Oral health-related quality of life (OHRQoL) and implant therapy: A prospective multicenter study of preoperative, intermediate, and posttreatment assessment.

The purpose of this multicenter continuation study was to use high patient numbers in order to generate reliable statements regarding the association between different implant indications and OHRQoL. Patients with various types of indication for dental implants, ranging from single tooth loss to edentulous jaws, were included. Quality of life relating to dental implants was assessed through the oral health impact profile (OHIP-G-21), which has a summary score from 0 to 20 in healthy patients. In total, 16 253 patients from 29 centers (European Centers for Dental Implantology (ECDI)) were involved in the study between 2009 and 2021.8251 patients (50.7%) completed the questionnaire after implant insertion, and 4996 patients (30.7%) after prosthodontic treatment. The average age was 54 years (range 18-88 years). Posterior single-tooth gap (28.5%) and free-end gap (27.8%) were the most frequent indications. The preoperative OHIP-G-21 score for all patients was 32.81 (SD 11.92), while the score during the healing period was 30.00 (SD 10.72), and after completion of treatment 27.24 (SD 9.26) (p < 0.001). The most significant improvements in OHIP-G-21 scores were in the indication of edentulous jaw (phase 1, 41.81 (SD 15.53); phase 2, 35.39 (SD 14.22); phase 3, 29.60 (SD 10.12) (p < 0.001). The study revealed significant improvements in the most frequently reported problems (chewing, serious concerns, appearance) (p < 0.001). Insertion of dental implants and prosthodontic rehabilitation led to an improved OHRQoL for patients with all indications for dental implants. Special attention should be paid to patients with edentulous jaw, since in comparison with other indications it had the greatest impact on improving OHRQoL. The psychological dissatisfaction scale of the OHIP-G-21 represented the most important factors for patients, and these scores were substantially influenced by implant therapy. Thus, treating physicians should increase their focus on these factors, in order to avoid dissatisfaction and increase the likelihood of complete implant therapy success.

Preprosthetic Surgery-Narrative Review and Current Debate.

This review describes the role of modern preprosthetic surgery. The atrophic edentulous jaw can cause severe functional impairment for patients, leading to inadequate denture retention, reduced quality of life, and significant health problems. The aim of preprosthetic surgery is to restore function and form due to tooth loss arising from congenital deformity, trauma, or ablative surgery. Alveolar bone loss is due to disuse atrophy following tooth loss. The advent of dental implants and their ability to preserve bone heralded the modern version of preprosthetic surgery. Their ability to mimic natural teeth has overcome the age-old problem of edentulism and consequent jaw atrophy. Controversies with preprosthetic surgery are discussed: soft tissue versus hard tissue augmentation in the aesthetic zone, bone regeneration versus prosthetic tissue replacement in the anterior maxilla, sinus floor augmentation versus short implants in the posterior maxilla-interpositional bone grafting versus onlay grafts for vertical bone augmentation. Best results for rehabilitation are achieved by the team approach of surgeons, maxillofacial prosthodontists/general dentists, and importantly, informing patients about the available preprosthetic surgical options.

Group 3 ITI Consensus Report: Materials and antiresorptive drug-associated outcomes in implant dentistry.

