Expert consensus on odontogenic maxillary sinusitis multi-disciplinary treatment

Odontogenic maxillary sinusitis (OMS) is a subtype of maxillary sinusitis (MS). It is actually inflammation of the maxillary sinus that secondary to adjacent infectious maxillary dental lesion. Due to the lack of unique clinical features, OMS is difficult to distinguish from other types of rhinosinusitis. Besides, the characteristic infectious pathogeny of OMS makes it is resistant to conventional therapies of rhinosinusitis. Its current diagnosis and treatment are thus facing great difficulties. The multi-disciplinary cooperation between otolaryngologists and dentists is absolutely urgent to settle these questions and to acquire standardized diagnostic and treatment regimen for OMS. However, this disease has actually received little attention and has been underrepresented by relatively low publication volume and quality. Based on systematically reviewed literature and practical experiences of expert members, our consensus focuses on characteristics, symptoms, classification and diagnosis of OMS, and further put forward multidisciplinary treatment decisions for OMS, as well as the common treatment complications and relative managements. This consensus aims to increase attention to OMS, and optimize the clinical diagnosis and decision-making of OMS, which finally provides evidence-based options for OMS clinical management.

Low-grade myofibrosarcoma of the maxillary sinus:Two case reports

BACKGROUND Low-grade myofibroblastic sarcoma(LGMS)is an extremely rare tumor characterized by the malignant proliferation of myofibroblasts.LGMS most commonly develops in adults,predominantly in males,in the head and neck region,oral cavity,especially on the tongue,mandible,and larynx.This article presents 2 cases of LGMS localized to the maxillary sinus and provides an overview of the available literature.CASE SUMMARY Two patients with LGMS located in the maxillary sinus underwent surgery at the Department of Head and Neck Surgery.Case 1:A 46-year-old patient was admitted to the clinic with suspected LGMS recurrence in the right maxillary sinus(rT4aN0M0),with symptoms of pain in the suborbital area,watering of the right eye,thick discharge from the right nostril,and augmented facial asymmetry.After open biopsy-confirmed LGMS,the patient underwent expanded maxillectomy of the right side with immediate palate reconstruction using a microvascular skin flap harvested surgically from the middle arm.The patient qualified for adjuvant radiotherapy for the postoperative bed,with an additional margin.Currently,the patient is under 1.5 years of observation with no evidence of disease.Case 2:A 45-year-old man was admitted to our clinic with facial asymmetry,strabismus,exophthalmos,and visual impairment in the right eye.Six months earlier,the patient had undergone partial jaw resection at another hospital for fibromatosis.A contrast-enhanced computed tomography scan revealed a tumor mass in the postoperative log after an earlier procedure.An open biopsy confirmed lowgrade fibrosarcoma(rT4aN0M0).The patient qualified for an extended total right maxillectomy with orbital excision and right hemimandibulectomy with immediate microvascular reconstruction using an anterolateral thigh flap.The patient subsequently underwent adjuvant radiotherapy to the postoperative area.After 9 months,recurrence occurred in the right mandibular arch below the irradiated area.The lesion infiltrated the base of the skull,which warranted the withdrawal of radiotherapy and salvage surgery.The patient qualified for palliative chemotherapy with a regimen of doxorubicin+dacarbazine+cyclophosphamide and palliative radiotherapy for bone metastases.The patient died 26 months after surgical treatment.The cases have been assessed and compared with cases in the literature.CONCLUSION No specific diagnostic criteria or treatment strategies have been developed for LGMS.The treatment used for LGMS is the same as that used for sinonasal cancer radical tumor excision;adjuvant radiotherapy or chemoradiotherapy should also be considered.They have low malignant potential but are highly invasive,tend to recur,and metastasize to distant sites.Patients should undergo regular follow-up examinations to detect recurrence or metastasis at an early stage.Patients should be treated and observed at the highest referral centers.

