Digital occlusal analysis of pre and post single posterior implant restoration delivery: A pilot study

Objectives The purposes of this study were to analyze the effects of single posterior implant restorations delivery on the redistribution of bite force and to evaluate the changes in occlusal force distribution of prostheses and potential influencing factors on occlusion variation at different stages. Materials and methods Thirty-two single posterior restorations in 30 participants (18 women and 12 men aged 27 to 75 years) were placed into either a unilateral single-tooth defect (n = 17) or on either side of a bilateral teeth defects (n = 15). The bite force (%) of the prostheses, teeth and segments at the maximum intercuspation position (MIP) was evaluated using a T-scan at 5 stages (pre-placement, immediately following placement, and 2 weeks, 3 months, and 6 months post-placement). Results The occlusal force of implant-supported prostheses was significantly (P = .000) lower than those of the control natural teeth at the baseline, then no significant difference was found with that of the mesial teeth at 3 months, and finally it was significantly (P = .000) lower than that of the distal teeth at 6 months; meanwhile, it significantly (P = .008) increased by a mean of 2.04 times from 2 weeks (3.39 ± 2.61%) to 3 months (6.90 ± 4.77%), whereas no significant difference (P = .900) was found from 3 months (6.90 ± 4.77%) to 6 months (7.31 ± 4.60%). In addition, the bite force of the posterior segment on the restored side of both unilateral and bilateral gaps was significantly (P = .013,.001) improved by 3.31% and 6.83%, respectively, although the discrepancy in bite force significantly (P = .039) increased from an initial 3.52% to 5.02% for subjects with bilateral defects, accompanying increases in the proportion (15.38%) of the level III bilateral bite force deviation (P >.05). Conclusions Bite force and masticatory ability can be improved with the immediate delivery of a single posterior implant restoration. The bite force distributed on the implant prosthesis inevitably increases after placement of implant prostheses, a routine follow-up and occlusal evaluation are strongly needed.