OBJECTIVES: The aim of Working Group 3 was to address the influence of both material- and anti-resorptive drug- related factors on clinical and biological outcomes and complications in implant dentistry. Focused questions were addressed on (a) implant materials other than titanium (alloy)s, (b) transmucosal abutment materials and (c) medications affecting bone metabolism were addressed. MATERIALS AND METHODS: Three systematic reviews formed the basis for discussion in Group 3. Consensus statements and clinical recommendations were formulated by group consensus based on the findings of the systematic reviews. Patient perspectives and recommendations for future research were also conveyed. These were then presented and accepted following further discussion and modifications as required by the plenary. RESULTS: Zirconia is a valid alternative to titanium as material for implant and transmucosal components, allowing soft and hard tissue integration with clinical outcomes-identified by implant survival, marginal bone loss and peri-implant probing depths-up to 5-years comparable to titatnium. However, most of the evidence for zirconia implants is based on 1-piece implants limiting the indication range. Furthermore, based on expert opinion, zirconia transmucosal components might be preferred in the esthetic zone. In patients receiving low-dose bisphosphonate therapy, the rate of early implant failure is not increased, while the long-term effects remain poorly studied. Although it has not been sufficiently addressed, similar outcomes can be expected with low-dose denosumab. A drug holiday is not recommended when considering implant placement in patients treated with low-dose ARD. However, the specific therapeutic window, the cumulative dose and the administration time should be considered. Access to peri-implant supportive care is mandatory to prevent peri-implantitis-related medication-related osteonecrosis of the jaw (MRONJ) or implant-related sequestra (IRS). In patients receiving low-dose anti-resorptive drugs (ARD) therapy, the risk of complications related to implant placement is high, and implant procedures in this specific population should be strictly treated in a comprehensive multidisciplinary center. Finally, healthy dental implants should not be removed before low or high-dose ARD. CONCLUSIONS: Zirconia implants can be an alternative to titanium implants in selected indications. However, the current state of evidence remains limited, especially for 2-piece implant designs. Administration of low-dose ARD did not show any negative impact on early implant outcomes, but careful follow-up and supportive care is recommended in order to prevent peri-implant MRONJ and IRS. Implant placement in high-dose patients must be strictly considered in a comprehensive multidisciplinary center.

Bone regeneration after maxillary sinus floor augmentation with different ratios of autogenous bone and deproteinized bovine bone mineral an in vivo experimental study.

OBJECTIVE: Test the hypothesis of no difference in bone regeneration after maxillary sinus floor augmentation (MSFA) with different ratios of iliac or mandibular autogenous bone (AB) graft and deproteinized bovine bone mineral (DBBM). MATERIALS AND METHODS: Forty minipigs were randomly allocated to bilateral MSFA using: (A) 100% AB, (B) 75% AB and 25% DBBM, (C) 50% AB and 50% DBBM, (D) 25% AB and 75% DBBM, or (E) 100% DBBM. The animals were euthanized 12 weeks after surgery. Percentage of bone, non-mineralized tissue, and residual DBBM were estimated by histomorphometric analysis in a randomly selected region of interest and summarized as mean percentage with 95% confidence interval (CI). RESULTS: Mean percentage of bone following MSFA with iliac or mandibular AB graft was: (A) 55.5% and 64.2%, (B) 60.3% and 61.6%, (C) 54.4% and 52.1%, (D) 51.8% and 53.1%, and (E) 47.6%, respectively. There was a significant trend toward a higher percentage of bone, with a higher ratio of AB within the graft (p < .01), regardless of the origin of AB graft (iliac or mandible). CONCLUSIONS: The hypothesis was rejected since percentage of bone was significantly increased with larger proportions of AB within the graft. Consequently, AB or a mixture of AB and diminutive quantities of DBBM seem to be the preferred graft for MSFA based solely on histomorphometric assessment. However, it should be emphasized that newly formed bone and residual AB graft particles could not be distinguished by the applied histologic procedure.

Modified Le Fort I interpositional grafting of the severe atrophied maxilla-a retrospective study of 106 patients over 10 years.