Asymmetric outcomes in bilateral maxillary impacted tooth extractions:A case report

BACKGROUND The extraction of maxillary impacted teeth is a common procedure in oral surgery,frequently complicated by oroantral communications.For less-experienced clinicians,accurately assessing the difficulty and associated risks of maxillary third molar extractions remain a significant challenge.CASE SUMMARY We present a case involving disparate outcomes following bilateral extraction of maxillary third molars.Using cone-beam computed tomography and three-dimensional software,we conducted a digital assessment of the factors contributing to extraction difficulty and risk,controlling for potential confounders.Key variables analyzed included alveolar bone volume,bone quality,crown-root angulation,and maxillary sinus mucosal thickness.Additionally,we introduce the novel concept of"tegmen bone"to quantitatively evaluate the bone mass between the teeth and the maxillary sinus.This unique case,with differing outcomes on opposite sides of the same patient,provided an opportunity to minimize extraneous variables and focus on the local anatomical factors influencing the procedures,thereby improving the precision of our analysis.CONCLUSION This case highlights the potential utility of predictive analysis in guiding the management of complex tooth extractions.

Diagnostic accuracy of the tongue blade test combined with clinical signs to detect maxillary and mandibular fractures in the emergency department

BACKGROUND: To evaluate the diagnostic accuracy of clinical signs combined with the tongue blade test(TBT) to detect maxillary and mandibular fractures.METHODS: A cross-sectional study enrolled patients with maxillary and mandibular injuries in the emergency department. Physical examination and the TBT were performed, followed by radiological imaging(facial X-ray or computed tomography [CT]). The diagnostic accuracy was calculated for individuals and a combination of clinical findings at predicting maxillary and mandibular fractures.RESULTS: A total of 98 patients were identified, of whom 31.6% had maxillary fractures and9.2% had mandibular fractures. The combination of malocclusion, tenderness on palpation and swelling with positive TBT had 100% specificity to detect maxillary and mandibular fractures. In the absence of malocclusion, the combination of tenderness on palpation and swelling with positive TBT produced a specificity of 97.8% for maxillary fracture and a specificity of 96.2% for mandibular fracture. A clinical decision tool consisting of malocclusion, tenderness on palpation, swelling and TBT revealed a specificity of 100% and a positive predictive value of 100%.CONCLUSION: The clinical decision tool is potentially useful to rule out mandibular fractures,thus preventing unnecessary radiation exposure.

Clinical and Therapeutic Characteristics of Acute Maxillary Rhinosinusitis in a Hospital of Cotonou

Introduction: Acute maxillary rhinosinusitis (AMRS) is one of the most common ear, nose and throat infections. The aim of this study was to contribute to the improvement of the management of the condition in sub-Saharan Africa. Material and Method: This was a cross-sectional, descriptive study that ran from January 1, 2017 to December 31, 2021 in the ENT-HNS department of the “Centre Hospitalier et Universitaire de Zone de Suru-Léré” (CHUZ SL) in Cotonou, Benin. It involved all patients who consulted during the study period and in whom the diagnosis of acute maxillary rhinosinusitis was made. Results: A total of 405 cases were identified. The mean age was 34.26 ± 15.26 years with extremes of 9 and 63 years. The predominance was female with a sex ratio of 0.61. Acute maxillary rhinosinusitis was bilateral in 371 cases (91.60%). The main symptoms were facial pain in 346 cases (85.43%), mucopurulent rhinorrhea: 315 cases (77.78%), headache: 283 cases (69.88%), and nasal obstruction: 244 cases (60.25%). The most frequent physical signs were pain on pressure of the maxillary sinus points in 405 cases or 100%, purulent secretions at the middle meatus: 11.35%, hyperemia of the nasal mucosa: 53.58%, hypertrophy of the middle turbinate: 41.48% and discharge of pus on the posterior pharyngeal wall: 36.79%. Amoxicillin + clavulanic acid was the main antibiotic prescribed. Vasoconstrictors were used in 228 cases 56.30%. The evolution was favorable in all cases. Conclusion: The diagnosis of acute maxillary rhinosinusitis is clinical. Treatment with antibiotic gives good results.

Maxillary Sinus Schwannoma—A Rare Tumor with Rarer Site of Occurrence

Schwannoma or neurilemmoma is a neurogenic tumor. Around 25% - 45% cases of schwannomas occur in the head and neck, of which less than 4% occurs in the nasal cavity and the paranasal sinuses. Isolated schwannomas of the maxillary sinus appear to be extremely rare. We present one such rare case of Right Maxillary Sinus schwannoma in a 48-year-old lady with swelling in the right cheek for 3 years. Infrastructure maxillectomy of the right side was done using Weber-Fergusson approach with Dieffenbach’s modification. The patient made a good postoperative recovery. We report this case keeping in mind the rarity in occurrence of isolated maxillary schwannomas.