modulus of the tooth is closest to bone [12].It is therefore believed that dental implants may be more prone to occlusal overloading which refers to stress around the implant components and bone implant interface that is not both technically and biologically acceptable, which is often regarded as one of the potential causes for peri-implant bone loss and failure of the implant/implant prosthesis [1].
Dental occlusion plays a central role in clinical dentistry and is essential for normal physiologic function [13].It means the contact relationship between the upper and lower teeth, and also refers to the contact action or process between the upper and lower dentition.Occlusion can be defined as "static" teeth contact when the mandible is at rest relative to the maxilla, or "dynamic" teeth contact as the mandible moving relative to the maxilla [14].For a single implant prothesis, the recommendations of occlusion are as follows: the force distribution should be equal bilaterally and maximized on adjacent teeth [15,16].Light contacts at heavy bite and no contact at light bite in maximum intercuspation position( MIP) are considered a reasonable approach to distribute the occlusal force on teeth and implants [17].Light to medium occlusal contact in maximum intercuspation is recommended for the adjacent, natural teeth, with lighter contact or clearance between the occlusal face and opposing tooth [17,18].Anterior guidance is recommended in lateral and protrusive excursions.In lateral excursions, posterior teeth should avoid heavy forces in the lateral direction by discluding [10].Avoiding Premature contacts [9] both working and nonworking contacts on implant restorations is vital to reduce shear forces in a nonaxial direction [16,19].An important reason of these considers is overloading resulting from improper occlusion [20].Implant occlusion should be examined not only in terms of conventional occlusal schemes but also from the standpoint of the role of overloading factors [1].Despite the above guidelines have been extensive applied in clinical practice, some problems have been in the state of exploration, which including the range of overload that biologically acceptable is also unknown [21][22][23], the effect of single implantsupported restorations on occlusal pressure distribution remains questionable [24], and the stability of this new occlusion constructed by implant insertion is still in doubt [25].It may result in the occurrence of potential occlusal overloading in the process of implant restoration, due to the habitual occlusion of the patient, the discrepancy of mobility between implant and natural tooth, the movement of natural teeth.Therefore, it is critical to analyze and re-evaluate the occlusion with post-insertion posterior single-implant restoration.Meanwhile, Force distribution between implants and natural teeth in a partially edentulous region can be accomplished with serial and gradient occlusal adjustments [17].
In the past, many occlusal studies have relied heavily on articulating papers, foils, and photocclusion to conduct analysis.However, articulating paper mark size has been shown to be an unreliable indicator of occlusal force [26,27] .None of the conventional methods, such as the use of articulating paper, shim-stock foil, and impression waxes were able to quantify occlusal contacts.Studies found no scientific correlation between the articulating paper mark size and the amount of applied force, which demonstrates the inadequacy of articulating paper in interpreting the occlusal load [28].T-Scan is a digital occlusion analysis system that records and measures tooth contact, force, and timing in real-time using a thin, flexible, pressure-sensitive bite transducer embedded in a dental arch-shaped recording sensor [29][30][31].Not only it can reflect the position of the occlusal contact point, and the area of the contact point, the strength and distribution of the contact point objectively, but also recording the instantaneous occlusal contact in the chewing cycle to the nearest 0.01 second dynamically, It is better than other occlusion recording methods on accuracy and sensitivity, That providing a good means of research for the quantitative study of occlusal balance.T-Scan is mainly composed of sensor, connection handle, computer and analysis software.The sensor is a thickness of 60-100 μm and placed on the occlusal surface of the subject.The diaphragm has a horseshoe-shaped sensing area with small wires arranged in a longitudinal and transverse direction.When the wire is subjected to the occlusion pressure, the current change which can be transmitted to the computer through the control device and analyzed by software occurs.After that, it is possible to detect the number of occlusal contact points and the change of the occlusal force in different parts with time.The T-scan III System [32] (Tekscan III, South Boston, MA) is the newest generation of occlusal Analysis applying in clinical and scientific research.Compared with the previous two generations of occlusion analysis systems, the T-scan III occlusion analysis system has a medium, lateral, anterior and habitual occlusion mode to create a personalized arch image.The bow image can check and analyze the occlusal contact from two-dimensional and three-dimensional perspective, detect the change of the occlusal contact synchronously with the change of time, and observe the occlusal contact distribution, position, contact intensity at each time point in the dynamic occlusion process.Furthermore, observing the distribution of bite force in different regions, the characteristics of bite force changing, the time of occlusion contact.It is a quantitative, objective and reliable "dynamic" occlusal evaluation method [33,34].Some scholars [35][36][37] have used it for the analysis of implants occlusion which including morphology and density, for the relationship between excessive force and bone loss, influence of occlusal loading on peri-implant clinical parameters and so on.
In summary, it is implied that heavy occlusal force and undesirable distribution of occlusal contacts may be factors of overloading, thus possibly leading to higher susceptibility to implant bone loss, implant fractures/loss, and prosthesis failures.Roque, M.A.'s study [24] showed that post-insertion of posterior implants cause significant changes in the bilateral bite force distribution.A research from Madani.A.S et al [25] concluded that intensity of occlusal contacts of implant supported prostheses opposed by natural dentition gradually increased after prosthesis insertion.In addition, it was reported that in 46% of patients, the occlusal load applied to implant prostheses changed within 18 months after prosthesis placement, and almost one-third of these changes took place during the first 6 months [38].Based on the above considerations, this study intends to further analyze and evaluate the occlusal parameters including occlusion time(OT), disclusion time(DT), distribution of force, occlusion interference(OI) after insertion of posterior single implant, and regularly assess the occlusion changes to eliminate possible risk factors to achieve balanced occlusion and stability.

Research questions
5.1 What are the effects of single posterior tooth on the bite force distribution and occlusal time after insertion?5.2 Whether the occlusal parameters including time, distribution, interference and so on will change after the insertion of single posterior implant?
5.3 How does this new occlusion created by the insertion of single posterior tooth change over the next period of time?
5.4 What factors do contribute to the establishment of balanced and stable occlusion with single posterior implant?6. Objectives of Research 6.1 Using T-scan that is a digital occlusion recording method with high accuracy and sensitivity, to obtain dynamic occlusion characteristics of posterior single-implant restoration, which including initial contact point, occlusion and disclusion time, force distribution and force outlier, interference in the movement of mandible.
6.2 At the same time, analyzing and regularly re-evaluating of those to remove potential occlusal risky factors and maintain balanced and stable occlusion.