OBJECTIVES: The objective of this study was to evaluate a modified Le Fort I interpositional grafting followed by dental implants for the rehabilitation of edentulous atrophied maxillae (Cawood classes IV and V). The surgical modification was a bilateral sinus floor augmentation prior to the osteotomy. This generated a closed recipient bed which allowed the use of particulated bone grafts (xenogenic bone mineral) and a reduced amount of autologous iliac bone grafts. MATERIALS AND METHODS: A total of 106 patients with maxillary interpositional bone grafts were included in this retrospective analysis between 2006 and 2020. The panoramic radiographs and lateral cephalograms were analyzed to assess the gain and stability of the maxillary bone and the peri-implant bone loss. In addition, the observational period of up to 14 years implant survival and success was evaluated. RESULTS: A stable vertical bone height with mean 0.63 ± 1.41 mm resorption over 5 years after implant loading was observed. A mean of 0.20 ± 0.37 mm marginal bone loss was noted after 5 years. The implant survival was 96.4% after 5 years and implant success can be rated 91.7% in a mean follow-up period of 93 months and 168 months maximal observation time. Perioperative complications included sinus membrane perforation (59.43%), wound healing disturbances (25.47%), and transient primary complications (13.78%). All receded apart from two subtotal graft losses (1.8%). CONCLUSIONS: The modified Le Fort I osteotomy with interpositional bone grafts is a predictable procedure in terms of bone and implant stability. Patients with atrophic maxillae who are fit for surgery should be informed about risks and benefits of this treatment alternative.

Prefabricated 3D-Printed Tissue-Engineered Bone for Mandibular Reconstruction: A Preclinical Translational Study in Primate.

The advent of three dimensionally (3D) printed customized bone grafts using different biomaterials has enabled repairs of complex bone defects in various in vivo models. However, studies related to their clinical translations are truly limited. Herein, 3D printed poly(lactic-co-glycolic acid)/ß-tricalcium phosphate (PLGA/TCP) and TCP scaffolds with or without recombinant bone morphogenetic protein -2 (rhBMP-2) coating were utilized to repair primate's large-volume mandibular defects and compared efficacy of prefabricated tissue-engineered bone (PTEB) over direct implantation (without prefabrication). 18F-FDG PET/CT was explored for real-time monitoring of bone regeneration and vascularization. After 3-month's prefabrication, the original 3D-architecture of the PLGA/TCP-BMP scaffold was found to be completely lost, while it was properly maintained in TCP-BMP scaffolds. Besides, there was a remarkable decrease in the PLGA/TCP-BMP scaffold density and increase in TCP-BMP scaffolds density during ectopic (within latissimus dorsi muscle) and orthotopic (within mandibular defect) implantation, indicating regular bone formation with TCP-BMP scaffolds. Notably, PTEB based on TCP-BMP scaffold was successfully fabricated with pronounced effects on bone regeneration and vascularization based on radiographic, 18F-FDG PET/CT, and histological evaluation, suggesting a promising approach toward clinical translation.

Technology-enhanced learning: a role for video animation.

The last 20 years has seen a shift in medical education from printed analogue formats of knowledge transfer to digital knowledge transfer via media platforms and virtual learning environments. Traditional university medical teaching was characterised by lectures and printed textbooks, which to a degree still have an important role to play in knowledge acquisition, but which in isolation do not engage the modern learner, who has become reliant on digital platforms and 'soundbite' learning. Recently, however, traditional methods of teaching and learning have been augmented by, and indeed sometimes replaced by, the alternative learning methods such as: problem-based learning; a greater integration of basic science and clinical considerations; smaller teaching groups; the 'flipped classroom' concept; and various technological tools which promote an interactive learning style. The aim of these new teaching methods is to overcome the well-documented limitations of traditional lectures and printed material in the transfer of knowledge from expert to student, by better engaging the minds of more visual learners and encouraging the use of diverse resources for lifelong learning. In this commentary paper, we share the concept of video animation as an additional educational tool, and one that can help to integrate molecular, cellular and clinical processes that underpin our understanding of biology and pathology in modern education. Importantly, while they can provide focused and attractive formats for 'soundbite' learning, their aim as a tool within the broader educational toolbox is to direct the interested reader towards more traditional formats of learning, which permit a deeper dive into a particular field or concept. In this manner, carefully constructed video animations can serve to provide a broad overview of a particular field or concept and to facilitate deeper learning when desired by the student.

Characterization of porcine mesenchymal stromal cells and their proliferative and osteogenic potential in long-term culture.

