped related 2 (Osr2), regulates limb, tooth, and kidney development in mouse embryos. However, the detailed expression pattern of Osr2 during neonatal development remains unclear. In this study, we investigated Osr2 expression patterns in mouse neonatal and embryo tissues using qPCR and in situ hybridization methods. First, we examined the tissue distribution of Osr2 by qPCR, and found it to be highly expressed in the uterus and moderately in the testes, small intestine, and prostate. That expression was also found in eye, kidney, placenta, lung, thymus, lymph node, stomach, and skeletal muscle tissues, and in all embryonic stages. On the other hand, Osr2 was not expressed in brain, heart, liver, or spleen samples. Next, we examined the tissue localization of Osr2 using in situ hybridization. Osr2 was found in the craniofacial region on E13.5, with notable expression in dental germ mesenchyme as well as the renal corpuscle on E17.5. As for neonatal tissues, Osr2 was expressed in the dental papilla, dental follicle, Harderian gland, nasal bone, eyelid dermis, synovial joint, and tibial subcutis. Our findings suggest that Osr2 functions in reproductive system organs, such as the uterus, testes, prostate, placenta, and ovaries. Furthermore, based on its expression in kidney, Harderian gland, eyelid dermis, and tibial subcutis tissues, this transcription factor may be involved in hormone synthesis and function. Together, our results demonstrate the role of Osr2 in postnatal development and embryogenesis.

The effect of peri-implant bone exposure on soft tissue healing and bone loss in two adjacent implants

PURPOSE

The purpose of this study was to evaluate the soft tissue and bone change around two adjacent implants in one-stage implant surgery.

METHODS

Eleven subjects (7 males, 4 females) who were needed placement of 2 adjacent implants in the molar area were included. The two implants were placed with the platform at the level of the alveolar crest. The interproximal bone between the 2 implants was not covered with gingiva. After surgery, an alginate impression was taken to record the gingival shape and radiographs were taken to evaluate implant placement. Using a master cast, the gingival height was measured at baseline, 4 weeks, and 12 weeks. In the radiograph, the alveolar bone level was measured at the mesial and distal side of both implants at baseline and 12 weeks.

RESULTS

The exposed bone was covered with gingiva at both 4 and 12 weeks. Loss of alveolar bone around implants was found in all areas. The alveolar bone level in the exposed bone area did not differ from that in the non-exposed area.

CONCLUSIONS

This study showed that the alveolar bone level and gingival height around 2 adjacent implants in the exposed bone area did not differ from that in unexposed bone area.

I-shaped incisions for papilla reconstruction in second stage implant surgery

PURPOSE

Pink gingival esthetic especially on the anterior teeth has been an important success criterion in implant-supported restoration. Inter-implant papillae are a critical factor for implant esthetics, and various techniques for inter-implant papilla reconstruction have been introduced. The aim of this study is to suggest and evaluate a surgical technique for reconstructing inter-implant papillae.

METHODS

A 28-year-old man had an implant placed on the #13 and #14 area. Four months after implant placement, a second stage surgery was planned for inter-implant papilla reconstruction. At the time of the abutment connection, I-type incisions were performed on the #13i & #14i area followed by full-thickness flap elevation and connection of a healing abutment on underlying fixtures without suture.

RESULTS

Two weeks after the second stage implant surgery, soft tissue augmentation between the two implants was achieved.

CONCLUSIONS

I-shaped incisions for papilla reconstruction performed during the second stage implant surgery were useful for inter-implant papilla reconstruction and showed a good esthetic result.