Hypotheses
Ho: There is no difference in occlusal parameters after posterior single-implant restoration insertion with the use of T-scan measurement.
Ha: There are differences in occlusal parameters after posterior single-implant restoration insertion with the use of T-scan measurement.
7.1 Bite force percentage (BFP)with single posterior implant restoration.Ho: There is no significant difference in bite force percentage for single posterior implant restoration during the 3 and 6-month period with the use of T-scan measurement.
Ha: There are significant differences in bite force percentage for single posterior implant restoration during the 3 and 6 -month follow up period.
7.2 Distribution of bite force (DBF) between anterior and posterior/bilateral teeth Ho: There is no significant difference in distribution of bite force between anterior and posterior/ bilateral teeth after posterior single-implant restoration insertion with the use of T-scan measurement.
Ha: There are significant differences in distribution of bite force between anterior and posterior/ bilateral teeth after posterior single-implant restoration insertion with the use of T-scan measurement.

Initial tooth contact (ITC)
Ho: There is no significant difference in the frequency of initial tooth contact of single implant restoration after posterior single-implant restoration insertion.
Ha: There are significant differences in the frequency of initial tooth contact of single implant restoration after insertion and 3 to 6-month follow up time.

Occlusion time (OT)
Ho: There is no significant difference in the occlusion time of MIP after posterior single-implant restoration insertion with the use of T-scan measurement.
Ha: There are significant differences in the occlusion time in MIP after posterior single-implant restoration insertion with the use of T-scan measurement.

Disclusion time (DT)
Ho: There is no significant difference in the disclusion time during the functional excursions after posterior single-implant restoration insertion with the use of T-scan measurement.
Ha: There are significant differences in the disclusion time during the functional excursions after posterior single-implant restoration insertion with the use of T-scan measurement.

Occlusion interference (OI)
Ho: There is no significant difference in occurrence of occlusion interference during lateral and protrusive movement after posterior single-implant restoration insertion with the use of T-scan measurement.
Ha: There are significant differences in occurrence of occlusion interference during lateral and protrusive movement after posterior single-implant restoration insertion with the use of T-scan measurement.

9.Scope of Study
The occlusal parameters of subjects will be evaluate at five phases of occlusion including before crown insertion, immediately after insertion and 2 weeks later,3 months and 6 months follow up period.27 subjects who will be placed posterior single-implant restoration at Faculty of Dentistry, Thammasat hospital will be enrolled in this study.10.Research Methodology 10.1 Study Population 27 subjects who will be placed posterior single-implant restoration at Faculty of Dentistry, Thammasat hospital will be enrolled in this study.