Background: Porcine mesenchymal stromal cells (pMSCs) are considered a valuable research model for bone tissue engineering, which requires adequate amounts of viable cells with sufficient potential for osteogenic differentiation. For isolation and expansion of these cells through long-term culture, appropriate culture conditions are needed. Objective: To study the effect of extended in vitro cultivation on pMSC proliferation and differentiation potential using different osteogenic and adipogenic induction media. Methods: pMSCs were isolated from the bone marrow of adult Göttingen minipigs, cultured, expanded to passage 20 (~160 days) and characterized by their expression of cell surface markers (wCD44, CD45, CD90, SWC9, fibronectin), alkaline phosphatase (ALP), and osteocalcin and their potential for osteogenic and adipogenic differentiation using different induction media. Results: pMSCs retained their capacity for proliferation and osteogenic differentiation, and the number of CD90-positive cells increased significantly over more than 60 population doublings. CD90 expression in uninduced cells correlated strongly with ALP expression following osteogenic induction. Medium enriched with calcium yielded a stronger osteogenic response. Conclusion: The selection of CD90-positive MSCs and adequate levels of calcium seem to enhance the osteogenic phenotype for bone tissue engineering.

Sandwich osteotomy in atrophic mandibles: A retrospective study with a 2- to 144-month follow-up.

OBJECTIVES: The aim of the present retrospective study was to assess the long-term clinical outcome of sandwich osteotomy in pre-implant augmentation of atrophic mandible. MATERIALS AND METHODS: Sandwich osteotomies were performed in partially and fully edentulous mandibles of 63 consecutive patients in the present study. The vertical bone gain, graft stability, and marginal bone loss were measured radiographically. Implant survival and success rates were estimated in the follow-up ranged from 2 to 144 months (mean, 58 months). RESULTS: A total of 75 procedures were reviewed. After an average healing time of 148 days, 220 implants were placed in 74 procedures. Perioperative complications included intraoperative fracture (1/75), transient paresthesia (18/75), wound healing disturbance (18/75), and keratinized tissue deficiency (14/75). The average vertical bone gain was 5.4 mm at the time of implant placement. Significant marginal bone loss occurred during the first 6 months, after which the resorption remained stable. The implant survival rate was estimated as 96.7%, and the success rate was 95.3%. Implant survival and success showed no significant correlation with higher age, anticoagulation therapy, cardiovascular disease, or thyroid disorder. Smoking was correlated with significant lower success rate. CONCLUSION: Sandwich osteotomy is a suitable augmentation procedure for atrophic mandible, allowing for implant placement with promising outcome.

Peri-implantitis and its prevention.

This perspective article on peri-implantitis and its prevention was produced as a supplement to a 3-D, computer-animated film aiming at presenting key characteristics of peri-implant health, the build-up of a biofilm and the ensuing host-response resulting in peri-implant mucositis and, subsequently, peri-implantitis. Treatment concepts for peri-implantitis were briefly reviewed, and prevention of the condition was brought to attention as a priority in implant dentistry. The overview also highlighted the 2017 World Workshop on Classification of Periodontal and Peri-implant diseases and Conditions, in which new disease definitions and case definitions were presented for peri-implant health, peri-implant mucositis, and peri-implantitis.

Current concepts in cleft care: A multicenter analysis.

The current surgical techniques used in cleft repair are well established, but different centers use different approaches. To determine the best treatment for patients, a multi-center comparative study is required. In this study, we surveyed all craniofacial departments registered with the German Society of Maxillofacial Surgery to determine which cleft repair techniques are currently in use. Our findings revealed much variation in cleft repair between different centers. Although most centers did use a two-stage approach, the operative techniques and timing of lip and palate closure were different in every center. This shows that a retrospective comparative analysis of patient outcome between the participating centers is not possible and illustrates the need for prospective comparative studies to establish the optimal technique for reconstructive cleft surgery.