Comparative Characterization of Maxillary Expansion and Alternate Maxillary Expansions and Constrictions in Rats

The purpose of this study was to evaluate whether the cranial and circumaxillary sutures react differently to maxillary expansion （ME） and alternate maxillary expansions and constrictions （Alt-MEC） in a rat model. Twenty-two male Sprague-Dawley rats （6 weeks old） were used and divided into three groups. In ME group （n=9）, an expander was activated for 5 days. In Alt-MEC group （9 animals）, an al- ternate expansion and constriction protocol （5-day expansion and 5-day constriction for one cycle） was conducted for 2.5 cycles （25 days total）. The control group comprised 4 animals with no appliances used, each of two sacrificed on day 5 and day 25 respectively. Midpalatal suture expansion or constriction levels were assessed qualitatively and quantitatively by bite-wing X-rays and cast models. Distances between two central incisors and two maxillary first molars were measured on cast models after each activation. Circumaxillary sutures （midpalatal, maxillopalatine, premaxillary, zygomaticotemporal and frontonasal suture） in each group were characterized histologically. Results showed that midpalatal suture was wid- ened and restored after each expansion and constriction. At the end of activation, the widths between both central incisors and first molars in Alt-MEC group were significantly larger than those in ME group （P〈0.05）. Histologically, all five circumaxillary sutures studied were widened in multiple zones in Alt- MEC group. However, only midpalatal suture was expanded with cellular fibrous tissue filling in ME group. Significant osteoclast hyperplasia was observed in all circumaxillary sutures after alternate expan- sions and constrictions, but osteoclast count increase was only observed in midpalatal suture in ME group. These results suggested that cranial and circumaxillary sutures were actively reconstructed after Alt-MEC, while only midpalatal suture had active reaction after ME.

Three-dimensional computed topography analysis of a patient with an unusual anatomy of the maxillary second and third molars

We present a case of a patient with rare anatomy of a maxillary second molar with three mesiobuccal root canals and a maxillary third molar with four separate roots, identified using multi-slice computed topography （CT） and three-dimensional reconstruction techniques. The described case enriched/might enrich our knowledge about possible anatomical aberrations of maxillary molars. In addition, we demonstrate the role of multi-slice CT as an objective tool for confirmatory diagnosis and successful endodontic management.

Cone beam computed tomographic analyses of alveolar bone anatomy at the maxillary anterior region in Chinese adults

To provide an anatomical basis for clinical implant esthetics,we evaluated the morphology of the nasopalatine canal（NPC） and analyzed labial and interproximal bone anatomy at the maxillary anterior region.We sought to investigate the effect of maxillary protrusion and tooth labiolingual inclination on labial bone anatomy in Chinese adults.Three dimensional（3D） images were reconstructed using cone-beam computed tomography（CBCT） images from 80 Chinese subjects and by SimPlant 11.04.The dimensions of the NPC,the thickness and profile of the labial bone,the width and height of the interproximal bone,angle sella-nasion-subspinale（SNA） and angle upper central incisor-nasion,subspinale（U1-NA） were measured.The incisive foramen of the NPC was markedly wider than its nasal foramen.The dimension of its labial bone wall demonstrated an increasing width from the crestal to apical measurements.The labial bone at the maxillary anterior region was rather thin,especially at 3 mm below the cemento-enamel junction（CEJ） and the mid-root level;the profile of the labial bone was more curved at the central incisor,and the interproximal bone became wider and shorter posteriorly.There were significant relationships between maxillary protrusion and labial bone profile,tooth labiolingual inclination and labial bone thickness（P 〈 0.02）.To achieve optimal esthetic outcome of implant,bone augmentation is necessary at the maxillary anterior region.For immediate or early placement at the maxillary anterior region,the implant should be located palatally to reduce labial bone resorption and marginal recession;its apex should be angulated palatally to avoid labial perforation at the apical region.To protect the NPC,implants at the central incisor region should be placed away from NPC.