Measurement of occlusion
Signing of Informed consent before and after crown insertion
(3) Successfully osseointegration has been completed in the implanting area.
(4) In occlusion with natural dentition, the opposed teeth are natural teeth.
(5) There is only one posterior tooth missing space in the dentition or even if more than one missing space, the remaining edentulous region had no effect on the results during the study period.
(2) use of known drugs that would affect the central nervous system or severe systemic diseases or known mental disorders.
(4) history of bruxism.⑴This study belongs to experimental research (not investigation), so the sample size is calculated according to the experimental research method (the proposed paper should specify the inclusion and exclusion criteria) .If the study is a prospective study, the study design of the repeated measurement data before and after insertion is based on a hypothesis that the rate of loss of follow-up is 10%, and the analysis index is "The change of the bite force distribution with a single posterior implant restoration before and after insertion", assuming that the bite force is the measurement data, the formula for calculating the sample size is as follows: ⑵It is considered that the average increase of 2 units of the bite force before and after insertion can be considered significant.If the standard deviation of the difference of the bite force for the subjects in the study is σ=3 units, α is 0.05 on both sides, and the test efficiency 1-β is 0.90.Then the standard deviation of sample bite force s = (σ =) 3 units, δ = 2 units of bite force change, α = 0.05, Z 0.05 / 2 = 1.96, β = 0.10, Z 0.10 = 1.282 , which were brought into the formula to get 23.65, that is, at least 24 subjects need to conduct their own before and after experiments comparison.Taking into account 10% of the loss of follow-up, the final sample size is 24 × 110% =26.4,So total 27 subjects will be included in this study.10.3.2Signing of informed consent Once subjects will be fulfilled the inclusion/exclusion criteria, the subjects will be informed thoroughly about the experimental procedure, related considerations, possible risks, as well as benefits gain.Written informed consent will be obtained.
10.4 Experimental Procedures (1) Explain to the study subjects, instruct the subjects to complete the following three jaw movements (including four positions) of occlusion training.
MIP: from the mandibular postural position to the most extensive and closest contact of the upper and lower dentitions, which is the maximum intercuspation position and simultaneously producing maximum bite force.
Protrusive excursion: from the intercuspation position sliding forward along the oblique direction of the anterior tangential path, and passing through the upper and lower anterior teeth opposed until it can not move forward; Lateral movement: from the intercuspation position moves along the lingual bevel of the left canine/right canine, and passing through the upper and lower canine teeth opposed until it can not move laterally.
(2) Select the appropriate sensor based on the width and length of the maxillary arch of the subject, open the T-scan occlusion analysis software, input the width of the incisors, adjust the width of another teeth on the graph, so that the distance from the proximal to the distal of the subject is consistent.To create a personalized dental arch model.
(3) The subjects are told to sit in the dental chair in a natural position with their relaxed natural posture, and the eyes looked straight ahead to maintain the natural head position.Place the sensor in mouth, paralleling to the occlusal plane, and the centerline is aligned.Let the subjects do the maximum occlusal interdigitation and select the appropriate sensitivity according to their occlusion.The appropriate sensitivity level is the red zone with the least distribution in the yellow and blue regions, usually no more than 1-2 columns of red and orange bars.
(4) Record the image of the occlusal staggered position of the study object: guide the research subjects naturally close from the mandibular postural position to the maximum intercuspation position.At the same time, the upper and lower dentition will be bit tight until the force fades, and the corresponding image is recorded and recorded three times.
(5) Record the image of the occlusal movement of the research subject: guide the research subjects naturally close from the mandibular postural position to the maximum intercuspation position.At this time, let the research subject move the mandible forward to the anterior teeth until the edge to edge and can not move forward, record the corresponding image, repeat the record three times.
(6) Record the image of the lateral occlusal motion, guide the research subjects naturally close from the mandibular postural position to the maximum intercuspation position.At this time, let the subjects make lateral occlusions to the left and right, record the corresponding images, and repeat the recording three times.
10.5 Data collection All measurements will be performed by one examiner.
(1) Characteristics of subject's demography, location and classification of missing single posterior teeth.
(2) Characteristics of prosthesis material and retention method, implant length, diameter, crown and implant ratio.
(3) The baseline of clinical data.
(4) The occlusal parameters of the follow up time.