Particulate Coral Hydroxyapatite Sheltered by Titanium Mesh for Localized Alveolar Rehabilitation After Onlay Graft Failure: A Case Report.

Reconstruction of bone loss in the alveolar ridge has long been challenging. Autologous bone grafts are considered as the "golden standard," while little research has focused on how to repair pronounced alveolar bone defects after autologous bone graft failure. The aim of this study was to detail a method based on the titanium mesh technique coupled with particulate coral hydroxyapatite to solve the onlay graft failure. With bone deficiency in the No. 11 and No. 24-25 regions, we harvested 2 autologous bone blocks for reconstruction. Two weeks after transplantation, the graft in the No. 11 region had healed uneventfully, while the graft in the anterior mandible became infected because of soft tissue dehiscence. After removal of the failed autologous bone block, pure coral hydroxyapatite stabilized within titanium mesh was used for alveolar rehabilitation. Six months later, the width of the local alveolar bone was evaluated. After the titanium mesh was removed, a biopsy was performed to study bone regeneration by micro computerized tomography and histology, following by a standard Straumann implant insertion. Although there was wound dehiscence 14 days after bone augmentation, repeated local rinsing and anti-inflammation therapy controlled the inflammatory reaction. The total horizontal bone gain was 4.2 ± 0.5 mm. Micro computerized tomography revealed that the closer the coral hydroxyapatite was to the host bone, the more was resorbed and the more bone regenerated. Histology showed mature lamellar bone structures, with evident residual coral hydroxyapatite. A 3-year follow-up revealed stable bone around the dental implant and successful function of the implant-born prosthesis. This study proposes that the method of particulate coral hydroxyapatite sheltered by titanium mesh is a promising solution in handling alveolar bone augmentation failure. More cases are needed for further research to form an efficient treatment procedure.

Facilitators and barriers influencing the readiness to receive dental implants in a geriatric institutionalised population-A randomized non-invasive interventional study.

OBJECTIVE: Although elderly people have many serious dental issues and are in need of prosthesis, few opt for dental implants. The aim of this study was to investigate barriers that prevent elderly people from receiving dental implants. Specifically, we examined (i) whether the message was delivered before or after the interview had an impact, and (ii) whether it did matter who delivered the message. MATERIALS AND METHODS: Sixty-six residents from seven residential homes in the Canton of Grisons, Switzerland were included. The sample was randomized to a treatment group that received comprehensive education about dental implants before the interview and a control group that received education after completing the questionnaire. RESULTS: The sample consisted of 54 women (81.8%) and 12 males (18.2%) with an average age of 86.2 years. Education before the interview did not show any impact on the attitude towards dental implants. Main reasons for a negative attitude towards implants were old age and high costs. Participants who received information about implants from their relatives and their own dentist and not from the study dentist were significantly more willing to receive implants. CONCLUSION: Providing an adequate education about benefits and risks of receiving dental implants does not change the attitude towards dental implants. The source of information/messenger does influence attitudes towards implants. If the person delivering the education and information is a relative or a known medical person, the person's attitude is more likely to change as compared to people receiving the information from an unrelated person.

Pre-augmentation soft tissue expansion improves scaffold-based vertical bone regeneration - a randomized study in dogs.