Minimally invasive endoscopic maxillary sinus lifting and immediate implant placement: A case report

BACKGROUND This case report discusses a modified approach for maxillary sinus augmentation,in which platelet-rich fibrin,endoscope,simultaneous implant placement,and sinus floor elevation(PESS)were applied for a maxillary sinus floor lift in a 40-year-old patient.CASE SUMMARY A 40-year-old woman suffered missing upper right first molar.Implant stability quotient and cone-beam computed tomography(CBCT)were used to evaluate the diagnosis.CBCT showed insufficient posterior maxillary bone with a mean residual alveolar bone height of only 3.5 mm.The patient underwent a minimally invasive sinus floor elevation endoscopically.The sinus membrane was elevated in two stages,and a 12-mm implant was placed immediately.At 3 mo postoperatively,the final impressions were accomplished,and a full-ceramic crown was fit-placed.A 6-mo follow-up demonstrated satisfactory aesthetic and functional results.CONCLUSION This is the first report to use an endoscope for maxillary sinus floor lifting in cases with severe and insufficient bone height.This case report demonstrates the advantages of the PESS technique,which include minimal invasiveness with high precision,being applicable in cases with a residual alveolar bone height<4 mm with a promising result,and a shortened treatment period from 12 to 3 mo.

Endodontic management of the maxillary first molars with two root canals: A case report and review of the literature

BACKGROUND The complex anatomy of the maxillary first molars has always been a major challenge for complete root canal treatment in endodontic therapy. Here, we present two cases of maxillary first molars, each with only two root canals, which have been rarely reported. We also perform a literature review of maxillary first molar anatomy.CASE SUMMARY The two patients were referred to the hospital after 1) finding a cavity in their tooth with a color change and, 2) a toothache during mastication, respectively.Both of these cases were diagnosed as apical periodontitis by X-ray imaging and cone beam computed tomography(CBCT). Non-surgical endodontic therapy was performed with the assistance of a dental operating microscope(DOM). CBCT showed rare but accurate images of both patients, each with two root canals and two roots in their maxillary first molars. Both roots were located in the buccal in the palatal direction, and each root had only one clear root canal. In addition,each maxillary first molar in both patients was symmetrical to that on the opposing side with only two separate root canals. Non-surgical endodontic therapy was performed with the assistance of a DOM. Finally, the teeth were restored using composite resin and the patients were satisfied with the results.CONCLUSION Making full use of CBCT and DOM would contribute to helping dentists make correct diagnoses and successfully treat teeth with rare root canal morphologies.

Three-dimensional analysis of the physiological foramen geometry of maxillary and mandibular molars by means of micro-CT

The aim of this study was to investigate the physiological foramen diameter, shape and distance between physiological and anatomical apex of maxillary and mandibular first and second molars. Accurate knowledge of the physiological foramina morphology; thus, inherent mechanical shaping technical hindrances, is decisive when taking the corresponding root canal final preparation decision. The morphological dimensions of a total of 1 727 physiological foramina were investigated by means of micro-computed tomography. Mean narrow and wide （to a high number, oval） diameters of the physiological foramen were 0.24, 0.22 and 0.33 mm and 0.33, 0.31 and 0.42 mm in mesiobuccal （MB）, distobuccal （DB） and palatal （P） roots in maxillary first molars; 0.24, 0.22 and 0.33 mm and 0.41, 0.33 and 0.44 in MB, DB, and P roots in maxillary second molars. Mandibular first molars showed mean narrow and wide diameters of 0.24 and 0.30 mm and of 0.39 and 0.46 mm in mesial （M） and distal （D） roots; second mandibular molars showed 0.25 and 0.31 mm and 0.47 mm in M and D roots. The mean distance between the physiological foramina and anatomical apex was 0.82, 0.81 and 1.02 mm and 0.54, 0.43 and 0.63 mm in MB, DB and P roots of the maxillary first and second molars, respectively. A mean distance of 0.95 mm （M） and 1.05 mm （D） in the first and 0.78 mm （M） and 0.81 mm （D） in the second mandibular molars was observed. Based on the results obtained, assumable recommendations for final preparation size of the physiological foramen were calculated. However, when taking into consideration, the resulting standard deviations of marginal errors must be cautiously considered when taking a final decision in clinical endodontic treatment.