Statistical Analysis
The statistical analysis method use one-way ANOVA, paired T test or Friedman test and Wilcoxon test.11.Participant accessibility detail/ methods / medical record 11.1 Participant will be recruited from patients who have been undergone dental implant treatment at Faculty of Dentistry, Thammasat hospital according to inclusion criteria.3 months before the study begin, the patients who have received successful single implant in the posterior teeth will be selected according to the inclusion criteria.The purpose, significance and requirements of the study will be explained to the subjects on the day of the appointment when the crown insertion.In the case of obtaining informed consent of the research subject, the research will be carried out.
11.2 The details of these patients will be obtained from the standard case record form(Appendix A)of the Implantology clinic, Faculty of Dentistry, Thammasat University.In order to judge whether it meets the inclusion criteria or not.(Zhou Ting) 13.Human Subjects protection 13.1The occlusion measurement requires patient to complete a normal occlusion exercise, it is free of any negative effects and adverse reactions.
13.2 The procedure(s) acted upon participant would be exactly the same as indicated in the information.Any of personal information will be kept confidential.Any of personal information which could be able to identify you will not appear in the report.
13.3 Participants have the right to withdraw from this research protocol at any time as he/she wish with no need to give any reason.This withdrawal will not have any negative impact upon you (eg: still receive the usual services).
13.4 If participants have any question or would like to obtain more information, the researcher can be reached at all time.If the researcher has new information regarding benefit on risk/harm, participants will be informed as soon as possible."This practice will provide an opportunity for participants to decide whether to stay/not stay with the project.
13.5 If participants are not treated as indicated in the information sheet, they can report to The Ethical Review Sub-Committee Board for Human Research Involving Sciences, Thammasat University, No. 3 (ECScTU), Room No. 110, Piyachart Building, 1st Floor, Thammasat University Rangsit Campus, Prathumthani 12121, Thailand, Tel: 0-2986-9213 ext.7358E-mail: ecsctu3@nurse.tu.ac.th 14.Expected Benefits 14.1 Clinicians usually evaluate the outcome based the success criterion most commonly reported in clinical reports is the survival rate, meaning whether the implant is still physically in the mouth or has been removed.As an alternative of natural teeth, the effects of Implants are self-evident.However, due to the difference between implant and natural teeth, how to maximize improve function and longevity of it is the lifelong pursuit of medical workers.It will improve the treatment outcome and protocol design by measuring and analysis of implant occlusion characteristic.
14.2 Although many clinical studies have shown high success rates with dental implant treatments, several studies have reported failures and complications for diverse reasons, in which including overloading resulting from improper occlusion.Therefore, it is necessary to analyze the implant occlusion and evaluate it regularly.This will conduce the elimination of potential risky factors and achieve longer-term stability.
14.3 At present, the clinically relies mainly on the articulating paper for the occlusion adjustment.Considering the low correlation between the articulating paper and over loading, the occlusal adjustment should be more accurate and objective under the guidance of T-scan, to achieve the better treatment outcome and balanced occlusion.
[3] Goh, E. and L.P. Lim, Implant maintenance for the prevention of biological complications: Are you ready for the next challenge?J Investig Clin Dent, 2017.8(4).distribution of the contact point objectively, but also recording the instantaneous occlusal contact in the chewing cycle to the nearest 0.01 second dynamically, It is better than other occlusion recording methods on accuracy and sensitivity, That providing a good means of research for the quantitative study of occlusal balance.T-Scan is mainly composed of sensor, connection handle, computer and analysis software.The sensor is a thickness of 60-100 μm and placed on the occlusal surface of the subject.The diaphragm has a horseshoe-shaped sensing area with small wires arranged in a longitudinal and transverse direction.When the wire is subjected to the occlusion pressure, the current change which can be transmitted to the computer through the control device and analyzed by software occurs.After that, it is possible to detect the number of occlusal contact points and the change of the occlusal force in different parts with time.It is a quantitative, objective and reliable "dynamic" occlusal evaluation method and some scholars have used it for the analysis of implants occlusion which including morphology and density, for the relationship between excessive force and bone loss, influence of occlusal loading on peri-implant clinical parameters and so on.

3….. File about T-scan bite analyzer
Remark: The protocol is approved for one year from the approval signature date.

ข้ าพเจ้ าผู ้ มี นามข้ างท้ ายนี ้ ขอยอมรั บการรั กษาตามหลั กวิ ทยาการ ณ สถานที ่ นี ้ ทุ กประการ แม้ การนั ้ นจะได้ กระท าโดยนั กศึ กษาและข้ าพเจ้ าขอรั บรองว่ า จะไม่ เรี ยกร้ องสิ ทธิ ใดๆทั ้ งสิ ้ นตามกฏหมาย
I agree to comply with the regulations of the Dental School Clinics.Permission is granted to the Dental School Faculty and students to perform procedures necessary for my therapy which will be used for teaching purposes.I understand that x-ray pictures and other records remain the property of the school and may be used for publication within the guidelines of Thammasat University Dental School.

( 5 )
unwilling to accept further follow-up.10.1.3Sample Size Calculation 10.1.3.1 Reference variables Reference variables from Article 1(Roque, M.A et al, 2017 )and Article 2 (Madani, A.S., et al.,2017) 10.1.3.2Information provided by reference materials ⑴Article 1: Prospective laboratory studies, no sample calculation source, only listed inclusion and exclusion conditions, using nonparametric statistical tests.Twentyfive cases were collected and four were lost to follow-up.Among the remaining 21, 10 are women and 11 are men.⑵Article 2: Retrospective cohort study, self-controlled study design, no sample calculation source, only listed inclusion and exclusion conditions.And the full text does not give the final sample number, only the percentage, no absolute value.10.1.3.3Calculation method