OBJECTIVE: Soft tissue (ST) dehiscence with graft exposure is a frequent complication of vertical augmentation. Flap dehiscence is caused by failure to achieve tension-free primary wound closure and by the impairment of flap microcirculation due to surgical trauma. Soft tissue expansion (STE) increases ST quality and quantity prior to reconstructive surgery. We hypothesized that flap preconditioning using STE would reduce the incidence of ST complications after bone augmentation and that optimized ST healing would improve the outcome of bone regeneration. MATERIALS AND METHODS: Self-filling tissue expanders were implanted in mandibular bone defects in ten beagle dogs. After expansion, alloplastic scaffolds were placed for vertical bone augmentation in STE sites and in control sites without STE pre-treatment. ST flap microcirculation was analysed using laser Doppler flowmetry. The incidence of graft exposures was evaluated after 2 weeks. Bone formation was assessed after 2 months, using histomorphometry and immunohistochemistry. RESULTS: Test sites showed significantly less impairment of perfusion and faster recovery of microcirculation after bone augmentation. Furthermore, no flap dehiscences occurred in STE sites. Bone regeneration was found in both groups; however, significantly greater formation of new bone was detected in test sites with preceding STE. CONCLUSIONS: Preconditioning using STE improved ST healing and bone formation after vertical augmentation. The combination of STE and the subsequent placement of alloplastic scaffolds may facilitate the reconstruction of severe bone defects.

Correlation between resonance frequency, insertion torque and bone-implant contact in self-cutting threaded implants.

The aim of this study was to evaluate the correlation between resonance frequency analysis (RFA) values and the histomorphometric bone-implant contact (BIC) immediately after insertion of the implant. Additionally, it was examined to define which extent peak insertion torque (PIT) was correlated with the latter measurements. 15 Xive® S plus root from dental implants were inserted in fresh porcine frontal bones. The insertion torque was measured with the Kavo Intrasurg 300 surgical unit. RFA connector was coupled to the implants and the mean value of 20 consecutive RFA measurements was calculated via Osstell® ISQ device. The implants were removed with the adjacent bone with a band saw. The blocks were processed for undecalcified histology. Two perpendicular longitudinal middle sections of the implant were made and stained with toluidine blue and the BIC was assessed by histomorphometry. The correlation coefficient (Spearman) between RFA and BIC was R = 0.579 (p = 0.026, F test). The correlation between PIT and BIC (0.33, p > 0.05) and PIT and RFA (0.153, p > 0.05) was not statistically significant. The present data confirmed a moderate and statistically positive correlation between RFA and BIC. No correlation between BIC and PIT and PIT and RFA was observed. Further studies considering different bone qualities would be beneficial in understanding the relation between RFA and BIC.

Cell-to-cell communication in guided bone regeneration: molecular and cellular mechanisms.

This overview provides insights into the molecular and cellular mechanisms involved in guided bone regeneration, in particular focusing on aspects presented in the 3D movie, Cell-To-Cell Communication in Guided Bone Regeneration. The information presented here is based almost exclusively on genetic mouse models in which single genes can be deleted or overexpressed, even in a specific cell type. This information needs to be extrapolated to humans and related to aspects relevant to graft consolidation under the clinical parameters of guided bone regeneration. The overview follows the ground tenor of the Cell-To-Cell Communication series and focuses on aspects of cell-to-cell communication in bone regeneration and guided bone regeneration. Here, we discuss (1) the role of inflammation during bone regeneration, including (2) the importance of the fibrin matrix, and (3) the pleiotropic functions of macrophages. We highlight (4) the origin of bone-forming osteoblasts and bone-resorbing osteoclasts as well as (5) what causes a progenitor cell to mature into an effector cell. (6) We touch on the complex bone adaptation and maintenance after graft consolidation and (7) how osteocytes control this process. Finally, we speculate on (8) how barrier membranes and the augmentation material can modulate graft consolidation.

Oral health-related quality of life and implant therapy: A prospective multicenter study of preoperative, intermediate, and posttreatment assessment.