Root canal morphology and configuration of 123 maxillary second molars by means of micro-CT

The aim of this study was to investigate the root canal configuration, accessory canals and number of main foramina of 123 maxillary second molars by means of micro-computed tomography. The teeth were scanned and reproduced with 3D software imaging. The root canal configuration and number of main foramina were evaluated by means of a four-digit system. The morphological complexity of human maxillary second molars is depicted by the number of accessory and connecting canals. The most frequently observed root canal configurations in the mesiobuccal root were 2-2-2/2 （19.5%）, 2-2-1/1 （14.6%） and 2-1-1/1 （13.0%）. A 1-1-1/1 configuration was observed in 93.5% and in 96.7% in the distobuccal and palatal roots, respectively. The MB1 mot canal had one accessory canal （18.7%）, and 8.9% of the MB2 root canal had one or two accessory canals. The distobuccal （11.3%） and palatal （14.6%） root canals had at least one accessory canal, and connecting canals were observed in 16.3% of mesiobuccal roots. The MB1, MB2, distobuccal and palatal root canals had one main foramen in 99.2%, 43.1%, 98.4% and 99.2% of samples, respectively. In the mesiobuccal root, one accessory foramen was detected in 14.6%, two were detected in 7.3%, and three were detected in 5.7%. The distobuccal root showed one or two accessory foramina in 9.1% of samples. The root canal configuration of maxillary second molars is quite heterogeneous; the mesiobuccal root has predominantly two root canal entrances （58.4%, 1 in 41.1%） with one main foramen （54.4%）. Two main foramina were observed in 43.0%. Morphological variations, connecting and accessory canals were observed in all apical thirds.

Sequential Fluorescent Labeling Observation of Maxillary Sinus Augmentation by a Tissue-engineered Bone Complex in Canine Model

Aim To evaluate the effects of maxillary sinus floor elevation by a tissue-engineered bone complex of β-tricalcium phosphate （β-TCP） and autologous osteoblasts in dogs. Methodology Autologous osteoblasts from adult Beagle dogs were cultured in vitro. They were further combined with β-TCP to construct the tissue-engineered bone complex. 12 cases of maxillary sinus floor elevation surgery were made bilaterally in 6 animals and randomly repaired with the following 3 groups of materials： Group A （osteoblasts/D-TCP）; Group B （β-TCP）; Group C （autogenous bone） （n=4 per group）. A polychrome sequential fluorescent labeling was performed post-operatively and the animals were sacrificed 24 weeks after operation for histological observation.Results Our results showed that autologous osteoblasts were successfully expanded and the osteoblastic phenol- types were confirmed by ALP and Alizarin red staining. The cells could attach and proliferate well on the surface of the ~3-TCP scaffold. The fluorescent and histological observation showed that the tissue-engineered bone complex had an earlier mineralization and more bone formation inside the scaffold than β-TCP along or even autologous bone. It had also maximally maintained the elevated sinus height than both control groups. Conclusion Porous 13-TCP has served as a good scaffold for autologous osteoblasts seeding. The tissue-engineered bone complex with β-TCP and autologous osteoblasts might be a better alternative to autologous bone for the clinical edentulous maxillary sinus augmentation.

Comparison of Maxillary Implant-Supported Prostpesis in Irradiated and Non-Irradiated Patients

In order to investigate the influence of radiation therapy after the treatment of maxillary implant-supported prostheses, 27 patients received a total of 131 implants in maxilla after oral cancer treatment and/or reconstructive surgery. Among them, 25 received maxillary implant-supported prostheses. The cumulative survival rates of implants and prostheses were evaluated by the product-limit-estimates method according to Kaplan-Meier. The cumulative survival rate of implants and prostheses in irradiated patients was compared with that in non-irradiated patients by statistical Log-rank test. The results showed that 112 implants were observed after implant loading. The implants cumulative survival rate was approximately 65 % for overall patients. The cumulative prosthesis successful rate was approximately 88 % for all 25 patients. Log-rank test analysis revealed that there was a significant difference in cumulative implants survival rates between non-irradiated and irradiated maxillary bone (P<0. 01). It was concluded that the implants and prostheses in irradiated patients have significantly lower survival rates than in non-irradiated patients.