PURPOSE: Loss of teeth is associated with a significant reduction in quality of life. The aim of this prospective multicenter study was to assess the impact of dental implants on oral health-related quality of life (OHRQoL). MATERIAL AND METHODS: Patients with various kinds of indications for dental implants ranging from single-tooth loss to edentulous jaws were included. Quality of life related to dental implants was assessed through the Oral Health Impact Profile (OHIP-G 21), which has a score from 0 to 20 in healthy patients. RESULTS: In total, 8689 patients from 17 centers from 2009 to 2014 were enrolled in the study. The sex distribution was almost even (53.3% men, 46.7% women). The most frequent indications for the insertion of dental implants were free-end gaps (30.6%) and posterior single-tooth gaps (27%). In all, 12.4% of patients had an edentulous jaw. For all indications, patients reported significant changes in mean OHIP scores after prosthetic reconstruction. The most significant improvements in the OHIP score occurred in the groups of patients with edentulous jaws (pretreatment score: 42.3) after prosthodontic reconstruction (score: 24.8) and in the patient group with an anterior single-tooth gap (pretreatment score: 36.4) after prosthodontic reconstruction (score: 24.8). CONCLUSION: The insertion of dental implants and prosthodontic rehabilitation led to an improved OHRQoL for patients with all indications for dental implants, with the most significant improvements in patients with edentulous jaws and anterior single-tooth gaps.

The current state of facial prosthetics ­ A multicenter analysis.

Even though modern surgical techniques are dominating reconstructive facial procedures, the capability to use facial epitheses for reconstruction is still an important skill for the maxillofacial surgeon. We present an international multicenter analysis to clarify which techniques are used to fixate facial prostheses. We contacted all maxillofacial departments in Germany, Austria, Switzerland and Norway which were registered with the German society for oral and maxillofacial surgery (DGMKG). These centers were asked via electronical mail to provide information on the type of epithesis fixation systems currently in use. The return rate from 58 departments was 43.1% (n = 25). Overall, implant fixation was the preferred fixation system (92%). Plates were the second most common fixation technique (32%). No centers reported the standard use of non-invasive fixation techniques for permanent epithesis fixation. The main retention systems in use were magnets (24/25), other retention systems are used much less often. The current preferred fixation technique for facial epitheses consists of implant-based, magnet-fixated epitheses. For nasal prostheses, a plate-based, magnet-fixated system is often used.

Cell-to-cell communication--periodontal regeneration.

BACKGROUND: Although regenerative treatment options are available, periodontal regeneration is still regarded as insufficient and unpredictable. AIM: This review article provides scientific background information on the animated 3D film Cell-to-Cell Communication - Periodontal Regeneration. RESULTS: Periodontal regeneration is understood as a recapitulation of embryonic mechanisms. Therefore, a thorough understanding of cellular and molecular mechanisms regulating normal tooth root development is imperative to improve existing and develop new periodontal regenerative therapies. However, compared to tooth crown and earlier stages of tooth development, much less is known about the development of the tooth root. The formation of root cementum is considered the critical element in periodontal regeneration. Therefore, much research in recent years has focused on the origin and differentiation of cementoblasts. Evidence is accumulating that the Hertwig's epithelial root sheath (HERS) has a pivotal role in root formation and cementogenesis. Traditionally, ectomesenchymal cells in the dental follicle were thought to differentiate into cementoblasts. According to an alternative theory, however, cementoblasts originate from the HERS. What happens when the periodontal attachment system is traumatically compromised? Minor mechanical insults to the periodontium may spontaneously heal, and the tissues can structurally and functionally be restored. But what happens to the periodontium in case of periodontitis, an infectious disease, after periodontal treatment? A non-regenerative treatment of periodontitis normally results in periodontal repair (i.e., the formation of a long junctional epithelium) rather than regeneration. Thus, a regenerative treatment is indicated to restore the original architecture and function of the periodontium. Guided tissue regeneration or enamel matrix proteins are such regenerative therapies, but further improvement is required. As remnants of HERS persist as epithelial cell rests of Malassez in the periodontal ligament, these epithelial cells are regarded as a stem cell niche that can give rise to new cementoblasts. Enamel matrix proteins and members of the transforming growth factor beta (TGF-ß) superfamily have been implicated in cementoblast differentiation. CONCLUSION: A better knowledge of cell-to-cell communication leading to cementoblast differentiation may be used to develop improved regenerative therapies to reconstitute periodontal tissues that were lost due to periodontitis.