Embryonal rhabdomyosarcoma in the maxillary sinus with orbital involvement in a pediatric patient:Case report

This report presents a case of embryonal rhabdomyosarcoma(e RMS) located in the left maxillary sinus and invading the orbital cavity in a ten-year-old male patient who was treated at a referral hospital.The images provided from the computed tomography showed a heterogeneous mass with soft-tissue density,occupying part of the left half of the face inside the maxillary sinus,and infiltrating and destroying the bone structure of the maxillary sinus,left orbit,ethmoidal cells,nasal cavity,and sphenoid sinus.An analysis of the histological sections revealed an undifferentiated malignant neoplasm infiltrating the skeletal muscle tissue.The immunohistochemical analysis was positive for the antigens:MyoD 1,myogenin,desmin,and Ki67(100% positivity in neoplastic cells),allowing the identification of the tumour as an eR MS.The treatment protocol included initial chemotherapy followed by radiotherapy and finally surgery.The total time of the treatment was nine months,and in 18-mo of follow-up period did not show no local recurrences and a lack of visual impairment.

Maxillary first molar with an O-shaped root morphology:report of a case

This case report is to present a maxillary first molar with one O-shaped root, which is an extended C-shaped canal system. Patient with chronic apical periodontitis in maxillary left first molar underwent replantation because of difficulty in negotiating all canals. Periapical radiographs and cone-beam computed tomography （CBCT） were taken. All roots were connected and fused to one root, and all canals seemed to be connected to form an O-shape. The apical 3 mm of the root were resected and retrograde filled with resin-modified glass ionomer. Intentional replantation as an alternative treatment could be considered in a maxillary first molar having an unusual O-shaped root.

Maxillary first premolars:Ⅰ.Morphology of the apical constriction

Objective： To investigated the apical constriction morphology of maxillary first premolars in the Chinese population. Methods： Eighty recently extracted human maxillary first premolars from a native Chinese population were used. The number and shape of apical constrictions were recorded under a dental operating microscope （DOM） at 12.5 × 2.5 magnification. After access preparation, a new K-file was inserted into the canal until the tip of the file was just seen at the apical constriction under the DOM. The teeth with files in the canals were X-rayed from a mesiodistal direction using a direct digital radiography （DDR） system, and the distance between the file tip and the center of radiographic apex was directly measured from the computer screen using DDR measurement software. Results： The percentage of teeth with an apical constriction was 78.5% （102/130）. The most common apical constriction shapes were oval （55.9%） and round （35.3%）. The mean distance between the apical constriction and the anatomical tip of the root was 0.61 mm, and 84.3% （86/102） were within 1 mm. Conclusion： The most common shape of an apical constriction was oval or round, and the distance to the apex was mostly within 1 mm, indicating that root canal therapy should stop 1 mm from the radiographic apex.

Stainless steel double loop appliance to correct ectopically positioned maxillary permanent first molar

Ectopic eruption is the abnormal eruption of a permanent tooth that often causes root resorption of an adjacent primary tooth which can be noted during routine dental radiographic evaluation. The mesial eruption of the permanent first molar may be a local eruption problem or may indicate developmental arch circumference deficiency requiring further consideration. Early treatment is mandatory to move the ectopically erupting tooth away from the tooth it is resorbing to allow the tooth to erupt into its normal position, maintaining a normal arch circumference. Although much has been written about ectopic eruption of the maxillary first permanent molar, no case report mentions correction of ectopically erupted maxillary permanent first molar by using double loop stainless steel.

Finite element analysis of stress distribution of obturator prostheses for acquired unilateral maxillary defects

Objective To assess stresses produced by different obturator prostheses. Methods Three-dimensional finite clement models of unilateral maxillary defects rehabilitated with different obturators were constructed. The different stresses were analyzed by three-dimensional finite element method under different load angle. Results The Von Mises stress values obtained for the remaining tissues adjacent to defect cavity were higher when rehabilitated by inferior hollow obturator in comparison with by superior hollow obturator. The maximum of Von Mises were higher when rehabilitated by resilient hollow obturator than by rigid hollow obturator. It was also observed that in the rigid type stress distribution contours formed in the remaining tissues adjacent to defect cavity, while in resilient hollow obturator prostheses the stress distributed mainly in the prosthesis itself. The oblique load shows the most maximum of Von Mises among all types of obturator prostheses. Conclusions A high lateral wall of an obturator may be more better in preserving the remaining structures than a shorter prosthesis lateral wall. A soft liner may be incorporated to reduce the pain of the residual maxillary structures and mucosa. When load on defect, higher stress would be generated to the residual maxillary structures. The adjustment of occlusual relationship is very important.